Changes

'''Keywords''': ''Avagaha sweda,'' fomentation,  ''jentaka sweda, nadi sweda, niragni sweda, ushma sweda,  pottali sweda, ruksha sweda, sagni sweda, sankara sweda, samyak swinna lakshana, snigdha sweda, sudation swedana, swedatiyoga, swedayoga, trayodasha sweda, upanaha sweda,'' fomentation, heat, sudation therapy, hydrosis.

'''Keywords''': ''Avagaha sweda,'' fomentation,  ''jentaka sweda, nadi sweda, niragni sweda, ushma sweda,  pottali sweda, ruksha sweda, sagni sweda, sankara sweda, samyak swinna lakshana, snigdha sweda, sudation swedana, swedatiyoga, swedayoga, trayodasha sweda, upanaha sweda,'' fomentation, heat, sudation therapy, hydrosis.

== Introduction ==

== Introduction ==

''[[Swedana]]'' should only be administered following a proper ''[[snehana]]'' (unless indicated otherwise). On application of unctuous substances like oil (''taila'') on various body parts, ''sweda'' forms an intervening viscous layer between the skin and the immediate environment prior to transdermal drug absorption. Thus the heat lost through sudation, along with large amounts of fluid and a marginal amount of Na+ and Cl- ions through radiation / conduction / convection / evaporation (which could potentially impair thermoregulation or cause hypothermia) does not happen too rapidly. Also, the procedure of ''[[swedana]]'' promotes the transdermal absorption of the ''sneha'' by inducing peripheral vasodilatation. However, environmental humidity and the duration of ''[[swedana]]'' procedure has to be strictly monitored, as exposure to small rise in temperature for a prolonged time can have a greater impact (more evaporation) than exposure to high temperature for a short time in a humid atmosphere<ref name="ref1">Cabanae, M., (2006), Journal of Applied Physiology, 100, Adjustable set point, 1338 – 1346.</ref>. Hence ''yathavath prayojithaihi'' has been written expressly to denote the optimal exposure to ''swedana''.

''[[Swedana]]'' should only be administered following a proper ''[[snehana]]'' (unless indicated otherwise). On application of unctuous substances like oil (''taila'') on various body parts, ''sweda'' forms an intervening viscous layer between the skin and the immediate environment prior to transdermal drug absorption. Thus the heat lost through sudation, along with large amounts of fluid and a marginal amount of Na+ and Cl- ions through radiation / conduction / convection / evaporation (which could potentially impair thermoregulation or cause hypothermia) does not happen too rapidly. Also, the procedure of ''[[swedana]]'' promotes the transdermal absorption of the ''sneha'' by inducing peripheral vasodilatation. However, environmental humidity and the duration of ''[[swedana]]'' procedure has to be strictly monitored, as exposure to small rise in temperature for a prolonged time can have a greater impact (more evaporation) than exposure to high temperature for a short time in a humid atmosphere<ref name="ref1">Cabanae, M., (2006), Journal of Applied Physiology, 100, Adjustable set point, 1338 – 1346.</ref>. Hence ''yathavath prayojithaihi'' has been written expressly to denote the optimal exposure to ''swedana''.

Proper application of ''[[snehana]]'' (''abhyanthara'' and ''bahya'') and ''[[swedana]]'' enhances gastro-intestinal motility. A study enumerates the instantaneous as well as prolonged benefits of continued ''[[swedana]]'', concluding that habitual use of ''[[swedana]]'' improves one’s heat tolerance capacity and physical endurance, while observing increased autonomic functions among patients due to intermittent purposeful heat stress.<ref>Sanjeev Rastogy & Francesco Chiappelli, (2013 April – June), AYU, 34(2): Heamodynamic effects of Sarvanga swedana (Ayurvedic passive heat therapy): a pilot observational study 154-159.</ref> There are numerous studies which claim that gastrointestinal motility disorders are caused due to decreased autonomic activity and its therapeutic increase, therefore helps cure motility disorders, thereby improving bowel-bladder functioning. [verse 3-5]

