You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

The rate of ventilation is controlled by arterial carbon dioxide concentrations

The blood brain barrier is permeable to carbon dioxide and even a slight increase in arterial (CO₂) causes a marked decrease in pH of CSF. The CSF bathes chemoreceptors close to the ventrolateral surface of the medulla and a decrease in CSF pH stimulates an increased ventilation rate. This is a natural homeostatic mechanism designed to increase carbon dioxide excretion and increase oxygenation of blood.

This mechanism has been used to stimulate respiration in apnoeic patients under general anaesthesia by adding small amounts of CO₂ to the oxygen flow administered by endotracheal tube. However, this technique should be used with caution in patients that have :

• Acidosis - as metabolic acidosis decreases the amount of bicarbonate in CSF, and as bicarbonate normally acts as a buffer to CO₂ this effectively increases the effects of CO₂ on the CSF pH, and so magnifies the effect of CO₂ on ventilation.
• Alkalosis or are under general anaesthesia - both reduce the effects of CO₂ on CSF pH, and reduce the effect on ventilation

Indeed, carbon dioxide administration to an already hypoxic patient may actually have the reverse effect and further depress ventilation, and studies in veterinary patients have concluded that carbon dioxide concentrations are already relatively high in the blood of most anaesthetised patients, so adding more may be detrimental, and could actually precipitate ventricular fibrillation .

Updated January 2016