The purpose of this study was to evaluate the relationship between changes in minute ventilation (V̇E) and oxygen consumption (V̇O2) in response to acute hypoxia in the newborn piglet. Twenty-five (mean ± SD; age, 4.7 ± 1.1 d; weight, 1451 ± 320 g) sedated, spontaneously breathing newborn piglets were studied. V̇E was measured by pneumotachography, and V̇O2 was measured by the open-circuit technique. Measurements were performed while the animals breathed room air and repeated after 10 min of hypoxia, which was induced by breathing 10% oxygen. Although the mean V̇E values during hypoxia displayed a typical biphasic ventilatory response, the individual pattern of this ventilatory response to hypoxia was variable. Thirteen animals sustained V̇E above baseline after 10 min of hypoxia, whereas the 12 remaining animals decreased V̇E after 10 min of hypoxia to values below their room air baseline. The V̇O2 values did not differ between groups during normoxia, and a similar decrease in V̇O2 occurred in both groups after 10 min of hypoxia. Furthermore, no correlation was observed between changes in V̇E and V̇O2 during hypoxia either in absolute values or in the percent change from room air baseline. Arterial PO2 decreased similarly in both groups, but PaCO2 decreased significantly only in the group that sustained V̇E above baseline after 10 min of hypoxia. These data demonstrate that in this animal model the hypoxic ventilatory depression is not determined by the decrease in V̇O2 that occurs during hypoxia.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health