Effect of maturity and infection on the rate of relaxation of the respiratory muscles in ventilated, newborn infants

Aim To assess the respiratory muscle time constant of relaxation (τ), an index of respiratory muscle function in ventilated newborns. Methods Sixty‐two infants (42 born prematurely) with a median gestational age of 29 [interquartile range (IQR) 26–37] weeks were prospectively studied. Measurement of τ was taken during spontaneous breathing on endotracheal continuous positive airway pressure prior to extubation, and τ was calculated from the reciprocal of the slope of the airway pressure decline versus time. Infants were classified as having had systemic or respiratory infection (positive microbiology) if they had any positive bacterial blood or respiratory culture prior to measurement. Results Measurement of τ was taken at a median post‐natal age of 6 (IQR 3–29) days. The median τ was higher in premature infants [17.4 (IQR 7.7–28.3) sec/cmH2O] compared to term infants [6.8 (IQR 4.4–8.7) sec/cmH2O, p