Bag-valve Device Research Articles

Effects of decreasing inspiratory flow rate during simulated basic life support ventilation of a cardiac arrest patient on lung and stomach tidal volumes

If the airway of a cardiac arrest patient is unprotected, basic life support with low rather than high inspiratory flow rates may reduce stomach inflation. Further, if the inspiratory flow rate is fixed such as with a resuscitator performance may improve; especially when used by less experienced rescuers. The purpose of the present study was to assess the effect of limited flow ventilation on respiratory variables, and lung and stomach volumes, when compared with a bag valve device. After institutional review board approval, and written informed consent was obtained, 20 critical care unit registered nurses volunteered to ventilate a bench model simulating a cardiac arrest patient with an unprotected airway consisting of a face mask, manikin head, training lung [with lung compliance, 50 ml/0.098 kPa (50 ml/cmH2O); airway resistance, 0.39 kPa/l/s (4 cmH2O/l/s)] oesophagus [lower oesophageal sphincter pressure, 0.49 kPa (5 cmH2O)] and simulated stomach. Each volunteer ventilated the model with a self-inflating bag (Ambu, Glostrup, Denmark; max. volume, 1500 ml), and a resuscitator providing limited fixed flow (Oxylator EM 100, CPR Medical devices Inc., Toronto, Canada) for 2 min; study endpoints were measured with 2 pneumotachometers. The self-inflating bag vs. resuscitator resulted in comparable mean±SD mask tidal volumes (945±104 vs. 921±250 ml), significantly (P<0.05) higher peak inspiratory flow rates (111±27 vs. 45±21 l/min), and peak inspiratory pressure (1.2±0.47 vs. 78±0.07 kPa), but significantly shorter inspiratory times (1.1±0.29 vs. 1.6±0.35 s). Lung tidal volumes were comparable (337±120 vs. 309±61 ml), but stomach tidal volumes were significantly (P<0.05) higher (200±95 vs. 140±51 ml) with the self-inflating bag. In conclusion, simulated ventilation of an unintubated cardiac arrest patient using a resuscitator resulted in decreased peak flow rates and therefore, in decreased peak airway pressures when compared with a self-inflating bag. Limited flow ventilation using the resuscitator decreased stomach inflation, although lung tidal volumes were comparable between groups.

Assessment of the use of the laryngeal tube for cardiopulmonary resuscitation in a manikin

During 60 3-min CPR sequences, the face mask, laryngeal tube and tracheal tube were compared using an Ambu Megacode Trainer. Ten 3-min sequences each were performed for both a combination of the face mask and laryngeal tube with a bag-valve device (compression–ventilation ratio 5:1). With continuous chest compressions, ten 3-min CPR sequences each were performed for a combination of the laryngeal tube and tracheal tube with a bag-valve device and ten 3-min CPR sequences each for a combination of the laryngeal tube and tracheal tube with an automatic transport ventilator. Signs of gastric inflation occurred only with the face mask. Ventilation with the laryngeal tube was significantly better than with the face mask and comparable to the tracheal tube during ventilation with the bag-valve device and with the automatic transport ventilator. Chest compressions caused a significant decrease in tidal volumes during ventilation with the automatic transport ventilator. The findings of this study support the idea of the laryngeal tube as a new adjunct for emergency airway management, but will have to be verified during clinical practice.

Ease of ventilation through the cuffed oropharyngeal airway (COPA), the laryngeal mask airway and the face mask in a cardiopulmonary resuscitation training manikin

The aim of this study was to compare ease of ventilation of a cardiopulmonary resuscitation manikin using a cuffed oropharyngeal airway (COPA), a laryngeal mask airway (LMA) and a face mask, by two groups of people with different levels of earlier experience in cardiopulmonary resuscitation (CPR). Enrolled were, 108 people identified as experienced (54), or inexperienced (54), in CPR. Training equipment included a manikin, a COPA ( n=10), an LMA ( n=4), a face mask ( n=4) and self-inflating bag-valve device. The same investigator explained the theoretical use and practice of the three techniques with the subjects in groups of three. The variables recorded were the number of attempts needed to achieve correct placement (and a tidal volume of 200 ml, was achieved), the insertion time for the COPA and the LMA, and the average time taken to achieve the first ten correct ventilations. The face mask and LMA required fewer attempts for correct placement than did the COPA. The LMA also took less time to insert than the COPA. The face mask required a significantly shorter total time with all attempts and the mean time of placement and time to achieve ten correct ventilations was shorter than with either the LMA or the COPA ( P=0.0001). We conclude that the face mask offers an easier and quicker way to provide ventilation for CPR manikins than does the COPA or the LMA. Earlier experience affects the ease of insertion of the LMA and the total time needed to achieve effective ventilation.

