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Mechanical Ventilation

Guidance tools only. Always interpret results within clinical context.

🫁 Predicted Body Weight (PBW)

ARDSnet-based calculation. Used to define lung-protective ventilation.

🫁 PCO₂ Adjustment

Inverse relationship between PCO₂ and minute ventilation. Does not replace blood gas analysis or clinical judgment.

🫁 Driving Pressure (ΔP) and Lung Compliance

ΔP = Plateau pressure − PEEP
Compliance (Crs) = VT / ΔP
Assessment of lung stress and respiratory mechanics.

🫁 Resistive Component

Resistive component = Peak pressure − Plateau pressure
If inspiratory flow is entered, airway resistance (Raw) is also calculated.

Clinical basis of mechanical ventilation in the ICU

Invasive mechanical ventilation is a fundamental intervention in the Intensive Care Unit (ICU), used to optimize gas exchange, reduce the work of breathing, and maintain adequate oxygenation in critically ill patients. Its use requires balancing ventilatory support with prevention of ventilator-induced lung injury (VILI).

Goal of mechanical ventilation

The main goal is to ensure adequate oxygenation and CO₂ elimination while maintaining hemodynamic stability and minimizing the risk of lung injury. Protective ventilation is the current standard in patients with pulmonary impairment.

Predicted body weight (PBW)

Calculation of predicted body weight (PBW) is essential to determine the appropriate tidal volume. Unlike actual body weight, PBW is based on height and sex, allowing safer and more physiological ventilation.

In patients with acute respiratory distress syndrome (ARDS), a tidal volume of approximately 6 mL/kg PBW is recommended, reducing the risk of volutrauma and improving clinical outcomes.

Driving Pressure (ΔP)

Driving Pressure (ΔP), defined as the difference between plateau pressure and PEEP, is an indicator of lung stress. Higher values have been associated with increased mortality in ventilated patients.

Keeping ΔP low is a key protective ventilation strategy, as it reflects better matching between tidal volume and lung compliance.

PCO₂ adjustment

CO₂ elimination depends on minute ventilation, which is the product of tidal volume and respiratory rate. There is an inverse relationship between minute ventilation and PCO₂, which allows ventilatory adjustment to correct acid-base disturbances.

However, adjustments must be made carefully to avoid complications such as hyperventilation, increased intrathoracic pressure, or lung injury.

Clinical application of results

Values obtained with these tools must be interpreted together with arterial blood gases, lung mechanics, and the overall clinical condition of the patient. Mechanical ventilation is a dynamic process that requires continuous reassessment.

Factors affecting ventilation

Factors such as lung compliance, airway resistance, sedation, spontaneous breathing, and hemodynamic status can significantly modify the response to mechanical ventilation.

Importance of protective ventilation

Protective ventilation aims to reduce lung injury by using low tidal volumes, limited plateau pressure, and appropriate PEEP. This strategy has been shown to improve survival in patients with ARDS.

Clinical warning

These tools are intended for educational and clinical support purposes only. They do not replace medical judgment or clinical guidelines. Decisions must be individualized according to the patient’s condition.

References

ARDSnet Ventilation Protocol.
Amato MB et al. Driving pressure and survival in ARDS.
International guidelines for mechanical ventilation in intensive care.