Basics of breathlessness

Question 1

What is hypoxia

Answer 1

the main drive for breathlessness

lack of oxygen

Question 2

4 stages of oxygenation

Answer 2

1. Oxygen has to get from the outside to the alveolar capillaries.
2. Oxygen needs to be taken up by Hb in the RBCs.
3. RBCs need to be transported to the areas of oxygen demand.
4. Oxygen is used by the cells in respiration.

Question 3

4 kinds of hypoxia

Answer 3

1. Hypoxic hypoxia
   
   1. Not enough oxygen getting into the blood from the environment (e.g., high altitude, hypoventilation- opiate toxicity, V/Q mismatch- PE)
2. Anaemic hypoxia
   
   1. Insufficient Hb to collect oxygen to carry in the blood
3. Stagnant hypoxia
   
   1. Oxygen in blood is ineffectively circulated to areas of demand
4. Histotoxic hypoxia
   
   1. Sufficient oxygenation to tissues, however cell cannot use it- cardiac failure

Question 4

what is cyanosis

Answer 4

Blue discolouration of the skin or mucous membrane due to the tissues near the skin surface having low oxygen saturation

Question 5

causes of central cyanosis

Answer 5

1. Respiratory
   
   1. (COPD, pneumonia, PE)
2. Cardiovascular
   
   1. (Heart failure, congenital heart disease)
3. CNS (resp depression)
   
   1. (drug overdose)

Question 6

causes of peripheral cyanosis

Answer 6

All causes of central plus

1. Reduced cardiac output
   
   1. (poor stroke volume/ shock)
2. Hypothermia
   
   1. (peripheral blood vessel shut down)
3. Arterial obstruction

Question 7

causes of breathlessness

Answer 7

RESPIRATORY

1. AIRWAYS: COPD, Asthma, Bronchiectasis
2. TISSUE: Interstitial Lung Disease (e.g. Idiopathic Pulmonary Fibrosis, Hypersensitivity Pneumonitis, Asbestosis).
3. PERFUSION: V/Q Mismatch, PE, PA Hypertension (secondary to chronic lung disease and hypo-perfusion).
4. OTHER: Effusion, Pneumonia, Lung Cancer.

Non-RESPIRATORY

1. Hypoxia Related: Anaemia, Cardiac Tamponade (Stagnant Hypoxia), Heart Failure (Stagnant Hypoxia), MI (Stagnant/Cytotoxic).
2. Compensatory: Acidosis, Splinting, Anxiety.

Question 8

causes of hyperventilation

Answer 8

• Physiological stress (i.e. increased CO2 production by active cells).
• Anxiety/Panic.
• Head Injury/Brain Injury.
• Respiratory Disease (e.g. Asthma/Pneumonia/COPD – difficult to eliminate CO2 from the body at normal respiratory rate).
• Cardiovascular Disease (e.g. Heart Failure, Anaemia).
• Acidosis (e.g. DKA, Lactic Acidosis).

Question 9

signs and symptoms of hyperventilation

Answer 9

Dizziness

Breathlessness

Heart palpitation

Numbness

Question 10

Oxygenation and COPD

Answer 10

94%-98% normal target for oxygen saturations

88-92% target oxygen saturations for those with COPD/ hyperventilation risk

Some patients with COPD become chronic CO2 retainers. In these patients, because CO2 is chronically high, the hyperventilation response to CO2 becomes less sensitive, and they rely on a HYPOXIC RESPIRATORY DRIVE instead.

Therefore, if we give uncontrolled oxygen, they lose their hypoxic drive and become bradypnoeic + ↑CO2.

Question 11

cough reflex

• what nerve relays receptor potential?
• which part of the brain recieves this stimulus?
• efferent fibres leave as which 3 efferent nerves?
• which 3 effector muscles are triggered?

Answer 11

• vagus nerve
• medulla oblangata (knwon as the Nucleus tractus solitarius)
• prehnic, spinomotor and recurrent laryngeal nerves
• respiratory muscles, laryngeal muscles and bronchial smooth muscle

Question 12

what products initiate cough

Answer 12

leukotrienes histamine

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