Respiration Flashcards
What is compliance?
measure of elasticity
What is another word for compliance?
distensibility
What is the equation for compliance?
Compliance = change in velocity/change in pressure
What is the definition for compliance?
the ease with which the lungs & thorax expand during pressure changes
If someone has low compliance, what does this lead to?
more work required to inspire e.g. pulmonary fibrosis - lung parenchyma is more rigid
If someone has high compliance, what does this lead to?
often involves more difficult expiring (loss of elastic recoil) e.g. emphysema
What is the result of fibrosis on lung compliance?
harder to expand the lungs - change is smaller
What is the result of emphysema?
the same change in pressure leads to a higher change in lung volume.
What are the 2 major component to the elastic recoil of the lungs?
- anatomical component - elastic nature of cells & extracellular matrix
- elastic recoil due to surface tension generated at air-fluid interface
What occurs when the elastin in the lungs are in a saline solution?
inflation with liquid - small pressure change = rapid change in lung volume (lack of surface tension)
What occurs when the elastin in the lungs are in air?
would have normal fluid - leading to surface tension to surface-water interface.
- despite increase in pressure, not much change in volume. This is because surface tension needs to be overcome.
- the alveoli will then pop open, leading to an increase in volume.
- surface tension not as significant during expiration
Why is surface tension created?
due to a difference in the forces of water molecules at the air/water interface develops
- in a gas bubble there is a balance between pressure exerted by the gas & the surface tension at the gas/water border
What equation explains surface tension?
Laplace:
P=2T/r
(Pressure generated in air bubble in water = 2 x surface tension/divided by radius)
Does surface tension remain constant?
yes
What level of pressure is in a small bubble?
small bubble = small radius = high pressure
What level of pressure is in a large bubble?
large bubble = large radius = low pressure
What are alveoli?
air sacs, surrounded by fluid
Where is pressure higher - larger sac or smaller alveoli sac?
smaller sac
What occurs as a result of air flowing from smaller alveoli to larger, due to the difference in pressure concentration?
they collapse
What is used to overcome the collapse of alveoli?
production of surfactant
What produces surfactant?
Type 2 pneumocystis
What is surfactant made of?
lipids & proteins
How does surfactant aim to prevent alveoli from collapse?
reduce surface tension. lipids partition the surface-water interface by creating a pull-upwards, reducing surface tension
What level of surfactant is found in small alveoli?
high
What is another use of surfactant?
the lungs can use surfactant to maintain steady volume & prevent over-expansion of alveoli
What volume can not be measured by spirometry?
residual lung volume
What are the 2 types of dead space?
- Anatomical dead space
- Physiological dead space
What is anatomical dead space?
volume of conducting airways. At rest approximately 30% of inspired air volume (150ml)
What is physiological dead space?
volume of lungs not participating in gas exchange.
- conducting zone + non-functional areas of respiratory zone.
- normally the 2 valves are almost identical.
What are the static values on a spirometer?
- Residual volume
- Vital capacity
- Total lung capacity
- FEV1
What is residual volume?
the air remaining in your lungs after maximum exhalation (can’t be measured via Spirometry)
What is vital capacity (VC)?
maximum inhalation to maximum exhalation
What is total lung capacity?
residual volume + vital capacity
What is FEV1?
Forced expiratory volume in 1 sec (following deep inhalation)
What are the dynamic values in a spirometer?
- Tidal volume
- Expiratory reserve volume
- Inspiratory reserve volume
What is tidal volume?
amount of air breathing and out
What is expiratory reserve volume?
air between bottom of vital volume & reserve volume
What is inspiratory reserve volume?
air between normal breath and how much you can breathe
What is functional residual capacity?
volume of air at the end of normal expiration down to full volume
What is inspiration capacity?
end of normal expiration - how much can you then breathe in
When does reserve volume change?
in response to the demand of metabolism
How do you calculate residual volume?
nitrogen-dilution techniques (helium dilution in the lungs)
Describe the nitrogen-dilution technique
- Breathe in & out of air chamber (with known volume).
- starting volume contains helium, which doesn’t pass across the alveoli.
- keep breathing & helium becomes diluted in the lungs.
- calcuate total volume
What is the equation for calculating residual volume?
volume 1 x concentration = volume 2 x concentration 2
Describe the relationship between flow rate & resistance
flow rate is inversely proportional to the resistance
What is the equation for flow rate?
flow = change in pressure (between alveoli & atmosphere)/ resistance
What does Poiseuille’s law impact?
the impact of resistance on flow is determined by Poiseuille’s law
Describe the relationship between airway resistance & gas viscosity & the length of the tube
airway resistance is proportional to gas viscosity
Describe the relationship between airway resistance & the fourth power of the radius
airway resistance is inversely proportional to the 4th power of the radius
How much % increase in resistance occurs with a 10% change in radius?
