Term
Makeup of conducting zone of airway
Characteristics |
|
Definition
Trachea -> main bronchi -> lobar bronchi -> segmental bronchi -> terminal bronchioles
No aveoli or gas exchange; anatomic dead space |
|
|
Term
Makeup of respiratory zone of airway
Characteristics |
|
Definition
respiratory bronhioles -> alveolar ducts -> alveolar sacs
Contain alveoli (scarce to many as one descends TB tree), gas exchange occurs |
|
|
Term
| Collective diameter of airways |
|
Definition
| Increases with divisions (like capillaries) |
|
|
Term
| Distribution of cartilaginous rings in airway |
|
Definition
Trachea: extensive
Bronchi: inconsistent
Bronchioles: nonexistent |
|
|
Term
| Speed of mucociliary elevator |
|
Definition
|
|
Term
| Cells of the alveolar wall and their functions |
|
Definition
I: Very thin, form airway side of blood-air barrier
II: Produce surfactant and act as stem cells of I and II
Macrophages: Provide defense |
|
|
Term
| Bronchial vs. pulmonary circulation |
|
Definition
Bronchial: Originates in LV, does not participate in gas exchange, in is superfluous
Pulmonary: Originates in RV, carries same amount of blood as systemic, and is a low R high capacitance system |
|
|
Term
| Makeup of air-blood interface |
|
Definition
| Alveolar epithelium, endothelium, and fused basement membrane in between |
|
|
Term
| 3 types of protection in lungs |
|
Definition
Impaction: In upper airway, air hits turbines and large particles get trapped (>10um). Also warms and moistens air
Sedimentation: Lower in airway, flow is slower and medium-sized (1-10um) particles deposit in mucus (cilia clear them)
Digestion: In alveoli, small particles (<1um) pass other systems and get engulfed by macrophages |
|
|
Term
Pulmonary function - supine vs. upright
Reason |
|
Definition
15% function loss, mostly in ERV
Only significant in disease
Though lung compliance is unaffected by position, chest wall is more compliant when upright (FRC decreased while supine) |
|
|
Term
| Effect of obstructive vs restrictive on lung volume plots |
|
Definition
Restrictive: Everything diminished proportionately
Obstructive: RV and TLC elevated. VC may be decreased |
|
|
Term
| Values not measurable from flow-volume loops |
|
Definition
|
|
Term
FEV1:
Obstructive vs restrictive |
|
Definition
In both, FEV1 is lowered
If FEV1/FVC ratio is low, signifies obstructive
If FEV1/FVC ratio is high, signifies normal or restrictive |
|
|
Term
|
Definition
He dilution method:
C1V1 = C2V2
C1 is initial He concentration and V1 is bag volume
C2 is final He concentration and V2 is total volume (bag+lung) |
|
|
Term
| Limitation of He-dilution method |
|
Definition
| Blebs are patches of lung that do not participate in gas exchange. Therefore, dilution can underestimate true lung volume. |
|
|
Term
|
Definition
Person lays in chamber and takes breath through external tube.
