Intervention 1 Flashcards
Purpose of Exercise Tolerance Test (ETT, GXT)
- to determine physiological responses during a measured exercise stress (increasing workloads)
- allows the determination of functional exercise capacity of an individual and detects present of ischemia
What does ETT/GXT serve as?
Basis for exercise prescription
- used as a screening measure for CAD in asymptomatic individuals
What is typically administered prior to start of Phase II outpatient cardiac rehab?
- Symptom limited exercise tolerance test
- also used following cardiac rehab as an outcome measure
ETT with radionuclide perfusion
- A pharmacological stress test is used when pt is unable to perform regular ETT
- common medicals used to increase cardiac demand are adenosine (increases HR), dobutamine (increases contractility), and persantine (vasodilates)
GXT Testing Modes
- Treadmill and cycle ergometry (arm or leg) allow for precise calibration of the exercise workload
- step test (upright or sitting) can be used for fitness screening, healthy population
Maximal GXT
- defined by target endpoint hear rate
- should only be completed in settings with advanced cardiac life support trained individuals with appropriate equipment to handle abnormal responses
When does risk of abnormal response increase significantly during GXTmax?
when working at intensities >85% of HRmax
Age predicted HRmax
- 220-age has high degree of error, esp with older and younger adults
- 208- (0.7xage) has less error associated across different populations
Heart Rate Range
- Karvonen’s formula
- 60% to 80%
(HRmax - HRresting) + resting HR = target HR
Submaximal GXT
- symptom limited or terminated at 85% of age predicted HRmax
- safe in all settings
when is submaximal GXT used?
- to evaluate the early recovery of patients after MI, coronary bypass, or coronary angioplasty
Continuous GXT
- workload is steadily progressed
- Two types: step test and ramp test
Continuous GXT - step test
workload increases every 2-3 mins, allowing patient to reach steady state
Continuous GXT - ramp test
workload increased every minute so patient is not permitted to reach steady state
Discontinuous (interval) GXT
- allows rest in between workloads/stages
- used for patients with more pronounced CAD
positive GXT
- indicates myocardial oxygen supply is inadequate to meet the myocardial oxygen demand
- positive for ischemia
Negative GXT
- indicates that at every tested physiological workload there is a balanced oxygen supply and demand
What is functional 6MWT highly correlated to?
- other exercise tolerance testing, submaximal and maximal VO2
Things to monitor during exercise and recovery
- patients appearance
- changes in HR
- changes in BP
- Rate pressure product
- RPE
- pulse oximetry
- ECG changes
When monitoring patient appearance, sxs of excessive effort and exertion intolerance, examine for:
- persistent dyspnea
- dizziness or confusion
- anginal pain
- severe leg claudication
- excessive fatigue
- pallor, cold sweat
- ataxia, incoordination
- pulmonary rales
Monitoring changes in HR
- HR increases linearly as a function of increasing workload and oxygen uptake
- plateaus just before maximal oxygen uptake (VO2max)
Monitoring changes in BP
- systolic BP should rise with increasing workloads and VO2
- diastolic VPB should remain about the same
Monitoring rate pressure product
- RPP is the product of systolic BP and HR (last two digits of 5 digit number are dropped)
- is often used as an index of myocardial oxygen consumption (MVO2)
- increased MVO2 is the result of increased coronary blood flow
- angina is usually precipitated at given RPP
RPE
- Borg Scale or Borg CR
- Allows subjective rating of feelings during exercise and impending fatigue
- important to use standardized instructions
Monitoring RPE
- increases linearly with increasing exercise intensity
- correlates closely with exercise heart rate and work rate
RPE reliability
- has intra-user reliability over time, but not inter-user reliability
- ratings can be influenced by psychological factors, mood states, environmental conditions, exercise modes, and age
when is RPE important to use
- when pts do not exhibit typical rise in HR with exercise
- ie on beta blockers
Borg scale
6-20
Borg CR 10
0-10
monitoring pulse oximetry
- measure arterial oxygen saturation levels before, during, and after exercise
5 ECG changes with exercise in a healthy individual
- tachycardia: HR increase is directly proportional to exercise intensity and myocardial work
- rate -related shortening of QT interval
- ST segment depression, upsloping, less than 1 mm
- reduced R wave, increased Q wave
- exertion arrhythmias: rate, single PVC
3 ECG changes with exercise in an individual with myocardial ischemia and CAD
- significant tachycardia: occurs at lower intensities of exercise or with reconditioned individuals with out ischemia
- exertion arrhythmias: increased frequent of ventricular arrhythmias during exercise and/or recovery
- ST segment depression, greater than 1 mm below baseline is indicative of myocardial ischemia
Delayed, abnormal responses to exercise
- can occur hours after exercise
- prolonged fatigue
- insomnia
- sudden weight gain due to fluid retention
- hypotension, especially in pts with heart failrure
What is ambulatory monitoring (telemetry)
- continuous 24 hour eCG monitoring
- allows documentation of arrhythmias and of ST segment depression or elevation, silent ischemia (if 12 leads)
What is transtelephonic ECG monitoring used for
monitoring patients as they exercise at home
What is an MET
the amount of oxygen consumed at rest (sitting)
- equal to 3.5 mL/kg per min
Direct measurement of MET
- MET levels (multiples of resting VO2) can be directly determined during ETT using collection and analysis of expired air
- not routinely done
MET estimation
- can be estimated during ETT during steady states exercise
- the max VO2, achieved on ETT is divided by resting VO2
- highly predictable with standardized testing modes
See MET activity chart
pg 267
table 4-15
