Pulse transit time measured by photoplethysmography improves the accuracy of heart rate as a surrogate measure of cardiac output, stroke volume and oxygen uptake in response to graded exercise.

Heart rate (HR) is a valuable and widespread measure for physical training programs, although its description of conditioning is limited to the cardiac response to exercise. More comprehensive measures of exercise adaptation include cardiac output (Q̇), stroke volume (SV) and oxygen uptake (V̇O2), but these physiological parameters can be measured only with cumbersome equipment installed in clinical settings. In this work, we explore the ability of pulse transit time (PTT) to represent a valuable pairing with HR for indirectly estimating Q̇, SV and V̇O2 non-invasively. PTT was measured as the time interval between the peak of the electrocardiographic (ECG) R-wave and the onset of the photoplethysmography (PPG) waveform at the periphery (i.e. fingertip) with a portable sensor. Fifteen healthy young subjects underwent a graded incremental cycling protocol after which HR and PTT were correlated with Q̇, SV and V̇O2 using linear mixed models. The addition of PTT significantly improved the modeling of Q̇, SV and V̇O2 at the individual level ([Formula: see text] for SV, 0.548 for Q̇, and 0.771 for V̇O2) compared to predictive models based solely on HR ([Formula: see text] for SV, 0.503 for Q̇, and 0.745 for V̇O2). While challenges in sensitivity and artifact rejection exist, combining PTT with HR holds potential for development of novel wearable sensors that provide exercise assessment largely superior to HR monitors.

Do we know how to set decision thresholds for diabetes?

The diagnosis of diabetes, based on measured fasting plasma glucose level, depends on choosing a threshold level for which the probability of failing to detect disease (missed diagnosis), as well as the probability of falsely diagnosing disease (false alarm), are both small. The Bayesian risk provides a tool for aggregating and evaluating the risks of missed diagnosis and false alarm. However, the underlying probability distributions are uncertain, which makes the choice of the decision threshold difficult. We discuss an hypothesis for choosing the threshold that can robustly achieve acceptable risk. Our analysis is based on info-gap decision theory, which is a non-probabilistic methodology for modelling and managing uncertainty. Our hypothesis is that the non-probabilistic method of info-gap robust decision making is able to select decision thresholds according to their probability of success. This hypothesis is motivated by the relationship between info-gap robustness and the probability of success, which has been observed in other disciplines (biology and economics). If true, it provides a valuable clinical tool, enabling the clinician to make reliable diagnostic decisions in the absence of extensive probabilistic information. Specifically, the hypothesis asserts that the physician is able to choose a diagnostic threshold that maximizes the probability of acceptably small Bayesian risk, without requiring accurate knowledge of the underlying probability distributions. The actual value of the Bayesian risk remains uncertain.

Opportunities for optimizing resource utilization in ambulatory academic practices.

Growing emphasis on ambulatory service delivery in academic medical centers has heightened interest in improving operational efficiencies, while providing an optimal educational experience for medical students and residents. One significant challenge in the academic environment is maximizing resource utilization (both physical plant and personnel), through scheduling and operational effectiveness. This article examines how academic ambulatory practices can apply operational and scheduling process redesign methodologies to improve throughput and productivity, while enhancing the educational experience for students/residents.

Pericarditis in AIDS.

A wide variety of organisms and conditions have been reported to cause pericarditis in patients that present and die with AIDS. Although pericarditis is remarkably common in patients dying of AIDS, no consistent pattern of cause emerges. Patients with AIDS are susceptible to pericarditis as a concomitant of the terminal condition, but it seldom contributes to the patient's death. Alternatively, pericarditis (as opposed to silent pericardial effusion) as a cardinal symptom in a patient's illness is likely to have an origin that can be ascribed to organisms typically associated with infectious pericarditis in those patients who have profound cellular immunodeficiency. Thus, it is important to make the diagnosis of infectious or neoplastic pericarditis in the setting of AIDS, since control of the agent has the potential of influencing the clinical course. In the absence of signs of hemodynamic compromise or inflammation, pericardial effusion may be accepted as an accompaniment of pleural effusions or ascites in the appropriate clinical context. Invasive diagnostic measures may be reserved for those cases in which pericardial disease is a prominent feature of the symptom complex or of accompanying pleural effusion. The study of epidemiology and biology of AIDS is a rapidly changing field. Explanations of the high incidence of pericardial disease in terminal disease may emerge with broad-ranging studies of the incidence of myocarditis in AIDS as well as the relative contribution to pericardial disease of agents used in the treatment of the illness.

