Chest
laboratory and animal investigationsThe Physiologic Effects of Inverse Ratio Ventilation
Section snippets
Experimental Preparation
Nine male, mongrel dogs were anesthetized with pentobarbital (10 mg/kg bolus and 10 mg/kg continuous infusion) after induction with the ultrashort-acting barbiturate thiopental (15 mg/kg). The animals were intubated with an 8.0-mm cuffed endotracheal tube, ventilated with 18 ml/kg tidal volume, and a fraction of inspired oxygen of 1.0 with a ventilator (Bear 2; Cambridge, MA). The rate was adjusted to maintain a normal PaCO2. The animals were then instrumented. Instrumentation included
RESULTS
The oleic acid induced significant lung injury, with wet lung weights of 43.6±5.5 g/kg and dry lung weights of 3.4±0.8 g/kg in the nine experimental dogs (average weight, 22.4±5.5 kg).
DISCUSSION
When mean airway pressure was increased with inverse ratio with extrinsic PEEP, there was a reduction in and VD/VT compared with conventional ventilation with full recruitment levels of extrinsic PEEP. When mean airway pressure was increased still further with inverse ratio with intrinsic PEEP, there was an increase in relative to inverse ratio with extrinsic PEEP. These results suggest that all methods of increasing mean airway pressure are not equivalent. In
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Cited by (22)
Effects of a 1:1 inspiratory to expiratory ratio on respiratory mechanics and oxygenation during one-lung ventilation in patients with low diffusion capacity of lung for carbon monoxide: A crossover study
2015, Journal of Clinical AnesthesiaCitation Excerpt :A single previous study suggests that applying a 1:1 I:E ratio increases arterial oxygenation [3]. The basis of this practice is that longer inspiratory times increase the gas flow to the alveoli of slow time constants, thereby improving oxygenation [4]. However, our previous study, which applied volume-controlled ventilation (VCV) with a 1:1 I:E ratio during OLV, showed no improvement in oxygenation when compared with the conventional 1:2 I:E ventilation ratio [5].
Inverse Ratio Ventilation
2008, Mechanical Ventilation: Clinical Applications and PathophysiologyThe effects of airway pressure and inspiratory time on bacterial translocation
2007, Anesthesia and AnalgesiaCitation Excerpt :In spite of the bacterial challenge, increasing I:E ratio protected oxygenation. Although the exact mechanism of IRV on oxygenation has not been clearly delineated, increasing MawP and iPEEP values were most likely responsible for improving gas exchange (11). We did not find any iPEEP in the prolonged inspiratory time groups.
Manuscript received September 5, 1997; revision accepted February 4, 1998.