Fig. 5
Optimizing recruitment with TCAV allows the lung to accommodate increased tidal volumes, without increases in driving pressure, due to a concomitant increase in compliance. a TCAV-induced lung recruitment over time (0–24 h) in a brain-dead organ donor. Driving pressure (ΔP) was calculated as tidal volume (Vt) divided by respiratory system compliance (CRS). The adaptive nature of TCAV delivers low Vt (7.3 ml/kg at 0 h) with lung collapse and low CRS, but adjusts Vt over time (Vt = 9.2 ml/kg at 12 h, Vt = 10.1 ml/kg at 24 h) as the lung opens and CRS increases. Notably, ΔP actually decreased despite increasing Vt (a). b Evolution of driving pressure (ΔP) and chest X-ray (CXR) over time: a CMV (conventional mechanical ventilation) on a brain-dead organ donor (55 kg) with baseline ventilator settings: VC-AC, Vt 420, rate 24, PEEP 8 cmH2O with Peak pressure 34 cmH2O, Vt 7.9 mL/kg/predicted body weight (PBW), and ΔP 26 ml/cmH2O. Chest X-ray showed severe bilateral infiltrates. TCAV = 3 h: 3 h after transition to TCAV with settings: CPAP phase pressure = 34 cmH2O, release set pressure = 0 cmH2O, CPAP time = 3.4 s, release phase duration = 0.35 s. Note the lower Vt of 347 ml (6.3 ml/kg/PBW), which gradually increased from a Vt of 5.4 ml/kg/PBW when first transitioned to TCAV (data not shown); both Vts using the TCAV protocol are lower than those on the conventional mode (CMV = 437 ml, 7.9 ml/kg/PBW). The CXR demonstrates radiographic clearing of densities with significant recruitment and a reduction in ΔP from 26 to 17 ml/cmH2O. TCAV = 29 h: 29 h on TCAV, a new chest radiograph for line placement indicated continued recruitment, and the CPAP phase pressure was subsequently decreased to 29 cmH2O. In addition, the angle of the expiratory flow curve became less acute (Fig. 6), and the release phase duration was increased to 0.4 s. The CPAP time was increased to 4.6 s because ventilation had improved. Despite a lower PHigh, the Vt continued to increase as did an improvement in CRS. The continued radiographic clearing of densities and reduction in ΔP fell to 14 ml/cmH2O despite continued Vt increase. TCAV = 84 h: The CPAP phase pressure was further decreased to 22cmH2O due to continued recruitment (CXR) with a ΔP of 11 ml/cmH2O. The lungs and the heart, liver, and both kidneys from this organ donor were all successfully transplanted