Extra Resp Phys Flashcards
What equation can be used to demonstrate resistance of an airway?
Poiseuille’s law: R = 8ƞl / πr^4.
ƞ = viscosity, l = length
Briefly describe inspiration.
Inspiration is an active process. The external intercostal muscles and diaphragm contract. The volume of the thoracic cavity increases and you get a negative intra-thoracic pressure; air is drawn in.
Briefly describe expiration.
Expiration is usually passive. The ribs move down and in, the diaphragm relaxes. The intra-thoracic volume decreases and the pressure increases.
The main driver is the by the elastic recoil of the internal intercostals
of the lungs
Air is forced out.
What is it called when you have a high V/Q ratio?
Dead space. Lots of ventilation but no perfusion.
Pulmonary Embolism
What is it called when you have a low V/Q ratio?
give example
Shunt. Lots of perfusion but no ventilation.
eg Pulmonary Oedema
Does the apex (top of lung) have a high or a low V/Q? Why?
High - effect of gravity, far more perfusion at the base of the lung.
Name 4 causes of hypercapnia
- Increased dead space ventilation; rapid, shallow breathing.
- V/Q mismatch.
- Increased CO2 production.
- Reduced minute ventilation.
Name 4 causes of hypoxia.
- Hypoventilation.
- V/Q mismatch.
- Diffusion abnormality.
- Reduced PiO2.
What is the alveolar gas equation?
PAO2 = PiO2 - (PaCO2/R)
r usually 0.8
What is Dalton’s law?
In a mixture of non reacting gases Ptotal = Pa + Pb. (P total is the sum of the pressures of individual gases).
What is Boyle’s law?
Pressure and Volume are inversely proportional:
P1V1 = P2V2.
What is Henry’s law?
THE SOLUBILITY of a gas is proportional to the partial pressure of the gas. S1/P1 = S2/P2.
At higher pressure, insoluble gasses are more likely to dissolve
E.g. nitrogen in joints whilst diving
What is the acid/base dissociation equation?
CO2 + H2O = H2CO3 = HCO3- + H+
What is Laplace’s law?
Whats the significance?
P = 2T/R.
(pleased 2Teach Rachel)
Small alveoli have greater pressure, more air will move from small to larger alveoli, = uneven aeration
When is surfactant produced?
It starts being produced from 34 weeks gestation and production increases rapidly 2 weeks before birth.
List 4 functions of surfactant.
- Prevents alveoli collapse.
- Allows homogenous aeration.
- Reduces surface tension.
- Maintains functional residual capacity.
What does the pneumotaxic area do and where is it located?
It switches off inspiratory neurones and so allows expiration. It is located in the upper pons.
What does the apneustic centre do and where is it located?
It inhibits expiration by activation inspiratory neurones. It is located in the lower pons.
Where are SASR (slow adapting stretch receptors) located?
What activates them?
Found in smooth muscle around airways.
Activated by lung distension
(to stop lungs from overstretching) Herring - Bruer Reflex)
How do SASR respond to activation?
They inhibit inspiration and so promote expiration. – Prevent overstretching
Where are RASR (rapidly adapting stretch receptors) located?
Between airway epithelial cells.
What activates RASR?
Respond by what?
Lung distension and irritants.
bronchoconstriction
What activates C fibres J receptors?
Increased interstitial fluid volume.
How do C fibres J receptors respond to activation?
They cause rapid, shallowing breathing. Bronchoconstriction and cardiovascular depression.
What do peripheral chemoreceptors detect?
Changes in ppO2 and H+ ion increase
(only activated when O2 is proper depleted, <90%
Carotid sinus there to detect O2 levels In the brain
They are faster, and less key for breathing (as O2 is
not the drive for respiration
What do central chemoreceptors detect?
