Total respiratory resistance and reactance in patients with diffuse interstitial lung disease

Abstract

In 54 patients with interstitial lung diseases and no signs of airway obstruction we measured lung volumes, maximal expiratory flows, diffusing capacity (DLCO), total respiratory resistance (Rrs) and reactance (Xrs) between 4 and 26 Hz by means of the forced oscillation technique. In all patients DLCO was less than 75% of the expected value. Patients were classified into two groups depending on total lung capacity (TLC): group A with TLC less than 80% of expected, and group B with TLC of 80% or more. Group A demonstrated a decrease of Xrs especially at low frequencies, with small, not significant changes in Rrs. In the patients in this group with the lowest values of TLC (less than 50%), we observed an increase of Rrs at low frequencies causing a negative frequency dependence of Rrs. In group B no distinct changes of Rrs and Xrs occurred. Canonical correlation analysis between routine lung function data and forced oscillation parameters, showed tight correlations between TLC in absolute value or VC in percent of the predicted value on the one hand and average level of Xrs and average slope of Xrs (and Rrs) vs frequency curves on the other hand. Measurements of lung mechanics in five additional patients and comparison with a model of the respiratory system suggest that the changes of Rrs and Xrs are not explained totally by the observed increase in lung tissue resistance and decrease in lung compliance. The observed changes in Rrs and Xrs are not specific for restrictive lung disorders; similar changes are met also in moderately advanced obstructive diseases.

Total respiratory resistance and reactance in ankylosing spondylitis and kyphoscoliosis

“…Secondly, the compliance of the longs was decreased, together with a decrease in transpulmonary pressure at TLC, which is a typical feature of pulmonary restriction caused by a reduced motion of the chest wall. In diffuse interstitial lung diseases, a fall in compliance of the lungs, together with an increase in tissue resistance also causes a small increase in Rrs at low frequencies and a decrease of Xrs [9]. Yet, the changes in Rrs and Xrs l n kyphoscoliosis are too large to be attributed to the observed small increase in Raw and decrease in lung compliance.…”

“…As in kyphoscoliosis many properties of airways, lungs and chest wall are altered, resulting in a marked increase and negative freque ncy dependence of Rrs and decrease of Xrs, this analysis requires a complex model, taking into account, in addition to elements representing airways and tissues of lungs and chest wall, the influence of the upper airway, and probably also that of intrathoracic airway wall compliance, and of gas compressibility. We fitted the 13-parameter model, described previously [9,10), on the data, incorporating in the model the measured values of Raw, lung compliance and gas compressibility and adjusting the values of chest wall compliance and resistance in order to obtain a good fit with the measured average Rrs and Xrs vs frequency curves. This was possible if chest wall resistance was increased to 0.6 kPa•P•s and compliance decreased to 0.08l•kPa• 1 • These figures should be regarded with caution, as approximations are highly dependent on this type of model; indeed, the latter was not validated by formal modelization techniques.…”

“…In pathological conditions of lungs and airways Rrs is generally increased with negative frequency dependence (i.e. lower values at higher frequencies); Xrs is reduced at all frequencies [6][7][8][9][10]. In a previous study [11], we found that strapping of the rib cage in healthy subjects caused similar changes in Rrs and Xrs: increase of Rrs at low oscillatory frequencies, resulting in a negative frequency dependence, and a decrease of Xrs with a shift of the resonant frequency to higher values.…”

Bronchial obstruction in osteogenesis imperfecta can be detected by forced oscillation technique

“…However, in obstructive diseases, the reactance tends to become more negative during expiration, when intrathoracic airway obstruction becomes more severe ( 33 ). Unlike previous studies where it was not possible to differentiate between a restrictive and an obstructive problem using FOT ( 36 ), our technique was able to assess the resistance, reactance, and the resonant frequency during both inspiration and expiration, giving insights in the respiratory function. Our findings provide support for the presence of obstructive lung disease in OI patients, as observed in four patients through standard PFTs and nearly all patients using FOT ( 16 , 32 ).…”

The use of forced oscillation technique for monitoring of lung mechanics during covid-19 pneumonia

“…At the rst glance it was expected that resistence component measured by FOT will correlate to obstructive pattern, but reactance (elastic component) -with restrictive one, however more detailed studies revealed that, paradoxically, airways obstruction more strongly in uenced reactance than the resistance parameters [10] [11]. At the same time it remains true that restrictive diseases like pulmonary brosis and other chronic interstitial lung diseases manifest in oscillometric recordings as changes in reactance [12] [13] [14].…”