Biomedical subjects

Helge Myklebust

Publications and source records attributed to Helge Myklebust.

13 recordsLinked to original sources

PubMed2006

Quality of cardiopulmonary resuscitation among highly trained staff in an emergency department setting.

BACKGROUND: Recent reports have highlighted the poor standard of cardiopulmonary resuscitation (CPR) achieved by health care professionals in diverse situations. We explored what can be achieved in an emergency department by highly trained permanent staff. METHODS: In a prospective observational study conducted from June 1, 2002, to August 31, 2005, 80 of 213 patients requiring CPR and admitted to the emergency department of a tertiary care hospital were eligible for study participation. Owing to several logistic problems with CPR, 133 patients could not be studied. The CPR team consisted of emergency- and critical care-trained physicians with more than 10 years of acute care experience, most of whom were instructors of European Resuscitation Council courses in basic and advanced life support. A specially designed defibrillator was used to assess the quality of CPR. RESULTS: For 80 patients, 95 data sets were available for analysis, yielding a total of 1065 minutes of cardiac arrest time. Chest compressions were performed at a rate of 114 (95% confidence interval [CI], 112-116) per minute, resulting in a mean of 96 (95% CI, 93-99) delivered chest compressions per minute. We further observed a mean hands-off ratio of 12.7% (95% CI, 12.3%-13.1%), and the hands-off ratio was linearly associated with the duration of CPR (R(2) = 0.95; mean, 4.3% increments per 5-10 minutes; P<.001). Patients were hyperventilated with a median of 18 (interquartile range, 14-24) ventilations per minute. CONCLUSIONS: Highly trained professionals in an emergency department can achieve appropriate chest compression rates during CPR with a low hands-off ratio. Increased attention must be paid in all situations to the avoidance of hyperventilation.

Aged↗

PubMed2006

Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study.

AIMS: To compare quality of CPR during out-of-hospital cardiac arrest with and without automated feedback. MATERIALS AND METHODS: Consecutive adult, out-of-hospital cardiac arrests of all causes were studied. One hundred and seventy-six episodes (March 2002-October 2003) without feedback were compared to 108 episodes (October 2003-September 2004) where automatic feedback on CPR was given. Automated verbal and visual feedback was based on measured quality with a prototype defibrillator. Quality of CPR was the main outcome measure and survival was reported as specified in the protocol. RESULTS: Average compression depth increased from (mean +/- S.D.) 34 +/- 9 to 38 +/- 6 mm (mean difference (95% CI) 4 (2, 6), P < 0.001), and median percentage of compressions with adequate depth (38-51 mm) increased from 24% to 53% (P < 0.001, Mann-Whitney U-test) with feedback. Mean compression rate decreased from 121 +/- 18 to 109 +/- 12 min(-1) (difference -12 (-16, -9), P = 0.001). There were no changes in the mean number of ventilations per minute; 11 +/- 5 min(-1) versus 11 +/- 4 min(-1) (difference 0 (-1, 1), P = 0.8) or the fraction of time without chest compressions; 0.48 +/- 0.18 versus 0.45 +/- 0.17 (difference -0.03 (-0.08, 0.01), P = 0.08). With intention to treat analysis 7/241 control patients were discharged alive (2.9%) versus 5/117 with feedback (4.3%) (OR 1.5 (95% CI; 0.8, 3), P = 0.2). In a logistic regression analysis of all cases, witnessed arrest (OR 4.2 (95% CI; 1.6, 11), P = 0.004) and average compression depth (per mm increase) (OR 1.05 (95% CI; 1.01, 1.09), P = 0.02) were associated with rate of hospital admission. CONCLUSIONS: Automatic feedback improved CPR quality in this prospective non-randomised study of out-of-hospital cardiac arrest. Increased compression depth was associated with increased short-term survival. TRIAL REGISTRATION: ClinicalTrials.gov (NCT00138996), http://www.clinicaltrials.gov/.

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PubMed2006

Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest.

