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Biomedical subjects

David Hostler

Publications and source records attributed to David Hostler.

At least 19 recordsLinked to original sources
PubMed2026

The effect of drysuit diving in warm water on body temperature and post immersion orthostatic hypotension.

INTRODUCTION: Warm-water diving can limit heat dissipation, particularly when performed in fully encapsulating protective gear, leading to substantial thermal and cardiovascular strain that may impair diver safety. Following immersion, removal of hydrostatic support combined with heat-induced vasodilation may reduce central blood volume and increase susceptibility to orthostatic intolerance during egress and recovery. The extent to which this thermal strain impairs post-immersion orthostatic tolerance remains unknown. METHODS: Four randomised, crossover immersion trials were conducted at 28&#xb0;C, 33&#xb0;C, 38&#xb0;C without precooling (38&#xb0;C), and 38&#xb0;C with precooling (38&#xb0;C + Cool), with subjects wearing fully encapsulating dive gear. Subjects walked for up to 60 minutes at approximately 50% of O2max heart rate (HR) or until core temperature (Tc) reached 38.5&#xb0;C, or they voluntarily stopped. Tc, HR, and perceptual measures were recorded every 10 minutes. Orthostatic tolerance was assessed after immersion via a 70&#xb0; head-up tilt test. RESULTS: Eight healthy adults completed all aspects of the study. Tc and HR were higher during both 38&#xb0;C conditions compared with 28&#xb0;C and 33&#xb0;C (all P < 0.01) with no differences between 38&#xb0;C and 38&#xb0;C + Cool. Sweat loss exceeded 1.2 (SD 0.67) L&#x22c5;h-1 in both 38&#xb0;C conditions compared with &#x2264; 0.3 (0.32) L&#x22c5;h-1 at 28&#xb0;C and 33&#xb0;C (P < 0.01). Survival analysis showed orthostatic tolerance decreased with increasing thermal stress (log-rank P = 0.027; trend P = 0.003). Precooling did not reduce peak Tc or HR, nor did it improve tolerance time in 38&#xb0;C water. CONCLUSIONS: Encapsulated warm-water diving causes heat stress and cardiovascular strain that persists after immersion, impairing orthostatic tolerance. Precooling does not significantly reduce these outcomes.

Humans↗
PubMed2006

Does the type of out-of-hospital airway interfere with other cardiopulmonary resuscitation tasks?

BACKGROUND: Out-of-hospital rescuers often perform tracheal intubation (TI) prior to other cardiopulmonary resuscitation (CPR) interventions. TI is a complex and error-prone procedure that may interfere with other key resuscitation tasks. We compared the effects of TI versus esophageal tracheal combitube (ETC) insertion on the accomplishment of other interventions during simulated cardiopulmonary resuscitation. METHODS: In this prospective trial using a human simulator, two-paramedic teams simulated resuscitation of a ventricular fibrillation cardiopulmonary arrest using standard Advanced Cardiac Life Support guidelines. In each of two trials, teams used either TI or ETC as the primary airway device. Following delivery of three rescue shocks, we measured time intervals to successful airway placement, intravenous (IV) line insertion, drug administration, delivery of fourth rescue shock and completion of all four tasks. We also measured the total time without chest compressions. We compared task completion times using non-parametric statistics (Wilcoxon signed-ranks test) with a Bonferroni-adjusted p-value of 0.008. RESULTS: Twenty teams each completed two scenarios. Participants required a median of 172.5 s (IQR: 146.5-225.5) to accomplish all four tasks. Elapsed time to airway placement was significantly less for ETC than TI (median difference 26.5 s (IQR 13-44.5), p=0.002). Time without chest compressions was less for ETC than TI (median difference 8.5 s (IQR 2.5-23.5), p=0.005). There were no differences between ETC and TI in times to IV placement (median difference 23.5 s (IQR -20 to 61), p=0.11), drug delivery (39.5 s (IQR -18 to 63), p=0.07), delivery of fourth rescue shock (39.5 s (IQR -21.5 to 87.5), p=0.07) or completion of all four tasks (33 s (IQR -11 to 74.5), p=0.08). CONCLUSION: Compared with TI, ETC reduced time to airway placement and time without chest compressions, but did not affect elapsed times to accomplish other interventions. Additional time differences may be realized if translated to clinical out-of-hospital conditions.

Cardiopulmonary Resuscitation↗
PubMed2006

Usefulness of vasopressin administered with epinephrine during out-of-hospital cardiac arrest.

