Programmed Multi-Level Ventilation: A Strategy for Ventilating Non-Homogenous Lungs

Abstract

Mechanical ventilation (MV) has been an integral method used in ICU care for decades. MV is typically viewed as a life-supporting intervention. However, it can also contribute to lung injury through stress and strain, as evidenced by ventilator-induced lung injury (VILI), even in previously healthy lungs. The negative impact may be worsened when significant lung non-homogeneity is present, eg. ALI and ARDS. Protective lung strategies to minimize VILI are to use low tidal volumes (Vt 4–6 mL/kg/PBW), plateau pressures (P plat ) <30 cmH 2 O and relatively high positive end-expiratory pressures (PEEP). Yet, use of constantly high PEEP levels is well recognized to result in hemodynamic compromise of the right ventricle, increased stress and strain through high mechanical energy impact on the lung and overdistension of relatively healthy lung tissue. Taking these issues into consideration, a different approach to mechanical ventilation was developed specifically for patients with non-homogeneity. This review focuses on a feature called programmed multi-level ventilation (PMLV). It is not a ventilation mode per se, but rather a form of extension that adjusts and modifies any ventilation mode (eg PCV,PSV, VCV, SIMV, etc.). PMLV is based on measured time constants (Tau) of the whole respiratory system, including artificial airways, breathing circuits, humidification devices and mechanical ventilator. Using a physiology-based approach presents a method to ventilate non-homogenous lungs through cyclic changes of different PEEP levels; recruitment takes place in lung areas with long time constants but protects relatively healthy lung areas from overdistension thus minimizing excessive mechanical power to the lung tissue.

A new method of ventilation inhomogeneity assessment based on a simulation study using clinical data on congenital diaphragmatic hernia cases

“…Depta, Čandik et al [24][25][26] presented a strategy based on recurrent changes in PEEP levels, enabling recruitment of lung area of long time constants and protecting the lung area of short time constants from overextension and injury. They also proposed the concept of optimal breath frequency, based on time constant measurement 24 .…”

“…Depta, Čandik et al [24][25][26] presented a strategy based on recurrent changes in PEEP levels, enabling recruitment of lung area of long time constants and protecting the lung area of short time constants from overextension and injury. They also proposed the concept of optimal breath frequency, based on time constant measurement 24 . Their studies in ARDS patients showed that applying this technique led to a significant rise in respiratory system compliance, and improvement in CO 2 washout, due to the increase of gas exchange area (lung recruitment) 25 , in comparison to the conventional mechanical ventilation.…”

Programmed multi-level ventilation in COVID-19-related acute respiratory distress syndrome: a multi-center retrospective observational study

“…PMLV is not a ventilation mode per se but rather a feature that adjusts and modifies any ventilation mode used (e.g., PCV, PSV, volume-controlled ventilation, synchronized intermittent mandatory ventilation). 15 PMLV is based on the measured expiratory time constant (TauE) of the whole respiratory system. First, knowing the time for which 63% of the expiratory tidal volume is exhaled (TauE) will help to determine the optimal ventilation frequency (the longer the TauE, the lower the total frequency and vice versa) to avoid intrinsic PEEP.…”

“…12 For this study, the PMLV setting (i.e., recommended respiratory rate and combined alternating PEEP levels) was mathematically predicted using the ventilator software. 15 From among the options given by the software, treating clinicians then decided whether two or three levels of PEEP should be used. On the basis of standard institutional clinical care and the implemented local ICU protocol, baseline PEEP was selected according to the predicted body weight (1 cmH 2 O for each 10 kg of predicted body weight, with minimum 5 cmH 2 O and maximum 10 cmH 2 O), and this did not change during the observation period.…”