Proper application of ''[[snehana]]'' (''abhyanthara'' and ''bahya'') and ''[[swedana]]'' enhances gastro-intestinal motility. A study enumerates the instantaneous as well as prolonged benefits of continued ''[[swedana]]'', concluding that habitual use of ''[[swedana]]'' improves one’s heat tolerance capacity and physical endurance, while observing increased autonomic functions among patients due to intermittent purposeful heat stress.<ref name="ref5">Sanjeev Rastogy & Francesco Chiappelli, (2013 April – June), AYU, 34(2): Heamodynamic effects of Sarvanga swedana (Ayurvedic passive heat therapy): a pilot observational study 154-159.</ref> There are numerous studies which claim that gastrointestinal motility disorders are caused due to decreased autonomic activity and its therapeutic increase, therefore helps cure motility disorders, thereby improving bowel-bladder functioning. [verse 3-5]

Environmental and age related factors also need to be considered for sudation. In extremely warm regions or during the peak of summer, there is remarkable body dehydration. And in an intensely humid climate or in an ill ventilated room where there is peripheral heat production from the body surface (and yet minimal evaporation), sudation has to be strictly monitored and precautionary procedures have to be well thought-out. Cold seasons are ideal for ''[[swedana]]'' procedures because body homeostasis favors or demands heat (evident from the behavioral response mechanisms adopted by each one of us in cold seasons). Among specific fomentation techniques, ''sarvangasweda'' is contraindicated in individuals at the extremes of age (i.e., infants and very elderly people) where there is ineffective thermoregulation, although ''ekanga'' and ''mridu sweda'' could be prescribed. [verse 6]

Environmental and age related factors also need to be considered for sudation. In extremely warm regions or during the peak of summer, there is remarkable body dehydration. And in an intensely humid climate or in an ill ventilated room where there is peripheral heat production from the body surface (and yet minimal evaporation), sudation has to be strictly monitored and precautionary procedures have to be well thought-out. Cold seasons are ideal for ''[[swedana]]'' procedures because body homeostasis favors or demands heat (evident from the behavioral response mechanisms adopted by each one of us in cold seasons). Among specific fomentation techniques, ''sarvangasweda'' is contraindicated in individuals at the extremes of age (i.e., infants and very elderly people) where there is ineffective thermoregulation, although ''ekanga'' and ''mridu sweda'' could be prescribed. [verse 6]

''Bala'' (physical fitness) of the individual has to be assessed through ''[[vyayama]] shakti'' (exercise capacity), which corresponds to the time taken for spending one’s ''ardha shakti'' (half strength). Based on the outcome of this assessment, ''pravara'' (maximum), ''avara'' (minimum) and ''madhyama'' (medium) ''bala'' have to be assessed. Based upon the results of these ''bala'' assessments, ''maha sweda'' (whole body sudation for an extended duration) and various minor/major ''sweda'' measures could be prescribed.

''Bala'' (physical fitness) of the individual has to be assessed through ''[[vyayama]] shakti'' (exercise capacity), which corresponds to the time taken for spending one’s ''ardha shakti'' (half strength). Based on the outcome of this assessment, ''pravara'' (maximum), ''avara'' (minimum) and ''madhyama'' (medium) ''bala'' have to be assessed. Based upon the results of these ''bala'' assessments, ''maha sweda'' (whole body sudation for an extended duration) and various minor/major ''sweda'' measures could be prescribed.

Exercise intolerance has a significant impact on heat intolerance. People who exhibit exercise intolerance (like in the case of mitochondrial diseases, or in persons leading a sedentary lifestyle) may have autonomic dysfunction including vascular autonomia characterized by tachycardia, dizziness, changes in heart rate and blood pressure, heat intolerance and unusual sweating pattern. Also, deficiency in energy metabolism may cause exercise intolerance and reduced stamina. It is evident that exercise intolerance leads to heat intolerance and abnormal sweating pattern, making it difficult - and hazardous- to conduct ''[[swedana]]'' in those individuals. An interesting observation is that if an individual is acclimatized to hot environment, he gradually attains exercise tolerance by an increase in plasma and thereby increase in blood volume, increased venous return, increased cardiac output, sub maximal heart rate, sustained sweat response, earlier onset of sweat and increased capacity for evaporative cooling, decreased osmolality of sweat and electrolyte conservation and decreased likelihood for fatigue<ref>Kondo, N., et. al, (2009), Global Environmental research, Thermoregulatory adaptations in Humans and its modifying factors, 13 (1), 35 - 41.- online research</ref>

