[Respiratory mechanics in professional flautists]. / Mécanique respiratoire des flûtistes professionnels.

Oesophageal, gastric, mouth, transdiaphragmatic, transpulmonary pressures, diaphragmatic EMG, sound and chest wall excursion were measured directly in 3 professional flautists whilst playing their instruments to determine: - what respiratory muscles and percent vital capacity were being used; - how mouth pressure, embouchure resistance, embouchure aperture, airflow and velocity affect sound loudness and frequency. Lung volume was estimated from transpulmonary pressure during playing and the static deflation pressure-volume curve was measured separately; flow was calculated from delta volume/delta time; embouchure resistance was calculated from mouth pressure/flow; velocity was calculated using Bernouilli's equation and mouth pressure. Staccati and sustained tones at different frequency and intensity were performed. Sound loudness was mainly related to airflow whilst sound frequency was determined by velocity. Flow and velocity were independently controlled by mouth pressure and embouchure aperture. Mean mouth pressures varied little from individual to an other (6-11 cm H(2)O) but the flautists used between 72-83% of their vital capacity suggesting inspiratory muscle activity while playing. However, rib cage and abdominal motion were different for each subject. Although different flautists use different strategies to control mouth pressure, their individual mastery of the instrument permits control of airflow and velocity to produce the desired intensity and frequency of sound.

Respiratory parameters during professional flute playing.

We studied three professional flautists while playing to determine: (1) what respiratory muscles and percent vital capacity (%VC) were used; (2) how mouth pressure (Pm), embouchure resistance (Rem), embouchure aperture (Aem), flow (V) and velocity (Vel) affect sound loudness (I) and frequency (F). We measured Pm, esophageal, gastric, transdiaphragmatic, transpulmonary (PL) pressures, diaphragmatic EMG, sound and chest wall displacements directly. Lung volume (VL) was estimated from PL during playing and the static deflation PL-VL curve measured separately; V from Delta VL/Delta t; Rem from Pm/(Delta VL/Delta t). Staccati and sustained notes at different F and I were performed. I increased mainly with V and F with Vel. V and Vel are independently controlled by Pm and Aem. The variation of mean Pm was small (6-11 cm H(2)O) and large for VC (72-83%) suggesting braking inspiratory muscle activity while playing. However, rib cage (RC) and abdominal (Ab) motion were different for each subject. One displaced Ab>RC at high VL and RC>Ab at low VL, another the opposite pattern; the third was in between. We conclude that while different flautists use different strategies to control Pm, the results are similar. Independent control of V and Vel by Pm and Aem allow flautists to control I and F regardless of how Pm is generated.

Optimum centrifugation conditions for the preparation of platelet and plasma products.

Units of whole blood were centrifuged for various periods of times and at various speeds to prepare platelet-rich plasma. It was found that several sets of centrifugation conditions resulted in an optimum yield of platelets and plasma. This optimum was approximately 8.3 x 10(10) platelets in 245 ml of plasma. When platelet-rich plasma was centrifuged, a maximum of approximately 95 per cent of the platelets could be recovered in the concentrate. Although this maximum was also achieved by several sets of centrifugation conditions, the most efficient method was 3,800 RPM (3731 x g) for four minutes at speed.