Respiration- mechanics + gas exchange Flashcards
What is the meaning of respiration
Two meanings:
Tissue respiration: the aerobic metabolism in cells.
Breathing: gas exchange and the associated processes
What is respiration mechanics
The study of mechanical properties of lung and chest wall
The process by which air enters and leaves the lungs
What is the job of the lungs
To bring in fresh air rich in the oxygen needed to fuel the body
and to expel the waste gas
(carbon dioxide, CO2) produced from cells in the body.
Why is respiratory mechanics important?
To understand how lung works normally and in disease states.
Almost all lung diseases affect mechanical properties of lung.
Death from lung disease usually due to inability to overcome changes in lung and/or chest mechanics.
What are the functions of upper airways in conducting air to lungs
Humidify (saturate with water)
Warm
Filter
What epithelium lines the upper airways
Pseudo-stratified ciliated, columnar epithelium
What is the difference between strenuous and quiet breathing
During inspiration in strenuous breathing there is greater contraction of the diaphragm
(1cm quiet, up to 10cm strenuous)
Respiratory skeletal muscles are active during more strenuous exercise
What are the average values of exchange during breathing
-At rest
-Walking
-Severe exercise
- 250ml O2/min & ~200ml CO2/min
-800ml O2/min & ~750ml CO2/min
-5000ml O2/min & 6000ml CO2/min
What is the difference in expiration during quiet and strenuous breathing
Quiet - passive
Strenuous - active
What are some respiratory skeletal muscles
-Inspiratory accessory muscles active, e.g., sternocleidomastoid, alae nasi, genioglossus
-Abdominal muscles (rectus abdominus, internal oblique, external oblique and transversus abdominus)
What is the alveolar pressure at the beginning of inspiration
0 (no flow)
What is the functional residual capacity
The volume of air in the lung at the end of expiration during quiet breathing
When are elastic recoil and outward recoil equal
At FRC these forces are opposite and equal and muscles are relaxed
Minimal lung volume
30 - 120 ml
Which breathing is more efficient in healthy lungs
Low level breathing (small muscle effort)
Why is higher intensity breathing less efficient
Gas flow is turbulent, using more muscles
The accessory muscles can fatigue easily to limit exercise
What is:
Ppl
Pel
Pa
Pl
Pb
Pleural pressure
Elastic recoil pressure
Alveolar pressure
Transpulmonary pressure
Barometric pressure
What is the pleural space
Space between lungs and chest wall
What is the Transpulmonary pressure (P L)
Difference between (pleural pressure) Ppl and Pa (alveolar pressure)
Why is the pleural pressure always negative
Chest wall is constantly pulling out while lung is trying to collapse in meaning pleural pressure is always negative (forces constantly applied) therefore increase in space (muscles contract) pressure becomes more negative and when lungs relax and fill space the pressure increases again to return to normal
What is the process of inspiration
- Beginning of inspiration, no flow: PA=0 PB=0.
- Inspiratory muscles contract – inc. thoracic volume.
- Pleural pressure becomes more negative.
- Increase in transpulmonary pressure.
- Lungs expand and alveolar volume increases.
- PA becomes negative (below PB).
- Air flows into alveoli (from higher to lower pressure).
- End inspiration - Muscles stop contracting, thorax and alveoli stop expanding, PA = PB (no flow).
How does exhalation/expiration occur
- Beginning expiration: Thoracic volume decreases. .
- Ppl & PL return to pre-inspiration values.
- Thorax and lungs recoil (elastic recoil pressure).
- Air in alveoli compressed.
- PA becomes greater than PB.
- Air flows out of lungs.
When/why does the flow into the lungs stop
When atmospheric and Pa are equal
What is partial pressure
Sum of the partial pressures or tensions of a gas must be equal to total pressure
The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own
