Continuous Non-invasive Arterial Pressure Monitoring Research Articles

Changes of blood pressure following initiation of physical inactivity and after external addition of pulses to circulation

PurposeTo determine whether an innovative, motorized, wellness device that effortlessly produces physical activity (JD) can mitigate the hypertensive effects of prolonged sitting or lying down.MethodsTwenty-two normotensive and hypertensive adults of both genders gave informed consent to participate in a randomized controlled crossover study of a passive simulated jogging device (JD) in both supine and seated postures. Each study participant was monitored with a continuous non-invasive arterial pressure monitoring device (CNAP) over 60 min. The initial 10 min served as baseline for each posture. The subjects were randomized to begin with either JD or SHAM control for 30 min, and monitoring was continued for an additional 10 min in one posture; three days later posture and order of JD or SHAM were changed.ResultsIn both seated and supine postures, SHAM was associated with a significant rise in blood pressure (BP) which was observed within 5–10 min; it continued to rise or remain elevated for over a 40-min observation period. In contrast, JD produced a significant decrease in both systolic and diastolic blood pressure in both postures. During recovery in seated posture JD decreased systolic and diastolic BP by − 8.1 and − 7.6 mmHg, respectively. In supine posture, a similar decrease in BP occurred.ConclusionsThere is rapid onset of increase in systolic and diastolic BP with physical inactivity in both supine and seated postures. Administration of JD significantly decreased BP in both postures. Further studies are needed to assess long-term effectiveness.

A17369 Application of Continuous Noninvasive Arterial Pressure Monitor in Patients with Cardiovascular Diseases plus Obstructive Sleep Apnea

Objectives: The hemodynamics of patient with cardiovascular diseases (CVD) plus obstructive sleep apnea (OSA) is changeable and complicated. A new continuous noninvasive arterial pressure monitor (CNAP) has been validated in screening the hemodynamics. The aim of our study is to assess the performance of CNAP in patients with CVD plus OSA. Methods: The hemodynamics of patient with cardiovascular diseases (CVD) plus obstructive sleep apnea (OSA) is changeable and complicated. A new continuous noninvasive arterial pressure monitor (CNAP) has been validated in screening the hemodynamics. The aim of our study is to assess the performance of CNAP in patients with CVD plus OSA. Results: Compared with the values monitored before sleeping, patients had higher mean systolic blood pressure (125.60 ± 17.19mmHg vs. 118.96 ± 17.97mmHg, P < 0.05), lower mean heart rate (66.41 ± 9.19bpm vs. 69.61 ± 12.57bpm, P < 0.05) during sleep apnea events. 10 patients have used continuous positive airway pressure (CPAP) to treat OSA. Compared with the values monitored before treatment by CPAP, patients using CPAP had lower cardiac output (5.41 ± 1.12l/min vs. 5.74 ± 1.19l/min, P < 0.05), cardiac index (2.85 ± 0.40l/min/m^2 vs. 3.02 ± 0.4l/min/m^2, P < 0.05), pulse pressure variation (5.67 ± 1.20% vs. 6.48 ± 1.20%, P < 0.05) and stroke volume variation (7.47 ± 1.60% vs. 11.03 ± 2.78%, P < 0.05). Conclusion: CNAP could be clinically useful to assess hemodynamics of patient with CVD plus OSA. When sleep apnea events happened, patients’ mean systolic blood pressure became higher while mean heart rate became lower. When patients using CPAP, cardiac output, cardiac index, pulse pressure variation and stroke volume variation all became lower.

Feasibility of continuous noninvasive arterial pressure monitoring in a prehospital setting, measurements during emergency transfer.

