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The sleep-apnea syndrome is classified into a so-called central type caused by an abnormality in the respiratory center, an obstructive type by an upper airway obstruction, and a mixed type by a combination thereof. Among the rest, the obstructive type is often observed clinically and is considered to be caused by a morphological abnormality in the upper airway tract, such as tonsillar hypertrophy or micrognathia, or by a tonus of the upper airway muscle for broadening the airway. The inventors of this application have clarified by experiments that the upper airway can be recovered from obstruction which causes apnea stimulatingthe genioglossus, which is one of the dilator muscles of the upper airway, with pulses of a frequency of 40 to 150 Hz, a peak value of 1 to 50 volts and a rise-up time constant of 0.2 seconds or more, and that control of the start and stop of the electric stimulation with apnea detection signals would make it possible to automatically take measures to deal with apnea even at night when it is particularly difficult to find a fit of apnea.
BACKGROUND OF THE INVENTION
The present invention relates to an apnea preventive stimulating device for preventing the occurrence of trouble which results from abnormality in the respiratory function in one's sleep.
Many studies have been reported on a so-called sleep-apnea syndrome, i.e. apnea which is accompanied by the suspension of breathing, for example, for 10 seconds or more in one's sleep at night. Such apnea in one's sleep decreases the alveolar ventilation volume and the partial pressure of arterial oxygen difference (PaO2) and increases the partial pressure of arterial carbon dioxide (PaCO2), and further, it lowers the chemoreceptor sensitivity and raises the upper airway resistance, thus constituting a causative factor in aggravation of the arterial blood gas. This causes pulmonary hypertension, right-sided heart failure, arrhythmia, or brain trouble, which may sometimes result in a sudden death if worst comes to worst. Thus, the breathing abnormality in one's sleep is a clinically important subject, and it is necessary to take measures for preventing the occurrence of the above-mentioned sleep-apnea.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a device effective for preventing the above-mentioned sleep-apnea.
To attain the above object of the present invention, there is provided an apnea preventive stimulating device characterized by the provision of: a respiration sensing circuit; a detection signal generator for detecting a respiration detection signal from the output of said respiration sensing circuit; an electric stimulating wave generating circuit which, when apnea has continued for 5 to 10 seconds after its detection by said detection signal generator, starts to operate and generates electric stimulating waves having a frequency of 40 to 100 Hz and a pulse peak value of 1 to 50 V; and a stimulating circuit composed of genioglossus stimulators which are supplied with the output of the said electric stimulating wave generating circuit.
The respiration sensing circuit is formed by a parallel circuit of sensors for sensing respiration through both nostrils and a sensor for sensing respiration through a mouth, or a microphone sensor to detect the breath tones. The intensity of the electric stimulating waves can be amplified at a predetermined time from a patient's bedtime, so that the lowering of stimulation on a patient by the electric stimulating wave during the patient's deep sleep is compensated for to wake up the patient.
The sleep-apnea syndrome is classified into a so-called central type caused by an abnormality in the respiratory center, an obstructive type by an upper airway obstruction, and a mixed type by a combination thereof. Among the rest, the obstructive type is often observed clinically and is considered to be caused by a morphological abnormality in