Changes in ppCO2, through increase in H+ ions in brain
(small changes of CO2 result in change in respiratory rate to compensate)
H+ ions can’t cross Blood Brain barrier, CO2 can:
CO2 when crosses BBB reacts with water to form H2CO3 (carbonic acid, a weak acidic) (catalysed by carbonic anhydrase) , which dissociates into HCO3- (Bicarbonate) and H+ ions
The H+ ions are then detected as a decrease in pH
They are slower, and more key for breathing
o2 dissociation curve - What happens further left you go? (to a lower Pao2)
haemoglobin has More affinity to O2, picks up O2 easier, harder to dissociate O2
o2 dissociation curve - What happens further right you go? (to a higher Pao2)
haemoglobin has Less affinity for O2, dissociates more easily.
what are Factors that drive curve more left? More affinity for O2
Higher pH (More alkaline), Decrease in CO2, Decrease in Temperature, Foetal Haemoglobin, Carbon Monoxide
LEFT = LOCKS IN MORE
what are Factors that drive curve more right? Less affinity for O2
Decrease in pH (more acidic) , More CO2, Increase in Temperature
What is forced vital capacity?
Volume of air that can be forcibly exhaled after maximum inhalation.
How could you diagnose a patient with having an obstructive lung disease?
The FEV1/FVC ratio would be less than 70% predicted value.
FVC would be normal, but FEV1 would be low -
Making the FEV1/FVC ratio low
How could you diagnose a patient with having an restrictive lung disease?
The FEV1/FVC ratio would be normal but their FVC value would be very low.
How can you work out total lung capacity?
Add vital capacity to residual volume.
What is tidal volume?
The volume of air moved into or out of the lungs during normal, quiet breathing.
What changes are seen in an aging lung?
Decreased compliance, muscle strength, elastic recoil, immune function. Decreased response to hypoxia and hypercapnia. Impaired gaseous exchange.
What is the sympathetic neurotransmitter in the lungs?
Noradrenaline.
What is the effect of Ach on the pulmonary vessels?
Bronchoconstriction and vasodilation.
What is the effect of noradrenaline on the pulmonary vessels?
Bronchodilation and vasoconstriction.
Name 2 receptors for Ach.
Muscarinic (G protein coupled) and Nicotinic (ligand gated ion channels).
Host defense: What is innate immunity?
Immunity that doesn’t require prior exposure. It usually involves phagocytosis and inflammation.
Define anatomical dead space
How much do we have of it?
- useless due to anatomy, the air that stays in our airway and does not enter the alveoli.
150ml
Define physiological dead space.
The volume of air that is taken in during a breath that does not take part in gas exchange.
the total of alveolar dead space and anatomical dead space 25ml + 150ml
Which alveoli are preferentially ventilated and perfused?
Those at the base of the lungs.
Why can hypoxia cause respiratory alkalosis?
Hypoxia leads to hyperventilation as the person tries to inhale more O2. This means you lose a lot of CO2 resulting in alkalosis.
Define functional residual capacity (FRC).
The volume of air remaining in the lungs after a tidal volume exhalation.
What 2 equations can be used to work out TLC?
- TLC = VC + RV.
2. TLC = TV + FRC + IRV.
Define expiratory reserve volume (ERV).
The additional volume of air that can be forcibly exhaled after a tidal volume expiration.
Define inspiratory reserve volume (IRV).
The additional volume of air that can be forcibly inhaled after a tidal volume inspiration
What is lung compliance?
A measure of the lung’s ability to stretch and expand. Compliance = ∆V/∆P.
Why does the residual volume increase in an ageing lung?
The chest wall changes shape. There is increased calcification and stiffness.
What is the main cell involved in acute inflammation?
Neutrophils.
pneumotaxic vs apneustic : which area can override which?
the pneumotaxic area can override the apneustic area
What layer of the tri-laminar disc is the respiratory tract derived from?
The endoderm.
Name 4 non-immune host defense mechanisms.
- Mucus.
- Muco-cilliary escalator.
- Epithelium.
- Cough.
Does the umbilical vein carry oxygenated blood or deoxygenated?
Oxygenated (umbilical artery carries deoxygenated).
What is the importance of the ductus venosus in foetal circulation?
It is used to bypass the liver. Oxygenated blood from the umbilical vein can go straight to the IVC and not through the liver.