ObjectivesIn severely injured or acutely ill patients close monitoring of blood pressure (BP) can be crucial. At the prehospital scene and during transfer to hospital, the BP is usually monitored using intermittent oscillometric measurements with an upper arm cuff every 3–5 min. The BP can be monitored noninvasively and continuously using the continuous noninvasive arterial pressure (CNAP) device. In this study, we investigated the feasibility of a CNAP device in a prehospital setting.Patients and methodsThe study was an observational convenience study. The CNAP device was applied to the patient once in the ambulance and measurements were carried out during transfer to hospital. The primary object was the number of patients in whom the CNAP device could monitor the BP continuously in a prehospital area en route to hospital.ResultsFifty-nine patients were enrolled in this study. Fifty-four (92%) patients had their BP monitored continuously by the CNAP device. The main reasons for missing data were a mean BP below the detectable range, reduced pulse wave caused by constricted arteries in the fingers, or patients’ excessive movements. The CNAP device provided continuous measurements after a median of 164.5 s. No complications and no adverse events were observed.ConclusionContinuous measurement of the BP obtained by the CNAP device is feasible and safe in a prehospital setting under potentially difficult conditions.

Continuous noninvasive arterial blood pressure monitoring using the vascular unloading technology during complex gastrointestinal endoscopy: a prospective observational study.

The innovative vascular unloading technology (VUT) allows continuous noninvasive arterial blood pressure (AP) monitoring. We aimed to investigate whether the VUT enables AP changes to be detected earlier compared with intermittent AP monitoring in patients undergoing gastrointestinal endoscopy. In this prospective observational study, we recorded continuous AP measurements with the VUT (CNAP system; CNSystems Medizintechnik AG, Graz, Austria) and intermittent AP measurements with upper arm cuff oscillometry in 90 patients undergoing complex gastrointestinal endoscopy (Department of Interventional Endoscopy at the University Medical Center Hamburg-Eppendorf, Hamburg, Germany). A "hypotensive phase" was defined as a time period of at least 30s during which ≥ 50% of the VUT-AP values were in a predefined range of hypotension, i.e., AP value a) ≥ 10% below the last oscillometric value and b) ≤ 65mmHg for mean AP or ≤ 90mmHg for systolic AP. In the 5-min-interval between two oscillometric measurements, one or more hypotensive phases were detected in 26 patients (29%) for mean AP and in 27 patients (30%) for systolic AP. Hypotensive phases had a mean duration of 195 ± 99s for mean AP and 197 ± 97s for systolic AP with a mean procedure duration of 36 (± 21) min. Continuous noninvasive AP monitoring using the VUT enables hypotensive phases to be detected earlier compared with intermittent AP monitoring during complex gastrointestinal endoscopy. These hypotensive phases may be missed or only belatedly recognized with intermittent AP monitoring. Continuous noninvasive AP measurement facilitates detecting hemodynamic instability more rapidly and therefore may improve patient safety.

The impact of continuous non-invasive arterial blood pressure monitoring on blood pressure stability during general anaesthesia in orthopaedic patients: A randomised trial.

In patients undergoing general anaesthesia, intraoperative hypotension occurs frequently and is associated with adverse outcomes such as postoperative acute kidney failure, myocardial infarction or stroke. A history of chronic hypertension renders patients more susceptible to a decrease in blood pressure (BP) after induction of general anaesthesia. As a patient's BP is generally monitored intermittently via an upper arm cuff, there may be a delay in the detection of hypotension by the anaesthetist. The current study investigates whether the presence of continuous BP monitoring leads to improved BP stability. Randomised, controlled and single-centre study. A total of 160 orthopaedic patients undergoing general anaesthesia with a history of chronic hypertension. The patients were randomised to either a study group (n = 77) that received continuous non-invasive BP monitoring in addition to oscillometric intermittent monitoring, or a control group (n = 83) whose BP was monitored intermittently only. The interval for oscillometric measurements in both groups was set to 3 min. After induction of general anaesthesia, oscillometric BP values of the two groups were compared for the first hour of the procedure. Anaesthetists were blinded to the purpose of the study. BP stability and hypotensive events. There was no difference in baseline BP between the groups. After adjustment for multiple testing, mean arterial BP in the study group was significantly higher than in the control group at 12 and 15 min. Mean ± SD for study and control group, respectively were: 12 min, 102 ± 24 vs. 90 ± 26 mmHg (P = 0.039) and 15 min, 102 ± 21 vs. 90 ± 23 mmHg (P = 0.023). Hypotensive readings below a mean pressure of 55 mmHg occurred more often in the control group (25 vs. 7, P = 0.047). Continuous monitoring contributes to BP stability in the studied population. NCT02519101.

