Tidal Volume Range Research Articles

Optimization of manual ventilation quality using respiratory function monitoring in neonates: A two-phase intervention trial

ObjectiveThe aim of this study was the evaluation of the impact of a respiratory function monitor (RFM, Neo100, Monivent AB, Gothenburg, Sweden) on the quality of ventilation in neonates. MethodsThis single-center two-phase intervention study was conducted at the Neonatal Intensive Care Unit and the delivery room of the Medical University of Vienna. Patients with clinical need for positive pressure ventilation were included in either of two consecutive study phases: (i) patients were ventilated with a hidden RFM (control) or (ii) visible RFM (intervention) during manual positive pressure ventilations. The duration of each phase was approximately six months. The primary outcome was the percentage of ventilations within a tidal volume range of 4–8 ml/kg (pVTe). ResultsA total of 90 patients (GA 22–66 weeks) were included. The primary outcome was significantly higher in the intervention group with a visible RFM (53.7%, SD 22.6) than in the control group without the monitor (37.3%, SD 20.5); (p < 0.001, mean difference [i.e., change in percentage points]: 16.95% CI: 7.4–35). In terms of secondary outcomes, excessive tidal volumes (>8ml/kg), potentially associated with an increased risk of brain injury, could be significantly reduced when a RFM was visible during ventilation (10.9% [IQR 26.4] vs. 29.5% [IQR 38.1]; p = 0.004). Furthermore, mask leakage could be significantly decreased (37.3% [SD 22.7] vs. 52.7% [SD 23.0]; p = 0.002). ConclusionOur results suggest that the clinical application of a RFM for manual ventilation of preterm and term infants leads to a significant improvement in ventilation parameters.

Research on pressure stability in an air cleaning and supplying system for motorcycle users

The article introduces the air purification system arranged on motorcycles to help provide clean air for motorcycle users. This is a new system that is being researched and tested to help reduce the harmful effects of air pollution. First, an air purification system model is proposed and a mathematical model is built. SolidWorks software is used to design 3D models and evaluate the effectiveness of the system. Finally, the article focuses on analyzing the pressure change of the air purification system when passing through the newly designed mechanical structures of the system. By examining the variation of the air flow circulating through the system from 15 l/min to 40 l/min, it has been shown that the air pressure supplied to the motorcycle users is always guaranteed to fluctuate around the standard value of 101325 Pa. This is important because, in the tidal volume range, the volume of air moved into or out of the lungs during a normal breath, is about 6.5 l/min to 8 l/min with comfortable pressure equal or greater 101325 Pa. From the results of the pressure study, the system will decide to choose the output pressure control mode to help the user feel comfortable.

Mechanical Ventilation in Pediatric and Neonatal Patients.

Pediatric acute respiratory distress syndrome (PARDS) remains a significant cause of morbidity and mortality, with mortality rates as high as 50% in children with severe PARDS. Despite this, pediatric lung injury and mechanical ventilation has been poorly studied, with the majority of investigations being observational or retrospective and with only a few randomized controlled trials to guide intensivists. The most recent and universally accepted guidelines for pediatric lung injury are based on consensus opinion rather than objective data. Therefore, most neonatal and pediatric mechanical ventilation practices have been arbitrarily adapted from adult protocols, neglecting the differences in lung pathophysiology, response to injury, and co-morbidities among the three groups. Low tidal volume ventilation has been generally accepted for pediatric patients, even in the absence of supporting evidence. No target tidal volume range has consistently been associated with outcomes, and compliance with delivering specific tidal volume ranges has been poor. Similarly, optimal PEEP has not been well-studied, with a general acceptance of higher levels of FiO2 and less aggressive PEEP titration as compared with adults. Other modes of ventilation including airway pressure release ventilation and high frequency ventilation have not been studied in a systematic fashion and there is too little evidence to recommend supporting or refraining from their use. There have been no consistent outcomes among studies in determining optimal modes or methods of setting them. In this review, the studies performed to date on mechanical ventilation strategies in neonatal and pediatric populations will be analyzed. There may not be a single optimal mechanical ventilation approach, where the best method may simply be one that allows for a personalized approach with settings adapted to the individual patient and disease pathophysiology. The challenges and barriers to conducting well-powered and robust multi-institutional studies will also be addressed, as well as reconsidering outcome measures and study design.

Comparison of Two Metabolic Simulators Used for Gas Exchange Verification in Cardiopulmonary Exercise Test Carts.

