Respiratory tract

Intranasal oxygen insufflation is indicated in any horse or foal showing signs of respiratory distress associated with the LRT or following acute upper airway occlusive events. Administering humidified nasal oxygen at flow rates between 5 and 30 liters/minute improves arterial oxygen tension in horses with severe respiratory compromise. Flow rates of 30 liters/minute (delivered by two nasal cannulae at 15 liters/minute) are associated with coughing and gagging in the horse. Transtracheal catheters have been used in both foals and adults to further increase FIO2. Nasal oxygen supplementation does not necessarily reduce breathing frequency, suggesting that stimulation of vagally-mediated afferents (perhaps responding to inflammatory mediators) is responsible for tachypnea.