Comparison of neurally adjusted ventilatory assist and synchronized intermittent mandatory ventilation in preterm infants after patent ductus arteriosus ligation: a retrospective study

OBJECTIVE

This study aimed to compare the efficacy of neurally adjusted ventilatory assist (NAVA) to synchronized intermittent mandatory ventilation (SIMV) in preterm infants requiring mechanical ventilation after patent ductus arteriosus (PDA) ligation.

METHODS

A retrospective analysis was conducted on intubated preterm infants who underwent PDA ligation at our hospital from July 2021 to January 2023. Infants were divided into NAVA or SIMV groups based on the ventilation mode after surgery.

RESULTS

Fifty preterm infants were included. During treatment, peak inspiratory pressure (PIP) and mean airway pressure (MAP) were lower with NAVA compared to SIMV (PIP: 19.1 ± 2.9 vs. 22.4 ± 3.6 cmH2O, P < 0.001; MAP: 9.1 ± 1.8 vs. 10.9 ± 2.7 cmH2O, P = 0.002). PaO2 and PaO2/FiO2 were higher with NAVA (PaO2: 94.0 ± 11.7 vs. 84.8 ± 15.8 mmHg, P = 0.031; PaO2/FiO2: 267 [220-322] vs. 232 [186-290] mmHg, P = 0.025). Less sedation was required with NAVA (midazolam: 1.5 ± 0.5 vs. 1.1 ± 0.3 μg/kg/min, P < 0.001).

CONCLUSION

Compared to SIMV, early use of NAVA post PDA ligation in preterm infants was associated with decreased PIP and MAP. Early NAVA was also associated with reduced sedation needs and improved oxygenation. However, further studies are warranted to quantify the benefits of NAVA ventilation.

The Diaphragmatic Initiated Ventilatory Assist (DIVA) trial: study protocol for a randomized controlled trial comparing rates of extubation failure in extremely premature infants undergoing extubation to non-invasive neurally adjusted ventilatory assist versus non-synchronized nasal intermittent positive pressure ventilation

BACKGROUND

Invasive mechanical ventilation contributes to bronchopulmonary dysplasia (BPD), the most common complication of prematurity and the leading respiratory cause of childhood morbidity. Non-invasive ventilation (NIV) may limit invasive ventilation exposure and can be either synchronized or non-synchronized (NS). Pooled data suggest synchronized forms may be superior. Non-invasive neurally adjusted ventilatory assist (NIV-NAVA) delivers NIV synchronized to the neural signal for breathing, which is detected with a specialized catheter. The DIVA (Diaphragmatic Initiated Ventilatory Assist) trial aims to determine in infants born 240/7-276/7 weeks' gestation undergoing extubation whether NIV-NAVA compared to non-synchronized nasal intermittent positive pressure ventilation (NS-NIPPV) reduces the incidence of extubation failure within 5 days of extubation.

METHODS

This is a prospective, unblinded, pragmatic, multicenter phase III randomized clinical trial. Inclusion criteria are preterm infants 24-276/7 weeks gestational age who were intubated within the first 7 days of life for at least 12 h and are undergoing extubation in the first 28 postnatal days. All sites will enter an initial run-in phase, where all infants are allocated to NIV-NAVA, and an independent technical committee assesses site performance. Subsequently, all enrolled infants are randomized to NIV-NAVA or NS-NIPPV at extubation. The primary outcome is extubation failure within 5 days of extubation, defined as any of the following: (1) rise in FiO2 at least 20% from pre-extubation for > 2 h, (2) pH ≤ 7.20 or pCO2 ≥ 70 mmHg; (3) > 1 apnea requiring positive pressure ventilation (PPV) or ≥ 6 apneas requiring stimulation within 6 h; (4) emergent intubation for cardiovascular instability or surgery. Our sample size of 478 provides 90% power to detect a 15% absolute reduction in the primary outcome. Enrolled infants will be followed for safety and secondary outcomes through 36 weeks' postmenstrual age, discharge, death, or transfer.

DISCUSSION

The DIVA trial is the first large multicenter trial designed to assess the impact of NIV-NAVA on relevant clinical outcomes for preterm infants. The DIVA trial design incorporates input from clinical NAVA experts and includes innovative features, such as a run-in phase, to ensure consistent technical performance across sites.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov , trial identifier NCT05446272 , registered July 6, 2022.

Study protocol for a randomised cross-over trial of Neurally adjusted ventilatory Assist for Neonates with Congenital diaphragmatic hernias: the NAN-C study

BACKGROUND

Neurally adjusted ventilatory assist (NAVA) is a mode of mechanical ventilation that delivers oxygen pressures in proportion to electrical signals of the diaphragm. The proportional assistance can be adjusted by the clinician to reduce the patient's work of breathing. Several case series of infants with congenital diaphragmatic hernias (CDH) have shown that NAVA may reduce oxygenation index and mean airway pressures. To date, no clinical trial has compared NAVA to standard methods of mechanical ventilation for babies with CDH.

