Standard Insertion Research Articles

Vascular-Access Infections in Hospitalized Patients

Vascular catheters are a common source of nosocomial infections, although many of these infections are potentially preventable. A long duration of catheterization, multiple catheter manipulations, the inexperience of some inserters, use of transparent plastic dressings, violations of aseptic technique, the use of multilumen catheters, and inadequate sterilization of reusable pressure transducers all increase the risk of these infections. The only interventions that have been proved to reduce the risk are standardized insertion and maintenance technique by an intravenous-therapy team, preinsertion skin preparation with chlorhexidine gluconate, and the use of topical antibiotics at the insertion site. The goal of the physician should be to prevent catheter infection, because the treatment of established infection can be difficult and costly. Treatment must be individualized for each patient on the basis of the clinical presentation and the causative organism.

Patellofemoral functional results and complications with the posterior stabilized total condylar knee prosthesis

The authors reviewed 73 knee arthoplasties performed with the Posterior Stabilized Total Condylar prosthesis, with an average follow-up period of 5.5 years. The function of the patellofemoral articulation was specifically analyzed. Patients with documented or suspected tibiofemoral problems were excluded. Using the Hospital for Special Surgery knee rating system, 48 knees (66%) had excellent, 20 had good (27%), and 5 (7%) had fair results. Patients with unilateral disease were able to negotiate stairs and transfer normally in 64% and 100% of the cases, respectively. The most frequent patellofemoral problem was impingement (21%), but reoperation was needed in only one patient. Stress fracture of the patella and subluxation were rare. A medial tilt of the patella on the axial view had no apparent ill effect. The patella was lowered 12 mm on average as a consequence of the standard bone resection sequence and insertion of the tibial component. The patella was significantly lower in patients with impingement than in normal joints. Routine complete patellofemoral resurfacing is advised in total knee joint arthroplasty. Complications are infrequent with appropriate prosthetic design and due technical care.

A note on the height of binary search trees

Let H n be the height of a binary search tree with n nodes constructed by standard insertions from a random permutation of 1, … , n . It is shown that H n /log n → c = 4.31107 … in probability as n → ∞, where c is the unique solution of c log((2 e )/ c ) = 1, c ≥ 2. Also, for all p > 0, lim n →∞ E ( H p n )/ log p n = c p . Finally, it is proved that S n /log n → c * = 0.3733 … , in probability, where c * is defined by c log((2 e )/ c ) = 1, c ≤ 1, and S n is the saturation level of the same tree, that is, the number of full levels in the tree.

Laboratory Attenuation of Earmuffs and Earplugs Both Singly and in Combination

For very high-level noise exposures, especially when 8-hour, time-weighted averages are greater than 105 dBA, the attenuation of a single hearing protection device may be inadequate. For such exposures, double hearing protection, i.e. muffs plus plugs, may be called for. It is well recognized that double hearing protection does not simply yield overall attenuation equal to the sum of the individual attenuation of each device due to the bone-conduction flanking paths and the acoustical-mechanical interaction between two such closely spaced devices. The incremental performance to be gained by double protection was investigated experimentally by measuring the real-ear attenuation at threshold for a number of combinations, according to ANSI S3.19-1974. All tests were conducted on 10 subjects, three replications per subject. Devices included foam plugs (partial, standard and deep insertion), fiberglass down, V-51R earplugs, medium and large volume commercially available earmuffs, and an experimental large-volume lead earmuff. All devices were examined singly and in combination. In all cases, plugs-plus-muffs outperformed either device individually, except at 1 kHz for one combination. Although the two pairs of commercially available earmuffs offered significantly different low frequency attenuation (125–1000 Hz), when either earmuff was combined with the V-51R or deeply inserted foam earplug, the improvements were similar. However, when the situation was reversed and the different inserts were examined in combination with a single earmuff, the choice of insert was important below 2 kHz. At and above 2 kHz all plug-plus-muff combinations that were studied provided attenuation approximately equal to the bone-conduction limits of the skull. Based on these laboratory results, it is clear that double hearing protection may provide the additional noise reduction needed in very high noise level environments.

