Bench studies evaluating devices for non-invasive ventilation: critical analysis and future perspectives

Impact of tracheostomy tube modalities on ventilatory mechanics: a bench study

PURPOSE

Tracheostomized patients often present with muscle weakness, altered consciousness, or swallowing difficulties. Hence, the literature is scarce regarding the challenging management of tracheostomy weaning. There is a need to strengthen the understanding of respiratory mechanisms with the different tracheostomy tube modalities that compose this weaning pathway. We aimed to evaluate the impact of these modalities on the work of breathing (WOB), total positive end-expiratory pressure (PEEPtot), and tidal volume (VT).

METHODS

With a three-dimensional (3D) printed head mimicking human upper airways, we added a tracheal extension, and pierced to allow insertion of a size 7.0 tracheostomy cannula. The whole was connected to an artificial lung. Three lung mechanics were simulated (normal, obstructive and restrictive). We compared five different tracheostomy tube modalities to a control scenario in which the tube was capped and the cuff was deflated.

RESULTS

A marginal difference was observed on the WOB within conditions with a slight increase + 0.004 [95% CI (0.003-0.004); p < 0.001] when the cuff was inflated in the normal and restrictive models and a slight decrease in the obstructive model. The highest PEEPtot that was reached was + 1 cmH2O [95% CI (1-1.1); p < 0.001] with high-flow therapy (HFT) with the cuff inflated in the obstructive model. We observed a statistically significant reduction in VT [up to - 57 mL 95% CI (- 60 to - 54); p < 0.001] when the cuff was inflated, in both the normal and obstructive models.

CONCLUSIONS

Our results support the use of conditions that involve cuff deflation. Intermediate modalities with the cuff deflated produced similar results than cannula capping.

Development of personalized non-invasive ventilation masks for critically ill children: a bench study

BACKGROUND

Obtaining a properly fitting non-invasive ventilation (NIV) mask to treat acute respiratory failure is a major challenge, especially in young children and patients with craniofacial abnormalities. Personalization of NIV masks holds promise to improve pediatric NIV efficiency. As current customization methods are relatively time consuming, this study aimed to test the air leak and surface pressure performance of personalized oronasal face masks using 3D printed soft materials. Personalized masks of three different biocompatible materials (silicone and photopolymer resin) were developed and tested on three head models of young children with abnormal facial features during preclinical bench simulation of pediatric NIV. Air leak percentages and facial surface pressures were measured and compared for each mask.

RESULTS

Personalized NIV masks could be successfully produced in under 12 h in a semi-automated 3D production process. During NIV simulation, overall air leak performance and applied surface pressures were acceptable, with leak percentages under 30% and average surface pressure values mostly remaining under normal capillary pressure. There was a small advantage of the masks produced with soft photopolymer resin material.

CONCLUSION

This first, proof-of-concept bench study simulating NIV in children with abnormal facial features, showed that it is possible to obtain biocompatible, personalized oronasal masks with acceptable air leak and facial surface pressure performance using a relatively short, and semi-automated production process. Further research into the clinical value and possibilities for application of personalized NIV masks in critically ill children is needed.

Are all ventilators for NIV performing the same? A bench analysis

Global pandemic due to COVID-19 has increased the interest for ventilators´ use worldwide. New devices have been developed and older ones have undergone a renewed interest, but we lack robust evidence about performance of each ventilator to match appropriate device to a given patient and care environment. The aim of this bench study was to investigate the performance of six devices for noninvasive ventilation, and to compare them in terms of volume delivered, trigger response, pressurization capacity and synchronization in volume assisted controlled and pressure support ventilation. All ventilators were tested under thirty-six experimental conditions by using the lung model ASL5000® (IngMar Medical, Pittsburgh, PA). Two leak levels, two muscle inspiratory efforts and three mechanical patterns were combined for simulation. Trigger function was assessed by measurement of trigger-delay time. Pressurization capacity was evaluated as area under the pressure-time curve over the first 500 ms after inspiratory effort onset. Synchronization was evaluated by the asynchrony index and by incidence and type of asynchronies in each condition. All ventilators showed a good performance, even if pressurization capacity was worse than expected. Leak level did not affect their function. Differences were found during low muscle effort and obstructive pattern. In general, Philips Trilogy Evo/EV300 and Hamilton C3 showed the best results. NIV devices successfully compensate air leaks but still underperform with low muscle effort and obstructive lungs. Clinicians´ must have a clear understanding of the goals of NIV both for devices´ choice and set main parameters to achieve therapy success.

Performance of helmet CPAP using different configurations: Turbine-driven ventilators vs Venturi devices

BACKGROUND

Traditionally, Venturi-based flow generators have been preferred over mechanical ventilators to provide continuous positive airway pressure (CPAP) through the helmet (h-CPAP). Recently, modern turbine-driven ventilators (TDVs) showed to be safe and effective in delivering h-CPAP. We aimed to compare the pressure stability during h-CPAP delivered by Venturi devices and TDVs and assess the impact of High Efficiency Particulate Air (HEPA) filters on their performance.

METHODS

We performed a bench study using an artificial lung simulator set in a restrictive respiratory condition, simulating two different levels of patient effort (high and low) with and without the interposition of the HEPA filter. We calculated the average of minimal (Pmin), maximal (Pmax) and mean (Pmean) airway pressure and the time product measured on the airway pressure curve (PTPinsp). We defined the pressure swing (Pswing) as Pmax - Pmin and pressure drop (Pdrop) as End Expiratory Pressure - Pmin.

