Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions Part 1: the VIASYS Hi-Ox80tm

Defence Research and Recherche et développement Development Canada pour la défense Canada

& DEFENCE DÉFENSE

Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions Part 1: The VIASYS Hi-Ox80TM

F. Bouak

D.J. Eaton

Defence R&D Canada – Toronto Technical Report DRDC Toronto TR 2005-207 November 2005

Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions Part 1: The VIASYS Hi-Ox80™

F. Bouak D. J. Eaton

Defence R&D Canada – Toronto Technical Report DRDC Toronto TR 2005-207 November 2005

Abstract

An experiment was carried out at Defence R&D Canada – Toronto to recommend an efficient oxygen breathing system for multiple casualties in remote areas. The objective was to improve the oxygen therapy capability and efficiency of the Canadian Forces Search and Rescue Technicians as well as any military organization that may potentially need to dispense oxygen to survivors of a mass casualty scenario such as in a field hospital or during submarine escape and rescue. Twenty-four trials were completed using twelve male and female volunteers (30- 55 years) to compare the VIASYS Hi-Ox80™ mask to a simple facemask. Measurements were made with the subjects at rest in seated and supine positions to simulate an injured person 80™ being administered oxygen (O2). The Hi-Ox delivered significantly higher O2 concentrations to the subjects at lower flow rates than the simple facemask. Given the high O2 concentrations, low O2 flow rates, low levels of inhaled carbon dioxide, constant levels of the exhaled carbon dioxide and low breathing resistance, the Hi-Ox80™ could be an efficient breathing unit for mass casualty treatment in a remote area. If an O2 concentration of 80% is adequate for treatment, the duration of a pressurized tank or the number of patients treated can at least triple with a flow rate of 4 litres per minute when compared to the currently used O2 systems. Furthermore, this O2 flow rate can allow the use of portable O2 concentrators, thereby increasing the efficiency while minimizing risks.

Résumé

RDDC Toronto a mené une expérience dans le but de recommander un appareil respiratoire à oxygène efficace dans le traitement d’un grand nombre de blessés dans les régions éloignées. Cette expérience visait à améliorer l’efficacité des soins d’oxygénothérapie offerts par les techniciens en recherche et sauvetage des Forces canadiennes ainsi que par toute autre organisation militaire qui pourrait être appelée à administrer de l’oxygène aux survivants d’un incident faisant de nombreuses victimes (p. ex. hôpital de campagne ou lors d’évacuation et sauvetage d’un sous-marin). On a mené 24 essais sur un échantillon de 12 volontaires des deux sexes (âgés de 30 à 55 ans) en vue de comparer le masque VIASYS Hi-Ox80MC avec un masque facial simple. Les mesures ont été prises alors que les sujets étaient au repos, en position assise ou couchée sur le dos, afin de simuler une personne blessée recevant de l’oxygène. Les résultats ont démontré que le masque Hi-Ox80MC est nettement supérieur au masque facial simple en ce qui concerne l’administration d’oxygène. Le masque Hi-Ox80 MC a permis d’administrer aux sujets des concentrations élevées d’oxygène à des débits plus faibles que le masque facial. Étant donné les concentrations élevées d’oxygène administrées, les faibles débits d’oxygène utilisés, les faibles concentrations de dioxyde de carbone inspiré, les concentrations constantes de dioxyde de carbone expiré et la faible résistance respiratoire, le masque Hi-Ox80MC pourrait constituer un appareil respiratoire efficace dans le traitement d’un grand nombre de blessés dans une région éloignée. Si une concentration d’oxygène de 80 % convient pour le traitement, la durée d’utilisation des bouteilles sous pression ou le nombre de patients traités pourrait être au moins triplé par rapport à la situation actuelle en réglant le débit à 4 litres par minute. De plus, ce débit d’oxygène rendrait possible l’utilisation de concentrateurs d’oxygène portables, augmentant ainsi l’efficacité tout en réduisant les risques.

DRDC Toronto TR 2005-207 i

This page intentionally left blank.

ii DRDC Toronto TR 2005-207

Executive summary

Introduction. In considering emergency response to major air or marine disasters, one of the most important initial actions is the dispensing of normobaric oxygen therapy (NBO) to survivors. Most of the available oxygen breathing systems used for oxygen (O2) therapy provide a very limited time on oxygen because of extremely inefficient oxygen use. Only two percent of the provided gas is actually used by the patient. The rest is exhaled into the atmosphere with each breath. This may be acceptable for treating accident victims in urban areas; however, to treat survivors in a remote area means more oxygen must be transported which increases weight, volume and risk to unacceptable levels. Defence R&D Canada – Toronto received support from the Search and Rescue (SAR) New Initiative Fund (NIF) to recommend an efficient oxygen breathing system for multiple victims. The objective was to improve the oxygen therapy capability of the CF Search and Rescue Technicians in remote areas. A review of the state-of-art [1] identified promising solutions for the CF, such as the 80™ ™ VIASYS Hi-Ox mask and the DAN REMO2 rebreather. These two breathing units were selected for manned evaluation. This report presents results for the Hi-Ox80 mask and compares its performance to the commonly used simple facemask. A second report [2] describes the evaluation of the REMO2.

Methods. Twelve male and female volunteers (30-55 years) were recruited. The procedure for testing the Hi-Ox80 and simple facemask consisted of five breathing periods of 15 minutes each separated by 10-minute air-breaks. Oxygen flow rate was either 4, 7, 8, or 9 litres per minute (L·min-1) during each breathing period. Subjects were at rest breathing calmly at their own resting respiratory rate in seated and supine positions to simulate an injured person being administered oxygen. Inhaled and end-tidal O2 and carbon dioxide fractions (CO2), blood oxygen saturation, mask pressures, exhaled gas volume for the Hi-Ox80 and inhaled gas temperature were continuously measured. Subjects rated their perceived breathing effort and mask discomfort.

Results. Twenty-four trials were carried out. Although both breathing units increased mean arterial oxygen saturation from 94.8% to over 98.2% (98.4% with the Hi-Ox80 and 98.2% with 80 80 the simple facemask), the Hi-Ox delivers more O2 at lower flow rates. With the Hi-Ox , the -1 inhaled O2 fraction (fIO2) was above 0.91 for flow rates greater than 7 L·min and was 0.80 -1 even at an O2 flow rate of 4 L·min while the highest fIO2 delivered by the simple facemask was just 0.60 at 9 L·min-1. Also, the Hi-Ox80 had low breathing resistance and maintained normal CO2 levels which would prevent excess CO2 elimination especially at high ventilation. There were no statistically significant differences in all variables between seated and supine positions.

Significance. If an fIO2 of 0.80 is adequate for treatment, the duration of a pressurized tank or the number of patients treated simultaneously can at least triple with an O2 flow rate of -1 4 L·min when compared to the currently used O2 systems. Furthermore, the combination of a 80 modified Hi-Ox and a portable O2 concentrator could greatly increase the efficiency and safety of O2 delivery. It would replace the need for bulky, dangerous compressed oxygen supplies and thereby make sustained mass casualty NBO feasible in the field. This would benefit SAR and other military emergency operations such as submarine escape and rescue.

Bouak, F. and Eaton, J. D. 2005. Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions, Part 1: The VIASYS Hi-Ox80™. DRDC Toronto TR 2005-207. Defence R&D Canada – Toronto.

DRDC Toronto TR 2005-207 iii

Sommaire

Introduction. L’une des interventions d’urgence initiales les plus importantes en cas de catastrophe aérienne ou maritime consiste à administrer de l’oxygène (O2) aux survivants. Toutefois, la plupart des appareils respiratoires à oxygène servant à l’oxygénothérapie ne permettent généralement qu’un traitement de très courte durée en raison de l’utilisation excessivement inefficace de l’oxygène. Seulement 2% d’O2 administré est effectivement utilisé par le patient. Bien que ce type d’appareil puisse convenir dans les régions urbaines, le traitement des survivants dans les régions éloignées nécessite le transport de grandes quantités d’O2, ce qui entraîne une augmentation inacceptable du poids, du volume et du risque. RDDC Toronto a reçu le soutien du Fonds des nouvelles initiatives de recherche et de sauvetage pour recommander un appareil respiratoire à oxygène efficace dans le traitement d’un grand nombre de blessés. On visait à améliorer l’efficacité des soins d’oxygénothérapie offerts par les techniciens en recherche et sauvetage des Forces canadiennes dans les régions éloignées. On a examiné les solutions de pointe [1] potentielles pour les Forces canadiennes, telles que le 80MC MC masque VIASYS Hi-Ox et l’appareil respiratoire à circuit fermé DAN REMO2 . Les deux systèmes ont été sélectionnés en vue d’un essai sur des sujets. Le présent rapport présente les résultats obtenus à l’aide du masque Hi-Ox80 et compare l’efficacité de ce dernier avec celle du masque facial simple couramment utilisé.