IntroductionMetabolic simulators (MS) produce simulated human breaths for the purpose of verification of cardiopulmonary exercise test (CPET) equipment. MS should produce consistent identical breaths with known CO2 and O2 gas concentrations over a range of breath rates and tidal volumes. Reliability of a CPET metabolic cart depends on ongoing quality control and maintenance of the device, including intermittent verification with a MS. We compared two MS devices against two standard CPET systems.MethodsThe Vacumed 17056 (Vacumetrics, Ventura, CA) and Relitech (Relitech Systems BV, Nijkerk, The Netherlands) were used with two standard metabolic carts (Vyntus CPX and Vyntus ONE, both Vyaire Medical, Mettawa, IL, United States). Tidal volume (VT) was set at 2 and 3 L and breathing frequency ranged from 20 to 80 breaths per minute for each MS. At each set point, we measured three sets of 40 breaths. Primary outcome parameters collected were VT, oxygen consumption (O2), carbon dioxide production (CO2), and respiratory exchange ratio (RER).ResultsVT, RER, O2, and CO2 results as obtained from both MS were all within the limits of acceptability, at both tidal volume settings, and all ventilatory rates. No significant trends were identified for either MS device. The Relitech MS produced tidal volumes that were closer to the target VT for both CPET carts at both VT and all rates, but the results of both MS were within acceptable ranges.ConclusionVerification of CPET equipment using either the VM or RT metabolic simulator, producing highly accurate and predictable simulated breaths of known composition, enabling CPET laboratory managers to rely on subject test data obtained during cardiopulmonary exercise testing.

Physiological Factors Affecting Lung Deposition

Ventilation and mechanics of breathing are an integral part of respiratory physiology that directly affect aerosol transport and deposition in the lung. Although natural breathing pattern varies widely among individuals, breathing pattern is controllable, and by using an appropriate breathing pattern, aerosol deposition can be substantially modified for desired purposes. Effects of breathing pattern have been investigated under carefully controlled inhalation conditions covering a wide range of tidal volumes (VT) and breathing frequencies (f) or respiratory times (T = 1/f). The studies have shown that lung deposition can increase or decrease as much as two times by changing the breathing pattern. Specific functional relationships have been found between lung deposition and breathing pattern parameters such that lung deposition can be estimated for any given breathing pattern. Both VT and T have shown strong effects on lung deposition, but their influence is variable depending on particle size, particularly, ultrafine vs. micron-sized particles. VT is more influential than T for micron-sized particles whereas VT and T are equally influential for ultrafine particles. Although effects of lung morphology are difficult to study systematically, comparison between normals and patients with obstructive airway disease has shown that lung deposition is closely related with the degree of airways obstruction and can be 2-3 times greater in patients with obstructive airway disease compared to normals. Thus, breathing pattern and the status of airways obstruction should be carefully considered in designing aerosol delivery and estimating deposition dose.

Continuous non‐contact respiratory rate and tidal volume monitoring using a Depth Sensing Camera

The monitoring of respiratory parameters is important across many areas of care within the hospital. Here we report on the performance of a depth-sensing camera system for the continuous non-contact monitoring of Respiratory Rate (RR) and Tidal Volume (TV), where these parameters were compared to a ventilator reference. Depth sensing data streams were acquired and processed over a series of runs on a single volunteer comprising a range of respiratory rates and tidal volumes to generate depth-based respiratory rate (RRdepth) and tidal volume (TVdepth) estimates. The bias and root mean squared difference (RMSD) accuracy between RRdepth and the ventilator reference, RRvent, across the whole data set was found to be -0.02 breaths/min and 0.51 breaths/min respectively. The least squares fit regression equation was determined to be: RRdepth = 0.96 × RRvent + 0.57 breaths/min and the resulting Pearson correlation coefficient, R, was 0.98 (p < 0.001). Correspondingly, the bias and root mean squared difference (RMSD) accuracy between TVdepth and the reference TVvent across the whole data set was found to be − 0.21 L and 0.23 L respectively. The least squares fit regression equation was determined to be: TVdepth = 0.79 × TVvent—0.01 L and the resulting Pearson correlation coefficient, R, was 0.92 (p < 0.001). In conclusion, a high degree of agreement was found between the depth-based respiration rate and its ventilator reference, indicating that RRdepth is a promising modality for the accurate non-contact respiratory rate monitoring in the clinical setting. In addition, a high degree of correlation between depth-based tidal volume and its ventilator reference was found, indicating that TVdepth may provide a useful monitor of tidal volume trending in practice. Future work should aim to further test these parameters in the clinical setting.

