ventilation, oxygenation, respiration Flashcards
A-a gradient equation
A-a = PAO2 - PaO2
what do you use to calculate the A-a gradient
alveolar gas equation and values from the arterial blood gas
the 5 main mechanisms of hypoxemia fall under what 2 main categories
- not enough oxygen getting into alveoli
2. not enough oxygen transferred into the capillary bed
with not enough oxygen getting into the alveoli, what is the A-a gradient
normal A-a gradient
with not enough oxygen transferred into the capillary, what is the A-a gradient
elevated A-a
what causes not enough oxygen getting into the alveoli
- low atmospheric pressure (ex high altitude)
- hypoventilation (ex heroin overdose)
what causes not enough oxygen transferred into the capillary blood
- ventilation-perfusion mismatch (ex atelectasis)
- right to left shunting (ex atrial septal defect)
- diffusion defects (ex pneumonia)
pulmonary ventilation
inflow and out flow of air b/w the atmosphere and lung aveoli
external respiration
diffusion of oxygen and carbon dioxide between the aveoli and the blood
internal respiration
transport of O2 and CO2 in the blood and body fluids to and from the body’s tissue and cells
what systems regulate ventilation and respiration?
CNS effects and Peripheral effects
lungs can be expanded and contracted in 2 ways. what are they?
- downward and upward movement of diaphragm (normal quiet breathing)
- elevation and depression of chest cavity (increase thoracic volume by 20%)
what are the 3 pressures that cause the movement of air in and out of the lungs
pleural
alveolar
trans pulmonary
what is pleural pressure
pressure of the fluid in the thin space between the lung pleura and chest wall pleura
what is another name for pleural pressure
intrapleural pressure
at rest, what is the pleural pressure
-5 cm H2O
which is negative suction
what is the pleural pressure during inspiration
increases to -7 cm H2O
what is alveolar pressure
pressure inside the lung alveoli
what is another name for alveolar pressure
intrapulmonary pressure
when is the alveolar pressure 0 cm H2O
when glottis is open and no air is moving the alveolar pressure
During inspiration, what is the alveolar pressure?
decreases to -1 cm H2O and 0.5 liters of air enters in 2 seconds
during experation, what is the alveolar pressure
alveolar pressure increases to +1 cm H2O and forces 0.5 liters of air out of lung
transpulmonary pressure is also known as “___ ____ pressure” which measures….
Elastic recoil pressure
the measure of the elastic force in the lungs
Pulmonary blood flow represents ____ and is usually the blood flow measured to determine ____ via the Swan Ganz catheter
represents total cardiac output and usually the blood flow measured to determine total cardiac output via the Swan Ganz catheter
at rest, the entire blood volume of the body passes through the ….
pulmonary circulation every 1 to 2 minutes and more frequently during exercise
in an adult at rest, the capillary blood volume is about how much and what does it approximate?
capillary blood volume is 140-200 ml
approximates the right heart stroke volume
The lung has dual circulation. what are the 2 circulations?
pulmonary circulation and bronchial circulation
what kind of vasculature is pulmonary circulation and what is it involved in?
a low-pressure, high-volume vasculature
involved in gas exchange that perfuses alveoli
what is bronchial circulation and what does it provide?
a high-pressure, low volume system
provides nutrients and gas exchange for the bronchial tree and conducting airways
Bronchial circulation is part of the ___ ____ and receives about 2% of the CO from the ___ ____
part of the systemic circulation and receives about 2% of the total CO from the left ventricles
where do the bronchial arteries arise from?
branches of the aorta, intercostal subclavian, or internal mammary arteries
how much does bronchial veins drain and from where?
about 1/3 of the venous drainage from the bronchial circulation via the azygos, hemiazygos, and intercostal veins
bronchial venous blood returns back to where
the right atrium
about 2/3 of the bronchial capillary blood is thought to drain into where?
anastomoses or communicating vessels that empty into the pulmonary veins to return to the left atrium
what does the bronchial capillary blood draining into the left atrium communication provide?
