CAL: respiratory pathophysiology

Question 1

What is a unilateral pneumothorax?

Answer 1

Pleural pressure atmospheric on one side. Leads to collapse of the lung. Lung remains perfused but is underventilated. This causes a ventilation-perfusion mismatch.

Question 2

What are the 2 broad causes of ventilation-perfusion mismatch? Examples?

Answer 2

• OBSTRUCTIVE PULMONARY DISEASE: nasal obstruction, trauma, BOAD, tracheal collapse
• COMPROMISE OF THE THORACIC CAVITY: fluid/air in pleural space, cardiomegaly, displacement of abdominal organs

Question 3

T/F: The amount of O2 offloaded in the peripheral tissues is always the same, irrespective of the level of arterial oxygen content.

Answer 3

True

Question 4

What is the physiological benefit of the relationship between PaO2 and SaO2?

Answer 4

The body is still able to transfer same amount of oxygen to the tissues with only one functioning lung.

Question 5

How is blood shunted away from perfusing the non-functioning lung?

Answer 5

The resistance to BF increases.

Question 6

What factors affect perfusion? How?

Answer 6

hypoxia (when alveolar O2 decreases below about 73mmHg BVs constrict. Opposite to systemic circulation. Effect = to distribute BF to where it is most effective.

Question 7

Define hypobaria

Answer 7

low ambient air pressure, this is present at altitude.

Question 8

What causes hypoxia acutely when a patient moves to altitude?

Answer 8

Decreased inspired oxygen due to a lower atmospheric partial pressure of oxygen.

Question 9

List the main adaptations to higher altitude.

Answer 9

– HYPERVENTILATION increased RR, - increased respiratory depth

• increased Hb concentration,
• increased RBC concentration (POLYCYTHAEMIA)
• increased Hb affinity for oxygen (also affected by temperature and pH).

Question 10

Define polycythaemia

Answer 10

having a high RBC concentration in your blood (therefore increases you Hb concentration and is an adaptation to altitude).

Question 11

What are other adaptations to altitude? 6

Answer 11

• Increases sensitivity of the carotid body to hypoxia
• Rightward shift of the O2 dissociation curve (moderate altitudes) or leftward shirt (higher altitudes)
• Number of capillaries per unit volume in peripheral tissues increases
• changes in the oxidative enzymes inside the cells
• maximum breathing capacity increases
• hypoxic pulmonary vasoconstriction.

Question 12

Does anaemia cause hypoxia?

Answer 12

Depends on where the hypoxia is

Question 13

Define hypoxia

Answer 13

insufficient levels of oxygen in blood or tissues.

Question 14

How is O2 carried in the blood?

Answer 14

97% bound to Hb. 3% is freely dissolved.

Question 15

Why do anaemic changes often have a tapping pulse? 2

Answer 15

due to lowered viscosity of blood AND due to vasodilatation of peripheral vasculature.