Work of breathing in adaptive pressure control continuous mandatory ventilation

Area of Science:

• Mechanical Ventilation
• Respiratory Mechanics
• Critical Care Medicine

Background:

• Adaptive pressure control (APC) adjusts ventilator pressure to meet target tidal volume (VT).
• Increasing patient effort during APC can lead to reduced inflation pressure, potentially impacting clinical appropriateness.
• Understanding the interplay between ventilator work and patient effort in APC is crucial.

Purpose of the Study:

• To evaluate the relationship between ventilator work output and patient effort in adaptive pressure control modes.
• To compare the responses of different APC algorithms to varying levels of patient-driven respiratory effort.

Main Methods:

• A lung simulator (ASL 5000) was used with set compliance and resistance.
• Simulated muscle pressure (Pmus) was systematically increased to represent escalating patient effort.
• Four APC modes (AutoFlow, VC+, APV, PRVC) were tested across different ventilator brands.

Main Results:

• Patient work of breathing (WOB) increased with rising Pmus.
• Target VT was maintained up to a Pmus of 10 cm H2O, after which VT increased linearly with Pmus.
• Ventilators exhibited three distinct patterns of WOB adjustment in response to increased patient effort.

Conclusions:

• APC algorithms demonstrate variability in managing increasing patient effort.
• Some APC modes permit patients to undertake the entire WOB.
• Certain ventilators ensure a minimum level of ventilator WOB irrespective of patient effort.