Respiratory Flashcards
What are the primary functions of the respiratory system?
- Provide area for gas exchange
- Protect respiratory surfaces (against pathogens)
- Sound production
- Control blood pressure, volume and pH
What is the anatomical classification of the respiratory system?
Upper respiratory system: frontal and sphenoidal sinuses, nasal conchae and cavity, external and internal nares, hyoid bone, nasopharynx, larynx
Lower respiratory system: trachea, bronchi (main, lobar, segmental) bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveoli.
What is the functional classification of the respiratory system?
Conducting zone: no gas exchange, function is to conduct air to respiratory zone and condition it (warm, wet and clean) Involves nares through to terminal bronchioles
Respiratory zone: Site of gas exchange. Involves respiratory bronchioles through to alveoli.
What are pseudostratified columnar epithelial cells, where are they and what are their functions?
Found in conducting zone. Form a protective barrier, move mucus. Damaged by smoking
What are goblet cells, where are they and what are their functions?
Found in conducting zone, in the bronchi. Secrete mucus. Damaged in asthma and smokers
What are basal cells, where are they and what are their functions?
Found in upper bronchi. They are stem cells
What are brush cells, where are they and what are their functions?
Found in the bronchi. Sensory cells
What are small granule cells, where are they and what are their functions?
Found in bronchi. Endocrine cells involved in secretion of histamine
What are club cells, where are they and what are their functions?
Found in bronchioles. Secrete watery mucus and antimicrobials. Marker of COPD
What are type I pneumocytes, where are they and what are their functions?
Found in alveoli. Very thin squamous cells making up 97% of alveolar surface area
What are type II pneumocytes, where are they and what are their functions?
They are found in the alveoli. They are cuboidal, highly metabolic cells responsible for secreting surfactant to reduce surface tension in the lungs
What are alveolar macrophages, where are they and what are their functions?
Found in the alveoli and in alveolar walls, function is defense.
Where is cartilage found in the resp. system and what is its function?
Found as C rings in trachea
Found as plates in bronchi
Keeps airways patent
Where are elastic fibres found in the resp. system and what is its function?
Found all the way through.
Responsible for compliance and recoil of lungs. Affected in COPD and emphysema
Where is collagen found in the resp. system and what is its function?
Found all the way through
Responsible for creating lung tension
Important in fibrosis
Where is smooth muscle found in the resp. system and what is its function?
Found all the way through up to the alveolar ducts
Controls diameter of bronchi and bronchioles to control airway tone.
Affected in asthma
How is mucus transported in the respiratory system?
Mucus is biphasic with a serous sol layer in which the cilia beat, and a viscous gel layer on top. The tips of the cilia catch in this layer (which is specialised to trap unwanted particles)
What are the functions of the trachea, bronchus and bronchioles?
T: Open for large volume of air
B: Open for large volume of air and increased branching to increase surface area
Bl: Control and tone of airflow
What are the bones surrounding the chest cavity? How are the ribs attached?
Sternum: Made up of manubrium (with jugularnotch)
This transitions to Sternum proper at the attachment of rib 2. These form a convex angle called the angle of Louis. Final part is xiphi process.
There are 12 ribs: 1-7 are true ribs, attaching directly to the sternum. 8-12 are false ribs, attaching via costal cartilage, or in the case of 11/12, floating freely. These have two facets inf. and sup. on their heads to articulate with the vertebral column. The inf. facet attaches to the matching numbered vertebra, the sup. head with the one above. On the inf. inner surface of the rib is the costal groove, where the neurovascular bundle runs.
Where are the boundaries of the thoracic cavity?
Upper: around rib I, over the jugular notch of the manubrium- forms the superior thoracic aperture. However, some of the pleural extends upwards in the suprapleural membrane
Lower: Costal cartilates of ribes and bottoms of ribs 11/12/ Forms the inferior thoracic aperture
What is contained in the costal neurovascular bundle?
Contain intercostal vein (superior), intercostal artery (middle) and intercostal nerve (inferior). The nerve may dip below the rib, putting it at risk.
What is the arterial supply of the thorax?
Aorta gives off:
- Brachiocephalic trunk: gives off right common carotid and right subclavian. Right subclavian gives off right internal thoracic, which then gives off anterior intercostal arteries
- Left carotid artery
- Left subclavian artery. Branches into left internal thoracic, and then gives off posterior intercostal arteries.