Méthodologie. On a recruté 12 volontaires des deux sexes âgés de 30 à 55 ans. La procédure d’essai du Hi-Ox80 et du masque facial simple consistait en cinq périodes de respiration de 15 minutes, chacune étant suivie d’une pause de 10 minutes. Le débit d’oxygène était soit 4, 7, 8 ou 9 litres par minute (L·min-1). Les sujets respiraient calmement à leur fréquence respiratoire normale au repos dans une position assise ou couchée sur le dos afin de simuler un patient recevant de l’oxygène. Les fractions d’oxygène et de dioxyde de carbone (CO2) dans l’air inspiré et en fin d’expiration, le taux de saturation du sang en O2, la pression dans le masque, le volume du gaz expiré pour le masque Hi-Ox80 et la température du gaz inspiré ont été mesurés de façon continue. Les sujets ont évalué l’effort de respiration et l’inconfort du masque.

Résultats. On a mené en tout 24 essais. Bien que les deux appareils respiratoires aient augmenté la saturation moyenne du sang artériel en O2 de 94,8% à plus de 98,2% (98.4% avec le Hi-Ox80 et 98.2% avec le masque facial simple), les résultats ont démontré que le Hi-Ox80 80 est nettement supérieur au masque facial simple. Le Hi-Ox délivre plus d’O2 à un débit plus faible. La fraction d’O2 dans l’air inspiré (fIO2) a dépassé 0,91 à des débits supérieurs à -1 -1 7 L·min et a atteint 0,80 même à 4 L·min , tandis que la fIO2 la plus élevée délivrée par le masque facial simple s’est élevée à 0,60 à 9 L·min-1. De plus, le Hi-Ox80 a maintenu une faible résistance à la respiration et le CO2 à des niveaux normaux, ce qui pourrait prévenir l’élimination du CO2 spécialement lorsque le taux de ventilation serait élevé. On n’a observé aucune différence statistiquement significative entre toutes les variables associées aux positions assise et couchée.

Signification. Si une fIO2 de 0,80 convient pour le traitement, la durée d’utilisation des bouteilles sous pression ou le nombre de patients traités en même temps pourrait être au moins triplé par rapport à la situation actuelle en réglant le débit d’oxygène à 4 L·min-1. De plus, la combinaison du Hi-Ox80 et d’un concentrateur d’oxygène portable pourrait grandement

iv DRDC Toronto TR 2005-207

accroître l’efficacité de l’administration d’oxygène : Elle éliminerait la nécessité de transporter des réserves d’O2 comprimé encombrantes et dangereuses et faciliterait l’administration continue d’O2 normobare à un grand nombre de blessés en campagne. Ceci pourrait énormément aider les techniciens en recherche et sauvetage des Forces canadiennes ainsi que toute autre organisation militaire qui pourrait être appelée à administrer de l’oxygène aux survivants d’un incident faisant de nombreuses victimes (p. ex. évacuation et sauvetage d’un sous-marin et installation d’un hôpital de campagne).

Bouak, F. and Eaton, J. D. 2005. Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions, Part 1: The VIASYS Hi-Ox80™. DRDC Toronto TR 2005-207. Defence R&D Canada – Toronto.

DRDC Toronto TR 2005-207 v

This page intentionally left blank.

vi DRDC Toronto TR 2005-207

Table of contents

Abstract...... i

Résumé ...... i

Executive summary ...... iii

Sommaire...... iv

Table of contents ...... vii

List of figures ...... ix

List of tables ...... x

Acknowledgements ...... xi

Introduction ...... 1 Simple facemask...... 2 Hi-Ox80™...... 2

Methods and Materials ...... 5 Subjects ...... 5 Experimental Set-up and Data Acquisition ...... 5 Procedures ...... 8 Statistical Analysis ...... 9

Results ...... 11 Performance of the two breathing units...... 11 Arterial oxygen saturation ...... 11

End-inspiratory O2 fraction ...... 12

End-inspiratory and end-tidal CO2 fractions ...... 12 Subjective rating and peak inhale and exhale pressures...... 14

DRDC Toronto TR 2005-207 vii

Discussion...... 17

Conclusion ...... 21

Future Directions ...... 23

References...... 25

Annex A: Experimental Data...... 27

Annex B: Breathing Units...... 29

Annex C: Psychophysical Test ...... 31

Annex D: Test Termination Criteria...... 35

Annex E: Subjects’ Comments ...... 37

Bibliography ...... 41

List of symbols/abbreviations/acronyms/initialisms...... 43

Distribution list ...... 45

viii DRDC Toronto TR 2005-207

List of figures

Figure 1. The simple facemask...... 2

Figure 2. The Hi-Ox80™ mask [6]...... 3

Figure 3. The Hi-Ox mask manifold and one-way valves: (a) side view; (b) front view...... 3

Figure 4. Experimental Set-up...... 6

Figure 5. Subject and instrumented mask details; (a) Simple facemask, (b) Hi-Ox...... 6

Figure 6. Perception Scale for Effort Rating ...... 8

Figure 7. Perception Scale for Discomfort Rating...... 8

Figure 8. Mean arterial oxygen saturation...... 11

Figure 9. Mean inhaled oxygen fractions of both breathing units...... 12

Figure 10. Mean inhaled carbon dioxide fractions of both breathing units...... 13

Figure 11. Mean end-tidal carbon dioxide fractions of both breathing units...... 13

Figure 12. Subject ratings for breathing effort and mask discomfort of both masks...... 14

Figure 13. Peak mask pressures of the Hi-Ox...... 15

Figure 14. Schematic of the Hi-Ox mask manifold...... 18

Figure 15. Respiratory Minute Volume and the flow rate of the air inhaled from the atmosphere...... 19

Figure B1. The Hi-Ox mask: Oronasal mask with straps...... 29

Figure B2. The Simple facemask: detail of the side ports...... 29

Figure B3. The Hi-Ox mask: Subject and Experimental set-up...... 30

Figure B4. The Hi-Ox mask: measurement locations on the oronasal mask...... 30

DRDC Toronto TR 2005-207 ix

List of tables

Table 1. Examples of current O2 breathing units and their characteristics...... 1

Table 2. Subjects Characteristics ...... 5

Table 3. Test procedure for the Hi-Ox and the simple facemask...... 9

Table A1. Physical Description of the Subjects...... 27

Table B1. Breathing unit specifications...... 29

x DRDC Toronto TR 2005-207

Acknowledgements

The investigation was funded by the National Search and Rescue Secretariat of Canada, in collaboration with Defence R&D Canada – Toronto. The authors would like to acknowledge the sustained dedication of Mr. David Eastman who provided operational support and undertook a wide variety of tasks before, during and after the experiment. These include installing and preparing the experimental set-up, overseeing subject recruitment, organizing medical screening and monitoring the experiment. The investigators would like to thank Mrs. Rachel Hogue for administrative support and valuable help, and Mr. Robert MacLean for installing and programming the data acquisition system. In addition, the Medical Assessment and Training section provided medical coverage; special thanks to Dr. Bill Bateman and Dr. Gary Gray for reviewing the experimental protocol. The authors would like to thank Mr. Ronald Nishi for his valuable assistance in reviewing the report.

DRDC Toronto TR 2005-207 xi

This page intentionally left blank.

xii DRDC Toronto TR 2005-207

Introduction

Oxygen (O2) is a colourless, odourless and tasteless gas that is essential for the body to function properly and survive. Oxygen therapy is a medical treatment in which supplemental oxygen, at concentrations greater than the surrounding air, is provided to the patient for respiration. It is often used to treat medical conditions such as hypoxia, blood loss, or pressure-related injuries such as the decompression illness.

In considering emergency response to major air or marine disasters, one of the most important initial actions is the dispensing of oxygen to survivors. Oxygen therapy in field operations can be at or near sea level (normobaric oxygen (NBO) therapy), under pressure to treat, for instance, decompression illness (hyperbaric oxygen (HBO) treatment) or at altitude to prevent hypoxia or treat altitude-related injuries (hypobaric oxygen).

