神经电活动辅助通气和压力支持通气对呼吸衰竭患者呼吸形式的影响

目的观察神经电活动辅助通气（NAVA）和压力支持通气（PSV）对急性呼吸衰竭患者呼吸形式的影响。 方法以2018年1月至2019年6月入住苏北人民医院ICU的12例急性呼吸衰竭行机械通气患者为研究对象,随机选择NAVA或PSV模式进行通气,NAVA和PSV通气支持水平均从5 cmH₂O（1 cmH₂O=0.098 kPa）开始,分4步递增,每10 min增加1次。PSV压力支持水平分别为5、10、15、20 cmH₂O,分别记为PSV1~4组。NAVA组的支持水平每10 min增加1倍,分别为起始NAVA支持水平的1、2、3、4倍,分别记为HAVA1~4组。观察不同支持条件下（PSV1~4组及NAVA1~4组）潮气量（V_T）、气道峰压（Ppeak）、呼吸机通气频率（VRR）、中枢呼吸频率（NRR）、膈肌电活动峰值（EAdipeak）、动脉血二氧化碳分压（PaCO₂）、无效触发发生情况、呼吸机送气时间（T_i-flow）、呼吸机呼气时间（T_e-flow）、神经吸气时间（T_i-neu）、神经呼气时间（T_e-neu）、总体V_T变异度等指标。 结果（1）随着通气支持水平的增加,PSV1~4组V_T、无效触发显著增加,VRR、NRR均明显减慢,组内比较差异均有统计学意义（F=13.471,F=30.521,F=13.672,F=9.357,P＜0.05）;PSV3~4组的V_T较同时点NAVA3~4组均显著增加,PSV4组无效触发显著高于NAVA4组,差异均有统计学意义（P＜0.05）;NAVA1~4组组内各时点的V_T比较,差异无统计学意义（P＞0.05）。（2）随着通气支持水平的增加,PSV1~4组组内各时点的T_i-neu,以及NAVA1~4组组内各时点的T_i-flow、T_e-flow、T_i-neu、T_e-neu均无显著增加,差异无统计学意义（P＞0.05）;PSV1~4组T_i-flow、T_e-flow、T_e-neu显著增加,组内比较差异均有统计学意义（F=9.564,F=13.431,F=21.126,P＜0.05）;PSV4组T_i-flow、T_e-flow、T_e-neu分别显著高于NAVA4组,差异均有统计学意义（P均＜0.05）。（3）NAVA组总体V_T变异度显著高于PSV组,差异有统计学意义（P＜0.05）;NAVA组Ppeak和EAdi显著相关（r=0.96±0.14,P＜0.05）。（4）PSV4组的PaCO₂较PSV1组显著降低,差异有统计学意义（P＜0.05）。 结论与PSV相比,NAVA通气支持时间、通气支持水平与自身呼吸形式更加匹配,对呼吸形式影响更小,一定程度上避免通气不足和过度通气。     

Noninvasive pressure support versus proportional assist ventilation in acute respiratory failure

Background Although conventional pressure ventilation (PSV) decreases the rate of intubation in acute respiratory failure, patient-ventilator dyssynchrony is a frequent cause of failure. In proportional assist ventilation (PAV), pressure is applied by the ventilator in proportion to the patient-generated volume and flow; therefore, there is automatic synchrony between the patient's effort and the ventilatory cycle.Objective The aim of this study was to compare the effects of PSV and PAV during noninvasive ventilation in the treatment of acute respiratory failure.Design Prospective randomised study.Setting A multidisciplinary 24-bed intensive care unit of an acute-care teaching hospital in Alicante, Spain.Patients This study included 117 consecutive adult patients with acute respiratory failure randomised to noninvasive ventilation delivered by PSV (n = 59) or PAV (n = 58).Measurements and results There were no statistically significant differences between patients assigned to each mode of ventilation with regard to baseline parameters and aetiological diagnoses of acute respiratory failure. With regard to outcome data, no significant differences were observed between PSV and PAV in the frequency of intubation (37% vs 34%), mortality rate (29% vs 28%), and mean length of stay. Subjective comfort (0–10 visual analogue scale) was rated higher and intolerance occurred less frequently (3.4% vs 15%, P = 0.03) in the PAV than in the PSV mode.Conclusions Although PAV seems more comfortable and intolerance occurred less frequently, no major differences exist in terms of physiological improvement or in terms of outcomes when comparing PSV and PAV.An editorial regarding this article can be found in the same issue ()     

