Influence of compliance and resistance of the test lung on the accuracy of the tidal volume delivered by the ventilator.

BACKGROUND: Large variations in respiratory system compliance and resistance may cause the accuracy of tidal volume (VT) delivery beyond the declared range. This study aimed at evaluating the accuracy of VT delivery using a test lung model to simulate pulmonary mechanics under normal or disease conditions. METHODS: In vitro assessment of the VT delivery accuracy was carried out on two commercial ventilators. Measurements of the inspired and expired VT from the ventilator and FlowAnalyser were compared to evaluate the separated and combined influences of compliance and resistance on the delivered VT accuracy. To do this, the errors of five delivered volumes (30 ml, 50 ml, 100 ml, 300 ml, and 500 ml) were checked under 29 test conditions involving a total of 27 combinations of resistance and compliance. RESULTS: For the tested ventilator S1 with a flow sensor near the expiratory valve, the average of expired VT errors (ΔVTexp) in three measurements (4 test conditions for each measurement) correlated to test lung compliance (r=-0.96, p = 0.044), and the average of inspired VT errors (ΔVTins) correlated to compliance (r = 0.89, p = 0.106); for the tested ventilator S2 with a flow sensor located at the Y piece, no clear relationship between compliance and ΔVTexp or ΔVTins was found. Furthermore, on two ventilators tested, the current measurements revealed a poor correlation between test lung resistance and ΔVTins or ΔVTexp, and the maximum values of ΔVTexp and ΔVTins correspond to the maximum resistance of 200 cmH2O/(L/s), at which the phenomenon of the flap fluttering in the variable orifice flow senor was observed, and the recorded peak inspiratory pressure (Ppeak) was much higher than the Ppeak estimated by the classical equation of motion. In contrast, at the lower resistance values of 5, 20, 50 and 100 cmH2O/(L/s), the recorded Ppeak was very close to the estimated Ppeak. Overall, the delivered VT errors were in the range of ± 14% on two ventilators studied. CONCLUSIONS: Depending on the placement site of the flow sensor in the ventilator circuit, the compliance and resistance of the test lung have different influences on the accuracy of VT delivery, which is further attributed to different fluid dynamics effects of the compliance and resistance. The main influence of compliance is to raise the peak inspiratory pressure Ppeak, thereby increasing the compression volume within the ventilator circuit; whereas a high resistance not only contributes to elevating Ppeak, but more importantly, it governs the gas flow conditions. Ppeak is a critical predictive indicator for the accuracy of the VT delivered by a ventilator.

Bench assessment of PC-CMVs modes in transport and emergency ventilators under ICU conditions.

Although there has been an increase in bench test evaluation of mechanical ventilators in recent years, a publication gap remains in assessing Pressure Control Continuous Mandatory Ventilation Modes with a set point targeting scheme PC-CMVs. This study evaluates the operational variability in PC-CMVs of eleven transport and emergency ventilators used in ICU units in Brazil during the COVID-19 pandemic. The assessment involved a comprehensive set of test scenarios derived from existing literature and the NBR ISO 80601-2-12:2014 standard. Nine parameters were computed for five consecutive breaths, offering a comprehensive characterization of pressure and flow waveforms. Most ventilators had Inspiratory pressure and PEEP values that fell outside of the tolerance ranges. Notably, three mechanical ventilators failed to reach the target pressures within the specified inspiratory times during test scenarios with a higher time constant (τ). We observed significant differences among emergency and transport ventilators in all assessed parameters, indicating a performance difference in PC-CMVs modes. The current results might help clinicians determine which ventilator models are suitable for specific clinical situations, particularly when unfavorable circumstances compel doctors to use ventilators that may not provide adequate support for patients in intensive care units.

Placement of the feline V-gel Advanced supraglottic airway device and tracheal selectivity during controlled mechanical ventilation: a clinical and tomodensitometric evaluation.

