A microprocessor-controlled tracheal insufflation-assisted total liquid ventilation system

Abstract

A prototype time cycled, constant volume, closed circuit perfluorocarbon (PFC) total liquid ventilator system is described. The system utilizes microcontroller-driven display and master control boards, gear motor pumps, and three-way solenoid valves to direct flow. A constant tidal volume and functional residual capacity (FRC) are maintained with feedback control using end-expiratory and end-inspiratory stop-flow pressures. The system can also provide a unique continuous perfusion (bias flow, tracheal insufflation) through one lumen of a double-lumen endotracheal catheter to increase washout of dead space liquid. FRC and arterial blood gases were maintained during ventilation with Rimar 101 PFC over 2-3 h in normal piglets and piglets with simulated pulmonary edema induced by instillation of albumin solution. Addition of tracheal insufflation flow significantly improved the blood gases and enhanced clearance of instilled albumin solution during simulated edema.

Assessment of mechanical ventilation parameters on respiratory mechanics

“…Overall, the results obtained from the present study reflecting the role of mechanical ventilation parameters, and when combined with optimization suggest that it is possible to obtain a set of mechanical ventilation strategies to avoid lung injuries in patients, using the automated and microprocessor based technologies [34,35].…”

“…The passive exhalation was described by the following equation. Airway young's modulus in circumferential direction 74.07 kPa [35] Airway Poisson's ratio 0.45 [35] where v is airflow velocity (m s −1 ), t is time (s), V 0 is the tidal volume (cm 3 ), and τ is a time constant equal to the product of lung compliance and resistance. The time constant in this study was chosen such that the ratios between the duration of inhalation and exhalation were 1/2, 1/4, and 1/8 for airflow rates of 30, 60, and 90 l min −1 , respectively [25].…”

A Liquid Ventilator Prototype for Total Liquid Ventilation Preclinical Studies

“…A decrease in the oxygen flow rate through the oxygenator is not a suitable solution, since they it compromises the PaCO 2 , before any effect on PaO 2 reduction. The choice of a bubble oxygenator could be seen as a limitation, since most research groups use membrane oxygenators with TLV (Corno et al 2003;Cox et al 2003;Hirschl et al, 1995;Larrabe et al, 2001;Parker et al, 2009;Pohlmann et al, 2011;Tredici et al, 2004). On the contrary, we strongly believe that bubble oxygenators are quite suitable for TLV.…”

“…However, all measurable volume errors do not include sensor non-linearities, machining tolerances and analog input precisions, so the lung volume can derive positively or negatively, if and only if such volume derivatives have no impact on the alveolar pressure. In the normal case, the control of the end-expiratory alveolar-pressure is equivalent to the control of the end-expiratory lung volume (EELV) because there is a direct relationship between these two variables (Degraeuwe et al, 2000b;Parker et al, 2009). …”

“…However, the insertion of a pressure sensor in the mouth can be problematic in a clinical context, thus the main issue is to adapt this pressure controlled mode without a pressure sensor in the trachea. Many efficient demonstrations of TLV have been performed with different prototypes (Corno et al 2003;Cox et al 2003;Degraeuwe et al, 2000a;Hirschl et al, 1995;Larrabe et al, 2001;Meinhardt et al, 2000;Parker et al, 2009;Pohlmann et al, 2011;Sekins et al, 1999;Tredici et al, 2004). With O 2 saturated PFC and limited to low minute ventilations (comparatively to CMV), they obtained acceptable ventilation.…”