Weaning Center Research Articles

Weaning units: lessons from North America?

In the United Kingdom over 5% of critical care beds are occupied by stable patients weaning from mechanical ventilation. In North America, diagnosis related groups (DRGs) were introduced over a decade ago. These provided an economic impetus to develop more cost effective regional weaning centres. The imminent introduction of Payment By Results may encourage similar developments in the UK. The evidence for weaning centres is reviewed and detailed organisational and outcome data from two North American centres presented. These units differ from UK critical care units in terms of nurse : patient ratios and types and numbers of ancillary staff. Limited data, mostly from North America, suggest that weaning centres may be better at improving outcome in ventilator-dependent patients compared with standard critical care. The existing evidence is not conclusive and highlights the need for UK-based studies on organisational approaches to the provision of weaning and longer term critical care.

Intrapulmonary percussive ventilation in tracheostomized patients: a randomized controlled trial

To investigate whether the addition of intrapulmonary percussive ventilation to the usual chest physiotherapy improves gas exchange and lung mechanics in tracheostomized patients. Randomized multicenter trial in two weaning centers in northern Italy. 46 tracheostomized patients (age 70 +/- 7 years, 28 men, arterial blood pH 7.436 +/- 0.06, PaO(2)/FIO(2) 238 +/- 46) weaned from mechanical ventilation. Patients were assigned to two treatment groups performing chest physiotherapy (control), or percussive ventilation (IMP2 Breas, Sweden) 10 min twice/day in addition to chest physiotherapy (intervention). Arterial blood gases, PaO(2)/FIO(2) ratio, and maximal expiratory pressure were assessed every 5th day for 15 day. Treatment complications that showed up in 1 month of follow-up were recorded. At 15 days the intervention group had a significantly better PaO(2)/FIO(2) ratio and higher maximal expiratory pressure; after follow-up this group also had a lower incidence of pneumonia. The addition of percussive ventilation to the usual chest physiotherapy regimen in tracheostomized patients improves gas exchange and expiratory muscle performance and reduces the incidence of pneumonia.

Post-ICU Mechanical Ventilation: Treatment of 2,369 Patients Over 16 Years at a Regional Weaning Center

Post-ICU Mechanical Ventilation: Treatment of 2,369 Patients Over 16 Years at a Regional Weaning Center

Hypothyroidism and Failure To Wean in Patients Receiving Prolonged Mechanical Ventilation at a Regional Weaning Center

Objective: Hypothyroidism is cited as an uncommon cause of ventilator-dependent respiratory failure. The objective of this study was to determine the incidence of hypothyroidism in patients with respiratory failure, receiving prolonged mechanical ventilation (PMV) with failure to wean, referred to a regional weaning center (RWC) for weaning. Setting: RWC. Design: Retrospective. Methods: Medical records were reviewed of 173 patients admitted to this RWC between January 1999 and March 2002. One hundred forty patients were noted to have had screening serum thyroid stimulating hormone (TSH) levels obtained at admission. Records of these patients were further evaluated. The following data were abstracted: age, sex, body mass index, serum TSH levels, number of patients with previously diagnosed hypothyroidism, and number of patients with hypothyroidism diagnosed clinically and by laboratory tests following admission to the RWC. Primary outcome was liberation from PMV, which was defined as being off ventilatory support for > 1 week. Univariate analysis was performed to determine relation between serum TSH levels and outcome; p < 0.05 was deemed statistically significant. Results: Of 140 patients studied, 67 were male (48%) and 73 were female (52%), with a mean age of 66 + 15 years (± SD). Only one patient had a history of previously diagnosed hypothyroidism. A clinical diagnosis of hypothyroidism was made in 4 of 140 patients (3%) following admission. Serum TSH levels ranged from 0.19 to 121 mU/L in the studied subjects. Seventeen of 140 patients (12%) had elevated serum TSH levels. Serum tri-iodothyronine and/or thyroxine levels confirmed diagnosis of hypothyroidism in four of these patients (3%). Patients with newly diagnosed hypothyroidism were treated with thyroid supplements, and three patients were liberated from PMV while one patient died from other medical causes. Of the140 patients, 92 patients (67%) were liberated from PMV while 48 patients (33%) could not be weaned. Mean serum TSH levels were 4.2 + 13 mU/L in the liberated patients and 4 + 4.7 mU/L in the patients who could not be weaned (p = 0.25). Conclusion: Hypothyroidism is an uncommon cause of failure to wean in patients receiving PMV (with an incidence of 3%). However, it is a potentially treatable cause and should be considered in all patients who fail to wean. Serum TSH level does not appear to affect successful weaning from PMV. Hypothyroidism is cited as an uncommon cause of ventilator-dependent respiratory failure. The objective of this study was to determine the incidence of hypothyroidism in patients with respiratory failure, receiving prolonged mechanical ventilation (PMV) with failure to wean, referred to a regional weaning center (RWC) for weaning. RWC. Retrospective. Medical records were reviewed of 173 patients admitted to this RWC between January 1999 and March 2002. One hundred forty patients were noted to have had screening serum thyroid stimulating hormone (TSH) levels obtained at admission. Records of these patients were further evaluated. The following data were abstracted: age, sex, body mass index, serum TSH levels, number of patients with previously diagnosed hypothyroidism, and number of patients with hypothyroidism diagnosed clinically and by laboratory tests following admission to the RWC. Primary outcome was liberation from PMV, which was defined as being off ventilatory support for > 1 week. Univariate analysis was performed to determine relation between serum TSH levels and outcome; p < 0.05 was deemed statistically significant. Of 140 patients studied, 67 were male (48%) and 73 were female (52%), with a mean age of 66 + 15 years (± SD). Only one patient had a history of previously diagnosed hypothyroidism. A clinical diagnosis of hypothyroidism was made in 4 of 140 patients (3%) following admission. Serum TSH levels ranged from 0.19 to 121 mU/L in the studied subjects. Seventeen of 140 patients (12%) had elevated serum TSH levels. Serum tri-iodothyronine and/or thyroxine levels confirmed diagnosis of hypothyroidism in four of these patients (3%). Patients with newly diagnosed hypothyroidism were treated with thyroid supplements, and three patients were liberated from PMV while one patient died from other medical causes. Of the140 patients, 92 patients (67%) were liberated from PMV while 48 patients (33%) could not be weaned. Mean serum TSH levels were 4.2 + 13 mU/L in the liberated patients and 4 + 4.7 mU/L in the patients who could not be weaned (p = 0.25). Hypothyroidism is an uncommon cause of failure to wean in patients receiving PMV (with an incidence of 3%). However, it is a potentially treatable cause and should be considered in all patients who fail to wean. Serum TSH level does not appear to affect successful weaning from PMV.