Inverse Pneumatic Artificial Muscles for Application in Low-Cost Ventilators.

The procurement and maintenance cost of high‐end ventilators preclude their stockpiles sufficient for the mass emergency situations. Therefore, there is a significant demand for mechanical ventilators in such situations. Herein, a low‐cost, portable, yet high‐performance design for a volume‐controlled mechanical ventilator is proposed. Pneumatic artificial muscles, such as air cylinders, are used in the inverse mode of operation to achieve mechanical ventilation. With the current design, the two fundamental modes of operation (controlled mode and assisted mode) are demonstrated. Unlike most intensive care unit ventilators, the proposed device does not need a high‐pressure air pipeline to operate. The device is capable of mechanical ventilation for respiration rate ranging from 10 to 30 b min−1 with a tidal volume (VT) range of 150–1000 mL and the I:E ratio of 1:1–1:5. A total cost of less than $400 USD is achieved to make one device. The cost to produce the device in larger volumes can be estimated to be less than $250 USD.

Validation of Novel Completely Sealed Nasal Positive Airway Pressure Device: SuperNO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;VA&amp;amp;trade; EtCO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Measurement and Pressure Test Performance

Background: SuperNO2VA™ Et Nasal Mask (Vyaire Medical, Inc., United States) is a new nasal mask with an integrated sampling hood to capture exhaled gases and enable accurate measurements of end tidal carbon dioxide (EtCO2). The authors hypothesized that the SuperNO2VA Et design would measure EtCO2 more accurately than a predicate EtCO2 sampling line, the Smart CapnoLine® Plus, Adult/Intermediate CO2 Oral-Nasal Set (Medtronic, United States). Methods: A simulated patient setup enabled comparison of the accuracy of CO2 measurements within the SuperNO2VA Et and a predicate device for eight condition combinations of input CO2; breath rate and tidal volume (VT); and O2 flow rates. These tests were repeated with simulating Nasal Breathing and Oral Breathing. Results: Testing demonstrated that measurements of 1% and 5% input CO2 within the SuperNO2VA Et were accurate for a range of respiratory rates, VT, O2 flows, and CO2 concentrations. CO2 measurement errors were significantly larger for the Oral-Nasal Set compared to the SuperNO2VA Et for both 1% Input CO2 (-0.12%vol vs. -0.01%vol, p = 0.0005) and 5% Input CO2 (-0.93%vol vs. -0.08%vol, p 0.0001). At 5% Input CO2, eight of the 12 trials for the Oral-Nasal Set failed to meet the ISO accuracy specification, while all SuperNO2VA Et measurements met the specification. The accuracy of CO2 measurement within the SuperNO2VA were not different for Oral and Nasal Breathing trials for both CO2 concentration (1%: p = 0.33, 5%: p = 0.064). With the Oral-Nasal Set, CO2 measurements were lower during Oral compared to Nasal Breathing (1%: p = 0.0005, 5%: p = 0.0091). Conclusions: Based on performance outcomes, use of the SuperNO2VA Et offers significantly more accurate measurement of EtCO2 than the predicate EtCO2 sampling line. Measurements of EtCO2 within the SuperNO2VA Et are accurate over a range of CO2, breathing rates, tidal volumes, and O2 flows, as well as for nasal and oral breathing.

Modelling approach to obtain regional respiratory mechanics using electrical impedance tomography and volume-dependent elastance model

Objective: This paper presents a method for breath-by-breath estimation of regional respiratory mechanics without the need for special manoeuvres (such as inspiratory pause or low-flow inflation) using electrical impedance tomography (EIT) associated with pressure/airflow waveforms. Approach: We developed a method to estimate regional parameters using the regional impedance fraction, by multiplying it by global flow and volume waveforms. A volume-dependent elastance model was used to obtain compliance, resistance, volume-independent (E1), and volume-dependent (E2) components. Three swine under invasive mechanical ventilation were used to assess internal consistency and illustrate potential applications of our method. One animal (case 1) was ventilated with a broad range of tidal volumes to compare the consistency between regional and global resistances and compliances. Two other animals (cases 2 and 3) had respiratory compliance decreased, respectively, by overdistension and collapse as quantified by x-ray computed tomography. Main results: In case 1, derived global estimates obtained from the independent regional estimates were strongly associated with direct measurements of global mechanics (correlation coefficients of 0.9976 and 0.9981 for compliances and resistances, respectively), suggesting consistency of our modelling. In cases 2 and 3, the development of lung overdistension and collapse over time was captured by regional estimates. Conclusions: Using EIT and pressure/airflow waveforms, regional respiratory parameters can be obtained cycle-by-cycle, refining lung function monitoring. Significance: The method allows real-time monitoring of regional parameters and their trends over time, which might be helpful to differentiate deterioration in lung compliance due to overdistension or collapse.

