Is controlled or spontaneous breathing required for a pulmonary embolism patient on mechanical ventilation?

Mechanical Ventilation Strategy for Pulmonary Embolism Patients

For pulmonary embolism patients requiring mechanical ventilation, controlled ventilation should be used initially with extreme caution regarding positive pressure effects, prioritizing non-invasive ventilation when feasible, and avoiding intubation unless absolutely necessary due to the severe hemodynamic consequences of positive pressure ventilation in right ventricular failure. 1

Primary Ventilation Approach

Non-invasive ventilation or high-flow nasal cannula should be strongly preferred over invasive mechanical ventilation whenever the patient can tolerate it, as intubation and positive pressure ventilation can precipitate catastrophic hemodynamic collapse in PE patients with right ventricular dysfunction 1. The 2019 ESC guidelines explicitly state that intubation should only be performed if the patient is unable to tolerate or cope with non-invasive ventilation 1.

Critical Hemodynamic Considerations

• Positive intrathoracic pressure from mechanical ventilation reduces venous return and directly worsens right ventricular failure, which is the primary cause of death in high-risk PE 1, 2
• Patients with RV failure are frequently hypotensive or highly susceptible to severe hypotension during induction of anesthesia, intubation, and initiation of positive-pressure ventilation 1
• Positive end-expiratory pressure (PEEP) must be applied with extreme caution in PE patients, as it can further compromise already tenuous hemodynamics 1, 2

When Invasive Mechanical Ventilation Is Unavoidable

If intubation becomes necessary due to extreme instability (cardiac arrest) or failure of non-invasive approaches, controlled mechanical ventilation should be used with lung-protective strategies 1:

Specific Ventilator Settings

• Tidal volumes of approximately 6 mL/kg lean body weight to minimize intrathoracic pressure effects 1
• Keep end-inspiratory plateau pressure <30 cm H₂O 1
• Use minimal PEEP (start with 5-8 cm H₂O) and increase only if absolutely necessary for oxygenation, while continuously monitoring hemodynamics 2
• Avoid hyperventilation and maintain normocapnia (PaCO₂ 40-45 mmHg or ETCO₂ 35-40 mmHg) 1

Anesthetic Considerations

• Avoid anesthetic drugs prone to causing hypotension during induction 1
• The hemodynamic instability risk is highest during the intubation process itself 1

Spontaneous vs. Controlled Breathing

The question of spontaneous versus controlled breathing is somewhat misleading in this context, as:

• Initial management requires full ventilatory support (controlled ventilation) if invasive mechanical ventilation is instituted, given the severity of illness and need for sedation 1
• The goal is to minimize the duration of positive pressure ventilation and transition away from mechanical ventilation as soon as pulmonary reperfusion is achieved 1
• Correction of hypoxemia will not be possible without simultaneous pulmonary reperfusion (via thrombolysis, thrombectomy, or anticoagulation), regardless of ventilation mode 1

Oxygenation Strategy

• Supplemental oxygen is indicated when SaO₂ <90% 1
• High-flow oxygen via nasal cannula should be considered before resorting to mechanical ventilation 1
• Severe refractory hypoxemia may indicate right-to-left shunt through patent foramen ovale or atrial septal defect 1

Critical Pitfall to Avoid

The most dangerous error is aggressive positive pressure ventilation with high PEEP in PE patients, as this can precipitate complete cardiovascular collapse by further impairing RV function and reducing venous return 1, 2. The European Society of Cardiology specifically warns that positive intrathoracic pressure may contribute to hemodynamic instability and worsen low cardiac output due to RV failure 1.