BACKGROUND: Cardiopulmonary resuscitation (CPR) and electrical defibrillation are the primary treatment options for ventricular fibrillation (VF). While recent studies have shown that providing CPR prior to defibrillation may improve outcomes, the effects of CPR quality remain unclear. Specifically, the clinical effects of compression depth and pauses in chest compression prior to defibrillation (pre-shock pauses) are unknown. METHODS: A prospective, multi-center, observational study of adult in-hospital and out-of-hospital cardiac resuscitations was conducted between March 2002 and December 2005. An investigational monitor/defibrillator equipped to measure compression characteristics during CPR was used. RESULTS: Data were analyzed from 60 consecutive resuscitations in which a first shock was administered for VF. The primary outcome was first shock success defined as removal of VF for at least 5s following defibrillation. A logistic regression analysis demonstrated that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio 1.86 for every 5s decrease; 95% confidence interval 1.10-3.15) and higher mean compression depth during the 30s of CPR preceding the pre-shock pause (adjusted odds ratio 1.99 for every 5mm increase; 95% confidence interval 1.08-3.66). CONCLUSIONS: The quality of CPR prior to defibrillation directly affects clinical outcomes. Specifically, longer pre-shock pauses and shallow chest compressions are associated with defibrillation failure. Strategies to correct these deficiencies should be developed and consideration should be made to replacing current-generation automated external defibrillators that require long pre-shock pauses for rhythm analysis.

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PubMed2006

Thoracic impedance changes measured via defibrillator pads can monitor ventilation in critically ill patients and during cardiopulmonary resuscitation.

OBJECTIVE: Monitoring of ventilation performance during cardiopulmonary resuscitation would be desirable to improve the quality of cardiopulmonary resuscitation. To investigate the potential for measuring ventilation rate and inspiration time, we calculated the correlation in waveform between transthoracic impedance measured via defibrillator pads and tidal volume given by a ventilator. DESIGN: Clinical study. SETTING: Emergency department of a tertiary care university hospital. PATIENTS: A convenience sample of mechanical ventilated patients (n = 32), cardiac arrest patients (n = 20), and patients after restoration of spontaneous circulation (n = 31) older than 18 were eligible. INTERVENTIONS: The Heartstart 4000SP defibrillator (Laerdal Medical Cooperation, Stavanger, Norway) with additional capabilities of recording thoracic impedance changes was used. MEASUREMENTS AND MAIN RESULTS: The relationship between impedance change and tidal volume (impedance coefficient) was calculated. The mean (sd) correlations between the impedance waveform and the tidal volume waveform in the patient groups studied were .971 (.027), .969 (.032), and .967 (.035), respectively. The mean (sd) impedance coefficient for all patients in the study was .00194 (.0078) Omega/mL, and the mean (sd) specific (weight-corrected) impedance coefficient was .152 (.048) Omega/kg/mL. The measured thorax impedance change for different tidal volumes (400-1000 mL) was approximately linear. CONCLUSIONS: The impedance sensor of a defibrillator is accurate in identifying tidal volumes, when chest compressions are interrupted. This also allows quantifying ventilation rates and inspiration times. However this technology, at its present state, provides only limited practical means for exact tidal volume estimation.

Adult↗

PubMed2006

Difficulty of cardiac arrest rhythm identification does not correlate with length of chest compression pause before defibrillation.