Hypothyroidism and failure to wean in patients receiving prolonged mechanical ventilation at a regional weaning center.

Hypothyroidism is cited as an uncommon cause of ventilator-dependent respiratory failure. The objective of this study was to determine the incidence of hypothyroidism in patients with respiratory failure, receiving prolonged mechanical ventilation (PMV) with failure to wean, referred to a regional weaning center (RWC) for weaning. RWC. Retrospective. Medical records were reviewed of 173 patients admitted to this RWC between January 1999 and March 2002. One hundred forty patients were noted to have had screening serum thyroid stimulating hormone (TSH) levels obtained at admission. Records of these patients were further evaluated. The following data were abstracted: age, sex, body mass index, serum TSH levels, number of patients with previously diagnosed hypothyroidism, and number of patients with hypothyroidism diagnosed clinically and by laboratory tests following admission to the RWC. Primary outcome was liberation from PMV, which was defined as being off ventilatory support for > 1 week. Univariate analysis was performed to determine relation between serum TSH levels and outcome; p < 0.05 was deemed statistically significant. Of 140 patients studied, 67 were male (48%) and 73 were female (52%), with a mean age of 66 + 15 years (+/- SD). Only one patient had a history of previously diagnosed hypothyroidism. A clinical diagnosis of hypothyroidism was made in 4 of 140 patients (3%) following admission. Serum TSH levels ranged from 0.19 to 121 mU/L in the studied subjects. Seventeen of 140 patients (12%) had elevated serum TSH levels. Serum tri-iodothyronine and/or thyroxine levels confirmed diagnosis of hypothyroidism in four of these patients (3%). Patients with newly diagnosed hypothyroidism were treated with thyroid supplements, and three patients were liberated from PMV while one patient died from other medical causes. Of the 140 patients, 92 patients (67%) were liberated from PMV while 48 patients (33%) could not be weaned. Mean serum TSH levels were 4.2 + 13 mU/L in the liberated patients and 4 + 4.7 mU/L in the patients who could not be weaned (p = 0.25). Hypothyroidism is an uncommon cause of failure to wean in patients receiving PMV (with an incidence of 3%). However, it is a potentially treatable cause and should be considered in all patients who fail to wean. Serum TSH level does not appear to affect successful weaning from PMV.

