Breath-ammonia testing of healthy subjects and patients with cirrhosis.

BACKGROUND: Hepatic encephalopathy (HE) is a serious neuropsychiatric complication in both acute and chronic liver disease. AIMS: To establish the utility of a portable noninvasive method to measure ammonia in the breath of healthy subjects and patients with HE. METHODS: The study included 106 subjects: 44 women and 62 men, 51 healthy and 55 cirrhotic. The breath ammonia was measured with an electrochemical sensor and expressed in parts/billion (ppb). RESULTS: The breath ammonia in healthy subjects had an average value of 151.4 ppb (95% confidence interval [CI]: 149.4-153.4) and the average value in cirrhotic patients was 169.9 ppb (95% CI: 163.5-176.2) (P < 0.0001). In cirrhotic patients with and without HE, the corresponding values were 184.1 ppb (95% CI: 167.7-200.6) and 162.9 ppb (95% CI: 158.8-167.0), respectively (P = 0.0011). Ammonia levels ≥ 165 ppb permitted a differentiation between healthy and cirrhotic subjects; the area under the receiver operating characteristic (ROC) curve for the ammonia-level values in cirrhotic versus control patients was 0.86 (95% CI: 0.79-0.93). In cirrhotic patients, ammonia levels ≥ 175 ppb permitted the distinction between patients with and without HE; the area under the ROC curve in cirrhotic patients with versus without HE was 0.83 (95% CI: 0.73-0.94). CONCLUSION: A portable sensor for measuring breath ammonia can be developed. If the results of the present study are confirmed, breath-ammonia determinations could produce a significant impact on the care of patients with cirrhosis and could even include the possibility of self-monitoring.

Electrochemical measurement of trace concentrations of biological hydrogen produced by Enterobacteriaceae.

Accurate measurements of the hydrogen gas produced by Escherichia coli and Hafnia alvei pure cultures during glucose metabolism were performed under different growth conditions: stagnant, with magnetic stirring or with vibrational shaking. These measurements were carried out using an electrochemical hydrogen sensor based on a platinum-coated solid polymer electrolyte membrane (Pt-SPE). The results obtained were dependent on the hydrodynamic conditions of the growth, with greater hydrogen production being associated with the stagnant conditions. These measurements will eventually enable us to elucidate whether the pathway used for glucose metabolism is either strictly or mainly anaerobic and to modify experimental conditions so as to influence the reaction.