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P A Steen

Publications and source records attributed to P A Steen.

At least 19 recordsLinked to original sources
PubMed2006

Compression force-depth relationship during out-of-hospital cardiopulmonary resuscitation.

BACKGROUND: Recent clinical studies reporting the high frequency of inadequate chest compression depth (<38 mm) during CPR, have prompted the question if adult human chest characteristics render it difficult to attain the recommended compression depth in certain patients. MATERIAL AND METHODS: Using a specially designed monitor/defibrillator equipped with a sternal pad fitted with an accelerometer and a pressure sensor, compression force and depth was measured during CPR in 91 adult out-of-hospital cardiac arrest patients. RESULTS: There was a strong non-linear relationship between the force of compression and depth achieved. Mean applied force for all patients was 30.3+/-8.2 kg and mean absolute compression depth 42+/-8 mm. For 87 of 91 patients 38 mm compression depth was obtained with less than 50 kg. Stiffer chests were compressed more forcefully than softer chests (p<0.001), but softer chests were compressed more deeply than stiffer chests (p=0.001). The force needed to reach 38 mm compression depth (F38) and mean compression force were higher for males than for females: 29.8+/-14.5 kg versus 22.5+/-10.2 kg (p<0.02), and 32.0+/-8.3 kg versus 27.0+/-7.0 kg (p<0.01), respectively. There was no significant variation in F38 or compression depth with age, but a significant 1.5 kg mean decrease in applied force for each 10 years increase in age (p<0.05). Chest stiffness decreased significantly (p<0.0001) with an increasing number of compressions performed. Average residual force during decompression was 1.7+/-1.0 kg, corresponding to an average residual depth of 3+/-2 mm. CONCLUSION: In most out-of-hospital cardiac arrest victims adequate chest compression depth can be achieved by a force<50 kg, indicating that an average sized and fit rescuer should be able to perform effective CPR in most adult patients.

Adolescent↗
PubMed2005

Practical issues in the evaluation of methods for the prediction of shock outcome success in out-of-hospital cardiac arrest patients.

There is a need for robust, effective predictors of the outcome from shock for out-of-hospital cardiac arrest patients. Such technology would enable the emergency responder to provide a therapy tailored to the patient's needs. Here we report our most recent findings while dwelling intentionally on the rationale behind the decisions taken during system development. Specifically, we illustrate the need for sensible data selection, fully cross-validated results and the care necessary when evaluating system performance. We analyze 878 pre-shock ECG traces, all of at least 10 s duration from 110 patients with cardiac arrest of cardiac aetiology. The continuous wavelet transform was applied to preshock segments of ECG trace. Time-frequency markers are extracted from the transform and a linear threshold derived from a training set to provide high sensitivity prediction of successful defibrillation. These systems are then evaluated on a withheld test set. All experiments are cross-validated. When compared to popular Fourier-based techniques our wavelet transform method, COP (Cardioversion Outcome Predictor), provides a 10-20% improvement in performance with values of 66 +/- 4 specificity at 95 +/- 4 sensitivity, 61 +/- 4 specificity at 97 +/- 2 sensitivity and 56 +/- 1 specificity at 98 +/- 2 sensitivity achieved for datasets limited to 3, 6, and 9 shocks per patient, respectively. Thus, the assessment of the wavelet marker was associated with a high specificity value at or above 95% sensitivity in comparison to previously reported methods. Therefore, COP could provide an optimal index for the identification of patients for whom shocking would be futile, and for whom an alternative therapy could be considered.

Animals↗
PubMed2005

The future of CPR.

Explore the source record for details and available documents.

Cardiopulmonary Resuscitation↗
PubMed2005

Have the implementation of a new specialised emergency medical service influenced the pattern of general practitioners involvement in pre-hospital medical emergencies? A study of geographic variations in alerting, dispatch, and response.

