Respiratory Physiology Flashcards
What kind of condition are Asthma, COPD and Lung cancer?
Obstructive
What kind of conditions are pulmonary fibrosis, pneumothorax, scoliosis (intrinsic/extrinsic)?
Pulmonary fibrosis = intrinsic restrictive
Pneumothorax, scoliosis = extrinsic restrictive
What extra muscles do you use for inspiration with increasing effort?
Neck muscles
Shoulder muscles
What extra muscles do you use for expiration with increasing effort?
Abdominal muscles
What does a spirometer measure?
Volume of air in and out of lungs during ventilation
What happens to the TLC, VC, FRC and RV in restrictive conditions?
All reduced
What happens to TLC, RV, and FRC in obstructive conditions?
RV is increased (cant get last bit of air out)
TLC is reduced (COPD) or increased (emphysema)
FRC is increased in emphysema
Are pulmonary fibrosis, kyphyscoliosis and circuferential burn associated with increased or reduced compliance?
Reduced (less stretchy)
Is emphysema associated with increased or reduced compliance?
Increased (more stretchy)
What is Laplaces law?
pressure = (2x surface tension)/radius of bubble
Why does surfactant prevent atelectasis?
Spread thicker in smaller alveoli so decreases the surface tension more greatly in them than larger alveoli so you end up with the same pressure
What is the make up of surfactant?
90% phospholipid
10% protein
In what syndrome is surfactant deficient?
Respiratory distress syndrome
From laminar flow to turbulent flow by how much is the work increased?
Power of 2
How much of energy expenditure is spent on respiration in health at rest>?
2-5%
How much energy expenditure is spent on respiration at maximum hyperventilation?
30%
How is work of respiration minimised in restrictive conditions?
Rapid slow volume breaths
How is work of respiration minimised in obstructive conditions?
Large volume, slow breaths
Why are breath sounds greater in larger airways than smaller airways?
Higher flow rate and therefore more turbulent flow in large airways
What is Dalton’s law about partial pressure of gas?
Partial pressure = total pressure x fraction of that gas
Why is partial pressure of oxygen in the alveoli lower than in inspired air? 3
1) Inspired air humidified
2) O2 taken up into blood stream while CO2 is added
3) Body consumes more O2 molecules than is produces CO2
What is the relationship of partial pressure of a gas and its solubility?
Partial pressure of a gas in solution is inversely proportional to its solubility
Why in someone with pulmonary fibrosis would the partial pressure of oxygen in the blood decrease if rate of respiration and heart rate increased?
Capillary transit time is shorter than the time take for diffusion of O2
What is carbon monoxide diffusing capacity used for?
To establish if someone with reduced exercise capacity has a problem with diffusion across the alveoli
What is adult respiratory distress syndrome?
Inflammatory process, difficult to distinguish from pulmonary oedema
What muscle holds the tongue against the palate in nasal breathing?
Genioglossus muscle
What muscle lifts the soft palate away from the back of the pharynx in mouth breathing?
Tensor palati
How does the pharyngeal dilator reflex work?
1) Pressure receptors in the mucosal lining of the pharynx detect air flow
2) Send a message to the brainstem
3) Brain stem causes pharyngeal muscle contraction to open pharynx and allow air flow
What is the problem in obstructive sleep apnoea?
Pharyngeal dilator reflex doesnt work properly or pharynx cant be help open (fat deposits around the muscle in obesity)
What substances can make sleep apnoea worse? 2
Drugs and alcohol
What is the treatment for sleep apnoea? 2
1) Weight loss
2) CPAP - constant positive air pressure
What 2 conditions is obstructive sleep apnoea associated with?
1) obesity
2) Hypertension - brain overcomes obstruction releases some ADR, over years get hypertension
What are the 2 clinical features of sleep apnoea?
1) Snoring
2) Daytime somnolence (sleepiness)
What are the 2 layers of airway lining fluid?
Mucous layer and periciliary layer
What 4 things can inhibit cilia in the airway?
1) Cigarette smoke
2) Infections
3) Air pollution
4) Inhaled anaesthetics
What are the 2 functions of airway lining fluid?
1) Humidification - affected by breathing pattern, heat and moisture exchanger on way out and in, does so through active control of pericilliary layer depending on humidity of air
2) Airway defence - mucociliary escalator and expectoration
Where are very large, large, small and very small inhaled particles caught?
Very Large (>8um) - nose and pharynx
Large (3-8um) - large airways
Small (0.5-3um) - bronchioles
Very small (
What are the 3 types of non immunological pulmonary defences?
