Work of Breathing Dynamics Under Changes of PEEP and Pressure Support in Non-invasive Mechanical Ventilation

In spontaneous ventilation patient governs his breaths and the correct configuration of the mechanical ventilator is indispensable to avoid extra load in the ventilation process. Parameters like PEEP and pressure support (PS) affects directly the ventilatory comfort of the patient, therefore, they should be adjustable to improve oxygenation and reduce work of breathing (WOB). The objective of this study is to assess the WOB dynamics during incremental stimuli of PEEP and PS as additional information to the absolute WOB value. Variations of 2 cmH2O for 3 min up to 10 cmH2O for PEEP and PS separately were carried out in healthy subjects to analyze the changes in the WOB dynamics. 31 male adults were enrolled in this study, the absolute WOB, and three indexes of WOB dynamics (inspiratory slope, expiratory slope and Delta Peak) were calculated from ventilatory signals. Inspiratory slope shows a linear trend with the absolute WOB, nevertheless after the threshold of 0.8 J/L has a high dispersion, which suggests that high values of WOB could be obtained under different breathing pattern. In conclusion, the inspiratory slope like an index of WOB dynamics provides extra information that in future works could be compared with muscular and ventilator variables to identify positive or negative increases of WOB which clinicians could analyze to make decision about the optimum treatment of the patient.