Towards a Simple System for Indicating Temporal Variations in Blood Pressure

Blood pressure is an important physiological parameter to be monitored. For several medical conditions, it is important to quickly know the rise or fall in blood pressure. While researchers are working to evolve a reliable continuous noninvasive arterial pressure (CNAP) monitoring devices based on sophisticated signal processing with various technologies including Penaz principle & pulse wave velocity (PWV); we present a very simple system to continuously indicate the variations in blood pressure. Using the typical shapes of the pulse wave obtained by infra-red photoplethysmography (PPG) from brachial and radial artery, we estimate the changes in pulse transit time (PTT). This change is effected onto a change in tone of an audio beep. The simple circuit was assembled and tested. The details are presented in the paper.

About the discovery of an explicit model to monitor blood pressure in a non-invasive way

Purpose: The objective of the study was to identify an explicit model to indirectly monitor blood pressure by using the electrocardiography and heart rate variability parameters, and the plethysmography. Those latter signals can be monitored through wearable non-invasive sensors, namely an electrocardiography sensor and a finger pulse oximeter sensor. The developed model was included in a real-time mobile monitoring system to realize a wearable continuous non-invasive arterial pressure monitor. Context: Continuous non-invasive arterial pressure methods can be used to continuously measure arterial blood pressure in real time and without any need for patient's body cannulation. Currently there is a high request for accurate and easy-to-use continuous non-invasive arterial pressure systems. Consequently, an increasing focus on these devices exists. Several non-invasive approaches to blood pressure have been attempted, some of which are described in [1]. Methods: The explicit model was developed under the form of a function by combining heart rate variability parameters and plethysmography measurements. We decided to avail ourselves of a Genetic Programming technique for this regression problem because it can automatically find an explicit model for the relationship between the independent variables and a dependent one, in this case one between the systolic and the diastolic blood pressure values. Therefore, once hypothesized the existence of a nonlinear relationship between heart activity, and thus electrocardiography and heart rate variability parameters, plethysmography and blood pressure values, and chosen a fitness function, we found, from among the huge number of possible models, the one that best describes the fundamental features of this relationship.

Continuous non-invasive monitoring to detect covert autonomic dysfunction in Parkinson's disease.

Lightheadedness on standing is a disabling symptom in Parkinson's disease associated with orthostatic hypotension and is thought to represent cardiovascular autonomic dysfunction. Traditional orthostatic blood pressures are normal in some patients with lightheadedness and other measures of cardiovascular dysautonomia can be insensitive. In this study, we used continuous non-invasive arterial pressure monitoring to measure beat-to-beat changes in blood pressure and heart rate on standing and during Valsalva as a potential marker of autonomic dysfunction. Subjects had a diagnosis of Parkinson's disease with or without documented orthostatic hypotension. Each participant underwent traditional measurement of orthostatic blood pressure and heart rate as well as measurement of beat-to-beat blood pressure and heart rate using continuous non-invasive arterial pressure monitoring during Valsalva maneuver and in response to standing. Orthostatic change in blood pressure and heart rate, and frequencies of normal and abnormal blood pressure responses to Valsalva maneuver were analyzed. In subjects without documented orthostatic hypotension, there was a higher proportion of abnormal blood pressure responses to Valsalva in subjects with symptoms of lightheadedness or dizziness upon standing compared to those without symptoms (p = 0.03). Additionally, the proportion of abnormal blood pressure responses during Valsalva observed in symptomatic subjects without orthostatic hypotension was indistinguishable from those with documented orthostatic hypotension (p = 0.7). Our findings suggest that continuous non-invasive arterial pressure monitoring may be more sensitive than traditional measurement of orthostatic blood pressure to detect subtle cardiac dysautonomia in Parkinson's disease and helpful in the diagnosis of unexplained lightheadedness.

Radial artery applanation tonometry for continuous noninvasive arterial blood pressure monitoring in the cardiac intensive care unit.