50%
What is the normal total airway resistance in a human?
1.5cm H2O.s litres -1
What % of total resistance occurs in the pharynx & larynx?
40%
Airways that have a diameter of >2mm make up what %?
40%
Airways that have a diameter of <2mm make up what %?
20%
Do airways with a diameter of >2mm have resistance in series or parallel?
Resistance in series
Do airways with a diameter of <2mm have resistance in series or parallel?
Resistance in parallel
Why do airways with more than 2mm contribute to resistance?
as there are a lot more tubes connected in series
How does airway diameter impact airway resistance?
increased mucus secretion will effectively reduce airway diameter - increased resistance
What is oedema?
increased fluid retention in lung tissue will cause swelling & narrowing of the airways - increased resistance
Why do airway collapse?
for example during forced expiration narrows airway, increasing resistance
How does the parasympathetic control the bronchial smooth muscle?
acetylcholine is released from the vagus, which acts on Muscarinic receptors, leads to CONSTRICTION.
How does the sympathetic control the bronchial smooth muscle?
norepinephrine is released from nervous - weak agonist leads to DILATION
What are humoral factors that affect the bronchial smooth muscle?
- Epinephrine circulating in the blood - better agonist leads to DILATION
- Histamine - released during inflammatory processes - leads to CONSTRICTION
What is the composition of air?
dry & wet at standard atmospheric pressure of 760mmHg
What is Dalton’s Law?
the total pressure of a mixture of gases is the sum of their individual partial pressure
What are the 2 most prevalent gases in the atmosphere?
- Nitrogen
- Oxygen
What is Henry’s law?
Gas[dis] = s x Pgas
s = solubility coefficient
P = is the partial pressure of the gas
How many subunits do haemoglobin have?
2a chains
2b chains
What subunits are found in foetal haemoglobin?
2a chains
2g chains
How many iron atoms are in foetal haemoglobin?
1
In what form does iron have to be in order for oxygen to bind?
Fe2+
What enzyme is used to convert Fe3+ to Fe2+
methaemoglobin
What are the 2 states that haemoglobin can exist?
- tense state
- relaxed state
Describe the affinity for O2 that haemoglobin has in its tense state
low affinity for O2
Describe the affinity for O2 that haemoglobin has in its relaxed state
high affinity for O2
What is majority of blood bound to?
haemoglobin
What factors affect the oxygen-haemoglobin dissociation curve?
- temperature
- CO2
- pH
- 2-3 diphosphoglycerate
Which way does the curve shift if there is an increase in temperature?
RIGHT - as the temperature increase, the haemoglobin is able to carry less oxygen
What is the name of the effect given, when the curve shifts to the right, as a result of an increase in pH?
Bohr effect
What is 2,3 diphosphogylcerate?
it is a metabolite in the glycotic pathway, meaning a high presence of 2,3 DPG indicates an area to be metabolically active (metabolically active tissue).
What causes a right shift in the oxygen-haemoglobin dissociation curve?
- increased temperature
- increased CO2 production
- decrease in pH (local acidification)
What is the result of a decreased affinity for O2 on haemoglobin?
more O2 released to the tissue
What does a lack of sensitivity for 2,3 DPG lead to?
a leftward shift in the oxygen-haemoglobin dissociation curve
What is the physiological benefit of foetal haemoglobin having being shifted left in the oxygen-haemoglobin dissociation curve?
it makes it easier for the placenta to take oxygen from the mother - leading to a higher affinity for oxygen
Carbon dioxide + water = ?
carbonic acid
What is carbonic acid broken down into?
bicarbonate & a proton (hydrogen ion)
How does CO2 affect the pH of a solution?
increase in CO2 = increase in acidity of a solution
What are different ways CO2 is carried in the blood?
- dissolved carbon dioxide
- carbonic acid
- bicarbonate
- carbonate
- carbamino compounds
How is the majority of CO2 transported in the blood?
in the form of bicarbonate
How much CO2 remains in the plasma?
10-11% - can dissolved in CO2 or can combine & make carbamino compounds
What reaction does the enzyme carbonic anhydrase speed up?
the conversion of CO2 + water –> bicarbonate
What 2 protein compounds allow for the transfer of CO2 into the cell (90% of it)?
- aquaporin 1
- rhesus-A glycoprotein
What % of CO2 dissolves in the cytoplasm of the erythrocytes?
4%
What does 20% of of CO2 bind to?
amino acid residues on the proteins, forming carbamino compounds
What does the enzyme carbonic anhydrase facilitate the production of?
bicarbonate
What transports bicarbonate out of the erythrocytes?
a carbon exchanger (chloride-bicarbonate exchanger) - chloride shift
