A pulse method of measuring respiratory system compliance

Area of Science:

• Pulmonary Physiology
• Respiratory Mechanics

Background:

• Accurate measurement of respiratory system compliance (Crs) is crucial for assessing lung function.
• Existing methods may not reliably distinguish between passive Crs and active muscle effort.

Purpose of the Study:

• To present a new method for measuring Crs using pulse airflow.
• To evaluate the method's ability to detect respiratory muscle relaxation.

Main Methods:

• A pulse airflow (0.3/s) was delivered via a pneumotachograph.
• Mouth pressure and integrated volume were recorded to generate volume-pressure loops.
• Respiratory system compliance (Crs) was calculated from the slope of the linear portion of the loop.

Main Results:

• The method produced straight volume-pressure lines with low variability (4.8% CV) in relaxed subjects.
• Irregular lines were observed when respiratory muscles were not relaxed.
• Mean Crs in 15 normal subjects was 0.86 +/- 0.016 L/cmH2O, aligning with published data when normalized by vital capacity.

Conclusions:

• The pulse airflow method provides an accurate measurement of respiratory system compliance.
• This technique offers the significant advantage of detecting respiratory muscle relaxation during measurement.