Intentional leaks in industrial masks have a significant impact on efficacy of bilevel noninvasive ventilation: a bench test study

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.

A New Full-Face Mask for Multifunctional Non-Invasive Ventilation

Background: Noninvasive ventilation (NIV) provides positive pressure through different interfaces. A multifunctional full-face mask prototype was developed to provide NIV from three sources: ICU ventilators, portable ventilators, and high-flow medical gas pipeline systems. This study aimed to evaluate the usability of this prototype mask. Methods: This was a quantitative experimental study, conducted in two phases: the development of a full-face mask prototype NIV interface, and the evaluation of its usability by health professionals (evaluators) using a heuristic approach. The Wolf Mask prototype is a multifunctional full-face mask that makes it possible to deliver positive pressure from three different sources: microprocessor-controlled ICU ventilators, portable ventilators with single-limb circuits, and high-flow medical gas. The evaluation was conducted in three stages: presentation of the prototype to the evaluators; skills testing via simulation in a clinical environment; and a review of skills. Results: The prototype was developed by a multidisciplinary team and patented in Brazil. The evaluators were 10 health professionals specializing in NIV. Seven skills related to handling the prototype were evaluated. Three of the ten evaluators called for (non-urgent) changes to improve recognition of the components of the prototype. Only one evaluator called for (non-urgent) changes to improve recognition of the pieces, assembly, and checking the mask. Conclusions: The newly developed multifunctional full-face mask prototype demonstrated excellent usability for providing noninvasive ventilation from multiple sources. Minor modifications may further improve the design.

Monitoring the patient-ventilator asynchrony during non-invasive ventilation

Patient-ventilator asynchrony is a major issue during non-invasive ventilation and may lead to discomfort and treatment failure. Therefore, the identification and prompt management of asynchronies are of paramount importance during non-invasive ventilation (NIV), in both pediatric and adult populations. In this review, we first define the different forms of asynchronies, their classification, and the method of quantification. We, therefore, describe the technique to properly detect patient-ventilator asynchronies during NIV in pediatric and adult patients with acute respiratory failure, separately. Then, we describe the actions that can be implemented in an attempt to reduce the occurrence of asynchronies, including the use of non-conventional modes of ventilation. In the end, we analyzed what the literature reports on the impact of asynchronies on the clinical outcomes of infants, children, and adults.

Monitoring Long Term Noninvasive Ventilation: Benefits, Caveats and Perspectives

Long term noninvasive ventilation (LTNIV) is a recognized treatment for chronic hypercapnic respiratory failure (CHRF). COPD, obesity-hypoventilation syndrome, neuromuscular disorders, various restrictive disorders, and patients with sleep-disordered breathing are the major groups concerned. The purpose of this narrative review is to summarize current knowledge in the field of monitoring during home ventilation. LTNIV improves symptoms related to CHRF, diurnal and nocturnal blood gases, survival, and health-related quality of life. Initially, patients with LTNIV were most often followed through elective short in-hospital stays to ensure patient comfort, correction of daytime blood gases and nocturnal oxygenation, and control of nocturnal respiratory events. Because of the widespread use of LTNIV, elective in-hospital monitoring has become logistically problematic, time consuming, and costly. LTNIV devices presently have a built-in software which records compliance, leaks, tidal volume, minute ventilation, cycles triggered and cycled by the patient and provides detailed pressure and flow curves. Although the engineering behind this information is remarkable, the quality and reliability of certain signals may vary. Interpretation of the curves provided requires a certain level of training. Coupling ventilator software with nocturnal pulse oximetry or transcutaneous capnography performed at the patient's home can however provide important information and allow adjustments of ventilator settings thus potentially avoiding hospital admissions. Strategies have been described to combine different tools for optimal detection of an inefficient ventilation. Recent devices also allow adapting certain parameters at a distance (pressure support, expiratory positive airway pressure, back-up respiratory rate), thus allowing progressive changes in these settings for increased patient comfort and tolerance, and reducing the requirement for in-hospital titration. Because we live in a connected world, analyzing large groups of patients through treatment of “big data” will probably improve our knowledge of clinical pathways of our patients, and factors associated with treatment success or failure, adherence and efficacy. This approach provides a useful add-on to randomized controlled studies and allows generating hypotheses for better management of HMV.

