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Biomedical subjects

B Buchler

Publications and source records attributed to B Buchler.

5 recordsLinked to original sources
PubMed2002

Surpassing the standard quantum limit for optical imaging using nonclassical multimode light.

Using continuous wave superposition of spatial modes, we demonstrate experimentally displacement measurement of a light beam below the standard quantum limit. Multimode squeezed light is obtained by mixing a vacuum squeezed beam and a coherent beam that are spatially orthogonal. Although the resultant beam is not squeezed, it is shown to have strong internal spatial correlations. We show that the position of such a light beam can be measured using a split detector with an increased precision compared to a classical beam. This method can be used to improve the sensitivity of small displacement measurements.

Journal Article↗
PubMed1986

Phrenic afferents and their role in inspiratory control.

In anesthetized cats, with vagi cut and the spinal cord severed at the C8 level, phrenic motor and/or sensory discharge was recorded. Small afferent phrenic fibers were identified through their activation by lactic acid, hyperosmotic NaCl solution, or phenyl diguanide. They exhibited a spontaneous but irregular low-frequency discharge. Block of their conduction by procaine had no effect on eupneic motor phrenic activity. Large afferent phrenic fibers showed a spontaneous rhythmic discharge, and cold block (6 degrees C) of these fibers significantly prolonged the phrenic discharge time (Tphr) and total breath duration (TT) during eupnea. The stimulation of all afferent phrenic fibers lowered the impulse frequency of phrenic motoneurons (f impulses) and shortened both Tphr and TT. When the stimulation was performed during cold block all of the effects on phrenic output persisted, but changes in timing were less pronounced. Under procaine block, only the effects of phrenic nerve stimulation on Tphr persisted. These results suggest that both large and small afferent phrenic fibers control the inspiratory activity with a prominent role of small fibers on phrenic motoneuron impulse frequency.

Afferent Pathways↗
PubMed1985

Effects of contraction frequency and duty cycle on diaphragmatic blood flow.

The effects of diaphragmatic contraction frequency (no. of intermittent tetanic contractions/min) at a given tension-time index and of duty cycle (contraction time/total cycle time) on diaphragmatic blood flow were measured in anesthetized mongrel dogs during bilateral supramaximal phrenic nerve stimulation. Diaphragmatic blood flow was measured by the radionuclide-labeled microsphere method. Contraction frequency was varied between 10 and 160/min at duty cycles of 0.25 and 0.75. Diaphragmatic blood flow increased with contraction frequency from 1.47 +/- 0.13 ml X min-1 X g-1 (mean +/- SE) at an average of 18/min to 2.65 +/- 0.16 ml X min-1 X g-1 at 74/min (P less than 0.01) with a duty cycle of 0.25 and from 1.32 +/- 0.19 ml X min-1 X g-1 at an average of 15/min to 1.96 +/- 0.15 ml X min-1 X g-1 at 80/min (P less than 0.02) with a duty cycle of 0.75. At higher contraction frequencies diaphragmatic blood flow did not increase further at both duty cycles. In addition, diaphragmatic blood flow was higher with a duty cycle of 0.25 than 0.75 at all contraction frequencies. We conclude that frequency of contraction is a major determinant of diaphragmatic blood flow and that high duty cycle impedes diaphragmatic blood flow.

Abdomen↗
PubMed1985

Effects of pleural pressure and abdominal pressure on diaphragmatic blood flow.

The aim of this experiment was to determine if blood flow to the diaphragm is affected by generating the transdiaphragmatic pressure mainly with positive abdominal pressure or mainly with negative pleural pressure, during both sustained and intermittent diaphragmatic contractions. Diaphragmatic blood flow was measured in anesthetized mongrel dogs by the radionuclide-labeled microsphere method. Sustained and intermittent tetanic diaphragmatic contractions were produced with 1) free abdomen and closed chest (high negative pleural pressure) and 2) bound abdomen and open chest (high positive abdominal pressure). During sustained contractions, diaphragmatic blood flow at maximum levels of activation was significantly higher with negative pleural pressure (P less than 0.05). In contrast with this, intermittent diaphragmatic contractions did not yield a significant difference between diaphragmatic blood flow with negative pleural pressure and with positive abdominal pressure at maximal levels of transdiaphragmatic pressure. During both sustained and intermittent contractions, blood pressure, as measured from the carotid artery, did not vary significantly between negative pleural pressure and positive abdominal pressure. We conclude that during sustained tetanic diaphragmatic contractions, diaphragmatic blood flow is obstructed by high positive abdominal pressures, but during intermittent diaphragmatic contractions, high positive abdominal pressures do not affect total blood flow, since any inhibition of blood flow during the contractile period can be compensated for during the relaxation period between contractions.

Abdomen↗