Download Changes in cardiovascular system during exercise and sleep

Lone Star College System – Kingwood Respiratory Care Program
RSPT 1207 Cardiopulmonary A & P
Unit 5. 3 Changes in cardiovascular system during exercise and sleep
Notes by Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP
Revised January 22, 2008
Normal Sleep physiology
1.
Describe normal sleep. List the normal sleep stages. [ page 406 Wilkins]
Normal sleep averages 8 hours a day. Normal sleep is characterized by alterations between two types
of sleep every 60 to 90 minutes: REM sleep and Non-REM sleep
2.
Non-REM sleep: non-rapid eye movement sleep
a. Has 4 stages:
i. first the patient goes into stage I in which he feels drowsy and his EEG 8-12
alpha waves
ii. Within minutes, he moves into stage 2 in which his EEK shows sleep spindles
and K complexes [Theta waves]. This is a deeper level of sleep and this is the
predominate stage of NREM sleep
iii. Quickly goes into stages 3 and 4 characterized by slow-wave sleep [delta
waves]. There are more delta waves in 4 than in 3. It is difficult to arouse
someone who is at that level of sleep
iv. after 60-90 minutes of non-REM sleep the patient moves into REM sleep
3.
REM sleep: rapid eye movement sleep
a. Has slow low voltage random waves with saw tooth
b. This is where we dream
c. He rotates in and out of REM sleep about 5 times a night. Early in the evening REM sleep
may only be 5 minutes long, but toward the morning, REM sleep can last as long as 30-60
minutes
d. In adults and kids, REM sleep accounts for only 20%-25% of all sleep, in newborns this REM
sleep lasts 55%-80% of the time.
Go here to see:
Alpha waves:
http://en.wikipedia.org/wiki/Alpha_waves
sleep spindles and k complexes
http://en.wikipedia.org/wiki/Sleep_spindle
delta Waves
http://en.wikipedia.org/wiki/Delta_wave
Thata Waves
http://en.wikipedia.org/wiki/Theta_wave
4.
5.
What are the Vital Signs during non-REM sleep? Respiratory rate slows and PaC02 rises 3-7
mmHg [Burton’s pg 297], Blood pressures drop about 5%-10% during the first 2 stages and then
down 8%-14% during the last two stages.
While respirations start out irregular in the first two stages, it becomes regular during deeper
stages.
What are the Vital signs during REM sleep? Because the patient is dreaming at this time,
skeletal muscles are so relaxed that a partial state of paralysis results. Respiratory efforts are
chaotic as response to hypercapnia and to hypoxia are blunted.
The patient is at most risk for upper airway obstruction and for hypoxemia during REM sleep
Heart rates are variable and the person is most at risk for cardiac arrhythmias at this point in sleep.
Blood pressure tends to rise higher than during N-REM sleep
Normal exercise physiology
Normal aerobic metabolism results in the creation of C02 as waste products and the
consumption of 02. This internal respiration under normal circumstance the body creates 200 ml/min of
C02 [VC02] and uses up 250 ml/min of 02 [V02].
The ratio of C02 produced/02 consumed is called the respiratory quotient [RQ]
[Madama pp. 278]
The normal RQ is 200 ml /min
250 ml /min
= .8
At the same time the ratio of 02 diffusion and C02 diffusion at the lung also occurs at the same level. This
is called the respiratory exchange ratio in which 200 ml/min of C0 2 diffuses out of the capillary into the
alveoli and the same time 250 ml/min of 02 diffuses into the blood stream from the alveoli. This is the
VLC02/VL02
When everything works properly, [the lungs, the pulmonary and systemic blood vessels and the heart] the
amount of 02 brought into the blood stream [VL02] equals the amount of 02 [V02] consumed at the cellular
level.
As we exercise, a healthy heart, patent responsive blood vessels with minimal resistance to flow and
unencumbered lungs should be capable of keeping this ratio of RQ and respiratory exchange ratio equal.
[Madama pp. 296] If the 02 pulled into the blood stream doesn’t keep up with cellular respiration, anaerobic
metabolism results in poor ATP [energy production] and excessive lactic acid production. The point at
which a person’s metabolism turns to anaerobic metabolism is called his aerobic threshold. Obviously, the
healthy cardiopulmonary system will reach this threshold later than the person who has poor lungs or poor
cardiovascular system.
When a person exercises, the consumption of 02 will have to rise to meet the increased need
for ATP. This rise in V02 & VC02 will , in turn, increase the patient’s VE to keep up with the increased
demand.
[Madama pp. 294]
The normal person can raise his 02 consumption about 7 x the normal value while the trained athlete can
raise his V02 about23x the baseline.
As a kind of early warning system, increased body motion will trigger increased VE even before the C02
starts to rise. Naturally, if the brain stem is intact, increases in C02 or CSF H+ will trigger increased VE.
There are limits to how much anyone can raise his V E. Normal VE of 5-6 LPM can rise to 100 LPM and in
the trained athlete to 200 LPM.
Because there are limits to increasing the VE there are limits to how much C02 can be eliminated. During
short intense exercise because the C02 produced cannot be removed, the RQ can rise during exercise to 1sometimes, rarely to 1.5.
Obviously, as the C02 rises in the bloodstream, the pH starts to drop. This will also trigger higher V E.
The capillary beds going to the skeletal muscles will open to flood this tissue. If the systemic blood flow is
unhampered, this added blood flow will not increase the blood pressure excessively. At the same time, as
the tissues of the muscle groups gets hypercapnia, the pH drops and Hb02 affinity decreases. There is a shift
to the right.
The pulmonary bed also undergoes widespread vasodilation so that blood flow through these vessels is
easier. The time it takes for gas diffusion to occur between alveoli and capillary is only .25 seconds, and
normal time spent in the pulmonary bed is .75 seconds. As blood flow increases, this time drops to .38
seconds—there is usually plenty of time for gas exchange.
The normal P(A-a)D02 at room air is 10 mmHg, and with maximal exercise this will rise to 20-30 mmHg
as both ventilation & circulation are stressed.
The heart will increase in both rate and stroke volume so that the Cardiac output can rise. At the same time
the systemic blood pressure rises with this increased demand.
Distribution of blood during exercise. [Madama pp. 304]
At rest the brain gets 14.5% of the CO, during maximal exercise, the amount of blood going to the brain
never drops, but the percentage of the CO drops to 2.9% of the entire CO.
At rest the skeletal muscles get only 21% of the CO, while at maximal exercise, they get 87.6% of the
blood flow.
The heart continues to receive the same 4.5% of the blood flow during rest and during every stage of
exercise this means that as the CO rises, the blood flow to the myocardium rises.
To keep the body cooler, perfusion to the skin increases during exercise, but this action is limited if the
skeletal muscles pull more blood toward them.
The kidneys, liver, and gut all drop considerably as blood is shunted to the skeletal muscles.
References:
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Wilkins, Krider & Sheldon Clinical Assessment in Respiratory Care. 4th edition Mosby
Burton, Hodges & Ward ed. Respiratory Care: A Guide to Clinical Practice 4th edition, Lippincott
Madama, Vincent C. Pulmonary Function Testing and Cardiopulmonary stress Testing. 2nd edition, Delmar.