Vasopressin administration has been suggested during cardiopulmonary resuscitation, and a previous clinical trial has suggested that vasopressin is most effective when administered with epinephrine. Adult subjects (n = 325) who received > or =1 dose of intravenous epinephrine during cardiopulmonary resuscitation for nontraumatic, out-of-hospital cardiac arrest were randomly assigned to receive 40 IU of vasopressin (n = 167) or placebo (n = 158) as soon as possible after the first dose of epinephrine. The rate of return of pulses was similar between the vasopressin and placebo groups (31% vs 30%), as was the presence of pulses at the emergency department (19% vs 23%). No subgroup appeared to be differentially affected, and no effect of vasopressin was evident after adjustment for other clinical variables. Additional open-label vasopressin was administered by a physician after the study drug for 19 subjects in the placebo group and 27 subjects in the vasopressin group. Results were similar if these subjects were excluded or were assigned to an actual drug received. Survival duration for subjects admitted to the hospital did not differ between groups. In conclusion, vasopressin administered with epinephrine does not increase the rate of return of spontaneous circulation.

Aged↗
PubMed2006

Inter-rater reliability for witnessed collapse and presence of bystander CPR.

OBJECTIVE: Witnessed collapse and bystander CPR are the variables most frequently associated with good outcome from out-of-hospital cardiac arrest (OOHCA). The reliability of abstracting witnessed collapse and bystander CPR from prehospital Emergency Medical Services (EMS) patient care records (PCRs) is not known. We sought to determine the inter-rater reliability for different methods of ascertaining and defining witnessed collapse and performance of bystander CPR. METHODS: A sample of 100 PCRs for patients with OOHCA was selected at random from a pool of 325 PCRs between May 2003 and January 2005. Paramedics used a drop down menu to indicate witnessed collapse and bystander CPR, and completed a narrative description of the event. An on-scene EMS physician also completed a data sheet. The PCR was examined by two separate evaluators to determine the presence of witnessed collapse and bystander CPR. A consensus was reached by three other reviewers using all available data sources. Inter-rater agreement was quantified using the unweighted kappa statistic. RESULTS: For witnessed collapse, there is substantial agreement between the following: individual evaluators (kappa=0.76, S.D.=0.07), individual evaluators and consensus group (kappa=0.61, S.D.=0.07 and 0.66, S.D.=0.07), and physician and consensus group (kappa=0.68, S.D.=0.08). Agreement between individual evaluators and the physician was fair to moderate (kappa=0.38, S.D.=0.07 and 0.44, S.D.=0.07). Agreement between individual evaluators, physician, consensus group and the PCR drop down menu was fair to moderate (kappa range 0.33, S.D.=0.09 to 0.54, S.D.=0.09). For bystander CPR, there is substantial agreement between the individual evaluators and the consensus group (kappa=0.64, S.D.=0.07 and 0.63, S.D.=0.06) and between the physician and the consensus group (kappa=0.61, S.D.=0.08). Agreement between the two individual evaluators is moderate (kappa=0.59, S.D.=0.07). Agreement between the physician and individual evaluators is fair (kappa=0.36, S.D.=0.07 and 0.38, S.D.=0.07). The PCR drop down menu had moderate to substantial agreement with the individual evaluators, physician, and consensus group (kappa range 0.50, S.D.=0.09 to 0.75, S.D.=0.09). CONCLUSIONS: Determination of witnessed collapse and bystander CPR during OOHCA may be less reliable than previously thought, and differences between methods of rating could influence study results.

Adult↗
PubMed2005

Quality of BLS decreases with increasing resuscitation complexity.

OBJECTIVE: Multiple procedures performed in parallel may cause each procedure to be performed less effectively than if performed in isolation. BLS performed by prehospital providers potentially includes artificial ventilations, chest compressions, and application of an automated external defibrillator (AED). This study examines the effectiveness of artificial ventilation and chest compressions both with and without an AED. METHODS: Thirty-six prehospital providers participated in a prospective observational study. Tested in pairs (n=18), subjects randomly completed three, 6-min scenarios [apneic patient with a pulse (VENT), a pulseless patient (CPR), and a pulseless patient with an AED available (CPR+AED)]. A full-torso manikin capable of generating a carotid pulse was connected to a computer to record number of ventilations, tidal volume, flow rate, number of compressions, and compression depth. Data were analyzed by t-test, ANOVA, and Mann-Whitney U-test. RESULTS: Artificial ventilation performed in isolation provided more correct ventilations than during CPR or CPR+AED (25.7%, 14.2%, 13.7%, p=0.02). Fewer ventilations were delivered during CPR and CPR+AED (p=0.03). More compressions were delivered with CPR alone vs. CPR+AED (51.9, 35.7 min(-1), p=0.00). More correct compressions were delivered during CPR alone vs. CPR+AED (p=0.05). CONCLUSIONS: Both the quality and quantity of BLS decreases as the number of procedures performed simultaneously increases. Further decrements might occur when ALS skills enter into resuscitation. These results suggest a need to automate and/or prompt the performance of BLS to optimize resuscitation.