RESULTS

Pswing across CPAP levels varied widely among all the tested devices. During "low effort", no difference in Pswing and Pdrop was found between Venturi devices and TDVs; during high effort, Pswing (p<0.001) and Pdrop (p<0.001) were significantly higher in TDVs compared to Venturi devices, but the PTPinsp was lower (1.50 SD 0.54 vs 1.67 SD 0.55, p<0.001). HEPA filter addition almost doubled Pswing and PTPinsp (p<0.001) but left unaltered the differences among Venturi and TDVs systems in favor of the latter (p<0.001).

CONCLUSIONS

TDVs performed better than Venturi systems in delivering a stable positive pressure level during h-CPAP in a bench setting.

Transition from intensive care unit to a portable ventilator in children with severe bronchopulmonary dysplasia

As the population of ventilator-dependent children (VDC) with tracheostomies due to underlying severe bronchopulmonary dysplasia grows, there is an increasing need to shift the care of these children from hospital to home. Transitioning the ventilator-dependent child from the hospital to home is a complex process that requires coordination between the medical team and the family. One crucial step in the process is transitioning from an Intensive care unit (ICU) ventilator to a portable home ventilator (PHV). The Clinical team needs to understand the nuances in transitioning to PHV, including assessing readiness to transition and choosing the optimum settings on an available home ventilator. In recent years, various ventilator modes have been available in PHV that can help achieve synchronous breathing to allow for adequate gas exchange for the infant. This review details some approaches to asses readiness to transition and the process of Transition along with commonly used modes of support available in PHV, as well as the primary and secondary settings in which we should be mindful in supporting a child with chronic respiratory failure in the home setting.

Comparative bench study evaluation of a modified snorkeling mask used during COVID-19 pandemic and standard interfaces for non-invasive ventilation

PURPOSE

The aim of this bench study is to compare the standard NIV and nCPAP devices (Helmet, H; Full face mask, FFM) with a modified full face snorkeling mask used during COVID-19 pandemic.

METHODS

A mannequin was connected to an active lung simulator. The inspiratory and expiratory variations in airways pressure observed with a high simulated effort, were determined relative to the preset CPAP level. NIV was applied in Pressure Support Mode at two simulated respiratory rates and two cycling-off flow thresholds. During the bench study, we measured the variables defining patient-ventilator interaction and performance.

RESULTS

During nCPAP, the tested interfaces did not show significant differences in terms of ∆Pawi and ∆Pawe. During NIV, the snorkeling mask demonstrated a better patient-ventilator interaction compared to FFM, as shown by significantly shorter Pressurization Time and Expiratory Trigger Delay (p < 0.01), but no significant differences were found in terms of Inspiratory Trigger Delay and Time of Synchrony between the interfaces tested. At RR 20sim, the snorkeling mask presented the lower ΔPtrigger (p < 0.01), moreover during all the conditions tested the snorkeling mask showed the longer Pressure Time Product at 200, 300, and 500 ms compared to FFM (p < 0.01). A major limitation of snorkeling mask is that during NIV with this interface it is possible to reach maximum 18 cmH₂O of peak inspiratory pressure.

CONCLUSIONS

The modified snorkeling mask can be used as an acceptable alternative to other interfaces for both nCPAP and NIV in emergencies.

Responses of Bilevel Ventilators to Unintentional Leak: A Bench Study

BACKGROUND

The impact of leaks has mainly been assessed in bench models using continuous leak patterns which did not reflect real-life leakage. We aimed to assess the impact of the pattern and intensity of unintentional leakage (UL) using several respiratory models.

METHODS

An active artificial lung (ASL 5000) was connected to three bilevel-ventilators set in pressure mode; the experiments were carried out with three lung mechanics (COPD, OHS and NMD) with and without upper airway obstruction. Triggering delay, work of breathing, pressure rise time, inspiratory pressure, tidal volume, cycling delay and the asynchrony index were measured at 0, 6, 24 and 36 L/min of UL. We generated continuous and inspiratory UL.

RESULTS

Compared to 0 L/min of UL, triggering delays were significantly higher with 36 L/min of UL (+27 ms) and pressure rise times were longer (+71 ms). Cycling delays increased from -4 [-250-169] ms to 150 [-173-207] ms at, respectively 0 L/min and 36 L/min of UL and work of breathing increased from 0.15 [0.12-0.29] J/L to 0.19 [0.16-0.36] J/L. Inspiratory leakage pattern significantly increased triggering delays (+35 ms) and cycling delays (+263 ms) but decreased delivered pressure (-0.94 cmH₂O) compared to continuous leakage pattern. Simulated upper airway obstruction significantly increased triggering delay (+199 ms), cycling delays (+371 ms), and decreased tidal volume (-407 mL) and pressure rise times (-56 ms).

CONCLUSIONS

The pattern of leakage impacted more the device performances than the magnitude of the leakage per se. Flow limitation negatively reduced all ventilator performances.

Extension of Non-invasive Ventilation Capabilities of MASI for the Care of Patients Affected by COVID-19

The MASI mechanical ventilator was developed in a state of emergency to meet the demand for ventilators caused by COVID-19. Although it has obtained positive results in its use with patients in intensive care units, not having an optimal quality non-invasive ventilation (NIV) modality prevents it from being used in the early treatment of patients, which has been shown to prevent admission to the ICU and reduce mortality. Therefore, the following study focuses on evaluating MASI's ability to provide NIV using different accessories in order to compare their performance and determine which one would work best with MASI, and under which conditions. To do this, the high-flow nasal cannula, facial mask, and ventilation helmet accessories were tested under different pressure parameter settings. The data was collected using a gas flow analyzer. After that, a statistical analysis of the results was carried out, which showed that the face mask is the best accessory to use for NIV with MASI, and that it performs with optimal accuracy and precision when the peak inspiratory pressure is set at a value lower than 25 cmH20. Clinical Relevance- This study presents an optimization of the non-invasive ventilation (NIV) modality of the MASI me-chanical ventilator by evaluating its performance with different accessories.

