Principles of Mechanical Ventilation
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Airway Pressures and Volutrauma
Airway Pressures and Volutrauma Airway Pressures and Volutrauma: Is Measuring Tracheal Pressure Worth the Hassle? Monitoring airway pressures during mechanical ventilation is a standard of care.1 Sequential recording of airway pressures not only provides information regarding changes in pulmonary impedance but also allows safety parameters to be set. Safety parameters include high- and low-pressure alarms during positive pressure breaths and disconnect alarms. These standards are, of course, based on our experience with volume control ventilation in adults. During pressure control ventilation, monitoring airway pressures remains important, but volume monitoring and alarms are also required. Airway pressures and work of breathing are also important components of derived variables, including airway resistance, static compliance, dynamic compliance, and intrinsic positive end-expiratory pressure (auto-PEEP), measured at the bedside.2 The requisite pressures for these variables include peak inspiratory pressure, inspiratory plateau pressure, expiratory plateau pressure, and change in airway pressure within a breath. Plateau pressures should be measured at periods of zero flow during both volume control and pressure control ventilation. Change in airway pressure should be measured relative to change in volume delivery to the lung (pressure-volume loop) to elucidate work of breathing. See the related study on Page 1179. Evidence that mechanical ventilation can cause and exacerbate acute lung injury has been steadily mounting.3-5 While most of this evidence has originated from laboratory animal studies, recent clinical reports appear to support this concept.6,7 Traditionally, ventilator-induced lung injury brings to mind the clinical picture of tension pneumothorax. Barotrauma (from the root word baro, which means pressure) is typically associated with excessive airway pressures. -
Vocal Cord Dysfunction JAMES DECKERT, MD, Saint Louis University School of Medicine, St
Vocal Cord Dysfunction JAMES DECKERT, MD, Saint Louis University School of Medicine, St. Louis, Missouri LINDA DECKERT, MA, CCC-SLP, Special School District of St. Louis County, Town & Country, Missouri Vocal cord dysfunction involves inappropriate vocal cord motion that produces partial airway obstruction. Patients may present with respiratory distress that is often mistakenly diagnosed as asthma. Exercise, psychological conditions, airborne irritants, rhinosinusitis, gastroesophageal reflux disease, or use of certain medications may trigger vocal cord dysfunction. The differential diagnosis includes asthma, angioedema, vocal cord tumors, and vocal cord paralysis. Pulmo- nary function testing with a flow-volume loop and flexible laryngoscopy are valuable diagnostic tests for confirming vocal cord dysfunction. Treatment of acute episodes includes reassurance, breathing instruction, and use of a helium and oxygen mixture (heliox). Long-term manage- ment strategies include treatment for symptom triggers and speech therapy. (Am Fam Physician. 2010;81(2):156-159, 160. Copyright © 2010 American Academy of Family Physicians.) ▲ Patient information: ocal cord dysfunction is a syn- been previously diagnosed with asthma.8 A handout on vocal cord drome in which inappropriate Most patients with vocal cord dysfunction dysfunction, written by the authors of this article, is vocal cord motion produces par- have intermittent and relatively mild symp- provided on page 160. tial airway obstruction, leading toms, although some patients may have pro- toV subjective respiratory distress. When a per- longed and severe symptoms. son breathes normally, the vocal cords move Laryngospasm, a subtype of vocal cord away from the midline during inspiration and dysfunction, is a brief involuntary spasm of only slightly toward the midline during expi- the vocal cords that often produces aphonia ration.1 However, in patients with vocal cord and acute respiratory distress. -
