Chapter 4: Respiratory Physio Flashcards
Tidal Volume
Volume of air inspired or expired in a single breath.
Inspiratory Reserve Volume
The max amount of air you can Inspire ABOVE the tidal volume
Expiratory Reserve VOlume
The amount of air that can be expired below Tidal Volume
Residual Volume
Volume left in lung after Expirtory Reserve Volume
NOTE: Cannot be measured by Spirometry
Anatomic Dead Space
Volume of the conducting airways (150 mL)
physiologic dead space
Volume of the Lungs that does not participate in gas exchange
In normal lungs it is equal to the Anatomic Dead Space
physiologic dead space (Equation)
Vd = Vt x ((PAco2 - PEco2)/ (PAco2))
Minute Ventilation
Tidal Volume x (Breaths/Min)
Alveolar Ventilation
(Tidal Volume - Dead Space ) x Breaths/Min
Essentially, the air that actually reaches the alveolus)
Inspiratory Capacity
Tidal Volume + Inspiratory Reserve Volume
Functional Residual Capacity
Expiratory Reserve Volume + Residual Volume
NOTE: Cannot Be Measured by Spirometry (Residual Volume is not measurable unless the patient is dead)
Vital Capacity
Inspiratory Capacity (IRV + TV) + Expiratory Reserve Volume
Volume of air that can be forcible expired after a maximal inspiration.
Total Lung Capacity
The entire volume of the lung
NOTE: Cannot Be measured by Spirometry since it contains the Residual volume
FEV1
Forced Expiratory Velocity
The amount of air that can be expelled form the lungs in the first second of a forced expiration
FEV1/FVC = .8 !
FVC = Forced Vital Capacity (Inspiratory Capacity + ERV)
FEV1 In Obstructive Diseases
Asthma and Emphysema . Can get air in but you cannot get it out, thus FEV1 is diminished
FEV1/FVC = Less than .8
FEV1 in REstrictive Lung Disease
Fibrosis
Cannot get Air In but can get it out
FEV1 is increased
FEV1/FVC = Greater than .8 (usually around .9)
Artificially higher than normal
Inspiration
Contration of the diaphragm, pushes the abdominal contents down and ribs are lifted up and out
Negative pressure is increased, air comes into lungs.
External Intercostal and Accessory Breathing muscles
used during exercise (not during normal relaxed breathing)
Muscles of expiration
Psych… in normal breathing this is a passive process
Only used during times of need : Internal Intercostals and Abdominals
Compliance
C = dV/dP
The ability to distend. In the face of changing volume, highly compliant vessels distend without large increases in pressure. (Pressure is Transmural Pressure)
The more elastic your lung, the more compliant it is
Slope of the Pressure-Volume Curve
Transmural Pressure
Alvolar - Intrapleural Pressure
When pressure outside the lungs (intrapleural) is negative, the lungs expand (we typically have a negative intrapleural pressure so, according to the equation this will lead to an expansion in the lung)
Transmural Should always be positive unless you have a rupture in the pleural space leading to an increased intrapleural pressure which will cause atalectasis.
What occurs to the compliance of the lungs in a patient with Emphysema ?
The compliance is increased (incredibly), thus the tendency to collapse is decreased since the lung can expand farther.
A new, higher FRC will occur (FRC is the state at which the expanding force of the chest wall and the collapsing force of the lung are equal so there is net equilibrium)
A higher FRC shows that a higher airway pressure is needed for the collapsing pressure of the lung to equal the expanding pressure of the Chest wall. (FRC is higher because you can’t get the air you take in out. bigger RV)
As stated in a previous card, The FEV1 is decreased in emphysema and asthma (due to the decreased tendency of the lung to collapse with the higher compliance seen in these diseases)
I know this was a long card, mainly did it for myself to see if i remembered this crap
What occurs to compliance in a patient with Fibrosis ( Restrictive lung disease)
The lungs tendency to collapse is increased due to decreased compliance
With this you will see a new, lower FRC to balance out the forces of expansion from the chest wall and collapse form the lung.
FRC is smaller since you can expel a larger proportion of the air you take in (intake is also restricted in restrictive disease, so it looks like the RV is small)
What is the cause of Surface tension in the alveoli ?
