Lung function in adult idiopathic scoliosis: a 20 year follow up.

Severe idiopathic scoliosis may lead to respiratory failure, which can be treated by assisted ventilation. Twenty four patients with surgically untreated idiopathic scoliosis who had been examined in 1968 were re-examined in 1988 to assess changes in lung function and risk factors for respiratory failure. The patients were aged 15-67 years in 1968 and had a scoliotic angle of 10-190 degrees and a vital capacity of 1.0-6.0 litres. Spirometric values and scoliotic angles were determined in 1968 and 1988, and arterial blood gas tensions in 1988. The decline in spirometric values over the 20 years was of the same magnitude as the predicted decline due to aging. Arterial blood gas tensions in 1988 were strongly correlated with the scoliotic angles and spirometric indices recorded in 1968. Hypoxaemia and hypercapnia was seen in four patients in 1988 (then aged 43-67 years) and these were the four patients who had a vital capacity below 43% predicted in 1968. The remaining 20 patients had blood gas values within normal limits. Two further patients had died from respiratory failure before 1988, so a total of six patients had developed respiratory failure. In a multiple logistic analysis vital capacity expressed as % predicted in 1968 was the strongest predictor of the development of respiratory failure, followed by the scoliotic angle. Respiratory failure occurred only in patients who had a vital capacity below 45% predicted in 1968 and an angle greater than 110 degrees. Thus respiratory failure develops in adults with scoliosis with a large angle and a low vital capacity when normal aging reduces the ventilatory capacity further. Such individuals merit close follow up.