European Journal of Underwater and Hyperbaric Medicine, ISSN: 1605-9204 Volume 6 No.4, December 2005 Review Articles MEDICAL EQUIPMENT FOR MULTIPLACE HYPERBARIC CHAMBERS Part I: Devices for Monitoring and Cardiac Support Jacek Kot National Centre for Hyperbaric Medicine, Institute of Maritime and Tropical Medicine, Gdynia, Medical University of Gdansk, Poland Kot J: Medical equipment for multiplace hyperbaric chambers. Part I: Devices for monitoring and cardiac support. Europ J Underwater Hyperbaric Med 2005, 6(4): 115-120. All medical devices introduced into the hyperbaric chamber should be of an appropriate design and fit for use in the hyperbaric environment and they should be certified by the manufacturer for hyperbaric conditions. However, until now only several medical devices are CE marked for usage in hyperbaric chambers. Therefore users often need to perform themselves checking of the medical equipment needed for continuation of intensive care during hyperbaric treatment. To make this task easier, this paper presents review of reports of usage of medical devices under increased pressure. Part 1 is concerning devices for monitoring and cardiac support. Part 2 will describe mechanical ventilators and Part 3 will be devoted to infusion pumps and syringes. Hyperbaric Oxygen Therapy, Medical Equipment, CE Marking INTRODUCTION installing. The structure of the device is checked from a Hyperbaric chamber is an active medical device, which is point of view of raised pressure, of oxygen enriched potentially hazardous taking into accounts its application, atmosphere and of electrical supply. Furthermore, the and exposure of people inside to increased ambient function of the device is checked under hyperbaric pressure and increased partial pressure of oxygen. conditions to verify the controls, the performances of the Therefore all hyperbaric systems have to be in accordance device's probes, the operating of the device's built-in with the Council Directive 93/42/EEC of 14 June 1993 electronics, the device's display and the flow rates, concerning medical devices (1). Moreover, according to pressures and frequencies with which the device this Directive all equipment which is introduced into the dispenses the medical products to the patients. hyperbaric chamber should be should be certified by In case of any doubt, the installation of this medical manufacturer for hyperbaric conditions and CE marked device in hyperbaric chamber should be abandoned. accordingly covering the hyperbaric environment To guide medical users, the review of literature is conditions. Unfortunately, nowadays only several medical presented here to report medical devices, which have been devices, which are needed, for continuation of intensive used under hyperbaric conditions. This is divided into care inside the hyperbaric chamber are marked by three parts: the part 1 is concerning devices for manufacturers as compatible with hyperbaric conditions. monitoring and cardiac support, the part 2 will describe Therefore users are still forced to perform some checking mechanical ventilators and the last part 3 will be devoted of devices before putting it into the chamber and usually to infusion pumps and syringes. this is done on the responsibility of the users. Equipment that does not belong to the internal equipment of the MONITORING DEVICES chamber and which is not a medical device, should be of Monitoring of patophysiological parameters during HBO an appropriate design and fit for use in the hyperbaric session strongly depends on severity of the illness and environment up to the maximum working pressure of the current status of the patient. The set of measured chamber it is used within (2). parameters can be as simple as only 3-leads The general recommendations for medical devices used in electrocardiography (ECG) up to many critical points of hyperbaric chamber systems are presented in the Annex B measurement including for example pulmonary capillary of the pr14931 “Pressure vessels for human occupancy wedge pressure (PCWP) or electroencephalography (PVHO) – Multi-place pressure chamber systems for (EEG) (4). hyperbaric therapy – Performance, safety requirements For the safety reasons the optimal method of collecting and testing” (3), which describes the potential hazards measurements is to perform acquisition of signals under which certain medical devices represent, the risks induced hyperbaric conditions, transfer it into the electrical signal by medical devices likely to be used within hyperbaric of low voltage or current and to transfer it out of the chamber systems intended for hyperbaric oxygen therapy chamber through the wall to the outside monitor to be and the recommendations for manufacturers of medical displayed and recorded. The transfer