Does the Efficacy of High Intensity Ventilation in Stable COPD Depend on the Ventilator Model? A Bench-to-Bedside Study

Purpose

The European Task Force for chronic non-invasive ventilation in stable COPD recommends the use of high pressure-support (PS) level to maximize the decrease in PaCO2. It is possible that the ventilator model can influence the need for higher or lower pressure levels.

Research Question

To determine the differences between ventilators in a bench model with an increased inspiratory demand; and to compare the degree of muscular unloading measured by parasternal electromyogram (EMGpara) provided by the different ventilators in real patients with stable COPD.

Patients and Methods

Bench: four levels of increasing progressive effort were programmed. The response of nine ventilators to four levels of PS and EPAP of 5 cm H2O was studied. The pressure-time product was determined at 300 and 500 msec (PTP 300/500).

Clinical Study

The ventilators were divided into two groups, based on the result of the bench test. Severe COPD patients with non-invasive ventilation (NIV) were studied, randomly comparing the performance of one ventilator from each group. Muscle unloading was measured by the decrease in EMGpara from its baseline value.

Results

There were significant differences in PTP 300 and PTP 500 in the bench study. Based on these results, home ventilators were classified into two groups; group 1 included four models with higher PTP 300. Ten COPD patients were recruited for the clinical study. Group 1 ventilators showed greater muscle unloading at the same PS than group 2.

Conclusion

The scale of pressure support in NIV for high intensity ventilation may be influenced by the ventilator model.

Clinical Trials.gov

NCT03373175.

A bench-to-bedside study about trigger asynchronies induced by the introduction of external gas into the non-invasive mechanical ventilation circuit

Treatments that require the introduction of external gas into the non-invasive ventilation (NIV) circuit, such as aerosol and oxygen therapy, may influence the performance of the ventilator trigger system. The aim of the study was to determine the presence and type of asynchronies induced by external gas in the NIV circuit in a bench model and in a group of patients undergoing chronic NIV. Bench study: Four ventilators (one with two different trigger design types) and three gas sources (continuous flow at 4 and 9 l/min and pulsatile flow at 9 l/min) were selected in an active simulator model. The sensitivity of the trigger, the gas introduction position, the ventilatory pattern and the level of effort were also modified. The same ventilators and gas conditions were used in patients undergoing chronic NIV. Bench: the introduction of external gas caused asynchronies in 35.9% of cases (autotriggering 73%, ineffective effort 27%). Significant differences (p < 0.01) were detected according to the ventilator model and the gas source. In seven patients, the introduction of external gas induced asynchrony in 20.4% of situations (77% autotriggering). As in the bench study, there were differences in the occurrence of asynchronies depending on the ventilator model and gas source used. The introduction of external gas produces alterations in the ventilator trigger. These alterations are variable, and depend on the ventilator design and gas source. This phenomenon makes it advisable to monitor the patient at the start of treatment.

Impact of end-expiratory pressure fluctuation on tidal volume in the trilevel positive airway pressure mode

INTRODUCTION

In noninvasive positive-pressure ventilation (NPPV), the changes in the expiratory positive airway pressure (EPAP) directly affect the magnitude of the tidal volume.

OBJECTIVES

This experimental study aims to verify the precise effects of end-expiratory fluctuation on the body tidal volume to better assist NPPV in clinical practice.

METHODS

We selected the TestChest-simulated lung simulation of different populations, including healthy subjects (normal group), patients with chronic obstructive pulmonary disease (COPD) with emphysema as their primary phenotype (COPD1 group), and patients with COPD with bronchitis as their primary phenotype (COPD2 group).

RESULTS

Regarding the tidal volume curves of the three groups under various conditions, sixfold charts revealed that the tidal volume changed with the end-expiratory pressure fluctuations. In addition, regression coefficients for end-expiratory pressure fluctuations, (IPAP-EPAP) and (IPAP-EEPAP) exhibited a significant contribution to the tidal volume. The two coefficients in the normal, COPD1 and COPD2 groups were 52.294 and 10.414, 46.192 and -8.816, and 11.922 and 17.947, respectively. The circuit simulation results showed that the simulation curve fitted the experimental curve better by changing the coefficient of the descending edge of the expiratory phase.

CONCLUSIONS

The study results suggest that the end-expiratory pressure fluctuation affects the body tidal volume. Compared with the bilevel positive airway pressure (PAP), the trilevel PAP provides additional respiratory support to the body during a respiratory difference in initial respiration and descent.

Low-cost, easy-to-build noninvasive pressure support ventilator for under-resourced regions: open source hardware description, performance and feasibility testing

Aim

Current pricing of commercial mechanical ventilators in low-/middle-income countries (LMICs) markedly restricts their availability, and consequently a considerable number of patients with acute/chronic respiratory failure cannot be adequately treated. Our aim was to design and test an affordable and easy-to-build noninvasive bilevel pressure ventilator to allow a reduction in the serious shortage of ventilators in LMICs.

Methods

The ventilator was built using off-the-shelf materials available via e-commerce and was based on a high-pressure blower, two pressure transducers and an Arduino Nano controller with a digital display (total retail cost <75 USD), with construction details provided open source for free replication. The ventilator was evaluated, and compared with a commercially available device (Lumis 150 ventilator; Resmed, San Diego, CA, USA): 1) in the bench setting using an actively breathing patient simulator mimicking a range of obstructive/restrictive diseases; and b) in 12 healthy volunteers wearing high airway resistance and thoracic/abdominal bands to mimic obstructive/restrictive patients.

