Table 2.

Search strategy on Medline via OvidSP

#	Searches	Results
1	(‘10712994’ or ‘10907593’ or ‘11296168’ or ‘11413349’ or ‘15817806’ or ‘15939243’ or ‘16289590’ or ‘16646959’ or ‘17426212’ or ‘18460522’ or ‘18547853’ or ‘19124359’ or ‘19401794’ or ‘19820080’ or ‘19881162’ or ‘20210889’ or ‘21143751’ or ‘21530214’ or ‘23445725’ or ‘23509896’ or ‘23681903’ or ‘23989961’ or ‘24013942’ or ‘24719850’ or ‘24929061’ or ‘25053884’ or ‘26252571’ or ‘26372312’ or ‘26491283’ or ‘26496331’ or ‘26497109’ or ‘26814886’ or ‘26916083’ or ‘26952317’ or ‘27142135’ or ‘27209003’).ui.	36
2	exp Pulmonary Disease, Chronic Obstructive/	43 308
3	Lung Diseases, Obstructive/	18 072
4	exp Pulmonary Emphysema/	14 866
5	(obstructive adj2 (pulmonary or (obstructive adj2 (pulmonary or lung$ or respirat$ or air$)).tw,kf.	44 058
6	(chronic air$ adj2 (obstruction$ or limitation$ or occlusion$)).tw,kf.	1428
7	(chronic bronch$ adj2 (obstruction$ or limitation$ or occlusion$)).tw,kf.	95
8	(chronic$ adj2 bronch$).tw,kf.	12 908
9	COPD.tw,kf.	32 628
10	COAD.tw,kf.	222
11	emphysema$.tw,kf.	24 011
12	(acos and asthm*).tw,kf.	86
13	or/2–12	99 543
14	Nitric Oxide/	78 284
15	(feno and (fraction* or exhal* or nitric)).tw,kf.	1099
16	(fe no and (fraction* or exhal* or nitric)).tw,kf.	401
17	nitric oxid*.tw,kf.	126 245
18	or/14–17	140 975
19	13 and 18	750
20	1 and 19	32
21	1 not 20	4