Human versus Computer Controlled Selection of Ventilator Settings: An Evaluation of Adaptive Support Ventilation and Mid-Frequency Ventilation

Abstract

Background. There are modes of mechanical ventilation that can select ventilator settings with computer controlled algorithms (targeting schemes). Two examples are adaptive support ventilation (ASV) and mid-frequency ventilation (MFV). We studied how different clinician-chosen ventilator settings are from these computer algorithms under different scenarios. Methods. A survey of critical care clinicians provided reference ventilator settings for a 70 kg paralyzed patient in five clinical/physiological scenarios. The survey-derived values for minute ventilation and minute alveolar ventilation were used as goals for ASV and MFV, respectively. A lung simulator programmed with each scenario's respiratory system characteristics was ventilated using the clinician, ASV, and MFV settings. Results. Tidal volumes ranged from 6.1 to 8.3 mL/kg for the clinician, 6.7 to 11.9 mL/kg for ASV, and 3.5 to 9.9 mL/kg for MFV. Inspiratory pressures were lower for ASV and MFV. Clinician-selected tidal volumes were similar to the ASV settings for all scenarios except for asthma, in which the tidal volumes were larger for ASV and MFV. MFV delivered the same alveolar minute ventilation with higher end expiratory and lower end inspiratory volumes. Conclusions. There are differences and similarities among initial ventilator settings selected by humans and computers for various clinical scenarios. The ventilation outcomes are the result of the lung physiological characteristics and their interaction with the targeting scheme.

Application of Mid-Frequency Ventilation in an Animal Model of Lung Injury: A Pilot Study

“…There was a nonsignificant reduction in V T ; associated with a nonsignificant increase in P aCO 2 . Lactate values decreased by 0.2 mg/dL.…”

“…These results are consistent with our previous theoretical work. 2,3 We demonstrated that a simple manual algorithm allowed implementation of MFV with a conventional ventilator.…”

“…2,3 MFV capitalizes on the properties of a pressure control breath and its response to changes in ven-tilatory frequency. The theoretical basis of MFV has been explained in detail elsewhere.…”

Mid-frequency ventilation: A potential strategy for lung protective neonatal mechanical ventilation

“…When the inflation pressure is adjusted so that the peak of this curve matches the desired target minute alveolar ventilation, V T will be minimized. The MFV "optimization" of ventilator settings often results in lower V T at higher than usual respiratory frequencies [20]. This approach is illustrated in Fig.…”

“…We found that the equations used for MFV choose ventilator settings (V T , frequency and inspiratory pressure) in concordance with clinical practice and lung physiology. In a follow up study, we evaluated the differences between clinicians' choices and MFV in terms of ventilation outcomes [20]. We created five hypothetical clinical scenarios of paralyzed patients with healthy lungs, acute respiratory distress syndrome, morbid obesity, emphysema and severe asthma.…”