fisiologia

Question 1

What is the term for the volume of air in excess of tidal volume that moves into the lung on inspiration?

Answer 1

Inspiratory reserve volume

Question 2

A man breathes calmly and quietly. He takes in a normal breath and then lets it out without any forcing. What volume of air is being moved?

Answer 2

Tidal volume, which is approximately 500 mL

Question 3

What is the term for the volume of air that can still be breathed out after a normal expiration?

Answer 3

Expiratory reserve volume

Question 4

What is the term for the volume of air in the lungs after maximal expiration?

Answer 4

Residual volume

Question 5

What is unmeasurable on spirometry: inspiratory reserve volume, tidal volume, expiratory reserve volume, residual volume?

Answer 5

Residual volume

Question 6

The inspiratory reserve volume plus the tidal volume equals what?

Answer 6

Inspiratory capacity

Question 7

The residual volume plus the expiratory reserve volume equals what?

Answer 7

The functional reserve capacity

Question 8

Describe the functional reserve capacity. What are its two components?

Answer 8

FRC = the total volume left in the lungs after normal expiration; residual volume + expiratory reserve volume = FRC

Question 9

Vital capacity equals the sum of what three lung volumes?

Answer 9

Tidal volume, inspiratory reserve volume, and expiratory reserve volume

Question 10

What is the term for the maximum volume of air that can be inhaled and exhaled?

Answer 10

Vital capacity

Question 11

A patient exhales as much as he can, inhales as much as he can, and then exhales as much as he can again. What volume of air has he moved?

Answer 11

His vital capacity (VC)

Question 12

Inspiratory reserve volume plus tidal volume plus expiratory reserve volume plus residual volume equals what?

Answer 12

Total lung capacity

Question 13

Name the four lung volumes.

Answer 13

Lung volumes (LITER) = Inspiratory reserve (IRV), Tidal (TV), Expiratory reserve (ERV), Residual (RV)

Question 14

What is the definition of a capacity?

Answer 14

The sum of greater than or equal to two physiologic volumes

Question 15

What is the equation for determining the volume of dead space in the lungs, where PaCO2 = arterial and PECO2 = expired air?

Answer 15

VD = VT × ([PaCO2 - PECO2]/PaCO2) (Taco, Paco, PEco, Paco, as the order of variables)

Question 16

You know a patient’s physiologic dead space, expired air CO2, and arterial CO2. Can you calculate their tidal volume (VT)?

Answer 16

Yes, as VD = VT × ([PaCO2 - PECO2]/PaCO2), where PaCO2 = arterial, and PECO2 = expired air

Question 17

A patient’s tidal volume is 500 mL, PaCO2 is 50 mmHg, and PECO2 is 35 mmHg. What is the physiologic dead space?

Answer 17

150 mL; VD = 500 mL × ([50 mmHg - 35 mmHg]/50 mmHg)

Question 18

Describe the parts of the airway that contribute to the physiologic dead space.

Answer 18

Conducting airways that contribute to anatomic dead space, and alveolar dead space

Question 19

Which alveolar section of the healthy lung contributes more to physiologic dead space: the apex or the base?

Answer 19

Apex

Question 20

What is the volume of inspired air that does not contribute to gas exchange?

Answer 20

Physiologic dead space, VD

Question 21

What is minute ventilation (VE)? How do you calculate it?

Answer 21

The total volume of gas entering the lungs each minute; VE = VT × respiratory rate

Question 22

A patient with a tidal volume of 400 mL is breathing 20 times per minute. What is his minute ventilation?

Answer 22

8000 mL/min, as minute ventilation (VE) = 400 mL × 20 breaths/min

Question 23

What is alveolar ventilation (VA)? How do you calculate it?

Answer 23

The volume of gas per unit time that reaches the alveoli; VA = (VT - VD) × respiratory rate

Question 24

A patient with a tidal volume of 650 mL is breathing 10 times per minute. His dead space is 150 mL. What is his alveolar ventilation?

Answer 24

5000 mL/min, as alveolar ventilation (VA) = (650 mL - 150 mL) × 10 breaths/min

Question 25

A patient is breathing naturally. Describe the natural tendency of movement of the lung and chest wall.

Answer 25

The lungs tend to collapse inward, and chest wall springs outward

Question 26

At what point in the respiratory cycle is the inward pull of the lung equal to the outward pull of the chest wall?

Answer 26

At functional residual capacity

Question 27

At the point of functional residual capacity, what is the value of the air pressure within the lungs?

Answer 27

At FRC, the pressure within the lungs is equal to atmospheric pressure

Question 28

A patient takes in a deep breath. What determines the combined volume of the chest wall and lungs?

