Suboptimal Ventilation Research Articles

CFD Evaluation of Respiratory Particle Dispersion and Associated Infection Risk in a Coach Bus with Different Ventilation Configurations

The COVID-19 pandemic has underscored the urgency of understanding virus transmission dynamics, particularly in indoor environments characterized by high occupancy and suboptimal ventilation systems. Airborne transmission, recognized by the World Health Organization (WHO), poses a significant risk, influenced by various factors, including contact duration, individual susceptibility, and environmental conditions. Respiratory particles play a pivotal role in viral spread, remaining suspended in the air for varying durations and distances. Experimental studies provide insights into particle dispersion characteristics, especially in indoor environments where ventilation systems may be inadequate. However, experimental challenges necessitate complementary numerical modeling approaches. Zero-dimensional models offer simplified estimations but lack spatial and temporal resolution, whereas Computational Fluid Dynamics, particularly with the Discrete Phase Model, overcomes these limitations by simulating airflow and particle dispersion comprehensively. This paper employs CFD-DPM to simulate airflow and particle dispersion in a coach bus, offering insights into virus transmission dynamics. This study evaluates the COVID-19 risk of infection for vulnerable individuals sharing space with an infected passenger and investigates the efficacy of personal ventilation in reducing infection risk. Indeed, the CFD simulations revealed the crucial role of ventilation systems in reducing COVID-19 transmission risk within coach buses: increasing clean airflow rate and implementing personal ventilation significantly decreased particle concentration. Overall, infection risk was negligible for scenarios involving only breathing but significant for prolonged exposure to a speaking infected individual. The findings contribute to understanding infection risk in public transportation, emphasizing the need for optimal ventilation strategies to ensure passenger safety and mitigate virus transmission.

A coronavirus disease 2019 outbreak in a residential living facility with suboptimal ventilation in resident rooms

We report a large outbreak of severe acute respiratory syndrome coronavirus 2 in a residential living facility. Measurements of carbon dioxide levels, aerosol particle clearance, and airflow were used to identify and remediate areas with suboptimal ventilation. A simple intervention involving continuous operation of bathroom fans was effective in significantly improving ventilation in resident rooms.

Carbon Dioxide Monitoring Demonstrates Variations in the Quality of Ventilation on Public Transportation Buses and University Student Shuttle Vans and Identifies Effective Interventions.

There is a risk for transmission of severe acute respiratory syndrome 2 (SARS-CoV-2) and other respiratory viruses in motor vehicles, particularly if ventilation is inadequate. We used carbon dioxide monitoring to examine the quality of ventilation in several public transportation buses and in university student shuttle vans in the Cleveland metro area during peak and non-peak travel times. Carbon dioxide levels above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation for the number of people present. In the shuttle vans, we evaluated the impact of an intervention to improve ventilation. In large articulated buses with 2 ventilation systems, carbon dioxide concentrations never exceeded 800 ppm, whereas in standard buses with 1 ventilation system concentrations rose above 800 ppm during peak travel times and on some trips during non-peak travel times. In shuttle vans, the ventilation system was not turned on during routine operation, and carbon dioxide levels rose above 800 ppm on all trips during peak and non-peak travel times. In the shuttle vans, an intervention involving operation of the existing ventilation system resulted in a significant reduction in carbon dioxide levels (mean concentration, 1,042 no intervention versus 785 with intervention; P < 0.001). Our findings demonstrate substantial variability in the quality of ventilation in public transportation buses and university shuttle vans. There is a need for efforts to assess and optimize ventilation in motor vehicles used for public transportation to reduce the risk for aerosol-mediated transmission of respiratory viruses. Carbon dioxide monitoring may provide a useful tool to assess and improve ventilation.

