Use of reactance to estimate transpulmonary resistance

Area of Science:

• Respiratory Physiology
• Pulmonary Mechanics
• Diagnostic Methods

Background:

• Assessing transpulmonary resistance (R(L)) typically requires invasive esophageal manometry.
• Forced oscillometry offers a non-invasive method to measure respiratory system resistance (R(rs)) and reactance (X(rs)).
• The relationship between oscillometry parameters and R(L) needs further clarification for clinical application.

Purpose of the Study:

• To investigate the correlation between respiratory system resistance (R(rs)) and reactance (X(rs)) with transpulmonary resistance (R(L)).
• To develop and validate prediction equations for R(L) using oscillometric parameters.
• To explore the underlying physiological mechanisms linking R(L) and X(rs).

Main Methods:

• Simultaneous forced oscillometry (5 Hz) and esophageal manometry were performed on asthmatic subjects during bronchoprovocation.
• Prediction equations for R(L) were derived from oscillometric data.
• These equations were tested on separate groups of asthmatic and non-asthmatic subjects.

Main Results:

• Respiratory system reactance (X(rs)) showed a stronger correlation with transpulmonary resistance (R(L)) than R(rs) in asthmatics.
• Predicted R(L) values from X(rs) demonstrated good agreement with measured values in asthmatics and non-asthmatics.
• Lumped element modeling indicated that airway wall shunting significantly influences the X(rs)-R(L) relationship.

Conclusions:

• Respiratory system reactance (X(rs)) is a more accurate predictor of transpulmonary resistance (R(L)) than respiratory system resistance (R(rs)).
• Non-invasive oscillometry, particularly X(rs), can effectively estimate R(L) across different respiratory conditions.
• The findings support the use of forced oscillometry for assessing R(L) non-invasively, simplifying lung function evaluation.