NAVA enhances tidal volume and diaphragmatic electro-myographic activity matching: a Range90 analysis of supply and demand.

Neurally adjusted ventilatory assist (NAVA) is a ventilation assist mode that delivers pressure in proportionality to electrical activity of the diaphragm (Eadi). Compared to pressure support ventilation (PS), it improves patient-ventilator synchrony and should allow a better expression of patient's intrinsic respiratory variability. We hypothesize that NAVA provides better matching in ventilator tidal volume (Vt) to patients inspiratory demand. 22 patients with acute respiratory failure, ventilated with PS were included in the study. A comparative study was carried out between PS and NAVA, with NAVA gain ensuring the same peak airway pressure as PS. Robust coefficients of variation (CVR) for Eadi and Vt were compared for each mode. The integral of Eadi (ʃEadi) was used to represent patient's inspiratory demand. To evaluate tidal volume and patient's demand matching, Range90 = 5-95 % range of the Vt/ʃEadi ratio was calculated, to normalize and compare differences in demand within and between patients and modes. In this study, peak Eadi and ʃEadi are correlated with median correlation of coefficients, R > 0.95. Median ʃEadi, Vt, neural inspiratory time (Ti_ ( Neural )), inspiratory time (Ti) and peak inspiratory pressure (PIP) were similar in PS and NAVA. However, it was found that individual patients have higher or smaller ʃEadi, Vt, Ti_ ( Neural ), Ti and PIP. CVR analysis showed greater Vt variability for NAVA (p < 0.005). Range90 was lower for NAVA than PS for 21 of 22 patients. NAVA provided better matching of Vt to ʃEadi for 21 of 22 patients, and provided greater variability Vt. These results were achieved regardless of differences in ventilatory demand (Eadi) between patients and modes.

Clinical review: Update on neurally adjusted ventilatory assist--report of a round-table conference.

Conventional mechanical ventilators rely on pneumatic pressure and flow sensors and controllers to detect breaths. New modes of mechanical ventilation have been developed to better match the assistance delivered by the ventilator to the patient's needs. Among these modes, neurally adjusted ventilatory assist (NAVA) delivers a pressure that is directly proportional to the integral of the electrical activity of the diaphragm recorded continuously through an esophageal probe. In clinical settings, NAVA has been chiefly compared with pressure-support ventilation, one of the most popular modes used during the weaning phase, which delivers a constant pressure from breath to breath. Comparisons with proportional-assist ventilation, which has numerous similarities, are lacking. Because of the constant level of assistance, pressure-support ventilation reduces the natural variability of the breathing pattern and can be associated with asynchrony and/or overinflation. The ability of NAVA to circumvent these limitations has been addressed in clinical studies and is discussed in this report. Although the underlying concept is fascinating, several important questions regarding the clinical applications of NAVA remain unanswered. Among these questions, determining the optimal NAVA settings according to the patient's ventilatory needs and/or acceptable level of work of breathing is a key issue. In this report, based on an investigator-initiated round table, we review the most recent literature on this topic and discuss the theoretical advantages and disadvantages of NAVA compared with other modes, as well as the risks and limitations of NAVA.

[Resilience engineering in intensive care]. / Résilience aux soins intensifs.

The process of health care delivery in Intensive Care Units (ICUs) is subject to significant workload fluctuations and unpredictable events. Medical and nursing staff, while relying on protocols, must adjust to these "out of the routine" disturbances by displaying initiative and innovation. The aim is to maintain the ratio risk-performance in admissible margins for the institution despite severe disruptions of operation. The assumption is that this resilience ability may be intentionally built by a specific work organization. The theoretical framework of "resilience engineering" described here could be a powerful tool in organizational designing suited to the ICUs.

[Neurally adjusted ventilatory assist: a revolution of mechanical ventilation?]. / Le "neurally adjusted ventilatory assist": vers une révolution de la ventilation mécanique?

