Ventilatory volumes using mouth-to-mouth, mouth-to-mask, and bag-valve-mask techniques

The volumes delivered to a resuscitation manikin were compared using four ventilatory techniques: mouth-to-mouth, mouth-to-mask, one-person bag-valve-mask, and two-person bag-valve-mask. The effects of experience and sex of the rescuer on the resuscitation volume delivered were also evaluated. The volume delivered using the one-person bag-valve-mask technique was significantly less than that using the other three techniques (P less than 0.001). The experience and sex of the rescuer made no significant difference in the volume delivered using any of the techniques. As compared with the one-person technique, bag-valve-mask ventilatory volume improved significantly when it was performed as a two-person technique. The mean volumes delivered using mouth-to-mouth and mouth-to-mask ventilation were lower than those recommended by the American Heart Association. Emphasis must be placed on ventilation with an adequate volume when these techniques are taught. When mouth-to-mouth and mouth-to-mask ventilation are taught, a spirometer should be used with the manikin so that the rescuer can learn how to estimate an adequate expired volume.     

Resistance to flow through the valves of mouth-to-mask ventilation devices

We conducted this study to determine the inspiratory and expiratory flow resistance of the valves of eight commercially available mouth-to-mask ventilation devices. METHODS & MATERIALS: We evaluated the valves of Intertech, Laerdal, Life Design Systems (LDS), Res-Q, Respironics, Rondex, Vital Signs, and White. The devices were supplied by the manufacturers and included the valve and any filter or extension tube supplied with the valve. Expiratory resistance was evaluated by directing air through the valve in the direction of flow when the patient exhales. Inspiratory resistance was evaluated by directing air through the valve in the direction of flow when a breath is delivered to the patient. Flow was controlled by a Timeter 0-75 flowmeter and measured using a calibrated Timeter RT-200. Flows of 10, 20, 30, 40, 50, 60, 70, 80, and 90 L/min were used. 'Back' pressure due to the resistance of the valves was measured using a calibrated Timeter RT-200. Resistance was calculated by dividing back pressure by flow. Five measurements were made at each flow setting for each valve. RESULTS: We observed significant differences in back pressures and resistances between the flows evaluated (p < 0.001 for both inspiratory and expiratory flows), and between the commercially available devices (p < 0.001 for both inspiratory and expiratory flows). At a flow of 50 L/min, the inspiratory back pressures produced by the devices were [mean (SD) in cm H2O] Intertech 5.2 (0.06), Laerdal 4.6 (0.09), LDS 4.7 (0.03), Res-Q 3.1 (0.04), Respironics 3.3 (0.04), Rondex 1.1 (0.02), Vital Signs 4.0 (0.06), and White 4.3 (0.10). At this same flow, the expiratory back pressures were Intertech 4.8 (0.30), Laerdal 9.1 (0.10), LDS 3.3 (0.02), Res-Q 3.7 (0.35), Respironics 0.5 (0.01), Rondex 1.4 (0.01), Vital Signs 3.6 (0.05), and White 13.7 (0.48). CONCLUSIONS: In some cases, the resistance through these devices might be considered excessive; however, most of the devices meet the International Standards Organization (ISO) standard (back pressure < 5 cm H2O at 50 L/min).     

Comparison of mouth-to-mouth resuscitation and Combitube ventilation in a bench model

CONTEXT: In addition to heart massage, the primary goal of cardiopulmonary resuscitation is efficient oxygenation and ventilation. OBJECTIVE: To compare the ease of learning and handling of standard mouth-to-mouth resuscitation with the Combitube (Tyco Healthcare Nellcor, Pleasanton, CA) ventilation. METHODS: After a 30 minute theoretical introduction and demonstration of mouth-to-mouth resuscitation and use of the Combitube in mannequins, following American Heart Association guidelines, 26 adolescent school children (15 of them 14 years old, 11 of them 10 years old) undertook two ventilation trials, each consisting of five single ventilations, with each technique. Only the second trial with each technique was evaluated. Qualitative implementation (grades: very good, good, failed) was evaluated, several procedure-related time points were recorded, and tidal volumes (ml) were measured. RESULTS: With mouth-to-mouth resuscitation, the time interval until start of first ventilation was 36.5 seconds shorter than with the Combitube (P < 0.001). With the Combitube, the time needed for five single ventilations was 6.4 seconds less than with mouth-to-mouth resuscitation (P < 0.001) and mean tidal volumes were higher (mouth-to-mouth resuscitation, 450 +/- 384 ml, versus Combitube, 735 +/- 358 ml; P < 0.05). CONCLUSION: Most of the school children performed both techniques to a high qualitative level. The study shows that mouth-to-mouth resuscitation and use of the Combitube have equal ease of learning, a precondition for proficient retention of skills. Tidal volumes were significantly higher with the Combitube and, not surprisingly, the time interval until the start of first ventilation was significantly shorter with mouth-to-mouth resuscitation. Regardless of the ventilation technique or device, we believe that subsequent retraining of ventilation skills is very important.     

