Error grid analysis for risk management in the difference between invasive and noninvasive blood pressure measurements

Smartphone-Based versus Non-Invasive Automatic Oscillometric Brachial Cuff Blood Pressure Measurements: A Prospective Method Comparison Volunteer Study

Introduction: Mobile health diagnostics have demonstrated effectiveness in detecting and managing chronic diseases. This method comparison study aims to assess the accuracy and precision of the previously evaluated OptiBP™ technology over a four-week study period. This device uses optical signals recorded by placing a patient's fingertip on a smartphone's camera to estimate blood pressure (BP). Methods: In adult participants without cardiac arrhythmias and minimal interarm blood pressure difference (systolic arterial pressure (SAP) < 15 mmHg or diastolic arterial pressure (DAP) < 10 mmHg), three pairs of 30 s BP measurements with the OptiBP™ (test method) were simultaneously compared using three pairs of measurements with the non-invasive oscillometric brachial cuff (reference method) on the opposite arm over a period of four consecutive weeks at a rate of two measurements per week (one in the morning and one in the afternoon). The agreement of BP values between the two technologies was analyzed using Bland-Altman and error grid analyses. The performance of the smartphone application was investigated using the International Organization for Standardization (ISO) definitions, which require the bias ± standard deviation (SD) between two technologies to be lower than 5 ± 8 mmHg. Results: Among the 65 eligible volunteers, 53 participants had adequate OptiBP™ BP values. In 12 patients, no OptiBP™ BP could be measured due to inadequate signals. Only nine participants had known chronic arterial hypertension and 76% of those patients were treated. The mean bias ± SD between both technologies was -1.4 mmHg ± 10.1 mmHg for systolic arterial pressure (SAP), 0.2 mmHg ± 6.5 mmHg for diastolic arterial pressure (DAP) and -0.5 mmHg ± 6.9 mmHg for mean arterial pressure (MAP). Error grid analyses indicated that 100% of the pairs of BP measurements were located in zones A (no risk) and B (low risk). Conclusions: In a cohort of volunteers, we observed an acceptable agreement between BP values obtained with the OptiBPTM and those obtained with the reference method over a four-week period. The OptiBPTM fulfills the ISO standards for MAP and DAP (but not SAP). The error grid analyses showed that 100% measurements were located in risk zones A and B. Despite the need for some technological improvements, this application may become an important tool to measure BP in the future.

Comparison of direct intra-arterial pressure and ClearSight finger cuff arterial pressure measurements in elderly patients undergoing transcatheter aortic valve replacement

OBJECTIVE

This study aimed to assess the agreement between direct intra-arterial pressure and ClearSight finger cuff arterial pressure measurements in elderly patients undergoing transcatheter aortic valve replacement (TAVR).

METHODS

A prospective observational study was conducted at Hitachi General Hospital, Japan, involving 30 patients aged 65 years and older who underwent TAVR under general anesthesia. Intra-arterial pressure and finger cuff arterial pressure measurements were recorded for 30 min after valve deployment. Bland-Altman analysis, four-quadrant plot analysis, and error grid analysis were used to assess the concordance between the two methods. Multiple regression analysis was performed to explore potential confounding factors affecting the agreement.

RESULTS

The bias and precision of ClearSight measurements were -4.88 ± 15.46 (mmHg) for SBP, 4.73 ± 8.95 (mmHg) for mean, and 9.53 ± 9.01 (mmHg) for DBP. The Bland-Altman analysis demonstrated acceptable agreement between intra-arterial pressure and finger cuff arterial pressure measurements. The four-quadrant plot analysis showed good trend-tracking ability, and the error grid analysis revealed that most of the observed values fell into the no-risk category. The mean BP match ratio and SBP match ratio were influenced by several factors such as age, BSA, ejection fraction, valve size, and gender.

CONCLUSION

The ClearSight finger cuff arterial pressure measurement showed good agreement with direct intra-arterial pressure in elderly patients undergoing TAVR. However, factors such as age, BSA, ejection fraction, valve size, and gender may influence the agreement between the two methods.