Hemodynamic monitoring plays a pivotal role in the treatment of patients in the cardiac intensive care unit (CICU). The innovative radial artery applanation tonometry technology allows for continuous noninvasive arterial blood pressure (AP) measurement. By closing the gap between continuous invasive AP monitoring (arterial catheter) and intermittent noninvasive AP monitoring (oscillometry) this technology might improve CICU patient monitoring. We therefore aimed to evaluate the measurement performance of radial artery applanation tonometry in comparison with a radial arterial catheter in CICU patients. In this prospective method comparison study, we simultaneously recorded AP noninvasively with radial artery applanation tonometry (T-line 200 pro device; Tensys Medical Inc., San Diego, CA, USA) and invasively with an arterial catheter (criterion standard) in 30 patients treated in the CICU of a German university hospital. We statistically analyzed 7,304 averaged 10-beat epochs of measurements of mean AP, systolic AP, and diastolic AP by using Bland-Altman analysis for repeated measurements. Our study revealed a mean difference ± standard deviation (95% limits of agreement; percentage error) between radial artery applanation tonometry and the criterion standard method (radial arterial catheter) of +2 ± 6 mmHg (-10 to +14 mmHg; 17%) for mean AP, -6 ± 11 mmHg (-28 to +15 mmHg; 20%) for systolic AP, and +4 ± 7 mmHg (-9 to +17 mmHg; 23%) for diastolic AP. In CICU patients, continuous noninvasive measurement of AP using radial artery applanation tonometry is feasible. The technology showed reasonable accuracy and precision in comparison with radial arterial catheter-derived AP values.

Evaluation of continuous non-invasive arterial pressure monitoring during induction of general anaesthesia in patients undergoing cardiac surgery.

Background and Aims:Continuous arterial pressure monitoring is essential in cardiac surgical patients during induction of general anaesthesia (GA). Continuous non-invasive arterial pressure (CNAP) monitoring is fast gaining importance due to complications associated with the invasive arterial monitoring. Recently, a new continuous non-invasive arterial pressure device (CNAP™) has been validated perioperatively in non-cardiac surgeries. The aim of our study is to compare and assess the performance of CNAP during GA with invasive arterial pressure (IAP) in patients undergoing cardiac surgeries.Methods:Sixty patients undergoing cardiac surgery were included. Systolic, diastolic, and mean arterial pressure (MAP) data were recorded every minute for 20 min simultaneously for both IAP and CNAP™. Statistical analysis was performed using mountain plot and Bland Altman plots for assessing limits of agreement and bias (accuracy) calculation. Totally 1200 pairs of data were analysed.Results:The CNAP™ systolic, diastolic and MAP bias was 5.98 mm Hg, −3.72 mm Hg, and − 0.02 mm Hg respectively. Percentage within limits of agreement was 96.0%, 95.2% and 95.7% for systolic, diastolic and MAP. The mountain plot showed similar results as the Bland Altman plots.Conclusion:We conclude CNAP™ provides real-time estimates of arterial pressure comparable to IAP during induction of GA for cardiac surgery. We recommend CNAP can be used as an alternative to IAP in situations such as cardiac patients coming for non-cardiac surgeries, cardiac catheterization procedures, positive Allen's test, inability to cannulate radial artery and vascular diseases, where continuous blood pressure monitoring is required.

Comparison of continuous non-invasive finger arterial pressure monitoring with conventional intermittent automated arm arterial pressure measurement in patients under general anaesthesia

For a majority of patients undergoing anaesthesia for general surgery, mean arterial pressure (MAP) is only measured intermittently by arm cuff oscillometry (MAPiNIAP). In contrast, the Nexfin(®) device provides continuous non-invasive measurement of MAP (MAPcNIAP) using a finger cuff. We explored the agreement of MAPcNIAP and MAPiNIAP with the gold standard: continuous invasive MAP measurement by placement of a radial artery catheter (MAPinvasive). In a total of 120 patients undergoing elective general surgery and clinically requiring MAPinvasive measurement, MAPiNIAP and MAPcNIAP were measured in a 30 min time period at an arbitrary moment during surgery with stable haemodynamics. MAPiNIAP was measured every 5 min. Data from 112 patients were analysed. Compared with MAPinvasive, modified Bland-Altman analysis revealed a bias (sd) of 2 (9) mm Hg for MAPcNIAP and -2 (12) mm Hg for MAPiNIAP. Percentage errors for MAPcNIAP and MAPiNIAP were 22% and 32%, respectively. In a haemodynamically stable phase in patients undergoing general anaesthesia, the agreement with invasive MAP of continuous non-invasive measurement using a finger cuff was not inferior to the agreement of intermittent arm cuff oscillometry. Continuous measurements using a finger cuff can interchangeably be used as an alternative for intermittent arm cuff oscillometry in haemodynamically stable patients, with the advantage of beat-to-beat haemodynamic monitoring. NCT 01362335 (clinicaltrials.gov).