Infant ventilation and oxygenation by basic life support providers: comparison of methods

INTRODUCTION: Little information is available in the performance of infant ventilation by basic life support (BLS) personnel. HYPOTHESIS: There are no significant differences between mouth-to-mouth (M-M), mouth-to-mask (M-Ma), pediatric bag-mask (PBM), and adult bag-mask (ABM) devices in the percent of acceptable breaths delivered by BLS providers. METHODS: Fifty certified BLS providers performed five ventilation methods in random sequences for 60 seconds each on a 5kg infant mannequin following standardized instructions. Supplemental oxygen, 10 l/min, was supplied with one M-Ma trial and PBM methods. Airway patency, peak airway pressure (PAP), ventilatory rate (VR), tidal volume, and delivered oxygen concentration (FiO 2) were recorded. The percent of breaths with excessive PAP (i.e., greater than 30 mmHg), percent of acceptable breaths using loose (i.e., 25-125ml) and strict (i.e., 50-100ml) criteria, and FiO 2 at 15, 30, 45, and 60 seconds were compared between ventilation methods using ANOVA. RESULTS: For all subjects and those with a patent airway (n=36), there were no significant differences in the percentage of acceptable breaths produced by PBM (56+/-6) (mean+/-SEM; all subjects) and ABM (41+/-6.2) was significantly greater than M-Ma, with and without a patent airway. Although RR and the percentage of excessive breaths were not significantly different, the percentage of acceptable breaths and FiO 2 delivered with each ventilation method was significantly better in the patent airway group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bench evaluation: three face-shield CPR barrier devices

Due to the fear of disease transmission, the practice of mouth-to-mouth (M-M) rescue breathing is rarely performed; to address this concern, many types of CPR barrier devices have been developed. These include bag-valve-mask devices, mouth-to-mask devices, and face shields (FS). The purpose of this study was to measure the volumes delivered during mouth-to-face shield (M-FS) breathing, to measure the back pressure and calculate the resistance to flow through their 1-way valves, and to test for backward leak of gas through the valves. METHODS: Three FS brands were evaluated: Kiss of Life (KOL), MicroSHIELD (Micro) and Res-Cue Key (RCK). Volume delivered during M-M and M-FS breathing was evaluated by 10 rescuers who used the devices while performing rescue breathing on a CPR mannequin. Back pressure was measured and resistance calculated by directing airflow through the 1-way valves. Backward leak was evaluated by measuring the O2 concentration at the rescuer side of the valve while 100% O2 was directed toward the patient side of the valve. Differences among the brands were evaluated using analysis of variance. RESULTS: The mean (SD) values for volumes in L were: M-M 1.00 (0.25), Micro 0.77 (0.20), RCK 0.64 (0.10), and KOL 0.24 (0.11). Mean values for back pressure in cm H2O at 50 L/min were Micro 16.7 (1.29), KOL 7.22 (0.13), and RCK 2.15 (0.16). Significant backward leak only occurred with RCK. CONCLUSION: Not one of the FSs tested met all of the requirements suggested by the American Heart Association and by the International Standards Organization.     

Decreasing peak flow rate with a new bag-valve-mask device: effects on respiratory mechanics,and gas distribution in a bench model of an unprotected airway

