Air Trapping During Mechanical Ventilation

Last updated: 02/20/2026

Key Points

Air trapping occurs when end expiratory lung volume increases beyond functional residual capacity resulting in dynamic hyperinflation.¹
The only sign of air trapping on the ventilator intraoperatively may be an elevated peak pressure.
Air trapping can worsen hypoxia, hypercarbia and cause hemodynamic instability due to decreased venous return in the setting of increased intrathoracic pressure.

Air trapping during mechanical ventilation occurs when insufficient expiratory time prevents complete exhalation to functional residual capacity before the next breath, resulting in progressive gas accumulation and dynamic hyperinflation.
This phenomenon generates intrinsic positive end-expiratory pressure (auto-PEEP), where alveolar pressure remains elevated above the set ventilator PEEP at end-expiration.
Perhaps move the consequences of air trapping here.

Patients with COPD have incomplete expiration.³
- For inspiration to begin, the intrapleural pressure must counteract the patient’s auto-PEEP, leading to both an increased expiratory load and an increased inspiratory load.³
- This tendency is exacerbated by mechanical ventilation where auto PEEP is directly proportional to tidal volume and inversely proportional to expiratory time.³
Hyperventilation of any patient (for example, when intentionally hyperventilating to decrease end tidal CO₂ during laparoscopy or to decrease intracranial pressure) risks air trapping.

Increased peak pressure may be the only sign of air trapping intraoperatively, although increased plateau pressures are more specific to air trapping.¹
Auto-PEEP can be measured by end-expiratory flow interruption on ICU ventilators.³

Hypoxia due to overdistention and compression of functional lung regions¹
Hypercarbia due to impaired gas exchange as hyperinflation worsens¹
Increased patient discomfort causes poor ventilator synchrony, further impairing gas exchange¹
Impaired venous return resulting in decreased cardiac output¹

When air trapping develops, immediate ventilator adjustments include¹
- Increasing expiratory time
- Decreasing respiratory rate²
- Changing the I:E ratio to allow more expiratory time
Increasing the PEEP may actually improve air trapping, but must be carefully titrated^1,3
The definitive management is optimally treating the underlying COPD and bronchospasm.^1,2

References

Ward N, Dushay K. Clinical concise review: Mechanical ventilation of patients with chronic obstructive pulmonary disease. Crit Care Med. 2008; 36 (5): 1614-9. PubMed
LM Galerneau et al. Management of acute exacerbations of chronic obstructive pulmonary disease in the ICU: An observational study From the OUTCOMEREA database, 1997-2018. Critical Care Medicine. 2023; 51 (6): 753-64. PubMed
Slinger P. Don’t make things worse with your ventilator settings: How you manage the lungs during the perioperative period affects postoperative futcomes. IARS 2013 Review Course Lectures. Link