[A comparative study between inflation and deflation pressure-volume curve in determining the optimal positive end-expiratory pressure].

OBJECTIVE: To determine the optimal positive end-expiratory pressure (PEEP) according to inflation and deflation pressure-volume curve (P-V curve) in patients with acute respiratory distress syndrome (ARDS). METHODS: ARDS models were reproduced in 20 dogs, and they were randomly divided into two groups. In both groups, Levenberg-Marquardt iterative algorithm was employed using software to explore parameters fitting with Boltzmann formula, by which the real inflection point of pressure (Pinf d) in deflation limb or lower inflection point pressure (PLip) in inflation limb on P-V curve were defined. For the control group (inflation curve) P-V curve of PLip + 2 cm H(2)O [1 cm H(2)O = 0.098 kPa] was applied as the best PEEP value. In the experimental group (deflation curve) the Pinf d was taken as the best PEEP value. The heart rate (HR), blood pressure (BP), fingertip pulse oxygen saturation [SpO(2)], static lung compliance (Cst), arterial partial pressure of oxygen [PaO(2)] and arterial partial pressure of carbon dioxide [PaCO(2)] were monitored at 0, 2, 6, 12, 24 and 48 hours. RESULTS: Oxygenation index increased significantly both in control and experimental groups. In experimental group, oxygenation index (mm Hg, 1 mm Hg = 0.133 kPa) of 12, 24 and 48 hours was respectively significantly higher than that of the control group (12 hours: 177.63 ± 8.94 vs. 165.60 ± 8.90, 24 hours: 194.19 ± 10.67 vs. 168.70 ± 10.60, 48 hours: 203.15 ± 13.21 vs. 171.26 ± 9.21, all P < 0.01). Cst [ml/cm H(2)O] at 2, 6, 12, 24 and 48 hours was respectively higher than that of the control group (2 hours: 41.00 ± 4.17 vs. 36.20 ± 3.90, 6 hours: 44.00 ± 4.65 vs. 36.88 ± 3.39, 12 hours: 46.92 ± 5.47 vs. 37.92 ± 3.10, 24 hours: 42.83 ± 8.97 vs. 37.92 ± 3.09, 48 hours: 42.64 ± 9.04 vs. 37.97 ± 2.98, P < 0.05 or P < 0.01). CONCLUSION: Determining optimal PEEP for ARDS with deflation P-V curve was better than that of inflation curve.

Extraction of phenol in wastewater with annular centrifugal contactors.

Solvent extraction is an effective way to treat and recover the phenolic compounds from the high content phenolic wastewater at present. The experimental study on treating the wastewater containing phenol has been carried out with QH-1extractant (the amine mixture) and annular centrifugal contactors. The distribution ratio of phenol was 108.6 for QH-1-phenol system. The mass-transfer process of phenol for the system was mainly controlled by diffusion. When the flow ratio (aqueous/organic) was changed from 1/1 to 4/1, the rotor speed was changed from 2500 to 4000 r/min, and the total flow of two phases was changed from 20 to 70 mL/min, the mass-transfer efficiency E of the single-stage centrifugal contactor was more than 95%. When the flow ratio was changed from 4.4/1 to 4.9/1, the rotor speed was 3000 r/min, and the total flow of two phases was changed from 43.0 to 47.0 mL/min, the extraction rate rho of the three-stage cascade was more than 99%. When 15% NaOH was used for stripping of phenol in QH-1, the stripping efficiency of the three-stage cascade was also more than 99% under the experimental conditions.