Carbon dioxide levels during pre-hospital active compression–decompression versus standard cardiopulmonary resuscitation
Introduction
Active compression combined with active decompression (ACD) improves organ perfusion during cardiopulmonary resuscitation (CPR) as compared with the standard technique where active compression is followed by passive decompression 1, 2, 3, 4, 5. ACD-CPR enhances intrathoracic blood flow and venous return, thus increasing cardiac output 6, 7, 8, 9, 10. The positive effects of this method upon cerebral and coronary blood flow have been demonstrated in numerous animal studies 11, 12, 13, 14, 15, 16, 17. However, only a few clinical studies revealed increased survival rates with ACD-CPR 18, 19, 20, 21, 22, 23, 24, 25, 26.
Studies of the haemodynamic effects of ACD-CPR as compared with standard CPR have been limited to laboratory or in-hospital settings. So far, invasive monitoring during CPR in a pre-hospital setting has been restricted to a few patients due to the sophisticated technical and intensive manpower requirements associated with these methods.
End-tidal carbon dioxide pressure (petCO2) correlates well with cardiac output, coronary perfusion pressure, and mean aortic pressure during CPR 27, 28, 29, 30, 31, 32. It is easy to measure and has therefore been used as an indirect parameter for haemodynamic monitoring during CPR in emergency departments, intensive care units, and pre-hospital emergency medical services (EMS) 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45. Capnometry allows comparison of different methods of CPR under various circumstances 34, 37, 38, 40, 46.
Our study aimed at comparing petCO2 levels during ACD and standard CPR in patients with out-of-hospital cardiac arrest. In a subgroup analysis petCO2 levels were compared in surviving and non-surviving patients.
Section snippets
Setting
The EMS system of the City of Mainz (190 000 inhabitants) comprises four emergency ambulances with paramedics in the first, and one physician-staffed mobile intensive care unit (MICU) in the second tier. Both the MICU and the emergency ambulance located closest to the emergency site are dispatched simultaneously by the control centre. Training in basic life support (BLS) and advanced life support (ALS) for all members of the EMS system follows international guidelines 46, 47.
Patients
Patients (N=120) of
Patients (Table 1)
In a 30-month period, 120 patients were included in the study. Patient groups were comparable as to age, gender, rate of witnessed arrests, incidence of bystander CPR, and first ECG-rhythm.
Time intervals (Table 2)
In all of the 120 patients a continuous time recording was started with the receipt of the call at the dispatch centre. In the case of a witnessed arrest (n=83) the time of collapse was additionally recorded.
There was no difference between the groups regarding the start of BLS measures, first defibrillation,
Discussion
In animal and in human studies ACD-CPR has been shown to improve myocardial and cerebral blood flow and cardiac output 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. However, these studies do not necessarily reflect clinical experience. Studies on haemodynamics were conducted within hospitals, with patients suffering from either extremely short or extremely long cardiac arrests, and conditions which allowed invasive monitoring during CPR 1, 2, 3. Pre-hospital conditions preclude routine use of invasive
Conclusion
In our prospective, randomised study there was no difference in petCO2 between patients resuscitated with the standard versus the ACD method. With the help of capnometry restoration of spontaneous circulation is noticed prior to a palpable pulse during both standard CPR and ACD-CPR. With both CPR methods a petCO2 of more than 15 mmHg during the first minutes of CPR indicates a successful resuscitation in the form of hospital admission. Due to its high prognostic value capnometry has become an
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