A simple strategy to improve first breath oxygen delivery by self inflating bag

The text book of Pediatric Advanced Life Support of the American Heart Association recommends that a reservoir is used with a self inflating bag valve device. The figure in the book suggests that if such a device is connected to an oxygen supply, the oxygen will fill the bag first and then go on to fill the reservoir. However the valve structure of the self-inflating device does not permit active entry of oxygen into the bag, unless the bag is deflated and allowed to reinflate, drawing oxygen from the reservoir. We did this study to test the concentration of oxygen delivered in the first few breaths with the help of a Miniox-III oxygen monitor probe (MSA Medical Products, Pittsburgh, PA 15230) inserted into a self inflating bag (AMBU). Twenty-one percent oxygen is delivered with first breath and it rose to 42 and 58% with the second and third inflations, respectively. Eighty percent oxygen was achieved after eight reinflation cycles. We developed a formula to calculate the concentration of oxygen in the bag after each inflation effort, assuming that there was no passive diffusion of oxygen. We suggest that compressing the bag 8–12 times prior to putting the mask to the face of the patient will allow 80% oxygen to be delivered with first breath.

Cultivating Conscience: Learning to Make End-of-Life Decisions in the Emergency Department

Cultivating Conscience: Learning to Make End-of-Life Decisions in the Emergency Department

Effectiveness of mask ventilation in a training mannikin. A comparison between the Oxylator EM100 and the bag-valve device

The demands for an optimal ventilation apparatus are that it can be easily handled, achieves a sufficiently high ventilation volume, and minimizes gastric inflation. Our aim was therefore to carry out a study in a training mannikin to find out whether the Oxylator EM100, compared with the bag, obtains improved ventilation and a decrease in gastric inflation. In a randomized crossover study, 72 subjects were selected (24 physicians, 44 nurses and 4 auxiliary nurses), chosen from the operating theatre, emergency department and intensive care unit of two hospitals. We used the Ambu®-Bag Mark III with mask No. 4, the Oxylator EM100 with a pressure setting of 35 cm H 2O run in the manual setting, the Ambu®-Man C mannikin as well as the Ambu®-CPR computer program. The resuscitation cycles of the standard two-rescuer's adult procedure lasted 3 min each, with a 3-min pause between the crossover procedure. The participants could improve their ventilatory volume with the Oxylator EM100 by 635 ml (95% confidence interval 578–692 ml) compared with the bag ventilation. The number of subjects who could attain a mean ventilatory volume of 800 ml or more increased from 15% to 98.6% ( P<0.001). Compared with the bag, the increase of adequate respirations (≥800 ml) obtained by the Oxylator EM100 for the individual participants amounted to a median of 91% ( P<0.001). Moreover, conventional ventilation caused in 42% one or several instances of gastric inflation, whereas no such reactions occurred with the Oxylator EM100. The Oxylator EM100 showed significantly better results in the mannikin than the bag. Of most importance is a significant lowering of gastric inflation and less so a marked increase in ventilatory volume. Our trial procedure with a relatively high lung compliance and a high oesophageal sphincter opening simulated favorable conditions. Owing to a large in vivo variability of these magnitudes, a direct testing in real patients with circulatory arrest is indicated.

Inadequate respiratory support in head injury patients

Hyperventilation with 100% inspired oxygen is standard practice in victims of head trauma and is directed at both reduction of intracranial pressure and ensuring adequate oxygenation. Previous studies have established that medical care providers are inconsistent in maintaining respiratory rate and depth of ventilation with a bag valve device (BVD), producing both respiratory alkalosis and acidosis. A retrospective review of arterial blood gases of 160 trauma patients who were intubated and hyperventilated with BVD during transport from the scene or referring hospital revealed that 98.7% were adequately oxygenated on arrival in the emergency department (ED). Only 53.8% were both adequately oxygenated and appropriately hyperventilated. Inadequate hyperventilation (38%) and over-ventilation (6.9%) occurred more frequently than hypoxia unaccompanied by a ventilatory change (1.3%). The authors conclude that even with the most skilled of emergency care providers, inappropriate ventilation occurred in almost half (45%) of the patients with uncontrolled BVD ventilation during transport to the ED. Future studies are needed to explore alternative strategies that ensure prehospital ventilation.

Two-thumb versus two-finger chest compression during CRP in a swine infant model of cardiac arrest.

