International journal of clinical monitoring and computing最新文献

Beat-to-beat heart rate variability analysis is a powerful tool for the diagnosis of neuropathy. Respiration-related heart rate variability (respiratory sinus arrhythmia, RSA) reflects the function of parasympathetic nervous system during spontaneous ventilation while awake. RSA is also claimed to monitor the depth of anaesthesia. Power spectrum analysis or various averaging techniques of the heart rate variability are usually applied. The current literature, however, does not usually interpret the ground rules and limitations of the method used, and this may sometimes lead to erroneous conclusions on the data. The aim of our study was to compare and analyse critically the performance of different methods of evaluating RSA during anaesthesia and positive pressure ventilation. Power spectrum analysis, the root mean square of the successive RR-interval difference (RMSSD), and two respiration related methods, RSA index and average phase RSA, were included in the comparison. To test these methods, 11 patients were anaesthetised with isoflurane and their lungs were ventilated mechanically with a frequency of 6 cycles min-1. Each patient received a bolus dose of atropine (20 micrograms kg-1) during the trial. Electrocardiogram, electroencephalogram and tracheal pressure signal from respirator were recorded and analyses were performed off-line. We demonstrated that general indices, such as RMSSD, may be strongly affected by heart rate level and other non-respiration related variations in heart rate. We also showed that the effect of unwanted fluctuations on RSA can be reduced with respiration dependent beat-to-beat methods. Furthermore we confirmed that in addition to the amplitude, also the pattern of respiratory sinus arrhythmia is of interest: the pattern is reversed in phase compared to spontaneous breathing while awake, as we have shown earlier. To analyse RSA during anaesthesia, we recommend the use of an average phase RSA method based on beat-to-beat variability that shows both the amplitude and pattern of RSA. Finally, no measure of RSA should be used without a presentation of the actual beat-to-beat heart rate curve.

Live video and sound from the 11th World Congress of Anaesthesiology in Sydney, Australia were broadcast over the Internet using the CuSeeme software package as part of an ongoing evaluation of Internet-based telecommunication in the delivery of Continuing Medical Education (CME). This was the first time such a broadcast had been attempted from a medical convention. The broadcast lasted for four days, during which a functioning combination of computer hardware and software was established. Technical issues relating to broadcast of these real time signals over ISDN links and the Internet itself were addressed. Over 200 anaesthetists from around the world were able to 'attend' the plenary sessions via the Internet. Evidenced by feedback received audio reception was quite good. Video reception was less successful for those receiving the broadcast via a modem based Internet connection. The received signal in such circumstances was adequate to provide a video presence of the speaker but inadequate to allow details of 35 mm slides to be visualised. We conclude that this technology will be of use in the delivery of CME materials to remote areas provided simultaneous viewing of high resolution still images is possible using another medium, such as the World Wide Web.

Objective: Fast paramagnetic oxygen analyzers have made it possible to measure inspiratory to end-tidal oxygen concentration difference (P(I-ET)O2) breath-by-breath. It is now frequently displayed on monitors during routine anesthesia. We wanted to study the effects of major changes in metabolism, ventilation and circulation on P(I-ET)O2.

Methods: Ten healthy male volunteers were studied under exercise. P(I-ET)O2 was measured with a fast-response paramagnetic differential oxygen sensor. Cardiac output was measured with non-invasive transthoracic electrical bioimpedance. Metabolism was measured with indirect calorimetry and ventilation with a side stream spirometer. After a rest period, the subjects cycled at 30 W and 60 W, 6 minutes on each work load and were then observed during 10 minutes of rest.

Results: P(I-ET)O2 corresponded well to VO2/VA (the oxygen uptake to alveolar ventilation quotient) correlation showed r = 0.79. P(I-ET)O2 was influenced by changes in cardiac output which occurred primarily at the start and at the end of exercise. Expired minute ventilation (VE) multiplied by P(I-ET)O2 was related to cardiac output with a high intrapersonal correlation.

Conclusion: P(I-ET)O2 is a good measure of adequate ventilation in relation to the oxygen consumption level and multiplied by VE it might offer a non-invasive bedside parameter indicating changes in cardiac output.

Although auscultation is commonly used as a continuous monitoring tool during anesthesia, the breath sounds of anesthetized patients have never been systematically studied. In this investigation we used digital audio technology to record and analyze the breath sounds of 14 healthy adult patients receiving general anesthesia with positive pressure ventilation. Sounds recorded from inside the esophagus were compared to those recorded from the surface of the chest, and corresponding airflow was measured with a pneumotachograph. The sound samples associated with inspiratory and expiratory phases were analyzed in the time domain (RMS amplitude) and frequency domain (peak frequency, spectral edge, and power ratios). There was a positive linear correlation (R2 > 0.9) between inspiratory flow and sound amplitude in the precordial and esophageal samples of all patients. The RMS amplitude of the inspiratory and expiratory sounds was approximately 13 times greater when recorded from inside the esophagus than from the surface of the chest in all patients at all flows (p < 0.001). The peak frequency (Hz) was significantly higher in the esophageal recordings than the precordial samples (298 +/- 9 vs 181 +/- 10, P < 0.0001), as was the 97% spectral edge (Hz) (740 +/- 7 vs 348 +/- 16, P < 0.0001). In the adult population esophageal stethoscopes yield higher frequencies and greater amplitude than precordial stethoscopes. Quantification of lung sounds may provide for improved monitoring and diagnostic capability during anesthesia and surgery.

