PT9111 - Lecture 19 (Modalities 3) Flashcards
Electrons
Negatively charged ions that are part of atoms
Electrical current
Flow of electrons from one area to another ([high] to [low])
Amperes
Rate of current
Voltage
Potential difference between high and low concentration areas of electrons
Ohm’s Law
Rate of current (I) is directly proportional to strength of driving force (V) and inversely proportional to resistance (R)
I=V/R
Name materials of high conductance
metal and water
Name materials of high resistance
Air, wood, glass
Tissues with high conductance
- High water content
- Blood
- Granulation Tissue
Tissues with high resistance
- Skin
- Bone
- Necrotic Tissue
What 3 factors increase skin impedance
- Cooler skin temp
- Hair and oil present
- Increased skin thickness
What 3 factors decrease skin impedance
- Remove excess hair
- Warming skin
- Washing skin
Describe the cathode and anode in terms of electric current
Cathode is black and is the negative pole that causes nerve depolarization and sends signal to positive/red anode where hyperpolarization then occurs down the nerve fibre so signal stays local
Name 6 characteristics that are different between anodes and cathodes
Cathode results in a [blank] reaction
Basic
Anode results in a [blank] reaction
Acidic
Name 3 types of currents
- Direct Current
- Alternating Current
- Pulsed Current
Direct Current
Continuous unidirectional movement of charged particles = net charge has polarity
Alternating Current
Uninterrupted bidirectional movement of electrically charge particles = no net charge
2 primary differences between direct and alternating current
Direct = flow of e- is unidirectional and polarity is constant
Alternating = Flow of e- reverses and no polar effects
Pulsed Current
Pulses of current flow interrupted by short periods
Name the 2 types of pulsed currents
- Biphasic
- Monophasic
Monophasic Pulsed Current
Isolated unit of unidirectional movement of charged particles separated by a finite period from another unit of charged particles = net charge has polarity
Biphasic Pulsed Current
Isolated unit of bidirectional movement of charged particles separated by finite period from another unit of charged particles = no net charge
Name two types of standard currents
- Household current = changes polarity
- Batteries = direct current
Name 6 characteristics of waveforms
- Duration
- Amplitude
- Frequency
- Bursting
- Rate of rise and decay (ramping)
- Waveform shape
Name 3 types of duration
- Pulse
- Phase
- Cycle
Pulse
Single waveform that may have one or more phases
Phase
Portion of pulse which rises above or below baseline and returns to baseline
Cycle
2 phases that each return to baseline
Amplitude
Magnitude of electromotive force driving e-
T or F: The greater the amplitude the stronger the current
T
Frequency
Number of pulses or cycles per second
At what frequency do we get tetanic muscle contraction
> 50 Hz
At what frequency do we get only muscle twitching
<50 Hz
T or F: As frequency increases, duration increases
F as frequency increases, duration decreases
Bursting
Train of pulses follow by short period of time with no activity to decrease accommodation by nerves of stimulus and elicit a strong muscle contraction
Ramping
Waves rising gradually to full amplitude and the falling gradually to zero current to allow muscle to warm up to stimulus and not cause too strong of a contraction immediately
T or F: Different waveform shapes can cancel each other out to cause no charge
T
Do biphasic, symmetrical currents have a charge?
No charge
Do biphasic, asymmetrical currents have a charge?
It depends, but yes, if they are not balanced
Do monophasic currents have a charge?
Yes
Why do we have to worry about a charge?
Build up of charge leads to acidic or basic chemical reactions so it is important to know the current used and if the phases are balanced (if biphasic)
What are the 3 most important characteristics to delivering a sufficient current
- Duration (usec)
- Amplitude (mA)
- Frequency (Hz)
**Combination of these values can result in subsensory stimulation, appropriate treatment, or noxious stimulation
Accomodation
Overtime, with a constant amplitude, frequency or duration of electrical energy, a nerve will become unexcitable
How to modulate so accommodation does not occur
Modify intensity, frequency (eg. bursting), duration or a combination of these
What are 8 contraindications to using electrical modalities
- Pacemaker/arrhythmia
- Over carotid sinus or excitable areas like chest, eyes and head
- Thrombophlebitis
- Impaired sensation, altered mental state, or poor communication skills
- Over pelvis, abdomen, trunk when pregnant
- Severe peripheral vascular disease (only with NMES because works body too hard and can cause damage)
- Over superficial metal implants
- Cancer
Name 3 precautions of electrical modalities
- Turn machine off before checking leads
- Be aware of ON:OFF cycles when adjusting amplitude
- Application of electrodes (evenly against skin with constant pressure)
Name 3 adverse reactions of electrical modalities
PSS:
Pain (P)-> requires good therapist
Skin reactions (s) -> burns due to build of ions (increased risk from long treatment, sweating, jewelery, creams)
Risk of Surge (S) -> Could be electrocuted