Interactions between liquid molecules lining the alveoli
LaPlaces Law
Collapsing pressure is directly related to the Surface Tension and Inversely proportional to the Radius
P = 2T/R
P= Collapsing Pressure T= Surface tension
Which have higher tendency to collapse: Large or Small alveoli
SMALL ( LaPlace Law… Collapsing pressure is inversely proportional to Radius… Small Radius = Larger Collapsing Pressure)
How does surfactant work ?
It interrupts the interactions between fluids on the innermost lining of the alveoli.
What cells Secrete Sufractant ?
Type II Pneumocytes.
What is the primary Phospholipid in surfactant which mediates its effects ?
Dipalmitoyl Phosphatidylcholine (DPPC)
When is surfactant seen in fetuses ?
24 weeks ( first viable DOB. Need to give mom’s who may have preterm birth steroids to help fetal lungs develop)
Airflow
Q = dP/R
Like Ohms law for all things Q= flow (current)
dP = Pressure (voltage)
R= Resistance
Resistance
Just like in the vascular system, we use Poiseulles law:
R = 8 x Viscosity x L / (pi x R^4)
Once again, changes in radius have the greatest effect on resistance. Smaller the radius the larger the resistance.
Major site of Airway Resistance
Medium Sized Bronchioles
Quiz: Where in the vasculature is the resistance the greatest ?? Arterioles fool !
Effect of Parasympathetics on the bronchioles
Bronchoconstriction !
M3 receptor
What is the effect of Sympathetics on the bronchioles
Bronchodilation
Via Beta 2 Receptors. (More sensitive to Epi than NE.. Explains why Epi pens are used for people in anaphylaxis and extreme asthma attacks)
Higher Resistance in High Lung Volume or Low Lung Volume ?
LOW
Think of it this way, the Brochioles are constricted at low lung volume –> Small radius, large
What is the alveolar pressure = to at rest / ? Intrapleural
Atmospheric Pressure (0 mmHg allegedly) Negative ( -3 cmH20)
What occurs to alveolar pressure as you inspire ? Intrapleural ?
It MUST decrease (become lower, than atmospheric so that air can be brought into the lungs)
Intapleural MUST become more negative
(from -3 to -6 cmH20)
During expiration, what occurs to Alveolar Pressure ? Intrapleuaral ?
It increases to over atmospheric (it must do this to expel air from the lung (collapsing force)
It returns to a less negative state (-3 cmH20)
Asthma has an increased or decreased FEV1/FVC ?
Decreased (FEV1 is lower in asthma)
There is an increased FRC (air can get in but not out
Emphysema hasan increased or decreased FEV1/FVC ?
decreased (FEV1 is decreased)
PINK PUFFERS !!!
Mild hypoxemia with normal alveolar ventilation
Chronic Bronchitis has an increased or decreased FEV1/FVC ?
Decreased (FEV1 is decreased)
BLUE BLOATERS
Severe Hypoxemia, Hypercapnia due to low alveolar ventilation
Daltons Law of Partial Pressure
Partial Pressur of Gas = Total Pressure x Fractional Gas Concentration
In dry air, P02 = 760 x .21 = 160 mmHg
In humid air: 760 - 47 (partial pressure of H20) x .21 = 150 mmHg
Dissolved Gas
Patial Pressure of gas (in blood) x Solubility of Gas in blood
Ex. o2 = 100 mmHg , solubility = .03
100 x .03 = .3 (its due to units, i know this it should be 3)
Perfusion Limited Exchange
Limitation of perfusion early along the capillary.
Equillibrium is reached early and is equal to the Alveolar Partial pressure
Diffusion Limited Exchange
Gas does not equilibrate by the time the blood reaches the end of the plum capillary
What two ways is oxygen carried in blood ?
Bound to hemoglobin or dissolved
Only dissolved is capable of diffusing to the tissues.
How many subunits are in a typical hemoglobin molecule ?
4
Each contain a heme ring
Heme contains iron in the Ferrous state (Fe 3+)
What are the subunits seen in fetal hemoglobin ? What is the affinity for oxygen compared to adult ?
