Bench-test comparison of 26 emergency and transport ventilators

A new physiological manikin to test and compare ventilation devices during cardiopulmonary resuscitation

Background

There is a lack of bench systems permitting to evaluate ventilation devices in the specific context of cardiac arrest.

Objectives

The objective of the study is to assess if a new physiological manikin may permit to evaluate the performances of medical devices dedicated to ventilation during cardiopulmonary resuscitation (CPR).

Methods

Specific CPR-related features required to reproduce realistic ventilation were implemented into the SAM (Sarthe Anjou Mayenne) manikin. In the first place, the manikin ability to mimic ventilation during CPR was assessed and compared to real-life tracings of airway pressure, flow and capnogram from three out of hospital cardiac arrest (OHCA) patients. In addition, to illustrate the interest of this manikin, ventilation was evaluated during mechanical continuous chest compressions with two devices dedicated to CPR: the Boussignac cardiac arrest device (B-card - Vygon; Ecouen France) and the Impedance Threshold Device (ITD - Zoll; Chelmsford, MA).

Results

The SAM manikin enabled precise replication of ventilation tracings as observed in three OHCA patients during CPR, and it allowed for comparison between two distinct ventilation devices. B-card generated a mean, maximum and minimum intrathoracic pressure of 6.3 (±0.1) cmH2O, 18.9 (±1.1) cmH2O and -0.3 (±0.2) cmH2O respectively; while ITD generated a mean, maximum and minimum intrathoracic pressure of -1.6 (±0.0) cmH2O, 5.7 (±0.1) cmH2O and -4.8 (±0.1) cmH2O respectively during CPR. B-card allowed to increase passive ventilation compared to the ITD which resulted in a dramatic limitation of passive ventilation.

Conclusion

The SAM manikin is an innovative model integrating specific physiological features that permit to accurately evaluate and compare ventilation devices during CPR.

Should Transport Ventilators Be Used in Times of Crisis? The Use of Emergency Authorized Nonconventional Ventilators Is Associated With Mortality Among Patients With COVID-19 Acute Respiratory Distress Syndrome

OBJECTIVES

Nonconventional ventilators (NCVs), defined here as transport ventilators and certain noninvasive positive pressure devices, were used extensively as crisis-time ventilators for intubated patients with COVID-19. We assessed whether there was an association between the use of NCV and higher mortality, independent of other factors.

DESIGN

This is a multicenter retrospective observational study.

SETTING

The sample was recruited from a single healthcare system in New York. The recruitment period spanned from March 1, 2020, to April 30, 2020.

PATIENTS

The sample includes patients who were intubated for COVID-19 acute respiratory distress syndrome (ARDS).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was 28-day in-hospital mortality. Multivariable logistic regression was used to derive the odds of mortality among patients managed exclusively with NCV throughout their ventilation period compared with the remainder of the sample while adjusting for other factors. A secondary analysis was also done, in which the mortality of a subset of the sample exclusively ventilated with NCV was compared with that of a propensity score-matched subset of the control group. Exclusive use of NCV was associated with a higher 28-day in-hospital mortality while adjusting for confounders in the regression analysis (odds ratio, 1.41; 95% CI [1.07-1.86]). In the propensity score matching analysis, the mortality of patients exclusively ventilated with NCV was 68.9%, and that of the control was 60.7% ( p = 0.02).

CONCLUSIONS

Use of NCV was associated with increased mortality among patients with COVID-19 ARDS. More lives may be saved during future ventilator shortages if more full-feature ICU ventilators, rather than NCVs, are reserved in national and local stockpiles.

Design of a flow modulation device to facilitate individualized ventilation in a shared ventilator setup

This study aims to resolve the unmet need for ventilator surge capacity by developing a prototype device that can alter patient-specific flow in a shared ventilator setup. The device is designed to deliver a predictable tidal volume (VT), requiring minimal additional monitoring and workload. The prototyped device was tested in an in vitro bench setup for its performance against the intended use and design criteria. The ventilation parameters: VT and airway pressures, and ventilation profiles: pressure, flow and volume were measured for different ventilator and device settings for a healthy and ARDS simulated lung pathology. We obtained VTs with a linear correlation with valve openings from 10 to 100% across set inspiratory pressures (IPs) of 20 to 30 cmH2O. Airway pressure varied with valve opening and lung elastance but did not exceed set IPs. Performance was consistent in both healthy and ARDS-simulated lung conditions. The ventilation profile diverged from traditional pressure-controlled profiles. We present the design a flow modulator to titrate VTs in a shared ventilator setup. Application of the flow modulator resulted in a characteristic flow profile that differs from pressure- or volume controlled ventilation. The development of the flow modulator enables further validation of the Individualized Shared Ventilation (ISV) technology with individualization of delivered VTs and the development of a clinical protocol facilitating its clinical use during a ventilator surge capacity problem.

