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Biomedical subjects

A B Otis

Publications and source records attributed to A B Otis.

14 recordsLinked to original sources
PubMed1985

Effective resistance of the respiratory system studied by a quick release technique.

A human subject with mouthpiece in place makes inspiratory or expiratory effort against a closed shutter which abruptly opens when a predetermined pressure (PO) is developed. Pressure at the mouth (Pao) and flow (V) are continuously recorded. When the shutter opens, Pao changes toward atmospheric - first abruptly and then gradually, while V rapidly rises to a peak value (Vpeak) and then gradually declines. In any series of trials PO is held constant, but resistance external to the subject (Rext) is changed with each trial. In different series PO is varied. In any series of trials at constant PO the relationship between Pao and V was linear. The slope (K) of the straight line fitted to the experimental points was interpreted as being equal in magnitude to the 'effective resistance' (Reff) of the respiratory system. Reff has two components - a true resistance (Rint) and a virtual one (Rfv) related to the force-velocity characteristic of the respiratory muscles. On the assumption that Rint is independent of PO but that Rfv varies linearly with it, Rint and Rfv can be evaluated.

Airway Resistance↗
PubMed1983

A perspective of respiratory mechanics.

Breathing was recognized very early to be a muscular action. The participation of the diaphragm, intercostals, and accessory muscles was appreciated by Galen. Consideration of a possible role for smooth muscle in breathing did not occur until much later. Even today smooth muscle is seldom included as a topic in discussions of "respiratory mechanics." Bronchial smooth muscle was first described in the classic study of Reisseisen in the early 19th century, although the presence of contractile elements in lungs had been demonstrated a few decades previously. An important comprehensive investigation of the action of bronchial smooth muscle was published in 1892 by Willem Einthoven. His experimental approach became a paradigm. On the other hand, his analysis of dynamic collapse of the airways received little attention and was independently arrived at half a century later. Although we now have a considerable understanding of the mechanics of bronchial smooth muscle and of the effects of numerous physiological and pharmacological agents on its behavior, the exact role it plays in normal physiological function is unclear. Numerous plausible suggestions have been made, but none has been convincingly demonstrated.

Asthma↗
PubMed1983

A Hall effect transducer for measuring length changes in mammalian diaphragm.

When a conductor through which a current is flowing is brought into a magnetic field, the isopotential lines are distorted (E. H. Hall, 1879). When a constant current is made to flow through a Hall generator, the measured voltage perpendicular to the current flow can be made to vary by altering the distance between a permanent magnet and a Hall generator. A length transducer useful for measuring length changes in the diaphragm of a dog is made by connecting a commercially available Hall generator to a Plexiglas plate (5 X 10 X 3 mm, 0.5 g), and suturing the plate to the surface of the muscle. A permanent magnet (20 X 10 X 4 mm, 1.5 g) is attached to the diaphragm at a distance of 2 or 3 cm along the expected direction of length change. Fine wires from the terminals of the Hall generator are connected to an external constant-current source and to solid-state circuitry which provides amplification, linearization, and temperature compensation of the output signal. Model experiments indicate that the length measurements may be accurate within 5% if the distance between the magnet and Hall generator is greater than 5 mm. With this type of transducer measurements of segmental length changes in the diaphragm of an anesthetized dog have been successfully recorded.

Animals↗
PubMed1977

Pressure-flow relationships and power output of breathing.

The pressure-flow relationship obtained by Agostoni and Fenn (1960) during maximal inspiratory efforts against various external resistances contains information from which inferences regarding the power output, and the internal impedance of the breathing system can be made. Similar inferences can be made from measurements obtained with submaximal but constant inspiratory efforts. An analysis is presented to reconcile the observed linear pressure-flow relationships with the usually observed hyperbolic force-velocity relationship of muscle.

Airway Resistance↗
PubMedDate not supplied

[Man's urge to model].

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Intercostal Muscles↗