PubMed · 4024440
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E A Thomas. 1985-06-29. Maggot control.. https://doi.org/10.1136/vr.116.26.699-a
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We tested the hypothesis that intracranial pressures and cerebral perfusion pressure in the newborn are more seriously affected by increasing airway pressure during high-frequency oscillatory ventilation (HFOV) than during conventional mechanical ventilation (CMV). Mean airway pressure was acutely elevated in stepwise fashion to 25 cm H2O in six anesthetized, paralyzed newborn lambs. Pressure (mean +/- SE) increased similarly during HFOV and CMV in the jugular vein (7 +/- 1 and 8 +/- 1 cm H2O, respectively), the sagittal sinus (6 +/- 1 and 7 +/- 1 cm H2O), and the cerebrospinal fluid of the lateral ventricle (4 +/- 1 and 6 +/- 1 cm H2O). Decreases in arterial blood pressure (-13 +/- 2 and -10 +/- 2 cm H2O) and cerebral perfusion pressure (-17 +/- 2 and -16 +/- 2 cm H2O) were also similar during HFOV and CMV. Intracranial pressure-volume curves were generated by incrementing cerebrospinal fluid volume in eight lambs. Curves generated during HFOV and CMV were similar, reflecting a similar intracranial compliance during the two ventilatory modes. These data indicate that intracranial compliance and the effects of increasing airway pressure upon intracranial pressures are not significantly different between HFOV and CMV.
Measurement of airway pressure is essential in the study of respiratory mechanics, and is usually done via a lateral tap in the conduit (e.g., endotracheal tube, cannula, or mouthpiece) leading into the subject's airway. Such pressure measurements, however, may be severely affected by the Bernoulli effect if the diameter of the conduit is small and the gas flow through it sufficiently high. We present in this note a simple method of assessing whether or not the Bernoulli effect is important in any particular situation. The technique involves comparing the pressure-flow relationships of the conduit obtained both by blowing air through it from one end and sucking air in the reverse direction by applying negative pressure at the same end. If the resistance of the conduit is the same for gas flow in both directions, then half the magnitude of the difference between the two pressure-flow relationships gives the magnitude of the Bernoulli effect pressure. We give results of an experimental situation in which this was the case. We also show that those conditions under which the Bernoulli effect is likely to be a problem are also those under which the velocity profile is likely to be approximately flat, thereby permitting the magnitude of the Bernoulli effect to be easily calculated.
We demonstrate the application of particle delivery to the transformation of mammalian somatic cells. Two mouse T-lymphocyte cell lines and Chinese hamster ovary (CHO) cells were transformed transiently with the RSV-ADH (alcohol dehydrogenase) gene. Stable gene transfer was also demonstrated in CHO cells at a frequency of 6 x 10(-4) and in T-cells at a frequency of 1 x 10(-4), using beta-Gal/neomycin-resistance gene constructs. The helium gas acceleration mechanism (PDS 1000/He) and particle delivery method allowed better velocity control and particle dispersion than the gunpowder driven instrument. These improvements have increased cell viability, transformation efficiency, and cellular targets.