Basic and Applied Sciences (anatomy, physiology, pharmacology, physics and equipment)
Core science the exam applies
The Basic and Applied Sciences domain tests how anatomy, physiology, pharmacology and physics explain anesthesia practice. Expect respiratory and cardiovascular anatomy, oxygen delivery, receptor pharmacology, gas laws, vaporizers and breathing-circuit physics.
- Oxygen cascade: PiO2 = FiO2 × (Patm − 47 mm Hg). At sea level, room air gives about 150 mm Hg; alveolar PAO2 then falls by PaCO2/R.
- FRC is about 30 mL/kg; it falls with supine position, obesity, pregnancy, anesthesia and abdominal insufflation. Closing capacity rises with age; when closing capacity exceeds FRC, atelectasis and shunt increase.
- Laplace: P = 2T/r. Small alveoli need surfactant to avoid collapse; surfactant deficiency explains neonatal RDS and why recruitment matters.
- Bernoulli/Venturi: a jet of gas creates low pressure and entrains air; this underlies nebulizers, Venturi masks and injectors.
- Vaporizer output depends on agent-specific vapor pressure, temperature compensation and flow over the liquid; desflurane needs a heated, pressurized vaporizer.
- MAC: sevoflurane about 2%, isoflurane about 1.15%, desflurane about 6%, nitrous oxide about 105%. MAC is a potency marker, not an immobility guarantee.
Worked example
An E cylinder reads 1,000 psi. A full E cylinder at 2,200 psi holds about 660 L. Remaining volume = (1,000/2,200) × 660 ≈ 300 L. At 5 L/min, duration ≈ 300/5 = 60 minutes. If flow rises to 10 L/min, duration halves to 30 minutes. The reasoning uses the linear pressure-volume relationship for a compressed gas cylinder, not gauge pressure alone.
Traps that cost marks
Do not confuse partial pressure with concentration; FiO2 100% at altitude still gives a lower PiO2. Do not treat pulse oximetry as ventilation. Do not apply adult FRC values to infants. Do not assume a vaporizer delivers a set percentage if it is tilted, overfilled or used at high altitude without correction.