Hypocapnia and increased ventilatory responsiveness in patients with idiopathic central sleep apnea

Ailiang Xie, Ruth Rutherford, Fiona Rankin, Brian Wong, T. Douglas Bradley

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Abstract

We previously demonstrated that central apneas during sleep in patients with idiopathic central sleep apnea (ICSA) are triggered by abrupt hyperventilation. In addition, baseline P(CO2) at the time of augmented breaths which triggered central apneas was lower than for augmented breaths which did not trigger apneas. These observations led us to hypothesize that patients with ICSA chronically hyperventilate maintaining their P(CO2) close to the threshold for apnea during sleep owing to increased chemical respiratory drive. To test these hypotheses, we recorded transcutaneous P(CO2) (Ptc(CO2)) during overnight sleep studies on nine consecutive patients with ICSA and nine sex-, age-, and body-mass-index-matched control subjects. Daytime Pa(CO2) as well as rebreathing and single breath ventilator/responses to CO2 were also measured. Compared with the control subjects, the patients had significantly lower mean Ptc(CO2) during sleep (37.8 ± 1.2 versus 42.7 ± 10.9 mm Hg, p < 0.01) and lower Pa(CO2) while awake (35.1 ± 1.3 versus 38.8 ± 0.9 mm Hg, p < 0.05). Furthermore, patients with ICSA had significantly higher ventilatory responses to CO2 for both the rebreathing (3.14 ± 0.34 versus 1.60 ± 0.32 L/min/mm Hg, p < 0.005) and single breath methods (0.51 ± 0.10 versus 0.25 ± 0.04 L/min/mm Hg, p < 0.05). We conclude that: (1) patients with ICSA chronically hyperventilate awake and asleep and (2) chronic hyperventilation is probably related to augmented central and peripheral respiratory drive which predisposes to respiratory control system instability.

Original languageEnglish (US)
Pages (from-to)1950-1955
Number of pages6
JournalAmerican journal of respiratory and critical care medicine
Volume152
Issue number6 I
DOIs
StatePublished - Dec 1995

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ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine

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