3. Lung physiology part 2

Question 1

How does haemoglobin bind to oxygen?

Answer 1

Co-operatively. Forming the first bond is the hardest but after that oxygen is accepted. Opposite is true at tissue.

Question 2

Describe the process of oxygen binding to foetal haemoglobin and myoglobin

Answer 2

Foetal haemoglobin- heamoglobin produced by children
Myoglobin- released by muscles in reposne to exercise

Both have a higher affinity for oxygen and so take priority in oxygen binding over hemoglobin.

Question 3

How does pH affect the binding of oxygen to heamoglobin?

Answer 3

Acidosis (exercise)- oxygen is released more freely

Alkalosis- oxygen is held onto

Question 4

How does carbon dioxide affect oxygens binding to heamoglobin?

Answer 4

Low CO2- oxygen is held onto

High CO2 (waste product of cellular respiration)- oxygen is freely let go

Question 5

How does temperature affect oxygen binding to heamoglobin?

Answer 5

Low temperature- oxyegn is held onto

High temperature (body working hard)- oxygen is released more freely

Question 6

How does 2,3 DPG (allosteric effector of heamoglobin) ((EPO)) affect oxygen binding

Answer 6

No 2,3 DPG- oxygen held onto

High 2,3 DPG (occurs in hypoxia) oxygen more readily freed

Question 7

What are the five main types of hypoxia?

Answer 7

Hypoxaemic hypoxia- reduced oxygen ventilation

Anemic hypoxia- reduced O2 due to anaemia

Stagnant hypoxia- Heart disease results in inefficient pumping of blood

Histotoxic hypoxia- poison

Metabolic hypoxia- oxygen delivery to the tissues does not meet increased oxygen demand by cell

Question 8

How does carbon dioxide affect acid base balance?

Answer 8

Hypoventilation (increased CO2) leads to increased hydrogen ions

Hyperventilation (reduced CO2) leads to decreased hydrogen ions

Question 9

How is ventilation controlled?

Answer 9

Respiratory centers in the pons and medulla fire repetitive action potentials which travel to inspiratory muscles to set a co-ordinated rhythm of breathing.

Question 10

What affects the firing of action potentials from respiratory centres?

Answer 10

Emotion

Voluntary override (via higher centres in the brain)

Mechano-sensory reflex (e.g. stretch receptors detectign deep breath)

Change in composition of the blood detected by chemoreceptors

Question 11

Describe where chemoreceptors lie?

Answer 11

Medulla (centrally)- respond to PCO2 (greater stimulus of ventilation)

Carotid and aortic bodies (peripherally)- respond to H+ and PO2

Question 12

How do durgs affect chemoreceptors?

Answer 12

Barbituates adn opidos depress repiratory centres in the brain

Nitrous oxide blunts peripheral chemoreceptors which is problematic to those with chronic lung disease who rely on hypoxic drive

Question 13

What does the colour of sputum tell you about the underlying pathology

Answer 13

Clear and colourless- chronic bronchitis

Yellow/green/brown- pulmoanry infection

Red- haemoptysis

Frothy pink- pulmonary oedema

Question 14

What are the normal oxygen saturation levels for a patient

Answer 14

Normal 94-98%

Pre existign apthologies that rely on hypoxic drive- 88-92%

Question 15

What are the different examples of a obstructive lung disease

Answer 15

Asthma, COPD, bronchiecstasis, CF

Question 16

What are the different examples of a restrictive lung disease?

Answer 16

Fibrosis, Sarcoidosis, Pneumoconiosis, connective tissue diseases, pleural effusions, obesity, kyphoscoliosis, neuromuscualar problems

Question 17

Describe the indications for performing a bronchoscopy?

Answer 17

Suspected lung cancer, slow resolving pneumonia, interstitial lung disease- diagnostic

Aspiration of mucous plugs, removal of foreign bodies, stenting tumours- therapeutic

Question 18

What investigations should e doen before carrying out a bronchoscopy?

Answer 18

FBC, coagulation, CXR, CT, spirometery, pulse oximetery.

Question 19

How can you perform lung biopsies?

Answer 19

Percutanous lung biospy (peripheral and pleural lesions)

Transbronchial biopsy- done with a bronchoscopy for interstitial lung disease, sarcoidosis, idiopathic pulmonary fibrosis

Question 20

What is a mediastinoscopy?

Answer 20

Allows examination and biopsy of mediastinal lymph nodes and lesions

Question 21

What is a thorascopy?

Answer 21

Allows eamiantion of pleural lesions, drainage of pleural effusions and pleurectomy

NOTE- can also drain pleural effusions using thoracentesis