Bed having low body pressure and alignment

Details Bed having low body pressure and alignment Bed having low body pressure and alignment

2002-06-01

2004-10-26

Grosz, Alexander (Department: 3673)

Beds

Mattress

Sectional with regard to firmness

C005S730000, C005S710000, C005S713000

Reexamination Certificate

active

06807698

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to beds and, more particularly, to improved mattresses for beds that enhance the quality of sleep.
Normally, everyone spends a large percentage of everyday sleeping and the quality of sleep is important to a person's good health and enjoyment of life. Comfortable mattresses are important in establishing restful sleep. During sleep, a healthy person typically passes through five levels of sleep which are called stages I-IV and REM (Rapid Eye Movement) sleep. Stages I and II are the lightest sleep and stages III and IV are the deepest. The REM stage is that level in which sleepers dream and receive the mental health benefits attendant dreaming. All levels of sleep are important, but stages III and IV are the deepest and most physically restful sleep, when, for example, human growth hormone is secreted. Normal sleep is cyclic passing through the stages from I to IV and back from IV to I and into REM. This sleep cycle is repeated a number of times over a normal sleep period, but can be disrupted due, for example, to body discomfort.
Restfulness and the quality of sleep is dependent upon the comfort of sleepers. When sleepers become uncomfortable, they move to relieve the discomfort and the resulting moves are a normal part of sleep. When sleepers move, they frequently change to lighter levels of sleep (stage I or II) or awaken. The more discomfort sleepers feel, the more they will move and the more time they will spend in lighter and less restful sleep. Good sleeping is normally associated with a low number of body shifts during the sleep period. Bed-induced shifts due to discomfort caused by the bed are a significant cause of poor sleep quality. On conventional mattresses (including feather beds, inner spring mattresses, orthopedic mattresses, waterbeds and the like), most people experience about forty major postural body shifts in the course of a night's sleep. Poor sleepers experience about sixty percent more major shifts than good sleepers. While some shifts during a sleep period are beneficial, the quality of sleep can be greatly improved for many by reducing the number of bed-induced shifts.
There are two major causes of bed-induced shifting that cause poor sleep. The first major cause of shifting is the buildup of pressures on parts of the body and the second major cause of shifting is poor body alignment. Considering the first major cause of shifting, the buildup of pressures results from prolonged lying in the same position. On conventional mattresses, the pressure tends to be greatest on the body's protrusions (such as shoulders and hips) where body tissues are put in high compression against the mattress. High compression tends to restrict capillary blood flow which is recognized by the body, after a period of time, as discomfort. The pressure threshold which causes a discontinuance of capillary blood flow is called the ischemic pressure. The ischemic pressure is normally considered to be approximately thirty mmHg. The discontinuance of capillary blood flow is observable as a red spot on the skin. After pressure is applied, a red spot on the skin is a precursor to tissue damage. When parts of the body (usually shoulders and hips in conventional mattresses) are subjected to pressures above the ischemic threshold, discomfort results and, hence, a person shifts to remove the discomfort and threat to tissue damage.
Considering the second major cause of shifting, poor body alignment results from lateral bending of the vertebral column of the body, particularly for a person in a side-sleeping position. Such lateral bending is typically caused by mattresses that allow sagging of the body. Conventional mattresses allow such sagging regardless of the hardness or the softness of the mattress but the sagging effect tends to be more pronounced on soft mattresses. A sagging mattress allows the waist to drop relative to the rib cage and hips and results in stress to muscles, tendons and ligaments. The stress from a sagging mattress frequently manifests as discomfort or even pain in the lumbar region of the back. Such discomfort causes the sleeper to shift in order to relieve the discomfort.
In U.S. Pat. No. 4,662,012 invented by Torbet, one of the inventors herein, an air mattress is disclosed for supporting a person in a reclining position while maintaining spinal alignment and while maintaining low supporting body surface pressure. The Torbet mattress utilized zones running laterally across the width of the mattress with differing air pressure in the zones longitudinally along the length of the mattress. The Torbet mattress has proved to be ideal for supporting sleepers while minimizing supporting body surface pressure and maintaining spinal alignment.
While the Torbet mattress has established a standard of comfort that has not been achieved by conventional mattresses, the Torbet mattress has not been distributed as widely as possible because of its high cost of manufacture. The superior benefits of the Torbet mattress have generally been available only to those, such as hospitals, sleep clinics and the wealthy, willing to pay a high price.
For the Torbet mattress and mattresses in general, persons of greater body weight tend to sink farther into and depress the mattress more than persons of lower body weight. Body protrusions (such as shoulders and hips) cause the highest depression of the mattress and need to be accommodated. The shoulder of a heavy body resting atop the mattress in a side-lying position should not bottom out, that is, the shoulder should not depress the mattress to the extent that an underlying hard supporting surface is felt.
Mattresses using foam and spring sections have been proposed to reduce the cost of the Torbet mattress. Foam or spring sections alone in mattresses, because of the vertical displacement properties of conventional foams and springs, have not satisfactorily achieved simultaneously spinal alignment and uniform low supporting body surface pressure along the interface between the mattress and the body.
An ideal mattress has a resiliency over the length of a body reclining on the mattress to support the body in spinal alignment, without allowing any part of the body to bottom out, and also has a low surface body pressure over all or most parts of the body in contact with the mattress. Since a reclining body has both varying density and varying contour in the longitudinal direction, the ideal mattress must conform to these variations. With such variations, in order to achieve spinal alignment, the supporting forces in the mattress, under load from the reclining body, must vary along the body to match the varying body density and shape. Also, when the body is in spinal alignment, in an ideal mattress, the supporting pressures in the mattress against the skin must be low. The preferred pressure against the skin of a person in bed for an ideal mattress is generally below the ischemic threshold. The preferred side-lying spinal alignment for a person in bed is generally defined as that alignment in which the spine is straight and on the same center line as the legs and head.
While the general principles of an ideal mattress have been recognized since the Torbet mattress, actual embodiments of mattresses that approach the properties of an ideal mattress at reasonable costs have not been forthcoming. Lateral zones, with varying compression in the longitudinal direction, of springs in spring mattresses are capable of achieving spinal alignment if the mattress is of sufficient depth to allow the shoulders and hips to sink into the mattress to a depth that maintains spinal alignment without bottoming out. However spring mattresses generally do not achieve spinal alignment for the primary reason that the compression forces in springs vary as a function of the vertical depression of the springs in compression. The taller the spring in the relaxed state, the greater is the vertical depression and compression of the spring before the force increases to balance the weight of the part of the body

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