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What fraction of a breath is in dead space
1/3
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In what branches is there no gas exchange, and in which is there gas exchange
- 1-16 no gas exchange
- 17-23 gas exchange
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What is FRC and what is its normal vol
- Functional residual capacity 3L
- This is the air left after a normal expiration includes the residual volume and the Expiratory reserve vol
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What is tidal volume and what is its normal vol
Normal quite breathing with a vol of about 500ml
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What is anatomical dead space and how does it differ from physiological dead space
- It is the amount of air that is located in spaces where no oxygen exchange is happening
- Physiological includes areas that normally have gas exchange but are damaged
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What Ig's are found in abundance on the surface of respiratory epithelium
A and G
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What is the Residual Vol (RV), how large is it
This is the amount of air that cannot be expired, 1.5 L
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What is the ERV, and how large is it (vol)
- Expiratory reserve volume 1.5 L
- The max amount of air that can be expired beyond tidal volume
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What is IRV and how large is it (vol)
- Inspiratory reserve volume 2.5 L
- The amount of air that can be inspired beyond tidal vol
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What is the VC
Vital capacity, the largest amount of air that can be inspired and expired including tidal volume
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What happens to the lung volumes as one ages
The vital capacity decreases after age aprox. 58 (increases till then) while the total lung capacity continually increases, and residual vol increases
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What are two very important variables to lung volume
Temp and Pressure
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What happens to the TLC and RV values in Obstructive lung disease and Restrictive lung disease respectively
- Obstructive (Emphysema, COPD) an increase in TLC and a large increase in RV
- Restrictive lung disease (Pulmonary fibrosis) a decrease in both
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What lung capacities require the helium addition
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Transmural pressure
Pressure across a wall
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Recoiling force is opposite of
Compliance
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A flat curve and a steep curve indicate what on a Vol/transmural pressure difference curve
- Flat = decrease compliance
- Steep = Increase compliance
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Max inspiration is resisted by
Lung
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Expiration is limited by
Chest wall
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What makes up 50% of the compliance in the lungs, and what make up the other 50%
- Elastic fibers and their arrangement
- Surface Tension
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What affects does a small radius have on the aveoli
There is larger inside pressure, and tendency to colapse
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What are the effects of surfactant
- Reduces surface tension
- Increase compliance of the lung
- Minimizes tendency to collapse aveoli
- Helps alveoli expand in equal amounts
- Reduces recoiling force
- Keeps inside of lungs dry
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What percent of surfactant is recycled, and where does the rest go
- 50% is recycled by type II Pneumocytes (some is destroyed by them as well)
- Removed by macrophages
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What is the resting volume of the lung
Minimal lung volume of 500ml, FRC 3L
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When does the respiratory system have its greatest compliance
At Functional Residual Capacity FRC
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Expiration above, and below FRC is
- Passive
- Active (energy required)
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Where is the least resistance located in the airways, and the greatest resistance
- Least, in the respiratory zone from 17-23 due to the total diameter increasing
- Greatest, first 7 branches (80%)
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Why is the measurement of resistance in a lung not a good indicator of small airway obstructions
Because the major site of resistance is in the upper airways
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What happens to lung compliance as the volume increases
It decreases
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If the lung volume increases, what happens to the recoiling force
It increases
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What factors affect the airway resistance
- Density and viscosity of air
- Concentration of CO2
- Sympathetic/Parasympathetic innervation
- Local metabolites
- Lung Volume
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What metabolites constrict the airway
- Histamine
- Acetylcholine
- Thromboxane A2
- Prostaglandin F2
- Leukotrienes
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How do patients with emphysema lungs expand in relation to a healthy individual
They don't breath from the FRC but from a higher lung volume do to the decrease in resistance
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What is an easy test a physician can perform to assess restrictive or obstructive lung disease
Forced expiration test
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What parameters are measured in a forced expiration test
- Forced expiratory volume after 1 second
- Forced vital capacity
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In a forced expiration test what is the normal vol expired in the first second
80% of the total volume
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Obstructive lung disease will show what result in a Forced expiration test