Physiological effects of high-intensity versus low-intensity noninvasive positive pressure ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease: a randomised controlled trial

Background

High-intensity noninvasive positive pressure ventilation (NPPV) is a novel ventilatory approach to maximally decreasing elevated arterial carbon dioxide tension (PaCO₂) toward normocapnia with stepwise up-titration of pressure support. We tested whether high-intensity NPPV is more effective than low-intensity NPPV at decreasing PaCO₂, reducing inspiratory effort, alleviating dyspnoea, improving consciousness, and improving NPPV tolerance in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Methods

In this physiological, randomised controlled trial, we assigned 24 AECOPD patients to undergo either high-intensity NPPV (n = 12) or low-intensity NPPV (n = 12). The primary outcome was PaCO₂ 24 h after randomisation. Secondary outcomes included gas exchange other than PaCO₂ 24 h after randomisation, inspiratory effort, dyspnoea, consciousness, NPPV tolerance, patient–ventilator asynchrony, cardiac function, ventilator-induced lung injury (VILI), and NPPV-related adverse events.

Results

Inspiratory positive airway pressure 24 h after randomisation was significantly higher (28.0 [26.0–28.0] vs. 15.5 [15.0–17.5] cmH₂O; p = 0.000) and NPPV duration within the first 24 h was significantly longer (21.8 ± 2.1 vs. 15.3 ± 4.7 h; p = 0.001) in the high-intensity NPPV group. PaCO₂ 24 h after randomisation decreased to 54.0 ± 11.6 mmHg in the high-intensity NPPV group but only decreased to 67.4 ± 10.6 mmHg in the low-intensity NPPV group (p = 0.008). Inspiratory oesophageal pressure swing, oesophageal pressure–time product (PTPes)/breath, PTPes/min, and PTPes/L were significantly lower in the high-intensity group. Accessory muscle use and dyspnoea score 24 h after randomisation were also significantly lower in that group. No significant between-groups differences were observed in consciousness, NPPV tolerance, patient–ventilator asynchrony, cardiac function, VILI, or NPPV-related adverse events.

Conclusions

High-intensity NPPV is more effective than low-intensity NPPV at decreasing elevated PaCO₂, reducing inspiratory effort, and alleviating dyspnoea in AECOPD patients.

Trial registration: ClinicalTrials.gov (NCT04044625; registered 5 August 2019).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01018-4.

Quality versus emergency: How good were ventilation fittings produced by additive manufacturing to address shortages during the COVID19 pandemic?

OBJECTIVE

The coronavirus disease pandemic (COVID-19) increased the risk of shortage in intensive care devices, including fittings with intentional leaks. 3D-printing has been used worldwide to produce missing devices. Here we provide key elements towards better quality control of 3D-printed ventilation fittings in a context of sanitary crisis.

MATERIAL AND METHODS

Five 3D-printed designs were assessed for non-intentional (junctional and parietal) and intentional leaks: 4 fittings 3D-printed in-house using FDeposition Modelling (FDM), 1 FDM 3D-printed fitting provided by an independent maker, and 2 fittings 3D-printed in-house using Polyjet technology. Five industrial models were included as controls. Two values of wall thickness and the use of coating were tested for in-house FDM-printed devices.

