Neurally adjusted ventilatory assist improves patient-ventilator interaction during postextubation prophylactic noninvasive ventilation

Clinical review of non-invasive ventilation

Non-invasive ventilation (NIV) is the mainstay to treat patients who need augmentation of ventilation for acute and chronic forms of respiratory failure. The last several decades have witnessed an extension of the indications for NIV to a variety of acute and chronic lung diseases. Evolving advancements in technology and personalised approaches to patient care make it feasible to prioritise patient-centred care models that deliver home-based management using telemonitoring and telemedicine systems support. These trends may improve patient outcomes, reduce healthcare costs and improve the quality of life for patients who suffer from chronic diseases that precipitate respiratory failure.

[Non-invasive Mechanical Ventilation in Acute Respiratory Failure. Clinical Practice Guidelines - on behalf of the German Society of Pneumology and Ventilatory Medicine]

The guideline update outlines the advantages as well as the limitations of NIV in the treatment of acute respiratory failure in daily clinical practice and in different indications.Non-invasive ventilation (NIV) has a high value in therapy of hypercapnic acute respiratory failure, as it significantly reduces the length of ICU stay and hospitalization as well as mortality.Patients with cardiopulmonary edema and acute respiratory failure should be treated with continuous positive airway pressure (CPAP) and oxygen in addition to necessary cardiological interventions. This should be done already prehospital and in the emergency department.In case of other forms of acute hypoxaemic respiratory failure with only mild or moderately disturbed gas exchange (PaO2/FiO2 > 150 mmHg) there is no significant advantage or disadvantage compared to high flow nasal oxygen (HFNO). In severe forms of ARDS NIV is associated with high rates of treatment failure and mortality, especially in cases with NIV-failure and delayed intubation.NIV should be used for preoxygenation before intubation. In patients at risk, NIV is recommended to reduce extubation failure. In the weaning process from invasive ventilation NIV essentially reduces the risk of reintubation in hypercapnic patients. NIV is regarded useful within palliative care for reduction of dyspnea and improving quality of life, but here in concurrence to HFNO, which is regarded as more comfortable. Meanwhile NIV is also recommended in prehospital setting, especially in hypercapnic respiratory failure and pulmonary edema.With appropriate monitoring in an intensive care unit NIV can also be successfully applied in pediatric patients with acute respiratory insufficiency.

Managing respiratory muscle weakness during weaning from invasive ventilation

Weaning is a critical stage of an intensive care unit (ICU) stay, in which the respiratory muscles play a major role. Weakness of the respiratory muscles, which is associated with significant morbidity in the ICU, is not limited to atrophy and subsequent dysfunction of the diaphragm; the extradiaphragmatic inspiratory and expiratory muscles also play important parts. In addition to the well-established deleterious effect of mechanical ventilation on the respiratory muscles, other risk factors such as sepsis may be involved. Weakness of the respiratory muscles can be suspected visually in a patient with paradoxical movement of the abdominal compartment. Measurement of maximal inspiratory pressure is the simplest way to assess respiratory muscle function, but it does not specifically take the diaphragm into account. A cut-off value of -30 cmH2O could identify patients at risk for prolonged ventilatory weaning; however, ultrasound may be better for assessing respiratory muscle function in the ICU. Although diaphragm dysfunction has been associated with weaning failure, this diagnosis should not discourage clinicians from performing spontaneous breathing trials and considering extubation. Recent therapeutic developments aimed at preserving or restoring respiratory muscle function are promising.

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.

Proportional assist ventilation relieves clinically significant dyspnea in critically ill ventilated patients

INTRODUCTION

Dyspnea is common and often severe symptom in mechanically ventilated patients. Proportional assist ventilation (PAV) is an assist ventilatory mode that adjusts the level of assistance to the activity of respiratory muscles. We hypothesized that PAV reduce dyspnea compared to pressure support ventilation (PSV).

PATIENTS AND METHODS

Mechanically ventilated patients with clinically significant dyspnea were included. Dyspnea intensity was assessed by the Dyspnea-Visual Analog Scale (D-VAS) and the Intensive Care-Respiratory Distress Observation Scale (IC-RDOS) at inclusion (PSV-Baseline), after personalization of ventilator settings in order to minimize dyspnea (PSV-Personalization), and after switch to PAV. Respiratory drive was assessed by record of electromyographic activity of inspiratory muscles, the proportion of asynchrony was analyzed.

RESULTS

Thirty-four patients were included (73% males, median age of 66 [57-77] years). The D-VAS score was lower with PSV-Personalization (37 mm [20‒55]) and PAV (31 mm [14‒45]) than with PSV-Baseline (62 mm [28‒76]) (p < 0.05). The IC-RDOS score was lower with PAV (4.2 [2.4‒4.7]) and PSV-Personalization (4.4 [2.4‒4.9]) than with PSV-Baseline (4.8 [4.1‒6.5]) (p < 0.05). The electromyographic activity of parasternal intercostal muscles was lower with PAV and PSV-Personalization than with PSV-Baseline. The asynchrony index was lower with PAV (0% [0‒0.55]) than with PSV-Baseline and PSV-Personalization (0.68% [0‒2.28] and 0.60% [0.31‒1.41], respectively) (p < 0.05).

CONCLUSION

In mechanically ventilated patients exhibiting clinically significant dyspnea with PSV, personalization of PSV settings and PAV results in not different decreased dyspnea and activity of muscles to a similar degree, even though PAV was able to reduce asynchrony more effectively.