OBJECTIVES: Emergency medical service systems in Norway are based on equity and equality. A toll free number (113) and criteria based dispatch are crucial components. The establishment of an emergency medical system (EMS) manned by an air and ground emergency physician (EP) has challenged the role of the general practitioner (GP) in emergency medical care. We investigated whether there were any geographical differences in the use of 113, alerts to GPs by the emergency medical dispatch centres (EMDCs), and of the presence of GPs on scene in medical emergencies leading to a turnout of the EP manned EMS. METHODS: This was a prospective, observational cohort study of 385,000 inhabitants covered by the two EMDCs of Rogaland county, Norway, including 1035 on scene missions of the EP manned EMS during the period 1998-99. RESULTS: The proportion of emergency calls routed through 113 was significantly lower, the proportion of alerts to GPs significantly higher, and the proportions of GPs on scene significantly higher in rural than urban areas. CONCLUSION: We found geographical differences in the involvement of GPs in pre-hospital emergency medical situations, probably caused by a specialised emergency medical service system including an EMDC and an air and ground EP manned EMS. There were geographical differences in public use of the toll free 113, and alerts to GPs by the EMDCs, which is likely to result from geographical conditions and proximity to medical resources. Future organisation of the EMS has to reflect this to prevent unplanned and unwanted autonomously emerging EMS systems.

Adolescent↗
PubMed2004

Oxygen delivery and return of spontaneous circulation with ventilation:compression ratio 2:30 versus chest compressions only CPR in pigs.

The need for rescue breathing during the initial management of sudden cardiac arrest is currently being debated and reevaluated. The present study was designed to compare cerebral oxygen delivery during basic life support (BLS) by chest compressions only with chest compressions plus ventilation in pigs with an obstructed airway mimicked by a valve hindering passive inhalation. Resuscitability was then studied during the subsequent advanced life support (ALS) period. After 3 min of untreated ventricular fibrillation (VF) BLS was started. The animals were randomised into two groups. One group received chest compressions only. The other group received ventilations and chest compressions with a ratio of 2:30. A gas mixture of 17% oxygen and 4% carbon dioxide was used for ventilation during BLS. After 10 min of BLS, ALS was provided. All six pigs ventilated during BLS attained a return of spontaneous circulation (ROSC) within the first 2 min of advanced cardiopulmonary resuscitation (CPR) compared with only one of six compressions-only pigs. While all except one compressions-only animal achieved ROSC before the experiment was terminated, the median time to ROSC was shorter in the ventilated group. With a ventilation:compression ratio of 2:30 the arterial oxygen content stayed at 2/3 of normal, but with compressions-only, the arterial blood was virtually desaturated with no arterio-venous oxygen difference within 1.5-2 min. Haemodynamic data did not differ between the groups. In this model of very ideal BLS, ventilation improved arterial oxygenation and the median time to ROSC was shorter. We believe that in cardiac arrest with an obstructed airway, pulmonary ventilation should still be strongly recommended.

Animals↗
PubMed2004

Arterial blood gases with 700 ml tidal volumes during out-of-hospital CPR.

The optimal tidal and minute ventilation during cardiopulmonary resuscitation (CPR) is not known. In the present study seven adult, non-traumatic, out-of-hospital cardiac arrest patients were intubated and mechanically ventilated at 12 min(-1) with 100% oxygen and a tidal volume of 700 ml (10 +/- 2 ml kg(-1)). Arterial blood gas samples were analysed after 6-8 min of unsuccessful resuscitation and mechanical ventilation. Mean PaCO2 was 5.2 +/- 1.3 kPa and mean PaO2 30.7 +/- 17.2 kPa. The patient with the highest (14 ml kg(-1)) and lowest (8 ml kg(-1)) tidal volumes per kg had the lowest and highest PaCO2 values of 2.6 and 6.8 kPa, respectively. Linear regression analysis confirmed a significant correlation between arterial pCO2 and tidal volume in ml/kg, r2 = 0.87. We conclude that aiming for an estimated ventilation of 10 ml kg(-1) tidal volume at frequency of 12 min(-1) might be expected to achieve normocapnia during ALS.

