Control of spontaneous respiration with continuous positive airway pressure using transthoracic electrical impedance. Studies in subjects with healthy lungs

A clinically practicable method for the control of intrapulmonary gas volume changes for patients with spontaneous respiration and CPAP has been evaluated. Changes of intrapulmonary gas volume caused by different continuous positive air-way pressures (CPAP) can be monitored sufficiently using a noninvasive technique of transthoracic electrical impedance (Z0). In 24 healthy volunteers Z0 (rheography) was measured. After stepwise increase of CPAP from 5-20 cm H2O a significant increase of Z0 could be observed. Z0 pressure relations, detected by regression analysis showed a correspondence of intrapulmonary gas filling changes and volume/pressure relation. We therefore conclude that the control of Z0 pressure relationship for the calculation of the maximum is of some importance for determination of therapeutic levels of CPAP.