How to ventilate obstructive and asthmatic patients

Exacerbations are part of the natural history of chronic obstructive pulmonary disease and asthma. Severe exacerbations can cause acute respiratory failure, which may ultimately require mechanical ventilation. This review summarizes practical ventilator strategies for the management of patients with obstructive airway disease. Such strategies include non-invasive mechanical ventilation to prevent intubation, invasive mechanical ventilation, from the time of intubation to weaning, and strategies intended to prevent post-extubation acute respiratory failure. The role of tracheostomy, the long-term prognosis, and potential future adjunctive strategies are also discussed. Finally, the physiological background that underlies these strategies is detailed.

Noninvasive Neurally Adjusted Ventilator Assist Ventilation in the Postoperative Period Produces Better Patient-Ventilator Synchrony but Not Comfort

Background

Noninvasive neurally adjusted ventilatory assist (NAVA) has been shown to improve patient-ventilator interaction in many settings. There is still scarce data with regard to postoperative patients indicated for noninvasive ventilation (NIV) which this study elates. The purpose of this trial was to evaluate postoperative patients for synchrony and comfort in noninvasive pressure support ventilation (NIV-PSV) vs. NIV-NAVA.

Methods

Twenty-two subjects received either NIV-NAVA or NIV-PSV in an object-blind, prospective, randomized, crossover fashion (observational trial). We evaluated blood gases and ventilator tracings throughout as well as comfort of ventilation at the end of each ventilation phase.

Results

There was an effective reduction in ventilator delays (p < 0.001) and negative pressure duration in NIV-NAVA as compared to NIV-PSV (p < 0.001). Although we used optimized settings in NIV-PSV, explaining the overall low incidence of asynchrony, NIV-NAVA led to reductions in the NeuroSync-index (p < 0.001) and all types of asynchrony except for double triggering that was significantly more frequent in NIV-NAVA vs. NIV-PSV (p = 0.02); ineffective efforts were reduced to zero by use of NIV-NAVA. In our population of previously lung-healthy subjects, we did not find differences in blood gases and patient comfort between the two modes.

Conclusion

In the postoperative setting, NIV-NAVA is well suitable for use and effective in reducing asynchronies as well as a surrogate for work of breathing. Although increased synchrony was not transferred into an increased comfort, there was an advantage with regard to patient-ventilator interaction. The trial was registered at the German clinical Trials Register (DRKS no.: DRKS00005408).

Effect of Neurally Adjusted Ventilatory Assist on Patient-Ventilator Interaction in Mechanically Ventilated Adults: A Systematic Review and Meta-Analysis

OBJECTIVES

Patient-ventilator asynchrony is common among critically ill patients undergoing mechanical ventilation and has been associated with adverse outcomes. Neurally adjusted ventilatory assist is a ventilatory mode that may lead to improved patient-ventilator synchrony. We conducted a systematic review to determine the impact of neurally adjusted ventilatory assist on patient-ventilator asynchrony, other physiologic variables, and clinical outcomes in adult patients undergoing invasive mechanical ventilation in comparison with conventional pneumatically triggered ventilatory modes.

DATA SOURCES

We searched Medline, EMBASE, Cochrane Database of Systematic Reviews, Cochrane Central, CINAHL, Scopus, Web of Science, conference abstracts, and ClinicalTrials.gov until July 2018.

STUDY SELECTION

Two authors independently screened titles and abstracts for randomized and nonrandomized controlled trials (including crossover design) comparing the occurrence of patient-ventilator asynchrony between neurally adjusted ventilatory assist and pressure support ventilation during mechanical ventilation in critically ill adults. The asynchrony index and severe asynchrony (i.e., asynchrony index > 10%) were the primary outcomes.

DATA EXTRACTION

Two authors independently extracted study characteristics and outcomes and assessed risk of bias of included studies.

DATA SYNTHESIS

Of 11,139 unique citations, 26 studies (522 patients) met the inclusion criteria. Sixteen trials were included in the meta-analysis using random effects models through the generic inverse variance method. In several different clinical scenarios, the use of neurally adjusted ventilatory assist was associated with significantly reduced asynchrony index (mean difference, -8.12; 95% CI, -11.61 to -4.63; very low quality of evidence) and severe asynchrony (odds ratio, 0.42; 95% CI, 0.23-0.76; moderate quality of evidence) as compared with pressure support ventilation. Furthermore, other measurements of asynchrony were consistently improved during neurally adjusted ventilatory assist.

CONCLUSIONS

Neurally adjusted ventilatory assist improves patient-ventilator synchrony; however, its effects on clinical outcomes remain uncertain. Randomized controlled trials are needed to determine whether the physiologic efficiency of neurally adjusted ventilatory assist affects patient-important outcomes in critically ill adults.

Intubation rate, duration of noninvasive ventilation and mortality after noninvasive neurally adjusted ventilatory assist (NIV-NAVA)

BACKGROUND

Asynchrony is a common problem in patients treated with noninvasive ventilation (NIV). Neurally adjusted ventilatory assist (NAVA) has shown to improve patient-ventilator interaction. However, it is unknown whether NIV-NAVA improves outcomes compared to noninvasive pressure support (NIV-PS).