RESULTS

Industrial and Polyjet-printed fittings had no parietal and junctional leaks, and satisfactory intentional leaks. In-house FDM-printed fittings had constant parietal leaks without coating, but this post-treatment method was efficient in controlling parietal sealing, even in devices with thinner walls (0.7 mm vs 2.3 mm). Nevertheless, the use of coating systematically induced absent or insufficient intentional leaks. Junctional leaks were constant with FDM-printed fittings but could be controlled using rubber junctions rather than usual rigid junctions. The properties of Polyjet-printed and FDM-printed fittings were stable over a period of 18 months.

CONCLUSIONS

3D-printing is a valid technology to produce ventilation devices but requires care in the choice of printing methods, raw materials, and post-treatment procedures. Even in a context of sanitary crisis, devices produced outside hospitals should be used only after professional quality control, with precise data available on printing protocols. The mechanical properties of ventilation devices are crucial for efficient ventilation, avoiding rebreathing of CO2, and preventing the dispersion of viral particles that can contaminate health professionals. Specific norms are still required to formalise quality control procedures for ventilation fittings, with the rise of 3D-printing initiatives and the perspective of new pandemics.

Telemonitoring for the Follow-Up of Obstructive Sleep Apnea Patients Treated with CPAP: Accuracy and Impact on Therapy

Continuous positive airway pressure (CPAP) telemonitoring (TMg) has become widely implemented in routine clinical care. Objective measures of CPAP compliance, residual respiratory events, and leaks can be easily monitored, but limitations exist. This review aims to assess the role of TMg in CPAP-treated obstructive sleep apnea (OSA) patients. We report recent data related to the accuracy of parameters measured by CPAP and try to determine the role of TMg in CPAP treatment follow-up, from the perspective of both healthcare professionals and patients. Measurement and accuracy of CPAP-recorded data, clinical management of these data, and impacts of TMg on therapy are reviewed in light of the current literature. Moreover, the crucial questions of who and how to monitor are discussed. TMg is a useful tool to support, fine-tune, adapt, and control both CPAP efficacy and compliance in newly-diagnosed OSA patients. However, clinicians should be aware of the limits of the accuracy of CPAP devices to measure residual respiratory events and leaks and issues such as privacy and cost-effectiveness are still a matter of concern. The best methods to focus our efforts on the patients who need TMg support should be properly defined in future long-term studies.

Telemonitoring for Home Assisted Ventilation: A Narrative Review

The recent advent of remote ventilator telemonitoring has the potential to revolutionize home-assisted ventilation care in the United States and elsewhere. Home ventilation machines (i.e., respiratory assist devices and portable ventilators) can now wirelessly transmit usage and performance data to cloud-based web servers for remote access by participating clinicians. In this Focused Review, we provide an update on available technology, suggest practical applications for clinical care and research, and review supporting literature. Remote monitoring permits early data review, refinement of device settings to optimize ventilatory function, and troubleshooting if a new problem arises after initial setup. Data from home spirometry and noninvasively measured blood gas tensions can complement ventilator data to reflect physiological response. Acknowledging a paucity of published outcome studies, remote telemonitoring may be a cost-effective strategy to reduce emergency room visits, urgent clinic appointments, and hospitalizations. Ongoing clinical trials in Europe aim to expand on the benefit of this rapidly evolving technology. However, several barriers may hinder widespread implementation, especially in the United States. Clinicians must familiarize themselves with each ventilator manufacturer’s proprietary software to safely leverage this technology for improving care. Legal and ethical considerations threaten clinician interest. Medical insurance payers must adapt a reimbursement scheme to incentivize clinicians and durable medical equipment companies to perform this time-consuming service. Cohort-level ventilator data will facilitate multicenter clinical trials focused on improving the respiratory care of this vulnerable population.

Short-term usage of three non-invasive ventilation interfaces causes progressive discomfort in healthy adults

Purpose

To evaluate the effect of three different non-invasive ventilation (NIV) interfaces on the subjective discomfort of healthy individuals, and on a set of physiological parameters hypothesized to change in correspondence to discomfort.

