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Original Research: Pulmonary Procedures |

Glottal Aperture and Buccal Airflow Leaks Critically Affect Forced Oscillometry MeasurementsArtifacts and Impulse Oscillometry

Andras Bikov, MD, PhD; Neil B. Pride, MD, PhD; Michael D. Goldman, MD, PhD; James H. Hull, MD, PhD; Ildiko Horvath, MD, PhD; Peter J. Barnes, DM, DSc, Master FCCP; Omar S. Usmani, MBBS, PhD; Paolo Paredi, MD, PhD
Author and Funding Information

From the Airway Disease Section (Drs Bikov, Hull, Usmani, and Paredi and Profs Pride, Goldman, and Barnes), National Heart and Lung Institute, Imperial College London and Royal Brompton Hospital, London, England; and Department of Pulmonology (Dr Bikov and Prof Horvath), Semmelweis University, Budapest, Hungary.

CORRESPONDENCE TO: Paolo Paredi, MD, PhD, Airway Disease Section, National Heart and Lung Institute, Imperial College, Dovehouse St, London, SW3 6LY, England; e-mail: p.paredi@imperial.ac.uk


†Deceased.

Drs Usmani and Paredi contributed equally to this manuscript.

FUNDING/SUPPORT: Dr Bikov was supported by a European Respiratory Society Long-Term Fellowship. Dr Usmani is a recipient of a National Institutes of Health Research (NIHR) UK Career Development Fellowship. The study was supported by the NIHR Respiratory Disease Biomedical Research Unit at the Royal Brompton and Harefield NHS Foundation Trust and Imperial College London.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;148(3):731-738. doi:10.1378/chest.14-2644
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BACKGROUND:  The forced oscillation technique (FOT) measures respiratory resistance and reactance; however, the upper airways may affect the results. We quantified the impact of glottal aperture and buccal air leaks.

METHODS:  In the glottal aperture study (1) 10 healthy subjects (aged 34 ± 2 years) performed a total lung capacity maneuver followed by 10-s breath-hold with and without total glottal closure and (2) the effects of humming (incomplete glottal narrowing) on FOT measurements were studied in six healthy subjects. Glottal narrowing was confirmed by direct rhinolaryngoscopy. In the air leak study, holes of increasing diameter (3.5, 6.0, and 8.5 mm) were made to the breathing filters. Eleven healthy subjects (aged 33 ± 2 years) and five patients with COPD (aged 69 ± 3 years) performed baseline FOT measurements with the three modified filters.

RESULTS:  Narrow glottal apertures and humming generated whole-breath resistance at 5 Hz (R5) peaks, increased R5 (1.49 ± 0.37 kPa/L/s vs 0.34 ± 0.01 kPa/L/s, P < .001), and decreased whole-breath reactance at 5 Hz (X5) values (−2.10 ± 0.51 kPa/L/s vs −0.09 ± 0.01 kPa/L/s, P < .001). The frequency dependency of resistance was increased. Holes in the breathing filters produced indentations on the breathing trace. Even the smaller holes reduced R5 in healthy subjects (0.33 ± 0.02 to 0.24 ± 0.02 kPa/L/s, P < .01) and patients with COPD (0.50 ± 0.04 to 0.41 ± 0.04 kPa/L/s, P < .05), whereas X5 became less negative (from −0.09 ± 0.01 to −0.05 ± 0.01 in healthy subjects, P < .01; from −0.22 ± 0.06 to −0.11 ± 0.03 kPa/L/s in patients with COPD, P < .05).

CONCLUSIONS:  Visual inspection of the data is required to exclude glottal narrowing and buccal air leaks identified as R5 peaks and volume indentations, respectively, because these significantly affect FOT measurements.

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