Pressure ulcers result from sustained pressure. Unrelieved pressure is a consequence of lack of mobility and movement. Manual movement, potentially hazardous to both patient and nurse, is the single most effective means of prevention. Mobility has a positive effect on physiological function of all bodily organs. Sophisticated pressure relieving technologies are available to treat at a symptomatic rather than causal level.
Passive wave motion is a new modality that can restore the required movement that patients are unable to supply for themselves, enhancing blood flow through peristalsis, and dynamically changing volumes in venous cavities. Passive wave motion is very comfortable, relaxing and well tolerated. It is the purpose of this study to establish the effectiveness of this approach and establish guidelines for its application. Introduction
Pressure ulcers are a major health care problem worldwide. About 23% of patients in skilled care and nursing home facilities have pressure ulcers (Langemo, Olson, Hunter, et al, 1989; Young, 1989). In acute care, the prevalence is about 11.1% (Meehan, 1994). In high-risk patients such as elderly individuals with femoral fractures or hospitalized persons with quadriplegia, the incidence and prevalence is over 60% (Richardson & Meyer, 1981; Versluysen, 1986). Among the elderly (70+), there is a fourfold increase in the rate of death. (Barczak, C.A., et al, 1997) Hospital stays increase by a factor of five, from 5.4 days to 27 days for patients afflicted with bedsores. (Statistical abstract of the US, 1995. Allman 1989)
Pressure ulcers are caused by unrelieved pressure that results in damaged skin, muscle, and underlying tissue, usually over bony prominences (Cohen, Diegelman, Lindblat, 1992). Extrinsic factors include pressure, shear, friction and moisture (Allman, Gosnell, Bergstrom, et al., 1993) as well as nutrition. (Breslow R. (1991)
Immobility influences the physiologic function of all body organs. Even with correct body support, regular turning is needed to prevent pressure ulcers (Norton, McLaren & Exton-Smith, 1975). It is not known how frequently patients need to be turned in order to prevent pressure-induced tissue damage, but the AHCPR Guidelines on Prediction and Prevention of Pressure Ulcers (1992) recommends turning patients at least every two hours.
"Prevention, rather than treatment, appears to be essential to reducing the burden of suffering associated with pressure ulcers." (Xakellis, G.C. 1995). "Everyone agrees that they are preventable, but many pressure sores still occur" (Webster, J.G. 1991).
The cost of treating bedsores is very high. Estimates for the US alone vary from $9 billion (Reuters 1998) to over $50 billion (National Decubitus Foundation 1999) depending on what costs are considered. This staggering cost is just the tip of the iceberg since it is impossible to quantify loss of life, needless suffering and opportunity cost in any meaningful way.
Prevention
There is general agreement that the problem of pressure sores needs to be addressed at the causal rather than symptomatic level. (Xakellis, G.C. 1995). There is also agreement that the cause of pressure sores is unrelieved pressure resulting from lack of movement. Lack of movement is causal.
Movement among the healthy (mobile) population is accomplished through intermittent active motion. Intermittent active motion is the movement that results from normal volitional activity as well as unconscious movement while resting or sleeping. At night we shift our weight at least twice every hour, even when we are supported on a fluidized bed. Mobility has a positive affect on physiologic function of all body organs. (Norton, McLaren & Exton-Smith, 1975)
The importance of movement is well documented, (AHCPR Guidelines on Prediction and Prevention of Pressure Ulcers [1992]), however the literature only addresses manual interventions as the movement means. This research is mostly geared to the identification of minimum movement requirements rather than optimal ones, presumably because this treatment is labour intensive, physically demanding for staff, hazardous and costly. There has been no research on passive movement because there have been no devices available to study this alternative nor have there been any studies on how much movement is optimal. The National Pressure Ulcer Advisory Panel in the US (NPUAP 1999) has identified inactivity and lack of mobility as key areas of research required to develop effective means of prevention. Optimum amounts of movement are likely many times greater than what is realistic through manual interventions. Among the healthy (mobile) population movement occurs unconsciously at least twice per hour even under circumstances of near perfect support. (Norton, McLaren & Exton-Smith, 1975) It appears that the maintenance of a minimum level of movement is necessary to maintain physiological function, however much more movement may well be optimal.