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REVIEW COPD Physiological and clinical relevance of exercise ventilatory efficiency in COPD J. Alberto Neder1, Danilo C. Berton1,2, Flavio F. Arbex3, Maria Clara Alencar4, Alcides Rocha3, Priscila A. Sperandio3, Paolo Palange5 and Denis E. O’Donnell1 Affiliations: 1Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen’s University and Kingston General Hospital, Kingston, ON, Canada. 2Division of Respiratory Medicine, Federal University of Rio Grande do Sul, Porto Alegre, Brazil. 3Pulmonary Function and Clinical Exercise Physiology, Respiratory Division, Federal University of Sao Paulo, Sao Paulo, Brazil. 4Division of Cardiology, Federal University of Minas Gerais, Belo Horizonte, Brazil. 5Dept of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy. Correspondence: J. Alberto Neder, 102 Stuart Street, Kingston, Ontario, Canada K7L 2V6. E-mail: [email protected] @ERSpublications Ventilatory efficiency is a key measurement for the interpretation of cardiopulmonary exercise testing in COPD http://ow.ly/1nsY307pbz8 Cite this article as: Neder JA, Berton DC, Arbex FF, et al. Physiological and clinical relevance of exercise ventilatory efficiency in COPD. Eur Respir J 2017; 49: 1602036 [https://doi.org/10.1183/13993003.02036- 2016]. ABSTRACT Exercise ventilation (V′E) relative to carbon dioxide output (V′CO2) is particularly relevant to patients limited by the respiratory system, e.g. those with chronic obstructive pulmonary disease (COPD). ′ − ′ High V E V CO2 (poor ventilatory efficiency) has been found to be a key physiological abnormality in symptomatic patients with largely preserved forced expiratory volume in 1 s (FEV1). Establishing an ′ − ′ association between high V E V CO2 and exertional dyspnoea in mild COPD provides evidence that exercise intolerance is not a mere consequence of detraining. -
The Use of Heliox in Treating Decompression Illness
The Diving Medical Advisory Committee DMAC, Eighth Floor, 52 Grosvenor Gardens, London SW1W 0AU, UK www.dmac-diving.org Tel: +44 (0) 20 7824 5520 [email protected] The Use of Heliox in Treating Decompression Illness DMAC 23 Rev. 1 – June 2014 Supersedes DMAC 23, which is now withdrawn There are many ways of treating decompression illness (DCI) at increased pressure. In the past 20 years, much has been published on the use of oxygen and helium/oxygen mixtures at different depths. There is, however, a paucity of carefully designed scientific studies. Most information is available from mathematical models, animal experiments and case reports. During a therapeutic compression, the use of a different inert gas from that breathed during the dive may facilitate bubble resolution. Gas diffusivity and solubility in blood and tissue is expected to play a complex role in bubble growth and shrinkage. Mathematical models, supported by some animal studies, suggest that breathing a heliox gas mixture during recompression could be beneficial for nitrogen elimination after air dives. In humans, diving to 50 msw, with air or nitrox, almost all cases of DCI can be adequately treated at 2.8 bar (18 msw), where 100% oxygen is both safe and effective. Serious neurological and vestibular DCI with only partial improvements during initial compression at 18 msw on oxygen may benefit from further recompression to 30 msw with heliox 50:50 (Comex therapeutic table 30 – CX30). There have been cases successfully treated on 50:50 heliox (CX30), on the US Navy recompression tables with 80:20 and 60:40 heliox (USN treatment table 6A) instead of air and in heliox saturation. -
Driving Pressure for Ventilation of Patients with Acute Respiratory
LWW 02/03/20 09:38 4 Color Fig(s): F1-2 Art: ALN-D-19-00974 CLINICAL FOCUS REVIEW Jerrold H. Levy, M.D., F.A.H.A., F.C.C.M., Editor LWW Driving Pressure for Ventilation of Patients with Acute Anesthesiology Respiratory Distress Syndrome AQ1 Angela Meier, M.D., Ph.D., Rebecca E. Sell, M.D., Atul Malhotra, M.D. ALN ANET nvasive mechanical ventilation is a remarkable advance, Low Tidal Volumes Ibut the possibility of ventilator-induced lung injury exists, Low V mechanical ventilation is a well-established particularly if the ventilator settings are not optimized. The T anet method that limits ventilator-induced lung injury and best methods to avoid lung injury during mechanical ven- has been shown to improve mortality in clinical trials. An tilation, either during ventilation of healthy lungs in the original study by the ARDS Network published in 2000 operating room or during ventilation as support during aln compared a low versus high VT strategy and demonstrated critical illness, are topics of debate. In this review, we sum- a clear mortality benefit with the low V (6 ml/kg ideal marize the current evidence and review a relatively new T body weight) approach compared to a higher delivered VT ALN concept to prevent lung injury: targeting driving pressure (12 ml/kg ideal body weight).9 defined by plateau pressure minus positive end-expiratory ALN pressure (PEEP), see table 1) when setting and adjusting T1 mechanical ventilation. Positive End-Expiratory Pressure A promising single-center study looked at adjusting 0003-3022 Lung Injury PEEP settings based on measuring transpulmonary pres- sures.2 The authors used an esophageal balloon manometer Lung injury results from excess transpulmonary pressure to estimate pleural pressures in patients with ARDS. -
