Respiratory Equations & Review Clickers

Question 1

What is the equation for minute ventilation?

Answer 1

Ve = VT x f

Tidal volume times frequency

Question 2

What is the equation for alveolar ventilation?

Answer 2

VA = (VT x f) - (VD x f)

VD = dead space volume

Question 3

What is the equation for alveolar ventilation based on exhaled CO2?

Answer 3

PACO2 = (0.863) x VCO2/VA

Question 4

What is the Alveolar Gas equation?

Answer 4

PAO2 = (760-pH2O)(0.21) - PaCO2/0.8

Question 5

What is the equation for pulmonary vascular resistance?

Answer 5

R = deltaP/Q

deltaP = pressure diff b/n pulm. artery and left atrium

Question 6

What is the normal A-a difference?

Answer 6

=2.5 + 0.21(age)

Question 7

What is the equation for anion gap?

Answer 7

DeltaAG = Na - Cl - HCO3

Question 8

Contraction of the abdominal muscles is important in:

A. normal (quiet) inspiration
B. forced (maximum) inspiration
C. normal (quiet) expiration
D. forced (maximum) expiration
E. none of the above

Answer 8

D. Forced (maximum) Expiration

Question 9

Air moves out of the lungs when the pressure inside the lungs is:

A) less than the pressure in the atmosphere.
B) greater than the pressure in the atmosphere.
C) equal to the pressure in the atmosphere.
D) greater than the intra-alveolar pressure.

Answer 9

B) greater than the pressure in the atmosphere.

Question 10

Pulmonary function testing supports the diagnosis of COPD. What would you anticipate his lung compliance to be?

A. Normal
B. Less than normal
C. More than normal

Answer 10

C. More than normal

Question 11

What is the equation for Compliance?

Answer 11

CL = delta V / Delta Transpleural pressure

Question 12

The patient inspires 600 ml from a spirometer. Pleural pressure before inspiration is –5 cm H2O and –7cm H2O at the end of inspiration. What is his compliance?

A.  200 ml/cm H20
B.  300 ml/cm H20
C.  100 ml/cm H20
D.  150 ml/cm H20
E.  550 ml/cm H20

Answer 12

B. 300 ml/cm H20

Question 13

What is the normal compliance of the lung?

Answer 13

200 mL/cmH2O

Question 14

The patient has an alveolar ventilation of 3 L/min, a frequency of 10 breaths/min, and a tidal volume of 700 ml. What is his “physiologic” dead space ventilation per minute?

A.  1 L/min
B.  2.5 L/min
C.  3 L/min
D.  4 L/min
E.  7 L/min

Answer 14

D. 4 L/min

Question 15

At which of the following sites is the partial pressure of oxygen (PO2) highest?

A. exhaled gas
B. anatomical dead space at the end of expiration
C. anatomical dead space at the end of inspiration
D. alveolar gas
E. about the same in all of the above (100 mmHg)

Answer 15

C. anatomical dead space at the end of inspiration

Question 16

In a young, healthy individual, the alveolar-arterial blood (A-a) difference is:

A. Less than 3 mm Hg
B.Created by venous admixture and anatomic shunt
C. Unaffected by bronchial circulation
D.23-27 mm Hg
E. Affected by barometric pressure changes

Answer 16

B.Created by venous admixture and anatomic shunt

Question 17

You obtain ABG’s on room air as part of your evaluation: pH 7.36/PCO2 58/PO2 56. What is the A-a gradient?

A.  12.5
B.  21.5
C.  56.5
D.  77.5
E.  94.5

Answer 17

B. 21.5

Question 18

What causes of hypoxemia cause an elevated A-a difference?

Answer 18

• a diffusion abnormality
• a Shunt
• Dead space

Question 19

A 33 year old man has a motor vehicle accident and is brought to the ER. Initial labs show a Hgb/Hct of 15/45, WBC of 4.8, Platelet count of 350K. His initial ABG is pH7.45/PaCO245/PaO2 100/Sat 98%.
What is his arterial blood oxygen content?

A.  20 ml O2/dL
B.  30 ml O2/dL
C.  40 ml O2/dL
D.  50 ml O2/dL
E.  60 ml O2/dL

Answer 19

A. 20 mL O2/dL

Question 20

What is the equation for arterial blood content?

