In the median nerve we usually obtain smaller amplitude of sensory nerve action potentials (SNAPs) in the orthodromic sensory nerve conduction studies than in the antidromic ones. To magnify the amplitude of SNAPs in the orthodromic method we designed an instrument of simultaneous three fingers stimulation. In the first place we recorded SNAPs of the median nerve between each finger and wrist segment of 14-cm distance using orthodromic and antidromic conduction studies in ten healthy individuals. The antidromic method, recorded at the finger where nerve trunk travels near the skin, gave 2.5 times larger SNAP from baseline to peak amplitude on the mean than in the orthodromic method, recorded at the wrist where nerve trunk travels relatively profound. In the orthodromic method separate stimulation after index finger, middle finger and ring finger gave 16.2 μV, 18.5 μV and 9.3 μV of SNAP on the mean, respectively. Simultaneous three fingers stimulation gave as large as 37.4 μV of SNAP on the mean. In the antidromic method separate recording from index finger, middle finger, ring finger and from simultaneous three fingers gave 44.6 μV, 46.3 μV, 26.8 μV, and 39.6 μV of SNAP, respectively. Then, we applied this instrument in four patients with carpal tunnel syndrome. In the orthodromic method mean amplitude of SNAPs recorded at the wrist were 3.0 μV, 2.9 μV, 1.6 μV and 5.3 μV after index, middle, ring finger and simultaneous three fingers stimulation, respectively. In the antidromic method after wrist stimulation, recorded SNAP amplitude from the index, middle, ring finger and simultaneous three fingers were 9.1 μV, 10.2 μV, 5.1 μV and 8.5 μV, respectively. Even in cases of advanced neuropathies in which a SNAP is difficult to be obtained by routine orthodromic method, we may be able to record it by using simultaneous three fingers stimulation in the orthodromic method. In the antidromic method simultaneous three fingers parallel recording gave average amplitude of SNAP compared with isolated recording from each finger.

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To evaluate the influence of elevated back part of beds (back angles to the horizontal of 0, 10, 20 and 30 degrees), we estimated subjective sleep quality and measured objective sleep variables by sheet-shaped body vibrometer which is placed under a mattress or a futon and can produce almost identical sleep/wake scores to wrist actigraphy. Thirteen healthy male subjects, aged 24–42 (mean 29.2), spent one night sleeping at home in each of the four back angles in random order. Sleep in back angles of 20 and 30 degrees resulted in poor subjective sleep quality and reduced sleep efficiency. These results suggest that back angles of 20 degrees or more decrease sleep quality and back angles of 10 degrees or less have little influence on sleep.

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