Adult↗
PubMed2005

A comparison of CPR delivery with various compression-to-ventilation ratios during two-rescuer CPR.

BACKGROUND: The number of chest compressions required for optimal generation of coronary perfusion pressure remains unknown although studies examining compression-to-ventilation ratios higher than 15:2 (C:V) in animals have reported higher C:V to be superior for return of spontaneous circulation and neurologic outcome. We examined human performance of two-rescuer CPR using various C:V. METHODS: Thirty six EMT-Basic students in their final week of training performed two-rescuer CPR using C:V of 15:2, 30:2, 40:2, 50:2, and 60:2 on a recording resuscitation manikin. Compression and ventilation variables were recorded by computer while the number of pauses for ventilations and the hands-off time (time not spent performing chest compressions) were abstracted by hand. Data were analyzed by ANOVA and significant differences from the standard treatment of C:V = 15:2 were assessed by Tukey's HSD post hoc test. FINDINGS: The number of compressions delivered per minute increased with increasing C:V while the hands-off time and pauses for ventilations decreased. All comparisons were significantly different from C:V = 15:2 (P < 0.001). The ventilation numbers decreased with increasing C:V although mean minute volume exceeded 1l for all C:V. INTERPRETATION: A 15:2 compression-to-ventilation ratio when performed during two-rescuer CPR results in 26s of hands off time each minute while only delivering 60 compressions. Alternative C:V ratios of 30:2, 40:2, 50:2, and 60:2 all exceed the AHA recommended 80 compressions/min while still delivering a minute volume in excess of 1l.

Cardiopulmonary Resuscitation↗
PubMed2005

Back strength and flexibility of EMS providers in practicing prehospital providers.

In the execution of prehospital care duties, an EMS provider may be required to carry equipment and patients over long distances or over multiple flights of stairs at any time of the day. At a minimum, a prehospital provider must have sufficient lower back strength and hamstring flexibility to prevent musculoskeletal injury while lifting. This study administered fitness assessments related to the occupational activities of the prehospital provider with the purpose of describing the incidence of occupational back injury and percentage of providers with known risk factors for back injury. Ninety subjects were tested during a regional EMS conference. Men were significantly taller and heavier than women and had significantly less hamstring flexibility. Body Mass Index was 30.7 +/- 7.2 in men and 28 +/- 5.7 in women. However, no significant differences were noted in an extension test of back strength. When surveyed, 47.8% of subjects reported a back injury in the previous 6 months but only 39.1% of these injuries were sustained while performing EMS duties. While only 13% of these injuries resulted in missed work, 52.2% reported their injury interfered with their daily activities. In spite of the physical nature of the profession, EMS providers in our sample were significantly overweight according to their Body Mass Index and may lack sufficient back strength and flexibilityfor safe execution of their duties. This group of professionals may be at risk for occupational injury and should be targeted for interventions to improve strength and flexibility.

Adult↗
PubMed2005

Differential effects of out-of-hospital interventions on short- and long-term survival after cardiopulmonary arrest.

AIM: The aim of this study was to describe the relationship between prehospital clinical variables, interventions and survival time after cardiac arrest and to determine whether various factors affect the risk of death differently at early and late time periods. METHODS: Time-to-death (days) after collapse was identified using the paramedic record, the social security death index or obituaries for adult (> or =18 years) out-of-hospital cardiac arrest (OOHCA) cases from Pittsburgh, Pennsylvania between 1998 and 2002. Clinical prehospital variables included age of patient, sex, witnessed collapse, bystander CPR, use of an automated external defibrillator (AED), initial ECG rhythm, medications and response time intervals. We used Cox regression with time varying coefficients to describe the effects of each covariate separately upon short-term (on day 1) and long-term (after day 1) survival. RESULTS: Of 1496 adult patients, overall mortality was 89.5%. The majority (75%) of deaths occurred on day 1. Of the 1339 deaths, 1213 (90.6%) occurred by day 3, 1272 (95.0%) occurred by day 7 and 1299 (97.0%) occurred by day 14. Witnessed collapse (hazard ratio 0.85; 95% CI: 0.75-0.97) or the use of epinephrine (adrenaline) (1.57; 1.20-2.07), lidocaine (0.78; 0.66-0.91) or dopamine (0.75; 0.56-1.00) were independently associated with risk of death on day 1 (day of collapse). Epinephrine use (1.84; 1.23-2.78) and age (1.02; 1.01-1.03) were independently associated with risk of death after day 1. The proportional hazards assumption was satisfied. CONCLUSIONS: Survival after out-of-hospital cardiac was characterized by a large number of deaths on day 1. Most subsequent deaths were identified within 14 days after collapse. Prehospital factors have markedly different relationships with short- and long-term survival. Linkage between prehospital intervention and short- and long-term outcomes must consider the survival time characteristics of this population.

