3.6.4. Shunt and V/Q Relationships Flashcards Preview

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Flashcards in 3.6.4. Shunt and V/Q Relationships Deck (16)
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1

How can we categorize respiratory failure?

1. Hypoxemic (Type I): oxygenation failure
2. Hypercarbic (Type II): ventilation failure (resp. pump fails in CO2 elimination)

2

What are the 5 causes of hypoxemia?

1. low inspired oxygen content
2. hypoventilation
3. diffusion abnormality
4. V/Q mismatch
5. Shunt

3

Define ventilation:

rate of air entering alveoli

4

Define perfusion:

rate of transfer of oxygen and carbon dioxide through respiratory membrane, determined by blood flow

5

What does a ventilation-perfusion ratio (V/Q) of zero mean?

-this means that there is no alveolar ventilation and alveolar gases equilibrate with blood gases
-in other words, there is more blood flow than ventilation at the lung base (shunt)

6

What does a high ventilation-perfusion ratio (V/Q) mean? (we talk about this in terms of infinity)

-there is no capillary blood flow and alveolar gases equilibrate with humidified inspired air
-in other words, there is more ventilation than blood flow at the lung apex (V/Q=infinity=dead space)

7

What are some causes of shunt?

1. Pulmonary: pneumonia, ARDS, near drowning, alveolar filling processes like blood, pus and cells
2. Cardiac: atrial septal defects, ventricular septal defects
3. Extracardiac: arterial venous malformations, hepatopulmonary syndrome

8

What could be causing hypoxia with a white x-ray?

-Pneumonia
-ARDS
-Pulmonary Edema
-Interstitial Lung Disease

9

What could cause V/Q mismatch?

-Pulmonary embolism
-Asthma
-COPD
-CHF

10

How is Type II Hypercarbic/Ventilatory Failure defined?

-defined by an elevated level of CO2 in the blood

11

What are some causes of respiratory failure due to abnormal airways?

-COPD
-Asthma
-Cystic fibrosis

12

What are some causes of respiratory failure due to peripheral neuromuscular weakness?

-Guillain-Barre Syndrome
-spinal cord injury
-polio
-botulism

13

What causes increased dead space (no chance for gas exchange in that unit)?

1. Anatomic: large airways, masks (if not vented)
2. Physiologic: pulmonary embolism, asthma

14

What causes increased CO2 production?

-Fever
-Sepsis
-Malignant Hyperthermia
-High Carbohydrate diet? (not really)
-Overfeeding (RQ>1.0)

15

Why is Ventilation/Perfusion matching important for respiratory function?

Effective gas exchange critically depends on the relationship between ventilation and perfusion in the gas exchange units.

16

What is a normal physiologic adaptation to adjust V/Q (matching)?

Hypoxic vasoconstriction