Neurally adjusted ventilatory assist or NAVA is a new assisted ventilatory mode which, in comparison with pressure support, leads to improved patient-ventilator synchrony and a more variable ventilatory pattern. It also improves arterial oxygenation. With NAVA, the electrical activity of the diaphragm is recorded through a nasogastric tube equipped with electrodes. This electrical activity is then used to pilot the ventilator. With NAVA, the patient's respiratory pattern controls the ventilator's timing of triggering and cycling as well as the magnitude of pressurization, which is proportional to inspiratory demand. The effect of NAVA on patient outcome remains to be determined through well-designed prospective studies.

Preparedness and Reorganization of Care for Coronavirus Disease 2019 Patients in a Swiss ICU: Characteristics and Outcomes of 129 Patients.

OBJECTIVES: In many countries, large numbers of critically ill patients with coronavirus disease 2019 are admitted to the ICUs within a short period of time, overwhelming usual care capacities. Preparedness and reorganization ahead of the wave to increase ICU surge capacity may be associated with favorable outcome. The purpose of this study was to report our experience in terms of ICU organization and anticipation, as well as reporting patient characteristics, treatment, and outcomes. DESIGN: A prospective observational study. SETTING: The division of intensive care at the Geneva University Hospitals (Geneva, Switzerland). PATIENTS: All consecutive adult patients with acute respiratory failure due to coronavirus disease 2019 admitted in the ICU between March 9, 2020, and May 19, 2020, were enrolled. Patients' demographic data, comorbidities, laboratory values, treatments, and clinical outcomes were collected. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The ICU was reorganized into cells of six to eight patients under the care of three physicians and five nurses. Its capacity increased from 30 to 110 beds, fully equipped and staffed, transforming the surgical intermediate care unit, the postoperative care facility, and operating theaters into ICUs. Surge capacity has always exceeded the number of patients hospitalized. Among 129 critically ill patients with severe acute hypoxemic respiratory failure, 96% required invasive mechanical ventilation. A total of 105 patients (81%) were discharged alive and 24 died, corresponding to a mortality of 19%. Patients who died were significantly older, with higher severity scores at admission, had higher levels of d-dimers, plasma creatinine, high-sensitive troponin T, C-reactive protein, and procalcitonin, and required more frequent prone sessions. CONCLUSIONS: A rapid increase in ICU bed capacity, including adequate equipment and staffing, allowed for a large number of critically ill coronavirus disease 2019 patients to be taken care of within a short period of time. Anticipation and preparedness ahead of the wave may account for the low mortality observed in our center. These results highlight the importance of resources management strategy in the context of the ongoing coronavirus disease 2019 pandemic.

[Anesthetic gases for the treatment of acute severe asthma]. / Emploi de mélanges d'agents volatils dans l'asthme aigu grave.

Halogenated gases have sometimes been used for treating acute severe asthma when this disorder is refractory to any drug. Presently, we only can rely on some sparsed observations, or to small retrospective series. Isoflurane seems to be the most studied gas: it has clearly a bronchodilating action, and its side-effects seem to be minor. However, to administer such medications, precise knowledge and technical skills are mandatory. In addition, the intensive care personnel must be protected from an accidental exposure. Therefore, intensive care physicians should be helped by an experienced anesthesiologist when using these gases.

Performance of noninvasive ventilation modes on ICU ventilators during pressure support: a bench model study.

OBJECTIVE: Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. DESIGN AND SETTING: Bench model study in an intensive care research laboratory of a university hospital. METHODS: Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to a lung model featuring a plastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. RESULTS: On most ventilators leaks led to an increase in trigger delay and workload, a decrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. CONCLUSIONS: The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilator.

Automatic adjustment of noninvasive pressure support with a bilevel home ventilator in patients with acute respiratory failure: a feasibility study.