small volume of poorly oxygenated bronchial venous blood to the freshly oxygenated blood in the pulmonary vein
Pulmonary circulation is in series with the _____ circulation, therefore blood flow is _____
in series with systemic circulation, therefore blood flow is the same in both
how do the vessel walls in the pulmonary circuit compare to the walls in the systemic circuit
Vessel walls of the pulmonary vasculature are much thinner and contain less smooth muscle compared to segments in the systemic circulation
Structurally, the ____ _____ more closely resemble systemic veins than arteries
pulmonary arteries more closely resemble systemic veins
speaking of high flow rates, does the pulmonary or systemic circulation have lower high flow rates?
pulmonary vascular pressures are considerably lower
average PA pressure
13-19 mmHg
what causes the lower pulmonary vascular pressure?
the lack of high resistance arterioles
-affects blood flow distribution in the lung
Fick principle for cardiac output
the amount of O2 uptake or consumption by the body per minute is equal to the cardiac output times the difference in oxygen content b/w arterial and mixed venous blood
The lung is greatly designed for gas exchange, but it is ideally suited for other functions unrelated to gas exchange because….
the large blood volume that passes through the lung each minute
-immense capillary surface available for metabolism
what are the four functions of pulmonary
- gas exchange
- blood filter
- blood reservoir
- metabolism of circulating substances
what does the meshwork of capillary vessels do to act has a blood filter in the lungs?
trap emboli and large particles to keep from reaching the coronary or systemic vasculature
how are emboli trapped by pulmonary vessels later removed?
enzymatic processes, macrophage ingestion, or absorption into the lymphatic system
how do the vessels of the pulmonary system help function as a blood reservoir?
vessels are very compliant and easily distant
since vessels are an extension of the left atrium, they act as a blood reservoir, supplying blood to the left ventricle and maintaining output
pulmonary vessels contain how much blood
450-900 ml of blood
which cells in the lumen are involved in the uptake or metabolic conversion of several vasoactive substances in the circulation
endothelial cells
what are some things that the lungs release that help with metabolism of circulating substances
- biologically active compounds into circulation
- histamine
- prostaglandins,
- leukotrienes
- platelet activating factor
- heparin
- serotonin
- nitric oxide
where are mast cells found
- in most tissues of body, especially those that interact with the environment
- skin, lungs, GI tract, mouth, nose, blood brain barrier
when do mast cells detect and respond to?
-foreign substances
when triggered, what do mast cells release?
- histamine
- prostaglandins
- heparin
- tryptase
- cytokines
Pulmonary artery branches rapidly give rise to nearly
300 billion pulmonary capillaries
gas exchange between the _____ and ____ occurs within the lung capillaries
alveolar gases and blood occurs within the lung capillaries
gas exchange between alveoli and pulmonary capillary blood is by
simple diffusion
O2 diffuses from the ___ to the ____
CO2 diffuses from the ____ to the ____
O2 diffuses from the alveolus to the pulmonary capillary blood
CO2 diffuses from the pulmonary capillary to the alveolus
what is the alveolar-arterial gradient?
a measure fo the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen
when is the alveolar-arterial gradient used?
