Automated measurement of respiratory mechanics in anaesthetized ventilated patients

The automated multilinear regression analysis method (MLRA) was recently proposed to measure respiratory mechanics in mechanically ventilated subjects [11]. The method is applicable whatever the inspiratory flow pattern and without any assumption as to the value of the parameter characterizing the non linear term of flow resistance. It was compared here in ten mechanically ventilated patients to the constant flow inflation (CFIM) method described by Rossi et al. [15]. The non linear term of flow resistance was lower in intubated patients than in corresponding isolated endotracheal tubes. When derived from the MLRA method, the values for the elastance of the respiratory system were significantly higher (p less than 0.01) than with the CFIM method, and those for the system resistance, significantly lower (p less than 0.01). These differences might be due to the recruitment of lung units in the early part of inflation. When additional resistances were inserted into the respiratory circuit, both methods proved able to determine their values accurately. They therefore appear suitable for respiratory resistance monitoring in anaesthetized ventilated patients.