Respiratory Complications

Abstract

Overview The respiratory system is particularly susceptible to complications of cancer and cancer therapy. This vulnerability arises from the stringent architectural requirements for gas exchange, the continuous exposure of the respiratory tract to the external environment, and the severe symptoms that can accompany respiratory compromise. Gas exchange requires patent airways, an effective musculoskeletal ventilatory pump, a thin alveolocapillary membrane, and adequate blood flow through the pulmonary circulation. In cancer patients, primary and metastatic tumors of the chest compromise major airways; pleural effusions externally compress the lungs and impair diaphragmatic function; direct, hematogenous or lymphangitic spread of tumor replaces functioning lung parenchyma; resectional surgery reduces parenchymal volume; nonresectional surgery can transiently impair lung function; radiotherapy, chemotherapy, stem cell therapy, and infection injure the vulnerable alveolocapillary membrane; tumors directly or indirectly compromise the musculoskeletal pump; venous thromboembolism and pulmonary vasculopathy obstruct pulmonary blood flow. The normal respiratory system contains considerable physiologic reserve, such that surgical loss of one lung is generally well tolerated. However, in cancer patients, insults to multiple components of the respiratory system may result in progressive loss of physiologic reserve and increasing dyspnea. Dyspnea, cough, wheezing, stridor, chest pain, and hemoptysis are common symptoms in the cancer setting that lead to pulmonary consultation. In this article, we will discuss the pathophysiology, diagnosis, and management of the major respiratory complications of cancer and its therapy. We begin with the direct effects of cancer and cancer therapies on the lungs, review major indirect effects of cancer on the lungs, and end with respiratory failure in the cancer patient.