Chest
Volume 107, Issue 2, February 1995, Pages 500-505
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Clinical Investigations in Critical Care
Predictors of Weaning After 6 Weeks of Mechanical Ventilation

https://doi.org/10.1378/chest.107.2.500Get rights and content

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≤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.

Section snippets

Data Collection

Data were gathered from the medical records of 421 consecutive ventilator-dependent patients (initial group) admitted over a 37-month period. Age, sex, results of routine laboratory tests on admission, and duration of mechanical ventilation prior to admission to BRH were noted. Presence and stage of decubitus ulceration were noted, as was level of consciousness on admission. The number of medications required to treat infection, bronchospasm, congestive heart failure, and arrhythmias was

Correlation With Outcome

Complete data were available in 395 of the initial 421 patient records reviewed. Eighteen patients were not included because of transfer to other acute care facilities for treatment of intercurrent surgical problems before outcome could be determined. The top portion of Table 1 displays all variables that correlated significantly with outcome in this initial patient data set. Selected variables and their correlation with outcome in the 170-patient validation group are shown in the lower part of

Clinical Information

Prediction has been widely decried as an imperfect science,9 but the clinical, economic, and ethical challenges posed by patients requiring prolonged ventilatory support generate a need for data on which to base decisions. In these patients, both duration of ventilator dependency and number of weaning attempts—the gradual withdrawal of the ventilator over usually weeks or even months, as opposed to hours to days—are different from ICU patients in whom outcome predictors have been extensively

REFERENCES (20)

  • ScheinhornDJ et al.

    Weaning from prolonged mechanical ventilation: the experience at a regional weaning center

    Chest

    (1994)
  • BartonR et al.

    The hypermetabolism: multiple organ failure syndrome

    Chest

    (1989)
  • GroegerJS et al.

    Descriptive analysis of critical care units in the United States: patient characteristics and intensive care unit utilization

    Crit Care Med

    (1993)
  • TomlinsonJR et al.

    A prospective comparison of IMV & T-piece weaning from mechanical ventilation

    Chest

    (1989)
  • KriegerBP et al.

    Evaluation of conventional criteria for predicting successful weaning from mechanical ventilatory support in elderly patients

    Crit Care Med

    (1989)
  • ScheinhornDJ et al.

    Age, absence of decubitus ulcers, measurements of gas exchange, & selected laboratory tests correlate with weaning from prolonged mechanical ventilation [abstract]

    Chest

    (1993)
  • ScheinhornDJ et al.

    Predictors of weaning after six weeks of mechanical ventilation [abstract]

    Am Rev Respir Dis

    (1993)
  • HanleyJA et al.

    The meaning and use of the area under a receiver operating characteristic (ROC) curve

    Radiology

    (1982)
  • HanleyJA et al.

    A method of comparing the areas under receiver operating characteristic curves derived from the same cases

    Radiology

    (1983)
  • CivettaJM

    “New and improved” scoring systems [editorial]

    Crit Care Med

    (1990)
There are more references available in the full text version of this article.

Cited by (48)

  • Predictive factors of weaning from mechanical ventilation and extubation outcome: A systematic review

    2018, Journal of Critical Care
    Citation Excerpt :

    Some parameters were discussed in two articles: level of consciousness [23,35], natriuretic peptide (BNP) [48,49], partial pressure of arterial oxygen (PaO2) [19,24], and heart failure [20,23]. Specific predictors for weaning success include the CORE index [19,50] (calculated as [Cdyn x (PImax/P0.1) x (PaO2/PAO2)]/f), arterial pH [19,20], blood urea nitrogen (BUN) level [32,35], the Integrative Weaning Index (IWI) [51,52], and the Oxygen Cost of Breathing (OCOB) [37,53]. Specific predictors of extubation success include the Occlusion Pressure (PO.1) [18,34], fluid balance [22,44], chronic obstructive pulmonary disease (COPD) [22,23], and lung compliance [23,31].

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Presented in part at the American College of Chest Physicians Annual Scientific Assembly, Chicago, October, 1992; and at the American Lung Association/American Thoracic Society International Conference, San Francisco, May, 1993.

This study was funded by grants from the Barlow Foundation, Harold R. and Winifred R. Swanton Foundation, and the Lluella Morey Murphey Foundation.

Manuscript received revision accepted June 10.

Reprint requests: Dr. Scheinhorn, Barlow Respiratory Hospital, 2000 Stadium Way, Los Angeles, CA 90026-2696

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