Volume-guaranteed pressure-support ventilation facing acute changes in ventilatory demand

Objective To compare volume support ventilation (VSV) in which the pressure support level is continuously adjusted to deliver a preset tidal volume, with pressure support ventilation (PSV), in terms of patient behavior and ventilator response when ventilatory demand was increased by addition of dead space to the circuit.Design and setting Randomized cross-over study in an intensive care unit university hospital.Interventions We assessed in ten patients being weaned off mechanical ventilation the effect of increasing the ventilatory demand by adding a heat-and-moisture exchanger to augment the dead space with a fixed level of PSV and VSV.Measurements and results Arterial blood gases, breathing pattern, and respiratory effort parameters at the end of each of the four steps. Adding dead space significantly increased minute ventilation and PaCO₂ values with both PSV and VSV. Indexes of respiratory effort (pressure-time index of respiratory muscles and work of breathing) increased with both ventilatory modes after dead-space augmentation. This increase was 2.5–4 times with VSV than with PSV and induced overt respiratory distress in two patients. The assistance delivered during VSV decreased significantly after dead-space augmentation, from 15.0±6.5 to 9.1±4.8 cmH₂O, whereas no change occurred with PSV.Conclusions With a fixed level of VSV, but not of PSV, an increase in ventilatory demand results in a decrease in the pressure support provided by the ventilator, opposite to the desired response. VSV may conceivably result in respiratory distress in clinical settings.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Physiologic response to varying levels of pressure support and neurally adjusted ventilatory assist in patients with acute respiratory failure

Objective  Neurally adjusted ventilatory assist (NAVA) is a new mode wherein the assistance is provided in proportion to diaphragm electrical activity (EAdi). We assessed the physiologic response to varying levels of NAVA and pressure support ventilation (PSV). Setting  ICU of a University Hospital. Patients  Fourteen intubated and mechanically ventilated patients. Design and protocol  Cross-over, prospective, randomized controlled trial. PSV was set to obtain a V t/kg of 6–8 ml/kg with an active inspiration. NAVA was matched with a dedicated software. The assistance was decreased and increased by 50% with both modes. The six assist levels were randomly applied. Measurements  Arterial blood gases (ABGs), tidal volume (V t/kg), peak EAdi, airway pressure (Paw), neural and flow-based timing. Asynchrony was calculated using the asynchrony index (AI). Results  There was no difference in ABGs regardless of mode and assist level. The differences in breathing pattern, ventilator assistance, and respiratory drive and timing between PSV and NAVA were overall small at the two lower assist levels. At the highest assist level, however, we found greater V t/kg (9.1 ± 2.2 vs. 7.1 ± 2 ml/kg, P < 0.001), and lower breathing frequency (12 ± 6 vs. 18 ± 8.2, P < 0.001) and peak EAdi (8.6 ± 10.5 vs. 12.3 ± 9.0, P < 0.002) in PSV than in NAVA; we found mismatch between neural and flow-based timing in PSV, but not in NAVA. AI exceeded 10% in five (36%) and no (0%) patients with PSV and NAVA, respectively (P < 0.05). Conclusions  Compared to PSV, NAVA averted the risk of over-assistance, avoided patient–ventilator asynchrony, and improved patient–ventilator interaction. This article is discussed in the editorial available at: doi:.     

