Volume-controlled inverse ratio ventilation: effect on dynamic hyperinflation and auto-PEEP

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Mechanical Ventilation

Background:

• Dynamic hyperinflation and auto-PEEP are critical concerns in mechanical ventilation.
• Understanding ventilation strategies is crucial for managing patients with ARDS and post-CABG.

Purpose of the Study:

• To compare the effects of Inverse Ratio Ventilation (IRV) and Positive End-Expiratory Pressure (PEEP) on dynamic hyperinflation and auto-PEEP.
• To evaluate these effects in patients with Adult Respiratory Distress Syndrome (ARDS) and post-Coronary Artery Bypass Graft (CABG) surgery.

Main Methods:

• Volume-controlled mechanical ventilation with constant tidal volume and respiratory rate.
• Two experimental protocols: increasing PEEP with constant I:E ratio, and changing I:E ratio with no PEEP.
• Measurements included airflow, tidal volume, peak airway pressure, static end-expiratory pressure, and end-expiratory lung volume.

Main Results:

• Both PEEP and IRV increased end-expiratory lung volume (EELV) and auto-PEEP in ARDS patients.
• In CABG patients, PEEP led to a greater increase in EELV compared to IRV.
• At equivalent auto-PEEP levels, EELV increase was similar between PEEP and IRV in both groups.
• Peak airway pressure reduction was minimal during IRV.

Conclusions:

• The impact of reduced expiratory time with IRV on EELV and auto-PEEP is comparable to using PEEP.
• Both ventilation strategies can be used to manage hyperinflation and auto-PEEP in critically ill patients.