Factors influencing ambulatory care education in the U.S. Department of Veterans Affairs.

The Department of Veterans Affairs (VA) is undergoing change in the way it delivers health care. Forces underlying this change include demographics of its population, new fiscal constraints, and the requirements of its academic affiliates. The benefit to the medical school affiliates will be the availability of patients in a structure useful for outpatient teaching of medical students and houseofficers. Barriers to effective delivery of ambulatory health care and education in VA facilities are (1) the historic focus on episodic, inpatient care, (2) continuous changes in eligibility requirements, (3) increases in patient care responsibilities for affiliated faculty, and (4) concomitant withdrawal of resources from the VA at a time when costs of health care and education are increasing. The VA medical centers will be increasingly forced to investigate innovative models for patient care delivery and education in the ambulatory setting.

Significance of the Argyll Robertson pupil in clinical medicine.

The Argyll Robertson pupil, a miotic pupil that fails to react to direct light, has been described for more than a century. Originally associated with tabes dorsalis, the sign has now been found in a number of conditions with lesions in the area of the nucleus of Edinger-Westphal. Magnetic resonance imaging studies have localized the lesion in patients with sarcoidosis and multiple sclerosis. With the declining incidence of neurosyphilis, the sign is increasingly likely to indicate another cause, although an assiduous search for lues should also be undertaken.

Systemic antibiotic treatment in burned patients.

Systemic antibiotics are a valuable therapeutic modality in the burned patient when properly used. Injudicious use, however, may not only fail to be beneficial to the patient but also may produce harmful effects--either through direct toxicity or by contributing to the emergence of resistant strains of micro-organisms. General guidelines and principles for systemic antibiotic use include the following: The burned patient, despite all efforts, will be exposed to microorganisms. No single agent or combination of agents can destroy all the organisms to which the burned patient is exposed. Treatment involves first identifying the organism responsible for clinical sepsis, then choosing appropriate agents. Combinations of antibiotics are not always synergistic or even additive in effect. Multiagent therapy may have the untoward effect of predisposing to superinfection by yeast, fungi, or resistant organisms. Antibiotics should be used for a long enough period to produce an effect, but not long enough to allow for emergence of opportunistic or resistant organisms. Dosages must be adjusted based on serum concentrations when serum assays are available. In general prophylactic systemic antibiotics are indicated in only a few clinical situations including the immediate preoperative and postoperative periods associated with excision and autografting, and possibly in the early phases of burns in children. The penetration of systemic antibiotics into burn eschar remains an area not fully studied; hence, they cannot be the only therapeutic modality used to treat burn wound infection. Systemic dosages of antibiotics in burns will require alteration depending on the clinical status of the patient. The choice of agent requires a thorough knowledge of side effects, toxicity, and potential benefit. Above all, active surveillance and monitoring of the burned patient and the environment in which he or she is being treated is mandatory for effective treatment. The increasing number of new antimicrobial agents has presented a new dilemma to the practicing clinician because many of these agents have not been evaluated thoroughly in the burned population. With further studies, the armamentarium of the burn treatment team will inevitably increase. It is in this manner only that so many of the unanswered questions will be solved, and that infection will start to decline as the major cause of death in the burned population.

Infections in burn patients.

