Abstract
This study analyses characteristics of lung injuries produced by alveolar overdistension in three animal species. Mechanical ventilation at normal tidal volume (10 mL/Kg) and high tidal volume (50 mL/Kg) was applied for 30 min in each species. Data were gathered on wet/dry weight ratio, histological score, and area of alveolar collapse. Five out of six rabbits with high tidal volume developed tension pneumothorax, and the rabbit results were therefore not included in the histological analysis. Lungs from the pigs and rats showed minimal histological lesions. Pigs ventilated with high tidal volume had significantly greater oedema, higher neutrophil infiltration, and higher percentage area of alveolar collapse than rats ventilated with high tidal volume. We conclude that rabbits are not an appropriate species for in vivo studies of alveolar overdistension due to their fragility. Although some histological lesions are observed in pigs and rats, the lesions do not appear to be relevant.
Highlights
Mechanical ventilation-associated lung injury is a clinically accepted fact and considered one of the main factors for the worsening or persistence of acute lung injury
This type of injury has been reported in larger animals, such as pigs or sheep [7, 8], but there have been far fewer studies, and it is suspected that the intensity of injury may vary among species, with large animals being more resistant to overdistension manoeuvres than small ones [9]
This hypothesis has not been verified, but there is evidence that distinct animal species behave differently against diverse lung injuries [10], suggesting that the response to alveolar overdistension may differ among animal species
Summary
Mechanical ventilation-associated lung injury is a clinically accepted fact and considered one of the main factors for the worsening or persistence of acute lung injury. Lung injuries from alveolar overdistension have been reported by several experimental research groups, predominantly in small animals (rats) [5, 6] This type of injury has been reported in larger animals, such as pigs or sheep [7, 8], but there have been far fewer studies, and it is suspected that the intensity of injury may vary among species, with large animals being more resistant to overdistension manoeuvres than small ones [9]. It may help to establish the degree to which results can be extrapolated, from the experimental to clinical setting and from one to another species
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