Modeling the particle deposition in the respiratory system during successive respiratory cycles

In this study, using a 5-lobe symmetric model, total, lobar and generational particle deposition in the lungs during successive cycles is investigated. It has been found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, considering the effect of successive cycles predicted more deposition fraction per cycle compared to a single cycle up to about 16 percent. The mentioned range of tidal volume is related to light or heavy physical activities. So, it can be understood that people exposed to particulate matter within the mentioned size range, when acting physically, are at more health risk compared not only to the resting state, but also to the same state calculations based on a single cycle. Finally, total and generational remaining mass fraction suspended in the respiratory tract after the completion of each cycle is calculated. This remaining mass fraction turned out to be negligible except for particles between 0.05 and 2 μm.

A SIMPLE INTERVENTION TO IMPROVE TARGETING APPROPRIATE TIDAL VOLUMES IN MECHANICALLY VENTILATED ADULTS IN THE MEDICAL ICU

SESSION TITLE: Call an RT! Novel Studies in Respiratory Care SESSION TYPE: Original Investigations PRESENTED ON: 10/09/2018 08:45 AM - 09:45 AM PURPOSE: Studies have shown that low tidal volume ventilation in acute respiratory distress syndrome (ARDS) reduces ventilator-associated lung injury and improves outcomes. Newer meta-analysis has shown that similar targets are beneficial in patients without ARDS. Lung ventilation strategies with tidal volumes less than 8mL/kg of predicted body weight (PBW) are generally accepted as appropriate targets to minimize ventilator-associated lung injury. In our medical intensive care unit (MICU), compliance with these targets was previously only 24%. We hypothesized a simple, low cost intervention of a clearly placed sticker identifying a patient's PBW and goal tidal volumes at 6mL/kg and 8mL/kg of PBW would improve compliance with appropriately targeted tidal volumes. This sticker would be placed atop each ventilator prior to use, and would be filled in by respiratory therapy at each new ventilator start. METHODS: A retrospective chart review was completed comparing all mechanically ventilated adults admitted to the MICU with acute hypoxic respiratory failure or ARDS from prior to the intervention in 2013 and after the intervention in 2015. Time spent in each tidal volume range (less than 8mL/kg of PBW or greater than 8mgL/kg of PBW) was compared between the study years. The study looked at time spent in traditional ventilator modes (pressure control, volume control, or pressure regulated volume control); airway pressure release ventilation and pressure support modes were excluded. The primary outcome was time spent at tidal volumes of less than 8mL/kg of PBW. Secondary outcomes included hospital length of stay and mortality. RESULTS: After the sticker implementation, there was an increase in the median percentage of time spent at tidal volumes of less than 8mL/kg of PBW [73.7% (interquartile range (IQR) 73.7) vs 23.83% (IQR) 78.4); p<0.001]. There were no differences between the study years for total ventilator time, age, sex, BMI, or PBW. Time spent at high tidal volumes of greater than 12mL/kg of PBW was reduced from a mean of 4.5% to 2.4% of the time (p=0.025). There was a decrease in median length of stay from 12.6 (IQR 12.42) to 10.8 (IQR 15.06) [p=.021], but no difference in mortality. CONCLUSIONS: It is well known that lower tidal volumes are associated with improved outcomes in ARDS and non-ARDS patients. Despite this knowledge, most institutions fail to meet these targets. We were able to improve our compliance with a simple, low cost intervention. A sticker placed on the ventilator listing PBW and suggested tidal volumes serves as a visual reminder to clinicians every time the patient is assessed. This increased awareness led to significantly more time spent in appropriate tidal volume ranges. CLINICAL IMPLICATIONS: This study shows that a simple, low cost intervention can have a major impact on hospital compliance with a vital component of ventilator management. DISCLOSURES: No relevant relationships by Stephanie Barrett, source=Web Response No relevant relationships by Christina Mingora, source=Web Response No relevant relationships by James Rudegeair, source=Web Response No relevant relationships by Dana Stauffer, source=Web Response No relevant relationships by Margaret Wojnar, source=Web Response

Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilationin two randomized controlled trials.

