CPAP machine performance and altitude.

UNLABELLED: STUDY RATIONALE AND OBJECTIVE: Sleep-disordered breathing is commonly treated with nasally applied continuous positive airway pressure (CPAP). Typically, pressures are titrated to pneumatically splint the airway to prevent its collapse in response to negative inspiratory pressure. This investigation was prompted by several patient complaints of sleep-related breathing difficulty associated with travel to high altitudes. CPAP devices create pressure with fan-generated airflow; therefore, CPAP performance should behave according to collective fan laws. MEASUREMENTS AND RESULTS: In the present study, we examined the effect of simulated altitude change on four commercially available CPAP machines. Machines were tested using anatomic airway mannequins in an altitude chamber. We made three simulated ascents to 12,000 feet with machines set at 5, 10, and 12 cm H2O sea level pressure equivalents. We measured pressure using water manometers at 2,000-foot increments during ascent and descent. Mask pressures varied systematically with changing altitude in three machines. One machine, equipped with a pressure regulation feature, maintained pressure within 1 mm H2O at all pressure and altitude combinations. CONCLUSIONS: Altitude significantly alters delivered pressure according to predictions made by the fan laws, unless a unit has pressure-compensating features. Clinicians should consider this factor when CPAP is prescribed for patients who live or travel to places located at significantly higher or lower elevations than the titration site.

Burnout in the internist--intensivist.

OBJECTIVES: Caring for acutely ill patients imposes significant demands on physicians. The environment and stresses of the ICU may lead to the burnout syndrome. The purpose of this study was to evaluate the prevalence of burnout among internal medicine intensivists and the contributing factors present in ICU practice. DESIGN: Mailed survey utilizing the Maslach Burnout Inventory (MBI). Increasing burnout has been shown to be associated with low levels on personal achievement and high scores on depersonalization and emotional exhaustion. SUBJECTS: Random sample of members of the Internal Medicine Section of the Society of Critical Care Medicine. MEASUREMENTS AND MAIN RESULTS: 248 people responded: 220 (88.7%) males and 28 females. Mean age of all respondents was 41.6 +/- 6.7 years. The majority (58.1%) worked in large hospitals (> 400 beds); 55.6% devoted more than 50% of their time to critical care. The emotional exhaustion subscale of the MBI averaged 22.2 +/- 9.5, with a third of respondents scoring in the high range. The depersonalization score averaged 7.1 +/- 5.1%, with 20.4% of respondents scoring in the high range. Similarly personal achievement subscores were poor, with a mean value of 30.9 +/- 6.4%, with 59% scoring in the low range. High levels of emotional exhaustion were associated with anticipating leaving critical care before retirement. CONCLUSIONS: Burnout as measured by the MBI appears to be common in internal medicine intensivists. High levels of emotional exhaustion and depersonalization are related not only to patient care issues but also to a poor support system.

Automated external versus blind manual defibrillation by untrained lay rescuers.

INTRODUCTION: sudden cardiac death is an important cause of mortality in the United States today. A major determinant of survival from sudden cardiac death is rapid defibrillation. Communities with high rates of bystander cardiopulmonary resuscitation (CPR) and early defibrillation enjoy the highest survival rates from out-of-hospital cardiac arrest. First responders and emergency medical technicians (EMTs) have been trained to use external defibrillators (AEDs). The period of instruction for successful use of the AED remains to be determined. It was the purpose of this study to compare AED versus blind manual defibrillation (BMD) by untrained lay rescuers using a simple instruction sheet and following a 20-min training period. METHODS: 50 employed volunteers were confronted with a stimulated cardiac arrest and asked to attempt defibrillation using either AED or BMD by following a written instruction sheet. Success was defined as delivery of three countershocks during the simulated resuscitation. Time to first and third shocks were recorded. RESULTS: 24 of 25 volunteers (96%) were successful in operating the AED compared to none in the BMD group. Time to delivery of first shock averaged 119.5 +/- 45.0 s and time to third shock averaged 158.7 +/- 46.3 s. A 95% confidence interval for time to first shock for untrained lay rescuers was 100.5-138.4 s. CONCLUSIONS: untrained lay rescuers demonstrated a very high success rate using the AED during simulated cardiac arrest. Success with BMD by untrained rescuers is poor. This study suggests that prehospital personnel can be successfully trained in the use of AED in a substantially shorter period of time than in current practice. Strategic placement of AEDs like fire hoses and pool-side life preservers could result in improved survival from sudden cardiac death.

Cardiopulmonary resuscitation: a review for clinicians.

