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

Abstract

Objectives: The aim of the present study was to evaluate the balloon procedure to measure exhaled nitric oxide (NO). Methods: This was performed by comparing the procedure with the well-established on-line measurement of NO (direct exhalation into the NO module). Using both procedures exhaled NO was measured in 16 healthy subjects on two days with different level of air pollution. Results: Exhaled NO measured on-line was 3.8–4.5 times lower than exhaled NO obtained using the balloon technique but the two sets of values correlated linearly (r 0.93–0.97). Mean NO level on day 1 with low air pollution and day 2 with high air pollution was 6.6 and 8.1 parts per billion (ppb; on-line measurement) and 25.2 and 36.9 ppb (balloon method), respectively. 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 balloon 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 increase in level of outdoor air pollution appears to be associated with a 49–65% increase in exhaled NO. Conclusion: Exhaled NO is proposed as a de novo individual biomarker to monitor the adverse effects of air pollution. The balloon procedure offers a sound and convenient alternative for the on-line procedure to measure exhaled NO in large populations as required in epidemiological studies.