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. The purpose of this study was to assess the effects of a newly developed bag-valve-mask device (SMART BAG), O-Two Systems International, Ont., Canada) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/cm H(2)O, airway resistance 4 cm H(2)O/l/s, lower oesophageal sphincter pressure 20 cm H(2)O and simulated stomach). Twenty nurses were randomised to each ventilate the manikin using a standard single person technique for 1 min (respiratory rate, 12/min) with either a standard adult self-inflating bag, or the SMART BAG. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG vs. standard self-inflating bag resulted in significantly (P<0.05) lower mean+/-S.D. peak inspiratory flow rates (32+/-2 vs. 61+/-13 l/min), peak inspiratory pressure (12+/-2 vs. 17+/-2 cm H(2)O), lung tidal volumes (525+/-111 vs. 680+/-154 ml) and stomach tidal volumes (0+/-0 vs. 17+/-36 ml), longer inspiratory times (1.9+/-0.3 vs. 1.5+/-0.3 s), but significantly higher mask leakage (26+/-13 vs. 14+/-8%); mask tidal volumes (700+/-104 vs. 785+/-172 ml) were comparable. The mask leakage observed is not an uncommon factor in bag-valve-mask ventilation with leakage fractions of 25-40% having been previously reported. The differences observed between the standard BVM and the SMART BAG are due more to the anatomical design of the mask and the non-anatomical shape of the manikin face than the function of the device. Future studies should remove the mask to manikin interface and should introduce a standardized mask leakage fraction. The use of a two-person technique may have removed the problem of mask leakage. In conclusion, using the SMART BAG during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate, peak inspiratory pressure, stomach tidal volume, and resulted in a significantly longer inspiratory time when compared to a standard self-inflating bag.     

Prevention of oral bacterial flora transmission by using mouth-to-mask ventilation during CPR

The Emergency Cardiac Care Committee of the American Heart Association has recently recommended utilizing protective barrier precautions during CPR (1,2). We assessed 17 mask and faceshield resuscitation devices for adequacy of barrier protection. Eight of the devices were faceshields (CPR Microshield, Hygenic, MedCare Mask, Resusci, Samaritan, Sealeasy, Portex); 8 were mask devices (Laerdal, Dyna Med, MTM Emergency Lung Ventilator, MTM Emergency Resuscitator, Res-Q-Flo, Rightway Mouth-to-Mask Resuscitation, Trufit), and one of the devices did not meet the criteria for either faceshield or mask (Lifesaver). All masks were disinfected, applied to the investigator's face as directed by the manufacturers' instructions, and then cultured for oral aerobic bacterial flora on the rescuer side. No mask devices cultured positive for oral aerobic bacterial flora, while 6 of 8 faceshield devices cultured positive for oral aerobic bacterial flora (P less than 0.007). The CPR Microshield and the Portex faceshield were the only devices that did not develop a positive culture. We conclude that all ventilation devices with a one-way valve, except the Sealeasy device, provide adequate barrier type protection from oral aerobic bacterial flora when simulating mouth-to-barrier type protection when performing mouth-to-mouth ventilation.     

A strategy to optimise the performance of the mouth-to-bag resuscitator using small tidal volumes: effects on lung and gastric ventilation in a bench model of an unprotected airway

When ventilating an unintubated patient with a standard adult self-inflating bag, high peak inspiratory flow rates may result in high peak airway pressures with subsequent stomach inflation. In a previous study we have tested a newly developed mouth-to-bag-resuscitator (max. volume, 1500 ml) that limits peak inspiratory flow, but the possible advantages were masked by excessive tidal volumes. The mouth-to-bag-resuscitator requires blowing up a balloon inside the self-inflating bag that subsequently displaces air, which then flows into the patient's airway. Due to this mechanism, gas flow and peak airway pressures are reduced during inspiration when compared with a standard bag-valve-mask-device. In addition, the device allows the rescuer to use two hands instead of one to seal the mask on the patient's face. The purpose of the present study was to assess the effects of the mouth-to-bag-resuscitator, which was modified to produce a maximum tidal volume of 500 ml, compared with a paediatric self-inflating bag (max. volume, 380 ml), and a standard adult self-inflating bag (max. volume, 1500 ml) in an established bench model simulating an unintubated patient with respiratory arrest. The bench model consisted of a face mask, manikin head, training lung (lung compliance, 100 ml/0.098 kPa (100ml/cm H2O); airway resistance, 0.39 kPa/(l s) (4 cm H2O/(l s)), and a valve simulating lower oesophageal sphincter pressure, 1.47 kPa (15 cm H2O). Twenty critical care nurses volunteered for the study and ventilated the manikin for 1 min with a respiratory rate of 20 min(-1) with each ventilation device in random order. The mouth-to-bag-resuscitator versus paediatric self-inflating bag resulted in significantly (P < 0.05) higher lung tidal volumes (302 +/- 41 ml versus 233 +/- 22 ml), and peak airway pressure (10 +/- 1 cm H2O versus 9 +/- 1 cm H2O), but comparable inspiratory time fraction (28 +/- 5% versus 27 +/- 5%, Ti/Ttot), peak inspiratory flow rate (0.6 +/- .01 l/s versus 0.6 +/- 0.2 l/s), and stomach inflation (149 +/- 495 ml/min versus 128 +/- 278 ml/min). In comparison with the adult self-inflating bag, there was significantly (P < 0.05) less gastric inflation (3943 +/- 4896 ml/min versus 149 +/- 495 ml/min versus 128 +/- 278 ml/min, respectively) with both devices, but the standard adult self-inflating bag had significantly higher lung tidal volumes (566 +/- 77 ml), peak airway pressure (13 +/- 1 cm H2O), and peak inspiratory flow rate (0.8 +/- 0.11 l/s). In conclusion, comparing the mouth-to-bag-resuscitator with small tidal volumes versus the paediatric self-inflating-bag during simulated ventilation of an unintubated patient in respiratory arrest resulted in comparable marginal stomach inflation, but significantly reduced the likelihood of gastric inflation compared to the adult self-inflating-bag. Lung tidal volumes were improved from approximately 250 ml with the paediatric self-inflating-bag to approximately 300 ml with the mouth-to-bag-resuscitator.     