Comparison of pressure support ventilation and assist control ventilation in patients with acute respiratory failure

We compared the effects of pressure support ventilation (PSV) with those of assist control ventilation (ACV) on the breathing pattern, work of breathing and blood gas exchange in 8 patients with acute respiratory failure. During ACV, the tidal volume was set at 10 ml/kg, and the inspiratory flow was set at 50 to 70l/min. During PSV, the pressure support level selected was 27±5 cm H₂O to make the breathing pattern regular. Tidal volume was significantly higher (908±179 ml vs. 633±96 ml) during PSV than during ACV at a lower peak airway pressure. Respiratory frequency was lower (15±4 breaths/min vs. 24±5 breaths/min) during PSV than during ACV, associated with a lower duty cycle, which improved synchrony between the patient and the ventilator. The oxygen cost of breathing, and estimate based on the inspiratory work added by a ventilator and the oxygen consumption, did not change significantly. PaO₂ was significantly higher during PSV than during ACV. We conclude that PSV using high levels of pressure support can improve the breathing pattern and oxygenation and fully sustain the patient's ventilation while matching his inspiratory efforts.     

History of mechanical ventilation may affect respiratory mechanics evolution in acute respiratory distress syndrome

Purpose

The aim of this study was to investigate the effect of mechanical ventilation (MV) before acute respiratory distress syndrome (ARDS) on subsequent evolution of respiratory mechanics and blood gases in protectively ventilated patients with ARDS.

Methods

Nineteen patients with ARDS were stratified into 2 groups according to ARDS onset relative to the onset of MV: In group A (n = 11), MV was applied at the onset of ARDS; in group B (n = 8), MV had been initiated before ARDS. Respiratory mechanics and arterial blood gas were assessed in early (≤3 days) and late (8-11 days) ARDS, on zero positive end-expiratory pressure and positive end-expiratory pressure of 10 cm H₂O.

Results

In group A, Pao₂/fractional inspired oxygen concentration increased (121 ± 43 vs 161 ± 60 mm Hg) and minimal resistance of respiratory system decreased (8.3 ± 1.8 vs 6.0 ± 2.1 cm H₂O L⁻¹ s⁻¹) from early to late ARDS. In group B, static elastance of respiratory system increased in the late stage (30.4 ± 7.8 vs 36.4 ± 9.9 cm H₂O/L). In both groups, positive end-expiratory pressure application resulted in Pao₂/fractional inspired oxygen concentration improvement and minimal resistance of respiratory system decreases in both stages.

Conclusion

In protectively ventilated patients with ARDS, late alteration of respiratory mechanics occurs more commonly in patients who have been ventilated before ARDS onset, suggesting that the history of MV affects the subsequent progress of ARDS even when using protective ventilation.     

压力支持通气辅助控制通气在治疗呼吸衰竭中的比较

目的 评估压力支持通气与辅助控制通气模式在治疗呼吸衰竭病人中是否可以互换。方法 对慢性阻塞性肺疾病、限制性肺疾病、神经肌肉疾病最终导致呼吸衰竭系机械通气支持的30例病人，行辅助控制通气2天以上，切换成压力支持通气后6小时，然后恢复辅助控制通气。结果 压力支持通气与辅助控制通气相,显示有更高的潮气量、每分通气量、吸气时间相对比较长。吸气／呼气比值增大，心率降低。结论 在呼吸衰竭病人中压力支持通气是一种可选择的有效通气模式。     

Comparison of the effects of pressure support ventilation delivered by three different ventilators during weaning from mechanical ventilation

