Tissue and airway impedance of excised normal, senile, and emphysematous lungs

Abstract

We partitioned pulmonary resistance (RL) in excised normal, senile, and emphysematous human lungs at various distending pressures; peripheral resistance (Rp) was measured by means of retrograde catheters and lung tissue resistance (Rti) by means of pleural capsules. By subtracting Rp from RL and Rti from Rp, we obtained, respectively, central (Rcaw) and peripheral (Rpaw) airway resistance. We determined also lung volumes, the elastic recoil pressure-volume curve, and the forced expiratory volume in 1 s-to-vital capacity ratio (FEV1/VC). The functional data were related to morphometry: mean linear intercept (Lm), diameter (d), and density (n/cm2) of membranous bronchioles. In the three groups of lungs, Rti demonstrates a marked negative frequency dependence and increases with transplumonary pressure. In emphysematous lungs, the increase of RL is mainly due to an increase of Rpaw; in addition, Rcaw and Rti are higher than normal. In the group of senile lungs, airway resistances are within normal range, but Rti is slightly increased. FEV1/VC is related to Rpaw and elastic recoil pressure; Rpaw is related to d and n/cm2, and Rti is related to dynamic elastance and to Lm.

Biomechanics of the Aging Lung Parenchyma

“…5.1 were determined in a C57BL/6 J mouse model of aging, both G and H statistically significantly decreased by 35 and 47 %, respectively, between 2 and 26 months of age [66]. In another human study using forced oscillations in isolated lung lobes, dynamic E L at 4 Hz was not different between normal and senile lungs, whereas the specific elastance increased with age from 5.9 kPa to 9.7 kPa at a PEEP of 0.6 kPa and from 19.4 to 29 kPa at a PEEP of 2 kPa [154]. The specific elastance is defined as the product of E L and lung volume and hence it is essentially the dynamic B.…”

“…The increase of the ratio with age suggests that tissue nonlinearity becomes stronger during aging age, whereas in humans, it increased till about 45 years of age, beyond which it seemed to stay constant or perhaps showed a slight decrease [96]. In another study, no change in η was found with advancing age in human isolated lung lobes measured by forced oscillations combined with the alveolar capsule technique that can partition total resistance to airway and tissue in an invasive manner [154]. In this study, there was a clear trend for η to increase with age but the alveolar pressure measurement is highly sensitive to local heterogeneity, which resulted in very large intersample variability of η.…”

Chronic obstructive pulmonary disease: molecular and cellularmechanisms

“…Retrograde catheter studies in excised lungs from patients with severe airflow obstruction due to COPD have all found large increases in peripheral resistance at standard PL [30][31][32]. But there are many other possible changes in airway function due to emphysema which would result in an increased resistance at a given PL, including abnormal angulation or compression of normal airways by surrounding overdistended lung, loss of parallel airways due to emphysematous destruction, or to functional loss of patent airways supplying poorly ventilated areas of lung.…”

Respiratory input impedance measurement: Forced oscillation methods

“…Using a peripheral catheter and alveolar capsules (local pressure-transducing devices glued to the pleural surface and pierced several times to make acoustic contract with local lung alveolar units), central and peripheral airway and tissue resistances were partitioned (VERBEKEN et aL, 1992). Tissue resistance decreased with increasing frequency, especially at higher distending pressures, as predicted by the CP model, in emphysema, major changes were found in peripheral resistance (elevated by a factor of 9), and tissue resistance was elevated.…”