What is the normal tidal volume in an adult?
500ml.
What is the epithelium of the vocal cords?
Stratified squamous non-keratinising.
Define peak expiratory flow (PEF).
The greatest rate of airflow that can be obtained during forced exhalation.
State the class of the immunoglobulin, the name of the cell and the name of the chemical mediator in Anaphylaxis
- Immunoglobulin: IgE.
- Cell: Mast cell.
- Chemical mediator: Histamine.
What can be some of the typical causes of acute inflammation?
Pathogens, damaged tissue.
What are the causative agents of chronic inflammation?
Persistent acute inflammation, persistent foreign bodies, autoimmune reactions.
What are main cells involved in acute inflammation?
Neutrophils! Also eosinophils and basophils.
What are main cells involved in chronic inflammation?
Mononuclear cells e.g. monocytes, macrophages, lymphocytes, plasma cells.
What nerves does the afferent limb of the cough reflex include?
Receptors within the sensory distributions of Cn 5, 9 and 10.
What nerves does the efferent limb of the cough reflex include?
Recurrent laryngeal and spinal nerves.
What is the function of B cells?
Antibody production.
What can be the case of
a) Type 1 hypersensitivity reactions
b) Type 2 hypersensitivity reactions
c) Type 3 hypersensitivity reactions
d) Type 4 hypersensitivity reactions
a) Pollen, cat hair, peanuts (allergies).
b) Transplant rejection, transfusion mismatch.
c) Fungal.
d) TB.
What comprises a respiratory acinus?
Respiratory bronchiole, alveolar duct and alveolus.
What part of the respiratory tract lies behind the sternal angle?
The tracheal bifurcation.
Give an example of
a) Restrictive lung disease
b) Obstructive lung disesae
a) Pulmonary fibrosis
b) COPD
What is the affect of pulmonary fibrosis on the following: FEV1, FVC, PEF, TLC and DLCO?
- FEV1 = reduced significantly.
- FVC = reduced significantly.
====> because of this, the FEV1/FVC ratio is likely to be NORMAL (both reduced)
- PEF = Typically not variable.
- TLC = reduced.
- DLCO = reduced.
What is the affect of COPD on the following: FEV1, FVC, PEF, TLC and DLCO?
- FEV1 = reduced.
- FVC = normal or slightly reduced.
==> Because of this, the FEV1/FVC ratio would be LOW - PEF = typically not variable.
- TLC = increased (hyperinflation).
What is DLCO?
Uptake of CO2 in ml at standard temperature and pressure.
What is the equation for trans-pulmonary pressure?
Transpulmonary pressure = alveolar pressure - pleural pressure. (TPP is always positive).
What layer of the trilaminar disc is pleura derived from?
Mesoderm.
Outline a Type 1 Hypersensitivity reaction
Antigen causes IgE to bind to Basophils and Mast cells ==> Release Histamines and chemokines
Causes Bronchoconstriction and Vasodilation (Hypoxia), Bronchospasms Inflammatory response
(Type 1 and Type 4 = similar thing but 1 is IgE mediated and releases histamines through binding to mast cells and 4 is T cell mediated and releases cytokines that activate macrophages)
Outline a Type 2 Hypersensitivity reaction
When IgM and IgG bind to cell surface associated antigens
==> Leads to tissue injury: Different to Type 3 as bound to cell surface antigen, not a soluble antigen that travels
(Type 2 and 3 are when IgG (and IgM for 2) bind to antigens either on the cell surface (2) or a soluble antigen in the blood (3))
Outline a Type 3 Hypersensitivity reaction
IgG Binds to a Soluble antigen, forms a circulatory immune complex.
