Neuromuscular Electrical Stimulation (NMES) Preserves Muscle Mass in Intensive Care Unit (ICU)

All participants have received standard physical therapy (SPT) sessions based on a passive range of motion mobilization protocol for the lower limbs. It consisted of a bilateral series of 10 repetitions of hip flexion, knee flexion and extension, and ankle flexion and extension. The procedure was performed twice a day: a morning (between 8am - 12pm) and an afternoon session (between 2pm - 6pm).

Electrical stimulation was performed twice a day after SPT. Two electrodes were attached to each thigh at the motor points of the quadriceps muscle. The point halfway between the anterior superior iliac spine and the base of the patella was used as reference and electrodes were placed 15 cm apart each other, 5 cm proximal and 10 cm distal from the reference point. After the first measurement, semi-permanent markers were used to indicate the position of electrodes. Electrical stimulation was performed using a 4-channels device (Sonopuls 492, series 4, Enraf-Nonius®, Rotterdam, Netherlands). The low-frequency protocol consisted of 100 Hz and 400 ms width pulses, delivered in trains of 5 s ON (ramp-up time: 1 s, plateau: 3 s, ramp-down time: 1 s) and 10 s OFF. Sessions had 20 min of duration (total of 40 min/day) and the current amplitude (mA) was adjusted to the identification of visible and palpable contractions and was rectified every 3 min to sustain the initial level of contraction.

Electrical stimulation was performed twice a day after SPT. Two electrodes were attached to each thigh at the motor points of the quadriceps muscle. The point halfway between the anterior superior iliac spine and the base of the patella was used as reference and electrodes were placed 15 cm apart each other, 5 cm proximal and 10 cm distal from the reference point. After the first measurement, semi-permanent markers were used to indicate the position of electrodes. Electrical stimulation was performed using a 4-channels device (Sonopuls 492, series 4, Enraf-Nonius®, Rotterdam, Netherlands).The medium-frequency protocol had similar parameters, but a carrier frequency of 2500 Hz and burst frequency of 100 Hz. Sessions had 20 min of duration (total of 40 min/day) and the current amplitude (mA) was adjusted to the identification of visible and palpable contractions and was rectified every 3 min to sustain the initial level of contraction.