1) Physical barrier and removal
2) Chemical inactivation (lysozyme, protease, antimicrobial peptides eg. beta defensins)
3) Alveolar macrophages (engulph carbon - move to lymphatic system)
What are the 2 immunological pulmonary defences?
1) Humoral - immunoglobulins
2) Cell mediated
What are the immunoglobulins involved in pulmonary defense?
1) IgA - nose and large airways
2) IgG - small airways
3) IgE - allergic disease
What are the 4 types of cell involved in immunological pulmonary defences?
1) Epithelial cells
2) Macrophages
3) Neutrophils (infection)
4) Eosinophils (allergy)
What is the relationship between protease enzymes in pulmonary defences and alpha-1 anti trypsin deficiency?
Protease enzymes are not pathogen specific so we have an anti protease system to protect body cells
If deficient in this then have alpha 1 anti trypsin deficiency
What are the 2 ways that oxygen can be carried in the blood, in which way is it mainly carried?
1) Dissolved in the blood
2) Carried by haemoglobin - main way
How is oxygen saturation (SO2) calculated?
HbO2 / (HbO2 + HHb) basically the percentage of Hb carrying oxygen
How is the volume of O2 carried in the blood by Hb calculated?
Volume of O2 = SO2 x [Hb] x 1.39
1.39 is the Huffner constant
What is the roughly normal amount of oxygen carried in the blood a) dissolved and b) combined with Hb?
Dissolved = ~0.29ml/dl
Combined with Hb = ~19ml/dl
In what state is it easier for O2 to bind to haemaglobin?
Relaxed state
In what state is O2 pushed out of the Hb molecule?
Tense state
What is P50?
PO2 at which SO2 = 50% (~3.5kPa)
What is the rough PO2 and SO2 of arterial and venous blood?
Arterial - PO2 = 12.5kPa, SO2 = 97%
Venous - PO2 = 6.3kPa, SO2 = 75%
What is the Bohr shift?
decrease in pH - curve shifts to the right
Bohr shift is the effect of CO2 on the oxygen dissociation curve so is a RIGHT SHIFT
What is the effect of temperature of the Hb dissociation curve?
Increase in temperature - shift to the right
decrease in temperature - shift to the left
What is the effect of 2,3 DPG on the Hb dissociation curve?
Increase in 2,3 DPG - shift to the right
Decrease in 2,3 DPG - shift to the left
More 2,3 DPG in hypoxic conditions
What is methaemaglobin?
Have Fe3+ Fe atom - drug induced
What is a buffer?
Minimises changes in free H+ - usually a weak acid and its base in equilibrium
What is the most common buffer in the body?
H2CO3 H+ + HCO3-
Within what range should blood pH be held?
7.35-7.45
Other than bicarbonate, what are the 3 other body buffering systems?
1) Plasma proteins
2) Haemaglobin
3) Phosphate
What 3 ways can CO2 be carried in the blood and which is the main way?
1) Dissolved in blood
2) Carbamino compounds (bound to NH2 groups on proteins)
3) As carbonic acid/bicarbonate - main way
Where does conversion of CO2 to carbonic acid/bicarbonate take place?
In the red blood cell
What is the hamburger shift?
Occurs in the RBC
After conversion of CO2 to carbonic acid/bicarbonate the H+ ions created are buffered by Hb but the HCO3- ions are pumped out of the cell in exchange for Cl- ions
At the alveoli, the whole process is reversed and CO2 is breathed out
What is the shape of the CO2 dissociation curve?
Straight line
What is the Haldane effect?
Ability of deoxygenated blood to carry more Co2 than oxygenated blood
What does the Henderson-Hasselbach equation relate?
pH, [CO2], [HCO3-] with a constant that is the same for all human beings at 37 degrees
Basically says that pH is a function of the ratio of PCO2 and serum HCO3-
What is ventilation and perfusion?
Ventilation = movement of gases in and out Perfusion = blood flow through any organ
What is the difference between alveolar vessels and extra alveolar vessels?
Alveolar vessels = capillary beds around alveoli
Extra alveolar vessels = running through lung parenchyma
What is hydrostatic pressure?
The force exerted by weight of fluid due to gravity
What did starlings resistor show?
Had a collapsible segment and showed that for the collapsible segment to stay patent then upstream pressure must be greater than the pressure outside of the collapsible segment
What is the relationship between arterial pressure, alveolar pressure and blood flow through alveolar vessels?
Arterial pressure must be greater than alveolar pressure for blood to flow through alveolar vessels
What affects the arterial pressure in different alveolar vessels?
