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Biomedical subjects

T D East

Publications and source records attributed to T D East.

At least 37 records · Page 2Linked to original sources
PubMed1994

Ethical implications of standardization of ICU care with computerized protocols.

Ethical issues related to the use of computerized protocols to control mechanical ventilation of patients with Acute Respiratory Distress Syndrome (ARDS) are identical to the ethical issues surrounding the use of any therapy or intervention. Four ethical principles must be considered: nonmaleficence, beneficence, autonomy, and distributed justice. The major ethical challenges to computerized protocol use as a specific application of clinical decision support tools are found within the principles of nonmaleficence and of beneficence. The absence of credible outcome data on which ARDS patient survival probabilities with different therapeutic options could be based is a constraint common to most ICU clinical decision making. Clinicians are thus deprived of the knowledge necessary to define benefit and are limited to beneficent intention in clinical decisions. Computerized protocol controlled decision making for the clinical management of mechanical ventilation for ARDS patients is ethically defensible. It is as well supported as most ICU therapy options.

Clinical Protocols↗
PubMed1993

Clinical performance of a rule-based decision support system for mechanical ventilation of ARDS patients.

We developed a clinical decision support system--ventilation protocols--that managed tidal volume and ventilator rate settings during mechanical ventilation of patients with the Adult Respiratory Distress Syndrome (ARDS). We applied these protocols for a total of 10,903 hours in 40 ARDS patients. The clinical staff suspended the protocols for only 5% of the total application time due to medical procedures, surgeries, transient clinical problems not addressed by the protocols, or because of attending physician request. Of 3,148 instructions generated by the ventilation protocols, the clinical staff followed 2,932 (93%). The staff did not follow some instructions because of patient data errors, computer software and protocol logic errors, inability of the clinical staff to implement protocol instructions because of more pressing duties, and clinical staff objections to specific instructions. Sixty percent of the patients treated by the ventilation protocols survived. Our results demonstrate that the ventilation protocols provided a practical and safe decision support system for the mechanical ventilation of ARDS patients.

Clinical Protocols↗
PubMed1992

A successful computerized protocol for clinical management of pressure control inverse ratio ventilation in ARDS patients.

We have developed a computerized protocol that provides a systematic approach for management of pressure control-inverse ratio ventilation (PCIRV). The protocols were used for 1,466 h in ten around-the-clock PCIRV evaluations on seven patients with severe adult respiratory distress syndrome (ARDS). Patient therapy was controlled by protocol 95 percent of the time (1,396 of 1,466 h) and 90 percent of the protocol instructions (1,937 of 2,158) were followed by the clinical staff. Of the 221 protocol instructions, 88 (39 percent) not followed were due to invalid PEEPi measurements. Compared with preceding values during CPPV, the expired minute ventilation was reduced by 27 percent during PCIRV while maintaining a pH that was not clinically different (mean difference in pH = 0.02). There was no difference in the PaO2, PEEPi, or the FIO2 between PCIRV and CPPV. The PEEP setting was reduced by 33 percent from 9 +/- 0.05 to 6 +/- 0.6 and the I:E ratio increased from 0.64 +/- 0.04 to 2.3 +/- 0.10. Peak airway pressure was reduced by 24 percent (from 59 +/- 1.5 to 45 +/- 0.6) and mean airway pressure increased by 27 percent (from 22 +/- 0.8 to 28 +/- 0.6) in PCIRV. Right atrial and pulmonary artery pressures were higher and cardiac output lower in PCIRV but blood pressure was unchanged. The success of this protocol has demonstrated the feasibility of using PEEPi as a primary control variable for oxygenation. This computerized PCIRV protocol should make the future use of PCIRV less mystifying, simpler, and more systematic.

Adult↗
PubMed1992

Computers in the ICU: panacea or plague?