Adult↗
PubMed2005

Procedural experience with out-of-hospital endotracheal intubation.

OBJECTIVE: Out-of-hospital rescuers likely need regular clinical experience to perform endotracheal intubation (ETI) in a safe and effective manner. We sought to determine the frequency of ETI performed by individual out-of-hospital rescuers. DESIGN: Analysis of an administrative database of all emergency medical services (EMS) patient care reports in Pennsylvania. SETTING: Commonwealth of Pennsylvania from January 1 to December 31, 2003. SUBJECTS: EMS advanced life support rescuers (paramedics, prehospital nurses, and EMS physicians) who reported at least one patient contact during the study period. INTERVENTIONS: None. MEASUREMENTS: We calculated individual rescuer ETI frequency and opportunity. We evaluated relationships between ETI frequency and the number of patient contacts. We also examined the relationship with practice setting (air medical vs. ground rescuers and urban vs. rural rescuers). MAIN RESULTS: In 1,544,791 patient care reports, 11,484 ETIs were reported by 5,245 out-of-hospital rescuers. The median ETI frequency was one (interquartile range, 0-3; range, 0-23). Of 5,245 rescuers, >67% (3,551) performed two or fewer ETIs, and >39% (2,054) rescuers did not perform any ETIs. The median number of ETI opportunities was three (interquartile range, 0-6; range, 0-76). ETI frequency was associated with patient volume (Spearman's rho = 0.67) and was higher for air medical (p = .006) and urban (p < .0001) rescuers. ETI frequency was not associated with response (Spearman's rho = -0.01) or transport (Spearman's rho = -0.06) times. CONCLUSIONS: Out-of-hospital ETI, an important and difficult resuscitation intervention, is an uncommon event for most rescuers.

Clinical Competence↗
PubMed2004

Prevalence of troponin-T elevation during out-of-hospital cardiac arrest.

To determine the prevalence of myocardial ischemia before out-of-hospital cardiac arrest (OOHCA), we determined the prevalence of elevated cardiac troponin-T levels in subjects at the time of OOHCA. Plasma was collected from 63 subjects during resuscitation. Troponin levels were elevated (> or =0.03 ng/ml) in 25 subjects (39.7%; 95% confidence intervals [CI] 29% to 52%). Increasing age was associated with elevated troponin (OR 1.10; 95% CI 1.04 to 1.17). Elevated troponin levels did not reliably predict short-term outcome. Because troponin increases hours after the onset of ischemia, these data reveal that about 40% of OOHCA cases can undergo intervention before collapse.

Adult↗
PubMed2004

Vasopressin administered with epinephrine is associated with a return of a pulse in out-of-hospital cardiac arrest.

OBJECTIVE: Recent data suggest that using vasopressin in combination with epinephrine (adrenaline) may improve treatment of out-of-hospital cardiac arrest. This study examined local experience with the combination of epinephrine and vasopressin administration. METHODS: Data were obtained from an urban, municipal emergency medical service that does not include vasopressin in its formulary. A physician is dispatched to the scene of all cardiac arrest patients treated by this system. Vasopressin could be administered in addition to epinephrine to subjects with out-of-hospital cardiac arrest by the on-scene physician. Demographic information, drug administration and return of pulses were abstracted from patient care records for a 1-year interval. Multivariate logistic regression was used to assess the relationship between vasopressin use and outcomes. RESULTS: During the study period, data were available for 298 subjects receiving epinephrine-only (n=231, 78%), a combination of 40 IU vasopressin and epinephrine (n=37, 12%) or no vasopressor drugs (n=30, 10%). Among patients receiving vasopressor drugs, pulse was restored for 74 subjects (28%), and 56 subjects (21%) had a pulse on arrival at the hospital. Return of pulses was associated with witnessed collapse, bystander CPR, and an initial ECG rhythm of ventricular fibrillation or tachycardia. Subjects receiving vasopressin and epinephrine were more likely to have a return of pulses during the resuscitation (LR: 2.73; 95% CI: 1.24, 6.03) and at hospital arrival (3.85; 1.71, 8.65) than subjects treated with epinephrine alone. CONCLUSIONS: There is an association between using vasopressin in combination with epinephrine and restoration of circulation after out-of-hospital cardiac arrest.