in diagnosing the source of hypoxemia
-helps isolate the location of the problem as either intrapulmonary (within lungs) or extra pulmonary (somewhere else in body)
An abnormally increase A-a gradient suggest a defect in
- diffusion
- V/Q (ventilation/perfusion ratio) mismatch
- or right-to left shunt
what is hypoxemia
low concentration of O2 in the blood
what is oxygenation
the process where oxygen enters the bloodstream via the lungs
adequate oxygenation of the blood depends on many factors such as…
- atmospheric pressure (Patm)
- fraction of oxygen in inspired air (FiO2)
- movement of oxygen into the lungs (ventilation)
- adequate blood flow in the pulmonary capillaries (perfusion)
- oxygenated alveoli that are perfused with blood (ventilation-perfusion matching)
- movement of oxygen across the alveolar-capillary membrane (diffusion)
any problems with one or more of these factors will cause inadequate oxygenation of the blood and would be reflected as
low arterial oxygen partial pressure
low O2 which is hypoxemia
hypoxemia is caused when
there is not enough oxygen getting into the alveoli
-not enough oxygen transferred into the capillary blood
what is the alveolar-arterial oxygen gradient (A-a gradient)
difference (gradient) between alveolar oxygen pressure and arterial oxygen pressure
the 5 main mechanisms of hypoxemia fall under what 2 main categories
- not enough oxygen getting into the alveoli (will have normal A-a)
- not enough oxygen transferred into the capillary blood (will have elevated A-a)
what 2 main mechanisms of hypoxemia fall under the category of not enough oxygen getting into the alveoli
- low atmospheric pressure ex: high altitude
2. hypoventilation ex: heroin overdose
what 3 main mechanisms of hypoxemia fall under the category of not enough oxygen transferred into the capillary bed
- ventilation-perfusion mismatch ex: atelectasis
- right-to-left shunting ex: atrial septal defect
- diffusion defects ex: pneumonia
what is the equation for A-a gradient
A-a gradient = PAO2 - PaO2
what is the expected normal A-a gradient
< (age/4) +4
how to calculate the A-a gradient
use the alveolar gas equation and values from the arterial blood gas
step 1: calculate PAO2 (at sea level)
PAO2 = (Patm-Pwater) FiO2 - PaCO2/.8
step2: calculate A-agradient: PAO2-PaO2
step 3: compare expected A-a to calculated A-a v
what pH is acidic
under 7.35
what pH is basic
over 7.45
what PaCO2 is acidic
greater than 45
what PaCO2 is basic
less than 35
what bicarb is acidic
less than 22
what bicarb is basic
greater than 26
respiratory acidosis is
low pH, high PaCO2, normal bicarb
what is respiratory alkalosis
high pH, low PaCO2, normal bicarb
what is metabolic acidosis (simple)
low pH, normal PaCO2, and low bicarb
what is metabolic alkalosis (simple)
high pH, normal PaCO2, and high bicarb
Repiratory processes alter the blood pH by changing the
carbon dioxide levels
what is the main way the human body eliminates acid and maintains acid-base homeostasis
CO2 elimination via the lungs
what is respiratory acidosis (explanation)
when CO2 accumulates in the blood (elevated PaCO2) like when a person hypo ventilates, acid builds up and the pH decreases
what is respiratory alkalosis (explanation)
increase CO2 elimination (low PaCO2) like when a person hyperventilates, the amount of acid in the blood decreases and the pH increases
in the following ABG, is there. respiratory acidosis or respiratory alkalosis?
ABG: 7.32/50/98
99% O2 saturation on room air
alkalosis
what is external respiration
the exchange of gas (CO2 and O2) between the lungs (alveoli) and blood (pulmonary capillaries)
gas exchange occurs down a pressure gradient via ____ across the ____ _____
via diffusion
across the respiratory membrane
gases move from an area of
high concentration (high pressure) to low concentration (low pressure)
factors affecting rate of gas diffusion
- thickness of membrane
- surface area of membrane
- diffusion coefficient of gas in membrane
- partial pressure (concentration) difference of gas on either side of membrane
CO2 diffuses ___ more rapidly than O2
20x
laws that govern gas exchange
Boyles
Charles
ideal gas
henry
Boyles law
at constant temperature, pressure and volume vary inversely
P1 x V1 = P2 x V2
Charles law
movement of gases is dependent on temperature
temperature and volume vary directly
V/T = k
ideal gas law (dalton’s)
each gas in a mixture will exert its own pressure depending on the # of moles present and the temperature and volume of the mixture
PV = nRT
henry’s law
the absolute concentration of a gas dissolved in a liquid is dependent on the solubility coefficient of that gas in that liquid
during quiet inspiration, what happens to the volume and pressure
lung volume increases
pressure in lungs decrease
thoracic pressure decreases (5 mmHg below atmospheric pressure)
what is the basic thing to remember about Charle’s law of gases
gases tend to expand when heated
Dalton’s law of partial pressures tells us that
the total pressure in a mixture of gas is the sum of the partial pressures of each gas
the solubility of a gas in any solvent is ____ as the pressure over the solvent increase
the solubility of a gas in any solvent is increased as the pressure over the solvent increases
the solubility of the gas increases in direct promotion to what
its partial pressure above the solution
the solubility of gases in water ____ with increasing temperatures
decreases with increasing temperatures
what pressure in the lung can influence the distribution of blood flow and vascular resistance?