What are the divisions of the thorax?
- Superior mediastinum- above angle of Louis
- Inferior mediastinum- below angle of Louis (includes heart)
What are the arteries supplying the breast?
Anterior intercostals
Axillary artery
Posterior intercostals
How can tumors present in the breast and why?
The breast is a mix of glandular and fatty tissue sitting on pec major. Normally there is a fascial plane between the breast and the muscle which allows sliding. In breast cancer, some tumors can grow through this fascia, and so when the arms are raised the breast will stay in the same place.
Where does the lymph of the breast tissue drain?
- 75% to axillary nodes
- Rest to parasternal nodes- this means tumors can cross the midline to metastatise further
- Some to abdominal nodes
What are some chest wall deformities?
- Pectus Excavatum: sternum very concave, impacts hung and heart development. Many comorbidities
- Pectus carinatum: Sternum very convex, assoc. with lung and heart issues
Kymphosis and lordosis- assoc. with severe neuromuscular disorder and affects lung function. Predisposes to chest infection
Scoliosis- lateral and rotational deviation of the spinal cord.
What is lung volume, and what are the assumptions made in its measurement?
Lung volume has the symbol V and is measured in ml/L. Its measurement is assumed to be at 0 degrees celsius, 101.3kPa/760mmHg of pressure, and dry.
How do you convert ambient lung temperature, pressure and humidity to standard conditions?
V(STPD) = (VATPS) x (273/273+T) x (P-PH2O)/760.
What is flow and what can it give us?
Flow has the symbolV*. Its units are L/min-1. It gives minute volume- the volume breathed in and out over a minute.
What is anatomic dead-space volume and what is its consequence?
It is the volume of the conducting airways- about 1/3 of Vt or approx. 150mL. This means that only 2/3 of each breath is fresh air, and 1/3 breathed out is also fresh air.
It can be used to calculate alveolar flow: V*A = frequency x (Vt-Vd)
VD is responsible for diluting the partial pressure of CO2 exhaled. The volume of the atomic dead space over the tidal volume is equal to the PaCO2-PECO2 / PaCO2. This shows that an absence of CO2 in the exhaled air is the result of a non-gas-exchanging lung, while if arterial/alveolar PCO2 is the same as expired PCO2, then the dead space has not contributed to the volume of expired air.
What factors affect resistance to air flow?
- For air to flow, one pressure must be greater than the other. The volume of air exhanged is equal to the pressure difference over the resistance, where resistance is proportional to viscosity, length and radius of the passage.
Turbulence: If flow becomes turbulent, the volume of flow is proportional to the square root of pressure change- a large gradient is needed to achieve flow - Diameter and generation: although each bifurcation in the airways makes the radius smaler, the cross sectional area increases. This means that resistance initially increases and then falls to near zero.
What nerves are the pleurae supplied by?
- Visceral- supplied by same nerves as the lung- puerly autonomic. Therefore, lung tumors are often not felt.
- Parietal- supplied by the intercostal nerves, so it has the same sensation as the chest.
How do the lungs develop?
Initially the lung bud pushes in through the medial surface of the pleura, squishing the fluid filling the sacs to the edges and forming the two layers of membrane.
What are pleural recesses and where are they located?
They are sections of the lung where the pleura has folded in onto itself. There are cost-diaphragmatic recesses beneath the lungs, deep to the ribs. These are found meeting at rib 2-4, moving laterally on the LHS at rib 4 and RHS at rib 6, in the midclavicular line at rib 8 and at the midaxillary line around rib 10.
The posterior aspect extends below the level of rib 12, making it increasingly at risk of puncture.
The lung also pops up above the clavicle, making it at risk in the neck.
What is the anatomy of the main bronchi?
They divide off the trachea at the point called the carina. The right main bronchus gives off two lobar bronchi and is more vertically aligned (foreign material more likely to be stuck here), while the left is more horizontal and shorter, giving off two lobar bronchi.
What is contained within the hilum of each lung?
- Primary bronchus (if not already branched)
- Pulmonary artery
- Pulmonary trunk
- Bronchial arteries
- Bronchial veins
- Pulmonary plexus
- Lymphatics (vessels and nodes)
- Pulmonary ligament (pleura folds back and attaches the lung)
Where do the lobes sit for each lung?
