Mason Respiratory Study Guide

Front 1

Where is the soft palate and what does it do?

Back 1

Soft palate suspended from posterior surface of hard palate. It acts as curtain between nose and mouth. The midline projection is the uvula

Front 2

What are the pleural layers?

Back 2

•The Pleura is a Double-walled membrane covering lung – it has 2 layers
oParietal pleura
Lines chest wall and diaphragm
Forms lymph (serous fluid in pleural cavity)
Rich supply of afferent nerve fibers
oVisceral pleura
Tightly adherent to surface of lung
Absorbs lymph

Front 3

What is the purpose of the pleural layers?

Back 3

•2 layers of pleura meet at hilum - Layers slide over each other aided by small amount of serous fluid in pleural cavity
oCreates partial vacuum of negative pressure
oAids in lung expansion, Lungs collapse if negative pressure lost
oPleural cavity is space between layers
oIncreased pressure on venous side can cause fluid to collect (pleural effusion)

Front 4

What produces surfactant?

Back 4

•Type II cells secrete surfactant

Front 5

What is the effect of surfactant?

Back 5

•Detergent like effect and Greatly reduces surface tension of water
oReverses law of Laplace

Front 6

What is the VQ normal value?

Back 6

•V/Q ratio averages 0.8
oVentilation normally 4 L/min & Perfusion or CO normally 5 L/min
oV/Q = 4/5 = 0.8
oConsidered an average and takes into account differences in ventilation and perfusion throughout the lungs

Front 7

What is the ideal VQ ratio?

Back 7

•Ideal V/Q ratio is one (Thought to occur at about 3rd rib)

Front 8

What is the VQ at base and apex?

Back 8

Apex
oVentilation in excess of perfusion
oV/Q greater than 1
Dead space
•Base
oPerfusion in excess of ventilation
oV/Q less than 1
Shunt

Front 9

What is VQ effect of Spontaneously breathing, upright patient?

Back 9

oPerfusion increases from apex to base of lung - Most of perfusion goes to dependent lung
oPleural pressure most negative at apex - Keeps alveoli distended
oDependent alveoli distended less and more compliant (Most of tidal volume goes to dependent alveoli)
oNo V/Q mismatch because higher ventilation matches higher perfusion in dependent lung

Front 10

What is VQ effect of Supine position?

Back 10

oAbdominal contents displace diaphragm upward more so in the posterior part
oA good thing in spontaneously breathing patient
oV/Q mechanics related to lung zones still applies
oMore perfusion in posterior (dependent) portion of lungs (Zone 3)
oMore ventilation in posterior portion (Zone 3)
oDiaphragm movement more effective in area where perfusion and ventilation are greatest

Front 11

What is the VQ effect of Lateral position, spontaneously breathing?

Back 11

oDistribution of perfusion and ventilation similar to upright but turned by 90 degrees
oBlood flow and ventilation significantly greater in dependent lung than nondependent lung

Front 12

What is the VQ effect of Lateral position, anesthetized patient?

Back 12

oLung volumes decrease
oUpper lung ventilated more, but Lower lung more perfusion
oPositive pressure ventilation favors upper lung (less compliant)
oMade worse by muscle relaxants b/c Abdominal contents move up against dependent diaphragm
oNondependent (upper) lung is well ventilated but poorly perfused (deadspacing)
oThe dependent lung is well perfused but poorly ventilated (shunting)

Front 13

_____always decreases when there is a V/Q mismatch.

Back 13

PaO2

Front 14

Concerning the zones of the lung the Determinants of flow along vertical axis are what?