vascular segments (arteries, capillaries, and veins)
extravascular pressures (intrathroacic or intrapleural)
transmural pressure
mean hydrostatic pressure in the arteries
pulmonary: 13-19
systemic: 90
mean hydrostatic pressure in capillaries
pulmonary: 10
systemic: 30
mean hydrostatic pressure in veins
pulmonary: 5
systemic: 10
mean hydrostatic pressure in atria
pulmonary: 4
systemic: 2
intravascular hydrostatic pressure refers to
the actual pressure inside pulmonary vessels relative to atmospheric pressure
the pressure drop b/w pulmonary artery and capillary is small compared to systemic vessels bc
the lung lacks high resistance arterioles
the lack of arterioles in the lungs minimizes what
active regulation of lung blood flow distribution
intravascular driving pressure for pulmonary circulation
the difference b/w inflow and outflow pressures
difference b/w pulmonary arterial (Pa) and left atrial pressure (Pla)
the normal mean driving pressure is about
11 mmHg
in the pulmonary circulation, a small driving pressure is adequate because
of the relatively low resistance to blood flow
what does transmural pressure refer to
the pressure difference between the inside and outside of some walled structure
because airway and blood vessels walls are distensible, pressure differences between the inside and outside can affect….
their diameter, therefore the resistance they offer to air or blood flow
what is intrathoracic pressure
the pressure immediately outside large lung vessels
during quiet breathing, intrathoracic pressure is less than
atmospheric pressure and becomes increasingly subatmospheric with inspiration
large vessels and airways tend to passively dilate with…
inspiration as the outside intrathoracic pressure decreases
these larger lung vessels, whose outside pressure is intrathoracic are referred to as
extra alveolar vessels
the pressure immediately outside the lung capillaries is
alveolar pressure
how does alveolar pressure affect alveolar vessels
the diameter and resistance to blood flow offered by these
when alveolar pressure is increased, what does it do to the lung capillary and flow
narrow (squeeze) the lung capillary and increase resistance to flow
the transmural pressure differences in alveolar vessels can also affect
resistance to blood flow
intravascular pressures
blood flow distribution
what is surfactant
phospholipid that reduces the surface tension of water and is secreted and lines the interior surface of the alveoli
surfactant decreases surface tension most at ____ and least at ____
most at low volumes and least at high volumes
surfactant makes surface tension in the alveoli vary with
lung volume
what is surface tension and what does it cause
cohesive force b/w liquid molecules
causes the inward collapse (recoil) of the alveoli
LaPlace law
P = 2T/rP
pressure required to keep alveolus open
small alveoli have higher ___ ____ and are harder to keep open
collapsing pressure
a decrease in alveolar surface tension by surfactant causes a decrease in….
collapsing pressure in alveolus
surfactant increases lung compliance which in turn decreases….
the work of expanding lungs during inspiration
neonatal respiratory distress syndrome is caused by
a deficiency or absence of surfactant
how does neonatal RDS affect V/Q
decreases V/Q
collapsed alveoli are not ventilated and do no participate in gas exchange which results in hypoxemia
additional important lung products
- prostaglandins
- histamine
- kallikrein
- inactive kininogens
- angiotensin-converting enzyme (ACE)
what does histamine do
binds receptors on smooth muscle cells induce vasodilation, bronchoconstriction
what does kallikrein do
catalyzes proteolytic cleavage of kininogens in kinin synthesis
ACE inactivates
bradykinin
ACE inhibitors increase…
bradykinin which leads to cough, angioedema
the upright human lungs measures about ____ from the apex to the base
30 cm
the pulmonary artery enters the lung at the level of the
hilum
about midway between the apex and base of the lung
in order for the right heart to pump blood to the apex of the lung, what must it pump against
a column of blood about 15 cm high or against a pressure head of about 15 cm H2O resulting from gravity
because the right heart has a lot to push against, the mean intravascular pressure at the lung apex is