Laboratory Attenuation of Earmuffs and Earplugs Both Singly and in Combination

For very high-level noise exposures, especially when 8-hour, time-weighted averages are greater than 105 dBA, the attenuation of a single hearing protection device may be inadequate. For such exposures, double hearing protection, i.e. muffs plus plugs, may be called for. It is well recognized that double hearing protection does not simply yield overall attenuation equal to the sum of the individual attenuation of each device due to the bone-conduction flanking paths and the acoustical-mechanical interaction between two such closely spaced devices. The incremental performance to be gained by double protection was investigated experimentally by measuring the real-ear attenuation at threshold for a number of combinations, according to ANSI S3.19-1974. All tests were conducted on 10 subjects, three replications per subject. Devices included foam plugs (partial, standard and deep insertion), fiberglass down, V-51R earplugs, medium and large volume commercially available earmuffs, and an experimental large-volume lead earmuff. All devices were examined singly and in combination. In all cases, plugs-plus-muffs outperformed either device individually, except at 1 kHz for one combination. Although the two pairs of commercially available earmuffs offered significantly different low frequency attenuation (125–1000 Hz), when either earmuff was combined with the V-51R or deeply inserted foam earplug, the improvements were similar. However, when the situation was reversed and the different inserts were examined in combination with a single earmuff, the choice of insert was important below 2 kHz. At and above 2 kHz all plug-plus-muff combinations that were studied provided attenuation approximately equal to the bone-conduction limits of the skull. Based on these laboratory results, it is clear that double hearing protection may provide the additional noise reduction needed in very high noise level environments.

On the correspondence between AVL trees and brother trees

We discuss the relationships of the classes of height-balanced (search) trees and the classes of brother (search) trees. In particular we characterize each class of height-balanced trees in terms of the class of “corresponding” brother trees and vice versa. Secondly, we show how this characterization leads to the notion of nonstandard updating algorithms. We derive a nonstandard insertion algorithm for height-balanced search trees to illustrate the notion. Finally we consider something of the similarities and differences between the standard and nonstandard insertion algorithms for height-balanced search rees.

Implantation of an endocardial tined lead to prevent early dislodgment

Early electrode dislodgment from the ventricular apex is a major complication associated with transvenous cardiac pacing. A new lead with flexible tines proximal to the tip electrode has been developed to minimize acute dislodgment incidence. The bipolar tined lead was implanted in 79 patients. This experience was compared to 48 implants of a standard bipolar endocardial lead. Stimulation threshold, sensing, and resistance measurements from both leads were comparable. Although the cephalic vein was the preferred venous route, the jugular vein was needed more often for tined lead insertion than for standard lead insertion. The incidence of early dislodgment with the tined lead was 2.5 percent compared to 8 percent with the standard lead (no significant difference). This preliminary experience can only suggest that the addition of flexible tined leads may reduce early electrode dislodgment.

Some Thoughts on Crossovers

In order to improve packing density and make fuller use of standard DIL insertion machines, a range of inexpensive multiple crossover networks in DIL packages is proposed.

Certification of Exhaust System Components

Various regulatory agencies have recognized the need for a reliable yet uncomplicated system of certifying and identifying exhaust systems and their elements with respect to noise control capability. Experts have cautioned that such a system could prove unworkable in view of the complex mix of exhaust gas parameters and system configurations which influence the installed attenuation of individual system elements. The present paper recognizes the potential importance of these complicating factors, yet advocates that a system of toleranced muffler class ratings (M.C. ratings) that take into account frequency selective properties and attenuation capability will yield performance predictions which will remain consistent from vehicle to vehicle. The approach advocated does not attempt to develop an engineering tool for manufacturers; rather, the objective is merely one of establishing comparative classification indices which permit the selection of equivalent replacement components. A parametric study on an exhaust flow simulator would model the exhaust in an increasingly sophisticated manner until the measured insertion loss matches that measured on a sample of real engines to within an acceptable statistical tolerance, thus providing a means of assessing the relative cost/effectiveness of an increasingly complex simulation facility. Once the standard insertion loss test facility is established, insertion loss characteristics for a respresentative sample of existing mufflers would be tabulated and statistically reduced to determine the M.C. contours. Regulation of the acceptable standard deviation from these contours would provide an additional means of quality assurance on muffler performance, discouraging mufflers with passbands or extremely narrow filter characteristics.

Construction and Operation of an Automated Dispensing Analyzer for the Assay of Individual Tablets

An automated system of modular design has been developed for the assay of single tablets. Commercially available proportioning pumps, continuous filter, tablet homogenizer, spectrophotometer, and recorder are mated to specially designed components for unattended operation. The system is constructed to analyze automatically up to 300 identifiable tablets with standards inserted prior to tablets, after any selected number of tablets, and at the end of the particular type of tablet being assayed. Up to six different cencentrations or types of tablets can be automatically processed sequentially, each with its own standard insertion. Provisions are made to alter automatically the dilution of samples as tablet strengths vary. Under normal program conditions the system can operate unattended for approximately 18 hr.

