Cath Lab Digest

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  Low-air-loss (LAL) mattress systems have been used for the treatment and prevention of pressure ulcers for many years. Pressure ulcer development is related, in part, to the accumulation of heat and perspiration on the skin. Heat and moisture increase skin susceptibility to the damaging effects of pressure and shear and decrease the resiliency of the epidermis to external forces.^1-3 Ongoing compressive forces on skin tissues are known to promote ischemia with subsequent development of pressure ulcers.² Therefore, controlling the microclimate of the skin and providing a quality patient support system appear to be necessary to prevent pressure ulcers. Low-air-loss mattresses were developed and are used in the belief that they help to control the microclimate of the skin.^1,3-5

Literature Review

  Clinical studies. Results of LAL effectiveness studies have been mixed. Ferrell⁶ reported that, compared with a 10-cm thick egg-crate foam mattress, pressure ulcer healing rate improved when patients were placed on an LAL surface. In addition, Ferrell et al⁷ concluded that LAL is cost-effective for patients with "good healing characteristics and 'mild' ulcers." Inman et al⁸ reported a significant decrease in the nosocomial pressure ulcer incidence rate for patients on LAL compared to standard hospital surfaces but found no differences in resolution of existing ulcers. Yarbrough et al,⁹ Holzapfel,⁴ and Charles et al¹⁰ reported clinical benefits of LAL. However, Hardin et al,¹¹ Jesurum et al,¹² and Warner¹³ reported no statistically significant difference with the use of LAL and other standard support surfaces.

  Maklebust¹⁴ and Callum et al¹⁵ point to the lack of well-designed, scientifically rigorous studies available in the literature and to an inability to draw conclusions from previous studies on the subject.

  Low-air-loss systems. Low-air-loss was first described in medical literature in 1971 by Scales et al.¹⁶ They discussed a system of interconnected air chambers with a flexible, vapor-permeable film between the skin and the support air. The goal of this bed was to minimize the volume of air and the size of the inflation air pump compared to high-air-loss surfaces; thereby, achieving uniform load distribution to accommodate body forms, evaporate water from the support area, and control temperature and humidity. Since that first description, the number of available products called LAL has multiplied rapidly. Currently, dozens of products are on the market, featuring nearly as many construction methods. Because no definition of LAL has been put forth by an independent body that has met with the acceptance of the medical and manufacturing communities, clinicians have been left with assumptions of LAL mattress design and performance. Despite the prevalence of these mattress systems, no clear, universally agreed upon definition exists for their design - nor any viable, reproducible standards on which to base their performance or to assess their anticipated effect in clinical settings.

  Intended specifically to remove or reduce perspiration accumulation and provide localized cooling of the skin to control the skin microclimate, LAL systems are used in conjunction with patient support systems to distribute torso loads.