METHODS

The aim of this dual-centre randomised cross-over trial is to compare post-operative NAVA with assist control ventilation (ACV) for infants with CDH. If eligible, infants will be enrolled for a ventilatory support tolerance trial (VSTT) to assess their suitability for randomisation. If clinically stable during the VSTT, infants will be randomised to receive either NAVA or ACV first in a 1:1 ratio for a 4-h period. The oxygenation index, respiratory severity score and cumulative sedative medication use will be measured.

DISCUSSION

Retrospective studies comparing NAVA to ACV in neonates with congenital diaphragmatic hernia have shown the ventilatory mode may improve respiratory parameters and benefit neonates. To our knowledge, this is the first prospective cross-over trial comparing NAVA to ACV.

TRIAL REGISTRATION

NAN-C was prospectively registered on ClinicalTrials.gov NCT05839340  Registered on May 2023.

Neurally adjusted ventilatory assist in infants: A review article

Neurally adjusted ventilatory assist (NAVA) and non-invasive (NIV)-NAVA are innovative modes of synchronized and proportional respiratory support. They can synchronize with the patients' breathing and promote patient comfort. Both techniques are increasingly being used these years, however experience with their use in newborns and premature infants in Taiwan is relatively few. Because increasing evidence supports the use of NAVA and NIV-NAVA in newborns and premature infants requiring respiratory assist to achieve better synchrony, the aim of this article is to discuss whether NAVA can provide better synchronization and comfort for ventilated newborns and premature babies. In a review of recent literature, we found that NAVA and NIV-NAVA appear to be superior to conventional invasive and non-invasive ventilation. Nevertheless, some of the benefits are controversial. For example, treatment failure in premature infants is common due to insufficient triggering of electrical activity of the diaphragm (EAdi) and frequent apnea, highlighting the differences between premature infants and adults in settings and titration. Further, we suggest how to adjust the settings of NAVA and NIV-NAVA in premature infants to reduce clinical adverse events and extubation failure. In addition to assist in the use of NAVA, EAdi can also serve as a continuous and real-time monitor of vital signs, assisting physicians in the administration of sedatives, evaluation of successful extubation, and as a reference for the patient's respiratory condition during special procedures.

Implementation of neurally adjusted ventilatory assist and high flow nasal cannula in very preterm infants in a tertiary level NICU

Preterm infants treated with invasive ventilation are often affected by bronchopulmonary dysplasia, brain structure alterations, and later neurodevelopmental impairment. We studied the implementation of neurally adjusted ventilatory assist (NAVA) and high flow nasal cannula (HFNC) in a level III neonatal unit, and its effects on pulmonary and central nervous system outcomes. This retrospective cohort study included 193 surviving infants born below 32 weeks of gestation in preimplementation (2007-2008) and postimplementation (2016-2017) periods in a single study center in Finland. The proportion of infants requiring invasive ventilation decreased from 67% in the pre- to 48% in the postimplementation period (p = 0.009). Among infants treated with invasive ventilation, 68% were treated with NAVA after its implementation. At the same time, the duration of invasive ventilation of infants born at or below 28 weeks increased threefold compared with the preimplementation period (p = 0.042). The postimplementation period was characterized by a gradual replacement of nasal continuous positive airway pressure (nCPAP) with HFNC, earlier discontinuation of nCPAP, but a longer duration of positive pressure support. The proportion of normal magnetic resonance imaging (MRI) findings at term corrected age increased from 62% to 84% (p = 0.018). Cognitive outcome improved by one standard score between the study periods (p = 0.019). NAVA was used as the primary mode of ventilation in the postimplementation period. During this period, invasive ventilation time was significantly prolonged. HFNC led to a decrease in the use of nCPAP. The change in the respiratory support might have contributed to the improvement in brain MRI findings and cognitive outcomes.

Successful conservative managements of extensive pneumatoceles in a preterm girl: A case report

We describe a preterm girl with severe respiratory distress syndrome, which was managed with mechanical ventilation. She developed severe ventilator induced lung injury, causing extensive unilateral emphysema. CT-scan of the lungs corresponded with extensive pneumatoceles. She was managed conservatively, using neurally adjusted ventilatory assist, with success and was extubated on day of life 38. She was discharged home without any respiratory support at 39 weeks of postmenstrual age. Our case illustrates the ongoing risk of severe ventilator induced lung injury and highlights a unique injury pattern in a preterm newborn that was managed conservatively using neurally adjusted ventilatory assist with an excellent outcome.

Cognitive function and mood at high altitude following acclimatization and use of supplemental oxygen and adaptive servoventilation sleep treatments