BackgroundDriving pressure (ΔPrs) across the respiratory system is suggested as the strongest predictor of hospital mortality in patients with acute respiratory distress syndrome (ARDS). We wonder whether this result is related to the range of tidal volume (VT). Therefore, we investigated ΔPrs in two trials in which strict lung-protective mechanical ventilation was applied in ARDS. Our working hypothesis was that ΔPrs is a risk factor for mortality just like compliance (Crs) or plateau pressure (Pplat,rs) of the respiratory system.MethodsWe performed secondary analysis of data from 787 ARDS patients enrolled in two independent randomized controlled trials evaluating distinct adjunctive techniques while they were ventilated as in the low VT arm of the ARDSnet trial. For this study, we used VT, positive end-expiratory pressure (PEEP), Pplat,rs, Crs, ΔPrs, and respiratory rate recorded 24 hours after randomization, and compared them between survivors and nonsurvivors at day 90. Patients were followed for 90 days after inclusion. Cox proportional hazard modeling was used for mortality at day 90. If colinearity between ΔPrs, Crs, and Pplat,rs was verified, specific Cox models were used for each of them.ResultsBoth trials enrolled 805 patients of whom 787 had day-1 data available, and 533 of these survived. In the univariate analysis, ΔPrs averaged 13.7 ± 3.7 and 12.8 ± 3.7 cmH2O (P = 0.002) in nonsurvivors and survivors, respectively. Colinearity between ΔPrs, Crs and Pplat,rs, which was expected as these variables are mathematically coupled, was statistically significant. Hazard ratios from the Cox models for day-90 mortality were 1.05 (1.02–1.08) (P = 0.005), 1.05 (1.01–1.08) (P = 0.008) and 0.985 (0.972–0.985) (P = 0.029) for ΔPrs, Pplat,rs and Crs, respectively. PEEP and VT were not associated with death in any model.ConclusionsWhen ventilating patients with low VT, ΔPrs is a risk factor for death in ARDS patients, as is Pplat,rs or Crs. As our data originated from trials from which most ARDS patients were excluded due to strict inclusion and exclusion criteria, these findings must be validated in independent observational studies in patients ventilated with a lung protective strategy.Trial registrationClinicaltrials.gov NCT00299650. Registered 6 March 2006 for the Acurasys trial.Clinicaltrials.gov NCT00527813. Registered 10 September 2007 for the Proseva trial.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1556-2) contains supplementary material, which is available to authorized users.

Choice of heat and moisture exchange filters for the 'in‐between size' paediatric patient

SummaryWe present a case of increased airway resistance due to the use of a small heat and moisture exchange filter (HMEF) in a 9‐year‐old male undergoing adenotonsillectomy. Paediatric HMEF size selection should be based on the tidal volume range as recommended by the manufacturer. In practice, however, it is more frequently based on the weight of the child. HMEF sizing based solely on the weight of the child may be inappropriate, especially for children who are 'in‐between sizes'. We highlight the important factors for consideration when selecting a paediatric HMEF.

Development of a bio-inspired mechatronic chest wall simulator for evaluating the performances of opto-electronic plethysmography.

Instrumented gait analysis based on optoelectronic systems is an expensive technique used to objectively measure the human movement features and it is generally considered as the gold standard. Opto-electronic plethysmography (OEP) is a particular motion analysis system able to: (i) determine chest wall kinematic via the evaluation of marker displacements placed on the thorax and (ii) compute respiratory volumes during breathing. The aim of this work is to describe the performances of a custom made, bio-inspired, mechatronic chest wall simulator (CWS), specifically designed to assess the metrological performances of the OEP system. The design of the simulator is based on the chest wall kinematic analysis of three healthy subjects previously determined. Two sets of experiments were carried out: (i) to investigate the CWS dynamic response using different target displacements (1 - 12 mm), and (ii) to assess the CWS accuracy and precision in simulating quite breathing, covering the physiological range of respiratory frequency and tidal volume. Results show that the CWS allows simulating respiratory frequency up to ~ 60 bpm. The difference between the actual displacement and the set one is always < 9 μm. The precision error, expressed as the ratio between measurement uncertainty and the actual displacement, is lower than 0.32 %. The observed good performances permit to consider the CWS prototype feasible to be employed for assessing the performances of OEP system in periodical validation routines.

