The effect of respiratory manoeuvres for patient-specific respiratory mechanics monitoring

Respiratory manoeuvres which from normal operation of the mechanical ventilator have been used to provide additional information to identify respiratory mechanics models, guide treatment, or provide more insight for clinicians. However, if the underlying respiratory mechanics are changed by a respiratory manoeuvre, then the application of respiratory manoeuvres may be significantly limited. This study identifies respiratory mechanics before and after super-syringe manoeuvres to investigate if the well-known super-syringe manouevre changes the underlying patient-specific respiratory mechanics. Thirty breaths before and after a super-syringe manouevre are analysed using a first order model for each of 16 patients. Median [IQR] absolute percentage changes in the median identified compliance and resistance distributions were 8.9% [2.1-16.8%] for compliance and 12.0% [3.5-19.3%] for resistance. 12 of 16 patients had significant changes in the distributions of compliance and 10 had significant changes in distribution of resistance (Wilcoxon ranksum test p<0.05). The magnitude and direction of the changes in parameters varied across patients. Some patients had very similar respiratory mechanics before and after the respiratory manouevre, others had large changes. Large changes in respiratory mechanics for some patients after a manoeuvre, limit the ability of using manoeuvres to guide treatment, as patients whose respiratory mechanics are greatly altered by respiratory manoeuvres cannot be known in advance. Therefore, consideration should be given to the potential clinical benefits and harms of respiratory manoeuvres before using them on patients.