The introduction of the intensive care unit (ICU) in the 1960s with its demands for management of large volumes of patient data drove the initial introduction of computers into the ICU. Since the mid-1960s computer systems for the ICU have evolved into the highly sophisticated bedside workstations commercially available today. Despite all of the technologic advances in computers, their application in ICUs in the United States continues to spread very slowly. One of the largest problems is justifying the cost of systems primarily designed to automate data charting and generation of care plans. Although the existing commercial systems do an excellent job, few conclusive studies prove that these systems have a favorable cost-to-benefit ratio. Research systems have demonstrated that if one extends these systems to incorporate a fully integrated database, decision-support tools, automation of data acquisition, and more sophisticated display and user-interface technology, then these ICU computer systems can have a significant impact on improving the quality and reducing the costs of patient care. For computers to be embraced in the ICU environment, commercial systems of the future must move beyond merely gathering and displaying information. They must help the clinician at the bedside assimilate the vast array of ICU data and help him to make more effective decisions.

Computer Systems↗
PubMed1992

Digital electronic communication between ICU ventilators and computers and printers.

UNLABELLED: Although many modern ICU ventilators offer the option of electronic communication, most of these systems are not used because there is a huge communication gap between the ventilator and the computer it might be connected to. When such systems are now used, a large part of what is communicated is artifactual and misleading. We need to overcome both legal and knowledge barriers in the effort to provide seamless communication between ventilators and computers. With regard to the specific issues raised in this paper, here are our answers. Issue #1: Is it essential to have a digital electronic communication port on an ICU ventilator? ANSWER: No, it is not essential. The purpose of the mechanical ventilator is to support pulmonary ventilation by supplying gas and pressure. There is no vital role for digital communication in the gas-delivery function of the ventilator; however, in the future it will be essential to have effective electronic communication in order to guarantee accurate and timely charting. Issue #2: What impact does electronic communication between a ventilator and a computer have on patient outcome? ANSWER: Our preliminary data show that electronic communication can reduce the number of charting errors and can improve the timeliness of data entry. However, there is little evidence, other than anecdotal, that this has any impact on patient outcome. Automated charting has been shown to reduce the time spent on charting. This time-savings could be used to increase time spent in direct patient care, but there is no conclusive evidence that this occurs. In fact, one report on computerized charting systems indicates that the result is less time spent in direct patient care. Issue #3: If electronic communication is to be effective in the future, how should these interfaces be configured for mechanical ventilation? ANSWER: We recommend an optimal algorithm for automated respiratory care charting that has been suggested. Sampling frequency: Sample data from the ventilator every 10 seconds. Ventilator-setting changes: Report every new setting if change lasts more than 3 minutes. Measured respiratory care data: Filter raw MIB-collected data with a 3-minute moving-median filter. Report one filtered value every hour for each variable. In addition, use a threshold table (Table 3) to define significant events. Report changes that remain above threshold more than 3 minutes. Report all measured respiratory-care data 1 minute following any ventilator-mode changes.

Computer Communication Networks↗
PubMed1991

Respiratory effects of clonidine alone and combined with morphine, in humans.

Because only limited and controversial data exist concerning the respiratory effects of clonidine in humans, the authors evaluated the respiratory effects of clonidine alone and in combination with morphine, in 12 healthy adult males. Subjects received clonidine (0.3-0.4 mg orally), morphine (0.21 mg/kg intramuscularly), or the same doses of the two drugs combined, at three separate sessions in a randomized fashion. The study was balanced for all possible sequences of drug administration. Blood pressure, heart rate, hemoglobin oxygen saturation via finger pulse oximetry, and ventilatory and occlusion pressure responses to CO2 were obtained before and 20, 40, 60, 90, 120, 180, 240, 300, and 360 min after administration of drug or drug combination. Systolic blood pressure decreased significantly only in the clonidine and clonidine plus morphine groups (P less than 0.05). Hemoglobin oxygen saturation decreased by a statistically significant (P less than 0.05), though clinically minor, degree only in the morphine or morphine plus clonidine groups. Clonidine alone did not depress the slope of either the ventilatory or the occlusion pressure response to CO2. In addition, clonidine did not significantly worsen morphine-induced depression of the slope of the ventilatory and occlusion pressure responses in the drug combination group. Both the ventilatory and occlusion pressure responses to CO2 were shifted to the right in all three drug groups (P less than 0.05) but were shifted to a significantly lesser degree by clonidine alone than by morphine and morphine plus clonidine. In healthy young adult males, clonidine alone produces little respiratory depression and does not significantly potentiate morphine-induced respiratory depression.

Adolescent↗
PubMed1991

Simultaneous comparison of intraarterial, oscillometric, and finapres monitoring during anesthesia.

