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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
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Dyspnea 9 Borg Scale
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V02 (ml/kg/min)
F (Breaths/min)
V02 (ml/kg/min)
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V02 (ml/kg/min)
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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.
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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
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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
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The Canadian Journal of Diagnosis / January 2004
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