Pulmonary Function Tests and Hematopoietic Stem Cell Transplantation

Abstract

Non-infectious pulmonary complications such as chronic airflow obstruction, bronchiolitis obliterans, bronchiolitis obliterans organizing pneumonia, radiation- and drug-induced lung injuries, diffuse pulmonary hemorrhage, and transfusion-related lung injury are well recognized in leukemia patients who receive highdose chemotherapy and supported with hematopoietic stem cell transplantation (HSCT). 1,2 These complications may cause transient or permanent damage to the lung parenchyma and pulmonary function changes in patients who achieve long-term survival. The frequently-encountered pulmonary function changes of non-infectious pulmonary complications after HSCT include obstructive ventilatory defects, restrictive ventilatory defects, obstructive ventilatory defects with reduced forced vital capacity (FVC), mixed obstructive and restrictive ventilatory defects, and reduction in the diffusing capacity of the lung for carbon monoxide (DLCO). 1,2 For adoption of preventive or therapeutic measures for those possible pulmonary complications after HSCT, transplantation oncologists in many institutes routinely perform pulmonary function studies for stem cell recipients before and after HSCT even though their predictive value and clinical usefulness are in doubt. 3 Pulmonary function studies encompass spirometry as well as determination of lung volumes and diffusion capacity. 4–7 Spirometry measures the rate of air exhaled or inhaled as a function of time. 4 The FVC, forced expiratory volume in the first second (FEV1), and the FEV1/FVC ratio are the most commonly reported values. The disproportionate reduction in FEV1/FVC to below the lower normal limit indicates an obstructive ventilatory change. The FEV1 is further used to determine the severity of the obstruction. Total lung capacity (TLC), residual volume (RV) and vital capacity (VC) are the 3 parameters mainly determined for lung volumes by most pulmonary function studies. 5 A proportional reduction in FEV1/FVC with a reduction in TLC confirms the presence of a restrictive pathologic process. DLCO is a measure of a patient’s ability to absorb alveolar gases into the capillary blood flow, which is influenced by alveolar membrane thickness, hematocrit level, cardiac output, and the uneven distribution of ventilation and perfusion over different lung regions. 6 A reduction in DLCO is the most common functional abnormality, and it can be associated with thoracic irradiation, chemotherapy toxicity, idiopathic pneumonia, and graft-versus-host disease (GVHD). Although pulmonary function studies have been widely used in HSCT patients, it should be noted that there are limitations in using the abovementioned tests to make conclusions in any patient. 3,7 A good quality