Intensive Care Medicine

, Volume 31, Issue 9, pp 1153–1160 | Cite as

Studying outcomes of intensive care unit survivors: measuring exposures and outcomes

  • Dale M. Needham
  • David W. Dowdy
  • Pedro A. Mendez-Tellez
  • Margaret S. Herridge
  • Peter J. Pronovost



Measurement of long-term outcomes and the patient and intensive care unit (ICU) factors predicting them present investigators with unique challenges. There is little systematic guidance for measuring these outcomes and exposures within the ICU setting. As a result measurement methods are often variable and noncomparable across studies.


We use examples from the critical care literature to describe measurement as it relates to three key elements of clinical studies: subjects, outcomes and exposures, and time. Using this framework we review the principles and challenges of measurement and make recommendations for long-term outcomes research in the field of critical care medicine.


Relevant challenges discussed include: (a) selection bias and heterogeneity of ICU research subjects, (b) appropriate selection and measurement of outcome and exposure variables, and (c) accounting for the effect of time in the exposure-outcome relationship, including measurement of baseline data and time-varying variables.


Addressing these methodological challenges will advance research aimed at improving the long-term outcomes of ICU survivors.


Epidemiological methods Prospective studies Respiratory distress syndrome, adult Process assessment (health care) Risk factors Outcome assessment (health care) 



The authors acknowledge the important contributions made by four anonymous peer reviewers.

Supplementary material

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(PDF 412 KB)


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Dale M. Needham
    • 1
    • 2
  • David W. Dowdy
    • 3
    • 4
  • Pedro A. Mendez-Tellez
    • 5
    • 6
  • Margaret S. Herridge
    • 2
    • 7
  • Peter J. Pronovost
    • 5
    • 6
    • 8
  1. 1.Division of Pulmonary and Critical Care MedicineJohns Hopkins UniversityBaltimoreUSA
  2. 2.Department of MedicineUniversity of TorontoTorontoCanada
  3. 3.School of MedicineJohns Hopkins UniversityBaltimoreUSA
  4. 4.Department of EpidemiologyJohns Hopkins Bloomberg School of Public HealthBaltimoreUSA
  5. 5.Department of Anesthesiology/Critical Care MedicineJohns Hopkins UniversityBaltimoreUSA
  6. 6.Department of SurgeryJohns Hopkins UniversityBaltimoreUSA
  7. 7.Interdepartmental Division of Critical Care MedicineUniversity of TorontoTorontoCanada
  8. 8.Department of Health Policy and ManagementJohns Hopkins Bloomberg School of Public HealthBaltimoreUSA

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