A novel smartphone app for blood pressure measurement: a proof-of-concept study against an arterial catheter

Smartphones may provide a highly available access to simplified hypertension screening in environments with limited health care resources. Most studies involving smartphone blood pressure (BP) apps have focused on validation in static conditions without taking into account intraindividual BP variations. We report here the first experimental evidence of smartphone-derived BP estimation compared to an arterial catheter in a highly dynamic context such as induction of general anesthesia. We tested a smartphone app (OptiBP) on 121 patients requiring general anesthesia and invasive BP monitoring. For each patient, ten 1-min segments aligned in time with ten smartphone recordings were extracted from the continuous invasive BP. A total of 1152 recordings from 119 patients were analyzed. After exclusion of 2 subjects and rejection of 565 recordings due to BP estimation not generated by the app, we retained 565 recordings from 109 patients (acceptance rate 51.1%). Concordance rate (CR) and angular CR demonstrated values of more than 90% for systolic (SBP), diastolic (DBP) and mean (MBP) BP. Error grid analysis showed that 98% of measurement pairs were in no- or low-risk zones for SBP and MBP, of which more than 89% in the no-risk zone. Evaluation of accuracy and precision [bias ± standard deviation (95% limits of agreement)] between the app and the invasive BP was 0.0 ± 7.5 mmHg [- 14.9, 14.8], 0.1 ± 2.9 mmHg [- 5.5, 5.7], and 0.1 ± 4.2 mmHg [- 8.3, 8.4] for SBP, DBP and MBP respectively. To the best of our knowledge, this is the first time a smartphone app was compared to an invasive BP reference. Its trending ability was investigated in highly dynamic conditions, demonstrating high concordance and accuracy. Our study could lead the way for mobile devices to leverage the measurement of BP and management of hypertension.

Perioperative Validation of the TensorTip™ MTX Device for Noninvasive Arterial Pressure Measurement: A Method Comparison Study

Background

The noninvasive TensorTip™ MTX measures blood pressure by interpreting blood diffusion color of the finger skin. In addition to blood pressure, the device is able to measure various vital signs: heart rate, oxygen saturation, stroke volume, and cardiac output. Studies about accuracy and precision thus far available have only been conducted by the manufacturer. The aim of our study was to investigate the accuracy and precision of the TensorTip MTX in comparison to invasive radial artery blood pressure values.

Methods

Forty-one patients scheduled for elective surgery were enrolled in this study. Placement of the arterial catheter had to be part of the standard of care. Once hemodynamic stable conditions were achieved, blood pressure was measured. Three measurements with the TensorTip MTX were averaged and compared with one invasive blood pressure measurement using Bland-Altman plot and error grid analysis.

Results

Systolic, diastolic, and mean blood pressure had a bias of respectively 6.2, -6.9 and 4.4 mm Hg. Corresponding standard deviation were respectively 30.1, 17.0 and 22.2. Calculated percentage errors were 47.6%, 52.9% and 52.3%. Proportional bias was present in all Bland-Altman analyses. Error grid analysis showed 61.0% of systolic blood pressure measurements, and 46.3% of mean blood pressure measurements were in the clinical acceptable zone.

Conclusions

The TensorTip MTX was not able to reliably measure blood pressure compared to blood pressure obtained with an arterial catheter and therefore, the measurement performance is not clinically acceptable. Moreover, a high malfunction rate makes the device unsuitable for use in perioperative period.

Clinical agreement of a novel algorithm to estimate radial artery blood pressure from the non-invasive finger blood pressure

STUDY OBJECTIVE

A new algorithm was developed that transforms the non-invasive finger blood pressure (BP) into a radial artery BP (B̂P_Rad), whereas the original algorithm estimated brachial BP (B̂P_Bra). In this study we determined whether this new algorithm shows better agreement with invasive radial BP than the original one and whether in the operating room this algorithm can be used safely.

DESIGN, SETTING AND PATIENTS

This observational study was conducted on thirty-three non-cardiac surgery patients.

INTERVENTION AND MEASUREMENTS

Invasive radial and non-invasive finger BP were measured, of the latter B̂P_Rad and B̂P_Bra were transformed. Agreement of systolic, mean, and diastolic arterial BP (SAP, MAP, and DAP, respectively) was assessed traditionally with Bland-Altman and trend analysis and clinically safety was quantified with error grid analyses. A bias (precision) of 5 (8) mmHg or less was considered adequate.

