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«LUCAS - Lund University Cardiopulmonary Assist System Liao, Qiuming Published: 01/01/2011 Link to publication Citation for published version (APA): ...»

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LUCAS - Lund University Cardiopulmonary Assist System

Liao, Qiuming

Published: 01/01/2011

Link to publication

Citation for published version (APA):

Liao, Q. (2011). LUCAS - Lund University Cardiopulmonary Assist System Department of Cardiothoracic

Surgery, Clinical Sciences, Lund University

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Download date: 17. Oct. 2016  LUCAS Lund University Cardiopulmonary Assist System Qiuming Liao, M.D.

     Doctorial Dissertation Copyright © 2011, Qiuming Liao Department of Cardiothoracic Surgery Faculty of Medicine Lund University 2011 ISBN 978-91-86671-82-2 ISSN 1652-8220 Faculty of Medicine Doctoral Dissertation Series 2011:34                  将此书献给我的父亲 廖小白   Contents List of publications 7 Summary 9 I TRODUCTIO 11 Background 11 History of LUCAS 13 Properties of LUCAS 17

Aim of the thesis 19

MATERIAL A D METHODS 21 RESULTS 23 Manual CPR compared to LUCAS-CPR 23 Normothermic versus hypothermic CPR 27 Hemodynamics of ventricular fibrillation

–  –  –

Papers I-III 51 List of publications This thesis is based on studies reported in the following papers, which are referred

to in the text by their Roman numerals:

I. Steen S, Liao Q, Pierre L, Paskevicius A, Sjöberg T: Evaluation of LUCAS, a new device for automatic mechanical compression and active decompression resuscitation. Resuscitation 2002;55:285-299.

II. Steen S, Liao Q, Pierre L, Paskevicius A, Sjöberg T. The critical importance of minimal delay between chest compressions and subsequent defibrillation: a haemodynamic explanation. Resuscitation 2003;58:249-258.

III. Liao Q, Sjöberg T, Paskevicius A, Wohlfart B, Steen S, Manual versus mechanical cardiopulmonary resuscitation. An experimental study in pigs. BMC Cardiovascular Disorders 2010;10:53.

www.biomedcentral.com/1471-2261/10/53.

Summary Lund University Cardiopulmonary Assist System (LUCAS) is a mechanical device providing automatic 5 cm deep chest compressions and active decompressions back to normal anatomical position with a frequency of 100 per minute, and a duty cycle of 50%, i.e., LUCAS is constructed to give chest compressions according to the latest international guidelines in cardiopulmonary resuscitation (CPR).

The aim of the thesis was to study cardiac arrest using different porcine models of ventricular fibrillation. Four hypotheses were

formulated:

1. LUCAS-CPR is superior to manual CPR regarding coronary perfusion pressure (CPP) and return of spontaneous circulation (ROSC).

2. Hypothermic LUCAS-CPR is superior to normothermic LUCAS-CPR in treating prolonged ventricular fibrillation.

3. The rate of ROSC after prolonged ventricular fibrillation will increase if LUCAS-CPR is given before defibrillation, and if defibrillation is given during on-going chest compressions.

4. LUCAS-CPR will cause fewer rib fractures than manual CPR.

LUCAS-CPR gave significantly higher rates of ROSC and significantly higher CPP than manual CPR. LUCAS-CPR combined with surface cooling to 34°C was superior to normothermic LUCASCPR during 1 hour of CPR for ventricular fibrillation. Defibrillation was more effective to obtain ROSC after prolonged ventricular fibrillation if chest compressions were done before the shock, and if the shock was given during on-going LUCAS-CPR. LUCAS-CPR caused significantly fewer rib fractures during 20 minutes of CPR compared to manual CPR.

I TRODUCTIO Background Sudden cardiac arrest, either as ventricular fibrillation (VF) or as asystole, is the single condition causing the most deaths in the Western world. It has been estimated that 375 000 people in Europe (1) and 275 000 in the USA (2) are victims of sudden cardiac arrest each year. The great majority of these cases occur out of hospital. In Sweden, about 10 000 people suffer sudden cardiac arrest each year, and it causes more than 10% of all deaths.

