Glottal Aperture and Buccal Airflow Leaks Critically Affect Forced Oscillometry Measurements.

Area of Science:

• Respiratory Physiology
• Pulmonary Function Testing

Background:

• The forced oscillation technique (FOT) is used to measure respiratory resistance and reactance.
• Upper airway influences, specifically glottal aperture and buccal air leaks, can impact FOT measurement accuracy.

Purpose of the Study:

• To quantify the impact of varying glottal apertures and buccal air leaks on FOT measurements.
• To determine the significance of these upper airway factors in altering respiratory resistance and reactance values.

Main Methods:

• Studies involved healthy subjects and patients with COPD.
• Glottal aperture effects were assessed by comparing FOT measurements during normal breathing, glottal closure, and humming.
• Buccal air leak effects were evaluated using breathing filters with progressively larger holes.

Main Results:

• Narrowing the glottis and humming significantly increased resistance (R5) and decreased reactance (X5) at 5 Hz.
• Frequency dependency of resistance was also increased by glottal narrowing.
• Air leaks through modified filters reduced R5 and made X5 less negative in both healthy subjects and COPD patients.

Conclusions:

• Glottal narrowing can manifest as peaks in R5, while buccal air leaks create volume indentations in the breathing trace.
• These artifacts significantly affect FOT measurements, necessitating visual data inspection for exclusion.
• Accurate interpretation of FOT requires careful consideration and exclusion of upper airway influences.