Variability, reproducibility and observer difference of body plethysmographic measurements

Area of Science:

• Pulmonary Physiology
• Respiratory Medicine
• Medical Instrumentation

Background:

• Body plethysmography is a key method for measuring static lung volumes and airways resistance (Raw).
• Accurate and reproducible measurements are crucial for diagnosing and monitoring respiratory disorders.
• Understanding the variability and interobserver differences in body plethysmography is essential for clinical application.

Purpose of the Study:

• To evaluate the variability, reproducibility, and interobserver differences of airways resistance (Raw) and static lung volumes.
• To assess these parameters using body plethysmography in healthy subjects and patients with respiratory disorders.

Main Methods:

• Measurements of Raw and static lung volumes (RV, FRC, TLC) were performed using body plethysmography.
• Variability was assessed via coefficient of variation of five consecutive measurements.
• Reproducibility was evaluated by comparing measurements at 1 h and 24 h.
• Interobserver differences were determined by independent readings of tracings by two observers.

Main Results:

• High variability was observed for Raw (28%), moderate for FRC (7-8%), and low for TLC (4-5%).
• No significant changes in Raw or lung volumes were found between 1 h and 24 h measurements.
• Interobserver differences for FRC and Raw were slight in normal subjects but significant in patients, with higher overestimation of Raw by observer 2 at larger values.

Conclusions:

• Body plethysmography demonstrates high variability for airways resistance measurements.
• Significant interobserver differences in patients necessitate caution when pooling data or comparing results from different technicians.
• Standardization of techniques and observer training are recommended for pulmonary function laboratories.