METHODS

This observational cohort study included patients 18 years or older receiving noninvasive ventilation using an oro-nasal face mask for more than 2 hours in a Danish ICU. The study included a NIV-NAVA cohort (year 2013-2015) and two comparison cohorts: (a) a historical NIV-PS cohort (year 2011-2012) before the implementation of NIV-NAVA at the ICU in 2013, and (b) a concurrent NIV-PS cohort (year 2013-2015). Outcomes of NIV-NAVA (intubation rate, duration of NIV and 90-day mortality) were assessed and compared using multivariable linear and logistic regression adjusted for relevant confounders.

RESULTS

The study included 427 patients (91 in the NIV-NAVA, 134 in the historic NIV-PS and 202 in the concurrent NIV-PS cohort). Patients treated with NIV-NAVA did not have improved outcome after adjustment for measured confounders. Actually, there were statistically imprecise higher odds for intubation in NIV-NAVA patients compared with both the historical [OR 1.48, CI (0.74-2.97)] and the concurrent NIV-PS cohort [OR 1.67, CI (0.87-3.19)]. NIV-NAVA might also have a longer length of NIV [63%, CI (19%-125%)] and [139%, CI (80%-213%)], and might have a higher 90-day mortality [OR 1.24, CI (0.69-2.25)] and [OR 1.39, CI (0.81-2.39)]. Residual confounding cannot be excluded.

CONCLUSION

This present study found no improved clinical outcomes in patients treated with NIV-NAVA compared to NIV-PS.

Comparison of NIV-NAVA and NCPAP in facilitating extubation for very preterm infants

BACKGROUND

Various types of noninvasive respiratory modalities that lead to successful extubation in preterm infants have been explored. We aimed to compare noninvasive neurally adjusted ventilatory assist (NIV-NAVA) and nasal continuous positive airway pressure (NCPAP) for the postextubation stabilization of preterm infants.

METHODS

This retrospective study was divided into two distinct periods, between July 2012 and June 2013 and between July 2013 and June 2014, because NIV-NAVA was applied beginning in July 2013. Preterm infants of less than 30 weeks GA who had been intubated with mechanical ventilation for longer than 24 h and were weaned to NCPAP or NIV-NAVA after extubation were enrolled. Ventilatory variables and extubation failure were compared after weaning to NCPAP or NIV-NAVA. Extubation failure was defined when infants were reintubated within 72 h of extubation.

RESULTS

There were 14 infants who were weaned to NCPAP during Period I, and 2 infants and 16 infants were weaned to NCPAP and NIV-NAVA, respectively, during Period II. At the time of extubation, there were no differences in the respiratory severity score (NIV-NAVA 1.65 vs. NCPAP 1.95), oxygen saturation index (1.70 vs. 2.09) and steroid use before extubation. Several ventilation parameters at extubation, such as the mean airway pressure, positive end-expiratory pressure, peak inspiratory pressure, and FiO2, were similar between the two groups. SpO2 and pCO2 preceding extubation were comparable. Extubation failure within 72 h after extubation was observed in 6.3% of the NIV-NAVA group and 37.5% of the NCPAP group (P = 0.041).

CONCLUSIONS

The data in the present showed promising implications for using NIV-NAVA over NCPAP to facilitate extubation.

Neurally adjusted ventilatory assist versus pressure support ventilation in patient-ventilator interaction and clinical outcomes: a meta-analysis of clinical trials

Background

The objective of this study was to conduct a meta-analysis comparing neurally adjusted ventilatory assist (NAVA) with pressure support ventilation (PSV) in adult ventilated patients with patient-ventilator interaction and clinical outcomes.

Methods

The PubMed, the Web of Science, Scopus, and Medline were searched for appropriate clinical trials (CTs) comparing NAVA with PSV for the adult ventilated patients. RevMan 5.3 was performed for comparing NAVA with PSV in asynchrony index (AI), ineffective efforts, auto-triggering, double asynchrony, premature asynchrony, breathing pattern (Peak airway pressure (Paw_peek), mean airway pressure (Paw_mean), tidal volume (V_T, mL/kg), minute volume (MV), respiratory muscle unloading (peak electricity of diaphragm (EAdi_peak), P 0.1, V_T/EAdi), clinical outcomes (ICU mortality, duration of ventilation days, ICU stay time, hospital stay time).

Results

Our meta-analysis included 12 studies involving a total of 331 adult ventilated patients, AI was significantly lower in NAVA group [mean difference (MD) -12.82, 95% confidence interval (CI): -21.20 to -4.44, I²=88%], and using subgroup analysis, grouped by mechanical ventilation, the results showed that NAVA also had lower AI than PSV (Mechanical ventilation, MD -9.52, 95% CI: -17.85 to -1.20, I²=87%), (Non-invasive ventilation (NIV), MD -24.55, 95% CI: -35.40 to -13.70, I²=0%). NAVA was significantly lower than the PSV in auto-triggering (MD -0.28, 95% CI: -0.51 to -0.05, I²=10%), and premature triggering (MD -2.49, 95% CI: -3.77 to -1.21, I²=29%). There were no significant differences in double triggering, ineffective efforts, breathing pattern (Paw_mean, Paw_peak, V_T, MV), and respiratory muscle unloading (EAdi_peak, P 0.1, V_T/EAdi). For clinical outcomes, NAVA was significantly lower than the PSV (MD -2.82, 95% CI: -5.55 to -0.08, I²=0%) in the duration of ventilation, but two groups did not show significant differences in ICU mortality, ICU stay time, and hospital stay time.

