respiratory mechanics Flashcards
what is the key equation
VE = TV x f
what is minute ventilation
The volume of air inspired or expired in one minute
what is VE response to exercise
BEFORE
Increase before due to anticipatory rise
START
Rapid increase in VE due to increased BR and TV
DURING
VE rises during steady state exercise, then reaches a plateau
AFTER
An initial rapid, then gradual decrease in VE to resting levels, as recovery is entered and demand for O2 redu
what are the average value for VE
rest-7.5L/min
maximal exercise- 200L/min
higher for elite athletes
why does VE continue to rise during exercise
This is due to stimulation of the respiratory centre by the receptors, in response to high levels of Co2 and lactic acid
This continues until VO2 max is reached
what happens to ventilation if the exercise is harder
The harder the exercise period, the higher the post-exercise ventilation rate remains (for longer)
Due to the removal of lactic acid and other waste by-products
what is tidal volume
The volume of air inspired or expired per breath
what is tidal volume affected by
Size of lungs
Age
Gender
Fitness
Respiratory conditions (e.g - asthma)
what is the average value for tidal volume
0.5ml at rest
trained at exercise- 3-3.5L
untrained at exercise - 2.5-3L
what is tidal volumes response to exercise
Depth of breathing increases proportionally to intensity (up to 3L for submaximal exercise)
Plateaus during sub-maximal exercise, because breathing rate becomes too fast.
Short and shallow breaths near exhaustion
what is respiratory rate
The number of inspirations or expirations (breaths) per minute:
what are the average values for respiratory rate
Resting average = 12-15/min
Trained Athlete = 11-12/min
at maximal exercise
untrained- 40-50 breaths/min
trained- 50-60 breaths/min
breathing rate response to exercise
Increases in proportion to intensity until maximum.
Max = 50-60 breaths per minute
Breathing rate plateaus during sub-maximal exercise, when O2 demand is met.
what happens when the inspiratory muscles contract
Both contract causing the rib cage to move upwards and outwards
……. Thrusting the sternum forward, increasing the size of the thoracic cavity.
what are the 2 main muslces involved in inspiration at rest
- external intercostals (lie between each rib)
- diaphragm (lies underneath the lungs, separates thoracic and abdominal cavity)
what is the diaphragm and what does it do
its a dome shaped muscle
The diaphragm contracts to moves down and flattens during contraction
what happens after the diaphragm contracts during inspiration
he volume of the thoracic cavity to increase
Lungs expand to fill larger space (cavity)
Greater space = decrease in pressure
Pressure inside the cavity is lower than pressure outside the body so = AIR RUSHES IN
what extra muscles are used during inspirsation at exercise
Sternocleidomastoid
Pectoralis minor
Scalenes
what happens to the demand during exercise
O2 increases, and as Co2 production increases, so does minute ventilation (to remove the Co2)
what do the accessory muscles do during inspiration
These help lift the ribs up further, increasing volume MORE, decreasing pressure MORE, so you get increased rate and depth of breathing and higher TV & VE
what kind of process is expiration
passive process- relies on lung elasticity
what 2 muscles relax to decrease the volume of the lung cavity
External intercostals - relax, resting in the ribs and sternum dropping down and in
Diaphragm - relaxes and return to dome shape
that happens in expiration
Inspiratory muscles relax, rib cage drops down and in.
Thoracic cavity volume reduces
Pressure in the lungs increases (as space smaller)
Greater pressure in the thoracic cavity means AIR RUSHES OUT
what kind of process is expiration during exercise
active
what accessory muscles are used during expiration during exercise
internal intercostals - pulls ribs down and in
Rectus abdominus - pushes diaphragm up
explain the role of the RCC
Located in medulla oblongata
The RCC has both an inspiratory and expiratory centre
Chemoreceptors (+PPCO2, -PO2), thermoreceptors, proprioceptors all inform the inspiratory centre should you need to recruit the sternocleidomastoid, scalenes, external intercostal muscles (intercostal nerve) & diaphragm (phrenic nerve) to contract with more force (increasing thoracic cavity further) to increase DEPTH OF BREATHING.
Baroreceptors, also known as stretch receptors (located in lung tissue and bronchioles) inform the expiratory centre of changes to lung inflation and tissue stretch.
If the lung tissue becomes excessively stretched, additional expiratory muscles (rectus abdominus) are recruited to contract, reducing the volume of the thoracic cavity.
