Expiratory phase and volume-adjusted tracheal gas insufflation: a lung model study

Area of Science:

• Mechanical Ventilation
• Respiratory Physiology

Background:

• Tracheal gas insufflation (TGI) is a technique used in mechanical ventilation.
• Continuous-flow TGI can lead to undesirable increases in system pressures and volumes.
• Optimizing TGI delivery is crucial for patient safety and ventilation efficacy.

Purpose of the Study:

• To evaluate expiratory-phase TGI and volume-adjusted TGI in a lung model.
• To assess the impact of these TGI methods on system pressures and volumes during ventilation.
• To compare these methods against continuous-flow TGI.

Main Methods:

• A single-compartment lung model was used in a university research laboratory.
• Expiratory-phase TGI was delivered using a ventilator-activated solenoid valve.
• Volume-adjusted TGI involved reducing tidal volume (VT) based on TGI flow and inspiratory time.
• Ventilation was performed under pressure control (20 cm H2O) or volume control, with a set rate (15 breaths/min) and PEEP (10 cm H2O).
• Various inspiratory times (1.0-2.5 secs), TGI flows (0-12 L/min), and lung model compliances/resistances were tested.

Main Results:

• Expiratory-phase TGI with pressure control ventilation maintained constant peak alveolar pressure, increased PEEP, and decreased VT.
• Expiratory-phase TGI with volume control ventilation and volume-adjusted TGI significantly increased peak alveolar pressure and PEEP.
• Volume-adjusted TGI's VT readjustment was compromised at longer inspiratory times and higher TGI flows.

Conclusions:

• Expiratory-phase TGI and volume-adjusted TGI can mitigate the adverse effects of continuous-flow TGI.
• These optimized TGI strategies help avoid excessive increases in system pressures and volumes.
• Further research may be needed to refine volume-adjusted TGI parameters for optimal performance.