Dual-task gait speed assessments with an electronic walkway and a stopwatch in older adults. A reliability study

BACKGROUND/OBJECTIVES

Slow gait speed prospectively predicts elevated risk of adverse events such as falls, morbidity, and mortality. Additionally, gait speed under a cognitively demanding challenge (dual-task gait) predicts further cognitive decline and dementia incidence. This evidence has been mostly collected using electronic walkways; however, not all clinical set ups have an electronic walkway and comparability with simple manual dual-gait speed testing, like a stopwatch, has not yet been examined. Our main objective was to assess concurrent-validity and reliability of gait speed assessments during dual-tasking using a stopwatch and electronic walkway in older adults with mild and subjective cognitive impairment (MCI and SCI).

DESIGN

Cross-sectional, reliability study.

SETTING

Clinic based laboratory at an academic hospital in London, ON, Canada.

PARTICIPANTS

237 walk tests from 34 community-dwelling participants (mean age 71.84 SD 5.38; 21 female - 62%, 13 male - 38%) with SCI and MCI. were included from the Comprehensive Assessment of Neurodegeneration and Dementia (COMPASS-ND) study.

INTERVENTION

Each participant performed seven walk tests: three single gait walks at their normal pace, three dual-task walks (walking and counting backwards by one, by sevens, and naming animals), and one fast walk.

MEASUREMENTS

Gait speed (cm/s) for each walk was measured simultaneously with an electronic walkway (Zeno Mat®) and a handheld stopwatch (Ultrak chronometer®). Dual-task cost (DTC) was calculated for the three individual dual-task walks as [((single gait speed - dual-task gait speed) / single gait speed) ∗ 100]. Level of agreement between the two measurement methods was analyzed using Pearson correlations, paired t-tests, and Bland-Altman plots.

RESULTS

Gait speed was consistently lower when measured with the stopwatch than with the electronic walkway (mean speed difference: 10.6 cm/s ± 5.1, p < 0.001). Calculating DTC, however, yielded very similar results with both methods (mean DTC difference: 0.19 ± 1.18, p = 0.872). The higher the DTC, the closer the measurement between methods.

CONCLUSION

Assessing and calculating DTC with a stopwatch is simple, accessible and reliable. Its validity and reliability were high in this clinical sample of community older adults with SCI and MCI.

Comparison of Human Surrogate Responses in Underbody Blast Loading Conditions

Impact biomechanics research in occupant safety predominantly focuses on the effects of loads applied to human subjects during automotive collisions. Characterization of the biomechanical response under such loading conditions is an active and important area of investigation. However, critical knowledge gaps remain in our understanding of human biomechanical response and injury tolerance under vertically accelerated loading conditions experienced due to underbody blast (UBB) events. This knowledge gap is reflected in anthropomorphic test devices (ATDs) used to assess occupant safety. Experiments are needed to characterize biomechanical response under UBB relevant loading conditions. Matched pair experiments in which an existing ATD is evaluated in the same conditions as a post mortem human subject (PMHS) may be utilized to evaluate biofidelity and injury prediction capabilities, as well as ATD durability, under vertical loading. To characterize whole body response in the vertical direction, six whole body PMHS tests were completed under two vertical loading conditions. A series of 50th percentile hybrid III ATD tests were completed under the same conditions. Ability of the hybrid III to represent the PMHS response was evaluated using a standard evaluation metric. Tibial accelerations were comparable in both response shape and magnitude, while other sensor locations had large variations in response. Posttest inspection of the hybrid III revealed damage to the pelvis foam and skin, which resulted in large variations in pelvis response. This work provides an initial characterization of the response of the seated hybrid III ATD and PMHS under high rate vertical accelerative loading.

