Noninvasive ventilation to prevent respiratory failure after extubation in high-risk patients

Brazilian recommendations of mechanical ventilation 2013. Part I

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumonia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Risk factors for and prediction by caregivers of extubation failure in ICU patients: a prospective study

OBJECTIVE

The influence of delirium, ICU-acquired paresis, and cardiac performance on extubation outcome has never been evaluated together. We aimed to assess the respective role of these factors on the risk of extubation failure and to assess the predictive accuracy of caregivers.

DESIGN AND SETTING

Prospective observational study of all planned extubations in a 13-bed medical ICU of a teaching hospital.

INTERVENTIONS

On the day of extubation, muscle strength of the four limbs, criteria for delirium, cardiac performance, cough strength, and the risk of extubation failure predicted by caregivers were prospectively assessed. Extubation failure was defined as the need for reintubation within the following 7 days.

MEASUREMENTS AND MAIN RESULTS

Over the 18-month study period, 533 patients required intubation. Among the 225 patients intubated for more than 24 hours who experienced a planned extubation attempt, 31 patients (14%) required reintubation within the 7 days following extubation. In multivariate analysis, duration of mechanical ventilation more than 7 days prior to extubation, ineffective cough, and severe systolic left ventricular dysfunction were the three independent factors associated with extubation failure. Although patients considered at high risk for extubation failure had higher reintubation rate, prediction of extubation failure by caregivers at time of extubation had high specificity but low sensitivity.

CONCLUSIONS

An ineffective cough, a prior duration of mechanical ventilation more than 7 days, and severe systolic left ventricular dysfunction were stronger predictors of extubation failure than delirium or ICU-acquired weakness. Only one-third patients who required reintubation were considered at high risk for extubation failure by caregivers.

Brazilian recommendations of mechanical ventilation 2013. Part I

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Comparison between noninvasive mechanical ventilation and standard oxygen therapy in children up to 3 years old with respiratory failure after extubation: a pilot prospective randomized clinical study

OBJECTIVES

The effectiveness of noninvasive positive-pressure ventilation in preventing reintubation due to respiratory failure in children remains uncertain. A pilot study was designed to evaluate the frequency of extubation failure, develop a randomization approach, and analyze the feasibility of a powered randomized trial to compare noninvasive positive-pressure ventilation and standard oxygen therapy post extubation for preventing reintubation within 48 hours in children with respiratory failure.

DESIGN

Prospective pilot study.

SETTING

PICU at a university-affiliated hospital.

PATIENTS

Children aged between 28 days and 3 years undergoing invasive mechanical ventilation for greater than or equal to 48 hours with respiratory failure after programmed extubation.

INTERVENTIONS

Patients were prospectively enrolled and randomly assigned into noninvasive positive-pressure ventilation group and inhaled oxygen group after programmed extubation from May 2012 to May 2013.

MEASUREMENTS AND MAIN RESULTS

Length of stay in PICU and hospital, oxygenation index, blood gas before and after tracheal extubation, failure and reason for tracheal extubation, complications, mechanical ventilation variables before tracheal extubation, arterial blood gas, and respiratory and heart rates before and 1 hour after tracheal extubation were analyzed. One hundred eight patients were included (noninvasive positive-pressure ventilation group, n = 55 and inhaled oxygen group, n = 53), with 66 exclusions. Groups did not significantly differ for gender, age, disease severity, Pediatric Risk of Mortality at admission, tracheal intubation, and mechanical ventilation indications. There was no statistically significant difference in reintubation rate (noninvasive positive-pressure ventilation group, 9.1%; inhaled oxygen group, 11.3%; p > 0.05) and length of stay (days) in PICU (noninvasive positive-pressure ventilation group, 3 [1-16]; inhaled oxygen group, 2 [1-25]; p > 0.05) or hospital (noninvasive positive-pressure ventilation group, 19 [7-141]; inhaled oxygen group, 17 [8-80]).

CONCLUSIONS

The study indicates that a larger randomized trial comparing noninvasive positive-pressure ventilation and standard oxygen therapy in children with respiratory failure is feasible, providing a basis for a future trial in this setting. No differences were seen between groups. The number of excluded patients was high.

Efficacy of noninvasive ventilation after planned extubation: A systematic review and meta-analysis of randomized controlled trials

The objective our meta-analysis is to update the evidence on the efficacy of noninvasive ventilation (NIV) compared with conventional oxygen therapy after planned extubation. We did a systematic literature review of database, including Pubmed, EMBASE, and Cochrane. We included randomized controlled trials comparing NIV with conventional oxygen therapy after planned extubation in medical intensive care unit (ICU) in our analysis. The results of our meta-analysis is consistent with the results of previous reviews and show that NIV decreased reintubation rate significantly as compared to conventional oxygen therapy in chronic obstructive pulmonary disease (COPD) and patients at high risk for extubation failure; COPD (RR, 0.33; 95% CI, 0.16-0.69; I2 = 0), high risk (RR, 0.47; 95% CI, 0.32-0.70; I2 = 0). However, in a mixed medical ICU population, there was no statistical difference of reintubation rate between the two groups (RR, 0.66; 95% CI, 0.25-1.73; I2 = 68%). Our study suggests that use of NIV after planned extubation significantly decreases the reintubation rate in COPD patients and patients at high risk for extubation failure, confirming the findings of previous reviews. There is no difference in the reintubation rate between the two groups in the mixed medical ICU population.

Non-invasive ventilation for very old patients with limitations to respiratory care in half-open geriatric ward: experience on a consecutive cohort of patients

INTRODUCTION

A leading role for non-invasive ventilation (NIV), as comfort treatment or palliative care, is actually recognized for very old patients suffering from ARF. NIV was frequently used in both ICU and respiratory ICU (RICUs) for very old patients and it is associated with a reduced rate of endotracheal intubations and mortality. This study aims to evaluate the effects of NIV, performed in a setting of half-open geriatric ward with family support, in a cohort of very old patients with ARF and DNI decision.

