by gnomey

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What are the 3 types of alveolar cells? functions?
Type 1- squamous cells that cover alveolar surface and provide surface for gas exchange
Type 2- replicate and modify to form type 1, produce surfactant, electrolyte balance
Type III- alveolar macrophages
How many pulmonary arteries are there?
4 pulmonary veins return to LA
What provides O2 to the conductive airways and pulmonary vessels?
bronchial arterial system
What is the "normal shunt"
2-5% of CO

This is an absolute shunt, anatomic connections between bronchial and pulmonary venous circulations
When outward and inward forces of the lung are equal, what does this represent?
What is the difference in intrapleural pressure from top to bottom of the lung?
What happens to surface tension within the alveoli during inspiration/expiration?
Inspiration- surface tension increases

Expiration- surface tension decreases
What is the purpose of surfactant?
Surfactant reduces surface tension. This is important because it increases the compliance of the alveoli, so that during inspiration less effort is needed. It also decreases fluid accumulation in alveoli and draws fluid across the alveolar membrane
What is the transpulmonary pressure?
Difference between intrapleural and alveolar pressure and is directly proportional to lung volume
The compliance curves shifts in which direction with restrictive lung disease?
Shifts to the right with decreased slope, representing decreased FRC
What is the benefit of using CPAP with decreased lung compliance?
shift vertical line to the right on the compliance sigmoidal curve, resulting in larger tidal volumes and lower resp rate
What is the effect of diseases that cause an increased lung compliance on the compliance sigmoidal curve?
pressure-volume curve shifts left and steepens, showing a larger than normal FRC
What are examples of lung diseases with increased lung compliance?
COPD and acute asthma
which type of flow in the airway is audible?
turbulent air flow
what is the benefit of laminar flow in airways? (cone)
alveolar ventilation can occur even when tidal volume is less than anatomic dead space because some gas reaches the alveoli before the bulk of gas
What type of air flow is utilized in high-frequency ventilation?
laminar flow, small tidal volumes allow for adequate alveolar ventilation
What physical property of gas determines laminar flow? example?
Viscosity of the gas

What type of gas flow is associated with high/low flow rates?
Low flow rates are associated with laminar flow

Turbulent flow is associated with high flow rates, especially in branched or irregularly shaped tubes
If there is resistenance to airflow, what type of gas flow occurs?
Turbulent flow
What are 4 conditions taht change laminar flow to turbulent flow?
1. high gas flow
2. sharp angles within a tube
3. branching in a tube
4. decrease in tube diameter
What 6 basic pathological changes increase airway resistenance?
1. smooth muscle hyperractivity (bronchospasm)
2. mucosal edema
3. mucous plugging
4. epithelial desquamation
5. tumors
6. foreign bodies
When is helium therapy most beneficial?
Helium therapy is most beneficial when there is turbulent flow because the viscosity of the gas is the same as air so it does not improve conditions where there is still laminal flow. Helium is less dense than air so it improves conditions where there is turbulent flow, thus creating more laminar flow
You do a PFT on a patient with emphysema what value lets you know that there PaCO2 is normal? y?
if FEV1 is <1L, PaCO2 is normal. This is because they have increaed respiratory muscle effort that overcomes the increased airway resistenance and maintains FRC
Your patient is an asthmatic (obstructive airway disease). IF you draw an ABG what finding is of great concern? y?
If their PaCO2 is elevated, because they normally are able to maintain alveolar ventilation through hyperventialation and increased insp/exp muscle use. A higher PaCO2 is a sign of exhausted compensatory mechanisms
What is the compensatory mechanism for mild expiratory resistenance?
Increased insp force to increase lung volumes to achieve a higher elastic recoil to overcome expiratory resistance
What are 4 normal changes to the aging lung?
1. dilation of the alveoli
2. enlargement of the airspaces
3. decrease in exchange surface area
4. loss of supporting tissue
What is the cause of increased residual volume and FRC in the aging person?
There is a decrease in the lung recoil causing natural air trapping
What happens to sensitivity of PaO2 and PaCO2 with aging?
Decreased sensitivity to both, causing a decreased ventilatory response
Where is the basic ventilatory control center?
medulla oblongota
What is the purpose of the dorsal respiratory group (DRG) of the medullary reticular formation?
Monitors electrical activity at end-inspiration and maintains ventilatory rhythmicity. So when there is no impulse to the DRG inspiration is triggered
What do the carotid and aortic bodies monitor?
Monitor and stimulated by decreased PaO2. Stimulation begins at PaO2<100mmHg, but do not causes significant augmentation until PaO2<60-65mmHg
If you have a COPD patient who is a chronic CO2 retainer, what must be done when withdrawling mechanical ventilation?
These patients now depend on a hypoxic ventilatory drive. Their normal PaO2 levels are within 60-65mmHg. So above this they will have a decrease in ventilatory response, so their PaO2 must fall below <65mmHg for them to spontaneously breath.
What 4 things activate the carotid bodies?
1. PaO2<100mmHg, significant at <65mmHg
2. Hyperthermia
3. Hypoperfusion of carotid body
4. some chemicals (Ach and Nicotine)
5. Cynadie posioning when blocking oxygen transport system will cause stimulation of carotid bodies
What is the ventilatory response that occurs with stimulation of peripheral chemoreceptors?
Increased RR and VT
What effect do the volatile inhalation anesthetics have on the carotid bodies?
They depress the hypoxic ventilatory response to hypoxemia.