P1V1 = P2V2, where P1 and P2 are initial and final pressures in breathing tube and V1 and V2 are initial and final volumes of the chamber |
|
|
Term
| Anatomical vs physiological dead space |
|
Definition
Anatomical: Determined by size of conducting airways (nose to lungs)
Physiological: Anatomic + alveolar dead space |
|
|
Term
| Physiological dead space equation |
|
Definition
Vd/Vt = (PaCO2 - PeCO2)/PaCO2
PaCO2~PACO2, so it is used in place because it is more easily measured
PaCO2 = (VeCO2/Va) * K
where Va is RR x Tv x (1-Vd/Vt) |
|
|
Term
| Alveolar ventilation equation |
|
Definition
|
|
Term
| Factors that increase PCO2 |
|
Definition
High VCO2 (fever, infection, increased metabolism)
Low RR
Low Vt
High Vd/Vt |
|
|
Term
|
Definition
Inhale 100% O2 and measure gas content of exhalation
Originally will have no nitrogen (dead space, all O2) and will eventually rise to alveolar plateau
Halfway between 0% and plateau is considered dead space volume |
|
|
Term
| PO2 levels throughout body |
|
Definition
Decreases from outside air -> inspired air -> avleolar air -> arterial blood -> venous blood
Rises in expired air due to mixing in dead space (same O2 as inspired air) |
|
|
Term
| PCO2 levels throughout body |
|
Definition
Increases from dry air (0) -> inspired air -> alveolar air -> arterial blood -> venous blood
Decreases in expired air because mixes with dead space (0 mmHg CO2) |
|
|
Term
| Relationship between PO2, PCO2 and Va |
|
Definition
As Va increases, PCO2 drops precipitously
As Va increases, PO2 rises only to a plateau |
|
|
Term
|
Definition
Apex: Well aerated (more negative pleural pressure holds alveoli open) and therefore low compliance
Base: Smaller pressure gradient so alveoli size change is greater during respiration (greater ventilation). Greater perfusion as well (heart pumps blood against less gravity) |
|
|
Term
Lung compliance
Definition, equation |
|
Definition
Measure of ease of expansionof lungs and thorax
C = V/P |
|
|
Term
|
Definition
| Opposition of TB tree to airflow |
|
|
Term
|
Definition
| Intrapleural pressure + alveolar elastic recoil pressure |
|
|
Term
|
Definition
| Pressure difference between inside and outside of lung |
|
|
Term
|
Definition
| Pressure difference between airways and outside of lung |
|
|
Term
|
Definition
Diaphragm and external intercostals: Primary muscles of inspiration
SCM and scalene: Secondary muscle of inspiration
Internal intercostals, SCM, scalene: Muscles of forced expiration |
|
|
Term
| Forces during inspiration |
|
Definition
Drop from slightly negative IP pressure to more negative IP pressure causes lung expansion.
At end of inspiration, alveolar recoil pressure = IP pressure and inflation stops |
|
|
Term
|
Definition
| Alveolar recoil pressure exceeds transmural pressure and lung shrinks |
|
|
Term
| Forces during pneumothorax |
|
Definition
| IP pressure becomes atmospheric and lung collapses. Cardiovascular collapse be occur as a result. |
|
|
Term
Negative pressure pulmonary edema
Description, when it occurs |
|
Definition
| If airway is closed during forceful inspiration (young patients under anesthesia), negative pressure pulls fluid into pleural space |
|
|
Term
| Work of breathing equation |
|
Definition
WOB = Wa(30%) + Wp(70%)
Wa = work done through airways = Q x Raw
Wp = work expanding lungs = P/Compliance |
|
|
Term
| Addition of resistance and compliance |
|
Definition
In series:
R added directly
C as reciprocals
In parallel:
R as reciprocals
C directly |
|
|
Term
| Airway resistance equation |
|
Definition
Raw = 8ηL/(πr^4 )
Therefore, r (airways size) is major determinant of R |
|
|
Term
|
Definition
Re = ρDV/η
Re<2000 is laminar, Re>3000 is turbulent |
|
|
Term
Heliox
What it is, how it works |
|
Definition
Mixture of He and O2 given to patients with severe asthma
It reduces density of air, making flow more laminar
Inconclusive if it is effective clinically |
|
|
Term
Two major symptoms with asthma
Treatment |
|
Definition
Narrowed airway: Inflammation and hypersecretion
Bronchial hyper-responsiveness: Smooth muscle twitch in airways in response to cold air, allergens
Treatment: Anti-inflammatory (corticosteroids), bronchodilators (B2-agonists) |
|
|
Term
| Lung compliance variation by respiratory cycle location |
|
Definition
Inspiration: Noncompliant at low and high lung volumes. Most compliant in middle
Expiration: Most compliant at low lung volumes |
|
|
Term
|
Definition
| Difference in shape of expiratory and inspiratory curve P vs. V curve |
|
|
Term
| Compliance (P vs. V plot) in obstructive and restrictive |
|
Definition
Obstructive: Very compliant at low volumes, but at functional volumes, curve plateaus (noncompliant)
Restrictive: Noncompliant at all points on curve (entire plot is shallower than normal curve) |
|
|
Term
| Surfactant makeup and function |
|
Definition
Phospholipid substance
Decreases tension forces, thereby equalizing pressure differences between airways |
|
|
Term
|
Definition
T = Pr by LaPlace's law
If T were the same for each alveolus, the smaller ones would collaps (greater P). Surfactant decreases surface tension for smaller alveoli, thereby equalizing pressures |
|
|
Term
Infant RDS
Cause, symptoms |
|
Definition
Premature infants have underdeveloped respiratory systems and therefore underproduction of surfactant
Airways collapse, lungs stiffen, alveolar edema builds up |
|
|
Term
|
Definition
| Each alveolus is surrounding by other alveoli that prevent it from collapsing. The same is true for the airway |
|
|
Term
|
Definition
Increased IP pressure during forced exhalation exceeds airway pressure and closes airway. Normal event in healthy individuals, makes next inspiration easier.
