Effects of prone and supine position on oxygenation and inflammatory mediator in a hydrochloric acid-induced lung dysfunction in rats

Abstract

Purpose:To compare the effectiveness of mechanical ventilation of supine versus prone position in hydrochloric acid (HCl)-induced lung dysfunction. Methods: Twenty, adult, male, Wistar-EPM-1 rats were anesthetized and randomly grouped (n=5 animals per group) as follows: CS-MV (mechanical ventilation in supine position); CP-MV (mechanical ventilation in prone position); bilateral instillation of HCl and mechanical ventilation in supine position (HCl+S); and bilateral instillation of HCl and mechanical ventilation in prone position (HCl+P). All groups were ventilated for 180 minutes. The blood partial pressures of oxygen and carbon dioxide were measured in the time points 0 (zero; 10 minutes before lung injury for stabilization), and at the end of times acid injury, 60, 120 and 180 minutes of mechanical ventilation. At the end of experiment the animals were euthanized, and bronchoalveolar lavages (BALs) were taken to determine the contents of total proteins, inflammatory mediators, and lungs wet-to-dry ratios. Results: In the HCl+P group the partial pressure of oxygen increased when compared with HCl+S (128.0±2.9 mmHg and 111.0±6.7 mmHg, respectively) within 60 minutes. TNF-α levels in BAL do not differ significantly in the HCl+P group (516.0±5.9 pg/mL), and the HCl+S (513.0±10.6 pg/mL). Conclusion:The use of prone position improved oxygenation, but did not reduce TNF-α in BAL upon lung dysfunction induced by HCl. Key words: Lung. Respiration, Artificial. Oxygenation. Inflammation Mediators. Rats. RESUMO Objetivo:Comparar os efeitos da ventilação mecânica em posição prona versus supina na disfunção pulmonar induzida por ácido clorídrico (HCl). Métodos: Vinte ratos, adultos, Wistar-EPM-1 foram anestesiados e distribuídos aleatoriamente em grupos (n=5 animais por grupo): CS-MV (controle, ventilado mecanicamente em posição supina); CP-MV (controle, ventilado mecanicamente em posição prona); instilação bilateral de HCl e ventilação mecânica em posição supina (HCl+S) ou ventilação em posição prona (HCl+P). Todos os grupos foram submetidos a ventilação mecânica por 180 minutos. As pressões parciais de oxigênio e dióxido de carbono no sangue arterial foram mensuradas nos tempos Injúria ácida (10 minutos após instilação de HCl), e ao final de cada período após lesão por HCl, 60, 120 e 180 minutos sob ventilação mecânica. Ao final do experimento os animais foram eutanasiados, os pulmões retirados para avaliação do peso úmido em relação ao peso seco do pulmão direito e realizamos o lavado broncoalveolar (BAL) para determinação de proteínas totais e o mediador inflamatório TNF-α. Resultados: No grupo HCl+P a pressão parcial de oxigênio, no tempo de 60 minutos, aumentou quando comparada com o grupo HCl+S (128.0±2.9 e 111.0±6.7 mmHg, respectivamente). Os níveis de TNF-α no lavado broncoalveolar não diferiram de maneira estatisticamente significante quando comparamos os grupos HCl+S (513.0±10.6 pg/mL) versus HCl+P (516.0±5.9 pg/mL). Conclusão: O uso da posição prona melhora a oxigenação, mas não reduz os níveis de BAL ...

Efeitos agudos da ventilação mecânica com hiperoxia na morfometria do diafragma de ratos

“…Thirdly, as the MV is used to reduce the work of the diaphragm, it becomes a cause of muscle deconditioning. According to Oliveira et al 20 , there was an increase in inflammatory mediators analyzed after 60, 120 and 180 minutes from the time of lung injury produced with hydrochloric acid in rats undergoing MV, which shows an early pro-inflammatory response that has been demonstrated in the pathogenesis of several models which are neutrophils mediated. In the experimental evaluation of the acute effects of MV with hyperoxia in the rat diaphragm, there was an increase in tissue vascularization and in the variation of the cross-sectional muscle diameter.…”

Immediate Prone Positioning After Massive Gastric Aspiration Reduces Lung Injury Possibly by Attenuating Interleukin-6-Mediated Lung-Tissue Inflammation in Pigs

“…In an experimental study using a model of mild extrapulmonary ARDS, Bianchi and colleagues (2016) found that ventilation with patients in the PP led to infiltration of fewer neutrophils in the interstitial space compared with ventilation in the supine position (SP) and was also associated with less severe inflammation and lung injury. Several animal studies have shown that the PP can reduce the lung injury induced by aspiration of hydrochloric acid (Oliveira et al, 2008;Yagui & Beppu, 2007). Easby, Abraham, Bonner, and Graham (2003) observed patients with respiratory failure secondary to witnessed aspiration and found that oxygenation could be improved after turning patients to the PP.…”