Resp Physiology Flashcards
Conductive vs respiratory zone?
Conductive is site if respiratory passage (warms and humidifies air) carrying air to site of exchange
Respiratory zone is site of gas exchange with increased cross sectional area from resp bronchioles to alveolar ducts
3 functions of the pleura?
- Reduce friction
- create suction
- compartmentalization preventing spread of infection
What is boyles law?
Increase volume = decreased pressure and gas flows from high to low pressure so by increasing chest volume, you decrease pressure allowing for air to enter alveoli
What muscles are used for inspiration and expiration?
Inspiration - diaphragm, scalene, external intercostal muscles, SCM
Expiration - internal intercostals, int/ext oblique, transverse abdominus
What is the atmospheric and intrapleural pressures?
Atmospheric - 760mmHg
Intrapleural - 756mmHg
How does alveolar pressure change with inspiration and expiration?
Inspiration - increase thoracic cavity increases lung volume which decreases alveolar pressure to 758mmHg causing air to flow in
Expiration - decrease thoracic cavity and decrease lung volume so alveolar pressure increases to 763mmHg causing air to flow out
Outline the different volumes for a spirometry chart? M/F?
TV - 500mL
IRV - 3100/1900 inspiratory reserve volume
ERV - 1200/700
RV - 1200/1100
TLC - 6000/4200
VC - 4800/3100
IC - 3600/2400
FRC - 2400/1800
Normal minute ventilation and alveolar ventilation values?
Minute - 7.5L/min
Alveolar - 5.25L/min
What two factors create resistance to breathing?
Elastic recoil of lungs and chest wall (65%)
Non-elastic resistance to airflow (35%)
What is elastance?
Tendency to recoil after inflation with the first kick to get air out of the body and back to initial size. Must overcome
Chest - at greater than 80% total lung capacity, recoil directed inwards, at less than 50% TLC, elastance directed outwards
Lungs - at high volume, elastin fibres will overstrech and loose elasticity and at low volumes, lung wants to collapse to 0mmHg but surfactants stops it
What does surfactant do?
Lowers surface tension by reducing attractive forces of H binding to open alveoli from 0mmHg. A lack of surfactant created huge surface tension which requires high pressures to overcome it.
Produced by type 2 pneumocytes around week 34
What is compliance and what happens if its low or high?
Compliance is the ability to increase volume or the stretchability of pulmonary or thoracic tissue.
Low compliance = stiff lung which is hard to inflate to high volumes and extra work required eventually leading to fibrosis and decrease in pulmonary compliance
High compliance = floppy lung which is hard to deflate from high volumes due to elastic tissue damage seen in COPD/emphysema
Which size bronchi display most resistance due to turbulence?
Medium bronchi
What is mucosal resistance and 3 examples of causes?
Mucosal oedema from histamine release with increased permeability leading to transduction of fluid through intracellular gaps
1. Histamine from mast cells increased mucous secretions and viscocity
2. Chronic bronchitis increased mucous production by lungs clogging bronchioles
3. CF with CFTR mutation meaning Cl transporters cannot remove Cl, disrupting osmotic gradient leading to increased mucous and difficulty for mucocillary elevator
What controls bronchodilation and bronchoconstriction?
Bronchodilation - parasympathetic b2 aadrenergic receports with endocrine (adrenaline) major control. Has no sympathetic nerves so adrenaline in blood acts as endocrine with longer lasting effects
Bronchoconstriction - muscarinic cholinergic receptor activation and histamine H1 receptor action
Outline control of the bronchial reflex system?
Bronchial epithelium responds to noxious stimuli - reflex - Ach - muscarinic R - sm
1.Constriction when increase of Ach - inhalation smoke, dust, chemicals, low CO2, cold, PE
2. Dilation when decreased Ach - during inspiration, arterial HT (carotid sinus reflex)
How is a flow-volume plot changed due to restrictive lung disease and what are the causes?
Decreased lung capacity due to reduced compliance and increasing stiffness which limits expansion. Change in lung volume is major problem so same shape as original but less volume to right shift
Causes
-lobectomy
-abnormalities in surrounding tissue
-weak inspiratory muscles