IMPLEMENTATION OF A DYNAMIC AND EXTENSIBLE MECHANICAL VENTILATOR MODEL FOR REAL-TIME PHYSIOLOGICAL SIMULATION

We have designed and implemented a generic virtual mechanical ventilator model into the open-source Pulse Physiology Engine for real-time medical simulation. The universal data model is uniquely designed to apply all modes of ventilation and allow for modification of the fluid mechanics circuit parameters. The ventilator methodology provides a connection to the existing Pulse respiratory system for spontaneous breathing and gas/aerosol substance transport. The existing Pulse Explorer application was extended to include a new ventilator monitor screen with variable modes and settings and a dynamic output display. Proper functionality was validated by simulating the same patient pathophysiology and ventilator settings virtually in Pulse as a physical lung simulator and ventilator setup.

Association of ventilator type with hospital mortality in critically ill patients with SARS-CoV2 infection: a prospective study

Background

To evaluate the association between ventilator type and hospital mortality in patients with acute respiratory distress syndrome (ARDS) related to COVID-19 (SARS-CoV2 infection), a single-center prospective observational study in France.

Results

We prospectively included consecutive adults admitted to the intensive care unit (ICU) of a university-affiliated tertiary hospital for ARDS related to proven COVID-19, between March 2020 and July 2021. All patients were intubated. We compared two patient groups defined by whether an ICU ventilator or a less sophisticated ventilator such as a sophisticated turbine-based transport ventilator was used. Kaplan–Meier survival curves were plotted. Cox multivariate regression was performed to identify associations between patient characteristics and hospital mortality. We included 189 patients (140 [74.1%] men) with a median age of 65 years [IQR, 55–73], of whom 61 (32.3%) died before hospital discharge. By multivariate analysis, factors associated with in-hospital mortality were age ≥ 70 years (HR, 2.11; 95% CI, 1.24–3.59; P = 0.006), immunodeficiency (HR, 2.43; 95% CI, 1.16–5.09; P = 0.02) and serum creatinine ≥ 100 µmol/L (HR, 3.01; 95% CI, 1.77–5.10; P < 0.001) but not ventilator type. As compared to conventional ICU (equipped with ICU and anesthesiology ventilators), management in transient ICU (equipped with non-ICU turbine-based ventilators) was associated neither with a longer duration of invasive mechanical ventilation (18 [IQR, 11–32] vs. 21 [13–37] days, respectively; P = 0.39) nor with a longer ICU stay (24 [IQR, 14–40] vs. 27 [15–44] days, respectively; P = 0.44).

Conclusions

In ventilated patients with ARDS due to COVID-19, management in transient ICU equipped with non-ICU sophisticated turbine-based ventilators was not associated with worse outcomes compared to standard ICU, equipped with ICU ventilators. Although our study design is not powered to demonstrate any difference in outcome, our results after adjustment do not suggest any signal of harm when using these transport type ventilators as an alternative to ICU ventilators during COVID-19 surge.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-00981-2.

OxVent: Design and evaluation of a rapidly-manufactured Covid-19 ventilator

BACKGROUND

The manufacturing of any standard mechanical ventilator cannot rapidly be upscaled to several thousand units per week, largely due to supply chain limitations. The aim of this study was to design, verify and perform a pre-clinical evaluation of a mechanical ventilator based on components not required for standard ventilators, and that met the specifications provided by the Medicines and Healthcare Products Regulatory Agency (MHRA) for rapidly-manufactured ventilator systems (RMVS).

METHODS

The design utilises closed-loop negative feedback control, with real-time monitoring and alarms. Using a standard test lung, we determined the difference between delivered and target tidal volume (VT) at respiratory rates between 20 and 29 breaths per minute, and the ventilator's ability to deliver consistent VT during continuous operation for >14 days (RMVS specification). Additionally, four anaesthetised domestic pigs (3 male-1 female) were studied before and after lung injury to provide evidence of the ventilator's functionality, and ability to support spontaneous breathing.

FINDINGS

Continuous operation lasted 23 days, when the greatest difference between delivered and target VT was 10% at inspiratory flow rates >825 mL/s. In the pre-clinical evaluation, the VT difference was -1 (-90 to 88) mL [mean (LoA)], and positive end-expiratory pressure (PEEP) difference was -2 (-8 to 4) cmH2O. VT delivery being triggered by pressures below PEEP demonstrated spontaneous ventilation support.

INTERPRETATION

The mechanical ventilator presented meets the MHRA therapy standards for RMVS and, being based on largely available components, can be manufactured at scale.

FUNDING

Work supported by Wellcome/EPSRC Centre for Medical Engineering,King's Together Fund and Oxford University.

