Clinical Analysis of PetCO2 in Predicting Abdominal Lifting and Compression CPR

Methods: 92 patient of cardiac arrest were in tubated and received ALP-CPR performed with a novel abdominal lifting/compression device by monitoring HR, PaO2, PaCO2 and PetCO2 according to the ultimate outcome of CPR, patients were divided into success group and failure group, the number of patients with 30min and 60min survival and the time of ROSC were recorded in successful group, and calculated the recovery success rate. Data according to the Utstein criteria, demographic information, medical data. we hypothesized that an PetCO2 level of 2.67kPa (20mmHg) or more after 20 minutes of standard advanced cardiac life support would predict ROSC.


Introduction
Early high quality and effective cardiopulmonary resuscitation (CPR) is the only effective first-aid measure to treat CA patients and improve their survival rate according to the current American Heart Association and European Resuscitation Council (ERC) CPR Guidelines. Consistent and discouraging low survival rates mandate are assessment of current resuscitative strategies and techniques [1][2][3][4]. We have invented a new device that could enhance abdominal wall lifting and compression, which made up for the lack of chest compressions (chest wall trauma or rib fracture). Clinical tests on this device show that it could reach a higher survival rate compared to chest compression in patients with cardiac arrests [5]. More studies are required to fully evaluate this abdominal lifting and compression boosting device before it can be recommended for widespread clinical use, and the most common of all decisions after initiation of CPR remains the decision of when to stop. Various clinical indicators have been used to determine when CPR efforts should be terminated [6][7][8]. Capnography (capnometry) potentially represents a useful clinical indicator of death that could guide decisions to terminate resuscitative efforts [9][10]. We sought to evaluate the hypothesis that partial pressure of PetCO 2 can evaluate and predict non survival in an independent cohort of patients suffering cardiac arrest. In the current study, we aim to

Patients
This was a prospective study conducted at emergency medical center of Zhengzhou People's Hospital and Hainan province People's Hospital from September 2014 to October 2016. A total of 92 patients who suffered a sudden cardiac arrest and were treated by a mobile emergency team were included in the present prospective study. The effectiveness, safety, and stability of the abdominal lifting and compression device used in this study have been verified in animal and human experiments [11]. This study was also approved by the Ethical Review Committee of Zhengzhou People's Hospital and Hainan province People's Hospital. All patient relatives or legal guardians received a detailed explanation of the study's possible risks and benefits and were permitted to request discontinuation of the study at any time. The requirements of the Declaration of Helsinki were strictly upheld throughout the research process. It was required that a close relative or legal guardian of the patient provide written informed consent to participate in the study.

The criteria include:
i.
Conforms to the ALP-CPR indications and had no contraindications. Indications include: Chest trauma caused cardiac arrest, respiratory muscle well weakness, and respiratory suppression of general anesthesia, especially thoracic deformity, chest fracture (including chest rib fractures appeared in the process of recovery, etc.), hemopneumothorax, and chest compression indication. ii.
Contraindications include: external injury to the abdomen, rupture of the diaphragm, bleeding in the abdominal cavity or internal organs, abdominal aortic aneurysm, and large tumor in the abdominal cavity, injury to the abdominal cavity or internal organs during abdominal compression, massive abdominal mass(such as pregnancy, intestinal obstruction, abdominal organ tumors, a large amount of ascites, giant ovarian cysts), etc.
Exclusion criteria: i.
Contraindication to the use of ALP-CPR, no indication for resuscitation or a do not resuscitate order. ii.
Disease that might significantly affect assessment of effectiveness (e.g., chronic wasting diseases such as malignancy or severe tuberculosis) and informed consent not obtained. Adults of both genders with a body weight of 40~150 kg meeting American Heart Association (AHA) guidelines for cardiopulmonary arrest seen in the emergency department were eligible for inclusion [12].