OBJECTIVES: The aims of the study was to assess the placement of the V-gel Advanced (V-gel-A) and to evaluate tracheal selectivity during controlled mechanical ventilation, using CT. METHODS: In this prospective clinical study, 20 healthy cats undergoing general anaesthesia for an elective procedure underwent four successive CT scans from the nose to the mid-abdomen: at baseline (no device); after the placement of the V-gel-A, after a controlled mechanical ventilation (CMV) period of 5 mins; and after the placement of an endotracheal tube (ETT). Using both a purpose designed position score and a gas score estimating the quantity of gas in different digestive regions, the position of the V-gel-A and presence of gas in the digestive tract at each step were evaluated. Number of attempts and times required to place the V-gel-A and ETT were recorded and compared. RESULTS: The V-gel-A was found to be correctly placed, with position scores of 3/5 in six cats, 4/5 in 13 cats and 5/5 in one cat. Imperfect positioning was due to minor axial rotation or incomplete occlusion of the oesophagus by the tip of the device. The gas scores significantly increased after placement of the V-gel-A compared with baseline and after CMV was initiated. Correct positioning of the device was mostly achieved at the first attempt; no significant difference was found in the time required to place V-gel-A vs ETT, nor in the number of attempts (P >0.05). CONCLUSIONS AND RELEVANCE: The V-gel-A was clinically easy to place and use in both spontaneous and controlled ventilation. The device properly fitted the larynx and was never observed to occlude the airway. However, incomplete occlusion of the oesophagus was frequently observed and may lead to a lack of complete tracheal selectivity.

Enhanced Manual Ventilation with a Handheld Audiovisual Device - BENGI - Insights from a Pilot Study in Special Operations Medicine.

BACKGROUND: In emergency casualty and evacuation situations, manual ventilation using self-inflating bags remains a critical skill; however, significant challenges exist in ensuring safety and effectiveness, since inaccurate manual ventilation is associated with life-threatening risks (e.g., gastric insufflation with aspiration, barotrauma, and reduced venous return). METHODS: This study assessed the impact of audiovisual feedback from the bag-valve-mask (BVM) emergency narration guided instrument (BENGI), a handheld manual ventilation guidance device, on improving performance and safety, immediately and 2 weeks after, with no additional manual ventilation training. In a crossover manikin simulation study with 20 participants, BENGI immediately and significantly improved tidal volume and respiratory rate accuracy. RESULTS: Intraand inter-participant variations were lower with BENGI, with Poincaré plot analysis showing improved performance that remained for at least 2 weeks following BENGI training. CONCLUSION: BENGI's audiovisual feedback improves manual immediately and persistently, making it invaluable for training and clinical use in diverse scenarios, from battlespace to civilian emergencies.

Noble element coatings on endotracheal tubes for ventilator-associated pneumonia prevention: A systematic review and meta-analysis of randomized controlled trials in emergency care settings.

BACKGROUND: Ventilator-associated pneumonia (VAP) is the second most prevalent nosocomial infection in emergency care settings. An emerging strategy to reduce this risk involves coating endotracheal tubes (ETTs) with noble elements, leveraging the antimicrobial properties of elements such as silver, gold, and palladium. This systematic review and meta-analysis aimed to evaluate the effectiveness of noble element coatings on ETTs in reducing VAP incidence rates, mortality, duration of mechanical ventilation, and length of stay in the intensive care unit (ICU). METHODS: Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a comprehensive search was conducted across 5 databases up to 2024. The quality of the randomized controlled trials was assessed using the updated Cochrane Risk of Bias (RoB) 2 tool. A random-effects meta-analysis was performed using RevMan 5.4 Comprehensive Meta-Analysis software. Statistical heterogeneity among the studies was evaluated using the Higgins I2 value, with P < .05 indicating statistical significance. RESULTS: Seven randomized controlled trials from 5 countries were identified. Four studies had some concerns regarding bias, 2 had a high RoB, and 1 had a low RoB. Noble metal-coated ETTs resulted in a lower incidence of VAP compared to noncoated ETTs (relative risk, 0.76 [95% confidence interval [CI], 0.60-0.96]). However, there was no significant difference in mortality rates (relative risk, 1.06 [95% CI, 0.93-1.20]), duration of mechanical ventilation (mean difference, -0.10 [95% CI, -1.62 to 1.41]), and ICU stay (mean difference, 0.07 [95% CI, -1.98 to 2.12]). CONCLUSION: Noble metal-coated ETTs effectively reduce the incidence of VAP but do not significantly impact mortality rates, the duration of mechanical ventilation, or ICU stay. Therefore, these coated ETTs should be integrated into a holistic care plan addressing all aspects of patient management in emergency care settings.