A Novel Ventilator Design for COVID-19 and Resource-Limited Settings

There has existed a severe ventilator deficit in much of the world for many years, due in part to the high cost and complexity of traditional ICU ventilators. This was highlighted and exacerbated by the emergence of the COVID-19 pandemic, during which the increase in ventilator production rapidly overran the global supply chains for components. In response, we propose a new approach to ventilator design that meets the performance requirements for COVID-19 patients, while using components that minimise interference with the existing ventilator supply chains. The majority of current ventilator designs use proportional valves and flow sensors, which remain in short supply over a year into the pandemic. In the proposed design, the core components are on-off valves. Unlike proportional valves, on-off valves are widely available, but accurate control of ventilation using on-off valves is not straightforward. Our proposed solution combines four on-off valves, a two-litre reservoir, an oxygen sensor and two pressure sensors. Benchtop testing of a prototype was performed with a commercially available flow analyser and test lungs. We investigated the accuracy and precision of the prototype using both compressed gas supplies and a portable oxygen concentrator, and demonstrated the long-term durability over 15 days. The precision and accuracy of ventilation parameters were within the ranges specified in international guidelines in all tests. A numerical model of the system was developed and validated against experimental data. The model was used to determine usable ranges of valve flow coefficients to increase supply chain flexibility. This new design provides the performance necessary for the majority of patients that require ventilation. Applications include COVID-19 as well as pneumonia, influenza, and tuberculosis, which remain major causes of mortality in low and middle income countries. The robustness, energy efficiency, ease of maintenance, price and availability of on-off valves are all advantageous over proportional valves. As a result, the proposed ventilator design will cost significantly less to manufacture and maintain than current market designs and has the potential to increase global ventilator availability.

Causes of use errors in ventilation devices - Systematic review

A systematic review according to the PRISMA reporting standard was performed to identify causes of use errors in mechanical ventilators described in the literature. The PubMed search resulted in the inclusion of 16 papers. The errors described were systematically analyzed with regard to their causes and categorized in an adapted cause-and-effect diagram. The causes of use errors were related to specific usability issues and to the general condition that medical staff often work with different ventilators. When many devices are used, the different user interfaces are a source of use errors, since, for example, the same ventilation modes have different names. In order to avoid the identified causes for use errors in the future, this work offers manufacturers of ventilation devices design recommendations and the possibility to include the results in their risk management. In addition, standardizing user interface content across all ventilators, as in ISO 19223, can help reduce use errors.

Ventilator change in children on home mechanical ventilation affected by the Philips respironics trilogy ventilator recall

The Philips Respironics recall notification issued in June 2021 affected many of their positive airway pressure devices and mechanical ventilators including the Trilogy 100 and 200 ventilators that are often utilized in children using home positive pressure ventilation via tracheostomy (PPV-T). Optimal strategies to replace ventilators in children using home PPV-T affected by the Philips recall are unknown. We conducted a retrospective study of children using home PPV-T with recalled Trilogy ventilators who underwent inpatient ventilator change to non-recalled portable home ventilators (PHV) using our collaborative institutional protocol. During the study period, there were 40 children using PPV-T with recalled Trilogy ventilators and 19 patients underwent inpatient ventilator change either during an elective hospitalization (n = 8) or during an unscheduled or postoperative hospitalization (n = 11). The median duration of hospitalization for ventilator change was 2 days (interquartile range: 6 days) and generally 1 day for patients admitted solely for ventilator change. In children using PPV-T with recalled Trilogy ventilators, a systematic protocol collaborating with the patients, physicians, and durable medical equipment companies may optimize transition to nonrecalled PHVs.

A Bench Evaluation of Eight Home-Care Ventilators

BACKGROUND

The growing number of patients on home mechanical ventilation has driven considerable progress in the performance and functionality of ventilators, with features comparable with those used in the ICU. However, a publication gap exists in the evaluation and comparison of their performance and each ventilator choice depends on machine characteristics defined by manufacturers.

METHODS

We bench tested 8 home-care ventilators that are currently available: Monnal T50, EOVE EO-150, Puritan Bennet 560, Weinmann, PrismaVent 50, Trilogy Evo, Astral 150, and Vivo 60 by using an active lung model. These devices were tested under 18 experimental conditions that combined 3 variables: respiratory mechanics, ventilatory mode, and inspiratory muscle effort. The volume delivered, trigger response, pressurization capacity, and synchronization were analyzed.

RESULTS

Significant differences were observed in the performance among the devices. Decreased inspiratory muscle effort caused changes in the delivered volume, which worsened the response-to-trigger time, pressurization capacity, and synchronization. Increased pressure support favored the development of asynchronies. All the ventilators developed asynchronies under at least 1 set of conditions, but the EOVE and Trilogy Evo ventilators showed the fewest asynchronies during the experimental conditions studied.

CONCLUSIONS

Great variability in terms of technical performance was observed among the 8 home-care ventilators analyzed. Asynchronies became a major issue when home mechanical ventilation was used under higher pressure-support values and lower muscle efforts. Our results may prove to be useful in helping choose the best suited machine based on a patient's clinical therapy needs.