Results

The designed ventilator provided inspiratory/expiratory pressures up to 20/10 cmH₂O, respectively, with no faulty triggering or cycling; both in the bench test and in volunteers. The breathing difficulty score rated (1–10 scale) by the loaded breathing subjects was significantly (p<0.005) decreased from 5.45±1.68 without support to 2.83±1.66 when using the prototype ventilator, which showed no difference with the commercial device (2.80±1.48; p=1.000).

Conclusion

The low-cost, easy-to-build noninvasive ventilator performs similarly to a high-quality commercial device, with its open-source hardware description, which will allow for free replication and use in LMICs, facilitating application of this life-saving therapy to patients who otherwise could not be treated.

Patients in under-resourced areas cannot be treated by mechanical ventilation given the unaffordable cost of conventional devices; here a low-cost, easy-to-build ventilator with open access details for free replication is designed and testedhttps://bit.ly/34UcbWp

Effects of assist parameter on the performance of proportional assist ventilation in a lung model of chronic obstructive pulmonary disease

BACKGROUND

How the assist parameters affect synchronization and inspiratory workload in proportional assist ventilation (PAV) remains unknown.

PURPOSE

This bench study aimed to optimize the PAV parameters by evaluating their effects on patient-ventilator synchrony and work of breathing (WOB) in a chronic obstructive pulmonary disease (COPD) model during noninvasive ventilation, compared with the pressure support ventilation (PSV) mode.

METHODS

The Respironics V60 ventilator was connected to an ASL5000 lung simulator, which simulates lung mechanics in COPD (compliance, 50mL/cmH₂O; expiratory resistance, 20 cmH₂O/L/s; respiratory rate, 15 breaths/min; inspiratory time, 1.6 s). PAV was applied with different assistance levels, including flow assist (FA, 40-90% respiratory resistance) and volume assist (VA, 50-90% elastance). PSV was assessed using the same model. Measurements were obtained at a leak flow rate of 25-28 L/min. Performance characteristics, simulator-ventilator synchrony, and WOB were assessed.

RESULTS

Runaway was prone to occur, and severe premature cycling was observed with VA75+FA level>65%. Compared with PSV, lower tidal volume (≤400mL) was observed during PAV with VA75+FA40-50 and FA50+VA40-80; similar and improved cycling synchrony was observed for FA50+VA80 and FA50+VA90 (cycling delay: -117.60±6.13 and -61.50±8.03 vs. -101.20±7.32ms). The reduced triggering workload was observed for VA75+FA60-65 and FA50+VA80-90. Total and patient WOB was improved with all tested assist level combinations, except for FA50+VA90.

CONCLUSIONS

PAV reduces WOB but can induce asynchrony if improper settings are set, but the most optimal settings still need more clinical observations.

Ventilator- and interface-related factors influencing patient-ventilator asynchrony during noninvasive ventilation

Patient-ventilator asynchrony (PVA) is common in patients receiving noninvasive ventilation (NIV). This occurs primarily when the triggering and cycling-off of ventilatory assistance are not synchronized with the patient's inspiratory efforts and could result in increased work of breathing and niv failure. In general, five types of asynchrony can occur during NIV: ineffective inspiratory efforts, double-triggering, auto-triggering, short-ventilatory cycling, and long-ventilatory cycling. Many factors that affect PVA are mostly related to the degree of air leakage, level of pressure support, and the type and properties of the interface used. Careful monitoring and adjustment of these factors are essential to reduce PVA and improve patient comfort. In this article, we discuss the machine and interface-related factors that influence PVA during NIV and its effect on the respiratory mechanics during pressure support ventilation, which is the ventilatory mode used most commonly during NIV. For that, we critically evaluated studies that assessed ventilator- and interface-related factors that influence PVA during NIV and proposed therapeutic solutions.

ISCCM Guidelines for the Use of Non-invasive Ventilation in Acute Respiratory Failure in Adult ICUs

A. ACUTE HYPERCAPNIC RESPIRATORY FAILURE A1. Acute Exacerbation of COPD: Recommendations: NIV should be used in management of acute exacerbation of COPD in patients with acute or acute-on-chronic respiratory acidosis (pH = 7.25-7.35). (1A) NIV should be attempted in patients with acute exacerbation of COPD (pH <7.25 & PaCO2 ≥ 45) before initiating invasive mechanical ventilation (IMV) except in patients requiring immediate intubation. (2A). Lower the pH higher the chance of failure of NIV. (2B) NIV should not to be used routinely in normo- or mildly hyper-capneic patients with acute exacerbation of COPD, without acidosis (pH > 7.35). (2B) A2. NIV in ARF due to Chest wall deformities/Neuromuscular diseases: Recommendations: NIV may be used in patients of ARF due to chest wall deformity/Neuromuscular diseases. (PaCO2 ≥ 45) (UPP) A3. NIV in ARF due to Obesity hypoventilation syndrome (OHS): Recommendations: NIV may be used in AHRF in OHS patients when they present with acute hypercapnic or acute on chronic respiratory failure (pH 45). (3B) NIV/CPAP may be used in obese, hypercapnic patients with OHS and/or right heart failure in the absence of acidosis. (UPP) B.