2 alpha units and 2 gamma units (adult has beta instead of gamma)
Higher affinity for oxygen than adult (lower partial pressures are needed to saturate, left shift on the curve)
Methemoglobin
Iron is in the Ferric (3+) state. Cannot bind 02
Hemoglobin S
Sickle Cell Hemoglobin (
02 Content in the blood
(02 binding capacity x %Saturation) + Dissolved O2
How much of hemoglobin is saturated at P02 of 100mmHg ? 40 mmHG ? 25 mmHg?
100% !
40%
25%
Hemoglobin can bind 4 Oxygens. Which has the higher affinity of binding, the first or the last 02 to bind ?
The LAST
As oxygen is added, the affinity for the next increases .
Decreased pH
2,3BPG
C02
Increased Temperature
Decrease the affinity for oxygen in hemoglobin
Leads to dissociation of O2 from heme
Shifts Curve to the Right
Fetal Hemoglobin has a higher affinity for oxygen. Will its curve be to the right or the left of the normal curve ?
To the left (lower partial pressures are needed for binding
Describe the paradox of Carbon Monoxide
Carbon Monoxide competes for binding sited on hemoglobin (with Oxygen)
Heme has 200x more affinity for CO
Binding of CO actually INCREASES the affinity of Heme for oxygen, in the sense that if oxygen was already bound it WILL NOT be released from hemoglobin and remaining sites will be filled. (This will shift curve to the LEFT, but once the sites are all bound 02 will not be released if CO is bound to one or more of the other sites)
Hypoxemia
Decrease in the arterial P02
A-a gradient
Alveolar P02 - arterial PO2
The gradient is increased in: Diffusion defect, V/Q defect, Right to Left Shunt
Hypoxia
Decreased 02 delivery to the tissues
Do not confuse with Hypoxemia, decreased arterial P02
What are the three forms of CO2
Dissolved
Bound to Hemoglobin
Bicarbonate (Major form)
What enzyme catalyzes the conversion of C02 + H20 —> HCO3- + H+
Carbonic Anhydrase
HCO3 is transported into the blood from the RBC in exchange for what ion ?
Cl- (both are anions)
At the same time H+ is buffered in the
What occurs when the RBC’s reach the Lungs in regards to CO2 handling ?
HCO3- enters the RBC in exchange for Cl- and is Converted back into H2C03 which composes to H20 and CO2.. C02 leaves the cell and is enters the alveolus via diffusion where it is expired
Alveolar Gas Equation (For PA02)
PA02 = (P(ins)02 - PAC02)/ R
PA02 = Alveolar PO2
PI02: P02 of inspired Air
PACO2 : Alveolar PC02 (same as arterial PCO2)
R: Respiratory exchange ratio. (Co2 prod/ O2 consumption)
How do pressure and resistance in the pulmonary circulation compare with that of systemic ?
Pulmonary pressure is lower (15 mmHg)
Pulmonary Resistance is also lower.
These two are proportionally low enough to propel CO through the lungs
Pulmonary blood flow =
CO of the right ventricle (duh)
Where in the lung is blood flow lowest ? Highest ?
APEX (zone 1)
BASE (zone 3)
In ZOne 1 (APex) how does alveolar pressure compare with arteriolar ?
ALveolar pressure is higher than arteriolar.
This may compress arterioles and lead to decreased perfusion of the lung (especially if there is hemorrhage or atelectasis)
blood flow is lowest in zone 1
In zone II , the blood flow is moderate between Zone 1 and 3. how does alveolar pressure compare with arteriolar ?
Arterial pressure is actually higher than alveolar.
Zone III (base) how does alveolar pressure compare with arteriolar
Arteriolar pressure is substantially higher than alveolar. ( in fact even venous pressure is higher than alveolar pressure at the base.
Explain why, despite having decreased blood flow and ventilation as compared to the base, the Apex has a higher Ventilation to perfusion ratio ?
Although the apex get less ventilation than the base, its perfusion is SUBSTANTIALLY lower than the perfusion of the base, in such that the V/Q is higher at the apex than at the base.
High PO2, Low PC02.. Apex or Base ?
APEX
The apex is ventilated but not perfused well, thusly, CO2 will not diffuse out into the alveoli and O2 will remain in the alveoli.
Unlike in most tissues, hypoxia in the lung leads to…
Vasoconstriction
This is a protective effect to ensure that areas without sufficient ventilation (hypoxic) will not be perfused ! This will cause blood to be pushed to areas of better ventilation.