Oxygen can be delivered from a supply to the casualty via a breathing unit in several ways. Pressurized cylinders are the most common. Oxygen can also be delivered from special systems, such as chemical O2 generators or O2 concentrators. Currently, only compressed oxygen and chemical generators are used for search and rescue (SAR) field operations. However, both supplies are neither an economical nor an efficient choice for SAR field operations [1]. For example, the CF SAR Technicians (SAR Techs) use the AVOX (formerly ® ® Scott) Aviox Duo-Pak system (a chemical O2 generator combined with a simple mask). The Aviox does not use compressed O2 so it reduces the safety hazard but it only treats one patient for 40 minutes. Consequently, the volume of oxygen available for remote treatment is very limited.

Breathing units are designed to deliver oxygen from the supply to either breathing or non- breathing patients. A wide variety of oxygen delivery units are available [1]. These systems can be open or closed circuit with continuous or on-demand flows. They essentially vary in the concentration and amount of oxygen effectively delivered to the patient (Table 1). In a review of literature, Bouak [1] reported that current O2 breathing systems are extremely inefficient. For example, a non-rebreathing mask (NRM) with a Jumbo D cylinder (640 litres) commonly used in first-aid oxygen therapy provides less than 40 minutes of O2 breathing to only one patient. Only two percent of the provided gas is used by the patient. The rest is exhaled into the atmosphere with each breath.

Table 1. Examples of current O2 breathing units and their characteristics.

O2 flow rate Mode Circuit type/Flow type -1 Delivered %O (L·min ) 2

Nasal cannula Open/Continuous 0.5 - 4 22 to 35

Simple facemask Open/Continuous 6 - 12 30 to 60

Non-rebreathing mask Open/Continuous 8 - 15 45 to 90

Demand valve with mask Open/Demand 9 – 160* Close to 100

(*) Actual O2 flow rate depends on breathing demand of the patient.

DRDC Toronto TR 2005-207 1

Defence R&D Canada – Toronto received support from the Search and Rescue (SAR) New Initiative Funds (NIF) to select, evaluate and recommend an efficient oxygen breathing system for multiple victims in remote areas. An appropriate efficient oxygen breathing system for remote treatment would consist of a compact, lightweight, non-hazardous O2 supply combined with a low-flow rate breathing unit that will minimize wasted gas. On the supply side, the use of a portable small O2 concentrator should greatly enhance O2 availability and the capability to dispense sustained mass casualty NBO in the field [1, 3-5]. Bouak [1] showed that two systems currently commercially available could possibly be paired with an 80™ ™ O2 concentrator. They were the VIASYS Hi-Ox mask (Hi-Ox) [6] and the DAN REMO2 rebreather (REMO) [7]. This report describes the results and conclusions of an experiment examining the feasibility of using the Hi-Ox for SAR rescue missions. The Hi-Ox performance was compared to a simple facemask (a standard Hudson® mask) as a control. The tests and performance of the REMO was reported separately [2].

Simple facemask

The simple facemask (commonly known as the standard Hudson® mask) is an open-circuit, continuous flow mask (Figure 1) and one of the most commonly used for O2 therapy. It is a commercial product and manufactured by a number of suppliers (e.g., O-Two Medical Technologies Inc.). The flexible mask covers the patient's nose and mouth and is kept on by one elastic strap. Oxygen from the supply passes via a tube (2.1 m long) into the mask where it mixes with the ambient air drawn in through ports in the side of the mask.

O2 supply hose

Elastic strap

Metal strip Side ports

Figure 1. The simple facemask.

Hi-Ox80™

The Hi-Ox (Figure 2) is a commercial product manufactured by VIASYS™ Healthcare. It is an open circuit continuous flow mask designed to improve gas usage efficiency, that is, low oxygen flow rates combined with high oxygen concentration. The Hi-Ox is also designed to prevent excess CO2 elimination so that respiratory centre excitation produced by CO2 chemoreceptors does not decrease. Somogyi et al. [8] showed that with the Hi-Ox the inhaled -1 O2 fraction (fIO2) can easily exceed 0.8 at a flow rate of 8 litres per minute (L·min ). In fact,

2 DRDC Toronto TR 2005-207

-1 the fIO2 of the Hi-Ox was 0.97 at 8 L·min when the patient was resting, more than 40% higher than the performance of a non-rebreathing mask with the same O2 flow rate and patient ventilation.

Elastic Metal strip straps

Manifold Facemask (no side ports)

O2 supply hose

Exhale port

Reservoir

™ Figure 2. The Hi-Ox80 mask [6].

(a) (b)

Exhale Inhale 1-way 1-way valve valve

Ambient air 1-way valve

O2 supply port Exhale to inhale 1-way valve

Figure 3. The Hi-Ox mask manifold and one-way valves: (a) side view; (b) front view.

DRDC Toronto TR 2005-207 3

The Hi-Ox includes a flexible oronasal mask with no side ports and supported by two elastic straps, an O2 reservoir bag, flexible supply hose (2.1 m long) and a manifold (Figures 2 and 3) with four (4) one-way valves (commonly called mushroom valves), one on the inhale side, a second on the exhale side and a third that interconnects inhale and exhale. These first three are all the same size. A fourth, smaller one-way valve is located just beside the inlet of the oxygen supply hose on the manifold (see Figure 3a). This ambient air 1-way valve was added for safety reasons as an anti-suffocation valve. This will be confirmed with the manufacturer. Two elastic straps hold the mask in place and a metal strip on the mask allows adjustment of the oronasal mask shape to fit the patient’s face. Table B1 in Annex B shows its principal specifications.

4 DRDC Toronto TR 2005-207

Methods and Materials

Subjects

A total of twelve healthy subjects (military and civilian) volunteered to participate in this study, ten male and two female between the ages of 30 and 55. They were recruited from DRDC Toronto staff. Prior to conducting the experiments, all subject candidates underwent a medical screening by a physician to determine respiratory symptoms and eligibility. All subjects gave their written consent after being informed of the details, discomforts and risks associated with the experiment protocol [9]. Remuneration for participation complied with guidelines established by DRDC Toronto. No subject withdrew from the study. Table 2 summarizes their physical characteristics. These are shown for each subject in Table A1, Annex A.

Table 2. Subjects Characteristics

Mean ± SD Range

Age (yr) 41.3 ± 7.5 31 – 55 Weight (kg) 82.46 ± 15.16 56 – 109 Height (m) 1.75 ± 0.08 1.60 – 1.83 Face Length* (mm) 120.33 ± 5.23 113 – 129

* Menton-Sellion height [10]

Experimental Set-up and Data Acquisition

The equipment was set up as illustrated in Figure 4, Aviator’s oxygen was provided from a K-cylinder using a high purity oxygen regulator (Matheson Gas Products, Model 3104C). The O2 flow rates were adjusted using a computer-controlled mass flow controller (Brooks 5850 series, 0-10 Standard L·min-1). A chain-compensated gasometer (Warren E. Collins, 120 L) was used to calibrate the flow controller.

The oronasal mask was instrumented (Figure 5) to measure O2 and CO2 fractions, temperature and pressure. A gas sample line (Intramedic polyethylene tubing by Clay Adams, Model PE-60, 0.76 mm I.D. x 1.22 mm O.D. x 1 m long) and the mask thermistor (Yellow Spring Instrument, Model 44004) were inserted into the facemask about one centimetre from the subject’s mouth and nose (Figure 5). Mask gas was constantly sampled at a flow rate of 30 millilitres per minute (mL·min-1). The sample line was connected to the mass spectrometer (Hiden HPR20) via a heated capillary line of about 1.9 m long. (For the flow rate and the sample line length used in this experiment, the sample line delay was about 6 sec.) The sampled gas was not returned to the breathing circuit.

DRDC Toronto TR 2005-207 5

Breathing unit

Regulator Control Valve

Pressure Transducer

Mask Thermistor O2 Tank Mass Spectrometer

TurbinePneumotach Flowmeter

Subject’s Pulse Oximeter DAQ finger

Ambient Thermistor

Ambient Pressure

Computer

Figure 4. Experimental Set-up

(a) (b)

Pressure Transducer Line

Thermistor Lead

Gas Sample Linel

Volume transducer

Figure 5. Subject and instrumented mask details; (a) Simple facemask, (b) Hi-Ox.

6 DRDC Toronto TR 2005-207

Before each trial, the mass spectrometer was calibrated using two calibration gases, one with 100% O2 and the other being a mixture of 4% CO2, 16% O2 and 80% nitrogen (certification tolerance: ±0.02mole %). A second sample line penetrated the left side of the mask and was dead-ended to a pressure transducer (Validyne DP-15, ±0.5 psi diaphragm) for measuring instantaneous mask pressure.