Study design
In compliance with 2016 expert consensus on ALP-CPR and the 2010 American heart association (AHA) guidelines,AmodelCPR-LW1000abdominallifting/compression device (patent number: ZL 2009 2 0164343.6,ZL 2009 2 0160376.3,ZL 2014 3 0044027.1) invented by Professor Li-xiang Wang of the General Hospital of Armed Police Forces' Emergency Medical Center and produced by the Beijing Germari Medical Equipment Co., Ltd., was used to perform ALP-CPR [13] (details of the study are reported in the Appendix). Detailed operation method introduction: a display panel, pressure application handles, and a negative pressure device make up of the device. Operators hold the pressure application handles and place the compression plate on the patient's abdomen. After turning on the device, negative pressure is generated which causes a tight bond between these pressure plates and the patient's abdomen. The operator then presses an indicator light prompted by an audio signal with a frequency of 100 times/minute, and the instrument performs alternate vertical downward compressions and upward lifting actions. The duration of compression and lifting was performed in a 1:1 ratio, the pressure was approximately 186 mmHg when the indicator light was on, and lifting force was approximately 112 mmHg. All patients were intubated and an end tracheal tube was immediately connected to the capnometer, multi-function cardiograph monitor was dynamically monitored. We monitored PetCO 2 continuously and recorded it during ALP-CPR, Measurements of PetCO 2 were taken using the side stream method with the infrared capnometer integrated into the LIFEPACK 12 defibrillator monitor or with BCI Capnocheck Model 20600A1.

Observational index
Multi-function cardio monitor, CO 2 detector and other equipment monitoring to evaluate ALP-CPR effect; The commissioner collected and recorded the information before, during and after resuscitation, and the professional statisticians analyze the parameters of ROSC. We defined return of spontaneous circulation (ROSC) in accordance with the Utstein style ('any ROSC'-palpabile pulse on carotid artery, regardless of duration, and ROSC with admission to hospital).Termination of lifesaving treatment: lifesaving treatment was considered successful and terminated with the appearance of an autonomous aortic pulse, moist facial complexion, the appearance of autonomous respiration, and shrinking pupils and reappearance of a light reflex, or the appearance of eyeball motion and limb spasms [14]. If after continued routine lifesaving efforts for at least 30 minutes no pulse or autonomous breathing was noted, lifesaving treatment was terminated after obtaining informed consent from family members.

Monitoring index
Heart rate (HR), MAP, PaO 2 , PaCO 2 were measured during pre-CPR, CPR, and post-CPR periods, and PetCO 2 was also monitored

Statistical analysis
Descriptive statistics are presented as mean±standard deviation for continuous variables. Analysis for caterogical variables were performed using X 2 test and exact Fisher test. Comparisons between groups were performed using t-test (normal distribution) and shapiro-Francia test (normality test failed). For PetCO 2 , Sensitivity and specificity were calaculated using standard formulae, multivariate analysis of repeated measurements with PetCO 2 at different time, receiver operating characteristic (ROC) curves were obtained. The greater the area under the ROC curve (AUROC), the better the predictive value of PetCO 2 , All statistical tests were two-sided with significance, the null hypothesis was considered to be rejected at P values less than 0.05 in all tests. All analyses were performed using SPSS 19 statistical software (IBM Corp., Armonk, NY, USA).

