Ventilation/Perfusion Flashcards
COPD causes
Long term exposure to toxic particles and gases
Rare genetic disorder called alpha-1 antitrypsin deficiency
Second hand smoke
Air pollution
Repeated lung infections as a child
COPD
Chronic obstructive pulmonary disease
Airflow limitation that is not reversible
Progressive
Abnormal inflammatory response of the lungs to noxious particles or gases
Ultimately ends in respiratory failure and death
Destruction of the lung and airflow obstruction
Increased compliance
COPD is mainly a combination of…
Chronic bronchitis (cough and sputum) Emphysema (dyspnea, no sputum)
Emphysema
Alveolar wall destruction with irreversible enlargement of the air spaces distal to the terminal bronchioles and without evidence of fibrosis
Chronic bronchitis
Productive cough that is present for a period of 3 months in each of 2 consecutive years
Absence of another identifiable cause of excessive sputum production
What percentages of FEV1 are classified as
- Mild
- Moderate
- Severe
- < 80%
- < 65%
- < 50%
What would you see in the histology of a COPD patient?
Increased mucus production causing a plugging of the airways
Inflammation of the bronchi
Infiltration with chronic inflammatory cells (CD8+)
Thickness of walls inducing narrowing of the small airways (airflow limitation)
Loss of elastic recoil causing an increase in compliance
How much air is in the anatomical dead space?
~150mL
Alveolar dead space
Accounts for diseased area in the lungs
Alveoli not perfused
Physiological dead space
Anatomic dead space + alveolar dead space
The total volume of the lungs which does not participate in gas exchange
Alveolar ventilation
Amount of air participating in gas exchange
Minute ventilation corrected for the dead space
How does the PACO2 change with VA
Increases in alveolar ventilation cause a decrease in PA CO2
Decreases in alveolar ventilation cause an increase in PACO2
Hypoventilation
Increase in ratio of CO2 production to alveolar ventilation
Alveolar PCO2 > 40 mmHg
Hyperventilation
Decrease in ratio of CO2 production to alveolar ventilation
Alveolar PCO2 < 40 mmHg
Minute ventilation is changed by which 3 factors?
- Arterial Pco2
- Plasma [H+]
- Arterial Po2 (but only after it drops to 60 mmHg)
Where is there the most blood flow in the lungs?
At the base
The lower lung also ventilates best
Pulmonary circulation is characterized by… (3)
Low pressure and low resistance
Same blood flow as systemic circulation
Uneven blood flow (gravitational effect)
What is the ideal ventilation/perfusion ratio?
0.8
What is the VQ ratio for
- Airway shunt
- Pulmonary embolus
- 0 (no ventilation)
2. infinity (no perfusion)
Hypoxia
An inadequate oxygen delivery to tissues
4 types of hypoxia
Hypoxic hypoxia
Anemic hypoxia
Ischemic hypoxia
Histotoxic hypoxia
Hypoxic hypoxia
Hypoxemia
Arterial PO2 is reduced
Can be caused by a lack of oxygenated air, pulmonary problem, lack of ventilation-perfusion coupling
Getting a low oxygenation of the blood
Anemic hypoxia
Total blood O2 content is reduced due to inadequate number of RBCs, deficient or abnormal Hb, or competition for Hb by CO (ex: CO poisoning)
Ischemic hypoxia
Blood flow to tissues is too low
Ex: due to obstruction of a blood vessel
Histotoxic hypoxia
Quantity of O2 reaching tissues is normal, but cell is unable to use it due to interference with cell’s metabolic apparatus
Ex: cyanide poisoning
Why does the lower lung ventilate best?
No weight load
Alveoli can shrink
High compliance
