Continuous tracheal gas insufflation during protective mechanical ventilation in juvenile piglets with acute lung injury induced by endotoxin

Low tidal volume mechanical ventilation is difficult to correct hypoxemia, and prolonged inhalation of pure oxygen can lead to oxygen poisoning. We suggest that continuous tracheal gas insufflation （TGI） during protective mechanical ventilation could improve cardiopulmonary function in acute lung injury. Totally 12 healthy juvenile piglets were anesthetized and mechanically ventilated at PEEP of 2 cmH2O with a peak inspiratory pressure of 10 cmH2O. The piglets were challenged with lipopolysaccharide and randomly assigned into two groups （n=6 each group）： mechanical ventilation （MV） alone and TGI with continuous airway flow 2 I/min. FIO2 was set at 0.4 to avoid oxygen toxicity and continuously monitored with an oxygen analyzer. Tidal volume, ventilation efficacy index and mean airway resistant pressure were significantly improved in the TGI group （P〈0.01 or P〈0.05）. At 4 hours post ALl, pH decreased to below 7.20 in the MV group, and improved in the TGI group （P〈0.01）. Similarly, PaCO2 was stable and was significantly lower in the TGI group than in the MV group （P〈0.01）. PaO2 and PaO2/FIO2 increased also in the TGI group （P〈0.05）. There was no significant difference in heart rate, respiratory rate, mean artery pressure, central venous pressure, dynamic lung compliance and mean resistance of airway between the two groups. Lung histological examination showed reduced inflammation, reduced intra- alveolar and interstitial patchy hemorrhage, and homogenously expanded lungs in the TGI group. Continuous TGI during MV can significantly improve gas exchange and ventilation efficacy and may provide a better treatment for acute lung injury.

Efficacy of continuous tracheal gas insufflation in spontaneously breathing canine with acute lung injury

Objective To investigate the effects of continuous tracheal gas insufflation (CTGI) combined with biphasic intermittent positive airway pressure (BIPAP) ventilation on dogs with spontaneous breathing. Methods Eight canine models with oleic acid induced lung injury and spontaneous breathing were ventilated in a random order by Evita 2 (Drager Inc., Germany) in modes of BIPAP (BIPAP group) and BIPAP with CTGI flow rate of 3, 6 and 9?L/min (T3, T6 and T9 groups), respectively. The setting parameters of BIPAP were fiction of inspired oxygen 60%, inspiratory to expiratory ratio 1∶1, respiratory rate 20 and positive end expiratory pressure 5?cm?H2O. Arterial and mixed venous blood gas, lung mechanics, systemic and pulmonary hemodynamics status were monitored at the same level of PaCO2 obtained by adjusting peak inspiratory pressure of BIPAP. Results Peak inspiratory pressure in the T6 group (14±4?cm?H2O) and in the T9 group (11±3?cm?H2O) were significantly lower than that of BIPAP (20±5?cm?H2O, P<0.01), but there was no significant difference among the T3, T6 and T9 groups or between the T3 and BIPAP groups. PaO2, mean artery blood pressure, mean pulmonary artery pressure, pulmonary artery wedge pressure, cardiac ouput, oxygen delivery and oxygen consumption all remained unchanged in four different conditions.Conclusions Using BIPAP combined with CTGI does not cause asynchrony between ventilator and spontaneous breathing, but significantly decreases airway pressure with no influence on hemodynamics and oxygenation. Therefore, BIPAP with CTGI may be a useful support technique, especially in cases where the airway pressure should be limited.

Effects of continuous tracheal gas insufflation during pressure limited ventilation on pulmonary surfactant in rabbits with acute lung injury

Background Pulmonary surfactant dysfunction may contribute to the development of ventilator induced lung injury （VILI）. Tracheal gas insuffiation （TGI） is a technique in which fresh gas is introduced into the trachea and augment ventilation by reducing the dead space of ventilatory system, reducing ventilatory pressures and tidal volume （VT） while maintaining constant partial arterial CO2 pressure （PaCO2）. We hypothesised that TGI limited peak inspiratory pressure （PIP） and VT and would minimize conventional mechanical ventilation （CMV） induced pulmonary surfactant dysfunction and thereby attenuate VILI in rabbits with acute lung injury （ALI）. Methods ALI was induced by intratracheal administration of lipopolysaccharide in anaesthetized, ventilated healthy adult rabbits randomly assigned to continuous TGI at 0.5 L/min （TGI group） or CMV group （n=8 for each group）, and subsequently ventilated with limited PIP and VT to maintain PaCO2 within 35 to 45 mmHg for 4 hours. Physiological dead space to VT ratio （VD/VT）, dynamic respiratory compliance （Cdyn） and partial arterial O2 pressure （PaO2） were monitored. After ventilation, lungs were analysed for total phospholipids （TPL）, total proteins （TP）, pulmonary surfactant small to large aggregates ratio （SA/LA） in bronchoalveolar lavage fluid （BALF） and for determination of alveolar volume density （Vv）, myeloperoxidase and interleukin （IL）-8. Results TGI resulted in significant （P〈0.05 or P〈0.01） decrease in PIP [（22.4±1.8） cmH20 vs （29.5±1.1） cmH2O], VT [（6.9±1.3） ml/kg vs （9.8±1.11） ml/kg], VD/VT [（32±5）% vs （46±2）%], TP [（109±22） mg/kg vs （187±25） mg/kg], SA/LA （2.5±0.4 vs 5.4±0.7）, myeloperoxidase [（6.2±0.5） U/g tissue vs （12.3±0.8） U/g tissue] and IL-8 [（987±106） ng/g tissue vs （24±3） mN/m] of BALF, and significant （P〈0.05） increase in Cdyn [（0.47±0.02） ml·cmH2O^-1·kg^-1 vs （0.31±0.02） ml·cmH2O^-1·kg^-1], PaO2 [（175±24） mmHg vs （135±26） mmHg], TPL/TP （52±8 vs 33±11） and Vv （0.65±0.05 vs 0.44±0.07） as compared with CMV. Conclusions In this animal model of ALI, TGI decreased ventilatory requirements （PIP, VT and VD/VT）, resulted in more favourable alveolar pulmonary surfactant composition and function and less severity of lung injury than CMV. TGI in combination with pressure limited ventilation may be a lung protective strategy for ALI.