METHODS

A consecutive cohort of 20 very old patients with DNI decision was admitted in our 26-bed geriatric ward during a 6 months' period. DNI decision was obtained in emergency room with an intensive care physician supported by a psychologist. Pressure support ventilation was the first choice of NIV. NIV has been performed by three adequately trained geriatricians, with one of them experienced in ICU, and in close collaboration with intensive care physicians. Arterial blood gases, to assess the response to ventilation, were obtained after 1, 6 and 12 h. NIV settings were modified according to arterial blood gas analyses or respiratory fatigue, if needed.

RESULTS

Therefore, 75% of patients were discharged home and 12 out of 20 patients had home respiratory support. PaO2/FiO2 ratio and pH increased while PaCO2 decreased during the 12 h of NIV with statistical significance. At the admission, alive patients had PaCO2 significantly lower than dead patients. After 12 h, alive patients had a better pH than dead patients. Dead patients experienced more complication than survivors.

CONCLUSION

Very old DNI patients with ARF could be treated with NIV in half-open geriatric ward with trained physicians and nurses. The presence of family members may improve patients' comfort and reduce anxiety level even at the end of life. Further studies are needed to address the effective role of NIV in very old patients with DNI decisions.

Brazilian recommendations of mechanical ventilation 2013. Part 2

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Noninvasive ventilation in acute respiratory failure

After the institution of positive-pressure ventilation, the use of noninvasive ventilation (NIV) through an interface substantially increased. The first technique was continuous positive airway pressure; but, after the introduction of pressure support ventilation at the end of the 20th century, this became the main modality. Both techniques, and some others that have been recently introduced and which integrate some technological innovations, have extensively demonstrated a faster improvement of acute respiratory failure in different patient populations, avoiding endotracheal intubation and facilitating the release of conventional invasive mechanical ventilation. In acute settings, NIV is currently the first-line treatment for moderate-to-severe chronic obstructive pulmonary disease exacerbation as well as for acute cardiogenic pulmonary edema and should be considered in immunocompromised patients with acute respiratory insufficiency, in difficult weaning, and in the prevention of postextubation failure. Alternatively, it can also be used in the postoperative period and in cases of pneumonia and asthma or as a palliative treatment. NIV is currently used in a wide range of acute settings, such as critical care and emergency departments, hospital wards, palliative or pediatric units, and in pre-hospital care. It is also used as a home care therapy in patients with chronic pulmonary or sleep disorders. The appropriate selection of patients and the adaptation to the technique are the keys to success. This review essentially analyzes the evidence of benefits of NIV in different populations with acute respiratory failure and describes the main modalities, new devices, and some practical aspects of the use of this technique.

The efficacy of noninvasive ventilation in managing postextubation respiratory failure: a meta-analysis

INTRODUCTION

To determine the effectiveness of noninvasive ventilation (NIV) in the management of postextubation respiratory failure.

METHODS

Databases including PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials were searched to find relevant trials. Randomized and quasi-randomized trials studying NIV in adult patients with postextubation respiratory failure were included. Effects on primary outcomes (i.e., reintubation rate, and ICU or/and hospital mortality) were accessed in this meta-analysis.

RESULTS

Ten trials involving 1382 patients were included: two used NIV in patients with established postextubation respiratory failure, and eight used NIV immediately after extubation. The use of NIV following extubation for patients (n = 302) with established respiratory failure did not decrease the reintubation rate (relative risk [RR] 1.02, 95% confidence interval [CI] 0.83-1.25) and ICU mortality (RR 1.14, 95% CI 0.43-3.00), compared to standard medical therapy (SMT). Early application of NIV after extubation (n = 1080) also did not decrease the reintubation rate (RR 0.75, 95% CI 0.45-1.15) significantly. However, in the planned extubation subgroup (n = 849), there were significant reductions in the reintubation rate (RR 0.65, 95% CI 0.46-0.93), ICU mortality rate (RR 0.41, 95% CI 0.21-0.82), and hospital mortality rate (RR 0.59, 95% CI 0.38-0.93) compared to SMT.

CONCLUSION

Current evidence suggests that the use of NIV in patients with established postextubation respiratory failure should be monitored cautiously. Early use of NIV can benefit patients with planned extubation by decreasing the reintubation rate and the ICU and hospital mortality rates.

[Esophageal cancer surgery: evolution of pain management, hemodynamics and ventilation practices during 16 years]

OBJECTIVE

To describe the evolution of perioperative anesthesia practices in for esophageal cancer surgery.

PATIENTS AND METHODS

We conducted an observational retrospective study in a single center evaluating main perioperative practices during 16 years (1994-2009). Statistical analysis was done on 4 chronologic quartiles of same sample size.

RESULTS

Two hundred and seven consecutive patients were included during the 4 periods 1994-1997 (n=52), 1997-1999 (n=52), 1999-2003 (n=52) and 2004-2009 (n=51). The main significant evolutions between the first and the fourth period were observed: (i) in ventilation: lower tidal volume (9.6[8.6-10.6] vs 7.6[7.0-8.3] mL/kg of ideal body weight (IBW), p<0.01), increased use of Positive End Expiratory Pressure (0 vs 83%, p<0.001) and increased use of post-operative non-invasive ventilation (0 vs 51%, p<0.001); (ii) in hemodynamic management: lower fluid replacement (20.6 [16.0-24.6] vs 12.6 [9.7-16.2] mL/h/kg of IBW, p<0.001); (iii) in analgesia: increased use of epidural thoracic anesthesia (31 vs 57%, p<0.001). Peroperative bleeding, type of fluid replacement, length of mechanical ventilation, length of stay in intensive care unit, ventilatory free days and mortality at day 28 didn't change.

CONCLUSIONS

During these previous years, anesthesia practices in ventilation, hemodynamics and analgesia for esophageal cancer surgery have changed.

The role of non-invasive positive pressure ventilation in post-extubation respiratory failure: An evaluation using meta-analytic techniques

Background:

The use of non-invasive positive pressure ventilation (NIPPV) in post-extubation respiratory failure is not well-established. Meta-analytic techniques were used to assess the effects of prophylactic application of NIPPV (prior to the development of respiratory failure) and therapeutic application of NIPPV (subsequent to the development of respiratory failure).