Conclusions

NAVA is more beneficial in patient-ventilator interaction than PSV, and could decrease the duration of ventilation.

Patient-ventilator asynchrony in adult critically ill patients

INTRODUCTION

Patient-ventilator asynchrony is considered a major clinical problem for mechanically ventilated patients. It occurs during partial ventilatory support, when the respiratory muscles and the ventilator interact to contribute generating the volume output. In this review article, we consider all studies published on patient-ventilator asynchrony in the last 25 years.

EVIDENCE ACQUISITION

We selected 62 studies. The different forms of asynchrony are first defined and classified. We also describe the methods used for detecting and quantifying asynchronies. We then outline the outcome variables considered for evaluating the clinical consequences of asynchronies. The methodology for detection and quantification of patient-ventilator asynchrony are quite heterogeneous. In particular, the Asynchrony Index is calculated differently among studies.

EVIDENCE SYNTHESIS

Sixteen studies established some relationship between asynchronies and one or more clinical outcomes, such as duration of mechanical ventilation (seven studies), mortality (five studies), length of intensive care and hospital stay (four studies), patient comfort (four studies), quality of sleep (three studies), and rate of tracheotomy (three studies). In patients with severe patient-ventilator asynchrony, four of seven studies (57%) report prolonged duration of mechanical ventilation, one of five (20%) increased mortality, one of four (25%) longer intensive care and hospital lengths of stay, four of four (100%) worsened comfort, three of four (75%) deteriorated quality of sleep, and one of three (33%) increased rate of tracheotomy.

CONCLUSIONS

Given the varying outcomes considered and the erratic results, it remains unclear whether asynchronies really affects patient outcome, and the relationship between asynchronies and outcome is causative or associative.

Prevalence and Prognosis Impact of Patient-Ventilator Asynchrony in Early Phase of Weaning according to Two Detection Methods

BACKGROUND

Patient-ventilator asynchrony is associated with a poorer outcome. The prevalence and severity of asynchrony during the early phase of weaning has never been specifically described. The authors' first aim was to evaluate the prognosis impact and the factors associated with asynchrony. Their second aim was to compare the prevalence of asynchrony according to two methods of detection: a visual inspection of signals and a computerized method integrating electromyographic activity of the diaphragm.

METHODS

This was an ancillary study of a multicenter, randomized controlled trial comparing neurally adjusted ventilatory assist to pressure support ventilation. Asynchrony was quantified at 12, 24, 36, and 48 h after switching from controlled ventilation to a partial mode of ventilatory assistance according to the two methods. An asynchrony index greater than or equal to 10% defined severe asynchrony.

RESULTS

A total of 103 patients ventilated for a median duration of 5 days (interquartile range, 3 to 9 days) were included. Whatever the method used for quantification, severe patient-ventilator asynchrony was not associated with an alteration of the outcome. No factor was associated with severe asynchrony. The prevalence of asynchrony was significantly lower when the quantification was based on flow and pressure than when it was based on the electromyographic activity of the diaphragm at 0.3 min (interquartile range, 0.2 to 0.8 min) and 4.7 min (interquartile range, 3.2 to 7.7 min; P < 0.0001), respectively.

CONCLUSIONS

During the early phase of weaning in patients receiving a partial ventilatory mode, severe patient-ventilator asynchrony was not associated with adverse clinical outcome, although the prevalence of patient-ventilator asynchrony varies according to the definitions and methods used for detection.

Efficacy of ventilator waveform observation for detection of patient-ventilator asynchrony during NIV: a multicentre study

The objective of this study was to assess ability to identify asynchronies during noninvasive ventilation (NIV) through ventilator waveforms according to experience and interface, and to ascertain the influence of breathing pattern and respiratory drive on sensitivity and prevalence of asynchronies.

35 expert and 35 nonexpert physicians evaluated 40 5-min NIV reports displaying flow–time and airway pressure–time tracings; identified asynchronies were compared with those ascertained by three examiners who evaluated the same reports displaying, additionally, tracings of diaphragm electrical activity. We determined: 1) sensitivity, specificity, and positive and negative predictive values; 2) the correlation between the double true index (DTI) of each report (i.e., the ratio between the sum of true positives and true negatives, and the overall breath count) and the corresponding asynchrony index (AI); and 3) the influence of breathing pattern and respiratory drive on both AI and sensitivity.

Sensitivities to detect asynchronies were low either according to experience (0.20 (95% CI 0.14–0.29) for expert versus 0.21 (95% CI 0.12–0.30) for nonexpert, p=0.837) or interface (0.28 (95% CI 0.17–0.37) for mask versus 0.10 (95% CI 0.05–0.16) for helmet, p<0.0001). DTI inversely correlated with the AI (r²=0.67, p<0.0001). Breathing pattern and respiratory drive did not affect prevalence of asynchronies and sensitivity.

Patient–ventilator asynchrony during NIV is difficult to recognise solely by visual inspection of ventilator waveforms.

Detection of patient–ventilator asynchrony during NIV by visual inspection of ventilator waveforms is difficulthttp://ow.ly/3ce930eGdn6

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.

