Background

In non-traumatic respiratory failure, pre-hospital application of CPAP reduces the need for intubation. Primary blast lung injury (PBLI) accompanied by haemorrhagic shock is common after mass casualty incidents. We hypothesised that pre-hospital CPAP is also beneficial after PBLI accompanied by haemorrhagic shock.

Methods

We performed a computer-based simulation of the cardiopulmonary response to PBLI followed by haemorrhage, calibrated from published controlled porcine experiments exploring blast injury and haemorrhagic shock. The effect of different CPAP levels was simulated in three in silico patients who had sustained mild, moderate, or severe PBLI (10%, 25%, 50% contusion of the total lung) plus haemorrhagic shock. The primary outcome was arterial partial pressure of oxygen (Pao₂) at the end of each simulation.

Results

In mild blast lung injury, 5 cm H₂O ambient-air CPAP increased Pao₂ from 10.6 to 12.6 kPa. Higher CPAP did not further improve Pao₂. In moderate blast lung injury, 10 cm H₂O CPAP produced a larger increase in Pao₂ (from 8.5 to 11.1 kPa), but 15 cm H₂O CPAP produced no further benefit. In severe blast lung injury, 5 cm H₂O CPAP inceased Pao₂ from 4.06 to 8.39 kPa. Further increasing CPAP to 10–15 cm H₂O reduced Pao₂ (7.99 and 7.90 kPa, respectively) as a result of haemodynamic impairment resulting from increased intrathoracic pressures.

Conclusions

Our modelling study suggests that ambient air 5 cm H₂O CPAP may benefit casualties suffering from blast lung injury, even with severe haemorrhagic shock. However, higher CPAP levels beyond 10 cm H₂O after severe lung injury reduced oxygen delivery as a result of haemodynamic impairment.

中文翻译：

---

爆炸性肺损伤和低血容量性休克后的院前持续气道正压通气：一项建模研究

背景

在非创伤性呼吸衰竭中，院前应用 CPAP 可减少插管的需要。大规模伤亡事件后，伴有失血性休克的原发性爆炸性肺损伤 (PBLI) 很常见。我们假设院前 CPAP 在伴有失血性休克的 PBLI 后也是有益的。

方法

我们对 PBLI 后出血的心肺反应进行了基于计算机的模拟，根据已发表的探索爆炸损伤和失血性休克的受控猪实验进行校准。在三名患有轻度、中度或重度 PBLI（全肺挫伤 10%、25%、50%）加失血性休克的计算机模拟患者中模拟了不同 CPAP 水平的影响。主要结果是每次模拟结束时的动脉氧分压 ( P a o _{2 )。}

结果

在轻度爆炸性肺损伤中，5 cm H ₂ O 环境空气 CPAP 使P a o ₂从 10.6 kPa 增加到 12.6 kPa。较高的 CPAP 并没有进一步改善P a o ₂。在中度爆炸性肺损伤中，10 cm H ₂ O CPAP 产生更大的P a o ₂增加（从 8.5 到 11.1 kPa），但 15 cm H ₂ O CPAP 没有产生进一步的益处。在严重的爆炸性肺损伤中，5 cm H ₂ O CPAP使P a o ₂从 4.06 kPa 增加到 8.39 kPa。进一步增加 CPAP 至 10–15 cm H ₂ O 降低P a o₂（分别为 7.99 和 7.90 kPa）由于胸内压增加导致的血流动力学障碍。

结论

我们的模型研究表明，环境空气 5 cm H ₂ O CPAP 可能会使遭受爆炸性肺损伤的伤员受益，即使是严重的失血性休克。然而，严重肺损伤后超过 10 cm H ₂ O 的较高 CPAP 水平会由于血流动力学障碍而减少氧气输送。