Since Kouwenhoven and coworkers published their landmark article in 1960 (3), manual closed-chest compressions (combined with mouth-to-mouth/mask ventilation) has been established as the initial treatment of choice for cardiac arrest, followed by defibrillation as soon as the equipment is available and if VF is the cause of the collapse.





For the last 50 years, the one-year survival rate after sudden cardiac arrest has remained extremely poor, in most studies less than 5%. In Sweden, the 30-day survival rate after sudden cardiac arrest was 7% in 2008 (4).

Several studies have been published showing how difficult it is to give optimal chest compressions manually (5-14). These studies have identified many factors that make manual CPR difficult (see Table 1).

Table 1. Difficulties with manual CPR.

Rescuer fatigue within 2 minutes (ineffective CPR).

Too shallow chest compressions (ineffective CPR).

Too deep chest compressions (multiple rib fractures, visceral injuries).

Too high/low compression rate (ineffective CPR).

Too high ventilation rate (impaired venous return).

Too small body size of rescuer (ineffective CPR).

Too long pre-shock pauses (ineffective defibrillation).

Too many interruptions of the chest compressions (ineffective CPR).

One of the problems with manual chest compressions is that during prolonged CPR, the thorax flattens due to multiple bilateral rib fractures with reduced thoracic wall recoil and venous return as a consequence. The CardioPump (AMBU, Copenhagen) was developed with the intention to overcome this problem (Fig 1).

Fig 1. The CardioPump in action.

Due to the suction-cup on the CardioPump active decompression can be obtained after each compression. Plaisance and coworkers (15) compared standard manual CPR (n=377 patients) with active compression/decompression CPR performed manually with the CardioPump (n=373 patients). The 1-year survival rate was very poor in both groups, 2% versus 5% (p=0.03); all resuscitation efforts with either method were performed only at the scene of the cardiac arrest, and only if the victims were successfully resuscitated at the scene were the patients transported to hospital. To use the CardioPump correctly, compressing and decompressing the thorax 100 times each minute, is very demanding, and in the study of Plaisance et al., to prevent fatigue, the rescuers alternated after every 3 min of CPR. Due to the difficulty to know the correct compression depth after each decompression, some compressions may become too deep, with injuries to visceral organs as a consequence (16-18).

History of LUCAS Willy Vistung was a Norwegian inventor. Once he happened to see the treatment of a patient with cardiac arrest in an ambulance speeding very fast through Oslo toward the hospital. One paramedic tried to give chest compressions, kneeling over the patient, losing his balance every time the ambulance rounded a corner.

Another person gave ventilation with an AmbuBag connected to a cylinder with oxygen. Willy Vistung had the idea during this ambulance transport of constructing a pneumatic mechanical system to do chest compressions. He bought the necessary components and made his first prototype. No enthusiasm for his project was to be found in Norway.

In 1995 he had a meeting with Stig Steen at the Department of Cardiothoracic Surgery in Lund. Stig Steen, also a Norwegian, was a cardiothoracic surgeon in charge of the cardiothoracic surgical laboratory, situated within Lund University Hospital. Stig Steen had never met Willy Vistung before, but the personal chemistry between them was perfect. Ethical permission was obtained to run a randomized study on pigs to test Willy Vistung’s prototype, and the result of that study showed that mechanical compressions with his device gave superior results as compared to manual compressions.

Willy Vistung became the victim of cardiac arrest and died. Stig Steen and coworkers, in full agreement with Vistung’s widow, and with economic support from Lund University Hospital, built a pneumatic universal machine where all relevant parameters for chest compression and decompression could be studied in pigs of all sizes (Fig 2-3). The results obtained with optimal mechanical chest compression/decompression were superior to manual CPR.

