Specificity Improvement for Network Distributed Physiologic Alarms Based on a Simple Deterministic Reactive Intelligent Agent in the Critical Care Environment

Automated physiologic alarms are available in most commercial physiologic monitors. However, due to the variability of data coming from the physiologic sensors describing the state of patients, false positive alarms frequently occur. Each alarm requires review and documentation, which consumes clinicians’ time, may reduce patient safety through ‹alert fatigue’ and makes automated physician paging infeasible. To address these issues a computerized architecture based on simple reactive intelligent agent technology has been developed and implemented in a live critical care unit to facilitate the investigation of deterministic algorithms for the improvement of the sensitivity and specificity of physiologic alarms. The initial proposed algorithm uses a combination of median filters and production rules to make decisions about what alarms to generate. The alarms are used to classify the state of patients and alerts can be easily viewed and distributed using standard network, SQL database and Internet technologies. To evaluate the proposed algorithm, a 28 day study was conducted in the University of Michigan Medical Center’s 14 bed Cardiothoracic Intensive Care Unit. Alarms generated by patient monitors, the intelligent agent and alerts documented on patient flow sheets were compared. Significant improvements in the specificity of the physiologic alarms based on systolic and mean blood pressure was found on average to be 99% and 88% respectively. Even through significant improvements were noted based on this algorithm much work still needs to be done to ensure the sensitivity of alarms and methods to handle spurious sensor data due to patient or sensor movement and other influences. Blum JM, Kruger GH, Sanders KL, Gutierrez J, Rosenberg AL. Specificity improvement for network distributed physiologic alarms based on a simple deterministic reactive intelligent agent in the critical care environment.     

Frequency,nature, effects,and correlates of conflicts of interest in published clinical cancer research

BACKGROUND:

Relationships between clinical researchers and industry are becoming increasingly complex. The frequency and impact of conflicts of interest in the full range of high‐impact, published clinical cancer research is unknown.

METHODS:

The authors reviewed cancer research published in 8 journals in 2006 to determine frequency of self‐reported conflicts of interest, source of study funding, and other characteristics. They assessed associations between the likelihood of conflicts of interest and other characteristics by using chi‐squared testing. They also compared the likelihood of positive outcome in randomized trials with and without conflicts of interest by chi‐squared testing.

RESULTS:

The authors identified 1534 original oncology studies; 29% had conflicts of interest (including industrial funding) and 17% declared industrial funding. Conflicts of interest varied by discipline (P < .001), continental origin (P < .001), and sex (P < .001) of the corresponding author and were most likely in articles with corresponding authors from departments of medical oncology (45%), those from North America (33%), and those with male first and senior authors (37%). Frequency of conflicts also varied considerably depending upon disease site studied. Studies with industrial funding were more likely to focus on treatment (62% vs 36%; P < .001), and randomized trials that assessed survival were more likely to report positive survival outcomes when a conflict of interest was present (P = .04).

CONCLUSIONS:

Conflicts of interest characterize a substantial minority of clinical cancer research published in high‐impact journals. Therefore, attempts to disentangle the cancer research effort from industry merit further attention, and journals should embrace both rigorous standards of disclosure and heightened scrutiny when conflicts exist. Cancer 2009. © 2009 American Cancer Society.     

Desflurane-mediated Sympathetic Activation Occurs in Humans Despite Preventing Hypotension and Baroreceptor Unloading

Background: Increasing concentrations of desflurane result in progressive decreases in blood pressure (BP) and, unlike other currently marketed, potent volatile anesthetics, heightened sympathetic nervous system activity. This study aimed to determine whether baroreflex mechanisms are involved in desflurane-mediated sympathetic excitation.

Methods: Healthy volunteers were anesthetized with desflurane (n = 8) or isoflurane (n = 9). Heart rate (HR; measured by electrocardiograph), blood pressure (BP; measured by arterial catheter), and efferent sympathetic nerve activity (SNA; obtained from percutaneous recordings from the peroneal nerve) were monitored. Baroreflex sensitivity was evaluated at baseline while volunteers were conscious and during 0.5, 1, and 1.5 minimum alveolar concentration (MAC) anesthesia via bolus injections of nitroprusside (100 micro gram) and phenylephrine (150 micro gram) to decrease and increase BP. To prevent the BP decline with increasing depths of anesthesia, phenylephrine was infused to maintain mean BP at the 0.5 MAC level.

Results: The HR, BP, and SNA were similar between the groups at the conscious baseline measurement. Efferent SNA did not change during higher MAC of isoflurane, but it increased progressively as desflurane concentrations were increased beyond 0.5 MAC, despite maintaining BP at the 0.5 MAC value with phenylephrine infusions (P < 0.05). Cardiac baroslopes (based on changes in HR) were progressively and similarly decreased with increasing concentrations of isoflurane and desflurane (P < 0.05). Sympathetic baroslopes (based on SNA) decreased with increasing isoflurane concentrations but were maintained with increasing concentrations of desflurane; the response was significantly different between groups.     

Volume of Preclinical Xenograft Tumors Is More Accurately Assessed by Ultrasound Imaging Than Manual Caliper Measurements

Objective. The volume of subcutaneous xenograft tumors is an important metric of disease progression and response to therapy in preclinical drug development. Noninvasive imaging technologies suitable for measuring xenograft volume are increasingly available, yet manual calipers, which are susceptible to inaccuracy and bias, are routinely used. The goal of this study was to quantify and compare the accuracy, precision, and inter‐rater variability of xenograft tumor volume assessment by caliper measurements and ultrasound imaging. Methods. Subcutaneous xenograft tumors derived from human colorectal cancer cell lines (DLD1 and SW620) were generated in athymic nude mice. Experienced independent reviewers segmented 3‐dimensional ultrasound data sets and collected manual caliper measurements resulting in tumor volumes. Imaging‐ and caliper‐derived volumes were compared with the tumor mass, the reference standard, determined after resection. Bias, precision, and inter‐rater differences were estimated for each mouse among reviewers. Bootstrapping was used to estimate mean and confidence intervals of variance components, intraclass correlation coefficients (ICCs), and confidence intervals for each source of variation. Results. The average deviation from the true volume and inter‐rater differences were significantly lower for ultrasound volumes compared with caliper volumes (P = .0005 and .001, respectively). Reviewer ICCs for ultrasound and caliper measurements were similarly low (1%), yet caliper volume variance was 1.3‐fold higher than for ultrasound. Conclusions. Ultrasound imaging more accurately, precisely, and reproducibly reflects xenograft tumor volume than caliper measurements. These data suggest that preclinical studies using the xenograft burden as a surrogate end point measured by ultrasound imaging require up to 30% fewer animals to reach statistical significance compared with analogous studies using caliper measurements.     

Anesthesia machine malfunction simulating spontaneous respiratory effort

We present a case in which a dip in the capnogram of an anesthetized patient, which may indicate clinical complications such as spontaneous respiratory effort, was caused by a malfunction of the anesthesia delivery system. The rubber diaphragm of the ventilator relief valve was found to be coated with a sticky substance which may have caused adhesion at the valve seat. This adhesion blocked the flow ot excess gas to the scavenging system during exhalation. It was demonstrated that a pressure of 5 cm H₂O was needed to overcome this adhesion.