Respiratory Mechanics in Spontaneous and Assisted Ventilation Daniel C Grinnan1 and Jonathon Dean Truwit2
Critical Care October 2005 Vol 9 No 5 Grinnan and Truwit Review Clinical review: Respiratory mechanics in spontaneous and assisted ventilation Daniel C Grinnan1 and Jonathon Dean Truwit2 1Fellow, Department of Pulmonary and Critical Care, University of Virginia Health System, Virginia, USA 2E Cato Drash Professor of Medicine, Senior Associate Dean for Clinical Affairs, Chief, Department of Pulmonary and Critical Care, University of Virginia Health System, Virginia, USA Corresponding author: Daniel C Grinnan, [email protected] Published online: 18 April 2005 Critical Care 2005, 9:472-484 (DOI 10.1186/cc3516) This article is online at http://ccforum.com/content/9/5/472 © 2005 BioMed Central Ltd Abstract mined by the following equation: C = ∆V/∆P, where C is ∆ ∆ Pulmonary disease changes the physiology of the lungs, which compliance, V is change in volume, and P is change in manifests as changes in respiratory mechanics. Therefore, measure- pressure. The inverse of compliance is elastance (E ~ 1/C). ment of respiratory mechanics allows a clinician to monitor closely Airway pressure during inflation is influenced by volume, the course of pulmonary disease. Here we review the principles of thoracic (lung and chest wall) compliance, and thoracic respiratory mechanics and their clinical applications. These resistance to flow. Resistance to flow must be eliminated if principles include compliance, elastance, resistance, impedance, compliance is to be measured accurately. This is flow, and work of breathing. We discuss these principles in normal conditions and in disease states. As the severity of pulmonary accomplished by measuring pressure and volume during a disease increases, mechanical ventilation can become necessary. -
The Basics of Ventilator Management Overview How We Breath
3/23/2019 The Basics of Ventilator Management What are we really trying to do here Peter Lutz, MD Pulmonary and Critical Care Medicine Pulmonary Associates, Mobile, Al Overview • Approach to the physiology of the lung and physiological goals of mechanical Ventilation • Different Modes of Mechanical Ventilation and when they are indicated • Ventilator complications • Ventilator Weaning • Some basic trouble shooting How we breath http://people.eku.edu/ritchisong/301notes6.htm 1 3/23/2019 How a Mechanical Ventilator works • The First Ventilator- the Iron Lung – Worked by creating negative atmospheric pressure around the lung, simulating the negative pressure of inspiration How a Mechanical Ventilator works • The Modern Ventilator – The invention of the demand oxygen valve for WWII pilots if the basis for the modern ventilator https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRI5v-veZULMbt92bfDmUUW32SrC6ywX1vSzY1xr40aHMdsCVyg6g How a Mechanical Ventilator works • The Modern Ventilator – How it works Inspiratory Limb Flow Sensor Ventilator Pressure Sensor Expiratory Limb 2 3/23/2019 So what are the goals of Mechanical Ventilation • What are we trying to control – Oxygenation • Amount of oxygen we are getting into the blood – Ventilation • The movement of air into and out of the lungs, mainly effects the pH and level of CO 2 in the blood stream Lab Oxygenation Ventilation Pulse Ox Saturation >88-90% Arterial Blood Gas(ABG) Po 2(75-100 mmHg) pCO 2(40mmHg) pH(~7.4) Oxygenation How do we effect Oxygenation • Fraction of Inspired Oxygen (FIO 2) – Percentage of the gas mixture given to the patient that is Oxygen • Room air is 21% • On the vent ranges from 30-100% • So if the patient’s blood oxygen levels are low, we can just increase the amount of oxygen we give them 3 3/23/2019 How do we effect Oxygenation • Positive End Expiratory Pressure (PEEP) – positive pressure that will remains in the airways at the end of the respiratory cycle (end of exhalation) that is greater than the atmospheric pressure in mechanically ventilated patients. -
Respiratory Therapy Pocket Reference