Accuracy and Precision of Continuous Noninvasive Arterial Pressure Monitoring Compared with Invasive Arterial Pressure

Continuous noninvasive arterial pressure monitoring devices are available for bedside use, but the accuracy and precision of these devices have not been evaluated in a systematic review and meta-analysis. The authors performed a systematic review and meta-analysis of studies comparing continuous noninvasive arterial pressure monitoring with invasive arterial pressure monitoring. Random-effects pooled bias and SD of bias for systolic arterial pressure, diastolic arterial pressure, and mean arterial pressure were calculated. Continuous noninvasive arterial pressure monitoring was considered acceptable if pooled estimates of bias and SD were not greater than 5 and 8 mmHg, respectively, as recommended by the Association for the Advancement of Medical Instrumentation. Twenty-eight studies (919 patients) were included. The overall random-effect pooled bias and SD were -1.6 ± 12.2 mmHg (95% limits of agreement -25.5 to 22.2 mmHg) for systolic arterial pressure, 5.3 ± 8.3 mmHg (-11.0 to 21.6 mmHg) for diastolic arterial pressure, and 3.2 ± 8.4 mmHg (-13.4 to 19.7 mmHg) for mean arterial pressure. In 14 studies focusing on currently commercially available devices, bias and SD were -1.8 ± 12.4 mmHg (-26.2 to 22.5 mmHg) for systolic arterial pressure, 6.0 ± 8.6 mmHg (-10.9 to 22.9 mmHg) for diastolic arterial pressure, and 3.9 ± 8.7 mmHg (-13.1 to 21.0 mmHg) for mean arterial pressure. The results from this meta-analysis found that inaccuracy and imprecision of continuous noninvasive arterial pressure monitoring devices are larger than what was defined as acceptable. This may have implications for clinical situations where continuous noninvasive arterial pressure is being used for patient care decisions.

Noninvasive Hemodynamic Monitoring Devices

Noninvasive Hemodynamic Monitoring Devices

Radial artery applanation tonometry for continuous non-invasive arterial pressure monitoring in intensive care unit patients: comparison with invasively assessed radial arterial pressure

BackgroundRadial artery applanation tonometry technology can be used for continuous non-invasive measurement of arterial pressure (AP). The purpose of this study was to evaluate this AP monitoring technology in intensive care unit (ICU) patients in comparison with invasive AP monitoring using a radial arterial catheter. MethodsIn 24 ICU patients (German university hospital), AP values were simultaneously recorded on a beat-to-beat basis using radial artery applanation tonometry (T-Line system; Tensys Medical, San Diego, CA, USA) and a radial arterial catheter (contralateral arm). The primary endpoint of the study was to investigate the accuracy and precision of the non-invasively assessed AP measurements with the Bland–Altman method based on averaged 10 beat AP epochs (n=2993 10 beat epochs). ResultsFor mean AP (MAP), systolic AP (SAP), and diastolic AP (DAP), we observed a bias (±standard deviation of the bias; 95% limits of agreement; percentage error) of +2 mm Hg (±6; −11 to +15 mm Hg; 15%), −3 mm Hg (±15; −33 to +27 mm Hg; 23%), and +5 mm Hg (±7; −9 to +19 mm Hg; 22%), respectively. ConclusionsIn ICU patients, MAP and DAP measurements obtained using radial artery applanation tonometry show clinically acceptable agreement with invasive AP determination with a radial arterial catheter. While the radial artery applanation tonometry technology also allows SAP measurements with high accuracy, its precision for SAP measurements needs to be further improved.

