med 610 clinical respiratory diseases & critcare med

Arterial Blood Gas

Case 5

A 68 year-old man with a history of very severe COPD (FEV1 ~ 1.0L, <25% predicted) and chronic carbon dioxide retention (Baseline PCO2 58) presents to the emergency room complaining of worsening dyspnea and an increase in the frequency and purulence of his sputum production over the past 2 days. His oxygen saturation is 78% on room air. Before he is place on supplemental oxygen, a room air arterial blood gas is drawn and reveals:

  • pH 7.25,
  • PCO2 68,
  • PO2 48,
  • HCO3- 31

Acid-base status:

Alveolar-arterial oxygen difference:

Explanation for the clinical picture:

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