key: cord-0833086-h417vias authors: Faghy, Mark A.; Sylvester, Karl P.; Cooper, Brendan G.; Hull, James H. title: Cardiopulmonary exercise testing in the COVID-19 endemic phase date: 2020-06-11 journal: Br J Anaesth DOI: 10.1016/j.bja.2020.06.006 sha: e6a8d5762307f6cec8a9a6ec77ce584ea56aac16 doc_id: 833086 cord_uid: h417vias nan The COVID-19 pandemic has presented significant challenges to healthcare systems across the 12 world. The substantial need to provide acute COVID-19-related care resulted in non-COVID-19 care 13 being immediately curtailed, with significant implications for the provision of normal or 'routine ' 14 healthcare. As the pressure from acute COVID-19 care begins to regress, it is timely to consider how 15 certain services, including those undertaking physiological measurements, will re-open and how they 16 will function within the constraints dictated by a COVID-19 endemic working environment. 17 Over the past decade, there has been evolving recognition of the importance and value of clinical 18 cardiopulmonary exercise testing (CPET) within healthcare settings. 1 Primarily, CPET is used to 19 evaluate the integrative response to incremental exercise, enabling clinicians to characterise 20 cardiorespiratory fitness and reasons for physical impairment. 2 It is recognised that CPET plays an 21 important role in clinical arenas including determining surgical operability and evaluating the risk of 22 perioperative death and postoperative complications. 3 It also has a function in supporting pre-23 operative planning algorithms, 4 as well as developing management strategies for pathological 24 conditions (e.g. heart failure) 5 and in disease prognostication (e.g. pulmonary hypertension). 6 Whilst there is considerable uncertainty regarding the ability to safely undertake CPET at the current time, 26 it remains an integral investigative tool in clinical practice and urgent consideration needs to be 27 given to determine how best to deliver CPET services in the COVID-19 endemic phase. 28 Role and delivery of CPET in the COVID-19 endemic phase 29 CPET remains highly relevant and indicated to help plan major surgical procedures for malignancy, 30 even within a COVID-19 endemic phase. It is envisaged that an additional requirement for these 31 procedures will emerge from requests to evaluate individuals recovering from severe COVID-19 32 infection. 7 In this context, measurements obtained from an assessment of cardiorespiratory 33 responses to physiological stress could provide insight regarding the integrity of the pulmonary-34 vascular interface and characterisation of any impairment or abnormal cardiorespiratory function. 35 CPET characterises oxygen consumption (V ሶ O 2 ) for a given level of external work, and the relationship 36 between carbon dioxide output and ventilation (e.g. as characterised by the V ሶ E /V ሶ CO 2 slope) can 37 detail pulmonary dead-space. It also characterises exercise-associated desaturation and hypoxaemia 38 (i.e. by allowing evaluation of the alveolar-arterial O 2 gradient and arterial to end-tidal CO 2 39 difference), and can be used to identify alterations in breathing patterns that may be relevant in the 40 aetiology of exertional dyspnoea. 8 Data from Severe Acute Respiratory Syndrome (SARS) related 41 illness showed significant exercise limitation in the months following hospital discharge, and the 42 pathophysiological mechanisms were described eloquently using CPET. 9 Functional disability and 43 recovery have also been reported in the 5 years following Acute Respiratory Distress Syndrome 44 (ARDS). 10 In individuals requiring invasive ventilatory support for COVID-19, the profound 45 musculoskeletal, neurological and de-conditioning sequalae are compounded by de-conditioning 46 from prolonged stays in critical care. Currently, there are no COVID-19 specific CPET data, but these 47 are likely to be important to inform future decision making. 11 Indeed CPET could be used to develop 48 support strategies for those with long-term disability and to assess the efficacy of developed 49 interventions. Use of CPET in the COVID-19 endemic phase should be a priority, but must be undertaken safely and 52 only when necessary. Indeed clinical resources will remain directed towards tackling the pandemic, 53 12 and shortages of personal protective equipment demand the correct use and deployment of any 54 investigation (Figure 1) . 55 Due to the nature of CPET testing, the risk of infective transmission due to forced exhalation, even 56 during sub-maximal exercise, is increased. There is controversy as to whether CPET is an aerosol-57 generating procedure 13 and strong evidence, either way, is currently lacking. An additional 58 consideration is that CPET does not incorporate bacterial and viral filters to collect exhaled particles. 59 The potential to produce infected droplets from a positive COVID-19 patient will increase the risk of 60 both airborne and surface transmission 14 This includes reverting to single-use masks, sensors, turbines and gas lines to prevent transmission 78 from repeated use. Testing facilities should be left for a minimum of 20 min to allow airborne 79 droplets to settle on surfaces and sterilised with appropriate cleaning solutions or by germicidal UV 80 cleaning. 81 We are not aware of cardiopulmonary exercise measurement systems that include a method of 83 filtration of exhaled breath. Routine lung function testing filters with ~99.9% efficiency against 84 viruses are available and guaranteed up to a flow rate that exceeds those achieved during CPET, to 85 account for the measurement of peak flow rates in the average population. Anecdotal evidence 86 suggests that these bacterial/viral filters have little impact on CPET measurements. These filters 87 have an inherent resistance to flow which in most circumstances is in the region of 80 Pa at a flow 88 rate of 90 L min -1 . This is unlikely to limit ventilation and impact exercise performance. However, at 89 the respiratory rates and tidal volumes associated with a maximal exercise test, the amount of water 90 vapour in exhaled breath will likely saturate the filter providing increased resistance to ventilation, 91 impacting the time to volitional tolerance, especially in those where ventilatory capacity is limited. 92 Therefore we would not recommend use of bacterial/viral filters manufactured specifically for lung 93 function testing to be used to filter exhalation during CPET. 94 A currently unquantified caseload of patients with a post-COVID-19 disability will require long-term 96 support from health care services. Whilst validated approaches exist that can be conducted remotely 97 (6-minute walk test, accelerometers and activity monitors) and in large volumes, these are 98 subjective and provide somewhat cursory insight regarding cardiorespiratory function. Where 99 possible interrogative procedures should be used. To alleviate the need for specialist laboratory 100 space and testing in confined spaces (that pose an additional risk of infection transmission), it is plausible that portable CPET systems could be utilised to provide insight into day to day activities. 102 Although a possible alternative, there is a need to develop standardisation approaches that are 103 associated with the performance of a ramped exercise test. 104 Cardiopulmonary exercise testing is an established investigative strategy for many clinical scenarios Prognostic Role of Cardiopulmonary Exercise Testing in Clinical Practice Cardiopulmonary Exercise Testing and Prescription of Exercise Textb Sports Exerc Cardiol Cardiopulmonary Exercise Testing (CPET) as Preoperative Test Before Lung Resection Cardiopulmonary exercise testing: basics of methodology and measurements Role of cardiopulmonary exercise testing in clinical 134 stratification in heart failure. A position paper from the Committee on Exercise Physiology and 135 Training of the Heart Failure Association of the European Society of Cardiology Cardiopulmonary exercise testing: what is 138 its value? 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