Medical applications of electronic nose technology: review of current status.

Electronic noses, or artificial sensors of odorants. have been developed over the last ten years to perform a variety of identification tasks in various industries. This powerful technology is only beginning to be introduced in the field of medicine, but is promising in its potential to assist in diagnosis. This article reviews electronic nose technology and some initial investigations of potential applicability of the technology in the field of medicine.

Artificial intelligence applications in the intensive care unit.

OBJECTIVE: To review the history and current applications of artificial intelligence in the intensive care unit. DATA SOURCES: The MEDLINE database, bibliographies of selected articles, and current texts on the subject. STUDY SELECTION: The studies that were selected for review used artificial intelligence tools for a variety of intensive care applications, including direct patient care and retrospective database analysis. DATA EXTRACTION: All literature relevant to the topic was reviewed. DATA SYNTHESIS: Although some of the earliest artificial intelligence (AI) applications were medically oriented, AI has not been widely accepted in medicine. Despite this, patient demographic, clinical, and billing data are increasingly available in an electronic format and therefore susceptible to analysis by intelligent software. Individual AI tools are specifically suited to different tasks, such as waveform analysis or device control. CONCLUSIONS: The intensive care environment is particularly suited to the implementation of AI tools because of the wealth of available data and the inherent opportunities for increased efficiency in inpatient care. A variety of new AI tools have become available in recent years that can function as intelligent assistants to clinicians, constantly monitoring electronic data streams for important trends, or adjusting the settings of bedside devices. The integration of these tools into the intensive care unit can be expected to reduce costs and improve patient outcomes.

Anesthetics, sedatives, and paralytics. Understanding their use in the intensive care unit.

This article reviews the use of inhalational, intravenous, and epidural agents used in the operating room and ICU. An emphasis is placed on the rationale for their selection. Additionally, the side effects and expected complications are discussed. By developing expertise with one's own repertoire of sedatives, narcotics, and neuromuscular blocking agents, one may decrease postoperative complications and lengths of stay.

Use of an electronic nose to distinguish cerebrospinal fluid from serum.

BACKGROUND: Efforts to mimic the biologic olfactory system have resulted in the development of an electronic nose, whereby volatile gases may be identified by means of organic semiconductors. Such devices have been used in the food and beverage industry for quality-control purposes, but to date have not been used in the field of medicine. OBJECTIVE: To present the application of an electronic nose for clinical decision making by assessing the ability of an electronic nose to distinguish cerebrospinal fluid (CSF) from serum. DESIGN: Randomized, prospective, masked study. SUBJECTS: Nineteen matched sets of CSF and serum from inpatients at a university hospital. RESULTS: The electronic nose was able to distinguish CSF from serum in 18 of 19 patients. The data points for 18 of 19 CSF and 18 of 19 serum samples were within statistically distinct cluster groups, suggesting that the device is able to identify an unknown sample as CSF or serum. CONCLUSIONS: This new technology is able to distinguish CSF from serum with a high degree of accuracy and speed, and with small sample quantity, potentially allowing the physician to identify reliably CSF otorrhea or rhinorrhea. This revolutionary diagnostic approach may have further, widespread application in the field of otorhinolaryngology and in medicine as a whole.

Cardiothoracic intensive care: operation and administration.

The cardiothoracic surgery intensive care unit (CTICU) has evolved as a separate entity from the general surgical intensive care unit as management for cardiac surgery patients has become streamlined and algorithm driven. Critical care is best managed when the service is designed for a homogeneous population with a circumscribed set of medical and surgical issues. The repetition involved with the subspecialty care allows health care providers such as primary care nurses, nurse practitioners, physician assistants, and other ancillary services to become appropriately focused on issues pertinent to this population. The goals of the CTICU include the attainment of rapid and safe recovery from surgery and anesthesia despite decreasing resources, increasing patient age and comorbidity, and increasing complexity of the operative procedure. The coordinated and systematic approach to the postoperative cardiac surgery patient under the direction of a staff physician offers the most effective opportunity to achieve these expectations at this time. The traditional model of staffing by a physician with responsibilities that conflict temporally with the immediacy often needed for the postoperative care of cardiac patients may expose patients to unnecessary risks. A responsible physician should be available in the CTICU, especially during the immediate postoperative period when physical assessment and direct hands-on involvement are essential. In an era when the operative team (ie, cardiac surgeon and cardiac anesthesiologist) must return to the surgical suite soon after the patient arrives in the intensive care unit, the presence of a physician dedicated to postoperative medical and surgical management becomes mandatory. According to the Joint Commission on Accreditation of Healthcare Organizations, "Each special care unit is properly directed and staffed according to the nature of the special patient care needs anticipated and scope of services provided." The assignment of staff is designed to match experience with patient acuity.

