Effects of different gas flow patterns on central circulation during respirator treatment

The effects of different inspiratory gas flow patterns on the central circulation during respirator treatment were investigated, first with a retrospective study consisting of 15 patients, where the effects on the mean intrathoracic pressure were represented by the variations in the amplitude and time development of the oesophageal pressure curve. In another study on eight intensive care patients undergoing respirator treatment, right-sided heart catheterisation was performed with pressure recordings in the central venous position, the right ventricle, the pulmonary artery and in the pulmonary capillary venous position. Estimations of the arterial-mixed venous oxygen content difference were also made. The development and transmission of the airway pressure curve to the central circulation were illustrated and discussed. The results showed very small effects on the mean intrathoracic pressure from different inspiratory gas flow patterns, and, therefore, it could be expected that the effects on the central circulation would be insignificant. This was also the conclusion in the catheterisation study. No important changes in the pressures of the a-vo2 difference occured. Most of the characteristics of a particular gas flow pattern are lost during the passage through the airways and are not transmitted to the oesophagus or the central vessels.