Methods

Continuous pressure NIV was applied to 20 subjects using Total Face, Nasal, and Face masks for 10 min each. Tidal volume (VT) and respiratory period (RP) were estimated from respiratory inductance plethysmography. Electrodermal activity was estimated from conductance signals. Heart rate variability was measured using the time-domain indices SDNN and RMSSD, and the respiratory sinus arrhythmia amplitude (RSAp). Parameters were referenced to 5-min rest periods at beginning and end of protocol. A Likert-like scale of subjective discomfort with the masks and the ventilation was applied after 1, 5, and 9 min using each mask.

Results

RP and VT increased with the three mask models. Whereas the mean heart rate and RSAp did not change, both SDNN and RMSSD increased during NIV with Nasal and Face masks. Spontaneous electrodermal activity fluctuations were less frequent during NIV than at rest, with significant differences for Total Face and Nasal masks. Discomfort with all masks increased from minutes 1 to 9, markedly in the Total Face mask, considered most uncomfortable by 11 subjects.

Conclusion

In healthy subjects, the three masks resulted in similar respiratory responses to NIV. Correspondence between changes in physiological parameters and discomfort with NIV interface could not be detected, whereas self-report with the Likert-like scale identified progressive discomfort and the Total Face mask as the most uncomfortable interface.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42600-020-00114-3.

Home mechanical ventilation: back to basics

Over recent decades, the use of home mechanical ventilation (HMV) has steadily increased worldwide, with varying prevalence in different countries. The key indication for HMV is chronic respiratory failure with alveolar hypoventilation (e.g., neuromuscular and chest wall disease, obstructive airway diseases, and obesity-related respiratory failure). Most modern home ventilators are pressure-targeted and have sophisticated modes, alarms, and graphics, thereby facilitating optimization of the ventilator settings. However, different ventilators have different algorithms for tidal volume estimation and leak compensation, and there are also several different circuit configurations. Hence, a basic understanding of the fundamentals of HMV is of paramount importance to healthcare workers taking care of patients with HMV. When choosing a home ventilator, they should take into account many factors, including the current condition and prognosis of the primary disease, the patient’s daily performance status, time (hr/day) needed for ventilator support, family support, and financial costs. In this review, to help readers understand the basic concepts of HMV use, we describe the indications for HMV and the factors that influence successful delivery, including interface, circuits, ventilator accessories, and the ventilator itself.

NIV Is not Adequate for High Intensity Endurance Exercise in COPD

Noninvasive ventilation (NIV) during exercise has been suggested to sustain higher training intensity but the type of NIV interface, patient-ventilator asynchronies (PVA) or technological limitation of the ventilator may interfere with exercise. We assessed whether these parameters affect endurance exercise capacity in severe COPD patients. In total, 21 patients with severe COPD not eligible to home NIV performed three constant workload tests. The first test was carried out on spontaneous breathing (SB) and the following ones with NIV and a nasal or oronasal mask in a randomized order. PVA and indicators of ventilator performance were assessed through a comprehensive analysis of the flow pressure tracing raw data from the ventilator. The time limit was significantly reduced with both masks (406 s (197–666), 240 s (131–385) and 189 s (115–545), p < 0.01 for tests in SB, with oronasal and nasal mask, respectively). There were few PVA with an oronasal mask (median: 3.4% (1.7–5.2)) but the ventilator reached its maximal generating capacity (median flowmax: 208.0 L/s (189.5–224.8) while inspiratory pressure dropped throughout exercise (from 10.1 (9.4–11.4) to 8.8 cmH2O (8.6–10.8), p < 0.01). PVA were more frequent with nasal mask (median: 12.8% (3.2–31.6), p < 0.01). Particularly, the proportion of patients with ineffective efforts > 10% was significantly higher with nasal interface (0% versus 33.3%, p < 0.01). NIV did not effectively improve endurance capacity in COPD patients not acclimated to home NIV. This was due to a technological limitation of the ventilator for the oronasal mask and the consequence either of an insufficient pressure support or a technological limitation for the nasal mask.

