Noninvasive continuous arterial blood pressure monitoring with Nexfin®.

BACKGROUND: If invasive measurement of arterial blood pressure is not warranted, finger cuff technology can provide continuous and noninvasive monitoring. Finger and radial artery pressures differ; Nexfin® (BMEYE, Amsterdam, The Netherlands) measures finger arterial pressure and uses physiologic reconstruction methodologies to obtain values comparable to invasive pressures. METHODS: Intra-arterial pressure (IAP) and noninvasive Nexfin arterial pressure (NAP) were measured in cardiothoracic surgery patients, because invasive pressures are available. NAP-IAP differences were analyzed during 30 min. Tracking was quantified by within-subject precision (SD of individual NAP-IAP differences) and correlation coefficients. The ranges of pressure change were quantified by within-subject variability (SD of individual averages of NAP and IAP). Accuracy and precision were expressed as group average ± SD of the differences and considered acceptable when smaller than 5 ± 8 mmHg, the Association for the Advancement of Medical Instrumentation criteria. RESULTS: NAP and IAP were obtained in 50 (34-83 yr, 40 men) patients. For systolic, diastolic, mean arterial, and pulse pressure, median (25-75 percentiles) correlation coefficients were 0.96 (0.91-0.98), 0.93 (0.87-0.96), 0.96 (0.90-0.97), and 0.94 (0.85-0.98), respectively. Within-subject precisions were 4 ± 2, 3 ± 1, 3 ± 2, and 3 ± 2 mmHg, and within-subject variations 13 ± 6, 6 ± 3, 9 ± 4, and 7 ± 4 mmHg, indicating precision over a wide range of pressures. Group average ± SD of the NAP-IAP differences were -1 ± 7, 3 ± 6, 2 ± 6, and -3 ± 4 mmHg, meeting criteria. Differences were not related to mean arterial pressure or heart rate. CONCLUSION: Arterial blood pressure can be measured noninvasively and continuously using physiologic pressure reconstruction. Changes in pressure can be followed and values are comparable to invasive monitoring.

Noninvasive cardiac output monitoring during exercise testing: Nexfin pulse contour analysis compared to an inert gas rebreathing method and respired gas analysis.

PURPOSE: Exercise testing is often used to assess cardiac function during physical exertion to obtain diagnostic information. However, this procedure is limited to measuring the electrical activity of the heart using electrocardiography and intermittent blood pressure (BP) measurements and does not involve the continuous assessment of heart functioning. In this study, we compared continuous beat-to-beat pulse contour analysis to monitor noninvasive cardiac output (CO) during exercise with inert gas rebreathing and respired gas analysis. METHODS: Nineteen healthy male volunteers were subjected to bicycle ergometry testing with increasing workloads. Cardiac output was deter- mined noninvasively by continuous beat-to-beat pulse contour analysis (Nexfin) and by inert gas rebreathing, and estimated using the respired gas analysis method. The effects of the rebreathing maneuver on heart rate (HR), stroke volume (SV), and CO were evaluated. RESULTS: The CO values derived from the Nexfin- and inert gas rebreathing methods were well correlated (r = 0.88, P < 0.01) and the limits of agreement were 30.3% with a measurement bias of 0.4 ± 1.8 L/min. Nexfin- and respired gas analysis-derived CO values correlated even better (r = 0.94, P < 0.01) and the limits of agreement were 21.5% with a measurement bias of -0.70 ± 1.6 L/min. At rest, the rebreathing maneuver increased HR by 13 beats/min (P < 0.01), SV remained unaffected (P = 0.7), while CO increased by 1.0 L/min (P < 0.01). Rebreathing did not affect these parameters during exercise. CONCLUSIONS: Nexfin continuous beat-to-beat pulse contour analysis is an appropriate method for noninvasive assessment of CO during exercise.

Comparison of Portapres with standard sphygmomanometry in pregnancy.