Monitoring the electric activity of the diaphragm during noninvasive positive pressure ventilation: a case report

BACKGROUND

In patients with post-extubation respiratory distress, delayed reintubation may worsen clinical outcomes. Objective measures of extubation failure at the bedside are lacking, therefore clinical parameters are currently used to guide the need of reintubation. Electrical activity of the diaphragm (EAdi) provides clinicians with valuable, objective information about respiratory drive and could be used to monitor respiratory effort.

CASE PRESENTATION

We describe the case of a patient with Chronic Obstructive Pulmonary Disease (COPD), from whom we recorded EAdi during four different ventilatory conditions: 1) invasive mechanical ventilation, 2) spontaneous breathing trial (SBT), 3) unassisted spontaneous breathing, and 4) Noninvasive Positive Pressure Ventilation (NPPV). The patient had been intubated due to an exacerbation of COPD, and after four days of mechanical ventilation, she passed the SBT and was extubated. Clinical signs of respiratory distress were present immediately after extubation, and EAdi increased compared to values obtained during mechanical ventilation. As we started NPPV, EAdi decreased substantially, indicating muscle unloading promoted by NPPV, and we used the EAdi signal to monitor respiratory effort during NPPV. Over the next three days, she was on NPPV for most of the time, with short periods of spontaneous breathing. EAdi remained considerably lower during NPPV than during spontaneous breathing, until the third day, when the difference was no longer clinically significant. She was then weaned from NPPV and discharged from the ICU a few days later.

CONCLUSION

EAdi monitoring during NPPV provides an objective parameter of respiratory drive and respiratory muscle unloading and may be a useful tool to guide post-extubation ventilatory support. Clinical studies with continuous EAdi monitoring are necessary to clarify the meaning of its absolute values and changes over time.

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).

Respiratory monitoring in adult intensive care unit

INTRODUCTION

The mortality of patients with respiratory failure has steadily decreased with the advancements in protective ventilation and treatment options. Although respiratory monitoring per se has not been proven to affect the mortality of critically ill patients, it plays a crucial role in patients' care, as it helps to titrate the ventilatory support. Several new monitoring techniques have recently been made available at the bedside. The goals of monitoring comprise alerting physicians to detect the change in the patients' conditions, to improve the understanding of pathophysiology to guide the diagnosis and provide cost-effective clinical management. Areas covered: We performed a review of the recent scientific literature to provide an overview of the different methods used for respiratory monitoring in adult intensive care units, including bedside imaging techniques such as ultrasound and electrical impedance tomography. Expert commentary: Appropriate respiratory monitoring plays an important role in patients with and without respiratory failure as a guiding tool for the optimization of ventilation support, avoiding further complications and decreasing morbidity and mortality. The physician should tailor the monitoring strategy for each individual patient and know how to correctly interpret the data.

Comparison Between Neurally Adjusted Ventilatory Assist and Pressure Support Ventilation Levels in Terms of Respiratory Effort

OBJECTIVES

To understand the potential equivalence between neurally adjusted ventilatory assist and pressure support ventilation levels in terms of respiratory muscle unloading. To compare the respiratory pattern, variability, synchronization, and neuromuscular coupling within comparable ranges of assistance.

DESIGN

Prospective single-center physiologic study.

SETTING

A 13-bed university medical ICU.

PATIENTS

Eleven patients recovering from respiratory failure.

INTERVENTIONS

The following levels of assistance were consecutively applied in a random order: neurally adjusted ventilatory assist levels: 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, and 7 cm H2O/μvolt; pressure support levels: 7, 10, 15, 20, and 25 cm H2O.

MEASUREMENTS AND MAIN RESULTS

Flow, airway pressure, esophageal pressures, and peak electrical activity of the diaphragm were continuously recorded. Breathing effort was calculated. To express the percentage of assist assumed by the ventilator, the total pressure including muscular and ventilator pressure was calculated. The median percentage of assist ranged from 33% (24-47%) to 82% (72-90%) between pressure support 7 and 25 cm H2O. Similar levels of unloading were observed for neurally adjusted ventilatory assist levels from 0.5 cm H2O/μvolt (46% [40-51%]) to 2.5 cm H2O/μvolt (80% [74-84%]). Tidal variability was higher during neurally adjusted ventilatory assist and ineffective efforts appeared only in pressure support. In neurally adjusted ventilatory assist, double triggering occurred sometimes when electrical activity of the diaphragm signal depicted a biphasic aspect, and an abnormal oscillatory pattern was frequently observed from 4 cm H2O/μvolt. For both modes, the relationship between peak electrical activity of the diaphragm and muscle pressure depicted a curvilinear profile.

CONCLUSIONS

In patients recovering from acute respiratory failure, levels of neurally adjusted ventilatory assist between 0.5 and 2.5 cm H2O/μvolt are comparable to pressure support levels ranging from 7 to 25 cm H2O in terms of respiratory muscle unloading. Neurally adjusted ventilatory assist provides better patient-ventilator interactions but can be sometimes excessively sensitive to electrical activity of the diaphragm in terms of triggering.

Non-invasive ventilation is useful in paediatric intensive care units if children are appropriately selected and carefully monitored

Non-invasive ventilation (NIV) is commonly used in paediatric intensive care units (PICUs) for respiratory failure. This review aims to improve paediatricians' understanding of NIV, by specifying technical or practical considerations, giving advice about selecting patients and presenting pertinent published data about NIV in different circumstances.