Answer 28

Elastic properties of both

Question 29

• In terms of lung pressures, explain how a pneumothorax is prevented.

Answer 29

At FRC, lung pressures are atmospheric, and opposing forces of the lung and chest wall create negative pressure in the intrapleural space

Question 30

• When is pulmonary vascular resistance at a minimum?

Answer 30

At functional residual capacity

Question 31

What is compliance?

Answer 31

The change in lung volume for a given change in pressure

Question 32

• A 43-y/o woman has pulmonary fibrosis. How does this affect her lung compliance? Other conditions that would affect compliance similarly?

Answer 32

Lung compliance decreases with pulmonary fibrosis, and in pulmonary edema and pneumonia

Question 33

Lung compliance ____ (increases/decreases) in a patient with emphysema, and with natural aging.

Answer 33

Increases

Question 34

• How many polypeptide subunits make up hemoglobin?

Answer 34

Four

Question 35

What are the two conformational forms of hemoglobin?

Answer 35

Relaxed (oxygenated) and taut (deoxygenated)

Question 36

Of the two forms of hemoglobin, the taut (T) form has ____ (high/low) affinity for oxygen. The relaxed (R) form has ____ (high/low) affinity.

Answer 36

Low; high (300 times more affinity in R form) (Taut in Tissues, Relaxed in Respiratory tract)

Question 37

Does hemoglobin have positive or negative cooperativity with respect to oxygen binding and affinity?

Answer 37

Positive

Question 38

Does hemoglobin have positive or negative allostery with respect to oxygen binding and affinity?

Answer 38

Negative

Question 39

An increase in which five factors will favor the taut form of hemoglobin over the relaxed form and will decrease affinity for oxygen?

Answer 39

Chloride (Cl-), protons (H+), carbon dioxide, 2,3-bisphosphoglycerate, and temperature

Question 40

A patient is exercising in the freezing cold. He is otherwise healthy. Is his hemoglobin more likely to be taut or relaxed?

Answer 40

Taut, as exercise (generating CO2) favors the taut form (the outside temperatures are meaningless, as body temperature is what matters)

Question 41

Fetal hemoglobin has ____ (higher/lower) affinity for 2,3-BPG than does adult hemoglobin, causing ____ a (higher/lower) affinity for oxygen.

Answer 41

Lower, higher

Question 42

Hemoglobin can act as a buffer for which ions?

Answer 42

H+

Question 43

Changes to hemoglobin can lead to decreased O2 ____ and ____, causing hypoxia in tissues.

Answer 43

• Saturation, content

Question 44

Normal Hb iron is ____(reduced/oxidized), or ____(ferric/ferrous). Methemoglobin iron is ____(reduced/oxidized), or ____(ferric/ferrous).

Answer 44

Reduced, ferrous (just the 2 of us: ferrous is Fe2+); oxidized, ferric (Fe3+)

Question 45

A man suffers from cyanide poisoning. What property of methemoglobin makes it useful for treatment?

Answer 45

The ferric (Fe3+) state of methemoglobin decreases the affinity for O2 but increases the affinity for cyanide

Question 46

A cyanotic patient is found to have chocolate-colored blood. Treatment?

Answer 46

Methylene blue (this patient has methemoglobinemia)

Question 47

• A child has cyanide poisoning. What is the mechanism of action of nitrites used in the treatment?

Answer 47

Nitrites oxidize iron to form methemoglobin, which readily binds cyanide, restoring function to cytochrome oxidase

Question 48

A patient has cyanide poisoning. What two treatments do you give?

Answer 48

Nitrites and subsequently thiosulfate

Question 49

A patient looks blue and has blood that has turned brown. What caused this?

Answer 49

Poisoning by nitrites or benzocaine

Question 50

What is the name of a form of hemoglobin in which carbon monoxide is bound instead of oxygen?

Answer 50

Carboxyhemoglobin

Question 51

When another molecule, such as carbon monoxide, binds to hemoglobin in place of oxygen, what are the systemic effects?

Answer 51

CO causes a left shift in the oxygen-hemoglobin curve, resulting in tissue hypoxia from decreased oxygen unloading

Question 52

Does carbon monoxide or oxygen have a greater affinity for hemoglobin?

Answer 52

CO has 200 times the affinity of oxygen for hemoglobin

Question 53

What is the shape of the oxygen-hemoglobin dissociation curve? Explain.

Answer 53

Sigmoidal due to positive cooperativity, as Hb can bind four O2 molecules—O2 binding is easier when more O2 is bound

Question 54

How does the structure of myoglobin affect its function?

Answer 54

It is monomeric and thus has no positive cooperativity as seen in hemoglobin, and it lacks the sigmoidal curve

Question 55

When the oxygen-hemoglobin dissociation curve shifts to the right, what happens to the affinity of hemoglobin for oxygen?

