S5. Respiratory Failure

Question 1

Hypoxia vs hypoxaemia

Answer 1

Hypoxaemia= low pO2 in arterial blood

Hypoxia = O2 deficiency at tissue level

Question 2

Effects of hypoxaemia

Answer 2

Acutely

• alteration in mental function (mild confusion)
• tachycardia
• tachypnea (due to triggering of peripheral chemoreceptors)
• cardiac arrhythmias and ishcahemia
• hypoxic vasoconstriction of pulmonary vessles
• central cyanosis (best seen in mucous membranes like mouth and tongue)

Question 3

Causes of hypoxaemia

Answer 3

• low insoired pO2 e.g. high altitude
• ventilation perfusion mismatch
• diffusion defect (problems of the alveolar capillary membrane)
• intra lung shunt (ARDS)
• hypoventilation

Question 4

Adaptations of those with chronic hypoxaemia

Answer 4

• increased EPO secreted by kidney to raise haemoglobin (polycythemia)
• increased 2,3 DPG (shifts Hb curve to right. O2 released more freely)
• increased capillary density

Question 5

Chronic hypoxic vasoconstriction of pulmonary vessels results in

Answer 5

• pulmonary hypertension
• right heart failure
• cor pulmonale