Cardiac arrest diagnostic accuracy of 9-1-1 dispatchers: a prospective multi-center study.

INTRODUCTION: We sought to determine the ability of 9-1-1 dispatchers to accurately determine the presence of out-of-hospital cardiac arrest (OOHCA) over the telephone, and to determine the frequency with which CPR instructions are initiated and chest compressions delivered in patients not in cardiac arrest. METHODS: We conducted a multi-center, prospective cohort study of adult OOHCA patients not witnessed by EMS for which resuscitation was attempted. Dispatchers were not health care professionals and received 6 weeks of training followed by a 6-month preceptorship. We reviewed 9-1-1 call digital recordings for all unconscious patients for which the possibility of cardiac arrest was considered using a piloted standardized data collection sheet. RESULTS: We reviewed 2260 recordings occurring between January 2008 and October 2009. Among those, 1536 were confirmed OOHCA, and 724 were not. Among the 1536 confirmed OOHCA cases, 1012 were recognized by dispatchers and 524 were not. Among the 724 cases not in cardiac arrest, dispatchers suspected cardiac arrest was present in 490 and absent in 234. OOHCA diagnostic accuracy characteristics were: sensitivity 65.9% (95% CI 63.5-68.2%), specificity 32.3% (95% CI 29.0-35.9%), PPV 67.4%, and NPV 30.9%. Dispatchers believed that OOHCA was present in 490/2260 (21.7%) cases when it was not, resulting in 54/490 (11.0%) patients inappropriately receiving chest compressions, or 54/2260 (2.4%) of the whole cohort. CONCLUSIONS: Dispatchers had a fair sensitivity and modest specificity for the recognition of OOHCA. We found a very small number of patients receiving CPR when not in cardiac arrest, supporting the current use of dispatch-assisted CPR instructions.

Strength gains: block versus daily undulating periodization weight training among track and field athletes.

Recently, the comparison of "periodized" strength training methods has been a focus of both exercise and sport science. Daily undulating periodization (DUP), using daily alterations in repetitions, has been developed and touted as a superior method of training, while block forms of programming for periodization have been questioned. Therefore, the purpose of this study is to compare block to DUP in Division I track and field athletes. Thirty-one athletes were assigned to either a 10-wk block or DUP training group in which sex, year, and event were matched. Over the course of the study, there were 4 testing sessions, which were used to evaluate a variety of strength characteristics. Although performance trends favored the block group for strength and rate of force development, no statistically significant differences were found between the 2 training groups. However, statistically different (P ≤ .05) values were found for estimated volume of work (volume load) and the amount of improvement per volume load between block and DUP groups. Based on calculated training efficiency scores, these data indicate that a block training model is more efficient than a DUP model in producing strength gains.

Relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition.

In this study, we examined the relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition. Seventeen untrained males volunteered and underwent a .[Vdot]O2max test, Wingate test, and an exercise-induced muscle damage protocol. Muscle soreness and blood samples were recorded before, immediately after, and 24, 48, 72, and 96 h after exercise. Biopsy samples from the vastus lateralis were collected one week after exercise-induced muscle damage and were assessed for muscle fibre composition. There was no significant relationship (P > 0.05) between muscle fibre composition and creatine kinase activity. A significant positive correlation (P < 0.05) was observed between soreness 48 h after exercise and type II and IIb fibres, and a significant negative correlation (P < 0.05) was observed between soreness 48 h after exercise and type I muscle fibres. Significant positive correlations were observed between soreness 48 h after exercise and the fatigue index, relative average power, and relative anaerobic capacity. Our results suggest that creatine kinase activity following exercise-induced muscle damage may not be related to muscle fibre proportions, and higher post-exercise muscular pain may be related to a predominance of type II muscle fibres and higher anaerobic capabilities.

Interrelationships between muscle structure, muscle strength, and running economy.

PURPOSE: The present study was designed to investigate possible differences in running economy (RE) among elite middle-distance runners by examining muscle structure and maximal isometric force (MVC). METHODS: Ten young male runners ran at six different running speeds. During the running bouts, respiratory gases, and blood lactate were measured. Muscle biopsies were obtained from the vastus lateralis muscle for analyzing fiber type distribution, muscle fiber area, myosin heavy chain (MHC) composition, activities of a number of metabolic enzymes (citrate synthase, lactate dehydrogenase, phosphofruktokinase, and 3-hydroxyacyl-CoA-dehydrogenase), and titin isoforms. RESULTS: Energy expenditure (EE) increased linearly up to the speed of 6.0 m.s. The relative distribution of the MHC isoforms was MHC I: 67.0%, MHC IIA: 31.5%, and MHC IIX: 1.5%. The present results demonstrated that higher the area of Type II fibers, higher the MVC (r = 0.59, P< 0.05). The amount of MHC II correlated inversely with EE when running close to the competition speed (r = -0.61, P< 0.05). Enzyme activities did not correlate significantly with either RE or EE. Titin analysis revealed that a faster-mobility titin band was observed in all subjects, whereas a lower-mobility titin band was observed only in the most economical runner. CONCLUSION: Differences in RE among homogeneous group of middle-distance runners were observed at various running speeds. This may partly be explained by differences in muscle fiber distribution, MHC composition, and titin isoforms.