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Central Haemodynamics, Oxygen Transport and Oxygen Consumption During Three Methods for CPAP
Author(s) -
Vuori A.
Publication year - 1981
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1981.tb01669.x
Subject(s) - medicine , cardiac index , anesthesia , continuous positive airway pressure , pulmonary wedge pressure , cardiac output , vascular resistance , hemodynamics , oxygenation , cardiology , mechanical ventilation , obstructive sleep apnea
During the weaning period after 18 hours of mechanical ventilation following open heart surgery, central haemodynamics, systemic oxygen transport and total oxygen consumption were assessed in a total of 17 patients, receiving continuous positive airway pressure (CPAP) therapy. Three different means of providing CPAP were studied: an electronically controlled method (mode S); a method based on the Venturi principle along with a continuous flow of gases via the T‐piece connector attached to the intubation tube (mode B); and a method employing an elastic inspiratory gas reservoir (mode C). The inspiratory pressure plateau was adjusted to be equal under the different methods for CPAP. The airway pressure range, the expiratory and mean airway pressures and the mean oesophageal pressure were seen to be highest during mode S. The pulmonary vascular resistance was higher during mode S than during modes B and C, and the mean pulmonary arterial pressure was higher during mode S than mode C. While the cardiac index remained statistically unchanged under the three methods for CPAP, the stroke index (SI) and the left ventricular stroke work index (LVSWI) were higher during mode C than mode S. As the transmural right atrial and pulmonary capillary wedge pressures were unchanged, these alterations in SI and LVSWI might be a consequence of airway pressure‐induced changes on the myocardial performance. Arterial oxygenation was good and unchanged during the study; mixed venous oxygen tension (Pvo 2 ) was higher and the arteriovenous oxygen content difference (avDo 2 ) was smaller during mode B than during mode C. During mode S, the total oxygen consumption was higher than during mode B. On the basis of the observations made, there seem to be no major differences in the effects of the three methods for CPAP on the parameters studied. The Venturi principle, employing a continuous flow of gases seems, however, to produce a slightly lower oxygen consumption, while the myocardial performance was best preserved with the system based on the elastic inspiratory gas reservoir.