Respiration Flashcards
What is the process underlying respiration in humans?
- Both ventilation (breathing) and transport of blood gases in the blood stream are accomplished by convection (bulk flow) and depend on a difference in total pressure
- Gas exchange at the lungs and at the level of tissues/cells is accomplished by diffusion and depends on the difference in the partial pressure of a given gas
What are the four basic steps of respiration?
- Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs
- Exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries
- Transport of O2 and CO2 by the blood between the lungs and the tissues
- Exchange of O2 and CO2 between the blood in the systemic capillaries and the tissues
What is the CO2 production of a normal individual at rest?
200ml/min
What is the O2 consumption of a normal individual at rest?
250ml.min
What is the respiratory quotient (RQ)?
the ratio of CO2 produced to O2 consumed = 0.8 = 8 molecules of CO2 produced for every 10 molecules of O2 consumed
What is gas exchange at the lungs and at the level of tissues/cells accomplished by? What does it depend on?
diffusion
- depends on difference in the partial pressure of a given gas
what are ventilation and transport of blood gases in the blood stream accomplished by? What do they depend on?
convection
- depend on a difference in total pressure
What are the major structures in the upper airways?
- nose, mouth, pharynx (throat), larynx(vocal cords)
Excluding the structures of the upper airway, what are the other respiratory airway structures?
- Trachea, right bronchus, carina, left bronchus, and the diaphragm
What is the upper airway?
a multipurpose passage for air, solid and liquid food and a common structure for breathing, digestion and phonation
What is the function of the Uvula?
closes the naso-pharynx during swallowing and inhibits nasal regurgitation
What is the function of the epiglottis?
movement of hyoid bone during swallowing brings it down stopping food from entering the trachea and directs food into the esophagus
What are the vocal cords/vocal folds and what are their function?
folds of mucous membrane that lie across the laryngeal opening and allow for phonation and prevent aspiration of food
How many muscles control the position of the 4 structures of the airway in order to keep it closed during swallowing and open during breathing? (upper airway dilators)
20 muscles
What are the 4 structures whose positions are regulated by the 20 upper airwayd dilators?
- soft palate
- tongue
- hyoid apparatus
- pharyngeal wall
What happens during obstructive sleep apnea with regards to the airway dilators?
decreased genioglossus muscle activity leads to obstruction of the airway by the tongue
What are the functions of the upper airway mucosal lining?
to heat and humidify the inspired air
How does the mucosal lining of the upper airway effect inspiration?
heat and moisture from the mucosal lining heats and humidifies the inspired air to 37 degrees, saturated water vapor
How does the mucosal lining of the upper airway recover from the heat and moisture lost during inspiration?
air releases heat and moisture during exhalation, partially warming and humidifying the mucosa. the remaining is from the systemic blood supplying the airways
What happens to the regulation of heat and moisture in a patient with a tracheostomy?
the trach tube usually has heating and humidifying functions, otherwise air would be cold and dry
How many lobes do the left and right lung have?
left = 2 lobes right = 3 lobes
What are the structures involved in the tracheobronchial tree?
- trachea, carina, left primary bronchus, right primary bronchus
What is a characteristic of the tracheobronchial tree in terms of branching?
every parent structure has two or more daughter structures (usually 2 but sometimes more)
What structures are part of the conducting zone?
trachea, bronchi, bronchioles and terminal bronchioles
What structures are part of the transitional and respiratory zones?
respiratory bronchioles, alveolar ducts and alveolar sacs
What happens as the diameter of the airways gets smaller?
the number of them increases
What function does cartilage serve in the airways?
prevents/resists collapse
What is the structure of the tracheal cartilage?
U shaped cartilage completed into A ring by the trachealis smooth muscle
What is the structure of the bronchi cartilage?