Objective To compare the effects of pressure support ventilation (PSV) delivered at the same level by three different ventilators on patients' work of breathing (WOB), breathing pattern and gas exchange.Design Prospective, self-controlled clinical study.Setting Intensive care unit of a tertiary university hospital.Patients Nine intubated adult patients during weaning from mechanical ventilation.Interventions Patients were randomly connected to one of three ventilators: the Siemens Servo 900 C (SC), the Ohmeda CPU 1 (CPU), and the Engström Erica (EE) during both zero cmH₂O PSV and 15 cmH₂O PSV.Measurements and results During zero PSV, there was no significant difference in terms of WOB, V_T, V_E, or auto-PEEP among the three ventilators, although there was a trend towards higher levels of WOB with EE. During 15 cmH₂O PSV, WOB was significantly less with SC than with EE or CPU (0.47±0.48 J/l for SC, 1.0±0.48 for EE and 0.78±0.51 for CPU 1,p=0.003). WOB was 64% less than at zero PSV with SC but only 38% less with EE. This was associated with a different pressurization shape, as assessed by the interior surface of Paw-V_T loops (1.23±0.09 J/l for SC, 0.9±0.02 for EE, and 0.79±0.18 for CPU;p<0.001). At 15 cmH₂O PSV, auto-PEEP was significantly lower with SC than with EE (1.7±2.1 cmH₂O for SC, 4.7±3.6 for EE, and 2.8±0.3 for CPU;p=0.04). External expiratory resistances, in cmH₂O/l/s, were significantly higher with EE than with CPU or SC (12.9±3.2 EE, 7.5±2.4 CPU, 5.9±0.5 SC;p<0.001).Conclusion During PSV, the different working principles of different mechanical ventilators profoundly affect patient's WOB. Among the various factors, velocity of pressurization of PSV may play a role in its efficacy in unloading the respiratory muscles.     

Airway pressure release ventilation in acute respiratory distress syndrome

Airway pressure release ventilation (APRV) is an alternative mode of ventilation that is increasingly used in patients with acute respiratory failure, acute lung injury (ALI), and acute respiratory distress syndrome (ARDS). Animal and clinical studies have demonstrated that, compared with conventional ventilation, APRV has beneficial effects on lung recruitment, oxygenation, end-organ blood flow, pulmonary vasoconstriction, and sedation requirements. Further studies, however, are required to directly compare APRV to ARDSnet protocol ventilation, specifically in patients with ALI/ARDS, and to determine whether managing ALI/ARDS with APRV will also achieve mortality reduction.     

Effects of noninvasive positive pressure ventilatory support in non-COPD patients with acute respiratory insufficiency after early extubation

Objective: To investigate the effects of noninvasive positive pressure ventilation (NPPV) on pulmonary gas exchange, breathing pattern, intrapulmonary shunt fraction, oxygen consumption, and resting energy expenditure in patients with persistent acute respiratory failure but without chronic obstructive pulmonary disease (COPD) after early extubation. Design: Prospective study. Setting: Multidisciplinary intensive care unit of a university hospital. Patients: 15 patients after prolonged mechanical ventilation (> 72 h) with acute respiratory insufficiency after early extubation. Interventions: Criteria for early extubation were arterial oxygen tension (PaO₂) L 40 mm Hg (fractional inspired oxygen 0.21), arterial carbon dioxide tension (PaCO₂) K 55 mm Hg, pH > 7.32, respiratory rate K 40 breaths per min, tidal volume (V_T) L 3 ml/kg, rapid shallow breathing index K 190 and negative inspiratory force L 20 cmH₂O. After extubation, two modes of NPPV were applied [continuous positive airway pressure (CPAP) of 5 cmH₂O and pressure support ventilation (PSV) with 15 cmH₂O pressure support]. Measurements and main results: Oxygenation and ventilatory parameters improved during both modes of NPPV (p < 0.05): increase in PaO₂ of 11 mm Hg during CPAP and 21 mm Hg during PSV; decrease in intrapulmonary shunt fraction of 7 % during CPAP and 12 % during PSV; increase in tidal volume of 1 ml/kg during CPAP and 4 ml/kg during PSV; decrease in respiratory rate 6 breaths/min during CPAP and 9 breaths/min during PSV. Oxygen consumption (15 % during CPAP, 22 % during PSV) and resting energy expenditure (12 % during CPAP, 20 % during PSV) were reduced (p < 0.05). PaCO₂ decreased, whereas minute ventilation and pH increased during PSV (p < 0.05). The median duration of NPPV was 2 days. Two patients had to be reintubated. Conclusions: In non-COPD patients with persistent acute respiratory failure after early extubation, NPPV improved pulmonary gas exchange and breathing pattern, decreased intrapulmonary shunt fraction, and reduced the work of breathing. Received: 14 May 1999 Final revision received: 25 June 1999 Accepted: 6 July 1999     