CONCLUSION

NIV is useful in PICUs if children are appropriately selected and carefully monitored. Technological advances and future clinical research will improve its use and success rate in PICU.

Neurally adjusted ventilatory assist

Purpose of review

Compared with the conventional forms of partial support, neurally adjusted ventilatory assist was repeatedly shown to improve patient–ventilator synchrony and reduce the risk of overassistance, while guaranteeing adequate inspiratory effort and gas exchange. A few animal studies also suggested the potential of neurally adjusted ventilatory assist in averting the risk of ventilator-induced lung injury. Recent work adds new information on the physiological effects of neurally adjusted ventilatory assist.

Recent findings

Compared with pressure support, neurally adjusted ventilatory assist has been shown to improve patient–ventilator interaction and synchrony in patients with the most challenging respiratory system mechanics, such as very low compliance consequent to severe acute respiratory distress syndrome and high resistance and air trapping due to chronic airflow obstruction; enhance redistribution of the ventilation in the dependent lung regions; avert the risk of patient–ventilator asynchrony due to sedation; avoid central apneas; limit the risk of high (injurious) tidal volumes in patients with acute respiratory distress syndrome of varied severity; and improve patient–ventilator interaction and synchrony during noninvasive ventilation, irrespective of the interface utilized.

Summary

Several studies nowadays prove the physiological benefits of neurally adjusted ventilatory assist, as opposed to the conventional modes of partial support. Whether these advantages translate into improvement of clinical outcomes remains to be determined.

Noninvasive support and ventilation for pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVE

Despite the widespread use of noninvasive ventilation in children and in children with acute lung injury and pediatric acute respiratory distress syndrome, there are few scientific data on the utility of this therapy. In this review, we examine the literature regarding noninvasive positive pressure ventilation and use the Research ANd Development/University of California, Los Angeles appropriateness methodology to provide strong or weak recommendations for the use of noninvasive positive pressure ventilation in children with pediatric acute respiratory distress syndrome.

DATA SOURCES

Electronic searches were made in PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus with the following specific keywords: noninvasive ventilation, noninvasive positive pressure ventilation, continuous positive airway pressure, and high-flow nasal cannula.

STUDY SELECTION

Studies were eligible for inclusion if they included 10 or more children between 1 month and 18 years old. Randomized and nonrandomized controlled trials, controlled before-and-after studies, concurrent cohort studies, interrupted time series studies, historically controlled studies, cohort studies, cross-sectional studies, and uncontrolled longitudinal studies were included for data synthesis.

DATA SYNTHESIS

The literature provides a solid physiological rationale for the use of noninvasive positive pressure ventilation in children with pediatric acute respiratory distress syndrome. The addition of noninvasive positive pressure ventilation can improve gas exchange and potentially prevent intubation and mechanical ventilation in some children with mild pediatric acute respiratory distress syndrome. Noninvasive positive pressure ventilation is not indicated in severe pediatric acute respiratory distress syndrome. Noninvasive positive pressure ventilation should be performed only in acute care setting with experienced team, and patient-ventilator synchrony is crucial for success. An oronasal interface provides superior support, but close monitoring of children is required due to the risk of progressive respiratory failure and the potential need for intubation. The use of high-flow nasal cannula is a promising treatment for respiratory disease; however, at this time, the efficacy of high-flow nasal cannula compared with noninvasive positive pressure ventilation is unknown.

CONCLUSION

Noninvasive positive pressure ventilation can be beneficial in children with pediatric acute respiratory distress syndrome, particularly in those with milder disease. However, further research is needed into the use of noninvasive positive pressure ventilation in children.

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.

Neurally adjusted ventilatory assist and proportional assist ventilation both improve patient-ventilator interaction

Introduction

The objective was to compare the impact of three assistance levels of different modes of mechanical ventilation; neurally adjusted ventilatory assist (NAVA), proportional assist ventilation (PAV), and pressure support ventilation (PSV) on major features of patient-ventilator interaction.

Methods

PSV, NAVA, and PAV were set to obtain a tidal volume (V_T) of 6 to 8 ml/kg (PSV₁₀₀, NAVA₁₀₀, and PAV₁₀₀) in 16 intubated patients. Assistance was further decreased by 50% (PSV₅₀, NAVA₅₀, and PAV₅₀) and then increased by 50% (PSV₁₅₀, NAVA₁₅₀, and PAV₁₅₀) with all modes. The three modes were randomly applied. Airway flow and pressure, electrical activity of the diaphragm (EAdi), and blood gases were measured. V_T, peak EAdi, coefficient of variation of V_T and EAdi, and the prevalence of the main patient-ventilator asynchronies were calculated.

Results

PAV and NAVA prevented the increase of V_T with high levels of assistance (median 7.4 (interquartile range (IQR) 5.7 to 10.1) ml/kg and 7.4 (IQR, 5.9 to 10.5) ml/kg with PAV₁₅₀ and NAVA₁₅₀ versus 10.9 (IQR, 8.9 to 12.0) ml/kg with PSV₁₅₀, P <0.05). EAdi was higher with PAV than with PSV at level₁₀₀ and level₁₅₀. The coefficient of variation of V_T was higher with NAVA and PAV (19 (IQR, 14 to 31)% and 21 (IQR 16 to 29)% with NAVA₁₀₀ and PAV₁₀₀ versus 13 (IQR 11 to 18)% with PSV₁₀₀, P <0.05). The prevalence of ineffective triggering was lower with PAV and NAVA than with PSV (P <0.05), but the prevalence of double triggering was higher with NAVA than with PAV and PSV (P <0.05).

