Impact of Breathing Pattern and Nebulization on Expelled Viral Content During Mechanical Ventilation Using an Ex Vivo...

Little is known about the fate of expelled viral particulates during the aerosolization of inhaled medications during mechanical ventilation. We hypothesized that breathing patterns that generate a greater degree of shear stress and turbulent air flow will produce a greater concentration of exhaled viral RNA with the presence of a nebulizer during mechanical ventilation.

Eight ex vivo pig lungs were utilized as the physiological model. Each lung was dedicated to a specific breathing pattern that consisted of tidal breathing, respiratory distress, cough, and sneeze. Breath simulations were carried out through a commercial mechanical ventilator. Ninety mL of a bacteriophage stock at a concentration of 10⁸ PFU/mL were introduced into the lungs during a 10-min sample collection session. The number of viral particles collected in exhalate was measured using quantitative polymerase chain reaction. The impact of breathing pattern on measured viruses was analyzed through two-way analysis of variance.

The interaction effect between nebulization and breath pattern on exhaled viral quantity was not statistically significant P = .80, partial η² = 0.167. The analysis of the main effects indicated that the effects of the breathing pattern and nebulization phase were not statistically significant P = .26, partial η² = 0.519; P = .98, partial η² = 0, respectively. There were no statistically significant differences among the breathing patterns related to measurable viral RNA. Coughing produced the most measurable increase in measured viral quantity during the nebulization phase and non-nebulization phase with a mean exhaled viral quantity (3.5 × 10⁵ ng/μL [95% CI 1.6 × 10⁵-5.5 × 10⁵] and 2.7 × 10⁵ ng/μL [95% CI 7.1 × 10³-5.5 × 10⁵], respectively). Tidal breathing with the presence of a nebulizer and respiratory distress without a nebulizer produced the lowest measured viral quantities (M = 1.1 × 10⁵ ng/μL [95% CI -1.7 × 10⁵ to 3.9 × 10⁵]; M = 1.2 × 10⁵ ng/μL [95% CI -1.6 × 10⁵ to 4.0 × 10⁵]).

In this ex vivo porcine model, the introduction of a nebulizer did not increase the mean viral RNA captured throughout all of the breathing patterns.