Basic Concepts for Tidal Volume and Leakage Estimation in Non-Invasive Ventilation

Non-invasive ventilation (NIV) aims to maintain sufficient alveolar ventilation, improve pulmonary gas exchange, assist respiratory muscles, and decrease work of breathing. Monitoring variables such as leaks, tidal volume, and minute ventilation during therapy is crucial to assess the effectiveness of NIV. However, most of the time, leaks and tidal volume are not measured but estimated by NIV devices. Moreover, there are limited data for the accuracy and reliability of these estimations. Herein, we address some technical considerations for tidal volume and leakage estimation during NIV and its impact in clinical practice.

Home noninvasive positive pressure ventilation with built-in software in stable hypercapnic COPD: a short-term prospective, multicenter, randomized, controlled trial

Background

The benefits of noninvasive positive pressure ventilation (NPPV) in patients with hypercapnic COPD are controversial. It is presumed that methodology and appropriate use of NIV ventilator might be crucial for the outcomes. With the new built-in software, the performance of NIV can be monitored at home, which can guarantee the compliance and appropriate use. This study investigated effects of home use of NIV in hypercapnia in COPD patients using the NIV ventilator with built-in software for monitoring.

Methods

The current multicenter prospective, randomized, controlled trial enrolled patients with stable GOLD stages III and IV hypercapnic COPD. Patients were randomly assigned via a computer-generated randomization sequence, with a block size of four patients, to continue optimized treatment (control group) or to receive additional NPPV (intervention group) for 3 months. The primary outcome was arterial carbon dioxide pressure (PaCO₂). Data were derived from built-in software and analyzed every 4 weeks. Analysis was carried out with the intention to treat. This study is registered with ClinicalTrials.gov, number NCT02499718.

Results

Patients were recruited from 20 respiratory units in China from October 1, 2015, and recruitment was terminated with a record of the vital statistics on May 31, 2016. A total of 115 patients were randomly assigned to the NPPV group (n=57) or the control group (n=58). Patients complied well with NPPV therapy (mean [± standard deviation] day use 5.6±1.4 h). The mean estimation of leaks was 37.99±13.71 L/min. The changes in PaCO₂ (−10.41±0.97 vs −4.32±0.68 mmHg, P=0.03) and 6-min walk distance (6MWD) (38.2% vs 18.2%, P=0.02) were statistically significant in the NPPV group versus the control group. COPD assessment test (CAT) showed a positive trend (P=0.06) in favor of the NPPV group. Pulmonary function and dyspnea were not different between groups.

Conclusion

Ventilators equipped with built-in software provided methodology for monitoring NIV use at home, which could facilitate the improvement of compliance and quality control of NIV use. It was shown that three months use of NIV at home could reduce the PaCO₂ and improve exercise tolerance (6MWD) in chronic hypercapnic COPD patients.

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

Multifaceted bench comparative evaluation of latest intensive care unit ventilators

BACKGROUND

Independent bench studies using specific ventilation scenarios allow testing of the performance of ventilators in conditions similar to clinical settings. The aims of this study were to determine the accuracy of the latest generation ventilators to deliver chosen parameters in various typical conditions and to provide clinicians with a comprehensive report on their performance.

METHODS

Thirteen modern intensive care unit ventilators were evaluated on the ASL5000 test lung with and without leakage for: (i) accuracy to deliver exact tidal volume (VT) and PEEP in assist-control ventilation (ACV); (ii) performance of trigger and pressurization in pressure support ventilation (PSV); and (iii) quality of non-invasive ventilation algorithms.

