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Diagnosis and monitoring of asthma rely on symptoms and laboratory measurement of reversible airflow obstruction. We evaluated a new tool that may detect wheeze outside the laboratory setting. Aims To evaluate a handheld electronic tool (AirSonea ® ) developed to measure wheeze in asthma patients by comparing it to change in lung function during a mannitol challenge. Methods Patients who required an inhaled mannitol challenge for the diagnosis of asthma at a hospital respiratory laboratory were recruited. After each dose of mannitol, the tool was held against the trachea for 30 seconds to measure wheeze as a percentage of breathing time, as specified by the manufacturer. Findings 20 patients aged 19-83 years were recruited (8 females, 12 males). Average baseline FEV1 was 97±13% predicted. 5 patients had a positive mannitol challenge test, with an average fall in FEV1 of 18±2%. At maximal fall in FEV1, only 1/5 positive mannitol tests had wheeze detected by the tool, giving a false negative rate of 4/5. 10/20 subjects had false positive tests, with wheeze detected in the absence of a drop in FEV1, though percentage wheeze was low at 1-3%. Conclusions The electronic wheeze detection tool evaluated did not reliably distinguish between positive and negative mannitol tests. False negatives may relate to low frequency, short duration ( |
