Arterial pressure measurement in preterm infants

We compared automatic oscillometric measurements of systolic, diastolic, and mean arterial pressures with simultaneous pressures measured from arterial catheters in six preterm infants. Oscillometric arterial pressure measurements were performed with the Omega automatic instrument, using the recommended cuff and the size-larger cuff. Despite highly significant overall correlation coefficients for oscillometric and catheter measurements, 29% to 42% of oscillometric measurements with both cuff sizes were outside the 5-mm Hg error limits, and 4.0% to 9.3% were more than 10 mm Hg different from catheter measurements. Changing the cuff size did not reduce inherent errors in the oscillometric method.     

Pulse oximetry and finger blood pressure measurement during open-heart surgery

Pulse oximeter arterial hemoglobin oxygen saturation (SpO₂) and finger arterial pressure (FINAP) were continuously monitored before, during, and after cardiopulmonary bypass in 15 male patients. SpO₂ was monitored simultaneously with two pulse oximeters, a Nellcor N-100 and an Ohmeda Biox III. The readings obtained from the two pulse oximeters were compared with arterial blood measurements obtained using a CO-oximeter. FINAP was monitored by a prototype device (Finapres) based on the Peaz volume-clamp method. FINAP was correlated with intraarterial pressure (IAP). Both pulse oximeters functioned well before cardiopulmonary bypass. The correlations with CO-oximeter values were 0.927 for the N-100 and 0.921 for the Biox III. Immediately after the onset of cardiopulmonary bypass, the N-100 pulse oximeter stopped displaying values. The Biox III pulse oximeter continued to display values during the cardiopulmonary bypass period; the correlation with CO-oximeter values was 0.813. After cardiopulmonary bypass, the N-100 began displaying values in 2 to 10 minutes. After cardiopulmonary bypass the correlation with CO-oximeter values was 0.792 for the N-100 and 0.828 for the Biox III pulse oximeter. The Finapres finger blood pressure device functioned well in 13 of 15 patients before cardiopulmonary bypass. The mean bias ± precision of FINAP-IAP for mean pressure was 8.3±10.2 mm Hg (SD) and the correlation coefficient was 0.814. During cardiopulmonary bypass, the Finapres device functioned well in 10 of 15 patients. The mean bias precision of FINAP-IAP, for mean pressure in these 10 patients was 6.6±8.7 mm Hg and the correlation coefficient was 0.902. Immediately after cardiopulmonary bypass, the Finapres functioned well in 11 of 15 patients. The mean bias ± precision of FINAP-IAP for mean pressure was 8.6±14.1 mm Hg and the correlation coefficient was 0.533. This study documented that devices for continuous noninvasive monitoring can usually function well under the extreme conditions seen during open-heart surgery. Pulse oximeters may find a place in the monitoring of patients during open-heart surgery, although they cannot totally replace the invasive techniques. Under the conditions of diminished pulsatile peripheral blood flow we observed some differences between the two pulse oximeters.     

Biases in the measurement of arterial pressure

We compared cuff to simultaneous direct intra-arterial pressure in 26 seriously ill patients, in order to: test the accuracy of oscillometric and auscultatory estimates of direct systolic pressure; test muffling and disappearance of sound as indices of direct diastolic pressure; gain insight into the timing of the different phases of Korotkoff sounds; and assess the local and general effects of cuff inflation on blood pressure. We found that conventional estimation of systolic blood pressure by auscultation of the first Korotkoff sound (K1) underestimates direct systolic pressure by an average of 16 to 17 mm Hg. Oscillometric pressure measurement provides a significantly better estimate than K1 but still underestimates by 7 to 8 mm Hg. These systolic cuff measurements are biased downward from direct values because of local cuff effect and cuff error. Diastolic cuff measurements deviate from direct values primarily because of a local cuff effect which produces an upward bias of 5 mm Hg at the point of sound muffling (K4), and 3 mm Hg at the point where sounds disappear (K5). We recommend oscillometric measurement of systolic pressure and K5 measurement of diastolic pressure as the best indirect estimates of blood pressure in critically ill patients.     

Does measurement of systolic blood pressure with a pulse oximeter correlate with conventional methods?