Computer assisted physiologic monitoring and stability assessment in vascular surgical patients undergoing general anesthesia--preliminary data.

BACKGROUND: Physiologic monitors present an influx of numerical data that can be overwhelming to the clinician. We combined several parameters in an effort to reduce the amount of information that must be continuously monitored including oxyhemoglobin saturation by pulse oximetry, end-tidal CO2 concentration, arterial blood pressure, and heart rate into an integrated measure--the health stability magnitude (HSM). The HSM is computed for a predetermined basal period, the reference HSM (RHSM), and recalculated continuously for comparison with the baseline value. In this study we present the HSM concept and examine changes in the HSM during abdominal aortic aneurysm surgery. MATERIALS AND METHODS: After IRB approval, nine patients were studied. The anesthesiologist recorded all significant intra-operative events. Within a defined time interval, data were recorded and used to calculate a combined parameter, the HSM. The baseline or reference value of this index (RHSM) was calculated after the induction of anesthesia. Individual HSM values were repeatedly calculated for ten second periods after the RHSM value was established. A > 30% deviation of the HSM from the RHSM was considered significant. Deviations in the HSM were compared with events recorded by the anesthesiologist on a paper record and with the record from an electronic record-keeping system. The deviation observed between two consecutive HSMs, called dHSM, was plotted against HSM to construct a contour diagram of data from all patients to which individual cases could be compared. RESULTS: The plot showed that dHSM vs. HSM values were tightly clustered. The inner contour on the distribution plot contained 90% of values. Individual patient's time course, projected on this diagram, revealed deviations form "normal" physiology. Fifty-nine events led to > 30% deviations in the HSM; 27 were anticipated events and 32 were unanticipated. CONCLUSION: The correlation between HSM and dHSM depicts changes in multiple monitored parameters that can be viewed using a single graphical representation. Projection of individual cases on the contour diagram may help the clinician to distinguish relative intraoperative stability from important events. Data reduction in this manner may guide clinical decision-making in response to unanticipated or unrecognized events.

Collaborative prototyping approaches for ICU decision aid design.

When computer-based aids do not support the human users' decision-making strategies or anticipate the organizational impacts of technological change, advances in information technology may degrade rather than enhance decision-making performance. Such failures suggest the design of human-computer cooperation for problem solving and decision-making must be driven by human cognitive and organizational process requirements rather than computer technology. Decision- and user-centered development techniques involve domain experts and end-users in the earliest phases of design to evolve an understanding of requirements through iterative prototyping. This paper presents a collaborative approach to cognitive systems engineering applied to developing a clinical aid to assist respiratory care in the surgical ICU.

Cardiovascular effects of inhaled nitric oxide in a canine model of cardiomyopathy.