Exhaled gas passed through a turbine volume transducer (Ventilation Measurement Modules . by Interface Associates) to compute minute ventilation (VE ). The volume transducer was incorporated in the exhale side of the Hi-Ox (Figure 5a). One rubber adapter (22 mm ID) was used, which added about 20 mL of dead-space. (The manufacturer reports the flow resistance -1 of the volume transducer as 0.5 cm H2O at 30 L·min [11]).

Arterial oxygen saturation (SaO2) was measured with a pulse oximeter (OXI by Radiometer Copenhagen) connected to the index or the middle finger of the subject’s right hand.

Ambient temperature Tamb (Yellow Spring Instrument 44004 thermistor) and barometric pressure PB (pressure transducer: Druck PDCR 910, 0-20 psiA) were also measured.

Data from the instruments were continuously measured at a sampling frequency of 20 Hz. As shown in Figure 4 (see also Figure B2 in Annex B), all lines from the instruments were connected to a data acquisition (DAQ) unit (Hewlett-Packard Model HP3852A). The DAQ unit was controlled using a PC-compatible computer connected via an IEEE 488 compatible interface. All experimental data were stored on the hard drive of the computer for further computation and statistical analysis. The DAQ unit and computer were controlled using custom written software in HP-Basic for the DAQ unit and LabVIEW™ (National Instruments) for the computer.

Custom-written analysis software (written using LabVIEW™) was used to derive variables from the measured values. Instantaneous O2 and CO2 fractions (fmO2, fmCO2) were used to compute end-inspiratory and end-tidal fractions (fIO2, fICO2 and fETCO2) for each breath. End- inhale and end-tidal values for carbon dioxide fractions were taken, respectively, at the times of the lowest and highest fmCO2 in each breath. Similarly, inhaled O2 fractions were determined from the maximum values of fmO2. Mean fIO2, fICO2 and fETCO2 were then computed for every minute. Finally, a mean value was calculated for the last five minutes of each breathing period for analysis. Mask thermistor and pressure data were used for determining end-inhalation and end-tidal temperatures and peak inhale and exhale pressures (PI and PExp), respectively. Respiratory rate (FV) was also determined from the mask pressure record.

Subjects rated their perceived level for breathing effort and mask discomfort (Annex C). Rating tests were based on a 0 – 10 subjective scale [12], as shown in Figure 6 for effort rating and Figure 7 for discomfort rating.

DRDC Toronto TR 2005-207 7

0 No Effort 0 No Discomfort 1 Very Light 1 Just Noticeable (or very slight) 2 2 Slight Discomfort 3 Fairly Light 3 Moderate 4 4 Somewhat Severe 5 Somewhat Hard 5 Severe 6 6 7 Hard 7 Very Severe 8 8 9 Very Hard 9 10 Extremely Hard 10 Extremely severe Discomfort (or Intolerable)

Figure 6. Perception Scale for Effort Rating Figure 7. Perception Scale for Discomfort Rating

Procedures

The DRDC Human Research Ethics Committee (HREC) approved the experiment protocol [9].

Baseline anthropometric measurements (weight, height and face length [10]) were collected for each subject (see Table A1, Annex A).

All tests were carried out at DRDC Toronto. Only one breathing unit was evaluated during a single trial with each subject evaluating sequentially the two units over a period of one to two test days. Subjects were assigned to the breathing units in a randomized order. Subjects went through the following procedures.

Subjects were first briefed on the test procedures, the use of the breathing unit to be tested and the psychophysical scales used to assess the breathing effort and mask discomfort (Figure 6 and 7).

An attendant assembled the breathing unit and instructed the subject in the proper use and fit of the breathing unit. The subject donned the breathing unit and was asked to breathe calmly at their own resting respiratory rate from the mask.

The experiment was broken into five periods of 15 min each separated by 10 min air-breaks (Table 3). Subjects rated breathing effort and mask discomfort at the end of each 15-min period. During these air-breaks, subjects took off their masks and breathed air. For each of the first four periods, the O2 flow rate was increased from one period to the next (Table 3). In the fifth period the flow rate was the same as the third, i.e. 8 L·min-1, but the subject switched from a seated to a supine position.

Any 15-minute period was halted when one of the criteria listed in Annex D were met.

8 DRDC Toronto TR 2005-207

Table 3. Test procedure for the Hi-Ox and the simple facemask.

Duration O2 flow rate Subject’s Period -1 min L·min Position 1 15 4 Seated 2 15 7 Seated 3 15 8 Seated 4 15 9 Seated 5 15 8 Supine

Statistical Analysis

Subjects evaluated the two delivered units in a balanced design. Arterial oxygen saturation, oxygen and carbon dioxide levels, mask pressures, and subjective rating for breathing effort and mask discomfort were analyzed using multi-factor, repeated measures analysis of variance (ANOVA) to determine any significant differences in the dependent variables between the two units, the O2 flow rates (breathing periods) and subject positions. When statistical significance was present, Tukey’s HSD post hoc was used to explore significant main effects and interactions. Relationships among measures were examined using Pearson correlation analysis. All statistical analyses were performed using the R programming environment [13].

DRDC Toronto TR 2005-207 9

This page intentionally left blank.

10 DRDC Toronto TR 2005-207

Results

Performance of the two breathing units

Twelve subjects completed 24 trials on the Hi-Ox and the simple facemask. Mean values of SaO2, fIO2, fICO2, subjective rating of breathing effort and mask discomfort, and peak inhale and exhale pressures of both breathing units, averaged across all 12 subjects, are shown in Figures 8 to 13 respectively.

Arterial oxygen saturation

As shown in Figure 8, both breathing units significantly increased the mean oxygen saturation from 94.8% without a mask to over 98.2% (F1, 22=113.2; p<0.0001 for the Hi-Ox, F1, 22=97.1; p<0.0001 for the simple facemask). The mean SaO2 was slightly higher with the Hi-Ox than with the simple mask. Flow rate and seated or supine position had no significant effect on SaO2 regardless of breathing unit.

100 Without mask

98 (%) 2

97 S I H M i Mean SaO 96 P O L x E 95

94 4 7 8 9 8 (Supine)

O2 flow rate (Standard L/min)

Figure 8. Mean arterial oxygen saturation.

DRDC Toronto TR 2005-207 11

End-inspiratory O2 fraction

Figure 9 compares fIO2 for the two breathing units. Regardless of O2 flow rate or subject position, the performance of the Hi-Ox was significantly higher than the simple facemask (F1, 110=586.14; p<0.0001). The existence of open side-ports on the simple facemask and leakage around the subject’s face (see Annex E for subject comments) diluted the oxygen -1 level delivered by the simple facemask. For O2 flow rates of 7 L·min and over, the Hi-Ox was able to maintain fIO2 level above 92%. For each mask, only the difference between 4 and -1 7 L·min was significant (F4, 55=11.89; p<0.0001for the Hi-Ox and F4, 55=2.99, p<0.05 for the simple mask). With both breathing units, subjects with facial hair had the lowest inhaled O2 levels, decreasing the overall mean inhaled O2 concentration by about 1.5%.

100.0

80.0

100 (%) 100 60.0

x H

2 i O I f O S x 40.0 I M P L E 20.0 4 7 8 9 8 (Supine) O flow rate (Standard L/min) 2

Figure 9. Mean inhaled oxygen fractions of both breathing units.

End-inspiratory and end-tidal CO2 fractions

On average, both units were able to maintain low fICO2 levels (<0.5%) as shown in Figure 10. However, mean inhaled CO2 levels of the simple facemask were significantly lower than the Hi-Ox (F1, 110=29.83; p<0.0001), regardless of O2 flow rate or subject position. Similarly, Figure 11 shows that the mean end-tidal CO2 fraction of the Hi-Ox was significantly higher than the simple facemask (F1, 110=200.44; p<0.0001). Moreover, the Hi-Ox maintained mean fETCO2 nearly constant and higher than 4.5% (i.e., end-tidal CO2 partial pressure (PETCO2) ≥ 34 mm Hg). With the simple facemask, the computed end-tidal CO2 fractions were low because the exhaled gas was diluted due to constant O2 flows and mask leakage.

