Shrinking Lung Syndrome as a Manifestation of Pleuritis: A New Model Based on Pulmonary Physiological Studies

Abstract

Objectives The pathophysiology of shrinking lung syndrome (SLS) is poorly understood. We sought to define the structural basis for this condition through the study of pulmonary mechanics in affected patients. Methods Since 2007, most patients evaluated for SLS at our institutions have undergone standardized respiratory testing including esophageal manometry. We analyzed these studies to define the physiological abnormalities driving respiratory restriction. Chest computed tomography data were post-processed to quantitate lung volume and parenchymal density. Results Six cases met criteria for SLS. All presented with dyspnea as well as pleurisy and/or transient pleural effusions. Chest imaging was free of parenchymal disease and corrected diffusing capacities were normal. Total lung capacities were 39-50% of predicted. Maximal inspiratory pressures were impaired at high lung volumes, but not low lung volumes, in 5 patients. Lung compliance was strikingly reduced in all patients, accompanied by increased parenchymal density. Conclusion Patients with SLS exhibited symptomatic and/or radiographic pleuritis associated with two characteristic physiological abnormalities: 1) impaired respiratory force at high but not low lung volumes, and 2) markedly decreased pulmonary compliance in the absence of identifiable interstitial lung disease. These findings suggest a model in which pleural inflammation chronically impairs deep inspiration, for example via neural reflexes, leading to parenchymal reorganization that impairs lung compliance, a known complication of persistently low lung volumes. Together these processes could account for the association of SLS with pleuritis as well as the gradual symptomatic and functional progression that is a hallmark of this syndrome.

Shrinking lung syndrome in systemic lupus erythematosus

“…[16,48,51] Pleuritic chest pain is a prominent feature of patients with SLS. Our literature search revealed that 76% of SLS patients had active pleuritic chest pain at or shortly before clinical manifestation of the syndrome.…”

“…[16,48] Respiratory muscle function is regulated not only by volition but also through neuronal reflex arcs. These include the intercostal–phrenic and pleural–phrenic reflexes, which are activated by stimulation of intercostal and pleural afferents, respectively, leading to phrenic nerve inhibition.…”

Diaphragm Dysfunction: Diagnostic Approaches and Management Strategies

“…Although is it generally thought to be a consequence of an inflammatory process targeting the diaphragm [38] or the phrenic nerves [39], one study reported normal or near-normal diaphragm contractility in nine out of 12 patients with the syndrome, assessed using phrenic nerve stimulation [40]. It has been suggested that the restrictive physiological defect found in these patients may be more dependent on an inflammatory pleural process impairing normal ventilation [41], possibly coupled to a reflex concomitant inhibition of diaphragm activation [42]. Among other collagen-tissue diseases, dermatopolymyositis is also frequently associated with bilateral diaphragm weakness and may be underdiagnosed [43].…”

Dr. Henderson, et al reply

“…We are grateful for the thoughtful commentary of Dr. Eberlein 1 on our recent study of shrinking lung syndrome (SLS) 2 .…”