Pulmonary diffusing capacity for carbon monoxide by rebreathing in mechanically ventilated patients

Area of Science:

• Pulmonary physiology
• Intensive care medicine
• Respiratory diagnostics

Background:

• Pulmonary diffusing capacity for carbon monoxide (DCO) is standard for spontaneous breathing but not for mechanically ventilated patients.
• Severe respiratory failure in intensive care necessitates reliable gas exchange assessment methods.

Purpose of the Study:

• To describe a novel rebreathing method for determining DCO in mechanically ventilated patients.
• To evaluate the method's applicability and reproducibility in intensive care settings.

Main Methods:

• An improved mathematical approach based on a two-compartment model was used for DCO determination.
• A rebreathing technique was employed, with optional addition of an inert gas (e.g., argon) for simultaneous functional residual capacity (FRC) measurement.
• The method's reproducibility was assessed through duplicate determinations.

Main Results:

• The rebreathing DCO method showed high reproducibility (+/- 3.8% for DCO, +/- 2.1% for FRC).
• It is less influenced by lung inhomogeneities, making it suitable for diseased lungs in intensive care.
• A pathological borderline for DCO during mechanical ventilation was established at approximately 10 ml . min-1 . mmHg-1.

Conclusions:

• The rebreathing DCO method is a reproducible and qualified parameter for evaluating pulmonary gas exchange in mechanically ventilated patients.
• It can effectively indicate the progression of respiratory failure in intensive care settings.
• Simultaneous FRC measurement is possible, enhancing its utility.