- COVID-19-related severe acute respiratory distress syndrome (ARDS) presents in 2 ways.
- 3 factors appear to interact: severity, ventilatory responsiveness to hypoxemia, and time between disease onset and hospitalization.
- These factors should guide recognition of phenotype and approach to treatment.
Why this matters
- The authors argue that treatment should rely on establishing the correct pathophysiology within 2 primary phenotypes: Type L and Type H.
- Use CT scans to identify patient type, or if unavailable, distinguish patients by respiratory system elastance and recruitability.
- Type L: 1) low elastance, 2) low ventilation-to-perfusion ratio, 3) low lung weight, 4) low lung recruitability.
- Course: patient status remains unchanged and then improves or worsens; negative intrathoracic pressure depth linked to increased tidal volume may drive progression to interstitial lung edema and dyspnea, worsening patient "self-inflicted" lung injury and causing transition to Type H.
- Type H: 1) high elastance, 2) high right-to-left shunt, 3) high lung weight, 4) high lung recruitability.
- Fully meets ARDS criteria.
- Reverse hypoxemia through increased FiO2.
- Dyspnea: esophageal manometry critical to assess pressure swings, drive noninvasive treatment selection.
- Inspiratory pleural pressure swing magnitude determines transition to type H, and >15 cmH2O indicates intubation need.
- If hypercapnic, ventilate with volumes >6 mL/kg to 8-9 mL/kg; use prone positioning for rescue only.
- Treat type H as severe ARDS.