The relationship between ventilation rates in schools and the indoor airborne transmission potential of COVID-19

ABSTRACT The requirement for natural ventilation strategies in classrooms to perform in respect to both their inherent and adaptive capacity is necessary to mitigate the risk of transmission associated with infectious airborne pathogens such as COVID-19. This paper assesses the performance of ten classrooms considering (a) the designed versus actual ventilation capacity; (b) the probability of airborne disease transmission by unit time resulting from calculated ventilation rates and (c) the reduction of transmission risk associated with mask wearing by all occupants. Monitored air changes per hour (ACH) range from 0.26–1.7, demonstrating that none of the classrooms meet designed ventilation rate whilst in operation. If the designed ventilation rate of 5 ACH were to be achieved, it would represent an infection risk of less than 1% during standard class durations and 5% over an 8-hour school day. The minimum achieved ventilation rate represents an infection risk of 7–12% (per class) and 75–100% (per school day) dependent on classroom specific parameters. Protection is afforded by the wearing of masks within the indoor school setting. During specified class durations in settings with sub-optimal ventilation rates, probability of infection can be reduced from 7–12% to 1–5%. Over an 8-hour school day, probability of infection can be reduced from 75–100% to 18–43%. These reductions are possible dependent on mask choice.

One-person versus two-person mask ventilation in preterm infants at birth: a pilot randomised controlled trial

BackgroundMask leak and airway obstruction are common with mask ventilation in newborn infants, leading to suboptimal ventilation. We aimed to perform a pilot study measuring respiratory mechanics during one-person and...

Ventilation during continuous compressions or at 30:2 compression-to-ventilation ratio results in similar arterial oxygen and carbon dioxide levels in an experimental model of prolonged cardiac arrest

BackgroundIn refractory out-of-hospital cardiac arrest, transportation to hospital with continuous chest compressions (CCC) from a chest compression device and ventilation with 100% oxygen through an advanced airway is common practice. Despite this, many patients are hypoxic and hypercapnic on arrival, possibly related to suboptimal ventilation due to the counterpressure caused by the CCC. We hypothesized that a compression/ventilation ratio of 30:2 would provide better ventilation and gas exchange compared to asynchronous CCC during prolonged experimental cardiopulmonary resuscitation (CPR).MethodsWe randomized 30 anaesthetized domestic swine (weight approximately 50 kg) with electrically induced ventricular fibrillation to the CCC or 30:2 group and bag-valve ventilation with a fraction of inspired oxygen (FiO2) of 100%. We started CPR after a 5-min no-flow period and continued until 40 min from the induction of ventricular fibrillation. Chest compressions were performed with a Stryker Medical LUCAS® 2 mechanical chest compression device. We collected arterial blood gas samples every 5 min during the CPR, measured ventilation distribution during the CPR using electrical impedance tomography (EIT) and analysed post-mortem computed tomography (CT) scans for differences in lung aeration status.ResultsThe median (interquartile range [IQR]) partial pressure of oxygen (PaO2) at 30 min was 110 (52–117) mmHg for the 30:2 group and 70 (40–171) mmHg for the CCC group. The median (IQR) partial pressure of carbon dioxide (PaCO2) at 30 min was 70 (45–85) mmHg for the 30:2 group and 68 (42–84) mmHg for the CCC group. No statistically significant differences between the groups in PaO2 (p = 0.40), PaCO2 (p = 0.79), lactate (p = 0.37), mean arterial pressure (MAP) (p = 0.47) or EtCO2 (p = 0.19) analysed with a linear mixed model were found. We found a deteriorating trend in PaO2, EtCO2 and MAP and rising PaCO2 and lactate levels through the intervention. There were no differences between the groups in the distribution of ventilation in the EIT data or the post-mortem CT findings.ConclusionsThe 30:2 and CCC protocols resulted in similar gas exchange and lung pathology in an experimental prolonged mechanical CPR model.