NIV IN ACUTE HYPOXEMIC RESPIRATORY FAILURE

B1. NIV in Acute Cardiogenic Pulmonary Oedema: Recommendations: NIV is recommended in hospital patients with ARF, due to Cardiogenic pulmonary edema. (1A). NIV should be used in patients with acute heart failure/ cardiogenic pulmonary edema, right from emergency department itself. (1B) Both CPAP and BiPAP modes are safe and effective in patients with cardiogenic pulmonary edema. (1A). However, BPAP (NIV-PS) should be preferred in cardiogenic pulmonary edema with hypercapnia. (3A) B2. NIV in acute hypoxemic respiratory failure: Recommendations: NIV may be used over conventional oxygen therapy in mild early acute hypoxemic respiratory failure (P/F ratio <300 and >200 mmHg), under close supervision. (2B) We strongly recommend against a trial of NIV in patients with acute hypoxemic failure with P/F ratio <150. (2A) B3. NIV in ARF due to Chest Trauma: Recommendations: NIV may be used in traumatic flail chest along with adequate pain relief. (3B) B4. NIV in Immunocompromised Host: Recommendations: In Immunocompromised patients with early ARF, we may consider NIV over conventional oxygen. (2B). B5. NIV in Palliative Care: Recommendations: We strongly recommend use of NIV for reducing dyspnea in palliative care setting. (2A) B6. NIV in post-operative cases: Recommendations: NIV should be used in patients with post-operative acute respiratory failure. (2A) B6a. NIV in abdominal surgery: Recommendations: NIV may be used in patients with ARF following abdominal surgeries. (2A) B6b. NIV in bariatric surgery: Recommendations: NIV may be used in post-bariatric surgery patients with pre-existent OSA or OHS. (3A) B6c. NIV in Thoracic surgery: Recommendations: In cardiothoracic surgeries, use of NIV is recommended post operatively for acute respiratory failure to improve oxygenation and reduce chance of reintubation. (2A) NIV should not be used in patients undergoing esophageal surgery. (UPP) B6d. NIV in post lung transplant: Recommendations: NIV may be used for shortening weaning time and to avoid re-intubation following lung transplantation. (2B) B7. NIV during Procedures (ETI/Bronchoscopy/TEE/Endoscopy): Recommendations: NIV may be used for pre-oxygenation before intubation. (2B) NIV with appropriate interface may be used in patients of ARF during Bronchoscopy/Endoscopy to improve oxygenation. (3B) B8. NIV in Viral Pneumonitis ARDS: Recommendations: NIV cannot be considered as a treatment of choice for patients with acute respiratory failure with H1N1 pneumonia. However, it may be reasonable to use NIV in selected patients with single organ involvement, in a strictly controlled environment with close monitoring. (2B) B9. NIV and Acute exacerbation of Pulmonary Tuberculosis: Recommendations: Careful use of NIV in patients with acute Tuberculosis may be considered, with effective infection control precautions to prevent air-borne transmission. (3B) B10. NIV after planned extubation in high risk patients: Recommendation: We recommend that NIV may be used to wean high risk patients from invasive mechanical ventilation as it reduces re-intubation rate. (2B) B11. NIV for respiratory distress post extubation: Recommendations: We recommend that NIV therapy should not be used to manage respiratory distress post-extubation in high risk patients. (2B) C.

APPLICATION OF NIV

Recommendation: Choice of mode should be mainly decided by factors like disease etiology and severity, the breathing effort by the patient and the operator familiarity and experience. (UPP) We suggest using flow trigger over pressure triggering in assisted modes, as it provides better patient ventilator synchrony. Especially in COPD patients, flow triggering has been found to benefit auto PEEP. (3B) D.

MANAGEMENT OF PATIENT ON NIV

D1. Sedation: Recommendations: A non-pharmacological approach to calm the patient (Reassuring the patient, proper environment) should always be tried before administrating sedatives. (UPP) In patients on NIV, sedation may be used with extremely close monitoring and only in an ICU setting with lookout for signs of NIV failure. (UPP) E.

EQUIPMENT

Recommendations: We recommend that portable bilevel ventilators or specifically designed ICU ventilators with non-invasive mode should be used for delivering Non-invasive ventilation in critically ill patients. (UPP) Both critical care ventilators with leak compensation and bi-level ventilators have been equally effective in decreasing the WOB, RR, and PaCO2. (3B) Currently, Oronasal mask is the most preferred interface for non-invasive ventilation for acute respiratory failure. (3B) F.

WEANING

Recommendations: We recommend that weaning from NIV may be done by a standardized protocol driven approach of the unit. (2B) How to cite this article: Chawla R, Dixit SB, Zirpe KG, Chaudhry D, Khilnani GC, Mehta Y, et al. ISCCM Guidelines for the Use of Non-invasive Ventilation in Acute Respiratory Failure in Adult ICUs. Indian J Crit Care Med 2020;24(Suppl 1):S61-S81.

The use of non-invasive ventilation in an exacerbation of chronic obstructive pulmonary disease: a case study

This article aims to assist nurses and other health professionals to care for patients who have type 2 respiratory failure as a result of chronic obstructive pulmonary disease, and who require non-invasive ventilation. It outlines findings of a case study that are commonplace in the acute medical setting and aims to highlight important factors that impact on patient care and patient outcome, and to help nursing staff to implement recommended and best practices.

Combined effects of leaks, respiratory system properties and upper airway patency on the performance of home ventilators: a bench study

Background

Combined effects of leaks, mechanical property of respiratory system and upper airway (UA) patency on patient-ventilator synchrony (PVA) and the level of clinically “tolerable” leaks are not well established in home ventilators.