In disease, dysfunctional lung parenchyma allows this to happen more readily. Air trapping occurs and RV is pathologically increased |
|
|
Term
| Effort independence (expiration) |
|
Definition
| End of forced expiration is effort independent |
|
|
Term
| Mathematical reason for compliance difference between lung regions |
|
Definition
Apex has greater (more negative) transmural pressure. It rests at a point on the P-V curve that is shallower
Base has a less negative pressure, and rests on a steeper part of the curve |
|
|
Term
Time constant
Definition, value during obstructive and restrictive disease |
|
Definition
How quickly lungs can be inflated or deflated. t = R x C
Normal: Easy inspiration and expiration
Obstruct: Easy inspiration (compliant), difficult expiration (low recoil, high resistance). High t, slow/deep breathing
Restrict: Difficult inspiration (noncompliant), easy expiration (high recoil, resistance unchanged). Low t, rapid, shallow breathing |
|
|
Term
|
Definition
v = A/T x D x (P1-P2)
A is area, T is thickness, D is diffusion coefficient, and P is partial pressure
D = solubility / sqrt(MW) |
|
|
Term
| Time it takes for blood to go from PvO2 to PaO2 in pulmonary capillary |
|
Definition
| 0.25s of the .75s it takes to traverse the capillary |
|
|
Term
| Diffusion curve for CO and N2O |
|
Definition
CO: Very shallow rise in PCO. Misleading because has very high affinity for Hb, so Hb absorbs the vast majority of it
N2O: Highly permeable, reaches PAO2 almost immediately, Hb has very low affinity for it |
|
|
Term
| Diffusion vs perfusion dependence |
|
Definition
Diffusion dependent: N2O crosses membrane readily, but limited by perfusion because blood quickly becomes saturated
Perfusion dependent: CO rate is limited by diffusion rate because concentration in bloodstream is minimal and therefore not a limiting factor.
O2 rate lies between these two extremes |
|
|
Term
| Cause of impaired alveolar diffusion and effect on O2 and CO2 levels |
|
Definition
Can be caused by pulmonary fibrosis (thickened alveolar wall)
O2: For as much as 1/4 diffusion capacity, blood has time to be fully oxygenated in capillaries (thanks to functional reserve). Deficit will be noticed during exercise (increase blood flow rate) or high altitude (decreased O2)
CO2: Will reduce rate of CO2 expulsion, but minimally (40 to 40.5 for 1/4 capacity). Biggest effect is on O2 levels |
|
|
Term
| Measurement of alveolar diffusion capacity |
|
Definition
About equal to diffusion capacity for CO (DLCO)
Vco = DLCO x (P1-P2) P2 = 0
DLCO = Vco/Pco |
|
|
Term
|
Definition
Goal is to measure membrane diffusion (Dm), but really measuring how much gas is picked up (DL). DL depends on diffusion rate and blood absorption rate (fudge factor).
