Intrasubject variability of maximal expiratory flow volume curve

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Diagnostic Testing

Background:

• Early diagnosis of chronic airways obstruction is crucial for timely intervention.
• Maximal expiratory flow-volume curve analysis is proposed for early detection.
• Prospective studies are needed to confirm the efficacy of early diagnosis and intervention.

Purpose of the Study:

• To assess the intrasubject variability of forced expiration tests for screening early airways obstruction.
• To determine the reliability of different flow-volume curve measurements in healthy young adults.

Main Methods:

• Measured expiratory flow-volume curves in 10 healthy adults (20-30 years) over six weeks.
• Collected data on forced expired volume in one second (FEV1), forced vital capacity (FVC), maximal expiratory flow rates (50% and 75% of FVC), and forced expiratory time (FET).
• Utilized analysis of variance to evaluate measurement variability and diurnal patterns.

Main Results:

• No consistent diurnal variation was observed in the measured parameters.
• FEV1 and FVC exhibited significantly lower intrasubject variability compared to maximal expiratory flow rates and FET.
• High variability in terminal flow rates and FET suggests limitations for detecting subtle airway changes.

Conclusions:

• FEV1 and FVC are more reproducible and suitable for cross-sectional screening of airways obstruction.
• Terminal portion flow rates and FET show high variability, potentially limiting their utility in early disease detection.
• Maximal expiratory flow-volume curves may be more valuable for longitudinal studies monitoring individual changes or short-term challenge tests.