Original ContributionsCorrelation of arterial Pco2 and Petco2 in prehospital controlled ventilation
Introduction
Prehospital critical care teams manage critically ill patients. Endotracheal intubation and controlled ventilation, initiated in the field, are required in these emergency situations. Quality of prehospital ventilation is difficult to monitor. Owing to new sophisticated portable ventilators, progress has been made in assisted prehospital ventilation, which enables a better adaptation to the patient's respiratory requirements. Indeed, the latest achievements of these new ventilators allow for several types of assisted or controlled ventilation; in this way they improve the quality of mechanical prehospital ventilation, which is more appropriate to the patient's ventilation requirements, pathology, and background. Until recently, mechanical prehospital ventilation was monitored on clinical symptoms and capnography monitoring.
Capnography is now an obligation in anesthesia units and in operating rooms [1]. In the same way, monitoring of end-tidal carbon dioxide pressure (Petco2) has become essential in emergency departments and critical care units for many reasons [2], [3]. Capnography confirms the correct placement of the endotracheal tube and monitors the integrity of mechanical ventilation equipment [4], [5], [6]. Petco2 is also very helpful in cardiac resuscitation; indeed, recent studies have shown Petco2 values were a good indication of the adequacy of chest massage and predict survival in cardiac arrest [7], [8], [9], [10].
It is also recommended for prehospital monitoring of severe head trauma patients to avoid hypo- or hypercapnia during transportation [11], [12], [13], [14], [15]. But the ability of Petco2 to predict capnia has not been clearly established in out-of-hospital patients [14]. The aims of this study were to (1) determine the level of Paco2 − Petco2 gradient and (2) analyze the gradient variation during transportation time.
Section snippets
Study setting and population
This prehospital study has been carried out in the French emergency medical services system (SAMU) based on physician-staffed ambulances over a 16-month period. The French emergency medical services system is based on 2 types of ambulances: emergency medical technician (EMT)–staffed ambulances for basic life support and physician-staffed ambulances for advanced life support [16], [17]. The EMTs are members of the fire department or members of the French Red Cross. The telephone number is a
Results
A total of 100 patients were included in this study (mean age, 58.4 ± 16.4 years; 57 were male). Patients' disease data are noted in Table 1. Hemodynamic and ventilation data are shown in Table 2. Arterial blood gases results and calculated Paco2 − Petco2 are recorded in Table 3. The gradient between Paco2 and Petco2 was available for 96 patients at T0 and for 82 patients at Tend. The missing data for 18 patients were due to technical difficulties to obtain blood gas samples at T0 or Tend.
Even
Discussion
The role of capnography in prehospital management is indisputable [25], [26], [27]. Thus, capnometry's role is not any more to show in several applications: ensure correct placement of endotracheal tube [28], [29], verify the integrity of mechanical ventilation equipment [26], [28], and predicting outcome in patient survival. Moreover, because Petco2 seems to be strongly linked to the cardiac output [14], Petco2 is now used also during cardiopulmonary resuscitation to optimize chest massage [8]
Acknowledgment
We thank all the physicians and nurses who took part in this study. The authors gratefully thank Mrs Fiona Richardson for her help with the English revision and Prof Jean Mantz for his help in the response to the reviewers.
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