1926. Risky businesses: Carbon dioxide monitoring to assess ventilation in grocery stores as an indicator of risk for respiratory virus transmission

Abstract Background Poorly ventilated indoor settings pose a risk for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses. Transmission often occurs in community, but limited information is available on the quality of ventilation in community settings. Methods We used carbon dioxide measurements to assess adequacy of ventilation in 6 grocery stores, including large warehouse stores, medium-sized stores, and small neighborhood groceries. Carbon dioxide levels were monitored continuously with values recorded once per minute using a handheld device during multiple shopping trips to each store during both busy (defined as long lines at checkout) and non-busy (defined as no lines at checkout) shopping times. Carbon dioxide readings above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation for the number of people present. Results Carbon dioxide levels remained below 800 ppm in all 6 grocery stores during trips at non-busy shopping times, except for transient rises above 800 ppm (peak = 860 ppm) during check out in 2 stores. In 3 of the 6 stores (50%), carbon dioxide levels rose above 800 ppm for prolonged periods during busy shopping times, with considerable variability in levels in different store locations (ie, increased levels in crowded store locations). The figure shows carbon dioxide levels for 1 medium-sized grocery store during typical shopping trips during busy and non-busy shopping periods. Increase in carbon dioxide levels in parts per million (ppm) in a grocery store during busy and non-busy shopping trips. Peak levels of carbon dioxide above 800 ppm (dotted lines) were considered an indicator of suboptimal ventilation for the number of occupants present. Conclusion Ventilation in grocery stores may be sufficient to minimize the risk for airborne transmission of respiratory pathogens during non-busy shopping periods, but in some stores may be sub-optimal in crowded locations during busy shopping times. There is a need for additional studies to assess the quality of ventilation in a wide range of community settings. Disclosures All Authors: No reported disclosures.

Evaluation of Interventions to Improve Ventilation in Households to Reduce Risk for Transmission of Severe Acute Respiratory Syndrome Coronavirus 2.

Inadequate ventilation may contribute to the high risk for household transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the effectiveness of several interventions recommended to improve ventilation in households. In 7 residential homes, carbon dioxide monitoring was conducted to assess ventilation in occupied open areas such as family rooms and in bedrooms and/or offices. Carbon dioxide levels above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation for the number of people present. In 1 of the 7 homes, various interventions to improve ventilation or to filter air were assessed in a kitchen area by measuring clearance of aerosol particles produced using an aerosol-based spray system and carbon dioxide generated by cooking with a gas stove. Carbon dioxide levels rose above 800 ppm in bedrooms and offices with 2 occupants when windows and doors were closed and in open areas during gatherings of 5 to 10 people; carbon dioxide levels decreased when windows or doors were opened. Clearance of carbon dioxide and aerosol particles significantly increased with interventions including running fans, operating portable air cleaners, and opening windows, particularly when there was a noticeable breeze or when a window fan was used to blow contaminated air outside. In households, several measures to improve ventilation or air filtration were effective in reducing carbon dioxide accumulation or enhancing clearance of carbon dioxide and aerosol particles. Studies are needed to determine if interventions to improve ventilation can reduce the risk for airborne transmission of SARS-CoV-2 in households.

Investigation of a cluster of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in a hospital administration building.

To investigate a cluster of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in employees working on 1 floor of a hospital administration building. Contact tracing was performed to identify potential exposures and all employees were tested for SARS-CoV-2. Whole-genome sequencing was performed to determine the relatedness of SARS-CoV-2 samples from infected personnel and from control cases in the healthcare system with coronavirus disease 2019 (COVID-19) during the same period. Carbon dioxide levels were measured during a workday to assess adequacy of ventilation; readings >800 parts per million (ppm) were considered an indication of suboptimal ventilation. To assess the potential for airborne transmission, DNA-barcoded aerosols were released, and real-time polymerase chain reaction was used to quantify particles recovered from air samples in multiple locations. Between December 22, 2020, and January 8, 2021, 17 coworkers tested positive for SARS-CoV-2, including 13 symptomatic and 4 asymptomatic individuals. Of the 5 cluster SARS-CoV-2 samples sequenced, 3 were genetically related, but these employees denied higher-risk contacts with one another. None of the sequences from the cluster were genetically related to the 17 control sequences of SARS-CoV-2. Carbon dioxide levels increased during a workday but never exceeded 800 ppm. DNA-barcoded aerosol particles were dispersed from the sites of release to locations throughout the floor; 20% of air samples had >1 log10 particles. In a hospital administration building outbreak, sequencing of SARS-CoV-2 confirmed transmission among coworkers. Transmission occurred despite the absence of higher-risk exposures and in a setting with adequate ventilation based on monitoring of carbon dioxide levels.

