<qa>  What is the cause of a cardiorespiratory comorbidity considered un- Patients identified having cardiorespiratory comorbidity considered unsuitable for surgery: unstable angina, myocardial infarction within last 3 months, severe aortic stenosis, pulmonary hypertension, HOCM, acute myopericarditis, chronic heart failure New York Heart Association class 3 and above and impaired left ventricular ejection fraction less than 43. Respiratory contraindications include severe COPD, emphysema, fibrosing alveolitis, Interstitial lung disease and FEV1 less than 1.5. 