Jan Bellows, DVM, DAVDC, DABVP, FAVD
Ventilation is the process of gas exchange in and out of the lungs (i.e. bringing in oxygen and flushing out carbon dioxide). The goal of assisted ventilation is to provide adequate respiratory support, which improves oxygenation and stabilizes the plane of anesthesia. What does ventilation have to do with veterinary dentistry? Whereas in human dentistry only local anesthesia is used for most procedures, veterinary dental procedures necessarily involve general anesthesia. Paying close attention to respiration, oxygenation and carbon dioxide levels increases the safety of our anaesthetic procedures and patient wellbeing.
Inhalant and injectable anaesthetics, including opioids and alpha-2 agonists, can lead to ventilatory suppression. In the absence of capnography, respiration can be observed subjectively by watching the anesthesia bag, the patient’s chest wall and condensation in the endotracheal tube, as well as by auscultation of breath sounds.
Many patient monitoring systems default respiration readings to impedance respiration, using the indirect method of deriving respiration from the up-and-down movement of the patient’s chest via the electrocardiogram leads. This indirect method is neither accurate nor reliable. Apnea monitors with loud alarms are also helpful in alerting the veterinary team to respiratory arrest.
An elevated respiratory rate may indicate progression from a moderate to light plane of anesthesia. Digital monitoring of respiratory rate and other signs of arousal during dental procedures can help avoid bite trauma to staff, radiography sensors or plates, and even monitoring equipment (Figure 1).