title: CO2 retention in lung disease; could there be a pre-existing difference in respiratory physiology.
abstract: Some patients with lung disease retain CO(2), while others with similar lung function do not. This could be explained if CO(2) retainers had a pre-existing low hypercapnic ventilatory response (HCVR) and, from this, a tendency to retain CO(2). To test if such a phenomenon exists in healthy people, we determined the change in end-tidal P(CO(2)) (deltaPET(CO(2))) produced by the addition of a dead-space (DS), during wakefulness and sleep, and related this to the HCVR measured awake. The group mean (n=14) HCVR slope was 2.2+/-1.1 (S.D.) L min(-1) mmHg(-1). The deltaPET(CO(2)) with the application of DS was 1.6+/-1.6 mmHg awake and 2.6+/-2.2 mmHg asleep. During wakefulness the deltaPET(CO(2)) with DS did not correlate with the HCVR slope. However, during sleep, four subjects had a marked increase in the deltaPET(CO(2)) (3.7, 4.3, 6.2, 8.0 mmHg) and a relatively low HCVR (slope 1.5, 1.7, 1.5, 1.7 L min(-1) mmHg(-1), respectively). We speculate that such individuals, should they develop lung disease, may be predisposed to retain CO(2).
authors.affiliation: Department of Respiratory Medicine, National Heart and Lung Institute, Imperial College School of Medicine, Charing Cross Campus, St. Dunstans Road, W6 8RP, London, UK.
authors.forename: Helen M A
authors.initials: HM
authors.lastname: Dunroy
authors.forename: Lewis
authors.initials: L
authors.lastname: Adams
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Corfield
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Morrell
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000378:metabolism*; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D007399:Interphase / Q000502:physiology; D008171:Lung Diseases / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D010313:Partial Pressure; D012143:Respiratory Physiological Phenomena; D012890:Sleep / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
chemical_list: D002245:Carbon Dioxide