Effects of the respiratory cycle on cardiac output measurements: reproducibility of data enhanced by timing the thermodilution injections in dogs.
Cardiac output (Q) was measured with the thermodilution technique at 4 points during the respiratory cycle in dogs. Boluses of an ice-cold solution were injected at mid- and end-inspiration while the animals were on intermittent positive-pressure ventilation (IPPV) or after induction of positive end-expiratory pressure (PEEP), with and without induction of experimental respiratory failure. Values were mot constant at end-inspiration. During IPPV without respiratory failure, the standard error of 74 measurements at end-inspiration was 5.1% and of 74 measurements randomly selected was 9.8%. Continuous infusion resulted in similar fluctuations in Q (r = 0.92). Values obtained during experimental respiratory failure were not significantly different. The authors conclude that timing the bolus injections with the respiratory cycle enhances the reproducibility of Q values obtained with the thermodilution technique.
D000818:Animals; D002302:Cardiac Output; D004285:Dogs; D007385:Intermittent Positive-Pressure Ventilation; D011175:Positive-Pressure Respiration; D012119:Respiration; D013815:Thermodilution / Q000295:instrumentation / Q000379:methods*