Patient–Ventilator Interaction Testing Using the Electromechanical Lung Simulator xPULM™ during V/A-C and PSV Ventilation Mode

During mechanical ventilation, a disparity between flow, pressure and volume demands of the patient and the assistance delivered by the mechanical ventilator often occurs. This paper introduces an alternative approach of simulating and evaluating patient–ventilator interactions with high fidelity using the electromechanical lung simulator xPULM™. The xPULM™ approximates respiratory activities of a patient during alternating phases of spontaneous breathing and apnea intervals while connected to a mechanical ventilator. Focusing on different triggering events, volume assist-control (V/A-C) and pressure support ventilation (PSV) modes were chosen to test patient–ventilator interactions. In V/A-C mode, a double-triggering was detected every third breathing cycle, leading to an asynchrony index of 16.67%, which is classified as severe. This asynchrony causes a significant increase of peak inspiratory pressure (7.96 ± 6.38 vs. 11.09 ± 0.49 cmH2O, p < 0.01)) and peak expiratory flow (−25.57 ± 8.93 vs. 32.90 ± 0.54 L/min, p < 0.01) when compared to synchronous phases of the breathing simulation. Additionally, events of premature cycling were observed during PSV mode. In this mode, the peak delivered volume during simulated spontaneous breathing phases increased significantly (917.09 ± 45.74 vs. 468.40 ± 31.79 mL, p < 0.01) compared to apnea phases. Various dynamic clinical situations can be approximated using this approach and thereby could help to identify undesired patient–ventilation interactions in the future. Rapidly manufactured ventilator systems could also be tested using this approach.

In vitro evaluation of disposable transport ventilators with combination aerosol therapy

Background

The COVID-19 pandemic has highlighted the need for alternative short-term, reliable means to aid in the treatment of patients requiring ventilatory support. Concurrent aerosol drug delivery is often prescribed to such patients. As such, this study examines one such short-term option, the disposable gas-powered transport ventilator to effectively deliver aerosol therapy. Factors such as aerosol generator type, patient breathing pattern, humidification and nebuliser position within the respiratory circuit were also examined.

Methods

Aerosol drug delivery characterisation was undertaken using two different disposable transport ventilators (DTVs). Two different nebuliser types, a closed circuit vibrating mesh nebuliser (VMN) and an open circuit jet nebuliser (JN), at different locations in a respiratory circuit, proximal and distal to an endotracheal tube (ETT), with and without passive humidification, were evaluated in simulated adult and paediatric patients.

Results

Placement of a nebuliser proximal to the ETT (VMN: 25.19%–34.15% and JN: 3.14%–8.92%), and the addition of a heat and moisture exchange filter (VMN: 32.37%–40.43% and JN: 5.60%–9.91%) resulted in the largest potential lung dose in the adult patient model. Irrespective of nebuliser position and humidification in the respiratory circuit, use of the VMN resulted in the largest potential lung dose (%). A similar trend was recorded in the paediatric model data, where the largest potential lung dose was recorded with both nebuliser types placed proximal to the ETT (VMN: 8.12%–10.89% and JN: 2.15%–3.82%). However, the addition of a heat and moisture exchange filter had no statistically significant effect on the potential lung dose (%) a paediatric patient would receive (p>>0.05).

Conclusions

This study demonstrates that transport ventilators, such as DTVs, can be used concurrently with aerosol generators to effectively deliver aerosolised medication in both adult and paediatric patients.

Effect of Different Interfaces on FIO2 and CO2 Rebreathing During Noninvasive Ventilation

BACKGROUND

Improving [Formula: see text] and reducing CO₂ rebreathing ([Formula: see text]) are the key means to improve the therapeutic efficacy of noninvasive ventilation (NIV). This study aimed to investigate the impact of interface design on [Formula: see text] and [Formula: see text] during NIV.

METHODS

A simulated lung model was established to analyze 17 different interfaces. CO₂ was injected into the outlet of the simulated lung, and the noninvasive ventilator was connected to the simulated lung to simulate the application of NIV in patients with COPD with hypercapnia. [Formula: see text] and [Formula: see text] were calculated by mathematical integration of synchronously collected data pertaining to real-time pressure, flow, oxygen concentration, and CO₂ concentration in the breathing circuit. Comparisons were performed between different types (nasal vs oronasal) and models of interfaces as well as between interfaces with different leak positions. Correlation of [Formula: see text] and [Formula: see text] with inner volume and leakage, respectively, and the correlation between [Formula: see text] and [Formula: see text] were analyzed.

RESULTS

[Formula: see text] levels were significantly different with a nasal or an oronasal mask (0.45 ± 0.05% vs 0.41 ± 0.08%, respectively; P < .001). [Formula: see text] levels associated with different models of interfaces varied significantly (all P < .001); [Formula: see text] did not differ significantly among the different interfaces (P = .19). Leak position significantly affected [Formula: see text] and [Formula: see text] (all P < .001). Both inner volume and leakage significantly correlated with [Formula: see text] (r = -0.23, P < .001; r = -0.08, P = .02). There was a significant correlation between [Formula: see text] and [Formula: see text] (r = 0.43, P < .01); the general linear equation was y = 0.17 + 0.02x (r = 0.43, R² = 0.19).

CONCLUSIONS

The design of the interface had a significant impact on [Formula: see text] and [Formula: see text] during NIV. [Formula: see text] and [Formula: see text] showed a significant positive correlation, although the effect size of correlation was moderate.