Back 14

oPressure in pulmonary artery (Ppa)
oPressure in alveoli (PA)
oPressure in pulmonary vein (Ppv)

Front 15

Zone 1

Back 15

oUpper part of lung, PA > Ppa > Ppv

Front 16

Zone 2

Back 16

oMiddle area, Ppa > PA > Pv
oWell-matched ventilation and perfusion (Contains most alveoli)

Front 17

Zone 3

Back 17

oMost gravity-dependent areas, Ppa > Pv > PA
oPerfusion high, in excess of ventilation – physiologic shunt

Front 18

What is deadspace? (3 types)

Back 18

oAnatomic dead space
Area of respiratory system that does not participate in gas exchange
Oropharynx to respiratory bronchioles
About 1 ml/lb or 2 ml/kg – 150 ml
Modified by ETT, tracheostomy, large lengths of tubing between ETT & circuit Y-piece
oAlveolar dead space
Ventilation of alveoli with little or no perfusion
Affected by pulmonary blood flow
Modified by changes in CO and pulmonary embolism
oPhysiologic dead space
Anatomic plus alveolar dead space
Anatomic dead space not affected by disease states
Changes in physiologic dead space related to changes in alveolar dead space

Front 19

What is a Shunt?

Back 19

Occurs in lung that is perfused but poorly ventilated. The part of CO that returns to L heart and systemic circulation without receiving O2 in lung

Front 20

What is an absolute shunt?

Back 20

Pulmonary blood not exposed to alveoli
Venous return form pleural, bronchiolar and thebesian veins flows directly into LA bypassing RV
2-5% of CO – absolute, anatomic shunt
V/Q = 0 [Ventilation is zero & Ventilation to perfusion ratio is zero (zero/Q)]

Front 21

What is a relative (venous admixture or partial) shunt?

Back 21

More common than absolute shunt
Occurs in areas where ventilation is deficient compared to perfusion
Hypoxemia from absolute shunt doesn’t get better with O2, but the Hypoxemia from venous admixture gets better with O2 – alveoli do contribute small amount of O2 to capillary bed
Produced by mild pulmonary edema and post-op atelectasis
0 < V/Q < 0.8
Ratio is greater than absolute shunt
There’s some exchange going on – but it’s less than normal
Ventilation < 4 L

Front 22

What is compliance?

Back 22

o Measure of elastic properties of lung and reflects lung distensibility….How easy can structures be “stretched”. Compliance is the ease with which something is stretched.

Front 23

What does increased and decreased compliance mean?

Back 23

oIncreased compliance - Abnormally easy to inflate or “stretch”
oDecreased compliance - More difficult to inflate

Front 24

What is hypoventilation?

Back 24

oInadequate alveolar ventilation in relation to metabolic demands
oResults in hypercapnia and respiratory acidosis
oOccurs with decreased MV

Front 25

What is hyperventilation?

Back 25

oAlveolar ventilation that exceeds metabolic demands
oResults in Hypocapnia
oOccurs with Severe anxiety, Acute head injury, & Conditions that cause insufficient oxygenation

Front 26

Compliance is _______ in emphysema/COPD

Back 26

increased

Front 27

Discuss ARDS and the effect of compliance and VQ

Back 27

oSurfactant inactivated
oLess compliance
oLess perfusion
oV/Q mismatch from more vasoconstriction in some parts of lung compared to others

Front 28

Discuss the differences b/t the R and L bronchi?

Back 28

• The right main bronchi is shorter, wider, and more vertical than the left bronchi. The Right Bronchi is 2.5 cm long compared to the left which is 5cm long. The Right has a 25 degree angle to the trachea and the left has a 45 degree angle to the trachea, thus aspiration is more likely to enter the right lung and intubations are more likely to be in the right main-stem.

Front 29

Discuss pulmonary compliance and artery diameter.

Back 29

•The pulmonary artery begins at the base of the RV and is short and wide. It is 5cm (2inches) long and 3cm (1.2inches) in diameter. The pulmonary artery divides into right and left branches to deliver deoxygenated blood to the lungs.
•The pulmonary arteries and arterioles have shorter, thinner walls, with greater diameter than the systemic arteries and arterioles. This allows for greater compliance (more distension) and lower resistance (less pressure). In comparison Pulmonary veins are more similar to systemic veins in distensibility, although shorter in length.

