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  #1  
Old 09-10-2011
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Lungs Two high yield Respiratory Physiology Questions!!!

1. A 35-year-old man has a vital capacity (VC) of 5 L, a tidal volume (TV) of 0.5 L, an inspiratory capacity of 3.5 L, and a functional residual capacity (FRC) of 2.5 L. What is his expiratory reserve volume (ERV)?

(A) 4.5 L
(B) 3.9 L
(C) 3.6 L
(D) 3.0 L
(E) 2.5 L
(F) 2.0 L
(G) 1.5 L


2. A healthy 65-year-old man with a tidal volume (TV) of 0.45 L has a breathing frequency of 16 breaths/min. His arterial PCO2 is 41 mm Hg, and the PCO2 of his expired air is 35 mm Hg. What is his alveolar ventilation?

(A) 0.066 L/min
(B) 0.38 L/min
(C) 5.0 L/min
(D) 6.14 L/min
(E) 8.25 L/min
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Old 09-10-2011
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G & D? I'm not very sure
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Two high yield Respiratory Physiology Questions!!!
1. A 35-year-old man has a vital capacity (VC) of 5 L, a tidal volume (TV) of 0.5 L, an inspiratory capacity of 3.5 L, and a functional residual capacity (FRC) of 2.5 L. What is his expiratory reserve volume (ERV)?

(A) 4.5 L
(B) 3.9 L
(C) 3.6 L
(D) 3.0 L
(E) 2.5 L
(F) 2.0 L
(G) 1.5 L


2. A healthy 65-year-old man with a tidal volume (TV) of 0.45 L has a breathing frequency of 16 breaths/min. His arterial PCO2 is 41 mm Hg, and the PCO2 of his expired air is 35 mm Hg. What is his alveolar ventilation?

(A) 0.066 L/min
(B) 0.38 L/min
(C) 5.0 L/min
(D) 6.14 L/min
(E) 8.25 L/min
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Old 09-10-2011
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Quote:
Originally Posted by bebix View Post
1. A 35-year-old man has a vital capacity (VC) of 5 L, a tidal volume (TV) of 0.5 L, an inspiratory capacity of 3.5 L, and a functional residual capacity (FRC) of 2.5 L. What is his expiratory reserve volume (ERV)?

(A) 4.5 L
(B) 3.9 L
(C) 3.6 L
(D) 3.0 L
(E) 2.5 L
(F) 2.0 L
(G) 1.5 L

A: VC = ERV + TV + IRV
IC = IRV + TV
So ERV = VC - IC = 5 - 3.5 = 1.5 L

2. A healthy 65-year-old man with a tidal volume (TV) of 0.45 L has a breathing frequency of 16 breaths/min. His arterial PCO2 is 41 mm Hg, and the PCO2 of his expired air is 35 mm Hg. What is his alveolar ventilation?

(A) 0.066 L/min
(B) 0.38 L/min
(C) 5.0 L/min
(D) 6.14 L/min
(E) 8.25 L/min
First one =
A: VC = ERV + TV + IRV
IC = IRV + TV
So ERV = VC - IC = 5 - 3.5 = 1.5 L

Second one = Cannot figure out this one, please help with explanation.

Last edited by donofitaly; 09-10-2011 at 09:22 AM. Reason: Explained better.
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Old 09-10-2011
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Default Isnt it G and c?

Dead space

(41-35) / 41 = .15 .... .45-.15 = .3
.3 x 16 = 4.8
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Volume of dead space=Tidal volume*(PAco2-PECo2)/PAco2
= 0.45*6/41
= 0.065
Alveolar ventilation=alveolar volume*respiratory rate
=(0.45-0.065)*16
=6.16
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Old 09-10-2011
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Quote:
Originally Posted by bebix View Post
1. A 35-year-old man has a vital capacity (VC) of 5 L, a tidal volume (TV) of 0.5 L, an inspiratory capacity of 3.5 L, and a functional residual capacity (FRC) of 2.5 L. What is his expiratory reserve volume (ERV)?

(A) 4.5 L
(B) 3.9 L
(C) 3.6 L
(D) 3.0 L
(E) 2.5 L
(F) 2.0 L
(G) 1.5 L


2. A healthy 65-year-old man with a tidal volume (TV) of 0.45 L has a breathing frequency of 16 breaths/min. His arterial PCO2 is 41 mm Hg, and the PCO2 of his expired air is 35 mm Hg. What is his alveolar ventilation?

(A) 0.066 L/min
(B) 0.38 L/min
(C) 5.0 L/min
(D) 6.14 L/min
(E) 8.25 L/min
1) ERV = vital capacity - Insp. capacity
= 5 - 3.5 = 1.5L

2) Alveolar ventilation = (Tidal vol. - Dead space) * Breaths/min
= (0.45L - {0.45*(41-35)/41}) * 16
= (0.45 - 0.065) * 16 ~ 6.14L/min
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Quote:
Originally Posted by whocares13 View Post
2) Alveolar ventilation = (Tidal vol. - Dead space) * Breaths/min
= (0.45L - {0.45*(41-35)/41}) * 16
= (0.45 - 0.065) * 16 ~ 6.14L/min
Could you please explain the complete formula and if possible, the logic behind your calculation?
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Default the logic

Quote:
Originally Posted by donofitaly View Post
Could you please explain the complete formula and if possible, the logic behind your calculation?

alveolar ventilation is less than minute ventilation as not all the inspired air gets to the alveoli some remain in the dead space. minute ventilation is respiratory rate multiplied by tidal volume
alveolar ventilation is less than minute ventilation, it is the actual gas reaching the alveoli and participating in exchange.

so you calculate the physiologic dead space, tidal volume multiplied by (partial pressure of arterial CO2 minus partial pressure of expired CO2 divided by PaCO2)

so the air that remains in the conducting portion and air in the alveoli that do not participate in gas exchange contains O2 and "dilutes" the expired air so that expired air has less PCO2 than arterial blood

i have made a mumbo jumbo of this explanation! sorry
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