Dyspnea is defined as an uncomfortable awareness of breathing. It is a subjective experience involving many factors that modulate the quality and intensity of its perception. Patients with comparable degrees of functional lung impairment and disease burden may describe varying intensities of dyspnea. Patients use a host of different words and phrases to describe the sensation of breathlessness. Terms such as tightness and suffocating are sometimes used.
Cancer of the colon is a highly treatable and often curable disease when localized to the bowel. Surgery is the primary form of treatment and results in cure in approximately 50% of the patients. Recurrence following surgery is a major problem and is often the ultimate cause of death.
Incidence and Mortality
Note: Estimated new cases and deaths from colon cancer in the United States in 2014:
New cases: 96,830 (colon cancer only).
Deaths: 50,310 (colon and rectal cancers combined)...
Reports on the frequency of dyspnea also vary, depending on the setting and the extent of disease. In one study, 49% of a general cancer population reported breathlessness, and 20% rated their breathlessness as moderate to severe. Patients with advanced cancer experience this symptom more frequently and more intensely than do patients with limited disease. One study found that 75 of 135 patients with advanced cancer reporting to an outpatient palliative care clinic were experiencing moderate-to-severe dyspnea. Breathlessness was a complaint at presentation in 60% of 289 patients with lung cancer. Results of a large study showed that 70% of patients suffered from dyspnea in the last 6 weeks of life. About one-third of patients who could report the intensity of their dyspnea rated it as moderate to severe. Another study revealed that half of patients with advanced cancer scored their dyspnea as moderate to severe.
Pathophysiology and Etiology
The pathophysiological mechanisms of breathlessness are numerous and complex. Peripheral and central mechanisms as well as mechanical and chemical pathways are involved with a variety of sensory afferent sources.[9,10,11]
The qualities of dyspnea can be appreciated as work/effort, tightness, and air hunger. The experience of excess work and effort is caused by sensory-perceptual mechanisms similar to those involved in muscles exercising. Tightness is caused by stimulation of airway receptors with bronchoconstriction. Intensity of air hunger and unsatisfied inspiration is caused by imbalances of respiratory drive, outgoing signals from the brain, and feedback from afferents in the respiratory system.
The direct causes of dyspnea in patients with advanced cancer are numerous; categorizing them can assist in the etiologic work-up. One approach is to divide direct causes into the following four groups:
Direct tumor effects such as intrinsic or extrinsic airway obstruction, pleural involvement, parenchymal involvement either by primary or metastatic disease, superior vena cava syndrome, lymphangitic carcinomatosis, and pericardial effusion.
Indirect tumor effects such as pneumonia, a pulmonary embolus, paralysis of a hemidiaphragm, or weakening of the respiratory muscles from sarcopenia.