Suporte ventilatório e Covid-19 / Ventilatory support and Covid-19

Trata-se de síntese de evidências sobre as possibilidades terapêuticas para insuficiência respiratória grave no contexto da pandemia de Covid-19. O tratamento inclui as possibilidades terapêuticas de ventilação não invasiva (VNI), intubação e ventilação mecânica invasiva (VMI). Considera as características dos métodos, suas vantagens e limitações.

This is a synthesis of evidence on the therapeutic possibilities for severe respiratory failure in the context of the Covid-19 pandemic. Treatment includes the therapeutic possibilities of noninvasive ventilation (NIV), intubation, and invasive mechanical ventilation (IMV). It considers the characteristics of the methods, their advantages and limitations.

Proportional assist ventilation versus pressure support ventilation for weaning from mechanical ventilation in adults: a meta-analysis and trial sequential analysis.

BACKGROUND: Pressure support ventilation (PSV) is the prevalent weaning method. Proportional assist ventilation (PAV) is an assisted ventilation mode, which is recently being applied to wean the patients from mechanical ventilation. Whether PAV or PSV is superior for weaning remains unclear. METHODS: Eligible randomized controlled trials published before April 2020 were retrieved from databases. We calculated the risk ratio (RR) and mean difference (MD) with 95% confidence intervals (CIs). RESULTS: Seven articles, involving 634 patients, met the selection criteria. Compared to PSV, PAV was associated with a significantly higher rate of weaning success (fixed-effect RR 1.16; 95% CI 1.07-1.26; I2 = 0.0%; trial sequential analysis-adjusted CI 1.03-1.30), and the trial sequential monitoring boundary for benefit was crossed. Compared to PSV, PAV was associated with a lower proportion of patients requiring reintubation (RR 0.49; 95% CI 0.28-0.87; I2 = 0%), a shorter ICU length of stay (MD - 1.58 (days), 95% CI - 2.68 to - 0.47; I2 = 0%), and a shorter mechanical ventilation duration (MD - 40.26 (hours); 95% CI - 66.67 to - 13.84; I2 = 0%). There was no significant difference between PAV and PSV with regard to mortality (RR 0.66; 95% CI 0.42-1.06; I2 = 0%) or weaning duration (MD - 0.01 (hours); 95% CI - 1.30-1.28; I2 = 0%). CONCLUSION: The results of the meta-analysis suggest that PAV is superior to PSV in terms of weaning success, and the statistical power is confirmed using trial sequential analysis.

Effects of assist parameter on the performance of proportional assist ventilation in a lung model of chronic obstructive pulmonary disease.

BACKGROUND: How the assist parameters affect synchronization and inspiratory workload in proportional assist ventilation (PAV) remains unknown. PURPOSE: This bench study aimed to optimize the PAV parameters by evaluating their effects on patient-ventilator synchrony and work of breathing (WOB) in a chronic obstructive pulmonary disease (COPD) model during noninvasive ventilation, compared with the pressure support ventilation (PSV) mode. METHODS: The Respironics V60 ventilator was connected to an ASL5000 lung simulator, which simulates lung mechanics in COPD (compliance, 50mL/cmH2O; expiratory resistance, 20 cmH2O/L/s; respiratory rate, 15 breaths/min; inspiratory time, 1.6 s). PAV was applied with different assistance levels, including flow assist (FA, 40-90% respiratory resistance) and volume assist (VA, 50-90% elastance). PSV was assessed using the same model. Measurements were obtained at a leak flow rate of 25-28 L/min. Performance characteristics, simulator-ventilator synchrony, and WOB were assessed. RESULTS: Runaway was prone to occur, and severe premature cycling was observed with VA75+FA level>65%. Compared with PSV, lower tidal volume (≤400mL) was observed during PAV with VA75+FA40-50 and FA50+VA40-80; similar and improved cycling synchrony was observed for FA50+VA80 and FA50+VA90 (cycling delay: -117.60±6.13 and -61.50±8.03 vs. -101.20±7.32ms). The reduced triggering workload was observed for VA75+FA60-65 and FA50+VA80-90. Total and patient WOB was improved with all tested assist level combinations, except for FA50+VA90. CONCLUSIONS: PAV reduces WOB but can induce asynchrony if improper settings are set, but the most optimal settings still need more clinical observations.