Materials and Methods:

Randomized controlled trials (RCTs) from 1966 to May 2010 were identified using electronic databases. RCTs, which reported the use of NIPPV in post-extubation respiratory failure with defined assessable endpoints: reintubation, mortality and length of stay, were included.

Results:

Reintubation was the primary outcome, mortality and lengths of stay were the secondary outcomes. Risk ratios (RR) were calculated for discrete outcomes and weighted mean differences (WMD) for continuous measures. There were 13 trials with 1420 patients; 9 prophylactic with 861 patients and 4 therapeutic with 559 patients. In the prophylactic group, NIPPV was associated with lower rates of reintubation: RR 0.53 (95% confidence interval [CI], 0.28-0.98), P = 0.04. In the therapeutic group, NIPPV showed a null effect on reintubation: RR 0.79 (95% CI, 0.50-1.25), P = 0.31. The analysis on the secondary outcomes suggested significant reduction of hospital mortality with prophylactic application of NIPPV: RR 0.62 (95% CI 0.4-0.97), P = 0.03, with no effect on the other outcomes. Therapeutic application of NIPPV reduced intensive care unit length of stay: WMD −1.17 (95% CI −2.82 to −0.33), P = 0.006, but no effect on the other secondary outcomes.

Conclusions:

The results of this review suggested prophylactic NIPPV was beneficial with respect to reintubation and the therapeutic use of NIPPV showed a null effect.

The decision to extubate in the intensive care unit

The day of extubation is a critical time during an intensive care unit (ICU) stay. Extubation is usually decided after a weaning readiness test involving spontaneous breathing on a T-piece or low levels of ventilatory assist. Extubation failure occurs in 10 to 20% of patients and is associated with extremely poor outcomes, including high mortality rates of 25 to 50%. There is some evidence that extubation failure can directly worsen patient outcomes independently of underlying illness severity. Understanding the pathophysiology of weaning tests is essential given their central role in extubation decisions, yet few studies have investigated this point. Because extubation failure is relatively uncommon, randomized controlled trials on weaning are underpowered to address this issue. Moreover, most studies evaluated patients at low risk for extubation failure, whose reintubation rates were about 10 to 15%, whereas several studies identified high-risk patients with extubation failure rates exceeding 25 or 30%. Strategies for identifying patients at high risk for extubation failure are essential to improve the management of weaning and extubation. Two preventive measures may prove beneficial, although their exact role needs confirmation: one is noninvasive ventilation after extubation in high-risk or hypercapnic patients, and the other is steroid administration several hours before extubation. These measures might help to prevent postextubation respiratory distress in selected patient subgroups.

Weaning from the ventilator and extubation in ICU

PURPOSE OF REVIEW

The decision to extubate is a crucial moment for intubated patients. In most cases, the transition to spontaneous breathing is uneventful, but in some patients, it implies a more challenging decision. Both extubation delay and especially the need for reintubation are associated with poor outcomes. We aim to review the recent literature on weaning and to clarify the role of certain interventions intending to help in this process.

RECENT FINDINGS

Cardiac dysfunction is probably one of the most common causes of weaning failure. Several studies have evaluated the ability of B-natriuretic peptides and echocardiographic tools to predict weaning outcome due to cardiac origin, attempting to prevent its failure. Noninvasive ventilation may have a potential benefit in preventing respiratory failure after extubation of hypercapnic patients, although more studies are needed to define a target population.

SUMMARY

Current research is focusing on preventing extubation failure, especially in the most challenging cases. The use of weaning protocols - written or computerized - attempts to early identify patients who are able to breathe spontaneously and to hasten extubation, resulting in better outcomes. Nevertheless, individualized care is needed in the most vulnerable patients, trying to prompt weaning without exposing patients to unnecessary risks.

Predicting laryngeal edema in intubated patients by portable intensive care unit ultrasound

PURPOSE

The purpose of this study is to determine the diagnostic accuracy of portable ultrasound for detection of laryngeal edema (LE) in intubated patients.

MATERIALS AND METHODS

We conducted a prospective, observational study from December 2010 to September 2011. We measured air column width differences (ACWD) in planned extubation patients admitted in intensive care unit by ultrasound. The primary outcome was the diagnostic accuracy of ACWD to predict the presence of LE.

RESULTS

A total of 101 patients were enrolled. The prevalence of LE was 16.8%. Baseline characteristics were similar between intubated patients with and without LE. The mean difference of increasing of air column width in patients without LE was higher than in LE group (1.9 vs 1.08 mm, P<.001). The sensitivity and specificity at ACWD higher or equal to 1.6 mm were 0.706 and 0.702, respectively. The positive predictive value and negative predictive value were 0.324 and 0.922, respectively. The area under the receiver operating characteristic curve of laryngeal ultrasound was 0.823 (95% confidence interval, 0.698-0.947) and that of cuff leak test was 0.840 (95% confidence interval, 0.715-0.964).

CONCLUSION

Portable intensive care unit ultrasound visualizing ACWD between predeflation and postdeflation cuff balloon is a promising objective tool, which aids in prediction of successful extubation regarding LE.

Improvement in process of care and outcome in patients requiring intensive care unit admission for community acquired pneumonia

Background

The present study was performed to assess the prognosis of patients admitted to the intensive care unit (ICU) for community acquired pneumonia (CAP) after implementation of new processes of care.

Methods

Two groups of patients with CAP were admitted to a 16-bed multidisciplinary ICU in an urban teaching hospital during two different periods: the years 1995–2000, corresponding to the historical group; and 2005–2010, corresponding to the intervention group. New therapeutic procedures were implemented during the period 2005–2010. These procedures included a sepsis management bundle derived from the Surviving Sepsis Campaign, use of a third-generation cephalosporin and levofloxacin as the initial empirical antimicrobial regimen, and noninvasive mechanical ventilation following extubation.