The pulse oximeter is commonly used in the operating room. We evaluated the use of a pulse oximeter to monitor systolic blood pressure in 20 healthy volunteers and 42 anesthetized patients. We compared the pulse oximeter method of measuring systolic blood pressure with the cuff methods using Korotkoff sounds and Doppler ultrasound as well as with direct pressure measurement through an intraarterial cannula. Systolic blood pressure values obtained by pulse oximeter correlated well with values obtained by other conventional methods. The best correlation was found with Doppler ultrasound (r = 0.996) and the worst with arterial cannulation (r = 0.880). We conclude that this method can be used intraoperatively to measure systolic blood pressure.     

Accuracy of oscillometric blood pressure measurement according to the relation between cuff size and upper-arm circumference in critically ill patients

OBJECTIVE: To evaluate the accuracy of oscillometric blood pressure measurement according to the relation between cuff size and upper-arm circumference in critically ill patients. DESIGN: Prospective data collection. SETTING: Emergency department in a 2,000-bed inner city hospital. PATIENTS: Thirty-eight patients categorized into three groups according to their upper-arm circumference (group I: 18-25 cm; group II: 25.1-33 cm; and group III: 33.1-47.5 cm) were enrolled in the study protocol. INTERVENTIONS: In each patient, all three cuff sizes (Hewlett-Packard Cuff 40401 B, C, and D) were used to perform an oscillometric blood pressure measurement at least within 3 mins until ten to 20 measurements for each cuff size were achieved. Invasive mean arterial blood pressure measurement was done by cannulation of the contralateral radial artery with direct transduction of the systemic arterial pressure waveform. The corresponding invasive blood pressure value was obtained at the end of each oscillometric measurement. MEASUREMENT AND MAIN RESULTS: Overall, 1,494 pairs of simultaneous oscillometric and invasive blood pressure measurements were collected in 38 patients (group I, n = 5; group II, n = 23; and group III, n = 10) over a total time of 72.3 hrs. Mean arterial blood pressure ranged from 35 to 165 mm Hg. The overall discrepancy between oscillometric and invasive blood pressure measurement was -6.7+/-9.7 mm Hg (p<.0001), if the recommended cuff size according to the upper-arm circumference was used (539 measurements). Of all the blood pressure measurements, 26.4% (n = 395) had a discrepancy of > or =10 mm Hg and 34.2% (n = 512) exhibited a discrepancy of > or =20 mm Hg. No differences between invasive and noninvasive blood pressure measurements were noted in patients either with or without inotropic support (-6.6 + 7.2 vs. -8.6 + 6.8 mm Hg; not significant). CONCLUSION: The oscillometric blood pressure measurement significantly underestimates arterial blood pressure and exhibits a high number of measurements out of the clinically acceptable range. The relation between cuff size and upper-arm circumference contributes substantially to the inaccuracy of the oscillometric blood pressure measurement. Therefore, oscillometric blood pressure measurement does not achieve adequate accuracy in critically ill patients.     

Noninvasive continuous blood pressure measurement: A clinical evaluation of the Cortronic APM 770

The Cortronic APM 770 (Cortronic, Ronkonkoma, NY) is a commercial device that claims to measure blood pressure noninvasively and continuously with the use of a standard blood pressure cuff. The aim of our study was to assess the performance of the continuous-mode blood pressure readings of the Cortronic during anesthesia and surgery. We recorded blood pressure in 5 patients bilaterally. An intraarterial pressure (IAP) curve was recorded from 1 arm and the Cortronic pressure curve (CPC) was recorded from the other. For statistical analysis the period between 2 Cortronic recalibrations was defined as the intercalibration interval. The duration of these intervals ranged from 20 to 0.5 minutes. Four paired samples were drawn from each interval. The first sample in an interval represented the recalibration blood pressure; the other samples represented the continuous blood pressure. A total of 1,232 samples were taken, of which 308 were recalibration. The median of the differences and the 2.5th and 97.5th percentile limits of agreement were determined. Their respective values for diastolic and systolic recalibration measurements were 5, –17, and 34 mm Hg, and 6, –12, and 38 mm Hg. Their values for continuous measurements were 4, –23.5, and 32 mm Hg, and 6, –30, and 70 mm Hg. Changes in CPC were evaluated against changes in the corresponding IAP by plotting them in 4-quadrant graphs. In these graphs the Spearman rank correlations were betweenr=–0.17 andr=0.01. We observed opposite CPC and IAP trends on 24 occasions during this study. We performed a simple simulation study to better understand the measurement method of the Cortronic. The study showed a positive relationship between pulsation volume and CPC amplitude, and between pulsation rate and CPC amplitude. We conclude that during anesthesia and surgery continuous-mode blood pressure readings of the Cortronic are unreliable, and suggest that the phenomenon of the two pressures' moving in opposite directions is inherent to the measurement principles of the device.     