Neurally adjusted ventilatory assist versus pressure support ventilation: a randomized controlled feasibility trial performed in patients at risk of prolonged mechanical ventilation.

BACKGROUND: The clinical effectiveness of neurally adjusted ventilatory assist (NAVA) has yet to be demonstrated, and preliminary studies are required. The study aim was to assess the feasibility of a randomized controlled trial (RCT) of NAVA versus pressure support ventilation (PSV) in critically ill adults at risk of prolonged mechanical ventilation (MV). METHODS: An open-label, parallel, feasibility RCT (n = 78) in four ICUs of one university-affiliated hospital. The primary outcome was mode adherence (percentage of time adherent to assigned mode), and protocol compliance (binary-≥ 65% mode adherence). Secondary exploratory outcomes included ventilator-free days (VFDs), sedation, and mortality. RESULTS: In the 72 participants who commenced weaning, median (95% CI) mode adherence was 83.1% (64.0-97.1%) and 100% (100-100%), and protocol compliance was 66.7% (50.3-80.0%) and 100% (89.0-100.0%) in the NAVA and PSV groups respectively. Secondary outcomes indicated more VFDs to D28 (median difference 3.0 days, 95% CI 0.0-11.0; p = 0.04) and fewer in-hospital deaths (relative risk 0.5, 95% CI 0.2-0.9; p = 0.032) for NAVA. Although overall sedation was similar, Richmond Agitation and Sedation Scale (RASS) scores were closer to zero in NAVA compared to PSV (p = 0.020). No significant differences were observed in duration of MV, ICU or hospital stay, or ICU, D28, and D90 mortality. CONCLUSIONS: This feasibility trial demonstrated good adherence to assigned ventilation mode and the ability to meet a priori protocol compliance criteria. Exploratory outcomes suggest some clinical benefit for NAVA compared to PSV. Clinical effectiveness trials of NAVA are potentially feasible and warranted. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01826890. Registered 9 April 2013.

Neurally Adjusted Ventilatory Assist versus Pressure Support Ventilation in Difficult Weaning: A Randomized Trial.

BACKGROUND: Difficult weaning frequently develops in ventilated patients and is associated with poor outcome. In neurally adjusted ventilatory assist, the ventilator is controlled by diaphragm electrical activity, which has been shown to improve patient-ventilator interaction. The objective of this study was to compare neurally adjusted ventilatory assist and pressure support ventilation in patients difficult to wean from mechanical ventilation. METHODS: In this nonblinded randomized clinical trial, difficult-to-wean patients (n = 99) were randomly assigned to neurally adjusted ventilatory assist or pressure support ventilation mode. The primary outcome was the duration of weaning. Secondary outcomes included the proportion of successful weaning, patient-ventilator asynchrony, ventilator-free days, and mortality. Weaning duration was calculated as 28 days for patients under mechanical ventilation at day 28 or deceased before day 28 without successful weaning. RESULTS: Weaning duration in all patients was statistically significant shorter in the neurally adjusted ventilatory assist group (n = 47) compared with the pressure support ventilation group (n = 52; 3.0 [1.2 to 8.0] days vs. 7.4 [2.0 to 28.0], mean difference: -5.5 [95% CI, -9.2 to -1.4], P = 0.039). Post hoc sensitivity analysis also showed that the neurally adjusted ventilatory assist group had shorter weaning duration (hazard ratio, 0.58; 95% CI, 0.34 to 0.98). The proportion of patients with successful weaning from invasive mechanical ventilation was higher in neurally adjusted ventilatory assist (33 of 47 patients, 70%) compared with pressure support ventilation (25 of 52 patients, 48%; respiratory rate for neurally adjusted ventilatory assist: 1.46 [95% CI, 1.04 to 2.05], P = 0.026). The number of ventilator-free days at days 14 and 28 was statistically significantly higher in neurally adjusted ventilatory assist compared with pressure support ventilation. Neurally adjusted ventilatory assist improved patient ventilator interaction. Mortality and length of stay in the intensive care unit and in the hospital were similar among groups. CONCLUSIONS: In patients difficult to wean, neurally adjusted ventilatory assist decreased the duration of weaning and increased ventilator-free days.

Evidence Supporting Clinical Use of Proportional Assist Ventilation: A Systematic Review and Meta-Analysis of Clinical Trials.

