Mechanical impedance of the lung periphery

Abstract

The mechanics of the regional airways and tissues was studied in isolated dog lobes by means of a modified wave-tube technique. Small-amplitude pseudorandom forced oscillations between 0.1 and 48 Hz were applied through catheters wedged in 2-mm-diameter bronchi in three regions of each lobe at translobar pressures (PL) of 10, 7, 5, 3, 2, and 1 cmH2O. The measured regional input impedances were fitted by a model containing the resistance (R1) and inertance (I) of the regular (segmental) airways, the resistance of the collateral channels (R2), and the damping (G) and elastance (H) of the local tissues. This model gave far better fits to the data on impedance of the lung periphery than when G and H were replaced by a single tissue compliance, which explains why interruption of segmental flow did not lead to monoexponential pressure decay in previous studies. The interlobar and intralobar variances of the parameters were equally significant, and poor correlations were found between the airway parameters R1 and R2 and between any airway and tissue parameter (e.g., R1 and H). R2 was on average approximately 10 times higher than R1, although the R2-to-R1 ratios and their dependencies on PL were regionally highly variable. However, for the total of 33 regions studied, the PL dependence was the same for R1 and R2, which may reflect similar morphological structures for the regular and collateral airways. The dependencies of G and H on PL showed high interregional variations; generally, however, they assumed their minima at medium PL values (approximately 5 cmH2O).

Acute Lung Injury and Pulmonary Vascular Permeability: Use of Transgenic Models

“…These data are then fit to a constant-phase model to separate a central Newtonian airway resistance (R aw ) from tissue resistance (R ti ) due to tissue viscous energy dissipation (damping; G) and stored tissue energy (elastance; H) that contribute to total respiratory system (R rs ) ventilation (14,15), endotoxin injury (23), or elastase injury (226). However, collapse of alveoli and small airways results in an increase in the elastance parameter, H, which can be reversed by a deep inspiratory sigh (15,189,284,285). Since heterogeneous tissue injury produced an overestimation of the tissue component of lung resistance using the single compartment model, Suki et al (459) proposed a distributed model with multiple resistance and elastance compartments that more accurately characterized the tissue response to heterogeneous regional injury.…”

Volume Dependence of High-Frequency Respiratory Mechanics in Healthy Adults

“…Zrs measurements were corrected for the cylindrical mouthpiece by treating the latter as another wavetube segment. 16 Volume change was obtained by integrating flow obtained from a pneumotachometer P3 (Hans Rudolph, MO, USA). Two types of FOT measurements were made with the subjects in the sitting position:…”

Simulation of Respiratory System for Identifying Airway Occlusion

“…O.-C-H R κ and the characteristic impedance Z S (6) For a normal lung, the recursive computation of the impedance is started at terminal link with Κ = 23 using equations (2)(3)(4)(5)(6) where Z U2 3 is the impedance condition at termination. However, for an occlusion at a particular generation N, the terminal impedance Z LT " is where recursion starts, using the same equations, and until K= 0.…”

“…This branching network found within the multiple succussive bifurcation of the pulmonary tree has received theoretical attention [1], Several attempts have been made to investigate the characteristics of healthy and unhealthy lungs. Some of them theoretical [1][2][3][4] while others are experimental [5][6], On the other hand, modelling of dynamic respiratory system has occupied a good bulk of those literatures. However, the mechanical and physical properties, which are believed to have a considerable impact on the overall dynamics of the system, have been overlooked with the exception of [4], Airway passages modelling in normal lungs is still another area of considerable attention, however, modelling during asthma or abnormal constriction has been the main driving force behind several investigations.…”

“…However, the mechanical and physical properties, which are believed to have a considerable impact on the overall dynamics of the system, have been overlooked with the exception of [4], Airway passages modelling in normal lungs is still another area of considerable attention, however, modelling during asthma or abnormal constriction has been the main driving force behind several investigations. References [6][7][8][9] have investigated the respiratory system characteristics with and without abnormal constrictions, which may be caused by an asthma attack. Further, Kaczka et al [10] examined the partitioning of total lung resistance into airway resistance and tissue resistance in patients with mild to moderate asthma before and after albuterol inhalation.…”