83 - Physiological Consequences of Elevated Pulmonary Pressure

Question 1

What does airflow obstruction result in?

Answer 1

Gas exchange difficulties, especially if there is low V/Q.

Question 2

Abestosis

Answer 2

A form of diffuse interstitial lung disease from exposure to asbestos fibres.
When inhaled, asbestos fibres can’t be broken down, can lead to progressive, diffuse inflammation and fibrosis.
Arises ~8-10 years after heavy exposure.

Question 3

Pathology of asbestosis

Answer 3

Causes a gas exchange and mechanical defect at capillary-alveoli membrane.
Decreased PaO2, increased A-a gradient, decreased lung volumes (restrictive ventilatory defect), decreased compliance, increased work of breathing.

Question 4

How do people with asbestosis present?

Answer 4

Clubbing, crepitations, +/- cyanosis.

Exertional breathlessness, cough

Question 5

What can sinus tachycardia mean?

Answer 5

Reduced stroke volume. Increase contraction rate to compensate

Question 6

What does right ventricular heave mean?

Answer 6

Right ventricle is contracting at a higher pressure than it is used to.

Question 7

What does tricuspid pansystolic murmur mean?

Answer 7

Incompetent tricuspid valve (can be from defective valve or from dilated ventricle, pulling on valve leaflets)

Question 8

What is spasm of pulmonary arterioles?

Answer 8

Lack of ventilation of bronchioles can lead to contraction of smooth muscle in arterioles leading to these gas exchange units.

Question 9

Does oxygen desaturation normally occur with exercise?

Answer 9

No

Question 10

Interstitial lung disease

Answer 10

A problem at the alveolar-capillary membrane

Question 11

How can you tell if someone has interstitial lung disease?

Answer 11

Shows up on a chest X-ray and can hear crepitations

Question 12

Diagnostic tests for pulmonary arteries
1
2

Answer 12

1) Pulmonary angiogram (dye is injected into a peripheral vein, a CT scan is performed to see where in the pulmonary circulation the dye goes)
2) Ventilation/perfusion scan (breathe in a radioactive substance, and inject radioactive substance. Injected substance gets lodged in pre-capillary arterioles). See if areas of ventilation and perfusion match up.

Question 13

What can a ventilation/perfusion test tell you?

Answer 13

If a problem with the lungs is due to a blockage of pulmonary vessels or obstruction of airways.

Question 14

What is the effect of pulmonary hypertension on right atrial and systemic venous pressures?

Answer 14

They increase

Question 15

Effect of increased systemic venous pressure on the systemic capilary bed

Answer 15

If severe enough, leads to peripheral oedema, ascites, pleural effusions

Question 16

Cor pulmonalae

Answer 16

Right heart failure from excessive pulmonary circulation pressure

Question 17

Causes of pulmonary hypertension
1
2
3

Answer 17

1) Increased pulmonary vascular resistance
2) Increased left atrial pressure
3) Increased pulmonary blood flow

Question 18

Causes of increased pulmonary vascular resistance
1
2
3

Answer 18

1) Vasoconstriction (low alveolar O2, EG: hypoventilation)
2) Obstruction (embolism, primary pulmonary hypertension)
3) Obliteration of vascular bed (arteritis, emphysema, pulmonary fibrosis)

Question 19

Right ventricular failure effects
1
2
3
4
5

Answer 19

1) Pulmonary hypertension leads to
2) Right ventricular dilation and hypertrophy, leading to
3) Increased systemic venous pressure, which leads to
4) Extravasation of fluid into tissues, peritoneal space, pleural spaces.
5) Right heart failure also leads to decreased cardiac output, which results in lassitude, tiredness.

Question 20

Primary abnormalities of acidosis
1
2

Answer 20

Respiratory acidosis from CO2 retention (hypoventilation)

Metabolic due to loss of HCO3 or addition of acid

Question 21

Compensatory mechanisms behind acidosis
1
2

Answer 21

1) Bicarbonate retention for respiratory acidosis (days)

2) Hyperventilation (low PaCO2) for metabolic acidosis (seconds)

Question 22

Examples of metabolic acidoses

Answer 22

Keto-acidosis (from starvation)
Lactic acid buildup
Diarrhoea (causes loss of bicarbonate)

Question 23

Which part of the body is responsible for bicarbonate retention

Answer 23

Kidneys

Question 24

Normal bicarbonate compensation for increasing CO2

Answer 24

~3.5mmol/L per 10mmHg increase CO2

Question 25

Primary alkalotic disorders
1
2

Answer 25

1) Respiratory due to low CO2 (hyperventilation)

2) Metabolic due to increased HCO3 or loss of acid

Question 26

Way for body to lose acid

Answer 26

Vomiting

Question 27

Compensation for respiratory alkalosis

Answer 27

Bicarbonate excretion (kidneys) for respiratory alkalosis

Question 28

Compensation for metabolic acidosis

Answer 28

Mild hypoventilation (can’t be much, as you still need to breathe in oxygen)

Question 29

Why is the body’s response to severe metabolic alkalosis limited?

Answer 29

Can’t reduce breathing rate much

Question 30

Normal serum bicarbonate concentration

Answer 30

22-29mmol/L

Question 31

If there is high PaCO2, does HCO3 have to be high from renal compensation?

Answer 31

Not necessarily, as elevated HCO3 can come about from elevated CO2 being in the blood (increased carbonic acid being made)

Question 32

How can you tell if an acid/base disorder is compensated from wither acidosis or alkalosis?

Answer 32

pH doesn’t return completely to normal. If a compensated alkalosis, pH will be at high end of normal, if compensated acidosis, will be at low end of normal.