Conclusions

PAV and NAVA both prevent overdistention, improve neuromechanical coupling, restore the variability of the breathing pattern, and decrease patient-ventilator asynchrony in fairly similar ways compared with PSV. Further studies are needed to evaluate the possible clinical benefits of NAVA and PAV on clinical outcomes.

Trial registration

Clinicaltrials.gov NCT02056093. Registered 18 December 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0763-6) contains supplementary material, which is available to authorized users.

Assessment of patient-ventilator breath contribution during neurally adjusted ventilatory assist in patients with acute respiratory failure

INTRODUCTION

We previously showed in animals that the ratio of inspired tidal volume (Vtinsp) to inspiratory peak electrical activity of the diaphragm (EAdipk) can be used to quantify the respective patient and ventilator breath contributions (PVBCs) during neurally adjusted ventilatory assist (NAVA). The PVBC index has not been tested clinically.

METHODS

We studied 12 intubated and mechanically ventilated patients with acute respiratory failure and measured EAdipk, airway (Paw) and inspiratory esophageal pressure (Pes) and Vtinsp. We applied 11 different NAVA levels, increasing them every 3 minutes in steps of 0.3 cm H₂O/μV from 0 to 3.0 cmH₂O/μV. At each NAVA level, one breath was non-assisted (NAVA level 0). PVBC indices were calculated by relating Vtinsp/EAdipk of the non-assisted breath to Vtinsp/EAdipk of the assisted breath(s) using one ((N1)PVBC) or the mean value of five preceding assisted breaths ((X5)PVBC). During assisted breaths, inspiratory changes in Pes (∆Pes) and transpulmonary (ΔPtp) pressures were used to calculate the relative contribution of patient to total inspiratory lung-distending pressures (ΔPes/ΔPtp). Matching of respiratory drive indices and squaring of the PVBC was evaluated for their effect on the correlation between PVBC and ΔPes/ΔPtp. Linear regression analysis and Bland-Altman analysis were applied to compare indices.

RESULTS

Using an average of five assisted breaths prior to the non-assisted breath and squaring the PVBC ((X5)PVBC(2)) improved determination coefficients (P <0.05), adjusted the regression slope and intercept between PVBC and ΔPes/ΔPtp toward identity (P <0.05) and reduced bias (P <0.05). Matching EAdipk between non-assisted and assisted breaths within the range of 0.77 to 1.30 improved the relationship between (X5)PVBC(2) and ΔPes/ΔPtp (P <0.05) and abolished the need for EAdi normalization in the PVBC calculation (R(2) = 0.96; bias = 0.16 ± 0.06; precision = 0.33 ± 0.08 (mean and 95% confidence interval)).

CONCLUSIONS

This clinical study confirms previous experimental results showing that the PVBC(2) predicts the contribution of the inspiratory muscles versus that of the ventilator during NAVA, when differences in effort (EAdi) between non-assisted and assisted breaths are limited. PVBC could help to quantify and standardize the adjustment of the level of assist, and hence reduce the risks of excessive ventilatory assist in patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01663480. Registered 9 August 2012.

Neurally adjusted ventilatory assist (NAVA) allows patient-ventilator synchrony during pediatric noninvasive ventilation: a crossover physiological study

Introduction

The need for intubation after a noninvasive ventilation (NIV) failure is frequent in the pediatric intensive care unit (PICU). One reason is patient-ventilator asynchrony during NIV. Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation controlled by the patient’s neural respiratory drive. The aim of this study was to assess the feasibility and tolerance of NIV-NAVA in children and to evaluate its impact on synchrony and respiratory effort.

Methods

This prospective, physiologic, crossover study included 13 patients requiring NIV in the PICU of Sainte-Justine’s Hospital from October 2011 to May 2013. Patients were successively ventilated in conventional NIV as prescribed by the physician in charge (30 minutes), in NIV-NAVA (60 minutes), and again in conventional NIV (30 minutes). Electrical activity of the diaphragm (EAdi) and airway pressure were simultaneously recorded to assess patient-ventilator synchrony.

Results

NIV-NAVA was feasible and well tolerated in all patients. One patient asked to stop the study because of anxiety related to the leak-free facial mask. Inspiratory trigger dys-synchrony and cycling-off dys-synchrony were significantly shorter in NIV-NAVA versus initial and final conventional NIV periods (both P <0.05). Wasted efforts were also decreased in NIV-NAVA (all values expressed as median and interquartile values) (0 (0 to 0) versus 12% (4 to 20) and 6% (2 to 22), respectively; P <0.01). As a whole, total time spent in asynchrony was reduced to 8% (6 to 10) in NIV-NAVA, versus 27% (19 to 56) and 32% (21 to 38) in conventional NIV before and after NIV-NAVA, respectively (P =0.05).

Conclusion

NIV-NAVA is feasible and well tolerated in PICU patients and allows improved patient-ventilator synchronization. Larger controlled studies are warranted to evaluate the clinical impact of these findings.

Trial registration

ClinicalTrials.gov NCT02163382. Registered 9 June 2014.

Spontaneous breathing in mild and moderate versus severe acute respiratory distress syndrome

PURPOSE OF REVIEW

This review summarizes the most recent clinical and experimental data on the impact of spontaneous breathing in acute respiratory distress syndrome (ARDS).

