SummaryPulse contour methods determine cardiac output semi-invasively using standard arterial access. This study assessed whether cardiac output can be determined non-invasively by replacing the intra-arterial pressure input with a non-invasive finger arterial pressure input in two methods, Nexfin CO-trek Ò and Modelflow Ò , in 25 awake patients after coronary artery bypass surgery. Pulmonary artery thermodilution cardiac output served as a reference. In the supine position, the mean (SD) differences between thermodilution cardiac output and Nexfin CO-trek were 0.22 (0.77) and 0.44 (0.81) l.min )1 , for intra-arterial and non-invasive pressures, respectively. For Modelflow, these differences were 0.70 (1.08) and 1.80 (1.59) l.min, respectively. Similarly, in the sitting position, differences between thermodilution cardiac output and Nexfin CO-trek were 0.16 (0.78) and 0.34 (0.83), for intra-arterial and non-invasive arterial pressure, respectively. For Modelflow, these differences were 0.58 (1.11) and 1.52 (1.54) l.min )1 , respectively. Thus, Nexfin CO-trek readings were not different from thermodilution cardiac output, for both invasive and non-invasive inputs. However, Modelflow readings differed greatly from thermodilution when using non-invasive arterial pressure input.

The proper understanding of the cardiovascular mechanisms involved in complaints of short-lasting dizziness and the evaluation of unexplained recurrent syncope requires continuous monitoring of cardiac stroke volume (SV) in addition to blood pressure and heart rate. The primary aim of the present study was to evaluate a pulse wave analysis method that calculates beat-to-beat flow from non-invasive arterial pressure by simulating a non-linear, time-varying model of human aortic input impedance (Modelflow; MF), by comparing MF stroke volume (SV(MF)) to Doppler ultrasound (US) flow velocity SV (SV(US)). A second purpose was to compare the two methods under two different conditions: the supine and head-up tilt (30 degrees ) position. SV(US) and SV(MF) with non-invasive arterial pressure (Finapres) as input to the aortic model were measured beat-to-beat during spontaneous supine breathing and in the passive 30 degrees head-up tilt (HUT30) position in six normotensive healthy humans [three females, mean age 24 (21-26) years]. There were variations in supine SV track between the two methods with zero difference and a SD of the beat-to-beat difference (MF-US) of 4.2%. HUT30 induced a systematic difference of 10.5% and an increase in SD to 6.9%, which was reproducible. Beat-to-beat changes in SV in the supine resting condition were equally well assessed by both methods. Systematic differences appear during HUT30 and show opposite signs. The difference between the two methods upon a change in body position may be attributed to limitations in each method.

PPLICATIONS OF AUTOIDENTIfication technologies such as radio frequency identification (RFID) in everyday life include security access cards, electronic toll collection, and antitheft clips in retail clothing. 1,2 RFID applications in health care have received increasing attention because of the potentially positive effect on patient safety and also on tracking and tracing of medical equipment and devices. 2-11 The current expenditure levels on RFID systems within health care in the United States are estimated to be approximately $90 million per year 12 with 10-year growth projections to $2 billion. 13 Possible applications of RFID include drug blister packs, which could be intelligently marked to prevent drug counterfeiting; and the quality of blood products being monitored with temperature-sensitive RFID tags. 2,10 The decreasing size and cost of RFID tags also permits incorporation into surgical sponges, endoscopic capsules, and endotracheal tubes, as well as the development of a syringeimplantable glucose-sensing RFID microchip. 3,8,9,14 However, the array of literature that promotes RFID in health care is not accompanied by research on the safety of RFID technology within the health care environment. 15 The potential for harmful electromagnetic interference (EMI) by electronic antitheft surveillance systems on implantable pacemakers and defibrillators has already been recognized, but EMI reports on critical care devices are lacking. 16,17 The focus of the present study was to assess and classify incidents of EMI by RFID on critical care equipment. For editorial comment see p 2898.

The aim of the present study was to investigate the effects of a pretest redistribution of blood volume and of a change in the neurohumoral condition on the blood pressure (BP) and heart rate (HR) responses to three commonly used cardiovascular reflex tests: standing up, forced breathing, and the Valsalva maneuver in 10 healthy male subjects. Base-line conditions were altered by changing posture and the duration of rest preceding the test stimulus. A continuous recording of finger BP was obtained noninvasively by a Finapres. The main observations from this study are with respect to standing up: lengthening the period of preceding rest from 1 to 20 min enlarges the initial BP (systolic/diastolic) decrease (from 8 +/- 10/9 +/- 4 to 27 +/- 8/19 +/- 4 mmHg, P less than 0.01) and the subsequent BP overshoot (from 17 +/- 10/12 +/- 7 to 31 +/- 10/18 +/- 7 mmHg, P less than 0.05); to forced breathing: inspiratory-expiratory changes in BP but not in HR are larger in the upright posture (P less than 0.05); and to the Valsalva maneuver: change in posture from supine to standing increases the phase II BP decrease (from 18 +/- 12/8 +/- 6 to 45 +/- 16/21 +/- 9 mmHg), phase IV systolic BP overshoot (from 26 +/- 16 to 71 +/- 17 mmHg), delta HRmax (from 30 +/- 10 to 47 +/- 12 beats/min), and the Valsalva ratio (HRmax/HRmin), from 2.0 +/- 0.3 to 2.6 +/- 0.7, all significant at P less than 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: This study assessed the relative importance of clinical and transport-related factors in physicians' decision-making regarding the interhospital transport of critically ill patients. Methods:The medical heads of all 95 ICUs in The Netherlands were surveyed with a questionnaire using 16 case vignettes to evaluate preferences for transportability; 78 physicians (82%) participated. The vignettes varied in eight factors with regard to severity of illness and transport conditions. Their relative weights were calculated for each level of the factors by conjoint analysis and expressed in β. The reference value (β = 0) was defined as the optimal conditions for critical care transport; a negative β indicated preference against transportability. Results: The type of escorting personnel (paramedic only: β = -3.1) and transport facilities (standard ambulance β = -1.21) had the greatest negative effect on preference for transportability. Determinants reflecting severity of illness were of relative minor importance (dose of noradrenaline β = -0.6, arterial oxygenation β = -0.8, level of peep β = -0.6). Age, cardiac arrhythmia, and the indication for transport had no significant effect. Conclusions: Escorting personnel and transport facilities in interhospital transport were considered as most important by intensive care physicians in determining transportability. When these factors are optimal, even severely critically ill patients are considered able to undergo transport. Further clinical research should tailor transport conditions to optimize the use of expensive resources in those inevitable road trips.