In 30 patients (15 with normal peripheral vascular status and 15 with peripheral vascular disease, hypertension, or a heavy smoking history), systolic, mean, and diastolic arterial pressures were recorded simultaneously every 5 min using a radial arterial catheter, an oscillometric arm cuff, and a Finapres finger cuff during 1-6 h of anesthesia and operation. The average accuracy of oscillometric and Finapres pressure measurements was good. Comparisons of arterial, oscillometric, and Finapres pressures showed only a small bias in the oscillometric and Finapres pressure estimations. Finapres pressures underestimated arterial pressures by 1 mm Hg more than oscillometric pressures did. Peripheral vascular status had no effect on comparisons made between pressures measured with these two techniques. Although bias was small, precision was often lacking as shown by the large variability of the difference between individual values from the three monitors. However, the precision of Finapres pressure measurements was about the same order of magnitude as that of oscillometric measurements.

Blood Pressure↗
PubMed1991

Real time data acquisition: experience with the Medical Information Bus (MIB).

Care of the acutely ill patient requires rapid acquisition, recording and communications of data. In the modern hospital it is not unusual for a patient to be connected to several monitoring and recording devices simultaneously. Each of these devices is typically made by a different manufacturer who may specialize in one sort of measurement, for example, pulse oximetry. Most of the modern monitoring and recording devices are micro-processor based and have communications capabilities. Unfortunately, there is no operable standard communications technology available from all devices. In addition different clinical staff (physicians, nurses, or respiratory therapists) may be responsible for collecting data. As a result there is a need to develop methods, standards, and strategies for timely and automatic collection of data from these monitoring and recording devices. We report on more than 5 years of clinical experience of automated ICU data collection using a prototype of the Medical Information Bus (MIB).

Computer Communication Networks↗
PubMed1990

Automated sulfur hexafluoride washout functional residual capacity measurement system for any mode of mechanical ventilation as well as spontaneous respiration.

A new sulfur hexafluoride (SF6) washout functional residual capacity (FRC) measurement system has been developed which will work with any mode of mechanical ventilation, as well as with spontaneous respiration. This system was evaluated in three different human studies. In the first two studies, the accuracy of the system was compared with He dilution and body plethysmography in 12 spontaneously breathing normal volunteers and in 12 spontaneously breathing chronic obstructive pulmonary disease (COPD) patients. In the third study, the reproducibility and efficacy of using the system in the ICU was tested in 12 adult respiratory distress syndrome (ARDS) patients who were mechanically ventilated with PEEP. In the normal volunteers, there was no significant difference between the three measurement techniques. In the COPD group, there was an overall significant difference between measurement techniques (F[2,28] = 17.18, p less than .0001) and the rank of the magnitude of the FRC measurements from lowest to highest was SF6 washout, He dilution, and body plethysmography. There was a significant difference in accuracy between the COPD and normal volunteer groups (F[2,28] = 12.24, p less than .0002). There were a total of 1,227 FRC measurements made on the 12 ARDS patients. The number of FRC measurements per patient was 102 +/- 13 (SEM). The "stable" periods were 14 +/- 2 h long and ranged from 60 min to 63.5 h. The reproducibility for all 12 patients was 188 +/- 17 ml or 11.7 +/- 0.7%. This automated SF6 washout system should make routine FRC measurements in patients who are being mechanically ventilated simple and easy to do.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Differences in magnitude and duration of opioid-induced respiratory depression and analgesia with fentanyl and sufentanil.

The magnitude and duration of analgesia and respiratory depression induced by fentanyl (1.0, 2.0, and 4.0 micrograms/kg) and sufentanil (0.1, 0.2, and 0.4 microgram/kg) after intravenous administration over 30 s were measured in 30 healthy young adult male volunteers divided into three groups and studied in a double-blind, randomized fashion. Each volunteer received one dose of fentanyl or sufentanil and no sooner than 48 h later, the corresponding equipotent dose of the other opioid. End-tidal CO2 and ventilatory and occlusion pressure responses to CO2 rebreathing were used to measure drug-induced respiratory effects. Analgesic effects were assessed by changes in the pain threshold to electric shock applied to the forearm. Plasma levels of fentanyl and sufentanil were measured by radioimmunoassay. Testing and sampling intervals were 5, 30, 60, 90, 120, 240, 300, and 360 min after drug administration. The magnitude and duration of depression of the ventilatory and occlusion pressure response were significantly less with sufentanil compared with fentanyl, irrespective of dose. Ventilatory and occlusion pressure responses returned to control values by 30 and 30 min, respectively, after sufentanil and by 240 and 120 min, respectively, after fentanyl. Statistically significant elevations of the pain threshold were, however, greater and longer lasting after sufentanil compared with fentanyl. Pain threshold returned to control values 180 min after sufentanil but only 90 min after fentanyl. These results suggest that sufentanil may provide better patient comfort with less respiratory depression than does fentanyl.