MAIN RESULTS

Thirty-three patients were included with an average of 676 (314) 20 s segments. For both comparisons, bias (precision) of MAP was within specified criteria, whereas for SAP, precision was higher than 8 mmHg. B̂P_Rad showed a better agreement than B̂P_Bra with BP_Rad for DAP values (bias (precision): 0.7 (6.0) and - 6.4 (4.3) mmHg, respectively). B̂P_Rad and B̂P_Bra both showed good concordance in following changes in BP_Rad (for all parameters overall degree was <7°). There were slightly more measurement pairs of MAP within the no-risk zone for B̂P_Rad than for B̂P_Bra (96 vs 77%, respectively).

CONCLUSIONS

In this cohort of non-cardiac surgery patients, we found good agreement between BP_Rad and B̂P_Rad. Compared to B̂P_Bra, B̂P_Rad shows better agreement although clinical implications are small. This trial was registered with ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT03795831).

Photoplethysmography-Based Blood Pressure Monitoring Could Improve Patient Outcome during Anesthesia Induction

During anesthesia, noncritical patients are routinely monitored via noninvasive cuff-based blood pressure (BP) monitors. Due to the noncontinuous nature of the monitoring, the BP values of the patient remain unavailable between consecutive cuff measurements, carrying the risk of missing rapid and sudden variations in BP. We evaluated the added value of using a photoplethysmography (PPG)-based continuous BP measurement device in addition to the standard cuff-based monitoring in a cohort of 40 patients in comparison with the current approach, in which only intermittent cuff-based measurements are available. When using a three-minute cuff measurement interval, using the PPG-based BP measurement in addition to the cuff-based monitor reduced the error (mean ± SD) of systolic (SBP) and mean (MBP) BP from 2.6 ± 19.6 mmHg and 1.2 ± 13.2 mmHg to 0.5 ± 11.2 mmHg and 0.0 ± 8.1 mmHg, respectively. Error grid analysis was also used to assess the improvement in patient safety. The additional use of the PPG-based BP measurement reduced the amount of data falling into higher risk categories. For SBP, points falling in the significant-, moderate-, and low-risk categories decreased from 1.1%, 8.7%, and 19.3% to 0.0%, 2.3%, and 9.6%, respectively. Similar results were obtained for MBP. These results suggest that using a PPG-based BP monitor—in addition to the standard cuff-based monitor—can improve patient safety during anesthesia induction, with no additional sensor needed.

Reliability of non-invasive arterial blood pressure measurement in patients with aneurysmal subarachnoid haemorrhage

Objective Invasively measured arterial blood pressure (ABP) is associated with complications, while non-invasively measured ABP is generally considered risk-free. This study aimed to investigate the reliability of non-invasive ABP measured using finger-cuff volume-clamp device compared to invasive ABP measured by an arterial catheter in patients with aneurysmal subarachnoid haemorrhage (SAH). Approach In 30 patients admitted for neurointensive care with SAH, invasive and non-invasive ABP were recorded simultaneously. Reliability was assessed for mean, diastolic and systolic ABP separately using intraclass correlation coefficient (ICC) agreement for each full period and each 3-second average. Main results A median of 3 (IQR: 2-3) periods were included for each participant. The full periods (n = 81) showed an ICC of 0.34 (95% CI: 0.14-0.52), 0.31 (95% CI: 0.10 to 0.49), and 0.20 (95% CI: 0.00 to 0.39) for mean, diastolic, and systolic ABP, respectively. Three-second averages (n = 33,786) for mean (ICC: 0.35; 95% CI: 0.33 to 0.36), diastolic (ICC: 0.25; 95% CI: 0.25 to 0.28), and systolic ABP (ICC: 0.26; 95% CI: 0.18 to 0.33) yielded similar findings. Pearson's correlation coefficient showed an R2 of 0.15 (p < 0.001), 0.15 (p < 0.001), 0.06 (p = 0.027) for mean, diastolic and systolic ABP, respectively. Significance In patients with SAH, non-invasive measurement of ABP using the widely used Nano system from Finapres Medical Systems - a finger-cuff volume-clamp device (Finapres, Chennai, India) showed poor reliability and therefore cannot be used interchangeably with invasively measured ABP.