Evaluation of a new hyperbaric oxygen ventilator during pressure-controlled ventilation.

Introduction: The stability of a new hyperbaric ventilator (Shangrila590, Beijing Aeonmed Company, Beijing, China) at different clinically relevant pressures in a hyperbaric chamber during pressure-controlled ventilation (PCV) was investigated. Methods: The ventilator was connected to a test lung in the multiplace hyperbaric chamber. The inspiratory pressure (PI) of the ventilator was set to 1.0, 1.5, 2.0, 2.5 and 3.0 kPa (approximately 10, 15, 20, 25 and 30 cmH2O). The compliance and resistance of the test lung were set to 200 mL·kPa⁻¹ and 2 kPa·L⁻¹·s⁻¹, respectively. Experiments were conducted at 101, 203 and 284 kPa ambient pressure (1.0, 2.0 and 2.8 atmospheres absolute respectively). At each of the 5 PI values, the tidal volume (VT), peak inspiratory pressure (Ppeak) and peak inspiratory flow (Fpeak) displayed by the ventilator and the test lung were recorded for 20 cycles. Test lung data were considered the actual ventilation values. The ventilation data were compared among the three groups to evaluate the stability of the ventilator. Results: At every PI, the Ppeak detected by the ventilator decreased slightly with increasing ambient pressure. The Fpeak values measured by the test lung decreased substantially as the ambient pressure increased. Nevertheless, the reduction in VT at 284 kPa and PI 30 cmH2O (compared to performance at 101 kPa) was comparatively small (approximately 60 ml). Conclusions: In PCV mode this ventilator provided relatively stable VT across clinically relevant PI values to ambient pressures as high as 284 kPa. However, because Fpeak decreases at higher ambient pressure, some user adjustment might be necessary for precise VT maintenance during clinical use at higher PIs and ambient pressures.

Modified nasopharyngeal airway for pressure support ventilation in airway management of a case of Robin sequence with bilateral temporomandibular joint ankylosis.

The association of Robin sequence (RS) with temporomandibular joint (TMJ) ankylosis is not a common occurrence. Due to restricted mouth opening, difficult bag valve mask ventilation and difficult intubation, such cases are always challenging for anaesthesiologists.A male patient in early childhood with RS and bilateral TMJ ankylosis was scheduled for bilateral gap arthroplasty. Airway management was planned with fibreoptic intubation under sedation to preserve spontaneous ventilation. After sedating the patient, a nasopharyngeal airway modified by using an endotracheal tube connector was inserted in the left nostril and connected to the ventilator circuit with a 15 mm universal connector. Pressure support ventilation was given with continuous end-tidal CO2 monitoring. Fibreoptic intubation was done through the right nostril with maintenance of spontaneous ventilation.Nasal pressure support ventilation assembly can be made with available equipment in the operation theatre. It can be a substitute for a high-flow nasal cannula in particular cases.

A micro-scale humanized ventilator-on-a-chip to examine the injurious effects of mechanical ventilation.