BACKGROUND: While proportional assist ventilation (PAV), generates pressure in proportion to effort without a preselected target, proportional assist ventilation plus (PAV+) measures compliance and resistance, calculates work of breathing, and adjusts support to a preset assistance level. OBJECTIVE: To summarize randomized controlled trials (RCTs) comparing invasive or noninvasive PAV or PAV+ in critically ill patients. Data Sources: We searched multiple databases to April 2017 without language restrictions and conference proceedings from 5 meetings to identify randomized parallel-group and crossover RCTs that compared invasive or noninvasive PAV or PAV+ to another mode in critically ill adults or children and reported at least 1 clinically important outcome. RESULTS: We identified 14 RCTs (11 parallel group and 3 crossover) assessing PAV (n = 7) and PAV+ (n = 7) involving 931 adult patients. We found no effect of noninvasive PAV (vs noninvasive pressure support [PS]) on intubation (risk ratio 0.92 [0.59 to 1.43], I2 = 0%) or invasive PAV (vs invasive PS) on percentage rapid eye movement sleep (mean difference [MD] -2.93% [-14.20 to ±8.34], I2 = 43%). Compared to invasive PS, invasive PAV+ showed a nonsignificant increase in weaning time (MD +0.54 [-0.67 to +1.75] hours, I2 = 0%), but no effect on hospital mortality, reintubation, or tracheostomy. CONCLUSIONS: Current evidence does not support the use of invasive or noninvasive PAV or invasive PAV+ in critically ill adults. Amid low to moderate heterogeneity, we identified 3 promising areas for future research including assessing the role of noninvasive PAV as an initial support strategy in patients with acute respiratory failure, invasive PAV on sleep quality during invasive ventilation, and possibly invasive PAV+ for weaning.

Neurally-Adjusted Ventilatory Assist Versus Noninvasive Pressure Support Ventilation in COPD Exacerbation: The NAVA-NICE Trial.

BACKGROUND: This study was conducted to compare the effectiveness of noninvasive ventilation (NIV) with pressure support (NIV-PSV) to noninvasive neurally-adjusted ventilatory assist (NIV-NAVA) during COPD exacerbation. METHODS: In this study, 40 subjects with COPD and acute hypercapnic respiratory failure were randomized to receive either NIV-NAVA (n = 20) or NIV-PSV (n = 20) via a critical care ventilator. Subjects' vital parameters, arterial blood gas values, patient-ventilator asynchrony events, and asynchrony index were noted at specific time intervals in both groups. The duration of NIV, rate of NIV failure, and length hospital stay were also recorded for these 2 modes of NIV. RESULTS: NIV-NAVA significantly reduced the total number (median [interquartile range]) of asynchrony events compared to NIV-PSV: 22 (15-32.5) versus 65 (50.75-104.25), respectively, P = .002. Severe asynchrony defined as asynchrony index > 10% was also significantly lower in NIV-NAVA than in NIV-PSV (P < .001). There was no significant difference between the 2 groups regarding improvement in gas exchange and vital parameters. Rate of failure of NIV (P = .73), duration of the requirement of ventilatory support (P = .40), and hospital length of stay (P = .46) were also comparable between the 2 modes of ventilation. CONCLUSIONS: Compared to NIV-PSV, NIV-NAVA was associated with better patient-ventilator synchrony and a reduction in the number of asynchrony events in subjects with an exacerbation of COPD, with similar effects on improvement in gas exchange, duration of NIV, hospital lenght of stay, and rate of NIV failure. (Clinicaltrials.gov registration NCT02912689.).