Methods

We comparatively assessed on a bench model, the highest leak level tolerated without inducing significant asynchrony (“critical leak”) in three home ventilators (Astral 150, Trilogy 100 and Vivo 60; noted as A150, T100 and V60 respectively) subjected to three simulated diseased respiratory conditions: chronic obstructive pulmonary disease (COPD), obesity hypoventilation (OHS) and neuromuscular disorders (NMD), with both open and closed UA. Also, total leak values in the device reports were compared to the bench-measured values.

Results

With open UA, all ventilators were able to avoid asynchrony up to a 30 L/min leak and even to 55 L/min in some cases. UA closure and respiratory diseases especially OHS influenced PVA. With closed UA, the critical leak of A150 and T100 remained higher than 55 L/min in COPD and OHS, while for V60 decreased to 41 and 33 L/min respectively. In NMD with closed UA, only T100 reached a high critical leak of 69 L/min. Besides, inspiratory trigger sensitivity change was often necessary to avoid PVA.

Conclusions

Home ventilators were able to avoid PVA in high-level leak conditions. However, asynchrony appeared in cases of abnormal mechanical properties of respiratory system or closed UA. In case of closed UA, the EPAP should be adjusted prior to the inspiratory trigger.

Trial registration

Not applicable.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0487-2) contains supplementary material, which is available to authorized users.

New setting of neurally adjusted ventilatory assist for noninvasive ventilation by facial mask: a physiologic study

Background

Noninvasive ventilation (NIV) is generally delivered using pneumatically-triggered and cycled-off pressure support (PS_P) through a mask. Neurally adjusted ventilatory assist (NAVA) is the only ventilatory mode that uses a non-pneumatic signal, i.e., diaphragm electrical activity (EAdi), to trigger and drive ventilator assistance. A specific setting to generate neurally controlled pressure support (PS_N) was recently proposed for delivering NIV by helmet. We compared PS_N with PS_P and NAVA during NIV using a facial mask, with respect to patient comfort, gas exchange, and patient-ventilator interaction and synchrony.

Methods

Three 30-minute trials of NIV were randomly delivered to 14 patients immediately after extubation to prevent post-extubation respiratory failure: (1) PS_P, with an inspiratory support ≥8 cmH₂O; (2) NAVA, adjusting the NAVA level to achieve a comparable peak EAdi (EAdi_peak) as during PS_P; and (3) PS_N, setting the NAVA level at 15 cmH₂O/μV with an upper airway pressure (Paw) limit to obtain the same overall Paw applied during PS_P. We assessed patient comfort, peak inspiratory flow (PIF), time to reach PIF (PIF_time), EAdi_peak, arterial blood gases, pressure-time product of the first 300 ms (PTP_300-index) and 500 ms (PTP_500-index) after initiation of patient effort, inspiratory trigger delay (Delay_TR-insp), and rate of asynchrony, determined as asynchrony index (AI%). The categorical variables were compared using the McNemar test, and continuous variables by the Friedman test followed by the Wilcoxon test with Bonferroni correction for multiple comparisons (p < 0.017).

Results

PS_N significantly improved patient comfort, compared to both PS_P (p = 0.001) and NAVA (p = 0.002), without differences between the two latter (p = 0.08). PIF (p = 0.109), EAdi_peak (p = 0.931) and gas exchange were similar between modes. Compared to PS_P and NAVA, PS_N reduced PIF_time (p < 0.001), and increased PTP_300-index (p = 0.004) and PTP_500-index (p = 0.001). NAVA and PS_N significantly reduced Delay_TR-insp, as opposed to PS_P (p < 0.001). During both NAVA and PS_N, AI% was <10% in all patients, while AI% was ≥10% in 7 patients (50%) with PS_P (p = 0.023 compared with both NAVA and PS_N).

Conclusions

Compared to both PS_P and NAVA, PS_N improved comfort and patient-ventilator interaction during NIV by facial mask. PS_N also improved synchrony, as opposed to PS_P only.

Trial registration

ClinicalTrials.gov, NCT03041402. Registered (retrospectively) on 2 February 2017.

Remifentanil effects on respiratory drive and timing during pressure support ventilation and neurally adjusted ventilatory assist

We assessed the effects of varying doses of remifentanil on respiratory drive and timing in patients receiving Pressure Support Ventilation (PSV) and Neurally Adjusted Ventilatory Assist (NAVA). Four incrementing remifentanil doses were randomly administered to thirteen intubated patients (0.03, 0.05, 0.08, and 0.1μg·Kg^-1·min^-1) during both PSV and NAVA. We measured the patient's (Ti/Ttot_neu) and ventilator (Ti/Ttot_mec) duty cycle, the Electrical Activity of the Diaphragm (EAdi), the inspiratory (Delay_trinsp) and expiratory (Delay_trexp) trigger delays and the Asynchrony Index (AI). Increasing doses of remifentanil did not modify EAdi, regardless the ventilatory mode. In comparison to baseline, remifentanil infusion >0.05μg/Kg^-1/min^-1 produced a significant reduction of Ti/Ttot_neu and Ti/Ttot_mec, by prolonging the expiratory time. Delay_trinsp and Delay_trexp were significantly shorter in NAVA, respect to PSV. AI was not influenced by the different doses of remifentanil, but it was significantly lower during NAVA, compared to PSV. In conclusion remifentanil did not affect the respiratory drive, but only respiratory timing, without differences between modes.

