Factors that may affect exhaled nitric oxide

Factors that increase FE_NO	Factors that decrease FE_NO
Age over 12 years	Alcohol, caffeine ingestion
Asthma	Bronchiectasis
Atopy	Cigarette smoking, environmental tobacco smoke
Drugs	Chemical exposure
Enalapril	Water vapor
Exacerbation of COPD	Nitrous oxide
Air pollution exposure	Heptane
Ingestion of arginine or nitrite/nitrate rich foods	100 percent oxygen
Chemical exposure	Drugs
Chlorine dioxide	Antileukotriene agents
Fluoride	Glucocorticoids
Formaldehyde	Oxymetazoline
Latex	NOS inhibitors
Ozone	Exercise
Nonasthmatic eosinophilic bronchitis	Hypothermia
Upper respiratory tract infections	Menses
	Moderate altitude
	Repeated spirometry
	Sputum induction

FE_NO: fractional exhaled nitric oxide; COPD: chronic obstructive pulmonary disease; NOS: nitric oxide synthase.

Adapted from: Kharitonov SA, Barnes PJ. Exhaled markers of pulmonary disease. Am J Respir Crit Care Med 2001; 163:1693.

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