12 DRDC Toronto TR 2005-207

0.7

0.6

0.5

0.4 100 (%) 100 x

2 0.3 CO H I f S i 0.2 I O M x P 0.1 L E 0.0 47898 (Supine) O flow rate (Standard L/min) 2

Figure 10. Mean inhaled carbon dioxide fractions of both breathing units

3 H

100 (%) 100 i x S 2 O I x CO 2 ET M f P L 1 E

0 4 7 8 9 8 (Supine)

O2 Flow (Standard L/min)

Figure 11. Mean end-tidal carbon dioxide fractions of both breathing units

DRDC Toronto TR 2005-207 13

Subjective rating and peak inhale and exhale pressures The results of the breathing effort and mask discomfort are presented in Figure 12. Overall, both units rated below “fairly light” (<3 on a 10-point scale) for breathing effort and below “very slight” (<1 on a 10-point scale) for mask discomfort. Breathing effort was rated higher with the Hi-Ox than the simple facemask (F1, 90=31.85; p<0.0001). Although, the averages of breathing effort for the four flow conditions were not significantly different, Figure 12 shows that it dropped slightly from 1.9 to 0.9 with the increase of the flow from 4 to 9 L·min-1. This observation was confirmed by most of the subjects (see their comments, Annex E). Similarly, -1 the peak inhale pressure (in absolute value) was greater at 4 L·min than with the other O2 flow rates (F4, 50=3.823; p<0.01) as shown in Figure 13. The breathing effort was significantly correlated with the peak inhale pressure (r=0.95; p=0.015). There were no significant differences among exhaled peak mask pressure for any of the flow conditions. With both units, mask pressure measurements made with subject seated and supine did not differ.

2 SIMPLE Hi-OX

1 Very Light Breathing Effort

0 No

2 Slight

1 Very Slight Mask Discomfort Mask

0 No 4 7 8 9 8 (Supine)

O2 flow rate (Standard L/min)

Figure 12. Subject ratings for breathing effort and mask discomfort of both masks.

14 DRDC Toronto TR 2005-207

2.5

2.0 Inhale Exhale 1.5

1.0

0.5

0.0 4 7 8 9 8 (Supine) -0.5

-1.0 Mask PressureMask (cm H2O)

-1.5

-2.0

-2.5 O flow rate (Standard L/min) 2 Figure 13. Peak mask pressures of the Hi-Ox.

Subjects were also asked to give overall comments on the unit or any other perceived discomforts (e.g., dryness, headache) (see Annex E). Several subjects mentioned that the Hi- Ox was light but seemed to be heavier during the last breathing period or when they were lying down. Most subjects indicated that the O2 delivered by the simple facemask was dry and leaked around the nose into the eyes (which caused dryness over time).

DRDC Toronto TR 2005-207 15

This page intentionally left blank.

16 DRDC Toronto TR 2005-207

Discussion

Most traditional O2 breathing systems used in first-aid treatment consist of pressurized oxygen cylinders and breathing units that require high flows to deliver high oxygen concentrations to the patient. Our literature review [1] showed that the simple facemask, one of the most commonly used breathing units, achieves an oxygen concentration of about 60% at a flow rate of 10 L·min-1. The side ports on this mask allow entrainment of ambient air during inhalation, thereby limiting the oxygen level with low flows. Furthermore, the patient uses only two to three percent of the delivered O2; the rest is exhaled into the atmosphere. Unless O2 is available in quantity, traditional O2 breathing systems allow a very limited time on oxygen because of inefficient gas use. This may be acceptable for treating accident victims in urban areas but to treat survivors in a remote area means more oxygen must be transported which increases, weight, volume and risk to unacceptable levels.

Other breathing systems are currently used, but none have the efficiency needed for self- contained remote operations. For example, SAR Techs use the AVOX (formerly Scott) ® ® Aviox Duo-Pak system (a chemical O2 generator combined with a simple mask). The Aviox does not use compressed O2 so it reduces the safety hazard but it only treats one patient for 40 minutes. Consequently, the volume of oxygen available for remote treatment is very limited.

An efficient oxygen breathing system for remote treatment would consist of an economical and unpressurized O2 supply combined with a low-flow rate breathing unit that minimizes wasted gas. The efficiency of the Hi-Ox makes it a candidate for a remote treatment system [1].

A total of 12 subjects used a simple facemask and a Hi-Ox to compare the performance of the two breathing units. In terms of inhaled oxygen level, the performance of the Hi-Ox mask was significantly superior to the simple facemask. The Hi-Ox provided a higher oxygen -1 concentration at lower flow rates. The data shows that at O2 flow rates of 4 to 9 L·min oxygen concentrations of all subjects varied from 69.1% to 99.6% with the Hi-Ox and from 38.3% to 75.5% with the simple facemask. The mean O2 concentration delivered by the Hi-Ox varied from 79.6±4.4% at a flow rate of 4 L·min-1 to 94.0±1.7% at 8 L·min-1. The highest -1 mean O2 level delivered by the simple facemask was 60±3% at 9 L·min . Therefore, with a -1 constant O2 flow rate of 4 L·min , delivered O2 concentration can increase from 50% with the simple facemask to about 80% with the Hi-Ox.

The Hi-Ox kept inhaled O2 concentrations high with all O2 flow rates principally because of the sequential flow of breathing gas produced by the manifold. As illustrated in Figure 14, the one-way valves produce a sequential flow of high concentration oxygen from the reservoir followed by a mixture of the last volume of expired gas and ambient air from the atmosphere after the bag empties. First, during the exhale phase of breathing, the Hi-Ox accumulates oxygen in the reservoir. The exhale one-way valve is open and the exhale side of the manifold fills with exhaled air containing 3% to 5% CO2. On inhalation, the exhale valve closes and the inhale valve opens. The first fresh gas of the tidal volume is high concentration O2 from the reservoir. When the reservoir is empty the exhale-to-inhale valve opens allowing an initial

DRDC Toronto TR 2005-207 17

small volume of exhaled air and then fresh ambient air to mix with the stream of 100% O2 to satisfy the volume demand during large inspirations. Therefore, the manifold collects O2 during exhale, some O2 is rebreathed during inhale, exhale gas is entrained into the inhale stream to prevent excess CO2 elimination and ambient air is used to make up the anatomical dead space volume to further reduce the O2 requirement. The effect of the sequential flow is well illustrated in Figure 15. The flow rate of the inhaled air was negatively correlated with the O2 flow rate. The amount of air inhaled from the atmosphere increased as the difference between the respiratory minute volume (RMV) and the O2 flow increases. For O2 flows greater than 4 L·min-1 the amount of inhaled air was less than 1 L·min-1 while at 4 L·min-1 it increased to 3.6 L·min-1.

Inhaled gas Legend To or from st 1 portion: high concentration facemask High concentration O2 O2 from supply and reservoir to During INHALATION fill alveoli. Last portion: Oxygen enriched During EXHALATION air to fill anatomic dead space.

Inhale Exhale 1-way valve 1-way valve

Ambient air 1-way valve

Exhale to inhale 1-way valve

O2 Supply

O2 to or from Ambient air reservoir

Figure 14. Schematic of the Hi-Ox mask manifold.

The present results are consistent with the literature [1, 8]. Somogyi et al. [8] showed that the Hi-Ox delivered higher O2 concentrations than the simple facemask (97% with the Hi-Ox -1 versus 52% with the simple facemask) at an O2 flow rate of 8 L·min . In addition, it was also reported [8] that the Hi-Ox was better than the non-rebreathing mask (NRM), the other most commonly used O2 breathing unit. Also, it is known that the NRM requires an O2 flow rate of -1 15 L·min or above to deliver high O2 levels (about 95%) [1]. The present results shows that the Hi-Ox can provide around 92% with a flow rate of 7 L·min-1, half the NRM requirements.

18 DRDC Toronto TR 2005-207

RMV 8

4 Flow rate (Actual L/min) (Actual Flow rate 2 Air from the atmosphere 0 4 789 8 (Supine)

O flow rate (Standard L/min) 2

Figure 15. Respiratory Minute Volume and the flow rate of the air inhaled from the atmosphere.

-1 Somogyi et al. [8] reported that the Hi-Ox with a flow rate of 8 L·min can deliver an O2 concentration of 97%, 3% greater than the level obtained in this study. Taking into account measurement techniques, computation errors, and experimental conditions (subject numbers (12 here, 3 for Somogyi et al.), data collection duration, etc.), the difference between the two investigations is minor. In addition, subjects with facial hair had the lowest inhaled O2 levels in this study, decreasing the overall mean inhaled O2 concentration by about 1.5%.

