Blood pressure. Pulse. Cholesterol. All good barometers of measuring a person’s health.
But a group of physicians and researchers believe that primary care doctors and others are leaving out the most reliable measure of all: cardiorespiratory fitness (CRF), that is, the body’s ability to efficiently transform oxygen into energy. Do you get out of breath climbing stairs? There’s a good chance your cardiorespiratory fitness isn’t so hot.
Efforts to measure and improve cardiorespiratory fitness should become a standard part of clinical encounters – that is, an accepted “vital sign,” says the American Heart Association in a recently published Scientific Statement. The statement, published in the journal Circulation, could open some avenues of discussion for Repertoire readers and their physician customers.
“It is quite possible that the AHA’s forward-thinking position on CRF as a new vital sign will drive many institutions to consider its powerful connection to driving outcomes,” says Thomas Schwieterman, M.D., vice president of clinical affairs and chief medical officer, Midmark. “Like any trusted professional organization, AHA has the scientific data to back up their position. The argument is well presented and offers a compelling reason for including CRF in the care management plan for all at-risk patients.”
The AHA statement says that “a growing body of epidemiological and clinical evidence demonstrates not only that CRF is a potentially stronger predictor of mortality than established risk factors, such as smoking, hypertension, high cholesterol, and type 2 diabetes mellitus, but that the addition of CRF to traditional risk factors significantly improves the reclassification of risk for adverse outcomes.
“Although CRF is now recognized as an important marker of cardiovascular health, it is currently the only major risk factor not routinely assessed in clinical practice.”
Adding CRF for risk classification “presents health professionals with unique opportunities to improve patient management and to encourage lifestyle-based strategies designed to reduce cardiovascular risk,” say the authors.
What is cardiorespiratory fitness?
Cardiorespiratory fitness is a reflection of total body health, as it involves numerous systems, including the lungs, heart, circulatory system, muscle cells and more.
“When we measure cardiorespiratory fitness, we get a picture of the whole body’s physiology and how it functions,” says Lenny Kaminsky, Ph.D., FAHA, FACSM, FAACVPR, director of Ball State University’s Fisher Institute of Health and Well-Being, and a member of the expert panel that wrote the American Heart Association statement. “If there’s any kind of disorder or disconnect – in the heart, lungs, muscles, etc. – it will probably be reflected in this measure.”
The body uses oxygen (O2) to produce energy, and then releases carbon dioxide (CO2) as a byproduct. During exercise or activity, the body processes more and more oxygen, but eventually reaches a point where it cannot process anymore. That is called the maximal point, or VO2 max.
Cardiorespiratory fitness has been a topic of discussion among healthcare providers for some time, says Kaminsky.
“Medical professionals get no training on lifestyle factors of health, like diet and physical fitness. Many aren’t aware of the impact of exercise, physical fitness or nutrition, other than what they read in reports such as ours. Conceptually, they know fitness is a risk factor, but they might not see it as powerful a factor as others, or they don’t understand it that way.
“Our statement is really saying this should be part of every routine evaluation. It’s something all clinicians should assess.” Calculating CRF should be as routine as taking a patient’s pulse, blood pressure or temperature.
How is it measured?
Metabolic cardiopulmonary metabolic testing is the gold standard for measuring cardiorespiratory fitness, says Kaminsky. Using a mask and mouthpiece, the practice monitors the person’s breathing – how much oxygen is taken in and how much carbon dioxide is exhaled – while the patient works out on an exercise device, such as a treadmill or cycle. To measure oxygen consumption this way, the practice would need to acquire a cardiopulmonary metabolic cart.
Short of that, the practice can use non-exercise-based equations or models to estimate CRF. Such equations, embedded in the electronic medical record, take into account a variety of factors, such as the patient’s age, sex, body weight, level of physical activity, smoking, etc.
“A limitation of these equations is that they tend to underestimate and overestimate CRF at the upper and lower ends of the distribution, respectively,” according to the American Heart Association statement. “The underestimation is unlikely to affect highly fit individuals, who will still be correctly classified into the higher CRF categories; how- ever, the overestimation for people with low CRF could be a concern because of the associated heightened risk among these men and women.”