OBJECTIVE: Performing high-quality cardiopulmonary resuscitation immediately before electrical defibrillation serves as an important predictor of shock success. Long preshock pauses in cardiopulmonary resuscitation frequently occur, as noted by recent clinical investigations. We sought to determine whether these long pauses were due to difficulties in identifying shockable rhythms or rather due to local factors during resuscitation attempts. DESIGN: Prospective in-hospital study of cardiac arrest resuscitation attempts coupled with a retrospective review of preshock pause rhythms by 12 trained providers. Reviewers scored rhythms by ease of identification using a discrete Likert scale from 1 (most difficult to identify) to 5 (easiest to identify). The resuscitation cohort was organized into preshock pause-duration quartiles for statistical analysis. Resident physicians were then surveyed regarding human factors affecting preshock pauses. RESULTS: A total of 118 preshock pauses from 45 resuscitation episodes were collected. When evaluated by quartiles of preshock pause duration, difficulty of rhythm identification did not correlate with increasing pause time. In fact, the opposite was found (longest preshock pause quartile of 23.8-60.2 secs vs. shortest pause quartile of 1.1-7.9 secs; rhythm difficulty scores, 3.2 vs. 3.0; p = .20). When 29 resident physicians who recently served on resuscitation teams were surveyed, 18 of 29 (62.1%) attributed long pauses to lack of time sense during resuscitation, and 16 of 29 (55.2%) thought that room crowding prevented rapid defibrillation. CONCLUSIONS: Long cardiopulmonary resuscitation pauses before defibrillation are likely due to human factors during the resuscitation and not due to inherent difficulties with rhythm identification. This preliminary work highlights the need for more research and training in the area of team performance and human factors during resuscitation.

Cardiopulmonary Resuscitation↗

PubMed2005

Quality of cardiopulmonary resuscitation during out-of-hospital cardiac arrest.

CONTEXT: Cardiopulmonary resuscitation (CPR) guidelines recommend target values for compressions, ventilations, and CPR-free intervals allowed for rhythm analysis and defibrillation. There is little information on adherence to these guidelines during advanced cardiac life support in the field. OBJECTIVE: To measure the quality of out-of-hospital CPR performed by ambulance personnel, as measured by adherence to CPR guidelines. DESIGN AND SETTING: Case series of 176 adult patients with out-of-hospital cardiac arrest treated by paramedics and nurse anesthetists in Stockholm, Sweden, London, England, and Akershus, Norway, between March 2002 and October 2003. The defibrillators recorded chest compressions via a sternal pad fitted with an accelerometer and ventilations by changes in thoracic impedance between the defibrillator pads, in addition to standard event and electrocardiographic recordings. MAIN OUTCOME MEASURE: Adherence to international guidelines for CPR. RESULTS: Chest compressions were not given 48% (95% CI, 45%-51%) of the time without spontaneous circulation; this percentage was 38% (95% CI, 36%-41%) when subtracting the time necessary for electrocardiographic analysis and defibrillation. Combining these data with a mean compression rate of 121/min (95% CI, 118-124/min) when compressions were given resulted in a mean compression rate of 64/min (95% CI, 61-67/min). Mean compression depth was 34 mm (95% CI, 33-35 mm), 28% (95% CI, 24%-32%) of the compressions had a depth of 38 mm to 51 mm (guidelines recommendation), and the compression part of the duty cycle was 42% (95% CI, 41%-42%). A mean of 11 (95% CI, 11-12) ventilations were given per minute. Sixty-one patients (35%) had return of spontaneous circulation, and 5 of 6 patients discharged alive from the hospital had normal neurological outcomes. CONCLUSIONS: In this study of CPR during out-of-hospital cardiac arrest, chest compressions were not delivered half of the time, and most compressions were too shallow. Electrocardiographic analysis and defibrillation accounted for only small parts of intervals without chest compressions.

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PubMed2005

Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest.