Evaluation of five adult disposable operator-powered resuscitators.

We evaluated the performance and safety of five adult disposable operator-powered resuscitators: BagEasy, Bag Mask Resuscitator, Pulmanex, 1st Response, and Stat Blue. METHOD: We tested the devices against the American Society for Testing and Materials (ASTM) Standard F-920-85. We tested each resuscitator by using it to ventilate a lung model, the Bio-Tek VT-1 Adult Ventilator Tester. RESULTS: All resuscitators met the requirements of VT 600 mL, f 20/min, and I:E less than 1:1. Standard F-920 specifies a fractional delivered O2 concentration (FDO2) greater than or equal to 0.85 with attachments and greater than or equal to 0.40 without attachments, at oxygen flows of 15 L/min and VE of 7.2 L (600 mL x 12). The Pulmanex with bag reservoir attached had a mean +/- SD FDO2 of 0.74 +/- 0.02, and the other four devices had an FDO2 of 0.93 +/- 0.02. Without attachments only the 1st Response and BagEasy had FDO2 greater than or equal to 0.40. All devices when disabled with simulated vomitus were restored to proper function within 20 s and were functional at O2 flow of 30 L/min. Only the Bag Mask Resuscitator did not pass the drop test. Only the Stat Blue did not pass the back-leak test. CONCLUSIONS: Although we do not have practical experience with these resuscitators, we conclude that only 1st Response and BagEasy meet the ASTM standard for operator-powered resuscitators and that, of the devices tested, only the 1st Response and BagEasy are acceptable replacements for permanent resuscitators.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of rescuer position on the kinematics of cardiopulmonary resuscitation (CPR) and the force of delivered compressions

BACKGROUND: Depending on the clinical setting, rescuers may provide CPR from a kneeling (if the patient is on the ground) or standing (if the patient is in a bed) position. The rescuer position may affect workload, and hence rate of fatigue and quality of CPR. PURPOSE: This study evaluates how three common rescuer positions affect the kinematics of CPR and the force of delivered compressions. METHODS: Subjects were 18 health care providers experienced in CPR. Each participant performed CPR from three different positions: kneeling beside the Resusci Anne manikin placed on the floor (F); standing beside the manikin placed on a Table 63 cm in height (H), and standing beside the manikin placed on a Table 37 cm in height (L). The compression to ventilation ratio was 15:2. CPR duration was 5 min for each position, with a rest period of 50 min in-between. The order of position was randomised. The manikin was equipped with a six-axial force load cell to collect 3D compression forces at a sampling rate of 1000 Hz. An eight-camera Motion Analysis Digital System was adopted to collect 3D trajectory information. Data were compared using crossover-design analysis of variance (p<0.05 was regarded as statistically significant). Ratings of Perceived Exertion (RPE) were measured by modified Borg scale. RESULTS: Significant differences were observed in the head, shoulder, lower trunk, hip and knee angles between the three methods. Lower trunk flexion angle (degrees) for H, L, and F were -14.52+/-1.13, -28.83+/-1.75, and 14.39+/-1.14, respectively. Hip flexion angle for H, L, and F were -16.21+/-3.30, -42.59+/-4.75, and -47.39+/-4.36, respectively. However, compression force (N) in H, L, and F were 455.8+/-17.6, 455.7+/-14.0, 461.5+/-13.5, respectively (p>0.05). Compression depths (mm) were: 43.5+/-3.4, 42.0+/-5.4, 44+/-5.2, respectively (p>0.05). Compression frequencies (times/min) were: 117.9+/-12.4, 116.6+/-13.4, 108.8+/-11.7, respectively (p>0.05). No differences were found between the three positions for RPE. CONCLUSIONS: In this study, while the kinematics of CPR differed significantly with varying rescuer position, these differences did not affect the compression force, depth and frequency as performed by experienced providers.     

