Increased blood glycohemoglobin A1c levels lead to overestimation of arterial oxygen saturation by pulse oximetry in patients with type 2 diabetes

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.