Cartilage plates interspersed within the bronchial smooth muscle ring
Which airways have no cartilage?
bronchioles, terminal bronchioles, respiratory bronchioles, and alveolar ducts
What are bronchioles mainly composed of?
smooth muscle
What is the function of the terminal bronchioles?
conducting function
What is an additional function of the respiratory bronchioles and why?
gas exchange due to presence of alveoli
What are the walls of the alveolar ducts covered in and what do they terminate in?
covered with alveoli and terminate in alveolar sacs
What are the three types of airflow in the airways?
turbulent, laminar and transitional
What is turbulent flow?
axial and radial in direction, noisy and rapid in speed
Where does turbulent flow occur?
in larger diameter airways where speed of air molecules is fast
- upper airways
- trachea during quiet breathing (at rest) and bronchi during exercise
What does turbulent flow depend on?
density of air
What is air composed of?
about 80% nitrogen and 20% oxygen
What would happen if you replaced the regular composition of air with a lighter gas mixture? Why might yu do this?
it would reduce turbulent flow in the airways and make laminar flow more likely
- can help patient who is having trouble breathing (don’t lose any energy)
What is laminar flow?
streamline (parabolic profile), silent and slow
- air molecules int he center are moving fastest
Where does laminar flow occur>
in the smaller airways (<2mm diameter) where speed of air molecules is slow
What are the characteristics of transitional flow?
intermediate between laminar and turbulent
Where is transitional flow present?
throughout most of the tracheo-bronchial tree
In general, what is the composition of the airway wall lining?
a gradual transition from proximal to distal airways to thinner epithelium with loss of mucous glands and cartilage
What are the two separate blood supplies?
- conducting zone by the bronchial circulation (part of systemic circulation)
- Respiratory zone (alveoli) by the pulmonary circulation
What are pores of Kohn?
collateral ventilation aids in introducing fresh air into an obstructed airway
How many alveoli are in contact with 100s of pulmonary capillaries?
300 million
What three cell types are the alveolus composed of?
- Type 1 Pneumocyte
- Type 2 Grandular Pneumocyte (AKA alveolar septal cell)
- Type 3 Alveolar Macrophage “dust cell”
What is the structure of a type 1 pneumocyte? How much surface area do they cover?
composed of flat squamous epithelium and covers 95% of the alveolar surface area
- thin
What is the structure of type 2 granular pneumoctyes?
Cuboidal in shape and contain lamellar inclusion bodies that store pulmonary surfactant
What is pulmonary surfactant?
a surface active agent that reduces alveolar surface tension
- mixture of lipids (mostly) and proteins
What is the key surface tension reducing agent in pulmonary surfactant?
Diphosphatidylcholine (DPPC)
Where are type 3 alveolar macrophages found?
at the extracellular lining of the alveolar surface
What is the function of a Type 3 alveolar macrophage?
It migrates and is phagocytic (defends against forgeign particles)
Starting at the blood plasma, what are the layers of the air-blood barrier or alveolar capillary membrane?
blood plasma, capillary endothelium, interstitium, alveolar epithelium, surfactant, air
What is the alveolar interstitium?
a fluid space between air and blood barrier in series with the lymphatic system allowing excess fluid drainage into the lymphatic system
What does the alveolar interstitium do?
joins and supports the structural elements via an elaborate fiber system (collagen and elastin fibers)
How is airway clearance of particles that are >10um in diameter achieved?
- filtered and trapped by nasal hairs
- irritant receptors lining the nasal passages initiate the sneeze reflex –> removal of particles
How is airway clearance of particles that are 2-10um in diameter achieved?
- mucociliary transport system lining the airways proximal to the terminal bronchioles
- irritant receptors in airway lining –> cough –> removal of particles
What is the structure of the mucociliary transport system?
mucous blanket with 2 layers: gel or mucus layer and a sol or aqueous periciliary layer
How is the mucociliary escalator and airway clearance achieved?
cillia with tip claws beat in a path or unified motion to push material upwards
What impaires the mucociliary transport system? How?
- smoking ( decreased ciliary motion and increased mucus production)
- Pathogenic microbes (release substances that paralyze ciliary motion)
- Primary ciliary dyskinesia (cilia dysfunction due to a structural defect - inherited disease)
- Cystic fibrosis (defective chloride channels involved in transport of water and sodium across the epithelium result in formation od viscous sticky mucus hard to clear from the lungs and pancreatic ducts - inherited disease)
What happens if particles <2um in diameter reach the alveoli?
