Predictors of Nocturnal Hypoxemic Burden in Patients Undergoing Elective Coronary Artery Bypass Grafting Surgery

Abstract

Background: Nocturnal hypoxemia has been linked to increased cardiovascular morbidity and mortality. Several common diseases, such as sleep-disordered breathing (SDB), heart failure (HF), obesity, and pulmonary disease, coincide with an elevated nocturnal hypoxemic burden with and without repetitive desaturations. Research question: This study aimed to evaluate the association of relevant common diseases with distinctive metrics of nocturnal hypoxemic burden with and without repetitive desaturations in patients undergoing coronary artery bypass grafting surgery. Study design and methods: In this subanalysis of the prospective observational study, CONSIDER-AF (NCT02877745) portable SDB monitoring was performed on 429 patients with severe coronary artery disease the night before cardiac surgery. Pulse oximetry was used to determine nocturnal hypoxemic burden, as defined by total recording time spent with oxygen saturation levels < 90% (T90). T90 was further characterized as T90 due to intermittent hypoxemia (T90_desaturation) and T90 due to nonspecific and noncyclic SpO₂-drifts (T90_non-specific). Results: Multivariable linear regression analysis identified SDB (apnea-hypopnea-index ≥ 15/h; B [95% CI]: 6.5 [0.4; 12.5], p = 0.036), obesity (8.2 [2.5; 13.9], p = 0.005), and mild-to-moderate chronic obstructive pulmonary disease (COPD, 16.7 [8.5; 25.0], p < 0.001) as significant predictors of an increased nocturnal hypoxemic burden. Diseases such as SDB, obesity and HF were significantly associated with elevated T90_desaturation. In contrast, obesity and mild-to-moderate COPD were significant modulators of T90_non-specific. Interpretation: SDB and leading causes for SDB, such as obesity and HF, are associated with an increased nocturnal hypoxemic burden with repetitive desaturations. Potential causes for hypoventilation syndromes, such as obesity and mild-to-moderate COPD, are linked to an increased hypoxemic burden without repetitive desaturations. Clinical Trial Registration: ClinicalTrials.gov identifier: NCT02877745.

Keywords: T90; heart failure; nocturnal hypoxemia; sleep apnea.

Figure 1

Study flowchart. CABG: coronary artery bypass grafting; SDB: sleep-disordered breathing; CPAP: continuous positive airway pressure.

Figure 2

Nocturnal hypoxemic burden index according to different comorbidities. The violin plots indicate the median and quartiles of the nocturnal hypoxemic burden index in percent of artifact-free total recording time according to different combinations of comorbidities for T90/TRT (A), T90_desaturation/TRT (B), and T90_non-specific/TRT (C). The violin plot outlines illustrate kernel probability density, i.e., the width of the shaded area represents the proportion of the data. SDB: sleep-disordered breathing; COPD: chronic obstructive pulmonary disease.

Figure 2

Nocturnal hypoxemic burden index according to different comorbidities. The violin plots indicate the median and quartiles of the nocturnal hypoxemic burden index in percent of artifact-free total recording time according to different combinations of comorbidities for T90/TRT (A), T90_desaturation/TRT (B), and T90_non-specific/TRT (C). The violin plot outlines illustrate kernel probability density, i.e., the width of the shaded area represents the proportion of the data. SDB: sleep-disordered breathing; COPD: chronic obstructive pulmonary disease.

Figure 3

Association of different comorbidities with an increased nocturnal hypoxemic burden index. Forest plot depicting the association between different comorbidities and metrics of an increased nocturnal hypoxemic burden index (i.e., T90/TRT, T90_desaturation/TRT, and T90_non-specific/TRT). Values are presented as B: beta coefficient and 95% CI: confidence interval. SDB: sleep-disordered breathing; TRT: artifact-free total recording time; COPD: chronic obstructive pulmonary disease.