The present results showed that the simple facemask and the Hi-Ox increased the mean arterial oxygen saturation from 94.8% to over 98.2%. The Hi-Ox provided an arterial O2 saturation slightly higher than the simple facemask (98.4±0.2 versus 98.2±0.1). The main factor that may possibly explain why the Hi-Ox provided about the same O2 saturation as the simple facemask despite its considerably superior performance in terms of inhaled O2 concentrations is the shape of the oxygen-haemoglobin dissociation curve (i.e., O2 saturation versus O2 arterial partial pressure (PaO2)). This curve is flatter when SaO2 is higher than 93% [15]. Therefore, relatively large increases of PaO2 (from inhaled O2 concentrations) will produce small increases in saturation. All subjects were healthy and since their SaO2 before breathing oxygen was higher than 94%, in the flat portion of the dissociation curve, they did not require high O2 concentrations to increase their SaO2 to the 98% level. But if a person’s SaO2 decreases to below 90% (such as at high-altitude areas or if the respiratory system is compromised) the difference in the O2 concentrations by the two systems would be revealed.

Since carbon dioxide is a very strong stimulus to respiration [15], maintaining fETCO2 (i.e.; CO2 fraction in the alveoli) constant, especially at high ventilation, will ensure equilibrium between CO2 in the alveoli and CO2 in the blood, thereby ensuring respiration while preventing hypocapnia. Both the Hi-Ox and the simple facemask maintained inhaled CO2 concentrations at low levels (< 0.5%) even at a flow rate as low as 4 L·min-1. The Hi-Ox manifold maintains higher mean inhaled CO2 levels than the simple facemask but within safe limits during resting ventilation. As indicated previously, if the subject’s RMV exceeded the

DRDC Toronto TR 2005-207 19

-1 O2 flow rate (as seen in Figure 15 at 4 L·min ), a combination of the last volume of the gas at the end of exhalation (containing about 5% CO2) plus ambient air from the atmosphere is inhaled in addition to the oxygen provided, slightly increasing fICO2 to maintain fETCO2 constant (0.045 ≤ fETCO2 ≤ 0.05), which keeps CO2 level in the blood at normal values regardless of the O2 flow rate or the ventilation rate [3, 14]. On the other hand, the simple facemask would most probably not maintain fETCO2 constant and high if the patient were hyperventilating [3], which can have critical physiological consequence [16].

The magnitude of the mask pressures was lower in the simple facemask than the Hi-Ox. The open side-ports on the simple facemask and leakage around the subject’s face decreased the cavity mask pressures of the simple facemask to very low values (in the range of -0.4 cm H2O to 0.6 cm H2O). The Hi-Ox peak inhale and exhale mean pressures were less than or equal to |1.58| cm H2O. The higher levels were caused by the 1-way valves in both inhale and exhale sides. In addition, peak pressures in the Hi-Ox were correlated to O2 flow. The peak inhale -1 -1 pressure at 4 L·min was higher than with O2 flow rates of 7 L·min and greater (e.g., -1 -1 -1.58 cm H2O at 4 L·min versus -1.01 at 8 L·min ). This was due to the inhale effort required to open the exhale-to-inhale 1-way valve and the anti-suffocation valve in addition to the inhale valve. Nevertheless, both breathing units were rated favourably in terms of breathing effort and mask discomfort.

The O2 delivered by the simple facemask was dry and leaked around the nose into the subject’s eyes (which caused dryness over time and discomfort). The Hi-Ox had minor O2 dryness and mask leaks; but, it seemed to be slightly heavier with time. Moreover, the plastic tabs used to retain the elastic straps tore through on three different Hi-Ox masks when the subjects were trying to tighten the mask. Although there are two straps, thereby providing redundancy, the tabs should be reinforced.

The Hi-Ox mask was investigated in ambient temperatures varying in the range 25-30°C. It is possible that cold temperatures may have some effects on the opening and closing of the 1-way valves. This should be investigated.

Assuming that the oxygen concentrations provided by a simple mask are adequate in many situations, it might be possible to use the Hi-Ox at flow rates lower than 4 L·min-1. Future experiments should investigate the Hi-Ox performance at lower flow rates. Nevertheless, a -1 4 L·min flow rate makes the Hi-Ox a candidate for use with a portable O2 concentrator. This would replace the need for bulky, dangerous compressed oxygen cylinders or chemical generators. Furthermore, Fisher [3] reported that the Hi-Ox can be modified to deliver high -1 inhaled O2 levels at lower flow rates (e.g., 100% O2 at 4 L·min or lower) than the currently available Hi-Ox. If Fisher’s claims are valid then the modified version of the Hi-Ox would increase the duration of a pressurized tank at least four fold or quadruple the number of patients treated simultaneously when compared to the current commonly used O2 systems. For -1 example, to deliver about 100% O2, Fisher claims that 4 L·min or lower would be needed by the modified Hi-Ox compared to about 9 L·min-1 by the current Hi-Ox and more than -1 15 L·min by the NRM [1]. If this modification works and an O2 concentrator is used, this mask will greatly enhance the efficiency of O2 therapy in providing sustained NBO in SAR missions.

20 DRDC Toronto TR 2005-207

Conclusion

The simple facemask is not only inefficient but subjects felt that it could be uncomfortable if used with high O2 flow rates during prolonged O2 treatments. On the other hand, the Hi-Ox can deliver higher O2 concentrations to a patient at lower flow rates while maintaining CO2 levels at equilibrium in the body. When O2 supplies are limited, the use of the Hi-Ox with an -1 O2 flow rate of 7 L·min may be more appropriate to achieve high inhaled O2 concentrations (> 91%). However, the Hi-Ox can maintain inhaled O2 concentrations at 80% using a flow rate of 4 L·min-1. If this is adequate for treatment, the Hi-Ox could be an efficient breathing unit for mass casualties in remote areas. Indeed, the duration of an O2 cylinder or the number of patients treated can at least triple with a flow rate of 4 L·min-1 when compared to the current situation.

-1 Given the low flow rate of only 4 L·min that can be used by the Hi-Ox to achieve high O2 levels, oxygen pressurized cylinders or chemical generators would no longer be the standard emergency sources for remote operations. A portable O2 concentrator could be an alternative. The combination of an efficient mask like the Hi-Ox with an O2 concentrator would replace the need for bulky, dangerous compressed oxygen supplies and thereby make sustained mass casualty NBO feasible in the field. This would benefit not only SAR squadrons but also other military organizations such as those who must respond to submarine escape and rescue.

DRDC Toronto TR 2005-207 21

This page intentionally left blank.

22 DRDC Toronto TR 2005-207

Future Directions

Our investigations to date suggest a number of avenues for improving oxygen therapy in remote operations:

1. The effect of cold temperatures on the Hi-Ox is unknown. It should be investigated for SAR missions.

-1 2. It is anticipated that the Hi-Ox could be used at a low O2 flow rate, e.g.; 1 L·min , to deliver inhaled oxygen concentrations as high as those delivered by the simple facemask -1 at higher flow rates (e.g., 9 L·min ). Further testing using the Hi-Ox with the O2 flow set at 0.5, 1, 2, & 3 L·min-1 is recommended.

3. In addition to the Hi-Ox, the DAN REMO2 rebreather is another efficient oxygen breathing unit commercially available that can be used in combination with either a pressurized tank or an O2 concentrator. The Hi-Ox results will be compared to those obtained from the evaluation of the rebreather.

4. When Fisher’s modified version of the Hi-Ox becomes available it should be carefully evaluated using traditional O2 sources.

5. To increase portability and safety, and provide sustainable O2 treatment in the field, the possibility of developing a lightweight portable and high-endurance oxygen concentrator should be explored. A developed prototype should be evaluated in combination with the modified version of the Hi-Ox.

DRDC Toronto TR 2005-207 23

This page intentionally left blank.

24 DRDC Toronto TR 2005-207

References

1. Bouak, F. (2004). Oxygen Therapy: Description and Advances in Oxygen Delivery Systems. (DRDC Toronto TM-112). Defence R&D Canada – Toronto.

2. Bouak, F. and Eaton, D. J. (2005). Possibilities for Mass Casualty Oxygen Systems in ™ Search and Rescue Missions. Part 2: The Divers Alert Network REMO2 . (DRDC Toronto TR 2005-257). Defence R&D Canada – Toronto.

3. Fisher, J. A. (2004). Private communication. University Health Network.

4. Litch, J. A. and Bishop, R. A. (2000). Oxygen Concentrators for the Delivery of Supplemental Oxygen in Remote High-Altitude Areas. Wilderness Environ Med, 11, 189-191.

5. Pollock, N. W. and Hobbs, G. W. (2002). Evaluation of the System O2 Inc Portable Nonpressurized Oxygen Delivery System. Wilderness Environ Med, 13, 253-255.

