Background: Accurate prediction of extubation outcome could result in a significant reduction of respiratory morbidity in premature neonates. Objectives: To assess whether the respiratory muscle time constant of relaxation (τ) predicted extubation outcome in mechanically ventilated, premature infants. Methods: Forty-six mechanically ventilated infants with a median gestational age of 26 (interquartile range [IQR] 25-29) weeks were prospectively studied. τ was calculated from the reciprocal of the slope of the decline in airway pressure as a function of time. Measurements of τ were done during 5-10 min of a spontaneous breathing test (SBT) prior to extubation. During the first and last minute of the SBT, τ1 and τ2, respectively, were assessed, and the difference between them was calculated (Δτ). Results: The median τ2 was significantly higher in infants whose extubation failed (20.7 [IQR 12.9-34.7] s/cm H2O) than in infants whose extubation succeeded (8.2 [IQR 6.2-17.8] s/cm H2O, p = 0.002). The median Δτ was significantly higher in infants whose extubation failed (10.3 [IQR 4.4-23.9] s/cm H2O) than in infants whose extubation succeeded (-1.63 [IQR -5.7 to 0.3] s/cm H2O, p = 0.001). Extubation failure was associated with τ2 (p = 0.011) and Δτ (p = 0.010) after correcting for postmenstrual age, patent ductus arteriosus, and intraventricular haemorrhage. Receiver operator characteristic curve analysis demonstrated that Δτ predicted extubation failure with an area under the curve of 0.937. A Δτ of +1.02 s/cm H2O predicted extubation failure with 94% sensitivity and 83% specificity. Conclusions: The respiratory muscle time constant of relaxation during an SBT was significantly greater in infants whose extubation failed and could be used to predict extubation outcome in prematurely born infants.
Numerous factors influence pulmonary dead space and thus an optimum tidal volume will differ according to the underlying demographics and respiratory status.
Ventilated neonates frequently require supplemental oxygen, but inappropriate levels can have detrimental effects for the infant. Consequently, peripheral oxygen saturations (SpO 2 ) are continuously monitored, and the inspired oxygen concentration (FiO 2 ) is frequently adjusted with the aim of maintaining SpO 2 within a pre-defined target range. 1The achievement of SpO 2 targets can be challenging as neonates experience frequent episodes of intermittent hypoxemia
Compliance of achievement of SpO 2 targets in preterm infants is low, especially in maintaining the SpO 2 below the upper limits of the target range and avoidance of hyperoxemia. 1 Closed-loop automated oxygen control (CLAC) systems may provide a solution as their use in preterm infants has been associated with fewer desaturations, 2 increased percentage of the time spent within the target oxygen saturation range and fewer manual adjustments to the inspired oxygen concentration. 3,4 In the interim analysis of a randomised crossover trial of CLAC, we demonstrated that automated oxygen control had similar benefits in ventilated infants born at or above 34 weeks gestation. 5 In the interim analysis, most of our patients had a low oxygen requirement, we continued recruitment to the target sample
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