Tuberculosis infection control in selected facilities managing drug-resistant tuberculosis in Bangladesh: Findings from a mixed-methods study

Background: Nosocominal Tuberculosis epidemics in hospitals are a major threat to the patient and health workers safety. On the other hand, implementation of Tuberculosis infection control policy, strongly influences the prevention and transmission of Tuberculosis in hospitals. Thus we aimed to check the status of Tuberculosis infection control in the major drug-resistant Tuberculosis management centers of Bangladesh. Methods and materials: We leveraged an explanatory mixed-methods design to contextualize this study. We included (n = 3) major drug-resistant Tuberculosis management centers of Bangladesh to check their complaiance with the national Tuberculosis infection control policy. Non-participatory observations (n = 18) using a structured observation checklist and record review using standard document review checklist were employed to check the extent of the implementation of infection control policy. After the quantitative data were analyzed, indivually at each hospital, we developed guidelines to explain the reasons for non-compliance with the Infection control standards. Hence, we conducted 9 Key-informant interviews with Managers,16 In-depth Interviews with health care providers, 12 In-depth Interviews with patients and 6 In-depth-phone Interviews with field staff (n = 43). The data collection commenced from November 2018 to December 2018. The ethical approval for this study was sought from BRAC James P Grant school of public health. Results: The infection control at drug-resistant Tuberculosis management centers have a scope of improvement. Survey findings revealed absence of dedicated budget for infection control, no capacity building activities, sub-optimal triage practices, sub-optimal ventilation, and non-compliance to personal protective equipment including N-95 masks. However, qualitative findings revealed that the reasons for non-compliance with infection control standards included; lack of funds, lack of infection control committee, lack of authority and lack of training. Conclusion: Infection control practices at drug-resistant Tuberculosis management centers of Bangladesh require special attention of the national policy makers. The reasons for non-compliance with infection control standards are interconnected and represent asymmetries at individual, hospital and national levels.

Respiratory management of adult patients with acute respiratory distress syndrome due to COVID-19.

Respiratory management of adult patients with acute respiratory distress syndrome due to COVID-19.

Cost effectiveness of a novel device for improving resuscitation of apneic newborns

BackgroundIntrapartum-related hypoxic events are a major cause of morbidity and mortality in low resource countries. Neonates who receive proper resuscitation may go on to live otherwise healthy lives. However, even when a birth attendant is present, these babies frequently receive suboptimal ventilation with poor outcomes. The Augmented Infant Resuscitator (AIR) is a low-cost, reusable device designed to provide birth attendants real-time objective feedback on measures of ventilation quality during resuscitations and is intended for use in training and at the point of care. The goal of our study was to determine the impact and cost-effectiveness of AIR deployment in conjunction with existing resuscitation training programs in low resource settings.MethodsWe developed a simulation model of the natural history of intrapartum-related neonatal hypoxia and resuscitation deriving parameters from published literature and model calibration. Simulations estimated the number of disability-adjusted life years (DALYs) averted with use of the AIR by birth attendants if deployed at the point of care. Potential decreases in neonatal mortality and long-term subsequent morbidity from disability were modeled over a lifetime horizon. The primary outcome for the analysis was the cost per DALY averted. Model parameters were specific to the Mbeya region of Tanzania.ResultsImplementation of the AIR strategy resulted in an additional cost of $24.44 (4.80, 73.62) per DALY averted on top of the cost of existing, validated resuscitation programs. Per hospital, this adds an extra $656 to initial training costs and averts approximately 26.84 years of disability in the cohort of children born in the first year, when projected over a lifetime. The findings were robust to sensitivity analyses. Total roll-out costs for AIR are estimated at $422,688 for the Mbeya region, averting approximately 9018 DALYs on top of existing resuscitation programs, which are estimated to cost $202,240 without AIR.ConclusionOur modeling analysis finds that use of the AIR device may be both an effective and cost-effective tool when used as a supplement to existing resuscitation training programs. Implementation of this strategy in multiple settings will provide data to improve our model parameters and potentially confirm our findings.

