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 (O2 requirement ≥28 days). PTIdi was calculated as mean to max transdiaphragmatic pressure ratio × inspiratory duty cycle (Pdimean/Pdimax × Ti/Ttot). PTIdi was computed over 10 consecutive breaths, before and after the application of inspiratory-flow resistance (200 cmH2O).
RESULTS: Baseline PTIdi was higher in CLD preterm infants (0.114 ±0.024)compared to those without CLD (0.063 ±0.018; P<0.001) and to infants born at term (0.053 ±0.011; P<0.001). Post-resistance PTIdi remained higher in CLD preterm infants (0.199 ±0.029) compared to those without CLD (0.113 ±0.038; P<0.001) and to term-born counterparts (0.071 ±0.017, P<0.001); in addition, PTIdi became higher in non-CLD preterm compared to term infants (P=0.001).Nine preterm infants (23.7%), including all with CLD, exceeded the fatigability threshold of 0.15 after the application of inspiratory resistance.
CONCLUSIONS: Preterm-born infants, especially those recovering from CLD, are at increased risk of diaphragmatic muscle fatigue under conditions of increased inspiratory loading.
- Copyright ©the authors 2016