Low mortality associated with low volume pressure limited ventilation with permissive hypercapnia in severe adult respiratory distress syndrome

Many animal studies have shown that high peak inspiratory pressures (PIP) during mechanical ventilation can induce acute lung injury with hyaline membranes. Since 1984 we have limited PIP in patients with ARDS by reducing tidal volume, allowing spontaneous breathing with SIMV and disregarding hypercapnia. Since 1987 50 patients with severe ARDS with a lung injury score 2.5 and a mean PaO₂/FiO₂ ratio of 94 were managed in this manner. The mean maximum PaCO₂ was 62 mmHg, the highest being 129 mmHg. The hospital mortality was significantly lower than that predicted by Apache II (16% vs. 39.6%,x ²=11.64,p<0.001). Only one death was due to respiratory failure, caused by pneumocystis pneumonia. 10 patients had a ventilator score >80, which has previously predicted 100% mortality from respiratory failure. Only 2 died, neither from respiratory failure. There was no significant difference in lung injury score, ventilator score, PaO₂/FiO₂ or maximum PaCO₂ between survivors and non-survivors. We suggest that this ventilatory management may substantially reduce mortality in ARDS, particularly from respiratory failure.     

Combination of high frequency oscillatory ventilation and interventional lung assist in severe acute respiratory distress syndrome

Background

The combination of high-frequency oscillatory ventilation (HFOV) and extracorporeal carbon dioxide removal with the interventional lung assist (iLA) in severe acute respiratory distress syndrome (ARDS) represents a novel treatment option.

Methods

The study used a retrospective single-center analysis of 21 consecutive adult patients with severe ARDS, ventilated with HFOV/iLA. Efficiency, side effects, and outcome of combined treatment are presented as median (interquartile range).

Measurements and Main Results

The following were used to determine patient characteristics: sequential organ failure assessment score, 14; simplified acute physiology score II, 41; and Murray score, 4. The duration of combined treatment was 6 days. The blood flow through the iLA was 1.9 L/min.The Pao₂/inspired fraction of oxygen ratio increased from 61 (47-86) to 98 (67-116) within 2 hours and to 106 (70-135) mm Hg at 24 hours. Paco₂ decreased from 58 (50-76) to 37 (29-47) mm Hg at 2 hours with normalization of pH 7.28 (7.16-7.36) to 7.43 (7.33-7.49) after 2 hours associated with hemodynamic stabilization. In 6 patients, complications due to iLA treatment were observed, and in 3 patients, complications associated with HFOV were seen. Weaning from HFOV/iLA was successful in 10 patients. The 30-day mortality rate was 43%, and hospital mortality rate was 57%.

Conclusion

The combination of HFOV/iLA is an option in severe pulmonary failure if conventional ventilation fails and pumpdriven extracorporeal membrane oxygenation therapy is not available.     