Accuracy of four indirect methods of blood pressure measurement,with hemodynamic correlations

In 38 adults undergoing cardiac surgery, 4 indirect blood pressure techniques were compared with brachial arterial blood pressure at predetermined intervals before and after cardiopulmonary bypass. Indirect blood pressure measurement techniques included automated oscillometry, manual auscultation, visual onset of oscillation (flicker) and return-to-flow methods. Hemodynamic measurements or calculations included heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect and intraarterial blood pressure values were compared by simple linear regression by patient and measurement period. Measurement errors (arterial minus indirect blood pressure) were calculated, and stepwise regression assessed the relationship between measurement error and heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect to intraarterial blood pressure correlation coefficients varied over time, with the strongest correlations often occurring at the first and last measurement periods (preinduction and 60 minutes after cardiopulmonary bypass), particularly for systolic blood pressure. Within-patient correlations between indirect and arterial blood pressure varied widely—they were consistently high or low in some patients. In other patients, correlations were especially weak with a particular indirect blood pressure method for systolic, mean, or diastolic blood pressure; in some cases indirect blood pressure was inadequate for clinical diagnosis of acute blood pressure changes or trends. The mean correlations between indirect and direct blood pressure values were, for systolic blood pressure: 0.69 for oscillometry, 0.77 for auscultation, 0.73 for flicker, and 0.74 for return-to-flow; for mean blood pressure: 0.70 for oscillometry and 0.73 for auscultation; and for diastolic blood pressure: 0.73 for oscillometry and 0.69 for auscultation. The mean measurement errors (arterial minus indirect values) for the individual indirect blood pressure methods were, for systolic: 0 mm Hg for oscillometry, 9 mm Hg for auscultation, -5 mm Hg for flicker, 7 mm Hg for return-to-flow; for mean: -6 mm Hg for oscillometry, and -3 mm Hg for auscultation; and for diastolic: -9 mm Hg for oscillometry and -8 mm Hg for auscultation. Mean measurement error for systolic blood pressure was thus least with automated oscillometry and greatest with manual auscultation, while standard deviations ranging from 9 to 15 mm Hg confirmed the highly variable nature of single indirect blood pressure measurements. Except for oscillometric diastolic blood pressure, a combination of systemic hemodynamics (heart rate, stroke volume index, systemic vascular resistance index, and cardiac index) correlated with each indirect blood pressure measurement error, which suggests that particular numeric ranges of these variables minimize measurement error. This study demonstrates that striking variability occurs in the relationship between indirect and arterial blood pressure measurements, and that the systemic hemodynamic state influences accuracy of indirect blood pressure measurements. When the reproducibility of repeated indirect blood pressure measurements appears unsatisfactory or inconsistent with other clinical observations, clinicians may find that an alternative indirect blood pressure method is a better choice. Of the methods tested, no single indirect blood pressure technique showed precision superior to the others, but two methods yielded data only for systolic pressure. These findings lend support to intraarterial blood pressure measurement in conditions of hemodynamic variability, and suggest the theoretical benefits of continuous indirect blood pressure measurements. Annual meeting of the American Society of Anesthesiologists, New Orleans, LA, Oct 1984.     

