The American Thoracic Society has grouped dyspnea therapy into the following four categories: reducing ventilator demand, decreasing ventilator impedance, improving respiratory muscle strength, or altering central perception.1
Reducing Ventilator Demand
Reducing ventilator demand can be accomplished by decreasing metabolic load or altering central respiratory drive. Decreasing metabolic load by strengthening respiratory muscles helps to get rid of lactic acid accumulation.46 Exercise also helps to prevent overall sensations of fatigue.47,48
Central respiratory drive can be altered in two ways, either with pharmacotherapy or supplemental oxygen. Pharmacotherapy aids focus on either oxygenation or the removal of carbon dioxide. Studies show that opioids, although only with small statistical significance, can be beneficial in treating dyspnea. Morphine is currently the mainstay of pharmacotherapy, but studies have yet to identify the best standard for dosing or optimal route for administration. In 1990, Bruera et al49 found that morphine improved dyspnea without negative impact on respiratory rate, oxygen saturation, or expiratory carbon dioxide.
Benzodiazepines help manage dyspnea by mitigating associated anxiety. Benzodiazepines have yet to be proven beneficial in a study with high statistical significance; however, reassurance and patient education that dyspnea is a common symptom can help allay anxiety. Patients living at home should have strong family support and reassurance that someone will be available to assist if an episode of dyspnea occurs.50
Supplemental oxygen can decrease the sensation of dyspnea by altering central respiratory drive. Oxygen should be given at the lowest effective dose and administered with humidified air to prevent desiccation of the respiratory tract. In 1993, Bruera et al51 showed that oxygen decreases dyspnea in hypoxic cancer patients.
In 1996, a double-blind crossover trial of 14 oncologic patients by Dudgeon et al42 indicated that oxygen helps decrease the sensation of dyspnea, respiratory rate, and breathing effort when compared to air. Improvement in carbon dioxide elimination with the use of breathing techniques such as diaphragmatic breathing and pursed lip breathing are also methods to decrease dyspnea sensation through alteration of the central respiratory drive. These breath-retraining techniques promote relaxed and gentle breathing, help minimize the work of breathing, and promote a sensation of well-being.44,52
Decreasing Ventilator Impedance
Ventilator impedance can result from bronchospasm, airway obstruction, effusions, or increased secretions. Treat airway obstruction from extrinsic compression or an endobronchial tumor with procedures such as balloon bronchoplasty, tracheobronchial stent placement, and brachytherapy. Pleural effusions can be treated using repeat thoracentesis or a thoracentesis with the placement of a chronic indwelling catheter; long-term control can be achieved using procedures such as pleurodesis and a thoracotomy with decortication. Manage secretions by using anticholinergic agents (eg, scopolamine) along with physical suctioning. Corticosteroids also help to reduce ventilator impedance by reducing tumor edema, lymphangitis, and bronchospasm.44 Unfortunately, these treatments are not without side effects and additional risks such as bleeding, infection, and pneumothorax.53
Improving Respiratory Muscle Strength
Maximum inspiratory pressure measures respiratory muscle strength. Normal values of negative pressure are usually greater than –50 cm H2O, and the average MIP found in cancer patients is only –16 cm H2O. Any level below –25 cm H2O is associated with severe respiratory muscle impairment. Maintaining adequate nutrition is important to help improve respiratory muscle strength.
Altering Central Perception
Limited trials suggest altering perception with the use of acupuncture and guided imagery may be of benefit. Morphine and other opiates also help to decrease oxygen requirements by altering central perception.49 Relaxation methods are most effective after a patient has gained the ability to alter and control sensation with breathing techniques.
Conclusion
Dyspnea is a chief complaint reported by the oncologic patients presenting to the ED for evaluation. Despite its prevalence in this patient population, diagnosis can be difficult since it is rarely the result of a single etiology. Consequently, dyspnea is often underdiagnosed and undertreated in the cancer population. Moreover, this condition is a composite of manifestations that are unique to each patient and his or her corresponding disease. These composite manifestations differ in timing and severity and require targeted interventions. Dyspnea that is primarily physiological in nature can be managed by reversing the causative mechanisms through treatments including oxygen therapy and antibiotics. Psychological components of dyspnea can be modified with interventions for anxiety and depression. Dyspnea is a complex composite of problems that deserves more attention in the literature and in practice.
Dr Wattana is an assistant professor in the department of emergency medicine, division of internal medicine at The University of Texas MD Anderson Cancer Center, Houston. Dr Miller is an associate professor in the department of emergency medicine, division of internal medicine at The University of Texas MD Anderson Cancer Center, Houston.