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Table 1 Study characteristics

From: Lower tidal volume at initiation of mechanical ventilation may reduce progression to acute respiratory distress syndrome: a systematic review

Randomized controlled trial

Author, year

n

Intervention

Location

Primary patient population

High-quality RCT?a

Primary outcome

Secondary outcome

Commentsb

Determann, 2010

150

VT 6 ml/kg PBW vs. 10 ml/kg PBW

Medical/surgical ICU

Cardiac arrest, neurologic disease

YES

Cytokine levels in BAL and plasma

Development of ARDS

Could be randomized up to 36 hours after mechanical ventilation

Observational studies

 

Cohort studies

 

Author, year

n

Study design

Location

Primary patient diagnoses

High quality c

Primary outcome

Secondary outcomes

Comments

Gajic, 2004

332

Retrospective

Medical/surgical ICUs

Shock, sepsis

NO

Development of ARDS

Hospital mortality, ventilator-free days

Excluded patients ventilated <48 hours

Gajic, 2005

3,261

Retrospective

Multicenter registry of medical/surgical ICUs

Postoperative, coma, pneumonia

NO

Development of ARDS

None mentioned

Excluded patients ventilated <48 hours

Kahn, 2006

620

Retrospective

Neuro ICU

Aneurysmal subarachnoid hemorrhage

NO

Development of ARDS

Incidence of lung-protective ventilation

Tidal volume obtained from author contact.

Mascia, 2007

82

Prospective

Four European ICUs

Severe traumatic brain injury

NO

Development of ARDS

ICU LOS, VF days, ICU mortality

Excluded patients with ARDS <24 hours from admission

Yilmaz, 2007

375

Prospective, before-after

Medical/surgical ICU

Sepsis, pneumonia

NO

Development of ARDS

Hospital mortality, duration of ventilation, ICU LOS, VF days

Excluded patients ventilated <48 hours

Plurad, 2007

2,346

Retrospective

Surgical ICU

Trauma

NO

Development of late ARDS

Not mentioned

Defined late ARDS as >48 hours after admission

Iscimen, 2008

160

Prospective

Medical ICU

Septic shock

NO

Development of ARDS

Hospital mortality, hospital length of stay

 

Jia, 2008

789

Retrospective

Medical/surgical/cardiac ICUs

Unclear

NO

Development of ARDS

Not mentioned

Excluded patients ventilated <48 hours. 341 patients had data missing on VT/PBW

Pasero, 2008

200

Prospective

Cardiac ICU

Patient status after cardiopulmonary bypass

NO

Development of ARDS

Not mentioned

Abstract only

Hughes, 2010

89

Retrospective

OR

Abdominal, orthopedic, vascular surgery within 24 hours of ICU admit

NO

Development of ARDS

Not mentioned

Assessed outcomes for 7 days.

Excluded many risks for ARDS development

Blum, 2011

53910

Retrospective

OR: all noncardiothoracic and nontransplant procedures

ASA I, II

NO

Development of ARDS

Not mentioned

Abstract only

Case-control study

Author, year

n

Study design

Location

Primary patient diagnoses

High quality

Primary outcome

Secondary outcomes

Comments

Fernandez-Perez, 2009

4,420

Prospective, nested

OR with general anesthesia for ≥3 hours

Elective operations

NO

Postoperative respiratory failure due to ARDS

Length of stay, 60-day survival, 1-year survival

Excluded patients with "prevalent" risk factors for ARDS. 1st hour ventilator variables were primary predictor variable

  1. aAs assessed by Cochrane Collaboration's tool for assessing risk of bias in clinical trials. Was assigned a grade of "A" (high quality) in the following methodology domains: random-sequence generation, concealment of allocation, and selective outcome reporting; assigned a grade of "C" (unknown) in the following methodology domain: blinding. To explain, for trials in which blinding is not feasible at the point of intervention (such as a tidal volume trial), a grade of "A" would be assigned if the investigator collecting the primary outcome were blinded to the treatment allocation. bFor the RCT, there was no reported assessment of adherence to the ventilator/intervention protocol. cAs assessed by STROBE guidelines. ARDS, acute respiratory distress syndrome; ASA, American Society of Anesthesiologists; BAL, bronchoalveolar lavage; ICU, intensive care unit; LOS, length of stay; PBW, predicted body weight; VF, ventilator free; VT, tidal volume.