11 cm H2O lower than arterial pressure at the hilum
mean intravascular pressure at the BASE of the lung is about
11 cm H2O higher than pulmonary arterial pressure at the hilum
due to gravitational forces, both intravascular pressures and blood flow are considerably ____ at the apex than at the base of the lung
less at the apex than at the base of the lung
when a person assumes a supine position, the pressure differences b/w the apex and base are ____, therefore results in more uniform distribution of blood flow and smaller vascular pressure differences
differences b/w the apex and base are less
alveolar pressure may be above atmospheric pressure in briefly during (2)
- forced expiration
2. chronically during positive pressure breathing
at a given blood flow, ____ in alveolar pressure are generally reflected by nearly equivalent increases in pulmonary arterial pressure up to about 8 cm H2O
increases
what is alveolar hypoxia
when the airway or alveolar PO2 is lower than normal
what is hypoxic pulmonary vasoconstriction
constriction of the arterial vessels leading to them
-redirects blood flow away from poorly oxygenated alveoli towards alveoli that have higher PO2 levels
HPV is a mechanism that normally operates to help optimize or improve…
gas exchange by decreasing blood flow to poorly oxygenated alveoli
pulmonary shunting is
portion of the cardiac output that moves from the right to the left side of the heart w/o being exposed to alveolar oxygen (blood flow with no O2) perfusion with out ventilation
V/Q = 0
always pathological
normal anatomic shunt
2-3% of cardiac output
thebesian veins, pleural and bronchial blood flow
abnormal anatomic cardiac shunt
ASD, VSD, TOF, DORV (double outlet right ventricle)
pulmonary shunt leads to
hypoxemia as alveoli collapse or fill with fluid or exudate (atelectasis, pulmonary edema, pneumonia)
major difference b/w shunt and V/Q mismatch
V/Q mismatch responds to oxygen therapy
shunt is refractory and doesn’t respond easily
true shunt are
autonomic shunts and capillary shunts
intrapulmonary shunting is
blood flow through pulmonary capillaries w/o participating in gas exchange
anatomic shunt exists when
blood passes through an anatomic channel of the heart and does not pass through the lungs
caused by: congenital heart disease, intrapulmonary fistula, vascular lung tumors
capillary shunts are commonly caused by
alveolar collapse or atelectasis, alveolar fluid accumulation or alveolar consolidation
capillary + anatomic shunt =
absolute or true shunt
does not respond well to O2 therapy bc alveolar oxygen does not meet the shunted blood
relative shunt
pulmonary capillary perfusion is in excess of alveolar ventilation
venous admixture
end result of pulmonary shunting
mixing of shunted, non-deoxygenated blood with deoxygenated blood
ventilation perfusion ratio
V/Q
the relationship of the overall alveolar ventilation to the overall pulmonary blood flow
normal: 4:5 or 0.8-1
patients with shunts are more ____ than those with VQ mismatch and they may require ___ _____
hypoxemia than those with VQ mismatch and they may require mechanical ventilators
Zone 1 of the lung
vessels are compressed and there is no blood flow but you get oxygenation
Palv > Pa > Pv
zone 2 of the lung
“vascular waterall”: the flow is independent of the eventual venous pressure and depends only on the difference b/w pulmonary arterial pressure and alveolar pressure
Pa > P alv > Pv = flow occurs but with resistance
Zone 3 of the lung
the venous pressure is greater than the alveolar pressure so that flow depends on the arteriovenous pressure difference
Pa > Pv > Palv = capillary dilation = less resistance = more flow
conditions that cause an entire lung to convert to zone 1
- blood loss (hemorrhage) hypovolemia
2. positive pressure ventilation
the bulk of the lung in most normal healthy people and in most postures is represented by what zone
2
which zone has the highest blood flow
zone 3
in patients, how can pulmonary vascular resistance be obtained?
by using a Swan-Ganz or pulmonary artery catheter
where is the Swan-Ganz and catheter inserted?
inserted into a systemic vein (ex: jugular) and advanced through the right heart into the pulmonary artery
what does the Swan-Ganz and catheter directly measure?
