Integrated control of breathing Flashcards
Define respiratory compensation
Increased PaCO2 in the presence of high pH
Decreased PaCO2 in the presence of low pH
Define metabolic compensation
Increased [HCO3⁻]in the presence of low pH
Decreased [HCO3⁻] in the presence of high pH
Define mixed acidosis
simultaneous high PaCO2 + low [HCO3⁻]
Define mixed alkalosis
simultaneous low PaCO2 + high [HCO3⁻]
How does panic attack lead to respiratory alkalosis?
- Anxiety trigger → panic attack
- Increased ventilation (tachypnoea) w/o increased metabolic demand
- Hyperventilation → Decreased PaCO2
- Respiratory alkalosis
How does altitude lead to respiratory alkalosis?
- 8000ft, PAtm ≈ 75kPa
- 21% O2 x 75kPa ≈ 15kPa, CO2 ≈ 0kPa
- ↑ alveolar ventilation maintains PAO2 and PaO2 (via hypoxic drive)
- Increased ventilation = ↓PaCO2
- Respiratory alkalosis
How does sepsis lead to metabolic acidosis?
Infection ↓ Pathological immune response ↓ Septic shock ↓ ↓oxygen delivery to tissues (hypoxia) ↓ ↑Lactic acid production & ↓pH
How is sepsis overcome?
Respiratory compensation to ↑O2 delivery and ↑lactic acid conversion
How does diabetic ketoacidosis lead to metabolic acidosis?
↑ fatty acid release from liver due to insulin deficiency =
↑ (acidic) ketone body production
How does renal failure lead to metabolic acidosis?
decreased HCO3- reabsorption in proximal tubule
How does diarrhoea lead to metabolic acidosis?
decreased HCO3- absorption in colon
Why does PaCO2 does not increase during exercise in healthy individuals?
ventilation increases before extra CO2 produced by muscles can increase PaCO2
Why does minute ventilation of lungs increase rapidly after exercise begins?
direct feedback between muscle activity/motor cortex and respiratory centres, changes in body temperature, or micro-oscillations in PaO2/PaCO2
