Monitoring lung impedance changes during long-term ventilator-induced lung injury ventilation using electrical...

Area of Science:

• Physiology
• Medical Imaging

Background:

• Long-term monitoring of lung conditions is crucial for patient management.
• Electrical impedance tomography (EIT) offers a non-invasive method for assessing lung function.
• Time-difference EIT (tdEIT) provides higher spatial resolution compared to absolute EIT (aEIT).

Purpose of the Study:

• To evaluate the feasibility of long-term monitoring of lung condition changes using tdEIT.
• To assess the stability and reliability of the Pulmovista 500® EIT system for extended measurements.
• To compare tdEIT with aEIT for monitoring end-expiratory lung impedance change (EELIC).

Main Methods:

• A Pulmovista 500® EIT system was tested on a resistive phantom for 50 hours.
• 36 pigs were ventilated at varying positive end-expiratory pressure (PEEP) levels (0-18 cmH2O) for up to 48 hours.
• EELIC was measured using both aEIT and tdEIT, and a new parameter, centre of end-expiratory change (CoEEC), was introduced.

Main Results:

• tdEIT demonstrated good agreement with aEIT for EELIC measurements (r² = 0.93-1.0) over 48 hours.
• EELIC varied from -0.07 Ωm day⁻¹ at PEEP 4 to -1.04 Ωm day⁻¹ at PEEP 18 cmH2O.
• The CoEEC shifted dorsally with increasing PEEP, unlike the stable centre of ventilation (CoV).

Conclusions:

• tdEIT is a feasible method for precise, long-term monitoring of EELIC in pigs.
• The study validates tdEIT's utility for tracking regional lung changes over extended periods.
• The novel CoEEC parameter offers insights into dynamic lung changes under varying PEEP levels.