ATS ARDS Flashcards
What are the severities of ARDS according to the Berlrin Definition as of the 2011 revision
Based on P/F ratios - mild <300, moderate <200, severe <100
How does the severity of ARDS relate to patient outcomes?
mild ARDS - 27% mortality, 5 days mechanical vntilation
moderate ARDS - 32% mortality, 7 days mechanical ventilation
severe ARDS - 45% mortality, 9 days mechanical ventilation
What is the Berlin Definition of ARDS?
symptoms within 1 week of known insult, bilateral opacities on imaging, non-cardiogenic pulmonary edema, oxygenation <300 P/F w/ PEEP of 5 (can be non-invasive)
Describe the study design of Herridge et al 2011 - Functional Disability 5 years after ARDS (NEJM)
Run by the Canadian critical care trials group. Prospective cohort study from 1 ICU in Toronto where they monitored outocomes at 3, 6, 12 and then annually up to 5 years
Describe the study population in Herridge et al 2011 - Functional Disability 5 years after ARDS (NEJM)
Enrollment occurred between 1998 and 2001 (ie before ARDS net). 109 patients. Median age 44 at time of enrollment. >75% had 1 or none coexisting conditions.
In general, what did follow up PFTs demonstrate in ARDS survivors in Herridge et al 2011 - Functional Disability 5 years after ARDS (NEJM). What was the most common imaging finding?
Normal or near normal pulmonary function. Most common CT finding was pulmonary fiborsis consitent with ventilator induced lung injury.
Describe some non-pulmonary sequellae for ARDS survirors found in Herridge et al 2011 - Functional Disability 5 years after ARDS (NEJM)
1) Decreased functional capacity as measured by 6 min walk test (66% predicted in year 1, 76% predicted in year 2)
2) Significant mental health co-morbidities w/ 51% being diagnosed w/ depression, anxiety or both
3) Delayed return to work
4) Decreased QoL as measured by a SF-36 survery
Describe ARDS illness severity in the study by Herridge et al 2011 - Functional Disability 5 years after ARDS (NEJM) in terms of inciting event, need for RRT, average ventilator use and hospital stay
In those patients who survived and followed up at 1 year - pneumonia and sepsis were the most common inciting event, only 13% required RRT, the median ventilation time was 21 days, and median hospitalization time was 47 days
What were the traditional tidal volumes in ARDS patients prior to the ARDSNet trial?
10-15 cc/kg
Describe the ARDSNet study design
Patients recruited from 1996-1999 across 10 sites. n=861 (stopped for efficacy), 1:1 randomization of low Vt (6-8) to standard Vt (12 or <50 mmHg PIP; min 45cm plat). Kept on ACVC until met weaning criteria (FiO2 .4) or 28 days. Patients followed for 180 days. Primary endpoint was death prior to discharge home and breathing on your own. If in a facility at 180 days this counts as success.
Describe relevant inclusion and exclusion criteria for ARDSNet patients
Inclusion: P/F < 300, less than 36 hours, not cardiogenic pulm edema
Exclusion: <18, “severe” chronic respiratory disease, prior BMT, burns, high ICP, neuromuscular disease affecting spontaneous breaths, >1kg per cm height
What are the primary findings of ARDSNet with respect to primary outcomes?
Lower mortality at 180 days compared to standard care (31 vs 39.8%)
Greater percentage breathing on own at day 28 (65% vs 55%)
More ventilator free days and days without organ failure in low Vt. Same barotrauma.
What was the trial design and primary outcome of the high vs low peep trial described in Browers et al 2004 NEJM paper.
Randomized 549 patients from 1999 to 2002 to low (traditional ARDSnet table) vs high PEEP tables based on their FiO2 requirement (FiO2 required to stay at PaO2 55-80). They required a minimum of high PEEP for 12 or 48 hours after intubation (depending on whether it was before or after the change to the protocol). Primary outcome was survival to discharge home breathing on own or alive at 60 days out of the hospital. Initial enrollment was supposed to be 750 but was stopped for futility.
In Browers et al 2004 NEJM paper describing high vs low peep, there was a change to the protocol made half way through - what was it and why?
Their steering committee advised that the average difference between the PEEP in their two groups was not large enough so they increased the “high” PEEP tables. Additionally, they went from mandating 12 peep for 12 hours to 14 peep for 48 hours. Lastly, they stopped doing recruitment maneuvers for the high PEEP group.
Describe the study participants for Browers et al 2004 NEJM paper, including notable differences and top causes of lung injury.
The high PEEP group was older (47 vs 54) and had worse lung injury by P/F ratio (161 vs 151). The top causes of lung injury were pneumonia, sepsis, and aspiration.
