Dyspnea can be constant or occur as breakthrough episodes. In the study by Reddy et al,23 39% of patients had constant dyspnea and 20% experienced breakthrough episodes. Breakthrough dyspnea is shorter in duration, lasting less than 5 minutes. Breakthrough dyspnea occurs approximately 5 to 6 times a day and is predominant with 80% of patients who are symptom-free between episodes. As opiates are the drug of choice for dyspnea treatment, differentiating the time course of dyspnea is important in terms of treatment strategy and response. For example, treating breakthrough dyspnea with standard opiate medications might not work given that symptom onset and resolution might occur even before the medication’s onset of action.
Pathophysiology and Psychology
The cause of dyspnea in an oncology patient can be physiological and/or psychological in nature, with more numerous and unique presentations as compared to dyspnea associated with cardiac or lung disease. Chemoreceptor stimulation, mechanical stimuli originating in the lung and chest wall receptors, and neuroventilatory effects all contribute to dyspnea.12,16 Physiological modalities contributing to dyspnea are outlined in Table 2.
Psychological Contributions to the Etiology of Dyspnea
Dyspnea is subjective and biopsychosocial factors play a large role in an oncologic patient’s self-report of this condition. Multiple studies demonstrate that objective signs may not match the patient’s perception of dyspnea.18,21,25 Other studies report a correlation between psychological distress and worsened perception of dyspnea. Psychological distress is often measured by anxiety and depression and is also augmented by the presence of pain.
Assessment
Dyspnea is more challenging to assess in the ED than the laboratory setting36 as the condition is multidimensional in nature, often characterized by three factors consisting of breathing effort, chest tightness, and air hunger.37,38 Since these are subjective symptoms, assessment is difficult if a patient has delirium or other symptoms that alter the ability to provide a coherent response. Also, the subjective nature of dyspnea can lead to bias during symptom measurement and management.39
Research has documented factors such as lung involvement, anxiety, and maximum inspiratory pressure as influential to the perceived intensity of dyspnea for oncologic patients.40 Therefore, the sensation of dyspnea is multifactorial and includes physiological and psychological components for cancer patients.40 Subjective sensation does not always correlate with physiological measurements, adding to the difficulty of objective assessments.
Tanaka et al39 describe six criteria that must be met when attempting to create a scale to measure dyspnea in oncology patients. The Cancer Dyspnea Scale (CDS) is a self-rating scale that has been found to be acceptable and practicable in the clinical setting. The 12-item scale was originally conducted in Japanese and has been validated when translated into Swedish (CDS-S) and English (CDS-E) versions.39,41 Uronis et al41 further tested a reduced Cancer Dyspnea Scale that dropped three items from the original CDS scale (r-CDS-E). According to Uronis, the CDS-E better measures global dyspnea whereas the r-CDS-E can be used to measure effects of an intervention on dyspnea. One of the limitations of the CDS is that the scale was only validated in patients with lung cancer.
Since a universally useful scale has yet to be validated, the findings of a comprehensive history and thorough physical examination are the most important considerations when assessing oncologic patients for dyspnea.18,42 The history and physical examination must assess both physical factors and psychological factors. Physical factors include symptom quality and associated symptoms, provoking and relieving factors, previous treatments and response to treatments, and past medical history. Psychological factors include the patient’s emotional status at onset; as symptoms progress, the EP must assess whether perception of dyspnea is related to emotions such as anxiety and fear.
The longitudinal progression of symptoms must be considered. Currow et al43 found that at days 10 and 3 before death, dyspnea increased in oncologic patients but remained unchanged in patients with a noncancer diagnosis. Thus, the longitudinal progression of dyspnea differs depending on the underlying condition. Nearing death, patients without cancer experience a sustained period of symptoms whereas patients with cancer frequently experience both increased symptom prevalence and intensity.44
Diagnostic testing may also help to identify treatable causes. Chest imaging can be performed by radiography and computed tomography. Complete blood counts and chemistry panels can assess for anemia and electrolyte abnormalities. Maximal inspiratory pressure (MIP), a measure that tests diaphragm and inspiratory muscle strength, is also helpful if no apparent cause is found using other diagnostic modalities.1
Treatment
Treatment of dyspnea in malignancy is uniquely challenging. Ideally, treatment should focus on correcting an underlying cause, but for malignancy, the cause is often not reversible. Therefore, dyspnea treatment often consists of palliative management to control the sensation of symptom burden.45 Terminal cancer patients oftentimes require hospitalization and sedation to adequately manage their symptoms.45