The latest studies have thrown considerable light upon the relationship between hypertension and various diseases. People, who are generally diagnosed as having hypertension, with a systolic blood pressure of 140 mmHg or more and a diastolic blood pressure of 90 mmHg or more, commonly develop cerebral hemorrhage and cerebral infarction. In view of this, the importance of health care has been further emphasized in order to prevent diseases caused by high blood pressure. For effective prevention of hypertension, not only periodic medical check-ups such as blood pressure taking but also awareness of the condition of blood pressure on a daily basis become necessary.
Recently, simplified sphygmomanometers which enable easy measurements of blood pressure on a daily basis are commercially available so that continuous, easy personal blood pressure control becomes possible. For such simplified sphygmomanometers, the so-called oscillometric method (pressure pulse wave oscillation method) is prevailing which is distinguished from the Korotcoff method that has been conventionally used as the stethoscopy in the medical field and others. The oscillometric method is carried out in such a manner that a cuff (arm wrap) is worn around fingers, a wrist or an upper arm; air is sent to the cuff to press an artery; pressure in the cuff is gradually released to detect pulse wave components with a pressure sensor; and blood pressure (systolic and diastolic blood pressures) is measured based on the detected pulse wave components.
A known electronic sphygmomanometer utilizing the oscillometric method is designed as follows: For setting of a target inflation value for the cuff, a cuff pressure signal is detected, for example, during inflation of the cuff. Then, a systolic blood pressure (e.g., a cuff pressure corresponding to one-half the maximum amplitude of the pulse wave) is simply estimated from the maximum amplitude value of the pulse wave included in the signal, and a value obtained by adding a specified value to the estimated systolic blood pressure is automatically set as a target inflation value. In this case, for the purpose of reducing the time required for a blood pressure measurement as well as the pain given to the person under measurement, the rising speed of pressure at the time of cuff inflation is set to a higher value than the speed of cuff deflation during which a measurement of systolic and diastolic pressures is made.
In the medical field, there have recently been advances in the studies of the association between hypertension and obesity and it has been found that obesity is not simply a state of overweight and the distribution of body fat bears relevance to blood pressure. It has been further reported that the distribution of abdominal body fat (visceral fat type obesity) deeply concerns hypertension.
In addition to BMI (Body Mass Index=body weight/(body height)2) that is widely used as an index indicative of the degree of obesity, various indices (e.g., percent body fat, the cross-sectional area of abdominal visceral fat, etc.) to an assessment of visceral fat type obesity have been devised and respectively proved to be useful in the clinical sites. Of these indices, percent body fat is obtained based on personal specific data on the subject such as height, weight, age and sex and based on the measurement of body impedance. The cross sectional area of abdominal visceral fat is obtained from a CT scan of the abdomen of the subject around his umbilicus and from estimation based on data on the waist size of the subject obtained by measuring the abdomen of the subject around his umbilicus as well as the personal specific data described above.
The above-described conventional sphygmomanometer has, however, revealed such a drawback that since it measures and deals with blood pressure alone, it cannot provide more accurate diagnosis of hypertension taking account of the relationship with the aforesaid visceral fat type obesity.
In addition, the conventional sphygmomanometer of this type presents another problem when setting a target inflation value for the cuff. Specifically, since the conventional sphygmomanometer is susceptible to the influence of noise caused by the fluctuation of a cuff pressure signal occurring just after cuff inflation, the detection of a pulse wave at the time of cuff inflation cannot be always carried out correctly, so that an estimated value of systolic blood pressure and, in consequence, a target inflation value based on the estimated value become wrong. Especially, if the target inflation value is set to an abnormally low value, there will occur an error in the later measurement of blood pressure values (i.e., systolic blood pressure and diastolic blood pressure) at the time of cuff deflation due to a lack of inflation.
The present invention has been directed to overcoming the foregoing shortcomings and a primary object of the invention is therefore to provide a visceral fat scale equipped with a sphygmomanometer with which a subject can keep track of his blood pressure values and grasp the state of obesity to realize more accurate, comprehensive and diversified diagnoses and disease prevention. Another object of the invention is to provide a visceral fat scale equipped with a sphygmomanometer wherein even if it fails in making an accurate measurement of the maximum amplitude value of a pulse wave at the time of cuff inflation, an error will not occur in the measurement of blood pressure values at the time of cuff deflation.