Unlocking synchrotron sources for THz spectroscopy at sub-MHz resolution.

Synchrotron radiation (SR) has proven to be an invaluable contributor to the field of molecular spectroscopy, particularly in the terahertz region (1-10 THz) where its bright and broadband properties are currently unmatched by laboratory sources. However, measurements using SR are currently limited to a resolution of around 30 MHz, due to the limits of Fourier-transform infrared spectroscopy. To push the resolution limit further, we have developed a spectrometer based on heterodyne mixing of SR with a newly available THz molecular laser, which can operate at frequencies ranging from 1 to 5.5 THz. This spectrometer can record at a resolution of 80 kHz, with 5 GHz of bandwidth around each molecular laser frequency, making it the first SR-based instrument capable of sub-MHz, Doppler-limited spectroscopy across this wide range. This allows closely spaced spectral features, such as the effects of internal dynamics and fine angular momentum couplings, to be observed. Furthermore, mixing of the molecular laser with a THz comb is demonstrated, which will enable extremely precise determinations of molecular transition frequencies.

Emergency medical services telephone referral program: an alternative approach to nonurgent 911 calls.

OBJECTIVE: To examine the effects of transferring nonurgent 911 calls to a telephone consulting nurse. It was hypothesized that the telephone referral program would result in fewer basic life support (BLS) responses with no adverse patient outcome or decrease in patient satisfaction. METHODS: A two-phased prospective study was conducted in an urban and rural setting with a population of 650,000. During phase I, a BLS unit was dispatched on all calls and a nurse intervention was simulated. During phase II, no BLS unit was dispatched for calls meeting study criteria. Callers were transferred to the nurse, and consulting nurse protocols were used to direct care. Data were collected from dispatch, BLS, nurse, and hospital records and patient self-assessment. RESULTS: During phase I, 38 callers were transferred to the consulting nurse with no nurse intervention. During phase II, 133 cases were transferred to the nurse line. There were no adverse outcomes detected. The nurse recommended home care for 31%, physician referral for 24%, referral back to 911 for 17%, community resource for 11%, and other referral for 17%. Nurses contacted 85 patients for telephone follow-up. Ninety-four percent of the patients reported feeling better, 6% felt the same, and none felt worse. Patients were satisfied with the outcome in 96% of the cases. CONCLUSION: Transferring 911 calls to a nurse line resulted in fewer BLS responses and no adverse patient outcomes, while maintaining high patient satisfaction. Dispatch criteria correctly identified cases with minimal medical needs. A high percentage of the patients reported feeling better after the intervention. This study has major implications for communities interested in efficient use of emergency medical services resources.

Out-of-hospital transcutaneous pacing by emergency medical technicians in patients with asystolic cardiac arrest.

BACKGROUND: Transcutaneous cardiac pacemakers generate electrical stimuli that pace the heart through external electrodes that adhere to the chest wall. Transcutaneous pacing has been useful in some patients with bradycardia, but its efficacy in patients with asystole and full cardiac arrest has been limited, possibly because of delays in the initiation of pacing. We studied the efficacy of early transcutaneous pacing in patients with out-of-hospital asystolic cardiac arrest. METHODS: For three years we provided transcutaneous pacemakers to about half the fire districts in a large emergency-medical-services system (the intervention group). In these districts, we authorized emergency medical technicians (EMTs) to begin transcutaneous pacing in patients with cardiac arrest and primary asystole or post-defibrillation asystole. Pacing was done as early as possible, before endotracheal intubation or intravenous medication. EMTs in the other fire districts (the control group) treated similar patients with basic cardiopulmonary resuscitation but without transcutaneous pacing. RESULTS: The EMTs in the intervention group initiated transcutaneous pacing in 112 of the 278 patients with primary asystole. Of these patients, 22 (8 percent) were admitted to the hospital, and 11 (4 percent) were discharged. Among the 259 patients treated by the EMTs in the control group, 21 (8 percent) were admitted to the hospital, and 5 (2 percent) were discharged. The two groups did not differ significantly with respect to the rate of hospital admission or survival. Survival after early pacing for post-defibrillation asystole was no better than survival after pacing for primary asystole. CONCLUSIONS: Transcutaneous pacing appears to offer no benefit in patients with asystolic cardiac arrest, even when it is performed as early as possible by EMTs in the field. Our data suggest that the widespread implementation of early transcutaneous pacing for out-of-hospital asystolic cardiac arrest would be ineffective.

Survival rates from out-of-hospital cardiac arrest: recommendations for uniform definitions and data to report.

