Pulmonary Math Questions (Exam III) Flashcards
Calculate the partial pressure of inspired humidified O₂ .
PIO₂ = FIO₂ (PB - PH₂O )
PIO₂ = 0.21 (760mmHg - 47mmHg)
PIO₂ = 150 mmHg
How can alveolar minute volume be calculated?
V̇A = V̇T - V̇D
4200mL/min = 6000mL/min - 1800mL/min
What is the percentage of O₂ in a humidified inspiration?
19.69%
↓
149.7 ÷ 760 = 19.69%
How much O₂ is in a VA inspiration?
- 68.9 mL O₂
350mL x [0.1969] = 68.915 mL O₂
How much of VA O₂ (in mLs) leaves per exhaled breath?
Assume PAO₂ = 104mmHg
PAO₂ after equilibrium = 104mmHg
↓
104mmHg ÷ 760mmHg = 0.1368 O₂ content.
↓
350mLO₂ x 0.1368 = 47.88 mLO₂
=
47.88 mL O₂ is unabsorbed with each breath.
How much of VA O₂ (in mLs) is absorbed per breath?
Assume PAO₂ = 104mmHg
Total inspired O₂ per breath = 68.915 mLO₂
↓
Total expired O₂ per breath = 47.88 mL O₂
↓
68.915 - 47.88 mLO₂ = 21.035 mLO₂ absorbed per breath.
How much total O₂ is exhaled per breath?
VA = 350mL
VD = 150mL
↓
350mL x 0.1368[O₂] = 47.88mLO₂
+
150mL x 0.1969[O₂] = 29.54mLO₂
↓
= 77.42 is the total O₂ (both VA and VD) expired per breath.
How much CO₂ is exhaled per minute?
Assume the patient has a respiratory rate of 12bpm and give your answer in liters.
PACO₂ = 40mmHg
↓
VD CO₂ content = 0
+
VA CO₂ = 40mmHg ÷ 760mmHg = .0526
↓
350mL x 0.0526[CO₂] = 18.42mLCO₂
↓
18.42mLCO₂ x 12bpm = 0.221 Liters of CO₂ per minute.
Suppose you had a spirometer of 10L with a Helium concentration of 10%.
After being attached to a patient and a respiratory cycle, the helium concentration becomes 8%.
What is the patient’s FRC?
1L He starting out
↓
0.08 * x = 1L He
↓
x = 12.5 (new total volume)
↓
12.5 - 10 = 2.5L = FRC
Calculate the normal Minute Alveolar Ventilation rate.
What will Alveolar PO2 be at the calculated Minute Alveolar Ventilation rate?
4.2 L/min
Respiratory Rate x Alveolar Volume
12 breaths/min x 350 mL = 4200 mL/min
At 4.2 L/min, PAO2 will be about 100 mmHg
Calculate the normal Minute Dead Space Ventilation rate.
1.8 L/min
Respiratory Rate x Dead Space Volume
12/breaths/min x 150 = 1800 mL/min
1.8 L/min
Calculate the oxygen concentration after it has been inspired and displaced by water vapor.
Partial Pressure of O2 = [O2] x Total Pressure
[O2] = Partial Pressure of O2 / Total Pressure
[O2] = 149 mmHg / 760 mmHg
[O2] = 0.1961
[O2]= 19.61%
How much O2 is brought into the gas exchange region during each breath?
VA (volume of air for gas exchange) = 350 mL
[Inspired O2] = 19.61%
350 x 0.1961=
68.62 mL of O2 enter the gas exchange region.
How much O2 is expired from the gas exchange regions during each breath?
VA (volume of air for gas exchange) = 350 mL
PAO2 (alveolar PO2 after gas exchange) = 100 mmHg
Total Pressure = 760 mmHg
Need to calculate [O2] after equilibrium (gas exchange)
[O2 after equilibrium] = PAO2 / Total Pressure
[O2 after equilibrium ] = 104 / 760
[O2 after equilibrium] = 0.1368
mL of O2 expired = [O2 after equilibrium] x VA
mL of O2 expired = [0.1368] x 350 = 47.89
47.89 mL expired from the gas exchange region during each breath
How much O2 is normally absorbed over the course of one breath?
How much O2 is normally absorbed in one minute?
O2 is brought into the gas exchange region during each breath: 68.62 mL
O2 is expired from the gas exchange regions during each breath: 47.89 mL
68.62 - 47.89 =
20.73 mL of O2 absorbed during each breath
20.73 x 12 breaths/min = 248.76 mL absorbed/min
How many mL/dL of O₂ return to the heart from systemic circulation?
- 15 mL/dL
How many mL/dL of O₂ leave the heart?
- 20 mL/dL
Calculate cardiac output from the following parameters:
- V̇O₂ = 240 mLO₂
- Arterial O₂ = 20 mLO₂
- Venous O₂ = 14 mLO₂
4 L/min
Calculate the concentration of PCO2 in the lungs at FRC.
Calculate the amount of CO2 in the lungs at FRC.
What will be the new concentration of CO2 if 350 mL of fresh air enters the lung?
What will be the new PCO2 in the lungs?