Patients with compromised respiratory function frequently require mechanical ventilation to survive. Unfortunately, non-uniform ventilation of injured lungs generates complex mechanical forces that lead to ventilator induced lung injury (VILI). Although investigators have developed lung-on-a-chip systems to simulate normal respiration, modeling the complex mechanics of VILI as well as the subsequent recovery phase is a challenge. Here we present a novel humanized in vitro ventilator-on-a-chip (VOC) model of the lung microenvironment that simulates the different types of injurious forces generated in the lung during mechanical ventilation. We used transepithelial/endothelial electrical impedance measurements to investigate how individual and simultaneous application of mechanical forces alters real-time changes in barrier integrity during and after injury. We find that compressive stress (i.e. barotrauma) does not significantly alter barrier integrity while over-distention (20% cyclic radial strain, volutrauma) results in decreased barrier integrity that quickly recovers upon removal of mechanical stress. Conversely, surface tension forces generated during airway reopening (atelectrauma), result in a rapid loss of barrier integrity with a delayed recovery relative to volutrauma. Simultaneous application of cyclic stretching (volutrauma) and airway reopening (atelectrauma), indicates that the surface tension forces associated with reopening fluid-occluded lung regions are the primary driver of barrier disruption. Thus, our novel VOC system can monitor the effects of different types of injurious forces on barrier disruption and recovery in real-time and can be used to interogate the biomechanical mechanisms of VILI.

Development of Prone Position Ventilation Device and Study on the Application Effect of Combined Life Support Technology in Critically Ill Patients.

Objective: This study aims to evaluate a novel prone position ventilation device designed to enhance patient safety, improve comfort, and reduce adverse events, facilitating prolonged tolerance in critically ill patients. Methods: A randomized controlled trial was conducted on 60 critically ill patients from January 2020 to June 2023. Of which, one self-discharged during treatment and another was terminated due to decreased oxygenation, leaving an effective sample of 58 patients. Patients were allocated to either a control group receiving traditional prone positioning aids (ordinary sponge pads and pillows) or an intervention group using a newly developed adjustable prone positioning device. A subset of patients in each group also received life support technologies such as extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). We assessed prone position ventilation tolerance, oxygen saturation increments postintervention, duration of prone positioning, CRRT filter lifespan, and the incidence of adverse events. Results: The intervention group exhibited significantly longer average tolerance to prone positioning (16.6 hours vs. 8.3 hours, P < 0.001 with a difference of 8.3 (4.4, 12.2) hours), higher increases in oxygen saturation postventilation (9% vs. 6%, P < 0.001 with a difference of 3.0 (1.5, 4.5)), and reduced time required for medical staff to position patients (11.7 min vs. 21.8 min, P < 0.001 with a difference of -10.1 (-11.9, -8.3)). Adverse events, including catheter displacement or blockage, facial edema, pressure injuries, and vomiting or aspiration, were markedly lower in the intervention group, with statistical significance (P < 0.05). In patients receiving combined life support, the intervention group demonstrated improved catheter blood drainage and extended CRRT filter longevity. Conclusion: The newly developed adjustable prone ventilation device significantly improves tolerance to prone positioning, enhances oxygenation, and minimizes adverse events in critically ill patients, thereby also facilitating the effective application of life support technologies.

Novel High-tech, Low-cost Ventilation for Military Use, Mass Casualty Incidents, Stockpiling, and Underserved Communities.

