Simulation of Late Inspiratory Rise in Airway Pressure During Pressure Support Ventilation

Abstract

BACKGROUND: Late inspiratory rise in airway pressure (LIRAP, P aw /⌬T) caused by inspiratory muscle relaxation or expiratory muscle contraction is frequently seen during pressure support ventilation (PSV), although the modulating factors are unknown. METHODS: We investigated the effects of respiratory mechanics (normal, obstructive, restrictive, or mixed), inspiratory effort (؊2, ؊8, or ؊15 cm H 2 O), flow cycle criteria (5-40% peak inspiratory flow), and duration of inspiratory muscle relaxation (0.18 -0.3 s) on LIRAP during PSV using a lung simulator and 4 types of ventilators. RESULTS: LIRAP occurred with all lung models when inspiratory effort was medium to high and duration of inspiratory muscle relaxation was short. The normal lung model was associated with the fastest LIRAP, whereas the obstructive lung model was associated with the slowest. Unless lung mechanics were normal or mixed, LIRAP was unlikely to occur when inspiratory effort was low. Different ventilators were also associated with differences in LIRAP speed. Except for within the restrictive lung model, changes in flow cycle level did not abolish LIRAP if inspiratory effort was medium to high. Increased duration of inspiratory relaxation also led to the elimination of LIRAP. Simulation of expiratory muscle contraction revealed that LIRAP occurred only when expiratory muscle contraction occurred sometime after the beginning of inspiration. CONCLUSIONS: Our simulation study reveals that both respiratory resistance and compliance may affect LIRAP. Except for under restrictive lung conditions, LIRAP is unlikely to be abolished by simply lowering flow cycle criteria when inspiratory effort is strong and relaxation time is rapid. LIRAP may be caused by expiratory muscle contraction when it occurs during inspiration. Key words: patient-ventilator asynchrony; pressure support ventilation; late inspiratory rise in airway pressure. [Respir Care 2015;60(2):201-209.

Limited predictability of maximal muscular pressure using the difference between peak airway pressure and positive end-expiratory pressure during proportional assist ventilation (PAV)

“…First, for the unique condition where P mus, oes is usually overestimated in PAV20, a reasonable cause could be the ventilator flow control algorithm. Because respiratory effort is maximal in PAV20, the proportional-integral-derivative algorithm of the flow control system is prone to an airway pressure overshoot by the end of inspiration, which is further exaggerated fourfold in PAV20 for the calculation of P mus, aw [19, 20]. Second is a possible discrepancy between PAV+ and CMV measured respiratory mechanics [10].…”

A Model-Based Approach to Synthetic Data Set Generation for Patient-Ventilator Waveforms for Machine Learning and Educational Use

“…Although it has been suggested by Athanasiades et al [12] that their work can be used to model different types of respiratory diseases, there has not been any research on this topic. Fortunately, there is a vast amount of literature on changes in lung mechanics under the influence of different disease types [20,21,22,23,24,25,26,27]. We use this literature to adapt the model by Athanasiades et al to different disease archetypes since the model parameters represent real physiological properties of the lung.…”