Impairments in cognitive function, mood, and sleep quality occur following ascent to high altitude. Low oxygen (hypoxia) and poor sleep quality are both linked to impaired cognitive performance, but their independent contributions at high altitude remain unknown. Adaptive servoventilation (ASV) improves sleep quality by stabilizing breathing and preventing central apneas without supplemental oxygen. We compared the efficacy of ASV and supplemental oxygen sleep treatments for improving daytime cognitive function and mood in high-altitude visitors (N = 18) during acclimatization to 3,800 m. Each night, subjects were randomly provided with ASV, supplemental oxygen (SpO2 > 95%), or no treatment. Each morning subjects completed a series of cognitive function tests and questionnaires to assess mood and multiple aspects of cognitive performance. We found that both ASV and supplemental oxygen (O2) improved daytime feelings of confusion (ASV: p < 0.01; O2: p < 0.05) and fatigue (ASV: p < 0.01; O2: p < 0.01) but did not improve other measures of cognitive performance at high altitude. However, performance improved on the trail making tests (TMT) A and B (p < 0.001), the balloon analog risk test (p < 0.0001), and the psychomotor vigilance test (p < 0.01) over the course of three days at altitude after controlling for effects of sleep treatments. Compared to sea level, subjects reported higher levels of confusion (p < 0.01) and performed worse on the TMT A (p < 0.05) and the emotion recognition test (p < 0.05) on nights when they received no treatment at high altitude. These results suggest that stabilizing breathing (ASV) or increasing oxygenation (supplemental oxygen) during sleep can reduce feelings of fatigue and confusion, but that daytime hypoxia may play a larger role in other cognitive impairments reported at high altitude. Furthermore, this study provides evidence that some aspects of cognition (executive control, risk inhibition, sustained attention) improve with acclimatization.

Feasibility of Non-invasive Neurally Adjusted Ventilator Assist After Congenital Diaphragmatic Hernia Repair

BACKGROUND

The use of neurally adjusted ventilator assist (NAVA) in congenital diaphragmatic hernia (CDH) patients has been historically deemed unwise, since the trigger for breaths is the electromyographic activity of the diaphragmatic muscle. We report on our NAVA experience in CDH patients.

METHODS

We performed an IRB-approved retrospective review of newborns from 1/1/2012-1/1/2017 at a Level I Children's Surgery Center undergoing CDH repair. Data obtained included demographics, defect type and repair, respiratory support, and outcomes.

RESULTS

Seven infants with CDH were placed on noninvasive-NAVA (NIV-NAVA) after extubation. All seven patients underwent open transabdominal repair, with five requiring patch repair. All survived to discharge, and one year after birth. When we compared this group to a contemporary cohort of patients who also underwent CDH repair, we found no significant differences in birth weight, postmenstrual age, or gender. However, there was a significantly higher need for inhaled nitric oxide (p = 0.002), high frequency oscillatory ventilation (p = 0.016), and extracorporeal membranous oxygenation support (p = 0.045) in the NIV-NAVA cohort.

CONCLUSION

This is the first report of NIV-NAVA being successfully utilized as an adjunct to wean infants from conventional ventilation after CDH repair, even in those who require patch repair or with more significant disease severity.

LEVELS OF EVIDENCE

III- Retrospective Comparative Study.

Adaptive Servoventilation as Treatment for Central Sleep Apnea Due to High-Altitude Periodic Breathing in Nonacclimatized Healthy Individuals

Orr, Jeremy E., Erica C. Heinrich, Matea Djokic, Dillon Gilbertson, Pamela N. Deyoung, Cecilia Anza-Ramirez, Francisco C. Villafuerte, Frank L. Powell, Atul Malhotra, and Tatum Simonson. Adaptive servoventilation as treatment for central sleep apnea due to high-altitude periodic breathing in nonacclimatized healthy individuals. High Alt Med Biol. 19:178-184, 2018.

AIMS

Central sleep apnea (CSA) is common at high altitude, leading to desaturation and sleep disruption. We hypothesized that noninvasive ventilation using adaptive servoventilation (ASV) would be effective at stabilizing CSA at altitude. Supplemental oxygen was evaluated for comparison.

METHODS

Healthy subjects were brought from sea level to 3800 m and underwent polysomnography on three consecutive nights. Subjects underwent each condition-No treatment, ASV, and supplemental oxygen-in random order. The primary outcome was the effect of ASV on oxygen desaturation index (ODI). Secondary outcomes included oxygen saturation, arousals, symptoms, and comparison to supplemental oxygen.

RESULTS

Eighteen subjects underwent at least two treatment conditions. There was a significant difference in ODI across the three treatments. There was no statistical difference in ODI between no treatment and ASV (17.1 ± 4.2 vs. 10.7 ± 2.9 events/hour; p > 0.17) and no difference in saturation or arousal index. Compared with no treatment, oxygen improved the ODI (16.5 ± 4.5 events/hour vs. 0.5 ± 0.2 events/hour; p < 0.003), in addition to saturation and arousal index.

CONCLUSIONS

We found that ASV was not clearly efficacious at controlling CSA in persons traveling to 3800 m, whereas supplemental oxygen resolved CSA. Adjustment in the ASV algorithm may improve efficacy. ASV may have utility in acclimatized persons or at more modest altitudes.

Neurally adjusted ventilatory assist compared to other forms of triggered ventilation for neonatal respiratory support

BACKGROUND

Effective synchronisation of infant respiratory effort with mechanical ventilation may allow adequate gas exchange to occur at lower peak airway pressures, potentially reducing barotrauma and volutrauma and development of air leaks and bronchopulmonary dysplasia. During neurally adjusted ventilatory assist ventilation (NAVA), respiratory support is initiated upon detection of an electrical signal from the diaphragm muscle, and pressure is provided in proportion to and synchronous with electrical activity of the diaphragm (EADi). Compared to other modes of triggered ventilation, this may provide advantages in improving synchrony.

