A Functional and Morphologic Analysis of Pressure-Controlled Inverse Ratio Ventilation in Oleic Acid-Induced Lung Injury: Discussion

However, there were no statistically significant differences between the former two modes, not in static end-inspiration, static end-expiration, or during dynamic conditions (Fig 3).
PaC>2 and venous admixture correlated well to the magnitude of poorly and nonaerated regions (r=—0.87, pCO.OOl, and r=0.88, pCO.OOl) and also to expiratory (r=—0.84, pCO.OOl, and r=0.88, pCO.OOl), inspiratory (r=—0.86, pCO.OOl, and r=0.91, pCO.OOl), and dynamic mean lung density (r=—0.86, pCO.OOl, and r=0.87, pCO.OOl).
FRC correlated closely to expiratory lung density (r=—0.80, pCO.OOl) and also to the difference between expiratory and inspiratory density (r=0.79, pCO.OOl).
There was a greater difference between expiratory and inspiratory lung density in VCV ZEEP than in VCV PEEP and PCIRV (pC0.05). No difference was found between the latter two modes.
The major finding of this study was that PCIRV was no better than VCV with similar PEEP levels in alveolar recruitment and aeration of the lung tissues or in oxygenating the blood. However, CO was lower with PCIRV than with VCV PEEP, thus causing lower oxygen delivery to peripheral tissue, a well-known finding in earlier studies. These findings are discussed in the following paragraphs, after a comment on the oleic acid lung injury model further purchase antibiotics online. Administration of oleic acid causes an increase in the pulmonary vascular permeability leading to hemorrhagic pulmonary edema. The gross appearance of the lungs and the change in ventilation/perfusion ratios resemble that seen in ARDS and post-traumatic respiratory failure. The model has been shown to be stable over time and was judged to be suitable for the purpose of these experiments. It should be noted that even during a slow infusion of oleic acid, there is marked circulatory instability with dramatic falls in blood pressure and various arrhythmias. In this experimental series, two pigs died during infusion of oleic acid, leaving ten animals in the study.


Figure 3. Regional lung density values in the right lung during static expiration (E), static inspiration (I), and during a full dynamic ventilatory cycle (ventilation frequency 15, scan time 4 ss) (D). Density values expressed as Hounsfield units. VCV ZEEP=volume-controlled zero PEEP ventilation; VCV PEEP=volume-controlled PEEP ventilation; PCIRV=pressure-controlled inverse ratio ventilation.

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