Scott K. Epstein

Extubation failure: magnitude of the problem, impact on outcomes, and prevention.

Extubation failure, defined as the need for reinstitution of ventilatory support within 24 to 72 hours of planned endotracheal tube removal, occurs in 2 to 25% of extubated patients. The pathophysiologic causes of extubation failure include an imbalance between respiratory muscle capacity and work of breathing, upper airway obstruction, excess respiratory secretions, inadequate cough, encephalopathy, and cardiac dysfunction. Compared with patients who tolerate extubation, those who require reintubation have a higher incidence of hospital mortality, increased length of ICU and hospital stay, prolonged duration of mechanical ventilation, higher hospital costs, and an increased need for tracheostomy. Given the lack of proven treatments for extubation failure, clinicians must be aware of the factors that predict extubation outcome to improve clinical decision making. Risk factors for extubation failure include being a medical, multidisciplinary, or pediatric patient; age greater than 70 years; a longer duration of mechanical ventilation; continuous intravenous sedation; and anemia. Tests designed to assess for upper airway obstruction, secretion volume, and the effectiveness of cough can help to improve prediction of extubation failure. Rapid reinstitution of ventilatory support in patients who fail extubation may improve outcome.

Characteristics and Outcomes of Ventilated Patients According to Time to Liberation from Mechanical Ventilation

RATIONALE A new classification of patients based on the duration of liberation of mechanical ventilation has been proposed. OBJECTIVES To analyze outcomes based on the new weaning classification in a cohort of mechanically ventilated patients. METHODS Secondary analysis included 2,714 patients who were weaned and underwent scheduled extubation from a cohort of 4,968 adult patients mechanically ventilated for more than 12 hours. MEASUREMENTS AND MAIN RESULTS Patients were classified according to a new weaning classification: 1,502 patients (55%) as simple weaning,1,058 patients (39%) as difficult weaning, and 154 (6%) as prolonged weaning.Variables associated with prolonged weaning(.7d)were: severity at admission (odds ratio [OR] per unit of Simplified Acute Physiology Score II, 1.01; 95% confidence interval [CI], 1.001–1.02), duration of mechanical ventilation before first attempt of weaning (OR per day, 1.10; 95% CI, 1.06–1.13), chronic pulmonary disease other than chronic obstructive pulmonary disease (OR,13.23; 95% CI, 3.44–51.05), pneumonia as the reason to start mechanical ventilation (OR, 1.82; 95% CI, 1.07–3.08), and level of positive end-expiratory pressure applied before weaning (OR per unit,1.09; 95% CI, 1.04–1.14). The prolonged weaning group had a nonsignificant trend toward a higher rate of reintubation (P ¼ 0.08),tracheostomy (P ¼ 0.15), and significantly longer length of stay and higher mortality in the intensive care unit (OR for death, 1.97;95%CI, 1.17–3.31). The adjusted probability of death remained constant until Day 7, at which point it increased to 12.1%.

Ineffective triggering predicts increased duration of mechanical ventilation.

Objectives: To determine whether high rates of ineffective triggering within the first 24 hrs of mechanical ventilation (MV) are associated with longer MV duration and shorter ventilator‐free survival (VFS). Design: Prospective cohort study. Setting: Medical intensive care unit (ICU) at an academic medical center. Patients: Sixty patients requiring invasive MV. Interventions: None. Measurements: Patients had pressure‐time and flow‐time waveforms recorded for 10 mins within the first 24 hrs of MV initiation. Ineffective triggering index (ITI) was calculated by dividing the number of ineffectively triggered breaths by the total number of breaths (triggered and ineffectively triggered). A priori, patients were classified into ITI >=10% or ITI <10%. Patient demographics, MV reason, codiagnosis of chronic obstructive pulmonary disease (COPD), sedation levels, and ventilator parameters were recorded. Measurements and Main Results: Sixteen of 60 patients had ITI >=10%. The two groups had similar characteristics, including COPD frequency and ventilation parameters, except that patients with ITI >=10% were more likely to have pressured triggered breaths (56% vs. 16%, p = .003) and had a higher intrinsic respiratory rate (22 breaths/min vs. 18, p = .03), but the set ventilator rate was the same in both groups (9 breaths/min vs. 9, p = .78). Multivariable analyses adjusting for pressure triggering also demonstrated that ITI >=10% was an independent predictor of longer MV duration (10 days vs. 4, p = .0004) and shorter VFS (14 days vs. 21, p = .03). Patients with ITI >=10% had a longer ICU length of stay (8 days vs. 4, p = .01) and hospital length of stay (21 days vs. 8, p = .03). Mortality was the same in the two groups, but patients with ITI >=10% were less likely to be discharged home (44% vs. 73%, p = .04). Conclusions: Ineffective triggering is a common problem early in the course of MV and is associated with increased morbidity, including longer MV duration, shorter VFS, longer length of stay, and lower likelihood of home discharge.

