Lecture 1: Response To Exercise Flashcards
What is the oxygen consumption equation?
VO2 = CO x (aO2- vO2diff)
What type of relationship does CO have with workload?
linear
What is CO equation?
SV X HR
During exercise what does SV do?
it increases linearly until 40% of VO2 max, after that mostly CO increase is due to HR not SV
Why does SV stop rising after 40% of VO2max?
because there is only so much room for the LV to fill up with blood
How do we increase preload to increase SV?
increase venous return through skeletal pump, thoracic pump etc.
How much does CO rise during exercise?
it may quadruple and 3/4 is due to HR increase
How much does HR rise with MET?
10 bpm for 1 MET
With multiple METs what assumptions must be true?
-exercise is primarily aerobic and is steady state, the exercise is being performed w/o any biomechanical inefficiencies
What is the definition of steady state?
if intensity is unchanged for 2-3 mins or more the HR tends to remain steady without sig. rise or fall
this continues until: pt fatigues (HR increases), cardiac drift occurs if in heat
What is the equation for max HR?
208- (.7 x age)
When would you not use this equation?
if they’ve had a max exercise test or are on beta blockers
What is an abnormal response to exercise with HR?
inability to increase HR with increasing activity , drop in HR with onset of activity or of unchanging intensity (worse)
What is SBP equation?
SBP= CO x TPR
What does TPR do during exercise?
decreases due to vasodilation but SBP still increases bc increase in CO far outweighs drop in TPR
What type of relationship does SBP have with exercise
curvilinear, SBP rises roughly 10 mmHG per MET
Why does the SBP response flatten towards maximal exercise?
can’t increase CO at max HR
What is a flat response with SBP?
rises slightly with activity and then fails to continue to rise with increasing intensity
What is falling response with SBP?
rises slightly with activity and then falls despite increases in HR and workload
What is fall with higher workloads with SBP?
rises with normal activity with submax work then falls quickly at higher workloads
due to heart not keeping up with metabolic demand
What does it mean if SBP is decreasing with activity?
- CO is not increasing to keep up with demand of tissues
2. CO is not keeping up with decreasing TPR
If a patient diastolic BP rises more than 20 mmHG during exercise what could this indicate?
CAD, value usually above 90
What happens with minute ventilation during exercise?
increases, Vt increases first b/c its metabolically efficient
eventually Vt maxs out so then RR rises
What is ventilatory threshold and when does it occur?
at 50% max exercise RR increases due to lactic acid increase
What DOE should we keep pts under?
5
Why would a pt have an abnormal ventilatory response?
due to inability to increase Vt first likely due to obstructive or restrictive disease, increase in RR creates dead space