40 mmHg/ 760 mmHg = 0.05263
[CO2] = 5.26%
0.05263 x 3L = 157.89 mL of CO2
157.89 mL / 3350 mL = 0.0471
New [CO2] = 4.71%
760 mmHg x 0.0471 = 35.7 mmHg
New PCO2 = 36 mmHg
If the partial pressure of oxygen is 100 mmHg, how many mL of O2 is dissolved in each dL?
100 mmHg PO2 x 0.003 mL O2/ (mmHg PO2 x dL) = 0.3 mL O2/dL
If the partial pressure of oxygen is 40 mmHg, how many mL of O2 is that per dL?
40 mmHg PO2 x 0.003 mL O2/ (mmHg PO2 x dL) = 0.12 mL O2/dL
At a saturation of 100%, how much O2 will be bound to Hgb?
What about at 75% saturation?
20.1 mL O2/dL of blood will be bound to Hgb at 100% saturation.
20.1 x 0.75 = 15 mL O2/dL of blood
Look at the anemia curve. At a PO2 of 100 mmHg, how much O2 mL will be carried/ dL of blood?
Anemia = 6 g Hgb / dL of blood
1.34 mL of O2/ g Hgb
6 g Hgb/ dL of blood x 1.34 mL of O2/ g Hgb = 8.04 mL of O2/ dL of blood
Even with anemia, there is still enough oxygen to meet the metabolic demand of 5 mL of O2/dL of blood for systemic circulation.
Calculate total oxygen in arterial blood.
20.1 + 0.3 = 20.4
CaO2 = 20.4 mL O2/dL of blood
Dr. Schmidt used 100% saturation instead of 97.4% saturation
Calculate total oxygen in venous blood.
15.08 + 0.12 = 15.2
CvO2 = 15.2 mL O2/ dL of blood
Calculate how much O₂ is dissolved per deciliter of arterial blood.
0.3 mL O₂ / dL of blood
Calculate how much O₂ is dissolved per deciliter of venous blood.
(0.003 mL O₂ ÷ 100mL blood x PO₂) x 40 mmHg =
0.12 mL O₂ / dL of blood
What would be the carrying capacity of someone who had a hemoglobin of 10 g/dL and Hb carrying capacity of 1.2 mLO₂ /gHb ?
12 mLO₂ / dL of blood
What is the CaO₂ assuming an SaO₂ of 97.4%, and PO₂ of 100mmHg?
19.88mL O₂ /dL blood
(dissolved: 0.3 mLO₂) + (Hb-bound 19.58 mLO₂)
What is the CvO₂ assuming an SvO₂ of 75%, and PvO₂ of 40mmHg?
15.195 mLCO₂ / dL blood
Dissolved: 0.12 mLCO₂
Bound: 15.075 mLCO₂
How much CO₂ is dissolved in arterial blood?
0.06 mLCO₂ x 40 mmHg (PCO₂) = 2.4 mLCO₂ per dL of blood
What is the partial pressure of CO₂ in Ē (mixed expired air) ?
Find PCO₂ of Ē
PCO₂ of VD = 0
PCO₂ of VA = ?
40mmHg ÷ 760mmHg → [CO₂] of 0.05263 → 350mls (VA) x 0.05263 = 18.42 mLs CO₂ per breath.
18.42 mLs CO₂ ÷ 500mLs = 0.03684 → 760mmHg x 0.03684 = 27.998mmHg
PCO₂ of Ē = 27.998mmHg
How much CO₂ is dissolved in venous blood?
0.06 mLCO₂ x 45 mmHg (PCO₂) = 2.7 mLCO₂ per dL of blood
Give an example of a Bohr equation with numbers.
VTotalDS / VT = (40mmHg - 28mmHg) ÷ 40mmHg
0.3 = VTotalDS ÷ 500mL
VTotalDS = 150mL
How would one find alveolar dead space?
VAlveolarDS = VTotalDS - VAnatomicDS
How can anatomical dead space be estimated?
1mL of deadspace per 1lb of body weight
(Ex. 200lbs = 200mL anatomic deadspace)
Solve for Respiratory System Compliance.
- CL = 0.2
- CCW = 0.2
- x = CRS
(1÷x) = (1÷0.2) + (1÷0.2)
↓
(1÷0.1) = (1÷0.2) + (1÷0.2)
↓
CTotalCompliance(RS) = 0.1L / cmH₂O
A 100kg patient presents with a PĒCO₂ of 25mmHg, a VT of 600mls, and a PaCO₂ of 42mmHg. What would the estimated alveolar dead space of this patient be?
VA = ?
VT = 600mls
VAnatomic = 220mls (100kg x 2.2 = 220lbs)
VD ÷ 600mls = (42 - 25) ÷ 42
VD = 242.86mls
VA = 22.86mls (242.86mls - 220mls)
What is Fick’s Principle/Equation?
CO = O₂ consumption ÷ (CaO₂ - CvO₂)
A patient has the following parameters:
- O₂ consumption of 750 mLO₂ / min
- Hgb of 15g/dL
- SvO₂ of 25%
What is the cardiac output of this patient?
CO = O₂ consumption ÷ (CaO₂ - CvO₂)
CO = 750 mLO₂/min ÷ (20 mLO₂/dL - 5 mLO₂/dL)
CO = 50 dL /min
↓
CO = 5L/min