RESULTS

In ACV, only six ventilators delivered an accurate VT and nine an accurate PEEP. Eleven devices failed to compensate VT and four the PEEP in leakage conditions. Inspiratory delays differed significantly among ventilators in invasive PSV (range 75-149 ms, P=0.03) and non-invasive PSV (range 78-165 ms, P<0.001). The percentage of the ideal curve (concomitantly evaluating the pressurization speed and the levels of pressure reached) also differed significantly (range 57-86% for invasive PSV, P=0.04; and 60-90% for non-invasive PSV, P<0.001). Non-invasive ventilation algorithms efficiently prevented the decrease in pressurization capacities and PEEP levels induced by leaks in, respectively, 10 and 12 out of the 13 ventilators.

CONCLUSIONS

We observed real heterogeneity of performance amongst the latest generation of intensive care unit ventilators. Although non-invasive ventilation algorithms appear to maintain adequate pressurization efficiently in the case of leakage, basic functions, such as delivered VT in ACV and pressurization in PSV, are often less reliable than the values displayed by the device suggest.

[Ventilator modes and settings during non-invasive ventilation: effects on respiratory events and implications for their identification. 2011]

Compared with invasive ventilation, non-invasive ventilation (NIV) has two unique characteristics: its non-hermetic nature and the fact that the ventilator-lung assembly cannot be considered as a single-compartment model because of the presence of variable resistance represented by the upper airways. When NIV is initiated, the ventilator settings are determined empirically based on clinical evaluation and blood gas variations. However, NIV is predominantly applied during sleep. Consequently, to assess overnight patient-machine "agreement" and efficacy of ventilation, more specific and sophisticated monitoring is needed. The effectiveness of NIV might therefore be more correctly assessed by sleep studies than by daytime assessment. The simplest monitoring can be done from flow and pressure curves from the mask or the ventilator circuit. Examination of these tracings can give useful information to evaluate if the settings chosen by the operator were the right ones for that patient. However, as NIV allows a large range of ventilatory parameters and settings, it is mandatory to have information about this to better understand patient-ventilator interaction. Ventilatory modality, mode of triggering, pressurization slope, use or not of positive end expiratory pressure and type of exhalation as well as ventilator performances may all have physiological consequences. Leaks and upper airway resistance variations may, in turn, modify these patterns. This article discusses the equipment available for NIV, analyses the effect of different ventilator modes and settings and of exhalation and connecting circuits on ventilatory traces and gives the background necessary to understand their impact on nocturnal monitoring of NIV.

Home mechanical ventilation through mask: monitoring leakage and nocturnal oxygenation at home

BACKGROUND

Leakage is common in patients receiving home mechanical ventilation (HMV) via a face mask. Although pressure ventilators have partial compensatory capacity, excessive leakage can compromise the effectiveness of treatment. Home ventilators are equipped with built-in software which provides information on leakage. However, the values of leakage and their effects in routine clinical practice are currently little known.

OBJECTIVE

To measure leakage in stable patients on nocturnal HMV and its impact on treatment effectiveness.

METHODS

Consecutive outpatients on HMV were recruited. Nocturnal pulse oximetry was performed at home and leakage was measured using the ventilator's built-in software. We measured: mean SpO(2), percentage of time with SpO(2) <90% (T90), mean leakage (meanL), maximum leakage (maxL), and minimum leakage (minL) during the ventilation session. We estimated ventilator capacity to compensate for leakage according to inspiratory positive airway pressure and divided the patients into two groups: those with leak compensation and those without.

RESULTS

The study included 41 patients [mean age, 64 years (SD 11.9); 23 (56%) women]. Nocturnal pulse oximetry showed an SpO(2) of 94% (±2.9) and a T90 of 10% (±21.7). Leakage (in l/min) was: meanL, 32.2 (±15.3); maxL, 64.8 (±28.5), and minL, 18.8 (±10.6). Seven cases (17%) had leakage greater than the ventilator compensatory capacity, but no significant difference in SpO(2) or T90 was observed between patients with or without leak compensation.

CONCLUSIONS

A wide variation between maxL and minL was observed in our series; 17% of cases had higher leakage values than the compensatory capacity of the ventilator, but this did not affect nocturnal oxygenation.

