Changes in the breathing pattern of newborn infants, such as apnea, may occur with increasing frequency during infections. To determine the effect of E.coli 055:B5 endotoxin infusion on the neonatal ventilatory response to hypoxia, 14 chronically instrumented and unanesthetised newborn piglets were studied in quiet sleep and a thermoneutral environment, before and 30 min after the administration of E.coli endotoxin (n=7; wt,2.1±0.5 kg; age, 5.7±0.9 d) or normal saline (n=7;wt, 1.8±0.4 kg; age, 5.3±0.5 d). Minute ventilation (VE), oxygen consumption (VO2), heart rate (HR) and arterial blood pressure(ABP) and blood gases were measured during normoxia (RA) and 10 min of hypoxia(FiO2=0.10). (see table).

Table 1 No caption available.
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The basal ventilation was not modified by E.coli endotoxin infusion but the ventilatory response to hypoxia was markedly attenuated at 1 and 10 min. A significant decrease in VO2 was observed during hypoxia post-E.coli endotoxin. There was a significant linear correlation between the changes in VE and VO2 with hypoxia post-E.coli (r=0.87;p<0.02). There was no significant difference in arterial blood gases and HR during hypoxia pre- and post- E.coli,while a significant decrease in ABP during hypoxia was observed post-E.coli. The cardiorespiratory response to hypoxia was not different between pre- and post-saline infusion. These data suggest that the attenuation in the ventilatory response to hypoxia induced by E.coli endotoxin is in part explained by a decrease in metabolic rate during hypoxia.