3rd principle of bedside ergonomics relative to 30 degree lateral turn position:
The angle of supported lateral turn is a function of 3 variables:
- The angle of the support device being used relative to the angle of the torso
- How close the support is to the dependent side of the torso
- The extent of accommodation of the torso such that supported surface area is evenly distributed between the bed surface and the support device.
Conversely, the further away from under the dependent side of the back the support is placed, the lower the angle of turn will be provided.
Thus, a wedge that is angled to precisely 30 degrees can effect a turned angle anywhere between 0 and 60 degrees, depending on how close it is placed to the dependent side (the side closest to the mattress) of the torso
Regardless of angle of support, there remains the a physiological and ergonomic tendency for a person to shift to the closest neutral angle (principle 2).
Figure 3: Angle of lateral turn is proportional to device angle + “dependent” surface + torso accomodation