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International audience; BACKGROUND: Studying ventilation and intrathoracic pressure (ITP) induced by chest compressions (CC) during Cardio Pulmonary Resuscitation is challenging and important aspects such as airway closure have been mostly ignored. We hypothesized that Thiel Embalmed Cadavers could constitute an appropriate model.METHODS: We assessed respiratory mechanics and ITP during CC in 11 cadavers, and we compared it to measurements obtained in 9 out-of-hospital cardiac arrest patients and to predicted values from a bench model. An oesophageal catheter was inserted to assess chest wall compliance, and ITP variation (ΔITP). Airway pressure variation (ΔPaw) at airway opening and ΔITP generated by CC were measured at decremental positive end expiratory pressure (PEEP) to test its impact on flow and ΔPaw. The patient's data were derived from flow and airway pressure captured via the ventilator during resuscitation.RESULTS: Resistance and Compliance of the respiratory system were comparable to those of the out-of-hospital cardiac arrest patients (C 42 ± 12 vs C 37.3 ± 10.9 mL/cmHO and Res 17.5 ± 7.5 vs Res 20.2 ± 5.3 cmHO/L/sec), and remained stable over time. During CC, ΔITP varied from 32 ± 12 cmHO to 69 ± 14 cmHO with manual and automatic CC respectively. Transmission of ΔITP at the airway opening was significantly affected by PEEP, suggesting dynamic small airway closure at low lung volumes. This phenomenon was similarly observed in patients.CONCLUSION: Respiratory mechanics and dynamic pressures during CC of cadavers behave as predicted by a theoretical model and similarly to patients. The Thiel model is a suitable to assess ITP variations induced by ventilation during CC.

Aim To investigate whether titration of inspired oxygen can be achieved through adjustment of oxygen flow into a self-inflating resuscitation bag with a reservoir of a type used in standard ambulance practice. Methods In a series of bench experiments, oxygen was delivered via a flow metre to a 1500ml self-inflating resuscitation bag with a 2500ml reservoir bag and connected to a test lung. The oxygen concentration delivered to the test lung by manual inflation of the resuscitation bag was measured using an anaesthetic machine while the delivered tidal volume was measured using a respirometer. The delivered oxygen concentration was measured at flows of 0.5, 2, 6, 12 and 15lmin −1 for tidal volumes of 300, 600, and 900ml with bag inflation rates of 10, 20 and 30min −1 . Results A wide range of delivered oxygen concentrations ranging between 24% and 99.5% were achieved with different oxygen flows, tidal volumes, and inflation rates. Overall, the mean delivered oxygen concentration increased significantly with each of the increments of oxygen flow tested ( p Conclusions Effective titration of oxygen delivery can be achieved using adjustment of oxygen flow with a standard self-inflating resuscitation bag and reservoir.

The study aims to compare the performances (ease of insertion, time to establish effective ventilation and maximal inflation pressure) of classic™ (cLMA), ProSeal™ (PLMA) and Supreme™ (SLMA) Laryngeal Mask Airway when used in a neonatal airway management manikin by inexperienced delivery room trainees. The quality of the three devices, as perceived by participants, was also evaluated.Health-care professional trainees were given a brief supervised training with the three devices. Every trainee was then observed positioning each of the three different LMAs in a single occasion. Success rate, time (IT) and maximal inflation pressure (PI(max)) were recorded by a single unblinded observer. A 4-point scale was used to rate participants' perceived quality.A total of 40 health-care professional trainees participated in the study. There were five, three and one failed insertions at the first attempt with the cLMA, PLMA and SLMA, respectively. No failures to establish an effective airway within three attempts were recorded. The success rate at first attempt was comparable among the three devices. The mean IT was significantly lower with the SLMA as compared with PLMA (p0.01), but not to cLMA. The mean PI(max) was higher with SLMA than with cLMA and PLMA (p0.01). The ease of insertion as well as the effectiveness of ventilation were perceived by the participants as superior with SLMA as compared with cLMA and PLMA (p0.01).Neonatal SLMA is superior to PLMA in terms of time to establish effective ventilation; furthermore, maximal inflation pressure and quality perceived by the operator are higher with neonatal SLMA than with cLMA and PLMA. These manikin data could provide a useful guide for planning potential future clinical research involving the newly developed supraglottic device in neonates.