CONTEXT: The survival benefit of well-performed cardiopulmonary resuscitation (CPR) is well-documented, but little objective data exist regarding actual CPR quality during cardiac arrest. Recent studies have challenged the notion that CPR is uniformly performed according to established international guidelines. OBJECTIVES: To measure multiple parameters of in-hospital CPR quality and to determine compliance with published American Heart Association and international guidelines. DESIGN AND SETTING: A prospective observational study of 67 patients who experienced in-hospital cardiac arrest at the University of Chicago Hospitals, Chicago, Ill, between December 11, 2002, and April 5, 2004. Using a monitor/defibrillator with novel additional sensing capabilities, the parameters of CPR quality including chest compression rate, compression depth, ventilation rate, and the fraction of arrest time without chest compressions (no-flow fraction) were recorded. MAIN OUTCOME MEASURE: Adherence to American Heart Association and international CPR guidelines. RESULTS: Analysis of the first 5 minutes of each resuscitation by 30-second segments revealed that chest compression rates were less than 90/min in 28.1% of segments. Compression depth was too shallow (defined as <38 mm) for 37.4% of compressions. Ventilation rates were high, with 60.9% of segments containing a rate of more than 20/min. Additionally, the mean (SD) no-flow fraction was 0.24 (0.18). A 10-second pause each minute of arrest would yield a no-flow fraction of 0.17. A total of 27 patients (40.3%) achieved return of spontaneous circulation and 7 (10.4%) were discharged from the hospital. CONCLUSIONS: In this study of in-hospital cardiac arrest, the quality of multiple parameters of CPR was inconsistent and often did not meet published guideline recommendations, even when performed by well-trained hospital staff. The importance of high-quality CPR suggests the need for rescuer feedback and monitoring of CPR quality during resuscitation efforts.

Adult↗

PubMed2005

Twelve-month retention of CPR skills with automatic correcting verbal feedback.

AIM: To evaluate the retention of CPR skills 12 months after initial training, using a manikin equipped with a computer-based voice advisory feedback system. METHODS: Thirty-five volunteers had individual 20 min training sessions without an instructor on a manikin with computer-based voice advisory feedback. The feedback depended on the performance as measured by the manikin computer system versus set limits for ventilation and compression variables. Twelve of the volunteers received additional ten 3-min self-training sessions during the following month making a total of 50 min training. All ventilation and compression variables when the volunteers were tested before, immediately after and 6 months after training have previously been reported. The volunteers were now tested 12 months after the initial training session with activated feedback. RESULTS: There were virtually no changes in CPR skills when tested with active feedback 12 months after initial training versus immediately or 6 months post-training. The only exception was a slightly lower number of compressions per minute at 12 months versus immediate post-training in the subgroup with 20 min of initial training, 47+/-4 versus 52+/-4, p = 0.008. There were no differences between the 20 and 50 min training subgroups at 12 months. CONCLUSIONS: Computer-based voice advisory feedback can improve the performance of basic life support skills on a manikin with no deterioration in feedback supported performance after 12 months.

Cardiopulmonary Resuscitation↗

PubMed2005

Reducing no flow times during automated external defibrillation.

There has recently been an increased attention focused on the importance of reducing time without blood flow from chest compressions (no flow time, NFT) during cardiopulmonary resuscitation (CPR). In this study we have analyzed and quantified the NFTs during external automatic defibrillation in 105 cardiac arrest patients. We found that for around half of the time (about 10 min), these patients were not perfused. We have proposed methods to reduce NFT in connection with analyses and shocks. The key factors were rhythm analysis during ongoing CPR, capacitor charging during analysis, 1 min of CPR immediately after a shock (with rhythm analysis during CPR at the end of the 1 min), and distinguishing between asystole and organized rhythm in analyses to skip pulse check if asystole. The potential reduction in NFT using these methods was calculated theoretically and we found a reduction in the total NFT of about 4.5 and 1 min, respectively, in the subgroups of patients having at least one shock and patients having received no shocks. In the present study, the median NFT ratio could theoretically be reduced from 51% to 34% or 49% to 39% depending on if the patient would have a shockable rhythm or not. By introducing the proposed methods into an AED, the NFT would be significantly reduced, hopefully increasing the survival.

Automation↗

PubMed2004

Feasibility of shock advice analysis during CPR through removal of CPR artefacts from the human ECG.