Lingual tonsillar hypertrophy, an unknown enemy

We report an unexpected difficult airway in a patient with unrecognized lingual tonsillar hypertrophy. A 54-year-old hypertensive woman presented for resection of a mediastinal mass under general anesthesia (GA). After induction, mask ventilation was impossible. Laryngeal mask airway (LMA) was used, achieving suboptimal ventilation. Fiberoptic intubation through LMA was attempted but tube advancement was hindered by a protrudingmass. Finally, intubation was achieved using the Frova introducer. After completion of the surgery, the patient was transferred, intubated, to the postanesthesia care unit. Ear, nose, and throat assessment concluded that the mass was a hyper-trophied lingual tonsil. Unexpected lingual tonsillar hypertrophy can complicate GA, making mask ventilation, and even intubation impossible. It is considered a frequent cause of unexpected difficult airway. Diagnosis cannot be made by standard airway physical examination. Once recognized, fiberoptic intubation is mandatory in subsequent surgeries.

88 A Retrospective Review of the Use of Airway Pressure Release Ventilation (APRV) in the Burn Operating Room

Airway Pressure Release Ventilation (APRV) is the preferred mode of mechanical ventilation for the initial treatment of inhalation injury at our burn center. APRV improves alveolar recruitment, thus improving oxygenation. However, general anesthesia cannot be administered when patients are on APRV, resulting in frequent interruptions in the circuit and subsequent alveolar derecruitment with prolonged periods of sub-optimal ventilation post-operatively. Total IV anesthesia (TIVA) allows for the continued use of APRV perioperatively. The purpose of this study was to assess the safety and efficacy of APRV during surgery. This was a retrospective chart review of patients that remained on APRV during surgery over a 3-year period. Demographic, injury, ventilator, and outcome data were collected. Pre (PRE) and post-operative (POST) FIO2, Rate (set & spontaneous), Tidal Volume (TV), Minute Volume (MV), P High/Low, T High/Low, and Mean Airway Pressures (MAP) were compared for each surgery. The charts of 55 patients were reviewed, mean age was 45 years, the majority were male (75%) and 9% had pre-existing pulmonary disease. The most common mechanism was flame/flash (67%) with total body surface area (TBSA) burned ranging from 0 - 92% (M 42%). Concomitant inhalation injury was present for 58% of patients. Total ventilator days (M 42.2, ±35.7), total APRV days (M 16, ±12.9). Total number of surgeries (M 9.4, ±7.94), total number of surgeries on APRV (M 3.4, ±2.65). There were 38 patients with complete PRE and POST ventilator data. Surgery 1 on APRV; there were no significant differences for FIO2, Rate, TV, MV, P High/Low, T High, MAP; POST T Low was lower (M 0.8) when compared to PRE (M 0.9), (p=0.0005). Surgery 2 (n=35), POST mean FIO2 requirements were higher; PRE (0.47) vs POST (0.57), (p=.0358). Surgery 3 (n=25) average TV was lower POST-OP; PRE-OP (630) vs POST (523), (p=.005). There were no significant differences between PRE and POST requirements for patients on APRV during surgeries 4 (n=16) and 5 (=13). No patients suffered complications pre, peri or post-operatively when on APRV. Overall inpatient mortality was 35%. Of survivors, 92% required transfer to a post-acute care facility. APRV can be continued intra-operatively with the use of TIVA. This retrospective study demonstrates that TIVA and intra-operative APRV are safe and effective. TIVA allows the continued use of APRV intra-operatively in burn patients requiring aggressive ventilator support.