Attempts at cardiopulmonary resuscitation (CPR) date from antiquity, but it is only in the last 50 years that a scientifically-based methodology has been developed. External chest compressions is the standard method for managing circulatory arrest, however, numerous alterations of this technique have been proposed in attempts to improve outcome from CPR. Defibrillation is the single most important therapy for the management of ventricular fibrillation or pulseless ventricular tachycardia. Adrenergic agents used to improve myocardial and cerebral perfusion are also the subject of considerable investigation with new agents entering clinical study. This paper reviews the history, current techniques and pharmacotherapy as well as controversial issues in the management of patients with cardiac arrest.

Should a cancer patient be resuscitated following an in-hospital cardiac arrest?

OBJECTIVE: Previous reports from general hospitals and cancer centers have identified the presence of malignancy as a poor prognostic indicator for successful cardiopulmonary resuscitation (CPR) for an in-hospital cardiac arrest. The purpose of this study was to evaluate the initial success of CPR as determined by return of spontaneous circulation (ROSC), patient survival to hospital discharge, and 1-year survival of this group as compared to previous studies in non-oncological centers. In addition, the charges incurred in caring for these patients were analyzed. MATERIALS AND METHODS: All cardiac arrests occurring between 1 January 1993 and 31 December 1994 were identified from a centralized morbidity and mortality database and reviewed retrospectively. Cardiac arrest was defined as the absence of a palpable pulse and initiation of CPR. Patients suffering pure respiratory arrest or shock without loss of pulse were excluded. Age, gender, primary site of malignancy, initial and ultimate outcome, including Zubrod's functional status (ZFS), and total hospital charges following cardiac arrest were recorded. Computerized billing records were used to tabulate total charges. RESULTS: 83 cardiac arrests occurred during the study period (42 women, 41 men). Mean age was 56.2 years. Forty-two percent of the patients had hematologic malignancies, 19% lung, 15% gastrointestinal, 5% head and neck cancers and 19% other malignancies. Sixty-six percent of the patients had ROSC. Only eight (9.6%) patients survived to hospital discharge: three died within 6 weeks under hospice care, two died within 6 months of discharge and only three (3.6%) patients survived to 1 year. Functional status follow-up of these three patients revealed two with ZFS 1 and one with ZFS 2. Total hospital charges for these 83 patients were US$ 2,959,740. CONCLUSIONS: Although ROSC after cardiac arrest in our patients was better than that reported for most series in general hospitals, their ultimate survival and hospital discharge was extremely poor.

Automatic external defibrillators: lessons from the past, present and future.

Coronary artery disease remains the leading cause of death in the United States and most developed countries. Many of the victims die from sudden cardiac arrests, resulting from dysrhythmias-most commonly ventricular fibrillation. Since most cardiac arrests occur outside the hospital, implementing emergency services in the field will have a great impact on survival. With the development of the modern automatic external defibrillator (AED), early recognition and correction of these dysrhythmias by lay rescuers can significantly improve outcome from sudden death. This paper reviews the past, present and future development and applications of AEDs.

Feasibility of noninvasive mechanical ventilation in the treatment of acute respiratory failure in postoperative cancer patients.

PURPOSE: Patients with cancer who require mechanical ventilation have high mortality rates. Although oncological patients have multiple clinical problems, including nutritional and immunological deficiencies, added complications from mechanical ventilation by themselves may be life-threatening and may further compromise the ability of these patients to recover from an episode of acute respiratory failure (ARF). Noninvasive mechanical ventilatory support (NIMV) using positive-pressure-ventilation delivered through a mask has gained popularity for the treatment of ARF and may limit some mechanical ventilation complications. The purpose of this study was to prospectively evaluate NIMV in cancer patients with ARF. MATERIALS AND METHODS: All patients admitted to the surgical intensive care unit (SICU) at The University of Texas M.D. Anderson Cancer Center from August 1, 1994, to April 15, 1996, with hypoxemic or hypercapnic ARF were eligible for this study. NIMV was delivered with the BiPAP S/T-D (Respironics, Murrysville, PA) device. The initial settings were adjusted to achieve a tidal volume of 5 to 7 mL/kg and a SaO2 greater than 0.90. Demographic data, duration of therapy, and need for endotracheal intubation were recorded for each patient. RESULTS: Sixty patients were included in this study. There were 21 women (35%) and 39 men. The primary cancer sites of these patients were gastrointestinal (25 patients), genitourinary (15), hematological (8), lung (6), sarcoma (4), and skin (2). Fifty-three patients (88%) had hypoxemic ARF and 7 had hypercapnic ARF. The mean duration of NIMV was 1.83 days (range, 1 to 5 days) with a median of 2 days. Forty-two patients (70%) were weaned from NIMV and were spared endotracheal intubation. The remaining 18 patients deteriorated and ultimately required intubation and assisted mechanical ventilation. No complications related to the use of NIMV were seen in this study population. CONCLUSIONS: NIMV was effective in the treatment of ARF in cancer patients at our institution substantially decreasing the need for intubation. This ventilatory technique is a viable option for cancer patients with ARF.