Noninvasive continuous versus intermittent arterial pressure monitoring: evaluation of the vascular unloading technique (CNAP device) in the emergency department

BackgroundMonitoring cardiovascular function in acutely ill patients in the emergency department (ED) is of paramount importance. Arterial pressure (AP) is usually monitored using intermittent oscillometric measurements with an upper arm cuff. The vascular unloading technique (VUT) allows continuous noninvasive AP monitoring. In this study, we compare continuous AP measurements obtained by VUT with intermittent oscillometric AP measurements in ED patients. In addition, we aimed to investigate whether continuous noninvasive AP monitoring allows detection of relevant hypotensive episodes that might be missed with intermittent AP monitoring.MethodsIn a German university hospital, 130 ED patients who required AP monitoring were analyzed in this prospective method comparison study. Continuous AP monitoring was performed using VUT (CNAP technology; CNSystems Medizintechnik AG, Graz, Austria) over a 2-hour period. The oscillometric AP values were recorded simultaneously every 15 minutes for the comparison of both methods. For statistical evaluation, Bland-Altman plots accounting for repeated AP measurements per individual were used.ResultsThe mean difference (±standard deviation) between AP measurements obtained by VUT and oscillometric AP measurements was -5 mmHg (±22 mmHg) for systolic AP (SAP), -2 mmHg (±15 mmHg) for diastolic AP (DAP), and -6 mmHg (±16 mmHg) for mean AP (MAP), respectively. In the interval between two oscillometric measurements, the VUT device detected hypotensive episodes (≥4 minutes) defined as either SAP <90 mmHg or MAP <65 mmHg in 30 patients and 16 patients, respectively. In 11 (SAP <90 mmHg) and 6 (MAP <65 mmHg) of these patients, hypotension was also detected by the subsequent intermittent oscillometric AP measurement.ConclusionsVUT using the CNAP system for noninvasive continuous AP measurement shows reasonable agreement with intermittent oscillometric measurements in acutely ill ED patients. Continuous AP monitoring allows immediate recognition of clinically relevant hypotensive episodes, which are missed or only belatedly recognized with intermittent AP measurement.

Closed‐loop double‐vasopressor automated system vs manual bolus vasopressor to treat hypotension during spinal anaesthesia for caesarean section: a randomised controlled trial

Hypotension necessitating vasopressor administration occurs commonly during caesarean section under spinal anaesthesia. We developed a novel vasopressor delivery system that automatically administers phenylephrine or ephedrine based on continuous non-invasive arterial pressure monitoring. A phenylephrine bolus of 50 μg was given at 30-s intervals when systolic blood pressure fell < 90% of baseline; an ephedrine bolus of 4 mg was given instead if systolic pressure fell < 90% of baseline together with a heart rate < 60 beats.min(-1). The control group used manual boluses of either phenylephrine 100 μg or ephedrine 8 mg, administered at 1-min intervals based on the same thresholds for systolic pressure and heart rate. This randomised, controlled, double-blinded trial involved 213 healthy women who underwent elective caesarean delivery under spinal anaesthesia using 11 mg hyperbaric bupivacaine with 15 μg fentanyl and 100 μg morphine. The automated vasopressor group had better systolic pressure control, with 37/106 (34.9%) having any beat-to-beat systolic pressure reading < 80% of baseline compared with 63/107 (58.9%) in the control group (p < 0.001). There was no difference in the incidence of reactive hypertension, defined as systolic pressure > 120% of baseline, with 8/106 (7.5%) in the automated vasopressor group vs 14/107 (13.1%) in the control group, or total dose of vasopressors. The automated vasopressor group had lower median absolute performance error of 8.5% vs control of 9.8% (p = 0.013), and reduced incidence of nausea (1/106 (0.9%) vs 11/107 (10.3%), p = 0.005). Neonatal umbilical cord pH, umbilical lactate and Apgar scores were similar. Hence, our system afforded better control of maternal blood pressure and reduced nausea with no increase in reactive hypertension when compared with manual boluses.