The effect of cuff pressure deflation rate on accuracy in indirect measurement of blood pressure with the auscultatory method

The importance of cuff deflation rate in the auscultatory method of measuring blood pressure was investigated using a computer-based model. To determine the relationship between the cuff deflation rate and the measurement error, two cuff deflation protocols were used, one based on heart rate (mm Hg per heartbeat), the other on a constant rate (mm Hg per second). The different deflation protocols and rates were tested using a constant blood pressure of 120/80 mm Hg and heart rates ranging from 40 to 120 beats/min. It was confirmed that a cuff deflation rate that is time based will introduce larger errors at low heart rates. Using heart rate as a basis for cuff deflation rate yields a constant error that is independent of heart rate. The currently used standard of 3 mm Hg/s could result in a maximum error of 2.5 mm Hg in both systolic and diastolic pressures at a heart rate of 72 beats/min. The maximum systolic and diastolic errors increase to more than 4 mm Hg at 40 beats/min. A deflation rate of 2 mm Hg/beat, however, yields a maximum error of 2 mm Hg for both systolic and diastolic pressures, independent of heart rate. A cuff deflation rate based on heart rate is recommended to help minimize changes in measurement error when measuring blood pressure if a wide range of heart rates will be encountered.Supported by grants from IVAC, San Diego, CA, and Physio Control, Redmond, WA.     

Continuous stroke volume monitoring by modelling flow from non-invasive measurement of arterial pressure in humans under orthostatic stress.

The relationship between aortic flow and pressure is described by a three-element model of the arterial input impedance, including continuous correction for variations in the diameter and the compliance of the aorta (Modelflow). We computed the aortic flow from arterial pressure by this model, and evaluated whether, under orthostatic stress, flow may be derived from both an invasive and a non-invasive determination of arterial pressure. In 10 young adults, Modelflow stroke volume (MFSV) was computed from both intra-brachial arterial pressure (IAP) and non-invasive finger pressure (FINAP) measurements. For comparison, a computer-controlled series of four thermodilution estimates (thermodilution-determined stroke volume; TDSV) were averaged for the following positions: supine, standing, head-down tilt at 20 degrees (HDT20) and head-up tilt at 30 degrees and 70 degrees (HUT30 and HUT70 respectively). Data from one subject were discarded due to malfunctioning thermodilution injections. A total of 155 recordings from 160 series were available for comparison. The supine TDSV of 113+/-13 ml (mean+/-S.D.) dropped by 40% to 68+/-14 ml during standing, by 24% to 86+/-12 ml during HUT30, and by 51% to 55+/-15 ml during HUT70. During HDT20, TDSV was 114+/-13 ml. MFSV for IAP underestimated TDSV during HDT20 (-6+/-6 ml; P<0.05), but that for FINAP did not (-4+/-7 ml; not significant). For HUT70 and standing, MFSV for IAP overestimated TDSV by 11+/-10 ml (HUT70; P<0.01) and 12+/-9 ml (standing; P<0.01). However, the offset of MFSV for FINAP was not significant for either HUT70 (3+/-8 ml) or standing (3+/-9 ml). In conclusion, due to orthostasis, changes in the aortic transmural pressure may lead to an offset in MFSV from IAP. However, Modelflow correctly calculated aortic flow from non-invasively determined finger pressure during orthostasis.     

Clinical Assessment of the Neonatal Dinamap 847 During Anesthesia in Neonates and Infants

Direct measurements of systolic, diastolic, and mean arterial blood pressure and electrocardiogram-derived heart rates were compared with indirect arterial blood pressure measurements using the Dinamap 847XT noninvasive monitor. A total of 260 paired comparisons from 16 patients were analyzed. A regression analysis of paired data over a wide range of blood pressure values gave the following results: for heart rate r = 0.97, for systolic arterial pressure r = 0.84, for mean arterial pressure r = 0.73, and for diastolic arterial pressure r = 0.52. The 95% confidence limits for systolic, mean, and diastolic arterial pressure were ±16 mm Hg, ±18 mm Hg, and ±21 mm Hg, respectively. The Dinamap monitor was found to be an accurate trend recorder of heart rate and blood pressure during anesthesia in neonates and small infants.     