Critical care transport.

The transport environment presents challenges not faced in the hospital arena. Both ground and air ambulance transport vehicles are hampered by space limitations, lack of universally available power, and physical forces of no importance in the stationary hospital environment. EMS personnel are typically used in ground and air transports augmented by hospital practitioners on request. The capabilities of EMS workers is limited, and their limits must be considered when any patient transport is conducted. Prior planning and understanding the limitations of the transport arena are the keys to successful transport. The future will likely see improvements in technology and integration of hospital delivery systems and patient management systems, expanding our ability to provide critical care outside the traditional ICU environment.

Recognition, assessment, and treatment of anxiety in the critical care patient.

A multidisciplinary group of experts involved in the treatment of critically ill patients participated in a workshop conference designed to develop practice recommendations for the recognition, assessment, and treatment of anxiety in the critical care environment. Anxiety was identified as a ubiquitous problem in critical care that may interfere with healing and recovery. The faculty agreed that clinicians should be familiar with the signs and symptoms of anxiety and should be able to determine when interventions are necessary. Whenever possible, nonpharmacologic methods for anxiolysis should be incorporated into intensive care protocols. Intensive care personnel should be trained in those interventions that require specialized expertise, and they should become familiar with the drugs available for the treatment of anxiety. Protocols for determining the best agents to be used in a given setting and their most appropriate method of administration should be established. Pharmacologic and nonpharmacologic treatments are not mutually exclusive but should be complementary. Finally, procedures for obtaining psychiatric consultation, when necessary, should be in place.

Congestive heart failure and pulmonary edema for the emergency physician.

Congestive heart failure (CHF) and pulmonary edema are major health problems in the United States as well as across the rest of the developing world. The prevalence of CHF and pulmonary edema in the general population results in a significant number of these patients presenting to Emergency Departments (EDs). Mortality from these disorders is substantial, with a 5-year mortality rate for patients requiring hospitalization of approximately 50%. Understanding of the clinical syndromes of CHF and pulmonary edema requires review of the basic determinants of cardiovascular performance. Preload, afterload, contractility, and heart rate may all be modified by pharmacological or mechanical techniques. Diuretics, vasodilators, cardiac glycosides, and other inotropes all may play a role in the ED management of CHF. In rare instances, mechanical devices for support of the heart and circulation may be indicated.

Mechanical ventilation: past and present.

Emergency physicians commonly manage patients with acute respiratory failure who require assisted mechanical ventilation. Several different modes of positive pressure mechanical ventilation can be used to manage these patients when they present to the emergency department. These modes of ventilation have evolved over the last three decades. A comprehensive review of the most important historical moments in mechanical ventilation as well as the different modes commonly used in the emergency department are presented. In addition, new techniques in noninvasive mechanical ventilation are presented.

Carbon monoxide poisoning: a review for clinicians.

Carbon monoxide (CO) poisoning continues to be a significant health problem both in the United States and in many other countries. CO poisoning is associated with a high incidence of severe morbidity and mortality. Epidemics of CO poisoning commonly occur during winter months and sources include: smoke from fires, fumes from heating systems burning fuels, and exhaust fumes from motor vehicles. The history of exposure and carboxyhemoglobin levels should alert the physician to this diagnosis. In the absence of exposure history, CO poisoning should be considered when two or more patients are simultaneously sick. The clinical presentation is non-specific and may range from nausea and headache to profound central nervous system dysfunction. The mainstay of therapy for CO poisoning is supplemental oxygen, ventilatory support, and monitoring for cardiac dysrhythmias. This article reviews up-to-date information of this potentially devastating exposure.

Acute thoracic aortic dissection: the basics.

With an increasing incidence, aortic dissection is the most common acute illness of the aorta. In the setting of chronic hypertension, with or without other risk factors for aortic dissection, this diagnosis should be considered a diagnostic possibility in patients presenting to the emergency department with acute chest or back pain. Left untreated, about 75% of patients with dissections involving the ascending aorta die within 2 weeks of an acute episode. But with successful initial therapy, the 5-year survival rate increases to 75%. Hence, timely recognition of this disease entity coupled with urgent and appropriate management is the key to a successful outcome in a majority of the patients. This article reviews acute thoracic aortic dissection, including ED diagnosis and management.

