Sleep apnea therapy devices (CPAP devices) generate a slight overpressure in the respiratory tracts of sleep apnea patients, thereby preventing closure of the pharynx or respiratory arrest. In controlled CPAP devices, pressure sensors continuously monitor the therapy pressure, thereby improving the comfort and quality of the treatment.
The slight overpressure of a few millibars is generated by a centrifugal blower and supplied to the patient via a tube system and respiratory mask. However, the set therapy pressure of the CPAP device is influenced by the patient's breathing. The pressure drops during each inspiration and rises during each expiration. This leads to increased breathing effort for the patient and to a lower quality of therapy. Higher-quality devices therefore have a precise pressure sensor that continuously compares the actual pressure value with the specified target therapy value. Pressure deviations can then be compensated very quickly by dynamically controlling the blower output. The pressure stability is an essential quality feature and an important comparative parameter of controlled CPAP devices.
First Sensor pressure sensors of the HDI and HCE series monitor the pressure value resulting at the device output or in the respiratory mask. Thanks to their very high accuracy and sensitivity, they detect pressure fluctuations in fractions of a millibar. In conjunction with modern control electronics and powerful blowers, the short response time of the sensors in the millisecond range enables pressure deviations to be compensated rapidly.
In order attain the highest accuracy with a total error spectrum better than ± 0.5 %FSS, First Sensor calibrates the HDI and HCE pressure sensors over the entire pressure and temperature range using an internal microprocessor. The processed sensor signal can be read out as a digital pressure value via an I²C or SPI bus interface. An analog voltage output signal is also available.