Results

A total of 317 patients were studied: 142 (44.8%) during the historical period and 175 (55.2%) during the intervention period. Sequential Organ Failure Assessment scores were higher in patients in the intervention group (7.2 ± 3.7 vs 6.2 ± 2.8; p=0.008). Mortality changed significantly between the two studied periods, decreasing from 43.6% in the historical group to 30.9% in the intervention group (p < 0.02). A restrictive transfusion strategy, use of systematic postextubation noninvasive mechanical ventilation in patients with severe chronic respiratory or cardiac failure patients, less frequent use of dobutamine and/or epinephrine in patients with sepsis or septic shock, and delivery of a third-generation cephalosporin associated with levofloxacin as empirical antimicrobial therapy were independently associated with better outcomes.

Conclusion

Positive outcomes in ICU patients with CAP have significantly increased in our ICU in recent years. Many new interventions have contributed to this improvement.

Complications of non-invasive ventilation techniques: a comprehensive qualitative review of randomized trials

Non-invasive ventilation (NIV) has become a common treatment for acute and chronic respiratory failure. In comparison with conventional invasive mechanical ventilation, NIV has the advantages of reducing patient discomfort, procedural complications, and mortality. However, NIV is associated with frequent uncomfortable or even life-threatening adverse effects, and patients should be thoroughly screened beforehand to reduce potential severe complications. We performed a detailed review of the relevant medical literature for NIV complications. All major NIV complications are potentially life-threatening and can occur in any patient, but are strongly correlated with the degree of pulmonary and cardiovascular involvement. Minor complications can be related to specific structural features of NIV interfaces or to variable airflow patterns. This extensive review of the literature shows that careful selection of patients and interfaces, proper setting of ventilator modalities, and close monitoring of patients from the start can greatly reduce NIV complications.

Efficacy and predictors of success of noninvasive ventilation for prevention of extubation failure in critically ill children with heart disease

The study aimed primarily to evaluate the efficacy of noninvasive ventilation (NIV) and to identify possible predictors for success of NIV therapy in preventing extubation failure in critically ill children with heart disease. The secondary objectives of this study were to assess the efficacy of prophylactic NIV therapy initiated immediately after tracheal extubation and to determine the characteristics, outcomes, and complications associated with NIV therapy in pediatric cardiac patients. A retrospective review examined the medical records of all children between the ages 1 day and 18 years who sustained acute respiratory failure (ARF) that required NIV in the cardiovascular intensive care unit (CVICU) at Lucile Packard Children's Hospital between January 2008 and June 2010. Patients were assigned to a prophylactic group if NIV was started directly after extubation and to a nonprophylactic group if NIV was started after signs and symptoms of ARF developed. Patients were designated as responders if they received NIV and did not require reintubation during their CVICU stay and nonresponders if they failed NIV and reintubation was performed. The data collected included demographic data, preexisting conditions, pre-event characteristics, event characteristics, and outcome data. The outcome data evaluated included success or failure of NIV, duration of NIV, CVICU length of stay (LOS), hospital LOS, and hospital mortality. The two complications of NIV assessed in the study included nasal bridge or forehead skin necrosis and pneumothorax. The 221 eligible events during the study period involved 172 responders (77.8 %) and 49 nonresponders (22.2 %). A total of 201 events experienced by the study cohort received continuous positive airway pressure (CPAP), with 156 responders (78 %), whereas 20 events received bilevel positive airway pressure (BiPAP), with 16 responders (80 %). In the study, 58 events (26.3 %) were assigned to the prophylactic group and 163 events (73.7 %) to the nonprophylactic group. Compared with the nonprophylactic group, the prophylactic group experienced significantly shorter CVICU LOS (median, 49 vs 88 days; p = 0.03) and hospital LOS (median, 60 vs 103 days; p = 0.05). The CVICU LOS and hospital LOS did not differ significantly between the responders (p = 0.56) and nonresponders (p = 0.88). Significant variables identifying a responder included a lower risk-adjusted classification for congenital heart surgery (RACHS-1) score (1-3), a good left ventricular ejection fraction, a normal respiratory rate (RR), normal or appropriate oxygen saturation, prophylactic or therapeutic glucocorticoid therapy within 24 h of NIV initiation, presence of atelectasis, fewer than two organ system dysfunctions, fewer days of intubation before extubation, no clinical or microbiologic evidence of sepsis, and no history of reactive airway disease. As a well-tolerated therapy, NIV can be safely and successfully applied in critically ill children with cardiac disease to prevent extubation failure. The independent predictors of NIV success include lower RACHS-1 classification, presence of atelectasis, steroid therapy received within 24 h after NIV, and normal heart rate and oxygen saturations demonstrated within 24 h after initiation of NIV.

Noninvasive ventilation immediately after extubation improves weaning outcome after acute respiratory failure: a randomized controlled trial

INTRODUCTION

Noninvasive ventilation (NIV), as a weaning-facilitating strategy in predominantly chronic obstructive pulmonary disease (COPD) mechanically ventilated patients, is associated with reduced ventilator-associated pneumonia, total duration of mechanical ventilation, length of intensive care unit (ICU) and hospital stay, and mortality. However, this benefit after planned extubation in patients with acute respiratory failure of various etiologies remains to be elucidated. The aim of this study was to determine the efficacy of NIV applied immediately after planned extubation in contrast to oxygen mask (OM) in patients with acute respiratory failure (ARF).

METHODS

A randomized, prospective, controlled, unblinded clinical study in a single center of a 24-bed adult general ICU in a university hospital was carried out in a 12-month period. Included patients met extubation criteria with at least 72 hours of mechanical ventilation due to acute respiratory failure, after following the ICU weaning protocol. Patients were randomized immediately before elective extubation, being randomly allocated to one of the study groups: NIV or OM. We compared both groups regarding gas exchange 15 minutes, 2 hours, and 24 hours after extubation, reintubation rate after 48 hours, duration of mechanical ventilation, ICU length of stay, and hospital mortality.