Inadequacy of visual alarms in helicopter air medical transport.

BACKGROUND: Air medical programs use medical equipment primarily designed for hospital and/or ground transport settings. Many of these medical devices are equipped with auditory alarms of malfunction or deteriorating clinical status. The high ambient noise requires visual scanning of medical devices to detect alarm conditions in the helicopter cabin. PURPOSE: To evaluate the adequacy of visual scanning for alarm conditions in the helicopter air medical environment. METHODS: The helicopter transport program used in this study is staffed with two medical crewmembers. Flight nurse response time (RT) to a visual alarm was assessed during 25 air medical patient flights. RT was measured using a battery powered dual timer device with a red LED visual alarm placed in a fixed position among the medical instruments. The device was activated at a random time point unknown to the medical crew during each patient flight. RT was defined as the elapsed time from activation of the alarm until it was physically switched off by the flight nurse. RESULTS: RT was surprisingly lengthy for the study population with a mean RT of 81.2 +/- 78.4 s (95% CI 48.8-113.5 s). The variability of RT was also surprising ranging from 3 s to > 5 min. CONCLUSION: RT to visual alarms in the air medical environment is lengthy and quite variable. Recognition of malfunction of medical equipment or early signs of clinical instability prior to clinical deterioration cannot be assured by visual scanning for alarm conditions. Alternative alarming systems should be considered and investigated for air medical transport.

Utilization of specialized services by air transported cardiac patients: an indicator of appropriate use.

Recent studies of appropriateness of air medical transport have not specifically examined the need of cardiac patients for specialized services not available in the original community setting. This study examined the subsequent use of specialized services (i.e., coronary bypass surgery, angioplasty) by 796 consecutively aeromedically transported cardiac patients as an indicator of appropriate use of air transport. At least one specialized service was received by 552 (69.3%) patients. Preflight or transport interventions outside the clinical scope of the available ground transport system--a narrow, but objective assessment of appropriateness--were received by 507 patients and were associated with subsequent receipt of posttransport specialized services (p less than 0.0001). We conclude that the use of specialized services by cardiac patients was high and associated with an objective measure of appropriateness of transport. Studies of aeromedical transport should consider the need for specialized services in addition to intensity of care in the determination of appropriate use.

Hypertensive crises. The need for urgent management.

Although hypertensive crises are now relatively uncommon, they often are life-threatening when they do occur and demand early recognition and management to minimize morbidity and mortality. Most patients have essential hypertension, and withdrawal from an antihypertensive drug is the most common cause of acute elevation of blood pressure. Short-acting parenteral agents are generally recommended for management of hypertensive crises. In most patients with hypertensive emergencies, the mean arterial pressure is lowered 25% over 2 to 4 hours. Both cerebral and coronary hypoperfusion must be avoided.

Cardiopulmonary resuscitation. New and controversial techniques.

Primary care physicians may need to perform cardiopulmonary resuscitation (CPR) from time to time. Knowledge regarding CPR has become extensive, and it is hoped that greater success will be achieved in the future with the advent of new methods. A number of techniques and devices have received attention in the lay and professional press. If appropriate care is to be delivered, practicing physicians must be aware of what is proven technology and what is investigational.

Acute exacerbations of obstructive lung disease. What to do when immediate care is crucial.

Obstructive lung disease is a major cause of morbidity and mortality in the United States, and the mortality rate is rising. Successful treatment of acute exacerbations begins with appropriate assessment and intervention. Supplemental oxygen is appropriate for all patients with hypoxemia, and mechanical ventilation should be considered in those with clouded consciousness, profound acidosis, or severe hypoxemia. Inhaled beta 2 agonists are the first line of therapy in acute exacerbations. Anticholinergics, methylxanthines, and corticosteroids may also be useful. Alternative therapies (eg, magnesium, glucagon, calcium channel blockers, clonidine, helium) are receiving increased attention and are undergoing investigation.

Air medical transport.

Emergency air medical transport has become an integral part of the practice of medicine. In 1990, there were more than 170 air medical programs in operation in the United States. The proper and safe use of air medical transport requires a basic understanding of the medical implications of flight and the capabilities and constraints involved in transporting patients by air. The purpose of this paper is to review this information and provide guidelines for the use of air medical transport.