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GI/ Resp. Physio > Week 3 Objectives > Flashcards

Week 3 Objectives Flashcards

1
Q

L3-1How does an iron lung cause a paralyzed person to breathe?

A

Iron lung cycles the atmospheric pressure of the patients’ thoracic cavity and causes it develop transmural pressure that facilitates breathing

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2
Q

L3-2 Why do victims of emphysema appear to have large chests?

A

They have high lung volume due the loss of elastic fibers in their alveoli and they also over-develop their accessory muscles in efforts to expel air. The destruction of alveoli also reduces the amount of surface area that would act to oppose the stretching of the chest wall. (loss of hysteresis); Less lung recoil causes FRC to rise (barrel chest)

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3
Q
  1. What lung volume is equal to the sum of the expiratory reserve volume and the residual volume?
A

The functional residual capacity is equal to the sum of the expiratory reserve volume and the residual volume. (approx. 3L)

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4
Q
  1. Write the equation that allows one to calculate alveolar ventilation (L/min).
A

Va =Vt-Vd (alveolar ventilation = volume breathed in/out through nose- dead space volume) the alveolar ventilation is less than the minute volume because the last part of each inspiration remains in the conducting airways and does not reach the alveoli Va= f (Vt-Vd) Alveolar ventilation is equal to the breaths/min times the difference in total volume and dead space volume (physiologic dead space = anatomic dead space + unperfused alveoli)

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5
Q
  1. Write the Bohr equation and explain why it allows one to calculate the volume of un-perfused alveoli.
A

Bohr equation makes use of concept that any measurable volume of carbon dioxide found in the mixed expired gases must come from the alveoli that are both ventilated and perfused
VdCO2/ Vt = (PaCO2 – PECO2)/ PaCO2

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6
Q

Define the trans respiratory system pressure.

A

the algebraic sum of the translung pressure and the trans thorax pressure

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7
Q

How would you create a more negative intrathoracic pressure?

A

cause the chest to expand my contracting thorax muscles

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8
Q

If alveolar pressure is decreasing, what does that mean for the overall flow of air in the lungs

A

air is leaving (expiration)

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9
Q

What causes wheezing?

A

airway collapse during forced expiration (great intrathroacic pressure is created during forced expiration which is sometimes greater than intrapleuric pressure, causing airways to collapse)

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10
Q

What has happened when you have the wind knocked out of you?

A

your lung is forcefully collapse, causing your lung to be reduced below the natural residual volume

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11
Q

Can residual volume be determined by spirometry?

A

No.

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12
Q

What do flow-volume loops record?

A

both flow and volume, effort dependence occurs only at high lung volume where as low lung volume is effort independent

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13
Q

How does anatomical dead space affect alveolar ventilation

A

add more volume to the end expiratory air in the reparatory system, the more anatomical dead space the larger the tidal volume or respiration rate to properly profuse the lung to the right partial pressure of O2 in the lung for diffusion

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14
Q

Why is hypoxi pulmonary vasoconstriction beneficial?

A

Diverts blood to places in the lung that are being maximally ventilated

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15
Q

In a variable extra thoracic obstruction would you expect an greater inspiration or expiration?

A

greater expiration (because extra-thoracic obstructions cause the air way to collapse during inspiration due to Patm> Pa

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16
Q

In variable intra-thoracic obstruction, would you expect greater inspiration or expiration?

A

greater inspiration as airway tumor or other obstruction would cause airway collapse on expiration because Pa< Ppl

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17
Q

What does Dalton’s law dictate?

A

the total pressure of a gas mixture equals the sum of pressure of the individual gases

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18
Q

What is the partial pressure of oxygen in atmospheric air at sea level?

A

PO2 =159 mmHg

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19
Q

What other gas pressures in the lung affect the partial pressure of oxygen

A

CO2 partial pressure and water vapor partial pressure cause a decrease in O2 partial pressure

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20
Q

The ratio of what two physiologic variables determine PCO2?

A

the rate of exchange of CO2 between blood and circulation and the rate of air coming into the lung

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21
Q

Write the equation to calculate alveolar pCO2 and pO2

A

Pa CO2 = VCO2/ Va

Pa O2 = PiO2- (PaCO2/R) +F

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22
Q

How is breathing regulated in regards to blood pH.

A

breathing is regulated to maintain arterial pH at 7.4 at PaCO2= 40 mmHg

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23
Q

What are the normal values for PAO2 and PACO2?

A 
PACO2 = PaCO2= 40mmHg
PAO2= 100mmHg
24
Q

Why are PACO2 and PaCO2 considered the same thing?

A

carbon dioxide diffuses across the reparatory barrier much more easily than oxygen

25
Q

Why does expired gas have a higher oxygen content than alveolar gas?

A

expired gas includes quite a bit of gas from dead space which has not lost its oxygen content

26
Q

What is the right to left shunt?

A

poor ventilation causes blood that is passing through an alveoli to not change blood gas chemistry, its just moving from the right side of the heart to the other with out ventilation

27
Q

What are the effects of gravity on ventilation?

A

Ventilation at the top of the lung is less due to greater inter pleural pressure (lung is hanging from top of cavity); gravity affects the position of the lung and the way it is stretched; there is also more change in the volume of the lower lung because this portion is not stretched to the same degree as the top of the lung

28
Q

What is the effect of vertical posture on blood flow per alveolus?

A

Blood flows more easily downhill from the heart than uphill.

29
Q

What are the effects of gravity on the ratio of ventilation/perfusion ratio?

