Respiration Flashcards
(35 cards)
Laminar flow
And sentence about proportions
Under conditions of laminar flow the movement of air into or out of the lungs is proportional to the pressure gradient and inversely proportionate to the resistance.
Laminar flow is steady flow down a tube in a uniform direction and speed.
The flow rate is maximal in the centre of the tube and reduced towards the edges.
What is turbulent flow and what causes it.
Pressure differences in turbulent and laminar
If the flow rate moves beyond a critical value an irregular current develops.
The rate of gas movement is proportional to the square root of pressure difference.
A greater pressure difference is needed to obtain the same flow as seen under laminar conditions.
Laminar flow needs less pressure to increase flow rate.
Laminar flow increases higher than turbulent even though the same pressure is applied.
Transitional flow
The high number of bifurcations in the lung creates eddies.
Laminar flow until the split is reached which creates turbulent.
How do we determine the flow type.
Reynolds number.
R= 2 x radius x velocity x gas density / viscosity
(2 x r x v x p) / n
If R is less than 1000 then it’s laminar.
If R is between 1000-1500 it’s unstable.
If R is above 1500 it’s turbulent.
Where do the rules of Reynolds number apply to.
Terminal bronchioles.
alveolar airways because there is a very high cross sectional area so the velocity is low. And the Reynolds number will be low.
the trachea because there is a low area and a high velocity so the Reynolds number is high and there is turbulent flow.
There is turbulent flow in all high airways except terminal alveoli.
What determines the resistance of flow.
Poiselles law.
Resistance is proportional to gas viscosity and the length of the tube but is inversely proportional to the fourth power of the radius.
R= (8/pie) x (nl/ r^4)
The main affecting factor of poiselles law.
Small changes in the radius have a big impact on resistance and hence flow rate.
Airway resistance of a normal person.
Which airways have the highest resistance
Percentages of each part of the lung that contribute to the total resistance
1.5cm H2O litres.
Larger airways.
Pharynx and larynx 40%
Airways with diameter bigger than 2mm-40%
Airways with diameter lower than 2mm-20%
Resistance in a COPD patient.
Total would be 5.0 H2O litres.
Pharynx and larynx 12%
Airways bigger than 2mm -18%
Airways smaller than 2mm - 70%
The airways smaller than 2mm have a large increase in resistance but the other parts of the lung keep their resistance proportionality the same.
How airway diameter impacts resistance
Increased mucus secretion will reduce diameter and increase resistance.
An odema is increased fluid retention in lung tissue which causes swelling and narrowing of airways which will increase resistance.
Inspiration and expiration pressure changes.
During inspiration there is forced expansion of some higher airways which decreases resistance.
During expiration there is forced collapse of some higher airways which increases resistance.
Airflow at the resting state.
No airflow and the lungs only contain the residual capacity.
Alveolar and external pressure are equal resulting in no movement of air as there is no pressure gradient.
The trans pulmonary pressure is +5.
Airflow pressure at inspiration
The airways dilate to create a low alveolar pressure and a decreased resistance . So air will travel into the lungs down the gradient.
The alveolar pressure is -15.
Trans pulmonary pressure is +5.
Airflow pressure at expiration.
There is constriction of airways to increase the pressure and resistance and make air leave the lungs down the gradient.
The alveolar pressure is +15.
Emphysema and how they breathe differently.
Airways compression is exaggerated.
Loss of elastic tissue and breakdown of alveolar walls.
The airways are flimsy during forced expiration and are less able to resist collapse.
To overcome this they exhale slowly and through pursed lips and take larger breaths.
Resistance in COPD
They have a higher resistance.
And it takes them longer to inspire because of the high resistance
What is total ventilation
The volume of air moved out of the lungs per unit time.
It is the tidal volume times by the number of breaths per minute.
What is the conducting zone and respiratory zone.
Conducting zone is not involved in gas exchange.
The respiratory zone is.
What is a new breath consisting of
Anatomical dead space is about 30% of the tidal volume at rest and is about 0.15L.
Each breath is 0.5L
- 15L of this new breath will be from the conducting zone (trachea) and of said to be stale air which is less oxygen rich.
- 35L will be fresh air.
What is alveolar ventilation
Volume of fresh air reaching the respiratory zone.
Total ventilation minus the dead space.
4.2L per minute.
What’s the partial pressure of CO2 during regular ventilation.
What is the partial pressure of alveoli.
What happens if you increase the ventilation rate
40mmHg
40mmHg
If you increase the ventilation rate then it become 20mmHg
Higher ventilation means lower CO2. This is because there is a higher volume due to higher ventilation causing lower pressure.
What affects lung ventilation.
Position of the body.
gravity when you’re standing or laying.
Higher ventilation at the base of the lung compared to the apex.
There is higher transpulmonary pressure in the apex so the alveoli will have a larger starting volume. They have a low compliance when the air enters because their volume was big to behind with.
Perfusion
What is the pulmonary circulatory system like.
Pressure values
The passage of fluid in the circulatory system to an organ or tissue.
Low pressure and resistance as the blood doesn’t have to travel far to the lungs.
Pulmonary artery 15mmHg
Aorta 95mmHg
Pulmonary venule 8mmHg
Pulmonary vs systemic driving pressure.
Where is the reference point for all pressures
Pulmonary 7mmHg
Systemic 93mmHg
Level of the left atrium.
