SIMULTANEOUS TRACHEAL AND ESOPHAGEAL PH MEASUREMENTS IN ASTHMATIC-PATIENTS WITH GASTROESOPHAGEAL REFLUX

Background - An association between asthma and gastro-oesophageal refl ux is well recognised but the underlying mechanism is unclear. One sug gestion is that gastric juice is aspirated into the tracheal and upper airways but detection of these events is difficult and involves radio isotopic studies. A new method of making direct measurements of trache al and oesophageal pH over a 24 hour period is described, together wit h its application to patients with asthma. Methods - The technique inv olves insertion of simultaneous tracheal and oesophageal pH probes und er general anaesthesia. Continuous monitoring of pH over a 24 hour per iod is possible, permitting comparison with peak flow readings during wakefulness and at night should the patient be disturbed. Representati ve data from four patients with asthma (mean FEV(1) 62% predicted) and symptomatic gastro-oesophageal reflux, together with data from three non-asthmatics, is presented. Results - Thirty seven episodes of gastr ooesophageal reflux lasting more than five minutes were recorded. Of t hese, five were closely followed by a fall in tracheal pH from a mean (SE) of 7.1 (0.2) to 4.1 (0.4) and a fall in peak expiratory flow (PEF R) of 84 (16) 1/min. When gastrooesophageal reflux occurred without tr acheal aspiration the fall in PEFR was 8 (4) 1/min. Conclusions - This new technique was well tolerated and allowed quantitation of the numb er, duration, and timing of episodes of tracheal micro-aspiration. Unl ike acid reflux without aspiration, these events appear to be related to significant acute changes in lung function in asthmatic patients. F urther studies with this new method may elucidate the role of gastrooe sophageal reflux in asthma.