Introduction
With the increase in life expectation, more admissions to hospital, use of mechanical ventilation (MV) and weaning trials in older patients have been observed.
Objective
To evaluate the variables associated with successful weaning from mechanical ventilation in older patients.
Methods
We evaluated a cohort from September 2004 to January 2008 with 479 patients. We excluded one patient aged under 18 years, 35 tracheostomized and 112 with neurologic diseases, resulting in 331 patients. Besides the conventional weaning indexes, we evaluated the performance of a new integrative weaning index (IWI). The study was approved by the Ethics Committee of Pedro Ernesto University Hospital (2206-CEP). The chances of successful weaning were investigated using relative risk and logistic regression. The Hosmer-Lemeshow goodness-of-fit test was used to calibrate and the C statistic was calculated to evaluate the association between predicted probabilities and observed proportions in the logistic regression model.
Results
Prevalence of successful weaning in the sample was 83.7%. There was no difference in mortality of older and nonolder patients (P = 0.16), in the days of mechanical ventilation (P = 0.22) and days of weaning (P = 0.55). In older patients, the IWI was the only variable associated with respiratory weaning in this population (P < 0.0001). See Tables 1 to 5.
Table 1.
Etiology and population
| Etiology | Population (%) |
|---|---|
| COPD, n (%) | 98 (29.6) |
| Pneumonia, n (%) | 68 (20.54) |
| Postoperative, n (%) | 63 (19.03) |
| Sepsis, n (%) | 39 (11.78) |
| ARDS/ALI, n (%) | 25 (7.55) |
| Trauma without brain injury, n (%) | 11 (3.32) |
| Acute pulmonary edema, n (%) | 10 (3.02) |
| Miscellaneous, n (%) | 17 (5.13) |
| Total | 331 |
ALI, acute lung injury; ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease.
Table 5.
Estimated probability of success according to the logistic model by age group
| Age | IWI ≥25.5 | APACHE ≤17 | Estimated probability (%) | 95% CI |
|---|---|---|---|---|
| ≥70 | No | 9.4 | 3.06 to 25.4 | |
| Yes | 99.2 | 94.5 to 99.9 | ||
| <70 | No | No | 4.3 | 0.58 to 25.2 |
| No | Yes | 57.7 | 27.5 to 83.1 | |
| Yes | Yes | 95.0 | 81.8 to 98.8 | |
| Yes | No | 99.8 | 98.0 to 100.0 |
CI, confidence interval: lower limit (%) to upper limit (%).
Table 2.
Analysis of the outcome variables by sample and by age
| Variable | Category | Total (%) | Age ≥70 (%) | Age <70 (%) | P value |
|---|---|---|---|---|---|
| Result | Success | 277 (83.7) | 125 (80.7) | 152 (86.4) | 0.16 |
| Failure | 54 (16.3) | 30 (19.4) | 24 (13.6) | ||
| Death | 17 (5.1) | 15 (9.7) | 2 (1.1) | 0.002 | |
| Evolution | Discharge | 277 (83.7) | 125 (80.7) | 152 (86.4) | |
| Return | 37 (11.2) | 15 (9.7) | 22 (12.5) | ||
| Days of MV | Mean ± DP/median | 9.1 ± 7.6/7 | 9.2 ± 8.6/6 | 9.1 ± 6.7/7 | 0.22 |
| Days of weaning | Mean ± DP/median | 2.7 ± 2.3/2 | 2.8 ± 2.6/2 | 2.6 ± 2.0/2 | 0.55 |
| APACHE II | Mean ± DP/median | 16.0 ± 5.6/15 | 16.9 ± 5.8/16 | 15.3 ± 5.2/14 | 0.009 |
Significant P < 0.05.
Table 3.
Analysis of the respiratory variables according to the results by age
| Age ≥70 | Age <70 | |||||||
|---|---|---|---|---|---|---|---|---|
| Variable | Success (%) | Failure (%) | RR | 95% CI | Success (%) | Failure (%) | RR | 95% CI |
| P/F ≥255 | 59.2 | 46.7 | 1.11 | 0.94 to 1.30 | 63.2 | 16.7 | 1.30 | 1.13 to 1.50 |
| Cqst.rs ≥30 | 80.8 | 23.3 | 1.83 | 1.38 to 2.43 | 84.2 | 29.2 | 1.62 | 1.25 to 2.10 |
| IWI ≥25.5 | 97.6 | 3.3 | 10.6 | 3.60 to 31.1 | 96.1 | 8.3 | 4.60 | 2.26 to 9.36 |
| P 0.1 ≤3.1 | 78.4 | 36.7 | 1.53 | 1.19 to 1.97 | 77.0 | 20.8 | 1.48 | 1.21 to 1.81 |
| f ≤29 | 72.8 | 33.3 | 1.43 | 1.16 to 1.77 | 68.4 | 20.8 | 1.33 | 1.14 to 1.56 |
| Vt ≥320 | 76.8 | 23.3 | 1.67 | 1.31 to 2.14 | 73.7 | 29.2 | 1.34 | 1.13 to 1.60 |
| f/Vt*P 0.1 ≤270 | 80.0 | 33.3 | 1.64 | 1.25 to 2.14 | 77.0 | 16.7 | 1.52 | 1.24 to 1.86 |
| f/Vt ≤100 | 81.6 | 23.3 | 1.87 | 1.40 to 2.51 | 78.3 | 25.0 | 1.47 | 1.20 to 1.81 |
RR, relative risk. Significant P < 0.0001, except for P/F on age ≥70.
Table 4.
Logistic regression to the success of weaning by age
| Age | Significant Variable | Coefficient | SE | P value | RR | 95% CI |
|---|---|---|---|---|---|---|
| ≥70 | Intercept | -2.2687 | 0.606 | 0.0002 | ||
| IWI ≥25.5 | 7.0727 | 1.173 | <0.0001 | 1,179.3 | 118 to 11,752 | |
| <70 | Intercept | -3.1147 | 1.035 | 0.003 | ||
| IWI ≥25.5 | 6.0547 | 1.187 | <0.0001 | 426.1 | 41.6 to 4,364 | |
| APACHE ≤17 | 3.4249 | 1.159 | 0.003 | 30.7 | 3.2 to 298 |
CI, confidence interval; RR, relative risk; SE, standard error of coefficient.
Conclusion
The IWI was the main independent variable in weaning of the older patient population, and it can contribute to this critical moment.