Pulmonary Physiology Volume Control Pressure Control Pressure Support Respiratory Therapy “AC” Assist Control; AC-VC, ~CMV (controlled mandatory Measure of static lung compliance. If in AC-VC, perform a.k.a. a.k.a. AC-PC; Assist Control Pressure Control; ~CMV-PC a.k.a PS (~BiPAP). Spontaneous: Pressure-present inspiratory pause (when there is no flow, there is no effect ventilation = all modes with RR and fixed Ti) PPlateau of Resistance; Pplat@Palv); or set Pause Time ~0.5s; RR, Pinsp, PEEP, FiO2, Flow Trigger, rise time, I:E (set Pocket Reference RR, Vt, PEEP, FiO2, Flow Trigger, Flow pattern, I:E (either Settings Pinsp, PEEP, FiO2, Flow Trigger, Rise time Target: < 30, Optimal: ~ 25 Settings directly or by inspiratory time Ti) Settings directly or via peak flow, Ti settings) Decreasing Ramp (potentially more physiologic) PIP: Total inspiratory work by vent; Reflects resistance & - Decreasing Ramp (potentially more physiologic) Card design by Respiratory care providers from: Square wave/constant vs Decreasing Ramp (potentially Flow Determined by: 1) PS level, 2) R, Rise Time ( rise time ® PPeak inspiratory compliance; Normal ~20 cmH20 (@8cc/kg and adult ETT); - Peak Flow determined by 1) Pinsp level, 2) R, 3)Ti (shorter Flow more physiologic) ¯ peak flow and 3.) pt effort Resp failure 30-40 (low VT use); Concern if >40. Flow = more flow), 4) pressure rise time (¯ Rise Time ® Peak v 0.9 Flow), 5) pt effort ( effort ® peak flow) Pplat-PEEP: tidal stress (lung injury & mortality risk). Target Determined by set RR, Vt, & Flow Pattern (i.e. for any set I:E Determined by patient effort & flow termination (“Esens” – PDriving peak flow, Square (¯ Ti) & Ramp ( Ti); Normal Ti: 1-1.5s; see below “Breath Termination”) < 15 cmH2O. -
Training Objectives for a Diving Medical Physician
The Diving Medical Advisory Committee Training Objectives for a Diving Medicine Physician This guidance includes all the training objectives agreed by the Diving Medical Advisory Committee, the European Diving Technology Committee and the European Committee for Hyperbaric Medicine in 2011. Rev 1 - 2013 INTRODUCTION The purpose of this document is to define more closely the training objectives in diving physiology and medicine that need to be met by doctors already fully accredited or board-certified in a clinical speciality to national standards. It is based on topic headings that were originally prepared for a working group of European Diving Technology Committee (EDTC) and the European Committee of Hyperbaric Medicine (ECHM) as a guide for diving medicine some 20 years ago by J.Desola (Spain), T.Nome (Norway) & D.H.Elliott (U.K.). The training now required for medical examiners of working divers and for specialist diving medicine physicians was based on a EDTC/ECHM standard 1999 and subsequently has been enhanced by the Diving Medical Advisory Committee (DMAC), revised and agreed in principle by DMAC, EDTC and ECHM in 2010 and then ratified by EDTC and ECHM in 2011. The requirements now relate to an assessment of competence, the need for some training in occupational medicine, the need for maintenance of those skills by individual ‘refresher training’. Formal recognition of all this includes the need to involve a national authority for medical education. These objectives have been applied internationally to doctors who provide medical support to working divers. (Most recreational instructors and dive guides are, by their employment, working divers and so the guidance includes the relevant aspects of recreational diving. -
A Review of the Use of Heliox in the Critically Ill
Special review A Review of the use of Heliox in the Critically Ill T. WIGMORE, E. STACHOWSKI Intensive Care Unit, Westmead Hospital, Westmead, NEW SOUTH WALES ABSTRACT Heliox, a mix of oxygen and helium, has a number of potential medical applications resulting from its relatively lower density. This paper reviews the physics underlying its utility and considers the evidence for its use. While there are studies that support its role, particularly in patients with exacerbations of asthma and chronic obstructive pulmonary disease (COPD), the data are inconclusive. (Critical Care and Resuscitation 2006; 8: 64-72) Key words: Heliox, helium, airway obstruction, asthma, chronic obstructive pulmonary disease Helium was discovered in 1868 by the French astro- a given pressure difference. Clinically this can be utilis- nomer Pierre-Jules-Cesar Janssen during a spectro- ed to assist patients who suffer from airway narrowing. scopic study of a total solar eclipse in India. It was named later the same year by the British astronomer