of the signal from devices and users of hyperbaric chamber systems, in order the inside to the outside of the chamber can be effectively to achieve the highest possible level of safety of the performed via wire connection or telemetric transmission. patient and the attendants. The significant disadvantage of the wire connection In cases when the medical devices need to be introduced through the chamber wall is a need for two additional into the hyperbaric environment and it is not certified by connectors to switch the cable from inside to outside. This the manufacturer for the use in such conditions, the user may result in decreasing the quality of signal being (personnel of hyperbaric centres) has to check it before transmitted, especially with the low signal-to-noise ratio. 115 European Journal of Underwater and Hyperbaric Medicine, ISSN: 1605-9204 Volume 6 No.4, December 2005 Transmission using telemetry ensures the continuous E. Transcutaneous partial pressure of the oxygen monitoring of the patient during all phases of the session (TcPO2). It is used for evaluation of oxygenation of including transportation of the patient to and from the the local tissues as result of vascular system and chamber. The quality of the signals transmitted depends efficacy of the hyperbaric therapy (7). Moreover, it on the quality of the emitter and receiver, the position of can be used for quality assurance system giving the antenna and the thickness of the chamber wall. independent measurement of the dose of oxygen Unfortunately, such systems usually allow transmission of absorbed by the patient leading to early detection of only some basic signals, like ECG, with no possibility to any leakage in breathing systems. Together with transmit more data collected from the patient. measurement of the transcutaneous partial pressure of The alternative method is to put the monitoring device the carbon dioxide (TcPCO2) it is used for control of under the hyperbaric conditions and to collect, display ventilation / perfusion status of the patient (8, 9). The and record all signals at the patient bed inside the sensors are connected to the patient skin and chamber. This solution is easier to be conducted and – in electrical signal from sensors is redirected to the basic version - does not need to make any modification to internal or external display. the existing construction of the chamber. If the user F. Electroencephalography (EEG). It can be acquired needs, it is possible to collect data inside the hyperbaric safely using computerized multi-channel systems to chamber and then to send it out of the chamber (again via avoid any artefacts (10, 11). Usually the signal cable connection through electrical ports or using obtained from head sensors is transferred out of the telemetry) to more sophisticated monitor located outside chamber to the external computer for further for further analysis. It is important to remember that evaluation (eg. spectral analysis). introducing of the electrical device inside the chamber G. Evoked potentials (EP). The usage of potentials increases the risk of fire, and therefore its careful evoked at a cortical and brainstem level by acoustic, evaluation is obligatory. visual and somatosensorial stimuli in humans during The following methods and techniques have been hyperbaric session have been described (10, 12) and reported to be used safely inside hyperbaric chambers. it has been used for research purposes up to 62.5 ATA (13). Non-invasive monitoring H. Laser-Doppler flowmetry (LDF). It is used for A. Electrocardiography. This is the basic monitoring assessment of peripheral microcirculation and is procedure for critically ill patients. The signal can be suitable for non-invasive monitoring of skin easily transferred outside the chamber to outside perfusion under hyperbaric conditions (14, 15). monitor or can be collected by internal one, eg. I. Trans-thoracic bioimpedance. It can be used for non- Propac Encore (5). It includes monitoring of heart invasive estimation of cardiac output (CO) and rate, analysis of arrhythmias and ST levels, power extravascular lung water (ELW). Regardless of spectrum analysis of heart rate variability, and tracing doubts arising for accuracy of this method in of respiration by monitoring the impedance variation measurement of cardiac output in haemodynamically between electrodes. unstable patients, it has been validated in hyperbaric B. Pulse oximetry. The value of the measurement is environment using the NNCCM3 Bohmed (16, 17, restricted to pulse frequency only, as breathing 18). hyperbaric oxygen leads to full saturation of the J. Echocardiography and Doppler studies. It can serve haemoglobin with only few exception of serious for non-invasive monitoring of haemodynamic status