The Use of i/t Curve in Assessment of Phototherapy Effects
Condition: Nerve Disorders
Study type: Interventional

Summary: 
      Conventional electrodiagnostic examination is useful in daily physiotherapeutic practice.
      Nevertheless, the subjective assessment of muscle contraction and perceived current
      vibrations carries the risk of error and thus is a limitation of the method. Therefore, the
      use of the I/T curve coefficient was proposed in this study. This coefficient is the
      arithmetic mean of the electrical charge needed to trigger a sensory or motor reaction at
      different widths of the electrical pulse. PILER (Polychromatic Incoherent Low-Energy
      Radiation) light affects the sensory and motor excitability of the tissue. The resulting
      changes may depend on the colour of the filter used in the irradiations.

      The study aimed to:

        1. To evaluate changes in neuromuscular excitability occurring after PILER irradiation
           using filters of different colours.

        2. To evaluate the usefulness of the I/T curve coefficient in neuromuscular excitation
           test.

      60 healthy volunteers were assigned to one of four groups irradiated with: 1 - Piler light +
      red filter, 2 - Piler light + blue filter, 3 - Piler light without a filter, 4 - placebo.

      Main Outcome Measures were plotting I/T curve coefficient for rectangular (■I/T coeff) and
      triangular (▲I/T coeff) pulses and the pressure pain threshold (PPT).
    

Detailed description: 
      Electrodiagnostic examination is a valuable addition to clinical trials and is useful in
      disorders of neuromuscular excitability.

      The I/T curve is a non-invasive electrodiagnostic method for the quantitative assessment of
      neuromuscular excitation. Plotting it makes it possible to determine the rheobase (minimum
      stimulus amplitude to reach the stimulation threshold with a long pulse duration /1000 ms/)
      and chronaxie (minimum duration of a stimulus with an amplitude twice that of the rheobase
      needed to reach the stimulation threshold.

      Traditional electrodiagnostic examination is popular among clinicians due to its
      availability, ease of administration and usefulness in physiotherapeutic practice. The
      subjective assessment of muscle contraction and perceived current vibrations carries the risk
      of error and thus is a limitation of the method. Therefore, use of the I/T curve coefficient
      was proposed in this study. This coefficient is the arithmetic mean of the electrical charge
      needed to trigger a sensory or motor reaction at different widths of the electrical pulse.

      Polarized polychromatic incoherent low-energy radiation (PILER light) can affect the sensory
      and motor excitability of living tissue. The biological activity of light results from the
      energy of its ordered electromagnetic waves acting on living cells. No thermal effect is
      present, as the density of the energy transmitted to the tissues is low.PILER therapy often
      uses filters of different colours, each showing a slightly different effect on excitable
      tissue.

      The research questions of this randomised experiment were:

        1. Does PILER light affect sensory and motor excitation?

        2. Does the electromagnetic wavelength of PILER light influence its effect?

        3. Is the I/T curve coefficient a useful measure of sensory and motor excitation?
    

Intervention name(s): Irradiations of the biceps brachii muscle with PILER light. The participants were randomized into 4 groups: group v - no filter/ group x - red filter/ group y - blue filter/ group z - placebo.
Intervention type(s): Radiation
Intervention description(s): Biceps brachii examination was carried out before (examination 1) and after (examination 2) a series of 10 PILER light treatments. It included a traditional electrodiagnostic examination and the assessment of the pressure pain threshold (PPT).
The electrodiagnostic examination of the muscle was performed using the unipolar stimulation method from the direct motor point. The passive electrode (6 cm x 6 cm) was attached to the side of the distal part of the forearm, and the distal edge of the electrode was adjacent to the proximal edge of the ulnar styloid process. The examination was performed with a Multitronic MT3 electrotherapy apparatus set.
PPT at the direct motor point was determined using an algometer (Algometer commander TM ITECH Medical Industries). A head with a rubber jacket with a surface area of 0.5 cm2 was used to cause pressure pain. Pressure was exerted until the participant reported pain, at which time the force (lbs) marked by the algometer was recorded.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: electrodiagnostics; i/t curve; neuromuscular excitation; PILER (Polychromatic Incoherent Low-Energy Radiation); algometry