Morphologic-physiologic correlates of the severity of fibrosis and degree of cellularity in idiopathic pulmonary fibrosis.

Abstract

A B S T R A C T Idiopathic pulmonary fibrosis (IPF) is a progressive disease of lung parenchyma characterized by a chronic inflammatory cellular infiltration and varying degrees of interstitial fibrosis. Current data indicate that the severity of fibrosis and the degree of cellularity determine, in part, the prognosis of IPF and the response to therapy. Whereas lung biopsy gives the best assessment of fibrosis and cellularity, physiologic studies are used to stage and monitor the disease process. To determine which physiologic studies correlate best with severity of fibrosis and degree of cellularity, these parameters were graded in lung biopsies of 23 patients with IPF and compared with a variety of physiologic studies.Although vital capacity, total lung capacity, and diffusing capacity are commonly used as objective monitors of the disease process, none of these parameters correlated with either the severity of fibrosis or the degree of cellularity in biopsy specimens. In contrast, almost all parameters of lung distensibility correlated with the morphologic assessment of degree of fibrosis; compliance had the best correlation. Parameters of distensibility, however, correlated poorly with the degree of cellularity.In comparison, gas exchange during exercise correlated with both morphologic parameters; the exercise-induced changes in arterial oxygen pressure per liter of oxygen consumed had a high correlation with the degree of fibrosis (r = 0.89; P < 0.001) and correlated to a lesser extent with the degree of cellularity (r = 0.56; P = 0.009). In contrast, neither the resting arterial oxygen tension nor the arterial oxygen tension at

Impaired lung compliance andDL,CObut no restrictive ventilatory defect in sarcoidosis

“…This may explain the low DL,CO and CL,s in the present patients with stage I sarcoidosis (low DL,CO in 13% and low CL,s in 17%). In previous studies, a reduced CL,s was frequently observed in ILD patients with reduced lung volumes [32][33][34][35][36]. However, in only one study was lung compliance measured in patients with ILD but normal lung volumes [37].…”

Recommendations on the use of exercise testing in clinical practice

“…Again, as for COPD, there are certain exercise response characteristics that are suggestive of ILD, although the diagnosis of ILD is rarely made with exercise testing. Pulmonary gas-exchange abnormalities during exercise may be the only physiological alteration evident in ILD [114,115].…”

Pulmonary Function Testing in Idiopathic Interstitial Pneumonias

“…Crystal and colleagues reported "good" correlation between fibrosis and the coefficient of retraction and the change in exercise Pa O 2 and P(a-a) O 2 but a "poor" correlation with spirometry, lung volumes, Dl CO , and resting gas exchange in 18 patients with IPF (22). In a more detailed analysis, Fulmer and colleagues provided a semiquantitative histologic description of 23 patients with IPF (6). Almost all parameters of lung distensibility correlated with the extent of fibrosis, although not with cellularity.…”

“…Lung recoil is increased over the range of the inspiratory capacity with a reduction of total lung capacity (TLC) and vital capacity (VC) (3)(4)(5), whereas the coefficient of retraction (pleural pressure at TLC/lung volume at TLC) is elevated compared with normal subjects (3,6). As a result of these changes, static lung volumes are typically reduced in DPLDs.…”

“…Characteristic arterial blood gas abnormalities in IPF include resting hypoxemia and increased alveolar-arterial oxygen pressure difference (P[a-a] O 2 ] (2). These abnormalities are more evident during exercise, where hypoxemia is quite prevalent (6,16,17). Additional abnormalities during exercise are noted, including reduced peak oxygen consumption, diminished ventilatory reserve, high-frequency/low tidal volume breathing pattern, and high submaximal ventilation related in part to elevated physiologic dead space and arterial desaturation (2).…”