- migrating and phagocytic macrophages engulf forgien particles on alveolar surface and degrade them
- non-degradable particles with sharp profiles injure alveolar epithelium and the alveolar macrophages leading to inflammation, scar formation (collagen deposition) and in turns pulmonary fibrosis
The lungs and chest wall both have what properties?
elastic
At full respiratory capacity (FRC) the outward recoil of the chest wall is equal in magnitude but opposite in direction to what?
the inward recoil of the lungs
Where is the pleural cavity?
in between the lungs and the chest wall
What do the cohesive forces of the pleural fluid do?
- attach the two compartments to each allowing the lungs to inflate and deflate with the movements of the chest wall
- Reduce friction as the lung tissue glides past the chest wall
What is the pleural pressure(Ppl)? Where is it?
-5cmH2O, in the pleural cavity
What is the alveolar pressure (Pa)? Where is it?
0cmH2O, in the lungs
What is transmural pressure?
pressure inside - pressure outside
What keeps the lungs open against their tendency to recoil inward?
the 5cmH2O Ptp pressure
- pressure gradient across the lung wall = alveolar pressure - pleural pressure
- Ptp = 5cmH2O
What keeps the chest wall from recoiling outwards?
the Ptw pressure of the same magnitude (as Ptp = 5cmH2O) acting in the opposite direction as the Ptp
- the pressure gradient across the thoracic wall = pleural pressure - atmospheric pressure
- Ptw = -5cmH2O
What is the transmural pressure of the respiratory system (Prs) at rest? What is the equation for it?
Prs = Pa - Pb = 0
What can pneumothorax result from? What is the result?
from a puncture of the lungs or chest wall
- result = collapsed lung
What two factors determines whether a pneumothorax is life threatening?
- the size - can be large or small resulting in complete or partial collapse of the lungs
- Trauma to the chest wall/lung could result in hemothorax or blood in the pleural cavity = bad
What is Boyle’s Law?
the relationship between pressure and volume.
- pressure is the force per unit area caused by gas molecules striking the walls of a container
- at constant temp, pressure is related inversely to the volume of the container
Using pressures, describe what happens during a quiet breath (inspiration).
- inspiratory muscles contract
- chest wall expands and the Ppl (pleural) and Pa (alveolar) pressures decrease. there is also a decrease in transmural pressure (Pa-Ppl) distending the lungs
- Air flows into the lungs until Pa = Pb
What is the key concept of respiratory pressures during a quiet breath (inspiration)?
change in thoracic volume leads to change in intra-thoracic pressures
What is the driving pressure for airflow in the lungs?
alveolar pressure
Why does alveolar pressure decrease and then swing back up during a quiet breath while pleural pressure decreases continuously?
to inspire we create a pressure less than atmosphere - we are negative pressure breathers
The polio epidemic required many to be treated with what?
the iron lung: a negative pressure breathing apparatus
Using pressures, describe what happens during a quiet breath (expiration)
- inspiratory muscles stop contracting
- lungs recoil inward (reducing thoracic volume, compressing and increasing the intrapleural pressure (Ppl) and rises the intra-alveolar pressure (Pa) above atmospheric pressure - lung transmural pressure decreases
- air flows out of the lung until Pa = Pb
What is the key concept of respiratory pressures during a quiet breath (expiration)?
quiet expiration is passive. Recoil of the lungs increases alveolar pressure above atmospheric pressure driving flow of air out of the lungs.