Table 1. Physical properties of pure gases at RTP Joseph Norman Lockyer and chemist Sir Edward (298 degrees Kelvin and 1 atmosphere pressure) Frankland, the name derived from helios, the Greek for Density Viscosity Thermal sun. It is an inert gas present in the atmosphere (ρ) (η) conductivity (0.00052%) and was used initially in airships and Kg/m3 microPoise W/m K balloons. Today, most commercial helium is recovered from Air 1.184 184.33 0.025 natural gas using a cryogenic separation process, foll- owing which it is refined and liquefied. Liquid helium is Carbon 1.811 148.71 0.017 shipped from the production site to various storage Dioxide facilities worldwide before being distributed in the Helium 0.166 197.61 0.14 gaseous form into cylinders for on-site use. -
Ventilatory Management of Acute Lung Injury and Acute Respiratory Distress Syndrome
CLINICAL REVIEW CLINICIAN’S CORNER Ventilatory Management of Acute Lung Injury and Acute Respiratory Distress Syndrome Eddy Fan, MD Context The acute lung injury and acute respiratory distress syndrome are critical Dale M. Needham, MD, PhD illnesses associated with significant morbidity and mortality. Mechanical ventilation is Thomas E. Stewart, MD the cornerstone of supportive therapy. However, despite several important advances, the optimal strategy for ventilation and adjunctive therapies for patients with acute OR NEARLY 4 DECADES SINCE THE lung injury and acute respiratory distress syndrome is still evolving. acute respiratory distress syn- Evidence Acquisition To identify reports of invasive ventilatory and adjunctive thera- drome (ARDS) was first de- pies in adult patients with acute lung injury and acute respiratory distress syndrome, scribed,1 research has been on- we performed a systematic English-language literature search of MEDLINE (1966- Fgoing in an effort to improve the 2005) using the Medical Subject Heading respiratory distress syndrome, adult, and outcome of this critical illness. Acute related text words, with emphasis on randomized controlled trials and meta-analyses. EMBASE and the Cochrane Central Register of Controlled Trials were similarly searched. respiratory distress syndrome is char- The search yielded 1357 potential articles of which 53 were relevant to the study ob- acterized by the acute onset of hypox- jectives and considered in this review. emia and bilateral infiltrates on chest Evidence Synthesis There is strong evidence to support the use of volume- and radiography in the absence of left atrial pressure-limited lung-protective ventilation in adult patients with acute lung injury and hypertension. Various pulmonary (eg, acute respiratory distress syndrome. -
EMS DIVISION 23.1 Rev. 07/31/2020 PROTOCOL 23 WATER RELATED INCIDENTS
PROTOCOL 23 WATER RELATED INCIDENTS A. Introduction “Drowning is the process of experiencing respiratory impairment from submersion / immersion in liquid” The word Drowning, should be used to refer to a person who drowned (death) or to a person who was rescued (fatal drowning or non-fatal drowning.) Water Rescue is the process of removing someone from the water in which dangerous conditions are present but the victim shows no signs of respiratory impairment. General Care 1. Initial assessment/Care Protocol 1. 2. Administer 15 L/min Oxygen via NRB mask. 3. Maintain normal body temperature to protect against hypothermia. B. Drowning EMR/BLS 1. Consider concurrent trauma and manage accordingly Protocol 21. 2. Consider insertion of I-gel with NG Tube (Lifeguards only) Procedure 49 and Procedure 12. 3. Determine important history from the patient or bystanders which includes: a) Duration of submersion b) Water temperature c) Any possibility of seizure activity d) Any associated drug or alcohol use e) How the patient entered the water 4. All non-fatal drowning victims must be transported to the closest appropriate facility for evaluation, regardless of how well they may seem to have recovered. Delayed death or complications due to pulmonary edema or aspiration pneumonia are common. ALS 5. Consider insertion of an NG/OG Procedure 12. EMS DIVISION 23.1 Rev. 07/31/2020 PROTOCOL 23 WATER RELATED INCIDENTS 6. Treat dysrhythmias per specific protocols. Consider hypoxia as a primary cause of the dysrhythmias. C. Decompression Sickness/Air Embolism EMR/BLS 1. Evaluate for specific signs and symptoms: a) Pain (primarily joint pain) b) Altered level of consciousness c) Generalized numbness or confusion d) Weakness or paralysis e) External or diagnosed internal bleeding f) Extreme vertigo 2.