Number can be altered by alveolar volume and amount of blood in lung |
|
|
Term
| Pulmonary vs systemic vessels |
|
Definition
| pulmonary are more compliant, thin walled, contain little smooth muscle, and dilated |
|
|
Term
|
Definition
| Catheter inserted into pulmonary artery and inflated to block circulation. After blockage, will equillibrate to estimate LAP. LAP ~ LVEDP ~ LVEDV/preload |
|
|
Term
|
Definition
|
|
Term
| Pulmonary and systemic vascular resistance calculation |
|
Definition
R = P/Q
PVR = (MPAP-PAOP) / Q
(15-5) / 5 = 2 wood units
SVR = (MABP - RAP) / Q
(93-2)/5 = 18 wood units |
|
|
Term
PVR and pulmonary blood pressure
Events that occur when BP increases |
|
Definition
As pressure rises, pulmonary resistance drops (opposite myogenic mechanisms)
Passive control mechanisms include recruitment of closed capillaries and distension of capillaries from flat to circular (compliance) |
|
|
Term
| Effect of exercise on PVR |
|
Definition
| Recruitment of capillaries leads to decreased PVR and increased surface area for gas exchange |
|
|
Term
| PVR relationship to lung volume |
|
Definition
During inspiration, negative pleura pressure pulls extra-alveolar vessels apart (decreased R) and the air pressure compresses alveolar vessels (increased R).
The opposite happens during expiration, and the curve of each type of vessel, when combined, becomes u shaped. The lowest resistance is in the middle, at FRC |
|
|
Term
Active control of PVR
Examples, overall effectiveness |
|
Definition
Direct: increase in Ca causes muscle contraction
Metabolites: NO dilates, endothelin and thromboxane A2 constrict
Low pH and sympathetic weakly constrict
Does much less than passive control. These do not kick in without severe hypoxia |
|
|
Term
| Regional hypoxic pulmonary vasoconstriction and VQ matching |
|
Definition
Damaged alveolus has low PO2 and high CO2
Entering capillary constricts to divert blood flow to better ventilated alveoli |
|
|
Term
Causes of generalized hypoxic pulmonary vasoconstriction
Consequences |
|
Definition
Low O2 environment, lung disease, fetal circulation
Over time, pulmonary hyperstension occurs |
|
|
Term
|
Definition
Attenuates hypoxic pulmonary vasoconstriction.
Specific to pulmonary vasculature
Improves oxygenation to well-ventilated alveoli (VQ matching) |
|
|
Term
| Cause of regional distribution of blood flow |
|
Definition
Zone I (apex, diseased state): PA > Pa > Pv. Effectively dead space, no gas exchange
Zone II (middle): Pa > PA > Pv. Capillary somewhat compressed, bloodflow depends on Pa-PA gradient. These are recruited during increases PAP
Zone III (base): Pa > Pv > PA. Capillary not compressed, blood flow depends on Pa-Pv gradient. Become distended when PAP increased |
|
|
Term
| Causes of pulmonary edema |
|
Definition
Increased capillary hydrostatic pressure (left heart failure)
Decreased capillary oncotic pressure (malnourishment)
Increased permeability (sepsis)
Increased surface tension (ARDS) |
|
|
Term
| Metabolic functions on lung |
|
Definition
ACE converts AngI to AngII and breaks down bradykinin
Serotonin taken up and stored
PGE2, PGF2, and leuktrienes removed
Heparin containing mast cells
IgA
Dipalmitoyl phosphatidylcholine synthesis (surfactant)
I SPLASH |
|
|
Term
|
Definition
Ferric (3+) instead of ferrous (2+)
It cannot bind O2 |
|
|
Term
O2 content of blood
Equation |
|
Definition
CO2 = (O2 capacity)(Hb amount)(O2 sat) + (O2 solubility)(PO2)
Ladder part is minimal because solubility is so low |
|
|
Term
| Factors that shift O2 dissociation curve to the right |
|
Definition
Decrease in pH
Increase in CO2, temperature
Presence of BPG |
|
|
Term
| Factors that shift O2 dissociation curve to the left |
|
Definition
Increase in pH
Decrease in CO2, temperature
Absence of BPG |
|
|
Term
|
Definition
| Describes effects of pH and PCO2 on O2 dissociation curve |
|
|
Term
HbF on O2 dissociation curve
Consequences |
|
Definition
Very left-shifted
Fetal blood has lower PO2 than mother. Higher affinity of Hb takes O2 from mothers blood
Caused by HbA to HbF affinity gradient |
|
|
Term
COHb on O2 dissociation curve
Characteristics and consequences |
|
Definition
Hb has much higher affinity for CO than O2 (240x)
At low PO2, there is a leftward shift (hinders unloading)
Max O2 is significantly reduced
Curve resembles anemia. CO poisoning called 'functional anemia' |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| Acclimatization to high altitude |
|
Definition
Hyperventilation to lower PACO2
Polycythemia (increase Hb) to incresae CO2
Increase BPG helps unloading (moderate altitude)
Respiratory alkalosis (from hyperventilation) shifts Hb curve back to left to favor O2 binding |
|
|
Term
|
Definition
Fine for healthy individuals.