Perceived barriers to the use of sedation protocols and daily sedation interruption: a multidisciplinary survey.

BACKGROUND Although use of sedation protocols and daily sedation interruption (DSI) improve outcome, their current use and barriers affecting their use are unclear. METHODS We designed a multidisciplinary, Web-based survey to determine current use of sedation protocols and DSI and the perceived barriers to each, and administered it to members of the Society of Critical Care Medicine. RESULTS The 904 responders were physicians (60%), nurses (14%), or pharmacists (12%); 45% worked in a university hospital. Of 64% having a sedation protocol, 78% used it for >or=50% of ventilated patients. Reasons for lack of protocol use included no physician order (35%), lack of nursing support (11%), and a fear of oversedation (7%). Daily sedation interruption was used by only 40%. Barriers to DSI included lack of nursing acceptance (22%), concern about risk of patient-initiated device removal (19%), and inducement of either respiratory compromise (26%) or patient discomfort (13%). Clinicians who prefer propofol were more likely to use DSI than those who prefer benzodiazepines (55% vs 40, P < .0001). CONCLUSIONS Current intensive care unit sedation practices are heterogeneous, and the barriers preventing the use of both sedation protocols and DSI are numerous. These barriers should be addressed on an institutional basis to boost the use of these evidence-based practices.

Randomized trial comparing daily interruption of sedation and nursing-implemented sedation algorithm in medical intensive care unit patients

IntroductionDaily interruption of sedation (DIS) and sedation algorithms (SAs) have been shown to decrease mechanical ventilation (MV) duration. We conducted a randomized study comparing these strategies.MethodsMechanically ventilated adults 18 years old or older in the medical intensive care unit (ICU) were randomly assigned to DIS or SA. Exclusion criteria were severe neurocognitive dysfunction, administration of neuromuscular blockers, and tracheostomy. Study endpoints were total MV duration and 28-day ventilator-free survival.ResultsThe study was terminated prematurely after 74 patients were enrolled (DIS 36 and SA 38). The two groups had similar age, gender, racial distribution, Acute Physiology and Chronic Health Evaluation II score, and reason for MV. The Data Safety Monitoring Board convened after DIS patients were found to have higher hospital mortality; however, no causal connection between DIS and increased mortality was identified. Interim analysis demonstrated a significant difference in primary endpoint, and study termination was recommended. The DIS group had longer total duration of MV (median 6.7 versus 3.9 days; P = 0.0003), slower improvement of Sequential Organ Failure Assessment over time (0.70 versus 0.23 units per day; P = 0.025), longer ICU length of stay (15 versus 8 days; P < 0.0001), and longer hospital length of stay (23 versus 12 days; P = 0.01).ConclusionIn our cohort of patients, the use of SA was associated with reduced duration of MV and lengths of stay compared with DIS. Based on these results, DIS may not be appropriate in all mechanically ventilated patients.Trial registrationClinicalTrials.gov NCT00205517.

