Limitations of the of the oscillometric method for blood pressure measurements in dialyzed patients.

BACKGROUND: Despite more frequent use of the oscillometric method (OSC) for arterial blood pressure (BP) measurement, little is known about OSC's accuracy when used with hemodialysed patients. This study was undertaken to determine if hemodialysis (HD) and individual features in examined patients can affect the accuracy of OSC for BP measurement. MATERIAL/METHODS: In 54 hemodialysed patients (57 ± 15 years), during 2 sessions (before and after HD), 3 pairs of BP measurements each were performed on arms, alternately employing OSC and auscultatory method, with mercury manometers by 2 observers (REF). RESULTS: No difference was found in systolic BP measured before and after HD (SBP before HD: REF -147.3 ± 27.3, OSC -147.5 ± 25.0 mmHg, p>0.05, SBP after HD: REF-141.1 ± 33.9, OSC-141.2 ± 31.5 mmHg, p>0.05, respectively), but diastolic BP (DBP) was significantly higher both before and after HD during REF measurement in comparison with OSC (DBP before HD: REF -79.0 ± 17.0, OSC -76.7 ± 15.0 mmHg, DBP after HD: REF -78.6 ± 18.8, OSC -76.7 ± 16.7 mmHg, p<0.001, respectively). No significant correlation between loss of body weight caused by HD and differences in BP measured by REF and OSC after HD was indicated (Pearson's correlation coefficients: for SBP -0.041, for DBP 0.030). However, a significant correlation between differences in BP measured by REF and OSC before HD and differences in BP measured by REF and OSC after HD was observed (Spearman's rank correlation coefficients: for SBP 0.502 and for DBP 0.557, p<0.000001). CONCLUSIONS: Our study found that individual features, not HD, determine the accuracy of OSC for BP measurement in hemodialysed patients.

Can the pressor response accompanying blood pressure measurement be limited in young, normotensive women?

BACKGROUND: A decrease in blood pressure (BP) values observed over consecutive measurements may lead to significant discrepancies, affecting individual diagnostic and therapeutic decision making. The goal of the study was to assess whether it was possible to limit or eliminate the tendency for BP values to decline in successive measurements. METHODS: In a group of 148 normotensive women aged 21.6+/-1.5 years, two series (S1, S2) consisting of three brachial BP measurements each (I, II, and III) were performed, using an Omron 907 oscillometric manometer. RESULTS: Systolic blood pressure (SBP) (mmHg) was higher in measurement I than in II and III, in both S1 and S2: S1-I: 114.9+/-10.5 vs. S1-II: 112.6+/-9.9, P<0.00003, vs. S1-III: 111.0+/-9.6, P<0.000001; S2-I: 111.5+/-9.8 vs. S2-II: 110.1+/-9.1 P<0.007, vs. S2-III: 110.1+/-9.2, P<0.0008. Furthermore, measurement II was higher than III in S1 (P<0.002). Similarly, diastolic blood pressure (mmHg) was higher in measurement I than in II and III, in both S1 and S2: S1-I: 68.3+/-8.4 vs. S1-II: 67.3+/-8.7, P<0.008, vs. S1-III: 65.7+/-8.7, P<0.000001; S2-I: 66.6+/-8.3 vs. S2-II: 65.8+/-8.2, P<0.04, vs. S2-III: 65.7+/-8.7, P<0.02. Measurement II was again higher than III in S1 (P<0.00003). CONCLUSIONS: The common alerting reaction to BP measurements cannot be avoided in young, normotensive women, but it can be limited, as demonstrated by the results of BP measurements in S2. The simple procedure of automatic cuff inflation and noninvasive, oscillometric BP measurement may carry an independent pressor effect, which corrupts the accuracy of BP measurements.

Estimation of operators' fatigue using optical methods for determination of pupil activity.

INTRODUCTION: The purpose of this study was to develop and initially validate an objective, yet quick, method for assessment of human fatigue. This aim can be achieved by the use of an optical, non-contact method of analysis of pupil activity. The study involved 2 phenomena typical for the behavior of the human pupil: pupillary reflex and pupillary movements. The 1st phenomenon is related to the pupillary light reflex (PLR), which presents the results of physiological adaptation mechanisms of the human eye. The pupillary unrest index (PUI) is an additional parameter referring to the tendency for instability of the pupil. MATERIAL AND METHODS: Indicators of these 2 mechanisms were assessed under the same experimental laboratory conditions. Assessment was conducted on a group of volunteers (N = 10) during 4 controlled series of measurements performed at night. Pupillary reflex parameters associated with PLR and pupillary unrest index (PUI) were recorded using F²D Fit-For-Duty, a commercially available system made by AMTech Pupilknowlogy GmbH. Baseline pupil diameter, oscillations, reflex latency, maximum reaction time, pupil constriction time, pupil dilation time, and constriction amplitude were recorded. RESULTS: As a result of the study, we were able to demonstrate correlation and confirm the usefulness of PLR and PST methods in the assessment of sleep deprivation. Parameters of PLR that may indicate human fatigue were identified. The effect of light impulse sequences on the dynamics of pupillary reflex and the relationship between PUI (pupillary unrest index) measurement duration and sleepiness assessment validity, were assessed. CONCLUSIONS: The results of the pilot studies were sufficient to develop minimum requirements for a PLR sensor that would be capable of estimating the level of fatigue with accuracy of a PUI method, but at a 5 times faster rate.

