Continuous tracheal gas insufflation during protective mechanical ventilation in juvenile piglets with acute lung injury induced by endotoxin

Abstract

Background: Low tidal volume mechanical ventilation is difficult to correct hypoxemia, and prolonged inhalation of pure oxygen can lead to oxygen poisoning. We suggest that continuous tracheal gas insufflation (TGI) during protective mechanical ventilation could improve cardiopulmonary function in acute lung injury.

Methods: Totally 12 healthy juvenile piglets were anesthetized and mechanically ventilated at PEEP of 2 cmH2O with a peak inspiratory pressure of 10 cmH2O. The piglets were challenged with lipopolysaccharide and randomly assigned into two groups (n=6 each group): mechanical ventilation (MV) alone and TGI with continuous airway flow 2 l/min. FIO2 was set at 0.4 to avoid oxygen toxicity and continuously monitored with an oxygen analyzer.

Results: Tidal volume, ventilation efficacy index and mean airway resistant pressure were significantly improved in the TGI group (P<0.01 or P<0.05). At 4 hours post ALI, pH decreased to below 7.20 in the MV group, and improved in the TGI group (P<0.01). Similarly, PaCO2 was stable and was significantly lower in the TGI group than in the MV group (P<0.01). PaO2 and PaO2/FIO2 increased also in the TGI group (P<0.05). There was no significant difference in heart rate, respiratory rate, mean artery pressure, central venous pressure, dynamic lung compliance and mean resistance of airway between the two groups. Lung histological examination showed reduced inflammation, reduced intra-alveolar and interstitial patchy hemorrhage, and homogenously expanded lungs in the TGI group.

Conclusion: Continuous TGI during MV can significantly improve gas exchange and ventilation efficacy and may provide a better treatment for acute lung injury.

Keywords: Acute lung injury; Lung protective strategy; Mechanical ventilation; Tracheal gas insufflation.

Figure 1

Typical photomicrographs (original magnification ×100) of lung sections stained with hematoxylin and eosin for both TGI and MV groups 4 hours after injury: A: dependent region for MV; B: non-dependent region for MV; C:dependent region for TGI; D: non-dependent region for TGI. The damage in both dependent and non-dependent sites was significantly reduced after TGI.

Figure 2

Regional lung injury scores for mechanical ventilation (MV) and continuous tracheal gas insufflation (TGI). Values are expressed as mean±SD. *P<0.05 versus the MV group.