Emphysema patients operate near steep part of O2 dissociation curve, so slight decrease in PiO2 can cause problems |
|
|
Term
|
Definition
As Hb becomes more deoxygenated, it is better able to carry CO2
In peripheral tissues, binds Hb for transport to lungs |
|
|
Term
| CO2 content vs PCO2 curve |
|
Definition
Steeper than O2 curve because CO2 more easily transported
However, physiological changes in PCO2 between a and v system are small (5 mmHg) so change in CO2 content is limited |
|
|
Term
| Factors affecting blood-tissue gas exchange |
|
Definition
Distance of tissue section between two capillaries
During exercise, extra capillaries open up and diffusion distance decreases |
|
|
Term
O2 delivery to tissues
Equation |
|
Definition
|
|
Term
|
Definition
Hypoxic: Low SpO2 and PO2 (lung disease)
Anemic: Low Hb (anemia or COHb)
Circulatory: Low Q (shock)
Histotoxic: Low O2 consumption (cyanide) |
|
|
Term
|
Definition
|
|
Term
|
Definition
(air pressure - 47) x %O2
47 is from vapor pressure in lungs |
|
|
Term
|
Definition
Diffusion limitation (least likely)
Shunt
Hypoventilation
V-Q mismatch (most likely) |
|
|
Term
Diffusion limitation
Definition, causes, treatment |
|
Definition
Incomplete diffusion of O2 across alveolar-capillary membrane
Caused by thickened blood-gas barrier (pulmonary edema, fibrosis), exercise, high altitude
Overcome with O2 supplementation |
|
|
Term
Shunting
Definition, examples of normal ones, examples of abnormal ones, distinguishing feature |
|
Definition
Blood entering systemic circulation without passing through ventilated lung.
Normal shunts: Bronchial artery, coronary artery
Abnormal: ASD, VSD, TofF
Distinguished by fact that supplemental O2 does not alleviate hypoxemia |
|
|
Term
|
Definition
| QS/QT = (CcO2-CaO2)/(CcO2-CvO2) |
|
|
Term
Hypoventilation
Effect on PO2 and explanation from equations |
|
Definition
Decreasing Va increases PACO2 (alveolar ventilation equation)
Increased PaCO2 decreases PAO2 (alveolar gas equation) |
|
|
Term
| Causes of hypoventilation |
|
Definition
Depression or injury to respiratory centers of brain
Respiratory muscle weakness/fatigue or interruption of nerve supply (spinal cord)
Change in lung or chest wall mechanics (obesity) |
|
|
Term
|
Definition
|
|
Term
| Effect of obstructed ventilation on V/Q ratio |
|
Definition
V/Q falls
Once it hits 0, acts as a shunt |
|
|
Term
| Effect of obstructed blood flow on V/Q ratio |
|
Definition
V/Q rises
As it approaches infinity, acts as dead space |
|
|
Term
|
Definition
| V/Q = 8.63R [(CaO2-CvO2)/PACO2] |
|
|
Term
| Regional distribution of V and Q in lung |
|
Definition
Both Q and V are greater at base than at apex
V/Q ratio rises because Q drops at a quicker rate when ascending the lung |
|
|
Term
| Alveolar gas composition in high V/Q vs low V/Q |
|
Definition
High V/Q: High O2 content, low CO2 content
Low V/Q: Low O2 content, high CO2 content |
|
|
Term
Inequality of V/Q:
Consequences of varied blood flow
Effect of inequality on O2 concentration |
|
Definition
Base of lung.
