Post-ICU weaning from mechanical ventilation: the role of long-term facilities.

A review of the largest observational studies on post-ICU weaning from prolonged mechanical ventilation yields evidence that more than half of such patients can be successfully liberated from mechanical ventilation. Success is likely to fall within a 3-month window, with late successes and partial ventilator independence still possible thereafter. There is a uniformity of practice in finishing difficult weaning with self-breathing trials of increasing duration.

Outcomes in post-ICU mechanical ventilation: a therapist-implemented weaning protocol.

BACKGROUND: Therapist-implemented protocols have been used to extubate or wean patients in the ICU setting. Barlow Respiratory Hospital (BRH) functions as a center for weaning patients from prolonged mechanical ventilation (PMV) in the post-ICU setting of a long-term acute-care (LTAC) facility. A therapist-implemented patient-specific (TIPS) weaning protocol was developed at BRH to standardize weaning from PMV. STUDY DESIGN: Prospective cohort study with historical control. METHODS: A weaning protocol incorporating the procedures and pace of LTAC weaning was developed using available scientific evidence and expert consensus. After training of staff, collection and analysis of pilot data, and revisions and refinement of the protocol, the TIPS protocol was implemented hospital-wide. It was monitored for outcome, variance, and respiratory care practitioner (RCP) and physician compliance. RESULTS: Forty-six RCPs worked with eight pulmonologists treating 271 consecutive patients admitted for weaning from PMV during an 18-month period. Nineteen patients were excluded from weaning attempts by any method after initial physician evaluation. The remaining 252 patients (9,135 total ventilator days) were compared with a group of 238 patients treated by the same physicians in the 2 years before instituting protocol weaning. Median time to wean declined significantly from 29 days in historical control subjects to 17 days for TIPS protocol patients (p < 0.001). Outcomes (scored at discharge) were comparable for the two groups (TIPS group vs control group): weaned, 54.7% vs 58.4%; ventilator-dependent, 17.9% vs 10.9%; died, 27.4% vs 30.7% (p = 0.10). Variances incurred by physicians and RCPs were 324 and 136, respectively, for the 9,135 ventilator days. CONCLUSIONS: Patients weaned from PMV using a new therapist-implemented protocol at BRH, an LTAC facility specializing in weaning, had significantly shorter time to weaning than historical control subjects, with comparable outcomes. The weaning outcome data collected after the implementation of the TIPS protocol are in fact attributable to its use, as we found a high degree of compliance with the protocol.

Approach to patients with long-term weaning failure.

Efforts to treat reversible disease processes that contribute to ventilator dependency in the intensive care unit (ICU) fail in up to 20% of patients, resulting in prolonged mechanical ventilation (PMV). Resolution of the insults that necessitated ICU admission and mechanical ventilation may be incomplete, and the economic pressure to transfer patients is ever increasing. The choice of post-ICU disposition depends on the patient's clinical condition, the resources of the transfer destination, and whether weaning attempts will continue. This article reviews data from a decade of weaning beyond the ICU, including outcomes of more than 2700 patients with PMV afforded continued attempts at liberation in long-term acute care facilities and other post-ICU weaning venues. Assessment and treatment, weaning strategies, and complications of patients with PMV are described.

Weaning from mechanical ventilation.

For the ventilator-dependent patient, weaning should be accomplished by withdrawing support safely, efficaciously, and efficiently. Success depends largely on physiologic determinants of respiratory system function, avoidance of ventilator-associated complications, and attention to patient readiness. Recent clinical trials, predictors of weaning, current techniques of weaning, the concept of reloading the respiratory pump, and determinants of ventilator dependency are all discussed.

Provision of long-term mechanical ventilation.

When patients suffer prolonged mechanical ventilation, physicians are faced with a series of decisions beginning in the intensive care unit (ICU) and extending into a broadening spectrum of post-ICU levels of care. This article reviews current thinking and outcome data on when and how to perform the tracheostomy, as well as when and where the patient should be transferred from the ICU for continued weaning efforts or support. Decannulation after success in weaning and continuation of ventilation at home are also addressed.

Patient-ventilator trigger asynchrony in prolonged mechanical ventilation.