From the Journal archives: Airway closure and lung volumes in surgical positions

Douglas B. Craig, W.M. Wahba, Hillary Don Can Anaesth Soc J 1971; 18: 92-9. Surgery and anesthesia expose patients to moderate and sometimes extreme positioning changes that are often unphysiological. The purpose of this article is to highlight and contextualize a seminal study from the Journal archives that explores the effect of several commonly utilized surgical positions (supine, Trendelenburg and lithotomy) and age on basic lung volumes as well as the volume at which small airway closure (AC) (also known as closing volume [CV]) occurs. These factors were examined with the aim of determining which patient position variables could be of clinical significance to gas exchange in the perioperative period. This work showed that supine positioning, when compared with the seated position, results in a decrease of all lung volumes and capacities, including functional residual capacity (FRC) and CV. Trendelenburg positioning further decreases FRC, with no further changes induced by lithotomy positioning. Age is a clinically important factor in AC, occurring within the tidal volume range at a lower age when supine as compared with the seated position. The work of Drs. D. Craig et al. published in the Journal more than 40 years ago was seminal to our understanding of how patient positioning has an important influence on lung volumes and on the age-related relationship between FRC and CV.

Evaluation of fully automated ventilation: a randomized controlled study in post-cardiac surgery patients

Discrepancies between the demand and availability of clinicians to care for mechanically ventilated patients can be anticipated due to an aging population and to increasing severity of illness. The use of closed-loop ventilation provides a potential solution. The aim of the study was to evaluate the safety of a fully automated ventilator. We conducted a randomized controlled trial comparing automated ventilation (AV) and protocolized ventilation (PV) in 60 ICU patients after cardiac surgery. In the PV group, tidal volume, respiratory rate, FiO(2) and positive end-expiratory pressure (PEEP) were set according to the local hospital protocol based on currently available guidelines. In the AV group, only sex, patient height and a maximum PEEP level of 10 cmH(2)O were set. The primary endpoint was the duration of ventilation within a "not acceptable" range of tidal volume. Zones of optimal, acceptable and not acceptable ventilation were based on several respiratory parameters and defined a priori. The patients were assigned equally to each group, 30 to PV and 30 to AV. The percentage of time within the predefined zones of optimal, acceptable and not acceptable ventilation were 12 %, 81 %, and 7 % respectively with PV, and 89.5 %, 10 % and 0.5 % with AV (P < 0.001). There were 148 interventions required during PV compared to only 5 interventions with AV (P < 0.001). Fully AV was safe in hemodynamically stable patients immediately following cardiac surgery. In addition to a reduction in the number of interventions, the AV system maintained patients within a predefined target range of optimal ventilation.

Effects of incrementally increasing tidal volume on the cross-sectional area of the right internal jugular vein

BackgroundDifferent tidal volume (TV) settings during mechanical ventilation alter intrathoracic blood volume, and these changes could alter central venous pressure and the cross sectional area (CSA) of the right internal jugular vein (RIJV). The aim of this study was to determine the optimal TV for maximizing the CSA of the RIJV in the supine and Trendelenburg positions in anesthetized patients.MethodsForty patients were randomly allocated to a supine group (Group S, n = 20) or a Trendelenburg group (Group T, n = 20) by computer generated randomization. RIJV CSAs were measured repeatedly after increasing the inspiratory volume in 1 ml/kg increments from a TV of 8 ml/kg to 14 ml/kg using ultrasound images.ResultsPeak inspiratory pressure increased significantly on increasing TV from 11 ml/kg to 14 ml/kg and between baseline (TV 8 ml/kg) and 11 ml/kg in both groups (P < 0.05). RIJV CSA was not increased versus baseline even after TV changes in either group and no intergroup difference was found.ConclusionsTV increases do not increase the CSA of the RIJV within the TV range 8 to 14 ml/kg in the supine or 10° Trendelenburg position.