A randomized, controlled trial of the role of weaning predictors in clinical decision making*

Objective:Weaning predictors are often incorporated in protocols to predict weaning outcome for patients on mechanical ventilation. The predictors are used as a decision point in protocols to determine whether a patient may advance to a spontaneous breathing trial. The impact of including predictors in a weaning protocol has not been previously studied. We designed a study to determine the effect of including a weaning predictor (frequency-tidal volume ratio, or ƒ/Vt) in a weaning protocol. Design:Randomized, blinded controlled trial. Setting:Academic teaching hospitals. Patients:Three hundred and four patients admitted to intensive care units at three academic teaching hospitals. Interventions:Patients were screened daily for measures of oxygenation, cough and secretions, adequate mental status, and hemodynamic stability. Patients were randomized to two groups; in one group the ƒ/Vt was measured but not used in the decision to wean (n = 151), but in the other group, ƒ/Vt was measured and used, using a threshold of 105 breaths/min/L (n = 153). Patients passing the screen received a 2-hr spontaneous breathing trial. Patients passing the spontaneous breathing trial were eligible for an extubation attempt. Measurements and Main Results:Groups were similar with regard to gender, age, and Acute Physiology and Chronic Health Evaluation II score. The median duration for weaning time was significantly shorter in the group where the weaning predictor was not used (2.0 vs. 3.0 days, p = .04). There was no difference with regard to the extubation failure, in-hospital mortality rate, tracheostomy, or unplanned extubation. Conclusions:Including a weaning predictor (ƒ/Vt) in a protocol prolonged weaning time. In addition, the predictor did not confer survival benefit or reduce the incidence of extubation failure or tracheostomy. The results of this study indicate that ƒ/Vt should not be used routinely in weaning decision making.

Aerobic capacity is associated with 100-day outcome after hepatic transplantation.

The shortage of donor organs highlights the need to better identify patients most likely to benefit from hepatic transplantation. Reduced aerobic capacity (decreased peak oxygen consumption [V̇O2] during symptom‐limited cardiopulmonary exercise testing) is frequently present in cirrhosis. Peak V̇O2 during cardiopulmonary exercise testing may predict short‐term outcome after hepatic transplantation. Symptom‐limited testing was performed on a cycle ergometer (continuous ramp protocol) and V̇O2 determined using a metabolic cart. One hundred fifty‐six patients were tested; 59 subsequently underwent hepatic transplantation. Results showed that survivors and nonsurvivors were similar in age, duration of liver disease, Child‐Pugh score, MELD score, resting cardiovascular function, pulmonary function, and gas exchange. The 6 (10.2%) patients dying within 100 days of transplantation were more likely to have reduced aerobic capacity (peak V̇O2 <60% predicted and V̇O2 at anaerobic threshold [V̇O2‐AT] <50% predicted peak V̇O2) compared to survivors (4/6 vs. 7/53, P < .01). Using a multiple logistic regression model controlling for duration and severity of liver disease and time to transplantation, reduced aerobic capacity was independently associated with 100‐day mortality. In conclusion, reduced aerobic capacity during cardiopulmonary exercise testing is associated with decreased short‐term survival after hepatic transplantation. Further study is needed to determine if cardiopulmonary exercise testing can be used to improve allocation of donor organs. To ensure optimum allocation of donor organs, it is important to identify patients most likely to benefit from transplantation. Investigators have identified a number of preoperative, intraoperative, and postoperative factors that predict increased risk for postoperative mortality. Unfortunately, predictive accuracy has not been high, and the timing of factor identification does not optimize organ utilization. Identification of predictors of survival at the time of listing for transplantation might lead to better resource allocation. (Liver Transpl 2004;10:418–424.)

Weaning from ventilatory support.