STUDY OBJECTIVE: To investigate patient-ventilator trigger asynchrony (TA), its prevalence, physiologic basis, and clinical implications in patients requiring prolonged mechanical ventilation (PMV). STUDY DESIGN: Descriptive and prospective cohort study. SETTING: Barlow Respiratory Hospital (BRH), a regional weaning center. PATIENTS: Two hundred consecutive ventilator-dependent patients, transferred to BRH over an 18-month period for attempted weaning from PMV. METHODS AND INTERVENTIONS: Patients were assessed clinically for TA within the first week of hospital admission, or once they were in hemodynamically stable condition, by observation of uncoupling of accessory respiratory muscle efforts and onset of machine breaths. Patients were excluded if they had weaned by the time of assessment or if they never achieved hemodynamic stability. Ventilator mode was patient triggered, flow control, volume cycled, with a tidal volume of 7 to 10 mL/kg. Esophageal pressure (Peso), airway-opening pressure, and airflow were measured in patients with TA who consented to esophageal catheter insertion. Attempts to decrease TA in each patient included application of positive end-expiratory pressure (PEEP) stepwise to 10 cm H2O, flow triggering, and reduction of ventilator support in pressure support (PS) mode. Patients were followed up until hospital discharge, when outcomes were scored as weaned (defined as >7 days of ventilator independence), failed to wean, or died. RESULTS: Of the 200 patients screened, 26 were excluded and 19 were found to have TA. Patients with TA were older, carried the diagnosis of COPD more frequently, and had more severe hypercapnia than their counterparts without TA. Only 3 of 19 patients (16%), all with intermittent TA, weaned from mechanical ventilation, after 70, 72, and 108 days, respectively. This is in contrast to a weaning success rate of 57%, with a median (range) time to wean of 33 (3 to 182) days in patients without TA. Observation of uncoupling of accessory respiratory muscle movement and onset of machine breaths was accurate in identifying patients with TA, which was confirmed in all seven patients consenting to Peso monitoring. TA appeared to result from high auto-PEEP and severe pump failure. Adjusting trigger sensitivity and application of flow triggering were unsuccessful in eliminating TA; external PEEP improved but rarely led to elimination of TA that was transient in duration. Reduction of ventilator support in PS mode, with resultant increased respiratory pump output and lower tidal volumes, uniformly succeeded in eliminating TA. However, this approach imposed a fatiguing load on the respiratory muscles and was poorly tolerated. CONCLUSION: TA can be easily identified clinically, and when it occurs in the patient in stable condition with PMV, is associated with poor outcome.

Post-ICU mechanical ventilation: treatment of 1,123 patients at a regional weaning center.

STUDY OBJECTIVES: To update our database, reporting changes in the results of weaning attempts and profile of patients transferred to us after prolonged mechanical ventilation (PMV) in the ICU. DESIGN: Retrospective record review, with prospective recording of physiologic measurements on admission from mid-1994. SETTING: Regional weaning center (RWC). PATIENTS: We studied 1,123 consecutive ventilator-dependent patients transferred for attempted weaning over an 8-year period. MEASUREMENTS AND RESULTS: Median (range) time of mechanical ventilation prior to transfer to the RWC declined from 37 (1 to 249) days in 1988 to 29 (1 to 120) days in 1996 (p<0.05). Acute physiology score of acute physiology and chronic health evaluation (APACHE) III was 32 (6 to 123) on RWC admission, equaling reported scores soon after ICU admission. Comparing other data on admission from 1988 to 1996, mean (+/-SD) serum albumin level declined from 2.92+/-0.58 to 2.43+/-0.50 g/dL, and alveolar-arterial oxygen pressure difference widened from 106+/-50 to 139+/-99 mm Hg. Prevalence of stage II or worse pressure ulceration on admission increased from 34% in 1988 to 46% in 1995. Despite these trends, there has been no significant change in patient outcome (55.9% weaned, 15.6% failed to wean, 28.8% died) or in median time to wean (29 [1 to 226] days). Overall survival at 1 year after discharge for the 8-year period is 37.9%, improving from 29% in 1988-1991 to 45% since 1992; survival in weaned patients discharged to home has improved from 45 to 59% during the respective time periods. CONCLUSIONS: Patients are being transferred from the ICU to our RWC for attempted weaning sooner in their course of PMV. Although more severely ill on arrival than in past years, mortality is unchanged, more than half of the patients continue to be successfully weaned, and survival after RWC discharge is improved.

Predictors of weaning after 6 weeks of mechanical ventilation.