OBJECTIVES

Primary• To determine whether NAVA, when used as a primary or rescue mode of ventilation, results in reduced rates of bronchopulmonary dysplasia (BPD) or death among term and preterm newborn infants compared to other forms of triggered ventilation• To assess the safety of NAVA by determining whether it leads to greater risk of intraventricular haemorrhage (IVH), periventricular leukomalacia, or air leaks when compared to other forms of triggered ventilation Secondary• To determine whether benefits of NAVA differ by gestational age (term or preterm)• To determine whether outcomes of cross-over trials performed during the first two weeks of life include peak pressure requirements, episodes of hypocarbia or hypercarbia, oxygenation index, and the work of breathing SEARCH METHODS: We performed searches of the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cohrane Library; MEDLINE via Ovid SP (January 1966 to March 2017); Embase via Ovid SP (January 1980 to March 2017); the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCO host (1982 to March 2017); and the Web of Science (1985 to 2017). We searched abstracts from annual meetings of the Pediatric Academic Societies (PAS) (2000 to 2016); meetings of the European Society of Pediatric Research (published in Pediatric Research); and meetings of the Perinatal Society of Australia and New Zealand (PSANZ) (2005 to 2016). We also searched clinical trials databases to March 2017.

SELECTION CRITERIA

We included randomised and quasi-randomised clinical trials including cross-over trials comparing NAVA with other modes of triggered ventilation (assist control ventilation (ACV),synchronous intermittent mandatory ventilation plus pressure support (SIMV ± PS), pressure support ventilation (PSV), or proportional assist ventilation (PAV)) used in neonates.

DATA COLLECTION AND ANALYSIS

Primary outcomes of interest from randomised controlled trials were all-cause mortality, bronchopulmonary dysplasia (BPD; defined as oxygen requirement at 28 days), and a combined outcome of all-cause mortality or BPD. Secondary outcomes were duration of mechanical ventilation, incidence of air leak, incidence of IVH or periventricular leukomalacia, and survival with an oxygen requirement at 36 weeks' postmenstrual age.Outcomes of interest from cross-over trials were maximum fraction of inspired oxygen, mean peak inspiratory pressure, episodes of hypocarbia, and episodes of hypercarbia measured across the time period of each arm of the cross-over. We planned to assess work of breathing; oxygenation index, and thoraco-abdominal asynchrony at the end of the time period of each arm of the cross-over study.

MAIN RESULTS

We included one randomised controlled study comparing NAVA versus patient-triggered time-cycled pressure-limited ventilation. This study found no significant difference in duration of mechanical ventilation, nor in rates of BPD, pneumothorax, or IVH.

AUTHORS' CONCLUSIONS

Risks and benefits of NAVA compared to other forms of ventilation for neonates are uncertain. Well-designed trials are required to evaluate this new form of triggered ventilation.

Feasibility and physiological effects of noninvasive neurally adjusted ventilatory assist in preterm infants

BackgroundNoninvasive neurally adjusted ventilator assist (NIV-NAVA) was introduced to our clinical practice via a pilot and a randomized observational study to assess its safety, feasibility, and short-term physiological effects.MethodsThe pilot protocol applied NIV-NAVA to 11 infants on nasal CPAP, high-flow nasal cannula, or nasal intermittent mandatory ventilation (NIMV), in multiple 2- to 4-h periods of NIV-NAVA for comparison. This provided the necessary data to design a randomized, controlled observational crossover study in eight additional infants to compare the physiological effects of NIV-NAVA with NIMV during 2-h steady-state conditions. We recorded the peak inspiratory pressure (PIP), FiO2, Edi, oxygen saturations (histogram analysis), transcutaneous PCO2, and movement with an Acoustic Respiratory Movement Sensor.ResultsThe NAVA catheter was used for 81 patient days without complications. NIV-NAVA produced significant reductions (as a percentage of measurements on NIMV) in the following: PIP, 13%; FiO2, 13%; frequency of desaturations, 42%; length of desaturations, 32%; and phasic Edi, 19%. Infant movement and caretaker movement were reduced by 42% and 27%, respectively. Neural inspiratory time was increased by 39 ms on NIV-NAVA, possibly due to Head's paradoxical reflex.ConclusionNIV-NAVA was a safe, alternative mode of noninvasive support that produced beneficial short-term physiological effects, especially compared with NIMV.

Non-invasive ventilation with intelligent volume-assured pressure support versus pressure-controlled ventilation: effects on the respiratory event rate and sleep quality in COPD with chronic hypercapnia

BACKGROUND

COPD patients who develop chronic hypercapnic respiratory failure have a poor prognosis. Treatment of choice, especially the best form of ventilation, is not well known.

OBJECTIVES

This study compared the effects of pressure-controlled (spontaneous timed [ST]) non-invasive ventilation (NIV) and NIV with intelligent volume-assured pressure support (IVAPS) in chronic hypercapnic COPD patients regarding the effects on alveolar ventilation, adverse patient/ventilator interactions and sleep quality.

METHODS

This prospective, single-center, crossover study randomized patients to one night of NIV using ST then one night with the IVAPS function activated, or vice versa. Patients were monitored using polysomnography (PSG) and transcutaneous carbon dioxide pressure (PtcCO2) measurement. Patients rated their subjective experience (total score, 0-45; lower scores indicate better acceptability).