Adolescent↗
PubMed1989

Computerized artifact detection for ventilatory inductance plethysmographic apnea monitors.

Ventilatory inductive plethysmography allows noninvasive monitoring of patient ventilation. Patient movements unrelated to breathing introduce severe errors in ventilator inductive plethysmographic measurements and restrict its usefulness. The purpose of this research was to develop and test a microprocessor-based real-time digital signal processor that uses an adaptive filter to detect patient movements unrelated to breathing. The adaptive filter processor was tested for retrospective identification of artifacts in 20 male volunteers who performed the following specific movements between epochs of quiet, supine breathing: raising arms and legs (slowly, quickly, once, and several times), sitting up, breathing deeply and rapidly, and rolling from a supine to a lateral decubitus position. Flow was simultaneously measured directly with a pneumotachography attached to a mouthpiece. A multilinear regression was used to continuously calculate the calibration constants that relate the pneumotachographic and ventilatory inductive plethysmographic signals. Ventilatory inductive plethysmographic data were then processed, and results scored. There were a total of 166 movements. The calibration coefficients changed dramatically in 146 (88%) of the 166 movements. These movements would have significant errors on ventilatory inductive plethysmographic flow calculation. The changes lasted for the duration of the movements and returned to baseline within two to three breaths. The changes in the coefficients were five or more times larger than the variability around baseline during quiet, supine breathing. All of the total body movements and changes in breathing patterns were detected accurately. The filter detected 46 of 53 upper body movements, 34 of 36 lower body movements, 38 of 38 total body movements, and 19 of 19 breathing pattern changes where the calibration changed.(ABSTRACT TRUNCATED AT 250 WORDS)

Apnea↗
PubMed1988

Functional residual capacity as a noninvasive indicator of optimal positive end-expiratory pressure.

We hypothesized that functional residual capacity (FRC) could be used as a noninvasive indicator of "optimal" positive end-expiratory pressure (PEEP), the level of PEEP that results in venous admixture below 15% with an inspired oxygen fraction less than 0.5. We compared several variables for PEEP optimization--oxygen transport, total respiratory system compliance, FRC-based compliance, mixed venous oxygen saturation, end-tidal to arterial carbon dioxide tension difference, and arterial oxygen saturation--by producing four different PEEP levels, 0, 5, 10 and 15 cm H2O, in 24 mongrel dogs in which pulmonary injury was produced. The data were regressed versus PEEP by using analysis of variance for regression. Venous admixture (F1,23 = 149.3; P less than 0.0001), end-tidal to arterial carbon dioxide tension difference (F1,23 = 64.9; P less than 0.0001), and oxygen transport (F1,23 = 95.1; P less than 0.0001) decreased linearly with PEEP. FRC (F1,23 = 248.1; P less than 0.0001) and arterial oxygen saturation (F1,23 = 66.9; P less than 0.0001) increased linearly with PEEP. Total respiratory system compliance (F1,23 = 66.6; P less than 0.0001) and mixed venous oxygen saturation (F1,23 = 12.2; P less than 0.002) had a quadratic relationship with respect to PEEP with a peak at 5 cm H2O. FRC-based compliance did not have a significant relationship to PEEP. The maximum values of total respiratory system compliance, FRC-based compliance, mixed venous oxygen saturation, and oxygen transport did not occur at PEEP levels that corresponded to a venous admixture below 15% ("optimal" PEEP).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1988

Computer-controlled positive end-expiratory pressure titration for effective oxygenation without frequent blood gases.

