Table 2.

Factors that may perturb FeNO measurements.

FRACTION OF EXHALED NITRIC OXIDE (FENO) AND INTERFERRAL FACTORS
INCREASED FeNO	DECREASED FeNO	STUDIES
Drug intake:	Drug intake:	Sumino H, et al [35], Holden WE, et al [36], Runer T, et al [37], Sippel JM, et al [38], Yates DH, et al [39]
(i) ACE inhibitors [35];	(i) Oxymetazoline [38];
(ii) Papaverin [36];	(ii) NOS inhibitors [39];
(iii) Sodium nitroprusside [37].
Food and Beverages:	Food and Beverages:	McKnight GM, et al [40], Tenero L, et al [41]
(i) Nitrite/Nitrate-enriched  food [40];	(i) Curcumin and Resveratrol [41]
(ii) Arginine ingestion [40].
Environmental factors:	Environmental factors:	Binding N, et al [42], Franklin P, et al. [43], Nightingale JA, et al [44]
(i) NO in air [42];	(i) Calibration of FeNO analyser [42];
(ii) Calibration of FeNO analyser [43];
(iii) Occupational exposure to ozone, chlorine dioxide,    formaldehyde [44];
Physiological and pathological conditions and tests:	Physiological and pathological conditions and tests:	Kharitonov SA, et al [45], Liu PF, et al [46], Chen FJ, et al [47], Uppalapati A, et al [48], Song WJ, et al [49], Xu X, et al [50], Yates DH, et al [51], Dimov PK, et al [52], Deykin A, et al [53], Piacentini A, et al [54], Pendergast DR, et al [55], Phillips CR, et al [56], Kharitonov SA, et al [57], Tang S, et al [58], Murri V, et al [59]
(i) Airway Infections [45];	(i) Tabagism [50];
(ii) Lung neoplasia [46];	(ii) Alcohol ingestion [51];
(iii) COPD [47];	(iii) Chronic hypoxia [52];
(iv) Asthma [47];	(iv) Spirometry [53];
(v) Systemic inflammatory conditions [48];	(v) Sputum induction [54];
(vi) Chronic cough [49].	(vi) Hypothermia [55];
	(vii) Hyperventilation [53];
	(viii) Physical exercise [56];
	(ix) Menstrual cycle [57];
	(x) Childhood [58];
	(xi) Female gender [59].
Sickle anemia [60], circadian rhythm [61], and pregnancy [62] are actually under consideration		Cohen RT, et al [60], Saito J, et al [61], Nittner-Marszalska M, et al [62]