Hydrostatic pressure which alters at different areas of the lungs determined by their position relative to the right ventricle
What is zone 1 in the lungs in terms of V/Q mismatch?
Dead space
Apical regions
Alveolar pressure is greater than arterial pressure so capillaries collapse
Good ventilation but no perfusion
What is zone 2 in the lungs in terms of V/Q mismatch?
Recruitment zone
Middle regions
Arterial pressure is greater than alveolar pressure so perfusion
Recruitment of alveoli in systole
What is zone 3 of the lungs in terms of V/Q mismatch?
Distension zone
Basal regions
Arterial pressure is greater than alveolar pressure so blood flow good
some alveoli may be collapsed
Why might you have expansion of the dead space (zone 1) of the lungs in haemorrhage or positive pressure ventilation?
Haemorrhage
Drop in arterial pressure - less of recruitment zone perfused
Positive pressure ventilation
Rise in alveolar pressure - so alveolar pressure is greater than arterial pressure and capillaries collapse
What would be the ideal V/Q?
1
What is the average V/Q and are the values higher or lower in the apical regions and basal regions?
Average = 0.8
Apical regions - higher (as much as 3.3)
Basal regions - lower (as low as 0.6)
What is anatomical dead space?
Conducting airways where no gas exchange could occur
What is alveolar dead space?
Unperfused or poorly perfused alveoli
What is physiological dead space?
Anatomical dead space + alveolar dead space
What happens to alveolar dead space in PE?
Increased
What is shunt?
Deoxygenated blood reaching the left side of the heart either by bypassing the heart or failing to be oxygenated in the lungs
How is minute ventilation calculated (VE)?
Breathing frequency x tidal volume
What are the 2 parts of the brain making up the respiratory center in the brain?
The Pons and the Medullar oblongata
What are the 2 parts of the medulla oblongata part of the respiratory center in the brain and what kind of neurones do they contain?
1) Ventral respiratory group - contains a mixture of neurones which fire during inspiration and expiration
2) Dorsal respiratory group - only contains neurones which fire during expiration
What kind of neurones are the neurones in the ventral and dorsal respiratory groups of the medulla oblongata?
Autonomic neurones - they never flat line - without any in puts they still fire
What ensures you dont get inspiratory and expiratory neurones in the medulla oblongata firing at the same time?
Reciprocal control between the ventral respiratory group (mixed) and dorsal respiratory group (only inspiration) so you dont get both inspiratory and expriatory neurones firing at the same time
Why is there very little if any expiratory activity at rest?
Expiration at rest is a passive process
What is the role of the pons part of the respiratory center in the brain?
To control the dorsal respiratory group of the medulla oblongata
What are the 2 parts of the pons part of the respiratory center in the brain an what does each do?
Apneustic center - stimulates inspiratory neurones
Pneumotaxic center - inhibits inspiratory neurones
Both only act on the dorsal respiratory group of the medulla oblongata (only contains inspiratory neurones)
What 6 factors provide information to the respiratory center in the brain?
1) Higher brain centers - voluntary control over breathing can overule
2) Stretch receptors in the lungs
3) Irritant receptors (take a deep breath in and cough)
4) Receptors in muscles and joints
5) Peripheral chemoreceptors - respond to decreased O2, increased Co2 and increased H+
6) Central chemoreceptors - only respond to increased CO2 and increased H+
What is meant by cortical and hypothalamic higher brain center influences on respiration?
Cortical - voluntary hyperventilation or breath holding
Hypothalamic - Emotions - anger/anxiety (hyperventilation) and sensory reflexes such as gasping in response to pain or cold
What happens to the firing of neurones in the medullar obongata in response to stretch receptors in the lungs as inspiration progresses?
As stretch receptors get more stretched
Get an increase firing of expiratory neurones in the ventral respiratory group
Decreased firing of inspiratory neurones in the dorsal respiratory group
What role do muscle spindles have in controlling respiration, where do they tend to be located?
Rich in intercostals, few in diaphragm
Activated in intercostals, associated with contraction in inspiration
How can baroceptors affect respiration?
They sense blood pressure but can also influence respiration
When they sense higher blood pressure you get decreased ventilation
What are J receptors and how can they affect respiration?
Next to capillaries around alveolar walls
Activated by traumas such as pulmonary oedema, inflammatory agents and thus increase ventilation
Where are peripheral chemoreceptors which control respiration located and what are the sensitive to?
Located in the carotid and aortic bodies
Sensitive to hypoxia, hypercapnia and acidosis
What kind of cells in peripheral chemoreceptors are sensitive to hypoxia?