RESULTS

Forty patients were randomized to receive NIV (20 patients) or OM (20 patients) after the following extubation criteria were met: pressure support (PSV) of 7 cm H2O, positive end-expiratory pressure (PEEP) of 5 cm H2O, oxygen inspiratory fraction (FiO2)≤40%, arterial oxygen saturation (SaO2)≥90%, and ratio of respiratory rate and tidal volume in liters (f/TV)<105. Comparing the 20 patients (NIV) with the 18 patients (OM) that finished the study 48 hours after extubation, the rate of reintubation in NIV group was 5% and 39% in OM group (P=0.016). Relative risk for reintubation was 0.13 (CI=0.017 to 0.946). Absolute risk reduction for reintubation showed a decrease of 33.9%, and analysis of the number needed to treat was three. No difference was found in the length of ICU stay (P=0.681). Hospital mortality was zero in NIV group and 22.2% in OM group (P=0.041).

CONCLUSIONS

In this study population, NIV prevented 48 hours reintubation if applied immediately after elective extubation in patients with more than 3 days of ARF when compared with the OM group.

TRIAL REGISTRATION NUMBER ISRCTN

41524441.

Effects of mechanical insufflation-exsufflation in preventing respiratory failure after extubation: a randomized controlled trial

Introduction

Weaning protocols that include noninvasive ventilation (NIV) decrease re-intubation rates and ICU length of stay. However, impaired airway clearance is associated with NIV failure. Mechanical insufflation-exsufflation (MI-E) has been proven to be very effective in patients receiving NIV. We aimed to assess the efficacy of MI-E as part of an extubation protocol.

Method

Patients with mechanical ventilation (MV) for more than 48 hours with specific inclusion criteria, who successfully tolerated a spontaneous breathing trial (SBT), were randomly allocated before extubation, either for (A) a conventional extubation protocol (control group), or (B) the MI-E extubation protocol (study group). During the postextubation period (48 hours), group A patients received standard medical treatment (SMT), including NIV in case of specific indications, whereas group B received the same postextubation approach plus three daily sessions of mechanical in-exsufflation (MI-E). Reintubation rates, ICU length of stay, and NIV failure rates were analyzed.

Results

Seventy-five patients (26 women) with a mean age of 61.8 ± 17.3 years were randomized to a control group (n = 40; mean SAPS II, 47.8 ± 17.7) and to a study group (n = 35; mean SAPS II, 45.0 ± 15.0). MV time before enrollment was 9.4 ± 4.8 and 10.5 ± 4.1 days for the control and the study group, respectively. In the 48 hours after extubation, 20 control patients (50%) and 14 study patients (40%) used NIV. Study group patients had a significant lower reintubation rate than did controls; six patients (17%) versus 19 patients (48%), P < 0.05; respectively, and a significantly lower time under MV; 17.8 ± 6.4 versus 11.7 ± 3.5 days; P < 0.05; respectively. Considering only the subgroup of patients that used NIV, the reintubation rates related to NIV failure were significantly lower in the study group when compared with controls; two patients (6%) versus 13 (33%); P < 0.05, respectively. Mean ICU length of stay after extubation was significantly lower in the study group when compared with controls (3.1 ± 2.5 versus 9.8 ± 6.7 days; P < 0.05). No differences were found in the total ICU length of stay.

Conclusion

Inclusion of MI-E may reduce reintubation rates with consequent reduction in postextubation ICU length of stay. This technique seems to be efficient in improving the efficacy of NIV in this patient population.

Noninvasive mechanical ventilation in chronic obstructive pulmonary disease and in acute cardiogenic pulmonary edema

Noninvasive ventilation (NIV) with conventional therapy improves the outcome of patients with acute respiratory failure due to hypercapnic decompensation of chronic obstructive pulmonary disease (COPD) or acute cardiogenic pulmonary edema (ACPE). This review summarizes the main effects of NIV in these pathologies. In COPD, NIV improves gas exchange and symptoms, reducing the need for endotracheal intubation, hospital mortality and hospital stay compared with conventional oxygen therapy. NIV may also avoid reintubation and may decrease the length of invasive mechanical ventilation. In ACPE, NIV accelerates the remission of symptoms and the normalization of blood gas parameters, reduces the need for endotracheal intubation, and is associated with a trend towards lesser mortality, without increasing the incidence of myocardial infarction. The ventilation modality used in ACPE does not affect the patient prognosis.

[Difficult to wean patients]

Approximately 10% of patients with mechanical ventilation experience prolonged weaning and also have an increased morbidity and mortality. Once spontaneous breathing trials have failed the organ systems responsible should be identified. This can be accomplished during the spontaneous breathing trial using clinical examination, measurement of blood gases, echocardiography and imaging techniques. Specific patterns allow the diagnosis of pathological respiratory mechanisms, weak ventilatory muscles, heart failure, myocardial ischemia and psychiatric problems. Respiratory and cardiac limitations of weaning can be overcome by reducing the ventilatory load, training of the ventilatory muscles and reducing cardiac workload. A cooperative sedation strategy as well as an early start of weaning and rehabilitation can prevent prolonged weaning in critically ill patients.

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

OBJECTIVES

To compare the respective impact of pressure support ventilation and naturally adjusted ventilatory assist, with and without a noninvasive mechanical ventilation algorithm, on patient-ventilator interaction.

DESIGN

Prospective 2-month study.

SETTING

Adult critical care unit in a tertiary university hospital.

PATIENTS

Seventeen patients receiving a prophylactic postextubation noninvasive mechanical ventilation.

INTERVENTIONS

Patients were randomly mechanically ventilated for 10 mins with: pressure support ventilation without a noninvasive mechanical ventilation algorithm (PSV-NIV-), pressure support ventilation with a noninvasive mechanical ventilation algorithm (PSV-NIV+), neurally adjusted ventilatory assist without a noninvasive mechanical ventilation algorithm (NAVA-NIV-), and neurally adjusted ventilatory assist with a noninvasive mechanical ventilation algorithm (NAVA-NIV+).

