Cardiovasc Diabetol. 2012;11(110)
Abstract
Background: Non-enzymatic glycation increases hemoglobin-oxygen affinity and reduces oxygen delivery to tissues by altering the structure and function of hemoglobin.
Objectives: We investigated whether an elevated blood concentration of glycosylated hemoglobin (HbA1c) could induce falsely high pulse oximeter oxygen saturation (SpO 2) in type 2 diabetic patients during mechanical ventilation or oxygen therapy.
Methods: Arterial oxygen saturation (SaO 2) and partial pressure of oxygen (PO 2) were determined with simultaneous monitoring of SpO 2 in 261 type 2 diabetic patients during ventilation or oxygen inhalation.
Results: Blood concentration of HbA1c was >7% in 114 patients and ≤ 7% in 147 patients. Both SaO 2 (96.2 ± 2.9%, 95% confidence interval [CI] 95.7–96.7% vs. 95.1 ± 2.8%, 95% CI 94.7–95.6%) and SpO 2 (98.0 ± 2.6%, 95% CI 97.6–98.5% vs. 95.3 ± 2.8%, 95% CI 94.9–95.8%) were significantly higher in patients with HbA1c >7% than in those with HbA1c ≤ 7% (Data are mean ± SD, all p < 0.01), but PO 2 did not significantly differ between the two groups. Bland-Altman analysis demonstrated a significant bias between SpO 2 and SaO 2 (1.83 ±0.55%, 95% CI 1.73% -1.94%) and limits of agreement (0.76% and 2.92%) in patients with HbA1c >7%. The differences between SpO 2 and SaO 2 correlated closely with blood HbA1c levels (Pearson’s r = 0.307, p < 0.01). Conclusions: Elevated blood HbA1c levels lead to an overestimation of SaO 2 by SpO 2, suggesting that arterial blood gas analysis may be needed for type 2 diabetic patients with poor glycemic control during the treatment of hypoxemia.
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