Accurate blood pressure measurement

The most critical requirement for obtaining accurate blood pressure measurements is that the Korotkoff sounds be loud. Loudness can be enhanced by various techniques of cuff inflation and chest piece placement. The type of manometer, cuff size, and cuff placement are also important factors in obtaining accurate blood pressure readings. Correct systolic pressure measurement depends on proper inflation and deflation of the cuff. True diastolic pressure is usually closer to the disappearance point of Korotkoff sounds than to the muffling phase. Blood pressure should be recorded to the nearest 5 mm Hg because measurement to the nearest 2 mm Hg is not meaningful and is too difficult and time-consuming.     

Use of A Neonatal Blood Pressure Cuff to Monitor Blood Pressure In The Adult Finger – Comparison With A Standard Adult Arm Cuff

Background. There are few suitable methods for monitoring blood pressure continously (or intermittently) for research in adult stroke patients, who are ill but do not justify invasive intensive care monitoring. Method. We tested a neonatal arm blood pressure in adults by placing it on the forefinger (finger cuff). We compared the repeatability of the finger cuff with blood pressure measured by a standard adult arm cuff using the oscillometric technique in 168 ambulatory outpatients attending a cerebrovascular disease clinic. Results. The mean difference between sequential mean blood pressure readings with the finger cuff was 0.55 mm Hg (95% confidence interval (CI) –14.36 to 15.47 mm Hg), and for the arm cuff was 3.31 mm Hg (95% CI –23.33 to 16.71 mm Hg). Measurements made with the arm cuff were shown to affect subsequent arm cuff readings made within a few minutes of the first. The mean difference between the finger cuff and arm cuff mean blood pressure readings was 0.03 mm Hg (95% CI –26.07 to 26.14 mm Hg) and agreement was better when the blood pressure was measured with the finger cuff first rather than the arm cuff. However, although there was no difference in the mean blood pressure recordings both systolic and diastolic blood pressure measurements differed systematically between arm and finger cuff. Conclusion. The reproducibility of sequential blood pressure measurements made with the finger cuff was better than with the arm cuff. The performance of the finger cuff compared with that of the arm cuff was sufficiently good to encourage use of the finger cuff in research involving automatic intermittent monitoring to observe sequential blood pressures over time in stroke patients. However, measurements of systolic and diastolic pressure were not the same with the two cuffs and further work on calibration of the finger cuff would be useful.     

Accuracy Of Beat-To-Beat Noninvasive Measurement Of Finger Arterial Pressure Using The Finapres: A Spectral Analysis Approach

Objective. Our objective was to test the accuracy of noninvasive recordings of finger arterial pressure (FAP) using the Ohmeda Finapres (Ohmeda Monitoring Systems, Englewood, CO).Methods. Twenty patients, aged 20 to 78 years, requiring admission to the intensive care unit and placement of intraarterial catheters participated in the study. Systolic and diastolic pressures were derived from 1-hr recordings of beat-to-beat FAP and from ipsilaterally recorded intraarterial pressure (IAP) signals. In all 20 cases, we analyzed beat-to-beat discrepancies between the actual magnitude of FAP and IAP, as well as the distribution of the consecutive differences within each of the two signals. In 10 cases, spectral analysis of the frequency content of both signals was performed.Results. The average systolic FAP (128.1 ± 22.4 mm Hg) did not differ from IAP (127.1 ± 19.7 mm Hg), whereas diastolic FAP (78.1 ± 11.9 mm Hg) was greater (71.5 ± 10.3 mm Hg) (p < 0.001). No differences in the linear trends of FAP and IAP were observed. Overall, systolic FAP and IAP were discrepant by 0.84 ± 13.3 mm Hg (-21.82 to 25.8 mm Hg); diastolic FAP and IAP were discrepant by 6.67 ± 5.23 mm Hg (2.68 to 13.05 mm Hg). Despite discrepancies in the magnitude of the two signals, the contour of IAP approximated that of FAP. Spectral analysis demonstrated good reproducibility and coherence between diastolic IAP and FAP fluctuations in both low-frequency (0.01 to 0.15 Hz) and high-frequency (0.15 to 0.33 Hz) bands. The low-frequency fluctuations in FAP systolic pressure were significantly amplified (p < 0.001) (gain 1.75), whereas the high-frequency fluctuations were not.Conclusions. Over the course of 1 hr, FAP followed the contour and frequency content of IAP. This work was supported by a grant to Dr R. Schondorf from the Heart and Stroke Foundation of Canada. The assistance of the physicians and of the nursing staff of the Sir Mortimer B. Davis Jewish General Hospital intensive care unit is greatly appreciated.     

