BP+
BP+ provides comprehensive non-invasive cardiovascular assessment from an upper arm cuff and is as easy to use as a conventional BP device.
| Central Blood Pressure | Measure aortic systolic and diastolic pressures. |
| Pulse Wave Analysis | Displays pressure changes at the aorta in a waveform in a 10 second strip that can be analysed by the BP+ Reporter or analysed visually. This can identify arrhythmias and pulse pressure fluctuations (rhythm strip). |
| Augmentation Index | Highly sensitive measure of vascular tone. |
| Stand-alone device | Press Start and get results in less than 90 seconds. |
| Digital patient archive, reporting and trending | BP+ Reporter is the software to accompany the Uscom BP+. |
| Accurate | Validated against cardiac catheters to surpass SP10, with built-in peripheral calibration. |
| Repeatable | Strong day-to-day and measure-to-measure repeatability with high intraclass correlation coefficient. |
| Fast and Comfortable | Complete measurement in less than 90 seconds. |
| Easy to use | Single upper-arm cuff, with one-button measurement. |
| Affordable | Advanced cardiovascular monitoring at home care prices. |
Measurements
Central Blood Pressure
Central blood pressure (BP) is the pressure the heart works against, and it is the strongest predictor of cardiovascular risk.
Central BP is the pressure in the aorta, just near the heart.
Central BP is different from conventional BP measured in the upper arm, which is a 'peripheral' artery. Peripheral BP is usually higher than central BP due to the increased peripheral resistance as the arterial branches increase in number and become smaller. The degree to which the peripheral BP is higher than central BP depends partly on the stiffness of the arteries.
Central BP has been shown to more strongly reflect vascular disease and predict outcomes than traditional upper arm BP. Central BP can also determine the different effects of different hypertension medications when upper arm BP and pulse wave velocity do not. Central BP is the pressure that the heart has to pump against to get blood to flow to the rest of the body. Higher central BP means that the heart consumes more energy to pump blood. This can eventually lead to heart failure. Central BP also reflects the pressure in the blood vessels feeding the brain. If central BP is high, it this may lead to aneurysms and strokes.
Augmentation Index
The augmentation index is a ratio calculated from the pulse pressure waveform, and is a measure of wave reflection and arterial stiffness. Augmentation index is commonly accepted as a measure of the (augmentation) of central aortic pressure by a reflected pulse wave.
Arrhythmias and Heart Rhythm
BP+ provides a 10 second rhythm strip that simplifies identification of abnormal heart rhythms. Atrial fibrillation and premature ventricular contractions can be detected using the rhythm strip.
Arrhythmias and Heart Rhythm irregularities are displayed in more detail on the BP+ Reporter and may be included in printed reports.
Repeatability
Three consecutive measurements over a period of approximately 10 minutes were taken in 282 subjects recruited from primary-care facilities. Measurements were taken in the left arm with subjects in a sitting position.
Measurement sets were excluded from analysis if any blood pressure or BP+ measure could not be calculated, if signal-to-noise ratio was less than 6 dB or if augmentation index was more than 300%.
The remaining 254 sets of measurements were then analyzed. Limits of agreement (LoA) were calculated as twice the standard deviation of the difference between the three pairs of each set of three measurements. Intraclass correlation coefficient (ICC) was calculated using a two-way consistency model. A repeatability aspect ratio (AR = LoA / Range) was also calculated.
|
Parameter |
Range |
LoA |
ICC |
AR |
|
Non-invasive blood pressure |
|
|
|
|
|
Systolic Pressure (mmHg) |
87 ~ 177 |
± 17 |
0.92 |
19% |
|
Diastolic Pressure (mmHg) |
45 ~ 102 |
± 9.6 |
0.92 |
17% |
|
Mean Pressure (mmHg) |
57 ~ 112 |
± 9.7 |
0.94 |
18% |
|
Pulse Rate (bpm) |
41 ~ 99 |
± 10 |
0.91 |
17% |
|
BP+ Parameters |
|
|
|
|
|
Augmentation Index (%) |
4.3 ~ 283 |
± 40 |
0.90 |
14% |
|
Central Systolic Pressure (mmHg) |
77 ~ 168 |
± 16 |
0.93 |
18% |
|
Central Diastolic Pressure (mmHg) |
46 ~ 103 |
± 9.8 |
0.92 |
17% |
|
Central Mean Pressure (mmHg) |
58 ~ 126 |
± 12 |
0.93 |
18% |
The ICC values indicate that BP+ parameters have excellent repeatability on par with standard oscillometric non-invasive blood pressure parameters.
The variability between the three consecutive recordings may be explained by true physiological changes such as minute-to-minute changes in blood pressure and vasoconstriction. They may also be due to arm motion or other environmental noise. In comparison, Frimodt-Moller et al.2 reports AR = 32% for inter-observer repeatability of tonometric augmentation index.
Augmentation index is calculated as a ratio of two numbers and therefore variability tends to increase with increasing augmentation index. For example, ICC for subjects with a median augmentation index below 150% (still significantly above the expected normal range) is 0.93.
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