Arterial blood gas parameters of normal foals born at 1500 metres elevation

Reasons for performing study: Arterial blood gas analysis is widely accepted as a diagnostic tool to assess respiratory function in neonates. To the authors' knowledge, there are no published reports of arterial blood gas parameters in normal neonatal foals at altitude. Objective: To provide information on arterial blood gas parameters of normal foals born at 1500 m elevation (Fort Collins, Colorado) in the first 48 h post partum. Hypothesis: Foals born at 1500 m will have lower PaO2 and PaCO2 than foals born at sea level due to low inspired oxygen and compensatory hyperventilation occurring at altitude. Methods: Sixteen foals were studied. Arterial blood gas analysis was performed within 1 h of foaling and subsequent samples were evaluated at 3, 6, 12, 24 and 48 h post partum. Data were compared to those previously reported in healthy foals born near sea level. Results: Mean PaO2 was 53.0 mmHg (7.06 kPa) within 1 h of foaling, rising to 67.5 mmHg (9.00 kPa) at 48 h post partum. PaCO2 was 44.1 mmHg (5.88 kPa) within one hour of foaling, falling to 38.3 mmHg (5.11 kPa) at 48 h. Both PaO2 and PaCO2 were significantly lower in foals born at 1500 m elevation than those near sea level at several time points during the first 48 h. Conclusions and potential relevance: Foals at 1500 m elevation undergo hypobaric hypoxia and compensatory hyperventilation in the first 48 h. Altitude specific normal arterial blood values are an important reference for veterinarians providing critical care to equine neonates.