From the Guidelines
ARDS progresses through two distinct stages: the exudative phase and the proliferative/fibrotic phase, as described in the latest consensus (Berlin Definition) and supported by recent clinical evidence 1. The exudative phase occurs first, typically within the initial week after lung injury, and is characterized by increased permeability of the alveolar-capillary membrane leading to protein-rich fluid leaking into the alveolar spaces. This results in pulmonary edema, surfactant dysfunction, and the formation of hyaline membranes. Clinically, patients experience severe hypoxemia, decreased lung compliance, and bilateral infiltrates on chest imaging.
- Key features of the exudative phase include:
- Increased permeability of the alveolar-capillary membrane
- Protein-rich fluid leaking into the alveolar spaces
- Pulmonary edema and surfactant dysfunction
- Formation of hyaline membranes
- The second stage, the proliferative/fibrotic phase, begins approximately 7-10 days after the initial injury and involves the organization of the exudate and repair processes. During this phase, type II pneumocytes proliferate to restore the alveolar epithelium, while fibroblasts migrate into the alveolar spaces and deposit collagen.
- Some patients recover with minimal residual damage, while others develop significant fibrosis leading to long-term respiratory impairment, as noted in the study published in Critical Care in 2017 1. The transition between these phases represents the body's attempt to repair the damaged lung tissue, but excessive inflammation in the exudative phase and dysregulated repair in the proliferative phase contribute to the high mortality and morbidity associated with ARDS, with ICU mortality rates still 35–40% and increasing with the severity of hypoxemia 1.
From the Research
Stages of ARDS
The two stages of Acute Respiratory Distress Syndrome (ARDS) are not explicitly described in the provided studies. However, the progression and management of ARDS can be understood through the following points:
- The initial stage of ARDS is characterized by inflammation and injury to the lung tissue, leading to impaired gas exchange and hypoxemia 2.
- The later stage of ARDS involves the use of mechanical ventilation and other supportive therapies to manage the condition and prevent further complications 2, 3, 4, 5, 6.
Key Considerations in ARDS Management
Some key considerations in the management of ARDS include:
- The use of low tidal volume ventilation and positive end-expiratory pressure (PEEP) to improve oxygenation and reduce lung injury 2, 3, 4, 5, 6.
- The importance of individualizing ventilator settings and PEEP levels to optimize patient-ventilator synchrony and reduce ventilator-induced lung injury (VILI) 2, 3, 5.
- The potential benefits and risks of adjunctive therapies, such as recruitment maneuvers, inhaled pulmonary vasodilators, and neuromuscular blockers, in improving oxygenation and outcomes in ARDS patients 2, 6.