Auto-PEEP: Complication of Mechanical Ventilation (2023)

Mechanical ventilation is a life-saving intervention that assists patients with respiratory failure by maintaining adequate gas exchange and supporting breathing.

However, problems can arise during the process, and one such complication is auto-PEEP.

This article will discuss the concept of auto-PEEP, its causes, clinical implications, and management strategies.

What is Auto-PEEP?

Auto-PEEP is a phenomenon that occurs during mechanical ventilation when positive pressure remains in the alveoli at the end of the exhalation phase of the breathing cycle.

This residual pressure can lead to increased lung volumes, reduced venous return, and potential hemodynamic compromise in the patient.

Auto-PEEP is often an unintended consequence of ventilator settings and patient factors, and recognizing its presence is essential in optimizing patient care.

Causes

Several factors contribute to the development of auto-PEEP, including:

• Air trapping
• Inadequate expiratory time
• Patient-ventilator asynchrony
• High respiratory rate
• High minute ventilation

Auto-PEEP is usually caused by air trapping that results from an inadequate expiratory time.

Therefore, if a patient’s expiratory time is not long enough, air remains in the lungs (i.e., air trapping), which results in positive pressure at end-exhalation.

Adverse Effects

Auto-PEEP is a complication of mechanical ventilation that can lead to several adverse effects, including the following:

• Air trapping
• Increased work of breathing
• Accessory muscle usage
• Respiratory muscle fatigue
• Hemodynamic instability
• Patient-ventilator asynchrony
• Difficulty weaning from the ventilator
• Difficulty triggering a breath
• Increased risk of barotrauma
• Increased anxiety

To minimize these adverse effects, it is essential for healthcare professionals to recognize the presence of auto-PEEP, understand its causes, and implement appropriate management strategies.

Management Strategies

The management of auto-PEEP involves a combination of ventilator adjustments and optimization of the patient’s clinical condition.

The best way to correct auto-PEEP is to increase the patient’s expiratory time, allowing a complete exhalation. Some strategies include:

• Decrease the respiratory rate
• Decrease the inspiratory time (e.g., by increasing the flow)
• Decrease the tidal volume

Optimizing the ventilator settings by decreasing the respiratory rate, reducing tidal volume, and adjusting the inspiratory-to-expiratory (I:E) ratio can reduce or prevent auto-PEEP from occurring.

How to Measure Auto-PEEP

Measuring auto-PEEP is a critical aspect of managing patients on the ventilator. It can be detected and quantified by a simple bedside maneuver that involves occluding the expiratory port occlusion at the end of exhalation.

By observing the airway pressure during this maneuver, healthcare professionals can estimate the level of auto-PEEP present.

Additionally, analyzing ventilator waveforms can provide valuable information about the presence of auto-PEEP and guide appropriate interventions.

Auto-PEEP Waveform

Auto-PEEP can be visualized on a flow-volume loop, a ventilator graphic that represents how air flows in and out of the lungs during a breathing cycle.

A typical flow-volume loop graphic during mechanical ventilation displays inspiration on the top and expiration on the bottom. As the patient exhales, the line returns to the baseline, forming a complete loop that represents an entire breathing cycle.

This graphic displays a representation of air trapping, which occurs when air remains in the lungs due to an incomplete exhalation.

This can be seen on the loop where the expiratory limb does not return to the baseline. Air trapping that results from an inadequate expiratory time is a primary cause of auto-PEEP, which can be visualized in this graphic.

Other Names for Auto-PEEP

Auto-PEEP is also known by several alternative names, including:

• Intrinsic PEEP
• Inadvertent PEEP
• Dynamic hyperinflation
• Occult PEEP

Though these terms may be used interchangeably, they all refer to the same phenomenon—positive pressure that remains in the alveoli at the end of the exhalation phase during mechanical ventilation, which can lead to complications if not properly managed.

FAQ

How to Correct Auto-PEEP?

The primary cause of auto-PEEP is an expiratory time that is not long enough. Therefore, to correct auto-PEEP, you must increase the patient’s expiratory time, allowing a complete exhalation.

You can do that by decreasing the respiratory rate, decreasing the inspiratory time, increasing the flow, or by decreasing the tidal volume.

What is the Difference Between Air Trapping and Auto-PEEP?

Air trapping and auto-PEEP are related concepts in the context of mechanical ventilation, but they represent distinct phenomena.

Air trapping refers to the retention of gas in the lungs at the end of exhalation due to incomplete emptying of the alveoli. This can occur in conditions with increased airway resistance, such as asthma or COPD, or when ventilator settings do not allow for sufficient expiratory time.

On the other hand, auto-PEEP is a complication of mechanical ventilation, characterized by the presence of positive pressure in the alveoli at the end of the exhalation phase of the breathing cycle.

While air trapping contributes to the development of auto-PEEP, not all instances of air trapping will result in auto-PEEP. auto-PEEP can cause a range of adverse effects on patients, including increased work of breathing, barotrauma, and hemodynamic compromise.

What are the Risks of Developing Auto-PEEP During Mechanical Ventilation?

The risks of developing auto-PEEP during mechanical ventilation are significant and can lead to a myriad of adverse effects. Auto-PEEP can result in air trapping and an increased work of breathing.

This can cause respiratory muscle fatigue, hemodynamic instability, and patient-ventilator asynchrony, complicating the process of weaning a patient from the ventilator.

Furthermore, auto-PEEP can also make it difficult for patients to trigger a breath, increase the risk of barotrauma, and heighten anxiety levels.

Final Thoughts

Auto-PEEP is a critical complication of mechanical ventilation that can adversely affect patients’ respiratory and hemodynamic status.

Recognizing its presence, understanding its causes, and implementing appropriate management strategies are crucial for optimizing patient outcomes during mechanical ventilation.

Therefore, clinicians and respiratory therapists must remain vigilant and tailor their interventions to minimize the risks associated with Auto-PEEP while ensuring adequate respiratory support.