Key result
Intermittent positive pressure ventilation during halothane anaesthesia lengthened electro-mechanical systole and pre-ejection period, while slightly shortening left ventricular ejection time.
Why the study?
Does intermittent positive pressure ventilation affect systolic time intervals in subjects undergoing halothane anaesthesia?
Observational (n=10)
Does intermittent positive pressure ventilation affect systolic time intervals in subjects undergoing halothane anaesthesia?
Intermittent positive pressure ventilation alters systolic time intervals, primarily by lengthening the pre-ejection period due to reduced venous return.
Answers are grounded in this paper and cite their sources.
Requires caution interpreting systolic time intervals during halothane IPPV; leaves open relevance to modern anesthetics or outcomes.
The measurement of systolic time intervals (STI) has been widely used as a non-invasive method of assessing the inotropic state of the heart, and normal values are available for healthy individuals breathing spontaneously. The present study was performed in order to evaluate how intermittent positive pressure ventilation (IPPV) affects STI. Ten subjects were investigated before and during halothane anaesthesia for routine surgery. Oesophageal pressure, respiratory minute volume and frequency, arterial blood-gas tensions, cardiac output and heart rate were also measured simultaneously. As expected, the institution of IPPV was associated with a reduction in cardiac output and an increase in oesophageal pressure. Paco2 was reduced. These changes were associated with a considerable lengthening of electro-mechanical systole. This was due to a lengthened pre-ejection period (PEP), whereas the left ventricular ejection time (LVET) was slightly shortened. These changes were even more marked during artifical hyperventilation. The changes in STI are attributed mainly to the reduction of venous return to the heart, subsidiary factors being intrathoracic pressure, myocardial inotropy and vascular resistance.
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Brundin et al. (1976) conducted an observational in routine surgery (n=10). Intermittent positive pressure ventilation (IPPV) vs. Before IPPV was evaluated on Systolic time intervals (STI). Intermittent positive pressure ventilation during halothane anaesthesia lengthened electro-mechanical systole and pre-ejection period, while slightly shortening left ventricular ejection time.
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