What are the major muscles of inspiration?
the sternum, ribs. external intercostal muscles and the diapragm
What are the muscles of active respiration?
the internal intercostal muscles and the abdominal muscles
What are the accessory muscles of inspiration?
the sternocleidomastoid and scalenus
What does the elevation of the ribs cause?
the sternum to move upward and outward, which increases the front-to-back dimension of the thoracic cavity (accessory muscles lift)
What does contraction of external intercostal muscles cause?
bucket-handle-like elevation of the ribs, which increases side-to-side dimension of thoracic cavity
What does the lowering of disphragm on contraction do?
increases vertical dimension of thoracic cavity
What does the contraction of internal intercostal muscles do?
flattens the ribs, and sternum, further reducing side-to-side and front-to-back dimensions of thoracic cavity
What does the return of diaphragm, ribs and sternum to resting position on relaxation of inspiratory muscles do?
restores thoracic cavity to preinspiratory size
What does the contraction of the abdominal muscles cause?
the diaphragm to be pushed upward, further reducing vertical dimension of thoracic cavity
What are the muscles and nerve involved in inspiration?
- Diaphragm - cervical spinal roots exiting C3-C5 as bilateral phrenic nerves
- External intercostals - intercostal nerves (T1-T12)
- Accessory muscles of the neck (C3-C8)
What are the muscles and nerves involved in active expiration?
- Internal intercostals - intercostal nerves (T1-T12)
2. Abdominal muscles - thoracic and lumbar nerves (T7-T12 and L1)
Which respiratory muscles are used during sniffing?
forced inspiration muscles - diaphragm, external intercostals and accessory muscles
Which respiratory muscles are used during coughing?
Active expiration - Internal intercostals, abdominal muscles
Which respiratory muscles are used during parturition?
abdominal muscles
Which respiratory muscles are used during walking down beach trying to look slim?
abdominals
Which respiratory muscles are used during nasal flaring?
forced inspiration muscles - diaphragm, external intercostals and accessory muscles
What does the change in respiratory pressure of the lungs reflect?
the force required to overcome two key factors affecting airflow
What are the two key factors affecting airflow?
- airway resistance
2. lung compliance
What is the total resistance to flow of air in the airways? (Raw)
about 250 fold less than that encountered generating the same airflow through a smokers pipe.
- VERY LOW
What are the resistive forces of the airway?
- inertia of the respiratory system
- friction
- lung and chest wall tissue surfaces gliding past each other
- lung tissue past itself during expansion
- frictional resistance to flow of air through airways
What represents 80% of total airway resistance
frictional resistance
What is the relationship between flow (V), driving pressure (Change in P) and resistance (Raw)?
Raw = (Pa - Pb) / V = -1.0cmH2O/-0.5L/sec = 2cmH2O/L/sec at peak flow during quiet inspiration
Change in P = P1 - P2 = pressure gradient = driving pressure
- V = flow
What is the direction of flow?
from high to low pressure
what is the design of the airway branching that allows it reduce the frictional resistance to airflow in the airways?
parallel design - much greater total cross-sectional area in periphery which creates little resistance to air flow
Where does the major contributor to airway resistance lie?
in the larger airways (generations 1-6)
What happens to airflow in airways that are diseased from smoking?
the smaller airways are the major sites of resistance to flow of air because of a reduction in their luminal size
Resistance is proportional to what?
1/ (Radius)^4
Flow is equal to what?
Change in pressure/resistance
How much will airflow be affected if the radius of an airway is halved in caliber?
decreases by a factor of 16
If the airway radius can not be changed, what can you change to increase air flow to the levels prior to the reduction in airway radius?
change pressure differential by breathing harder (using muscles)
What does asthma effect/do?
- tightening of bronchi - bronchoconstriction
- Inflammation
- Excess mucus production
What does COPD effect/do
- tightening of bronchi - bronchoconstriction
2. Inflammation
What does chronic bronchitis effect/do?
- Inflammation
2. Excess mucus production
What does bronchiolitis effect/do?
Inflammation
What does cyctic fibrosis effect/do?
Excess mucus production
What does emphysema effect/do?
reduced alveolar elastic recoil
- reduced recoil means less tethering on neighboring airway which in turn will be reduced in caliber
In all the cases of Emphysema, asthma, broncholitis, etc, what happens?
increase in airway resistance and a decrease in maximal expiatory flow.
- have a hard time breathing out.