BACKGROUND: The inhalation of nitric oxide (NO) in patients with heart failure decreases pulmonary vascular resistance (PVR) and is associated with an increase in pulmonary artery wedge pressure (PAWP). The mechanism for this effect remains unclear. METHODS: In dogs rapid-paced for 8 weeks to induce cardiac dysfunction, we performed left ventricular pressure-volume analysis of unpaced hearts in situ to determine whether during NO inhalation (80 ppm), the mechanism for the rise in PAWP is due to: 1) primary pulmonary vasodilation; 2) a direct negative inotropic effect; or 3) impairment of ventricular relaxation. RESULTS: Inhalation of NO decreased PVR by 51%+/-3.8% (257+/-25 vs 127+/-18 dynes x sec x cm(-5) [NO 80 ppm]; p < 0.001) and increased PAWP (15.4+/-2.4 vs 18.1+/-2.6 mm Hg [NO 80 ppm]; p < 0.001). Calculated systemic vascular resistance remained unchanged. Left ventricular (LV) end-diastolic pressure rose (16.4+/-1.9 vs 19.1+/-1.8 mm Hg [NO 80 ppm]; p < 0.001), as did LV end-diastolic volume (83.5+/-4.0 vs 77.0+/-3.4 mL [NO 80 ppm]; p = 0.006). LV peak +dP/dt was unchanged by NO (1,082+/-105 vs 1,142+/-111 mm Hg/sec [NO 80 ppm]; p = NS). There was a trend toward a stroke volume increase (17.4+/-1.2 vs 18.8+/-1.3 mL; p = NS), but the relaxation time constant and end-diastolic pressure-volume relation were both unchanged. CONCLUSIONS: In this canine model of cardiomyopathy, inhaled NO decreases pulmonary vascular resistance. The associated increase in left ventricular filling pressure appears to be secondary to a primary pulmonary vasodilator effect of NO without primary effects on the contractile or relaxation properties of the left ventricle.

Platelet anesthesia with nitric oxide with or without eptifibatide during cardiopulmonary bypass in baboons.

OBJECTIVE: This study tested the hypothesis that nitric oxide or nitric oxide and eptifibatide (Integrilin) reversibly inhibit platelet activation and consumption during cardiopulmonary bypass and rapidly restore platelet numbers and function after bypass. METHODS: Nitric oxide, a short-acting, reversible platelet inhibitor, was studied with and without eptifibatide, a short-acting, reversible glycoprotein IIb/IIIa inhibitor, in 21 baboons that underwent 60 minutes of normothermic cardiopulmonary bypass with peripheral cannulas. A control group, a group that received 80 ppm nitric oxide, and a group that received both nitric oxide and eptifibatide were studied. Blood samples were obtained at several time points to determine platelet count, aggregation in response to adenosine diphosphate, and levels of beta-thromboglobulin, prothrombin fragment 1.2, and thrombin-antithrombin complex. Template bleeding times were measured before and at 4 intervals after cardiopulmonary bypass. RESULTS: Both nitric oxide and the combination of the 2 drugs significantly attenuated platelet consumption, improved postbypass function, and reduced plasma beta-thromboglobulin release with respect to values in control animals. Both nitric oxide and the combination restored baseline bleeding times 55 minutes after cardiopulmonary bypass ended. No significant differences between nitric oxide and the combination were found for any measurement. CONCLUSION: Nitric oxide with or without eptifibatide protects platelets during cardiopulmonary bypass and accelerates restoration of normal bleeding times after operation in a baboon model. Although nitric oxide and eptifibatide reversibly inhibit platelets by different mechanisms, in the absence of a wound no synergistic effect was demonstrated.

Effects of an organized critical care service on outcomes and resource utilization: a cohort study.

OBJECTIVE: To determine whether the presence of an on-site, organized, supervised critical service improves care and decreases resource utilization. DESIGN: The study compared two patient cohorts admitted to a surgical intensive care unit during the same period of time. The study cohort was cared for by an on-site critical care team supervised by an intensivist. The control cohort was cared for by a team with patient care responsibilities in multiple sites supervised by a general surgeon. The main outcome measures were duration of stay, resource utilization, and complication rate. SETTING: Study patients were general surgical patients in an academic medical center. RESULTS: Despite having higher Acute Physiology and Chronic Health Evaluation II scores, patients cared for by the critical care service spent less time in the surgical intensive care unit, used fewer resources, had fewer complications and had lower total hospital charges. The difference between the two cohorts was most evident in patients with the worst APACHE II score. CONCLUSIONS: Critical care interventions are expensive and have a narrow safety margin. It is essential to develop structured and validated approaches to study the delivery of this resource. In this study, the critical care service model performed favorably both in terms of quality and cost.

A multicenter evaluation of a new continuous cardiac output pulmonary artery catheter system.