Ability of Noninvasive Intermittent Blood Pressure Monitoring and a Continuous Noninvasive Arterial Pressure Monitor (CNAP) to Provide New Readings in Each 1-Minute Interval During Elective Cesarean Section Under Spinal Anesthesia

Ability of Noninvasive Intermittent Blood Pressure Monitoring and a Continuous Noninvasive Arterial Pressure Monitor (CNAP) to Provide New Readings in Each 1-Minute Interval During Elective Cesarean Section Under Spinal Anesthesia

CNAP – Evolution of Continuous Non-Invasive Arterial Blood Pressure Monitoring

Article CNAP – Evolution of Continuous Non-Invasive Arterial Blood Pressure Monitoring was published on September 7, 2013 in the journal Biomedical Engineering / Biomedizinische Technik (volume 58, issue SI-1-Track-G).

CNAP® does not reliably detect minimal or maximal arterial blood pressures during induction of anaesthesia and tracheal intubation

CNAP(®) provides continuous non-invasive arterial pressure (AP) monitoring. We assessed its ability to detect minimal and maximal APs during induction of general anaesthesia and tracheal intubation. Fifty-two patients undergoing surgery under general anaesthesia were enrolled. Invasive pressure monitoring was established at the radial artery, and CNAP monitoring using a finger sensor recording was begun before induction. Statistical analysis was conducted with the Bland-Altman method for comparison of repeated measures and intraclass correlation coefficient (ICC). Patients' median age was 67 years [interquartile range (59-76)], median American Society of Anesthesiologists score was 3 [interquartile range (2-3)]. Bias was 5 and -7 mmHg for peak and nadir systolic AP (SAP), with upper and lower limits of agreement of (42:-32) and (27;-42), respectively. The corresponding ICC values were 0.74 [95% confidence interval (CI) = 0.57-0.84] and 0.60 (95% CI = 0.44-0.73). Time lags to reach these values were 7.5 s (95% CI = -10.0 to 60.0) for the highest SAP and 10 s (95% CI = -12.5 to 72.5) for the lowest SAP. Bias, lower and upper limits of agreement for diastolic, and mean AP were -14 (-36 to 9) and -12 (-37 to 13) for the nadir value and -7 (-29 to 15) and -2 (-28 to 25) for the peak value. The CNAP monitor could detect acute change in AP within a reasonable time lag. Precision of its measurements is not satisfactory, and therefore, it could only serve as a clue to the occurrence of changes in AP.

Investigation of the agreement of a continuous non-invasive arterial pressure device in comparison with invasive radial artery measurement

Arterial pressure (AP) monitoring should be accurate, easy to use, free of risks, and ideally continuous. The continuous non-invasive arterial pressure (CNAP) device is non-invasive and provides continuous pressure readings. This study was performed to compare the agreement of CNAP and invasive AP monitoring. Ninety patients undergoing surgery under general anaesthesia were enrolled. Invasive pressure monitoring was established at the radial artery. CNAP monitoring using a finger sensor recording was begun before induction of anaesthesia. Statistical analysis was conducted with the Bland-Altman method for comparisons of repeated measures. We obtained 16 843 valid pressure readings from 85 patients. Mean (sd) bias during maintenance of anaesthesia was: systolic AP: 4.2 (16.5) mm Hg; mean AP (MAP): -4.3 (10.4) mm Hg; and diastolic AP: -5.8 (6) mm Hg. The results of a subgroup analysis of patients who had a mean intra-arterial pressure of <70 mm Hg were as follows: systolic pressure: -0.3 (9.7) mm Hg; mean pressure: -6.8 (7.6) mm Hg; and diastolic pressure: -7.9 (7.2) mm Hg. Bias and percentage error during the induction period were greater in both the main and subgroup analyses, probably due to recalibration being omitted after induction. The CNAP monitor showed an acceptable agreement and was interchangeable with invasive pressure monitoring for MAP during normotensive conditions. During induction of anaesthesia and when the AP was low, the agreement was less good and interchangeability was not achieved. These results suggest that CNAP is not statistically equivalent to invasive monitoring during all periods of anaesthesia but may be a useful additional AP monitor.