Survival rates for out-of-hospital cardiac arrest vary widely among locations. We surveyed the definitions used in published studies of out-of-hospital cardiac arrest. Data from 74 studies involving 36 communities showed survival rates ranging from 2% to 44%. There were five different case definitions and 11 different definitions of survivors. The absence of uniform definitions prevents meaningful intersystem comparisons, prohibits explorations of hypotheses about effective interventions, and interferes with the efforts of quality assurance. The most satisfactory numerator for a survival rate appears to be survival to hospital discharge; the most appropriate denominator appears to be witnessed adult cardiac arrest of presumed heart disease etiology, with ventricular fibrillation as the initial identified rhythm. Proposed definitions for the data emergency medical services systems should report as they examine their cardiac arrest survival rates are presented.

Cardiac arrest and resuscitation: a tale of 29 cities.

Published reports of out-of-hospital cardiac arrest give widely varying results. The variation in survival rates within each type of system is due, in part, to variation in definitions. To determine other reasons for differences in survival rates, we reviewed published studies conducted from 1967 to 1988 on 39 emergency medical services programs from 29 different locations. These programs could be grouped into five types of prehospital systems based on the personnel who deliver CPR, defibrillation, medications, and endotracheal intubation; the five systems were three types of single-response systems (basic emergency medical technician [EMT], EMT-defibrillation [EMT-D], and paramedic) and two double-response systems (EMT/paramedic and EMT-D/paramedic). Reported discharge rates ranged from 2% to 25% for all cardiac rhythms and from 3% to 33% for ventricular fibrillation. The lowest survival rates occurred in single-response systems and the highest rates in double-response systems, although there was considerable variation within each type of system. Hypothetical survival curves suggest that the ability to resuscitate is a function of time, type, and sequence of therapy. Survival appears to be highest in double-response systems because CPR is started early. We speculate that early CPR permits definitive procedures, including defibrillation, medications, and intubation, to be more effective.

Training lay persons to use automatic external defibrillators: success of initial training and one-year retention of skills.

This study was conducted to determine the feasibility of recruitment of lay persons to use automatic external defibrillators (AEDs), the effectiveness of their initial training, and the need for and frequency of retraining over time. Volunteers (n = 146), recruited from a variety of settings, included security personnel and administrative staff from large corporate centers, supervisors from senior care and exercise facilities, and employees in high-rise office buildings. Seven sites for 14 AEDs were recruited. In a single, two-hour class, participants learned to identify and respond to cardiac arrest, to notify emergency personnel, to retrieve and attach the semiautomatic (shock advisory) AED, and to respond to instructions presented on the display screen of the device. A skills check list was used to grade each student on performance of cardiopulmonary resuscitation, operation of the device, and time required to deliver an electric countershock. Retesting was performed one or more times after initial training to assess skill retention. The study lasted 1 year. All age groups, both sexes, and each responder type easily learned to operate the AED, with a trend for lower performance scores in people aged greater than 60 years. Performance time and skills declined significantly after initial training, but returned to satisfactory levels after one retraining session and were even higher after two retraining sessions. With retesting, errors that would have prevented delivery of countershocks to patients in ventricular fibrillation were rare (six of 146 tests, 4%). During the year of this study only three cardiac arrests occurred in the study sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the automatic external defibrillator in homes of survivors of out-of-hospital ventricular fibrillation.

This 57-month study evaluated the use of automatic external defibrillators (AEDs) in the homes of high risk cardiac patients (survivors of out-of-hospital ventricular fibrillation [VF]). The goal was to determine the utility of these devices by trained lay persons in actual cardiac arrest episodes. Ninety-seven survivors of out-of-hospital VF were enrolled in the study; 59 patients received AEDs, and 38 patients served as a control group. During the study period, 7 deaths occurred in the hospital without preceding out-of-hospital cardiac arrest or from noncardiac causes. There were 14 out-of-hospital cardiac arrests, 10 in the AED group and 4 in the control group. There was 1 long-term survivor in the control group. In the AED group, among the 10 cardiac arrests for which the device was available, it was used in 6. Only 2 patients were in VF; 1 was resuscitated with residual neurologic deficits and survived several months. This study observed a small potential for AEDs to save high risk patients.

Improved survival from cardiac arrest in the community.

