Dynamic Description of the Cardiac Performance during Intermittent Positive Pressure Ventilation in Dogs

Abstract

Hemodynamic data change throughout each respiratory cycle (RC) indicating that ventilation and circulation are related. To study this phenomenon, we developed a computerised method that describes coupling between ventilation and circulation in dogs during intermittent positive pressure ventilation. Dogs were anaesthetised and the lungs mechanically ventilated with a tidal volume of 12 ml kg^{− 1}and a frequency of 20 per minute. After control measurements, hemodynamic changes were produced by three rates of dobutamine perfusion: 10, 20, 40 µg.kg^{− 1}.min^{− 1}. Aortic pressure (AP) was detected by a Cournand catheter (9F) positioned in the ascending aorta; left ventricular pressure (LVP) was detected by transthoracic puncture; airway pressure (AwP) was detected by a Cournand catheter positioned in the trachea. AP, LVP, AwP were stored on magnetic tape after A/D conversion at 200 Hertz.