Cardiovascular/Hematopoeitic Systems Flashcards
What are the majority of exercise intolerance issues due to?
Musculoskeletal problems, respiratory issues, cardiovascular issues
(in that order)
What does splenic contraction do for the horse?
Increases circulating blood volume which increases oxygen carrying capacity of the blood
What how much does hematocrit increase doe splenic contraction result in?
from 40% (resting) to 60-70%
What can be an issue with increased PCV?
Also increases the viscosity of the blood which can decrease the perfusion
More reasons why blood doping is dumb
What is the issue with exogenous EPO administration in order to boost blood production?
Immune mediated reaction that results in bone marrow suppression and lifelong/fatal anemia
What is cardiac output a product of?
Heart rate and stroke volume
How much does cardiac output increase from rest to exercise?
25L/min to 300L/min
What is the typical exercise HR of a horse?
200-250BPM
What factors contribute to increased stroke volume?
- Myocardial contractility
- Venous return
- Blood volume
- Filling time
What is venous return enhanced by?
Vasoconstriction, muscular contraction, air pressure changes in the thorax
Air pressure likely the most important component
How much volume can splenic contraction contribute?
12L
~25% of normal circulating BV
What cardiac event dysfunction is most likely to contribute to exercise intolerance and poor performance?
Atrial contraction dysfunction
How much does SV increase with submaximal exercise?
20-50%
T/F: Increased heart rate will always have a positive effect on stroke volume.
False- if heart rate is high enough to decrease diastolic filling time it will negatively impact it
What system is believed to be the primary limiting factor to maximal exercise?
Respiratory system
What pathology supports the thought that the respiratory system is the limiting factor for maximal exercise?
Exercise induced pulmonary hemorrhage
What is the difference in respiratory volume between rest and exercise?
80L/min vs 1800L/min
How is tidal volume increased?
- Increasing diaphragm contraction
- Increasing pleural pressure changes
- Increasing flow
- Limiting muscular activity
Why does limiting muscular activity help increase tidal volume?
The energy needed to increase ventilation uses more oxygen than it delivers.
At what speeds does the horses respiratory rate match the stride frequency?
Gallop and canter
Feet cannot go faster than the breathing
What is the respiratory rate limited to at a gallop and canter?
~130 breaths/min
What acts as a pump to assist breathing at a gallop and canter?
Visceral contents
As the front feet hit the ground the contents hit the diaphragm which causes the horse to exhale and visa versa
What A-V O2 gradient favors diffusion of gases?
High gradient- improves O2 extraction
What what kind of shit of the O2 dissociation curve favors offloading?
Right shift due to hypercarbia, high temps, or tissue acidosis
