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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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256 S. Steen et al. / Resuscitation 58 (2003) 249 Á/258 Fig. 8. Systolic intrathoracic aortic pressure during the first hour after ROSC. Mean value9/S.E.M., n0/5.

success in VF if a shock can be given within 4Á/5 min of different effects of chest compression on the haemodyits onset. Only a tiny minority of cardiac arrest victims namics within and outside the thorax. Extrathoracic can be defibrillated within that short period of time. organs (e.g. the brain) receive perfusion pressure and The present study sheds light on the pathophysiology flow during both the compression and decompression of acute ventricular fibrillation. Blood is pooled in the phases. The arrested heart, however, is only perfused venous circulation, with the result that the right heart during the decompression phase, since the pressure in becomes more and more distended and the left heart the ascending aorta is less or equal to the pressure in the more and more empty over about 3 min of VF. When right atrium during the compression phase (Fig. 2).

the blood pressure on the arterial side equals that on the Furthermore, as the right heart becomes more and more venous side, after about 5 min, the coronary perfusion distended, the coronary pressure needed to provide pressure and the carotid flow fall to zero. When chest adequate perfusion increases correspondingly.

compressions are initiated, flow in the carotid artery In the group I animals, sinus rhythm was achieved by increases to acceptable values within 10 s, but it takes 1 defibrillation after 6.5 min of VF, but there was no min to bring a negative coronary perfusion pressure detectable arterial pressure or flow (PEA). At this time back to zero, and a further half minute to bring it up to the right ventricle remained greatly distended and did an adequate level. This time discrepancy is due to the not move, while the empty and non-stretched left

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Manual versus mechanical cardiopulmonary resuscitation. An experimental study in pigs Qiuming Liao, Trygve Sjöberg, Audrius Paskevicius, Björn Wohlfart, Stig Steen* Abstract Background: Optimal manual closed chest compressions are difficult to give. A mechanical compression/ decompression device, named LUCAS, is programmed to give compression according to the latest international guidelines (2005) for cardiopulmonary resuscitation (CPR). The aim of the present study was to compare manual CPR with LUCAS-CPR.

Methods: 30 kg pigs were anesthetized and intubated. After a base-line period and five minutes of ventricular fibrillation, manual CPR (n = 8) or LUCAS-CPR (n = 8) was started and run for 20 minutes. Professional paramedics gave manual chest compression’s alternating in 2-minute periods. Ventilation, one breath for each 10 compressions, was given to all animals. Defibrillation and, if needed, adrenaline were given to obtain a return of spontaneous circulation (ROSC).

Results: The mean coronary perfusion pressure was significantly (p 0.01) higher in the mechanical group, around 20 mmHg, compared to around 5 mmHg in the manual group. In the manual group 54 rib fractures occurred compared to 33 in the LUCAS group (p 0.01). In the manual group one severe liver injury and one pressure pneumothorax were also seen. All 8 pigs in the mechanical group achieved ROSC, as compared with 3 pigs in the manual group.

Conclusions: LUCAS-CPR gave significantly higher coronary perfusion pressure and significantly fewer rib fractures than manual CPR in this porcine model.

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Figure 1 The design of the study (upper panel). The number of pigs with return of spontaneous circulation (ROSC) is indicated within the ROSC rectangle. VF: ventricular fibrillation; CPR: cardiopulmonary resuscitation; D1-D6: defibrillations; A: adrenaline 0.01 mg/kg given intravenously.

The lower panel shows the mean systolic pressure and during CPR the compression pressure, in the intrathoracic aorta during the experiment.

The CPR period is marked. The break in the manual CPR curve marks where n is changed from 8 to 3 individuals. Mean ± SEM is included in 2 places in each curve; n = 8, except for the ROSC period for manual CPR, where n = 3.

Liao et al. BMC Cardiovascular Disorders 2010, 10:53 Page 3 of 8 http://www.biomedcentral.com/1471-2261/10/53 tube. The tube was connected to a Servo Ventilator 300 so that the compressions could start at scheduled time.

