Ultrashort inspiratory times homogenize ventilation distribution in an inhomogeneous two‐compartment model of the neonatal lung

Abstract

Background: Inhomogeneous lung ventilation and pulmonary air leaks are common adverse effects of mechanical ventilation in preterm infants suffering from respiratory distress syndrome. We hypothesized that shortening of inspiratory times can improve the homogeneity of lung aeration. We assumed that ultrashort inspiratory times lead to a full build-up of pressure in regions with low compliance while maintaining incomplete filling of regions with high compliance. Methods: We connected a two-compartment model of the lung with different compliances of the two compartments to a neonatal ventilator. Pressures and flow rates were measured separately for each compartment at inspiratory times ranging from 0.1 to 0.8 s and various combinations of tidal volumes. Results: An inspiratory time of 0.8 s resulted in near total pressure equalization between the airway pressure and the two compartments, as 97% of the maximum applied peak pressure was reached in the low compliance compartment and 95% in the high compliance compartment. The distribution of the tidal volume was proportional to the compartment compliance. Ultrashort inspiratory times lowered the peak pressure and tidal volume in the high compliance compartment but maintained higher pressure and volume in the low compliance compartment. An inspiratory time of 0.2 s resulted in a peak pressure of 80% of peak airway pressure in the low compliance compartment and in 61% of peak airway pressure in the high compliance compartment (p < .001). Conclusion: Ventilation with ultrashort inspiratory times may improve homogeneity of air distribution in inhomogeneous lungs of ventilated preterm or term infants.

Pediatric pulmonology year in review 2021 and 2022: Physiology

“…Several other papers focusing on different aspects of pulmonary physiology were published in 2021 and 2022. Baumgartner et al 56 studied the effect of ultrashort inspiratory times (0.1‐0.2 second)s) on ventilation inhomogeneity in a two compartment neonatal lung model of differential ventilation consisting of a low compliance and high compliance lung unit. They found that shorter inspiratory times (e.g., 0.2 s) resulted in more homogeneous ventilation, suggesting that using such inspiratory times in conditions such as bronchopulmonary dysplasia may be beneficial.…”