BACKGROUND: Continuous beat-to-beat noninvasive blood pressure (BP) measurement is possible with Portapres. It constructs finger arterial waveforms beat-to-beat. Dedicated software is used to analyze the arterial waveforms. A new technique has been developed to reconstruct brachial intra-arterial pressure that uses return to flow (RTF). This method has been validated against invasive intra-arterial measurements in nonpregnant individuals. OBJECTIVES: To validate Portapres in normal and preeclamptic pregnant women against standard aneroid sphygmomanometry according to Riva-Rocci-Korotkoff (RRK). METHODS: In 30 normotensive (10 in each trimester) and 20 preeclamptic women, two trained observers blinded from each other's results took BP measurements with a standard sphygmomanometer. These measurements were compared with sequential same-arm averaged measurements obtained during 30 sec by Portapres, following protocols from the Association for the Advancement of Medical Instrumentation (AAMI, mean accepted difference < or = 5 mmHg, SD < or = 8) and British Hypertension Society (BHS, gradings A down to D). RESULTS: A total of 150 measurement pairs were analyzed. Cumulative percentages of absolute pressure differences for all women (BHS) and mean pressure differences (SD) for different trimesters and preeclampsia (AAMI) between sphygmomanometry and Portapres were calculated. Overall, mean difference (SD) for systolic BP was 5 (SD 8) and for diastolic BP was -3 (SD 8), although analysis of variance revealed a significant effect for preeclampsia on diastolic differences between the two methods of BP measurement ( p<0.001). CONCLUSIONS: Portapres with RTF, developed to equal intra-arterial brachial pressure, compares reasonably well to RRK and overall meets the criteria set by the AAMI. According to the BHS, Portapres receives a B-grading for diastolic BP and a C-grading for systolic BP. As Portapres measures BP and calculates cardiac output continuously and noninvasively, it would appear worthwhile to further evaluate this device in pathological pregnancies.

Diagnostic value of simultaneous non-invasive continuous, ambulatory finger blood pressure and electrocardiogram monitoring in a patient with hypertrophic obstructive cardiomyopathy.

BACKGROUND: The pathophysiology of hypertrophic obstructive cardiomyopathy (HOCM) is complex and heterogeneous, and it may be difficult to disentangle the various pathophysiologic properties leading to complaints. OBJECTIVES: To elucidate the sequence of acute pathophysiologic changes leading to complaints in a patient with HOCM. METHODS: Cardiopres measurements [the combination of non-invasive, continuous finger artery blood pressure monitoring, and three-lead electrocardiogram (ECG) recordings] were performed during physiologic, supine exercise--before and after replacement of metoprolol by verapamil. Within 24 h of the Cardiopres measurement standard Doppler echocardiography was performed. Finger artery pressure wave was analysed using Beatscope software (BMI-TNO, Amsterdam, The Netherlands), ST analysis was performed with H-Scribe (Mortara Instrument, Bilt, The Netherlands). RESULTS: Exercise under metoprolol: finger BP decreased from 130/65 mmHg to 90/60 mmHg, heart rate increased from 65 bpm to 100 bpm and ST analysis revealed significant ST depression in all leads. The occurrence of ST depression preceded the hypotension. Echocardiography showed a dynamic gradient of 70 mmHg. Exercise under verapamil: the patient had less complaints, BP increased from 125/60 mmHg to 165/65 mmHg, heart rate increased from 75 bpm to 107 bpm and ST analysis showed no ST depression > 1 mm. Echocardiography showed no change. CONCLUSIONS: The use of the Cardiopres during a physiological stimulus showed improvement in exercise capacity in a patient with HOCM, while the standard test, stress-echocardiography, showed no correlation with clinical status. The Cardiopres is a useful diagnostic and research tool, allowing non-invasive, ambulatory monitoring of blood pressure and ECG changes.

Noninvasive arterial blood pressure waveforms in patients with continuous-flow left ventricular assist devices.

