What are the advantages of preserved spontaneous breathing versus controlled mechanical ventilation?

Advantages of Preserved Spontaneous Breathing versus Controlled Mechanical Ventilation

Preserved spontaneous breathing during mechanical ventilation offers significant physiological benefits including improved pulmonary gas exchange, systemic blood flow, and oxygen supply to tissues compared to controlled mechanical ventilation, particularly in patients with mild to moderate ARDS. 1

Physiological Benefits of Preserved Spontaneous Breathing

• Spontaneous breathing improves gas exchange by redistributing ventilation and end-expiratory gas to dependent, juxtadiaphragmatic lung regions, thereby promoting alveolar recruitment 1
• Spontaneous breathing counters undesirable cyclic alveolar collapse in dependent lung regions, which can help prevent ventilator-induced lung injury 1
• Maintained spontaneous breathing can reduce the need for deep sedation, which decreases the duration of mechanical ventilator support, length of ICU stay, and overall costs of care 1

Clinical Outcomes with Preserved Spontaneous Breathing

• Daily spontaneous breathing trials in mechanically ventilated patients who meet readiness criteria can significantly reduce the duration of mechanical ventilation (median 4.5 days vs 6 days with conventional weaning) 2
• Spontaneous breathing trials are associated with fewer complications such as unplanned extubation, reintubation, tracheostomy, and prolonged mechanical ventilation 2
• Using protocols that incorporate daily spontaneous breathing trials can reduce ICU costs (median $15,740 vs $20,890 with conventional care) 2

Ventilation Modes Supporting Spontaneous Breathing

• Pressure support ventilation (PSV) has been shown to improve sleep quality in patients with prolonged weaning compared to completely unsupported spontaneous breathing 3
• Assist-control ventilation (ACV) has been associated with greater sleep efficiency than minimal pressure support ventilation in patients with acute on chronic respiratory failure 3
• Pressure control ventilation for nighttime respiratory muscle rest can increase sleep efficiency, slow-wave sleep, and REM sleep compared to low-level PSV in patients with severe COPD 3

Considerations Based on ARDS Severity

• Spontaneous breathing should be considered beneficial in mild to moderate ARDS but may be harmful in severe ARDS 4
• In severe ARDS, controlled mechanical ventilation with muscle paralysis in the first 48 hours has been shown to improve survival compared to ventilation strategies allowing spontaneous breathing 4
• The decision between spontaneous and controlled ventilation should be based on ARDS severity rather than suppressing spontaneous breathing in all ARDS patients 4

Potential Risks of Spontaneous Breathing

• Spontaneous breathing during mechanical ventilation can cause negative swings in alveolar pressure, potentially contributing to lung injury in certain patients 5
• High levels of pressure support may cause sleep disruption from periodic breathing and central apneas due to hypocapnia 3
• Patient-ventilator asynchrony during spontaneous breathing modes can contribute to sleep fragmentation and potentially worse outcomes 3

Recommendations for Clinical Practice

• Guidelines recommend using spontaneous breathing trials in mechanically ventilated patients with sepsis who are ready for weaning (strong recommendation, high quality of evidence) 3
• Patients should satisfy specific criteria before attempting spontaneous breathing trials: being arousable, hemodynamically stable without vasopressors, no new serious conditions, low ventilatory and PEEP requirements, and low FiO2 requirements 3
• A weaning protocol should be in place for mechanically ventilated patients with sepsis-induced respiratory failure who can tolerate weaning (strong recommendation, moderate quality of evidence) 3

Implementation of Spontaneous Breathing Trials

• Spontaneous breathing trials can be conducted using either T-piece breathing or flow-triggered ventilation with continuous positive airway pressure of 5 cmH2O 3
• Patients who tolerate a spontaneous breathing trial for 2 hours have approximately 85% success rate with complete discontinuation of mechanical ventilation 3
• For the initial spontaneous breathing trial, guidelines suggest using inspiratory pressure augmentation (5-8 cmH2O) rather than T-piece or CPAP alone (conditional recommendation, moderate quality evidence) 3