An adaptive lung ventilation controller

Abstract

Closed loop control of ventilation is traditionally based on end-tidal or mean expired CO2. The controlled variables are the respiratory rate RR and the tidal volume VT. Neither patient size or lung mechanics were considered in previous approaches. Also the modes were not suitable for spontaneously breathing subjects. This report presents a new approach to closed loop controlled ventilation, called Adaptive Lung Ventilation (ALV). ALV is based on a pressure controlled ventilation mode suitable for paralyzed, as well as spontaneously breathing, subjects. The clinician enters a desired gross alveolar ventilation (V'gA in l/min), and the ALV controller tries to achieve this goal by automatic adjustment of mechanical rate and inspiratory pressure level. The adjustments are based on measurements of the patient's lung mechanics and series dead space. The ALV controller was tested on a physical lung model with adjustable mechanical properties. Three different lung pathologies were simulated on the lung model to test the controller for rise time (T90), overshoot (Ym), and steady state performance (delta max). The pathologies corresponded to restrictive lung disease (similar to ARDS), a "normal" lung, and obstructive lung disease (such as asthma). Furthermore, feasibility tests were done in 6 patients undergoing surgical procedures in total intravenous anesthesia. In the model studies, the controller responded to step changes between 48 seconds and 81 seconds. It did exhibit an overshoot between 5.5% and 7.9% of the setpoint after the step change.(ABSTRACT TRUNCATED AT 250 WORDS)

A Randomized Controlled Trial to Compare Adaptive Support Ventilation and Pressure Support Ventilation for Weaning COPD Patients

“…With similar results, Kirakli et al (39) reported a significant shorter duration of weaning with ASV than PSV in AECOPD patients [median (IQR) 24 (20-62) h versus 72 (24-144) h, p = 0.041]. ICU stay was also shorter in ASV group [median (IQR) 11 (6-15) days versus 13 (8)(9)(10)(11)(12)(13)(14) days, p = 0.5] but this difference was not statistically significant, while results from our study had significantly shorter LOS in ICU [median (IQR) 4 (2.5-9) days versus 6 (3-11) days, p < 0.001].…”

“…Adaptive support ventilation (ASV), first described by Laubscher (10) , it relies on closedloop regulation of settings in response to changes in respiratory mechanics and spontaneous breathing, with wide-ranging, automated, pressure modes from pressure-controlled ventilation to pressure-support ventilation. (11)(12)(13)(14) Some studies have evaluated the use of ASV in weaning cardiac surgery patients and have shown a reduction in weaning time, a reduced need for arterial blood gas (ABG) analyses, and fewer ventilator adjustments.…”

Knowledge-based systems for automatic ventilatory management

“…• The introduction of a new mode of ventilation such as PAV 50 , ALV 28 or ARIS 5 is a long and difficult process. Therefore, we chose i) to ventilate patients with a standard ventilation mode, pressure support ventilation, largely used for weaning, and ii) to add heuristic knowledge to improve its use and to facilitate the weaning process.…”

Harmonic excitation of linear respiratory mechanics for physiological dual controlled ventilation

“…Among the different systems proposed for implementing DCV [5,[15][16][17][18][19][20], ALVS exhibits the following suitable functional features [6,7]: 1) opportunity of applying any airways pressure waveform of clinical interest during the time of controlled breathing without distortions, i.e. identical to that selected;…”