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Respir Res. 2017 Jun 28;18(1):130. doi: 10.1186/s12931-017-0607-9.

Independent associations between arterial bicarbonate, apnea severity and hypertension in obstructive sleep apnea.

Author information

1
Center for Sleep and Vigilance Disorders, Department of Internal Medicine and Clinical Nutrition, Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 8B, Box 421, SE-40530, Gothenburg, Sweden.
2
Center for Sleep and Vigilance Disorders, Department of Internal Medicine and Clinical Nutrition, Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 8B, Box 421, SE-40530, Gothenburg, Sweden. zou.ding@lungall.gu.se.
3
Johns Hopkins Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
4
Interdisciplinary Center of Sleep Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany.
5
International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic.

Abstract

BACKGROUND:

Obstructive sleep apnea is characterized by intermittent hypoxia and hypercapnia. CO2 production, transport and elimination are influenced by the carbonic anhydrase enzyme. We hypothesized that elevated standard bicarbonate, a proxy for increased carbonic anhydrase activity, is associated with apnea severity and higher blood pressure in patients with obstructive sleep apnea.

METHODS:

A retrospective analysis of a sleep apnea cohort (n = 830) studied by ambulatory polygraphy. Office systolic/diastolic blood pressure, lung function, and arterial blood gases were assessed during daytime.

RESULTS:

Arterial standard bicarbonate was increased with apnea severity (mild/moderate/severe 24.1 ± 1.8, 24.4 ± 1.7 and 24.9 ± 2.9 mmol/l, respectively, Kruskal-Wallis test p < 0.001). Standard bicarbonate was independently associated with apnea hypopnea index after adjustment for sex, age, body mass index, smoking, alcohol, hypertension, pO2 and pCO2 (standard bicarbonate quartile 1 vs. quartile 4, β = 10.6, p < 0.001). Log-transformed standard bicarbonate was associated with a diagnosis of hypertension or diastolic blood pressure but not systolic blood pressure adjusting for cofounders (p = 0.007, 0.048 and 0.45, respectively).

CONCLUSIONS:

There was an independent association between sleep apnea severity and arterial standard bicarbonate. The link between high standard bicarbonate and daytime hypertension suggests that carbonic anhydrase activity may constitute a novel mechanism for blood pressure regulation in sleep apnea.

KEYWORDS:

Acid base; Blood pressure; Carbonic anhydrase; Hypercapnia; Obstructive sleep apnea

PMID:
28659192
PMCID:
PMC5490198
DOI:
10.1186/s12931-017-0607-9
[Indexed for MEDLINE]
Free PMC Article

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