Upper lobe in anterior and supieror
Middle lobe is anterior and inferior (beneath horizontal fissure
Inferior lobe is posterior (below the oblique fissure
Upper lobe is anterior
Inferior lobe is posterior
What is the circulation of the lungs in adulthood, and how is this different from foetal pulmonary circulation?
Adulthood: SVC and IVC –> RA –> Tricuspid valve –> RV –> pulmonary valve –> Pulmonary trunk –> R and L pulmonary arteries –> Lungs –> Right/Left Pulmonary veins, bronchial veins –> LA –> Mitral valve –> LV –> aortic valve –> aorta
In foetuses, the right ventricle goes straight into the aorta via the ductus arteriosus (which shrivels into the ligamentum arteriosus) and from the right atrium into the left atrium via the foramen ovale (which closes off to form the fossa ovale)
What is the pulmonary plexus?
Nerve running anterior and posterior to the hilum of the lungs. There is no somatic supply; rather, it contains sympathetic ANS from the sympathetic trunk (opens bronchioles and vasoconstricts BVs) and the vagus nerve as parasympathetic ANS, shutting the bronchioles and vasodilating the BVs.
Where is the best place to insert a chest drain and why?
Best place is just above whatever rib is most appropriate- if you have time you should always get an ultrasound to see where the fluid is located, although in emergencies it’s best to go for the subcostal recess as it’s less likely to puncture the area
In conscious patients, anaesthetize the area as the needle goes through skin, fascia, external, internal, innermost intercostals and the parietal pleura, all of which have somatic nervous supply.
For fluid, it’s best to go lower when a patient is prone, and in a pneumothorax, go higher. (air rises, fluid sinks)
What forces need to be acting for inspiration to occur?
- The pressure inside the alveoli must be lower than arometric pressure. The speed of inflow is proportional to this change. This is due to expansion of the chest wall and flattening of the diaphragm lowering the lung pressure.
What forces are acting at FRC?
This is the point at which each tidal breath ends. At this point, barometric pressure equals alveolar pressure, and the expansive forces of the chest wall equal the contractile forces of the lung.
What is compliance, and what factors affect this?
Compliance is refered to at the change in volume per change in pressure. It is measures in L/(cmH2O-1)
It is affected by tissue compliance, surface tension and atelectasis (alveolar collapse).
How does the compliance of a lung change at different pressures?
INHALATION: At only slight negative pressures, the gradient of volume is quite flat, but this increases with decreasing pressure this speeds up- a sigmoid graph. On the exhalation graph, it is smoother. This is called a hysteresis loop.
It’s much more responsive when saline is used- therefore the loop is determined by air. With just air, it takes a lot greater pressure to increase the lung- as the alveoli collapse and it’s hard to reinflate them.
What do soap bubbles have to do with lung compliance?
- The tension of a soap bubble wall is inversely proportional to its radius- those with larger radii have lower tension. However, the small alveoili don’t collapse into larger ones due to tethering in the lung- the structures of the alveolar walls prevent their collapse.
What is the formula for combined lung/chest wall compliance? What does gravity mean for lunch compliance at different points.
1/CT = 1/CL + 1/CCW
Gravity deforms the lung, pulling the bottom part down and narrowing the top part. This means that in the upright position, the base of the lung is more compliant than the apex. This also means the bottom of the lung is more well ventilated.
What are some problems that can cause difficult inspiration?
Pulmonary fibrosis makes inspiration difficult
Alveolar oedema puts water in the alveoli, causing an additional load
Increased blood pressure in the pulmonary veins means it’s more difficult to push blood through the pulmonary trunk and the lung becomes stiffer
Atelectasis causes is alveolar collapse
A deficiency in pulmonary surfactant
Anything increasing the stiffness of the thorax
What forces must the pressure difference overcome in order to ventilate the lungs?
To inhale, the force exerted must be greater than resistance to airflow and lung compliance.
Change in pressure = change in volume x elastance + flow x resistance.
How is Change in pressure = change in volume x elastance + flow x resistance represented on a graph?
Lung pressure: When inhaling, the lung has resistance pressure shown as a smaller downward triangle of lines inside the main one- these are the pressures the lung must overcome to inspire at different lung volumes.
Intrapleural pressure: Similar thing. Except, at the opposite ends of these lines is a line for elastic pressure- overcoming the tendency of the lungs to want to recoil inwards.
