Pulmonary Complications

After hematopoietic stem cell transplant (HSCT), up to 60 % of patients develop pulmonary complications. In spite of antibacterial, antiviral, and antifungal prophylaxis, reduced host defenses render the HSCT patient vulnerable to pulmonary and other infections in the early weeks and even months post-transplantation. This chapter suggests an integrative approach followed by a description of the most common pulmonary syndromes seen in HSCT patients, including diffuse alveolar hemorrhage (DAH), idiopathic pneumonia syndrome (IPS), bronchiolitis obliterans syndrome (BOS), and cryptogenic organizing pneumonia (COP). The high risk of developing pulmonary complications after HSCT necessitates a pre-transplant pulmonary workup. Pulmonary function tests (PFTs) are done prior to HSCT and include spirometry and diffusion capacity of carbon monoxide (DLCO). Low DLCO and alveolar–arterial oxygen gradient on PFTs carry increased mortality post-HSCT. Decreased DLCO and forced expiratory volume in one second (FEV1) < 80 % are indicators of developing respiratory failure post-HSCT. Investigating new pulmonary complaints is challenging. All patients should undergo an extensive workup of new pulmonary findings, including dyspnea, cough, fever, and hypoxia. In the first 4–6 weeks post-HSCT, immunocompromised patients can develop bacterial pneumonia. Pathogens include gram-negative rods (Pseudomonas or Klebsiella), Staphylococcus aureus, and Nocardia. While chest X-rays could show typical lobar or multilobar opacities, computed tomography (CT) scan of the chest (noncontrast CT scans are adequate for workup of infectious processes) may yield additional characteristic findings (nodules, ground glass opacities, etc.). Fungal pneumonias, primarily aspergillus, can also develop in this early period. There is a very strong association between invasive Aspergillus pneumonia and neutropenia lasting more than 10 days. Viral pneumonia may develop as well in this patient population; however, it tends to occur later. Cytomegalovirus (CMV) is the most common viral pathogen, but with monitoring and preemptive therapy, the incidence has declined. Other viruses have emerged as pathogens, including respiratory syncytial virus (RSV), influenza, parainfluenza, and human metapneumovirus (see Chap. 17).