The balloon technique: a convenient method to measure exhaled NO in epidemiological studies

Objectives: The aim of the present study was to evaluate the balloon proced ure to measure exhaled nitric oxide (NO). Methods: This was performed by co mparing the procedure with the well-established online measurement of NO (d irect exhalation into the NO module). Using both procedures exhaled NO was measured in 16 healthy subjects on two days with different level of air pol lution. Results: Exhaled NO measured online was 3.8-4.5 times lower than ex haled NO obtained using the balloon technique but the two sets of values co rrelated linearly (r 0.93-0.97). Mean NO level on day 1 with low air pollut ion and day 2 with high air pollution was 6.6 and 8.1 parts per billion (pp b; on-line measurement) and 25.2 and 36.9 ppb (balloon method), respectivel y. The day 1 to day 2 ratio differed per subject but was independent of the technique of measurement. Mean day-to-day ratio of exhaled NO using the ba lloon technique (1.65 +/- 0.13) was not different (P < 0.05) from the ratio of NO levels measured on-line (1.49 +/- 0.13). Based on these ratios the i ncrease in level of outdoor air pollution appears to be associated with a 4 9-65% increase in exhaled NO. Conclusion: Exhaled NO is proposed as a de no vo individual biomarker to monitor the adverse effects of air pollution. Th e balloon procedure offers a sound and convenient alternative for the on-li ne procedure to measure exhaled NO in large populations as required in epid emiological studies.