Lecture 5: Exercise Testing Flashcards
what is VO2 max
max O2 consumption a person can consume at max physical exertion
measures cardiopulmonary fitness and aerobic endurance
what is a MET
metabolic equivalent of a task
used to describe intensity of exercise
1 MET = amount of energy used for 1 min quiet rest
directly correlated with VO2 max
exercise at a metabolic rate 5x the resting VO2 rate is equivalent to 5 mets
1 MET is equal to what
3.5 mL O2 x kg x min
what is the RPE scale
rate of perceived exertion
pt perceived intensity of exercise
used heavily in cardiopulmonary population
downside = subjective and dependent on pt reporting
what is heart rate reserve
difference between Max HR and resting HR
describe slow twitch mm fibers
aka oxidative
aerobic metabolism; used O2 + glucose to produce ATP
slow to fatigue
contacts slowly over long period of time
describe fast twitch mm fibers
aka glycolytic
anaerobic metabolism; uses proteins + glucose to produce ATP with lactic acid byproduct
fatigues quickly
past contractions for short amount of time
what are ventilatory thresholds
below certain intensities, aerobic metabolism is used to fuel the body
kidneys provide HCO3 to buffer the lactic acid produced by CO2 in anaerobic metabolism
what happens at 1st and 2nd ventilatory thresholds
1st (VT1) = less aerobic metabolism, increasing anaerobic metabolism
2nd (VT2) = mostly anaerobic metabolism, virtually no aerobic metabolism
how does the body switch between ventilatory thresholds
kidneys release HCO3 once blood lactate levels >2 at VT1
once kidneys can’t keep up with lactate being produced, blood pH signals respiratory center in brain to increase breathing rate to “blow off” excess CO2 between VT1 and VT2
if we have to breathe so fast to keep up with increasing CO2 levels, we cannot maintain simultaneous conversion at VT2
impact of chronic exercise
reduce body mass
decrease risk of multiple chronic diseases
increased VO2 max; improved O2 extraction
lower HR and SBP at submit and max exercise intensities
increase number/size of mitochondria in mm
increased skeletal mm blood flow at max exercise intensity
improved QOL, concentration, mood, and self esteem
decreased anxiety, stress, and depression
what is exercise testing
systematic and progressive increase in O2 demand; evaluate responses to increased demand
non-invasive and can be used in diagnosis and management of pts with CAD
indications for a graded exercise test (GXT)
atypical chest pain
CAD evaluation
pre-participation exercise screening
functional assessment
assessment of arrhythmia, HTN, or other instability with exercise
absolute contraindications to GXT
recent (<4-6 wks) MI
recent change in ECG
cardiac infection
unstable angina
decompensated HF
severe or symptomatic aortic stenosis
acute PE
2nd or 3rd degree AV heart block
unstable arrhythmia causing hemodynamic instability
any acute illness
relative contraindications for GXT
ST depression on resting ECG
significant (>200/110 at rest) or uncontrolled HTN
L main CAD
valvular heart disease
compensated HF
cognitive impairment
uncontrolled metabolic disease
tachyarrhythmia or bradyarrhythmia
electrolyte abnormalities
MSK conditions
things to remember/consider for exercise testing safety
signed informed consent
have appropriate equipment and supplies available to manage an emergency
knowledge of: when to exclude pts, when to terminate GXT, and skills needed to react to abnormal response
when to use a low level GXT and examples
usually performed shortly after MI or CABG
helps predict subsequent course and identify high risk pts
examples: gait speed, 5x STS, 6MWT or 2MWT
in a low level GXT what is the most valuable indicator of prognosis after MI
ST depression > 2.0 mm
early onset ST related to increased incidence of coronary events
what does it indicate if a low level GXT induces ventricular arrhythmias
2.5x higher chance of sudden cardiac death
limited exercise with low level GXT is highly correlated with what
Heart failure and increased mortality
submit vs max GXT
submax = terminated at predetermined end point (usually % HR max); more feasible
max = terminated at max HR or when symptom limited; better sensitivity of testing for CVD/CAD
Low level GXT protocol
vitals before, during, and after
edu to pt on protocol and equipment
warm up period
monitor HR at least 2x per stage
terminate at 85%. HR max
cool down period
continuous monitoring during recovery until pretest values reached
describe Bruce treadmill test protocol
mostly in athletic population
can be max or submax
preferred method to predict functional capacity
speed = start at 1.7 mph, increase every 3 min
grade = start at 10%, increase 2% every 3 min
untrained subject usually tolerates <10 min to test
Balke GXT protocol
large use in athletic population
stays at 3.3 mph
starts at 0% grade, increase to 2% after 1 min
after 2 min and each min after incline increases 1%
YMCA step test
12 in step @ 24 steps/min x3 min
HR measured 1 min post test
compare max and 1 min recovery to age related norms
12 min run test (cooper’s run test)
measure distance run or walked in 12 min
compare to norm data
Astrand Rhyming Cycle Ergometer Test
estimates VO2 max
6 min cycling with pre determined wattage setting for 50 rpm
goal is to reach steady state HR between 125 and 170
Wingate max exercise test
athletic and training situations
stationary ergonometer
after warm up:
- 30 sec resistance free max speed pedaling
- resistance added at predetermined level
- pedal as long as possible
situations that constitute termination of GXT
angina
reaching 6 METs
poor perfusion (AMS, dizzy, cyanosis)
claudication
SBP decrease with work
BP > 250/115
1-2 mm ST depression
>9 VCs/min
any ventricular arrhythmia
subject requests stop
absolute contraindications GXT
recent MI
recent change to ECG
cardiac infection
unstable angina
decompensated HF
severe/symptomatic aortic stenosis
acute PE
2nd or 3rd degree AV heart block
unstable arrhythmia/hemodynamic instability
any acute illness
relato=ive contraindications for GXT
ST depression on resting ECG
significant or uncontrolled HTN
L main CAD
valvular heart disease
compensated HF
cognitive impairment
uncontrolled metabolic disease
tachyarrhythmia or Bradyarrhythmia
electrolyte abnormalities
MSK conditions
what is pharmacologic stress testing
used if pt is unable to perform standard treadmill or cycle stress test
medication injected to induce physiological stress
same guidelines used while watching vital signs and response to exertion
most common in acute care or cardiologist