While passive movement of a sleeping surface has not been studied, several other treatment devices have been advocated as means of prevention. The National Decubitus Foundation (NDF 1999) has pointed out that fluidized beds that consistently maintain a support pressure well below 32mm Hg are a cost-effective means of prevention as well as the most effective means of cure. Beds of this type have been refined and developed since their inception over 30 years ago. (Hargest, T.S., et al, 1969) They are arguably the best support surfaces to consistently maintain skin contact pressure low enough to avoid ulcer formation in the absence of motion. (NDF 1999)
Fluidized beds are unlikely to gain widespread acceptance and application as a means of prevention. They typically weigh over 1000 pounds, consume over 1000 watts of electrical power and cost $60 to $150 per day in capital and operating costs. It is estimated (NDF 1999) that these devices, if provided to all hospital patients, would cost the US health care system $5 billion per annum and save over $40 billion. Less costly low air loss and alternating pressure products reduce the probability of incidence but have not been shown to be a consistently reliable means of prevention. (NDF 1999) These latter products however are becoming increasingly sophisticated. The latest developments in this arena may well be more effective than their earlier technological predecessors. There are however consistent problems with compliance since many patients complain of discomfort when air cells inflate and deflate. (Benhow 1999) Relieving pressure does not address the cause, rather it treats the symptom. There is research that shows that any prolonged pressure as low as 11 mm. Hg can give rise to pressure occlusion of capillaries. (Ek et al 1987) In fact, in resting tissues, blood flow stops in capillaries merely due to contraction of metarterioles and precapillary sphincters and the fact that red blood cells are frequently larger than the capillaries they go through. (Ganong, 1987 P483) The real problem is in lack of mobility that sustains pressure. It is unlikely that pressure relief or redistribution systems can effectively address this cause. Even patients on fluidized beds require periodic repositioning.
Passive motion (mechanical motorized movement) is relatively new as a treatment modality. Dr. R.B. Salter is the primary advocate of this treatment and his research has resulted in a major change in the practice of orthopedic rehabilitation around the world. Devices developed by Saringer, in collaboration with Salter, are now available to treat all the major joints of the body. Saringer holds more patents in the field of passive motion devices than anyone else in the world. Passive movement has improved quality of life for tens of millions of patients and their families in over 50 countries. Sick Kids Hospital has put out several full page ads in all the daily newspapers with Dr. Salter's research and Saringer's CPM devices featured as one of Sick Kid's most notable contributions of the past decades.
CPM was conceived by Salter as a means for preventing degeneration of joint cartilage through passive motion of limbs through their physiologic range of motion. Through his pioneering work at Toronto's Sick Kids Hospital, Salter has shown that CPM is more effective than intermittent active motion or immobilization in recovery of orthopedic injuries. (Salter R.B., et al, 1984) CPM has been shown to decrease pain (and the need for medication), reduce swelling, increase blood flow (reduction in DVT), reduce hospitalization and accelerate wound healing (Van Royen, et al 1986). All of these effects are ancillary benefits arising from joint motion. They are also precisely the effects sought in preventing and treating pressure ulcers.
CPM (Continuous Passive Motion) refers to the continuous uninterrupted movement of a joint of the body, back and forth through an adjustable range of movement. The movement is typically one cycle per minute. The benefits are numerous. Joint cartilage heals without scarring and may even thicken. The Steadman Hawkins clinic in Vail Colorado uses CPM devices to thicken the cartilage of US Ski team athletes by drilling small holes in the knees to trigger a tissue healing response. In the presence of continuous passive motion, the traumatized knee generates new hyaline cartilage. In fact CPM is the key to making possible a whole new world of reconstructive surgery. As this specialty evolves, it will slowly displace more radical prosthetic joint replacement. No artificial limbs have so far come close to being as effective as the joints they replace.