STUDY OBJECTIVE: To identify variables associated with weaning outcome in long-term ventilator-dependent patients. Using those variables, to construct models to predict weaning success and to test the accuracy of those models. DESIGN: Retrospective medical record review. SETTING: Regional weaning center (RWC). PATIENTS: An initial group of 421 and a subsequent group of 170 consecutive patients referred for attempted weaning after 6 weeks of mechanical ventilation. MEASUREMENTS AND RESULTS: Data obtained on admission to our facility were analyzed for correlation with weaning outcome. In the initial patient group, selected variables which correlated with weaning success were alveolar-arterial oxygen pressure difference (P[A-a]O2), BUN, BUN/creatinine ratio (each with p < or = 0.001), and female gender (p = 0.04). We used these variables in logistic regression models to predict weaning success in this population. We then tested the models in the 170-patient validation group using both standard and receiver operating characteristic (ROC) curve analysis. The ROC analysis indicated 59% accuracy using P(A-a)O2 alone and 68% accuracy using all previously mentioned variables. We used data from all 565 patients with known outcome and omitted BUN/creatinine ratio to fashion a simple scoring system to predict weaning success with 70% accuracy using P(A-a)O2, BUN, and Gender--the A+B+G score. CONCLUSION: In patients suffering prolonged mechanical ventilation, models incorporating simple measurements allowed construction of a score to predict weaning success at our RWC.

Weaning from prolonged mechanical ventilation. The experience at a regional weaning center.

STUDY OBJECTIVE: The aim of this study was to describe the facility, patient population, outcome of treatment, and survival of patients transferred to a regional weaning center (RWC) after prolonged mechanical ventilation in the ICU setting. DESIGN: Retrospective record review. SETTING: Regional weaning center. PATIENTS: Four hundred twenty-one consecutive ventilator dependent patients were transferred from ICU care for attempted weaning over a 36-month period. MEASUREMENT AND RESULTS: Acute catastrophic surgical, traumatic, or septic illness resulted in ventilator dependency with much greater frequency than decompensated COPD. Of the 421 patients, 116 died and 287 survived with outcome known at discharge. Of the 287 who survived, 212 were freed from ventilator support. Patients who weaned were ventilator-dependent for 46.9 +/- 2.9 days before transfer to the RWC. Almost half of those weaned were discharged to their homes. Survival at 6 months and 1 year after discharge was 44 percent and 28 percent respectively, and it was greater for those at home than for those discharged to an extended care facility (ECF). The RWC care was approximately $1,500 per patient day less costly than ICU care, and $208 per patient day less costly than noninvasive respiratory care unit care. CONCLUSIONS: Selected patients who become ventilator dependent for prolonged periods in the ICU may be transferred to an RWC with the expectation of successful weaning in a majority of cases.

Evaluation of single-breath helium dilution total lung capacity in obstructive lung disease.

We examined the effect of obstructive lung disease on the single-breath helium dilution method of measuring total lung capacity (TLC). In test results of 79 patients, we found this dilution method underestimated the TLC determined by a radiographic method by a mean of 2.3% in normal subjects, 10.4% in patients with mild, 21.8% in those with moderate, and 38.0% in those with severe obstruction. The ratio of forced expiratory volume in one second to forced vital capacity was used to group the patients; the differences in the degree of underestimation of TLC between groups were significant (p less than 0.05). In addition, we found a strong correlation between the degree of underestimation of TLC by the helium method and the severity of obstruction when patients were considered as a continuous population. Using a regression equation based on this correlation, we derived a method for correcting the helium dilution TLC. This allows use of this test in patients whose obstructive disease would otherwise render it inaccurate.

Incentive spirometer for bedside studies.

We evaluated an incentive spirometer (IS) for monitoring changes in lung function in hospitalized patients. Accuracy and reproducibility of IS measurements of known volumes were adequate (r = 0.87). Flow dependency was demonstrated but was not significant in the clinically useful range. Reproducibility of IS measurements in five normal subjects was good, with a small training effect uncovered. In 15 patients with asthma and chronic obstructive lung disease, change in IS values closely correlated with spirometrically measured changes in volume and flows (best correlation: IS versus FEV1/FVC%, r = 0.98) and in peak flow. The performance of the IS as tested and its availability in most hospitals outweigh its limitations. We advocate its use as an adjunct in monitoring progress of hospitalized patients with obstructive lung disease.

Screening test for airflow limitation.

Forced expiratory time (FET), the time in seconds required to exhale the vital capacity forcefully, was examined as a self-test for airflow limitation. Following only written instructions, 180 subjects measured their own FET. Neither laboratory equipment nor personnel were used. Results were compared with usual spirometric measurements of airflow limitation. Correlation between FET and spirometric measurements was significant. No training effect was evident after a coached spirogram, indicating adequacy of effort and understanding in the performance of the FET test. An FET of greater than five seconds was significantly associate with spirometric abnormality. The FET test missed significant airflow limitation in 9% of subjects, and misclassified 14% of subjects as abnormal. This self-test FET is sensitive enough to warrant field trials.