Validation of Continuous Noninvasive Blood Pressure Monitoring Using Error Grid Analysis

BACKGROUND

Error grid analysis was recently proposed to compare blood pressure obtained by 2 measurement methods. This study aimed to compare continuous noninvasive blood pressure (CNBP) with invasive blood pressure (IBP) using the error grid analysis and investigate the confounding risk factors attributable to the differences between CNBP and IBP.

METHODS

Sixty adult patients undergoing general anesthesia were prospectively enrolled. Simultaneous comparative data regarding CNBP and IBP were collected. The Bland-Altman analysis was conducted to compare CNBP and IBP for systolic blood pressure (SBP) and mean blood pressure (MBP; acceptable accuracy: mean bias <5 mm Hg; standard deviation <8 mm Hg). The clinical relevance of the discrepancies between CNBP and IBP was evaluated by the error grid analysis, which classifies the differences into 5 zones from "no risk" (A) to "dangerous risk" (E). Additionally, an ordinal logistic regression analysis was performed to evaluate the relationship between the risk zones for MBP, classified by the error grid analysis and covariates of interest.

RESULTS

A total of 10,663 pairs of CNBP/IBP were finally analyzed. The Bland-Altman analysis showed an acceptable accuracy with a bias of -3.3 ± 5.6 mm Hg for MBP but a poor accuracy with a bias of 5.4 ± 10.5 mm Hg for SBP. The error grid analysis showed the proportions of zones A to E as 96.7%, 3.2%, 0.1%, 0%, and 0% for SBP, respectively, and 72.0%, 27.9%, 0.1%, 0%, and 0% for MBP, respectively. The finger cuff missed 23.9% of epochs when SBP <90 mm Hg and 55.3% of epochs when MBP <65 mm Hg. The ordinal logistic regression analysis revealed that older age (adjusted odds ratio for decade: 1.54, 95% confidence interval [CI], 1.15-2.08; P = .004) and length of time from the initiation of finger cuff inflation (adjusted odds ratio for 60 minutes: 1.40, 95% CI, 1.13-1.73; P = .002) were significant factors of being in a more dangerous zone of the error grid.

CONCLUSIONS

The error grid analysis revealed the larger clinical discrepancy between CNBP and IBP in MBP compared with that in SBP. Old age and longer finger cuff inflation time were significant factors of being in a more dangerous zone of the error grid, which could affect the hemodynamic management during surgery.

Evaluation of a novel mobile phone application for blood pressure monitoring: a proof of concept study

To provide information about the clinical relevance of blood pressure (BP) measurement differences between a new smartphone application (OptiBP™) and the reference method (automated oscillometric technique) using a noninvasive brachial cuff in patients admitted to the emergency department. We simultaneously recorded three BP measurements using both the reference method and the novel OptiBP™ (test method), except when the inter-arm difference was > 10 mmHg BP. Each OptiBP™ measurement required 1-min and the subsequent reference method values were compared to the values obtained with OptiBP™ using a Bland-Altman analysis and error grid analysis. Among the 110 patients recruited, OptiBP™ BP values could be collected on 61 patients (55%) and were included in the statistical analysis. The mean of differences (95% limits of agreement) between the reference method and the test method were - 0.1(- 22.5 to 22.4 mmHg) for systolic arterial pressure (SAP), - 0.1(- 12.9 to 12.7 mmHg) for diastolic arterial pressure (DAP) and - 0.3(- 18.1 to 17.4 mmHg) for mean arterial pressure (MAP). The proportions of measurements in risk zones A-E were 86.9%, 13.1%, 0%, 0%, and 0% for MAP and 89.3%, 10.7%, 0%, 0%, and 0% for SAP. In this pilot study conducted in stable and awake patients admitted to the emergency department, the absolute agreement between the OptiBP™ and the reference method was moderate. However, when BP measurements were made immediately after an initial calibration, error grid analysis showed that 100% of measurement differences between the OptiBP™ and reference method were categorized as no- or low-risk treatment decisions for all patients.Trial Registration: ClinicalTrials.gov Identifier: NCT04121624.