Prise en charge du sevrage difficile et prolongé ; expérience du centre médical de Bligny : à propos de 146 cas sur une période de dix ans

In this retrospective study, the authors present their experience in caring for patients with prolonged and difficult weaning from mechanical ventilation. During a period of 10 years, 146 tracheostomised patients with a mean age of 68.2 ± 8.5 were transferred from different intensive care units (ICUs) to the Centre Médical de Bligny for difficult weaning, after a mechanical ventilation duration of 57 ± 33 days. One hundred and one patients were suffering from chronic lung disease (group 1) while 45 remaining patients were not (group 2). Group 1 patients were hospitalised for a mean duration of 25 ± 24 days in the ICU, and for 48 ± 43 days in the Pneumology department. In-hospital mortality was 27%. Complete weaning was obtained in 65% of the survivors. One-year survival was 64%. Group 2 patients were hospitalised for a mean duration of 24 ± 18 days in the ICU, and for 38 ± 31 days in the Pneumology department. In-hospital mortality was 23%. Complete weaning was obtained in 85% of survivors. One-year survival was 74%. The authors conclude on the necessity to develop weaning centers in France.

The need for a regional weaning centre, a one-year survey of intensive care weaning delay in the Northern Region of England.

Over a period of one year, a weekly telephone survey identified 161 stable patients with weaning delay (defined as patients ventilated for at least 6 h per day for more than 2 weeks) in intensive care units in the Northern Region of England. Their median age was 69 years (range 21-88 years). Sixty patients (37%) were admitted with medical conditions, 89 (55%) were postoperative patients, whereas 12 (8%) were surgical but required non-operative admission. One hundred and thirty (89%) were weaned and discharged from the intensive care unit during the year. Twenty-two (14%) died and two were transferred to the home ventilation service. Seven patients remained ventilated in intensive care at the end of the study period. Twenty patients (12%) required more than 28 days of respiratory support. These patients occupied on average 6.0% of available intensive care unit beds in the region. This study suggests that in the Northern Region of England there are a significant number of stable but ventilator-dependent patients occupying intensive care beds.

Creatinine Height Index and Nutritional Status as Predictors of Successful Liberation From Prolonged Mechanical Ventilatio

PURPOSE: Malnutrition reduces respiratory muscle mass and can contribute to failure to wean and ventilator dependency in patients on prolonged mechanical ventilation (PMV). Creatinine Height Index (CHI), which reflects lean muscle mass, is regarded as the most accurate indicator of malnutrition. No previous studies have assessed the relation between CHI and weaning. The objective of this study was to determine if CHI can predict successful weaning in patients on PMV in comparison with traditional nutritional indices in a regional weaning center (RWC).

Thyroid Disorders and Failure to Wean in Patients on Prolonged Mechanical Ventilation at a Regional Weaning Cente

PURPOSE: Hypothyroidism is known to cause respiratory failure. We have noted the occurrence of clinically undiagnosed hypothyroidism in patients admitted with failure to wean to this regional weaning center . The objective of this study was to determine the incidence of hypothyroidism in patients on prolonged mechanical ventilation (PMV) with failure to wean and assess it's relation with successful weaning.

Weaning from prolonged mechanical ventilation

The development of weaning failure and need for PMV is multifactorial in origin, involving disorders of pulmonary mechanics and complications associated with critical illness. The underlying disease process is clearly important when discussing mechanisms of ventilator dependence; interventions therefore must be tailored to individual patients. Unfortunately, the main conclusion that can be drawn from the sum of the studies investigating patients on PMV to date is that an evidence-based approach to weaning is not possible and more research needs to be done. New studies need to incorporate severity-of-illness scores and an assessment of principal and comorbid conditions to allow for comparison of the findings from different centers. The best approach to a patient requiring PMV after exclusion of easily treatable conditions is not known. The literature regarding both acute and chronic cases suggests that a systematic approach to weaning involving the participation of multiple caregivers, including nurses, physicians, and respiratory, physical, and speech therapists facilitates liberation from MV. Although a gradual decrement in ventilator support would seem prudent, Scheinhorn et al have begun to identify a subpopulation of patients who can tolerate an acceleration of the weaning process. Given the known complications associated with MV, it is crucial that further research be performed to identify patients as soon as they are capable of breathing spontaneously. The literature demonstrates through multiple studies that satisfactory patient outcomes are attainable and can be achieved at LTAC facilities in a more cost-effective manner than in an ICU setting. The trend toward the concentration of patients into specialized regional weaning centers should facilitate the research process and continue to improve outcomes in this population.

Preliminary results on nursing workload in a dedicated weaning center.