What does the elastic recoil of alveoli do?
drives flow and keeps the bronchioles open
- creates the driving pressure that results in air flow
- creates radial traction on neighboring airways, tethering them open (Passive regulation of airway caliber)
What does airway patency depend on?
airway transmural pressure
What happens to airways during forced expiration?
reduce in size (develop airway limiting segment) distal to development of an equal pressure point.
What are the receptors on the airway smooth muscle?
- cholinergic receptors
2. adrenergic receptors
What are cholinergic receptors stimulated by? How do they work?
stimulated by acetylcholine from postganglionic parasympathetic innervation of the airway smooth muscle (Vagus nerve) –> muscarinic M3 receptors –> bronchoconstriction
What are adrenergic receptors stimulated by? How do they work?
mainly stimulated by adrenaline which is released by the adrenal medulla and circulating in the blood –> B2 receptors –> bronchdialation
When are cholinergic receptors dominant? Adrenergic?
cholinergic - at rest
adrenergic - not at rest
What is lung compliance?
measure of distensibility or how easily the lung can be stretched
compliance = 1/elastance
- thicker + harder to stretch = less compliant
What is elastance?
the inverse of compliance and refers to the tendency of an object to oppose stretch or distortion, as well as its ability to return to its original form after the distorting force is removed
What are the physical properties that determine lung compliance?
- lung tissue elasticity (lung tissue surrounding the airways)
What are the key connective tissue fibers and why?
- collagen - strong, high tensile strength, inextensible
2. Elastin - weak, low tensile strength, extensible
Changes in lung compliance can be a result of what?
loss of connective tissue (cause of aging)
What is emphysema?
disappearing lung disease - alveolar wall destruction and increased lung compliance (floppy lungs –> fill fine but don’t empty well)
What is pulmonary fibrosis?
collagen deposition in alveolar walls (response to lung injury) and decreased lung compliance (stiff lungs –> empty quick but don’t fill easily)
What is static compliance of the lungs determined by?
the PV curve of the lungs and depends on lung volume
Cl= slope = change in V / change in P (on a graph of lung volume vs. transpulmonary pressure)
- determined by the PV slope at full respiratory capaticy
What are the physical properties determining lung compliance?
- alveolar surface tension
What is surface tension?
water molecules at the surface of a liquid-gas interface are attached strongly to the water molecules within a liquid mass. surface tension is this force.
- creates an inward recoil that leads to alveolar collapse
How does alveolar surface tension created in the lungs/alveoli?
- air entering the lungs is humidified and saturated with water vapor at body temperature
- water molecules cover the alveolar surface
- surface water molecules create substantial surface tension
What does pulmonary surfactant secreted from type 2 alveolar cells do?
reduces alveolar surface tension, prevents collapse and stabilizes the alveoli
What is smokers lung or a case of high airway resistance and high alveolar compliance?
inflamed, narrowed airways, destroyed alveolar walls.
What is Neonatal Respiratory Distress Syndrome? (NRDS)
Premature babies born with inadequate production of pulmonary surfactant and have stiff lungs that are hard to inflate at birth.
- life threatening
- ventilator dependent
What does a spirometer do?
measures static lung volumes. Allows you to plot lung volume against time
What are the factors that determine static lung volumes? How?
- Height - taller individuals have larger lungs
- Gender - males have larger lung volumes than females
- Age - in children, lung volume increases with growth. In adults volume is stable, as they get older Their Residual volume (RV) and Functional residual capacity (FRC) increases and their Expiratory reserve volume (ERV) decreases
- Ethnicity - consider asian, black, inuit
What are the two main categories of ventilatory defects?
- restrictive diseases
2. obstructive diseases
What is the first step in diagnosing respiratory diseases?
the forced vital capacity maneuver.
What do restrictive diseases do?
make it more difficult to get air into the lungs - they restrict vintilation
What are some examples of Restrictive diseases?
- pulmonary fibrosis
- stiff chest wall
What do obstructive diseases do?
make it more difficult to get air out of the lungs - they obstruct and limit air flow during expiration.