We now know that the elements required to achieve the highest survival rates from out-of-hospital cardiac arrest include: witnessed arrest, rapid telephone notification of the emergency medical service, early initiation of cardiopulmonary resuscitation, rapid arrival within minutes of emergency personnel equipped with a defibrillator, and early advanced airway management and intravenous pharmacology. In the United States, and in several other countries innovative approaches have been tried to bring all these elements together in one system. These approaches include community-wide CPR training programs, telephone-assisted CPR instruction delivered at the time of a cardiac arrest, early defibrillation performed by family members of high risk patients, early defibrillation performed by minimally trained community responders, and early defibrillation performed by minimally trained ambulance personnel. Controlled, prospective studies have demonstrated the effectiveness and practicality of all of these approaches. New studies are in progress with the prehospital use of early transcutaneous cardiac pacing and these show promise. This article reviews the evidence that supports these multi-layered and innovative approaches to the treatment of out-of-hospital cardiac arrest.

Automatic external defibrillators used by emergency medical technicians. A controlled clinical trial.

In a randomized controlled clinical trial, the effectiveness of emergency medical technician (EMT) use of automatic external defibrillators (AEDs) was compared with EMT use of standard defibrillators for patients in cardiac arrest. A total of 321 cardiac arrest patients were treated during the study: 116 were treated by EMTs using the AED (AUTO group), 158 were treated by EMTs using the standard defibrillators (standard group), and 47 were treated by EMTs using the standard defibrillator when they were assigned to use the AED. There was no significant differences in hospital admission or discharge rates between the AUTO group (54% admitted, 28% discharged) and the standard group (52% admitted, 23% discharged) for patients in ventricular fibrillation (VF), for patients in non-VF rhythms, or for all patients combined. The only significant difference observed was in the time from power ON to first shock: 1.1 minutes average AUTO group and 2.0 minutes average standard group. The treatment groups did not differ significantly in sensitivity for VF (78% AED, 76% standard), specificity for non-VF rhythms (100% AED, 95% standard), or rates of defibrillation to a non-VF rhythm (62% AED, 57% standard). We conclude that in clinical outcomes and device performance, AEDs are comparable with standard defibrillators and should be considered an acceptable alternative. Automatic external defibrillators appear to have advantages over standard defibrillators in training, skill retention, and faster operation. Such devices can make early defibrillation available for a much larger portion of the population. They are a major innovation for the prehospital care of cardiac arrest patients.

Identification of cardiac arrest by emergency dispatchers.

Prompt identification of cardiac arrest by emergency dispatchers can save valuable time and increase the likelihood of successful resuscitation. The authors reviewed 516 cardiac and 146 non-cardiac calls to identify features of a probable cardiac arrest call. The results indicate that information about sex, location, and activity is of little use in the identification of cardiac arrest. When the patient is over 50 years old and the caller is emotional, the possibility of cardiac arrest is high, suggesting that questions about consciousness and breathing should be asked immediately. Additional information can be obtained or telephone cardiopulmonary resuscitation (CPR) instructions can be given after dispatch of an emergency vehicle.

What is a "save"?: Outcome measures in clinical evaluations of automatic external defibrillators.

Automatic external defibrillators (AEDs) represent an important technologic innovation in the management of out-of-hospital cardiac arrest. We propose the following concept: AEDs are machines with the limited task of ventricular fibrillation (VF) identification, countershock delivery, and defibrillation. They cannot be expected to produce "saves" independently. This study tested this concept by using the same AED in two different emergency medical systems: outcomes dependent upon the device should be the same in both groups, whereas outcomes dependent upon patient and system factors should be different. Paramedics, with the AED as their initial monitor/defibrillator, treated 16 cardiac arrest patients in VF; EMTs (emergency medical technicians), with the same AED, treated 17 patients in VF. There were no significant differences in the outcomes proposed to be machine-dependent: sensitivity, defined as the percentage of VF rhythm segments shocked; specificity, defined as the percentage of non-VF rhythms not shocked; and defibrillation of segments of VF to non-VF rhythms. There were, however, differences in the outcomes dependent on patient and system factors (paramedic group presented first): percent converted to a perfusing rhythm (23% vs 69%; p less than 0.05); percent admitted to the hospital (19% vs 65%; p less than 0.025); and percent discharged from the hospital (6% vs 29%; p = N.S.). We conclude that AEDs should be compared and evaluated on device-dependent outcomes and not on the basis of producing "saves".

Automatic external defibrillators: clinical, training, psychological, and public health issues.

