Distinguishing Cardiovascular from Respiratory System Dyspnea If a patient has evidence of both pulmonary and cardiac disease, a cardiopulmonary exercise test should be carried out to determine which system is responsible for the exercise limitation. If, at peak exercise, the patient achieves predicted maximal ventilation, demonstrates an increase in dead space or hypoxemia (oxygen saturation below 90%), or develops bronchospasm, the respiratory system is probably the cause of the problem. Alternatively, if the heart rate is 85% of the predicted maximum, if anaerobic threshold occurs early, if the blood pressure becomes excessively high or drops during exercise, if the. | Chapter 033. Dyspnea and Pulmonary Edema Part 5 Distinguishing Cardiovascular from Respiratory System Dyspnea If a patient has evidence of both pulmonary and cardiac disease a cardiopulmonary exercise test should be carried out to determine which system is responsible for the exercise limitation. If at peak exercise the patient achieves predicted maximal ventilation demonstrates an increase in dead space or hypoxemia oxygen saturation below 90 or develops bronchospasm the respiratory system is probably the cause of the problem. Alternatively if the heart rate is 85 of the predicted maximum if anaerobic threshold occurs early if the blood pressure becomes excessively high or drops during exercise if the O2 pulse O2 consumption heart rate an indicator of stroke volume falls or if there are ischemic changes on the electrocardiogram an abnormality of the cardiovascular system is likely the explanation for the breathing discomfort. Dyspnea Treatment The first goal is to correct the underlying problem responsible for the symptom. If this is not possible one attempts to lessen the intensity of the symptom and its effect on the patient s quality of life. Supplemental O2 should be administered if the resting O2 saturation is 90 or if the patient s saturation drops to these levels with activity. For patients with COPD pulmonary rehabilitation programs have demonstrated positive effects on dyspnea exercise capacity and rates of hospitalization. Studies of anxiolytics and antidepressants have not demonstrated consistent benefit. Experimental interventions . cold air on the face chest wall vibration and inhaled furosemide to modulate the afferent information from receptors throughout the respiratory system are being studied. Pulmonary Edema Mechanisms of Fluid Accumulation The extent to which fluid accumulates in the interstitium of the lung depends on the balance of hydrostatic and oncotic forces within the pulmonary capillaries and in the surrounding tissue. Hydrostatic .
