| 摘要 |
<p>An automated blood pressure instrument has a noise level detector which makes sound pick-up analogous to that in the human ear. The sounds arriving from the patient's artery are converted to electrical signals which are fed through filters to the noise level detector. The signals arriving are used to calculate a noise level such that the values of the expected Korotkoff sound levels, which are higher than an estimated level, are ruled out. The noise level determined varies depending on the state of the patient as well as between individuals, and is therefore used as a reference value for identifying the Korotkoff sound. The device comprises comparators for discrimination of the Korotkoff sounds from the sounds arriving by comparing the sound levels with a Korotkoff sound reference level which is proportional to the noise level and represents a variable level characteristic of the state of the patient. The device can detect the differences in the arriving sound signals in the same way as the human ear and can therefore guarantee accurate measurement. As soon as the comparator detects that the sound signals have a level exceeding the reference level of the Korotkoff sounds it generates a Korotkoff sound signal representing the Korotkoff sound. A display unit responds to the occurrence and disappearance of the Korotkoff sound signal in order to display the systolic or diastolic blood pressure.</p> |