1) It has greater blood perfusion. Therefore, makes up most of PaO2
2) O2 concentration in high V/Q regions ( is only slightly greater than middle. O2 concentration in low V/Q regions is far below middle(O2 dissociation curve). It therefore has a greater effect on average. |
|
|
Term
|
Definition
Areas with high V/Q cannot eliminate CO2 (low perfusion)
Areas with low V/Q cannot absorb O2 (low ventilation) |
|
|
Term
| V/Q mismatch and hypercapnia |
|
Definition
Mismatch causes CO2 buildup, but compensated by hyperventilation (sensed by chemoreceptors)
Hyperventilation does not have much of an effect on increasing PO2 |
|
|
Term
|
Definition
Higher centers: Cortex and limbic
Controller: Medulla and pons
Effectors: Diaphragm, intercostals
Sensors: Central, peripheral, and lungs |
|
|
Term
| Three main groups of controller |
|
Definition
Medullary respiratory center
Pneumotaxic center (upper pons)
Apneustic center (lower pons) |
|
|
Term
| Location of breathing control receptors |
|
Definition
| Chemoreceptors on ventral brain stem, chemoareceptors at periphery, stretch receptors in lungs |
|
|
Term
| Types of chemoreceptors for breathing, and location |
|
Definition
CO2 sensors are central (actually pH sensors) and peripheral (carotid and aortid bodies)
H and O2 sensors are in carotid bodies |
|
|
Term
| Permeability of BBB to H, HCO3, and CO2 |
|
Definition
H is impermeable
HCO3 is partially permeable
CO2 is fully permeable |
|
|
Term
| Mechanism of central CO2 chemoreceptor stimulation |
|
Definition
CO2 diffuses across BBB, joins with H2O to form H+, drops pH, stimulates receptors
CO2 is carrier of H
These receptors do not respond to blood pH because H cannot cross BBB |
|
|
Term
PCO2 and Va curve
Shape, factors that affect it |
|
Definition
Relationship is linear (increase in CO2 leads to increase in Va)
Metabolic acidosis steepens curve (Va more sensitive to CO2)
Anesthesia, sleep, and narcotics shallow the curve |
|
|
Term
O2 sensors
Location, mechanism |
|
Definition
In carotid bodies
Only sense PaO2 (not PvO2, not CaO2)
Therefore, anemias do not trigger them |
|
|
Term
|
Definition
Stretch: Hering-Breuer inflation and deflation reflex (stop over-inflation/deflation)
Irritation: Located throughout respiratory tree and cause coughing, sneezing, bronchospasm |
|
|
Term
Central vs. peripheral chemoreceptors
Importance, timing |
|
Definition
Importance: Central >> peripheral
Peripherals can be excised without much effect
Peripherals do minute-to-minute PCO2
Centrals do PCO2, pH, and blood flow, but a bit slower |
|
|
Term
| Henderson Hasselbalch for carbonic anhydrase |
|
Definition
| pH = 6.1 + log ([HCO3]/0.03PCO2) |
|
|
Term
| Fate of CO2 from respiration |
|
Definition
Expiration of CO2
Generation of HCO3 |
|
|
Term
|
Definition
| H+ = 25 x (pCO2/[HCO3]) x 10E-9 |
|
|
Term
| Causes of respiratory acidosis |
|
Definition
| Hypoventilation, inhibition of medullary respiratory center, paralysis of respiratory muscles (polio), airway obstruction, failure of gas alveolar exchange (obstructive lung) |
|
|
Term
| Cause of respiratory alkalosis |
|
Definition
| Hyperventilation, stimulation of medullary respiratory center (alkalosis), hypoxia (high altitude), pulmonary disease |
|
|
