What breathing technique can help decrease carbon dioxide (CO2) levels in patients?

Breathing Technique to Decrease CO2

Pursed-lip breathing is the most effective breathing technique to decrease CO2 levels, reducing PaCO2, respiratory rate, and dyspnea while improving tidal volume and oxygen saturation in patients with chronic obstructive pulmonary disease. 1

How Pursed-Lip Breathing Works

Pursed-lip breathing involves prolonging active expiration through half-opened lips, which helps prevent airway collapse and improves gas exchange. 1 The technique specifically:

• Reduces respiratory rate and minute ventilation, allowing more complete exhalation of CO2 1, 2
• Decreases PaCO2 compared to spontaneous breathing at rest 1
• Improves tidal volume and oxygen saturation in resting conditions 1
• Reduces dynamic hyperinflation by preventing air trapping 3

Patient Selection Matters

Not all patients respond equally to pursed-lip breathing. The evidence shows:

• COPD patients with low peak expiratory flow (PEF <47.7% predicted) are most likely to benefit, showing improved exercise tolerance and reduced dynamic hyperinflation 3
• Patients instinctively adopt this technique and report decreased dyspnea with its use 1
• Training with ear oximetry can help patients learn to increase oxygen saturation through pursed-lip breathing 4

Important Caveats

Disease-Specific Considerations

• Diaphragmatic breathing is NOT recommended - controlled studies do not support its use in COPD patients 1
• Interstitial lung disease patients should avoid pursed-lip breathing - it worsens dyspnea, reduces walking distance, and increases metabolic demands without improving gas exchange 5

Clinical Application

• The technique is most effective at rest and during submaximal exercise, with less clear benefits during peak exercise 2, 3
• Requires proper instruction and repeated practice with monitoring to ensure correct technique 6
• Some patients (approximately 17%) may develop thoracoabdominal asynchrony with pursed-lip breathing, making them non-responders 3

Complementary Positioning Strategies

Forward leaning with arm support enhances CO2 clearance by:

• Improving diaphragm length-tension relationships and geometry 1
• Decreasing dyspnea and increasing exercise capacity when using a rollator/walker 1
• Being the most commonly adopted body position by COPD patients 1

When CO2 Reduction May Be Harmful

Avoid aggressive hyperventilation in certain contexts:

• In mechanically ventilated patients with ARDS, permissive hypercapnia (allowing CO2 to rise while using small tidal volumes) reduces mortality and prevents lung injury 1
• Maintain arterial pH >7.20 even if PaCO2 is elevated 1
• Normalization of blood gases is not always the therapeutic goal 1