From the Guidelines
Auto-PEEP is a critical condition that occurs when a patient cannot fully exhale before the next breath begins, leading to trapped air in the lungs, and its management is crucial to prevent decreased cardiac output, barotrauma, and patient-ventilator asynchrony. Auto-PEEP, also known as intrinsic PEEP or air trapping, is a condition that arises when expiratory time is insufficient, commonly in patients with obstructive lung diseases like COPD or asthma 1. The trapped air creates an unintended positive end-expiratory pressure that isn't set on the ventilator but develops within the patient's respiratory system. Clinically, auto-PEEP can cause decreased cardiac output, barotrauma, and patient-ventilator asynchrony, and it's identified by observing flow not returning to zero before the next breath, increased peak and plateau pressures, and hemodynamic compromise 2.
Causes and Identification
The causes of auto-PEEP include obstructive lung diseases, inappropriate ventilator settings, and abnormalities in a patient's respiratory mechanics 1. It can be identified by observing flow not returning to zero before the next breath, increased peak and plateau pressures, and hemodynamic compromise.
Management
Management of auto-PEEP includes extending expiratory time by decreasing respiratory rate or tidal volume, bronchodilator therapy, and in some cases applying external PEEP to counterbalance the intrinsic PEEP 2, 1. This helps stabilize airways and reduce work of breathing. For severe cases, deep sedation or neuromuscular blockade may be necessary. Regular assessment of ventilator waveforms and patient response is essential for early detection and management of auto-PEEP. The most effective management strategy for auto-PEEP is to extend expiratory time and apply external PEEP to counterbalance the intrinsic PEEP, as recommended by the most recent and highest quality study 3.
Clinical Implications
The clinical implications of auto-PEEP are significant, and its management is crucial to prevent decreased cardiac output, barotrauma, and patient-ventilator asynchrony. In patients with acute respiratory distress syndrome (ARDS), higher PEEP strategies may improve alveolar recruitment, reduce lung stress and strain, and prevent atelectrauma, but may also increase the risk of barotrauma and hemodynamic compromise 3. Therefore, the management of auto-PEEP should be individualized and based on the patient's underlying condition and response to treatment.
Key Points
- Auto-PEEP is a critical condition that occurs when a patient cannot fully exhale before the next breath begins, leading to trapped air in the lungs.
- Management of auto-PEEP includes extending expiratory time, applying external PEEP, and bronchodilator therapy.
- Regular assessment of ventilator waveforms and patient response is essential for early detection and management of auto-PEEP.
- The most effective management strategy for auto-PEEP is to extend expiratory time and apply external PEEP to counterbalance the intrinsic PEEP, as recommended by the most recent and highest quality study 3.
From the Research
Definition and Measurement of Auto-PEEP
- Auto-PEEP, or intrinsic positive end-expiratory pressure (PEEPi), occurs when alveolar pressure fails to decrease to zero at the end of exhalation 4.
- It can be measured in paralyzed or apneic patients by occlusion of the ventilator expiratory valve at end-exhalation (PEEPi-OC) 4.
- In spontaneously breathing patients, auto-PEEP can be estimated by simultaneous recordings of airflow and airway and esophageal pressure, respectively 5.
- Noninvasive measurement of changes in end-expiratory thoracic gas volume by respiratory inductive plethysmography (RIP) is a convenient alternative method to estimate auto-PEEP in both controlled, assisted, and spontaneously ventilating patients 4.
Clinical Significance of Auto-PEEP
- Auto-PEEP can cause severe respiratory and hemodynamic compromise 5.
- It is a common occurrence in patients with acute respiratory failure requiring mechanical ventilation 5.
- Auto-PEEP can lead to increased work of breathing, barotrauma, hemodynamic instability, and difficulty in triggering the ventilator 6.
- Failure to recognize the hemodynamic consequences of auto-PEEP may lead to inappropriate fluid restriction or unnecessary vasopressor therapy 6.
Strategies to Reduce Auto-PEEP
- Reduction of minute ventilation, use of small tidal volumes, and prolongation of the time available for exhalation may reduce auto-PEEP 5.
- Application of low-levels of external PEEP can reduce dyspnea, reduce work of breathing, improve patient-ventilator interaction, and cardiac function in patients with auto-PEEP caused by expiratory flow limitation 5.
- Neurally adjusted ventilatory assist, a novel strategy of ventilatory assist, may improve patient-ventilator interaction in patients with auto-PEEP 5.
- Providing external PEEP to 75-80% of auto-PEEP in patients who are spontaneously breathing during mechanical ventilation can decrease the work of breathing 6.