| 摘要 |
The invention concerns a method and apparatus for monitoring respiratory condition by impedance pneumography. An electrical signal is applied at a plurality of frequencies to a human subject by way of a first pair of spaced electrodes applied to the trunk of the body, whilst the resulting electrical signal is monitored at said plurality of frequencies at different points on the body by way of a second pair of spaced electrodes. From the resulting electrical signal a measure of the impedance of a part of the body at the plurality of frequencies is obtained, and a difference signal representing the impedance change with frequency is calculated. The difference signal is normalised with respect to a signal representative of the impedance measure itself at one or more frequencies, thereby suppressing the effect of those impedance signal components -such as movement artefact- whose frequency dependent change is substantially proportional to the impedance signal value. The invention improves the reliability of impedance pneumography, especially when employed in situations in which it is difficult to restrict subject movement, such as during sleep. It has particular application in neonatal and infant sleep apnoea detection systems.
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