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/cmH(2)O); airway resistance, 0.39 kPa/l/s (4 cmH(2)O/l/s)] oesophagus [lower oesophageal sphincter pressure, 0.49 kPa (5 cmH(2)O)] 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.     

Basic life support skills of doctors in a hospital resuscitation team

The aim of the present study was to evaluate the basic life support skills of doctors in a hospital resuscitation team and to identify potential factors affecting those skills. Twelve anesthesiology residents were induced in this study. Each doctor was asked to perform mouth-to-mouth ventilation for 10 minutes and then chest compression for another 10 minutes on a Laerdal Skillmeter Resusci-Anne manikin during the day (10 am) and at night (10 pm). The rates of correct ventilation, correct chest compression, ventilation errors (i.e., excessive inflation, stomach insufflation, insufficient ventilation), and compression errors (i.e., insufficient chest compression/decompression, excessive chest compression, incorrect hand placement) were determined for each 2-min interval up to 10 min. In addition, effects of sex, seniority, CPR duration, and time of day (day vs night) on those skills were assessed. The mean rates of correct ventilation were 53.3+/-23.9% (day) and 60.4+/-16% (night); the mean rates of correct chest compression, 76.9+/-15% (day) and 76.5+/-14.7% (night). During the first 2-minutes period of testing at night, men doctors more frequently achieved correct ventilation than did women doctors (p<0.05). Overall, the practical CPR skills of the study participants were not influenced by sex, seniority, CPR duration, or time of day; however, the participants' skills were poor. This suggests that all medical staff, especially members of in-hospital resuscitation teams, should undergo regular, periodic CPR training.     

Evaluation of ten disposable manual resuscitators

We evaluated the performance and safety of 10 disposable resuscitators -- six adult units: SPUR, Code Blue, 1st Response, Hospitak MPR, CPR Bag, and Pulmanex; and four pediatric units: CPR Bag, 1st Response, Hospitak MPR, and LSP Bag Mask. METHOD: We tested the devices against the American Society for Testing and Materials (ASTM) Standard F-920. We tested each resuscitator by using a lung model, the Bio-Tek VT-1 Ventilator Tester. RESULTS: All resuscitators met the ventilation requirements for VT and f (adult: 600 mL x 12/min; child: 300 mL x 20/min and 70 mL x 30/min) and I:E less than 1:1. Standard F-920 specifies a fractional delivered O2 concentration (FDO2) greater than or equal to 0.85 with attachments and greater than or equal to 0.40 without attachments, at oxygen flow of 15 L/min, and VE of 7.2 L (600 mL x 12/min) for adult units and VE of 6 L (300 mL x 20/min) for pediatric units. All 10 resuscitators met standard F-920 for FDO2 with attachments. Nine resuscitators met the FDO2 standard without attachments. The 10 resuscitators passed the test for valve function after contamination with simulated vomitus, at an oxygen flow of 30 L/min, and for backward leakage. Three pediatric resuscitators (1st Response, Hospitak MPR, and LSP Bag Mask) did not pass the pressure-limit requirement of 40 +/- 10 cm H2O. Four resuscitators, Hospitak MPR (adult and pediatric) and CPR Bag (adult and pediatric), were unable to pass the test for mechanical shock (a fall from a height of at least 1 meter). CONCLUSION: We conclude that only Code Blue, 1st response, Pulmanex (with tube-type reservoir), and SPUR meet ASTM Standard F-920 and are acceptable replacements for permanent resuscitators.     

Comparison of methods of bag and mask ventilation for neonatal resuscitation.