Exercise intolerance has a significant impact on heat intolerance. People who exhibit exercise intolerance (like in the case of mitochondrial diseases, or in persons leading a sedentary lifestyle) may have autonomic dysfunction including vascular autonomia characterized by tachycardia, dizziness, changes in heart rate and blood pressure, heat intolerance and unusual sweating pattern. Also, deficiency in energy metabolism may cause exercise intolerance and reduced stamina. It is evident that exercise intolerance leads to heat intolerance and abnormal sweating pattern, making it difficult - and hazardous- to conduct ''[[swedana]]'' in those individuals. An interesting observation is that if an individual is acclimatized to hot environment, he gradually attains exercise tolerance by an increase in plasma and thereby increase in blood volume, increased venous return, increased cardiac output, sub maximal heart rate, sustained sweat response, earlier onset of sweat and increased capacity for evaporative cooling, decreased osmolality of sweat and electrolyte conservation and decreased likelihood for fatigue<ref name="ref2"> Kondo, N., et. al, (2009), Global Environmental research, Thermoregulatory adaptations in Humans and its modifying factors, 13 (1), 35 - 41.</ref>

Contemporary science believes that heat has a beneficial effect (through thermotherapy, for instance) on pain relief. Effect of heat on pain is mediated by heat-sensitive channels. These channels respond to heat by increasing intracellular calcium (Ca). An increase in intracellular Ca generates action potentials that increase the stimulation of sensory nerves. These channels are a part of a family of receptors called TRPV receptors. TRPV1 and TRPV2 channels are sensitive to noxious heat, while TRPV4 channels are sensitive to normal physiological heat. These channels have certain characteristics in common, such as sensitivity to menthol, etc. Multiple binding sites allow a number of factors to activate these channels. Once activated, they can also inhibit the purin pain receptors. These receptors, termed as P2X2 and P2Y2, are mediated pain receptors located in the peripheral small nerve endings. For peripheral pain, heat can directly inhibit pain. However when pain is originating from deeper tissues, heat stimulates peripheral pain receptors that can alter what can be termed as “gating” in the spinal cord and reduce the sensation of deep pain. Another effect of heat is its ability to increase circulation. These same TRPV1 and TRPV4 receptors, along with nociceptor, increase blood flow in response to heat. The initial response to heat is mediated through the sensory nerves that release substance P and calcitonin-related peptide to increase circulation. After approximately one minute, Nitric Oxide is produced in vasculature endothelial cells and is responsible for sustained response of circulation to heat. This increase in circulation is considered to be essential in tissue protection from heat and repair of damaged tissue. Thermotherapy is of two types: dry and moist. A study was conducted to assess the effect of moist and dry heat on delayed onset of muscle soreness. Moist heat not only had similar benefits as dry heat but in some cases was more beneficial, requiring only 25% of time for application as dry heat. This study was conducted on quadriceps muscles. The study also witnessed immediate (and maximum) reduction in pain on application of moist heat, since moist heat penetrates deeper tissues faster than dry heat. Also, dry heat draws out moisture from the areas of application leaving them dehydrated, unlike moist heat.  

Contemporary science believes that heat has a beneficial effect (through thermotherapy, for instance) on pain relief. Effect of heat on pain is mediated by heat-sensitive channels. These channels respond to heat by increasing intracellular calcium (Ca). An increase in intracellular Ca generates action potentials that increase the stimulation of sensory nerves. These channels are a part of a family of receptors called TRPV receptors. TRPV1 and TRPV2 channels are sensitive to noxious heat, while TRPV4 channels are sensitive to normal physiological heat. These channels have certain characteristics in common, such as sensitivity to menthol, etc. Multiple binding sites allow a number of factors to activate these channels. Once activated, they can also inhibit the purin pain receptors. These receptors, termed as P2X2 and P2Y2, are mediated pain receptors located in the peripheral small nerve endings. For peripheral pain, heat can directly inhibit pain. However when pain is originating from deeper tissues, heat stimulates peripheral pain receptors that can alter what can be termed as “gating” in the spinal cord and reduce the sensation of deep pain. Another effect of heat is its ability to increase circulation. These same TRPV1 and TRPV4 receptors, along with nociceptor, increase blood flow in response to heat. The initial response to heat is mediated through the sensory nerves that release substance P and calcitonin-related peptide to increase circulation. After approximately one minute, Nitric Oxide is produced in vasculature endothelial cells and is responsible for sustained response of circulation to heat. This increase in circulation is considered to be essential in tissue protection from heat and repair of damaged tissue. Thermotherapy is of two types: dry and moist. A study was conducted to assess the effect of moist and dry heat on delayed onset of muscle soreness. Moist heat not only had similar benefits as dry heat but in some cases was more beneficial, requiring only 25% of time for application as dry heat. This study was conducted on quadriceps muscles. The study also witnessed immediate (and maximum) reduction in pain on application of moist heat, since moist heat penetrates deeper tissues faster than dry heat. Also, dry heat draws out moisture from the areas of application leaving them dehydrated, unlike moist heat.  