Front 30

What is the function of the capillary membrane basement?

Back 30

• The function of the membrane is to control diffusion of gasses. The rate of diffusion is inversely proportional to the thickness of the membrane. Emphysema cases a decrease in the thickness of the membrane. The rate of diffusion is also determined by the concentration gradient of gas; molecules move from higher to lower concentration.

Front 31

Gas exchange begins with what?

Back 31

•Gas exchange begins with diffusion across the respiratory membrane
Gas exchange begins at the 16th division, the respiratory (terminal) bronchioles.

Front 32

Elastic recoil lungs affected by?

Back 32

• Elastic properties (recoil and compliance) of the lungs permit the lungs and chest to expand during inspiration and return to resting volume during expiration. It is caused by elastin and collagen fibers in the alveolar walls, small airways, and pulmonary capillaries, as well as by surface tension in the alveoli. Accessory muscles are used if disease compromises recoil (emphysema) or blocks airways.

Front 33

What is the Law of Laplace?

Back 33

•The Law of Laplace states that for cylindrically shaped structures, T=Pr (where T= wall tension, P= pressure of liquid within cylinder, and r = radius).
•P = 2 (surface tension) /
radius
•This means as the radius of a sphere becomes smaller more pressure is required to inflate it. In a sphere, surface tension makes expansion more difficult.

Front 34

What are the characteristics and causes of cyanosis?

Back 34

• The term cyanosis means blueness of the skin, and its cause is excessive amounts of deoxygenated hemoglobin in the skin blood vessels, especially in the capillaries. In general definite cyanosis appears whenever the arterial blood contains more than 5 grams of deoxygenated hemoglobin in each 100 milliliters of blood. A normal person contains about 15 grams of hemoglobin in each 100 milliliters of blood. A person with anemia almost never becomes cyanotic because there is not enough hemoglobin for 5 grams to be deoxygenated in 100 milliliters of arterial blood. Conversely a person with polycythemia (excess RBCs) can frequently become cyanotic in even normal conditions.

Front 35

Discuss systemic and pulmonary blood flow.

Back 35

•The volume of blood flowing through the lungs is identical to the volume flowing through the systemic circulation. Blood flow through the lungs essentially equals cardiac output.

•Pulmonary circulation is a low pressure, low resistance system. The pulmonary vessels are normally passive, distensible tubes that get bigger when pressure increases and smaller when pressure decreases.
•The pulmonary veins carry oxygenated blood to the LA to LV to the systemic circulation. The pulmonary arteries carry de-oxygenated blood to the lungs to become oxygenated.

Front 36

When will hypoxic pulmonary circulation occur?

Back 36

•If there is decreased oxygen in alveoli then hypoxic pulmonary vasoconstriction may occur. This causes blood to be directed to areas of better ventilation and to areas where gas exchange (ventilation) can occur. The effects of low O2 on systemic vessels causes vasodilation and it causes vasoconstriction on the pulmonary vessels. The reason for this is unknown. It starts to occur when PaO2 falls to 70 mmHg and below.

Front 37

Intracardiac shunt will cause the PaO2 to do what?

Back 37

•Right to Left cardiac shunt (venous to arterial shunt) causes venous that is not oxygenated to become shunted to the pulmonary capillaries. The greater the shunt the greater the amount of blood that fails to be oxygenated as it passes through the lungs, which causes a lower PaO2. Normal PaO2 averages 104 mmHg and normal PCO2 averages 40 mmHg.

Front 38

What is vapor pressure?

Back 38

• THE PARTIAL PRESSURE THAT THE WATER MOLECULES EXERT TO ESCAPE THROUGH THE SURFACE IS CALLED VAPOR PRESSURE OF THE WATER.

•Pressure exerted by the water molecules escape is vapor pressure = 47 mm Hg . At normal body temperature, 37 degrees C. this vapor pressure is 47mm Hg.