RESULTS

Fourteen patients were included (4 females, age 59.4±8.9 years). The total number of respiratory events was low, and similar under pressure-controlled (5.4±6.7) and IVAPS (8.3±10.2) conditions (P=0.064). There were also no clinically relevant differences in PtcCO2 between pressure-controlled and IVAPS NIV (52.9±6.2 versus 49.1±6.4 mmHg). Respiratory rate was lower under IVAPS overall; between-group differences reached statistical significance during wakefulness and non-rapid eye movement sleep. Ventilation pressures were 2.6 cmH2O higher under IVAPS versus pressure-controlled ventilation, resulting in a 20.1 mL increase in breathing volume. Sleep efficiency was slightly higher under pressure-controlled ventilation versus IVAPS. Respiratory arousals were uncommon (24.4/h [pressure-controlled] versus 25.4/h [IVAPS]). Overall patient assessment scores were similar, although there was a trend toward less discomfort during IVAPS.

CONCLUSION

Our results show that IVAPS NIV allows application of higher nocturnal ventilation pressures versus ST without affecting sleep quality or inducing ventilation- associated events.

Neurally adjusted ventilatory assist as an alternative to pressure support ventilation in adults: a French multicentre randomized trial

PURPOSE

Neurally adjusted ventilatory assist (NAVA) is a ventilatory mode that tailors the level of assistance delivered by the ventilator to the electromyographic activity of the diaphragm. The objective of this study was to compare NAVA and pressure support ventilation (PSV) in the early phase of weaning from mechanical ventilation.

METHODS

A multicentre randomized controlled trial of 128 intubated adults recovering from acute respiratory failure was conducted in 11 intensive care units. Patients were randomly assigned to NAVA or PSV. The primary outcome was the probability of remaining in a partial ventilatory mode (either NAVA or PSV) throughout the first 48 h without any return to assist-control ventilation. Secondary outcomes included asynchrony index, ventilator-free days and mortality.

RESULTS

In the NAVA and PSV groups respectively, the proportion of patients remaining in partial ventilatory mode throughout the first 48 h was 67.2 vs. 63.3 % (P = 0.66), the asynchrony index was 14.7 vs. 26.7 % (P < 0.001), the ventilator-free days at day 7 were 1.0 day [1.0-4.0] vs. 0.0 days [0.0-1.0] (P < 0.01), the ventilator-free days at day 28 were 21 days [4-25] vs. 17 days [0-23] (P = 0.12), the day-28 mortality rate was 15.0 vs. 22.7 % (P = 0.21) and the rate of use of post-extubation noninvasive mechanical ventilation was 43.5 vs. 66.6 % (P < 0.01).

CONCLUSIONS

NAVA is safe and feasible over a prolonged period of time but does not increase the probability of remaining in a partial ventilatory mode. However, NAVA decreases patient-ventilator asynchrony and is associated with less frequent application of post-extubation noninvasive mechanical ventilation.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02018666.

[The influence of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation]

OBJECTIVE

To study the effects of condensate in the piezometric tube on patient ventilator interaction during noninvasive positive pressure ventilation.

METHODS

Eleven healthy adults volunteered to receive noninvasive positive pressure ventilation. Different capacity of physiological saline was injected gradually into the piezometric tube until the volunteers could not trigger the ventilator or the total volume of the water reached 1.5 ml. The dynamic changes of the pressure of mask(Pmask), piezometric tube near mask (Ppro), piezometric tube near breathing machine(Pdis), and the flow were observed.

RESULTS

With increasing volume of saline injected, the trigger time TItri(Pmask) increased from 0.09(0.07-0.11) to 0.31(0.22-0.39)s, the trigger pressure TPtri(Pmask) increased from 0.26(0.15-0.33) to 2.29(1.76-3.09)cmH2O, and the pressure-time product PTP (Pmask) increased from 0.02(0.01-0.03) to 0.55(0.41-0.68) cmH2O·s. Ineffective triggering rate increased from 0 up to 9 times/min, and spurious triggering rate increased from 0 up to 33 times/min. The plateau pressure of Pmask and Ppro exceeded the preset parameters, increased significantly as compared with 0 ml, from (9.74±0.34)to (15.79±3.10) cmH2O and from(9.80±0.31) to(15.44±3.47) cmH2O. The change of plateau pressure of Pdis was not significant [from (9.85±0.29)to (12.58±2.64)cmH2O]. The baseline pressure of Pmask, Ppro and Pdis changed from (3.67±0.36) to (8.40±3.22) cmH2O, from (3.71±0.32) to (8.13±3.55) cmH2O and from( 3.77±0.32) to (5.36±1.25) cmH2O, respectively. The pressure fluctuation of platform of Pmask increased significantly compare with 0 ml, from 0.60(0.48-0.71) to 7.94(7.11-8.63)cmH2O. The frequency of fluctuation of platform increased as many as 7 times during a single respiratory period. The time when the pressure of the Pdis began to change was delayed to Pmask and Ppro, 0.11(0.08-0.12)s compared with 0 ml.

