Inhalational challenge using hypertonic saline in asthmatic subjects: a comparison with responses to hyperpnoea, methacholine and water

Non-isotonic aerosols are being used increasingly for bronchial provocation testing in patients with asthma. We investigated changes in forced expiratory volume in one second (FEV1) in response to inhaling ultrasonically nebulized 4.5% saline in 10 normal subjects and 68 subjects with asthma. A comparison of the sensitivity to this challenge was made with sensitivity to challenge with methacholine, water, exercise and eucapnic voluntary hyperventilation (EVH). In normal subjects the FEV1 was reduced by 6 +/- 2% (mean +/- SD) after inhalation of 33 ml of aerosol. Eighty four percent of the asthmatic subjects exhibited a fall in FEV1 of greater than 20% after inhaling 4.5% saline. The provoking dose (geometric mean +/- 95% confidence limits) of saline to induce a 20% fall (PD20) was 2.05 ml (1.34-4.48). The sensitivity to inhaled 4.5% saline was significantly related (p less than 0.001) with responsiveness to methacholine, exercise and EVH, but not to water. Those patients recording a PD20 to 4.5% saline had a PD20 to methacholine less than 2 mumol which is a response consistent with moderate to severe bronchial hyperresponsiveness.