i.e with a high MAC and low PaO2 there wont be an increase in RR and VT
Where are central chemoreceptors located?
near the origin CN IX and X in the area of the inferolateral brainstem that is in close contact with the CSF

surface beneath the ventral medulla is very sensitive to extracellular fluid H+ concentration
What stimulates the central chemoreceptors? y?
They are stimulated by increased H+ concentrations

CO2 passes the BBB into the CSF, CO2 binds with H2O and dissaccosiates into H+ and HCO3 ions. The H+ ion gets trapped and this is what stimulates the central chemorecptors
What is the difference between arterial and central values of PaCO2?
Central values are 10mmHg higher than arterial, d/t H+ trapping
What is the ventilatory response to PaCO2 levels?
acute rise in PaCO2 stimulates increased Vt and RR within 1-2 minutes after the change in levels
What can depress the central chemoreceptors to PaCO2?
cold CSF and LA applied to medullary surface
What is the purpose of the ventral respiratory group of the medullary reticular formation?
Prohibits further inspiratory effort by negative feedback, and allows for passive expiration

VRG blocks the DRG impulse
What does the apneustic center do? location?
Located in the middle or lower pons.

When acitvated it sustains inspiration (inspiratory spasm)
What is the function of the pneumotaxic center? location?
Located in the rostral pons

Limits the depth of inspiration and at maximal activation increaes respiratory rate (no pacemaker function though)

Abolition of the pneumotaxic center results in decrease rate and increase tidal volume
General stimulation of the RAS results in what change to ventilation?
Increase rate and amplitude
What effect does the hypothalamus have on ventilation?
It has descending pathwasys from anterior/posterior sides to the pneumotaxic center on upper pons, and responds to temperature changes to increase/decrease depth of respiration
What changes in insp/expir occur to produce a cough?
There must be a deep inspiration and forced exhalation against a closed glottis to increase intrathoraci pressure
What conditions cause stretching of the pulmonary airway stretch receptors?
Pulm edema and atelectasis, these receptors are more sensitive to pressure changes than to volume distention
What purpose do golgi tendon organs play in the respiratory system?
Intercostal muscles, not diaphragm, have a large amount of tendon spindles. When there is a stretch of the intercostal muscles due to inspiration they send an impulse to further inhibit inspiration (probably to the VRG)
Where are peripheral chemoreceptors located? basic function
Carotid bodies at bifurcation of the common carotid artery. ventilatory effects

Aortic bodies located at aortic arch and its branches, circulation effects
What cranial nerves are associated with the carotid and aortic bodies? innervation?
Carotid- afferent glossopharyngeal nerve to central respiratory centers

Aortic- afferent vagus nerve to medullary centers
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