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Biomedical subjects

E N Bruce

Publications and source records attributed to E N Bruce.

60 records · Page 4Linked to original sources
PubMed1981

Pattern of diaphragmatic activity during forced expiratory vital capacity.

We measured transdiaphragmatic pressure (Pdi) during forced expiratory vital capacity (FVC) maneuvers in 13 normal subjects and electromyographic activity of the diaphragm (edi) in 8 of these subjects. In all subjects, Pdi increased at the initiation of the FVC. In most, this increase lasted 30--50 ms and reached levels well above the Pdi observed at total lung capacity (TLC). After the initial transient increase, approximately half of the subjects demonstrated a substantial fall in Pdi to values near the relaxation level in the mid-vital capacity (VC) volume range, while half showed a second large increase in Pdi in this volume range. Seven of eight subjects tested showed a rapid decrease in Edi at the onset of the FVC, reaching a minimum in 30--50 ms. After this initial transient decrease, Edi increased in six subjects in the mid-VC volume range, in association with secondary rises in Pdi. In two subjects, Edi remained low throughout the remainder of the FVC, and Pdi in the mid VC range was generally lower. These results are consistent with the conclusion that the diaphragm is neither electromyographically silent nor mechanically unimportant during the FVC. Changes in abdominothoracic configuration, superimposed upon "antagonistic" activity of the diaphragm, result in substantial reductions in pleural (esophageal) pressure that may influence regional lung emptying during the FVC.

Abdominal Muscles↗
PubMed1980

Intercostal muscle reflexes and sleep breathing patterns in the human infant.

Breathing variability and apnea characteristic of rapid eye movement (REM) sleep was investigated in a newborn infant with complete interruption of intercostal to phrenic neural pathways due to intrapartem transection of the cervical spinal cord. Breath-to-breath variability in inspiratory duration (TI), breath duration (Ttot), tidal volume (VT), and ventilation (VI) was significantly greater in REM than in quiet sleep and was similar to the variability in these parameters seen in normal infants. In addition, brief periods of diaphragmeatic apnea were observed during REM sleep. The phenomenon of shortened TI during airway occlusion previously attributed to intercostal-to-phrenic reflexes was examined in the quadriplegic infant and in seven healthy term infants. The frequency of this response was increased when airway occlusion was delayed until after onset of inspiration. Shortening of TI by occlusion occurred no less frequently in the quadriplegic than in the control infants. The constant paradoxical inward movement of the rib cage during inspiration observed in the quadriplegic infant suggests that supraspinal innervation of intercostal muscle limits such paradoxical movements in the normal infant. The quadriplegic infant's end-expiratory volume was consistently above his passive functional residual capacity, as inferred from respiratory volume and pressure measurements.

Birth Injuries↗
PubMed1980

Smoothing of MEFV curves by digital filtering of flow as a function of volume.

Noise in flow records limits the degree to which one can characterize local features of maximum expiratory flow-volume (MEFV) curves, i.e., the volume dependence of flow over small volume intervals such as 5-10% of the vital capacity. Such noise includes instrument noise, cardiogenic pulsations, and rapid flow oscillations due to audible turbulence. Noise removal by analog filtering of the flow vs. time signal often is unacceptable because the initial rapid onset of flow can be severely distorted. A digital technique for directly filtering the flow vs. volume record that does not distort the initial rapid flow transient has been developed. Flow values are determined at 256 volume points equally spaced over the vital capacity. This sequence of flow values is passed through a linear phase, finite impulse response, Hamming window filter. The output sequence of filtered flow values, plotted against the corresponding volumes, quantitatively retains the local shape features of the MEFV curve without the noise.

Computers↗
PubMed1977

A digital computer technique for analyzing respiratory muscle EMG's.

A method is described for extracting from the electromyograms of respiratory muscles a continuous signal which has primarily the periodicity of respiratory pressure and flow wave forms. The EMG is first band-pass-filtered from 50 to 500 Hz, then digitized, full-wave rectified, passed through a nonlinear voltage window to reduce noise (particularly ECG) artifacts, then low-pass filtered with a digital continuous, or moving, averager. An average wave form corresponding to one respiratory cycle is produced by ensemble averaging of the wave forms from several consecutive breaths. Diaphragmatic electromyograms from a human and from a rabbit are processed in this manner, and the effect on the processed wave forms of changes in inspired CO2 and of a change in end-expiratory lung volume are demonstrated.

Animals↗