OBJECTIVE: To validate a new system of continuous cardiac output monitoring. DESIGN: Multicenter, prospective, nonrandomized clinical study. SETTING: Four university hospitals. PATIENTS: Forty-seven adult intensive care unit patients. INTERVENTIONS: Pulmonary artery catheterization. MEASUREMENTS AND MAIN RESULTS: Continuous and bolus cardiac output measurements were obtained over 72 hrs. The 327 continuous cardiac output measurements compared favorably with bolus cardiac output measurements (bias = 0.12 L/min, precision = +/-0.84). The continuous cardiac measurement was not adversely affected by temperatures of <37 degrees C or >38 degrees C, high (>7.5 L/min) or low (<4.5 L/min) cardiac output values, or duration (72 hrs) of the study. CONCLUSIONS: This continuous cardiac output system provides a reliable estimate of cardiac output for clinical use if applied in conditions similar to this study. The combination of a continuous measure of cardiac output with other continuous physiologic monitoring (arterial and mixed venous oxygen saturation, oxygen consumption, etc.) may provide important information that no single parameter could achieve.

Improved oxygenation with prostaglandin F2alpha with and without inhaled nitric oxide in dogs.

Dogs of mixed breed (n = 7) were anesthetized, right lung atelectasis was established, and the cyclooxygenase pathway was blocked with ibuprofen. Measurements of pulmonary gas exchange were performed (fractional concentration of inspired O2 = 0.95) after infusions of prostaglandin F2alpha (PGF2alpha; 2 microg . kg-1 . min-1), ventilation with nitric oxide (NO; 40 ppm), or both (PGF2alpha + NO) in random order. The arterial PO2 (PaO2) under control conditions was 117 +/- 16 Torr (shunt = 33 +/- 2.5%), was unchanged with NO alone (PaO2 = 114 +/- 17 Torr; shunt = 35.7 +/- 3. 1%), but was significantly improved with PGF2alpha alone (PaO2 = 180 +/- 28 Torr; shunt = 23.2 +/- 2.8%) and with the combination of PGF2alpha + NO (PaO2 = 202 +/- 30 Torr; shunt = 20.9 +/- 2.5%). The addition of NO did not significantly enhance the effectiveness of the PGF2alpha on PaO2. Simulation of these data in a computer model, combining pulmonary gas exchange and pulmonary blood flow, reproduced the results on the basis that vasoconstriction with PGF2alpha was maximal under hypoxia in the atelectatic lung and reduced by hyperoxia in the ventilated lung, consistent with the hypothesis of O2 dependence of PGF2alpha vasoconstriction.

Mechanical ventilation and pharmacologic strategies for acute respiratory distress syndrome.

Acute or adult respiratory distress syndrome (ARDS) contributes to mortality and morbidity in the intensive care environment. Appropriate application of microprocessor-controlled mechanical ventilatory support, pathophysiology of the disease, and new pharmacologic modalities are currently being investigated. Mechanical ventilation is usually begun when respiratory failure is caused by alveolar hypoventilation or hypoxia. Primary choices for this therapy are control-mode ventilation, assist-control ventilation, pressure-control ventilation, intermittent mandatory ventilation, and synchronized intermittent mandatory ventilation with the addition of positive end-expiratory pressure. Patients who deteriorate despite these interventions may require alternative modes of ventilation. Pharmacologic agents in ARDS is important due to the multifactorial pathophysiologic and pharmacodynamic processes that are part of the disease. Clinical studies will continue to determine advantageous agents. Unfortunately, no convincing data exist that any pharmacologic or nonpharmacologic strategy is superior for the support of these patients or results in a better outcome than others.

Outcome-based justification for implementing new point-of-care tests: there is no difference between magnesium replacement based on ionized magnesium and total magnesium as a predictor of development of arrhythmias in the postoperative cardiac surgical patient.

