Why does low tidal volume ventilation increase survival in Acute Respiratory Distress Syndrome (ARDS)?

From the Guidelines

Low tidal volume ventilation increases survival in ARDS by reducing ventilator-induced lung injury, and the recommended approach is to use tidal volumes of 4-6 mL/kg of predicted body weight, as supported by the American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline 1. The use of lower tidal volumes in mechanical ventilation for ARDS patients has been shown to decrease mortality and improve outcomes by limiting lung stress and strain. This approach is based on the principle of preventing overdistension of alveoli (volutrauma), reducing the damaging shear forces that occur when alveoli repeatedly open and collapse (atelectrauma), and decreasing the release of inflammatory mediators (biotrauma) 1. Some key points to consider when implementing low tidal volume ventilation include:

• Calculating the patient's predicted body weight based on height and gender, rather than actual weight, to determine the appropriate tidal volume 1
• Adjusting ventilator settings to maintain plateau pressures less than 30 cm H2O while providing adequate oxygenation with PEEP adjustments and permissive hypercapnia if needed 1
• Considering the use of driving pressure (ΔP = Pplat – PEEP) to titrate tidal volume, as it has been shown to predict outcomes better than other ventilatory parameters in patients with ARDS 1
• Being aware that lower tidal volumes may lead to higher CO2 levels, but this respiratory acidosis is generally well-tolerated and preferable to the lung damage caused by higher volumes 1 Overall, the use of low tidal volume ventilation in ARDS patients is a crucial strategy for reducing morbidity and mortality, and improving quality of life, as supported by the latest clinical practice guidelines and expert opinions 1.

From the Research

Mechanism of Low Tidal Volume Ventilation

• Low tidal volume ventilation is a strategy used in the management of Acute Respiratory Distress Syndrome (ARDS) that has been shown to decrease mortality and increase the number of days without ventilator use 2.
• The use of lower tidal volumes (6 ml per kilogram of predicted body weight) compared to traditional tidal volumes (12 ml per kilogram of predicted body weight) results in decreased mortality and increased number of days without ventilator use 2.
• The mechanism behind this is thought to be related to the reduction of stretch-induced lung injury, which is a common complication in patients with ARDS 2.

Clinical Evidence

• A systematic review and meta-analysis of 13 randomized controlled trials found that low tidal volume ventilation (4-8 ml/kg) was associated with reduced risk of mortality in patients with ARDS compared to higher tidal volume ventilation (> 8 ml/kg) 3.
• Another study found that the use of low tidal volume ventilation was associated with improved outcomes in patients with ARDS, including decreased mortality and increased number of days without ventilator use 2.
• A retrospective cross-sectional study found that low tidal volume ventilation was underutilized in patients with ARDS, with only 19.3% of patients receiving this treatment 4.

Clinical Practice

• The cornerstone of ARDS care for mechanically ventilated patients is low-tidal volume ventilation based on ideal body weight 5.
• Adjunctive therapies, such as prone positioning and neuromuscular blockade, may have a role in the management of ARDS depending on patient and department characteristics 5.
• A rational stepwise approach with frequent monitoring for improvement or harm can be achieved in the management of severe respiratory failure in ARDS, with low tidal volume ventilation being a key component of this approach 6.