1. Definition
1.1. Berlin Definition of ARDS
|
Clinical criteria |
Level of severity |
|
Timing: Onset within 1 week of known insult or of new or worsening respiratory symptoms. |
Mild: 200 mm Hg < PaO2/FiO 2 ratio ≤ 300 mm Hg with positive end-expiratory pressure (PEEP) or continuous positive airway pressure ≥ 5 cm H2O. |
|
Imaging (x-ray or CT of chest): Bilateral opacities not fully explained by effusions, lobar or lung collapse, or nodules. |
Moderate: 100 mm Hg < PaO2/FiO 2 ratio ≤ 200 mm Hg with PEEP ≥ 5 cm H2O. |
|
Origin of edema: Respiratory failure not fully explained by heart failure or fluid overload. |
Severe: PaO2/FiO 2 ratio ≤ 100 mmHg with PEEP ≥ 5 cm H2O. |
1.2. Global definition of ARDS
|
Risk factors and origin of edema |
Precipitated by an acute predisposing risk factor, such as pneumonia, nonpulmonary infection, trauma, transfusion, aspiration, or shock. Pulmonary edema is not exclusively or primarily attributable to cardiogenic pulmonary edema/fluid overload, and hypoxemia/gas exchange abnormalities are not primarily attributable to atelectasis. However, ARDS can be diagnosed in the presence of these conditions if a predisposing risk factor for ARDS is also present. |
|
|
Timing |
Acute onset or worsening of hypoxemic respiratory failure within 1 week of the estimated onset of the predisposing risk factor or new or worsening respiratory symptoms. |
|
|
Chest imaging |
Bilateral opacities on chest radiography and computed tomography or bilateral B lines and/or consolidations on ultrasound not fully explained by effusions, atelectasis, or nodules/masses. |
|
|
Criteria That Apply to Specific ARDS Categories |
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|
Nonintubated ARDS |
Intubated ARDS |
Modified Definition for Resource-Limited Settings |
|
PaO2:FiO 2 < 300 mm Hg or SpO2:FiO 2 < 315 (if SpO2< 97%) on HFNC with flow of >30 L/min or NIV/CPAP with at least 5 cm H2O end-expiratory pressure. |
Mild: 200, PaO2:FiO2< 300 mm Hg or 235, SpO2:FiO2< 315 (if SpO 2 < 97%). Moderate: 100, PaO2:FiO 2 < 200 mm Hg or 148, SpO2:FiO 2 < 235 (if SpO 2 < 97%). Severe: PaO2:FiO 2 < 100 mm Hg or SpO2:FiO 2 < 148 (if SpO 2 < 97%). |
SpO2:FiO 2 < 315 (if SpO2< 97%). Neither positive end-expiratory pressure nor a minimum flow rate of oxygen is required for diagnosis in resource-limited settings. |
2. Ventilatory Management of ARDS
2.1. A tidal volume around 6 mL/kg of predicted body weight (PBW) should be used as a first approach in patients with recognized ARDS, in the absence of severe metabolic acidosis, including those with mild ARDS.
2.2. Once tidal volume is set to around 6 mL/kg PBW, plateau pressure should be monitored continuously and should not exceed 30 cm H2O.
2.3. Tidal volume should not be increased when the plateau pressure is well below 30 cm H 2 O, except in cases of marked, persistent hypercapnia despite reduction of instrumental dead space and increase of respiratory rate.
2.4. PEEP should be above 5 cm H2O in all patients presenting with ARDS. High PEEP should probably be used in patients with moderate or severe ARDS, but not in patients with mild ARDS.
2.5. High-frequency oscillation ventilation should not be used in ARDS patients.
2.6. A neuromuscular blocking agent should probably be considered in ARDS patients with a PaO2/FiO 2 ratio < 150 mmHg to reduce mortality. The neuromuscular blocking agent should be administered by continuous infusion early (within 48 h after the start of ARDS), for no more than 48 h, with at least daily evaluation.
2.7. After the acute phase of ARDS, ventilation with a pressure mode allowing spontaneous ventilation can be used when ensuring that the tidal volume generated is close to 6 mL/kg PBW and does not exceed 8 mL/kg PBW.
2.8. Prone positioning should be used in ARDS patients with PaO2/FiO 2 ratio < 150 mmHg to reduce mortality. Sessions of at least 16 consecutive hours should be performed.
Higher PEEP/Lower FiO 2 table for ARDS
|
FiO 2 |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
0.4 |
0.4 |
0.5 |
0.5 |
0.5-0.8 |
0.8 |
0.9 |
1.0 |
1.0 |
|
PEEP |
5 |
8 |
10 |
12 |
14 |
14 |
16 |
16 |
18 |
20 |
22 |
22 |
22 |
24 |
Further Readings:
1. Saguil A, Fargo MV. Acute Respiratory Distress Syndrome: Diagnosis and Management. Am Fam Physician. 2020;101(12):730-738
2. Fan, E., Del Sorbo, L., Goligher, E. C., Hodgson, C. L., Munshi, L., Walkey, A. J., ... & Brochard, L. J. (2017). An official American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline: mechanical ventilation in adult patients with acute respiratory distress syndrome. American journal of respiratory and critical care medicine, 195(9), 1253-1263.
3. Papazian, L., Aubron, C., Brochard, L., Chiche, J. D., Combes, A., Dreyfuss, D., ... & Faure, H. (2019). Formal guidelines: management of acute respiratory distress syndrome. Annals of intensive care, 9(1), 1-18.
4. Tasaka, S., Ohshimo, S., Takeuchi, M., Yasuda, H., Ichikado, K., Tsushima, K., ... & Sanui, M. (2022). ARDS clinical practice guideline 2021. Journal of intensive care, 10(1), 32
5. Griffiths, M. J., McAuley, D. F., Perkins, G. D., Barrett, N., Blackwood, B., Boyle, A., ... & Baudouin, S. V. (2019). Guidelines on the management of acute respiratory distress syndrome. BMJ open respiratory research, 6(1), e000420.