While reconstructive surgery is the most profound area of application for CPM, the most common and lucrative application of CPM has been in speeding recovery of patients following joint replacement where there is no joint or cartilage involved. CPM consistently reduces pain (and the need for medication), reduces swelling, improves blood flow, reduces deep vein thrombosis, increases range of motion, reduces hospitalization and speeds the road to complete recovery. Most importantly, it reduces costs of care. It is even used to arrest the progress of arthritis, in retraining following strokes, for burn patients as well as paraplegics to reduce joint and soft tissue atrophy. Unfortunately, outside of progressive orthopedic rehabilitation centres, CPM is barely known. After 20 years, less than 10% of the potential market has been penetrated. Cost and the complexity of operating the equipment have always been obstacles.
Many of the beneficial effects of CPM have nothing to do with the movement of the joint. A prosthesis does not require movement to function, yet strangely, moving the joint triggers other benefits. The expansion, contraction and stimulation of soft tissue give rise to all sorts of problems from pain to blood clotting being reduced. Arthritis occurs most frequently in the joints most often immobilized. Ribs, under the constant movement of breathing, rarely develop joint problems. Nobody stops breathing after breaking a rib and ribs recover just fine.
Our bodies are meant to move. Rocking comforts infants. Rocking chairs keep many elderly in better health. People who move more stay fit, live longer and enjoy a healthier life.
20 years of experience with CPM has made Saringer very familiar with the benefits of passive movement and he has made the development of this technology the major priority and commitment of his life. Saringer has long sought an inexpensive and comfortable way of accomplishing passive movement so that this treatment modality can be accessible, affordable and comfortable for everyone when they need it.
A practical passive motion bed has never been available until recently. Saringer's development of a moving mechanical wave system has provided the first reliable and inexpensive means of delivering passive motion to a sleep support surface. There are a number of advantages to waves over any other forms of movement.
Waves are the most natural and energy efficient means of movement. The regular undulation of a mechanical wave not only provides a continuous change of pressure at all support points but goes further by applying a peristaltic pumping effect through the skin surface. Peristalsis is a normal physiological process of moving material through the body by squeezing a channel in a wavelike manner in the flow direction. It is much like squeezing a toothpaste tube. Laboratory peristaltic pumps operate on the same principle. The wave applied to the external surface of the dermis causes occlusion of blood vessels at the point of contact. As this occlusion moves in the normal direction of venous flow, blood is pumped toward the heart. Between the crests of the wave, the support pressure is relieved (to well below 32 mm. Hg) several times every minute as the crest of the wave continuously moves under the entire support surface. The speed of the wave is within the normal range (2-25 cm/sec) of peristalsis and faster than the normal blood flow rate through capillaries (~0.07 cm/sec, Ganong 1987 pg. 488), hence the peristaltic effect will enhance blood flow rather than retard it. This is an important consideration since in resting tissues, the metarterioles and precapillary sphincters contract, hereby impeding or even blocking flow even in the absence of occlusion. (Ganong 1987, P489) It also follows that the wave motion needs to be applied continuously to generate this beneficial effect.
The wave motion also operates at a more subtle level to increase blood flow. Blood flow is generally enhanced through bodily movement of all kinds as the volume in flow cavities enlarges and contracts from the motion of surrounding soft tissues. This is particularly evident with the expansion and contraction of muscles. Coupled with the effect of venous valves that prevent back flow, this dynamic change of blood vessel volume increases blood flow back to the heart. The wave motion is also pulsatile. This is important since in nonpulsatile flow, there is a gradual rise in vascular resistance, and tissue perfusion fails. (Ganong, 1987 P485)
The wave mechanism is a flexible flat sheet supporting a thin foam mattress with a mechanism attached to its underside that deforms the sheet into a pseudo-sinusoidal (wave) and, when powered, propels this wave toward the heart proportional to motor speed. The amplitude and wavelength is 0.75" (+/- 0.375") and 15" respectively with three full waves (crests and valleys) propagating through the support surface at any one time. The mechanism for generating waves is subject to patents pending as is its application to a therapeutic sleep surface. It is a very simple, inexpensive and robust design. It can be built to last well over 10,000 hours of continuous use. It can replace the surface of virtually any type and size of mattress or fitted directly to a frame of a hospital or other type of bed. At typical slow (sleeping) operating speeds, it will run on less than 10 Watts of power. It can also be battery powered to fit a portable operating room table.