6. Hi-Ox80. (Online) VIASYS Healthcare www.viasyshealthcare.com/prod_serv/prodDetail.aspx?config=ps_prodDtl&prodID=149 (02 Mar. 2004).

7. DAN products. (Online) Divers Alert Network. www.diversalertnetwork.org (27 Feb. 2004).

8. Somogyi, R., Preiss, D., Vesely, A., Prisman, E., Tesler, J., Volgyesi, G., Fisher, J., Sasano, H., and Iscoe, S. (2002). Behind the Mask, RT J. for Respiratory Care Practitioners, Oct.-Nov. 2002.

9. Bouak, F. and Eaton, D. J. Performance of Oxygen Breathing Systems For Search Missions. DRDC Human Research Ethics Committee Protocol #L-472, Amendment#1. Defence R&D Canada – Toronto. 10 Sep. 2004.

10. Chamberland, A., Carrier, R., Forest, F. and Hachez, G. (1998). Anthropometric Survey of the Land Forces. DCIEM Contract Report (98-CR-15).

11. Interface Associates. (1988). Ventilation Measurement Modules Operating Instructions for VMM-2 and VMM-2A.

12. Eaton, D. J. (1988). Estimating motor performance decrements using ratings of perceived discomfort. M.Sc. Thesis, University of Guelph, Guelph, Ontario, Canada.

13. Ihaka, R. and Gentleman, R. (1996). R; a language for data analysis and graphics. J. Computational and Graphical Statistics, 5, 299-314.

14. Goodman, L. (2003). Private communication. Defence R&D Canada – Toronto.

DRDC Toronto TR 2005-207 25

15. Guyton A. C. (1977). Textbook of Basic Human Physiology: Normal Function and Mechanisms of Disease. 2nd ed.: W. B. Saunders, p 931

16. Laffey, J.G. and Kavanagh, B.P. (2002). Hypocapnia. New England Journal of Medicine, 347, 43-53.

26 DRDC Toronto TR 2005-207

Annex A: Experimental Data

Table A1. Physical Description of the Subjects

ID Gender Age Weight Height Face Length* year kg m mm S01 Female 40 70.5 1.66 113.0 S02 Male 43 72.6 1.74 114.0 S03 Female 40 56.3 1.60 118.5 S04 Male 32 92.1 1.83 114.0 S05 Male 55 99.0 1.83 127.0 S06 Male 31 97.5 1.80 119.5 S07 Male 48 83.9 1.75 124.7 S08 Male 41 70.3 1.70 122.5 S09 Male 41 84.4 1.73 117.9 S10 Male 40 108.9 1.83 129.1 S11 Male 33 70.0 1.73 120.0 S12 Male 52 84.0 1.83 123.8 Mean 41.3 82.46 1.75 120.33 SD 7.5 15.16 0.08 5.23

* Menton-Sellion Height [10]

DRDC Toronto TR 2005-207 27

This page intentionally left blank.

28 DRDC Toronto TR 2005-207

Annex B: Breathing Units

Table B1. Breathing unit specifications

Assembled Multi-unit Unit Breathing Packed Unit Unit Unit Circuit/ Unit pack Number Unit Dimensions1 Weight Price Flow Dimensions1 dimensions1 /pack cm cm kg cm kg CA $

80 Open/ Hi-Ox 39 x 15 x 7 32 x 25 x 8 0.172 16 x 46.5 x 36 10 $20.00 Continuous

Simple Open/ 13.5 x 8 x 6.5 15 x 15 x 9 0.076 34 x 39 x 30 50 $1.03 facemask Continuous

(1) Height x Length x Depth (2) Breathing hoses not expanded

The Hi-Ox comes in a zipper-lock plastic bag fully assembled and ready for use. The Hi-Ox is for single patient use only and not intended for re-use. It is sold in a box of 10 units. Similarly, the simple facemask comes assembled and sold in a box of 50 units.

Figure B1. The Hi-Ox mask: Oronasal mask with straps.

Figure B2. The Simple facemask: detail of the side ports.

DRDC Toronto TR 2005-207 29

Mass spectrometer

Figure B3. The Hi-Ox mask: Subject and Experimental set-up.

Sensor ports

Figure B4. The Hi-Ox mask: measurement locations on the oronasal mask.

30 DRDC Toronto TR 2005-207

Annex C: Psychophysical Test

DRDC Toronto TR 2005-207 31

This page intentionally left blank.

32 DRDC Toronto TR 2005-207

DRDC Toronto TR 2005-207 33

34 DRDC Toronto TR 2005-207

Annex D: Test Termination Criteria

Experiments were stopped when any of the following criteria were reached:

• On subject request associated with fatigue, discomfort or any other reason.

• Total pure O2 breathing duration reaches 75 minutes.

• Loss of O2 supply.

• Inhaled O2 partial pressure goes below 0.21 ATA (21%)

• Arterial O2 saturation goes below 92%.

• Loss of room ventilation.

• Excessive breathing resistance (peak inhale or exhale pressures no greater than ±1.5 kPa (i.e., ±15 cm H2O)).

• Inhaled CO2 partial pressure exceeds 0.005 ATA (3.8 mm Hg or 0.5% by volume).

DRDC Toronto TR 2005-207 35

This page intentionally left blank.

36 DRDC Toronto TR 2005-207

Annex E: Subjects’ Comments

Simple facemask:

ID Breathing Effort Mask Discomfort

S01 No effort at all. The mask material is fairly rigid therefore the edge of the mask has a harder right-angled shape to fit against the face. The ridge created can be felt as pressure from tightening mask is applied. It is also very narrow which is important around the nose but could be wider at the mouth for those with wider mouths. It may disperse some of the discomfort of the ridge if it was wider.

S03 The adjustment of breathing I can feel the pressure of the mask with very slight of was a very light effort. It discomfort. I can feel the air coming from the top of was caused by the stress of my nose coming into my eyes. The mask is a little the experiment. bit too long and it holds better when I lay down.

S05 3rd breathing period - Blowing by nose into eyes.

S08 The only item to mention is that the O2 flow is directed toward the eyes causing dryness.

S09 First few minutes of 5th Discomfort (slight) came mostly from strap around period (8 L·min-1 and supine) head and nose piece (hard to adjust for comfort. Also it was harder to get a breath - Air leaks out around eyes - (drying out eyes). then it eased off and became easier.

S11 • Comfortable to wear • Slight problem to secure mask • Mask doesn't stay tight when laying down.

DRDC Toronto TR 2005-207 37

Hi-Ox:

ID Breathing Effort Mask Discomfort

S01 The breathing effort was minimal at Mask is very light and comfortable, the beginning with slight resistance at particularly when you get used to adjusting earlier flow rates (Period 1 and 2). it. The weight of the mask seems to increase slightly when lying down.

S02 Very small discomfort around the nose.

S03 I had lots of problems to breathe at the I don't feel leak and the mask well adjusted 1st period. I was searching for air and to my face. But I feel the mask on my it was giving me stress at the lower lip. Also, I get pressure on my ears beginning. After all, it went well. from the elastics. It feels better when I lay down because it was becoming heavier.

S05 Tingling on face during last period.

S08 Very light.

S09 A bit of effort required to gain a The mask is a little heavy and digs into the breath, not much though. sides of the face a little.

S12 Effort on inspiration only and only Slight smell of urea/plastic that becomes after the breathing bag is emptied out. less noticeable after 5 minutes

38 DRDC Toronto TR 2005-207

Overall Comments

Simple facemask:

ID Overall Comments

S01 The vent cut away at the ridge of the nose on the mask I presume is to ensure condensation doesn't build up in mask, but I find the gas flow is then funnelled between your eyes which could be irritating over time (tickles, causes tearing or dry eyes).

S02 Dry out. Feel more pressure with the increase of O2 flow especially on "upper cheek".

S03 We can feel that it's very dry and I have a small headache.

S12 Starting with the 3rd period, there was some leakage that could have been stopped if the "shoe lace" cinching system allowed the mask to be held against the face with more pressure. Leak stopped on 4th run with nose pincher (metal clip in mask).

Hi-Ox:

ID Overall Comments

S01 The mask contours well to the face, a truly one size fits all. No leaks or condensation during these short periods.

S02 Better then the Simple facemask: less dryness

S05 Maybe slight leaks around nose.

S07 The unit did not seal well round nose and needed to be held to stop from leaking.

