Adaptive Dynamic Sub-tidal Ventilation (ADSV Technology): Lung Protection by Millisecond Adjustments in Gas Flow, Volume, and Pressure at the Alveolar Level

Acute respiratory distress syndrome (ARDS) leads to complex, regional, and heterogeneous alteration in alveolar and alveolar duct mechanics, predisposing the lung to a secondary ventilator-induced lung injury (VILI). In Chapters 1 , 3 – 5 , a unifying hypothesis (Fig. 1.2 ) on the mechanisms by which these mechanical alterations cause VILI-induced tissue damage was established. In addition, the current lung-protective ventilation strategies (Chaps. 2 and 6 ) and the applied physiology of a novel Time-Controlled Adaptive (TCAV) protective ventilation method (Chap. 8 ) were discussed in detail. However, the quest for the optimal protective ventilation strategy continues. The challenge lies in ventilating the injured lung with its microenvironment consisting of normal tissue, unstable tissue, and collapsed or edema-filled tissue adjacent to each other and scattered throughout the entire lung. The ideal solution is a ventilator technology that responds to changes in lung pathophysiology at the micro-level and considers global lung elastance and resistance. The innovative approach of Adaptive Dynamic Sub-tidal Ventilation (ADSV technology) offers a promising solution to ventilate the heterogeneous, acutely injured lung protectively. The physics of ADSV-technology is based on the Law of Conversation of Energy and the Bernoulli and Venturi, similar to high-frequency percussive ventilation (HFPV) (Kunugiyama and Schulman AACN Adv Crit Care 23:370–80, 2012). ADSV technology delivers rapid pulses (milliseconds) of sub-tidal volume gas into a Sliding Venturi. The Sliding Venturi has an entrainment port that will add to the size of the sub-tidal volume delivered by the gas pulse depending on the downstream respiratory system resistance (RRS). The amount of gas entrained with each millisecond pulse depends on lung pathophysiology. In a lung with severe ARDS, the pressure necessary to inflate the lung will be high. High RRS will generate back pressure in the airways all the back into the Sliding Venturi entrainment chamber, reducing the size of the sub-tidal volume gas pulse by decreasing the volume of entrained gas. Thus, ADSV technology will lessen the sub-tidal volume (S-VT) in an acutely injured lung while increasing S-VT in the normal lung, all directed by changes in lung physiology. The gas pulse then enters a constricted section of the Sliding Venturi, mixing the pulse and entrained gas, and then moves into an expanded section of the Venturi to increase airway pressure before entering the trachea. In a patient with acute lung injury, the volume of gas delivered with each pulse will be reduced (less entrainment), preventing overdistension and volutrauma. At the same time, the airway pressure is increased (Pressure = Flow × Resistance) to facilitate the recruitment of collapsed tissue. As the patient’s lungs improve, the RRS-induced pressure in the Sliding Venturi) will decrease, increasing entrainment and the S-VT and lowering airway pressure. Thus, in an ARDS patient, ADSV technology will deliver a low S-VT at a higher airway pressure, preventing overdistension of lung tissue with the low volume and recruiting collapse tissue with the higher pressure. As the lung is reinflated and RRS drops, the gas volume and pressure delivered to the lung reverse with a higher S-VT, necessary for a fully inflated lung and a lower airway pressure since the lung no longer needs recruitment. In summary, ADSV technology employs a high-velocity gas delivered in millisecond pulses, with personalized and adaptive volume and pressure adjustments based on lung pathophysiology. It provides high-pressure sub-tidal volumes necessary to recruit collapsed tissue in the acutely injured lung while ensuring that partially collapsed regions receive low volume to prevent volutrauma. Gas entrainment increases in milliseconds as lung tissue recruits, delivering the extra gas volume necessary to avoid the re-collapse of the newly opened tissue. Although applied physiology suggests that ADSV technology would be highly lung protective, future studies will be needed to identify if it can improve patient outcomes.