Effect of caffeine ingestion on exhaled nitric oxide measurements in patients with asthma.

Abstract

Exhaled nitric oxide (FENO) measurements may be influenced by a number of confounding factors. Reports have offered conflicting evidence as to whether caffeine consumption increases or decreases FENO. In this study we aimed to confirm whether caffeine ingestion affects FENO in patients with asthma. On two separate days, 20 patients with asthma (10 steroid-naive and 10 steroid-treated) received a standard cup of either caffeinated or noncaffeinated coffee (15 g) (control) in a randomized, double-blind, cross-over manner. FENO measurements were obtained at baseline, and 30, 60, 120, and 180 minutes after ingestion. Serum caffeine levels were also measured at 0 and 60 minutes. No significant changes in FENO occurred after caffeine compared with the control. We conclude that caffeinated foods and beverages are unlikely to acutely influence FENO in subjects with asthma, and protocols for laboratory measurement do not need to take this factor into account.