A

at the top of the lung the ratio is greater than 1 (meaning the ventilation is greater than the perfusion rate) ; at the bottom of the lung the ratio is less than one (meaning perfusion rate is greater than ventilation); point of demarcation is about rib 3

30
Q

How does exercise effect the effects of gravity of ventilation and perfusion?

A

Exercise reduces the effect because the top of the lung becomes better perfused

31
Q

Describe zone 1 lung and its perfusion and ventilation state.

A

the alveolar pressure is equal or greater to the pulmonary artery pressure so there is no perfusion

32
Q

Describe zone 2 lung its perfusion and ventilation state

A

in zone 2 pulmonary artery pressure is greater than alveolar pressure so blood flow does occur

33
Q

Describe zone 3 lung and its perfusion and ventilation state

A

pulmonary artery pressure and the pulmonary vein pressure are both greater than alveolar pressure

34
Q

In which zone is capillary diameter smallest?

A

zone 1, the capillary is occluded

35
Q

In all three lung zones Pa>Pv, Why?

A

Pa must be greater than Pv to cause flow from the right side of the heart to the left side

36
Q

What is PEEP

A

Positive End Expiratory Pressure causes alveolar pressure to be substantially high causing large areas of zone 1 (ie. in a patient on a positive-pressure ventilator)

37
Q

What forces determine the net filtration of vascular liquid out of lung capillaries?

A

hydrostatic pressure of pulmonary vessels and the colloid osmotic pressure of the blood flowing through vessels in the lung

38
Q

What types of pathologically an iatrogenic conditions could cause pulmonary edema?

A

infections, circulating or inhaled toxins, oxygen toxicity and causing the osmolarity of blood can destroy the integrity of the capillary endothelium and increase its permeability to lead to localize or generalized pulmonary edema- if the capillary hydrostatic pressure increases dramatically, the filtration of fluid across the capillary endothelium will exceed the lymphatic drainage (ie. left sided lung failure or mitral stenosis)

39
Q

What forces determine the net filtration of vascular liquid out of lung capillaries?

A

hydrostatic pressure of pulmonary vessels and the colloid osmotic pressure of the blood flowing through vessels in the lung

40
Q

What types of pathologically an iatrogenic conditions could cause pulmonary edema?

A

infections, circulating or inhaled toxins, oxygen toxicity and causing the osmolarity of blood can destroy the integrity of the capillary endothelium and increase its permeability to lead to localize or generalized pulmonary edema

41
Q

How long does a RBC reside with in a pulmonary capillary under normal resting conditions.

A

on average .75- -1.2 s (all oxygen diffusion happens in the first .75s of transit)

42
Q

How is RBC residence time in the lung affected by exercise?

A

the time of residence that occurs after oxygen has diffused is reduced because exercise increases blood pumping through lung due to increase CO

43
Q

Which has greater oxygen solubility, blood plasma or simply whole blood?

A

whole blood due to its content of hemoglobin

44
Q

What does P50 describe?

A

at what partial pressure the blood is half saturated

45
Q

How long does a red blood cell reside within a pulmonary capillary under normal resting conditions?

A

on average .75-1.2 seconds, during exercise, transit time is reduced to .75s

46
Q

How does having half the normal hemoglobin (anemia) affect a patients oxygen content?

A

will have reduced capacity of carrying oxygen

47
Q

At rest, mixed venous blood has 75% hemoglobin saturation, who is that important under stress?

A

under enhanced metabolic needs the body can extract more oxygen from the hemoglobin

48
Q

At a normal hemoglobin concentration of 15 g Hb/ 100mL blood, ho many millimeters of oxygen can be transported by each liter of blood?

A

20.1 mL of 02 per 100mL of blood

49
Q

A right shift of the hemoglobin curve signifies what for its affinity for oxygen?

A

decreased affinity- occurs in the tissues

50
Q

What factors are responsible for shifts in the oxy-hemoglobin dissociation curve?

A

right: increased temp, increased pCO2, increased DPG and increased acidity, with the converse also true

51
Q

How does myoglobin facilitate oxygen use by muscle tissue?

A

myoglobin buffers tissue O2 concentrations to minimize variations in capillary O2 delivery

52
Q

Describe the affect of carbon monoxide on the P50.

A

Carbon monoxide markedly lowers the p50 because once it is bound to a single subunit it changes the binding capability of other subunits to bind oxygen (note anemic blood will have reduced oxygen carrying capacity but will release O2 very easily in tissue)

53
Q

Name the 3 ways carbon dioxide is transported in the blood and their relative percentages.

A

5% carbamino compounds; 5% dissolved in plasma, 90% as HCO3-

54
Q

What is the Haldane effect?

A

increased blood content of CO2 and reduced O2 content increases the blood capacity to carry CO2

55
Q

Why does chloride shift into red blood cells as blood flows through peripheral tissue?

A

in tissues, CO2 is entering the erythrocyte with water, which forms bicarbonate which is exported in exchange for Cl-; near the lungs, water and CO2 leave RBC and which requires the exchange of bicarbonate for Cl- (out)

56
Q

Why do low VA/Q lung units depress the arterial blood oxygen concentration more than high VA/Q units raise it?

A

based on the hemoglobin saturation curve the amount of oxygen can be interpolated by the average of the percent saturation (at the top of the curve the relationship is less steep, at the middle, the curve is more steep- greater change in oxygen carrying for each percent saturation)

GI/ Resp. Physio (4 decks)

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