INTRODUCTION: Despite the significant need for mechanical ventilation in- and out-of-hospital, mechanical ventilators remain inaccessible in many instances because of cost or size constraints. Mechanical ventilation is especially critical in trauma scenarios, but the impractical size and weight of standard mechanical ventilators restrict first responders from carrying them in medical aid bags, leading to reliance on imprecise manual bag-mask ventilation. This is particularly important in combat-related injury, where airway compromise and respiratory failure are leading causes of preventable death, but medics are left without necessary mechanical ventilation. To address the serious gaps in mechanical ventilation accessibility, we are developing an Autonomous, Modular, and Portable Ventilation platform (AMP-Vent) suitable for austere environments, prolonged critical care, surgical applications, mass casualty incidents, and stockpiling. The core system is remarkably compact, weighing <2.3 kg, and can fit inside a shoebox (23.4 cm × 17.8 cm × 10.7 cm). Notably, this device is 65% lighter than standard transport ventilators and astoundingly 96% lighter than typical intensive care unit ventilators. Beyond its exceptional portability, AMP-Vent can be manufactured at less than one-tenth the cost of conventional ventilators. Despite its reduced size and cost, the system's functionality is uncompromised. The core system is equipped with closed-loop sensors and advanced modes of ventilation (pressure-control, volume-control, and synchronized intermittent mandatory ventilation), enabling quality care in a portable form factor. The current prototype has undergone preliminary preclinical testing and optimization through trials using a breathing simulator (ASL 5000) and in a large animal model (swine). This report aims to introduce a novel ventilation system and substantiate its promising performance through evidence gathered from preclinical studies. MATERIALS AND METHODS: Lung simulator testing was performed using the ASL 5000, in accordance with table 201.105 "pressure-control inflation-type testing" from ISO 80601-2-12:2020. Following simulations, AMP-Vent was tested in healthy 10-kg female domestic piglets. The Children's Hospital of Philadelphia Institutional Animal Care and Use Committee approved all animal procedures. Swine received 4-min blocks of alternating ventilation, where AMP-Vent and a conventional anesthesia ventilator (GE AISYS CS2) were used to titrate to varied end-tidal carbon dioxide (EtCO2) goals with the initial ventilator switching for each ascending target (35, 40, 45, 50, 55 mmHg). RESULTS: During ASL 5000 simulations, AMP-Vent exhibited consistent performance under varied conditions, maintaining a coefficient of variation of 2% or less within each test. In a large animal study, AMP-Vent maintained EtCO2 and SpO2 targets with comparable performance to a conventional anesthesia ventilator (GE AISYS CS2). Furthermore, the comparison of minute ventilation (Ve) distributions between the conventional anesthesia ventilator and AMP-Vent at several EtCO2 goals (35, 40, 45, 50, and 55 mmHg) revealed no statistically significant differences (p = 0.46 using the Kruskal-Wallis rank sum test). CONCLUSIONS: Preclinical results from this study highlight AMP-Vent's core functionality and consistent performance across varied scenarios. AMP-Vent sets a benchmark for portability with its remarkably compact design, positioning it to revolutionize trauma care in previously inaccessible medical scenarios.

Device associated complications in the intensive care unit.

Invasive devices are routinely used in the care of critically ill patients. Although they are often essential components of patient care, devices such as intravascular catheters, endotracheal tubes, and ventilators are a common source of complications in the intensive care unit. Critical care practitioners who use these devices need to use strategies for risk reduction and understand approaches to management when adverse events occur. This review discusses the identification, prevention, and management of complications of vascular, airway, and mechanical support devices commonly used in the intensive care unit.

Evaluating endotracheal tube length in very and extremely preterm infants.

OBJECTIVE: Our study objective was to evaluate changes in ETT tube depth throughout the initial intubation course in very and extremely preterm infants in order to evaluate the risk of outgrowing an endotracheal tube (ETT). METHODS: This was a retrospective cohort study of preterm infants born at <32 weeks of gestation who were admitted to the NICU between 2012 and 2021 and required intubation for mechanical ventilation. Infants who were intubated only for surfactant administration and those with airway malformations were excluded. Descriptive statistics were used to define the range of ETT depths at the time of extubation, stratified by gestational age (<28 weeks vs 28-32 weeks of gestation). Relative ETT depth was defined as the final depth minus the initial depth. RESULTS: Out of 496 infants, 140 patients met all criteria for inclusion. Descriptive analysis of extubation depths across the populations demonstrated median relative ETT depth of 0 cm for the 28-32-week gestational age group, and -0.25 cm for the <28-week gestational age group. The 95th percentile for both gestational age groups was a relative depth of 0.5 cm and the 99th percentile was 1.0-1.5 cm. CONCLUSION: The results of our study suggest that the vast majority of patients in the NICU are unlikely to "outgrow" ETT tube length which should be taken into account when deciding where to trim the ETT in order to minimize airway resistance.

