Exam 2 - Topic 3 - Electrical Safety Flashcards
Ground
- safety feature for current to flow through in case of short
Systemic pressure
- LV to RA
Pulmonary pressure
- RV to LA
Ohm’s law applied to the CV circulation
- V = IR
Or…. - BP = Q*SVR
Poiseuille’s law of Flow
Q = (pressure diff)(pi)(r^4) / (L)(V)(8)
V = viscosity
- Radius affects flow the most since a factor of 4
Poiseuille’s law of Resistance
R = (8)(V)(L) / (pi)(r^4)
Laminar flow
- smooth flow in one direction
- ideal for CPB
Turbulent flow
- Random flow in multiple directions
- Not smooth
- Good for Oxygenators but nothing else
Why is electricity dangerous
- Tissue injury (tissue acts as resistor)
- Uncontrolled muscle contraction
- Fib of heart
Ventricular Fib
- Random stimulation of heart
- CO is zero when this happens
Leakage current
- Inherent current that escapes electronic device when used
- All electrical equipment has some leakage current
Macroshock
- Travels through whole body and skin and tissue
- high value arm to arm current that eventually passes through heart
- miliamps
Microshock
- Low value current that passes directly though heart
- microamps
- cannot go through skin/tissue but dangerous directly to heart
Human resistance value
1000 ohms
Macroshock thresholds
1-10 mA : can just feel it / still harmless
10-20 mA : painful / the “let go” threshold
20-50 mA : extreme pain / cannot let go / heart and lungs still ok
100-200 mA : nerve damage / VFib / lungs still ok / pass out
200+ : cardiac arrest / sever burns / possible death
SAFE = 5 mA for 60 Hz leakage
