Influence of elevated abdominal pressure (EAP) on lung mechanics and gas exchange during PCV with and without spontaneous breathing

Introduction

EAP may lead to compromise of chest wall mechanics and worsening of lung mechanics and gas exchange. Temporary relief may further lead to reperfusion injury. We investigated the effects of EAP and reperfusion injury on respiratory system mechanics and gas exchange under pressure controlled ventilation (PCV) without and with spontaneous breathing.

Methods

In a porcine model, EAP was set to 30 cmH₂O by CO₂ insufflation twice for 9 hours each, with a pressure relief of 3 hours between and at the end. Anesthetised pigs (46.3 ± 3.3 kg) received PCV (n = 10) or biphasic positive airway pressure (BIPAP) (n = 10) with positive end expiratory pressure of 5 cmH₂O, allowing up to 20% spontaneous of total ventilation, and were randomly assigned to the control group (n = 4) without EAP or the EAP group (n = 6) in each mode. Measurements of lung mechanics and gas exchange were performed every 2 hours.

Results

In the control group, no changes were observed with time or between modes. For results of the EAP group see Table 1. During the second EAP phase lung mechanics deteriorated further, and returned to baseline value after pressure relief only with BIPAP. In both modes, oxygenation after the last pressure relief was worse than baseline.

Table 1

Conclusion

An EAP applied twice for 9 hours each worsened the chest wall and lung mechanics and impaired gas exchange regardless of the ventilation mode. These changes were not completely reversed after pressure relief. If spontaneous breathing was present during BIPAP, there was less impairment of lung compliance and oxygen delivery, but this did not lead to differences in gas exchange.