Emergency ventilator for COVID-19

The COVID-19 pandemic disrupted the world in 2020 by spreading at unprecedented rates and causing tens of thousands of fatalities within a few months. The number of deaths dramatically increased in regions where the number of patients in need of hospital care exceeded the availability of care. Many COVID-19 patients experience Acute Respiratory Distress Syndrome (ARDS), a condition that can be treated with mechanical ventilation. In response to the need for mechanical ventilators, designed and tested an emergency ventilator (EV) that can control a patient's peak inspiratory pressure (PIP) and breathing rate, while keeping a positive end expiratory pressure (PEEP). This article describes the rapid design, prototyping, and testing of the EV. The development process was enabled by rapid design iterations using additive manufacturing (AM). In the initial design phase, iterations between design, AM, and testing enabled a working prototype within one week. The designs of the 16 different components of the ventilator were locked by additively manufacturing and testing a total of 283 parts having parametrically varied dimensions. In the second stage, AM was used to produce 75 functional prototypes to support engineering evaluation and animal testing. The devices were tested over more than two million cycles. We also developed an electronic monitoring system and with automatic alarm to provide for safe operation, along with training materials and user guides. The final designs are available online under a free license. The designs have been transferred to more than 70 organizations in 15 countries. This project demonstrates the potential for ultra-fast product design, engineering, and testing of medical devices needed for COVID-19 emergency response.

Reliability and limits of transport-ventilators to safely ventilate severe patients in special surge situations

BACKGROUND

Intensive Care Units (ICU) have sometimes been overwhelmed by the surge of COVID-19 patients. Extending ICU capacity can be limited by the lack of air and oxygen pressure sources available. Transport ventilators requiring only one O₂ source may be used in such places.

OBJECTIVE

To evaluate the performances of four transport ventilators and an ICU ventilator in simulated severe respiratory conditions.

MATERIALS AND METHODS

Two pneumatic transport ventilators, (Oxylog 3000, Draeger; Osiris 3, Air Liquide Medical Systems), two turbine transport ventilators (Elisee 350, ResMed; Monnal T60, Air Liquide Medical Systems) and an ICU ventilator (Engström Carestation-GE Healthcare) were evaluated on a Michigan test lung. We tested each ventilator with different set volumes (Vt_set = 350, 450, 550 ml) and compliances (20 or 50 ml/cmH₂O) and a resistance of 15 cmH₂O/l/s based on values described in COVID-19 Acute Respiratory Distress Syndrome. Volume error (percentage of Vt_set) with P_0.1 of 4 cmH₂O and trigger delay during assist-control ventilation simulating spontaneous breathing activity with P_0.1 of 4 cmH₂O and 8 cmH₂O were measured.

RESULTS

Grouping all conditions, the volume error was 2.9 ± 2.2% for Engström Carestation; 3.6 ± 3.9% for Osiris 3; 2.5 ± 2.1% for Oxylog 3000; 5.4 ± 2.7% for Monnal T60 and 8.8 ± 4.8% for Elisee 350. Grouping all conditions (P_0.1 of 4 cmH₂O and 8 cmH₂O), trigger delay was 50 ± 11 ms, 71 ± 8 ms, 132 ± 22 ms, 60 ± 12 and 67 ± 6 ms for Engström Carestation, Osiris 3, Oxylog 3000, Monnal T60 and Elisee 350, respectively.

CONCLUSIONS

In surge situations such as COVID-19 pandemic, transport ventilators may be used to accurately control delivered volumes in locations, where only oxygen pressure supply is available. Performances regarding triggering function are acceptable for three out of the four transport ventilators tested.

A Novel Low-Cost Ventilator for Use in a Worldwide Pandemic: The Portsmouth Ventilator

The ongoing severe acute respiratory syndrome coronavirus 2 or coronavirus disease 2019 pandemic has demonstrated the potential need for a low-cost, rapidly deployable ventilator. Based on this premise, we sought to design a ventilator with the following criteria: 1) standard components that are accessible to the public, 2) "open-source" compatibility to allow anyone to easily recreate the system, 3) ability to ventilate in acute respiratory distress syndrome, and 4) lowest possible cost to provide adequate oxygenation and ventilation.

Design

We pursued development of a pneumatic-type ventilator. The basic design involves three electrically controlled solenoid valves, a pressure chamber, the patient breathing circuit, a positive end-expiratory pressure valve, and an electronics control system. Multiple safety elements were built into the design. The user-friendly interface allows simple control of ventilator settings. The ventilator delivers a hybrid form of pneumatic, assist-control ventilation, with predicted tidal volumes of 300-800 mL, positive end-expiratory pressure 0-20 cm H₂O, and Fio₂ 21-100%.

Main Results

The ventilator was extensively tested with two separate high-fidelity lung simulators and a porcine in vivo model. Both lung simulators were able to simulate a variety of pathologic states, including obstructive lung disease and acute respiratory distress syndrome. The ventilator performed well across all simulated scenarios. Similarly, a porcine in vivo model was used to assess performance in live tissue, with a specific emphasis on gas exchange. The ventilator performed well in vivo and demonstrated noninferior ventilation and oxygenation when compared with the standard ventilator.

Conclusions

The Portsmouth Ventilator was able to perform well across all simulated pathologies and in vivo. All components may be acquired by the public for a cost of approximately $250 U.S.D. Although this ventilator has limited functionality compared with modern ventilators, the simple design appears to be safe and would allow for rapid mass production if ventilator surge demand exceeded supply.