Professor Steen contacted the Swedish industry entrepreneur Lars Sunnanväder, the owner of Jostra AB, a company producing heart-lung machines in Lund. Lars Sunnanväder and Jostra’s CEO, Lennart Sjölund, enthusiastically supported the plans to make industry out of mechanical CPR, and Sunnanväder started a new company, Jolife AB, for this purpose. Professor Steen and his research team were given generous economic support from Jolife to continue the research and test different new prototypes (Fig 4-5). The first commercial version needed a name, and LUCAS was chosen, which stands for Lund University Cardiopulmonary Assist System.

1. Compression force

2. Downstroke-time

3. Stroke length

4. Time down

5. Decompression force

6. Upstroke-time

7. Time up

8. Frequency Fig 2. Chest compression/decompression variables.

Compression phase = “duty cycle” = “systole” = 2+4.

Decompression phase = “diastole” = 6+7.

Fig 3. The Universal Igelösa research machine constructed to study all parameters of mechanical chest compression and active decompression on all sizes of animals.

Fig 4. The first model used on patients at Lund University Hospital. This apparatus was the first to save the life of a patient after conventional CPR failed, see paper I.

Fig 5. This model was used in the heart intensive care unit of Lund University Hospital in the year 2000.

Due to the suction cup that makes active decompression possible, LUCAS moves the chest both down and up, thereby creating both circulation and ventilation, which is the reason that C in LUCAS stands for “cardiopulmonary”.

LUCAS was introduced in clinical practice by Professor Steen and coworkers in the year 2000, and the first scientific report on its properties, based on 100 pig experiments and the use on 20 patients, was published in 2002 (I).

Properties of LUCAS Fig 6. The first commercial LUCAS model tested on a pig.

LUCAS provides automatic compressions and decompressions back to the initial chest position (Fig 6). The maximum compression depth is 5 cm, the maximum compression force is 500 N, and the compression frequency is 100 per minute with a duty cycle of 50%. LUCAS is programmed to give compressions according to the recommendation from the international resuscitation guidelines (19-22). The weight of the device is 6.5 kg. The first versions were gas-driven (Fig 7). Since 2009 LUCAS exists also in an electrically-driven version (Fig 8).

Fig 7. A pneumatic version of LUCAS.

Fig 8. Since 2009, LUCAS is commercially available as an electrical version, LUCAS2.

Aim of the thesis The aim of the thesis was to study cardiac arrest using different porcine models of ventricular fibrillation. Four hypotheses were

formulated:

1. LUCAS-CPR is superior to manual CPR regarding coronary perfusion pressure (CPP) and return of spontaneous circulation (ROSC).

2. Hypothermic LUCAS-CPR is superior to normothermic LUCAS-CPR in treating prolonged ventricular fibrillation.

3. The rate of ROSC after prolonged ventricular fibrillation will increase if LUCAS-CPR is given before defibrillation, and if defibrillation is given during on-going chest compressions.

4. LUCAS-CPR will cause fewer rib fractures than manual CPR.

MATERIAL A D METHODS

For a complete description of the materials and methods, see I – III.

Research animals In study I and II, 124 pigs with body weights in the range of 20-25 kg were used.

In study III, 16 pigs with body weights in the range of 28-33 kg were used. The anterio-posterior chest diameter for the smaller pigs is around 20 cm, i.e., the same as for adult humans of mean size (I). The larger pigs simulate humans larger than of mean size. Ketamine was used as the main anesthetic drug.

Methods The parameters listed below were used to evaluate the efficiency of CPR. Rib fractures and other injuries were documented at the autopsy.

• Intrathoracic aortic pressure

• Right atrial pressure

• Intrapericardial pressure

• Coronary perfusion pressure

• Intratracheal pressure (via Boussignac tube)

• Cardiac output (via Swan Ganz catheter)

• End-tidal CO2

• Left carotid artery blood flow

• Esophageal temperature

• Blood gases

• Electrocardiogram (ECG) Figure 9 shows a schematic drawing of the porcine vascular system.

The placement of pressure catheters and a blood flow probe are also shown.

1. Ascending Aorta

2. Right coronary artery

3. Left coronary artery

4. Coronary sinus

5. Right atrium

6. Right carotid artery

7. Catheters (two in each position) for continuous pressure measurements and blood gases



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