Automatic external defibrillators (AEDs) will be used by spouses, family members, emergency first-responders, and the citizenry at large. Such use, however, raises a number of clinical, training, psychological, and public health issues. Clinical issues: Is cardiac arrest to be verified by the operator or the AED? Second verification systems, such as breath detectors, produce errors of omission, but greatly expand the pool of potential users. The relative merits of high sensitivity and low specificity in arrest verification must be defined by clinicians relative to the setting and the potential users. AEDs require cessation of basic CPR during their assessment periods; clinicians must determine the tradeoff between long interruption of basic life support and much earlier delivery of countershocks. Training issues: Criteria for those to be trained include consideration of who the patient will be and who the AED operator might be. AEDs pose a familiar adult education problem, that is, acquisition of a new psychomotor skill and retention of that skill for long periods before performance. What are the best teaching techniques? Currently available AEDs have different designs for device-operator interaction. Which design is most likely to assure proper performance during an actual arrest? Psychological issues: What are the psychological effects of learning about, living with, and eventually using an AED? The development of the automatic external defibrillator constitutes the most recent attempt to achieve early defibrillation of patients in cardiac arrest. The potential public health effect of such devices is enormous.

Automatic external defibrillation: evaluations of its role in the home and in emergency medical services.

Many recent efforts to improve emergency medical services (EMS) and increase survival rates are simply efforts to get defibrillation to patients as rapidly as possible. In the 1960s physicians traveled in mobile coronary care units to bring the defibrillator to cardiac arrest patients. Later, paramedics, rather than physicians, were used. During the late 1970s the concept of early out-of-hospital defibrillation expanded as emergency medical technicians (EMTs) learned to defibrillate. Researchers in several settings confirmed the effectiveness of early defibrillation by EMTs. The automatic detection of ventricular fibrillation (VF) creates new opportunities for the early defibrillation concept. This includes both automatic implantable defibrillators and automatic external defibrillators (AED). The King County, Washington, EMS is conducting two projects to evaluate AEDs. One is a randomized, controlled crossover study in which EMTs use either an AED or a standard manual defibrillator. Outcome measurements include time to countershock, conversion rates, and survival rates. In the second project family members of patients who have survived out-of-hospital VF randomly receive an AED and cardiopulmonary resuscitation (CPR) instruction, or CPR instruction alone. This study was designed to determine whether family members can be trained adequately to use the device effectively. Psychological tests measure the effect of learning about, living with, and using such technology. These studies may help define the role of AEDs in the future management of out-of-hospital VF.

Diagnostic sensitivity bias -- an epidemiologic explanation for an apparent brain tumor excess.

Preliminary data showing over-representation of the Eastman Kodak Company (Rochester) on death certificates of brain tumor patients, and higher risk for older workers when compared to the general population, led to a case-control epidemiologic study. Chemical exposure histories of 56 workers with brain tumors were compared with those of other Kodak employees. No differences were found in exposure to a variety of chemicals. In addition, employees with brain tumors were compared to other upstate New York brain tumor patients; there was no difference in histology. However, the Kodak employees had diagnoses more frequently confirmed by histologic examination and more thorough diagnostic studies. Thus, the apparent initial excess of diagnosed tumors may have resulted from a "diagnostic sensitivity bias" arising from more complete medical evaluation of Kodak employees.

Out-of-hospital cardiac arrest: a review of major studies and a proposed uniform reporting system.

The scientific literature from January 1970 to June 1979 was reviewed for articles reporting outcomes from out-of-hospital cardiac arrest treated by paramedic programs. Only articles appearing in refereed professional journals and reporting 25 or more attempted resuscitations were included. A total of 21 articles from 15 U.S. locations were found. Four separate case definitions were distinguished. Methods and reporting formats varied considerably. Few studies used an experimental or quasi-experimental design, or control or comparison groups. The range of attempted resuscitations varied from 26 to 1.106 patients. Patients admitted to hospital varied between 22 per cent and 65 per cent (mean 38 per cent, S.D. +/- 12.4 per cent). Patients discharged alive varied from 3.5 per cent to 31 per cent (mean 17.2 per cent, S.D. +/- 7.1 per cent). Post discharge survival was either not reported or reported in different formats. A simplified reporting format is proposed using factors known to be associated with successful resuscitation: 1) underlying heart disease etiology; 2) witnessed arrest; 3) cardiac rhythm of ventricular fibrillation/ventricular tachycardia; 4) hospital admission and discharge and, when possible, by time from collapse to initiation of CPR and definitive care. Uniform reporting of outcomes will improve comparability and accurate measurement of the impact of emergency programs on out-of-hospital cardiac arrest.

Epidemiologic investigation of employees chronically exposed to methylene chloride. Mortality analysis.

A large male employee population with continuous low level work exposures to methylene chloride for up to 30 years was examined for mortality experience using non-concurrent prospective and proportionate mortality techniques. Mortality of the study group was consistent with industrial controls and less than the New York State general population. Life table analysis of the 1964 methylene chloride exposed cohort was followed through 1976 and demonstrated age group specific probabilities or 13 year survivorship equal to or better than that of three control male populations: Kodak Park, New York State, and United States.