The Total Lift Bed allows clinicians to position patients in all traditional modes; including cardiac chair position. However the TLB is the only hospital bed in the world that also allows for one very important position that consequently benefits the lungs; the standing position. The TLB's patented moving footboard actually moves to the patients feet providing support while being tilted anywhere from 0° to 82° safely and securely with one staff member; simply with the push of a button.
LUNG VOLUME CHANGES
- TIDAL VOLUME
This is the volume of air exchanged during normal breathing and is typically around 500ml. In a supine person, the weight of the body restricts the free movement of the rib cage, reducing tidal volume.
It has been estimated that, when a person is upright, 78% of tidal exchange is due to the motion of the rib cage but, in the supine position, restriction of rib cage movement reduces this to around 32%.
During prolonged bedrest, patients may develop fixed contractures of the costovertebral joints, further reducing tidal exchange and potentially leading to permanent restrictive pulmonary disease.
- RESIDUAL VOLUME
This is the air remaining in the lungs after a full forced breath out and is typically around 1.5L.
The residual volume of the lungs drops in bedridden patients, potentially increasing the risk of portions of the lung collapsing.
This reduction in residual volume appears to be due to:
• Airway obstruction, potentially due to pooled mucus.
• A shifting of the internal abdominal organs towards the thorax, which press on the diaphragm and compress the lungs.
- FVC & FEV1
Forced vital capacity (FVC) is the amount of air that can be forced out of the lungs after a maximum intake of breath, and is typically around 4.5L.
The supine position reduces both FVC and another measure called forced expiratory volume in one second (FEV1). It is thought these effects are due to a combination of:
• Movement of blood away from the lower limbs into the abdomen and thorax, increasing pulmonary blood volume.
• Increased resistance in the airways and a loss of elastic recoil as a result of structural changes within the lungs.
- When a person is mobile, the airways of the lower respiratory tract are coated evenly with a thin layer of mucus, which keeps the airways moist and traps particles that have been inhaled.
- Contaminated mucus is continually being swept upwards by rhythmic beating of cilia on the lining of the respiratory tract (the ciliary escalator) and, when it reaches the pharynx, it is swallowed to be sterilized by the acid in the stomach.
- When a patient is confined to bed there is a tendency for mucus to pool, under the influence of gravity, in the lower part of the airway. These accumulated secretions can swamp the lower portion of the ciliary escalator, reducing its function.
- These effects are often compounded in bedridden patients by dehydration, leading to the pooled mucus becoming thick and difficult to expectorate.
- The diameter of the airways, particularly the bronchioles, decreases after a period of immobility. Even healthy people can show airway narrowing after being in the supine position for some time; this is more pronounced in people who are older, overweight or smokers.
- This reduction in airway size, together with pooled mucus and the extra weight the recumbent body places on the rib cage, combine to make breathing more labored, and patients tend to take fewer deep breaths.
- The results can include the collapse of airways and small areas of lung tissue (atelectasis), which reduces the area available for gaseous exchange.
- Many studies have shown that prolonged bed rest dramatically increases the risk of respiratory tract infections. People cannot cough as easily or as well, which allows pooled mucus to stagnate and reduces the clearance of potentially pathogenic material and irritants.
- Stroke patients confined to bed for 13 days or more are two to three times more likely to develop respiratory tract infections compared with mobile people.
- Frequently turning and repositioning patients can help to prevent abnormal distribution and pooling of mucus in the respiratory tract. Bedridden patients can also be encouraged to try cough exercises to help shift pooled mucus and reduce the chance of an infection.
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