The resistance volumes are highest at the greatest rate of volume change.
How do you interpret pressure-flow diagrams?
X axis is pressure of the airway opening minus the oesophageal pressure (same as the intrapleural). This results in positive X axis values (representing negativity of intrapleural pressure).
At FRC and at max. volume, V* = 0, as there is no air flowing in or out of the lungs. A vertical line can be drawn between these two points to represent elastance. The closer to this line the pressure-volume loop runs, the slower the breath is, as to inhale at a pressure only just overcoming elastance requires a slow, bare intake of breath.
As the loop grows larger on the X axis, this represents inhalation, and as it returns smaller this is exhalation.
What is involved with the work of breathing?
Work must be done to overcome lung and tissue elastance, and resistance to airflow.
Work must be done during inspiration, and is not done during passive expiration, instead producing heat as work is done by the lung rather than on the lung.
Work increases at high breath frequency, whereas elastic work depends only on the tidal volume.
COPD reduces frequency of breath due to lung stiffness, and decreases tidal volume.
At fixed ventilation work, both resistance and elasticity vary with resp. frequency
Elastance increases at slower resp. frequencies, and resistance increases with higher frequency.
What are 3 common lung function tests?
- Forced vital capacity and FEV-1. Forced amount of air out in 1 second- normal is 95%
- Flow rates at various volumes during a forced expiration. Normal increases rate very quickly, which then tapers a little and then a lot.
- Maximum volume of ventilation
Why does airway collapse and obstruction cause a poor result for flow rates?
Normally, there are intrapulmonary forces acting on the lung which either force it open or closed. Once the expiratory forces make intrapulmonary pressure positive, it will cause the collapse of the air ducts and air trapping in the lungs. Once this happens, the graph shows a flat flow rate despite increased pressures.
What are the four components of the chest that can be abnormal on a chest Xray?
- Mediastinum
- Pleura
- Lungs
- Chest wall
What are some common radiological mediastinum abnormalities?
Tumor
Presence of a surgical pack (when intentional)
What are some common radiological pleural abnormalities?
Pneumothorax (air in chest cavity) Pleural effusion (fluid in chest cavity- CHF overload, asbestos exposure, pleurisy, cancer or trauma)- presents with meniscoid appearance Tumors (with calcium plaques?) Lung cancer Metastases Mesothelioma- thickening of pleura
What are some common radiological lung abnormalities?
Tumors- can be pulmonary (fuzzy borders, acute angle with lung boundaries). Can be extrapulmonary (lung makes obtuse angles, sharp borders)
What are some common radiological chest wall abnormalities?
Tumors- of ribs, soft tissues (eg. osteosarcoma)
Fractures
What is partial pressure of a gas, and how is it calculated?
Partial pressure is the pressure required to prevent a gas from diffusing out of a solution. It is the same in the gaseous form and liquid form.
It is the fraction of the gas in the air multiplied by that gas’s barometric pressure.
It is determined by solubility- the increase in content for each increase in partial pressure is determined by how soluble the gas is (content = solubility x pressure)
What are the factors affecting alveolar O2 diffusion, and how is diffusive capacity expressed?
Diffusion is affected by:
- Partial pressure of oxygen in the alveolus
- Partial pressure of oxygen in the capillary
- Area of the alveolar membrane (75m2)
- Thickness of the alveolar membrane (500nm)
- Diffusivity of oxygen
- Solubility of oxygen
However, d, A, D, and solubility can’t be directly measured- they are combined into ‘diffusing capacity of the lung’: DL.
How do we test the diffusing capacity of the lung?
Using carbon monoxide: This has a similar solubility to O2, and has a high affinity for Hb. Therefore, we know that the CO remaining after expiration is that which has not been taken up, rather than being clouded by what’s been expired.
DL(CO) = (V*CO / PA(CO) )
How do partial pressures of different gasses change over the time course it’s in the capillaries?
It begins its journey at about 40% partial pressure, due to what comes back unused from the tissues. Normally, it is 100% by .25 seconds, but in abnormal capillaries it can take more than .75 seconds.
N2O has a very high solubility and so it can reach 100% pressure very quickly
CO only reaches a small percentage of partial pressure due to the fact that it doesn’t sit in the blood plasma, but binds directly to Hb.