MEASUREMENTS AND MAIN RESULTS

Breathing pattern descriptors, diaphragm electrical activity, leak volume, inspiratory trigger delay, inspiratory time in excess, and the five main asynchronies were quantified. Asynchrony index and asynchrony index influenced by leaks were computed. Peak inspiratory pressure and diaphragm electrical activity were similar for each of the four experimental conditions. For both pressure support ventilation and neurally adjusted ventilatory assist, the noninvasive mechanical ventilation algorithm significantly reduced the level of leakage (p < .01). Inspiratory trigger delay was not affected by the noninvasive mechanical ventilation algorithm but was shorter in neurally adjusted ventilatory assist than in pressure support ventilation (p < .01). Inspiratory time in excess was shorter in neurally adjusted ventilatory assist and PSV-NIV+ than in PSV-NIV- (p < .05). Asynchrony index was not affected by the noninvasive mechanical ventilation algorithm but was significantly lower in neurally adjusted ventilatory assist than in pressure support ventilation (p < .05). Asynchrony index influenced by leaks was insignificant with neurally adjusted ventilatory assist and significantly lower than in pressure support ventilation (p < .05). There was more double triggering with neurally adjusted ventilatory assist.

CONCLUSIONS

Both neurally adjusted ventilatory assist and a noninvasive mechanical ventilation algorithm improve patient-ventilator synchrony in different manners. NAVA-NIV+ offers the best compromise between a good patient-ventilator synchrony and a low level of leaks. Clinical studies are required to assess the potential clinical benefit of neurally adjusted ventilatory assist in patients receiving noninvasive mechanical ventilation.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier NCT01280760.

Noninvasive positive-pressure ventilation in clinical practice at a large university-affiliated Brazilian hospital

OBJECTIVES

To describe noninvasive positive-pressure ventilation use in intensive care unit clinical practice, factors associated with NPPV failure and the associated prognosis.

METHODS

A prospective cohort study.

RESULTS

Medical disorders (59%) and elective surgery (21%) were the main causes for admission to the intensive care unit. The main indications for the initiation of noninvasive positive-pressure ventilation were the following: post-extubation, acute respiratory failure and use as an adjunctive technique to chest physiotherapy. The noninvasive positive-pressure ventilation failure group was older and had a higher Simplified Acute Physiology Score II score. The noninvasive positive-pressure ventilation failure rate was 35%. The main reasons for intubation were acute respiratory failure (55%) and a decreased level of consciousness (20%). The noninvasive positive-pressure ventilation failure group presented a shorter period of noninvasive positive-pressure ventilation use than the successful group [three (2-5) versus four (3-7) days]; they had lower levels of pH, HCO3 and base excess, and the FiO2 level was higher. These patients also presented lower PaO2:FiO2 ratios; on the last day of support, the inspiratory positive airway pressure and expiratory positive airway pressure were higher. The failure group also had a longer average duration of stay in the intensive care unit [17 (10-26) days vs. 8 (5-14) days], as well as a higher mortality rate (9 vs. 51%). There was an association between failure and mortality, which had an odds ratio (95% CI) of 10.6 (5.93 -19.07). The multiple logistic regression analysis using noninvasive positive pressure ventilation failure as a dependent variable found that treatment tended to fail in patients with a Simplified Acute Physiology Score II ≥ 34, an inspiratory positive airway pressure level ≥ 15 cmH2O and pH<7.40.

CONCLUSION

The indications for noninvasive positive-pressure ventilation were quite varied. The failure group had a longer intensive care unit stay and higher mortality. Simplified Acute Physiology Score II ≥ 34, pH<7.40 and higher inspiratory positive airway pressure levels were associated with failure.

Diaphragm ultrasonography to estimate the work of breathing during non-invasive ventilation

PURPOSE

Ultrasonography allows the direct observation of the diaphragm. Its thickness variation measured in the zone of apposition has been previously used to diagnose diaphragm paralysis. We assessed the feasibility and accuracy of this method to assess diaphragmatic function and its contribution to respiratory workload in critically ill patients under non-invasive ventilation.

METHODS

This was a preliminary physiological study in the intensive care unit of a university hospital. Twelve patients requiring planned non-invasive ventilation after extubation were studied while spontaneously breathing and during non-invasive ventilation at three levels of pressure support (5, 10 and 15 cmH(2)O). Diaphragm thickness was measured in the zone of apposition during tidal ventilation and the thickening fraction (TF) was calculated as (thickness at inspiration - thickness at expiration)/thickness at expiration. Diaphragmatic pressure-time product per breath (PTP(di)) was measured from oesophageal and gastric pressure recordings.

RESULTS

PTP(di) and TF both decreased as the level of pressure support increased. A significant correlation was found between PTP(di) and TF (ρ = 0.74, p < 0.001). The overall reproducibility of TF assessment was good but the coefficient of repeatability reached 18% for inter-observer reproducibility.

CONCLUSIONS

Ultrasonographic assessment of the diaphragm TF is a non-invasive method that may prove useful in evaluating diaphragmatic function and its contribution to respiratory workload in intensive care unit patients.

Lung physiology and obesity: anesthetic implications for thoracic procedures

Obesity is a worldwide health problem affecting 34% of the American population. As a result, more patients requiring anesthesia for thoracic surgery will be overweight or obese. Changes in static and dynamic respiratory mechanics, upper airway anatomy, as well as multiple preoperative comorbidities and altered drug metabolism, characterize obese patients and affect the anesthetic plan at multiple levels. During the preoperative evaluation, patients should be assessed to identify who is at risk for difficult ventilation and intubation, and postoperative complications. The analgesia plan should be executed starting in the preoperative area, to increase the success of extubation at the end of the case and prevent reintubation. Intraoperative ventilatory settings should be customized to the changes in respiratory mechanics for the specific patient and procedure, to minimize the risk of lung damage. Several non invasive ventilatory modalities are available to increase the success rate of extubation at the end of the case and to prevent reintubation. The goal of this review is to evaluate the physiological and anatomical changes associated with obesity and how they affect the multiple components of the anesthetic management for thoracic procedures.

Results of noninvasive ventilation in very old patients

Background

Noninvasive ventilation (NIV) is frequently used for the management of acute respiratory failure (ARF) in very old patients (≥ 80 years), often in the context of a do-not-intubate order (DNI). We aimed to determine its efficacy and long-term outcome.

Methods

Prospective cohort of all patients admitted to the medical ICU of a tertiary hospital during a 2-year period and managed using NIV. Characteristics of patients, context of NIV, and treatment intensity were compared for very old and younger patients. Six-month survival and functional status were assessed in very old patients.

