What is the management of auto-PEEP (intrinsic positive end-expiratory pressure)?

Management of Auto-PEEP

The primary management of auto-PEEP involves immediate ventilator adjustments: decrease respiratory rate, reduce tidal volumes to 6-8 mL/kg, shorten inspiratory time (increase inspiratory flow to 80-100 L/min), and prolong expiratory time (I:E ratio 1:4 or 1:5) to allow complete lung emptying. 1

Immediate Recognition and Emergency Management

Acute Hemodynamic Compromise

• If auto-PEEP causes significant hypotension, immediately disconnect the patient from the ventilator circuit to allow passive exhalation and PEEP dissipation. 1
• Press on the chest wall after disconnection to assist active exhalation, which should lead to immediate resolution of hypotension. 1
• Use the DOPE mnemonic (tube Displacement, tube Obstruction, Pneumothorax, Equipment failure) plus auto-PEEP when evaluating any acute deterioration in mechanically ventilated patients. 1

Detection Methods

• Monitor for absent end-expiratory flow on the ventilator flow-time waveform, which indicates incomplete exhalation. 2
• Measure static auto-PEEP using end-expiratory occlusion: manually occlude the expiratory port during the last 0.5 seconds of expiration and observe the pressure rise on the manometer. 1, 3
• In spontaneously breathing patients, measurement requires esophageal pressure monitoring to account for active inspiratory muscle effort. 1

Ventilator Strategy Adjustments

Primary Interventions

• Decrease minute ventilation by reducing respiratory rate rather than increasing inspiratory flow alone. 2, 3
• Use tidal volumes of 6-8 mL/kg to minimize breath stacking and barotrauma risk. 1
• Set inspiratory flow rates to 80-100 L/min in adults to shorten inspiratory time and maximize expiratory time. 1
• Target I:E ratios of 1:4 or 1:5, which are longer than standard ratios used in patients without obstructive physiology. 1

Permissive Hypercapnia

• Accept mild hypoventilation and elevated PaCO₂ to reduce barotrauma risk, as hypercapnia is typically well tolerated. 1
• This strategy prioritizes preventing ventilator-induced lung injury over normalizing blood gases. 1

Application of External PEEP

Indications and Technique

• Apply low levels of external PEEP (typically 5 cm H₂O or less) in spontaneously breathing patients to counterbalance intrinsic PEEP and reduce inspiratory threshold load. 1, 4
• External PEEP reduces work of breathing, improves patient-ventilator synchrony, and decreases ineffective triggering efforts. 1, 2
• Never set external PEEP levels exceeding the measured intrinsic PEEP, as this worsens hyperinflation and causes hemodynamic compromise. 4

Flow vs. Pressure Triggering

• Use flow triggering instead of pressure triggering in patients with auto-PEEP, as flow triggers are more sensitive and reduce patient-ventilator asynchrony. 4
• Flow triggering detects changes in bias flow rather than requiring pressure changes, making it easier for patients to initiate breaths despite the auto-PEEP threshold. 4

Sedation and Paralysis Considerations

• Provide adequate sedation to optimize ventilation, decrease ventilator dyssynchrony, and minimize auto-PEEP generation. 1
• Consider paralytic agents only if auto-PEEP persists despite adequate sedation and the patient displays significant ventilator dyssynchrony. 1
• Sedation allows better tolerance of permissive hypercapnia and reduces patient fighting against the ventilator. 1

Addressing Underlying Causes

Bronchodilation

• Continue aggressive bronchodilator therapy (inhaled albuterol) through the endotracheal tube, as airway obstruction is often the primary driver of auto-PEEP. 1
• Ensure adequate delivery of inhaled medications despite mechanical ventilation. 1

Airway Management

• Use the largest endotracheal tube available (8-9 mm) to minimize airway resistance if intubation is required. 1
• Check for and eliminate mucous plugging, tube kinking, or other sources of increased expiratory resistance. 1

Monitoring and Troubleshooting

Routine Assessment

• Monitor pressure-time and flow-time scalars continuously in all mechanically ventilated patients at risk for auto-PEEP. 4
• Measure peak inspiratory pressure, plateau pressure, and mean airway pressure regularly. 4
• Document measured auto-PEEP values and correlate with clinical signs of hemodynamic compromise. 4

High-Risk Populations

• Patients with severe asthma, COPD exacerbations, or those receiving high minute ventilation are at highest risk. 4, 2, 3
• Trauma patients with hypermetabolic states requiring high minute ventilation commonly develop auto-PEEP (56% in one series). 5

Expert Consultation

• Obtain expert consultation for optimal ventilator management, as settings require ongoing careful review of ventilation flow and pressure curves. 1

Common Pitfalls to Avoid

• Do not hyperventilate patients, as this exacerbates auto-PEEP by not allowing sufficient expiratory time. 1
• Avoid inappropriately attributing hypotension to hypovolemia when auto-PEEP is the actual cause, which may lead to unnecessary fluid administration or vasopressor therapy. 3
• Do not delay disconnection from the ventilator if severe hypotension occurs—this is a life-saving emergency maneuver. 1
• Recognize that applying external PEEP during controlled ventilation (when patients are not triggering) has no proven benefit and may worsen hyperinflation. 3