Optimal Use of PEEP in CVICU

Physiological Effects of PEEP

PEEP maintains positive alveolar pressure at end-expiration, preventing alveolar collapse and improving functional residual capacity, which is particularly important in ventilator-dependent cardiac patients 1, 2
In ventilator-dependent patients, PEEP counterbalances intrinsic PEEP (auto-PEEP), reducing the inspiratory threshold load during both spontaneous breathing and patient-triggered ventilation modes 3, 4

High levels of PEEP can decrease cardiac output by increasing intrathoracic pressure, reducing venous return, and potentially worsening right ventricular function in patients with pulmonary hypertension or right heart failure 3, 5
When mechanical ventilation is required in patients with cardiovascular compromise, PEEP should be applied with caution as positive intrathoracic pressure may reduce venous return and worsen right ventricular failure 5

Intrinsic PEEP can be measured using either end-expiratory airway occlusion technique or simultaneous recording of flow and pleural pressure 4
The American Thoracic Society recommends using plateau pressure measurements to guide ventilator settings and titrate PEEP levels 6
For patients without ARDS, plateau pressures should be maintained below 25 cmH2O, while for ARDS patients, plateau pressures should remain below 30 cmH2O to prevent ventilator-induced lung injury 6

Application of low levels of PEEP (5-10 cmH2O) can significantly improve patient-ventilator interaction and reduce the magnitude of inspiratory effort during assisted ventilation and weaning 3
For patients with acute lung injury or ARDS in the CVICU, PEEP improves oxygenation and may reduce ventilator-induced lung injury 3

When implementing PEEP in cardiac patients, careful cardiovascular monitoring is essential to detect and address any adverse hemodynamic effects 5
In patients with right ventricular dysfunction or pulmonary hypertension, lower PEEP levels may be preferable to minimize adverse effects on pulmonary blood flow 5

Patient-ventilator asynchrony can lead to inaccurate PEEP measurements; ensuring the patient is not actively breathing during measurement is crucial 6
When using PEEP in patients with cardiac conditions, the balance between respiratory benefits and potential cardiac effects must be carefully evaluated, with continuous monitoring of both systems 5

The American College of Chest Physicians recommends that extrinsic PEEP counteracts auto-PEEP by reducing the inspiratory threshold load that patients must overcome to trigger the ventilator, effectively counterbalancing the intrinsic positive pressure without necessarily increasing total end-expiratory pressure when applied judiciously 7
Auto-PEEP creates an inspiratory pressure threshold load during both spontaneous breathing and patient-triggered mechanical ventilation modes, requiring patients to generate sufficient negative pleural pressure to counterbalance it before initiating inspiratory flow 7
Application of low levels of external PEEP significantly improves patient-ventilator interaction and reduces the magnitude of inspiratory effort during assisted ventilation by counterbalancing auto-PEEP at least in part 7

The American Thoracic Society guidelines support measuring auto-PEEP using the end-expiratory airway occlusion technique, which is the gold standard and requires the patient to be passive 7
External PEEP should be applied conservatively at approximately 50-85% of the measured auto-PEEP value to avoid exacerbating hyperinflation and potential hemodynamic compromise 7
It is recommended to never exceed the measured auto-PEEP level with external PEEP, as setting PEEP greater than intrinsic PEEP can be harmful and worsen hyperinflation 7

External PEEP provides multiple benefits in the presence of auto-PEEP, including improved ventilator triggering sensitivity, which reduces wasted efforts and patient-ventilator asynchrony 7
The use of external PEEP can also reduce the work of breathing during machine-assisted cycles, improving patient comfort and reducing the risk of respiratory muscle fatigue 7

Avoid applying external PEEP blindly without measuring auto-PEEP first, as this can lead to excessive total PEEP and worsen hyperinflation 7
Excessive external PEEP can decrease cardiac output by increasing intrathoracic pressure and reducing venous return, particularly in patients with right ventricular dysfunction or pulmonary hypertension 7