Respiratory mechanics at different PEEP level during general anesthesia in the elderly: a pilot study

Area of Science:

• Anesthesiology
• Respiratory Physiology

Background:

• General anesthesia can lead to expiratory flow limitation (EFL) by increasing closing capacity relative to functional residual capacity.
• This reduction in maximal expiratory flow can compromise respiratory mechanics during surgical procedures.

Purpose of the Study:

• To validate a novel positive end-expiratory pressure (PEEP) test for detecting EFL during anesthesia.
• To investigate the association between anesthesia and the development of EFL.
• To assess if low-level PEEP can mitigate negative effects of lung volume ventilation.

Main Methods:

• Fifty-two abdominal surgery patients were randomized into two groups: ZEEP (PEEP 0 cmH2O) and PEEP (PEEP 5 cmH2O).
• Expiratory flow limitation (EFL) was assessed using the negative expiratory pressure (NEP) test pre-operatively and the PEEP test intra-operatively.
• Respiratory mechanics were measured at the start and end of anesthesia.

Main Results:

• The PEEP test effectively detected EFL.
• Anesthesia induced EFL in 8 patients post-induction.
• In the ZEEP group, 7 additional patients developed EFL by the end of surgery, compared to only 1 in the PEEP group.
• The ZEEP group showed significant decreases in expiratory flow and worsened respiratory mechanics.

Conclusions:

• The PEEP test is a valuable tool for identifying EFL during anesthesia.
• Applying 5 cmH2O of PEEP effectively prevented the deterioration of lung mechanics observed in the ZEEP group during surgery.