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The effect of sustained positive airway pressure on derived cardiac output in children
J B Clough1, A W Duncan, P D Sly
1Clinical Sciences Division, Western Australian Research Institute for Child Health, Subiaco, Western Australia.
Insights
Positive pressure ventilation can decrease cardiac output. This study found that while cardiac output falls with increased airway pressure in children, the effect on stroke volume is more pronounced in older children.
Area of Science:
- Pediatric Anesthesiology
- Cardiovascular Physiology
- Respiratory Mechanics
Background:
- Positive pressure ventilation (PPV) can impair cardiac output and oxygen delivery.
- Clinical observations suggest age-related differences in tolerance to PPV-induced hemodynamic changes.
Purpose of the Study:
- To quantify the impact of sustained positive airway pressure on cardiac output and stroke volume in children.
- To investigate the age-related relationship of these hemodynamic changes.
Main Methods:
- Twenty-eight children undergoing general anesthesia were studied.
- Cardiac output and stroke volume were measured using pulsed wave Doppler at varying positive airway pressure levels.
- A general linear model analyzed the relationship between airway pressure, age, cardiac output, and stroke volume.
Main Results:
- Cardiac output significantly decreased with increasing positive airway pressure (P = 0.001).
- The reduction in stroke volume for a given increase in airway pressure was greater in older children (P = 0.02).
Conclusions:
- Positive airway pressure negatively affects cardiac output and stroke volume in pediatric patients.
- The age-dependent increase in the magnitude of stroke volume fall suggests distinct physiological responses in children of different ages.
Abstract:
It is well established that the improvement in gas exchange that occurs with positive pressure ventilation may come at the expense of a decrease in cardiac output and oxygen delivery. Clinical observation suggests that children and infants may be more resistant than adults to the falls in cardiac output induced by positive airway pressure. The aims of this study were to quantify the effect of a sustained increase in intrathoracic pressure on cardiac output and stroke volume, and to determine whether this change is age-related. Twenty-eight children undergoing general anaesthesia were studied. Cardiac output was derived using pulsed wave Doppler techniques at four different levels of sustained positive airway pressure, and stroke volume was calculated. The relationship between airway pressure and both cardiac output and stroke volume was examined using a general linear model which included age as a continuous variable. Cardiac output decreased with increasing levels of sustained positive airway pressure (P = 0.001). The fall in SV for a given airway pressure increased with increasing age (P = 0.02). The mechanisms responsible for the increase of the magnitude of the fall in stroke volume with age remain to be elucidated.