Noninvasive Arterial Blood Pressure Monitoring Research Articles

Increased impedance to inspiration ameliorates hemodynamic changes associated with movement to upright posture in orthostatic hypotension: A randomized blinded pilot study

Movement to upright posture may result in marked drop of blood pressure with susceptibility to injury from syncope and falls in patients with orthostatic hypotension. The purpose of this study was to determine if increasing negative intrathoracic pressure by using an inspiratory impedance threshold device before change of posture diminishes blood pressure fall by enhancing venous return. Eighteen healthy subjects and 22 orthostatic hypotension patients were randomized to either an active (impedance 7 cmH2O) or sham (no inspiratory impedance) impedance threshold device. Arterial blood pressure, heart rate, and estimated stroke volume and total peripheral resistance were recorded in the supine and upright postures using a noninvasive finger arterial blood pressure monitor. After a rest period, the alternate impedance threshold device (sham or active) was tested in each individual. Compared with the sham impedance threshold device test, the active impedance threshold device resulted in significant reduction in the magnitude of upright posture-induced fall in blood pressure and a greater increase of total peripheral resistance after standing in both healthy subjects and orthostatic hypotension patients. Stroke volume was not measurably altered. Among all subjects who exhibited a postural blood pressure drop >10 mmHg on the day of study, active impedance threshold device treatment consistently blunted blood pressure fall during the initial 100 seconds after standing (<0.04). Induced orthostatic symptoms were less severe with the active impedance threshold device both at onset of upright posture and during 30 seconds of standing. Enhancing impedance to inspiration may prove useful as adjunctive therapy for diminishing symptoms associated with movement to upright posture in individuals with orthostatic hypotension.

A Comparison of the Vasotrac with Invasive Arterial Blood Pressure Monitoring in Children After Pediatric Cardiac Surgery

The Vasotrac is a device that provides near-continuous and noninvasive arterial blood pressure monitoring and may be an alternative to direct intraarterial measurement. It has been evaluated in adult patients, but minimal information is available for pediatric patients. We evaluated agreement between measurements of arterial blood pressure and heart rate obtained from the Vasotrac versus an arterial catheter in a pediatric population. Children undergoing corrective cardiac surgery were enrolled. Simultaneous arterial blood pressure measurements were obtained postoperatively from the Vasotrac unit and an arterial catheter. Bland-Altman plots were constructed to assess agreement. Paired correlation analysis, bias, and precision calculations were performed. Sixteen patients, mean age 10.1 +/- 2.3 yr and weight 34.6 +/- 11.9 kg, were enrolled. Four-thousand-one- hundred- two paired measurements were obtained. Arterial blood pressures measured noninvasively correlated with catheter measurements with Pearson r values of 0.90, 0.80, and 0.91 for systolic, diastolic, and mean arterial blood pressures, respectively (all P < 0.001). There was excellent agreement between arterial blood pressure measurement methods. Absolute mean differences based on mixed-model regression with 95% confidence intervals were 4.0 mm Hg (3.0-5.0 mm Hg), 4.3 mm Hg (3.1-5.5 mm Hg), and 3.5 mm Hg (2.5-4.0 mm Hg) for systolic blood pressure, diastolic blood pressure, and mean blood pressure, respectively. Arterial blood pressure measurements obtained from the Vasotrac agreed well with invasive arterial monitoring in pediatric patients.

Noninvasive 24-hour ambulatory arterial blood pressure monitoring in cirrhosis

Cirrhotic patients have disturbed systemic hemodynamics with reduced arterial blood pressure, but this has not been investigated during daily activity and sleep. Systolic (SBP), diastolic (DBP), and mean arterial blood pressure (MAP), and heart rate (HR) were measured by an automatic ambulant device for monitoring blood pressure in 35 patients with cirrhosis and 35 healthy matched controls. During the daytime, SBP, DBP, and MAP were significantly lower in the patients than in the controls (median 118 vs. 127; 70 vs. 78; 86 vs. 94 mm Hg, P < .0001 to P < .05). The nighttime blood pressures were almost similar in the two groups (108 vs. 110; 65 vs. 67; 78 vs. 82 mm Hg, NS). Conversely, HR was significantly higher in the patients both in the daytime (86 vs. 72/min, P < .0001) and at night (80 vs. 64/min, P < .0001). Consequently, the reduction in blood pressure and HR from daytime to nighttime was significantly lower in the patients than in the controls ( P < .0001 to P < .01). Multiple regression analysis showed HR, serumalbumin, serum sodium, and clotting factors 2, 7, and 10 as significant independent predictors of SBP in cirrhosis. In conclusion, cirrhotic patients have elevated HR, but surprisingly normal arterial blood pressure during the nighttime, and the circadian variation in blood pressure and HR is diminished, probably because of an almost unaltered cardiac output during the 24 hours. These results may reflect a major defect in the ability of optimal regulation of blood pressure in cirrhotic patients.

The prolonged antihypertensive effect of once daily atenolol: a study of continuous non-invasive arterial blood pressure monitoring.

This study was carried out on 12 hospitalized hypertensive patients to assess the antihypertensive efficiency and the duration of action of a once daily dose of atenolol. 100 mg of atenolol was given at 8 am every day for 5 days. Before and during the therapeutic period. 24-h blood pressure recordings were obtained with a continuous, automatic, non-invasive method working on the principle of oscillometry (Dinamap 845.950). Atenolol induced a significant reduction in mean blood pressure from 119 +/- 3.6 to 102.3 +/- 4.7 (P less than 0.001). This effect was significant from the very first day of treatment and was maintained over the duration of the study in ten patients. The decrease in blood pressure induced by atenolol lasted 24 h. Clinical tolerance of atenolol was excellent. In particular no case of excessive bradycardia was noted.