OBJECTIVE: To test the feasibility of applying noninvasive ventilation (NIV) using a prototype algorithm implemented in a bilevel ventilation device designed to adjust pressure support (PS) to maintain a clinician-set alveolar ventilation in patients with acute respiratory failure after initial stabilization. DESIGN AND SETTING: Prospective crossover interventional study in an intensive care unit, university hospital. PATIENTS: 19 patients receiving NIV for acute hypercapnic respiratory failure (13 men, 6 women; mean age 70+/-11 years). METHODS: The same bilevel ventilator was used with manually adjusted PS and with the automated algorithm (autoPS), set to maintain the same alveolar ventilation as in PS. Sequence (measurements at end of each period): (a) prior to initiating NIV (baseline 1); (b) 45 min with manually set PS; (c) 60 min without NIV; (d) 45 min with autoPS; (e) 60 min without NIV; (f) 45 min with manually set PS. RESULTS: The magnitude of decrease in PaCO(2) and increase in pH with autoPS was comparable to that of conventional PS, with the same alveolar ventilation and level of PS. No technical problem occurred in autoPS mode, and no NIV trial had to be discontinued because of patient discomfort. CONCLUSIONS: These results suggest that the alveolar ventilation based automatic control of PS during NIV with a bilevel device is feasible and leads to beneficial effects in patients with acute respiratory failure comparable to those of manually set PS. Further studies should now explore the potential of this system over longer periods in patients with acute and chronic respiratory failure.

[Heliox in acute severe asthma]. / Emploi de mélanges hélium-oxygène (héliox) dans l'asthme aigu grave.

In acute severe asthma, the use of heliox can reduce dyspnea, when the patient is spontaneously breathing as well as in mechanical ventilation. This effect is due to a decrease in airway resistance. A better penetration of aerosolized bronchodilators has also been observed. However, the clinical benefit of these physiological measurable effects remains undetermined. Heliox could nevertheless be interesting in emergency situations in order to avoid endotracheal intubation, and in very difficult cases when mechanical ventilation is almost impossible to perform. This gas mixture could also be used with non-invasive mechanical ventilation, but this indication is presently investigated.

Automatic adjustment of pressure support by a computer-driven knowledge-based system during noninvasive ventilation: a feasibility study.

OBJECTIVE: To evaluate the feasibility of using a knowledge-based system designed to automatically titrate pressure support (PS) to maintain the patient in a "respiratory comfort zone" during noninvasive ventilation (NIV) in patients with acute respiratory failure. DESIGN AND SETTING: Prospective crossover interventional study in an intensive care unit of a university hospital. PATIENTS: Twenty patients. INTERVENTIONS: After initial NIV setting and startup in conventional PS by the chest physiotherapist NIV was continued for 45 min with the automated PS activated. MEASUREMENTS AND RESULTS: During automated PS minute-volume was maintained constant while respiratory rate decreased significantly from its pre-NIV value (20+/-3 vs. 25+/-3 bpm). There was a trend towards a progressive lowering of dyspnea. In hypercapnic patients PaCO(2) decreased significantly from 61+/-9 to 51+/-2 mmHg, and pH increased significantly from 7.31+/-0.05 to 7.35+/-0.03. Automated PS was well tolerated. Two system malfunctions occurred prompting physiotherapist intervention. CONCLUSIONS: The results of this feasibility study suggest that the system can be used during NIV in patients with acute respiratory failure. Further studies should now determine whether it can improve patient-ventilator interaction and reduce caregiver workload.

Clinical review: patient-ventilator interaction in chronic obstructive pulmonary disease.

Mechanically ventilated patients with chronic obstructive pulmonary disease often prove challenging to the clinician due to the complex pathophysiology of the disease and the high risk of patient-ventilator asynchrony. These problems are encountered in both intubated patients and those ventilated with noninvasive ventilation. Much knowledge has been gained over the years in our understanding of the mechanisms underlying the difficult interaction between these patients and the machines used to provide them with the ventilatory support they often require for prolonged periods. This paper attempts to summarize the various key issues of patient-ventilator interaction during pressure support ventilation, the most often used partial ventilatory support mode, and to draw clinicians' attention to the need for sufficient knowledge when setting the ventilator at the bedside, given the often conflicting goals that must be met.

