Research

Estimation of airway obstruction using oximeter plethysmograph waveform data

Donald H Arnold¹ , David M Spiro^{* 2} , Renee' A Desmond^{* 3} and James S Hagood^{* 4}

¹Departments of Emergency Medicine and Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

²Department of Pediatrics, Section of Emergency Medicine, Yale University School of Medicine, New Haven, Connecticut, USA

³Department of Medicine, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, USA

⁴Department of Pediatrics, Division of Pulmonary Medicine, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, USA

author email corresponding author email* Contributed equally

Respiratory Research 2005, 6:65doi:10.1186/1465-9921-6-65

Published:	28 June 2005

Abstract

Background

Validated measures to assess the severity of airway obstruction in patients with obstructive airway disease are limited. Changes in the pulse oximeter plethysmograph waveform represent fluctuations in arterial flow. Analysis of these fluctuations might be useful clinically if they represent physiologic perturbations resulting from airway obstruction. We tested the hypothesis that the severity of airway obstruction could be estimated using plethysmograph waveform data.

Methods

Using a closed airway circuit with adjustable inspiratory and expiratory pressure relief valves, airway obstruction was induced in a prospective convenience sample of 31 healthy adult subjects. Maximal change in airway pressure at the mouthpiece was used as a surrogate measure of the degree of obstruction applied. Plethysmograph waveform data and mouthpiece airway pressure were acquired for 60 seconds at increasing levels of inspiratory and expiratory obstruction. At each level of applied obstruction, mean values for maximal change in waveform area under the curve and height as well as maximal change in mouth pressure were calculated for sequential 7.5 second intervals. Correlations of these waveform variables with mouth pressure values were then performed to determine if the magnitude of changes in these variables indicates the severity of airway obstruction.

Results

There were significant relationships between maximal change in area under the curve (P < .0001) or height (P < 0.0001) and mouth pressure.

Conclusion

The findings suggest that mathematic interpretation of plethysmograph waveform data may estimate the severity of airway obstruction and be of clinical utility in objective assessment of patients with obstructive airway diseases.