Figure 1: Flow chart of case.
During the period of evaluation, our centre was involved in 92 emergency interventions in which there was absence of signs of circulation at the start of intervention. Ultimately, 37patients were resuscitated.20min after ROSC was achieved in 37 patients (40.2%). yet, by the binomial distribution theory, 30 and 60min after ROSC overall survival to hospital admission occurred in 17.4% (16 patients), which has no statistically significant difference with 17.5% (7/40) [15] in pre-experiment (P>0.05). patients' HR, MAP, PaO 2 and PaCO 2 were significantly improved during ALP-CPR (P<0.05). 20min after ROSC MAP, PaO 2 and PaCO 2 were all higher than those in the ALP-CPR process (P<0.05) ( Table  1) At beginning of ALP-CPR, PetCO 2 of both groups were about 9 ̃ 10mmHg (P>0.05). PetCO 2 was gradually rising in success group during ALP-CPR process and increased slightly at 2~5min after ALP-CPR, then progressively decreased in failure group (P<0.05). PetCO2 values of 2.67kPa (20mmHg) or less discriminated between the 37 patients with ROSC and 55 patients without (P<0.05), but the success recovery rate at 60 min after ROSC was 17.4% (16/92) in successful group. The difference of MAP, PaO2 and PaCO 2 after ROSC 20min compared with abdominal lifting and compression CPR process was statistically significant (P< 0.05).When a 20minute PetCO 2 value of 2.67 kPa (20mmHg) or less was used as a screening test to predict ROSC, area under the receiver operating characteristic curve (95%CI) is 0.845, the sensitivity and specificity were respectively 0.80, 0.83 (Figure 1-4) Table 2 ROSC, return of spontaneous circulation; ALP-CPR, abdominal lifting and compression cardiopulmonary resuscitation. ALP-CPR, abdominal lifting and compression cardiopulmonary resuscitation; HR, heart rate; MAP, mean arterial pressure; PaO 2 , arterial oxygen partial pressure; PaCO 2 , arterial partial pressure of carbon dioxide;1 mmHg=0.133 kPa.

Discussion
In 2015 CPR guidelines of American Heart Association recommend that the primary goals of patients with CA is ROSC, and then restoring ventilation, reducing complication, so as to realize the ultimate goal of the hospital survival. Due to complex etiology, medical conditions, rescue time and other restrictions, resulting in different hospitals CA rescue level is uneven [16]. Therefore, finding a rapid, accurate and effective method of resuscitation is a challenge for medical workers. Investigators have suggested that there is a close correlation between PetCO 2 and cardiac output, stroke volume, and coronary and cerebral perfusion pressure during CPR. Kalenda [17] first reported a decrease in PetCO 2 in patients who could not be resuscitated, and a significant rise in PetCO 2 in those patients in whom ROSC could be achieved. Falk and coworkers [18] found that PetCO 2 decreased from mean of 1.4% before arrest to 0.4% after the onset of cardiac arrest. It then increased with CPR and ROSC. Sanders and colleagues [19] found that PetCO 2 level predicted successful resuscitation after in hospital and out of hospital cardiac arrest. In our study we found that PetCO 2 was gradually rising in success group during ALP-CPR process and increased slightly at 2~5min after ALP-CPR, then progressively decreased in failure group (P<0.05). PetCO 2 values of 2.67kPa (20mmHg) or less discriminated between the 37 patients with ROSC and 55 patients without (P<0.05), and when a 20minute PetCO 2 value of 2.67kPa (20mmHg) or less was used as a screening test to predic ROSC, the sensitivity, specificity were all high. We also found that PetCO 2 values under 1.9 kPa (14.3mmHg) after 20 minutes of

Journal of Complementary Medicine & Alternative Healthcare
ALP-CPR are incompatible with ROSC. This is time of the end of haemo dynamic phase of ALP-CPR. These values may represented irreversible hemodynamic collapse, with inadequate coronary or myocardial perfusion pressure, or may represent perfusion pressures supplied too late (after the haemo dynamic phase), with consequent irreversible tissue damage [20,21]. Our study data, combined with the findings of other investigators, provide strong support for a resuscitation thresholds 2.67 kPa (20 mmHg) after 20 minutes of ALP-CPR. Values at 20 minutes reflect the patient's' response' to resuscitation efforts. We recommend 20-minute (final PetCO 2 ) to be ranked in Utstein-style reports. The results of the study confirm that PetCO 2 can play a pivotal role in the multi factorial decision-making process of whether to discontinue resuscitative efforts. Application of our findings could improve clinical prediction rules in the field and reduce the number of patients with cardiac arrest who undergo prolonged, futile resuscitation efforts; furthermore, there is less cost involved in the transfer of the patient to the hospital.