Venous blood redistribution alters the accuracy of Omron HEM-705CP.

BACKGROUND: Validation procedures of automated blood pressure measuring devices are carried out at rest only. DESIGN: We aimed to determine whether venous blood redistribution affects the accuracy of the OMRON HEM-705CP (Osc). Lower body negative pressure stimulus (-40 mmHg) (LBNP) was used to simulate changes of body position. METHODS: Fifty-four young healthy volunteers had their blood pressure (BP) measured simultaneously by Osc and mercury sphygmomanometer (HgS) at rest (at 3 and 5 min) and during LBNP (at 7 and 9 min). RESULTS: Differences (delta) between HgS and Osc for systolic and diastolic BP (SBP and DBP) were calculated. The deltaSBP obtained in minute 9 (deltaSBP-9) was bigger than the one taken in minute 5(deltaSBP-5) (-2.89+/- 4.3 versus -1.35+/-5.2 mmHg, P<0.02). The rest of the deltaSBP values and all the deltaDBP values were constant at rest and during venous blood redistribution caused by LBNP. We calculated the fall in SBP separately for HgS and Osc by subtracting SBP-9 from SBP-5 for each patient. The fall measured by Osc was bigger than by HgS (-5.87+/-4.0 versus -4.3+/-4.5 mmHg; P<0.02). When graded according to British Hypertension Society protocol, Osc remained in the class of recommendation (A or B) for every minute of the procedure. CONCLUSIONS: Even if an oscillometric device passes various validation tests, they do not give sufficient information about its accuracy during venous blood redistribution. This knowledge is of particular importance when BP regulation abnormalities occurring during changes in body position are diagnosed with the oscillometric method.

Polish Research Ethics Committees in the European Union system of assessing medical experiments.

The Polish equivalents of Research Ethics Committees are Bioethics Committees (BCs). A questionnaire study has been undertaken to determine their situation. The BC is usually comprised of 13 members. Nine of these are doctors and four are non-doctors. In 2006 BCs assessed an average of 27.3 +/- 31.7 (range: 0-131) projects of clinical trials and 71.1 +/- 139.8 (range: 0-638) projects of other types of medical research. During one BC meeting an average of 10.3 +/- 14.7 (range: 0-71) projects of medical research were assessed (2006). The amendment of Polish laws according with Directive 2001/20/EC caused a percentage increase in BCs which assessed less than 20 projects per year (16% vs. 33% or 42% in 2003 vs. 2005 or 2006 respectively, p < 0,05). The results confirm the usefulness of the current practice of creating BCs by medical universities, medical institutes and regional chambers of physicians and dentists but rationalization of the workload for individual BCs is necessary.

Accuracy of SpaceLabs 90207 is altered by venous blood redistribution.

Validation protocols that have been introduced for automated blood pressure (BP) measuring devices recommend procedures carried out at rest only. We aimed to determine whether venous blood redistribution affects the accuracy of the oscillometric method of BP measurement. For this purpose, we chose a popular oscillometric ambulatory BP monitor--the SpaceLabs 90207 (Osc). Lower body negative pressure (-40 mmHg) (LBNP) was used to simulate changes of body position. Fifty-one young healthy volunteers had their BP measured simultaneously by Osc and mercury sphygmomanometer (HgS) at rest (min 3 and 5), during LBNP (min 7 and 9) and after LBNP (min 11). Differences (delta, mmHg) between HgS and Osc for systolic (SBP) and diastolic BP (DBP) were calculated for every measurement minute. For SBP, deltaSBP-7 and deltaSBP-9 were significantly different from deltaSBP-5 (0.65 +/- 2.6 and 0.33 +/- 2.4 mmHg vs -0.80 +/- 2.9 mmHg, p < 0.003 and p < 0.02, respectively). deltaSBP-11 also differed significantly from deltaSBP-3 and deltaSBP-5 (1.16 +/- 2.5 mmHg vs -0.06 +/- 3.1 mmHg and -0.80 +/- 2.9, p < 0.01 and p < 0.00007, respectively). When graded according to British Hypertension Society protocol, Osc remained in the A class in every measurement minute. The accuracy of SpaceLabs 90207 is altered by venous blood redistribution. These inaccuracies may constitute an additional limitation of oscillometric ambulatory BP monitoring.