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Original Research: Sleep DisordersIs a Raised Bicarbonate, Without Hypercapnia, Part of the Physiologic Spectrum of Obesity-Related Hypoventilation?
Section snippets
Study Design and Setting
This was an open cross-sectional study of obese subjects with and without conventionally defined OHS. The work was carried out in the Oxford Sleep Unit, Oxford Centre for Respiratory Medicine, Churchill Hospital, England, which is a National Health Service secondary and tertiary referral center. Subjects were recruited and studied between June 2011 and September 2013. The study was registered prospectively with a global trials registry site (NCT01380418). It has been reported in accordance with
Results
Seventy-one obese subjects (37, 52%, men) were studied during the 27-month recruitment period. Demographic and anthropometric data are reported for each group in Table 1. There were no differences in age, weight, or BMI between the groups, although the P value for BMI approached significance (P = .056) between groups.
The ventilatory drive measurements at baseline and after hypoxic and hypercapnic challenge testing are shown in TABLE 2, TABLE 3, TABLE 4, respectively. Table 5 shows the sleep
Discussion
In this prospective observational cohort study, we have demonstrated that obese subjects with a raised BE, but with a normal daytime Paco2, have a ventilatory response between those of normal obese subjects (without evidence of awake hypoventilation) and those with hypercapnia and, thus, conventionally defined OHS. This evidence suggests that these subjects are in the middle of a spectrum, and indeed they could be considered as patients with “early OHS,” albeit we do not have longitudinal data
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Cited by (58)
Arterial bicarbonate is associated with hypoxic burden and uncontrolled hypertension in obstructive sleep apnea - The ESADA cohort
2023, Sleep MedicineCitation Excerpt :Given the link between [HCO3-] and CA activity, it is possible that the current association reflects the potential role of CA in OSA related hypertension. Finally, an elevated [HCO3-] without hypercapnia has been suggested as an early marker of obesity related hypoventilation [31–33]. Although we excluded patients with manifest daytime hypercapnia from our analysis, two third of patients were obese in the current cohort.
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2022, Sleep MedicineCitation Excerpt :Isolated increase in base excess, and 3. Daytime hypercapnia and elevated base excess), Manuel et al. found that patients with isolated base excess elevation represented an intermediate group, who were more similar to the third group with established OHS [12]. The Task Force of the European Respiratory Society (ERS) proposes 5 different stages of obesity-related respiratory disorders (Table 1) [13].
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2020, Sleep MedicineCitation Excerpt :According to an earlier definition of OHS, daytime hypercapnia (PaCO2 >45 mm Hg) is mandatory [1]. But because OHS is the most severe form of nocturnal hypoventilation, the earlier definition covers only the extreme and most severe forms of nocturnal hypoventilation, whereas patients with less severe nocturnal hypoventilation (without daytime hypercapnia) were not considered a part of OHS [3]. The rationale behind this is arbitrary because OHS is a sleep-related hypoventilation disorder and relying only on elevated PaCO2 leads to a significant number of undiagnosed cases.
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FUNDING/SUPPORT: This work was supported by the Oxford Health Services Research Committee, the Oxford Biomedical Research Centre, and the Oxford Radcliffe Hospital Charitable Funds. The NICO 2 device was kindly donated by Koninklijke Philips N.V.