Results

During the study period, 1,019 patients needed ventilatory support and 376 (37%) received NIV. Among them, 163 (16%) very old patients received ventilatory support with 60% of them managed using NIV compared with 32% of younger patients (p < 0.0001). Very old patients received NIV more frequently with DNI than in younger patients (40% vs. 8%). Such cases were associated with high mortality for both very old and younger patients. Hospital mortality was higher in very old than in younger patients but did not differ when NIV was used for cardiogenic pulmonary edema or acute-on-chronic respiratory failure (20% vs. 15%) and in postextubation (15% vs. 17%) out of a context of DNI. Six-month mortality was 51% in very old patients, 67% for DNI patients, and 77% in case of NIV failure and endotracheal intubation. Of the 30 hospital survivors, 22 lived at home and 13 remained independent for activities of daily living.

Conclusions

Very old patients managed using NIV have an overall satisfactory 6-month survival and functional status, except for endotracheal intubation after NIV failure.

Postoperative respiratory failure after cardiac surgery: use of noninvasive ventilation

OBJECTIVES

To analyze the use of noninvasive ventilation (NIV) in respiratory failure after extubation in patients after cardiac surgery, the factors associated with respiratory failure, and the need for reintubation.

DESIGN

Retrospective observational study.

SETTING

Intensive care unit in a university hospital.

PARTICIPANTS

Patients (n = 63) with respiratory failure after extubation after cardiac surgery over a 3-year period.

INTERVENTIONS

Mechanical NIV.

MEASUREMENTS AND MAIN RESULTS

Demographic and surgical data, respiratory history, causes of postoperative respiratory failure, durations of mechanical ventilation and spontaneous breathing, gas exchange values, and the mortality rate were recorded. Of 1,225 postsurgical patients, 63 (5.1%) underwent NIV for respiratory failure after extubation. The median time from extubation to the NIV application was 40 hours (18-96 hours). The most frequent cause of respiratory failure was lobar atelectasis (25.4%). The NIV failed in 52.4% of patients (33/63) who had a lower pH at 24 hours of treatment (7.35 v 7.42, p = 0.001) and a higher hospital mortality (51.5% v 6.7%, p = 0.001) than those in whom NIV was successful. An interval <24 hours from extubation to NIV was a predictive factor for NIV failure (odds ratio, 4.6; 95% confidence interval, 1.2-17.9), whereas obesity was associated with NIV success (odds ratio, 0.22; 95% confidence interval, 0.05-0.91).

CONCLUSIONS

Reintubation was required in half of the NIV-treated patients and was associated with an increased hospital mortality rate. Early respiratory failure after extubation (≤24 hours) is a predictive factor for NIV failure.

Outcomes of extubation failure in medical intensive care unit patients

OBJECTIVE

Extubation failure is associated with a poor prognosis, but the respective roles for reintubation per se and underlying disease severity remain unclear. Our objectives were to evaluate the impact of failed extubation, whether planned or unplanned, on patient outcomes and to identify a patient subset at risk for extubation failure.

DESIGN

Prospective 1-yr observational study with daily data collection.

SETTING

: Thirteen-bed medical intensive care unit in a teaching hospital.

PATIENTS

Consecutive patients requiring invasive mechanical ventilation were screened and followed until discharge or death.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 168 planned extubations in 340 patients, 26 (15%) failed. Of these 26 patients, seven (27%) had pneumonia and 13 (50%) died after reintubation. Compared with successfully extubated patients, the patients with failed extubation were not significantly different regarding disease severity, mechanical ventilation duration, or blood gas values. Age and underlying diseases were the only factors associated with extubation failure, and extubation failure occurred in 34% of patients >65 yrs with chronic cardiac or respiratory disease compared with only 9% of other patients (p < .01). Unplanned extubation occurred in 9% of patients, and inadequate endotracheal tube position was a risk factor. Failure of both planned and unplanned extubation was specifically associated with significant rapid worsening of daily organ dysfunction scores.

CONCLUSIONS

Patients >65 yrs with underlying chronic cardiac or respiratory disease are at high risk for extubation failure and subsequent pneumonia and death. Contrasting with successful extubation, failed planned or unplanned extubation was followed by marked clinical deterioration, suggesting a direct and specific effect of extubation failure and reintubation on patient outcomes.

Noninvasive ventilation and weaning in patients with chronic hypercapnic respiratory failure: a randomized multicenter trial

RATIONALE

The use of noninvasive ventilation (NIV) as an early weaning/extubation technique from mechanical ventilation remains controversial.

OBJECTIVES

To investigate NIV effectiveness as an early weaning/extubation technique in difficult-to-wean patients with chronic hypercapnic respiratory failure (CHRF).

METHODS

In 13 intensive care units, 208 patients with CHRF intubated for acute respiratory failure (ARF) who failed a first spontaneous breathing trial were randomly assigned to three groups: conventional invasive weaning group (n = 69), extubation followed by standard oxygen therapy (n = 70), or NIV (n = 69). NIV was permitted as rescue therapy for both non-NIV groups if postextubation ARF occurred. Primary endpoint was reintubation within 7 days after extubation. Secondary endpoints were: occurrence of postextubation ARF or death within 7 days after extubation, use of rescue postextubation NIV, weaning time, and patient outcomes.

MEASUREMENTS AND MAIN RESULTS

Reintubation rates were 30, 37, and 32% for invasive weaning, oxygen-therapy, and NIV groups, respectively (P = 0.654). Weaning failure rates, including postextubation ARF, were 54, 71, and 33%, respectively (P < 0.001). Rescue NIV success rates for invasive and oxygen-therapy groups were 45 and 58%, respectively (P = 0.386). By design, intubation duration was 1.5 days longer for the invasive group than in the two others. Apart from a longer weaning time in NIV than in invasive group (2.5 vs. 1.5 d; P = 0.033), no significant outcome difference was observed between groups.

CONCLUSIONS

No difference was found in the reintubation rate between the three weaning strategies. NIV decreases the intubation duration and may improve the weaning results in difficult-to-wean patients with CHRF by reducing the risk of postextubation ARF. The benefit of rescue NIV in these patients deserves confirmation.