What are some examples of Obstructive diseases?
- chronic pulmonary disease COPD
- asthma
- chronic bronchitis
- emphysema
What does Alveolar inward recoil do and how?
creates radial traction on neighboring airways in order to keep them open (airways)
what does the elastic recoil of alveoli contribute to?
driving pressure for expiration and patency of neighboring airways.
What does non-cartilaginous airway patency depend on?
airways transmural pressure
What is minute ventilation (Ve) equal to?
Tidal volume x breathing frequency = 6.0L/min
- volume per minute = total amount of air in and out per minute
What is minute ventilation (Ve) a combination of?
Dead space (150mL) and Alveolar (350mL)
What is alveolar ventilation(Va)?
Va x breathing frequency = 350mL x 12 = 4.2L/min
- this air participates in gas exchange
What is dead space ventilation (Vds)?
Vds x brathing frequency = 150mL x 12 = 1.8L/min
- this air does not participate in gas exchange
What does pattern of breathing effect?
alveolar ventilation and gas exchange
What is the vital capacity maneuver?
take deep breath all the way in and then exhale, forcing all air out.
Is panting effective in improving gas exchange? Why?
NO! since you are not taking in very much air each breath all of the air is going into the dead space. Therefore very low alveolar ventilation per minute
What does deep and slow breathing lead to?
greater alveolar ventilation and thus, gas exchange.
What is anatomical dead space?
from the nose to the terminal bronchi
What is the dead space of an individual that is on a mechanical ventilator?
nose to terminal bronchi + the ventilator tube.
What is alveolar ventilation?
the proportion of breathing that reaches the alveoli and participates in gas exchange
What are the two key players in gas exchange?
alveolar ventilation and alveolar perfusion
What does the matching of ventilation and perfusion affect?
the partial pressure of respiratory gases in the alveolus and pulmonary capillary.
After equilibriating with alveolar gas, what happen to the concentration of O2 and CO2 in the blood?
blood increases in O2 and decreases in CO2
What happens if blood flow to the alveoli is obstructed?
can lead to alveolar dead space (blood doesn’t see the air so won’t have gas exchange)
What is alveolar dead space?
the portion of breathing that reaches the alveoli and does not participate in gas exchange because of inadequate perfusion to the alveolus
- important in disease states
What happens if the blood flow to the alveoli is only partially obstructed?
values of CO2 and O2 would be somewhere between that of the blood and that of the air in the alveoli.
= high ventilation relative to perfusion
In the equation: ideal unit = V/Q = 1. what does V and Q stand for?
V= alveolar ventilation Q = Rate of blood flow (alveolar perfusion)
What is perfusion?
blood flow
How does the body try to keep values for perfusion and ventilation as close to 1 as possible in and area in which airflow is greater than blood flow?
Homeostasis mechanisms.
- Increase O2 in area –>relaxation of local pulmonary-arteriolar smooth muscle–>dialation of blood vessels–> decreased vascular resistance–> increased blood flow –> helps balance small blood flow
- decrease in CO2 in area–> increase contraction of local airway smooth muscle–> constriction of local airways–> increase airway resistance–> decrease airflow –> helps balance large air flow
How does the body try to keep values for perfusion and ventilation as close to 1 as possible in and area in which airflow is less than blood flow?
- decrease O2 in area–> increase contraction of local pulmonary arteriolar smooth muscle–> constriction of local blood vessels–> increase vascular resistance–> decrease blood flow –> helps balance Large blood flow
- Increase CO2 in area–> relaxation f local airway smooth muscle –> dilation of local airways–> decreased airway resistance–> increased airflow–> helps balance small airflow
What happens if the airway if plugged? What does V/Q=?
alveoli will come to equilibrium with blood supply eventually but no oxygen can get to blood.
V/Q=0
How many static lung volumes are there and the combination of these gives rise to what?
4 static lung volumes and the combination gives rise to four lung capacities
What determines alveolar ventilation and the amount of air available for gas exchange?
breathing pattern
