Respiration - Mechanics Flashcards
What is oxygen pressure in blood at rest?
PO2 = 100+/-2 mmHg
What is carbon dioxide pressure in blood at rest?
PCO2 = 40+/-2 mmHg
What is the oxygen exchange at rest?
250ml/min
What is carbon dioxide exchange at rest?
200ml/min
What is the oxygen exchange and carbon dioxide exchange when walking 3mph?
800ml/min
750ml/min
What is the oxygen exchange and carbon dioxide exchange when exercising extremely?
5000ml/min
6000ml/min
What is the function of the upper airways?
conduct air into lungs
humidify air
warm air
filter air
What is the lining of the upper airways
pseudo-stratified ciliated columnar epithelium
What is the value of ventilation at rest?
6-7 L/min
How many breathes are taken per min at rest?
12-15 breathes of 500ml
What is max value of ventilation?
160 L/min
What are max breathes taken per min?
40 breathes of 40L
What is cardiac output, bpm and blood per beat during rest?
5L/min, 70bpm, 70ml/beat
What is max cardiac output, bpm and blood per beat?
25L/min, 200bpm, 125ml/beat
In quiet breathing what process is active and what process is passive?
inspiration = active
expiration = passive
What happens during inspiration in quiet breathing?
diaphragm contracts downwards pushing abdominal contents outwards
external intercostal muscles pull ribs upwards and outwards
What happens during expiration in quiet breathing?
elastic recoil
In strenuous breathing what process is active and what process is passive?
inspiration = active
expiration = active
What happens during inspiration in strenuous breathing?
greater contraction of diaphragm and external intercostal muscles
inspiration accessory muscles are activated (sternocleidomastoid, alae nasi, genioglossus)
What happens during expiration in strenuous breathing?
abdominal muscles are engaged (internal and external oblique, rectus abdominus, transverse abdominus)
internal intercostal muscles oppose external intercostal muscles pushing ribs down and inwards
What happens to the diaphragm during inspiration?
domes flatten as the muscle contracts
What are the muscles of inspiration (main + accessory)?
main - diaphragm, external intercostals
accessory - sternocleidomastoid, alae nasi, genioglossus
What are the muscles of forced expiration?
internal intercostal, abdominal muscles, (rectus abdominus, transverse abdominus, external/ internal oblique)
What do the internal intercostal and abdominal muscles do?
depress ribs
What is pleural pressure?
pressure surrounding the lung, within the pleural space.
generated by the opposing elastic recoils of the lung and chest wall and the forces generated by respiratory muscles.
What is alveolar pressure?
pressure inside of the alveoli
What is transpulmonary pressure?
Transpulmonary pressure is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity.
What is the alveolar pressure at the beginning of inspiration?
= barometric
What happens to the pleural pressure when muscles contract during inspiration?
becomes more negative
What happens when the alveolar volumes increases during inspiration to the alveolar pressure?
becomes negative
What is the barometric/atmospheric pressure?
the air pressure outside the body
When does inspiration end and therefore flow?
when the alveolar pressure and the barometric pressure are equal
What happens at the start of expiration?
thoracic volume decreases and pleural and transpulmonary values return to pre-inspiration
When does air flow out of lungs?
when alveolar pressure is higher than barometric
Why does air enter and leave the lungs?
air travels from high pressure to low pressure
Describe volume changes and pressure during inspiration
- Beginning of inspiration - alveolar P = barometric P
- Muscles contract, increasing thoracic volume - pleural P becomes more negative, increase in transpulmonary P
- Lungs expand and alveolar volume increases, air enters into alveoli from a high to low concentration - alveolar P becomes negative (less than barometric)
- End inspiration, muscles stop contracting thorax stops expanding -alveolar P = barometric P
Describe volume changes and pressure during expiration?
- Beginning of expiration, thoracic volume decreases, pleural P and transpulmonary P return to pre-inspiration values
- thorax and lungs recoil, air in alveoli becomes compressed and exits - alveolar P becomes higher than barometric P
What’s the difference of depth of diaphragm contraction in relaxed vs strenuous breathing?
1cm relaxed
up to 10cm strenuous
How much oxygen per litre breathed in healthy relaxed lungs?
1ml (2% of resting energy expenditure)
What breathing is more efficient and less turbulent?
low level breathing (less muscles used)
What is the functional residual capacity (FRC)?
Volume of air in lungs at the end of expiration during quiet breathing
ERV + residual volume
Outward and inward forces and equal and chest is relaxed
Why does the FRC decrease in patients with neuromuscular disorders?
chest muscles are weaker therefore lung elastic recoil is greater and forces are unbalanced
What is the tidal volume (TV)?
volume during relaxed breathing
usually 500ml
What is the inspiratory reserve volume (IRV)?
forceful inhalation
3300ml
What is the expiratory reserve volume (ERV)?
forceful exhalation
1000ml
What is residual volume?
air present we cannot exhale
1200ml
What is the vital capacity?
the TV + IRV + ERV
What is the total lung capaccity in males vs females?
males = 6000ml
females = 4200ml
What is the FVC?
forced vital capacity - similar to VC however it is the maximum air inhaled and exhaled