The effect of deep-tissue massage therapy on blood pressure and heart rate

AIM: In the present study, we describe the effects of deep tissue massage on systolic, diastolic, and mean arterial blood pressure. MATERIALS AND METHODS: The study involved 263 volunteers (12% males and 88% females), with an average age of 48.5. Overall muscle spasm/muscle strain was described as either moderate or severe for each patient. Baseline blood pressure and heart rate were measured via an automatic blood pressure cuff. Twenty-one (21) different soothing CDs played in the background as the deep tissue massage was performed over the course of the study. The massages were between 45 and 60 minutes in duration. The data were analyzed using analysis of variance with post-hoc Scheffe's F-test. RESULTS: Results of the present study demonstrated an average systolic pressure reduction of 10.4 mm Hg (p<0.06), a diastolic pressure reduction of 5.3 mm Hg (p<0.04), a mean arterial pressure reduction of 7.0 mm Hg (p<0.47), and an average heart rate reduction of 10.8 beats per minute (p<0.0003), respectively. CONCLUSIONS: Additional scientific research in this area is warranted.     

Evaluation of two prototype devices producing noninvasive,pulsatile, calibrated blood pressure measurement from a finger

We evaluated two prototype instruments that measure pulsatile blood pressure continuously and noninvasively and compared the mean arterial pressure obtained from these devices with that obtained mvasivcly m 17 male surgical patients. Each prototype consisted of an infrared photoplethysmograph mounted inside a finger cuff. The cuff was connected to a pressure control valve, which rapidly changed the cuff pressure so as to maintain a null pressure difference across the finger arterial wall. The resultant cuff pressure rapidly tracked the pulsatile intraarterial pressure. The prototypes reproduced absolute pressure, as well as pressure changes, accurately and linearly over a wide range of mean arterial pressures (from 2 to 164 mm Hg), with an average offset error of 0.8 mm Hg (SD ± 3.8; range, -4.6 to 7.9), a mean scatter error of 5.3 mm Hg (range, 3.6 to 8.6), a mean regression slope of 0.97 (range, 0.79 to 1.22) and a mean correlation coefficient of the regression of 0.96 (range, 0.89 to 0.98). Both prototypes worked satisfactorily on all 17 patients, but not all the time on all patients. In 7 patients, probable arterial spasm prevented measurement of finger blood pressure 12.1% of the time, or 5.4% of the time for all patients. Ninety-six percent of the lost samples occurred with prototype 2, suggesting an instrument-related cause, rather than one related to the principle itself. The prototypes were simple to use and were almost free from artifact. Continuous monitoring for up to 7 hours on a single finger caused no harm to the finger.     

二维和多普勒超声心动图对动脉导管未闭肺循环量、肺动脉压及肺阻力的定量研究

本文联合应用二维、脉冲式和连续式多普勒技术测定了15例动脉导管未闭患儿的主动脉体积血流、动脉导管两侧收缩期最大压力阶差、舒张末期压力阶差和平均压力阶差,并同时用袖带法测量肱动脉压,由此分别计算肺循环量、肺动脉收缩压、舒张压和平均压及肺总阻力,与心导管术测值比较相关性良好(相关系数r=0.87～0.94)。提出并证实了应用二维/多普勒超声心动图可对动脉导管未闭的肺循环血流动力学改变作出系统的定量诊断。     

Effects of peripheral cold application on core body temperature and haemodynamic parameters in febrile patients