Front 39

Partial Pressure values of inspired air, alveolar gas

Back 39

Gas Inspired air Alveolar air
N2 597 569
02 159 104
C02 0.3 40
H20 3.7 47
Total 760 760

Front 40

PaO2 estimates

Back 40

Total oxygen content includes that combined with Hgb plus that dissolved in plasma (0.3ml per 100ml of blood).

•PaO2= 102 -age/3
•HYPOXEMIA (PaO2 < 60)

Front 41

What does the oxyhemoglobin dissociation curve express?

Back 41

Shows the relationship between PaO2 and SaO2, how much Hgb is saturated with O2.

Front 42

Shift to the right means what?

Back 42

Hgb’s affinity for O2 goes down
•Rt. Shift lowers Hgb’s affinity for O2, displacing it from Hgb and making more available for tissue
•A right shift occurs with-acidosis, increased CO2, Hyperthermia, increased 2,3-DPG

Front 43

Shift to the Left means what?

Back 43

curve shifts to the left, Hgb’s affinity for O2 increases-binds tighter and less is available for tissue
•Left shift when-alkalosis, decreased CO2, Hypothermia, decreased 2,3-DPG, presence of abnormal Hgb (fetal and methemoglobin)

Front 44

What is the diffusion capacity for CO2?

Back 44

•Diffusing Capacity for CO2. The diffusing capacity for CO2 has never been measured because of the following technical difficulty: CO2 diffuses through the respiratory membrane so rapidly that the average PCO2 in the pulmonary blood is not far different from the PCO2 in the alveoli-the average difference is less than 1 mm Hg- and with the available techniques, this difference is too small to be measured.
•Because the diffusion coefficient of CO2 is slightly more than 20 times that of oxygen, one would expect a diffusing capacity for capacity CO2 under resting conditions of about 400 to 450 ml/min/mm Hg and during exercise of about 1200 to 1300 ml/min Hg.

Front 45

Discuss the CO2 transport mechanism.

Back 45

•Transport of CO2 by the blood is not nearly as problematical as transport of oxygen is, because even in the most abnormal conditions, CO2 can usually be transported in far greater quantities than oxygen can be. However, the amount of CO2 in the blood has a lot to do with the acid-base balance of the body fluids. Under normal resting conditions, an average of 4 ml of CO2 is transported from the tissue to the lungs in each 100 ml of blood.

Front 46

What % of CO2 is transported and how?

Back 46

•Transport of CO2 in the blood-Approx. 0.3ml of CO2 in dissolved form in each 100ml blood (7% of CO2 transport), Approx. 70% reacts with water to form carbonic acid within RBC, Approx. 23% transported in combination with Hgb.

Front 47

What are the 3 buffer systems of the body?

Back 47

1-chemical acid-base buffer system of the body fluids, which immediately combine with acid or base to prevent excessive changes H+ concentrations,
2- respiratory center-regulates the removal of CO2 (and therefore, H2CO3) from the extracellular fluid,
3- Kidneys-which can excrete either acid or alkaline urine, thereby readjusting the extracellular fluid H+ concentration toward normal during acidosis or alkalosis.

Front 48

How do the buffer systems work?

Back 48

•Buffer system do not eliminate H+ from or add them to the body but only keep them tied up until balance can be established.
•The Hgb in the cells is an excellent acid-base buffer (as is true of most proteins) so that the red blood cells are responsible for most of the acid-base buffering power of the whole blood (Medical Physiology, Ch 32, pg 419).
•The pH of the cells, although slightly lower than in the extracellular fluid, nevertheless changes approx. in proportion to extracellular fluid pH changes. There is a alight amount of diffusion of H+ and HCO3 through the cell membrane, although these ions require several hours to come to equilibrium with the extracellular fluid, EXCEPT FOR RAPID EQUILIBRIUM THAT OCCURS IN THE RBCs.