(Servo Ventilator 300, Siemens, Solna, Sweden) using The compressions were given on sternum between the pressure-regulated (max 30 cmH 2 O = 23 mmHg) and inferior 1/3 and superior 2/3 of sternum. The marked volume-controlled intermittent positive pressure ventila- place was used for both manual and mechanical chest tion (IPPV). Normo-ventilation (end-tidal CO2 around compressions. The anterior-posterior diameter of the

5.3 kPa = 40 mmHg) was obtained by using a tidal thorax was measured by means of a ruler before and after volume of 8 ml/kg body weight, 20 breaths/min, a PEEP CPR.

of 5 cmH2O and a FiO2 of 0.21. LUCAS (V2US; Jolife AB), also used in humans, was During CPR ventilation was given, without interrup- used to deliver the mechanical chest compressions.

tion of chest compressions, by means of a Ruben bag in According to an international agreement (Utstein-style both the manual CPR and the LUCAS-CPR group. Ven- guidelines for uniform reporting of laboratory CPR tilation was given with 100% oxygen, the frequency was research. Resuscitation 1996;33:69-84) 20-25 kg pigs 1 ventilation after every 10th compression (= 10 ventila- are recommended to use as they have similar anteriortions/min) in both groups. After return of spontaneous posterior diameter as adult humans.

circulation (ROSC) the animals in both groups were given baseline ventilation by the Servo Ventilator 300 Return of spontaneous circulation with a FiO2 of 1.0. Defibrillations, if indicated, were done externally using biphasic shocks (Lifepak 12, Medtronic, Minneapolis, MN, USA), using 360 J energy through pads (see Figure 1).

Preparation and monitoring Four catheters for blood pressure measurements and Between each shock, chest compressions for 2 minutes blood sampling were introduced into the right carotid were to be given. At manual CPR there was to be minimal artery and the right internal jugular vein. The catheters delay (around 2 seconds) between chest compression and were inserted into the ascending aorta and into the defibrillation. With LUCAS-CPR, defibrillation was given right atrium, respectively. An ultrasonic flow probe con- during ongoing CPR. The research leader judged whether nected to a MediStim flowmeter apparatus (CM-4000, ROSC had been obtained after each defibrillation (systolic MediStim ASA, Oslo, Norway) was placed on the left arterial pressure above 60 mmHg for 1 minute). How to internal carotid artery. A temperature probe was give defibrillation and adrenaline was adjusted to the inserted into the esophagus. Three-lead electrocardio- experimental situation. If ROSC was not obtained after 3 gram (ECG) were obtained by electrodes corresponding defibrillations, adrenaline 0.01 mg/kg was given in the cento R,L,F and ground were adhered to the skin. tral venous catheter 3 times, with 2-minute intervals of chest compressions between each dose. After the third dose of adrenaline, CPR was continued for 2 minutes and Chest compressions VF was induced with a 5-20 mA and 6-14 Hz square then terminated. If ROSC was obtained, measurements formed wave current delivered to the epicardial surface continued for 1 hour.

via a needle electrode puncture through the upper abdomen. CPR was started 5 minutes after induction of VF. Autopsy In the manual CPR experiments, 16 paramedics and After terminating each experiment an autopsy was perambulance nurses from Lund Ambulance Station, 10 men formed. For obvious reasons (suction marks on the skin) and 8 women (mean length 175 cm, range 162-188 cm, could the autopsy not be made blinded. The position of mean weight 76 kg, range 55-95 kg) were responsible for catheters and the presence of any fractures in ribs or the chest compressions and ventilations. Two paramedics sternum, or injuries on lungs, heart and abdominal carried out the compressions at each manual CPR experi- organs were noted.

ment and they shifted between doing chest compressions and ventilation every second minute. A sound indicator Calculation of the coronary perfusion pressure was used to keep the frequency of the manual compres- The coronary perfusion pressure (CPP) was computed sions at 100/min. Within 14 days before the experiments as the difference between the intrathoracic aortic and were done, all rescuers had to undergo manual CPR train- the right atrial pressure in the end-decompression ing on a mannequin and were instructed to give chest phase. The beginning of each compression cycle was compressions according the international guidelines from defined as the maximal pressure rise ratio (see Figure 2).

2005. The exact spot for delivery of the manual chest com- The end-decompression phase was measured in a winpressions were decided by placing of LUCAS on all pigs in dow between 0.1 to 0.05 seconds before the compresboth groups and mark the optimal compressions spot by sion. The mean of the sampled values during that drawing an ink line around the suction cup. During the window of 0.05 seconds (10 values, i.e., 200 Hz) was 5 minutes with VF, LUCAS was placed in correct position calculated.