Aged↗
PubMed2004

Long-term prognosis after out-of-hospital cardiac arrest and primary percutaneous coronary intervention.

AIMS: To study the long-term survival after out-of-hospital cardiac arrest and successful cardiopulmonary resuscitation (CPR) in patients with acute ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). MATERIAL AND METHODS: In-hospital and 2-year survival of 40 patients treated with primary PCI after out-of-hospital cardiac arrest and STEMI was compared with that of a reference group of 325 STEMI patients, without cardiac arrest, also treated with primary PCI in the same period. RESULTS: In the group with out-of-hospital cardiac arrest, both in-hospital and 2-year mortality was 27.5%. In the reference group, in-hospital and 2-year mortality was 4.9 and 7.1%, respectively. After discharge from hospital there was no significant difference in mortality between the groups. CONCLUSION: Long-term prognosis is good in selected patients after successful out-of-hospital CPR and STEMI treated with primary PCI.

Adult↗
PubMed2003

Dispatcher-assisted cardiopulmonary resuscitation. An evaluation of efficacy amongst elderly.

Bystander cardiopulmonary resuscitation (CPR) increases survival rates. The largest group of cardiac arrest patients are men over the age of 60 in the home, and the most probable potential CPR provider is an older woman who is not likely to have received CPR training. One method to increase the percentage of bystander-initiated CPR in this setting is for CPR instruction to be provided by nurse dispatchers via telephone. Two male and 18 female volunteers with a median age of 78 years and no previous CPR experience performed 9 min of telephone assisted CPR on a manikin. They were randomised to receive telephone instructions in chest compressions alone or standard CPR including mouth-to-mouth ventilation. Variables were registered by a recording manikin, visual observations, and video and audiotape recordings. The median period from dispatcher contact until continuous CPR was significantly longer for standard instructions than for compression only, 4.9 versus 3.4 min, and fewer chest compressions were provided during the 9 min test period, median 124 versus 334 compressions. In both groups the overall CPR performance was of very poor quality, and unlikely to have affected outcome in a real situation. Other telephone assisted CPR scripts should be tested in this potential bystander group.

Aged↗
PubMed2003

In-hospital factors associated with improved outcome after out-of-hospital cardiac arrest. A comparison between four regions in Norway.

INTRODUCTION: While pre-hospital factors related to outcome after out-of-hospital cardiac arrest (OHCA) are well known, little is known about possible in-hospitals factors related to outcome. HYPOTHESIS: Some in-hospital factors are associated with outcome in terms of survival. MATERIAL AND METHODS: An historical cohort observational study of all patients admitted to hospital with a spontaneous circulation after OHCA due to a cardiac cause in four different regions in Norway 1995-1999: Oslo, Akershus, Østfold and Stavanger. RESULTS: In Oslo, Akershus, Østfold and Stavanger 98, 84, 91 and 186 patients were included, respectively. Hospital mortality was higher in Oslo (66%) and Akershus (64%) than in Østfold (56%) and Stavanger (44%), P=0.002. By multivariate analysis the following pre-arrest and pre-hospital factors were associated with in-hospital survival: age -3.5 mmol l(-1), body temperature <or=37.8 degrees C, and serum glucose <or=10.6 mmol l(-1) 1-24 h after admittance with OR (95% CI) 2.72 (1.09-8.82, P=0.033), 1.12 (1.02-1.23, P=0.016), 2.67 (1.17-6.20, P=0.019) and 2.50 (1.11-5.65, P=0.028), respectively. Pre-arrest overall function, whether adrenaline was used, body temperature, the occurrence of hypotensive episodes, and the degree of metabolic acidosis differed between the four regions in parallel with the in-hospital survival rates. CONCLUSION: Both pre-arrest, pre- and in-hospital factors were associated with in-hospital survival after OCHA. It seems important also to report in-hospital factors in outcome studies of OCHA. The design of the study precludes a conclusion on causability.