In the fetus, the lungs are almost completely vasoconstricted and blood flow through them is minimal. Upon taking the first breath of air. neonatal alveoli are oxygenated leading to vasodilation and perfusion.
Tetralogy of Fallot leads to what kind of shunt ?
Right to Left .
What occurs to PaO2 in a person with a right to left shunt ?
THe PaO2 DECREASES due to admixture of poorly oxygenated blood going into the
Patent Ductus Arteriosus is an example of what kind of shunt ?
Left to Right
More common due to higher pressure on the left side of the heart.
No significant change in PaO2
What is a nomal V/Q ratio ?
.8
Results in PaO2 of 100 mmHg and a PaC02 of 40 mmHg
Blockage of an airway but normal blood flow to the portion of the lung obstructed will lead to a V/Q ratio of
0 (no Ventilation)
What are the two portions of the MEDULLARY Respiratory Group
Dorsal Respiratory group : regulates inspiration.Generates the basic rhythm of breathing
Ventral Respiratory Group: Regulates Expiration. Not active during normal quiet breathing. Active during exercise
What nerves are responsible for input to the Dorsal respiratory group ?
CN IX and X .
CNX relays info from peripheral chemoreceptors and mechanoreceptors of the lung
CN IX relays info from the peripheral chemoreceptors
Apneustic Center
Seen in the upper pons
Stimulates a gasping inspiration
Pneumotaxic Center
Upper pons
Inhibits inspiration (coordinates respiratory rate)
Gets information from stretch receptors
Cerebral Control
Voluntary breathing (hypo or hyperventilation)
Where are the Central Chemoreceptors found ? What do they sense ?
Medulla
pH ( low pH or High CO2) –> Increased breathing .
CO2 in the CSF diffuses across BB where it will be converted to H+ and HCO3- by Carbonic Anhydrase. H+ acts on chemoreceptor and stimulates breathing.
Where are the peripheral chemoreceptors located ? What do they sense ?
Carotid and Aortic Bodies
Highly sensitive to low P02 (below 60mmHg).
Also sensitive to High PC02 and High [H+]
Effect is less potent than central Chemoreceptors to CO2
Explain the relationship of Carotid body Chemoreceptors with H+ and PC02
Carotid body Chemoreceptors are Highly sensitive to H+ even with absence of increased PCO2.
Metabolic acidosis causes the Carotid Body Chemoreceptors to activate increased breathing (Dorsal Respirtory Group)
Where are lung stretch receptors located ?
Smooth Muscle of airways.
What occurs when stretch receptors are activated ?
Leads to a reflex in which the there is a decrease in breathing frequency (Hering Breuer Reflex)
irritant receptors
located between epithelial cells of the airway (noxious stimuli)
Juxtacapillary Receptors
located in alveolar wall close to the capillaries
Engorging of the capillaries leads to rapid shallow breathing
(Left sided heart failure –> engorgement of capillaries)
Joint and muscles Receptors
Active during exercise ( may stimulate increased breathing)
What occurs to the MEAN values of P02 and PCO2 during exercise ?
Nothing, they remain relatively constant !
pH may change only in strenuous exercise due to lactic acidosis.
Arterial values stay the same but Venous values for PCO2 may increase.
What occurs to physiologic dead space in exercise ?
It decreases.
At high altitude, what occurs to PO2 ?
PAO2 decreases due to lower atmospheric pressures –> Hypoxemia
This will stimulate the peripheral chemoreceptors (Carotid and Aortic Bodies) leading to increased breathing
Increased breathing will blow off C02 –> Respiratory Alkalosis
Treat with Acetazolamide !
What occurs to RBC counts in patients with Hypoxemia ?
Renal cells sense the low oxygen and lead to release of erythropoietin and increased RBC production.
Will 2,3BPG be increased or decreased in hypoxemia ?
INCREASED .. reduces the Hb affinity for oxygen so that it is dissolved in blood and can diffuse to tissues
Shifts Curve to the RIGHT
Hypoxemia may lead to hypoxia in the lung tissue. What will occur to the heart of a patient if this occurs ?
Vasoconstriction will occur in the hypoxic portions of the lung, this will increases Pulmonary pressures. If this occurs for long enough, the Right Side of the heart may hypertrophy since it must work against higher pulmonary pressures in the lung.
