Central Blood Pressure Monitoring via a Standard Automatic Arm Cuff

Figures

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  Figure 1. (a) Conventional method for monitoring central blood pressure (BP) via a special automatic arm cuff device. The oscillogram is the variable cuff pressure oscillation amplitude versus cuff pressure function; PVP, pulse volume plethysmography; SP, systolic BP; DP, diastolic BP. (b) Physiologic method for monitoring central BP via a standard automatic arm cuff device. The sub-methods are shown in Fig. 2.

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  Figure 2. (a) Patient-specific method for estimating brachial BP levels from a cuff pressure waveform obtained during conventional deflation by leveraging a physiologic model and optimization. The method is described in detail in19; and figure adapted from20 © 2016 IEEE. Reprinted, with permission, from IEEE (IEEE Transactions on Biomedical Engineering). (b) Ensemble averaging/calibration method for extracting a brachial BP-like waveform from the cuff pressure waveform obtained during conventional deflation. The method extracts a deflation PVP waveform by normalizing and then averaging similar waveform beats from the deflation end (wherein PVP and BP waveform shapes may better agree due to relatively constant brachial artery compliance) and then scales the waveform to brachial SP and DP. (c) Variable transfer function (VTF) method for converting the brachial-like BP waveform to the central BP waveform. The method defines the transfer function in terms of the pulse transit time (Td) and wave reflection coefficient (Γ) parameters of an arterial tube-load model and then varies Td based on its well-known inverse relationship with mean BP (MP). MP is estimated as the time average of the…

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  Figure 3. Central SP, pulse pressure (PP), and DP bias errors (μ) and precision errors (σ) (average ± SE) of the patient-specific method (Fig. 2a) versus the office device (a population average method) and the physiologic method (Fig. 1b) versus the conventional method (Fig. 1a) in the testing dataset. Note that the patient-specific method and office device measure brachial BP levels, so the upper plots represent errors between brachial BP levels and central BP levels (i.e., starting point errors prior to applying the transfer function). *p ≤ 0.01 compared to corresponding method via paired t-test for μ and Pitman-Morgan test for σ.

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  Figure 4. Bland-Altman plots of the central SP, PP, and DP errors of the physiologic method and conventional method in the testing dataset.

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  Figure 5. Central SP, PP, and DP bias errors (average ± SE) of the patient-specific method versus the physiologic method versus the physiologic method with VTF replaced by GTF for different PP amplification (ratio of reference brachial PP to central PP) subgroups in the testing dataset. Again note that the patient-specific method measures brachial BP levels. *p ≤ 0.01 between physiologic method and other method via paired t-test. The precision errors of the methods were similar for the subgroups.