BACKGROUND: There are a variety of manual bagging devices used for neonatal resuscitation. To our knowledge, there has been no comparison of the ability of different operators to utilize such devices for the delivery of predetermined inspiratory and end-expiratory pressures. In addition, the use of prolonged inflation may be of benefit for infants who require bag and mask ventilation, and there has been no evaluation of the ability of a variety of operators to reliably deliver such breaths using currently available equipment. METHODS: We utilized a neonatal manikin (Laerdal Armonk, NY) with a functional larynx and lungs, and a clear cushioned mask (Owens-BriGam, Morganton, NC). We studied a latex-free disposable anesthesia type bag (Model 5126 Vital Signs, Totawa, NJ), a Jackson-Rees (JR) type anesthesia bag (Model E191 Anesthesia Associates, San Marcos, CA) fitted with a Norman elbow and a flow-control tail-piece (Dupaco, Oceanside, CA), and the Neopuff (Fisher and Paykel, Auckland, New Zealand), an FDA approved mechanical device that is flow-controlled and pressure-limited, specifically designed to facilitate neonatal resuscitation. The ventilating pressures were continuously recorded throughout the process. We evaluated neonatal nurses, neonatal nurse practitioners, neonatal staff and fellows, pediatric residents and neonatal respiratory therapists. RESULTS: The peak inspiratory pressure (PIP) was significantly different between operators using either anesthesia bag, P<0.001. Similar results were found for positive end-expiratory pressure (PEEP) with a significant difference among the operator groups, P<0.001. All the differences in post hoc analysis were between the therapists and the other groups, P<0.05. Therapists produced significantly higher pressures than the other groups for both PIP and PEEP (P<0.001). The PIP was similar for all groups using the Neopuff device. The PIP and PEEP delivered by the Neopuff differed from the other two devices independent of the operators (P<0.05). On post hoc analysis, there was a significant difference between the disposable anesthesia bag and Neopuff for both PIP and PEEP for the therapists, whereas among the non-therapists, there was a difference in PIP with the JR device producing a greater PIP (26.6+/-3.8 cmH(2)O) compared with the Neopuff and disposable anesthesia bag (24.8+/-1.1 cmH(2)O, 24.8+/-4.3 cmH(2)O). The level of PEEP was significantly different among all three devices for the non-therapists (1.3+/-1.6 cmH(2)O, Disposable; 2.9+/-1.2 cmH(2)O, JR; 4.7+/-0.5 cmH(2)O, Neopuff; P<0.05). Only the therapists were able to consistently deliver PEEP with the anesthesia bags, whereas all operators could generate the target PEEP with the Neopuff (P<0.05). We compared the pressure delivered during the first second to the pressure delivered during the fifth second during prolonged 5-s inflations. The absolute differences between the first and fifth second for the Neopuff versus the anesthesia bags were significantly different with a median of 7.1 cmH(2)O for the anesthesia bags compared with 0.2 cmH(2)O for the Neopuff, P<0.001, reflecting the difficulty in obtaining and maintaining the target inflation pressures. CONCLUSIONS: Our experience suggests that the Neopuff, a purpose-built neonatal resuscitator ventilator, facilitates the delivery of the desired airway pressures while maximizing the operators ability to obtain and maintain a patent airway, and facilitates the delivery of prolonged inflations. Further research is required to determine the clinical benefit of end-expiratory pressure and prolonged inflations in neonatal resuscitation.     

An evaluation of manual tidal volume and respiratory rate delivery during simulated resuscitation

Introduction: Excessive minute ventilation during cardiac arrest may cause lung injury and decrease the effectiveness of cardiopulmonary resuscitation (CPR). However, little is known about how clinicians deliver tidal volumes and respiratory rates during CPR. Methods: In this cross-sectional study, licensed practitioners attending an American Heart Association (AHA) Advanced Cardiac Life Support (ACLS) course performed CPR and manual ventilation on a high-fidelity simulator during the megacode portion of the course. Delivered tidal volumes and respiratory rates were measured on a monitor. During the first scenario, results were not displayed to participants, but were displayed during the second scenario. Results: Fifty-two clinicians participated in this study. Average height was 169 (157,178) cm. Pre-monitor display tidal volumes delivered were larger in male participants compared to female participants (684.6 ± 134.4 vs 586.7 ± 167.6 ml, P = 0.05). Those using medium-sized gloves delivered smaller tidal volumes than those using small or large gloves. Twenty-two (42.3%) delivered tidal volume in the range of 5–8 ml/kg of predicted body weight for the simulation manikin, and 35 (67.3%) delivered tidal volumes with >20% variability among breaths. All participants met the target respiratory rate around 10 breaths/min. Conclusion: Tidal volume delivery varied greatly during manual ventilation and fewer than half participants delivered tidal volume at 5–8 ml/kg to the manikin. Sex and glove size appeared to impact tidal volume delivery when the participants were unaware of what they were delivering. Participants were able to meet the target respiratory rate around 10 without audio or visual feedback.     