急性呼吸窘迫综合征患者机械通气和营养支持治疗37例分析

目的探讨急性呼吸窘迫综合征（ARDS）患者机械通气和营养支持治疗的临床特点及治疗效果。方法回顾性分析37例ARDS患者经机械通气和营养支持治疗的临床资料。结果37例ARDS机械通气患者1次脱机成功者30例,2次脱机成功者5例,3次脱机成功者2例。机械通气3—10d,无一例依赖呼吸机。全胃肠外营养（TPN）支持4-12d,TPN支持期间合并高血糖5例,消化道出血4例,肺感染、呼吸衰竭5例,无一例中心静脉置管并发症。结论机械通气和营养支持治疗ARDS临床效果较好。但应注意营养供给方式的选择。     

Extended prone position ventilation in severe acute respiratory distress syndrome: A pilot feasibility study

Objectives

The aim of the study was to evaluate the safety of extended prone position ventilation (PPV) and its impact on respiratory function in patients with severe acute respiratory distress syndrome (ARDS).

Design

This was a prospective interventional study.

Setting

Patients were recruited from a mixed medical-surgical intensive care unit in a university hospital.

Patients

Fifteen consecutive patients with severe ARDS, previously unresponsive to positive end-expiratory pressure adjustment, were treated with PPV.

Intervention

Prone position ventilation for 48 hours or until the oxygenation index was 10 or less (extended PPV).

Results

The elapsed time from the initiation of mechanical ventilation to pronation was 35 ± 11 hours. Prone position ventilation was continuously maintained for 55 ± 7 hours. Two patients developed grade II pressure ulcers of small extent. None of the patients experienced life-threatening complications or hemodynamic instability during the procedure. The patients showed a statistically significant improvement in Pao₂/Fio₂ (92 ± 12 vs 227 ± 43, P < .0001) and oxygenation index (22 ± 5 vs 8 ± 2, P < .0001), reduction of PaCo₂ (54 ± 9 vs 39 ± 4, P < .0001) and plateau pressure (32 ± 2 vs 27 ± 3, P < .0001), and increment of the static compliance (21 ± 3 vs 37 ± 6, P < .0001) with extended PPV. All the parameters continued to improve significantly while they remained in prone position and did not change upon returning the patients to the supine position.

Conclusions

The results obtained suggest that extended PPV is safe and effective in patients with severe ARDS when it is carried out by a trained staff and within an established protocol. Extended PPV is emerging as an effective therapy in the rescue of patients from severe ARDS.     

Continuous positive airway pressure vs. proportional assist ventilation for noninvasive ventilation in acute cardiogenic pulmonary edema

Objective To compare continuous positive airway pressure (CPAP) and proportional assist ventilation (PAV) as modes of noninvasive ventilatory support in patients with severe cardiogenic pulmonary edema. Design and setting A prospective multicenter randomized study in the medical ICUs of three teaching hospitals. Patients Thirty-six adult patients with cardiogenic pulmonary edema (CPA) with unresolving dyspnea, respiratory rate above 30/min and/or SpO₂ above 90% with O₂ higher than 10 l/min despite conventional therapy with furosemide and nitrates. Interventions Patients were randomized to undergo either CPAP (with PEEP 10 cmH₂O) or PAV (with PEEP 5–6 cmH₂O) noninvasive ventilation through a full face mask and the same ventilator. Measurements and results The main outcome measure was the failure rate as defined by the onset of predefined intubation criteria, severe arrythmias or patient's refusal. On inclusion CPAP (n = 19) and PAV (n = 17) groups were similar with regard to age, sex ratio, type of heart disease, SAPS II, physiological parameters (mean arterial pressure, heart rate, blood gases), amount of infused nitrates and furosemide. Failure was observed in 7 (37%) CPAP and 7 (41%) PAV patients. Among these, 4 (21%) CPAP and 5 (29%) PAV patients required endotracheal intubation. Changes in physiological parameters were similar in the two groups. Myocardial infarction and ICU mortality rates were strictly similar in the two groups. Conclusions In the present study PAV was not superior to CPAP for noninvasive ventilation in severe cardiogenic pulmonary edema with regard to either efficacy and tolerance. T. Rusterholtz and P.-E. Bollaert contributed equally to this study. This work was supported in part by Respironics Inc., Murrysville, PA, USA.     

