Inspiratory Effort and Dynamic Transpulmonary Driving Pressure in Extremely Preterm Infants

Background: In preterm infants receiving noninvasive ventilation, data about inspiratory effort (ΔPes) and transpulmonary driving pressure (ΔPL) are scarce. Electrical activity of the diaphragm (EAdi) can estimate ΔPes and ΔPL when patient size precludes more accurate measurements. This estimation may reveal new insights into respiratory pathophysiology and potential risk of self-inflicted lung injury in neonates receiving noninvasive support. Research question: What are the characteristics of ΔPes and ΔPL in extremely preterm infants undergoing noninvasive ventilation? Study design and methods: Prospective, observational pilot cohort study, in which EAdi was recorded in neonates receiving noninvasive ventilation during recovery from respiratory distress syndrome (RDS), in those with evolving bronchopulmonary dysplasia (BPD), and in term controls. EAdi was used to estimate ΔPes and ΔPL. In a subset of patients with RDS and BPD, diaphragmatic thickening fraction (TF) and oxygen saturation (Spo2)/Fio2 were recorded. Results: Ten patients with RDS, 25 patients with evolving BPD, and 5 control term neonates were studied. Average EAdi, ΔPes, ΔPL, and TF were similar between control infants and those with RDS and BPD. Inter-patient variability of ΔPes (RDS, 24 [9]%; BPD, 28 [9]%; controls, 10 [6]%; P < .001) and ΔPL (RDS, 25 [7]%; BPD, 27 [9]%; controls, 17 (7)%; P = .05) was higher in patients than in controls. Breaths with ΔPes > 10 cm H2O occurred more often in BPD than in RDS patients (P = .035) and control infants (P = .006). Breaths with ΔPL > 20 cm H2O occurred similarly in patients with BPD or RDS and more frequently than in control infants (P < .001). EAdi-based estimations correlated with TF, and ΔPL had an inverse correlation with Spo2/Fio2 (ρ = -0.64; P = .018). Interpretation: ΔPes and ΔPL show relevant variability in preterm infants. High ΔPes is more common in patients with BPD than in those with RDS or control infants. High ΔPL was observed in patients with BPD and RDS, occurred more often than in control infants, and correlated with the degree of oxygenation impairment.