Effect of inspiratory resistive loading on diaphragmatic muscle function of preterm and term infants

Abstract

BACKGROUND: Preterm infants, especially those with chronic lung disease (CLD), may present limited ability to adapt to additional respiratory load, such as acute respiratory illness. The diaphragmatic pressure-time index (PTIdi) reflects the pressure-generating reserve of the diaphragm; in adults, a PTIdi >0.15 indicates impending diaphragmatic fatigue. AIMS: To assess diaphragmatic muscle functionin term and preterm infants, before and after the application of inspiratory resistive loading. METHODS: 15 term and 23 preterm infants were studied when breathing spontaneously on room air, prior to discharge from NICU; 6 preterm infants had CLD (O 2 requirement ≥28 days). PTI di was calculated as mean to max transdiaphragmatic pressure ratio × inspiratory duty cycle (P dimean /P dimax × T i /T tot ). PTI di was computed over 10 consecutive breaths, before and after the application of inspiratory-flow resistance (200 cmH 2 O). RESULTS: Baseline PTI di was higher in CLD preterm infants (0.114 ±0.024)compared to those without CLD (0.063 ±0.018; P CONCLUSIONS: Preterm-born infants, especially those recovering from CLD, are at increased risk of diaphragmatic muscle fatigue under conditions of increased inspiratory loading.