Low-Complexity System and Algorithm for an Emergency Ventilator Sensor and Alarm

In response to anticipated shortages of ventilators caused by the COVID-19 pandemic, many organizations have designed low-cost emergency ventilators. Many of these devices are pressure-cycled pneumatic ventilators, which are easy to produce but often do not include the sensing or alarm features found on commercial ventilators. This work reports a low-cost, easy-to-produce electronic sensor and alarm system for pressure-cycled ventilators that estimates clinically useful metrics such as pressure and respiratory rate and sounds an alarm when the ventilator malfunctions. A low-complexity signal processing algorithm uses a pair of nonlinear recursive envelope trackers to monitor the signal from an electronic pressure sensor connected to the patient airway. The algorithm, inspired by those used in hearing aids, requires little memory and performs only a few calculations on each sample so that it can run on nearly any microcontroller.

Retour d’expérience sur les transports Smur des patients Covid-19

Dès la fin du mois de février 2020, les urgentistes français ont été confrontés à une situation inédite et complexe dans la gestion des cas les plus sévères d’infections pulmonaires associées au nouveau coronavirus (SARSCoV- 2). Les informations en provenance de Chine et les recommandations initiales de l’Organisation mondiale de la santé ont rapidement amené à considérer l’intubation et la ventilation mécanique précoce des malades atteints par la pneumonie de la Covid-19. Or, dès la fin du mois de mars 2020, grâce aux retours d’expérience et de prise en charge, d’abord de la part des réanimateurs et urgentistes italiens, puis espagnols, les pratiques et les recommandations concernant les modalités d’oxygénation et de ventilation des patients Covid-19 ont évolué. Le caractère exceptionnel de cette pandémie et la grande adaptabilité des services de Samu/Smur de France, en l’espace de quelques semaines, pour prendre en charge ces patients oxygénodépendants, justifient que nous en fassions le retour d’expérience, et ce, d’autant plus que nous sommes exposés à un risque de recrudescence d’infections respiratoires graves associées au SARS-CoV-2 à court terme, risquant de saturer une nouvelle fois notre système de santé. Nous détaillons donc ici le retour d’expérience des prises en charge médicales préhospitalières concernant principalement les supports d’oxygénation et de ventilation mécanique.

Does endo-tracheal tube clamping prevent air leaks and maintain positive end-expiratory pressure during the switching of a ventilator in a patient in an intensive care unit? A bench study

Objectives

When patients with acute respiratory distress syndrome are moved out of an intensive care unit, the ventilator often requires changing. This procedure suppresses positive end expiratory pressure and promotes lung derecruitment. Clamping the endotracheal tube may prevent this from occurring. Whether or not such clamping maintains positive end-expiratory pressure has never been investigated. We designed a bench study to explore this further.

How the study was done

We used the Elysee 350 ventilator in ‘volume controlled’ mode with a positive end-expiratory pressure of 15 cmH2O, connected to an endotracheal tube with an 8 mm internal diameter inserted into a lung model with 40 ml/cmH2O compliance and 10 cmH2O/L/s resistance. We measured airway pressure and flow between the distal end of the endotracheal tube and the lung model. We tested a plastic, a metal, and an Extra Corporeal Membrane Oxygenation clamp, each with an oral/nasal, a nasal, and a reinforced endotracheal tube. We performed an end-expiratory hold then clamped the endotracheal tube and disconnected the ventilator. We measured the change in airway pressure and volume for 30 s following the disconnection of the ventilator.

Results

Airway pressure decreased thirty seconds after disconnection with all combinations of clamp and endotracheal tube. The largest fall in airway pressure (-17.486 cmH₂O/s at 5 s and -18.834 cmH₂O/s at 30 s) was observed with the plastic clamp combined with the reinforced endotracheal tube. The smallest decrease in airway pressure (0 cmH₂O/s at 5 s and -0.163 cmH₂O/s at 30 s) was observed using the Extra Corporeal Membrane Oxygenation clamp with the nasal endotracheal tube.

Conclusions

Only the Extra Corporeal Membrane Oxygenation clamp was efficient. Even with an Extra Corporeal Membrane Oxygenation clamp, it is important to limit the duration the ventilator is disconnected to a few seconds (ideally 5 s).

