Computer algorithms for STEMI identification

Prehospital Electrocardiographic Computer Identification of ST-segment Elevation Myocardial Infarction

Prehospital Emergency Care: Posted online on October 15, 2012.

Identifying ST-segment elevation myocardial infarctions (STEMIs) in the field can decrease door-to-balloon times. Paramedics may use a computer algorithm to help them interpret prehospital electrocariograms (ECGs). It is unknown how accurately the computer can identify STEMIs.

The aim of the research was to determine the sensitivity and specificity of prehospital ECGs in identifying patients with STEMI.

Retrospective cross-sectional study of 200 prehospital ECGs acquired using Lifepak 12 monitors and transmitted by one of more than 20 emergency medical services (EMS) agencies to the emergency department (ED) of a Summa Akron City Hospital, a level 1 trauma center between January 1, 2007, and February 18, 2010. The ED sees more than 73,000 adult patients and treats 120 STEMIs annually. The laboratory performs 3,400 catheterisations annually. The first 100 patients with a diagnosis of STEMI and cardiac catheterisation laboratory activation from the ED were analysed  For comparison, a control group of 100 other ECGs from patients without a STEMI were randomly selected from our Medtronic database using a ra

© Gary Wilson/ Pre-hospital Research Forum

ndom-number generator. For patients with STEMI, an accurate computer interpretation was “acute MI suspected.” Other interpretations were counted as misses. Specificity and sensitivity were calculated with confidence intervals (CIs). The sample size was determined a priori for a 95% CI of ±10%.

Zero control patients were incorrectly labeled “acute MI suspected.” The specificity was 100% (100/100; 95% CI 0.96–1.0), whereas the sensitivity was 58% (58/100; 95% CI 0.48–0.67). This would have resulted in 42 missed cardiac catheterization laboratory activations, but zero inappropriate activations. The most common incorrect interpretation of STEMI ECGs by the computer was “data quality prohibits interpretation,” followed by “abnormal ECG unconfirmed.”

The authors found that prehospital computer interpretation is not sensitive for STEMI identification and should not be used as a single method for prehospital activation of the cardiac catheterising laboratory. Because of its high specificity, it may serve as an adjunct to interpretation. Other methods to identify STEMI include the use of telemetry or paramedic interpretation.

Oxygen versus air driven nebulisers for COPD

Randomised controlled crossover trial of the effect on PtCO2 of oxygen-driven versus air-driven nebulisers in severe chronic obstructive pulmonary disease

Emerg Med J 2012;29:894-898

The comparative safety of oxygen versus air-driven nebulised bronchodilators in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) is uncertain. A randomised controlled trial was performed to assess the effect on the arterial partial pressure of carbon dioxide of nebulised bronchodilator driven with oxygen versus air in stable severe COPD. While a large proportion of nebulisers used in the pre-hospital environment are oxygen driven, there have been questions on whether ambulances should have a compressed air supply, in addition to oxygen.

In an open label randomised study, 18 subjects with stable severe COPD attended on 2 days to receive nebulised bronchodilator therapy driven by air or oxygen. Subjects received 5 mg salbutamol and 0.5 mg ipratropium bromide by nebulisation over 15 min, then, after 5 min, 5 mg salbutamol nebulised over 15 min, followed by 15 min of observation. Transcutaneous carbon dioxide tension (PtCO2) and oxygen saturations were recorded at 5 min intervals during the study. The primary outcome was the PtCO2 after the completion of the second bronchodilator treatment.

PtCO2 was higher with nebulised bronchodilator therapy delivered by oxygen, but decreased back to the level associated with air nebulisation 15 min after completion of the second nebulised dose. One subject experienced an increase in PtCO2 of 11 mm Hg after the first bronchodilator nebulisation driven by oxygen. The mean PtCO2 difference between the oxygen and air groups after the second nebulisation was 3.1 mm Hg (95% CI 1.6 to 4.5, p<0.001).

The authors found that nebulisers driven with oxygen result in significantly higher levels of PtCO2 than those driven with air in patients with severe COPD.

Extended care paramedics in New Zealand

Introduction of an extended care paramedic model in New Zealand

Emergency Medicine Australasia: Article first published online: 23 Oct 2012

The first extended care paramedic (ECP) model of care in New Zealand was introduced in the Kapiti region, north of Wellington in 2009. The ECP model aimed to increase the proportion of patients presenting to the ambulance service who could be treated in the community. This study evaluated the first 1,000 patients seen by ECPs.

The first 1,000 presentations attended by ECPs were examined to determine the proportions of patients transported to the ED and treated in the community. For patients treated in the community we determined the number presenting to the ED within 7 days of ECP attendance.

A total of 797 patients (mean age 62 years) had 1,000 clinical presentations. In 59% the patient was treated either at home or in the local community, with 40% transported to the ED. Within the same region and time period 74% of patients attended by standard paramedics were transported to the ED. The rate of ECP transport to the ED differed significantly by clinical condition, with 71% of cardiac presentations versus 19% of patients with spinal problems taken to the ED. In 31 cases (5%) where the patient had been managed in the community there was an acute ED presentation within seven days.

The authors observed that ECPs have significant potential to reduce hospital ED attendances by treating more patients in the community, and this is associated with a low rate of subsequent ED presentations. Prioritisation of dispatch of ECPs to particular types of patients might be useful in maximising this reduction.

ECG use in neonatal resuscitation

Electrocardiogram Provides a Continuous Heart Rate Faster Than Oximetry During Neonatal Resuscitation

PEDIATRICS Vol. 130 No. 5 November 1, 2012

The aim of the research was to compare the time required to obtain a continuous audible heart rate signal from an electrocardiogram (ECG) monitor and pulse oximeter (PO) in infants requiring resuscitation.

Infants who had both ECG and PO placed during resuscitation were analysed using video and analog recordings. The median times from arrival until the ECG electrodes and PO sensor were placed, and the time to achieve audible tones from the devices, were compared.

© Gary Wilson/ Pre-hospital Research Forum

Forty-six infants had ECG and PO data. Thirty infants were very low birth weight (23–30 weeks). There was a difference in the median total time to place either device (26 vs 38 seconds), and a difference in the time to achieve an audible heart rate signal after ECG lead (2 seconds) versus PO probe (24 seconds) placement. In infants weighing >1500 g, the median time (interquartile range) to place the ECG was 20 seconds (14–43) whereas the time to place the PO was 36 seconds (28–56). The median times (interquartile range) to acquire a signal from the ECG and PO were 4 seconds (1–6) and 32 seconds (15–40, P = .001), respectively. During the first minutes of resuscitation, 93% of infants had an ECG heart rate compared with only 56% for PO.

The authors found that early application of ECG electrodes during infant resuscitation can provide the resuscitation team with a continuous audible heart rate, and its use may improve the timeliness of appropriate critical interventions.