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Objective To study the ways which ensure the delivery of enough tidal volume to patients under various conditions close to the demand of the physician. Methods The volume control ventilation model was chosen,and the simulation lung type was active servo lung ASL 5000 or Michigan lung 1601. The air resistance,air compliance and lung type in simulation lungs were set. The tidal volume was obtained from flow analyzer PF 300. At the same tidal volume,the displaying values of tidal volume of E5,Servo i,Evital 4,and Evital XL ventilators with different lung types of patient,compliance of gas piping,leakage,gas types,etc. were evaluated. Results With the same setting tidal volume of a same ventilator,the tidal volume delivered to patients was different with different lung types of patient,compliance of gas piping,leakage,gas types,etc. Reducing compliance and increasing resistance of the patient lungs caused high peak airway pressure,the tidal volume was lost in gas piping,and the tidal volume be delivered to the patient lungs was decreased. If the ventilator did not compensate to leakage,the tidal volume delivered to the patient lungs was decreased. When the setting gas type of ventilator did not coincide with that applying to the patient,the tidal volume be delivered to the patient lungs might be different with the setting tidal volume of ventilator. Conclusion To ensure the delivery of enough tidal volume to patients close to the demand of the physician, containable factors such as the compliance of gas piping,leakage,and gas types should be controlled.
RESUMO
BACKGROUND: Protein kinase C represents an important component of a signal transduction pathway that regulates vascular smooth muscle contraction. This study was performed with an inhibitor and activators of protein kinase C to determine their effects on hypoxic pulmonary vasoconstriction (HPV) in isolated rat lung model. METHODS: Isolated lungs from Sprague-Dawley rats were ventilated with a normoxic gas (21%O2-5%CO2-balanced N2) and a hypoxic gas (3%O2-5%CO2-balanced N2) alternatively, and then perfused with constant pulmonary blood flow. Baseline hypoxic pressor responses (delta PAP) were measured as the difference of pulmonary artery pressure between normoxic ventilation and hypoxic ventilation. After baseline delta PAP had obtained, rats were randomly divided into a chelerythrine group, an phorbol 12, 13-dibutyrate (PDBu) group, and a farnesylthiotriazole (FTT) group. The different concentrations of each drug were added into the perfusate sequentially. delta PAP in the different concentrations of each drug were calculated as a percentage of the delta PAP in each concentration of drug to the baseline delta PAP in the absence of drug (%delta PAP). RESULTS: The %delta PAP of chelerythrine were 83.7 +/- 19.2%, 71.5 +/- 24.1% and 68.4 +/- 28.3% at 0.1, 1, and 10micrometer, respectively (P < 0.05). The %delta PAP of PDBu were 111.3 +/- 10.1%, 144.4 +/- 37.8% and 168.4 +/- 89.1% at 20, 100, and 300 nM, respectively (P < 0.05). The %delta PAP of FTT were 80.1 +/- 25.1%, 61.0 +/- 17.2% and 30.1 +/- 18.4% at 1, 10, and 30micrometer, respectively (P < 0.05). CONCLUSIONS: The results of this study suggest that regulator of protein kinase C influence HPV.