Pulmonary function testing
Before a procedure, all patients with clinical evidence of respiratory impairment should have pulmonary function tests such as spirometry and pulse oximetry. Consider measuring diffusing capacity of the lung for carbon monoxide (DLCO) in patients with abnormal spirometry and oxygen saturation levels, and also in high-risk patients and patients undergoing high-risk procedures. If these tests cannot be performed because the patient is physically or developmentally disabled, perform thorough clinical examination, chest X-ray, and blood tests to assess for hypercapnia (partial pressure of carbon dioxide in arterial blood [PaCO2] more than 45 mmHg or serum bicarbonate concentration 27 mmol/L or more) and polycythaemia; monitor patients carefully after the procedure.
For patients using oxygen therapy, monitor for and prevent hyperoxaemia; see Principles of oxygen therapy and Potential harms of oxygen therapy for considerations in oxygen therapy.
Patients with any of the following have a very limited respiratory reserve and need expert preprocedural assessment:
- forced expiratory volume in 1 second (FEV1) less than 60% of predicted
- DLCO less than 60% of predicted
- PaCO2 higher than 45 mmHg
- moderate or severe pulmonary hypertension
- oxygen saturation measured by pulse oximetry (SpO2) 90% or less on room air
- a requirement for long-term domiciliary oxygen therapy or noninvasive ventilation.
Patients with untreated obstructive sleep apnoea or obesity hypoventilation syndrome need expert assessment if a procedure cannot be delayed until adequate treatment is in place.
In some cases, additional physiological investigations, including cardiopulmonary cycle exercise testing (VO2 max) and electrocardiogram (ECG), are performed before procedures involving general anaesthesia.
Lobectomy is associated with a low risk of postprocedural complications if DLCO is greater than 60% of predicted, but risk is usually considered high if VO2 max is less than 15 mL/min/kg.