RESUMEN
To study hypoxemic episodes in newborn undergoing mechanical ventilation. Tidal volume, respiratory rate, oxygen saturation, heart rate, and body movement were continuously recorded in 10 low birth weight infants [LBWI] who exhibited episodes of hypoxemia during mechanical ventilation [birth weight, 829 +/- 139 gm; postconceptional age at study, 2.5 +/- 1 week]. Frequency of hypoxemic episodes was compared in both prone and supine positions. Seventy-six percent of hypoxemic episodes began in association with body movement as well as heart rate acceleration. Thereafter the spontaneous and delivered minute ventilation both decreased during the first 15 seconds of hypoxemia. The former decrease was due to a significant decrease in frequency of spontaneous respiration, whereas the latter was associated with a significant decrease in delivered tidal volume. Minute ventilation returned to normal before recovery of oxygenation. A change in body position from supine to prone significantly decreased the frequency of hypoxemic episodes. Hypoxemic episodes in infants who are on ventilatory support are characterized by: movement and cardioacceleration at initiation; adecrease in both spontaneous and delivered minute ventilation, and a lower incidence in the prone position. We speculate that spontaneous movement during sleep can trigger cardiopulmonary reflex responses that initiate and propagate these episodes