Infant tidal flow-volume parameters and arousal state

Abstract

<b>Background:</b> Infant lung function can be assessed with tidal flow-volume (TFV) loops. While guidelines advocate measuring TFV loops in sleeping infants, the influence of arousal state is not established. <b>Aim:</b> To determine if TFV parameters in healthy infants differed in the awake compared to the sleeping state at three months of age. <b>Methods:</b> From the population-based Scandinavian PreventADALL birth cohort, 93 infants had reproducible TFV loops measured with Exhalyzer® D in both the awake and sleeping state at three months of age. TFV loops were selected by a manual standardized procedure. The ratio of time to peak tidal expiratory flow by expiratory time (<i>t</i>_PTEF/<i>t</i>_E) and the corresponding volume ratio (<i>V</i>_PTEF/<i>V</i>_E), as well as tidal volume (<i>V</i>_T) and respiratory rate (RR) were compared using non-parametric tests. <b>Results:</b> The mean (95% CI)&nbsp;<i>t</i>_PTEF/<i>t</i>_E&nbsp;was significantly higher in the awake compared to the sleeping state, 0.39 (0.37, 0.41) and 0.28 (0.27, 0.30) respectively. Corresponding, the&nbsp;<i>V</i>_PTEF/<i>V</i>_E&nbsp;was higher in the awake compared to the sleeping state, 0.38 (0.36, 0.40) and 0.29 (0.28, 0.30) respectively. The&nbsp;<i>V</i>_T&nbsp;was similar, while the RR was higher in the awake compared to the sleeping state, 53 (51, 56) and 38 (37, 40) respectively. <b>Conclusion:</b> The infants had higher&nbsp;<i>t</i>_PTEF/<i>t</i>_E,&nbsp;<i>V</i>_PTEF/<i>V</i>_E&nbsp;and RR, but similar&nbsp;<i>V</i>_T&nbsp;in the awake compared to the sleeping state, suggesting that separate normative values according to arousal state in infancy are required.