title: Hypobaric hypoxia is not a direct dyspnogenic factor in healthy individuals at rest.
abstract: Dyspnea consists of various uncomfortable respiratory sensations. It is believed that hypoxia causes dyspnea, but whether hypoxia is a direct dyspnogenic factor remains uncertain. We investigated whether hypoxia has a direct dyspnogenic effect. We evaluated changes in vital signs, arterial blood gases, SaO2, CaO2, Borg scale, and Mini-Mental State Examination in seven mountain climbers by using a hypobaric hypoxic chamber in which the barometric pressure was lowered to the simulated altitude of 4500 m. PaO2 and CaO2 both decreased significantly as the simulated altitude increased. On the other hand, Borg scale score which reflects dyspnea showed no significant difference. At the simulated altitude of 4500 m, Borg scale score was 1.5 ± 1.2 (mean ± SD), despite the presence of absolute hypoxia (PaO2, 46.8 ± 8.3T; CaO2, 16.4 ± 0.6 mL/dL). These results suggest that hypoxia is not a direct dyspnogenic factor in healthy individuals capable of breathing without restriction at rest.
authors.affiliation: Division of General Thoracic Surgery, Department of Surgery, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan. Electronic address: nakanot11299119@yahoo.co.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Division of General Thoracic Surgery, Department of Surgery, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan. Electronic address: iwasaki@is.icc.u-tokai.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iwazaki
authors.affiliation: Sasao Naika, 698-5 Minamiyana, Hadano, Kanagawa 257-0003, Japan. Electronic address: gensasao@m4.dion.ne.jp.
authors.forename: Gen
authors.initials: G
authors.lastname: Sasao
authors.affiliation: Department of Pulmonary Medicine, Tokai University Tokyo Hospital, 1-2-5 Yoyogi, Shibuya, Tokyo 151-0053, Japan. Electronic address: asuka_nagai@tok.u-tokai.ac.jp.
authors.forename: Asuka
authors.initials: A
authors.lastname: Nagai
authors.affiliation: Department of Pulmonary Medicine, Tokai University Tokyo Hospital, 1-2-5 Yoyogi, Shibuya, Tokyo 151-0053, Japan. Electronic address: akinoriebihara@hotmail.com.
authors.forename: Akinori
authors.initials: A
authors.lastname: Ebihara
authors.affiliation: Department of Pulmonary Medicine, Tokai University Tokyo Hospital, 1-2-5 Yoyogi, Shibuya, Tokyo 151-0053, Japan. Electronic address: cypns833@yahoo.co.jp.
authors.forename: Tokuzen
authors.initials: T
authors.lastname: Iwamoto
authors.affiliation: Department of Pulmonary Medicine, Tokai University Tokyo Hospital, 1-2-5 Yoyogi, Shibuya, Tokyo 151-0053, Japan. Electronic address: kuwahira@tok.u-tokai.ac.jp.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kuwahira
mesh_terms: D056352:Athletes; D001274:Atmospheric Pressure; D001784:Blood Gas Analysis; D004417:Dyspnea / Q000150:complications* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology*; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D012146:Rest; D012720:Severity of Illness Index; D055815:Young Adult
keywords: Dyspnea; High altitude; Hypoxemia; Hypoxia; Hypoxic ventilatory response