Aged↗
PubMed2003

Analysis of pesticide residues on museum objects repatriated to the Hupa tribe of California.

In the past, it was common practice for museum professionals and private collectors to apply a variety of pesticide agents to objects in their collections to preserve them from depredations by microorganisms, fungi, and other pests. The Native American Graves Repatriation and Protection Act allows federally recognized tribes to request that museums return objects taken from their ancestors. Given that poor records were kept on the treatment of individual objects, it is unknown whether specific objects are contaminated with these pesticide agents. Although chemical analysis represents the only reliable means to determine the types and levels of pesticides on these objects, surprisingly few publications document the extent of this contamination in museum collections. This paper reports on the determination of arsenic, mercury, and several organic pesticides on 17 objects that were recently repatriated to the Hupa tribe in northern California. Four samples were taken from each object: two for arsenic and mercury analysis via flame atomic absorption spectrophotometry and two for organic pesticide analysis via gas chromatography/mass spectrometry. Percent levels (wt/wt) of mercury were detected on many samples, and 0.001 to 0.183% (wt/wt) levels of p-dichlorobenzene, naphthalene, thymol, lindane, and/or DDT were detected on many of the samples. These results indicate that Hupa tribal members should not wear these objects in religious ceremonies, proper precautions should be followed when dealing with potentially contaminated objects, and that more serious consideration should be given to this issue at a national level.

Arsenic↗
PubMedDate not supplied

Comparison of times to intubate a simulated trauma patient in two positions.

BACKGROUND: The nature of the trauma patient's injuries may compromise the airway and ultimately lead to death or neurological devastation. The same injuries complicate protecting the airway in these patients by preventing manipulation of the cervical spine for direct laryngoscopy. A recent study has shown that misplaced endotracheal tubes occur significantly more often in trauma patients than in medical patients. OBJECTIVES: The authors hypothesized that elevating the long spine board would reduce the amount of time required for paramedics to intubate a simulated trauma patient. METHODS: Paramedics from an urban emergency medical services division were given up to two opportunities to intubate a manikin in a type I ambulance in each of two positions in random order: supine and with the head elevated. The manikin was secured to a long spine board with three straps, a semi-rigid cervical collar, and a cervical immobilization device. An investigator maintained cervical spine alignment and provided cricoid pressure. The elevated position was accomplished by raising the head of the stretcher 27 degrees, resulting in 7 degrees of spine board elevation. Each attempt was timed. If the first attempt was unsuccessful, the times for both the first and second attempts were totaled to determine the total time required for intubation. Times for successful intubation in each position were compared with a Mann-Whitney test. First-attempt success rates for each position were compared with chi2 analysis. Multinomial regression was used to determine whether experience, paramedic height, or previous intubation success influenced intubation time in either position. RESULTS: Fifty-five paramedics provided informed consent and completed the study. Average time to intubate the supine manikin was significantly longer than needed to intubate the head-elevated manikin (35.6 +/- 19.0 seconds vs 27.9 +/- 12.8 seconds, p = 0.025). The manikin was successfully intubated on the first attempt 84% in the supine position and 95% in the head-elevated position (p = 0.200). Regression analysis identified intubation position as the only significant predictor of intubation time (p = 0.007). CONCLUSIONS: Modest elevation of the head of an immobilized patient appears to allow more rapid intubation. With the spine board properly secured to the stretcher, this technique potentially offers improved intubation time without additional cost or equipment.

Airway Obstruction↗
PubMedDate not supplied

Pneumococcal vaccination: an opportunity for emergency medical services.

This report examines the literature regarding pneumococcal disease and the current state of pneumococcal vaccination. Improvements in medical care have reduced the number of deaths from pneumococcal disease. However, vaccination is still the most effective measure. The U.S. Department of Health and Human Services, through the Healthy People 2000 and Healthy People 2010 reports, have recommended widespread pneumococcal vaccination practices. In spite of this, vaccination rates remain low among all segments of the population, with minorities and groups at risk for pneumococcal disease the most neglected. The authors propose implementation of emergency medical services (EMS)-delivered vaccination against pneumococcal disease. The epidemiology of pneumococcal disease is presented. The efficacy, availability, and use recommendations for the vaccine are described within this report. Finally, the benefits and possible implementation strategies for EMS delivery are detailed.

Aged↗