Mechanical activity from chest compressions and ventilations during cardiopulmonary resuscitation (CPR) introduces artefact components into the electrocardiogram (ECG). CPR must therefore be discontinued for reliable shock advice analysis in automated external defibrillators. Reducing or eliminating this detrimental "hands-off" time by removing the CPR artefacts, should significantly improve the defibrillation success rate. The feasibility of this was tested by removing the CPR artefacts using a multichannel adaptive filter, the multichannel recursive adaptive matching pursuit (MC-RAMP) algorithm. Human ECG and reference channel data from episodes with both shockable and non-shockable underlying heart rhythms were recorded from 105 patients with out-of-hospital cardiac arrest. The performance of a shock advice algorithm was evaluated before and after artefact removal using the MC-RAMP algorithm. From a test set consisting of 92 shockable and 174 non-shockable episodes a sensitivity of 96.7% and specificity of 79.9% was achieved, an increase of approximately 15 and 13%, respectively, compared to no filtering. Good sensitivity was achieved, enabling ECG analysis during CPR that would reduce the hands-off time on patients with shockable rhythms. However, CPR artefact removal on non-shockable rhythms proved a more difficult problem. We need a better understanding of the physiological mixing of artefacts and the underlying heart rhythm and suggest clinical trials to investigate the nature of CPR artefacts further.

Algorithms↗

PubMed2002

Retention of basic life support skills 6 months after training with an automated voice advisory manikin system without instructor involvement.

AIM: To evaluate the retention of skills 6 months after training in ventilation and chest compressions (CPR) on a manikin with computer based on-line voice advisory feedback and the possible effects of initial overtraining. METHODS: Thirty five volunteers had 20 min provisional CPR training on a manikin with computer based voice advisory feedback but without an instructor. The appropriate feedback was taken from a pre-recorded list depending on performance measured by the manikin--computer system versus set limits for ventilation and compression variables. One group in addition was randomised to receive 10 similar 3 min training sessions during 1 week in the following month (overtrained group). All ventilation and compression variables were measured without feedback before and after the initial training session, with feedback immediately thereafter, and both without and with feedback 6 months after the initial training session. RESULTS: The initial training improved all variables. Compressions with correct depth increased from a mean of 33 to 77%, and correct inflations from a mean of 9 to 58%. After 6 months, the results for the controls were not significantly different from pre-training, except for a higher of correct inflations (18%), while the overtrained group had better retention of skills including the correct compression depth (mean 61%) and inflations (mean 42%). When verbal feedback was added both the compressions and ventilations immediately improved both when tested immediately and 6 months after the initial training session. CONCLUSIONS: The computer-based voice advisory manikin (VAM) feedback system can improve immediate performance of basic life support (BLS) skills, with better long-term retention with overtraining.

Adult↗

PubMed2002

Compression depth estimation for CPR quality assessment using DSP on accelerometer signals.

Chest compression is a vital part of cardiopulmonary resuscitation (CPR). This paper demonstrates how the compression depth can be estimated using the principles of inertia navigation. The proposed method uses accelerometer sensors, one placed on the patient's chest, the other beside the patient. The acceleration-to-position conversion is performed using discrete-time digital signal processing (DSP). Instability problems due to integration are combated using a set of boundary conditions. The proposed algorithm is tested on a mannequin in harsh environments, where the patient is exposed to external forces as in a boat or car, as well as improper sensor/patient alignment. The overall performance is an estimation depth error of 4.3 mm in these environments, which is reduced to 1.6 mm in a regular, flat-floor controlled environment.

Algorithms↗

PubMed2002

Removal of cardiopulmonary resuscitation artifacts from human ECG using an efficient matching pursuit-like algorithm.

We present a computationally efficient and numerically robust solution to the problem of removing artifacts due to precordial compressions and ventilations from the human electrocardiogram (ECG) in an emergency medicine setting. Incorporated into automated external defibrillators, this would allow for simultaneous ECG signal analysis and administration of precordial compressions and ventilations, resulting in significant clinical improvement to the treatment of cardiac arrest patients. While we have previously demonstrated the feasibility of such artifact removal using a multichannel Wiener filter, we here focus on an efficient matching pursuit-like approach making practical real-time implementations of such a scheme feasible for a wide variety of sampling rates and filter lengths. Using more realistic data than what have been previously available, we present evidence showing the excellent performance of our approach and quantify its computational complexity.

Algorithms↗