Aged↗
PubMed2003

Quality of CPR with three different ventilation:compression ratios.

Current adult basic cardiopulmonary resuscitation (CPR) guidelines recommend a 2:15 ventilation:compression ratio, while the optimal ratio is unknown. This study was designed to compare arterial and mixed venous blood gas changes and cerebral circulation and oxygen delivery with ventilation:compression ratios of 2:15, 2:50 and 5:50 in a model of basic CPR. Ventricular fibrillation (VF) was induced in 12 anaesthetised pigs, and satisfactory recordings were obtained from 9 of them. A non-intervention interval of 3 min was followed by CPR with pauses in compressions for ventilation with 17% oxygen and 4% carbon dioxide in a randomised, cross-over design with each method being used for 5 min. Pulmonary gas exchange was clearly superior with a ventilation:compression ratio of 2:15. While the arterial oxygen saturation stayed above 80% throughout CPR for 2:15, it dropped below 40% during part of the ventilation:compression cycle for both the other two ratios. On the other hand, the ratio 2:50 produced 30% more chest compressions per minute than either of the two other methods. This resulted in a mean carotid flow that was significantly higher with the ratio of 2:50 than with 5:50 while 2:15 was not significantly different from either. The mean cerebrocortical microcirculation was approximately 37% of pre-VF levels during compression cycles alone with no significant differences between the methods. The oxygen delivery to the brain was higher for the ratio of 2:15 than for either 5:50 or 2:50. In parallel the central venous oxygenation, which gives some indication of tissue oxygenation, was higher for the ratio of 2:15 than for both 5:50 and 2:50. As the compressions were done with a mechanical device with only 2-3 s pauses per ventilation, the data cannot be extrapolated to laypersons who have great variations in quality of CPR. However, it might seem reasonable to suggest that basic CPR by professionals should continue with ratio of 2:15 at present if it can be shown that similar brief pauses for ventilation can be achieved in clinical practice.

Animals↗
PubMed2003

Bispectral index, serum drug concentrations and emergence associated with individually adjusted target-controlled infusions of remifentanil and propofol for laparoscopic surgery.

BACKGROUND: Target-controlled infusions (TCI) are used to simplify administration and increase precision of i.v. drugs during general anaesthesia. However, there is a limited relationship between preset targets and measured concentrations of drugs and between measured concentrations and measures of brain function, such as the bispectral index (BIS). METHODS: We set out to evaluate the performance of TCI devices for propofol (Diprifusor) and remifentanil (Remifusor, prototype), during laparoscopic cholecystectomy in 21 patients. We also checked if there was any correlation between serum concentrations of propofol and BIS during individually adjusted anaesthesia. RESULTS: The Diprifusor and Remifusor had a median absolute performance error of 60% and 25% respectively. Propofol concentrations were underpredicted by a median of 60%, and remifentanil concentrations were slightly overpredicted by a median of 7%. When anaesthesia was adjusted to keep BIS values between 45 and 60, no correlation existed between measured concentrations of propofol and the corresponding BIS values, although both BIS and serum propofol concentration discriminated well between the awake and asleep states. Emergence was rapid and uneventful in all patients. Female patients had a more rapid emergence than male patients (6.6 and 11.6 min respectively). CONCLUSIONS: TCI devices for remifentanil and propofol result in large variation in measured serum concentrations. The lack of correlation between BIS and serum concentrations of propofol adds to the debate about whether BIS measures hypnosis as a graded state during surgery. This study confirms that women wake up faster than men, but provides no explanation for this repeatedly shown difference.

Adult↗
PubMed2003

Cardiac output, pulmonary artery pressure, and patent ductus arteriosus during therapeutic cooling after global hypoxia-ischaemia.

