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Biomedical subjects

M C Brown

Publications and source records attributed to M C Brown.

261 records · Page 15Linked to original sources
PubMedDate not supplied

The effect of cervical sympathectomy on cochlear electrophysiology.

The purpose of this study was to examine the electrophysiologic responses to sound from guinea pig cochleas, 3--6 days after a unilateral cervical sympathectomy. After recovery from surgery the guinea pigs developed a Horner's syndrome on the sympathectomized side. Some days later their bullas were opened and electrodes were placed bilaterally on the round windows. Most of the sympathectomized cochleas showed signs of decreased sensitivity to sound. They had a smaller dynamic range for the click- and tone-burst evoked compound action potential (CAP) compared with the non-sympathectomized cochleas. The threshold sound levels for the CAPs and the sound levels to produce 1 muV of cochlear microphonic potentials were unaffected. In other animals with chronic implanted electrodes, the same electrical responses were measured with only light sedation before and after sympathectomy and showed the same results. In additional animals the crossed olivocochlear bundle (COCB) was electrically stimulated and a similar inhibition of the CAP was registered on both the intact and the sympathectomized side. The results suggest that the sympathetic nerves to the cochlea, coming from the ipsilateral cervical ganglion and ending near the habenula perforata, may be important for the sound perception as they influence the CAP.

Action Potentials↗
PubMedDate not supplied

Test procedures for continuous-flow anaesthetic apparatus.

Equipment management arrangements in hospitals, including safety and function testing, relating to continuous-flow anaesthetic apparatus have been found wanting following examination of a number of recent incidents. A problem exists with the complexity of the tests required and the number of necessary test instruments. In this article the required tests are examined, and a specially designed test set to make fuller testing a practical proposition for hospital staff and for manufacturers' service technicians is described.

Anesthesia, Inhalation↗
PubMedDate not supplied

The effectiveness of hourly cuff deflation in minimizing tracheal damage.

The efficacy of hourly endotracheal tube cuff deflations in minimizing tracheal damage has not been clearly established. Two investigations which specifically address this question arrive at differing conclusions. These investigations fail to report important variables which may have explained the difference in their results. The present study examined the effects of hourly cuff deflations in minimizing tracheal damage in mechanically ventilated, anesthetized dogs over a 72 hour test period. Variables which may influence tracheal damage were measured and reported. Three groups of dogs received either continuous cuff inflation, hourly 5 minute cuff deflations, or a continuous air leak. The air leak group had significanlty less damage than the continuous inflation group (P less than 0.05) and the hourly deflation group (P less than 0.01). There was no significant difference between the continuous inflation group and the 5 minute hourly deflation group.

Animals↗
PubMedDate not supplied

Magnetic detection to position human nasogastric tubes.

Placement of nasogastric tubes is one of the most commonly performed diagnostic and therapeutic medical procedures. Proper placement of the tube in the digestive tract below the diaphragm is crucial for efficacy and safety. This study evaluates a magnet detection system that allows percutaneous non-radiographic localization of the nasogastric tube tip. Each volunteer subject had the magnet detector placed over the abdomen, and was then intubated with a magnet-tagged nasogastric tube. Eighty-eight nasogastric tube placements were performed in 22 volunteers. The detection system located the nasogastric tube tip below the diaphragm in all 88 placements. Location in all attempts was confirmed by fluoroscopy. This method of correctly locating the tip of nasogastric tubes may obviate the need for radiographic imaging in most cases.

Adult↗
PubMedDate not supplied

A method for measuring the mean pressure gradient across prosthetic heart valves under in vitro pulsatile flow conditions.

A method is described for measuring the mean pressure gradient that occurs across a prosthetic heart valve over the forward flow phase in a simulated cardiac pumping cycle. The procedure is to simultaneously gate both the pressure signal and a manually controlled reference voltage of opposite polarity. The gated pressure signal is used to charge up a capacitor, while at the same time the gated reference signal is used to remove charge from the capacitor. The reference voltage is equal to the mean value of the pressure gradient voltage when there is zero net voltage on the capacitor. The gating procedure is simple and straightforward. Sample results for the system, which has been used extensively to study valve performance in vitro, are given.

Aortic Valve↗
PubMedDate not supplied

Multisite mucous membrane bleeding due to a possible interaction between warfarin and 5-fluorouracil.

A 59-year-old man being treated for colon cancer experienced epistaxis, hematemesis, hematuria, and hematochezia. Laboratory evaluation revealed a greatly prolonged prothrombin time. It is possible that the bleeding was due to an interaction between 5-fluorouracil and warfarin. The former may inhibit the synthesis of cytochrome P-4502C9, leading to impaired metabolism of the latter.

Anticoagulants↗