A36-09 Performance of Salbutamol Metered-Dose Inhalers Under Hyperbaric Conditions: Implications for Emergency Airway Management

Abstract Rationale Hyperbaric oxygen therapy is increasingly used for decompression illness, carbon monoxide poisoning, and chronic wound management. Patients with reactive airway disease may experience acute bronchospasm during hyperbaric oxygen sessions. Emergency extraction from hyperbaric chambers is precluded by mandatory decompression protocols, necessitating in-chamber bronchodilator administration. Previous data suggest metered-dose inhalers (MDIs) may exhibit reduced drug delivery under increased ambient pressure, potentially compromising acute asthma management. We systematically evaluated the performance of two commercially available salbutamol MDIs across clinically relevant hyperbaric pressures to determine device reliability for emergency airway management. Methods Two salbutamol MDIs available in Switzerland were evaluated: Ventolin® aerosol-nebulizer (GlaxoSmithKline, manually-activated) and Salamol® Autohaler (Teva Pharma, breath-activated). Testing occurred in a HAUX-STARMED 2400 hyperbaric chamber at three pressure levels: 1.0 atmospheres absolute (ATA, sea level), 2.5 ATA, and 4.0 ATA. Each device underwent gravimetric analysis by weighing before and after 15 consecutive actuations. Three canister fill conditions were tested: full, half-empty, and nearly empty. All experiments were performed in triplicate (n = 9 per device per pressure). Statistical analysis employed Kruskal-Wallis tests for group comparisons and robust linear regression modeling to assess pressure-device interactions while controlling for potential outliers. Results Ventolin® demonstrated significant pressure-dependent performance degradation (p = 0.03). Mean aerosol delivery decreased from 1079.8±21.0 mg at 1.0 ATA to 1001.6±21.2 mg at 2.5 ATA (7.2% reduction) and 837.8±37.1 mg at 4.0 ATA (22.4% reduction). In contrast, Salamol® Autohaler maintained consistent delivery across all pressures: 517.0±23.3 mg at 1.0 ATA, 492.2±14.6 mg at 2.5 ATA, and 501.6±23.5 mg at 4.0 ATA (p 0.05). Robust regression analysis confirmed significant pressure-device interaction (p 0.001), indicating differential pressure sensitivity between devices. Canister fill level did not significantly influence aerosol delivery for either device at any tested pressure (p 0.05). The manually-activated Ventolin® system proved vulnerable to pressure effects, while the breath-activated Salamol® mechanism remained pressure-independent (Figure). Conclusions Salbutamol MDI performance under hyperbaric conditions is device-dependent, with clinically significant implications for emergency airway management. The 22% reduction in Ventolin® output at 4.0 ATA may result in inadequate bronchodilation during acute exacerbations, potentially compromising patient safety. Breath-activated devices (Salamol®) demonstrate superior pressure-independence compared to manually-activated systems (Ventolin®). Hyperbaric facilities should preferentially stock breath-activated MDIs for emergency bronchodilator therapy. These findings warrant investigation of MDI performance in other extreme pressure environments, including high-altitude and aeromedical transport settings. Clinical validation studies during actual asthma exacerbations under hyperbaric conditions are needed to confirm therapeutic adequacy. This abstract is funded by: None