ALTERED CONSCIOUSNESS IN FLOTATION-REST AND CHAMBER-REST: EXPERIENCE OF EXPERIMENTAL PAIN AND SUBJECTIVE STRESS

Social Behavior and Personality, 2004 by Kjellgren, Anette, Sundequist, Ulf, Sundholm, Ulla, Norlander, Torsten, Archer, Trevor

Twenty-three sportsmen were given one 45-minute exposure to flotation-REST and one exposure to chamber-REST on two occasions, incorporating random assignment to either flotation-REST followed by chamber-REST or vice versa. On each occasion, the Restricted Environmental Stimulation Technique (REST) procedure was followed immediately by testing experimentally induced pain to one arm using a blood pressure cuff. It was found that flotation-REST induced a significantly higher degree of altered states of consciousness (ASC), as measured with an instrument assessing experienced deviation from normal state (EDN), than did chamber-REST. Participants experiencing High EDN in the flotation-REST condition reported higher levels of both "experienced pain" and "experienced stress" than did those experiencing Low EDN. These results suggest that the particular distinguishing features of flotation-REST and chamber-REST may cause selective deviations from normal levels of consciousness, under experimental conditions, that may underlie the subjective experience of pain and stress thresholds.

Experimental methods for studying pain processes may elucidate questions arising in clinical pain research. For example, experimental pain studies may be used to develop "coping" strategies as well as to evaluate the efficacy of these strategies (Edens & Gil, 1995). Nevertheless, studies involving experimentally induced pain are severely limited in their capacity to model the pain experienced, for example, in chronic pain conditions, since among restrictions the affective component is missing generally in the experimental setting (Rang, Dale, & Ritter, 1999). Furthermore, whereas experimental pain is usually predictable, this is not the case in chronic pain, as participants in a pain experiment may terminate the study at any time in full knowledge that at no time are they at risk for tissue damage (Edens & Gil).

Although several methods exist for induction of experimental pain, induced ischemia (due to lack of oxygen) and cold-presser pain are considered methodsof-choice as models of chronic pain condition (Rainville, Feine, Bushnell & Duncan, 1992). In the latter case, the participant is required to submerge his/her hand into a bucket of ice water whereas in the former ischemic pain is induced by elevating pressure at the blood pressure cuff on the participant's arm. In ischemic pain, lack of tissue oxygen at the cuff inhibits the sodium-potassium pump thereby increasing extracellular K+ concentrations which in turn depolarize pain receptors with consequent impulse generation and perception of pain (Nisell & Lundeberg, 1993). Lack of tissue oxygen leads also to bradykinin accumulation, further reinforcing the pain (Nisell & Lundeberg, 1993; Rang, Dale, & Ritter, 1999).

Measurement of pain intensity can be performed using a Visual Analog Scale (VAS) from 0-100, which is expressed often as being the "gold standard" for assessment of pain (Yarnitsky, Sprecher, Zaslansky, & Hemli, 1996), although verbal descriptions are utilized too. Comparisons of VAS with verbal descriptor techniques indicate that both methods are equally sensitive for quantification of pain intensity and its affective component (Duncan, Bushnell, & Lavigne, 1989).

At present, there are only a few studies on human participants involving experimental pain in combination with relaxation/stress-reduction, whereas there are a substantial number of studies showing the analgetic effect of relaxation when using flotation-REST on clinical pain (e.g., Kjellgren, Sundequist, Norlander, & Archer, 2001). Flotation-REST (Restricted Environmental Stimulation Technique) is a mild form of sensory deprivation where the participant is comfortably floating on his/her back in a saline solution contained in a dark, anechoic tank. In order to further reduce incoming sensory perceptions, the participant wears earplugs and the saline water solution is heated to skin temperature, thus reducing auditory and tactile stimulation. The method induces a state of relaxation and stress-reduction (e.g. Norlander, Kjellgren, & Archer, 2001).

The studies that have been made with REST and pain relief have in common the fact that they study an already existing, chronic pain which is present when the REST-treatment is begun (Kjellgren et al., 2001). These studies in no way claimed that the pain relief was to be explained by the elevation of the participant's pain threshold, but rather noted that the participants experienced attenuation of the existing pain over time as REST-treatments were continued.

The aim of this study was consequently to investigate whether or not the degree or level of altered state of consciousness could be of importance for the subjective experience of experimental pain induced when the participant was already in a mild altered state of consciousness. In order to practically achieve this altered state of consciousness; sensory deprivation was used in a flotationREST tank and on a couch in a dark, silent room (chamber-REST), respectively.