To test the hypothesis that two-thumb chest compression generates higher arterial and coronary perfusion pressures than the current American Heart Association-approved two-finger method. Randomized, crossover experimental trial. Animal laboratory experiment with seven swine of either sex weighing 9.4 kg (SD, 0.8 kg), representing infants less than 1 year old. Animals were sedated with IM ketamine/xylazine, intubated with a 6.0 Hi-Lo endotracheal tube, anesthetized with alpha-chloralose, and paralyzed with pancuronium. ECG was monitored continuously. Left femoral arterial and Swan-Ganz catheters were placed. Cardiac arrest was induced with an IV bolus of KCl and verified by ECG and pressure tracings. Five American Heart Association-certified basic rescuers were randomly assigned to perform external chest compressions for one minute by either the currently recommended two-finger method or the two-thumb and thorax-squeeze method. After all five completed their first trial, rescuers crossed over to the other method for a second minute of compressions. Ventilation was performed with a bag-valve device, and no drugs were given during CPR. After three complete cycles, the fourth through sixth cycles of compressions were recorded. Every compression was analyzed for arterial systolic, diastolic, mean, and coronary perfusion pressures. One thousand fifty compressions were analyzed with repeated-measures analysis of variance and Scheffé multiple comparisons. Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and coronary perfusion pressure were all significantly higher (P < .001) with the two-thumb thoracic squeeze technique: systolic blood pressure, 59.4 versus 41.6 mm Hg; diastolic blood pressure, 21.8 versus 18.5 mm Hg; mean arterial pressure, 34.2 versus 26.1 mm Hg; and coronary perfusion pressure, 15.1 versus 12.2 mm Hg. The two-thumb method of chest compression generates significantly higher arterial and coronary perfusion pressures than the two-finger method in this infant model of cardiac arrest.

Pneumothorax Reexacerbated by a Self-inflating Bag-valve Device

Pneumothorax Reexacerbated by a Self-inflating Bag-valve Device

Pneumothorax Reexacerbated by a Self-inflating Bag-valve Device

Pneumothorax Reexacerbated by a Self-inflating Bag-valve Device

An evaluation of cannulae and oxygen sources for pediatric jet ventilation

The authors evaluated the cannulae and oxygen sources available for pediatric translaryngeal ventilation. Peak flow rates were measured and maximum tidal volumes (MTV) calculated for each combination of cannula and oxygen source. Standard 22, 20, 18, and 16 gauge intravenous catheters and a 14 gauge cannula designed for pediatric jet ventilation were tested. The oxygen sources evaluated included an adult bag-valve device; a continuous flow source regulated between 6 to 15 L/min; and a high pressure jet source regulated between 5 to 50 psi. Mean calculated MTV delivered to the cannula tip (22 g to 14 g) were: 26 to 235 mL with the bag-valve source; 91 to 236 mL with the continuous flow sources; and 58 to 1034 mL with the jet sources. Assuming that in normal subjects approximately 70% of the flow from the tip of a translaryngeal cannula reaches the distal respiratory tree, the authors conclude that bag-valve and continuous flow low pressure sources are unlikely to deliver sufficient tidal volumes to sustain normal ventilation in apneic children when coupled with standard cannulae. Jet oxygen sources with standard cannulae provide a wide range of tidal volumes, sufficient to sustain normal ventilation in apneic pediatric patients.

Myths and pitfalls in emergency translaryngeal ventilation: correcting misimpressions.

Translaryngeal jet ventilation has been proven an effective emergency airway alternative. However, confusion exists as to the proper cannulae and oxygen sources for this technique. Our study was designed to determine the delivered volumes of gas using cannulae and oxygen sources recommended in previous reports on translaryngeal jet ventilation. From this, we hope to clarify the proper technique of translaryngeal jet ventilation. Using a variety of oxygen sources and cannulae, peak flow rates were measured using a digital flowmeter. Delivered volumes of gases generated with each combination were then calculated. All of the cannulae tested (standard 16-gauge IV cannulae and larger) provided peak flow rates high enough so that predicted tidal volumes would be adequate to maintain adequate ventilation in apneic adults when a 50-psi source was used. Only a 4-mm tracheal cannula provided comparable values when a bag-valve device was used. No cannulae provided sufficient flow rates to ensure adequate ventilation in apneic adults when a demand-valve mechanism of 60 cm H2O driving pressure served as the source. Our observations were consistent with previous clinical studies and suggest that standard translaryngeal jet ventilation cannulae (12 to 16 gauge) must be connected to an oxygen source of 50 psi in apneic adults. Demand-valve devices do not provide sufficient driving pressures for these cannulae. A cannula of 4 mm ID should be placed if only a bag-valve device is available for ventilation.