Measurement of bronchial responsiveness by forced oscillation technique in occupational epidemiology

Abstract

M Me ea as su ur re em me en nt t o of f b br ro on nc ch hi ia al l r re es sp po on ns si iv ve en ne es ss s b by y f fo or rc ce ed d o os sc ci il ll la at ti io on n t te ec ch hn ni iq qu ue e i in n o oc cc cu up pa at ti io on na al l e ep pi id de em mi io ol lo og gy y Changes in resistance (∆R 0 %), frequency dependence of resistance (∆P) and resonant frequency (∆F%) determined by the FOT were compared to the ∆FEV 1 %. Receiver operating characteristic (ROC) curves were established to determine values of the changes in FOT parameters which corresponded to the best sensitivity and specificity for classifying the subjects as hyperresponsive or nonresponsive on the methacholine challenge test.Significant correlations were observed between ∆FEV 1 % and ∆R 0 %, ∆P and ∆F% respectively. The ROC curves showed the following cut-off values of FOT parameters to be the best values for classifying the subjects according to the presence or absence of 20% fall in FEV 1 : a 65% increase in R 0 (sensitivity 75%; specificity: 76%); a decrease of 65×10 -3 hPa·l -1 ·s 2 in P (sensitivity 58%; specificity 83%); a 50% increase in F (sensitivity 75%; specificity 62%).Our results suggest that the FOT is a useful test for assessment of bronchial hyperresponsiveness when compared to spirometry, and can be applied to epidemiological studies of a bronchial challenge test in normal active working populations.

Respiratory resistive impedance in obstructive patients: linear regression analysis vs viscoelastic modelling

“…In normal subjects, resistive impedance (Rω) can be fairly well described over 4-32 Hz by a linear frequencydependent model characterized by its intercept with the ordinate axis and its slope, which is generally close to zero [1][2][3][4][5][6][7]. By contrast, in obstructive patients, Rω exhibits a negative frequency-dependence, which mostly occurs below 16 Hz, and is better described by two regression lines [8].…”

“…In normal subjects, the resistive respiratory impedance derived from this technique, appears to be a linear function of frequency over the usual range (4-32 Hz). Resistive impedance can, therefore, be characterized by two parameters, namely its intercept with the ordinate axis, which represents respiratory resistance extrapolated at zero frequency (R0), and its slope (S) which is then close to zero [1][2][3][4][5][6][7]. By contrast, in patients with airway obstruction or in subjects shown to be hyperreactive on bronchial challenge, resistive impedance displays a marked negative frequency dependence up to about 16 Hz, and at least two straight line segments are then necessary to approximate it by linear functions of frequency.…”

Respiratory impedance response to continuous negative airway pressure in awake controls and OSAS

“…It also appeared interesting to consider the parameters derived from respiratory reactance. Indeed, parallel variations of R0 and RF have been reported in the course of bronchial challenge tests to inhaled methacholine [22], and any increase in tissue elastance is associated with an increase in Ers, and thereby in RF. …”

Impulse Oscillometry for Leukotriene D4Inhalation Challenge in Asthma

“…By using the average reaction in IOS parameters and linear regression model, Wang et al 25 reported that an 80% increase in resonance frequency, 50% increase in Z 5 or R 5 , or 100% increase in X 5 could be regarded as significant. Pairon et al 26 reported an assay sensitivity of 0.75 and specificity of 0.76 for a 65% increase in total resistance for methacholine bronchial provocation test in active workers with normal baseline spirometry. They also showed that the positive threshold was 65% and 50% for elastance at 10 Hz and resonance frequency: results similar to our study.…”