Blood pressure is usually determined by arm sphygmomanometry. However, this technique does not allow continuous blood pressure monitoring. Over the last years, a technique introduced by Peñaz makes it feasible to determine blood pressure noninvasively and continuously from the finger artery. Study on 46 normotensives showed that both methods have high retest-reliabilities for systolic blood pressure while for diastolic blood pressure, arm sphygmomanometry resulted in lower reliabilities than the Peñaz-method. Between-method-comparisons showed only small correlations. Diastolic blood pressure levels were significantly lower in the Peñaz-method than in arm sphygmomanometry. In conclusion, blood pressure levels determined by arm sphygmomanometry and the Peñaz-method differ systematically because of different methodologies. If blood pressure or blood pressure changes are determined, the method and the circumstances of its application need to be carefully reported.

Objective: Many drugs are known to affect the results of laboratory tests. This may cause problems in the interpretation of clinical laboratory data and lead to wrong diagnoses, unnecessary further tests and additional costs. A computerized monitoring system of potential drug effects on laboratory tests was developed in Turku University Central Hospital. In the present study the incidence and nature of potentially interfering drug effects in thyroid function diagnostics was examined in order to ease the clinical implementation of the system.

Methods: Computerized medication data of 754 hospital in-patients whose thyroid function was tested were combined with a knowledge base of drug effects on laboratory tests. All medications that potentially affected the levels of serum thyrotropin or free thyroxin in study patients were detected.

Results: 40% (292 of 735) of the patients tested for thyrotropin and 32% (107 of 333) of the patients tested for free thyroxin received potentially interfering medication during the tests. The most common potentially interfering medication was acetylsalicylic acid, but the daily dose was usually low, 100 mg.

Conclusions: The coincidence of potentially interfering medication and thyroid function tests was substantial. On-line hints of drug effects on thyroid function tests might offer valuable decision support to clinicians, but further development of the system is needed to regulate the prevalence of warnings into a clinically optimal level.

A PC-based system capable of measuring R-R intervals in the electrocardiogram and detecting respiration phases is presented. It consists of standard amplifiers for ECG and respiration signals and a personal computer that detects QRS complexes, inspiration and expiration using low-pass, high-pass and differentiation processes. The performance of the method is evaluated using an application for real ECG and respiratory data.

The HP CareVue system is an object-oriented, client-server system optimized for critical care, inpatient and special care environments. It is a fully graphical system, highly visual in its mode of operation, which requires no commands to operate. Data review may be performed by clinical users without specific instructions. Several different kinds of interfaces are provided for the system. These allow it to be connected to most hospital data-producing systems, physiologic monitors and bedside devices, such as ventilators, urimeters and oximeters. Flowsheet charting, free text, structured notes, clinical pathways, configurable forms, medication administration records and many other types of displays and reports allow the system to function as a nearly complete Electronic Medical Record (EMR). The system is highly configurable by lead nurses, physicians or technicians without programming knowledge or experience. Configuration and linking of multiple CareVue systems is possible, including a complete testing environment for verification of charting changes before clinical activation. All CareVue data is exportable for purposes of electronic archiving, warehousing and real-time decision support.

Objective: To identify factors which influence the choice of nurses to use automated collection of i.v. pump data from a prototype Medical Information Bus.

Design: Observational study for a duration of three and one-half months.

Setting: Four intensive care units, each with different missions, in an adult hospital.

Subjects: One hundred fifty-eight registered nurses including both full and part time.

Measurements and main results: Data were collected from the hospital information system about infusion orders including the type of medication, the number of rate changes, the method of documenting rate changes and the infusion methods. The method of documentation for infusion rate changes was defined as either automated, using a prototype Medical Information Bus (MIB), or manual, using the keyboard at a bedside computer terminal. The method of infusion was defined as either straight gravity feed without an i.v. pump ('no pump'), infusion using a pump but without connection to the hospital information system ('pump only') and infusion using a pump which was connected to the hospital information system using a prototype Medical Information Bus ('automated'). A total of 22,199 rate changes were documented during the study period and of those, 22,055 (99.35%) used the 'automated' method. Medications with the highest average rate change per single container were; Nitroprusside Sodium (9.50), Epinephrine (9.08) and Epoprostenol (7.50).

Conclusions: The nurses used automated i.v. pump data acquisition with medications which required frequent rate changes.

The assessment of respiratory system performance may involve issues such as pulmonary gas exchange, respiratory mechanics, oxygen transport and other factors. This paper describes an MS-DOS program called Respiratory Consultant that was designed for use with a hand-held MS-DOS computer, but can also run under Windows 3.1 and Windows 95 if desired. Respiratory Consultant performs a number of computational tasks potentially appropriate to respiratory care in the ICU and elsewhere. These include: predicted arterial oxygen tension from age, interconversion of oxygen tension and saturation, calculation of gas exchange indices and oxygen transport parameters, dead-space estimation, and pulmonary function test interpretation. Respiratory Consultant is freeware that will run easily on most IBM-compatible PCs and may be downloaded from the Internet.