Introduction Resting cardio-respiratory investigations may not indicate a cause for unexplained breathlessness and exercise intolerance (UB&EI). CPET is an objective, non-invasive tool to measure cardio-respiratory function during exercise. Increased BMI can contribute to exercise intolerance. We present a review of CPET in evaluating patients referred to our centre with UB&EI.
Methods We did retrospective analysis of CPET results in patients referred to our centre over a two year period (2010 to 2012). All patients had resting cardio-respiratory function tests including coronary angiogram and stress echo cardiogram in some cases. CPET was performed by maximum symptom limited incremental protocol on a cycle ergometer starting with 3 minutes of rest followed by 3 minutes of unloaded cycling and subsequent increase in workload as per ATS recommendations. We defined obesity as BMI of ≥30 kg/m2. Tests were supervised by two qualified physiologists and reported by a consultant chest physician.
Results Of 243 CPET tests performed during this period, 68 (28%) were done to evaluate UB&EI. 38 patients(56%) were obese. Overall, obesity was the sole cause of UB&EI in 22 patients (32%) and was a contributory factor in a further 15 patients (22%). In the obese subgroup, it was the sole cause in 21 patients (55%) and contributory in a further 16 patients (43%). Being overweight (BMI 29) was the sole cause of unexplained breathlessness in 1 non-obese patient. Obesity appeared to be the major contributing factor for UB&EI even when present with other factors. In 23 patients (34%) more than one contributory factor was present (Cardiovascular/Respiratory/VQ mismatch/physical de-conditioning/functional). Physical de-conditioning was the sole cause in 5 patients (7%) and Hyperventilation in 2 patients (3%).
Conclusion While the causes of UB&EI are multi factorial, in our study obesity was a contributory and often key factor in over half the patients. In the obese subgroup, being overweight was the sole factor in over half and played a contributory role in almost all patients. CPET is a useful test to determine specific causes of UB&EI when resting cardio-respiratory tests are non-contributory and can help with reassurance, dietary advice and exercise prescription.
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