- used to measure pulmonary arterial (Pa) and estimate left atrial pressure (Pla) and determine blood flow (ex: CO)
- can therefore compute PVR
how much of the total PVR resides in the capillaries
50-60%
PVR is ____ of SVR bc
1/10 of SVR b/c low pressure system
important to recognize that the distribution of PVR likely varies with changes in
blood flow, left atrial pressure, alveolar pressure and body position
whenever blood flow to the lung or left atrial pressure is increase, what happens to the calculated PVR
decreases
PVR declines with increase in blood flow and is accounted for by
capillary recruitment and distension
when blood flow or Pla is increase, previously closed capillaries are ___ and patent capillaries are further distended
recruited (opened)
With more and wider parallel channels (capillaries) available for flow, what happens to the flow and resistance
calculated resistance to flow declines bc resistances arranged in parallel
Lung inflation affects PVR because of the influence of
intrathoracic pressure and alveolar size upon extra-alveolar and alveolar vessels
intrapleural (intrathoracic) pressure becomes more sub atmospheric during ____ which increases transmural pressure to ______
inspiration
which increases transmural pressure to passively dilate extra-alveolar vessels
flow resistance in these vessels diminish as
lung volume increases
As lung volume is increased from residual volume (RV) to total lung capacity (TLC), what happens to vascular resistance
steadily declines in extra-alveolar vessels
as alveoli expand to larger volumes, they to do what to alveolar vessels
tend to compress and narrow alveolar vessels
when is PVR typicaly lowest or at, or close to
FRC (function residual capacity) or normal resting end-expiration
what is hematocrit
percentage of the total blood that is occupied by red cells
an increase in the number of red cells (increased hematocrit) increases the viscosity of red cells and therefore calculated PVR is also
increased
increase PVR (7)
sympathetic innervation a-Adrenergic agonist thromboxane/PGE2 endothelin-1 angiotension histamine alveolar hypoxemia
decrease PVR (7)
parasympathetic innervation acetylcholine B-adrenergic agents PGE1 prostacyclin nitric oxide bradykinin
adult lung has about how much alveoli
300 million alveoli each surrounded by a capillary mesh
gas exchange is optimal in alveoli where
the fraction of alveolar ventilation (V) is matched to the fraction of cardiac output (Q) perfusing that alveolus
some alveoli may be over ventilated relative to their blood flow and exhibit a V/Q of
over 1.0
other alveoli may be over-pursued relative to their ventilation and have a V/Q of
<0.8
at extremes, some alveoli may be ventilated but received no perfusion, so V/Q is
infinite V/Q
alveoli may be perfused but not ventilated which makes the V/Q
very low V/Q
V/Q match
local mechanisms adjust for poor air flow and/or poor blood flow
Pulmonary arterioles have receptors that sense
H+ concentrations and low O2 (chemoreceptors)
Fick’s law of diffusion: diffusion is proportional to
partial pressure difference (gradient) and surface area
Fick’s law of diffusion is inversely proportional to
membrane thickness and diffusion distance
hemoglobin contains
4 heme molecules and 1 globing molecule
each heme molecule can carry
4 O2 molecules
1mg hemoglobin can carry
1.34 ml of O2
internal respiration occurs as
simple diffusion
carbon dioxide diffuses out of the __ and goes where
diffuses out of the tissue, cross the interstitial fluid and enter the blood
-then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form
oxygen delivery is a function of
arterial oxygen content and cardiac output
oxygen consumption
is the rate at which tissues take up oxygen and is a function of oxygen delivery and amount of oxygen that is extracted by tissues
Hgb is 50% saturated at a plasma PO2 of approx
27 mmHg
Normal venous blood has PvO2 at ___ and oxyhemoglobin sat at ___
40 mmHg
sat of 75%
normal arterial blood has PaO2 of ___ and oxyhemoglobin sat of
97 mmHg
sat of 97%
Haldane effect
PO2 affects the ability of the blood to carry CO2
Bohr effect
a decrease in pH shifts the curve to the right
incr pCO2, incr temp, incr DPG
an increased P50 causes a
decreased affinity of Hb to O2
lower P50 indicates a
leftward shift and a higher affinity of Hb to O2
fetal hemoglobin has a
higher affinity for oxygen
causes a leftward shift and lower P50
methemoglobinaemia
Fe3+
leftward shift = lower P50
carbon monoxides binds to hemoglobin ___ times more readily than with oxygen
240 times
shifts curve to the left
with an increased level of carbon monoxide, a person can suffer from
severe hypoxemia while maintaining a normal PO2
anemia in terms of blood O2/PO2 curve
increase in 2,3-DPG shifts curve to the right
-decreased affinity for O2 translates to better O2 offloading to tissues
acute high altitude
thin air, causes hyperventilation
decreases PCO2 and increase pH shifts curve to the left
acclimation to high altitude
polycythemia occurs
increases 2,3 DPG and shifts curve to the right
factors that increase C(a-v)O2 and decrease SvO2
- decreased CO
- exercise
- hyperthermia
- seizures
- shivering in post-op patient
factors that decrease the C(a-v)O2 and increase SvO2
- increased CO
- skeletal muscle relaxation
- peripheral shunting
- certain poisons
- hypothermia
when the C(a-v)O2 increases….