How do you distinguish between airways of the respiratory zone?
- Respiratory bronchioles- have random alveoli along them
- Alveolar ducts- Literally a row of alveolar buds and smooth muscle plugs
- Alveolar acs- bunch of alveoli
- Alveoli
Describe the interalveolar septa
These form the structural barriers between alveoli. They contain elastic fibres allowing recoil during tidal breathing. Collagen is important for structure. Fibroblasts produce both these components
Thin part forms the blood-air barrier, thick part supports and contains blood vessels
Describe the dual blood supply of the lungs
Circuit 1: Carries low pressure deoxygenated blood to the alveoli and then the the left atrium. Pulmonary arteries run with airways -> pulmonary capillaries -> pulmonary veins -> run within lobules-> heart
Circuit 2: Carries systemic pressure, oxygenated blood that supplies the conducting zone. Systemic vessels -> bronchial arteries
-> capillaries -> bronchial veins.
The bronchial veins empty into the pulmonary veins, meaning the ‘oxygenated’ blood is actually partially de-oxygenated
Compare and contrast the two lung circuits?
Pulmonary: Large volume, lumens. Arteries Thin walled, carries de-oxygenated blood alongside airways at low pressure. Veins are lonely, found in lung substance. carry ox blood at very low pressures
Systemic: supply airway tissues with O2 blood at systemic pressures. Veins are thin walled, low pressure, carry de-O2 blood
What is the general pathology of emphysema?
Inflammation destroys elastin, so decreased elastic recoil and connective tissue. Air spaces increases, so there is increased compliance (air gets trapped in the chest) and the gas exchange area decreases.
What are the three most important things determined by pulmonary function testing?
- Is the respiratory pump working?
- Is the alveolar membrane functioning properly?
- Is the lung adequately perfused?
What is spirometry and what does it indicate?
- It’s a measure of dynamic lung volume- mostly using FVC, FEV1 and max volumes during forced inspiration and expiration. Doesn’t measure total lung capacity, but can determine airflow.
It can establish/confirm a diagnosis of obstructive ventilatory defect
Assess effects of intervention
Assesses fitness for activities
Preoperative evaluation of airway obstruction
Impact of workplace exposure on resp function
What are the measures of static lung volume and what do they do?
- Plethysmography
- H2 dilution
- N2 washout
These are able t establish/confirm a diagnosis of restrictive ventilatory defect. They can also differentiate lung disease processes. They measure TLC and other static volumes, rather than flow
What is plethysmography?
Based on the law (P1 x V1 = V2 x V2)
Patient is seated in a box, breathing into a flow sensing defice, wearing nose clip and supporting cheeks. Patient gently pants, and change in flow over change in pressure in the box is measured to approximate airway resistance.
A mouth shutter is closed, and change in pressure of mouth over box is measured, allowing the measurement of thoracic gas volume.
What is helium dilution?
Used to measure functional residual capacity and total lung capacity. It uses (C1 x V1 = C2 x V2). Patient is connected to a chamber with a known concentration and volume of He (C/V1) and breathes deeply and rapidly, while He content is analysed at the mouth. Eventually the concentration stops fluctuating, indicating that lung He = chamber He. Therefore, the volume of chamber+lungs and therefore lungs can be determined.
What is N2 washout?
Uses (C1 x V1 = C2 x V2).
Patient breathes 100% O2 until there is no more N2 being exhaled- the total volume of N2 expired is therefore known and can be used to calculate total thoracic volume
What is the problem with H2 dilution and N2 washout methods?
Both are prone to error as lung pathology can change these concentrations
How do you measure airway resistance? What does this indicate?
- Panting with shutter open- measures volume and flow
- Panting with shutter closed- measures pressure and plethysmograph lung volume
Airway resistance = pressure/flow
Indicates restrictive ventilatory defect. Differentiates lung disease process. Aids in diagnosis of obstructive lung diseases
What is a bronchodilator response and what does it indicate?
The performance of a test (mostly FEV1) before and after use of a bronchodilator.
Percentage change = (highest pre FEV1 - Highest Post FEV1) / Highest pre FEV1 x100
To be considered successful it has to have an increased FEV1 of 12-15% and at least 200mL
Indicates reversibility of airway obstruction
Evaluaton of drug regimens
Reversal of bronchospasm
Postoperative evaluation
