Mechanical properties of lungs and chest wall during spontaneous breathing

Abstract

Using a forced oscillation technique, we measured the resistance (Rrs) and reactance (Xrs) of the respiratory system between 2 and 32 Hz at three different lung volumes in 15 healthy subjects and 7 patients with chronic obstructive pulmonary disease. Rrs and Xrs were partitioned, by means of a pressure recording in the esophagus, into the resistance and reactance of lung and airways (L) and the chest wall. The measurements were validated by checking the adequacy of the frequency response of the esophagus, by the lack of difference between thoracic and mouth flow, by an estimation of the error introduced by the shunt impedance of the cheeks, and by comparisons with the values of pulmonary compliance and resistance determined in the same subjects with classical techniques. In both healthy subjects and patients, the chest wall has a low resistance that increases somewhat at low lung volumes and behaves functionally as a two-compartment system, with low capacitance at frequencies exceeding 4 Hz. Rrs varies with lung volume and is markedly frequency dependent in patients; both phenomena are due primarily to corresponding variations of RL. In healthy subjects, at and above functional residual capacity (FRC) level, the lungs behave as a one-compartment system, the reactance of which is mainly determined by the gaseous inertance, at least beyond 2 Hz. In patients and in healthy subjects breathing below FRC, the observed frequency dependence of resistance and the simultaneous increase in resonant frequency can be simulated satisfactorily by Mead's two-compartment model, assuming a large increase in peripheral airways resistance.

Evaluation of impulse oscillation system: comparison with forced oscillation technique and body plethysmography

“…At random, resistance was measured by the SensorMedics 6200 body plethysmograph (SensorMedics, Yorbe Linda, CA, USA; airway resistance (Raw)), the Jaeger impulse oscillation system (IOS, Erich Jaeger) [1,2] and the Landsèr forced oscillation technique [5,7,10] within a time period of 30-60 min.…”

“…With the FOT, a pseudorandom noise signal was applied [5,7] linear regressions and dispersions from the line of identity, according to the method of BLAND and ALTMAN [20].…”

“…Most often this complex number is represented by its real part, the respiratory resistance (Rrs), and its imaginary part, the respiratory reactance (Xrs). Many studies have been published on FOT, especially since microprocessor techniques became available in the 1970s, allowing the analysis of complex signals by Fourier transform [5][6][7]. The clinical potential of the method became apparent because it is rapid, demands only passive cooperation (i.e.…”

Efeito da obstrução de vias aéreas nas variações das propriedades resistivas e elásticas do sistema respiratório de asmáticos, mediadas pelo uso de salbutamol

“…Using linear regression of the Rrs curve, carried out in the 4-16 Hz frequency range, we obtained the resistance at the intercept (R 0 ). (2,10,17) Based on the Xrs curve, the dynamic compliance (Cdyn) of the respiratory system at the 4-Hz frequency was calculated as follows (17,19) : Cdyn = −2ω × f × Xrs, 4 Hz The analysis of R 0 and Cdyn was performed using the values for the variation between prebronchodilator and postbronchodilator measurements in the different groups (control, mild, moderate and severe) and subgroups (BR+ and BR−).…”

Respiratory system impedance in patients with acute left ventricular failure: pathophysiology and clinical interest.

“…The difference observed between our group 1 and 2 patients is not due to a particular observation tilting the mean in small groups. In particular, there is no The negative slope of resistance at low frequencies associated with a low reactance is not specific to pulmonary vascular congestion and has been described in obstructive lung diseases 14,24,29,30 Mechanical inhomogeneities of the lung and upper airways have usually been invoked to interpret this characteristic Zrs frequency dependence.11 14,30 According to the model described by Mead,3 an increase in slope of resistance vs frequency could be associated with an increase of resistance of the small airways. Numerous animal4'1 and human studies'8 have shown that pulmonary vascular congestion could induce small airways dysfunction, as shown by an increase in closing volume and peripheral airways resistance and by a decrease in dynamic compliance.…”