Systemic sepsis resulting from invasive infection remains the leading cause of death among patients hospitalized with major thermal injury. Prevention of infection and death in burn patients requires a thorough knowledge of the multiple predisposing factors involved and expert application of appropriate diagnostic, supportive, and therapeutic modalities. The improved survival in this population is a result of all these factors, not any one. It is this principle and the adherence to a treatment program that encompasses all the modalities which are so essential in the care of burn patients if continuing progress is to be made in this field. This article describes the current management of infection and infection control in burn patients. The burn wound and pulmonary system remain the major foci for infection in this population. Less common types of infection include suppurative thrombophlebitis, suppurative chondritis, bacterial endocarditis, urinary tract sepsis, sinusitis, intra-abdominal sepsis, and infections of the eyes. Prophylaxis protocols involve proper control of the environment and an anticipation of bacterial colonization. A number of specific monitoring and treatment guidelines have evolved that have proved effective over the years in minimizing morbidity and mortality.

Sporadic occurrence of zoonotic swine influenza virus infections.

Two infections by swine influenza virus, antigenically similar to A/New Jersey/76 (H1N1) virus, were detected during community epidemics with other influenza viruses. The swinelike viruses were obtained during virological surveillance of acute respiratory illnesses, and the clinical symptoms of these two patients were similar to those caused by other respiratory viruses. Both patients reported contact with swine a few days before onset of illness, but in one case it was brief. Serological studies suggested that one patient may have transmitted the virus to his roommate, but spread into the community was not indicated.

Prophylactic effect of low doses of human leukocyte interferon against infection with rhinovirus.

The prophylactic effect of low doses of human leukocyte interferon (HuIFN-alpha) against infection with rhinovirus was measured in double-blind, placebo-controlled studies with volunteer subjects. An antihistamine (chlorpheniramine) was given before administration of single or multiple doses of HuIFN-alpha but saturated cotton pledget or by aerosol; volunteers were then challenged with rhinovirus. When the results for all groups were combined, a lower frequency of respiratory illness was demonstrated in the HuIFN-alpha-treated volunteers (20 of 39 vs. 11 of 38, P less than 0.05). A significant improvement in mean symptom scores was found only in the volunteers who received HuIFN-alpha by cotton pledget. The total numbers of isolates of rhinovirus and seroconversions were similar for HuIFN-alpha-treated and control volunteers. No significant side effects were noted in the HuIFN-alpha-treated volunteers. Higher concentrations or improved methods of delivery of HuIFN-alpha will be necessary for improving the clinical efficacy of HuIFN-alpha against viral infections in the respiratory system.

Partial artificial heart (ALVAD) use with subsequent cardiac and renal allografting in a patient with stone heart syndrome.

The abdominal left ventricular assist device (ALVAD) is an order of magnitude more effective than conventional intra-aortic balloon pumping (IABP) in unloading and providing circulatory support to the failing left ventricle. This is a report of a unique case which demonstrates that in the absence of pulmonary vascular obstruction or constriction, the ALVAD can substitute for both left and right heart function. A 21-year-old patient with a congenital bicuspid aortic valve developed acute valvular endocarditis which rapidly progressed to congestive heart failure. An operation was undertaken, the mitral and aortic valves were excised and replaced by porcine heterografts, and a fistula from the right sinus of Valsalva to the right ventricle was closed. When coronary circulation was restored, irreversible ischemic contracture of the left ventricle, or "stone heart" syndrome, developed and emergency ALVAD or partial artificial heart implantation was effected. This device functioned as a total artificial heart for nearly six days, while a donor heart was sought. The patient then underwent removal of the ALVAD and cardiac and renal allografting. The transplanted heart functioned well, but the patient expired fifteen days later from gram-negative sepsis.

Total support of the circulation of a patient with post-cardiotomy stone-heart syndrome by a partial artificial heart (ALVAD) for 5 days followed by heart and kidney transplantation.

A patient with acute bacterial endocarditis in whom ischaemic contracture of the left ventricle (stone-heart syndrome) developed during aortic and mitral valve replacement had an emergency implantation of an intracorporeal partial artificial heart (an abdominal left-ventricular assist device of ALVAD). This device functioned as a total artificial heart for nearly 6 days, while a donor heart for transplantation was sought. The ALVAD was then removed, and the patient received allografts of a heart and a kidney. The transplanted heart functioned well, but the patient died 15 days later from gram-negative sepsis. There was no evidence of cardiac or renal allograft rejection.