We have previously designed a computerized system to automatically deliver PEEP to maintain functional residual capacity (FRC) at a desired value. The purpose of this study was to compare the computerized PEEP titration system with a standard clinical PEEP titration algorithm in the animal adult respiratory distress syndrome (ARDS) model. Thirty mongrel dogs were anesthetized, paralyzed, intubated, and ventilated. An acute pulmonary injury was produced using 0.09 ml/kg of oleic acid. The animals were then given PEEP for 5 h. Arterial and venous blood gases, BP, thermodilution cardiac output, heart rate, body temperature, total respiratory system compliance (Ctr), and end-tidal CO2 were measured every 30 min. FRC was measured using an automated sulfur hexafluoride washout system every 15 min. The animals were allocated randomly to three ten-animal groups. The first group had PEEP titrated using a standard clinical protocol; the remaining two groups had PEEP updated at 15-min intervals under computer control to maintain FRC at 1.4 times the postanesthetized, postparalyzed, preinjury value. The second group received fixed 3-cm H2O PEEP steps. The third group had variable size PEEP steps depending on the output of a proportional, integral, and derivative (PID) controller. PaCO2 was maintained at 35.8 +/- 3.4 (SD) torr. There was a significant difference in PEEP delivered between the three groups (p = .0006) and in FRC (p = .005). There was no significant difference in PaO2 (p = .80) or venous admixture (Qva/Qt) (p = .84) between the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Automated measurement of functional residual capacity by sulfur hexafluoride washout.

We have constructed a computerized, totally automated system for measuring functional residual capacity (FRC) during mechanical ventilation, at any positive end-expiratory pressure (PEEP) and fraction of inspired oxygen. This system uses washout of a small amount (0.5 to 1.0%) of an insoluble, nontoxic tracer gas, sulfur hexafluoride, to measure FRC. It requires no modification of the ventilator and only minimal changes in the breathing circuit; it can be programmed to make measurements routinely without manual intervention. The system was evaluated with three tests. The prototype sulfur hexafluoride analyzer characteristic curve was determined, and the analyzer was evaluated to determine carbon dioxide interference. A comparison with nitrogen washout FRC measurements was made in an extensive bench test with a Plexiglas lung model. The bench test was designed to determine the effects of changing gas composition and minute volume. A study was done in six healthy dogs to determine reproducibility of the FRC measurements at four PEEP levels (0, 5, 10, and 15 cm H2O: two repetitions in each animal). The sulfur hexafluoride analyzer was well characterized by an exponential equation with a multiple r2 = 0.996. The analyzer was not affected by the presence of carbon dioxide (paired t test, t19 = 1.23, P greater than 0.10). The bench test indicated that FRC (measured) = 0.969 X FRC (true) - 5.3 ml. (Multiple r2 = 0.979.) This was significantly better than the nitrogen washout system, whose regression equation was also a function of minute volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Microcomputer data acquisition and control.

In medicine and biology there are many tasks that involve routine well defined procedures. These tasks are ideal candidates for computerized data acquisition and control. As the performance of microcomputers rapidly increases and cost continues to go down the temptation to automate the laboratory becomes great. To the novice computer user the choices of hardware and software are overwhelming and sadly most of the computer sales persons are not at all familiar with real-time applications. If you want to bill your patients you have hundreds of packaged systems to choose from; however, if you want to do real-time data acquisition the choices are very limited and confusing. The purpose of this chapter is to provide the novice computer user with the basics needed to set up a real-time data acquisition system with the common microcomputers. This chapter will cover the following issues necessary to establish a real time data acquisition and control system: Analysis of the research problem: Definition of the problem; Description of data and sampling requirements; Cost/benefit analysis. Choice of Microcomputer hardware and software: Choice of microprocessor and bus structure; Choice of operating system; Choice of layered software. Digital Data Acquisition: Parallel Data Transmission; Serial Data Transmission; Hardware and software available. Analog Data Acquisition: Description of amplitude and frequency characteristics of the input signals; Sampling theorem; Specification of the analog to digital converter; Hardware and software available; Interface to the microcomputer. Microcomputer Control: Analog output; Digital output; Closed-Loop Control. Microcomputer data acquisition and control in the 21st Century--What is in the future? High speed digital medical equipment networks; Medical decision making and artificial intelligence.

Artificial Intelligence↗