Optimizing bag-valve-mask ventilation with a new mouth-to-bag resuscitator

When ventilating an unintubated patient with a self-inflating bag, high peak inspiratory flow rates may result in high peak airway pressure with subsequent stomach inflation; this may occur frequently when rescuers without daily experience in bag-valve-mask ventilation need to perform advanced airway management. The purpose of this study was to assess the effects of a newly developed self-inflating bag (mouth-to-bag resuscitator; Ambu, Glostrup, Denmark) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used, consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/0.098 kPa (100 ml/cm H(2)O)); airway resistance, 0.39 kPa/l per second (4 cm H(2)O/l/s), oesophagus (LESP, 1.96 kPa (20 cm H(2)O)) and simulated stomach. Twenty nurses were randomised to ventilate the manikin for 1 min (respiratory rate: 12 per minute) with either a standard self-inflating bag or the mouth-to-bag resuscitator, which requires the rescuer to blow up a single-use balloon inside the self-inflating bag, which in turns displaces air towards the patient. When supplemental oxygen is added, ventilation with up to 100% oxygen may be obtained, since expired air is only used as the driving gas. The mouth-to-bag resuscitator therefore allows two instead of one hand sealing the mask on the patient's face. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The mouth-to-bag resuscitator versus standard self-inflating bag resulted in significantly (P<0.05) higher mean+/-S.D. mask tidal volumes (1048+/-161 vs. 785+/-174 ml) and lung tidal volumes (911+/-148 vs. 678+/-157 ml), longer inspiratory times (1.7+/-0.4 vs. 1.4+/-0.4 s), but significantly lower peak inspiratory flow rates (50+/-9 vs. 62+/-13 l/min) and mask leakage (10+/-4 vs. 15+/-9%); peak inspiratory pressure (17+/-2 vs. 17+/-2 cm H(2)O) and stomach tidal volumes (16+/-30 vs. 18+/-35 ml) were comparable. In conclusion, employing the mouth-to-bag resuscitator during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate and improved lung tidal volumes, while decreasing mask leakage.     

Influence of an impedance threshold valve on ventilation with supraglottic airway devices during cardiopulmonary resuscitation in a manikin

Aim This study investigates if a n impedance threshold valve (ITV) might improve survival after cardiac arrest by increasing vital organ blood flow. The combination of ITV and supraglottic airway devices (SADs) has not been previously studied. This simulation study in a manikin aimed at analysing differences in ventilation with different SADs without and with an ITV.

Methods

In a resuscitation manikin, cardiopulmonary resuscitation (CPR) was performed with interrupted (30:2) and continuous chest compressions using facemask, tracheal tube and 10 SADs (six different laryngeal masks, LT-D, LTS-D, Combitube^® and Easy Tube^®). Ventilation was performed with and without an ITV. A total of 550 CPR cycles of 3-min duration were performed with chest compressions and ventilation standardised by use of a mechanical thumper device and an emergency ventilator.

Results

Sufficient ventilation was possible with all devices tested. For ventilation during continuous chest compressions, there were significantly reduced tidal volumes for all airway devices with ITV use. By contrast, during interrupted chest compressions, no differences in tidal volumes with the ITV occurred in the majority of devices. The maximum reduction of tidal volume for any device was 7.8% of the volume reached without the ITV.

Conclusion

Based on the findings of this manikin trial, the use of an ITV for ventilation during CPR is possible in combination with supraglottic airway devices. Merging these two strategies warrants further clinical evaluation to judge the relevance of tidal volume reduction found in this trial.     

Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. This study was designed to yield enough power to determine whether employing an inspiratory gas flow limiting bag-valve device (SMART BAG, O-Two Medical Technologies Inc., Ontario, Canada) would also decrease the likelihood of stomach inflation in an established bench model of a simulated unintubated respiratory arrest patient. The bench model consists of a training lung (lung compliance, 50 ml/cm H2O; airway resistance, 4 cm H2O/l/s) and a valve simulating lower oesophageal sphincter opening at a pressure of 19 cm H(2)O. One hundred and ninety-one emergency medicine physicians were requested to ventilate the manikin utilising a standard single-person technique for 1 min (respiratory rate, 12/min; Vt, 500 ml) with both a standard adult bag-valve-mask and the SMART BAG. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG versus standard bag-valve-mask resulted in significantly (P < 0.001) lower (mean +/- S.D.) mean airway pressure (14 +/- 2 cm H2O versus 16 +/- 3 cm H2O), respiratory rates (13 +/- 3 breaths per min versus 14 +/- 4 breaths per min), incidence of stomach inflation (4.2% versus 38.7%) and median stomach inflation volumes (351 [range, 18-1211 ml] versus 1426 [20-5882 ml]); lung tidal volumes (538 +/- 97 ml versus 533 +/- 97 ml) were comparable. Inspiratory to expiratory ratios were significantly (P < 0.001) increased (1.7 +/- 0.5 versus 1.5 +/- 0.6). In conclusion, the SMART BAG reduced inspiratory flow, mean airway pressure and both the incidence and actual volume of stomach inflation compared with a standard bag-valve-mask device while maintaining delivered lung tidal volumes and increasing the inspiratory to expiratory ratio.     

A human immunodeficiency virus-resistant airway for cardiopulmonary resuscitation.

Due to fear of transmitted disease, mouth-to-mouth cardiopulmonary resuscitation (CPR) is now rare, even though early CPR is associated with a fivefold to 30-fold increase in survival. The authors have devised a one-piece silicone mask (Kiss of Life [KOL], Brunswick Biomedical Technologies, Inc, Warehom, MA) with a one-way valve and circular recess to form a no-contact lip seal, enabling mouth-to-mouth CPR to be given. The ventilatory volume during mannequin CPR using the KOL mask was 0.75 +/- 0.235 L. This volume was significantly (P less than .05) greater than that generated by alternate widely used airways (range, 0.195 +/- 0.147 to 0.617 +/- 0.208 L). To assess mask performance in vivo, the authors measured exhaled volumes in 10 apneic anesthetized patients under three conditions: with the KOL mask, a standard anesthetic mask and bag, and an anesthetic mask with an endotracheal tube. The results were: anesthetic mask and tube, 1.5 L (range, 1.2 to 1.7 L); KOL mask, 1.1 L (range, 1.0 to 1.3 L); anesthetic mask alone, 0.7 L (range, 0.5 to 0.8 L). To test permeability, we exposed two KOL masks to a high titer of human immunodeficiency virus (HIV)-1 soup (10(6) culture infection doses/mL) for 10 and eight masks for 60 minutes, respectively, and cultured swabs of the interior of the valve for 1 month. There was no growth in any culture. These data suggest that the KOL mask has excellent ventilating characteristics, is practical (pocket-portable, disposable), experimentally impermeable to HIV-1, and inexpensive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arterial blood gases during basic life support of human cardiac arrest victims

BACKGROUND: Ventilation with tidal volumes sufficient to raise the victim's chest is an integral part of guidelines for lay-rescuer basic life support, but optimal tidal volume, frequency and ratio to chest compressions are not known. METHODS: Adults with non-traumatic, out-of-hospital cardiac arrest, who were not successfully resuscitated following advanced life support by the staff of a physician-manned ambulance, were included. Advanced life support comprised tracheal intubation and mechanical ventilation with tidal volume of 700 ml and 100% oxygen, 12 times per min. An arterial blood sample was drawn at the end of the resuscitation attempt and analysed on the scene. After the victim was declared dead, basic life support was initiated with chest compressions and mouth-to-mask or mouth-to-tracheal tube ventilation (15:2), with volumes sufficient to make the chest rise. The tracheal tube was equipped with an impedance valve to avoid passive ventilation secondary to chest compressions. Arterial blood samples were drawn after 7-8 min of basic life support and analysed on the scene. RESULTS: Six men and two women, median (range) age 72 (32-86) years, were included in the study. Four of these received mouth-to-mask ventilation and four mouth-to-tracheal tube ventilation. Mean (S.D.) arterial blood carbon dioxide and oxygen tension during advanced life support were 6.4 (1.4)kPa and 22 (15)kPa, respectively. Similar values during basic life support were 9.6 (1.9)kPa and 8.5 (1.6)kPa, respectively, with no differences between the ventilation methods. CONCLUSION: Ventilation during basic life support performed according to international guidelines (2000) resulted in arterial hypercapnia and hypoxia.