The experience of lying on the bed is like floating on gentle ocean waves. When it runs it feels like rollers rolling up the length of your body in an endless procession as the crests of the wave propagate through the sheet. The wave goes from foot to head to enhance blood flow (pushing toward the heart.) and has sufficient undulation to cause some joint and soft tissue movement. At speeds at or below sleep breathing rates (20 cycles/minute or less), it induces relaxation and sleep. The operation is so smooth, quiet and rhythmic that you can become unaware of the motion within a half-hour.
The wave mechanism is built as a component of a mattress and will fit within a standard hospital bed. The wave bed provides the first mechanized means for preventing pressure ulcers at a causal level by passively delivering the motion that patients are unable to provide for themselves, enhancing blood flow through peristalsis, and dynamically changing volumes in venous cavities. Compared to fluidized beds, the mechanism weighs considerably less (under 30 pounds compared to over 1000 pounds), costs less (estimated $10/day or less compared to over $100/day) and is more energy efficient (less than 10 watts compared to over 1000 watts). Wave mechanisms are potentially a very inexpensive addition that can be retroactively applied to any hospital bed. The therapeutic and economic benefits are potentially enormous.
Passive motion and its effects on wound healing have also been studied:
"With respect to the breaking force, tensile strength, strain at failure, stiffness, and toughness, the wounds in the continuous-passive-motion group were significantly stronger, stiffer, and tougher than those in the cast (immobilized) group. Histologically, the structural organization of the collagen fibres was also superior in the scars treated with continuous-passive-motion. The results of the present investigation indicate that compared to immobilization, continuous passive motion enhances post operative wound healing in rabbits.". (Van Royen, B.J., et al 1986)
It is the purpose of the proposed study to investigate the therapeutic potential of passive wave motion in the prevention and treatment of pressure sores.
Preliminary Research Protocol
We propose to carry out research to investigate the effects of passive wave motion on the prevention and/or treatment of pressure sores in a progression of steps. The outcome of each step will result in the further refinement and design of the following stages. The overall objective is to establish whether or not passive wave motion can effectively prevent the formation of, and/or accelerate recovery from, pressure ulcers.
The first of these steps has been completed. The second step is proposed to take place at Lyndhurst Hospital in March 1999.
Step 1: Trials of wave bed with healthy subjects: The purpose of this stage was to answer the following questions:
a) Is the wave motion tolerable and comfortable?
The wave bed has been applied to almost 3000 people for a very short period of time. Over 95% of all subjects reported that the bed was very relaxing and soothing. These same subjects reported that they would benefit from the use of the bed. Less than 5% of all subjects found the movement uncomfortable. Most of these subjects indicated that they were prone to dizziness and balance (inner ear) problems. 2% complained of nausea at higher wave speeds.
b) Is it possible to sleep comfortably on a wave bed?
Ten subjects have slept on the wave bed for one or more nights. Of these, seven reported that they slept better with the wave bed than on their own beds. Two indicated that the bed was equal in comfort to their own bed. One subject reported that they preferred their own bed to a wave bed. All subjects reported that the slowest wave speeds (10 cycles/minute or slower) were the most comfortable for sleeping. There also appears to be an increase in the amount of time subjects remain on a wave bed and an increase in the depth of sleep. Most subjects reported that their awareness of motion disappeared after being on the bed for more than 30 minutes.
Twenty-six subjects have tried the bed for over one hour concurrently with massage therapy for the purpose of relieving stress symptoms. All subjects consistently reported that their experience was greatly enhanced with wave motion. Breathing rates dropped as thoracic movement entrained to the lower wave speeds. Wave motion appears to be a valuable adjunct to massage.
Step 2: Preliminary trials of a wave bed at Lyndhurst Hospital.
a) What are the minimum ergonomic, regulatory and functional requirements that need to be met for an acute care bed?
b) Are there contraindications for the application of the bed, (e.g., do medicated patients experience nausea)?
c) Is the bed comfortable and well tolerated?
Step 3: Based on the outcome of step 2.
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