Hypoxaemia during one lung ventilation

As the name suggests, one lung ventilation (OLV) involves selectively ventilating only one of the patient's lungs. One lung ventilation is required to facilitate thoracic surgery and—less commonly—to help manage thoracic injury or disease. Cessation of ventilation to one lung creates an obligatory intrapulmonary shunt, which can lead to hypoxaemia. Indeed, hypoxaemia is one of the most common problems encountered by anaesthetists during OLV, affecting ∼5% of cases.1 Although there is no agreed definition, an arterial oxygen saturation (Sao2) <90% despite an inspired oxygen concentration (Fio2) of 1.0 is a commonly accepted standard.