Heat therapy shows best results in increasing extensibility of collagen tissues, decreasing joint stiffness, relieving muscle spasm, reducing pain, inflammation, and edema. It also helps in post acute phase of healing and increasing blood flow. Examples of applications of dry heat in contemporary medicine include  diathermy, ultra sound, and heat packs, while examples of moist heat include hydrocololator heat packs (1650F), heat regulated hydrotherapy (1050 F) (basically for 5-20 mins).<ref>Aroun Prasath, R., (2014), Journal of Science, Volume 4, Issue 1, A comparative study to assess the effectiveness of Infrared radiation and hot water fomentation on pain among patients with osteoarthritis of Knee, 1-3.</ref>

Heat therapy shows best results in increasing extensibility of collagen tissues, decreasing joint stiffness, relieving muscle spasm, reducing pain, inflammation, and edema. It also helps in post acute phase of healing and increasing blood flow. Examples of applications of dry heat in contemporary medicine include  diathermy, ultra sound, and heat packs, while examples of moist heat include hydrocololator heat packs (1650F), heat regulated hydrotherapy (1050 F) (basically for 5-20 mins).<ref name="ref3">Aroun Prasath, R., (2014), Journal of Science, Volume 4, Issue 1, A comparative study to assess the effectiveness of Infrared radiation and hot water fomentation on pain among patients with osteoarthritis of Knee, 1-3.</ref>

Practically, ''valuka sweda'' may be considered to be an extreme form of ''ruksha sweda'' and taila droni as an ultimate form of ''snigdha sweda''. ''Patrapotala sweda, jambheera pinda sweda'' etc are ''na atisnigdharuksha'' (neither too unctuous nor too dry) in nature. From this, a spectrum of ''[[swedana]]'' techniques could be formulated starting from ''valuka sweda'' (sudation using sand as driest form) and ending in ''taila droni'' (dipping in warm oil as most unctuous form). The complete sequence of techniques would imply ''valuka sweda'' at one end of the spectrum, followed by ''thusha sweda, kareesha sweda, pinyakasweda, dhanyamla dhara, churnapindasweda, jambheera panda sweda, patrapotala sweda, anda sweda, shashtika pinda sweda, sarvanga dhara'' and eventually ending with ''taila droni''. [verse 7-8]

Practically, ''valuka sweda'' may be considered to be an extreme form of ''ruksha sweda'' and taila droni as an ultimate form of ''snigdha sweda''. ''Patrapotala sweda, jambheera pinda sweda'' etc are ''na atisnigdharuksha'' (neither too unctuous nor too dry) in nature. From this, a spectrum of ''[[swedana]]'' techniques could be formulated starting from ''valuka sweda'' (sudation using sand as driest form) and ending in ''taila droni'' (dipping in warm oil as most unctuous form). The complete sequence of techniques would imply ''valuka sweda'' at one end of the spectrum, followed by ''thusha sweda, kareesha sweda, pinyakasweda, dhanyamla dhara, churnapindasweda, jambheera panda sweda, patrapotala sweda, anda sweda, shashtika pinda sweda, sarvanga dhara'' and eventually ending with ''taila droni''. [verse 7-8]

A sudden increase in body temperature produces a corresponding increase in cutaneous vascular conductance. This is followed by an increase in systemic conductance which produces alterations in cardiac output (decrease in central venous pressure and increase in cardiac output thereby increased left ventricular ejection fraction), oxygen consumption and water loss. Heart rate increases.  