The effect of inner tube placement on resistance and work of breathing through tracheostomy tubes: a bench test

To reduce the risk of tracheostomy tube blockage, a removable inner tube can be used. However, this will reduce the size of the lumen and will increase airflow resistance and work of breathing. The magnitude of this increase in workload is unknown. We undertook a bench test to measure the effect. A lung model was developed to 'breathe' through the tracheostomy tube. We created pressure-volume curves from which we calculated work of breathing with and without an inner tube using 6-10 mm tracheostomy tubes over a range of respiratory rates and tidal volumes. The inner tube increased the resistive work of breathing by an average factor of 2.2. The extra work of breathing imposed easily exceeded the normal total work of breathing. Our results will aid a risk-benefit analysis when deciding whether to use inner tubes. Selecting a larger tracheostomy tube is likely to aid weaning from mechanical ventilation.

The Performances of Standard and ResMed Masks During Bag–Valve–Mask Ventilation

Background. A tight mask seal is frequently difficult to obtain and maintain during single-rescuer bag–valve–mask (BVM) ventilation. The ResMed mask (Bella Vista, NSW, Australia) is a continuous-positive-airway-pressure mask (CM) designed for noninvasive ventilation. Objective. In this study, we compared the ventilation performances of a standard mask (SM) and a ResMed CM using a simulation manikin in an out-of-hospital single-rescuer BVM ventilation scenario. Methods. Thirty emergency medical technicians (EMTs) performed two 2-minute attempts to ventilate a simulation manikin using BVM ventilation, alternatively, with the SM or the ResMed CM in a randomized order. Ventilation parameters including tidal volume and peak airway pressure were measured using computer analysis software connected to the simulation manikin. Successful volume delivery was defined as delivery of 440–540 mL of tidal volume in accord with present cardiopulmonary resuscitation guidelines. Results. BVM ventilation using the ResMed CM produced higher mean (± standard deviation) tidal volumes (452 ± 50 mL vs. 394 ± 113 mL, p = 0.014) and had a higher proportion of successful volume deliveries (65.3% vs. 26.7%, p < 0.001) than that using the SM. Peak airway pressure was higher in BVM ventilation using the ResMed CM (p = 0.035). Stomach insufflation did not occur during either method. Twenty-nine of the participants (96.7%) preferred BVM ventilation using the ResMed CM. Conclusions. BVM ventilations using ResMed CM resulted in a significantly higher proportion of successful volume deliveries meeting the currently recommended range of tidal volume. Clinical studies are needed to determine the value of the ResMed CM for BVM ventilation.

Correlation Between Capnography and Arterial Carbon Dioxide Before, During, and After Severe Chest Injury in Swine

The relationship between end-tidal carbon dioxide (EtCO(2)) and arterial carbon dioxide (PaCO(2))-if better defined-could facilitate the difficult task of ventilation in prehospital trauma patients. We aimed to study the PaCO(2)-EtCO(2) relationship before, during, and after chest trauma, hemorrhage, and resuscitation in swine. Twenty-four swine were intubated, anesthetized, and monitored in an animal intensive care unit during three phases: phase 1 (day 1, healthy animals); phase 2 (day 2, injury), which consisted of blunt chest trauma, hemorrhage, and resuscitation; and phase 3 (day 2, after injury). "Respiratory maneuvers" (changes in respiratory rate and tidal volume [TV], intended to vary the PaCO(2) over a range of 25 to 85 mmHg, were performed during phases 1 and 3. End-tidal CO(2) and PaCO(2) were recorded after each respiratory maneuver and analyzed using linear regression. During phase 1, PaCO(2) and EtCO(2) were strongly correlated (r(2) = 0.97, P < 0.01). During phase 2, animals developed decreased oxygenation (PaO(2):FiO(2) [fraction of inspired oxygen] ratio <200) and hypotension (mean arterial pressure, 20-50 mmHg); the PaCO(2)-EtCO(2) relationship deteriorated (r(2) = 0.25, P < 0.0001). During phase 3, oxygenation, hemodynamics, and the PaCO(2)-EtCO(2) relationship recovered (r(2) = 0.92, P < 0.01). End-tidal CO(2) closely correlates to PaCO(2) in healthy animals and after injury/resuscitation across a wide range of respiratory rates and tidal volumes. Once oxygenation and hemodynamics are restored, EtCO(2) can be used to predict PaCO(2) following chest trauma/hemorrhage and should be considered for patient monitoring. This work demonstrated that EtCO(2) alone can reliably be used to estimate PaCO(2) in uninjured subjects and in those subjects who have been resuscitated from severe injury. Immediately after blunt chest injury, the correlation between EtCO(2) and PaCO(2) is temporarily unstable. Under these circumstances (with abnormal oxygenation and/or hemodynamics), greater caution and other monitoring tools may be required.