On-line impedance analysis system for studying the pulmonary vascular response to hypoxia

The response of the pulmonary circulation to hypoxia is generally assessed in terms of cardiac output and pulmonary vascular resistance. However, due to pulsatility, the opposition to blood flow can be described accurately only by the input impedance to the pulmonary bed. For assessment of impedance, a system was developed consisting of implantable pressure transducers and an improved muitichannel continuous wave Doppler flow meter. A computer system was used to analyze the data, which was based on power output of the right heart, power dissipation in the pulmonary circulation, and impedance spectra. Data have been obtained from dogs exposed to various levels of acute hypoxia.