Decreased expiration volume in the first second, and a decrease percentage in the first second compared to the overall expiration
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What results would be seen in a forced expiration test with someone with restrictive lung disease
A decrease in the FEV1 and a decrease in FVC, but a normal or high FEV1/FVC
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Expiratory muscles have an optimal length when
When the vol of the lungs is increased
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In restrictive lung diseases the lung volumes are affected how
All lung volumes are proportionally smaller, but the compliance is reduced, and therefore the recoiling force increased
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What happens to extralveolar capillaries upon inspiration
They dilate as pulmonary capillaries constrict
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What is the only active control of pulmonary resistance
Hypoxia
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How are the effects of hypoxia in the alveolar different from those in the vessels
Hypoxia in the alveolar causes constriction of the vessels surrounding them, low CO2 in the vessels themselves causes dilation
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What is the mechanism that causes constriction of alveolar during hypoxia
Hypoxia inhibits K+ channels, the cell depolarizes, Ca++ channels open, and the muscle contracts
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When is generalized hypoxia good
During fetal development, but bad following birth
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High altitude pulmonary edema (HAPE)
- Caused by greater hypoxic vasoconstriction response
- that causes pulmonary hypertension
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What happens to capillaries in the lungs that are above the heart
The alveolar pressure exceeds that of the pulmonary artery pressure disallowing blood air exchange
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What are some anatomical shunts that are found in a normal adult
- Thebesian veins taking deoxygenated blood from coronary arteries to left atrium and ventricle
- Bronchial veins contributing to pulmonary veins
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How much oxygen is dissolved in the blood
About 15 ml/min during normal cardiac output of 5L/min
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What is the saturation of Hb with O2 at 40 and 100 mmHg in the blood respectively
75% and 98%
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A decrease in the amount of red blood cells like in an anemic patient would have what affects on Hb saturation and Oxygen blood concentration
- Saturation would not be affected
- Concentration of blood would be decreased (PaO2 isn't effected though)
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What happens to the intrapleural pressure during inspiration and why
It is more negative do to the effects of the recoiling force
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What is the definition of hypo and hyperventilation
Hypo is an increase in PaCO2 Hyper is a decrease
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CO, NO, and O2 are limited how
- CO diffusion limited
- NO is perfusion limited
- O2 is perfusion limited normally
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How does pulmonary vascular resistance compare to TPR
It is 16x smaller
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Decrease alveolar O2 has what effect on the blood vessels
Constriction of pulmonary blood vessels
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High altitude has what affect on the arterial CO2 pressure
Decrease
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Where is the V/Q ratio highest
Apex of the lung
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Diffusion limitation only happens when
- High Altitudes
- Lung Disease
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What are the three ways CO2 can be carried in the blood
- Diffused in blood
- Bicarbonate
- Carbamate (much lower concentration)
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Bronchopulmonary sequestration
Lung lobes or segments without connection to airways, but has its own blood supply from the aorta
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What are the three classes of atelectasis
- Resorption - Complete obstruction of airways
- Compressive - Fluid or air in plueral cavity
- Patchy - Often found in RDS
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What are the two subcategories of pulmonary edema
- Hemodynamic causes - pressure increase
- Microvascular - capillary damage
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Adult respiratory distress syndrome (ARDS) aka. Diffuse Alveolar Damage (DAD)
- Alveolar capillary damage due to inflammation
- May cause cyanosis, organ failure, pulmonary adema, 50% mortality
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Why are small embolims of the lung rare
Lungs have a double blood supply
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What is the difference between exudate and transudate
- Exudate is fluid from the circulatory system usually RBC, platelets, plasma proteins
- Transudate is extravascular fluid w/ low protein content
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Terminal respiratory unit
Final stage of bronchiole tree containing bronchiole, alveolar ducts and sacs
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What are the two primary types of Emphysema
- Panacinar - enlargement of acinus uniformly
- Centriacinar - elargement of the central parts of the acinus, not the ends
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Acinus
Respiratory segment of bronchioles
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Alpha 1 antitrypsin and emphysema relate how
It's inactivation is beleived to cause it
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Honeycomb lungs is caused by
Pulmonary fibrosis (Restrictive disease)
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Pneumoconiosis
Fibrosis (restrictive) of lungs via inhilation of certain inorganic dusts
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What are the different types of hypoxia
- Stagnant
- Anemic
- Histotoxic
- Arterial