Conclusion
PetCO 2 levels should be monitored during ALP-CPR and could be regarded as having prognostic value for determining the outcome of resuscitative efforts. PetCO 2 levels should be monitored during CPR and considered as a useful prognostic value for determining the outcome of resuscitative efforts and when to cease CPR in the field. Based on our study findings, we believe that PetCO 2 monitoring should be included in advanced cardiac life support and ranked in Utstein-style reports to provide insight into the condition of patients suffering cardiac arrest.

Preliminary swine study using the abdominal lifting/ compression device
In the preliminary study of the abdominal/lifting compression device, 30 pigs were randomly divided into 2 groups with 15 pigs in each group. A coronary arrest model was produced by asphyxia as a result of clamping the trachea, and abdominal lifting and compression cardiopulmonary resuscitation (ALP-CPR) was performed in one group and standard CPR in the other group. Electrocardiogram (ECG), pulse oxygen saturation (SpO 2 ), arterial partial pressure of oxygen (PaO 2 ), end-tidal partial pressure of carbon dioxide (PEICO 2 ), aorta systolic blood pressure (SBP), diastolic blood pressure (DBP), central venous pressure (CVP), and tidal volume (V T ) were monitored continuously from 10 minutes before asphyxia to the end of the experiment. The aorta mean arterial pressure (MAP), coronary perfusion pressure (CPP), and minute ventilation (MV) were calculated from the aforementioned data. Arterial blood samples were collected for blood gas analysis at 10 minutes before asphyxia, 10 minutes after asphyxia, and at 5, 10, and 20 minutes after resuscitation. Restoration of spontaneous circulation (ROSC) rate, 24-hour survival rate, and 24-hour neurological function score were the outcome measures. There were no significant differences in all mentioned indexes between the 2 groups at 10 minutes before and 10 minutes after asphyxia. At 2 minutes after the resuscitation, the MAP and CPP in the standard CPR group were significantly higher than those in the ALC-CPR group (MAP: 43.60±12.91 vs. 33.40±6.59 mmHg, respectively, P <0.05; CPP: 21.67±11.28 vs. 11.80±4.16mmHg, respectively, P< 0.01). The V T and MV in the ALC-CPR group were significantly higher than in the standard CPR group (V T : 111.6 ±18.12 vs. 56.60±7.76 ml, respectively; MV: 11.17 ± 1.81 vs. 5.54 ± 0.79L/min, respectively, both, P < 0.01). At 20 minutes after resuscitation, pH, PaO 2 in ALC-CPR group were significantly higher than in the standard CPR group (pH: 7.16±0.16 vs. 7.01±0.14; PaO 2 : 82.73±13.20 vs. 58.33±17.77mmHg; respectively), HCO 3 -and base excess (BE) were significantly lower (HCO 3 -: 27.71±3.11 vs. 21.044±3.62mmol/L; BE: -4.78±4.30 vs. -10.23±2.12mmol/L, respectively) (all, P< 0.05). PaCO2, K + , and lactic acid were significantly lower in the ALP-CPR group than in the standard CPR group (PaCO 2 : 49.40±15.60 vs. 79.80±15.35mmHg; K + : 7.18±1.76 vs. 8.55±1.02mmol/L; lactic acid: 8.17±1.46 vs. 10.39±1.92mmol/L, respectively) (all, P< 0.05). The ROSC rate and 24-hour survival rate in ALC-CPR group were significantly higher than on the standard CPR group (ROSC rate: 80.0 vs. 26.7%, P < 0.01; 24 hour survival rate: 60.0 vs. 13.3%, respectively, P < 0.05). The 24-hour neurological function score was significantly lower in the ALP-CPR group than in the standard CPR group (1.11 ± 0.33 vs. 3.50±0.70, respectively, P < 0.01). These data lead us to conclude that ALP-CPR was at least as effective as standard CPR and that a clinical study was warranted.