Noninvasive positive pressure ventilation in unplanned extubation

BACKGROUND:

Unplanned extubation is quite common in intensive care unit (ICU) patients receiving mechanical ventilatory support. The present study aimed to investigate the effectiveness of noninvasive positive pressure ventilation (NPPV) in patients with unplanned extubation.

MATERIALS AND METHODS:

A total of 15 patients (12 male, age: 57 ± 24 years, APACHE II score: 19 ± 7) monitored at the medical ICU during the year 2004 who developed unplanned extubation were included in the study. NPPV was tried in all of them following unplanned extubation. Indications for admission to the ICU were as follows: nine patients with pneumonia, three with status epilepticus, one with gastrointestinal bleeding, one with cardiogenic pulmonary edema and one with diffuse alveolar bleeding.

RESULTS:

Eleven of the patients (74%) were at the weaning period at the time of unplanned extubation. Among these 11 patients, NPPV was successful in 10 (91%) and only one (9%) was reintubated due to the failure of NPPV. The remaining four patients (26%) had pneumonia and none of them were at the weaning period at the time of extubation, but their requirement for mechanical ventilation was gradually decreasing. Unfortunately, an NPPV attempt for 6–8 h failed and these patients were reintubated.

CONCLUSIONS:

Patients with unplanned extubation before the weaning criteria are met should be intubated immediately. On the other hand, when extubation develops during the weaning period, NPPV may be an alternative. The present study was conducted with a small number of patients, and larger studies on the effectiveness of NPPV in unplanned extubation are warranted for firm conclusions.

Non-invasive ventilation after extubation in patients with chronic obstructive airways disease: a randomised controlled trial

Non-invasive positive pressure ventilation (NPPV) is a well established therapy for acute respiratory failure in patients with chronic obstructive pulmonary disease, however its role in post-extubation period is uncertain. The objective of this study was to find the effect of NPPV on rate of re-intubation, intensive care unit and hospital stay, and physiological parameters in severe chronic obstructive pulmonary disease patients after planned extubation. Forty patients with severe chronic obstructive pulmonary disease were randomised immediately after planned extubation to receive NPPV (n=20) or conventional therapy (n=20). NPPV was delivered with mean levels of inspiratory positive-airway pressure of 12.10 +/- 1.37 cmH2O and expiratory positive-airway pressure of 6.50 +/- 1.00 cmH2O for a mean period of 34.75 +/- 10 hours for 7 to 11 hours/day. Patients in conventional therapy group received usual treatment. Reintubation rate among NPPV (15%) and conventional (25%) were similar (P=0.44). The duration of intensive care unit stay after extubation (2.05 +/- 2.15 vs 1.55 +/- 0.82 days, P=0.34) and hospital stay (16.10 +/- 6.29 vs 18.25 +/- 7.91 days, P=0.34) in both groups were comparable. Given the load of chronic obstructive pulmonary disease patients and wide availability of NPPV it is safe to recommend its use in these patients soon after extubation, although clear benefit is not documented in this study.

Outcome of reintubated patients after scheduled extubation

PURPOSE

The main objective of study was to evaluate the outcome of patients who require reintubation after elective extubation.

MATERIALS AND METHODS

This is an observational, prospective cohort study including mechanically ventilated patients who passed successfully a spontaneous breathing trial. Patients were observed for 48 hours after extubation. During this time, reintubation or use of noninvasive positive pressure ventilation was considered as a failure. Reintubated patients were followed after the reintubation to register complications and outcome.

RESULTS

A total of 1,152 extubated patients were included in the analysis. Three hundred thirty-six patients (29%) met the criteria for extubation failure. Extubation failure was independently associated with mortality (odds ratio, 3.29; 95% confidence interval, 2.19-4.93). One hundred eighty patients (16% of overall cohort) required reintubation within 48 hours after extubation. Median time from extubation to reintubation was 13 hours (interquartile range, 6-24 hours). Reintubation was independently associated with mortality (odds ratio, 5.18; 95% confidence interval, 3.38-7.94; P < .001). Higher mortality of reintubated patients was due to the development of complications after the reintubation.

CONCLUSIONS

In a large cohort of scheduled extubated patients, one third of patients developed extubation failure, of whom half needed reintubation. Reintubation was associated with increased mortality due to the development of new complications after reintubation.

End-expiratory lung volume and ventilation distribution with different continuous positive airway pressure systems in volunteers

BACKGROUND

Continuous positive airway pressure (CPAP) has been shown to improve oxygenation and a number of different CPAP systems are available. The aim of this study was to assess lung volume and ventilation distribution using three different CPAP techniques.

METHODS

A high-flow CPAP system (HF-CPAP), an ejector-driven system (E-CPAP) and CPAP using a Servo 300 ventilator (V-CPAP) were randomly applied at 0, 5 and 10 cmH₂O in 14 volunteers. End-expiratory lung volume (EELV) was measured by N₂ dilution at baseline; changes in EELV and tidal volume distribution were assessed by electric impedance tomography.

RESULTS

Higher end-expiratory and mean airway pressures were found using the E-CPAP vs. the HF-CPAP and the V-CPAP system (P<0.01). EELV increased markedly from baseline, 0 cmH₂O, with increased CPAP levels: 1110±380, 1620±520 and 1130±350 ml for HF-, E- and V-CPAP, respectively, at 10 cmH₂O. A larger fraction of the increase in EELV occurred for all systems in ventral compared with dorsal regions (P<0.01). In contrast, tidal ventilation was increasingly directed toward dorsal regions with increasing CPAP levels (P<0.01). The increase in EELV as well as the tidal volume redistribution were more pronounced with the E-CPAP system as compared with both the HF-CPAP and the V-CPAP systems (P<0.05) at 10 cmH₂O.

CONCLUSION

EELV increased more in ventral regions with increasing CPAP levels, independent of systems, leading to a redistribution of tidal ventilation toward dorsal regions. Different CPAP systems resulted in different airway pressure profiles, which may result in different lung volume expansion and tidal volume distribution.