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What’s Your Diagnosis? “I can’t catch my breath!” What’s your diagnosis? a) Early interstitial lung disease (ILD) b) Heart failure c) Recurrent pulmonary emboli d) Deconditioning 20 15 10 5 0 25 50 75 100 125 150 Dyspnea 9 Borg Scale 25 6 5 4 3 3 2 1 0 0 5 100 90 80 70 60 50 40 0 5 100 80 60 40 20 0 10 15 20 25 30 5 10 15 20 25 30 35 0 V02 (ml/kg/min) F (Breaths/min) V02 (ml/kg/min) 50 40 30 20 10 0 0 5 50 40 30 20 10 0 10 15 20 25 30 120 100 80 60 40 0 5 10 15 20 25 30 35 V02 (ml/kg/min) 20 40 60 80 100 0 V02 (ml/kg/min) 140 10 15 20 25 30 35 V02 (ml/kg/min) Ventilation (L/min) HR (%Predicted max) Work Rate (Watts) VT (%predicted VC) PaCO2 (mmHg) The patient has an athletic build, and the remainder of the physical exam is essentially normal. Her blood work, chest X-ray, electrocardiogram, and pulmonary function tests (PFTs) are unremarkable. Her cardiopulmonary exercise test (CPET) is shown in Figure 1. 35 30 0 Vo/VT (9%) A Po2 (mmHg) 39-year-old woman presents with a seven-month history of exertional dyspnea. The dyspnea has now progressed to a level where she experienced it on moderate activity (Medical Research Council rating III). She is a non-smoker, is not taking any medications, and denies the use of recreational drugs. She is married with two children, holds an office job in an accounting firm, and denies any environmental exposures. Her physical exam reveals: • Blood pressure: 118/68 mmHg • Heart rate: 78 beats per minute • No evidence of respiratory distress at rest • Oxygen saturation: 96% on room air • Normal breath sounds • Absence of any clubbing • A loud S2, with no other findings of heart failure V02 (ml/kg/min) Kayvan Amjadi, MD, FRCPC; and Denis E. O’Donnell, MD, FRCPC 50 45 40 35 30 0 5 10 15 20 25 30 35 V02 (ml/kg/min) Figure 1. Results of the patient’s CPET. Answer on page 38 The Canadian Journal of Diagnosis / January 2004 35 What’s Your Dx? Answer: Recurrent pulmonary emboli Given the CPET findings (Table 1), the differential diagnosis would include chronic obstructive pulmonary disease, ILD, and pulmonary hypertension (from any cause). Since the chest radiograph and PFTs are normal, the most likely diagnosis would be pulmonary hypertension. An echocardiogram is done, which rules out any cardiac cause for the symptoms, but fails to demonstrate elevated right ventricular systolic pressures. Therefore, pulmonary angiogram is required as a definitive test. The angiogram demonstrates elevated pulmonary arterial pressures and multiple, bilateral filling defects consistent with the presence of acute and subacute pulmonary emboli. More on CPET CPET is being increasingly used in clinical medicine, as it can offer objective assessment of patients’ cardiac or respiratory reserves. It has a wide spectrum of clinical applications, but is mainly used for the evaluation of impairment or disability, in pre-operative evaluation for lung resection, for evaluation of unexplained dyspnea, and for prediction of survival and response to therapeutic interventions. Making the diagnosis of early or mild pulmonary hypertension through tests performed on a patient at rest can be extremely difficult. Such patients often present with dyspnea or fatigue of unknown origin, which are classic indications for CPET. By the time patients are symptomatic, their Dr. Amjadi is a senior respiratory fellow, Queen’s University, Kingston, Ontario. Dr. O’Donnell is a professor, medicine and physiology, Queen’s University, and head, division of respiratory and critical care medicine, Kingston General Hospital, Kingston, Ontario. 38 Table 1 Results of the CPET • Exercise limitation secondary to severe breathlessness • Normal oxygen saturation throughout the exercise • Reduced symptom limited peak of oxygen utilization (VO2 max) • Hyperventilation during submaximal exercise • High dead space (wasted ventilation), suggesting a perfusion defect • Blunted fall in dead space during exercise, with an eventual plateau • Reduced PAO2 and widened A-a gradient CPET: Cardiopulmonary exercise test PAO2: Partial pressure of oxygen in alveolar gas gradient A-a: Partial pressure of oxygen gradient between alveolar gas and arterial blood maximum oxygen uptake is generally decreased due to depressed cardiac output and arterial oxygen desaturation. Ventilation is often excessive and inefficient. These patients do not have the normal pulmonary vascular distension and recruitment during exercise, leading to increased dead space and ventilatory requirements during activity. The exaggerated widening of the partial pressure of oxygen gradient between alveolar gas and arterial blood with exercise is a gas exchange feature that helps distinguish pulmonary arterial from venous hypertension. CPET is a safe, useful, and relatively inexpensive investigation that provides objective information regarding patients’ functional limitations. It can also provide important mechanistic insight into the origin of exertional symptoms. Dx Share your cases with us! Our mailing address: 955 boul. St-Jean, Suite 306 Pointe Claire, Quebec H9R 5K3 The Canadian Journal of Diagnosis / January 2004 Our fax number: (514) 695-8554 Our e-mail address: [email protected]