How should a patient with an arterial blood gas (ABG) showing pH 7.52, partial pressure of carbon dioxide (PCO2) 29.2, and partial pressure of oxygen (PO2) 59 be managed?

Respiratory Alkalosis with Severe Hypoxemia Requiring Immediate Oxygen Therapy

This patient has severe hypoxemia (PO2 59 mmHg) with respiratory alkalosis (pH 7.52, PCO2 29.2 mmHg) and requires immediate supplemental oxygen to achieve a PO2 >60 mmHg, with repeat ABG within 30-60 minutes to ensure adequate response without worsening alkalosis. 1

Immediate Management Priority

• Administer supplemental oxygen immediately because PO2 of 59 mmHg represents life-threatening hypoxemia requiring urgent intervention 1
• The primary goal is to achieve a PO2 of at least 60 mmHg (or ideally >90 mmHg) to prevent tissue hypoxia 2, 1
• Target SpO2 of 94-98% for most patients without risk of hypercapnic respiratory failure 1

Critical Assessment Within 60 Minutes

• Recheck arterial blood gases within 30-60 minutes after initiating or changing oxygen therapy to confirm adequate oxygenation response 2, 1
• Monitor whether oxygen supplementation maintains or improves PO2 without causing deterioration in pH 2
• If the patient remains stable with normalized PO2 and pH, pulse oximetry monitoring may be sufficient for ongoing assessment 2

Interpretation of This ABG Pattern

• pH 7.52 indicates alkalemia (normal is 7.40) 1
• PCO2 29.2 mmHg indicates hypocapnia (normal is <40 mmHg), suggesting hyperventilation as the primary process 1
• PO2 59 mmHg represents severe hypoxemia requiring immediate correction 1
• This pattern suggests respiratory alkalosis driven by hyperventilation, likely compensatory for the severe hypoxemia 3, 4

Underlying Etiology Investigation

The combination of severe hypoxemia with respiratory alkalosis suggests several possible causes that require evaluation:

• Acute pulmonary pathology such as pneumonia, pulmonary embolism, acute respiratory distress syndrome, or interstitial lung disease 3
• Ventilation-perfusion mismatch or shunting as mechanisms of hypoxemia 3
• The hyperventilation (low PCO2) represents the body's compensatory attempt to increase oxygen delivery despite severe hypoxemia 3

Oxygen Delivery Method

• For controlled oxygen delivery, use Venturi masks starting at 28% FiO2 or nasal cannulae at 2 L/min if there is any concern for underlying COPD 2
• If no history of COPD or chronic CO2 retention, higher flow oxygen can be administered to rapidly correct the life-threatening hypoxemia 1
• Increase inspired oxygen concentration incrementally until PO2 exceeds 60 mmHg (ideally >90 mmHg) 2, 1

Common Pitfall to Avoid

• Do not delay oxygen therapy due to concerns about the elevated pH—the severe hypoxemia (PO2 59 mmHg) takes absolute priority over the alkalosis 1
• The respiratory alkalosis is likely compensatory hyperventilation in response to hypoxemia and should improve once oxygenation is corrected 3
• However, if the patient has known COPD with chronic CO2 retention, use controlled oxygen delivery to avoid precipitating hypercapnic respiratory failure 2, 5

Monitoring and Reassessment

• Repeat ABG measurement at any time if clinical situation deteriorates 2
• Continue monitoring respiratory rate, work of breathing, and mental status 2
• Once PO2 is stabilized above 60 mmHg and pH normalizes, ongoing pulse oximetry may be adequate if the patient remains clinically stable 2