Development of a New Method for Evaluating Heat and Moisture Exchanger Performance.

BACKGROUND: A model system described in International Organization for Standardization 9360 is the standard method for estimating the humidifying performance of heat and moisture exchangers (HMEs). However, there are no reliable bedside methods for evaluating the ongoing humidification performance of HMEs. Therefore, this study aimed to develop 2 clinically applicable methods for estimating the ongoing humidifying performance of HMEs and to evaluate their reliability in a model system. METHODS: Physiologically expired gas was simulated using a heated humidifier, and ventilation was delivered using a ventilator with constant flow through 3 different types of HMEs. Relative humidity (RH) was measured using a capacitive-type moisture sensor. Water content lost during expiration was calculated by integrating absolute humidity (AH), instantaneous gas flow measured at the expiratory outlet of the ventilator, and time. We also calculated the water content released and captured by the HMEs during tidal ventilation by integrating the difference in AH across the HMEs, instantaneous gas flow, and time. RESULTS: We found that the RH, temperature, and AH were almost constant on the expiratory outlet of the ventilator but rapidly varied near the HMEs. The water content lost by the 3 HMEs was associated with the manufacturer-reported values and inversely correlated with the calculated values of the water content exchanged by the HMEs. The water content released and captured by HMEs was closely correlated with the difference in HME weight measured at the end of inspiration and expiration; however, the water content captured by HMEs seemed to be overestimated. CONCLUSIONS: Our results demonstrated that our system was able to detect the differences in the performance of 3 models of HMEs and suggest that our method for calculating water loss is reliable for estimating the water retention performance of HMEs during mechanical ventilation, even in the presence of a constant flow.

Consequences of Pausing Heated Humidification During Invasive Ventilation.

BACKGROUND: During invasive mechanical ventilation, where medical gases are very dry and the upper airway is bypassed, appropriate gas conditioning and humidification are mandatory at all times. Results of in vitro studies suggest that dry gases may improve lung deposition during nebulization, but this has not been confirmed through in vivo studies. The objective of this study was to measure gas humidity under multiple conditions to better describe gas hygrometry when heated humidifiers are turned off. METHODS: We measured, on a bench, the hygrometry of different gases at steady state: medical gases, at the Y-piece without humidifier, with the humidifier switched off, and with humidifier switched on. We measured gas humidity every 10-60 s during dynamic conditions after switching off the heated humidifier and after switching on the heated humidifier. Hygrometry was measured by using the psychrometric method with at least 3 measurements for each tested condition. RESULTS: We performed 287 psychrometric measurements in different situations. The mean ± SD gas absolute humidity at steady state during different conditions were the following: 1.6 ± 0.2 mg H2O/L for the medical gases, 4.5 ± 0.9 mg H2O/L at the Y-piece without humidifier, 9.1 ± 0.3 mg H2O/L at the Y-piece with heated humidifier turned off, and 34.2 ± 2.2 mg H2O/L at the Y-piece with the heated humidifier turned on. During the dynamic evaluation, after turning off the humidifier, humidity was < 30 mg H2O/L after a few minutes, attained 15 mg H2O/L after 15 min, and was below 10 mg H2O/L after 1 h but never reached the level of dry medical gases. After turning on the heated humidifier, the gas hygrometry reached 30 mg H2O/L after 5 min. CONCLUSIONS: When heated humidifiers are turned off, gas humidity levels are very low but not as low as medical gases. The clinical impact of repeated shutdowns is unknown. As recommended, heated humidifiers should never be turned off during nebulization.