New Setting of Neurally Adjusted Ventilatory Assist during Noninvasive Ventilation through a Helmet

BACKGROUND

Compared to pneumatically controlled pressure support (PSP), neurally adjusted ventilatory assist (NAVA) was proved to improve patient-ventilator interactions, while not affecting comfort, diaphragm electrical activity (EAdi), and arterial blood gases (ABGs). This study compares neurally controlled pressure support (PSN) with PSP and NAVA, delivered through two different helmets, in hypoxemic patients receiving noninvasive ventilation for prevention of extubation failure.

METHODS

Fifteen patients underwent three (PSP, NAVA, and PSN) 30-min trials in random order with both helmets. Positive end-expiratory pressure was always set at 10 cm H2O. In PSP, the inspiratory support was set at 10 cm H2O above positive end-expiratory pressure. NAVA was adjusted to match peak EAdi (EAdipeak) during PSP. In PSN, the NAVA level was set at maximum matching the pressure delivered during PSP by limiting the upper pressure. The authors assessed patient comfort, EAdipeak, rates of pressurization (i.e., airway pressure-time product [PTP] of the first 300 and 500 ms after the initiation of patient effort, indexed to the ideal pressure-time products), and measured ABGs.

RESULTS

PSN significantly increased comfort to (median [25 to 75% interquartile range]) 8 [7 to 8] and 9 [8 to 9] with standard and new helmets, respectively, as opposed to both PSP (5 [5 to 6] and 7 [6 to 7]) and NAVA (6 [5 to 7] and 7 [6 to 8]; P < 0.01 for all comparisons). Regardless of the interface, PSN also decreased EAdipeak (P < 0.01), while increasing PTP of the first 300 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.01) and PTP of the first 500 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.001). ABGs were not different among trials.

CONCLUSIONS

When delivering noninvasive ventilation by helmet, compared to PSP and NAVA, PSN improves comfort and patient-ventilator interactions, while not ABGs. (Anesthesiology 2016; 125:1181-9).

Effectiveness of Inspiratory Termination Synchrony with Automatic Cycling During Noninvasive Pressure Support Ventilation

Background

Pressure support ventilation (PSV) is a standard method for non-invasive home ventilation. A bench study was designed to compare the effectiveness of patient-ventilator inspiratory termination synchronization with automated and conventional triggering in various respiratory mechanics models.

Material/Methods

Two ventilators, the Respironics V60 and Curative Flexo ST 30, connected to a Hans Rudolph Series 1101 lung simulator, were evaluated using settings that simulate lung mechanics in patients with chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS), or normal lungs. Ventilators were operated with automated (Auto-Trak) or conventional high-, moderate-, and low-sensitivity flow-cycling software algorithms, 5 cmH₂O or 15 cmH₂O pressure support, 5 cmH₂O positive end-expiratory pressure (PEEP), and an air leak of 25–28 L/min.

Results

Both ventilators adapted to the system leak without requiring adjustment of triggering settings. In all simulated lung conditions, automated cycling resulted in shorter triggering delay times (<100 ms) and lower triggering pressure-time product (PTPt) values. Tidal volumes (V_T) increased with lower conventional cycling sensitivity level. In the COPD model, automated cycling had higher leak volumes and shorter cycling delay times than in conventional cycling. Asynchronous events were rare. Inspiratory time (Tinsp), peak expiratory flow (PEF), and cycling off delay time (Cdelay) increased as a result of reduction in conventional cycling sensitivity level. In the ARDS and normal adult lung models, premature cycling was frequent at the high-sensitive cycling level.

Conclusions

Overall, the Auto-Trak protocol showed better patient-machine cycling synchronization than conventional triggering. This was evident by shorter triggering time delays and lower PTPt.

New versus Conventional Helmet for Delivering Noninvasive Ventilation: A Physiologic, Crossover Randomized Study in Critically Ill Patients

BACKGROUND

The helmet is a well-tolerated interface for noninvasive ventilation, although it is associated with poor patient-ventilator interaction. A new helmet (NH) has proven to attenuate this limitation of the standard helmet (SH) in both bench study and healthy volunteers. The authors compared a NH and a SH in intensive care unit patients receiving noninvasive ventilation for prevention of postextubation respiratory failure; both helmets were also compared with the endotracheal tube in place before extubation.

METHODS

Fourteen patients underwent 30-min trials in pressure support during invasive ventilation and then with a SH and a NH in a random order. The authors measured comfort, triggering delays, rates of pressurization (airway pressure-time product [PTP] of the first 300 [PTP(300-index)] and 500 [PTP(500-index)] ms from the onset of effort, and the first 200 ms from the onset of insufflation [PTP200]), time of synchrony between effort and assistance (Time(synch)/Ti(neu)), respiratory drive and frequency, arterial blood gases (ABGs), and rate of asynchrony.

RESULTS

Compared with SH, NH improved comfort (5.5 [5.0 to 6.0] vs. 8.0 [7.8 to 8.0]), respectively, P < 0.001), inspiratory trigger delay (0.31 [0.22 to 0.43] vs. 0.25 [0.18 to 0.31] s, P = 0.007), and pressurization (PTP(300-index): 0.8 [0.1 to 1.8] vs. 2.7 [7.1 to 10.0]%; PTP(500-index): 4.8 [2.5 to 9.9] vs. 27.3 [16.2 to 34.8]%; PTP200: 13.6 [10.1 to 19.6] vs. 30.4 [24.9 to 38.4] cm H2O/s, P < 0.01 for all comparisons) and Time(synch)/Ti(neu) (0.64 [0.48 to 0.72] vs. 0.71 [0.61 to 0.81], P = 0.007). Respiratory drive and frequency, ABGs, and rate of asynchrony were not different between helmets. Endotracheal tube outperformed both helmets with respect to all variables, except for respiratory rate, ABGs, and asynchronies.