These can be deposited in the lung and elsewhere and cause local inflammation and tissue damage
(Type 2 and 3 are when IgG (and IgM for 2) bind to antigens either on the cell surface (2) or a soluble antigen in the blood (3))
Outline a Type 4 Hypersensitivity reaction
Antigen activates T helper cells that secrete cytokines which activate Macrophages
Cytokines are proteins that allow leukocytes and tissue cells to talk to each other
(Type 1 and Type 4 = similar thing but 1 is IgE mediated and releases histamines through binding to mast cells and 4 is T cell mediated and releases cytokines that activate macrophages )
What do host cells need to have in order to be recognised and bound to by T cells
When they have major histocompatibility complex (MHC) proteins on their plasma membrane. Cells bearing these MHC proteins function as antigen-presenting cells (APCs)
What is general ADAPTIVE immunity mainly consist of?
What about INNATE immunity?
adaptive - largely made up of lymphocytes
Innate - largely made up of Neutrophils and macrophages
What is the average tidal volume?
500ml
What is the normal total lung capacity?
5000ml
what is the normal residual volume
1250ml
How far through the capillary is haemoglobin normally saturated at?
25%
What are pneumocytes joined up by?
tight junctions
What is the epithelium of the nasal sinuses?
Respiratory epithelium (i think)
Why is giving lots of O2 to a patients with T2RF dangerous?
patients undertake less gas exchange, and their damaged lungs are unable to deflate and exhale - so they are unable to get rid of co2 so easily
Therefore, their CO2 levels are chronically higher - Chemoreceptors get used to high co2 levels – resort to hypoxic drive so oxygen now for the respiratory drive, not CO2 levels
This is why if you give too much oxygen you’ll remove the pts desire to breathe, killing them
Define alveolar dead space
How much do we have of it ?
The air that reaches the alveoli only to be not perfused.
25ml
where would you find the parietal pleura?
What is it innervated by?
– on thoracic wall against lungs, phrenic innervation (nociception). Needs anaesthetizing for surgery
Continuous with Visceral pleura at root of lung
Intrapleural fluid fills space, lubricating surfaces
where would you find the visceral pleura?
What is it innervated by?
Visceral – on lung surface, autonomic innervation
Continuous with parietal pleura at root of lung
Intrapleural fluid fills space, lubricating surfaces
define minute ventilation
Minute ventilation is the volume of gas inhaled or exhaled from a person’s lungs per minute. It is an important parameter in respiratory medicine due to its relationship with blood carbon dioxide levels.
how many m below sea level do you need to go for a charge of 1atm?
10m
eg - Atmospheric pressure at 160m = 17 (since every 10m = 1atm, and don’t forget to count the 1atm at the surface!)
What is the normal pH range of the blood?
7.35 - 7.45
What is normal
PaCO2
PaO2
PaO2 = 10.5 - 13.5KPa PaCO2 = 4.5 - 6.0KPa
How do macrophages fight infections?
Alveolar macrophages functions to destroy bacteria swiftly through
phagocytosis where the macrophage engulfs the bacteria within a phagosome
(1)
- The membrane fuses with a lysosome containing hydrolytic enzymes, forming
the phagolysosome (1)
- The lysosome enzymes break down and destroy the bacteria (1)
What are the two measurements that are taken in spirometry that lead to a diagnosis
of an obstructive disease, and the values you would expect to see?
Forced Vital Capacity (FVC) (1)
- Forced Expiratory Volume in 1 second (FEV1)
Decreased FEV1, but FVC remains similar.
There fore would have a REDUCED FEV1/FVC RATIO BELOW O.7 (“scalloped”)
What would expect to see in a restrictive lung disease like pulmonary fibrosis?
reduced compliance of lungs, reducing both FEV1 and FVC
THEREFORE RATIO REMAINS THE SAME BUT ALL OTHER PARAMETERS REDUCE
Lung tests - patient to get transfer estimates What gas would you use for testing how quickly
gas is transferred across the alveolar epithelium? And why?
Carbon Monoxide (1) because it has a high affinity for haemoglobin
In respiratory acidosis, what happens?
this renal compensation occurs where the kidneys
increase H+ secretion in the form of ammonium (NH4+) and also release more HCO3- which
increases pH as a result of the use of the ammonium buffer.
NOTE THAT THE OPPOSITE SYSTEM (aka in this case, the renal system) will respond
What is another name for the 3 lung receptors?
stretch, irritant and juxtapulmonary capillary (J).
