1. Field of the Invention
This invention relates generally to a transcutaneous electrical nerve stimulation (TENS) apparatus and more particularly to a TENS therapy apparatus and method having safety features and automatic operation.
2. Discussion of the Background
Various kinds of transcutaneous electrical stimulation of tissues have been utilized, especially in the last twenty years, for a variety of medical treatments. In particular, the stimulation has been used in order to treat various kinds of pain associated with various kinds of medical conditions and injuries to stimulate muscles, to reduce swelling and inflammation and for various other medical treatments.
The prior art includes many devices which have specialized features for protecting the patient, making the device easier to use and improving the results of the procedure. While these improvements have made the treatment of patients more safe, more effective and more comfortable, there remain many problems and areas for improvement for each device.
In U.S. Pat. No. 4,233,986, an apparatus and method is shown for a transcutaneous electrical stimulation treatment for pain. The apparatus includes a pulse generator and skin electrodes for applying the pulses. The width of the pulses may be varied. The electrodes also include a method for finding nerves in the patient's skin.
Another related device shown in U.S. Pat. No. 4,088,141 describes a fault control circuit for use with an electrical stimulator used on a patient. The device is disabled when the electrode impedance exceeds the threshold level or when the output current level undergoes a large change.
Another use of this type of apparatus is found in U.S. Pat. No. 4,016,870 which is used to locate acupuncture points on the skin. While this device locates the desired points, it does not involve actual electrical stimulation.
Another therapeutic apparatus is shown in U.S. Pat. No. 4,580,570. This apparatus discloses different modes of operation so that current may be either continuously applied or periodically interrupted.
Other electrical stimulation devices are shown in other U.S. patents such as U.S. Pat. Nos. 4,598,713, Re. 32,091, 3,645,267, 3,894,532 and 3,983,881.
These devices generally have the same basic function of applying electrical stimulation to the patient through some form of probes. Some of these devices contain safety features so that the patient is not subjected to a sudden shock and so that the device may be shut off if the probe is not in good contact. Other devices show various methods of controlling the various parameters associated with the electrical pulses. Some of the other devices have various forms of controls for making the application of the pulses more comfortable and effective for the patient.
Although these devices and their methods of operation have provided great relief of pain for the patient and have been reasonably effective in their application, several problems still remain in their use. The use of these devices is still not completely safe and comfortable for the patient in many cases. If the probe does not remain in good contact with the patient's skin, it is often possible to have a sudden increase in the voltage applied to the body. This results in a sudden jolt to the patient which is most uncomfortable. Also, many patients find that the sudden application of the high voltage pulses at the beginning of the treatment is similarly uncomfortable. Accordingly, there is definite room for improvement in order make the patients more comfortable. Operators also find the application of these devices to be somewhat inconvenient at various times. It is difficult to control the placement of the probe on a particular place on the body while having to constantly readjust the various dials and to monitor the various displays on the device. This may lead to discomfort for the patient if the operator's attention is diverted to adjust the dials and the probe is either moved or loses contact with the skin. The necessity to constantly reset the dials is also a problem for the operator. Most of the devices also do not include all the features shown in the different patents listed above and while some of the devices may have some form of some features, none of the devices contain all of the features indicated.