The citric acid cough threshold and the ventilatory response to carbon dioxide on ascent to high altitude.
Ventilatory control undergoes profound changes on ascent to high altitude. We hypothesized that the fall in citric acid cough threshold seen on ascent to altitude is mediated by changes in the central control of cough and would parallel changes in central ventilatory control assessed by the hypercapnic ventilatory response (HCVR). Twenty-five healthy volunteers underwent measurements of HCVR and citric acid sensitivity at sea level and during a 9 day sojourn at 5200m. None of the subjects had any evidence of respiratory infection. Citric acid cough threshold fell significantly on ascent to 5200m. The slope, S, of the HCVR increased significantly on ascent to 5200m and during the stay at altitude. There was no correlation between citric acid sensitivity and HCVR. We conclude that the change in citric acid cough threshold seen on exposure to hypobaric hypoxia is unlikely to be mediated by changes in the central control of cough. Sensitivity to citric acid may be due to early subclinical pulmonary edema stimulating airway sensory nerve endings.
Thompson
A A Roger
AA
Academic Unit of Respiratory Medicine, University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK. r.thompson@sheffield.ac.uk
Baillie
J Kenneth
JK
Bates
Matthew G D
MG
Schnopp
Martin F
MF
Simpson
Alistair
A
Partridge
Roland W
RW
Drummond
Gordon B
GB
Mason
Nicholas P
NP
D000293:Adolescent; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000378:metabolism / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000378:metabolism* / Q000502:physiology; D019343:Citric Acid / Q000008:administration & dosage*; D003080:Cold Temperature; D003371:Cough / Q000209:etiology* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006813:Humidity; D006935:Hypercapnia / Q000378:metabolism / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010366:Peak Expiratory Flow Rate; D012016:Reference Values; D012684:Sensory Thresholds / Q000502:physiology; D055815:Young Adult
D002245:Carbon Dioxide; D019343:Citric Acid