Bod: Respiratory: Review Of Respiratory Physiology

Front 1

What is the principle method of quantifying obstructive defects?

Back 1

Spirometry

Front 2

What is the principle method of quantifying restrictive defects?

Back 2

Measurements of lung volumes

Front 3

What is the principle method of quantifying vascular/air-blood interface defects?

Back 3

Lung diffusion capacity (DLCO)

Front 4

c/c FVC and FEV1

Back 4

Forced Vital Capacity is the amount of air that can be forceably exhaled from the lungs.

The Forced Expired Volume in one second is the maxium volume of air that can be exhaled in the first second on exhalation.

Front 5

What is RV?

Back 5

Residual volume is the amount of air left in the lungs after exhalation.

Front 6

What types of diseases cause a decrease in FEV1?

Back 6

Obstructive diseases because high pleural pressures during exhalation cause the obstructed airways to close up, trapping air in the lungs.

Front 7

c/c FVC and FEV1 in obstructive disease.

Back 7

FEV1 will be affected out of proportion to FVC, thereby lowering the FEV1/FVC ratio so it is below 0.80.

Front 8

What does a FEV1/FVC ratio below 0.8 indicate?

Back 8

Obstructive disease.

Front 9

(extra credit)

What is a limitation of the FEV1/FVC ratio?

Back 9

It is sensitive mainly to changes in large airways.

Front 10

c/c FEV1 and FVC in restrictive disease.

Back 10

In restrictive disease, FEV1 and FVC decrease IN PROPORTION to each other.

Thus the ratio is NORMAL in restrictive disease.

Front 11

c/c the FEV1/FVC ratio in obstructive disease vs. the FEV1/FVC ratio in restrictive disease.

Back 11

The FEV1/FCV ratio in obstructive disease is BELOW 0.80

The FEV1/FCV ratio in restrictive disease is normal.

Front 12

What is TLC?

Back 12

Total Lung capacity is the total amount of air in the lungs.

Front 13

What is VC?

Back 13

Vital Capacity is the amount of air that you can exhale after a full, forced inspiration.

Note: this does not include the residual volume.

Front 14

What is TV?

Back 14

Tidal Volume is the amount of air inhaled/exhaled during a normal breath.

Front 15

What is FRC?

Back 15

Functional Residual Capacity is the amount of air that remains in the lung after a normal, passive exhalation.

Note that this includes residual volume.

Front 16

What is the "hallmark" of a restrictive defect?

Back 16

A TLC below 80%

Front 17

Other than the FEV1/FCV ratio, what are the "hallmark" changes in the capacities of the lungs in obstructive disease?

Back 17

Air trapping causes RV to increase --> TLC stays the same, thus --> VC must decrease.

In some obstructive diseases such as emphysema, TLC may increase, but this increase is much smaller than the increase in RV.

Front 18

What 2 types of lung diseases decrease the lungs' diffusion capacity?

Back 18

1. Diseases of the lung parenchyma.

2. Pulmonary embolism.

Front 19

Arterial blood gases:

***/***/***/***/***

Back 19

Arterial blood gases:

pH/PaCO2/PaO2/O2 sat/HCO3

Front 20

What are some of the major factors that affect the relationship between PaO2 and the % O2 saturation?

Back 20

1. pH
2. Temperature
3. PaCO2

Front 21

What causes the oxyhemoglobin dissociation curve to shift to the right?

Back 21

Inc temp
Inc [2,3-DPG]
Inc PaCO2
Dec pH

Front 22

What causes the oxyhemoglobin dissociation curve to shift to the left?

Back 22

Dec temp
Dec [2,3-DPG]
Dec PaCO2
Inc pH

Front 23

What is CaO2?

Back 23

CaO2 is the oxygen content of blood. It refers to all the molecular oxygen in the blood.

This is the sum of the oxygen bound to hemoglobin AND the oxygen dissolved in the plasma.

Front 24

How do you calculate the "bound oxygen?"

Back 24

Bound oxygen = the oxygen carrying capacity of the blood (1.34 * [Hgb]) times the % saturation of hemoglobin.

Front 25

How do you calculate dissolved oxygen?

Back 25

PaO2 * 0.0031

0.0031 is the solubility of oxygen in the blood.

Front 26

ABGs:

Question 1 of 5: Are the reported values internally consistent?

Back 26

Things to check:

At pH of 7.40, [H+] = 40 nM

Each change of 0.01 in pH corresponds with a 1 nM change in [H+].

If the blood gas is internally consistent, then:

[H+] = 24 * (PaCO2/HCO3)

On room air measurements, PaCO2 + PaO2 should not be greater than 150. If it is, the ABG is not internally consistent.

Front 27

On room air, the sum of PaCO2 + PaO2 should not be higher than what?

Back 27

150

Front 28

Each change of ___ in pH corresponds to a change of ___ in [H+].

Back 28

Each change of 0.01 in pH corresponds to a change of 1 nM in [H+].

Front 29

At a pH of 7.40, the [H+] = ?

Back 29

40 nM

Front 30

ABGs:

Question 2 of 5: Is there hypoxemia?

Back 30

PaO2 = 104 - 0.42 * age patient supine
PaO2 = 104 - 0.27 * age patient upright

Front 31

c/c the PaCO2 and the PaO2 in the atmosphere.