Veno-venous extracorporeal membrane oxygenation: cannulation techniques.

The development of extracorporeal membrane oxygenation (ECMO) technology allows a new approach for the intensive care management of acute cardiac and/or respiratory failure in adult patients who are not responsive to conventional treatment. Current ECMO therapies provide a variety of options for the multidisciplinary teams who are involved in the management of these critically ill patients. In this regard, veno-venous ECMO (VV-ECMO) can provide quite complete respiratory support, even if this highly complex technique presents substantial risks, such as bleeding, thromboembolic events and infection. While VV-ECMO circuits usually include the cannulation of two vessels (double cannulation) in its classic configuration, the use of a single cannula is now possible for VV-ECMO support. Recently, experienced centers have employed more advanced approaches by cannulating three vessels (triple cannulation) which follows veno-arterio-venous (VAV) or veno-arterio-pulmonary-arterial cannulation (VAPa). However, 'triple' cannulation expands the field of application but increases the complexity of ECMO systems. In the present review, the authors focus on the indications for VV-ECMO, patient assessment prior to cannulation, the role of ultrasound-guided vessel puncture, double lumen single bicaval cannulations, and finally triple cannulation in VV-ECMO.

Performance characteristics of 10 home mechanical ventilators in pressure-support mode: a comparative bench study.

OBJECTIVE: Inspiratory pressure (Pi) support delivered by a bilevel device has become the technique of choice for noninvasive home ventilation. Considerable progress has been made in the performance and functionality of these devices. The present bench study was designed to compare the various characteristics of 10 recently developed bilevel Pi devices under different conditions of respiratory mechanics. DESIGN: Bench model study. SETTING: Research laboratory, university hospital. MEASUREMENTS: Ventilators were connected to a lung model, the mechanics of which were set to normal, restrictive, and obstructive, that was driven by an ICU ventilator to mimic patient effort. Pressure support levels of 10 and 15 cm H(2)O, and maximum were tested, with "patient" inspiratory efforts of 5, 10, 15, 20, and 25 cm H(2)O. Tests were conducted in the absence and presence of leaks in the system. Trigger delay, trigger-associated inspiratory workload, pressurization capabilities, and cycling were analyzed. RESULTS: All devices had very short trigger delays and triggering workload. Pressurization capability varied widely among the machines, with some bilevel devices lagging behind when faced with a high inspiratory demand. Cycling was usually not synchronous with patient inspiratory time when the default settings were used, but was considerably improved by modifying cycling settings, when that option was available. CONCLUSIONS: A better knowledge of the technical performance of bilevel devices (ie, pressurization capabilities and cycling profile) may prove to be useful in choosing the machine that is best suited for a patient's respiratory mechanics and inspiratory demand. Clinical algorithms to help set cycling criteria for improving patient-ventilator synchrony and patient comfort should now be developed.

Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated patients with chronic obstructive pulmonary disease.

OBJECTIVE: To evaluate the impact of helium-oxygen (He/O2) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support. DESIGN AND SETTING: Prospective crossover interventional study in the medical ICU of a university hospital. PATIENTS AND PARTICIPANTS: Ten patients. INTERVENTIONS: Sequential inhalation (30 min each) of three gas mixtures: (a) air/O2, (b) He/O2 (c) air/O2, at constant FIO2 and level of pressure support. MEASUREMENTS AND RESULTS: Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO2 were 14+/-3 cmH2O and 0.33+/-0.07 respectively. Compared to Air/O2, He/O2 reduced the number of ineffective breaths (4+/-5 vs. 9+/-5 breaths/min), intrinsic PEEP (3.1+/-2 vs. 4.8+/-2 cmH2O), the magnitude of negative esophageal pressure swings (6.7+/-2 vs. 9.1+/-4.9 cmH2O), pressure-time product (42+/-37 vs. 67+/-65 cmH2O s(-1) min(-1)), and total WOB (11+/-3 vs. 18+/-10 J/min). Elastic (6+/-1 vs. 10+/-6 J/min) and resistive (5+/-1 vs. 9+/-4 J/min) components of the WOB were decreased by He/O2. CONCLUSIONS: In intubated COPD patients ventilated with pressure support He/O2 reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O2 could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weaning.

