MEASUREMENT OF THE EXPIRATORY AMMONIA CONCENTRATION AND ITS CLINICAL-SIGNIFICANCE

Although gaseous ammonia (NH3) can freely enter cells through the plas ma membrane where NH3 is cyto(neuro)toxic, NH3 and ionic ammonia (NH4) contents have not been studied in biological materials. We developed a new method for measurement of expiratory NH3 concentration, which m ay reflect blood NH3 concentrations. The method is a sensor tube type- gas assay system. Expiratory NH3 concentration in patients with chroni c liver diseases increased when their blood ammonia (NH4+ + NH3) conce ntrations increased above 90 mu g/dl (normal range; 12-66 mu g/dl). Ho wever, cirrhotic patients, who had relatively higher expiratory NH3 co ncentration compared to blood NH, concentrations (calculated from Hend erson-Hasselbalch formula), were found to have subclinical encephalopa thy. Measurement of expiratory NH3 concentration may be of clinical si gnificance for the diagnosis of encephalopathy associated with hyperam monemia.