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

BACKGROUND: Asynchrony is a common problem in patients treated with noninvasive ventilation (NIV). Neurally adjusted ventilatory assist (NAVA) has shown to improve patient-ventilator interaction. However, it is unknown whether NIV-NAVA improves outcomes compared to noninvasive pressure support (NIV-PS). METHODS: This observational cohort study included patients 18 years or older receiving noninvasive ventilation using an oro-nasal face mask for more than 2 hours in a Danish ICU. The study included a NIV-NAVA cohort (year 2013-2015) and two comparison cohorts: (a) a historical NIV-PS cohort (year 2011-2012) before the implementation of NIV-NAVA at the ICU in 2013, and (b) a concurrent NIV-PS cohort (year 2013-2015). Outcomes of NIV-NAVA (intubation rate, duration of NIV and 90-day mortality) were assessed and compared using multivariable linear and logistic regression adjusted for relevant confounders. RESULTS: The study included 427 patients (91 in the NIV-NAVA, 134 in the historic NIV-PS and 202 in the concurrent NIV-PS cohort). Patients treated with NIV-NAVA did not have improved outcome after adjustment for measured confounders. Actually, there were statistically imprecise higher odds for intubation in NIV-NAVA patients compared with both the historical [OR 1.48, CI (0.74-2.97)] and the concurrent NIV-PS cohort [OR 1.67, CI (0.87-3.19)]. NIV-NAVA might also have a longer length of NIV [63%, CI (19%-125%)] and [139%, CI (80%-213%)], and might have a higher 90-day mortality [OR 1.24, CI (0.69-2.25)] and [OR 1.39, CI (0.81-2.39)]. Residual confounding cannot be excluded. CONCLUSION: This present study found no improved clinical outcomes in patients treated with NIV-NAVA compared to NIV-PS.

Current Trends in Aortic Root Surgery: The Mini-Bentall Approach.

OBJECTIVE: The mini-sternotomy approach is becoming a widespread technique for aortic valve surgery. However, its safety for aortic root replacement has yet to be established. The aim of the present study was to compare the operative outcomes of patients who underwent aortic root replacement via upper mini-sternotomy (mini-Bentall) to patients who underwent Bentall procedure via median sternotomy (full-sternotomy Bentall). METHODS: Between November 1998 and November 2016, 91 consecutive patients underwent full-sternotomy Bentall procedure and 26 patients underwent mini-Bentall procedure. The mini-Bentall procedure was performed via an upper hemisternotomy incision extending to the right fourth intercostal space. Patients with concomitant procedures and those who underwent deep hypothermic circulatory arrest were excluded from the analysis. Outcome variables were operative mortality and major surgical complications, including prolonged length of hospital stay, transfusion rates, reoperation for bleeding, and prolonged ventilatory support. RESULTS: No significant differences were observed on the preoperative, operative, and postoperative characteristics between the two treatment groups. The median cardiopulmonary bypass and aortic cross-clamp times were 169 minutes (interquartile range = 156.0-188.5) and 148 minutes (interquartile range = 131.3-160.3) in the mini-Bentall group, respectively. The median duration of hospitalization in the mini-Bentall group was 6.5 days (interquartile range = 5.0-11.0 days). In-hospital mortality and new renal insufficiency occurred at a frequency of 1.1% and reoperation for bleeding at 6.6% in the group of patients who underwent the conventional Bentall procedure compared with 0% for all these measures in the mini-Bentall group (P > 0.33). There was no significant difference in intraoperative red blood cell transfusion and other major postoperative complications. No strokes were observed in either group, and there were no conversions to median sternotomy in the mini-Bentall group. CONCLUSIONS: An upper hemisternotomy is a feasible technique in patients undergoing elective aortic root replacement surgery. However, future prospective studies are required before these procedures become the standard of care.

Robotic Beating Heart Totally Endoscopic Coronary Artery Bypass in Higher-Risk Patients: Can It be Done Safely?

OBJECTIVE: Patients with a high Society of Thoracic Surgeons (STS) predicted risk of mortality undergoing coronary artery bypass surgery are known to have worse outcomes. Less invasive approaches have been shown to improve morbidity and mortality for these patients. In this study, we examined perioperative outcomes in higher-risk patients undergoing robotic totally endoscopic beating heart coronary artery bypass surgery. METHODS: The STS predicted risk of mortality was reviewed for patients undergoing robotic totally endoscopic beating heart coronary artery bypass surgery at our institution between January 2013 and May 2017. We identified a higher-risk cohort (n = 50) and compared them to a lower-risk cohort (n = 220) during the same period. The higher-risk group was formed from patients with the 50 highest STS scores. Perioperative data were collected retrospectively. RESULTS: There were 50 patients in the higher-risk group (mean STS score = 7.05 ± 4.9, mean age = 73 years) and 220 patients in the lower-risk group (mean STS score = 0.89 ± 0.6, mean age = 64 years). The higher-risk group had significantly greater rates of renal insufficiency, peripheral vascular disease, and lower ejection fraction. The incidence of postoperative re-exploration for bleeding, stroke, myocardial infarction, and prolonged ventilation was similar. Perioperative blood transfusion and hospital length of stay were greater in the higher-risk group. Mortality was lower in the higher-risk group (0% vs 1.8% P = 0.045). Cardiac-related mortality was similar at midterm follow-up. CONCLUSIONS: We conclude that beating heart totally endoscopic beating heart coronary artery bypass surgery can be performed in patients with a higher STS predicted risk of mortality with excellent outcomes. Further studies are warranted to evaluate long-term results of totally endoscopic beating heart coronary artery bypass surgery in this challenging group of patients.

