title: 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.
  
  
  OBJECTIVE
  We investigated whether an elevated blood concentration of glycosylated hemoglobin (HbA1c) could induce falsely high pulse oximeter oxygen saturation (SpO2) in type 2 diabetic patients during mechanical ventilation or oxygen therapy.
  
  
  METHODS
  Arterial oxygen saturation (SaO2) and partial pressure of oxygen (PO2) were determined with simultaneous monitoring of SpO2 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 SaO2 (96.2 ± 2.9%, 95% confidence interval [CI] 95.7-96.7% vs. 95.1 ± 2.8%, 95% CI 94.7-95.6%) and SpO2 (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 PO2 did not significantly differ between the two groups. Bland-Altman analysis demonstrated a significant bias between SpO2 and SaO2 (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 SpO2 and SaO2 correlated closely with blood HbA1c levels (Pearson's r = 0.307, p < 0.01).
  
  
  CONCLUSIONS
  Elevated blood HbA1c levels lead to an overestimation of SaO2 by SpO2, suggesting that arterial blood gas analysis may be needed for type 2 diabetic patients with poor glycemic control during the treatment of hypoxemia.
authors.affiliation: Department of Cardiology, Shanghai Rui Jin Hospital, Shanghai, People's Republic of China.
authors.forename: Li Jin
authors.initials: LJ
authors.lastname: Pu
authors.forename: Ying
authors.initials: Y
authors.lastname: Shen
authors.forename: Lin
authors.initials: L
authors.lastname: Lu
authors.forename: Rui Yan
authors.initials: RY
authors.lastname: Zhang
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.forename: Wei Feng
authors.initials: WF
authors.lastname: Shen
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D016009:Chi-Square Distribution; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis / Q000628:therapy; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010102:Oxygen Inhalation Therapy; D010108:Oxyhemoglobins / Q000378:metabolism; D010313:Partial Pressure; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D006442:Glycated Hemoglobin; D010100:Oxygen; D010108:Oxyhemoglobins; C517652:hemoglobin A1c protein, human