Exhaled nitric oxide in mylar balloons: influence of storage time, humidity and temperature.

BACKGROUND Mylar balloons are used to collect exhaled air for analysis of fractional nitric oxide concentration (FENO). AIM We studied the effect of storage conditions on the stability of nitric oxide (NO) in mylar balloons. METHODS Exhaled air samples and calibration gases were stored in mylar balloons at 4, 21 and 37 degrees C, with or without silica gel. NO was measured after 0, 6, 9, 24 and 48 h. Scheffe F-tests were used to compare NO values. RESULTS NO remained stable in balloons for 9 h at all temperatures, without silica gel. NO increased between 9 and 48 h, but only with low initial FENO. Silica gel increased variability. CONCLUSIONS FENO in mylar balloons is stable for at least 9 h. The storage temperature is not critical, but silica gel increases variability.