Background: Chlorine gas may induce severe acute lung injury. Improvement of pulmonary gas exchange in patients and animals with acute lung injury nursed in the prone position was observed in recent years. The purpose of this study was to evaluate the effects of prone and supine positions on pulmonary and cardiovascular functions following experimental chlorine gas lung injury.

Methods: Twenty anesthetized and mechanically ventilated pigs were exposed to chlorine gas (400 p.p.m. in air) for 20 min in the supine position, then assigned randomly to ventilation in the supine or prone positions (n=10 in each group). Hemodynamics, gas exchange, lung mechanics and oxygen transport were evaluated for 5 h.

Results: All animals showed severe pulmonary dysfunction immediately after chlorine gassing with a threefold increase in pulmonary vascular resistance index, a drop in arterial oxygenation (12.3±1.3 kPa to 5.4±0.7 kPa) and a fall in lung-thorax compliance (22±1 ml cmH₂O⁻¹ to 8±2 ml cmH₂O⁻¹). Venous admixture (Qs/Qt) improved in animals in the prone position while there was no change in the supine position (prone 32±11% vs. supine 42±9% at 5 h,P<0.05). Lung-thorax compliance improved significantly with time in the prone group only (P<0.01). Oxygen delivery increased significantly in prone animals compared with animals nursed in the supine posture (P<0.001).

Conclusion: Immediate prone positioning after chlorine gas injury not only inhibited deterioration of gas exchange but was also associated with improved pulmonary function and oxygen transport.

Objective: To examine the time window between injury and treatment during which nebulized corticosteroid lessens lung injury induced by chlorine gas inhalation.

Design: An experimental laboratory study.

Setting: Academic research laboratory.

Subjects: Twenty-four juvenile female pigs.

Interventions: Twenty-four mechanically ventilated pigs were exposed to chlorine gas (400 PPM in air) for 20 min, then divided into four groups (six in each group). Nebulized budesonide (BUD) was given immediately (BUD 0 min), 30 min (BUD 30 min) or 60 min (BUD 60 min) after chlorine gas exposure. Six pigs receiving nebulized saline served as controls.

Measurements and main results: Hemodynamics, gas exchange and lung mechanics were evaluated for 5 h after chlorine gas exposure. All animals had an immediate increase in airway and pulmonary artery pressure and a sharp drop of arterial oxygenation. The mean arterial oxygen tension of BUD 0 min and BUD 30 min animals was significantly higher than in the control and the BUD 60 min groups (p<0.001). The recovery of lung compliance in the BUD 0 min and the BUD 30 min groups was significantly more rapid than in the control and the BUD 60 min groups (p<0.001). The pulmonary wet to dry weight ratio was greater in the control group than in the BUD-treated groups (p<0.05).

Conclusion: Treatment with inhaled budesonide immediately or 30 min after chlorine gas lung injury had similar positive effects on symptoms and signs of pulmonary injury, whereas treatment delayed for 60 min was less effective.