Delivery of proteins to CNS as seen and measured by positron emission tomography

Presently, there are no effective treatments for several diseases involving the central nervous system (CNS). While several novel molecular approaches are being developed, many of them require delivery of macromolecular or supramolecular agents to the CNS tissues protected by the blood-brain and blood-arachnoid barriers. A variety of approaches that are being developed for overcoming or bypassing the barriers are based on complex transfer processes. The delivery of biopharmaceuticals and other macromolecules and particulates to the CNS, especially through the leptomeningeal (intrathecal) route, includes a variety of stages, such as leptomeningeal propagation, drainage to the systemic circulation, and penetration into the CNS. The investigation of complex pharmacokinetics that includes convective, as well as diffusional and active transfer processes, greatly benefit from real-time non-invasive in vivo monitoring of the drug transport. Pharmacological positron emission tomography (PET) imaging, which enables such monitoring, plays an increasingly significant role in drug delivery and biopharmacology. PET is a powerful tool for quantitative in vivo tracking of molecules labeled with positron-emitting radionuclides. The high sensitivity, format, and accuracy of the data (similar to those of conventional tissue sampling biodistribution studies) make PET a readily adoptable pharmacological technique. In contrast to the conventional studies, PET also allows for longitudinal nonterminal same-animal studies. The latter may not only improve the data statistics, but also enable preclinical studies (especially in large and/or rare animals) not feasible under the conventional approach. This paper is intended to demonstrate the character of data that can be obtained by PET and to demonstrate how the main patterns of the leptomeningeal route pharmacokinetics can be investigated using this method. Examples of data processing are taken from our recent studies of five model proteins in rats and nonhuman primates.

Death due to bioterrorism-related inhalational anthrax: report of 2 patients

On October 9, 2001, a letter containing anthrax spores was mailed from New Jersey to Washington, DC. The letter was processed at a major postal facility in Washington, DC, and opened in the Senate's Hart Office Building on October 15. Between October 19 and October 26, there were 5 cases of inhalational anthrax among postal workers who were employed at that major facility or who handled bulk mail originating from that facility. The cases of 2 postal workers who died of inhalational anthrax are reported here. Both patients had nonspecific prodromal illnesses. One patient developed predominantly gastrointestinal symptoms, including nausea, vomiting, and abdominal pain. The other patient had a "flulike" illness associated with myalgias and malaise. Both patients ultimately developed dyspnea, retrosternal chest pressure, and respiratory failure requiring mechanical ventilation. Leukocytosis and hemoconcentration were noted in both cases prior to death. Both patients had evidence of mediastinitis and extensive pulmonary infiltrates late in their course of illness. The durations of illness were 7 days and 5 days from onset of symptoms to death; both patients died within 24 hours of hospitalization. Without a clinician's high index of suspicion, the diagnosis of inhalational anthrax is difficult during nonspecific prodromal illness. Clinicians have an urgent need for prompt communication of vital epidemiologic information that could focus their diagnostic evaluation. Rapid diagnostic assays to distinguish more common infectious processes from agents of bioterrorism also could improve management strategies.

Experimental evaluation of a modified Amplatzer duct occluder

The purpose of this study was to evaluate a new device specifically designed for patent ductus arteriosus (PDA) occlusion based on PDA anatomy. Percutaneous closure of aortopulmonary shunts was attempted in 10 dogs. Shunts were surgically created in the location and orientation of PDA. The occlusion prosthesis consisted of a cylindrical frame filled with polyester and a 32 degree angled retention disk. The delivery system of the device included a 6 Fr thin-walled Teflon introducing sheath, an antirotating delivery catheter, and cable. Complete occlusion of the shunt was obtained in nine animals. One animal died before device placement. Temporary hemolysis occurred in one dog after device placement. The disk of device was completely covered by smooth glistening neoendothelium at 1-3 months postmortem examination. None of the devices protruded into the lumen of the aorta. The device is an improvement over the standard Amplatzer duct occluder. The angled retention disk lies flatly against the aortic wall, avoiding turbulence or an aortic pressure gradient.

Mutations in the human delta-sarcoglycan gene in familial and sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality. Two genes have been identified for the X-linked forms (dystrophin and tafazzin), whereas three other genes (actin, lamin A/C, and desmin) cause autosomal dominant DCM; seven other loci for autosomal dominant DCM have been mapped but the genes have not been identified. Hypothesizing that DCM is a disease of the cytoskeleton and sarcolemma, we have focused on candidate genes whose products are found in these structures. Here we report the screening of the human delta-sarcoglycan gene, a member of the dystrophin-associated protein complex, by single-stranded DNA conformation polymorphism analysis and by DNA sequencing in patients with DCM. Mutations affecting the secondary structure were identified in one family and two sporadic cases, whereas immunofluorescence analysis of myocardium from one of these patients demonstrated significant reduction in delta-sarcoglycan staining. No skeletal muscle disease occurred in any of these patients. These data suggest that delta-sarcoglycan is a disease-causing gene responsible for familial and idiopathic DCM and lend support to our "final common pathway" hypothesis that DCM is a cytoskeletalopathy.

