Work of breathing and volume targeted ventilation in respiratory distress

Abstract

Objective: To determine the level of volume targeting (VT) associated with the lowest work of breathing (WOB) for prematurely born infants being ventilated with acute respiratory distress.

Design: Prospective study.

Setting: Tertiary neonatal intensive care unit.

Patients: 18 infants, median gestational age 29 (range 25-34) weeks, being ventilated for acute respiratory distress.

Interventions: Infants were studied first without VT (baseline). Volume targeted levels of 4 ml/kg, 5 ml/kg and 6 ml/kg were then delivered in random order. After each VT level, the infants were returned to baseline. Each step was maintained for 20 minutes.

Main outcome measure: The transdiaphragmatic pressure time product (PTPdi) as an estimate of the WOB.

Results: The mean PTPdi was higher at a VT level of 4 ml/kg (median 154 cm H(2)O·s/min) compared to baseline (median 112 cm H(2)O·s/min) (p<0.001) and a VT level of 6 ml/kg (median 89 cm H(2)O·s/min) (p<0.001).

Conclusion: A low level of VT increased the WOB in infants with acute respiratory distress syndrome. The authors' results suggest that, during acute respiratory distress, a VT level of at least 5 ml/kg rather than a lower level might avoid an increased WOB. The most appropriate level of VT needs to be determined in a randomised controlled trial with long-term outcomes.