A sudden increase in body temperature produces a corresponding increase in cutaneous vascular conductance. This is followed by an increase in systemic conductance which produces alterations in cardiac output (decrease in central venous pressure and increase in cardiac output thereby increased left ventricular ejection fraction), oxygen consumption and water loss. Heart rate increases.  

There is a significant hemodynamic change at the beginning of ''[[swedana]]'' like significant cardiovascular stress which causes an increase in blood pressure (systolic and diastolic) and pulse rate. Whole body fomentation is therefore contraindicated in elderly and those with cardiomyopathy, congestive heart disease, bundle branch block, anemia, MI, hyperthyroidism etc.<ref> Sanjeev Rastogy & Francesco Chiappelli, (2013 April – June), AYU,34(2): Hemodynamic effects of Sarvanga swedana ( Ayurvedic passive heat therapy): a pilot observational study 154-159.</ref> Extra caution needs to be exercised when it comes to administering ''[[swedana]]'' procedure to patients with heart conditions .

There is a significant hemodynamic change at the beginning of ''[[swedana]]'' like significant cardiovascular stress which causes an increase in blood pressure (systolic and diastolic) and pulse rate. Whole body fomentation is therefore contraindicated in elderly and those with cardiomyopathy, congestive heart disease, bundle branch block, anemia, MI, hyperthyroidism etc.<ref name="ref5"/> Extra caution needs to be exercised when it comes to administering ''[[swedana]]'' procedure to patients with heart conditions .

Regarding eyes, the scientific community is interested in knowing more about the side effects of transpupillary thermotherapy (TTT). A study conducted on normal mouse retina reveals that retinas  treated with a power of 70 mW exhibited progressive retinal damage that was almost exclusively restricted to the photo-receptors. In those cases, early damage to the outer segments of the photo-receptors was seen one day after the thermotherapy and saw degeneration of outer nuclear layer after five days. At the same time, an accumulation of pigmented cells, presumably of macrophages, was seen in the sub-retinal space. No apparent damage was seen in the RPE or choroid. Today, researchers are considering the importance of using sub-threshold effects while applying TTT to patients with neurovascular age-related macular degeneration.<ref>A.P. Kvanta, P. Algvere  Department of Ophthalmology, St Erik's Eye Hospital, Stockholm, Sweden, Effect of Transpupillary Thermotherapy (TTT).</ref> [verse 10] These practices are very common nowadays except for the usage of wheat balls.  When lotus petals are unavailable, rose flower petals are substituted these days. Even cotton balls soaked in cold water, bandaged with cloth are commonly used to protect eyes while sudation. [verse 11]

Regarding eyes, the scientific community is interested in knowing more about the side effects of transpupillary thermotherapy (TTT). A study conducted on normal mouse retina reveals that retinas  treated with a power of 70 mW exhibited progressive retinal damage that was almost exclusively restricted to the photo-receptors. In those cases, early damage to the outer segments of the photo-receptors was seen one day after the thermotherapy and saw degeneration of outer nuclear layer after five days. At the same time, an accumulation of pigmented cells, presumably of macrophages, was seen in the sub-retinal space. No apparent damage was seen in the RPE or choroid. Today, researchers are considering the importance of using sub-threshold effects while applying TTT to patients with neurovascular age-related macular degeneration.<ref>A.P. Kvanta, P. Algvere  Department of Ophthalmology, St Erik's Eye Hospital, Stockholm, Sweden, Effect of Transpupillary Thermotherapy (TTT).</ref> [verse 10] These practices are very common nowadays except for the usage of wheat balls.  When lotus petals are unavailable, rose flower petals are substituted these days. Even cotton balls soaked in cold water, bandaged with cloth are commonly used to protect eyes while sudation. [verse 11]

#Expanded plasma volume  

#Expanded plasma volume  

#lower core temperature at an equivalent workload, and  

#lower core temperature at an equivalent workload, and  

#Superior Na and Cl reabsorption from sweat, and an elevated sweat secretion. <ref name="ref2">Kondo, N., et. al, (2009), Global Environmental research, Thermoregulatory adaptations in Humans and its modifying factors, 13 (1), 35 - 41.</ref> [verse 13]

#Superior Na and Cl reabsorption from sweat, and an elevated sweat secretion. <ref name="ref2"/> [verse 13]