the SvO2 decreases
three main forms of CO2 transport in blood
- as bicarbonate ions (70%)
- as carbamino-hemoglobin (15-25%)
- dissolved in plasma (5%)
where are three influences on control of respiration
- chemical influences of the respiratory center of the brain neural influences
- cortical influences voluntary controls in the medullary rhythmicity center and pontine respiratory center neurons limit inspiratory
- proprioceptive stretch receptors in the lungs
how does the medullary rhythmicity center control respiration
autorythmic inspiratory and expiratory neurons sets the basal ventilation
how does the pontine respiratory center neurons limit inspiratory
impulses causing shorter cycles which increases ventilation rate
the respiratory center of the brain is controlled by a
negative feedback pathway
Increased pO2, decreased pCO2, and a drop in H+ all interact to
discourage ventilation to retain more CO2
decreased pO2, increased pCO2, and a rise in H+ all interact to
encourage ventilation to blow off more CO2
central chemoreceptors control ___% of the responses
70%
medulla
peripheral chemoreceptors control ___% of responses
30%
carotid and aortic bodies
Pulmonary arteries have thin walls and are under lower pressure. what does this create?
lower hydrostatic pressure gradients
this minimizes the tendency for fluid to filter out of the pulmonary capillaries into the airspaces
hydrostatic pressure
tends to push fluid out of vessels
colloid oncotic pressure tends to
pull fluid into vessels
what are the causes of pulmonary edema
- high pressure
2. low pressure
high pressure edema
- hydrostatic, cardiogenic
- common w left heart failure results in more fluid filtration from the vascular space than can be returned by plasma oncotic forces
-left atrial pressure threshold for pulmonary edema is about 25 mmHg
low pressure edema
- high permeability, noncardiogenic
- results from an increase in permeability of the barrier that separates blood from the tissues
what is neurogenic pulmonary edema
from head injury, SAH, intercebral hemorrhage
cariogenic pulmonary edema comes from
heart failure and fluid overload (kidney and liver)
noncardiogenic pulmonary edema comes from
lung and capillary
5 causes from pulmonary edema in relation to starling forces
- increased hydrostatic pressure
- reduced oncotic pressure
- reduced lymphatic drainage
- increased surface tension
- increased capillary permeability
starling forces favor movement of fluid from
inside capillaries to the interstitial space
what is obstructive lung disease
- have SOB due to difficulty exhaling all the air from the lungs.
- exhaled air comes out more slowly than normal
what are types of obstructive lung disease
- COPD
- asthma
- bronchiectasis
- cystic fibrosis
what is restrictive lung disease
cannot fully fill their lungs with air
types of restrictive Lung disease
- interstitial lung disease
- sarcoidosis
- obesity
- scoliosis
neuromuscular disease
in an oxygenator, gas transfer from the
gas to the liquid phase
what is gas transfer driven by in an oxygenator
diffusion according to the partial pressure difference of the particular gas
the region in which variation in velocity occurs is defined as
boundary layer
blood or any other viscous fluid flowing past either a stationary surface or a bubble will have variations in velocity from
zero at the interface surface to that of the free stream
the major resistance to gas diffusion occurs in the
blood phase
efforts to improve gas exchange
- increase welling times
- increasing driving gradient
- decreasing the diffusion path by making the surface of the membrane irregular or positioning the elements within the flow stream to disrupt the smooth flow
an eddy current has an impact on the
boundary layer of the fiber, disrupting its development and reducing its thickness