The interpretation of cocaine and benzoylecgonine concentrations in postmortem cases

This study examined cocaine and benzoylecgonine concentrations in 100 consecutive deaths where either compound was identified in blood or urine specimens to determine whether any relationship between these concentrations and cause of death can be found. Forty-seven of the 100 cases were deaths attributed to cocaine, narcotic or combined cocaine and narcotic intoxication. There were 13 cases of cocaine intoxication where no psychoactive substance other than ethanol was detected. The mean cocaine concentration in these deaths was 908 ng/ml; three cases had cocaine concentrations greater than 2000 ng/ml, while the other ten cases had cocaine concentrations less than or equal to 700 ng/ml. The mean cocaine concentration in non-cocaine deaths where no psychoactive substance other than ethanol was detected was 146 ng/ml. This difference was not statistically significant. However, the average blood benzoylecgonine concentration in the 13 cocaine deaths was significantly higher than in the 19 non-cocaine deaths. A review of combined cocaine and narcotic deaths suggest that the narcotic is the main causative agent in these deaths.

The role of mycorrhizal fungi and microsites in primary succession on Mount St. Helens

This study was designed to examine the role of vesicular-arbuscular mycorrhizae (VAM) and microsites on the growth of pioneer species. Flat, rill, near-rock, and dead lupine microsites were created in plots in barren areas of the Pumice Plain of Mount St. Helens. VAM propagules were added to the soil in half of the plots. Six pioneer species were planted into both VAM and non-VAM inoculated microsites. Plants in dead lupine microsites were greater in biomass than those in flat, rill, and near-rock microsites. Significant effects of VAM on plant biomass did not occur. Microsites continue to be important to plant colonization on the Pumice Plain, but VAM do not yet appear to play an important role. This may be due to limited nutrient availability and the facultatively mycotrophic nature of the colonizing plant species. It is unlikely that VAM play an important role in successional processes in newly emplaced nutrient-poor surfaces.

Retrospective risk analysis for early heart-related death after cardiomyoplasty. The Worldwide Cardiomyoplasty Group

BACKGROUND

Dynamic cardiomyoplasty is an evolving treatment for heart failure that uses an electrically stimulated latissimus dorsi muscle wrapped around the heart to improve cardiac function. Preoperative patient characteristics and deaths after cardiomyoplasty have been recorded during the past 5 years in a cumulative database representing worldwide experience of 42 medical centers.

METHODS

Statistical models of hazards (monthly death rates) were used to identify risk factors for transiently increased risk of cardiovascular mortality within 2 months after cardiomyoplasty.

RESULTS

Actuarial survival (n = 261) was 88%, 80%, and 76% at 1, 3, and 6 months after cardiomyoplasty, respectively. The peak hazard of 6% dying per month occurred during the first month after the surgical procedure. Lower ejection fraction, increased number of major coronary arteries with > or = 70% stenotic lesions, and lower chronotropic responses during exercise were independent risk factors for the transient increase in early cardiovascular mortality. Early risk of cardiovascular mortality was significantly reduced as centers gained experience with more than 3 patients.

CONCLUSION

Early survival after cardiomyoplasty has improved with experience and might be reduced further by preoperative assessments that identify patients at highest risk.

Norepinephrine increases the economy of pressure development in isolated canine hearts

To test for oxygen wasting by norepinephrine (NE) without relying on normalization by measures of performance such as the pressure-volume area, myocardial oxygen consumption (MVO2) was determined for isovolumic beats at five different left ventricular (LV) end-diastolic volumes (EDV) in nine isolated cross-perfused canine hearts in each of three states: a basal anesthetic state (B); after depression with halothane (H); and after adding NE to increase contractility back to the B state (H+NE). The end-diastolic and peak systolic pressure-volume lines were identical for B and H+NE. The R2 for a linear regression of MVO2 per beat for B vs. H+NE for beats originating at the same EDV and developing similar (within 10%) peak isovolumic pressures for all hearts was 0.85. The slope and intercept were 0.83 and 0.01, which are significantly less than one (P less than 0.001) and greater than zero (P less than 0.001), respectively. These data suggest that NE increases both the economy of pressure development as well as activation energy of an isovolumically contracting LV.