CONCLUSION

Condensate in the piezometric tube during noninvasive positive pressure ventilation could influence patient-ventilator synchrony. To improve patient ventilator interaction in noninvasive positive pressure ventilation, condensate in the piezometric tube should be avoided.

Treatment of neonates with meconium aspiration syndrome by proportional assist ventilation and synchronized intermittent mandatory ventilation: a comparison study

BACKGROUND

This study aimed to compare the relevant clinical parameters of neonates with MAS who are supported by proportion assisted ventilation (PAV) and synchronized intermittent mandatory ventilation (SIMV).

METHODS

Forty neonates diagnosed as MAS who required mechanical ventilation were divided randomly into PAV group and SIMV group (N.=20). The respiratory rate (RR), heart rate (HR), peak inspiratory pressure (PIP), mean arterial blood pressure (MABP), arterial-to-alveolar oxygen tension ratio (a/APO2), fraction of inspiration oxygen (FiO2), mean airway pressure (MAP) and tidal volume (VT) were measured before the ventilation, 1,12, 24, 48 hours after the ventilation and before weaning.

RESULTS

We observed no significant differences in the mechanical ventilation time, oxygen supply time, hospital stay between PAV and SIMV groups. In addition, we found no significant differences in HR, MABP, a/APO2 and FiO2 at every time point between two groups (P>0.05). However, we observed significant differences in RR, MAP, PIP and VT at every time point between two groups (P<0.05).

CONCLUSIONS

PAV and SIMV might be a useful ventilator mode to support the neonates with MAS who require ventilation. To achieve the same effect, PAV adopts rapid shallow breathing pattern, with smaller tidal volume and lower MAP and PIP.

Neurally-adjusted ventilatory assist (NAVA) in children: a systematic review

INTRODUCTION

Application of mechanical ventilation in spontaneously breathing children remains a challenge for several reasons: mainly, small tidal volumes and high respiratory rates, especially in the presence of leaks, interfere with patient-ventilator synchrony. Leaks also cause unreliable monitoring of respiratory drive and respiratory rate. Furthermore, ventilator adjustment must take into account that infants have strong vagal reflexes, demonstrate central apnea and periodic breathing, with a high variability in breathing pattern. Neurally-adjusted ventilatory assist (NAVA) is a mode of ventilation whereby the timing and amount of ventilatory assist is controlled by the patient's neural respiratory drive. Since NAVA uses the diaphragm electrical activity (Edi) as the controller signal, it is possible to deliver synchronized assist, both invasively and non-invasively (NIV-NAVA), to follow the variability in breathing pattern, and to monitor patient respiratory drive, independent of leaks.

EVIDENCE ACQUISITION

This article provides a review of the scientific literature pertaining to the use of NAVA in children (neonatal and pediatric age groups). Both the invasive and non-invasive NAVA publications are summarized, as well as the use of Edi monitoring.

EVIDENCE SYNTHESIS

Overall, the use of NAVA and Edi monitoring is feasible and safe. Compared to conventional ventilation, NAVA improves patient-ventilator interaction, and provides lower peak inspiratory pressure.

CONCLUSIONS

Evidence from a few trials suggests improved comfort, less sedation, and reduced length of stay.

In vitro assessment of the effect of proportional assist ventilation on the work of breathing

During proportional assist ventilation, elastic and resistive unloading can be delivered to reduce the work of breathing (WOB). Our aim was to determine the effects of different levels of elastic and resistive unloading on the WOB in lung models designed to mimic certain neonatal respiratory disorders. Two dynamic lung models were used, one with a compliance of 0.4 ml/cm H2O to mimic an infant with respiratory distress syndrome and one with a resistance of 300 cm H2O/l/s to mimic an infant with bronchopulmonary dypslasia. Pressure volume curves were constructed at each unloading level. Elastic unloading in the low compliance model was highly effective in reducing the WOB measured in the lung model; the effective compliance increased from 0.4 ml/cm H2O at baseline to 4.1 ml/cm H2O at maximum possible elastic unloading (2.0 cm H2O/ml). Maximum possible resistive unloading (200 cm H2O/l/s) in the high-resistance model only reduced the effective resistance from 300 to 204 cm H2O/l/s. At maximum resistive unloading, oscillations appeared in the airway pressure waveform.

CONCLUSION

Our results suggest that elastic unloading will be helpful in respiratory conditions characterised by a low compliance, but resistive unloading as currently delivered is unlikely to be of major clinical benefit.

WHAT IS KNOWN

• During PAV, the ventilator can provide elastic and resistive unloading. What is New: • Elastic unloading was highly effective in reducing the work of breathing. • Maximum resistive unloading only partially reduced the effective resistance.

Health economic modeling of the potential cost saving effects of Neurally Adjusted Ventilator Assist

OBJECTIVES

Asynchrony between patient and ventilator breaths is associated with increased duration of mechanical ventilation (MV). Neurally Adjusted Ventilatory Assist (NAVA) controls MV through an esophageal reading of diaphragm electrical activity via a nasogastric tube mounted with electrode rings. NAVA has been shown to decrease asynchrony in comparison to pressure support ventilation (PSV). The objective of this study was to conduct a health economic evaluation of NAVA compared with PSV.