Determination of respiratory system compliance during pressure support ventilation by small variations of pressure support.

In mechanically ventilated patients, measurement of respiratory system compliance (Crs) is of high clinical interest. Spontaneous breathing activity during pressure support ventilation (PSV) can impede the correct assessment of Crs and also alter the true Crs by inducing lung recruitment. We describe a method for determination of Crs during PSV and assess its accuracy in a study on 20 mechanically ventilated patients. To assess Crs during pressure support ventilation (Crs,PSV), we performed repeated changes in pressure support level by ± 2 cmH2O. Crs,PSV was calculated from the volume change induced by these changes in pressure support level, taking into account the inspiration time and the expiratory time constant. As reference methods, we used Crs, measured during volume controlled ventilation (Crs,VCV). In a post-hoc analysis, we assessed Crs during the last 20% of the volume-controlled inflation (Crs,VCV20). Values were compared by linear regression and Bland-Altman methods comparison. Comparing Crs,PSV to the reference value Crs,VCV, we found a coefficient of determination (r2) of 0.90, but a relatively high bias of - 7 ml/cm H2O (95% limits of agreement - 16.7 to + 2.7 ml/cmH2O). Comparison with Crs,VCV20 resulted in a negligible bias (- 1.3 ml/cmH2O, 95% limits of agreement - 13.9 to + 11.3) and r2 of 0.81. We conclude that the novel method provides an estimate of end-inspiratory Crs during PSV. Despite its limited accuracy, it might be useful for non-invasive monitoring of Crs in patients undergoing pressure support ventilation.

Effects of neurally adjusted ventilatory assist on air distribution and dead space in patients with acute exacerbation of chronic obstructive pulmonary disease.

BACKGROUND: Neurally adjusted ventilatory assist (NAVA) could improve patient-ventilator interaction; its effects on ventilation distribution and dead space are still unknown. The aim of this study was to evaluate the effects of varying levels of assist during NAVA and pressure support ventilation (PSV) on ventilation distribution and dead space in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). METHODS: Fifteen mechanically ventilated patients with AECOPD were included in the study. The initial PSV levels were set to 10 cmH2O for 10 min. Thereafter, the ventilator mode was changed to NAVA for another 10 min with the same electrical activity of the diaphragm as during PSV. Furthermore, the ventilation mode was switched between PSV and NAVA every 10 min in the following order: PSV 5 cmH2O; NAVA 50%; PSV 15 cmH2O; and NAVA 150% (relative to the initial NAVA support level). Ventilation distribution in the lung was evaluated in percentages in regions of interest (ROI) of four anteroposterior segments of equal height (ROI1 to ROI4 represents ventral, mid-ventral, mid-dorsal, and dorsal, respectively). Blood gases, ventilation distribution (electrical impedance tomography), diaphragm activity (B-mode ultrasonography), and dead space fraction (PeCO2 and PaCO2) were measured. RESULTS: The trigger and cycle delays were lower during NAVA than during PSV. The work of trigger was significantly lower during NAVA compared to PSV. The diaphragm activities based on ultrasonography were higher during NAVA compared to the same support level during PSV. The ventilation distribution in ROI4 increased significantly (P < 0.05) during NAVA compared to PSV (except for a support level of 50%). Similar results were found in ROI3 + 4. NAVA reduced dead space fraction compared to the corresponding support level of PSV. CONCLUSIONS: NAVA was superior to PSV in AECOPD for increasing ventilation distribution in ROI4 and reducing dead space. TRIAL REGISTRATION: Clinicaltrials.gov, NCT02289573 . Registered on 12 November 2014.

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.