Answer 20

Cao2 = (Hb x 1.34 x SaO2) + (0.003 x PaO2)

Question 21

In the plasma, the quantity of oxygen in solution is:

A. only about 1.5% of the oxygen content
B. the majority of the oxygen content
C. about equal to the oxygen combined with hemoglobin
D. greater than the oxygen combined with hemoglobin
E. not present except where it is combined with carrier molecules

Answer 21

A. only about 1.5% of the oxygen content

Question 22

How is the bulk of carbon dioxide carried in blood?

A) chemically combined with the amino acids of hemoglobin as carbaminohemoglobin in the red blood cells
B) as the bicarbonate ion in the plasma after first entering the red blood cells
C) as carbonic acid in the plasma
D) chemically combined with the heme portion of hemoglobin

Answer 22

B) as the bicarbonate ion in the plasma after first entering the red blood cells

Question 23

Decreased affinity of hemoglobin for oxygen is associated with:

A.An increase in PCO2
B.Metabolic alkalosis
C.2,3 DPG depletion
D. Leftward shift in the oxyhemoglobin equilibrium curve
E.Cooling form 37 to 32°C

Answer 23

A.An increase in PCO2

Question 24

Assume that CO2 production is constant; what factor determines PaCO2 most directly?

A.Tidal volume
B.Minute ventilation
C.Breathing frequency
D.Alveolar ventilation
E.Dead space ventilation

Answer 24

D.Alveolar ventilation

Question 25

Assuming a normal CO2 production, what would you estimate as the alveolar ventilation associated with the following arterial blood gases: pH 7.31, PaCO2 66, PaO2 54? ``` A. 2512 ml/min B. 2615 ml/min C. 3390 ml/min D. 5290 ml/min E. 6615 ml/min ```

Answer 25

B. 2615 ml/min

Question 26

Which of the following contribute to alveolar dead space? A.   Alveoli that are ventilated but not perfused B.  Alveoli that are perfused but not ventilated C.  Gas exchange regions with low VA/Q D.  Dilation of peripheral airways E. Trachea and main stem bronchi

Answer 26

A.   Alveoli that are ventilated but not perfused

Question 27

Which of the following would decrease venous admixture (shunt)? A.  An increase in bronchial blood flow B.  Inhaling a peanut C.  Changing from supine to upright posture D.  Increasing regional VA/Q from 0.6 to 0.9 E.  Decreasing ventilation

Answer 27

D.  Increasing regional VA/Q from 0.6 to 0.9

Question 28

Which of the following would most likely promote pulmonary edema? A.   Mechanical ventilation using positive inflation pressures B.   Loss of surfactant C.   Fall in pulmonary artery pressure D. Increased colloid osmotic pressure E.    Driving from high altitude to sea level

Answer 28

B.   Loss of surfactant

Question 29

According to Fick’s law, which of the following changes would decrease gas diffusion in the lung: A. Increase surface area of the blood-gas interface B.  Decrease molecular weight of the gas C.  Increase thickness of the blood –gas interface D.  Increase the partial pressure differential of the gas across the blood-gas interface E. Increase solubility of the gas

Answer 29

C.  Increase thickness of the blood –gas interface

Question 30

When is the resistance to blood flow of the pulmonary vascular bed lowest? A. When a person is at rest sitting up B. When a person is at rest lying down C. When a person is breathing air at high altitude D. When a person is exercising maximally E. None of the above because pulmonary vascular resistance is constant

Answer 30

D. When a person is exercising maximally

Question 31

The apex of the upright human lung compared with the base has: ``` A. A higher Po2. B. A higher ventilation. C. A lower pH in end-capillary blood. D. A higher blood flow. E. Smaller alveoli. ```

Answer 31

A. A higher Po2.

Question 32

Which of the following is representative of Zone 3 of pulmonary circulation? ``` A. Pv > Pa > PA B. PA > Pa > Pv C. PA > Pv > Pa D. Pa > PA > Pv E. Pa > Pv > PA ```

Answer 32

E. Pa > Pv > PA

Question 33

The most important afferent (sensory) receptors for the respiratory response to systemic arterial carbon dioxide (Pa-CO2) are the: A. CO2 receptors of the aortic and carotid bodies B. H+ receptors of the aortic and carotid bodies C. CO2 receptors in the medulla of the brain D. H+ receptors in the medulla of the brain E. CO2 receptors in the airways and lungs

Answer 33

D. H+ receptors in the medulla of the brain