METHODS

We developed a model based on an indirect link between improved synchrony with NAVA versus PSV and fewer days spent on MV in synchronous patients. Unit costs for MV were obtained from the Swedish intensive care unit register, and used in the model along with NAVA-specific costs. The importance of each parameter (proportion of asynchronous patients, costs, and average MV duration) for the overall results was evaluated through sensitivity analyses.

RESULTS

Base case results showed that 21% of patients ventilated with NAVA were asynchronous versus 52% of patients receiving PSV. This equals an absolute difference of 31% and an average of 1.7 days less on MV and a total cost saving of US$7886 (including NAVA catheter costs). A breakeven analysis suggested that NAVA was cost effective compared with PSV given an absolute difference in the proportion of asynchronous patients greater than 2.5% (49.5% versus 52% asynchronous patients with NAVA and PSV, respectively). The base case results were stable to changes in parameters, such as difference in asynchrony, duration of ventilation and daily intensive care unit costs.

CONCLUSION

This study showed economically favorable results for NAVA versus PSV. Our results show that only a minor decrease in the proportion of asynchronous patients with NAVA is needed for investments to pay off and generate savings. Future studies need to confirm this result by directly relating improved synchrony to the number of days on MV.

Assisted mechanical ventilation: the future is now!

Assisted ventilation is a highly complex process that requires an intimate interaction between the ventilator and the patient. The complexity of this form of ventilation is frequently underappreciated by the bedside clinician. In assisted mechanical ventilation, regardless of the specific mode, the ventilator's gas delivery pattern and the patient's breathing pattern must match near perfectly or asynchrony between the patient and the ventilator occurs. Asynchrony can be categorized into four general types: flow asynchrony; trigger asynchrony; cycle asynchrony; and mode asynchrony. In an article recently published in BMC Anesthesiology, Hodane et al. have demonstrated reduced asynchrony during assisted ventilation with Neurally Adjusted Ventilatory Assist (NAVA) as compared to pressure support ventilation (PSV). These findings add to the growing volume of data indicating that modes of ventilation that provide proportional assistance to ventilation - e.g., NAVA and Proportional Assist Ventilation (PAV) - markedly reduce asynchrony. As it becomes more accepted that the respiratory center of the patient in most circumstances is the most appropriate determinant of ventilatory pattern and as the negative outcome effects of patient-ventilator asynchrony become ever more recognized, we can expect NAVA and PAV to become the preferred modes of assisted ventilation!

The Esophageal Pressure-Guided Ventilation 2 (EPVent2) trial protocol: a multicentre, randomised clinical trial of mechanical ventilation guided by transpulmonary pressure

INTRODUCTION

Optimal ventilator management for patients with acute respiratory distress syndrome (ARDS) remains uncertain. Lower tidal volume ventilation appears to be beneficial, but optimal management of positive end-expiratory pressure (PEEP) remains unclear. The Esophageal Pressure-Guided Ventilation 2 Trial (EPVent2) aims to examine the impact of mechanical ventilation directed at maintaining a positive transpulmonary pressure (PTP) in patients with moderate-to-severe ARDS.

METHODS AND ANALYSIS

EPVent2 is a multicentre, prospective, randomised, phase II clinical trial testing the hypothesis that the use of a PTP-guided ventilation strategy will lead to improvement in composite outcomes of mortality and time off the ventilator at 28 days as compared with a high-PEEP control. This study will enrol 200 study participants from 11 hospitals across North America. The trial will utilise a primary composite end point that incorporates death and days off the ventilator at 28 days to test the primary hypothesis that adjusting ventilator pressure to achieve positive PTP values will result in improved mortality and ventilator-free days.

ETHICS AND DISSEMINATION

Safety oversight will be under the direction of an independent Data and Safety Monitoring Board (DSMB). Approval of the protocol was obtained from the DSMB prior to enrolling the first study participant. Approvals of the protocol as well as informed consent documents were also obtained from the Institutional Review Board of each participating institution prior to enrolling study participants at each respective site. The findings of this investigation, as well as associated ancillary studies, will be disseminated in the form of oral and abstract presentations at major national and international medical specialty meetings. The primary objective and other significant findings will also be presented in manuscript form. All final, published manuscripts resulting from this protocol will be submitted to PubMed Central in accordance with the National Institute of Health Public Access Policy.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov under number NCT01681225.

[Application of lung recruitment maneuver in preterm infants with respiratory distress syndrome ventilated by proportional assist ventilation]

OBJECTIVE

To understand the effect of lung recruitment maneuver (LRM) with positive end-expiratory pressure (PEEP) on oxygenation and outcomes in preterm infants with respiratory distress syndrome (RDS) ventilated by proportional assist ventilation (PAV).

METHOD

From January 2012 to June 2013, thirty neonates with a diagnosis of RDS who required mechanical ventilation were divided randomly into LRM group (n=15, received an LRM and surport by PAV) and control group (n=15, only surport by PAV). There were no statistically significant differences in female (7 vs. 6); gestational age [(29.3±1.2) vs. (29.5±1.1) weeks]; body weight[(1,319±97) vs. (1,295±85) g]; Silverman Anderson(SA) score for babies at start of ventilation (7.3±1.2 vs. 6.9±1.4); initial FiO2 (0.54±0.12 vs. 0.50±0.10) between the two groups (all P>0.05). LRM entailed increments of 0.2 cmH2O (1 cmH2O=0.098 kPa) PEEP every 5 minutes, until fraction of inspired oxygen (FiO2)=0.25. Then PEEP was reduced and the lung volume was set on the deflation limb of the pressure/volume curve.When saturation of peripheral oxygen fell and FiO2 rose, we reincremented PEEP until SpO2 became stable. The related clinical indicators of the two group were observed.

