Effects of Non-invasive Ventilation on Respiratory Function and Lung Volume in Foals

Abstract: Background – Respiratory disease and prolonged recumbency impair ventilation in foals due to lung collapse. Non-invasive ventilation (NIV) is used in many intensive care settings, and may offer improved respiratory support to foals.

Hypothesis/Objectives – NIV using pressure support mode with increasing positive end-expiratory pressure (PEEP) would be associated with improved respiratory function in sedated recumbent foals.

Animals – Six healthy foals from a university teaching herd.

Methods – A prospective, randomised cross-over study evaluated NIV in sedated foals with low (2 and 4 cmH₂O) and high PEEP (4, 7 and 10 cmH₂O) protocols. Spirometry and arterial blood gas analysis were used to assess respiratory function and gas exchange, respectively. Physiological dead space (VD_phys) and volume of CO₂ exhaled per breath (VCO₂/br) were determined using volumetric capnography. Pulmonary aeration and lung volume were determined by computer tomography.

Results – NIV was associated with decreased respiratory rate and increased tidal volume (both P< 0.001); no change was observed in VD_phys. Arterial oxygenation increased (P=0.011) with higher PEEP values, and no changes in carbon dioxide partial pressures were observed. VCO₂/br, pulmonary aeration and lung volume increased in a dose-dependent manner with higher PEEP settings.

Conclusions and clinical importance – NIV at high PEEP levels improved respiratory function in sedated foals, increased ventilated lung area and enhanced CO₂ elimination per breath without alveolar overdistension. NIV should be considered for respiratory support of neonates with impaired respiratory function.