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Increased ventilator use during the COVID-19 pandemic resurrected persistent questions regarding mechanical ventilation including the difference between physiological and artificial breathing induced by ventilators (i.e., positive- versus negative-pressure ventilation, PPV vs NPV). To address this controversy, we compare murine specimens subjected to PPV and NPV in ex vivo quasi-static loading and quantify pulmonary mechanics via measures of quasi-static and dynamic compliances, transpulmonary pressure, and energetics when varying inflation frequency and volume. Each investigated mechanical parameter yields instance(s) of significant variability between ventilation modes. Most notably, inflation compliance, percent relaxation, and peak pressure are found to be consistently dependent on the ventilation mode. Maximum inflation volume and frequency note varied dependencies contingent on the ventilation mode. Contradictory to limited previous clinical investigations of oxygenation and end-inspiratory measures, the mechanics-focused comprehensive findings presented here indicate lung properties are dependent on loading mode, and importantly, these dependencies differ between smaller versus larger mammalian species despite identical custom-designed PPV/NPV ventilator usage. Results indicate that past contradictory findings regarding ventilation mode comparisons in the field may be linked to the chosen animal model. Understanding the differing fundamental mechanics between PPV and NPV may provide insights for improving ventilation strategies and design to prevent associated lung injuries.

BACKGROUND: The coronavirus disease (COVID-19) pandemic has raised concern of transmission of infectious organisms through aerosols formation in endonasal and transoral surgery. METHODS: Retrospective review. We introduce the negative-pressure otolaryngology viral isolation drape (NOVID) system to reduce the risk of aerosol. NOVID consists of a plastic drape suspended above the patients head and surgical field with a smoke evacuator suction placed inside the chamber. RESULTS: Four patients underwent endonasal (4) and endo-oral surgery (1). Fluorescein was applied to the surgical field. Black light examination of fluorescein-treated operative fields revealed minimal contamination distant to the surgical field. In two prolonged cases with high-speed drilling, droplets were identified under the barrier and on the tip of the smoke evacuator. Instruments and cottonoids appeared to be a greater contributor to field contamination. CONCLUSIONS: Negative-pressure aspiration of air under a chamber barrier, which appears to successfully keep aerosol and droplet contamination to a minimum.