Impact of prehospital mechanical ventilation: A retrospective matched cohort study of 911 calls in the United States

Prehospital use of ventilators by emergency medical services (EMS) during 911 calls is increasing. This study described the impact of prehospital mechanical ventilation on prehospital time intervals and on mortality.This retrospective matched-cohort study used 4 consecutive public releases of the US National Emergency Medical Services Information System dataset (2011-2014). EMS activations with recorded ventilator use were randomly matched with activations without ventilator use (1 to 1) on age (range ± 2 years), gender, provider's primary impression, urbanicity, and level of service.A total of 5740 EMS activations were included (2870 patients per group). Patients in the ventilator group had a mean age of 69.1 (±17.3) years with 49.4% males, similar to the non-ventilator group. Activations were mostly in urban settings (83.8%) with an advanced life support level of care (94.5%). Respiratory distress (77.8%) and cardiac arrest (6.8%) were the most common provider's primary impressions. Continuous positive airway pressure was the most common mode of ventilation used (79.2%).Mortality was higher at hospital discharge (29.0% vs 21.1%, P = .01) but not at emergency department (ED) discharge (8.4% vs 7.4%, P = .19) with prehospital ventilator use. Both total on-scene time and total prehospital time intervals increased with reported ventilator use (4.10 minutes (95% confidence interval [CI]: 2.71-5.49) and 3.59 minutes (95% CI: 3.04-4.14), respectively).Ventilator use by EMS agencies in 911 calls in the US is associated with higher prehospital time intervals without observed impact on survival to ED discharge. More EMS outcome research is needed to provide evidence-based prehospital care guidelines and targeted resource utilization.

Effect of Jet Nebulization on Noninvasive Positive-Pressure Ventilation Administered with Noninvasive or Intensive Care Unit Ventilators: A Bench Study

BACKGROUND

Most of the patients on noninvasive positive pressure ventilation require aerosol inhalation therapy to moisturize the airways or deliver drugs in acute settings. However, the effect of jet nebulization on noninvasive positive pressure ventilation (NPPV) has not been determined.

OBJECTIVES

This study was designed to investigate the impact of jet nebulization on NPPV applied in ventilators.

METHODS

Aerosol therapy during NPPV was conducted in a simulated lung. The jet nebulizer was connected at both the distal and proximal end of the exhalation valve for the noninvasive ventilators, while it was placed both in front of the Y tube proximal to the patient and at 15 cm distance from the Y-tube inspiratory limb distal to the patient for the intensive care unit (ICU) ventilators. Driving flow was set at 4 and 8 L/min, respectively.

RESULTS

TPmin (time from the beginning of the lung simulator's inspiratory effort to the lowest value of airway pressure needed to trigger the ventilator), Ttrig (time to trigger), and Ptrig (the magnitude of airway pressure drop needed to trigger) were not significantly altered by jet nebulization in the noninvasive ventilators, while they were significantly increased in the ICU ventilators. The greater the driving flow, the stronger the impact on TPmin, Ttrig, and Ptrig. The actual tidal volume and control performance were not significantly affected by jet nebulization in either noninvasive or ICU ventilators. The tidal volume monitored was significantly increased at 8 L/min driving flow. The greater the driving flow, the stronger the impact on the tidal volume monitored.

CONCLUSION

The effect of jet nebulization on NPPV was different when compared to invasive ventilation. Jet nebulization only affected the tidal volume monitored in the noninvasive ventilator. Jet nebulization also affected the triggering performance and tidal volume monitored in the ICU ventilator.

Ventilator use by emergency medical services during 911 calls in the United States

BACKGROUND

Emergency and transport ventilators use in the prehospital field is not well described. This study examines trends of ventilator use by EMS agencies during 911 calls in the United States and identifies factors associated with this use.

METHODS

This retrospective study used four consecutive releases of the US National Emergency Medical Services Information System (NEMSIS) public research dataset (2011-2014) to describe scene EMS activations (911 calls) with and without reported ventilator use.

RESULTS

Ventilator use was reported in 260,663 out of 28,221,321 EMS 911 scene activations (0.9%). Patients with ventilator use were older (mean age 67±18years), nearly half were males (49.2%), mostly in urban areas (80.2%) and cared for by advanced life support (ALS) EMS services (89.5%). CPAP mode of ventilation was most common (71.6%). "Breathing problem" was the most common dispatch complaint for EMS activations with ventilator use (63.9%). Common provider impression categories included "respiratory distress" (72.5%), "cardiac rhythm disturbance" (4.6%), "altered level of consciousness" (4.3%) and "cardiac arrest"(4.0%). Ventilator use was consistently higher at the Specialty Care Transport (SCT) and Air Medical Transport (AMT) service levels and increased over the study period for both suburban and rural EMS activations. Significant factors for ventilator use included demographic characteristics, EMS agency type, specific complaints, provider's primary impressions and condition codes.

CONCLUSIONS

Providers at different EMS levels use ventilators during 911 scene calls in the US. Training of prehospital providers on ventilation technology is needed. The benefit and effectiveness of this intervention remain to be assessed.

A new global and comprehensive model for ICU ventilator performances evaluation

Background

This study aimed to provide a new global and comprehensive evaluation of recent ICU ventilators taking into account both technical performances and ergonomics.

Methods

Six recent ICU ventilators were evaluated. Technical performances were assessed under two FIO₂ levels (100%, 50%), three respiratory mechanics combinations (Normal: compliance [C] = 70 mL cmH₂O⁻¹/resistance [R] = 5 cmH₂O L⁻¹ s⁻¹; Restrictive: C = 30/R = 10; Obstructive: C = 120/R = 20), four exponential levels of leaks (from 0 to 12.5 L min⁻¹) and three levels of inspiratory effort (P0.1 = 2, 4 and 8 cmH₂O), using an automated test lung. Ergonomics were evaluated by 20 ICU physicians using a global and comprehensive model involving physiological response to stress measurements (heart rate, respiratory rate, tidal volume variability and eye tracking), psycho-cognitive scales (SUS and NASA-TLX) and objective tasks completion.

