title: Effect of inspiration of 12% O₂ (balance N₂) on cardiac output, respiration, oxygen saturation, and oxygen delivery.
abstract: Low arterial oxygen saturation (SaO(2)) will result in a reduced rate of arterial oxygen delivery to the tissues (DO(2)), unless there is a compensatory increase in cardiac output (CO) or haemoglobin concentration (Hb). An adequate DO(2) can therefore be maintained by increasing ventilation, CO, or both. Sustaining a tissue specific oxygen extraction is thought to play an important part in overall compensation. The present study has examined responses to acute hypoxic exposure in 8 volunteers (breathing 12% oxygen, balance nitrogen) and describes changes in CO, ventilation and the SaO(2). Aims included: examination of the extent of intersubject variations and seeing whether DO(2) was maintained. SaO(2), PCO(2), respiration (via stethograph) and Finapress (non-invasive) arterial blood pressure (BP) were recorded, firstly on air and then on 12% oxygen. CO was derived, off-line, from the BP record. CO was increased in 5 subjects (22%-45%) but was virtually unchanged in 3, and yet comparison for all 8 subjects showed that DO(2) on 12% oxygen was not significantly different from DO(2) on air (mean on air 1017 ml. min(-1); hypoxia 1080 ml. min(-1), p = 0.27). SaO(2) on 12% oxygen ranged between 85% and 93%. In conclusion, exposure to the same hypoxic gas mixture resulted in differing individual ventilatory and CO responses. However, DO(2) was well maintained.
authors: St. Catherine's Hospital, Doncaster, UK.
authors: M
authors: M
authors: Bell
authors: C D
authors: CD
authors: Thake
authors: C B
authors: CB
authors: Wolff
mesh_terms: D002302:Cardiac Output; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011659:Pulmonary Gas Exchange; D012119:Respiration
chemical_list: D006454:Hemoglobins; C041364:nitrox; D009584:Nitrogen; D010100:Oxygen