It is very essential to differentiate heat exhaustion from heatstroke. Both come under the concept of ''atiswinna'' (over sudation). But from the treatment advised for ''atiswinna'', we may infer it as heat exhaustion. Contemporary science advises fluid replacement therapy for heat exhaustion whereas rapid aggressive cooling techniques are prescribed for heat stroke. [[Charak Samhita]] advises treatment procedures that include ''greeshma ritucharya'' along with ''madhura, snigdha, seethala prayogas'' as ''ahara'' & ''vihara''. Symptoms of heat exhaustion include normal to slightly elevated core temperature (39 – 40°C), fatigue or malaise, orthostatic hypotension, tachycardia, clinical signs of dehydration, nausea, vomiting, and diarrhea (due to splanchnic and renal vasoconstriction). Similarly, Symptoms of heat stroke include elevated core temperature (usually greater than 40.5°C), vague symptom of weakness, nausea, vomiting, headache, CNS symptoms including confusion, ataxia, coma, seizures, delirium, hot, dry skin, hyperdynamic cardiovascular systems (high central venous pressure [CVP], low systemic vascular resistance [SVR], tachycardia), elevated hepatic transaminases (usually in the tens of thousands range), coagulopathy, rhabdomyolysis, and renal failure <ref name="ref1" /> [verse 14-15]

It is very essential to differentiate heat exhaustion from heatstroke. Both come under the concept of ''atiswinna'' (over sudation). But from the treatment advised for ''atiswinna'', we may infer it as heat exhaustion. Contemporary science advises fluid replacement therapy for heat exhaustion whereas rapid aggressive cooling techniques are prescribed for heat stroke. [[Charak Samhita]] advises treatment procedures that include ''greeshma ritucharya'' along with ''madhura, snigdha, seethala prayogas'' as ''ahara'' & ''vihara''. Symptoms of heat exhaustion include normal to slightly elevated core temperature (39 – 40°C), fatigue or malaise, orthostatic hypotension, tachycardia, clinical signs of dehydration, nausea, vomiting, and diarrhea (due to splanchnic and renal vasoconstriction). Similarly, Symptoms of heat stroke include elevated core temperature (usually greater than 40.5°C), vague symptom of weakness, nausea, vomiting, headache, CNS symptoms including confusion, ataxia, coma, seizures, delirium, hot, dry skin, hyperdynamic cardiovascular systems (high central venous pressure [CVP], low systemic vascular resistance [SVR], tachycardia), elevated hepatic transaminases (usually in the tens of thousands range), coagulopathy, rhabdomyolysis, and renal failure <ref name="ref1" /> [verse 14-15]

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Poultice type of fomentation is useful in cases where both ''agneya'' and ''niragneya'' fomentation can be done. In ''agneya'', articles are heated over fire and warm medicine is applied to the skin. ''Niragneya'' is more important since in this case self-generated heat is utilized for fomentation. When the medicines of ''upanaha'' (which also contain sediments of toddy or ethanolic preparations, vinegar, buttermilk, grains etc.) are made into a paste and kept covered overnight, heat is generated within the preparation either due to acetic acid fermentation, or anerobic culture of microorganism. The temperature generated is stable and continuous. The inclusion of various oils, sour items, and salt items in the mixture ensures the exclusive ''vata'' alleviating property of ''upanaha sweda''.

Poultice type of fomentation is useful in cases where both ''agneya'' and ''niragneya'' fomentation can be done. In ''agneya'', articles are heated over fire and warm medicine is applied to the skin. ''Niragneya'' is more important since in this case self-generated heat is utilized for fomentation. When the medicines of ''upanaha'' (which also contain sediments of toddy or ethanolic preparations, vinegar, buttermilk, grains etc.) are made into a paste and kept covered overnight, heat is generated within the preparation either due to acetic acid fermentation, or anerobic culture of microorganism. The temperature generated is stable and continuous. The inclusion of various oils, sour items, and salt items in the mixture ensures the exclusive [[vata]] alleviating property of ''upanaha sweda''.

Thirteen types of ''agnisweda'' mentioned in [[Charak Samhita]] are based on four principles of heat transfer, namely, conduction, convection, radiation, and evaporation. Conduction is the transfer of heat between two surfaces that are in direct contact with each other and depends on the temperature gradient between body & surface, the total body surface area, velocity of the cutaneous blood flow & thickness of subcutaneous insulating tissue. Examples of ''agnisweda'' that leverage conduction include ''sankara, prastara, parisheka, avagaha,'' and ''ashmaghna''.