Neurally adjusted ventilatory assist: assessing the comfort and feasibility of use in neonates and children

Aim: To evaluate the practical feasibility for nurses working with neurally adjusted ventilatory assist (NAVA) and assess patient comfort and safety when NAVA is initiated. Background: NAVA is a relatively new mode of ventilation. Its application in neonates and children has been widely documented. However, its practical feasibility from a nursing point of view as well as its safety and comfort in these populations compared with conventional modes of ventilation has not been described. Design: A prospective, observational crossover pilot study. Method: NAVA was compared with the conventional mode of ventilation for 3 h each, and practical feasibility, patient comfort level and safety were assessed. Results: Twenty‐one neonates and children were enrolled into the study. There were no reported adverse events. In most patients, the NAVA catheter was placed too shallow, as measured by the distances from the nose, ear, xiphisternum (NEX) method, according to the manufacturer's instructions. Accurate placement was confirmed by visual inspection of the NAVA positioning window. Patients' comfort did not differ between the conventional mode and NAVA. Conclusions: NAVA is feasible, once an accurate signal of the electrical activity of the diaphragm is achieved and seems safe and well tolerated in both neonates and children. Nurses need to gain experience in placing the NAVA catheter and practical recommendations are given. Relevance to clinical practice: NAVA is a promising new mode of ventilation. This article contributes to an increasing body of evidence that NAVA is feasible in neonates and children. There are practical considerations when NAVA is applied in these patient‐groups.     

32例严重胸腹部复合伤并发急性呼吸窘迫综合征患者的救治

目的探讨严重胸腹部复合伤并发急性呼吸窘迫综合征的有效救治方法。方法回顾性分析32例患者严重胸腹部复合伤并发急性呼吸窘迫综合征的急救方法及治疗效果。结果32例均有胸腹部的严重复合伤,均合并多发肋骨骨折或肺挫伤而致急性呼吸窘迫综合征,均行抗休克、合理补充血容量、合理的机械通气及急诊外科手术抢救治疗。临床治愈26例,死亡6例,死亡率18．75%。结论早期诊断、及时抗休克、合理补充血容量和处理胸腹部外伤以及尽早正确采用机械通气,是治疗严重胸腹部复合伤并发急性呼吸窘迫综合征的关键,也是降低死亡率的有效措施。     

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.

     

Weaning from mechanical ventilation with pressure support in patients failing a T-tube trial of spontaneous breathing

Objective Evidence that PS may facilitate weaning from mechanical ventilation (MV), although not confirmed by randomized trials, prompted us to investigate whether patients could be weaned with PS after failing a T-tube trial.Design and setting This was a prospective, non-randomized study in two French intensive care units.Patients and participants One hundred eighteen patients were enrolled and underwent a T-tube trial, after which 87 were extubated. Thirty-one underwent a further trial with PS, after which 21 were extubated.Interventions All patients under MV >24 h meeting the criteria for a weaning test underwent a 30-min T-tube trial. If this was successful, they were immediately extubated. Otherwise, a 30-min trial with +7 cm H₂O PS was initiated with an individualized pressurization slope and trigger adjustment. If all weaning criteria were met, the patients were extubated; otherwise, MV was reinstated.Measurements and Results The extubation failure rate at 48 h did not differ significantly between the groups: 11/87 (13%) versus 4/21 (19%), P=0.39. The groups were comparable with regard to endotracheal tube diameter, MV duration, the use of non-invasive ventilation (NIV) after extubation, initial severity score, age and underlying pathology, except for COPD. A significantly higher percentage of patients with COPD was extubated after the trial with PS (8/21–38%) than after a single T-tube trial (11/87–13%) (P=0.003).Conclusions Of the patients, 21/118 (18%) could be extubated after a trial with PS, despite having failed a T-tube trial. The reintubation rate was not increased. This protocol may particularly benefit patients who are most difficult to wean, notably those with COPD.