Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans.
Almost all studies of the effects of prolonged hypoxia on ventilation (VE) in humans have been performed with the end-tidal PCO2 (PETCO2) left uncontrolled. The purpose of this study was to compare the effects of 8 h of hypoxia with PETCO2 held constant with 8 h of hypoxia with PETCO2 left uncontrol...
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| Format: | Journal article |
| Language: | English |
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1995
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| _version_ | 1826284822034644992 |
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| author | Howard, L Robbins, P |
| author_facet | Howard, L Robbins, P |
| author_sort | Howard, L |
| collection | OXFORD |
| description | Almost all studies of the effects of prolonged hypoxia on ventilation (VE) in humans have been performed with the end-tidal PCO2 (PETCO2) left uncontrolled. The purpose of this study was to compare the effects of 8 h of hypoxia with PETCO2 held constant with 8 h of hypoxia with PETCO2 left uncontrolled. Ten subjects completed the study. Each was seated inside a chamber in which the inspired gas could be controlled so as to maintain the desired partial pressures of end-tidal gases (sampled via nasal catheter) constant (see L.S.G.E. Howard et al. J. Appl. Physiol. 78:1088-1091, 1995.). Three 8-h protocols were employed: 1) isocapnic hypoxia, at an end-tidal PO2 of 55 Torr with PETCO2 held at the subject's resting value; 2) poikilocapnic hypoxia, at the same end-tidal PO2; and 3) control, where the inspired gas was air. VE was measured (over 3 min) at 0 and 20 min and at hourly intervals between 1.5 and 7.5 h. There was a rise in VE during isocapnic hypoxia [from an initial VE of 16.2 +/- 1.3 (SE) l/min to a final VE of 24.8 +/- 1.6 l/min], which was significant compared with poikilocapnic hypoxia and control values (P < 0.001, analysis of variance). There was no significant progressive rise in VE during poikilocapnic hypoxia compared with control values. These results show that isocapnic hypoxia produces a progressive increase in VE when sustained over an 8-h period. The onset of this response is faster than has been noted in studies of the progressive rise in VE associated with the poikilocapnic hypoxia of altitude. |
| first_indexed | 2024-03-07T01:19:36Z |
| format | Journal article |
| id | oxford-uuid:8fe32c34-e754-4d03-8201-008fd2e77d0c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:19:36Z |
| publishDate | 1995 |
| record_format | dspace |
| spelling | oxford-uuid:8fe32c34-e754-4d03-8201-008fd2e77d0c2022-03-26T23:07:30ZVentilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:8fe32c34-e754-4d03-8201-008fd2e77d0cEnglishSymplectic Elements at Oxford1995Howard, LRobbins, PAlmost all studies of the effects of prolonged hypoxia on ventilation (VE) in humans have been performed with the end-tidal PCO2 (PETCO2) left uncontrolled. The purpose of this study was to compare the effects of 8 h of hypoxia with PETCO2 held constant with 8 h of hypoxia with PETCO2 left uncontrolled. Ten subjects completed the study. Each was seated inside a chamber in which the inspired gas could be controlled so as to maintain the desired partial pressures of end-tidal gases (sampled via nasal catheter) constant (see L.S.G.E. Howard et al. J. Appl. Physiol. 78:1088-1091, 1995.). Three 8-h protocols were employed: 1) isocapnic hypoxia, at an end-tidal PO2 of 55 Torr with PETCO2 held at the subject's resting value; 2) poikilocapnic hypoxia, at the same end-tidal PO2; and 3) control, where the inspired gas was air. VE was measured (over 3 min) at 0 and 20 min and at hourly intervals between 1.5 and 7.5 h. There was a rise in VE during isocapnic hypoxia [from an initial VE of 16.2 +/- 1.3 (SE) l/min to a final VE of 24.8 +/- 1.6 l/min], which was significant compared with poikilocapnic hypoxia and control values (P < 0.001, analysis of variance). There was no significant progressive rise in VE during poikilocapnic hypoxia compared with control values. These results show that isocapnic hypoxia produces a progressive increase in VE when sustained over an 8-h period. The onset of this response is faster than has been noted in studies of the progressive rise in VE associated with the poikilocapnic hypoxia of altitude. |
| spellingShingle | Howard, L Robbins, P Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title | Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title_full | Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title_fullStr | Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title_full_unstemmed | Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title_short | Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans. |
| title_sort | ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans |
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