Cardioespiratory physiological perturbations after acute smoke-induced lung injury and during extracorporeal membrane oxygenation support in sheep

Background: Numerous successful therapies developed for human medicine
involve animal experimentation. Animal studies that are focused solely on
translational potential, may not sufficiently document unexpected
outcomes. Considerable amounts of data from such studies could be used to
advance veterinary science. For example, sheep are increasingly being used
as models of intensive care and therefore, data arising from such models
must be published. In this study, the hypothesis is that there is little
information describing physiological data from sheep models of intensive
care and the author aimed to analyse such data to provide biological
information that is currently not available for sheep that received
extracorporeal life support (ECLS) following acute smoke-induced lung
injury. Methods: Nineteen mechanically ventilated adult ewes undergoing
intensive care during evaluation of a form of ECLS (treatment) for acute
lung injury were used to collate clinical observations. Eight sheep were
injured by acute smoke inhalation prior to treatment (injured/treated),
while another eight were not injured but treated (uninjured/treated). Two
sheep were injured but not treated (injured/untreated), while one received
room air instead of smoke as the injury and was not treated
(placebo/untreated). The data were then analysed for 11 physiological
categories and compared between the two treated groups. Results: Compared
with the baseline, treatment contributed to and exacerbated the
deterioration of pulmonary pathology by reducing lung compliance and the
arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2)
ratio. The oxygen extraction index changes mirrored those of the PaO2/FiO2
ratio. Decreasing coronary perfusion pressure predicted the severity of
cardiopulmonary injury. Conclusions: These novel observations could help
in understanding similar pathology such as that which occurs in animal
victims of smoke inhalation from house or bush fires, aspiration pneumonia
secondary to tick paralysis and in the management of the severe
coronavirus disease 2019 (COVID-19) in humans.