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

PURPOSE

Because non-invasive mechanical ventilation (NIV) is increasingly used, new devices, both ventilators and interfaces, have been continuously proposed for clinical use in recent years. To provide the clinicians with valuable information about ventilators and interfaces for NIV, several bench studies evaluating and comparing the performance of NIV devices have been concomitantly published, which may influence the choice in equipment acquisition. As these comparisons, however, may be problematic and sometimes lacking in consistency, in the present article we review and discuss those technical aspects that may explain discrepancies.

METHODS

Studies concerning bench evaluations of devices for NIV were reviewed, focusing on some specific technical aspects: lung models and simulation of inspiratory demand and effort, mechanical properties of the virtual respiratory system, generation and quantification of air leaks, ventilator modes and settings, assessment of the interface-ventilator unit performance.

RESULTS

The impact of the use of different test lung models is not clear and warrants elucidation; standard references for simulated demand and effort, mode of generation and extent of air leaks, resistance and compliance of the virtual respiratory system, and ventilator settings are lacking; the criteria for assessment of inspiratory trigger function, inspiration-to-expiration (I:E) cycling, and pressurization rate vary among studies; finally, the terminology utilized is inconsistent, which may also lead to confusion.

CONCLUSIONS

Consistent experimental settings, uniform terminology, and standard measurement criteria are deemed to be useful to enhance bench assessment of characteristics and comparison of performance of ventilators and interfaces for NIV.

Value of gas exchange recording at home in children receiving non-invasive ventilation

Non-invasive positive pressure ventilation (NPPV) is preferentially performed at home. The objectives of the study were to evaluate the feasibility of an overnight gas exchange recording at home and to compare recordings performed in the hospital and at home. Twenty-nine pairs of overnight gas exchange recordings during NPPV were performed at home and in the hospital in 11 children with neuromuscular disease and 13 children with other disorders treated with long-term NPPV. No technical problem occurred during the recordings performed at home and one pulse oximetry (SpO(2)) recording failed in the hospital. For the two groups, SpO(2) and transcutaneous carbon dioxide (PtcCO(2)) values did not differ significantly between the hospital and the home. However, correlations between SpO(2) and PtcCO(2) values obtained in the hospital and at home were better for mean values than for minimal and maximal values, and in patients with other disorders as compared to patients with neuromuscular disease. Overnight gas exchange recordings with NPPV by a combined PtcCO(2) /SpO(2) monitor are feasible at home and show results comparable to hospital recordings. Home PtcCO(2) /SpO(2) recordings may be integrated in the care of children treated with domiciliary NPPV and are associated with less disruption of family life and decreased health care costs.

Monitoring Patient/Ventilator Interactions: Manufacturer's Perspective

The introduction of reduced and more powerful electronics has allowed the transition of medical equipment such as respiratory support devices from the hospital to the patient’s home environment. Even if this move could be beneficial for the patient, the clinician ends up in a delicate situation where little or no direct supervision is possible on the delivered treatment.

Progress in technologies led to an improved handling of patient-device interaction: manufacturers are promoting new or improved ventilation modes or cycling techniques for better patient-ventilator coupling. Even though these ventilation modes have become more responsive to patient efforts, adversely they might lead to events such as false triggering, autotriggering, delayed triggering.

In addition, manufacturers are developing tools to enhance the follow-up, remotely or offline, of the treatment by using embedded memory in the respiratory devices. This logging might be beneficial for the caregiver to review and document the treatment and tune the settings to the patient’s need and comfort. Also, remote telemedicine has been raised as a potential solution for many years without yet overall acceptance due to legal, technical and ethical problems.

Benefits of new technologies in respiratory support devices give the technical foundation for the transition from hospital to home and reducing patient/ventilator asynchronies. Healthcare infrastructure has to follow this trend in terms of cost savings versus hospital stays.