Lung aeration and ventilation after percutaneous tracheotomy measured by electrical impedance tomography in non-hypoxemic critically ill patients: a prospective observational study

BackgroundPercutaneous dilatational tracheotomy (PDT) may lead to transient impairment of pulmonary function due to suboptimal ventilation, loss of positive end-expiratory pressure (PEEP) and repetitive suction maneuvers during the procedure. Possible changes in regional lung aeration were investigated using electrical impedance tomography (EIT), an increasingly implied instrument for bedside monitoring of pulmonary aeration.MethodsWith local ethics committee approval, after obtaining written informed consent 29 patients scheduled for elective PDT under bronchoscopic control were studied during mechanical ventilation in supine position. Anesthetized patients were monitored with a 16-electrode EIT monitor for 2 min at four time points: (a) before and (b) after initiation of neuromuscular blockade (NMB), (c) after dilatational tracheostomy (PDT) and (d) after a standardized recruitment maneuver (RM) following surgery, respectively. Possible changes in lung aeration were detected by changes in end-expiratory lung impedance (Δ EELI). Global and regional ventilation was characterized by analysis of tidal impedance variation.ResultsWhile NMB had no detectable effect on EELI, PDT led to significantly reduced EELI in dorsal lung regions as compared to baseline, suggesting reduced regional aeration. This effect could be reversed by a standardized RM. Mean delta EELI from baseline (SE) was: NMB − 47 ± 62; PDT − 490 ± 180; RM − 89 ± 176, values shown as arbitrary units (a.u.). Analysis of regional tidal impedance variation, a robust measure of regional ventilation, did not show significant changes in ventilation distribution.ConclusionThough changes of EELI might suggest temporary loss of aeration in dorsal lung regions, PDT does not lead to significant changes in either regional ventilation distribution or oxygenation.

Newborn manikin study shows that physicians often fail to detect correct lung compliance when using a self-inflating bag.

Recognising changes in lung compliance can help clinicians to adjust initial inflations during resuscitation at birth. We examined whether physicians sensed low and normal compliance with a self-inflating bag before and after an educational intervention that used a manikin connected to a newborn lung simulator. We asked 43 physicians with neonatal duties to perform two low compliance ventilation attempts and two normal-compliance ventilation attempts in a randomised order at baseline and after the educational intervention, with 34 taking part in a retest three months later. The physicians correctly recognised low and normal compliance in 71% and 66% of the ventilations at baseline, 80% and 66% of the ventilations after the intervention and 74% and 81% at retest. Correct recognition of normal compliance improved from baseline to retest (p = 0.04). Ventilations in low- vs normal-compliance settings resulted in lower tidal volumes (4.4 vs 23.0 mL, p < 0.001), lower ventilation rates (42 vs 51, p < 0.001) and higher peak inflating pressure (35.2 vs 31.4 cmH2 O, p < 0.001). Around one in four physicians failed to recognise correct compliance levels when using a self-inflating bag and showed limited improvement after an educational intervention. Ventilations in a low-compliance setting resulted in suboptimal ventilation.

Real-Time Breath-to-Breath Asynchrony Event Detection using Time-Varying Respiratory Elastance Model

Asynchronous events (AE) occur during mechanical ventilation (MV) therapy when the patient's breathing is not synchronised with the ventilator support. Frequent AE indicates sub-optimal ventilation therapy and may lead to further complications. Asynchrony Index (AI) gives the percentage of AEs as a percentage of total breaths, but is only assessed via manual scrutiny. Thus, there is a need to automate AE detection in real-time. A model-based approach using time-varying elastance to detect AEs is developed and retrospectively assessed in MV patients. Data from 14 mechanically ventilated respiratory failure patients, enrolled in an observational study in Christchurch Hospital, New Zealand were used to investigate the performance of the method. Patient data is sorted according to the ventilation mode used, and AI is calculated for each episode separately. The model-based approach accurately identifies AEs, and shown not to give false positive readings when compared to manual detection (gold standard). None of the ventilation modes give significantly different AI levels (P > 0.05). AI decreases when ventilation mode changes and increases overall time indicate worsen patient-ventilator interaction. The model-based method is able to successfully and accurately calculate AI. Real time use of this metric will enable patients with sub-optimal ventilator settings to be automatically identified for the first time and the settings adjusted as necessary, improving the efficacy of mechanical ventilation therapy, and providing a quantified metric to help guide MV care.