Liao et al. BMC Cardiovascular Disorders 2010, 10:53 Page 4 of 8 http://www.biomedcentral.com/1471-2261/10/53 Figure 2 The coronary perfusion pressure in the two groups (upper panel). The lower panels show typical pressure curves in the intrathoracic aorta (triangles) and the right atrium (circles) during two cycles of CPR in the manual CPR (left) and LUCAS-CPR (right) groups just after a ventilation. A bar (|–|) is inserted before one compression in both panels. The 0.05-second long bar shows where in the cycle CPP is calculated (as the difference between the pressure in aorta and right atrium). The level of the bar shows the CPP in this registration; 7 mmHg in the manual group and 22 mmHg in the LUCAS group.

Liao et al. BMC Cardiovascular Disorders 2010, 10:53 Page 5 of 8 http://www.biomedcentral.com/1471-2261/10/53 Statistics where it varied between 10 and 25 mmHg (p 0.05). The A sample size of 8 in each group was used. By use of right atrial pressure during the decompression phase was the following parameters sample size calculation showed between 5 and 10 mmHg in the manual group whereas it that n had to be at least n = 7 in each group. 1: A stan- was significantly lower in the LUCAS group, where it vardard deviation of 4.9 mmHg for the measurement of ied between -5 and 5 mmHg (p 0.01).

CPP during manual compressions as found in an earlier study [14]. 2: A difference of 7 mmHg between groups. Coronary perfusion pressure 3: A significance level of 5%. The coronary perfusion pressure was between 20 and Global interpretation of data was done by means of 25 mmHg in the LUCAS group during CPR which was the area under curve comparing different variables significantly (p 0.01) higher than in the manual group between the two groups during the CPR period. Stu- where it was between 5 and 10 mmHg (Figure 2). There dent’s t-test for unpaired observations was used. Data was no overlap of CPP between the two groups.

obtained during the first 90 seconds of the CPR period was excluded from the statistical calculations because Left carotid artery flow this is the time required to reach plateau. Fisher’s Exact The mean flow at baseline was 176 ± 17 ml/min in the Test was used for autopsy findings. A p-value 0.05 was manual group and 212 ± 33 ml/min in the LUCAS regarded as indicative of a statistically significant differ- group (not significant). During CPR, the flow was signifence between the groups. icantly higher (p 0.05) in the LUCAS-CPR group during the first 10 minutes (Figure 3).

Results ROSC Electrocardiogram In the manual group five pigs did not achieve ROSC. All ECG recordings just before initiation of ventricular One pig obtained ROSC after 1 defibrillation, 1 pig fibrillation showed sinus rhythm with a mean rate of obtained ROSC after 1 defibrillation followed by 2 min- 95/min (n = 16).

utes of manual CPR and 1 pig obtained ROSC after 1 In the LUCAS group there was no sign of ischemia defibrillation followed by 10 minutes of manual CPR 1 hour after ROSC; in the 3 animals with ROSC in the and intravenous adrenaline 0.01 mg/kg 3 times at manual group, ECG was also normal, except in one pig 2-minute intervals, according to the protocol (Figure 1). where negative T-waves were seen.

In the LUCAS group all 8 animals obtained ROSC. In 5 pigs, ROSC was obtained after the first defibrillation. End-tidal CO2 In 2 pigs ROSC was obtained after one defibrillation fol- The ETCO2-values were around 3.4 kPa in the LUCAS lowed by 2 minutes of LUCAS-CPR. In 1 pig, ROSC group and around 2.2 kPa in the manual group; this difwas obtained after 1 defibrillation, 4 minutes of LUCAS- ference was statistically significant (p 0.05).

CPR and the first dose of 0.01 mg/kg of intravenous adrenaline according to the protocol (Figure 1).

Number of compressions given during the 20-minute CPR-period About two thousand compressions were given to each animal in the LUCAS group. The mean time for the paramedics to change between compression and ventilation was 4 ± 1 seconds, i.e., each pig received about 60 compressions less in the manual group.

Aortic pressure during compression phase The aortic compression pressure in the LUCAS-group was around 65 mmHg, and in the manual group around 55 mmHg during the CPR period (p 0.05)(Figure 1).

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