This study designed to assess the effects of peripheral cold application (PCA) on core body temperature and haemodynamic parameters in febrile patients. This study was an experimental, repeated‐measures performed in the neurosurgical intensive‐care unit. The research sample included all patients with fever in postoperative period. PCA was performed for 20 min. During fever, systolic blood pressure, mean arterial blood pressure and arterial oxygen saturation (O₂Sat) decreased by 5.07 ± 7.89 mm Hg, 0.191 ± 6.00 mm Hg and 0.742% ± 0.97%, respectively, whereas the pulse rate and diastolic blood pressure increased by 8.528 ± 4.42 beats/ min and 1.842 ± 6.9 mmHg, respectively. Immediately after PCA, core body temperature and pulse rate decreased by 0.3°C, 3.3 beats/min, respectively, whereas systolic, diastolic, mean arterial blood pressure and O₂Sat increased by, 1.40 mm Hg, 1.87 mm Hg, 0.98 mmHg and 0.27%, respectively. Thirty minutes after the end of PCA, core body temperature, diastolic, mean arterial blood pressure and pulse rate decreased by 0.57°C, 0.34 mm Hg, 0.60 mm Hg and 4.5 beats/min, respectively, whereas systolic blood pressure and O₂Sat increased by 0.98 mm Hg and 0.04%, respectively. The present results showed that PCA increases systolic, diastolic, mean arterial blood pressure and O₂Sat, and decreases core body temperature and pulse rate.     

Continuous Noninvasive Determination of Pulsus Paradoxus: A Pilot Study

Objective: To evaluate two methods of continuous, noninvasive monitoring of pulsus paradoxus (PP). Methods: A single-subject, nonblind assessment was conducted of the ability of noninvasive monitoring techniques to measure experimentally induced PP. Variable degrees of PP were induced in a healthy adult breathing through a oneway valve to which a series of external airway resistances were added. Intra-arterial pressure (IAP), finger arterial blood pressure (FINAP), pulse oximeter pulse waveform, and chest wall motion were continuously recorded. For each resistance, PP was calculated from the IAP (PP_IAP) and the FINAP (PP_FINAP) recordings. PP was measured manually (PP_manual) in the opposite arm. The percentage pulse waveform decrease on inspiration (%PWD_pleth) was derived from the oximeter pulse waveform. These measurements were compared with the PP_IAP. Bias was assessed as the mean difference between PP measures. Results: PP_FINAP, was highly correlated with PP_IAP (r = 0.96; 95% CI 0.93 to 0.98; p < 0.0001). There was a weak correlation between PP_manual and PP_IAP (r = 0.27; 95% CI -0.05 to 0.55; p = 0.0963). The %PWD_pleth correlated with PP_IAP (r = 0.59, 95% CI 0.32 to 0.78; p = 0.0002). Bias was -1.515 ± 5.6 mm Hg between PP_IAP and PP_FINAP; and -4.508 ± 23.4 mm Hg between PP_IAP and PP_manual. Conclusion: An accurate and continuous PP can be measured noninvasively using a FINAP monitor. This method has much better agreement with IAP measurements than do manual measurements. The qualitative information provided by the oximeter pulse waveform is less accurate than that provided by the FINAP monitor, but is a potentially useful screening tool for detection of significant PP.     

Blood pressure decrease prior to initiating pharmacological therapy in nonemergent hypertension

In order to characterize the decrease in blood pressure that occurs in the emergency department (ED) setting in cases of nonemergent hypertension before beginning pharmacological therapy, 94 consecutive cases of hypertension seen at the University of Illinois Hospital were reviewed. Each patient in the analysis had a triage blood pressure recorded by the nursing staff and second blood pressure reading taken between 10 minutes and 2 hours after the triage pressure before pharmacological therapy was begun. Patients with diastolic pressures less than 90 mm Hg were excluded, as were patients with acute end-organ pathology secondary to hypertension. In the remaining 54 cases, the mean arterial pressure fell by 6% (P less than .003), the systolic pressure fell by 6% (P less than .022), and the diastolic pressure fell by 6.4% (P less than .003), suggesting that in nonemergent hypertension, a significant decrease in blood pressure occurs in the ED before pharmacological therapy is begun. The blood pressure decrease was not statistically different when sex and age were considered, but when patients were grouped into those with diastolic pressures between 90 mm Hg and 114 mm Hg and those with diastolic pressures greater than or equal to 115 mm Hg, there was a statistically significant decrease in systolic, diastolic, and mean arterial pressures only in patients with diastolic pressures greater than or equal to 115 mm Hg. Our findings suggest that patients with nonemergent hypertension do not always require immediate and aggressive pharmacological intervention in the ED setting and are best observed for a short period and then reassessed before beginning pharmacological therapy.