Challenges of CRF testing
Says Schwieterman, “Cardiovascular fitness is not an easy clinical marker to quantify at the point of care. As stated in the AHA position paper, most methods of measurement are subject to interpretation by the provider. The current cohort of ‘vital signs’ readings (BP, temp, pulse, pulse ox, weight, height) are much less open to clinical interpretation, as each provides the clinician a solitary and repeatable number(s); those are results that are hard to dispute.
“In addition to the problem of CRF currently being open to interpretation, a CRF test can be time-consuming and problematic to achieve in a clinical setting,” he continues. “With healthcare providers already feeling overtaxed in their obligations at the point of care, adding in another pre-visit test is difficult to employ without compromising efficiency.
“Finally, obtaining a fitness measure may have connotations of judgment or blame toward the patient. Many patients dread standing on a scale in a semi-public area for fear of guilt or embarrassment. A CRF test might incur an even greater sense of angst for the patient and be potentially uncomfortable for the provider, who must find a way to address the findings – and clearly convey the implications and risks – without instilling blame or shame to the patient.”
All that said, Schwieterman predicts that as payment models shift to value-based models, in which payment is based on outcomes, CRF measurements are likely to factor more prominently into the routine clinical assessment.
“Simply stated, it is difficult to imagine outcomes improving dramatically (and thus payments to care teams) without proper attention being given to a patient’s overall physiologic fitness. Medications, procedures and external interventions of all types can do incredible things to improve how patients fare with chronic disease, but their impact is limited – and in some cases, muted – in the face of headwinds experienced with poor CRF.
“Finally, most physicians are keenly aware that clinical outcomes are, in part, driven by a patient’s own choices outside the clinic walls,” Schwieterman continues. “Choices such as food selection, exercise habits, tobacco use and alcohol consumption are seen as difficult to impact by many competent providers. Many try to influence them, only to see lackluster results.
“With a national effort to include CRF into the vitals acquisition set, perhaps physicians can increase their impact in the overall fitness arena,” says Schwieterman. “Perhaps with the advent of new clinically valid data to qualify and quantify fitness, the argument by providers could have greater influence on patient choices and behavior. With the CRF index being part of the whole care management plan endorsed by the patient’s provider, it may assume a role that goes beyond ‘it is a good idea’ and more viewed as ‘an important part of my overall disease management plan.’”
To view the American Heart Association Scientific Statement, “Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign,” go to this URL: http://circ.ahajournals.org/content/circulationaha/early/2016/11/21/CIR.0000000000000461.full.pdf
Key takeaways about cardiorespiratory fitness
Some conclusions from the American Heart Association Scientific Statement, “Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign.”
In addition to being a strong predictor of cardiovascular and all-cause mortality, cardiorespiratory fitness could be especially helpful in the preoperative risk assessment of patients undergoing cardiovascular and noncardiovascular surgery, predicting surgical complications and short-term outcomes in patients subjected to abdominal aortic aneurysm repair, hepatic transplantation, lung cancer resection, upper gastrointestinal surgery, intra-abdominal surgery bariatric surgery, and coronary artery bypass grafting.
- CRF strongly predicts outcomes across a wide spectrum of cardiovascular-disease outcomes, including those related to stroke, heart failure and surgery.
- Optimizing CRF prior to surgical interventions (termed “prehabilitation”) improves outcomes, including surgical risk, mortality, and function in the postsurgical period.
- The addition of CRF to traditional risk factors significantly improves reclassification of risk for adverse health outcomes.
- CRF is responsive to therapy, and periodic measures of CRF are valuable in risk stratification. Individuals whose CRF increases between examinations have a lower risk of adverse health and clinical outcomes than those whose CRF decreases, and this should be communicated to patients.
- Non-exercise estimates of CRF may be useful to provide an initial estimate of one’s CRF, particularly to identify those at increased risk of cardiovascular disease. But in most cases, non-exercise estimated CRF should not be viewed as a replacement for objective assessment of CRF.
Source: “Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign,” American Heart Association, http://circ.ahajournals.org/content/circulationaha/early/2016/11/21/CIR.0000000000000461.full.pdf