Participant Characteristics
Data from 7,185 ICU admissions were included in this study (Table 1). Half of the patients were men (57%), and the median patient age was 65 years (age range = 18–100 years, SD = 16.24). The median Charlson Comorbidity Index (CCI) scores on admission were 6 (range = 0–19, SD 2.82). The median duration of mechanical ventilation was 38.5 hours (range = 10–98 hours, SD = 24.3).
The extubation failure group consisted of 1,339 patients that needed to be re-intubated within 72 hours of their initial extubation. An independent t-test was used to compare the means of patient gender and indicated that the composition of both groups was comparable, with slightly more males than females in both. Additionally, the extubation failure group (66.1 years old) was, on average, older than the success group (64.7) and remained mechanically ventilated for a longer period, 42.5 compared to 37.6 hours. The extubation success patients received lower scores on both the Acute Physiology and Chronic Health Evaluation II (APACHE II) and CCI assessments, 50.8 and 5.8 respectively.
When using the Fisher’s Exact Test to compare comorbidity specifics, the failure group had a statistically higher number of patients with congestive heart failure, Peripheral vascular disease (PVD), Chronic Pulmonary Disease (CPD), and cerebrovascular disease. Both the success and failure groups had a higher number of patients with diabetes, 30.4 and 30.2 respectively.
Table 1
Demographic and clinical variables of the extubation success and failure groups.
Variables | All Patients | Extubation Failure | Extubation Success | p-value |
| | (n = 7,364) | (n = 1,339) | (n = 6,025) | |
Male patients | 4190 (56.9%) | 746 (55.7%) | 3444 (57.2%) | 0.333 a |
Age (years) | 64.9 ± 16.2 (18–100) | 66.1 ± 15.3 (18–97) | 64.7 ± 16.4 (18–100) | 0.003 b |
Vent Duration (hrs) | 38.5 ± 24.3 (10–98) | 42.5 ± 24.8 (10–98) | 37.6 ± 24 (10–98) | < 0.001 b |
APACHE II | 53.5 ± 23.3 (6-167) | 66 ± 24.2 (6-163) | 50.8 ± 22.1 (6-167) | < 0.001 b |
CCI | 6.15 ± 2.8 (0–19) | 6.2 ± 2.8 (0–19) | 5.8 ± 3.1 (0–18) | < 0.001 b |
| Myocardial Infarct | 1333 (18.1%) | 254 (19%) | 1090 (18.1%) | 0.248 c |
| CHF | 2312 (31.5%) | 466 (34.8%) | 1844 (30.6%) | 0.004 c |
| PVD | 935 (12.7%) | 198 (14.8%) | 735 (12.2%) | 0.011 c |
| CVD | 1340 (18.2%) | 315 (23.5%) | 1024 (17%) | < 0.001 c |
| CPD | 2069 (28.1%) | 450 (33.6%) | 1615 (26.8%) | < 0.001 c |
| Renal Disease | 1664 (22.6%) | 296 (22.1%) | 1368 (22.7%) | 0.660 c |
| Solid Tumor | 1068 (14.5%) | 177 (13.2%) | 892 (14.8%) | 0.151 c |
| Liver Disease | 1171 (15.9%) | 225 (16.8%) | 946 (15.7%) | 0.315 c |
| Diabetes | 2231 (30.3%) | 404 (30.2%) | 1832 (30.4%) | 0.947 c |
Deaths | 944 (12.8%) | 295 (22%) | 649 (10.8%) | < 0.001 a |
LOS in hospital | 15.5 ± 15.9 (0-249) | 23.8 ± 20.1 (2-249) | 13.70 ± 14.2 (0-249) | < 0.001 b |
LOS in ICU | 5.8 ± 6.2 (0-103) | 13.3 ± 10.1 (1-103) | 4.1 ± 2.9 (0–39) | < 0.001 b |
Expressed as mean ± SD (range) or n (%); APACHE II = Acute Physiology and Chronic Health Evaluation, CCI = Charlson Comorbidity Index, CHF = Congestive Heart Failure, PVD = Peripheral Vascular Disease, CVD = Cerebrovascular Disease, CPD = Chronic Pulmonary Disease, LOS = Length of stay. a Independent t-test, b Mann-Whitney U Test, c Fisher's Exact Test |
Mortality and Length of Stay
Of the 944 (12.8%) patients who died in the hospital, the mortality rate was significantly higher in the EF group. Additionally, the Mann-Whitney U comparison of total hospital length of stay and ICU-specific length of stay indicated that patients in the extubation failure group had statistically significant longer stays, 23.8 days and 13.3 days respectively (Table 1).
Vital Sign Changes
In the Wilcoxon Signed-Rank analysis, statistically significant differences in patients’ vital signs recorded 1-hour pre-extubation when compared to their average vital signs recorded throughout their initial intubation were identified for both the EF and ES groups (Table 2). In ES patients, a significant change in respiratory rates was identified at one-hour pre-extubation (M = 18, SD = 3) when compared to their average respiratory rate during intubation (M = 18, SD = 5); however, in EF patients, no significant change in respiratory rates was identified.
