High-frequency oscillation and tracheal gas insufflation in patients with severe acute respiratory distress syndrome and traumatic brain injury: an interventional physiological study

INTRODUCTION: In acute respiratory distress syndrome (ARDS), combined high-frequency oscillation (HFO) and tracheal gas insufflation (TGI) improves gas exchange compared with conventional mechanical ventilation (CMV). We evaluated the effect of HFO-TGI on PaO(2)/fractional inspired O(2 )(FiO(2)) and PaCO(2), systemic hemodynamics, intracranial pressure (ICP), and cerebral perfusion pressure (CPP) in patients with traumatic brain injury (TBI) and concurrent severe ARDS. METHODS: We studied 13 TBI/ARDS patients requiring anesthesia, hyperosmolar therapy, and ventilation with moderate-to-high CMV-tidal volumes for ICP control. Patients had PaO(2)/FiO(2 )<100 mm Hg at end-expiratory pressure ≥10 cm H(2)O. Patients received consecutive, daily, 12-hour rescue sessions of HFO-TGI interspersed with 12-hour periods of CMV. HFO-TGI was discontinued when the post-HFO-TGI PaO(2)/FiO(2 )exceeded 100 mm Hg for >12 hours. Arterial/central-venous blood gases, hemodynamics, and ICP were recorded before, during (every 4 hours), and after HFO-TGI, and were analyzed by using repeated measures analysis of variance. Respiratory mechanics were assessed before and after HFO-TGI. RESULTS: Each patient received three to four HFO-TGI sessions (total sessions, n = 43). Pre-HFO-TGI PaO(2)/FiO(2 )(mean ± standard deviation (SD): 83.2 ± 15.5 mm Hg) increased on average by approximately 130% to163% during HFO-TGI (P < 0.01) and remained improved by approximately 73% after HFO-TGI (P < 0.01). Pre-HFO-TGI CMV plateau pressure (30.4 ± 4.5 cm H(2)O) and respiratory compliance (37.8 ± 9.2 ml/cm H(2)O), respectively, improved on average by approximately 7.5% and 20% after HFO-TGI (P < 0.01 for both). During HFO-TGI, systemic hemodynamics remained unchanged. Transient improvements were observed after 4 hours of HFO-TGI versus pre-HFO-TGI CMV in PaCO(2 )(37.7 ± 9.9 versus 41.2 ± 10.8 mm Hg; P < 0.01), ICP (17.2 ± 5.4 versus 19.7 ± 5.9 mm Hg; P < 0.05), and CPP (77.2 ± 14.6 versus 71.9 ± 14.8 mm Hg; P < 0.05). CONCLUSIONS: In TBI/ARDS patients, HFO-TGI may improve oxygenation and respiratory mechanics, without adversely affecting PaCO(2), hemodynamics, or ICP. These findings support the use of HFO-TGI as a rescue ventilatory strategy in patients with severe TBI and imminent oxygenation failure due to severe ARDS.