Non-invasive ventilation in the recovery room for postoperative respiratory failure: a feasibility study.

BACKGROUND: Non-invasive ventilation (NIV) has become a standard of care in acute respiratory failure. However, little data is available on its usefulness in recovery ward patients after general surgery. The present study aimed to document the feasibility of implementing NIV in this setting, and its impact on lung function. METHODS: During a 12-month period, all adult patients who underwent elective general surgical procedures under general anaesthesia during weekdays, were transferred to the recovery ward after extubation, and those who required NIV were included in this prospective observational study. NIV was applied with a bilevel device (VPAP II ST, ResMed, North Ryde, Australia). RESULTS: 4622 patients were admitted to the recovery ward, 83 of whom needed NIV. NIV increased pH (7.38 +/- .06 vs 7.30 +/- .05), reduced PaCO2 (7.38 +/- .06 vs 7.30 +/- .05) in hypercapnic patients (44 +/- 9 vs 55 +/- 10 mm Hg), and increased PaO2 in non-hypercapnic patients (80 +/- 10 vs 70 +/- 11 mm Hg). No complications attributable to NIV occurred. Most patients improved after 1-2 NIV trials, and all were transferred to the ward the same day. CONCLUSIONS: In recovery ward patients after general surgery, NIV is seldom required. When applied, NIV seems to exert favourable effects on lung function. NIV can be safely implemented with a bilevel device in a recovery ward not accustomed to the use of ICU ventilators. The cost-effectiveness of its systematic use in this setting should be assessed.

Comparative bench study of triggering, pressurization, and cycling between the home ventilator VPAP II and three ICU ventilators.

OBJECTIVE: To compare triggering, pressurization, and cycling of the home ventilator VPAP II with those of three ICU ventilators (Evita 4, Galileo, and Servo 300). DESIGN AND SETTING: Two-compartment lung model study in a research laboratory, university hospital. METHODS: One compartment was driven by an ICU ventilator to mimic "patient" inspiratory effort, while the other was connected to the tested ventilator. Pressure support of 10, 15, 20, and 25 cmH2O, and inspiratory efforts of 5, 10, 15, 20, and 25 cmH2O (inspiratory time 1 s) were used in normal, obstructive, and restrictive conditions. Triggering delay (Td), triggering workload, pressurization at 300 and 500 ms, and difference between the "patient's" inspiratory time and that of the ventilator were analyzed. RESULTS: No difference was noted in triggering workload between VPAP II, Evita 4, and Galileo while Servo 300 had a lower value. Pressurization at 300 ms on Evita 4 and Servo 300 reached 75% of the ideal value, on Galileo 35%, and on VPAP II 45%. Pressurization at 500 ms on Evita 4 and Servo 300 reached 85% of the ideal value, on Galileo 50%, and on VPAP II 55%. Cycling was delayed in obstructive conditions and premature in restrictive conditions with each of the devices. CONCLUSIONS: The VPAP II performed as well as one ICU ventilator and less well than two. Home devices for noninvasive ventilation in acute respiratory failure outside the ICU could prove attractive as they are smaller, less costly, and easier to use than ICU machines.

Comparative effects of helium-oxygen and external positive end-expiratory pressure on respiratory mechanics, gas exchange, and ventilation-perfusion relationships in mechanically ventilated patients with chronic obstructive pulmonary disease.