CONCLUSIONS

Compared with a SH, a NH improved comfort and patient-ventilator interaction.

Technology for noninvasive mechanical ventilation: looking into the black box

Current devices for providing noninvasive respiratory support contain sensors and built-in intelligence for automatically modifying ventilation according to the patient's needs. These devices, including automatic continuous positive airway pressure devices and noninvasive ventilators, are technologically complex and offer a considerable number of different modes of ventilation and setting options, the details of which are sometimes difficult to capture by the user. Therefore, better predicting and interpreting the actual performance of these ventilation devices in clinical application requires understanding their functioning principles and assessing their performance under well controlled bench test conditions with simulated patients. This concise review presents an updated perspective of the theoretical basis of intelligent continuous positive airway pressure and noninvasive ventilation devices, and of the tools available for assessing how these devices respond under specific ventilation phenotypes in patients requiring breathing support.

Current devices for intelligent noninvasive ventilation should be tested to better understand clinical performance http://ow.ly/XAS6Z

Brazilian recommendations of mechanical ventilation 2013. Part I

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumonia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Brazilian recommendations of mechanical ventilation 2013. Part I

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Effect of dynamic random leaks on the monitoring accuracy of home mechanical ventilators: a bench study

BACKGROUND

So far, the accuracy of tidal volume (VT) and leak measures provided by the built-in software of commercial home ventilators has only been tested using bench linear models with fixed calibrated and continuous leaks. The objective was to assess the reliability of the estimation of tidal volume (VT) and unintentional leaks in a single tubing bench model which introduces random dynamic leaks during inspiratory or expiratory phases.

METHODS

The built-in software of four commercial home ventilators and a fifth ventilator-independent ad hoc designed external software tool were tested with two levels of leaks and two different models with excess leaks (inspiration or expiration). The external software analyzed separately the inspiratory and expiratory unintentional leaks.

RESULTS

In basal condition, all ventilators but one underestimated tidal volume with values ranging between -1.5 ± 3.3% to -8.7% ± 3.27%. In the model with excess of inspiratory leaks, VT was overestimated by all four commercial software tools, with values ranging from 18.27 ± 7.05% to 35.92 ± 17.7%, whereas the ventilator independent-software gave a smaller difference (3.03 ± 2.6%). Leaks were underestimated by two applications with values of -11.47 ± 6.32 and -5.9 ± 0.52 L/min. With expiratory leaks, VT was overestimated by the software of one ventilator and the ventilator-independent software and significantly underestimated by the other three, with deviations ranging from +10.94 ± 7.1 to -48 ± 23.08%. The four commercial tools tested overestimated unintentional leaks, with values between 2.19 ± 0.85 to 3.08 ± 0.43 L/min.

CONCLUSIONS

In a bench model, the presence of unintentional random leaks may be a source of error in the measurement of VT and leaks provided by the software of home ventilators. Analyzing leaks during inspiration and expiration separately may reduce this source of error.

Noninvasive ventilation: practical advice

PURPOSE OF REVIEW

This critical review discusses the key points that would be of practical help for the clinician who applies noninvasive ventilation (NIV) for treatment of patients with acute respiratory failure (ARF).

RECENT FINDINGS

In recent years, the growing role of NIV in the acute care setting has led to the development of technical innovations to overcome the problems related to gas leakage and dead space. A considerable amount of research has been conducted to improve the quality of the devices as well as optimize ventilation modes used to administer NIV. As a result, also mechanical ventilators have been implemented with modalities aimed at delivering NIV.

SUMMARY

The success of NIV in patients with ARF depends on several factors, including the skills of the clinician, selection of patient, choice of interface, selection of ventilation mode and ventilator setting, monitoring, and the motivation of the patient. Recent advances in the understanding of the physiological aspects of using NIV through different interfaces and ventilator settings have led to improve patient-machine interaction, enhancing favorable NIV outcome.

Bench comparative evaluation of a new generation and standard helmet for delivering non-invasive ventilation

OBJECTIVE

To evaluate the performance of a new helmet (NH) recently introduced into clinical use relative to that of the standard helmet (SH) in terms of delivering non-invasive continuous positive airway pressure (nCPAP) and pressure support ventilation (nPSV).

DESIGN

This was a bench study using a mannequin connected to an active lung simulator. The SH was fastened to the mannequin by armpit braces, which are not needed to secure the NH.

MEASUREMENTS

The inspiratory and expiratory variations in nCPAP delivered with two different simulated efforts (Pmus), were determined relative to the preset CPAP level. nPSV was applied at two simulated respiratory rates (RR) and two cycling-off flow thresholds. We measured inspiratory trigger delay (Delay trinsp), expiratory trigger delay (Delay trexp), time of synchrony (Time sync), trigger pressure drop (ΔP trigger), airway pressure-time product during the triggering phase (PTPt), the initial 200 ms from the onset of the ventilator pressurization (PTP 200), and the initial 300 and 500 ms from the onset of the simulated effort; this two latter parameters were expressed as the percentage of the area of ideal pressurization (PTP 300-index and PTP 500-index, respectively).

RESULTS

In nCPAP, at both Pmus, the differences between the two interfaces at both Pmus were small and clinically irrelevant. In nPSV, regardless of the setting, NH resulted in significantly smaller trigger delays, ΔP trigger, and PTPt. Time sync, PTP 200, PTP 300-index, and PTP 500-index were also significantly higher with the NH compared to the SH, irrespective of the setting.

CONCLUSIONS

Compared to the SH, the NH is equally effective in delivering nCPAP and more effective in delivering nPSV, and it is used to avoid the need for armpit braces.