RESULT

The doses of surfactant administered (1.1±0.3 vs. 1.5±0.5, P=0.027), Lowest FiO2 (0.29±0.05 vs. 0.39±0.06, P=0.000), time to lowest FiO2[ (103±18) vs. (368±138) min, P=0.000] and O2 dependency [(7.6±1.0) vs.( 8.8±1.3) days, P=0.021] in LRM group were lower than that in control group (all P<0.05). The maximum PEEP during the first 12 hours of life [(8.4±0.8) vs. (6.8±0.8) cmH2O, P=0.000] in LRM group were higher than that in control group (P<0.05). FiO2 levels progressively decreased (F=35.681, P=0.000) and a/AO2 Gradually increased (F=37.654, P=0.000). No adverse events and no significant differences in the outcomes were observed.

CONCLUSION

LRM can reduce the doses of pulmonary surfactant administered, time of the respiratory support and the oxygen therapy in preterm children with RDS.

[NEURALLY ADJUSTED VENTILATORY ASSIST (NAVA)]

Neurally Adjusted Ventilatory Assist (NAVA) is a new mode of mechanic ventilation and it's based on the electrical signal of the dia- phragm activity (Edi) for the ventilation control. This signal directly represents the central ventilatory drive reflecting the duration, frequency and intensity that the patient wants to ventilate. To capture the diaphragmatic electrical impulse, is required some specific electrodes inserted in a probe nasogastric tube. For this mode, depending upon proper placement positioning and care (probe Edi), the nurse is essential for their proper functioning.

Adaptive servoventilation for treatment of opioid-associated central sleep apnea

RATIONALE

Opioids have become part of contemporary treatment in the management of chronic pain. Although severe daytime ventilatory depression is uncommon, chronic use of opioids could be associated with severe central and obstructive sleep apnea.

OBJECTIVES

To determine the acute efficacy, and prolonged use of adaptive servoventilation (ASV) to treat central sleep apnea in patients on chronic opioids.

METHODS

Twenty patients on opioid therapy referred for evaluation of obstructive sleep apnea (OSA) were found to have central sleep apnea (CSA). The first 16 patients underwent continuous positive airway pressure (CPAP) titration, which showed persistent CSA. With the notion that CSA will be eliminated with continued use of CPAP, 4 weeks later, 9 of the 16 patients underwent a second CPAP titration which proved equally ineffective. Therefore, therapy with CPAP was abandoned. All patients underwent ASV titration.

MAIN RESULTS

Diagnostic polysomnography showed an average apnea-hypopnea index (AHI) of 61/h and a central-apnea index (CAI) of 32/h. On CPAP 1, AHI was 34/h and CAI was 20/h. Respective indices on CPAP 2 were AHI 33/h and CAI 19/h. During titration with ASV, CAI was 0/h and the average HI was 11/h on final pressures. With a reduction in AHI, oxyhemoglobin saturation nadir increased from 83% to 90%, and arousal index decreased from 29/h of sleep to 12/h on final ASV pressures. Seventeen patients were followed for a minimum of 9 months and up to 6 years. The mean long-term adherence was 5.1 ± 2.5 hours.

CONCLUSIONS

Chronic use of opioids could be associated with severe CSA which remains resistant to CPAP therapy. ASV device is effective in the treatment of CSA and over the long run, most patients remain compliant with the device. Randomized long-term studies are necessary to determine if treatment of sleep apnea with ASV improves quality of life and the known mortality associated with opioids.

A control system for mechanical ventilation of passive and active subjects

Synchronization of spontaneous breathing with breaths supplied by the ventilator is essential for providing optimal ventilation to patients on mechanical ventilation. Some ventilation techniques such as Adaptive Support Ventilation (ASV), Proportional Assist Ventilation (PAV), and Neurally Adjusted Ventilatory Assist (NAVA) are designed to address this problem. In PAV, the pressure support is proportional to the patient's ongoing effort during inspiration. However, there is no guarantee that the patient receives adequate ventilation. The system described in this article is designed to automatically control the support level in PAV to guarantee delivery of patient's required ventilation. This system can also be used to control the PAV support level based on the patient's work of breathing. This technique further incorporates some of the features of ASV to deliver mandatory breaths for passive subjects. The system has been tested by using computer simulations and the controller has been implemented by using a prototype.

Inappropriate use of neurally adjusted ventilator assist

Neurally adjusted ventilator assist (NAVA) is a ventilator mode based on providing assistance to the patient in proportion to the electrical activity of the diaphragm. NAVA may improve patient-ventilator interactions. We describe a very complex case of a child with a permanent ventricular assist device where we attempted to use NAVA during the weaning process and then realised that it was impossible to use.