OBJECTIVE: To compare the effects of He/O(2) and external PEEP (PEEPe) on intrinsic PEEP (PEEPi), respiratory mechanics, gas exchange, and ventilation/perfusion (V(A)/Q) in mechanically ventilated COPD patients. DESIGN AND SETTING: Prospective, interventional study in the intensive care unit of a university hospital. INTERVENTIONS: Ten intubated, sedated, paralyzed, mechanically ventilated COPD patients studied in the following conditions: (a) baseline settings made by clinician in charge, air/O(2), ZEEP; (b) He/O(2), ZEEP; (c) air/O(2), ZEEP; (d) air/O(2), PEEPe 80% of PEEPi. Measurements at each condition included V(A)/Q by the multiple inert gas elimination technique (MIGET). RESULTS: PEEPi and trapped gas volume were comparably reduced by He/O(2) (4.2+/-4 vs. 7.7+/-4 cmH(2)O and 98+/-82 vs. 217+/-124 ml, respectively) and PEEPe (4.4+/-1.3 vs. 7.8+/-3.6 cmH(2)O and 120+/-107 vs. 216+/-115 ml, respectively). He/O(2) reduced inspiratory and expiratory respiratory system resistance (15.5+/-4.4 vs. 20.7+/-6.9 and 19+/-9 vs. 28.8+/-15 cmH(2)O l(-1)s(-1), respectively) and plateau pressure (13+/-4 vs. 17+/-6 cmH(2)O). PEEPe increased airway pressures, including total PEEP, and elastance. PaO(2)/FIO(2) was slightly reduced by He/O(2) (225+/-83 vs. 245+/-82) without significant V(A)/Q change. CONCLUSIONS: He/O(2) and PEEPe comparably reduced PEEPi and trapped gas volume. However, He/O(2) decreased airway resistance and intrathoracic pressures, at a small cost in arterial oxygenation. He/O(2) could offer an attractive option in COPD patients with PEEPi/dynamic hyperinflation.

Helium-oxygen ventilation.

Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.

Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interaction during non-invasive ventilation delivered by face mask.

PURPOSE: To determine if, compared to pressure support (PS), neurally adjusted ventilatory assist (NAVA) reduces patient-ventilator asynchrony in intensive care patients undergoing noninvasive ventilation with an oronasal face mask. METHODS: In this prospective interventional study we compared patient-ventilator synchrony between PS (with ventilator settings determined by the clinician) and NAVA (with the level set so as to obtain the same maximal airway pressure as in PS). Two 20-min recordings of airway pressure, flow and electrical activity of the diaphragm during PS and NAVA were acquired in a randomized order. Trigger delay (T(d)), the patient's neural inspiratory time (T(in)), ventilator pressurization duration (T(iv)), inspiratory time in excess (T(iex)), number of asynchrony events per minute and asynchrony index (AI) were determined. RESULTS: The study included 13 patients, six with COPD, and two with mixed pulmonary disease. T(d) was reduced with NAVA: median 35 ms (IQR 31-53 ms) versus 181 ms (122-208 ms); p = 0.0002. NAVA reduced both premature and delayed cyclings in the majority of patients, but not the median T(iex) value. The total number of asynchrony events tended to be reduced with NAVA: 1.0 events/min (0.5-3.1 events/min) versus 4.4 events/min (0.9-12.1 events/min); p = 0.08. AI was lower with NAVA: 4.9 % (2.5-10.5 %) versus 15.8 % (5.5-49.6 %); p = 0.03. During NAVA, there were no ineffective efforts, or late or premature cyclings. PaO(2) and PaCO(2) were not different between ventilatory modes. CONCLUSION: Compared to PS, NAVA improved patient ventilator synchrony during noninvasive ventilation by reducing T(d) and AI. Moreover, with NAVA, ineffective efforts, and late and premature cyclings were absent.