Role of the oesophagus in asthma induced by the ingestion of ice and acid.

Twelve Asian patients with a history of asthma exacerbated by ingestion of ice and acidic drinks were selected for study. To determine the site of response to ingested ice and acid they were challenged with ice or dilute hydrochloric acid, which was orally retained on one day and swallowed on another. On a third day a placebo was given. The airway response was assessed by measuring FEV1 and the provocative concentration of histamine that reduced the FEV1 by at least 20% (PC20). There was no significant change in FEV1 or histamine PC20 after placebo or the orally retained challenges for the group as a whole or for any individual. After the ice and hydrochloric acid had been swallowed there was a small but statistically significant mean fall in FEV1, increasing to a maximum 90 minutes after ingestion, together with a significant increase in bronchial responsiveness. As conditioning of the inspired air would have been similar after orally retained and after swallowed ice or acid, the response is likely to be due to oesophageal stimulation. The mechanism of the response to oesophageal stimulation is unclear, but the slow time course seems to preclude a simple neural reflex.