Table 2
Wilcoxon Signed Rank Test Results: Intubation average − 1-hr pre-extubation average
Variables | Intubation Average | 1-hour Pre-extubation Average | Z | P |
Extubation Success (n = 6,025) | | | |
| Heart Rate | 83 ± 14 (42–135) | 84 ± 17 (44–145) | -4.492 | < 0.001 a |
| SBP | 117 ± 14 (80–190) | 123 ± 21 (54–195) | -23.470 | < 0.001 a |
| DBP | 61 ± 10 (32–95) | 63 ± 13 (25–110) | -7.919 | < 0.001 a |
| Respiratory rate | 18 ± 3 (10–29) | 18 ± 5 (4–36) | -2.346 | 0.019 a |
| Temperature | 37.1 ± 0.4 (35.6–38.6) | 37.1 ± 0.5 (35.6–38.7) | -9.526 | < 0.001 a |
| SpO2 | 98 ± 1 (93–100) | 98 ± 2 (90-1000) | -11.197 | < 0.001 b |
| Blood Glucose | 138 ± 38 (65–265) | 132 ± 43 (44–415) | -17.840 | < 0.001 b |
Extubation Failure (n = 1,339) | | | |
| Heart Rate | 84 ± 14 (50–135) | 86 ± 16 (43–144) | -3.270 | 0.001 a |
| SBP | 117 ± 13 (80–162) | 123 ± 22 (56–198) | -11.020 | < 0.001 a |
| DBP | 60 ± 9 (33–92) | 620 ± 13 (26–108) | -3.814 | < 0.001 a |
| Respiratory rate | 19 ± 3 (12–29) | 19 ± 5 (5–36) | -1.726 | 0.084 a |
| Temperature | 37.1 ± 0.5 (35.5–38.5) | 37.1 ± 0.5 (35.5–38.7) | -2.409 | 0.016 a |
| SpO2 | 98 ± 1 (92–100) | 98 ± 2 (90–100) | -6.471 | < 0.001 b |
| Blood Glucose | 137 ± 34 (71–253) | 131 ± 36 (54–252) | -7.829 | < 0.001 b |
Expressed as mean ± SD (range). SBP = systolic blood pressure; DBP = diastolic blood pressure; SpO2 = Oxygen saturation. a Based on positive ranks, b Based on negative ranks |
The Mann-Whitney U test results examined the differences between the extubation failure and success groups' vital sign averages from 1-hour pre-extubation and intubation (see Additional file 2). There were significant differences between the EF and ES groups both in their intubation averages and 1-hour pre-extubation averages. EF patients had significantly lower diastolic blood pressure in both their intubation average (M = 60, SD = 9) and 1-hour pre-extubation (M = 62, SD = 13) than ES patients, M = 61 (SD = 10) and M = 63 (SD = 13) respectively. Significantly higher respiratory rates (M = 19, SD = 3) and lower oxygen saturations (M = 98, SD = 2) were also present in the EF groups. No significant differences were identified in the comparison of intubation averages and 1-hour pre-extubation averages for systolic blood pressure, temperature, or blood glucose levels.
Multivariate analyses showed five risk factors—DBP, Respiratory rate, Temperature, SpO2, and Blood Glucose—independently associated with extubation failure rates in ICU patients (Table 3).
Table 3
Vital sign predictors for extubation failure using a logistic regression model (n = 7,364).
Variables | Odd ratio | 95% confidence interval | p-value |
Lower | Upper |
Intubation Average |
| Heart Rate | 1.426 | -0.097 | 0.807 | 0.123 |
| SBP | 1.206 | -0.396 | 0.770 | 0.529 |
| DBP | 0.271 | -1.774 | -0.835 | 0.000 |
| Respiratory rate | 3.791 | 0.920 | 1.745 | 0.000 |
| Temperature | 0.353 | -1.494 | -0.589 | 0.000 |
| SpO2 | 0.277 | -1.546 | -1.021 | 0.000 |
| Blood Glucose | 0.594 | -0.870 | -0.172 | 0.003 |
1-hour Pre-extubation Average |
| Heart Rate | 1.357 | -0.108 | 0.718 | 0.147 |
| SBP | 1.078 | -0.427 | 0.577 | 0.769 |
| DBP | 0.334 | -1.593 | -0.602 | 0.000 |
| Respiratory rate | 2.418 | 0.485 | 1.281 | 0.000 |
| Temperature | 0.389 | -1.357 | -0.531 | 0.000 |
| SpO2 | 0.316 | -1.394 | -0.912 | 0.000 |
| Blood Glucose | 0.426 | -1.431 | -0.273 | 0.004 |
SBP = systolic blood pressure; DBP = diastolic blood pressure; SpO2 = Oxygen saturation.