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Respir Physiol Neurobiol. 2014 Jan 15;191:44-51. doi: 10.1016/j.resp.2013.10.014. Epub 2013 Nov 4.

Transcutaneous CO(2) plateau as set-point for respiratory drive during upper airway flow-limitation.

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Graduate School of Medical Faculty, University of Tampere, Tampere, Finland. Electronic address:
Division of Medicine, Department of Pulmonary Diseases, Turku University Hospital, Turku, Finland; Sleep Research Unit, Department of Physiology, University of Turku, Lemminkäisenkatu 14-18 A, 20520 Turku, Finland.
School of Health Sciences, University of Tampere, Terveystieteiden yksikkö, 33014, Tampereen Yliopisto, Tampere, Finland.
VTT Technical Research Centre of Finland, Itäinen pitkäkatu 4C, PL 106, 20521 Turku, Finland.
Graduate School of Medical Faculty, University of Tampere, Tampere, Finland.
Department of Respiratory Medicine, University of Tampere and Tampere University Hospital, Tampere, Finland.


Upper airway flow-limitation is often but not always associated with prolonged gradually increasing respiratory effort. We investigated the changes in transcutaneous carbon dioxide tension (tcCO(2)) during episodes of upper airway flow limitation during sleep with or without respiratory effort response. Seventy-seven episodes of progressive flow-limitation were analyzed in 36 patients with sleep-disordered breathing. TcCO(2) and arterial oxyhaemoglobin saturation (SaO2) were measured during steady breathing and during episodes of flow-limitation with and without effort response. After lights-off tcCO(2) increased and leveled-off at plateau, when breathing stabilized. During flow-limitation tcCO(2) increased at rate of 4.0kPa/h. Flow-limitation with increasing respiratory effort associated with tcCO(2) increase above the plateau (terminating at 105.2%, p<0.001), whereas flow-limitation without effort response associated with tcCO(2) increase starting below the plateau (95.8%, p<0.001). We conclude that the nocturnal tcCO(2) plateau indicates the level above which the increasing respiratory effort is triggered as response to upper airway flow-limitation. We propose that flow-limitation below the tcCO(2) plateau is an event related to stabilization of sleep and breathing.


Carbon dioxide; Sleep apnea; Sleep-disordered breathing; Snoring

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