Abstract
Summary: Pulmonary petechial hemorrhages are typically observed in sudden infant death syndrome (SIDS), but their cause has not been determined. Some data suggest that SIDS infants die with an obstructed airway. Inspiratory efforts against the closed airway can decrease the efficiency of the cardiac pump by increasing the afterload on the left ventricle and/or by decreasing left ventricular compliance. If these effects are augmented by hypoxia-induced decreases in cardiac contractility as occlusion is maintained, the resultant failure of the left ventricle could produce a large increase in end-diastolic pressure. Increases in left ventricular end-diastolic pressure will then increase pressures in the pulmonary circuit, where rupture of small blood vessels gives rise to petechial hemorrhages.
To evaluate this postulated mechanism of petechiae formation, lightly anesthetized adult rabbits were sacrificed using three 1-min end-expiratory airway occlusions plus a fourth occlusion maintained until death; systemic arterial, intratracheal, and pulmonary wedge pressures (the latter approximating left atrial pressure) were measured during inspiratory efforts and expiratory intervals. Those animals showing minimal evidence of left heart failure, as evidenced by a relatively small difference between wedge and intratracheal pressures during obstructed breathing, showed few pulmonary petechiae. When the above pressure difference was large (greater than 25 mmHg during inspiratory efforts and greater than 10 mmHg during expiratory intervals) numerous pulmonary petechiae (usually n > 40) could be observed. Progressive increases in pulmonary wedge pressure and bradycardia during occlusion suggested that direct and/or reflex hypoxic depression of the myocardium contributed to the observed effects. The occlusions produced little change in systemic arterial pressure. These results are consistent with the possibility that mechanical interactions between the heart and lung pumps, along with hypoxia-induced decreases in cardiac contractility accompanying airway obstruction, account for intrathoracic petechiae in SIDS.
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Farber, J., Catron, A. & Krous, H. Pulmonary Petechiae: Ventilatory-Circulatory Interactions. Pediatr Res 17, 230–233 (1983). https://doi.org/10.1203/00006450-198303000-00013
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DOI: https://doi.org/10.1203/00006450-198303000-00013
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