Purpose of reviewIn intubated patients, mechanical ventilation offers essential ventilatory support, while the respiratory system recovers from acute respiratory failure. Yet, invasive mechanical ventilation is associated with risks and complications that prolong the duration of mechanical ventilation and increase the risk for death. Therefore, safely weaning the patient from the ventilator as soon as possible is paramount. Recent randomized trials have addressed a number of key areas of interest. Recent findingsDetermining readiness for spontaneous breathing, the first step in weaning, is best achieved using liberal oxygenation criteria; does not require routine use of weaning predictors; and can be conducted, in certain patient populations, using protocols driven by respiratory therapists or ICU nurses. Spontaneous breathing trials can be conducted on low levels of pressure support, continuous positive airway pressure, or T-piece. Weaning failure often results from an imbalance between respiratory load and capacity. There is increasing appreciation that cardiac dysfunction can limit weaning. Recent randomized trials suggest that noninvasive ventilation (in patients with chronic obstructive pulmonary disease) and computer-driven approaches show promise as weaning strategies. New techniques have been employed to identify patients at increased risk for extubation failure. Noninvasive ventilation, when used in high-risk patients, can decrease extubation failure. SummaryWeaning from mechanical ventilation continues to be an area of considerable importance. Recent randomized controlled trials provide high-level evidence for the best approaches to weaning and extubation.

Observational study of patient-ventilator asynchrony and relationship to sedation level.

PURPOSE Clinicians frequently administer sedation to facilitate mechanical ventilation. The purpose of this study was to examine the relationship between sedation level and patient-ventilator asynchrony. MATERIALS AND METHODS Airway pressure and airflow were recorded for 15 minutes. Patient-ventilator asynchrony was assessed by determining the number of breaths demonstrating ineffective triggering, double triggering, short cycling, and prolonged cycling. Ineffective triggering index (ITI) was calculated by dividing the number of ineffectively triggered breaths by the total number of breaths (triggered and ineffectively triggered). Sedation level was assessed by the following 3 methods: Richmond Agitation-Sedation Scale (RASS), awake (yes or no), and delirium (Confusion Assessment Method for the intensive care unit [CAM-ICU]). RESULTS Twenty medical ICU patients underwent 35 observations. Ineffective triggering was seen in 17 of 20 patients and was the most frequent asynchrony (88% of all asynchronous breaths), being observed in 9% +/- 12% of breaths. Deeper levels of sedation were associated with increasing ITI (awake, yes 2% vs no 11%; P < .05; CAM-ICU, coma [15%] vs delirium [5%] vs no delirium [2%]; P < .05; RASS, 0, 0% vs -5, 15%; P < .05). Diagnosis of chronic obstructive pulmonary disease, sedative type or dose, mechanical ventilation mode, and trigger method had no effect on ITI. CONCLUSIONS Asynchrony is common, and deeper sedation level is a predictor of ineffective triggering.

Arm training reduces the VO2 and VE cost of unsupported arm exercise and elevation in chronic obstructive pulmonary disease

BACKGROUND Patients with severe chronic obstructive pulmonary disease (COPD) may develop dyspnea with minimal arm activity, thoracoabdominal dyssynchrony with unsupported arm exercise (UAEX) and increased oxygen uptake (VO2), and minute ventilation (VE) with simple unsupported arm elevation (UAE) and UAEX. We investigated whether unsupported arm training, as the only form of exercise, could decrease the VO2 and VE cost (percentage increase from resting baseline) associated with unsupported arm elevation and exercise, respectively. METHODS Twenty-six patients with severe COPD were randomized to 21-24 sessions of unsupported arm (ARMT) or low-intensity resistive breathing (RBT) training as the only form of exercise. Patients were studied before and after training using a metabolic cart and esophageal and gastric pressures to evaluate metabolic and respiratory muscle function. RESULTS After ARMT, the VO2 (58% vs 38% increase, P < 0.05) and VE (41% v. 21% increase, P < 0.05) cost for UAEX at exercise isotime decreased and endurance time increased. Similarly the VO2 (25% vs 18% increase, P < 0.05) cost decreased and VE no longer increased in response to 2 minutes of UAE after ARMT. The RBT group showed no such change. No improvement in ventilatory load or respiratory muscle function could be identified to explain the physiologic changes observed. After ARMT, mean inspiratory flow (VT/TL), a measure of central respiratory drive, was reduced during UAEX and the expected increase during UAE did not occur. CONCLUSION We conclude that arm training reduces the VO2 and VE cost of UAE and UAEX, possibly through improved synchronization and coordination of accessory muscle action during unsupported arm activity.