RECENT FINDINGS

Spontaneous breathing during assisted as well as nonassisted modes of mechanical ventilation improves lung function and reduces lung damage in mild and moderate ARDS. New modes of assisted mechanical ventilation with improved patient ventilator interaction and enhanced variability of the respiratory pattern offer additional benefit on lung function and damage. However, data supporting an outcome benefit of spontaneous breathing in ARDS, even in its mild and moderate forms, are missing. In contrast, controlled mechanical ventilation with muscle paralysis in the first 48 h of severe ARDS has been shown to improve survival, as compared with placebo. Currently, it is unclear whether ventilator settings, rather than the severity of lung injury, determine the potential of spontaneous breathing for benefit or harm.

SUMMARY

Clinical and experimental studies show that controlled mechanical ventilation with muscle paralysis in the early phase of severe ARDS reduces lung injury and even mortality. At present, spontaneous breathing should be avoided in the early phase of severe ARDS, but considered in mild-to-moderate ARDS.

Automated patient-ventilator interaction analysis during neurally adjusted non-invasive ventilation and pressure support ventilation in chronic obstructive pulmonary disease

INTRODUCTION

Delivering synchronous assist during non-invasive ventilation (NIV) is challenging with flow- or pressure-controlled ventilators, especially in patients with chronic obstructive pulmonary disease (COPD). Neurally adjusted ventilatory assist (NAVA) uses diaphragm electrical activity (EAdi) to control the ventilator. We evaluated patient-ventilator interaction in patients with COPD during NIV with pressure support ventilation (PSV) and NAVA using a recently introduced automated analysis.

METHODS

Twelve COPD patients underwent three 30-minute trials: 1) PSV with dedicated NIV ventilator (NIV-PSVVision), 2) PSV with intensive care unit (ICU) ventilator (NIV-PSVServo-I), and 3) with NIV-NAVA. EAdi, flow, and airway pressure were recorded. Patient-ventilator interaction was evaluated by comparing airway pressure and EAdi waveforms with automated computer algorithms. The NeuroSync index was calculated as the percentage of timing errors between airway pressure and EAdi.

RESULTS

The NeuroSync index was higher (larger error) for NIV-PSVVision (24 (IQR 15 to 30) %) and NIV-PSVServo-I (21 (IQR 15 to 26) %) compared to NIV-NAVA (5 (IQR 4 to 7) %; P <0.001). Wasted efforts, trigger delays and cycling-off errors were less with NAVA (P <0.05 for all). The NeuroSync index and the number of wasted efforts were strongly correlated (r2 = 0.84), with a drastic increase in wasted efforts after timing errors reach 20%.

CONCLUSIONS

In COPD patients, non-invasive NAVA improves patient-ventilator interaction compared to PSV, delivered either by a dedicated or ICU ventilator. The automated analysis of patient-ventilator interaction allowed for an objective detection of patient-ventilator interaction during NIV. In addition, we found that progressive mismatch between neural effort and pneumatic timing is associated with wasted efforts.

Advances in Ventilation — Neurally Adjusted Ventilatory Assist (NAVA)

This review aims to introduce neurally-adjusted ventilatory assist (NAVA) to readers who do not have experience in using this form of ventilation. We will describe the basic principles and theoretical advantages of NAVA together with our experiences of introducing and using this mode in an intensive care unit.

Effects of Neurally Adjusted Ventilatory Assist (NAVA) levels in non-invasive ventilated patients: titrating NAVA levels with electric diaphragmatic activity and tidal volume matching

BACKGROUND

Neurally adjusted ventilatory assist (NAVA) delivers pressure in proportion to diaphragm electrical activity (Eadi). However, each patient responds differently to NAVA levels. This study aims to examine the matching between tidal volume (Vt) and patients' inspiratory demand (Eadi), and to investigate patient-specific response to various NAVA levels in non-invasively ventilated patients.

METHODS

12 patients were ventilated non-invasively with NAVA using three different NAVA levels. NAVA100 was set according to the manufacturer's recommendation to have similar peak airway pressure as during pressure support. NAVA level was then adjusted ±50% (NAVA50, NAVA150). Airway pressure, flow and Eadi were recorded for 15 minutes at each NAVA level. The matching of Vt and integral of Eadi (ʃEadi) were assessed at the different NAVA levels. A metric, Range90, was defined as the 5-95% range of Vt/ʃEadi ratio to assess matching for each NAVA level. Smaller Range90 values indicated better matching of supply to demand.

RESULTS

Patients ventilated at NAVA50 had the lowest Range90 with median 25.6 uVs/ml [Interquartile range (IQR): 15.4-70.4], suggesting that, globally, NAVA50 provided better matching between ʃEadi and Vt than NAVA100 and NAVA150. However, on a per-patient basis, 4 patients had the lowest Range90 values in NAVA100, 1 patient at NAVA150 and 7 patients at NAVA50. Robust coefficient of variation for ʃEadi and Vt were not different between NAVA levels.

CONCLUSIONS

The patient-specific matching between ʃEadi and Vt was variable, indicating that to obtain the best possible matching, NAVA level setting should be patient specific. The Range90 concept presented to evaluate Vt/ʃEadi is a physiologic metric that could help in individual titration of NAVA level.

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.