Back 31

The PaCO2 in the atmosphere is 0

The PaO2 in the atmosphere is 160

Front 32

c/c the PaCO2 and the PaO2 in the alveolus.

Back 32

The PaCO2 in the alveolus is 40

The PaO2 in the alveolus is 100

Front 33

What is the approximate PaCO2 of blood returning to the heart?

Back 33

Approx 46 mm Hg

Front 34

What is the approximate PaO2 of blood leaving the heart?

Back 34

Approx 97 mm Hg

Front 35

ABGs:

Question 3: What is the A-a gradient?

Back 35

The A-a gradient is the difference between the partial pressure of oxygen in the alveoli and the partial pressure of oxygen in the arterial blood.

PAO2 = PIO2 - (PaCO2/R)

Here, PAO2 is the partial pressure of oxygen in the alveoli, and PIO2 is the partial pressure of oxygen in the inspired air (150), and R is the respiratory quotient = 0.8

So

PAO2 = 150 - (PaCO2/0.8) OR PAO2 = 150 - (1.25 * PaCO2)

for example if PaCO2 = 40 then the above equalls 50. 150 minus 50 is 100. If the arterial oxygen is around 97 like it should be, then there will be a minimal A-a gradient
A normal A-a gradient is below 10. It increases to the high teens with age. An A-a gradient above 20 is almost always abnormal.

Front 36

PIO2 = ?

Back 36

PIO2 = FiO2 * (Patm - PH2O)

At sea level on room air, this equals

PIO2 = FiO2 * (Patm - PH2O)
PIO2 = 0.21 * ( 760 - 47 )
PIO2 = 150

Front 37

What is the normal range for an A-a gradient? Abnormal?

Back 37

Normal is usually under 10.
Abnormal is above 20.

Should equal 2.5 + 0.21 * (age)

Front 38

What causes hypoxemia with a NORMAL A-a difference?

Back 38

Low ambient PIO2
Alveolar hypoventilation

Front 39

What causes hypoxemia with an INCREASED A-a gradient?

Back 39

V/Q inequalities
Right-to-left shunts
Membrane diffusion impairments

Front 40

What are the five basic causes of hypoxemia?

Back 40

1. Low ambient PIO2
2. Alveolar hypoventilation
3. V/Q mismatch
4. Right-to-left shunts
5. Membrane diffusion impairments

Front 41

c/c ventilation and perfusion in the apex of the lung vs. the base of the lung.

Back 41

The apex of the lung has larger, less compliant alveoli, thus there is less ventilation. Gravity makes blood flow to the base of the lung more, thus there is more perfusion in the base of the lung (lower resistance).

The base of the upright lung receives about 2x as much ventilation and about 4x as much perfusion as the apex.

(The PO2 in the upper parts of the lung is greater, though!)

Front 42

How can we distinguish between a V/Q mismatch and a right-to-left shunt?

Back 42

Give 100% oxygen. Measure the PaO2/FiO ratio.

If the ratio is around 600-700, then there is no problem - this is a normal response.

If the ratio is between 200-300, then there is a V/Q mismatch.

If the ratio is below 200, then there is right-to-left shunting.

Front 43

ABGs:

Question 4 of 5: Is there an acidemia or an alkalemia?

Back 43

Normal range is approximately from 7.36 to 7.44.

Front 44

ABGs:

Question 5 of 5: Is the cause of the pH disturbance primarily due to a respiratory or metabolic problem, and, if primarily respiratory, is the disturbance acute or chronic?

Back 44

If pH is low (ACIDOSES) and:
1. If PaCO2 is low (< 40) and HCO3 is low (< 24), then the acidosis is a METABOLIC ACIDOSIS.
2. If PaCO2 is high (> 40) and HCO3 is high (> 24), then the acidosis is a RESPIRATORY ACIDOSIS.

If the pH is high (ALKALOSIS) and:
1. If the PaCO2 is low (< 40) and the HCO3 is low (< 24) then it is a RESPIRATORY ALKALOSIS.
2. If the PaCO2 is high (> 40) and the HCO3 is also high (> 24), then it is a METABOLIC ALKALOSIS.

Front 45

In ACUTE ACIDOSIS, for every ___ mm Hg increase in PaCO2, there should be a _ mEq increase in HCO3.

Back 45

In acute acidosis, for every 10 mm Hg increase in PaCO2, there should be a 1 mEq increase in HCO3.

Front 46

In CHRONIC ACIDOSIS, for every ___ mm Hg increase in PaCO2, there should be a _ mEq increase in HCO3.

Back 46

In chronic acidosis, for every 10 mm Hg increase in PaCO2, there should be a 3.5 mEq increase in HCO3.

Front 47

What is the formula used to predict if compensation is appropriate during metabolic acidosis?

Back 47

The Winter Formula

Expected PaCO2 = (1.5 * HCO3) + 8 +/- 2

Front 48

In ACUTE ALKALOSIS, for every ___ mm Hg decrease in PaCO2, there should be a _ mEq decrease in HCO3.

Back 48

In ACUTE ALKALOSIS, for every 10 mm Hg decrease in PaCO2, there should be a 2 mEq decrease in HCO3.

Front 49

In CHRONIC ALKALOSIS, for every ___ mm Hg decrease in PaCO2, there should be a _ mEq decrease in HCO3.

Back 49

In CHRONIC ALKALOSIS, for every 10 mm Hg decrease in PaCO2, there should be a 5 mEq decrease in HCO3.