This is a study to look at the effect on breathing of various ways to package a person in a rescue litter. We will measure lung function in a litter, lying down, lying down in a vacuum mattress, one the side in a vaccum mattress, and vertical in a vacuum mattress.
After acknowledging informed consent, each subject will do baseline sitting pulse oximetry (device) and forced vital capacity (FVC) and 1-second forced expiratory volume (FEV1) three times. After obtaining a baseline, the subject will be secured with a MedTech-VSB 6 foot vacuum mattress (MedTechSweden, Geneseo, IL) in a Ferno-Washington Model 71 litter (Ferno-Washington, Wilmington, OH) using 1-inch tubular webbing, following the methodology of the National Cave Rescue Commission but with no padding and no blankets, see figure 1 .8 The mattress will be deflated (stiffened) to start after securing into the litter with webbing. The litter will be rigged for suspension in the horizontal supine and horizontal lateral positions. We will measure FEV1 and FVC will be repeated in each of 4 positions; supine on a non-stiffened mattress in a horizontal litter (see figure 1), supine on a stiffened mattress in a horizontal litter, in lateral decubitus position in a stiffened mattress in a horizontal litter (see figure 2), and supine, with a stiffened mattress in a vertical litter. The order will be randomly assigned to eliminate any learning effect. The calculated sample size is 10, which should be easily enough to see a difference between baseline and just lying flat. The anticipated change in pulmonary function in the mattress will be in addition to lying down, but not as big as this. So to find this smaller change we anticipate needing 24, this allows for doing all 24 potiential orders of 4 procedures. We will do a preliminary analysis after 12 person, but will continue to 24 if there is no demonstrated difference with the mattress at 12, (see Table 1). In each case, the patient will stay in the position for 1 minute after completing spirometry to measure oxygen saturation again.
1,2,3,4 2,1,3,4 3,1,2,4 4,1,2,3 1,2,4,3 2,1,4,3 3,1,4,2 4,1,3,2 1,3,2,4 2,3,1,4 3,2,1,4 4,2,1,3 1,3,4,2 2,3,4,1 3,2,4,1 4,2,3,1 1,4,2,3 2,4,1,3 3,4,1,2 4,3,1,2 1,4,3,2 2,4,3,1 3,4,2,1 4,3,2,1 Table 1, orders of testing
The litter will be raised 6 inches off of the ground prior to measurement. Anchors to support his will be the patio sun structure at UCSF which has been approved by local building supervisors and used for several other trials, or using trees at other sites. The PI and co-PIs have extensive training and experience evaluating anchors for life support in technical rope exercises. We will not use a crash pad in this set of experiments as the subject will be no more than 6 inches off of the ground and a six inch thick pad will make it harder to quickly intervene even if something did go wrong.