Measuring Frequency Characteristics of Linear Two-Port Networks Automatically

This paper presents a new automatic technique for complete linear characterization of transistors and general two-port devices from standard insertion and bridging measurements. This technique includes a calibration sequence and mathematical transformation to provide parameters independent of actual test set impedances, as well as a special hardware design which allows for convenient self-measurement of the test set impedances. Knowledge of these impedances is used to reduce the measured quantities to arbitrary device parameters referenced entirely to a set of calibration standards. This independence of the parameters from the measuring set impedances allows for considerable reduction in the design constraints on the test set impedances and device connecting jigs.

Extracolonic Manifestations of Chronic Ulcerative Colitis

The purpose of this institutional review board-approved, single-blinded, randomized controlled trial was to evaluate the effectiveness of bedside peripherally inserted central catheter (PICC) tip placement using a nonproprietary electocardiogram (EKG) machine and wide-mouth EKG clip connected to the right arm lead and PICC guide wire. The hospital site in this study was an 800-bed community, nonacademic, Magnet hospital in the southeastern United States.All patients who provided consent and were eligible for bedside PICC insertion were randomly assigned to either standard PICC insertion or standard PICC insertion plus EKG guidance. Placement was identified by observing for P wave changes, which indicated PICC tip location in relationship to the sinoatrial node in the superior vena cava. After the PICC lines were placed, 2 radiologists blinded to treatment assignment independently reviewed confirmatory chest radiographs. De-identified data were collected and analyzed.One hundred eighty-seven patients participated in this study. Of all patients, 94.6% had a baseline rhythm with a discernable P wave. The time to insert the PICC while using EKG guidance increased by a mean difference of 9 minutes (P = .001). The time to notification of the floor nurse that the PICC was read by a radiologist and ready to use for infusions was not significant between groups. In the control group, 91.8% of PICC lines were placed to completion at the bedside vs 90.2% in the experimental group (P = .710). PICCs placed with EKG guidance were successfully placed with the first attempt or 1 pass (89%; n = 91) vs PICCs placed without EKG guidance (75%; n = 63; P = .01). Of the control group, 40% (n = 34) and of the experimental group, 48% (n = 49) had PICC lines placed within 1.5 cm of the sinoatrial junction. Of the control group, 53% (n = 45) and of the experimental group, 65% (n = 66) had PICC lines placed within 1.5 cm of the sinoatrial junction to 3.0 cm above the sinoatrial junction (P = .10). Of the control group, 64.8% (n = 55) and of the experimental group, 82.2% (n = 84) had PICC lines placed within 1.5 cm of the sinoatrial junction to 6.0 cm above the sinoatrial junction (P = .3). Of the control group, 7.1% (n = 6) and of the experimental group, 2.9% (n = 3) had PICC lines placed 6.1 cm or more above the sinoatrial junction. Of the control group, 18.8% (n = 16) and of the experimental group, 8.8% (n = 9) had PICC lines placed too deep in the superior vena cava and below 1.6 cm (P < .05). PICCs inserted with or without EKG guidance statistically had the same amount of chest radiograph images performed (P = .083). Three groups reviewed the chest radiographs to determine the PICC tip location and they agreed to the location 82% of the time and a significant positive correlation between all 3 groups existed. The PICC Team subjectively identified 22 patients as obese. No statistical significance was realized among patients not identified as obese vs those identified as obese.The data revealed that the control and experimental groups were equally distributed for baseline demographic characteristics such as sex and age. Importantly, it was determined that 94% of participants had a discernable P wave and were candidates for the use of EKG guidance. The time to insert a PICC line at bedside with the use of EKG guidance increased the procedure time by a mean of 9 minutes; however, the ultimate influence on patient care resulted in a savings of 67 minutes after factoring in an average of 76 minutes for radiograph confirmation. Complications and the need to reposition PICC lines were not found to be significant or vastly different or improved with or without the use of EKG guidance. PICC lines placed with the use of EKG guidance were significantly unlikely to be repositioned. Lastly, it was found that obesity did not play any particular role. Based on these findings, the facility determined that EKG guidance is effective and its use was implemented for all bedside PICC placements in which a P wave was discernable.

MODIFIED SOFT EAR INSERT

Twenty-one selected patients were tested at the Audiology and Speech Correction Center, Walter Reed Army Hospital, with a modified soft plastic ear insert which is fitted into the hearing-aid receiver, and the findings were compared with the results of tests done with a standard soft insert.¹Although there appeared to be no significant difference in speech reception and speech discrimination while the patient was using one or the other insert, the modified insert made manifest the advantages of added comfort to the patient, less fabrication time, and lower cost. Because of these positive results, the improved insert, which is made with an open channel, now replaces its predecessor, the standard soft insert, and is issued at Walter Reed Army Hospital to each patient requiring a hearing aid. Figures 1, 2, and 3 show the three stages of ear inserts, which have been used successively at Walter Reed Army Hospital