Hydrotherapy

• Temperature Regulation


  Our bodies must maintain optimal temperature ranges to be capable of working properly to sustain life and function. There are several temperature regulatory systems in place that help to maintain a relatively stable body temperature or help restore that temperature if fluctuations occur.
• Homeostasis


  A stable state or state of equilibrium wherein body systems operate more efficiently, maintained through the interaction of local and central neural mechanisms
• Hypothalamus


  Acts as the "body's thermostat" to maintain a normal range of human body temperature from 36°C to 38°C
• Temperature-regulating mechanisms


  1. Changes in circulation (e.g., vasodilation or vasoconstriction of blood vessels)

  2. Shivering, to maintain heat

  3. Sweating, to lose heat
• Neural transmission


  • Function of first-, second-, and third-order afferent and efferent neurons or nerve fibers
• Neural transmission


  1. Afferent neurons conduct sensory information from the periphery to the spinal cord and brain

  2. Efferent neurons conduct motor information from the brain to the periphery

  3. First-order neurons transmit information from thermal receptors or free nerve endings and terminate in the dorsal horn of the spinal cord

  4. Second-order neurons transmit information along ascending or descending tracts of the white matter of the spinal cord and terminate in the thalamus

  5. Third-order neurons transmit ascending sensory and descending motor information between the thalamus and the cerebral cortex
• Pathway of heat loss

  • Skin (major pathway)
  • Respiratory tract (secondary pathway)
  • Urinary tract (minor pathway)
  • Digestive tract (minor pathway)
• Conduction


  Thermal loss or gain through direct contact between materials with different temperatures
• Conduction

  • Heat absorbed by the body when using a hot pack
  • Heat lost from the skin via cold packs
• Convection


  Transference of thermal energy to a body by the movement of air, matter, or liquid around or past the body
• Convection


  • Convection oven
  • Freezer
• Radiation


  Radiant energy transfers heat through air from a warmer source to a cooler source
• Radiation


  • Infrared heat lamp
• Conversion


  Temperature changes that result from energy being transformed from one form into another, such as the conversion from mechanical or electrical energy into heat energy
• Conversion


  • Continuous wave or uninterrupted therapeutic ultrasound
• Evaporation


  Transformation from a liquid state to a gas state, which requires an energy exchange and results in heat being given off
• Evaporation


  • Sweating
  • Vapocoolant sprays
• Heat flow through matter (tissues) varies with the nature of the material (type of tissue) and is called thermal conductivity
• Changes in surface tissue temperature from heating modalities depend on the intensity of the heat applied, the time of heat exposure, and the thermal medium (product of thermal conductivity, density, and specific heat) for surface heat
• The greatest degree of temperature elevation with heating modalities occurs in the skin and the subcutaneous tissues within 0.5 to 2 cm of the skin surface
• In areas of adequate blood supply, temperature will increase to a maximum within 6 to 8 minutes of exposure
• Muscle temperature at depths of 1 to 2 cm will increase to a lesser degree and will require a longer duration of exposure (15 to 30 minutes) to reach peak values
• At a depth of 3 cm, muscle temperature elevation can be expected to be about (1°C) or less
• Fat provides insulation against heat; it has a low thermal conductivity. Therefore, tissues under adipose tissue are likely to be minimally affected by heating modalities
• To elevate deep tissues to therapeutically desired levels without burning the skin and subcutaneous tissue, a heating modality such as continuous ultrasound or shortwave diathermy should be selected
• Thermotherapy


  Application of therapeutic heat to change the cutaneous, intra-articular and core temperature of soft tissue with the intention of improving the symptoms of certain conditions
• Types of thermotherapy


  • Local heating (e.g. hot packs, paraffin wax, fluidotherapy)
  • General heating (e.g. hubbard tank, exercise pool)
• Effects of heat


  • Hemodynamic effects
  • Neuromuscular effects
  • Metabolic effects
  • Tissue extensibility effect

  
• Hemodynamic effects of heat

  1. Direct reflex inhibition of smooth muscles of blood vessels

  2. Local release of chemical mediators (e.g. bradykinin, nitrous oxide) causing vasodilation
• Neuromuscular effects of heat


  1. Increased nerve conduction velocity and decreased pain perception

  2. Increased pain threshold (direct and indirect effects)

  3. Decreased firing rate leading to muscle relaxation
• Metabolic effects of heat


  Increased metabolic rate and oxygen delivery to tissues
• Tissue extensibility effect

  Increased temperature leads to increased soft tissue extensibility
• Heating modalities to increase tissue temperature 1-3 cm depth


  • Moist heat packs
  • Paraffin wax bath
  • Fluidotherapy
  • Warm whirlpool
  • Microwavable gel packs
  • Air-activated heat wraps
  • Electric heating pads
• Heating modalities to increase tissue temperature 1-5 cm depth


  • Continuous ultrasound
  • Continuous shortwave diathermy

  
• Hot packs heat the skin more quickly than paraffin due to higher thermal conductivity of water
• Fluidotherapy heats more slowly than hot packs due to lower thermal conductivity of air, but maintains constant temperature
• Conductive heat modalities


  • Thermal conductivity of tissues
  • Body volume exposed
  • Time of exposure

  
• Moist heat packs/hot packs

  Made of bentonite (hydrophilic silicate gel) covered in canvas, stored in hot water cabinet
• Hot packs should be heated for at least 2 hours before initial use and 30 minutes between uses
• Electric heating pads


  Not recommended for clinical use as they do not cool during application and can easily cause burns