What is the ideal tidal volume for pulmonary edema due to cardiomyopathy in a postpartum woman?

From the Guidelines

The ideal tidal volume for pulmonary edema due to cardiomyopathy in a postpartum woman is 6 ml/kg of predicted body weight (PBW).

Rationale

• The use of lower tidal volumes is supported by several studies, including a seminal prospective RCT by the ARDS Network, which found that a ventilatory strategy targeting a tidal volume of 6 ml/kg PBW was associated with reduced mortality in patients with ARDS compared to a strategy targeting a tidal volume of 12 ml/kg PBW 1.
• The American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline recommends mechanical ventilation with strategies that limit tidal volumes to 4-8 ml/kg PBW in adult patients with ARDS 1.
• Some studies suggest that even lower tidal volumes (less than 6 ml/kg) may be preferable, but this may require higher PEEP levels to maintain oxygenation 1.
• The driving pressure (ΔP = Pplat – PEEP) is a better predictor of outcomes than tidal volume or plateau pressure, and values exceeding 15 cmH2O are of particular concern 1.

Key Considerations

• Tidal volume should be titrated according to PBW, not ideal body weight (IBW), due to a better relationship with lung size in healthy subjects 1.
• In patients with ARDS, the proportion of the lung available for ventilation is decreased, and tidal volume should be scaled to compliance using the driving pressure 1.
• The use of extracorporeal carbon dioxide removal (ECCO2R) with very low tidal volume (3-4 ml/kg PBW) may limit the development of ventilator-induced lung injury (VILI), but more studies are needed to support this approach 1.

From the Research

Ideal Tidal Volume for Pulmonary Edema due to Cardiomyopathy

The ideal tidal volume for pulmonary edema due to cardiomyopathy in a postpartum woman is a critical consideration in mechanical ventilation. The following points summarize the key findings:

• A tidal volume of 6 mL/kg ideal body weight has been shown to improve ARDS outcome, compared to 12 mL/kg 2.
• Adjustments to tidal volume should be made based on plateau pressure, with a commonly quoted threshold of 30-35 cm H2O 2.
• A low-tidal-volume strategy may need to be modified in patients with high spontaneous tidal volume demand to avoid worsening pulmonary edema 3.
• A novel equation, Vt = 20*(Ht-60) + 300, has been derived to predict a 6-8 mL/kg ideal body weight tidal volume 4.
• Low tidal volumes (5 mL/kg) with PEEP have been shown to provide comparable arterial oxygenation and intrapulmonary shunt fraction during one-lung ventilation as higher tidal volumes (10 mL/kg) without PEEP 5.
• Ultra-low tidal volume ventilation (3 mL/kg predicted body weight) may attenuate inflammation in patients with cardiogenic pulmonary edema and veno-arterial extracorporeal membrane oxygenation 6.

Key Considerations

• The choice of tidal volume should be individualized based on patient factors, such as plateau pressure and spontaneous tidal volume demand.
• The use of PEEP and other ventilatory strategies should be considered in conjunction with tidal volume selection.
• The potential for ventilator-associated lung injury should be weighed against the need for adequate oxygenation and ventilation.