(15) Ventilation/Perfusion Relationships

Question 1

(Terminology)

1. excess of CO2 in blood
2. deficiency of CO2 in blood

Answer 1

1. hypercapnea, hypercarbia
2. hypocapnea, hypocarbia

Question 2

(terminology)

1. increased amount of air entering the alveoli resulting in lowered PCO2 and respiratory alkalosis
2. decreased amount of air entering the alveoli resulting in increased PCO2 and respiratory acidsois
3. decrease in arterial PO2
4. decrease in O2 delivery to, or utilization by, the tissues

Answer 2

1. hyperventilation
2. hypoventilation
3. hypoxemia
4. hypoxia

Question 3

(Regulation of Pulmonary Blood Flow)

1. When there is a hypoxemia (and hypoxia) what has the body adapted to account for this?
2. Give me the order of the things leading to hypoxic vasoconstriction (starting with alveolar hypoxia)
3. What are other factors?

Answer 3

1. a mechanism for the constriction of blood vessels to that site so the animal is not wasting blood flow to areas that aren’t being ventilated
2. Alveolar hypoxia –> vascular smooth muscle depolarization –> voltage gated Ca2+ channels –> Ca2+ entry and binding –> Vascular smooth muscle contraction
3. Fetal Circulation, Prostanoids (he didnt’ really mention these)

Question 4

(Distribution of Pulmonary Blood Flow)

In the human lung the distribution of blood flow is uneven and driven by gravitational effects - we aren’t learning about humans though dammit

Are there zones in the animal lung like there are in the human?

What is the horse lung like?

Answer 4

no not really - kind of in apes

distribution of blood flow in the equne lung is more even and less driven by gravitational effects (this is typical of most animals)

Question 5

(Assessment of Ventilation/Perfusion Relationship by Arterial Blood Gas)

(Assessing abnormal PCO2 levels)

1. How is adequacy of alveolar ventilation diagnosed?
2. Is there a diffusion impediment for movement of CO2 between capillaries and alveolar air?
3. Does arterial PCO2 accurately reflect alveolar PCO2?

Answer 5

1. by arterial PCO2 measurements
2. no
3. yes

Question 7

(Assessment of Ventilation/Perfusion Relationship by Arterial Blood Gas)

(Assessing abnormal PO2 levels)

1. Is adequate movement of O2 into the capillary blood affected by only ventilation?
2. Does arterial PO2 accurately reflect O2 levels in the alveoli?

Answer 7

1. no, effectd by other factors as well
2. it may not scott

Question 8

(Alveolar Hypoventilation)

1. What is the Hallmark?
2. Defines what?
3. What are the four causes?

Answer 8

1. Increased PCO2 and low PO2
2. Respiratory acidosis

3.

1. Bronchoconstriction (inflammation, allergy, obesit, sleep apnea syndrome) - bulldog with shoved in face
2. Brachycephalic Airway Syndrome
3. Increated anatomic deadspace - tracheal tubes
4. anesthetic gases, particularly barbituates

Question 9

(Alveolar Hyperventilation)

1. What is the hallmark?
2. What does it define?
3. What are the 3 causes?

Answer 9

1. decreased PCO2 and increased PO2 in alveoli
2. respiratory alkalosis

3.

1. overzealous mechanical ventilation
2. pulmonary thromboembolism (in the picture)
3. excessive panting (tachypnea)

Question 10

Assessment of Hypoxemia (5 major causes)

1. What are the 5 major causes?

Answer 10

1. hypoventilation (hypoalveolar ventilation)
2. low inspired PO2 (high altitude breathing)
3. Pulmonary diffusion impairment
4. righ-to-left shunts
5. ventilation/perfusion (V/Q) mismatch

Question 11

(Hypoxemia Cause #1 - Alveolar Hypoventilation)

• these are the same things as described in the alveolar hypoventialtion slide

Question 12

(Hypoxemia Cause #2 - Low Inspired PO2)

1. What is the cause of low inspired PO2?

Answer 12

1. high elevation

Question 13

(Hypoxemia Cause #3 - Pulmonary Diffusion Impairment)

1. Is PO2 normal or abnormal in the alveolus? What is impaired?
2. What are three disease states that can cause this?

Answer 13

1. normal, diffusion is impaired
2. Pneumonia, pulmonary edema, pneumonitis - in the picture (inflammatory)

Question 14

(Hypoxemia Cause #4 - right-to-left shunts)

1. What are two types of shunts that cause this?

Answer 14

1. Pulmonary circulation shunts (if alveoli collapse), cardiac arterio-venous shunts

Question 15

(Ventiliation/Perfusion Relationships)

• any number of these
  1. Diagrammatically do what?
  2. What does this represent?
  3. What are two causes of this?

Answer 15

1. loss of reoxygentation of blood
2. serious discrepancy between alveolar ventilation and capillary perfusion
3. pulmonary embolism, lateral recumbency in horses (compress a lung cause of weight)