Expiratory Limb Ventilation during Unique Failure of the Anesthesia Machine Breathing Circuit

Expiratory Limb Ventilation during Unique Failure of the Anesthesia Machine Breathing Circuit

Thinking Twice before Using the LMA for Obese and Older Patients - A Prospective Observational Study

Introduction: Laryngeal Mask Airways (LMAs) have traditionally been used for short surgery under general anesthesia with good results. Many studies have reported favourable outcomes in safety profile, complication risk, ease of insertion, recovery of patients and cost analyses. However, there is an under reporting of complications arising during ventilation with this device and the risk factors associated with such complications in adult patients. These include laryngospasm, difficulty with insertion, suboptimal ventilation, bronchospasm, aspiration, desaturation, hypotension and conversion to intubation with ETT. These can be significantly serious and life threatening. Often times it is wrong patient selection for the wrong surgery that results in an undesirable outcome. Methods: By means of this prospective observational study we aimed to audit all general anesthesia cases performed with an LMA at our hospital over six months from February till August 2012. Included in the parameters observed were induction techniques, ventilation strategies and intraoperative problems during LMA ventilation. By means of a data collection form, the Anaesthetist in charge indicated the intraoperative events and outcomes. Results: 1,095 patients were included in the audit. The mean age of the patients was 40 years and mean weight was 66.4kg. The patients were given GA for a variety of procedures. LMA Proseal™ was used in 78.4% of patients while the LMA Supreme™ was favored when the surgeries required a lateral position. 7.1% of patients encountered problems with insertion whilst 7.8% had intraoperative problems related to difficulty with ventilation. This was more prevalent with the LMA Supreme™ (p=0.031). Age and BMI of the patient increased the incidence of complications (p=0.002 and 0.0008). A BMI >30 and an age >46 years are associated with a significant 2-fold increase in the probability of all ventilatory problems intraoperatively. Conclusion: LMA use in our Operating Theatre is generally safe as long as potential problems are recognised and managed accordingly. The risk of problems increases 2-folds with patients with a BMI>30 and age>46 years. LMA Supreme was more problematic compared with Proseal.

Smaller self-inflating bags produce greater guideline consistent ventilation in simulated cardiopulmonary resuscitation

BackgroundSuboptimal bag ventilation in cardiopulmonary resuscitation (CPR) has demonstrated detrimental physiological outcomes for cardiac arrest patients. In light of recent guideline changes for resuscitation, there is a need to identify the efficacy of bag ventilation by prehospital care providers. The objective of this study was to evaluate bag ventilation in relation to operator ability to achieve guideline consistent ventilation rate, tidal volume and minute volume when using two different capacity self-inflating bags in an undergraduate paramedic cohort.MethodsAn experimental study using a mechanical lung model and a simulated adult cardiac arrest to assess the ventilation ability of third year Monash University undergraduate paramedic students. Participants were instructed to ventilate using 1600 ml and 1000 ml bags for a length of two minutes at the correct rate and tidal volume for a patient undergoing CPR with an advanced airway. Ventilation rate and tidal volume were recorded using an analogue scale with mean values calculated. Ethics approval was granted.ResultsSuboptimal ventilation with the use of conventional 1600 ml bag was common, with 77% and 97% of participants unable to achieve guideline consistent ventilation rates and tidal volumes respectively. Reduced levels of suboptimal ventilation arouse from the use of the smaller bag with a 27% reduction in suboptimal tidal volumes (p = 0.015) and 23% reduction in suboptimal minute volumes (p = 0.045).ConclusionSmaller self-inflating bags reduce the incidence of suboptimal tidal volumes and minute volumes and produce greater guideline consistent results for cardiac arrest patients.