Effect of body temperature on the pattern of spontaneous breathing in extremely low birth weight infants supported by proportional assist ventilation

Abstract

The optimum body temperature for infants <1000 g is unknown. We investigated body temperature effects on spontaneous breathing using proportional assist ventilation (PAV), because this mode supports spontaneous breathing such that all breathing pattern variables remain controlled by the infant. Minute volume (MV), respiratory rate (RR), tidal volume (Vt), incidence and duration of respiratory pauses, arterial oxygen desaturations <85%, and arterial Pco2 levels will remain unaffected by targeting core body temperature to 36.1-36.5°C (low normal range) versus 37.7-37.9°C (upper normal). Twenty infants (mean ± SD: birth weight, 696 ± 155 g; gestational age, 25 ± 1 wk; age, 5 ± 3 d) who were supported by PAV were exposed to each target temperature range on 2 consecutive days in four 2-h intervals for a total of 8 h with the sequence of the temperature ranges randomized. Core body temperature was 36.5 ± 0.2°C and 37.9 ± 0.2°C in the two conditions. MV was 291 and 314 mL · min-1 kg-1, respectively (7% difference; p < 0.001) as a result of a difference in RR (8%; p < 0.001). The infants maintained their blood CO2 levels and Vt (5.25 ± 0.6 versus 5.19 ± 0.6 mL/kg). Incidence and duration of respiratory pauses were not different between conditions. Extremely immature infants who are supported by PAV modify their spontaneous breathing in response to changes in thermal environment such that Pco2 levels are appropriately maintained early in postnatal life. This response pattern occurred consistently and is currently of uncertain clinical significance.