Correlation of endomyocardial biopsy findings with autopsy findings in human cardiac allografts

To determine the reliability of endomyocardial biopsies in the detection of rejection, we took biopsy specimens from 22 autopsied human cardiac allografts by direct visualization. Five specimens were taken from each of four sites: left ventricular free wall, left ventricular septum, right ventricular free wall, and right ventricular septum. The findings in individual biopsy specimens and the summed diagnosis in the five biopsy specimens from each site were graded for rejection by a grading system similar to the Billingham criteria. Grading of the five specimens from each site also was done using criteria recommended by the International Society for Heart and Lung Transplantation. These findings were compared with the rejection grade determined by examination of large tissue sections from the autopsied hearts, used as the standard. Overall, X-Y correlation for single-specimen grading had an r value of 0.792. Grading based on five biopsy specimens from all sites using the modified Billingham criteria grading scheme had an r value of 0.845; the r value was 0.857 for the new grading system. Specificity of findings was high for all grades. Sensitivity of findings, however, was dramatically less for grades 1, 2, and 3. Predictive values for these grades also were less for grades 1, 2, and 3, but to a lesser degree than sensitivity. No difference in detection of rejection was found from specimens taken from different areas of the heart. We conclude that a significant number of hearts with middle grades of rejection may be underestimated by routine biopsies. The criteria for grading of the International Society for Heart and Lung Transplantation had a slight advantage over a more traditional grading system.

AT2433-A1, AT2433-A2, AT2433-B1, and AT2433-B2 novel antitumor antibiotic compounds produced by Actinomadura melliaura. Taxonomy, fermentation, isolation and biological properties

Compounds AT2433-A1 (A1), AT2433-A2 (A2), AT2433-B1 (B1), and AT2433-B2 (B2) were isolated from the cultured broth of Actinomadura melliaura sp. nov. (SCC 1655). Structurally these materials are closely related to rebeccamycin (1), an indolocarbazole antitumor antibiotic. A1, A2, B1, and B2 were active against Staphylococcus aureus A9537, Streptococcus faecalis A20688, Streptococcus faecium (ATCC 9790), Micrococcus lutea (ATCC 9341), Bacillus subtilis (ATCC 6633). A1 and B1 were active against P388 leukemia in mice.

Retinal leakage in retinal vein occlusion: reduction after hyperbaric oxygen

A 54-year-old woman with a history of bilateral central retinal vein occlusion, probably due to an inflammatory process, developed a hemispheric retinal vein occlusion with cystoid macular edema in her only seeing eye. Five months later, in the absence of improvement in vision and macular edema, she received on two occasions a 2-weekly course of twice daily 100% hyperbaric oxygen. After each course retinal leakage, as assessed by vitreous fluorophotometry, decreased from abnormal to the normal range while visual acuity improved by two lines. The possible implications are discussed.

Time dependence of the oxygen cost of force development during systole in the canine left ventricle

To determine whether the oxygen cost of force development in the canine left ventricle is constant throughout systole, we inserted fluid-filled Latex balloons into eight isolated canine left ventricles perfused via support dogs. Balloon volumes were varied by a hydraulic servoactuator designed to withdraw preset volumes rapidly (0.5 ml/msec) beginning at a specified ejection pressure. Oxygen consumption was related to force-time integrals for 9-12 different ejections patterns formed by ejecting three or four different volumes from the same end-diastolic volume, each ejection beginning at three different pressures, isovolumic beats with four or five different end-diastolic volumes, including those used for the ejections. The force-time integral vs. oxygen consumption data are nonlinear for ejections that began at low pressures, with oxygen consumption exceeding that predicted from regression lines fitted to the isovolumic data. This difference appeared to peak at relatively low force-time integrals and then curve back to converge with the isovolumic line. This pattern was not evident for ejections that began late in systole. Although these results suggest that the energy required for force development is greater than expected early in systole, they also are consistent with the hypothesis that oxygen consumption is a function only of instantaneous ventricular volume.