Rheobase And Chronaxie Time Flashcards Preview

IBHRE Exam > Rheobase And Chronaxie Time > Flashcards

Flashcards in Rheobase And Chronaxie Time Deck (10):

Define Rheobase

Rheobase is the lowest point on a strength duration curve at an infinitely long pulse duration.


In cardiac pacing, when is Rheobase Usually reached?

Between one and 2 ms, at shorter durations, threshold rises


Define chronaxie time

Chronaxie time Is the pulse width at twice the rheobase value

Chronaxie time Approximates the most efficient stimulation pulse duration


Define the strength duration curve

The quantity of charge, current, voltage, or energy required to stimulate the heart at a series of pulse durations


List points to remember when determining energy

The strength duration curve (SDC) is the quantity of charge, current, voltage or energy required to stimulate the heart at a series of pulse durations

These values very significantly as a function of pulse duration

Only charge is approximately linear

In order to set a voltage or pasta ration for parameter output programming, the position that a specific voltage or post a ration occupies on the curve must be known i.e. constants


List the steps to determine Rheobase and chronaxie

1.Determine the Rheobase, which is the minimum stimulation strength that will produce a response. This is the voltage to which the strength duration curve approximates.
2. Calculate two times Rheobase
3. Determine chronaxie, which is the stimulus generation that yields a response when the stimulus strength is set to exactly 2 times Rheobase


What dothe root words Rheo and base mean?

Current and foundation
Therefore Rio base is the foundation or minimum current that will produce a response


What do the root words chron and axie is mean?

Cron means time and axie means axis

Therefore, chronaxie is measured along the time axis and is a duration that gives a response when the nerve is stimulated at twice the Rheobase strength


Formula for charge in microulombs

C (charge)= I (current) x T ( pulse width in msec)


Formula for energy

E (energy in micro joules) =
I (current) x V x T (pulse width in msec)

Multiply mean current by mean voltage by pulse duration