Acute Bronchiolitis in Infants on Invasive Mechanical Ventilation: Physiology Study of Airway Closure.

Abstract

Objectives: This study aimed to explore whether airway closure can be detected in patients with severe acute bronchiolitis on invasive mechanical ventilation.

Design: Single-center prospective physiologic study carried out in 2023-2024.

Setting: PICU in a tertiary-care general hospital.

Patients: Infants with acute bronchiolitis undergoing invasive mechanical ventilation.

Interventions: Under deep sedation and neuromuscular blockade, the mechanical ventilator, in a volume-controlled mode, was transiently set with a respiratory rate of five breaths/min, a tidal volume of 6 mL/kg of ideal body weight, positive end-expiratory pressure 0 cm H2O, a flow rate of 2 L/min, an inspiratory-expiratory ratio of 1:1, and a Fio2 of 1.0. After recording three breath cycles, the patient was returned to baseline ventilatory settings.

Measurements and main results: We identified the presence of airway closure through the low-flow pressure-volume curve obtained from a pneumotachometer with a flow sensor placed at the Y-piece and simultaneously from the pressure-impedance curve and ventilation maps acquired using electrical impedance tomography. We included 12 patients, and airway closure was detected in seven of them. The median (interquartile range [IQR]) airway opening pressure was 14 cm H2O (IQR, 11-17 cm H2O). Patients with airway closure exhibited high levels of driving pressure, with a median of 16 cm H2O (IQR, 11-17 cm H2O), and low levels of respiratory system compliance, with a median of 0.41 mL/cm H2O/kg (IQR, 0.38-0.59 mL/cm H2O/kg). When these parameters were corrected for airway opening pressure, there was a significant decrease in driving pressure to 9 cm H2O (IQR, 8-12 cm H2O; p = 0.018) and a significant increase in respiratory system compliance to 0.70 mL/cm H2O/kg (IQR, 0.53-0.81 mL/cm H2O/kg; p = 0.018).

Conclusions: Airway closure requiring high opening pressures can be detected in ventilated infants with acute bronchiolitis, and this phenomenon may impact respiratory mechanics.