General description

The Percutaneous Electrical Muscle Stimulator was developed by the Swiss company Syderal. This is a second generation of the PEMS device, the first generation PEMS having flown on the Space Shuttle in 1996.

The Percutaneous Electrical Muscle Stimulator (PEMS) is a self-contained, locker stowed item. Its purpose is to deliver electrical charge pulse stimulation to non-thoracic muscle groups of the human test subject, thereby creating contractile responses from the muscles. Its main purpose is to support human neuromuscular research. The device can provide either single pulse or pulse trains with two selectable pulse widths and variable amplitudes.

PEMS is portable, and designed to be used in conjunction with other physiological instruments, in particular the Muscle Atrophy Research and Exercise System (MARES). PEMS will be checked out and commissioned in the US Laboratory. Eventually PEMS should be used together with the MARES in the European Columbus laboratory.

The PEMS stimulation can be controlled manually at the PEMS front panel to select pulse stimulation or select an experiment protocol to provide pulse train stimulation. In addition, the PEMS stimulation can be controlled remotely.

PEMS has two operational configurations:

• Stand-alone
• Remote

In stand-alone mode, PEMS can be operated locally using the front panel controls. It is possible to select and activate one of a number of pre-loaded Protocols, each protocol defining a particular sequence of pulses.

In the remote configuration where PEMS is operated in conjunction with MARES, it is possible for MARES to take over the control of the full operational capability of PEMS, including the download of Protocols and the selection and initiation of the appropriate Protocol.

In both operational configurations, PEMS requires to be supplied with 28 V DC electrical power.

PEMS can also be connected directly to the HRF PC to enable the downloading of experiment protocols.

Functional requirements

PEMS is capable of:

• Delivering controlled percutaneous electrical stimulation to the following muscle groups to provide a contractile response:
  • Triceps surae (ankle);
  • Quadriceps (knee);
  • Adductor pollicis (thumb);
  • Triceps brachii (elbow);
  • Biceps brachii (elbow);
  • Flexor carpi ulnaris/radialis (wrist);
  • Extensor carpi ulnaris/radialis (wrist);
• Accommodating fully programmable pulse interval;
• Providing for automatic fault detection and protocol termination;
• Providing for manual termination of test protocol;
• Allowing for manually operated 'single twitch' stimulation pulse.

Technical specifications

• PEMS provides two pulse widths of 50 µseconds and 250 µseconds ± 5%
• For the 50 µsecond pulse width, pulse intensity is selectable in the range 50, 100...800 mA in steps of 50mA;
• For the 250 µsecond pulse width, pulse intensity is selectable in the range 10, 20...160mA in steps of 10mA;
• For both pulse widths the associated duration of the negative part of the bipolar pulse is less than 250 µseconds to maintain charge neutrality;
• For both pulse widths the rise and fall times (10% to 90% amplitude points) is less than 5 µseconds;
• For both pulse widths the electrode voltage for the positive and negative amplitude is limited to 500 volts;
• Include a pre-determined or a random delay before initiation of the pulse protocol;
• A protocol consists of an integer number of pulse trains, the number of lying between 1 to 100;
• A pulse train consists of an integer number of pulses in the range 1 to 64000;
• The pulse repetition rate is selectable from 1, 10, 20, 30, 50 and 100 Hz.

Mass: 7 kg, total system mass including cables: 10 kg
Height: 15 cm
Width: 30 cm
Depth: 40 cm
Operating power: 25 W