Respiratory system Respiratory system

Age-related degenerative changes progressively decrease pulmonary function and physical changes occur in the lungs and chest wall. There is reduced alveolar surface area and diffusion capacity, pulmonary fibrosis, reduced lung elasticity, and reduced mechanical ventilation reserve. Chronic obstructive lung disease is common in old dogs and cats.

All of these changes impair gaseous exchange during anaesthesia hence oxygen supplementation is beneficial, and in some cases the use of bronchodilators may be indicated.

Impaired laryngeal function (sometimes laryngeal paralysis in older dogs - particularly Labrador retrievers) and increased respiratory dead space necessitate correct endotracheal intubation during anaesthesia and careful preparation of the patient to avoid vomiting. The use of antiemetic drugs (e.g. metoclopramide) might be indicated in patients requiring emergency surgical treatment, those with oesophageal or gastric motility problems or

those with conditions likely to cause nausea (e.g. uraemia). A recent study suggests that older animals have a greater risk of developing gastro-oesophageal reflux during anaesthesia.

Pulmonary embolism is a common postoperative complication in old people, and may be more common than is currently appreciated in veterinary patients. In human general surgery patients the incidence of deep vein thrombosis is reported to be as high as 45% in those aged over 40, and 65% in patients over 71 (Consensus Conference 1986; Borow and Goldson 1981).