OBJECTIVE: To determine whether introducing a new laboratory test, ionized magnesium (iMg++), would affect outcome, where outcome was defined as the rate of arrhythmias in a population of postoperative cardiopulmonary bypass (CPB) patients. DESIGN: A prospective randomized trial. SETTING: Cardiothoracic surgical intensive care unit of a university hospital. PATIENTS: One hundred fifty consecutive post-CPB patients with randomized to two groups, one of which received routine reporting of iMg++ levels on all postoperative electrolyte requests while the other had access to total magnesium (tMg++) levels on demand and no access to iMg++ levels. Groups were compared for rate of arrhythmias, total amount of magnesium repleted, and demographics. MEASUREMENTS AND MAIN RESULTS: Eighty-five patients were randomized to the tMg++ group and 65 to the iMg++ group. The two groups did not differ in the rate of arrhythmias (chi-square test): 13/85 (15%) of the tMg++ patients and 12/65 (18%) of the iMg++ patients developed an arrhythmia. The groups also did not differ in the amount of magnesium sulfate (MgSO4) administered (2 tailed t-test): tMg++ patients received 1.5 +/- 0.15 (SEM) gm of MgSO4, whereas iMg++ patients received 1.3 +/- 0.15 gm. CONCLUSION: The study does not support the hypothesis that magnesium repletion titrated to iMg++ reduces arrhythmia development in post-CPB patients. The lack of a difference in the amount of magnesium replacement between the two groups suggests that tMg++ level is a reasonable indicator of iMg++ level. Routine measurement of iMg++ does not, therefore, appear to have advantages over tMg++ in the postoperative management of CPB patients.

Metabolic acidosis.

Metabolic acidosis is a pathophysiologic state that is associated with serious morbidities and mortality. The diagnosis of metabolic acidosis is perplexing for novice and expert advanced practice nurses for many reasons. Its differential diagnosis is broad and includes common and rare, complex disease. The diagnosis of metabolic acidosis is also difficult because it is frequently associated with mixed, acid-base disorders. Its clinical manifestations are often nonspecific or subclinical, which means that its diagnosis is made from laboratory and other diagnostic tests. Timely diagnosis of metabolic acidosis is needed to institute appropriate therapy to avoid negative physiologic effects.

Improvement in oxygenation by phenylephrine and nitric oxide in patients with adult respiratory distress syndrome.

BACKGROUND: Inhaled nitric oxide (NO), a selective vasodilator, improves oxygenation in many patients with adult respiratory distress syndrome (ARDS). Vasoconstrictors may also improve oxygenation, possibly by enhancing hypoxic pulmonary vasoconstriction. This study compared the effects of phenylephrine, NO, and their combination in patients with ARDS. METHODS: Twelve patients with ARDS (PaO2/FIO2 180; Murray score 2) were studied. Each patient received three treatments in random order: intravenous phenylephrine, 50-200 micrograms/min, titrated to a 20% increase in mean arterial blood pressure; inhaled NO, 40 ppm; and the combination (phenylephrine+NO). Hemodynamics and blood gas measurements were made during each treatment and at pre- and posttreatment baselines. RESULTS: All three treatments improved PaO2 overall. Six patients were "phenylephrine-responders" (delta PaO2 > 10 mmHg), and six were "phenylephrine-nonresponders." In phenylephrine-responders, the effect of phenylephrine was comparable with that of NO (PaO2 from 105 +/- 14 to 132 +/- 14 mmHg with phenylephrine, and from 110 +/- 14 to 143 +/- 19 mmHg with NO), and the effect of phenylephrine+NO was greater than that of either treatment alone (PaO2 from 123 +/- 13 to 178 +/- 23 mmHg). In phenylephrine-nonresponders, phenylephrine did not affect PaO2, and the effect of phenylephrine+NO was not statistically different from that of NO alone (PaO2 from 82 +/- 12 to 138 +/- 28 mmHg with NO; from 84 +/- 12 to 127 +/- 23 mmHg with phenylephrine+NO). Data are mean +/- SEM. CONCLUSIONS: Phenylephrine alone can improve PaO2 in patients with ARDS. In phenylephrine-responsive patients, phenylephrine augments the improvement in PaO2 seen with inhaled NO. These results may reflect selective enhancement of hypoxic pulmonary vasoconstriction by phenylephrine, which complements selective vasodilation by NO.