From the Guidelines
Auto-positive end-expiratory pressure (auto-PEEP) in an intubated patient is a condition where air becomes trapped in the lungs during mechanical ventilation, creating unintended positive end-expiratory pressure, and can be managed by adjusting ventilator settings to decrease respiratory rate, decrease tidal volume, or increase expiratory time, as recommended by the 2010 American Heart Association guidelines 1.
Definition and Causes
Auto-PEEP, also known as intrinsic PEEP, occurs when a patient doesn't have enough time to fully exhale before the next breath is delivered, commonly seen in patients with obstructive lung diseases like COPD or asthma 1. This can lead to complications such as hyperinflation, tension pneumothorax, and hypotension.
Management
To manage auto-PEEP, the following adjustments can be made:
- Decrease respiratory rate
- Decrease tidal volume
- Increase expiratory time by increasing inspiratory flow rate or decreasing I:E ratio to at least 1:3 or greater 1 Sedation may be necessary if the patient is fighting the ventilator, and bronchodilators like albuterol (2.5-5mg every 4-6 hours) can help reduce airway resistance.
Concerns and Measurement
Auto-PEEP is concerning because it can cause barotrauma, decrease venous return, reduce cardiac output, and create patient-ventilator asynchrony. It can be measured by performing an end-expiratory hold maneuver on the ventilator, with values above 5 cmH2O generally considered significant 1.
Key Considerations
Key considerations in managing auto-PEEP include:
- Minimizing auto-PEEP by decreasing the respiratory rate or tidal volume or both
- Using sedation to optimize ventilation and decrease ventilator dyssynchrony
- Administering inhaled medications, such as albuterol, through the endotracheal tube
- Monitoring for signs of auto-PEEP, such as hyperinflation, tension pneumothorax, and hypotension, and taking prompt action to address these complications 1.
From the Research
Definition and Causes of Auto-PEEP
- Auto-positive end-expiratory pressure (auto-PEEP) is a physiologic event that occurs in mechanically ventilated patients, where intrinsic positive end-expiratory pressure is created by the mechanical and physiological properties of the pulmonary system and the mechanical ventilator 2.
- Auto-PEEP can be caused by various factors, including a reduction in expiratory time by increasing the respiratory rate, tidal volume, or inspiratory time 2.
- It is commonly found in acute severe asthma, chronic obstructive pulmonary disease, or patients receiving inverse ratio ventilation 2.
Effects of Auto-PEEP
- Auto-PEEP can predispose the patient to increased work of breathing, barotrauma, hemodynamic instability, and difficulty in triggering the ventilator 2.
- It can also interfere with weaning from mechanical ventilation and cause severe respiratory and hemodynamic compromise 3.
- Failure to recognize the hemodynamic consequences of auto-PEEP may lead to inappropriate fluid restriction or unnecessary vasopressor therapy 2.
Measurement and Detection of Auto-PEEP
- Auto-PEEP can be detected and quantified by a simple bedside maneuver: expiratory port occlusion at the end of the set exhalation period 2.
- The measurement of static and dynamic auto-PEEP differs and depends upon the heterogeneity of the airways 2.
- In patients receiving controlled mechanical ventilation, auto-PEEP can be estimated by measuring the rise in airway pressure during an end-expiratory occlusion maneuver 3.
Management and Treatment of Auto-PEEP
- Strategies that may reduce auto-PEEP include reduction of minute ventilation, use of small tidal volumes, and prolongation of the time available for exhalation 3.
- The application of low-levels of external PEEP can reduce dyspnea, reduce work of breathing, improve patient-ventilator interaction, and cardiac function, all without worsening hyperinflation 3.
- Sedation and fluid management are important adjunctive therapies in the treatment of auto-PEEP 4.