OBJECTIVE: To assess by Doppler echocardiography the effects of 24 hours of whole body mild hypothermia compared with normothermia on cardiac output (CO), pulmonary artery pressure (PAP), and the presence of a persistent ductus arteriosus (PDA) after a global hypoxic-ischaemic insult in unsedated newborn animals. DESIGN: Thirty five pigs (mean (SD) age 26.6 (12.1) hours and weight 1.6 (0.3) kg) were anaesthetised with halothane, mechanically ventilated, and subjected to a 45 minute global hypoxic-ischaemic insult. At the end of hypoxia, halothane was stopped; the pigs were randomised to either normathermia (39 degrees C) or hypothermia (35 degrees C) for 24 hours. Rewarming was carried out for 24-30 hours followed by 42 hours of normothermia. Unanaesthetised pigs were examined with a VingMed CFM 750 ultrasound scanner before and 3, 24, 30, and 48 hours after the hypoxic-ischaemic insult. Aortic valve diameter, forward peak flow velocities across the four valves, and the occurrence of a PDA were measured. Tricuspid regurgitation (TR) velocity was used to estimate the PAP. Stroke volume was calculated from the aortic flow. RESULTS: Twelve animals (seven normothermic, five hypothermic) had a PDA on one or more examinations, which showed no association with cooling or severity of insult. There were no differences in stroke volume or TR velocity between the hypothermic and normothermic animals at any time point after the insult. CO was, however, 45% lower at the end of cooling in the subgroup of hypothermic pigs that had received a severe insult compared with the pigs with mild and moderate insults. CO and TR velocity were transiently increased three hours after the insult: 0.38 (0.08) v 0.42 (0.08) litres/min/kg (p = 0.007) for CO; 3.0 (0.42) v 3.4 (0.43) m/s (p < 0.0001) for TR velocity (values are mean (SD)). CONCLUSIONS: The introduction of mild hypothermia while the pigs were unsedated did not affect the incidence of PDA nor did it lead to any changes in MABP or PAP. Stroke volume was also unaffected by temperature, but hypothermic piglets subjected to a severe hypoxic-ischaemic insult had reduced CO because the heart rate was lower. Global hypoxia-ischaemia leads to similar transient increases in CO and estimated PAP in unsedated normothermic and hypothermic pigs. There were no signs of metabolic compromise in any subgroup, suggesting that 24 hours of mild hypothermia had no adverse cardiovascular effect.

Animals↗
PubMed2003

Effect of global hypoxia-ischaemia followed by 24 h of mild hypothermia on organ pathology and biochemistry in a newborn pig survival model.

BACKGROUND: Perinatal asphyxia may lead to multiorgan damage as well as brain injury. Posthypoxic hypothermia (HT) may protect other organs in addition to the brain. The aim of this study was to assess the systemic effects of our global hypoxic-ischaemic (HI) insult and compare the effect of mild 24-hour HT with normothermia (NT) during unsedated recovery. METHOD: Thirty-eight newborn pigs were subjected to 45 min of global HI by ventilating them with approximately 6% O2. On reoxygenation, pigs were randomised to NT or HT. The 18 NT piglets were maintained at rectal temperature 39.0 degrees C for 72 h. Twenty-three HT pigs (20 experimental HT and 3 sham controls) were cooled to rectal temperature 35 degrees C for 24 h before NT was resumed and the animals then survived a further 48 h. RESULTS: All lesions were small with no apparent clinical effect. The incidence of any damage to the heart (6 HT vs. 9 NT), liver (9 HT vs. 7 NT), kidney (6 HT vs. 9 NT) or intestinal injury (8 HT vs. 2 NT, p = 0.07) was not different in the two groups. More HT piglets developed lung injury, 10 HT and 3 NT. Plasma [Na], [K], [Ca] and [Mg] increased significantly after the HI insult as compared to baseline values. For the 24-hour period plasma [K] and [Ca] were significantly higher in the HT group, the mean area under the curve (AUC) being for [K] AUC(HT) 4.4 mmol/l vs. AUC(NT) 3.9 mmol/l, p = 0.04 and for [Ca] AUC(HT) 2.7 mmol/l vs. AUC(NT) 2.5 mmol/l, p = 0.01, respectively. Aspartate aminotransferase peaked at 48 h in the HT group and at 24 h in the NT group. Creatinine peaked at >72 h in the HT pigs and at 48 h in the NT pigs. White blood cells (WBC) peaked at 12 h for the HT pigs and at 6 h for the NT animals. AUC of the WBC during the cooling was significantly lower in the HT pig (AUC(HT) 11.1 vs. AUC(NT) 15.3 10(3)/mm3, p = 0.04). The HT pigs needed more glucose to maintain normal glucose during the last 12 h of HT. Also HT animals needed more oxygen during cooling to maintain PaO2. CONCLUSION: Twenty-four hours of mild HT did not reduce damage in any organ. There was a slight increase in lung damage in the HT group. None of the biochemical or pathological changes were of clinical significance. We conclude that mild HT for 24 h does not affect the organ systems adversely when compared to NT. Additional glucose and oxygen is needed during cooling to maintain normal values.