Results

Few differences in terms of technical performance were observed between devices. Non-invasive ventilation modes had a huge influence on asynchrony occurrence. Using our global model, either objective tasks completion, psycho-cognitive scales and/or physiological measurements were able to depict significant differences in terms of devices’ usability. The level of failure that was observed with some devices depicted the lack of adaptation of device’s development to end users’ requests.

Conclusions

Despite similar technical performance, some ICU ventilators exhibit low ergonomics performance and a high risk of misusage.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0285-2) contains supplementary material, which is available to authorized users.

The usability of ventilators: a comparative evaluation of use safety and user experience

Background

The design complexity of critical care ventilators (CCVs) can lead to use errors and patient harm. In this study, we present the results of a comparison of four CCVs from market leaders, using a rigorous methodology for the evaluation of use safety and user experience of medical devices.

Methods

We carried out a comparative usability study of four CCVs: Hamilton G5, Puritan Bennett 980, Maquet SERVO-U, and Dräger Evita V500. Forty-eight critical care respiratory therapists participated in this fully counterbalanced, repeated measures study. Participants completed seven clinical scenarios composed of 16 tasks on each ventilator.

Use safety was measured by percentage of tasks with use errors or close calls (UE/CCs). User experience was measured by system usability and workload metrics, using the Post-Study System Usability Questionnaire (PSSUQ) and the National Aeronautics and Space Administration Task Load Index (NASA-TLX).

Results

Nine of 18 post hoc contrasts between pairs of ventilators were significant after Bonferroni correction, with effect sizes between 0.4 and 1.09 (Cohen’s d). There were significantly fewer UE/CCs with SERVO-U when compared to G5 (p = 0.044) and V500 (p = 0.020). Participants reported higher system usability for G5 when compared to PB980 (p = 0.035) and higher system usability for SERVO-U when compared to G5 (p < 0.001), PB980 (p < 0.001), and V500 (p < 0.001). Participants reported lower workload for G5 when compared to PB980 (p < 0.001) and lower workload for SERVO-U when compared to PB980 (p < 0.001) and V500 (p < 0.001). G5 scored better on two of nine possible comparisons; SERVO-U scored better on seven of nine possible comparisons. Aspects influencing participants’ performance and perception include the low sensitivity of G5’s touchscreen and the positive effect from the quality of SERVO-U’s user interface design.

Conclusions

This study provides empirical evidence of how four ventilators from market leaders compare and highlights the importance of medical technology design. Within the boundaries of this study, we can infer that SERVO-U demonstrated the highest levels of use safety and user experience, followed by G5. Based on qualitative data, differences in outcomes could be explained by interaction design, quality of hardware components used in manufacturing, and influence of consumer product technology on users’ expectations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1431-1) contains supplementary material, which is available to authorized users.

Passive continuous positive airway pressure ventilation during cardiopulmonary resuscitation: a randomized cross-over manikin simulation study

While controlled ventilation is most frequently used during cardiopulmonary resuscitation (CPR), the application of continuous positive airway pressure (CPAP) and passive ventilation of the lung synchronously with chest compressions and decompressions might represent a promising alternative approach. One benefit of CPAP during CPR is the reduction of peak airway pressures and therefore a potential enhancement in haemodynamics. We therefore evaluated the tidal volumes and airway pressures achieved during CPAP-CPR. During CPR with the LUCAS™ 2 compression device, a manikin model was passively ventilated at CPAP levels of 5, 10, 20 and 30 hPa with the Boussignac tracheal tube and the ventilators Evita^® V500, Medumat^® Transport, Oxylator^® EMX, Oxylog^® 2000, Oxylog^® 3000, Primus^® and Servo^®-i as well as the Wenoll^® diver rescue system. Tidal volumes and airway pressures during CPAP-CPR were recorded and analyzed. Tidal volumes during CPAP-CPR were higher than during compression-only CPR without positive airway pressure. The passively generated tidal volumes increased with increasing CPAP levels and were significantly influenced by the ventilators used. During ventilation at 20 hPa CPAP via a tracheal tube, the mean tidal volumes ranged from 125 ml (Medumat^®) to 309 ml (Wenoll^®) and the peak airway pressures from 23 hPa (Primus^®) to 49 hPa (Oxylog^® 3000). Transport ventilators generated lower tidal volumes than intensive care ventilators or closed-circuit systems. Peak airway pressures during CPAP-CPR were lower than those during controlled ventilation CPR reported in literature. High peak airway pressures are known to limit the applicability of ventilation via facemask or via supraglottic airway devices and may adversely affect haemodynamics. Hence, the application of ventilators generating high tidal volumes with low peak airway pressures appears desirable during CPAP-CPR. The limited CPAP-CPR capabilities of transport ventilators in our study might be prerequisite for future developments of transport ventilators.