Gloma cells
What is the prominent driver for respiration?
Changes in H+ and CO2 levels
Where are central chemoreceptors located?
Close to the medulla respiratory centers
What are central chemoreceptors sensitive to?
CO2 and H+ in cerebrospinal fluid
H+ cannot pass the blood brain barrier, how are central chemoreceptors informed of H+ levels?
CO2 can pass the BBB
In cerebrospinal fluid CO2 dissolves to form H+ which informs of H+ levels
What is the most important driver of respiration in chronic respiratory conditions?
Hypoxic drive - get used to a high level of CO2
What is the oxygen cascade?
The drop on PO2 as you pass from dry air to mitochondria
What is PO2 in arteries?
13.6kPa
What did the Krogh model show?
Tissue is like a cylinder with a capillary moving through it
PO2 gradient decreases as you move along the cylinder and out towards the edges of the cylinder - you end up with a lethal corner - furthest point along the cylinder at the edge
What is the definition of oxygen delivery?
Amount of O2 leaving the heart in one minute (DO2)
Calculated as the product of cardiac output and the amount of O2 carried in the blood
What is the definition of O2 consumption?
Amount of O2 used by the body in 1 minute
What 3 factors affect VO2?
1) Age - peak at 0-2 years then rate falls for the rest of your life
2) Temperature - metabolic rate doubles with every 10 degree increase in temp
3) Exercise
What are the 4 physiological responses to anaemia?
1) Increased 2,3 DPG - shifts the curve to the right
2) Reduced blood flow to non essential organs
3) Increased O2 extraction from the blood
4) Increased cardiac output
What is the physiological response to high altitude?
O2 saturation decreases with altitude and the amount of Hb increases
What is the respiratory exchange ratio?
The ratio of CO2 production (VCO2) to O2 consumption (VO2)
What is a persons respiratory quotient?
RER at rest - normal value = 1
What 3 things affect the respiratory quotient?
1) Acid Base balance
2) Hyperventilation
3) Metabolic fuel
In cardio pulmonary exercise testing at what point is the anaerobic threshold reached in terms of VO2 and VCO2?
The point when VO2 is still increasing but VCO2 has stopped increasing at the same rate
What are the 3 circles in Barcroft classification of cellular hypoxia?
1) Anoxic - lack of O2 in blood
2) Stagnant - lack of blood supply
3) Anaemic - lack of Hb
Why is cardiopulmonary testing sometimes carried out on patients before they have surgery?
To make sure the have sufficient VO2 as demand during and after surgery for O2 is high so have to make sure you have sufficient VO2 max
What happens to FiO2 and PiO2 at altitude?
FiO2 stays the same but overall air pressure decreases and therefore PiO2 decreases
What is the physiological response to high altitude? 4
1) Hyperventilation and respiratory alkalosis - get rid of CO2 to make room for O2
2) Increased 2,3DPG - shift curve to the right
3) Polycythaemia - slow to develop
4) Bicarbonate excretion from kidneys
What are the symptoms of mountain sickness? 6
1) Headache
2) Nausea
3) Loss of apetite
4) Difficulty sleeping/exercising
5) Amnesia
6) Dizziness
What happens in severe mountain sickness?
Cheyne strokes respiration
Cerebral/pulmonary oedema
Can be lethal
What is the problem with free diving in terms of oxygen delivery to the tissues?
As dive the lungs compress so although the volume of air decreases the pressure rises so you have sufficient PiO2
When you rise the volume increases and pressure decreases, the FiO2 has decreased aswell as you used some oxygen thus with both those factors PiO2 can decrease greatly
Main problem with free diving is severe hypoxia on ascent
When does decompression sickness (bends/staggers/creeps) occur?
Too rapid decrompression of the body causes nitrogen bubbles to form in the tissues of the body as N2 comes out of solution in the tissues
Can causes pain in the muscles and joints, cramps, numbness, nausea and paralysis
How is decompression sickness treated?
With decompression tanks
How is PiO2 kept normal in deep sea diving?
In deep sea diving as descend atmospheric pressure increases
In order to keep PiO2 normal then a lower FiO2 has to be used
What is hyperoxia and what can it cause?
Cellular oxygen toxicity
Can cause fitting due to free radical generation
Can also cause pulmonary fibrosis/ARDs (acute respiratory distress syndrome)
What is the dive reflex?
Innate reflex of many mammals
Vasoconstriction - O2 conserved to heart lungs and brain
Reflex vagal bradychardia
Suppressed ventilation drive
