High vs Low PEEP in Patients With ARDS Exhibiting Intense Inspiratory Effort During Assisted Ventilation: A...

Area of Science:

• Mechanical Ventilation
• Respiratory Physiology
• Critical Care Medicine

Background:

• Positive end-expiratory pressure (PEEP) is a mechanical ventilation strategy that may influence inspiratory effort (ΔPes).
• Inspiratory effort is a key factor in the development of self-inflicted lung injury (SILI).
• Understanding the modulation of ΔPes by PEEP is crucial for optimizing ventilator settings in ARDS.

Purpose of the Study:

• To investigate whether high PEEP reduces inspiratory effort (ΔPes) in patients with moderate-to-severe ARDS receiving assisted mechanical ventilation.
• To assess the impact of high PEEP on respiratory system mechanics, lung stress, and tidal volume distribution.

Main Methods:

• A randomized crossover study involving 16 ARDS patients with Pao2/Fio2 ≤ 200 mmHg and ΔPes ≥ 10 cm H2O.
• Patients were subjected to two PEEP levels (5 cm H2O and 15 cm H2O) combined with synchronous (PSV) or asynchronous (PC-IMV) inspiratory assistance.
• Measurements included esophageal manometry for ΔPes and respiratory mechanics, and electrical impedance tomography for alveolar recruitment, overinflation, lung strain, and tidal volume distribution.

Main Results:

• High PEEP did not significantly alter ΔPes, respiratory system driving pressure, or transpulmonary driving pressure compared to low PEEP.
• The effect of high PEEP on ΔPes and driving pressures was variable and correlated with changes in respiratory system compliance (r = -0.85, P < .001).
• High PEEP induced alveolar recruitment and redistributed tidal volume, reducing dynamic strain in ventral lung regions, but this effect was dependent on PEEP-induced alveolar overinflation.

Conclusions:

• The impact of high PEEP on inspiratory effort and lung stress in ARDS is interindividually variable.
• High PEEP may mitigate the risk of self-inflicted lung injury only if it improves lung and respiratory system compliance.
• Optimizing PEEP requires careful consideration of its effects on respiratory mechanics and potential for alveolar overinflation.