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Biomedical subjects

S F Austin

Publications and source records attributed to S F Austin.

6 recordsLinked to original sources
PubMed1997

The effect of subglottal resonance upon vocal fold vibration.

An experiment with excised larynges was undertaken to investigate the interaction between acoustic pressures in a pseudotrachea and the amplitude of vibration of the vocal folds. Pressure was measured beneath the vocal folds at three specific moments of the vibratory cycle: (a) when the superior margin of the vocal folds began to separate, (b) when the vocal folds were maximally apart, and (c) when the inferior margin of the vocal folds began to touch. Results indicate that in half the larynges investigated, the maximum amplitude of vibration increased as a function of: (a) increased positive pressure at the moment of opening, and (b) reduced subglottal pressure when the vocal folds were maximally apart. The implications of these experiments regarding involuntary register transitions related to trachea resonance are discussed in light of a previously proposed register theory.

Acoustics↗
PubMed1997

Movement of the velum during speech and singing in classically trained singers.

The present study addresses two questions: (a) Is the action and/or posture of the velopharyngeal valve conducive to allow significant resonance during Western tradition classical singing? (b) How do the actions of the velopharyngeal valve observed in this style of singing compare with normal speech? A photodetector system was used to observe the area function of the velopharyngeal port during speech and classical style singing. Identical speech samples were produced by each subject in a normal speaking voice and then in the low, medium, and high singing ranges. Results indicate that in these four singers the velopharyngeal port was closed significantly longer in singing than in speaking samples. The amount of time the velopharyngeal port was opened was greatest in speech and diminished as the singer ascended in pitch. In the high voice condition, little or no opening of the velopharyngeal port was measured.

Humans↗
PubMed1985

Use of sufficient hemodilution to prevent coagulopathies following surgical correction of cyanotic heart disease.

During surgical correction of cyanotic heart disease with associated polycythemia, sufficient reduction of hemoglobin and hematocrit values has proved effective in preventing postoperative coagulopathies. Three groups of surgical patients were studied: Group I--a control group consisting of 75 adults undergoing uncomplicated correction of acquired heart disease and requiring no blood or blood component transfusion; Group II--15 patients with tetralogy of Fallot whose intraoperative hemoglobin values remained above 10 gm/dl with conventional hemodilution techniques; and Group III--21 cyanotic surgical patients whose intraoperative hemoglobin values were lowered to less than 10 gm/dl with sufficient hemodilution. Group III was further broken down into a subgroup of six patients (Group IIIa) who underwent sequential laboratory determinations, as in Group I. In Group IIIa, postoperative coagulation function tests were only slightly more abnormal than in the nonpolycythemic control group (Group I). Patients in Group III (who had ample hemodilution) experienced 45% less bleeding and required 54% fewer blood components than those in Group II (who underwent conventional hemodilution).

Adolescent↗
PubMed1981

Alteration of coagulation and selected clinical chemistry parameters in patients undergoing open heart surgery without transfusions.

Alteration of coagulation status and certain clinical chemistry laboratory determinations of 75 adult patients undergoing cardiopulmonary bypass procedures for acquired heart disease was studied during and after surgery. None of the patients was given transfusions of blood or blood components. With hemodilution, the mean hematocrit value dropped from 38% to 28% during the procedure. Fibrin degradation products and euglobulin lysis time were transiently abnormal. Factor V diminished somewhat during the procedure, whereas factors VIII and IX increased after surgery. Clottable fibrinogen values decreased slightly, but increased to an abnormally high value at 24 and 48 hours. Mean value of platelet counts decreased from 194,000 to 144,000/microliter immediately after surgery. Knowledge of expected deviation of coagulation factors and certain clinical chemistry tests following open heart surgery is helpful in evaluating the status of the postoperative patient.

Blood Coagulation↗
PubMedDate not supplied

Stability of factors V and VIII in thawed fresh frozen plasma units.

Factors V and VIII, commonly regarded as unstable in unfrozen plasma, were assayed at various intervals up to 24 hours using plasma from 20 thawed fresh frozen plasma (FFP) units. Comparisons were made between units stored at 4 and 25 C. The mean factor V value did not significantly change during the postthaw test period. Mean factor VIII activity prior to freezing was 121 per cent, dropped to 89 per cent four hours after thawing, and gradually decreased to 67 per cent at 24 hours. There was no difference between those units stored at 4 C and those stored at 25 C after thawing; therefore, refrigeration does not appear necessary for factor V or VIII stability up to 24 hours after thawing.

Adolescent↗