K H Rühle1, U Domanski, K J Franke, G Nilius. 1. Klinik Ambrock, Klinik für Pneumologie, Allergologie und Schlafmedizin, Universität Witten/Herdecke, Hagen. Klinik-Ambrock.Pneumo@t-online.de
Abstract
INTRODUCTION: An effective CPAP-treatment is only possible, if greater mask-and mouth leakages are prevented. In the case of greater leakages the CPAP decreases and the flow induces side effects as rhinitis and conjunctivitis. In addition to mask-and mouth leakages there exists a leakage through the exhaust valve of the mask which is necessary to avoid CO2-rebreathing. This leakage changes are dependent on the pressure. In many automatic CPAP devices the hard- and software registers the leakage in parallel with the pressure variations. However it is unclear which leakages are considered. We analysed therefore the signal of the leakage of 4 automatic CPAP-devices concerning following questions: Does the leakage measurement of the devices correspond with the pneumotachographically measured flow. How is the leakage of the mask exhaust valve taken into account. METHOD: We simulated normal breathing with a mechanical ventilator. The respective device was connected by a y-piece with a 5 mm aperture (leakage). With an external flow analyser the flow of the leakage was registered and compared with the flow measured by the automatic CPAP-device. RESULTS: The flow of the devices A to C differed during 10 mbar CPAP from the value of the flow analyser by 5.0 %, 4.3 % and 11.3 %. The software of device D subtracts the leakage through the mask exhaust valve so that the indicated leakage corresponds with the mouth and mask leakage. CONCLUSION: The leakage was sufficiently well recorded by the tested automatic devices. When evaluating the leakage signal the flow through the mask exhaust valve should be taken into account.
INTRODUCTION: An effective CPAP-treatment is only possible, if greater mask-and mouth leakages are prevented. In the case of greater leakages the CPAP decreases and the flow induces side effects as rhinitis and conjunctivitis. In addition to mask-and mouth leakages there exists a leakage through the exhaust valve of the mask which is necessary to avoid CO2-rebreathing. This leakage changes are dependent on the pressure. In many automatic CPAP devices the hard- and software registers the leakage in parallel with the pressure variations. However it is unclear which leakages are considered. We analysed therefore the signal of the leakage of 4 automatic CPAP-devices concerning following questions: Does the leakage measurement of the devices correspond with the pneumotachographically measured flow. How is the leakage of the mask exhaust valve taken into account. METHOD: We simulated normal breathing with a mechanical ventilator. The respective device was connected by a y-piece with a 5 mm aperture (leakage). With an external flow analyser the flow of the leakage was registered and compared with the flow measured by the automatic CPAP-device. RESULTS: The flow of the devices A to C differed during 10 mbar CPAP from the value of the flow analyser by 5.0 %, 4.3 % and 11.3 %. The software of device D subtracts the leakage through the mask exhaust valve so that the indicated leakage corresponds with the mouth and mask leakage. CONCLUSION: The leakage was sufficiently well recorded by the tested automatic devices. When evaluating the leakage signal the flow through the mask exhaust valve should be taken into account.
Authors: Hendrik S Fischer; Charles C Roehr; Hans Proquitté; Hannes Hammer; Roland R Wauer; Gerd Schmalisch Journal: Intensive Care Med Date: 2009-11 Impact factor: 17.440
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