High oxygen concentration in blood may be harmful in the reperfusion phase after cardiopulmonary resuscitation. We compared the effect of 30 and 100% inspired oxygen concentrations on blood oxygenation and the level of serum markers (NSE, S-100) of neuronal injury during the early post-resuscitation period in humans.Patients resuscitated from witnessed out-of-hospital ventricular fibrillation were randomised after the return of spontaneous circulation (ROSC) to be ventilated either with 30% (group A) or 100% (group B) oxygen for 60 min. Main outcome measures were NSE and S-100 levels at 24 and 48 h after ROSC, the adequacy of oxygenation at 10 and 60 min after ROSC and, in group A, the need to raise FiO(2) to avoid hypoxaemia. Blood oxygen saturation95% was the threshold for this intervention.Thirty-two patients were randomised and 28 (14 in group A and 14 in group B) remained eligible for the final analysis. The mean PaO(2) at 10 min was 21.1 kPa in group A and 49.7 kPa in group B. The corresponding values at 60 min were 14.6 and 46.5 kPa. PaO(2) values did not fall to the hypoxaemic level in group A. In another group FiO(2) had to be raised in five cases (36%) but in two cases it was returned to 0.30 rapidly. The mean NSE at 24 and 48 h was 10.9 and 14.2 microg/l in group A and 13.0 and 18.6 microg/l in group B (ns). S-100 at corresponding time points was 0.21 and 0.23 microg/l in group A and 0.73 and 0.49 microg/l in group B (ns). In the subgroup not treated with therapeutic hypothermia in hospital NSE at 24h was higher in group B (mean 7.6 versus 13.5 microg/l, p=0.0487).Most patients had acceptable arterial oxygenation when ventilated with 30% oxygen during the immediate post-resuscitation period. There was no indication that 30% oxygen with SpO(2) monitoring and oxygen backup to avoid SpO(2)95% did worse that the group receiving 100% oxygen. The use of 100% oxygen was associated with increased level of NSE at 24h in patients not treated with therapeutic hypothermia. The clinical significance of this finding is unknown and an outcome-powered study is feasible.

It is believed that victims of traumatic hemorrhagic shock (HS) benefit from breathing 100% O(2). Supplying bottled O(2) for military and civilian first aid is difficult and expensive. We tested the hypothesis that increased FiO(2) both during severe volume-controlled HS and after resuscitation in rats would: (1) increase blood pressure; (2) mitigate visceral dysoxia and thereby prevent post-shock multiple organ failure; and (3) increase survival time and rate. Thirty rats, under light anesthesia with halothane (0. 5% throughout), with spontaneous breathing of air, underwent blood withdrawal of 3 ml/100 g over 15 min. After HS phase I of 60 min, resuscitation phase II of 180 min with normotensive intravenous fluid resuscitation (shed blood plus lactated Ringer's solution), was followed by an observation phase III to 72 h and necropsy. Rats were randomly divided into three groups of ten rats each: group 1 with FiO(2) 0.21 (air) throughout; group 2 with FiO(2) 0.5; and group 3 with FiO(2) 1.0, from HS 15 min to the end of phase II. Visceral dysoxia was monitored during phases I and II in terms of liver and gut surface PCO(2) increase. The main outcome variables were survival time and rate. PaO(2) values at the end of HS averaged 88 mmHg with FiO(2) 0.21; 217 with FiO(2) 0.5; and 348 with FiO(2) 1. 0 (P0.001). During HS phase I, FiO(2) 0.5 increased mean arterial pressure (MAP) (NS) and kept arterial lactate lower (P0.05), compared with FiO(2) 0.21 or 1.0. During phase II, FiO(2) 0.5 and 1. 0 increased MAP compared with FiO(2) 0.21 (P0.01). Heart rate was transiently slower during phases I and II in oxygen groups 2 and 3, compared with air group 1 (P0.05). During HS, FiO(2) 0.5 and 1.0 mitigated visceral dysoxia (tissue PCO(2) rise) transiently, compared with FiO(2) 0.21 (P0.05). Survival time (by life table analysis) was longer after FiO(2) 0.5 than after FiO(2) 0.21 (P0. 05) or 1.0 (NS), without a significant difference between FiO(2) 0. 21 and 1.0. Survival rate to 72 h was achieved by two of ten rats in FiO(2) 0.21 group 1, by four of ten rats in FiO(2) 0.5 group 2 (NS); and by four of ten rats of FiO(2) 1.0 group 3 (NS). In late deaths macroscopic necroses of the small intestine were less frequent in FiO(2) 0.5 group 2. We conclude that in rats, in the absence of hypoxemia, increasing FiO(2) from 0.21 to 0.5 or 1.0 does not increase the chance to achieve long-term survival. Breathing FiO(2) 0.5, however, might increase survival time in untreated HS, as it can mitigate hypotension, lactacidemia and visceral dysoxia.

In the clinical literature there are reports of patients failing to breathe and becoming comatose when supplied with 100% oxygen for respiratory distress. This effect has been attributed to a loss of respiratory drive. Recent studies have established that this explanation is incorrect, but have left the phenomenon unexplained. We propose that the apnea and coma reported is due to carbon dioxide narcosis. We have reproduced this effect in an animal model and have documented PCO2 values in excess of 250 mmHg during the apneic period. Our results suggest that this level of PCO2 suppresses both brainstem auditory evoked potentials and spontaneous respiration. The high PCO2 is due to inadequate gas exchange, and is easily remedied by provision of adequate ventilation.