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Stagnat hypoxia
Blood flow reduced
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Anemic Hypoxia
O2 capacity of blood is low such as Hb availability low, or CO poisoning
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Histotoxic hypoxia
Tissues aren't using O2, cyanide or hydrogen sulfide poison can cause it
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Arterial hypoxia
Reduction in blood O2 saturation, only hypoxia where PO2 is diminished (altitude is a common cause)
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Anoxia
Complete absence of O2 in tissue
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Why are anemic patients unlikely to get cyanosis
Because they have such a small amount of RBC's, to reach the deoxyhemoglobin 5g/100ml blood required for cyanosis signs to be expressed, they would be dead
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What is a common cause of peripheral cyanosis
A low perfusion, meaning the blood has more time to diffuse O2 into the tissues
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What is a normal arteriole/alveoli O2 concentration difference
3-10 mm Hg
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Why doesn't a PCO2 difference have much of an effect
It takes a very large concentration difference to effect the CO2 partial pressure
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How can you tell the difference between a mismatch or a Diffusion problem
A diffusion problem will show a decrease in CO when tested, a mismatch will not
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When trying to decide the reason for a patient having arterial hypoxia (low PaO2), what would be the best set of steps
- If increased PaCO2 it is hypoventilation, decreased Low PIO2 (altitude)
- If PaCO2 is normal try 100% O2, if it doesn't fix the problem it is a shunt if it does try the last step
- Do a CO diffusion test, if they show a low capacity it is diffusion problems, if not, it is a mismatch
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What are the two causes of hypercapnia
- Hypoventilation
- Ventilation perfusion inequality
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What is the only hypoxemia that will not be effected by 100% oxygen treatment
Shunts
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The oxygen concentration is highest where in the lung and why
At the top of the lung, because the ventilation to perfusion ratio is high. Meaning, there is less blood flow and therefore less oxygen exchange leaving leftovers
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How can the alveolar prefusion be measured
By measuring the alveolar-arterial PO2 differences
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Sensory information for breathing is coordinated where
- Medulla (Ventral respiratory group, Dorsal respiratory group)
- Pons (Pneumotaxic center)
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What is the job of the Pneumotaxic center in the brain
It controls inhibitory effects and regulates inspiration volume and respiratory rate
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What is the job of the Dorsal respiratory group
Inspiration and generates the basic rhythm for breathing
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The dorsal group receives input from where and output is sent where
- Vagus N. (peripheral chemoreceptors and mechanoreceptors from lungs)
- Glossopharyngeal N. (peripheral chemoreceptors)
- Output to phrenic nerve to diaphragm
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The ventral group is primarily responsible for
Expiration, not active in quiet breathing, active in exercise
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Slow adapting stretch receptors are located where, and have what function
- Airway smooth muscles (inn. by vagal n.)
- Terminates inspiration and expiration
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Rapidly adapting stretch receptors are located where and have what function
- Airway epithelium (inn. by vagal n.)
- Cough reflex and gasping
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Where are C-fiber and J-receptors found, and what is their function
- Near capillaries (non myelinated vagal)
- These are activated by disease conditions and cause shallow breathing, bronchoconstriction, and cardiovascular depression
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Central chemosensitive regions are found where and have what function
- On the ventral lateral surface of the medulla
- They are stimulated by H+ and inhibited by cold or anesthetics
- They will increase respiration when Ph is low
- Not triggered by Hypoxia
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Where are peripheral chemoreceptors found and what is there job
- They are found in the junction of the carotid arteries and on the aortic arch.
- Triggered by Hypoxia, PCO2 and Ph levels stimulating breathing and raising blood pressure
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An increase in CO2 will effect what receptor most and how
The central receptors will be the only ones effected, and it responds 80% to the lower Ph as a result of the high CO2
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What is the difference of effect of ventilation with someone with acute hypercapnia and chronic
- Acute will immediately trigger a response of increased ventilation trying to compensate for the low O2 and high CO2.
- Chronic elevation in CO2 will only exhibited a slightly higher ventilation due to the renal compensation of low Ph. PCR is operating independently after renal compensation
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Hypoxia will cause what chain of events
- Increase ventilation
- Decrease PCO2
- Large Ph decrease if chronic
- Compensatory Ph by kidneys
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How does ventilation change with acute vs chronic hypoxia (high elevation)
Acute is a short change of ventilation due to is being brought back after normal oxygen levels return from hyper ventilation
Chronic will cause alkylosis due to hyperventilation inhibiting the CO2 and Ph receptors in both the PCR and CCR. Ph will be compensated for by the kidneys and then normal breathing will return at the higher ventilation
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