Adrenal Glands↗
PubMed2002

Effectiveness of ventilation-compression ratios 1:5 and 2:15 in simulated single rescuer paediatric resuscitation.

Current guidelines for paediatric basic life support (BLS) recommend a ventilation-compression ratio of 1:5 during child resuscitation compared with 2:15 for adults, based on the consensus that ventilation is more important in paediatric than in adult BLS. We hypothesized that the ratio 2:15 would provide the same minute ventilation as 1:5 during single-rescuer paediatric BLS due to the reduced time required to change between ventilations and compressions. Fourteen lay rescuers were trained with both ratios and thereafter performed single rescuer BLS for approximately 4 min with each of the two ratios in random order on a child-sized manikin with a built-in respiratory monitor. Quality of chest compressions was assessed by measurement of the rate, depth and position. There were no significant differences in tidal volumes or minute ventilation between the ratios. Nearly all chest compressions were within acceptable limits for depth and place with both methods, but the mean number of chest compressions per minute was 48+/-15% greater with ratio 2:15. In conclusion, there was no difference in ventilation, but nearly one and a half times as many compressions with a ratio of 2:15 than 1:5 for lay rescuers during single rescuer paediatric CPR. In order to simplify CPR training for laypersons, we recommend a 2:15 ratio for both single- and two-person, adult and paediatric layperson BLS.

Adult↗
PubMed2002

Prehospital advanced life support provided by specially trained physicians: is there a benefit in terms of life years gained?

BACKGROUND: The benefit of prehospital advanced life support (ALS) is disputed, as is the prehospital use of specially trained, hospital-based physicians. The purpose of the study was to assess the health benefit from an anesthesiologist-manned prehospital emergency medical service (EMS), and to separate the benefit of the anesthesiologist from that of rapid transport. METHODS: The anesthesiologist-manned helicopter and rapid response car service at Rogaland Central Hospital assisted 1106 patients at the scene during the 18-month study period. Two expert panels assessed patients with a potential health benefit for life years gained (LYG) using a modified Delphi technique. The probability of survival as a result of the studied EMS was multiplied by the life expectancy of each patient. The benefit was attributed either to the anesthesiologist, the rapid transport or a combination of both. RESULTS: The expert panels estimated a benefit of 504 LYG in 74 patients (7% of the total study population), with a median age of 54 years (range 0-88). The cause of the emergency was cardiac diseases (including cardiac arrest) in 61% of the 74 patients, trauma in 19%, and cardio-respiratory failure as a result of other conditions in 20%. The LYG were equally divided between air and ground missions, and the majority (88%) were attributed solely to ALS by the anesthesiologist. CONCLUSION: The expert panels found LYG in every 14th patient assisted by this anesthesiologist-manned prehospital EMS. There was no difference in LYG between the helicopter and the rapid response car missions. The role of the anesthesiologist was crucial for health benefits.

Adolescent↗