Arterial blood pressure and echocardiography may provide useful physiological information regarding cardiac support in patients with continuous-flow left ventricular assist devices (cf-LVADs). We investigated the accuracy and characteristics of noninvasive blood pressure during cf-LVAD support. Noninvasive arterial pressure waveforms were recorded with Nexfin (BMEYE, Amsterdam, The Netherlands). First, these measurements were validated simultaneously with invasive arterial pressures in 29 intensive care unit patients. Next, the association between blood pressure responses and measures derived by echocardiography, including left ventricular end-diastolic dimensions (LVEDDs), left ventricular end-systolic dimensions (LVESDs), and left ventricular shortening fraction (LVSF) were determined during pump speed change procedures in 30 outpatients. Noninvasive arterial blood pressure waveforms by the Nexfin monitor slightly underestimated invasive measures during cf-LVAD support. Differences between noninvasive and invasive measures (mean ± SD) of systolic, diastolic, mean, and pulse pressures were -7.6 ± 5.8, -7.0 ± 5.2, -6.9 ± 5.1, and -0.6 ± 4.5 mm Hg, respectively (all <10%). These blood pressure responses did not correlate with LVEDD, LVESD, or LVSF, while LVSF correlated weakly with both pulse pressure (r = 0.24; p = 0.005) and (dP(art)/dt)max (r = 0.25; p = 0.004). The dicrotic notch in the pressure waveform was a better predictor of aortic valve opening (area under the curve [AUC] = 0.87) than pulse pressure (AUC = 0.64) and (dP(art)/dt)max (AUC = 0.61). Patients with partial support rather than full support at 9,000 rpm had a significant change in systolic pressure, pulse pressure, and (dP(art)/dt)max during ramp studies, while echocardiographic measures did not change. Blood pressure measurements by Nexfin were reliable and may thereby act as a compliment to the assessment of the cf-LVAD patient.

Noninvasive blood pressure measurement by the Nexfin monitor during reduced arterial pulsatility: a feasibility study.

Noninvasive blood pressure measurements are difficult when arterial pulsations are reduced, as in patients supported by continuous flow left ventricular assist devices (cf-LVAD). We evaluated the feasibility of measuring noninvasive arterial blood pressure with the Nexfin monitor during conditions of reduced arterial pulsatility. During cardiopulmonary bypass(CPB) in which a roller pump based or a centrifugal pump based heart-lung machine generated arterial blood pressure with low pulsatility, noninvasive arterial pressures (NAP)measured by the Nexfin Monitor were recorded and compared with invasively measured radial artery pressures (IAP).We also evaluated NAP in 10 patients with a cf-LVAD during a pump speed change procedure (PSCP). During CPB in 18 patients, the NAP-IAP average difference was -1.3 +/- 6.5 mmHg. The amplitude of pressure oscillations were 4.3 +/- 3.8 mmHg measured by IAP. Furthermore, in the cf-LVAD patients, increase in pump speed settings led to an increase in diastolic and mean arterial pressures (MAP) while the NAP acquired a sinusoidal shape as the aortic valve become permanently closed. In conclusion, NAP was similar to IAP under conditions of reduced arterial pulsatility. The device also measured the blood pressure waveform noninvasively in patients supported by a cf-LVAD.

ST segment depression criteria and the prevalence of silent cardiac ischemia in hypertensives.

The reported prevalence of silent cardiac ischemia as assessed by ambulatory electrocardiographic recording varies widely. The influence of the stringency of the analysis criteria has never been reported. We performed 24-hour, 12-lead ambulatory electrocardiographic recording in patients with hypertension but without proven coronary artery disease. The recordings were analyzed according to strict ST segment depression criteria adapted from the American College of Cardiology/American Heart Association guidelines and according to basic ST segment depression criteria adapted from studies with only concise descriptions of ambulatory electrocardiographic recording analysis. Also, we performed 24-hour ambulatory blood pressure monitoring. More than 4400 hours of ambulatory electrocardiographic recording and ambulatory blood pressure monitoring in 194 patients with hypertension were analyzed. Medication was withdrawn in 45% of the patients. The average systolic blood pressure during the day was 152+/-13 (mean+/-SD); diastolic blood pressure was 94+/-17 mm Hg. According to the basic ST segment depression criteria, we found a prevalence of silent ischemia of 11.3%, and with the strict criteria the prevalence was 5.2%. The patients who were considered positive according to the basic criteria but not according to the strict criteria (false-positive) in the majority of cases (58%) had depression of an elevated baseline ST segment. We found a lower prevalence of silent cardiac ischemia as assessed by ambulatory electrocardiographic recording than generally reported. The stringency of applied analysis criteria appear to play an important role in this outcome.