S12 During 2nd period the upper elastic band of the mask broke off the left side of the mask when the plastic tab on the left side of the mask failed around the top left hole - the plastic tab is too flimsy.

DRDC Toronto TR 2005-207 39

This page intentionally left blank.

40 DRDC Toronto TR 2005-207

Bibliography

1. Guyton A. C. (1977). Textbook of Basic Human Physiology: Normal Function and Mechanisms of Disease. 2nd ed.: W. B. Saunders, p 931.

2. Department of National Defence. (1998). National Search and Rescue Manual. B-GA- 209-001/FP-001, DFO 5449, Department of National Defence. Canada.

3. Canadian Forces. (2002). Submarine Escape and Rescue Manual (CFCD 103). C-23- SUB-002/MS-001, Maritime Command, Department of National Defence, Canada.

4. NOAA Diving Manual. Diving for Science and Technology. (2001). Diving Physiology. In National Oceanic and Atmospheric Administration. US Department of Commerce. 4th Edition.

5. Department of National Defence. (1989). Underwater Diving in the Canadian Armed Forces, Volume 1, History, physics and physiology. B-GG-380-000/FP-001, Department of National Defence, Canada.

DRDC Toronto TR 2005-207 41

This page intentionally left blank.

42 DRDC Toronto ECR 2005-…

List of symbols/abbreviations/acronyms/initialisms

ANOVA Analysis of variance

ATA Atmosphere absolute

CF Canadian Forces

CO2 Carbon dioxide

COTS Commercial Off-The-Shelf

DAN Divers Alert Network

DAQ Data acquisition system

DND Department of National Defence

DRDC Defence Research and Development Canada

EDU Experimental Diving Unit fmA Instantaneous fraction of gas A (O2 or CO2) fETA End-tidal fraction of gas A (O2 or CO2) fIA Inhaled fraction of gas A (O2 or CO2)

Hi-Ox VIASYS Hi-Ox80TM

HREC Human Research Ethics Committee

I.D. Inside diameter kg Kilogram

L·min-1 Litre per minute m, cm, mm Metre, centimetre, millimetre mL millilitre

O2 Oxygen

N2 Nitrogen

DRDC Toronto TR 2005-207 43

NBO Normobaric oxygen therapy: administration of oxygen to a patient at or near sea level pressure

NRM Non-rebreathing mask

O.D. Outside diameter

PExp Exhale peak pressure (cm H2O)

PI Inhale peak pressure (cm H2O) psi or psig Pound square inch or pound square inch gage

REMO2 or REMO Remote Emergency Medical Oxygen system

RMV Respiratory Minute Volume (Actual L·min-1)

S Supine

SAR NIF Search and Rescue New Initiative Fund

SD Standard deviation

SaO2 Arterial oxygen saturation (%)

Techs Technicians

o Tamb Ambient Temperature ( C)

o TI Inhaled gas temperature ( C)

Minute ventilation (Actual L·min-1) V&E

%O2 Oxygen concentration

44 DRDC Toronto ECR 2005-…

Distribution list

INTERNAL DISTRIBUTION DRDC Toronto TR 2005-207

1 – CO/CFEME (Associate Director General of DRDC Toronto

1 – Section Head Experimental Diving Unit

2 – F. Bouak (Author)

1 – D. Eaton (Co-author)

1 – R. Y. Nishi

1 – D. Eastman

1 – EDU’s Administrative Officer (Section’s Library)

EXTERNAL DISTRIBUTION DRDC Toronto TR 2005-207

3 – Canadian Forces Search And Rescue Operational Units (424 And 413 Squadrons)

1 – Chief of Maritime Staff (DND Headquarters) Attn: LCdr F. Trepanier (MCP 3-6) Submarine Project Director

1 – Formation Health Services Centre (Atlantic) Attn: Cdr D.R. Wilcox (Formation Surgeon)

1 – Director Maritime Health Services (CMS) Attn: Col. D.R. Sanschagrin

1 – DND Health Services (ADM (HR-Mil)) Attn: LCol. K. Glass R&D Coordinator

DRDC Toronto TR 2005-207 45

UNCLASSIFIED

DOCUMENT CONTROL DATA (Security classification of the title, body of abstract and indexing annotation must be entered when the overall document is classified)

1. ORIGINATOR (The name and address of the organization preparing the document, Organizations 2. SECURITY CLASSIFICATION for whom the document was prepared, e.g. Centre sponsoring a contractor's document, or tasking (Overall security classification of the document agency, are entered in section 8.) including special warning terms if applicable.) Publishing: DRDC Toronto UNCLASSIFIED Performing: DRDC Toronto Monitoring: Contracting:

3. TITLE (The complete document title as indicated on the title page. Its classification is indicated by the appropriate abbreviation (S, C, R, or U) in parenthesis at the end of the title) Possibilities for Mass Casualty Oxygen Systems in Search and Rescue Missions Part 1: The VIASYS Hi−Ox80™ (U)

4. AUTHORS (First name, middle initial and last name. If military, show rank, e.g. Maj. John E. Doe.) F. Bouak ; D.J. Eaton

5. DATE OF PUBLICATION 6a NO. OF PAGES 6b. NO. OF REFS (Month and year of publication of document.) (Total containing information, including (Total cited in document.) Annexes, Appendices, etc.) November 2005 16 55

7. DESCRIPTIVE NOTES (The category of the document, e.g. technical report, technical note or memorandum. If appropriate, enter the type of document, e.g. interim, progress, summary, annual or final. Give the inclusive dates when a specific reporting period is covered.) Technical Report

8. SPONSORING ACTIVITY (The names of the department project office or laboratory sponsoring the research and development − include address.) Sponsoring: National Search and Rescue Secretariat Tasking:

9a. PROJECT OR GRANT NO. (If appropriate, the applicable 9b. CONTRACT NO. (If appropriate, the applicable number under which research and development project or grant under which the document was the document was written.) written. Please specify whether project or grant.) SAR NIF Project # 6/03

10a. ORIGINATOR'S DOCUMENT NUMBER (The official 10b. OTHER DOCUMENT NO(s). (Any other numbers under which document number by which the document is identified by the originating may be assigned this document either by the originator or by the activity. This number must be unique to this document) sponsor.) DRDC Toronto TR 2005−207

11. DOCUMENT AVAILABILIY (Any limitations on the dissemination of the document, other than those imposed by security classification.) Unlimited distribution

12. DOCUMENT ANNOUNCEMENT (Any limitation to the bibliographic announcement of this document. This will normally correspond to the Document Availability (11), However, when further distribution (beyond the audience specified in (11) is possible, a wider announcement audience may be selected.)) Unlimited announcement

UNCLASSIFIED UNCLASSIFIED

DOCUMENT CONTROL DATA (Security classification of the title, body of abstract and indexing annotation must be entered when the overall document is classified)

13. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual.) (U) An experiment was carried out at Defence RDCanada – Toronto to recommend an efficient oxygen breathing system for multiple casualties in remote areas. The objective was to improve the oxygen therapy capability and efficiency of the Canadian Forces Search and Rescue Technicians as well as any military organization that may potentially need to dispense oxygen to survivors of a mass casualty scenario such as in a field hospital or during submarine escape and rescue. Twenty−four trials were completed using twelve male and female volunteers (30−55 years) to compare the VIASYS Hi−Ox80™ mask to a simple facemask. Measurements were made with the subjects at rest in seated and supine positions to simulate an injured person being administered oxygen (O2). The Hi−Ox80™ delivered significantly higher O2 concentrations to the subjects at lower flow rates than the simple facemask. Given the high O2 concentrations, low O2 flow rates, low levels of inhaled carbon dioxide, constant levels of the exhaled carbon dioxide and low breathing resistance, the Hi−Ox80™ could be an efficient breathing unit for mass casualty treatment in a remote area. If an O2 concentration of 80% is adequate for treatment, the duration of a pressurized tank or the number of patients treated can at least triple with a flow rate of 4 litres per minute when compared to the currently used O2 systems. Furthermore, this O2 flow rate can allow the use of portable O2 concentrators, thereby increasing the efficiency while minimizing risks.

14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g. Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.) (U) Oxygen breathing system; Simple facemask; VIASYS Hi−Ox80; Open circuit; Oxygen therapy; Search and Rescue; paramedics; First−aid oxygen; Normobaric oxygen; Oxygen concentrator

UNCLASSIFIED Defence R&D Canada R & D pour la défense Canada Canada’s Leader in Defence Chef de file au Canada en matière and National Security de science et de technologie pour Science and Technology la défense et la sécurité nationale

& DEFENCE DÉFENSE