To evaluate the nursing time required for difficult-to-wean patients in a dedicated weaning center (WC) and to examine the correlation of the nursing time with nursing workload (NW) scores and with clinical severity and dependency. Four-bed WC of a pulmonary rehabilitation department. None. Prospective, observational study of 46 consecutive patients admitted to a long-term WC. Time required by items of the Time Oriented Score System (TOSS) and other tasks specific to respiratory intermediate intensive care units were evaluated for all the activities performed on each patient in the first 2 days after admission. Patient dependency and level of nursing care at admission were measured using the Dependence Nursing Scale (DNS) and the Intermediate Therapeutic Intervention Score System (TISS-int). The Acute Physiology and Chronic Health Evaluation (APACHE) II score was also recorded at admission. On the first day each patient needed 45 +/- 15% (63 +/- 23%, 45 +/- 22%, and 29 +/- 14% for the three nursing shifts) of allocated single nursing time. On the TOSS on the first day patients required a daily mean 28 +/- 10% of total available nursing time; on the second day the results did not change. Time of care in the first 24 h was only weakly related to DNS, APACHE II score, and TISS-int; only DNS was able (although weakly; r = 0.45) to predict minutes of nursing care. In difficult-to-wean patients from mechanical ventilation the nursing time in the first 2 days after admission is high. The use of TOSS may underestimate NW by about 38%. Although only DNS showed the ability to predict minutes of care, the weak relationship limits its value in clinical practice.

Patient-Ventilator Trigger Asynchrony in Prolonged Mechanical Ventilation

To investigate patient-ventilator trigger asynchrony (TA), its prevalence, physiologic basis, and clinical implications in patients requiring prolonged mechanical ventilation (PMV). Descriptive and prospective cohort study. Barlow Respiratory Hospital (BRH), a regional weaning center. Two hundred consecutive ventilator-dependent patients, transferred to BRH over an 18-month period for attempted weaning from PMV. 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. 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. 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

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. Retrospective record review, with prospective recording of physiologic measurements on admission from mid-1994. Regional weaning center (RWC). We studied 1,123 consecutive ventilator-dependent patients transferred for attempted weaning over an 8-year period. 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. 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.

Impact of renal dysfunction on weaning from prolonged mechanical ventilation.

BACKGROUND: In the intensive care unit (ICU) setting, the combination of mechanical ventilation and renal replacement therapy (RRT) has been associated with prolonged length of hospital stay, high cost of care and poor outcome. We gathered outcome data on patients who had severe renal dysfunction on transfer to our regional weaning center (RWC) for attempted weaning from prolonged mechanical ventilation (PMV). We screened the admission laboratory values of 1077 patients transferred to our RWC over an 8-year period. We reviewed the medical records of patients with serum creatinine > 2.5 mg/dl. RESULTS: Sixty-three patients met screening criteria and 40 patients were on RRT at the time of transfer. Eighteen patients had begun chronic RRT at least 2 months prior to admission to the transferring hospital for their current illness. Twenty-two patients had RRT initiated at the transferring hospital. Ten patients had RRT initiated at the RWC; eight patients had improvement or resolution of azotemia at our facility. RRT was withheld at patient/family request in five patients with progressive renal failure. None of the 50 patients who received RRT recovered renal function during treatment at our RWC. Intermittent hemodialysis was the standard RRT at the RWC. Duration of mechanical ventilation prior to transfer to the RWC was 49.7 +/- 33.5 days (mean +/- SD).Outcome of weaning attempts in the 63 patients was as follows: 13% weaned, 3% failed to wean and 84% died. These outcomes were significantly worse (P<0.001) than those in the 1014 patients whose admission serum creatinine was </= 2.5 mg/dl (58% weaned, 15% failed to wean, 27% died). The five patients in whom RRT was withheld were predominantly in progressive multisystem organ failure, and were unlikely to have survived regardless of RRT. From the study cohort, only one of the 10 patients discharged alive returned home, in contrast to 42% of the control group. No patient with severe renal dysfunction survived to 1 year post-discharge, compared to a 1-year survival of 38% in the control group (P = 0.029). Only four of the 10 patients survived more than 1 month, with the longest survival being 122 days. CONCLUSIONS: Patients who require PMV and RRT have a very poor prognosis. The small number of patients with renal insufficiency not requiring RRT had a more favorable hospital outcome and mortality, but long-term survival remained poor.

Predictors of Weaning After 6 Weeks of Mechanical Ventilation

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. Retrospective medical record review. Regional weaning center (RWC). An initial group of 421 and a subsequent group of 170 consecutive patients referred for attempted weaning after 6 weeks of mechanical ventilation. 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. 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

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. Retrospective record review. Regional weaning center. Four hundred twenty-one consecutive ventilator dependent patients were transferred from ICU care for attempted weaning over a 36-month period. 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. 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.