Thirteen types of ''agnisweda'' mentioned in [[Charak Samhita]] are based on four principles of heat transfer, namely, conduction, convection, radiation, and evaporation. Conduction is the transfer of heat between two surfaces that are in direct contact with each other and depends on the temperature gradient between body & surface, the total body surface area, velocity of the cutaneous blood flow & thickness of subcutaneous insulating tissue. Examples of ''agnisweda'' that leverage conduction include ''sankara, prastara, parisheka, avagaha,'' and ''ashmaghna''.

The thirteen ''agniswedas'' mentioned in [[Charak Samhita]] either refer to any one of the above mentioned heat-transfer techniques or a combination of these. This classification can be made only when heat transfer is considered. But as the drugs used are completely different in many of the procedures, the effect of herbs has yet to be explored.  

The thirteen ''agniswedas'' mentioned in [[Charak Samhita]] either refer to any one of the above mentioned heat-transfer techniques or a combination of these. This classification can be made only when heat transfer is considered. But as the drugs used are completely different in many of the procedures, the effect of herbs has yet to be explored.  

A study2 has been conducted regarding ''sarvanga sweda''. It mentioned the hemodynamic effects of ''sarvanga sweda''. The remarkable points from this study are:  

A study2 has been conducted regarding ''sarvanga sweda''. It mentioned the hemodynamic effects of ''sarvanga sweda''. The remarkable points from this study are:  

#Significant rise in the blood pressure (systolic & diastolic) was observed immediately after ''sarvanga [[swedana]]'' (found to reach near base levels after five minutes rest). Hence five minutes is the minimal period for which the patient should be kept in a supine posture, preferably at the same place. A continued ''sarvanga [[swedana]]'' therapy was noted to cause a significant decrease in pulse rate & systolic BP compared to the base levels observed at the beginning of the procedure.

#Significant rise in the blood pressure (systolic & diastolic) was observed immediately after ''sarvanga [[swedana]]'' (found to reach near base levels after five minutes rest). Hence five minutes is the minimal period for which the patient should be kept in a supine posture, preferably at the same place. A continued ''sarvanga [[swedana]]'' therapy was noted to cause a significant decrease in pulse rate & systolic BP compared to the base levels observed at the beginning of the procedure.

#The study recommended lying or supine posture during the procedure as opposed to sitting posture with head tilted downwards with cold draping over the head, since heat stress is supposed to cause a reduction in central venous pressure and a shift in blood volume from splanchnic to cutaneous area. Hence supine posture is considered ideal. Maximum time should be 8 – 10 minutes.<ref name="ref3">Aroun Prasath, R., (2014), Journal of Science, Volume 4, Issue 1, A comparative study to assess the effectiveness of Infrared radiation and hot water fomentation on pain among patients with osteoarthritis of Knee, 1-3.</ref>

#The study recommended lying or supine posture during the procedure as opposed to sitting posture with head tilted downwards with cold draping over the head, since heat stress is supposed to cause a reduction in central venous pressure and a shift in blood volume from splanchnic to cutaneous area. Hence supine posture is considered ideal. Maximum time should be 8 – 10 minutes.<ref name="ref3"/>

Another study reported that infrared radiation application was more effective than hot water fomentation in minimizing the level of pain among patients with osteoarthritis of the knee <ref name="ref3">.

Another study reported that infrared radiation application was more effective than hot water fomentation in minimizing the level of pain among patients with osteoarthritis of the knee.<ref name="ref3"/>

=== ''Pizhicchil'' ===

=== ''Pizhicchil'' ===

After proper ''[[swedana]]'' person is equally exhausted as after doing moderate to severe exercise (increased sweating, fatigue etc). Hence if a person indulges in ''[[vyayama]]'' after ''[[swedana]]'' it results in ''atiswedana'' or ''ativyayama''.

After proper ''[[swedana]]'' person is equally exhausted as after doing moderate to severe exercise (increased sweating, fatigue etc). Hence if a person indulges in ''[[vyayama]]'' after ''[[swedana]]'' it results in ''atiswedana'' or ''ativyayama''.

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== References ==

== References ==