ARDS ventilation mortality benefit: low tidal volume ~6 mL/kg predicted/ideal body weight and plateau pressure ≤30. EM board-style question review.
ARDS board questions reliably reward recognition of low tidal volume ventilation (~6 mL/kg predicted/ideal body weight) with plateau pressure limitation as the intervention linked to improved mortality.
You intubate a 30-year-old woman for acute respiratory distress syndrome (ARDS). Which of the following respirator settings is associated with decreased mortality in patients with ARDS?
Answer Options:
A. Plateau pressure > 30 cm H2O
B. Positive end-expiratory pressure (PEEP) of 10-15 H2O
C. Peak inspiratory pressure > 30 cm H2O
D. Tidal volume 6 to 7 mL/kg/ideal body weight (IBW)
Low tidal volume ventilation (classically 6 mL/kg predicted/ideal body weight) is the most consistently guideline-backed ventilator strategy associated with improved mortality in ARDS, along with limiting plateau pressure to ≤30 cm H₂O (ATS/ESICM/SCCM 2017). PEEP is generally used in ARDS and titrated to oxygenation and recruitability (often via PEEP/FiO₂ tables); it is not accurate to teach “little or no PEEP” as a mortality-improving strategy.
| Option | What It Tests / Implies | Why It’s Wrong Here |
|---|---|---|
| A. Plateau pressure > 30 cm H₂O | Understanding of plateau pressure limits | Plateau pressures **>30** increase risk of ventilator-induced lung injury; guidelines emphasize **≤30 cm H₂O**. |
| B. PEEP 10–15 cm H₂O | PEEP selection in ARDS | PEEP is not a single fixed mortality setting; ARDS management uses **PEEP/FiO₂ titration** (and often higher PEEP in more severe ARDS), not “10–15” as a universal mortality-improving choice. |
| C. Peak inspiratory pressure > 30 cm H₂O | Confusion between peak vs plateau pressure | Peak pressure reflects airway resistance + compliance; targeting a *high* peak pressure is not protective and is not the mortality-linked parameter. |
| D. Tidal volume 6–7 mL/kg IBW | Lung-protective low VT ventilation | This is the best-supported mortality-reducing setting (conceptually **~6 mL/kg PBW/IBW**, within 4–8) in ARDS. |
In ARDS, the mortality-associated ventilator strategy is low tidal volume (~6 mL/kg PBW/IBW) while keeping plateau pressure ≤30 cm H₂O.
1. Identify the ventilator parameter in ARDS with the strongest association with reduced mortality: low tidal volume based on predicted/ideal body weight.
2. Distinguish plateau pressure (alveolar distending pressure; target ≤30) from peak inspiratory pressure (includes airway resistance) in ARDS test questions.
This item exploits two common board traps: (1) offering “high pressure” options that sound like they might improve ventilation but actually worsen VILI risk, and (2) offering a plausible PEEP range even though PEEP is titrated and not the single most test-reliable mortality association compared with low VT based on PBW/IBW.
A 68-year-old man meets Berlin criteria for ARDS. Which initial tidal volume is most appropriate to reduce ventilator-induced lung injury?
- A. 10–12 mL/kg actual body weight
- B. 6 mL/kg predicted (ideal) body weight
- C. 8–10 mL/kg ideal body weight
- D. 4 mL/kg actual body weight for all patients
- E. 12–15 mL/kg ideal body weight
Which ventilator change has the best evidence for mortality reduction in ARDS?
- A. Increase tidal volume to normalize PaCO₂
- B. Avoid permissive hypercapnia at all costs
- C. Reduce tidal volume to ~6 mL/kg predicted body weight
- D. Use zero PEEP to prevent barotrauma
- E. Increase FiO₂ to 1.0 indefinitely
A 5'2" (157 cm) woman with obesity is ventilated for ARDS. To set lung-protective ventilation, tidal volume should be calculated using:
- A. Actual body weight
- B. Predicted/ideal body weight based on height and sex
- C. BMI category
- D. Lean body mass measured by bioimpedance
- E. Body surface area
How would your ventilator adjustments differ between (1) ARDS with severe hypoxemia requiring escalating PEEP/FiO₂ and (2) obstructive physiology with high peak pressures but normal plateau pressures?
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