Answer 55

A right shift decreases the affinity of hemoglobin for oxygen

Question 56

When the oxygen-hemoglobin dissociation curve shifts to the right, what happens to the O2 saturation (%) at a PO2 of 50 mmHg?

Answer 56

• A right shift decreases oxygen saturation (higher oxygen pressure is required to saturate hemoglobin)

Question 57

A shift of the oxygen-hemoglobin dissociation curve to the right facilitates what process in tissue?

Answer 57

The unloading of oxygen to tissue

Question 58

When the oxygen-hemoglobin dissociation curve shifts to the left, what happens to the affinity of hemoglobin for oxygen?

Answer 58

A left shift increases the affinity of hemoglobin for oxygen

Question 59

Increases in the amount of which six factors cause a right shift of the oxygen-hemoglobin dissociation curve?

Answer 59

Right = ACE BATs right handed (Acid [H+], CO2, Exercise, 2,3-BPG, Altitude, Temperature)

Question 60

When the oxygen-hemoglobin dissociation curve shifts to the left, what happens to the O2 saturation (%) at a PO2 of 50 mmHg?

Answer 60

A left shift increases oxygen saturation (less oxygen pressure is required to saturate hemoglobin)

Question 61

Decreases in the amount of which factors cause a left shift of the oxygen-hemoglobin dissociation curve?

Answer 61

Acid (H+), CO2, exercise, 2,3-BPG, altitude, temperature

Question 62

A fetus's oxygen-hemoglobin dissociation curve is investigated. How does it compare to an adult's oxygen-hemoglobin dissociation curve?

Answer 62

It is shifted to the left (fetal hemoglobin has higher affinity for oxygen than has adult hemoglobin)

Question 63

A patient in shock develops a lactic acidosis. This decrease in pH causes what kind of shift in the oxygen-hemoglobin dissociation curve?

Answer 63

Right shift (due to increased acid [or H+] lowering the pH)

Question 64

A patient's chest is injured and her partial pressure of CO2 is increased. How does this affect her oxygen-hemoglobin dissociation curve?

Answer 64

Shifts it to the right

Question 65

A patient is exercising. What effect would this have on his oxygen-hemoglobin dissociation curve?

Answer 65

• A right shift

Question 66

An increase in 2,3-bisphosphoglycerate (2,3-BPG) causes a ____ (left/right) shift in the oxygen-hemoglobin dissociation curve.

Answer 66

Right

Question 67

A hiker scales an extremely tall mountain. High altitude induces what change in the oxygen-hemoglobin dissociation curve?

Answer 67

A right shift

Question 68

A patient develops a fever. An increase in temperature causes what kind of shift in the oxygen-hemoglobin dissociation curve?

Answer 68

A right shift

Question 69

What is the equation for oxygen content in the blood?

Answer 69

O2 content = (O2 binding capacity × percent saturation) + dissolved O2

Question 70

What is the normal level of hemoglobin in the blood. How many milliliters of oxygen can it bind?

Answer 70

Normal Hb amount = 15 g/dL; each gram can bind 1.34 mL of oxygen

Question 71

A previously healthy patient develops blue lips and fingertips. What does this say about the value of her deoxygenated hemoglobin level?

Answer 71

Her deoxygenated hemoglobin must be >5 g/dL (this is cyanosis)

Question 72

What is the normal value of the O2 binding capacity?

Answer 72

• 20.1 mL O2/dL

Question 73

As Hb falls, what happens to each parameter (increase/decrease/unchanged): O2 content of arterial blood, O2 saturation, arterial PO2?

Answer 73

O2 content of arterial blood decreases, O2 saturation and arterial PO2 remain unchanged

Question 74

How do you calculate oxygen delivery to the tissues?

Answer 74

O2 delivery to tissues = cardiac output × O2 content of blood

Question 75

A woman has CO poisoning. What are the likely levels of her Hb, %O2 saturation of Hb, dissolved O2 (PaO22 content?

Answer 75

• Hb is normal, %O2 saturation of Hb is decreased (CO competes with O2), PaO2 is normal, and total O2 content is decreased

Question 76

A woman has fatigue and pallor. What are the likely levels of her Hb, %O2 saturation of Hb, dissolved O2 (PaO2), and total O2 content?

Answer 76

Hb is decreased, %O2 saturation of Hb is normal, PaO2 is normal, and total O2 content is decreased (she has anemia)

Question 77

A man has polycythemia. What are the likely levels of his Hb, %O2 saturation of Hb, dissolved O2 (PaO2), and total O2 content?

Answer 77

Hb is increased, %O2 saturation of Hb is normal, PaO2 is normal, and total O2 is content increased