CI: Body Weight and Outcomes: Mixed ICU Patients (2007)


El-Solh A, 2001, Pawan Sikka, Erkan Bozkanat, Wafaa Jaafar and Joan Davies. Morbid Obesity in the Medical ICU. Chest. 2001;120:1989-1997. 

PubMed ID: 11742933
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The purpose of this research is to describe the clinical course, complications, and prognostic factors of morbidly obese patients admitted to the ICU compared to a control group of nonobese patients.
Inclusion Criteria:

Adult medical ICU patients

  • Group 1: patients with BMI > 40
  • Group 2: used computer-generated random numbers to select nonobese patient sample (BMI < 30)
Exclusion Criteria:
Adult patients admitted to the ICU with 30>BMI<40 or who were not selected in the computer-generated random selection of nonobese patients with BMI < 30.
Description of Study Protocol:


Database review of all hospitalized morbidly obese (BMI>40) adult patients admitted to medical ICUs of two university affilitated hospitals January 1994 and June 2000. Nonobese cohort (BMI<30) was selected by computer generated random numbers in proportion to the number of morbidly obese patients over the same time period.


Retrospective cohort study

Blinding used (if applicable)

Not applicable

Intervention (if applicable)

Not applicable

Statistical Analysis

  • Analyzed parametric interval data using two-tailed Student's t-test; reported as mean ± SD.
  • Man-Whitney U test or Kruskal-Wallis test used to examine non-parametric data.
  • Nominal data analyzed by X2 with Yates continuity correction or Fisher's Exact Test.
  • Used multiple linear regression to compare length of stay variables (days on vent and in hospital) after controlling for covariates of gender, comorbidities, and APACHE II scores.
Data Collection Summary:

Timing of Measurements

Not applicable

Dependent Variables

  • Presence of cardiac, pulmonary, and endocrine comorbidities
  • Length of ICU stay
  • Length of mechanical ventilation

Independent Variables

  • Body Mass Index

Initial N: 249

  • 117 BMI > 40 (77% male gender)
  • 132 BMI < 30 (80% male gender)

Attrition: N/A


  • BMI > 40 mean age 44.4 ± 18.2 yrs;
  • BMI < 30 mean age 46.2 ± 21.7

Ethnicity: Not described

Anthropometrics: Body Mass Index (0=0.001)

  • morbidly obese BMI 51.3 ± 25.9
  • non-obese BMI 27.6 ± 3.1
Description of Actual Data Sample:

Inclusion criteria:

  • Group 1: BMI ≥ 40
  • Group 2: used computer-generated random numbers to select nonobese group sample (BMI < 30)

Exclusion criteria: 30>BMI≤40


Database review of all hospitalized morbidly obese (BMI ≥ 40) adult patients admitted to medical ICUs of two university affiliated hospitals January 1994 and June 2000. Nonobese cohort (BMI < 30) was selected by computer-generated random numbers in proportion to the number of morbidly obese patients over the same time period.


Summary of Results:

Patients in morbidly obese group had significantly higher prevalence of cardiac, pulmonary, and endocrine morbidities--especially hypertension and sleep-related disorders. Immunodeficiency was more frequently noted in nonobese group because there were 8 nonobese patients with AIDS.


Variable Morbidly Obese Nonobese p value or other
Mortality 30% 17% 0.02
Mean length of mechanical ventilation 7.7 ± 9.6 days 4.7 ± 7.1 days p< .0001
Hospital length of stay 17.7 ± 19.8 days 11.3 ± 10.8 days p=0.0007
Mean length of ICU stay 9.3 ± 13.5 days 5.8 ± 8.2 days p=0.0007
Duration of mechanical ventilation 7.7 ± 10.6 days 4.6 ± 7.1 days p=0.0004
Respiratory failure 61% 46% p=0.02
Multiorgan failure  OR 4.6, 95% CI 2.1-16.6    p=0.003

No difference in APACHE II scores (p=0.6) between obese and non-obese groups

NS difference in rate of infection (venous catheter-related bacteremia) p=0.1.

Other Findings

Factors independently associated with ICU mortality in morbidly obese (by multivariate analysis).

  • PaO2/fraction of inspired oxygen < 200 for > 48 hrs; OR 2.3; 95% CI 1.2 to 7.8 (p=0.02)
  • Depressed left ventricular ejection fraction < 40% ; OR 11.4; 95% CI 1.03 to 13.8 (p=0.04)
  • Pulmonary problems were the main reasons for ICU admissions in both groups. In the morbidly obese, asthma was the predominant disorder in 71% of patients whereas COPD was the prevalent disorder in the nonobese patients. There was a significant difference in respiratory failure: 61% vs. 46% in obese and nonobese groups respectively.

After multiple linear regression, BMI only significant independent determinant of time on mechanical ventilation between the morbidly obese and non-obese groups. (p=0.03)

Author Conclusion:
  1. Critically ill morbidly obese patients have higher mortality compared to nonobese patients.
  2. Morbid obesity associated with prolonged mechanical ventilation and extended weaning period.
  3. Multiple organ failure best predictor of ICU mortality.
  4. Assessment of severity of illness by general scoring system is insufficient in predicting hospital outcome.
  5. No significant differences in complications attributed to cannulation of central venous circulation; subclavian and internal jugular were more common sites in morbidly obese group.
Funding Source:
University/Hospital: University at Buffalo School of Medicine and Biomedical Sciences, Research for Health in Erie County Inc
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes