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Biomedical subjects

E H Wood

Publications and source records attributed to E H Wood.

At least 19 recordsLinked to original sources
PubMed1992

Potential hazards of high anti-Gz suit protection.

Although balanced positive pressure breathing increases protection by G suits and reduces fatigue during sustained high Gz exposures, it does not prevent dependent pulmonary right-to-left shunts (arterial hypoxemia) and potentially dangerous distention of nondependent alveoli. An incident of acute incapacitating mediastinal emphysema in a healthy young man during a sustained exposure to 5.5 Gx documents this possibility. This, plus neurogenic bradycardia during sustained high Gz exposures without pressure breathing, suggests that testing of full counterpressure to neck level suits at sustained > 9 Gz exposures may be hazardous. Fully instrumented studies of animal surrogates with comparable thoracic dimensions are indicated.

Acceleration↗
PubMed1992

Prevention of +Gz-induced loss of consciousness.

Objective recordings of respiratory and cardiovascular parameters at heart and head levels on human centrifuges and in flight provided the physiologic insights which led to development, during and shortly after World War II, of very effective anti-G suits and simultaneous use of positive pressure respiratory straining maneuvers. The high sustained Gz capabilities of current and future fighter planes have forced recourse to these techniques with minimal awareness of their origins. Possible catastrophic limitations of very effective full coverage anti-G suits, including water immersion to the apex of the thorax, especially when used without positive pressure breathing, were also documented at that time.

Aerospace Medicine↗
PubMed1990

Partial supination versus Gz protection.

Visual and loss of consciousness endpoints during 2 G/s onset G forces sustained for 5 s in 14 and for 10 s in 27 untrained pilots indicated high tolerances when upright, and increases of greater than 3 G when supinated to 60 degrees. Protection against visual symptoms of only 1.1 G when tilted 60 degrees and especially none when experienced subjects were tilted 45 degrees from vertical were unexpected results in 1942. Subsequent findings by others of slight decreases in tolerance at 30 degrees are contrary to hydrostatic basis of G tolerance. Presumably factors other than heart to brain distance (e.g., increased intracranial and intraocular pressures) affect G tolerance when subjects are supinated 30 degrees. We conclude that the apparent increased incidence of G-LOC since the incorporation of 30 degrees seat in F-16 and other fighters in mid-1970's supports the current relevance of these data and suggests that all aircrew should follow the lead of veteran test pilots who sit upright in preparation for and during high G maneuvers (10).

Adult↗
PubMed1990

Drug information skills for pharmacy students: curriculum integration.

For pharmacy students to provide optimal and complete pharmaceutical care, it is vital that they develop drug information skills. At the University of Southern California, the School of Pharmacy and the Norris Medical Library have established an interactive educational program. Library programs support an increasingly complex progression of information retrieval, evaluation, organization, application, and communication. Librarians are systematically involved in all four years of coursework for the doctor of pharmacy degree. Training and experience in computer literacy and online database searching are included in the library components. Description of the educational program covers its beginning a decade ago, current status, and future in an environment of rapidly advancing technology.

California↗
PubMed1990

Hydrostatic homeostatic effects during changing force environments.

The G tolerance of internal organs depends on how closely force environments in body cavities mimic an aqueous system. Hydrostatic gradients in peritoneal and pericardial cavities sustain venous return and uniform transmyocardial pressures so that normotensive arterial pressures at heart level persist during initial (about 7 s) sudden sustained exposures to Gz acceleration followed by a compensatory baroreceptor-mediated hypertension. Further, cerebrospinal fluid hydrostatics-mediated negative intracranial pressures sustain cerebral perfusion and cognition in spite of Gz-produced zero or near zero systolic pressures at head level. Differences in the approximately 0 and 1.0 specific gravities of intra-alveolar gases and surrounding blood and tissues, respectively, render lung anatomy and functions highly susceptible to the force environment. Hydrostatic gradients in dependent regions, simultaneously with small gradients in superior regions, appear to be nature's method for decreasing force environment-mediated regional ventilation and perfusion inequalities within the thorax.

Aerospace Medicine↗
PubMed1989

Human centrifuge non-invasive measurements of arterial pressure at eye level during Gz acceleration.

An apparatus for successful repetitive, indirect photokymographic recordings of systolic blood pressure (Ps) on a human centrifuge during World War II is described. Proportionately to 1 Gz hydrostatic heart-to-head Ps differences, eye level Ps decreased approximately 30 mm Hg per delta G, during 15 s Gz exposures of three relaxed volunteers, a finding confirmed subsequently by continuous intra-arterial pressures in 18 subjects. At 2 G.s-1 onset rates, maximal decreases occurred within 7 s after 1.5 Gz followed by compensatory recoveries while acceleration was maintained. Contours of simultaneously recorded decreases in ear opacity (blood content) were closely similar. Anti-G suit protection against subjective visual symptoms was similar to objective decreases in ear blood content but significantly less than against decreases in Ps at eye level. This may be due to relatively higher intraocular pressures secondary to increased intra-abdominal, cerebrospinal fluid and venous pressure produced by inflation, particularly of the abdominal bladder of the suit.

Acceleration↗
PubMed1987

Development of anti-G suits and their limitations.

Initial anti-G suits were based on the belief that decreased venous return was the critical effect of increased weight of blood during acceleration. Cumbersome water filled, pneumatic gradient or pulsatile pressure suits resulted. Subsequent centrifuge studies implicated arterial pressure, rather than venous return, as the major determinant of G tolerance in the sitting position. Consequently, methods of increasing arterial pressure were developed. Findings that the hypertensive, associated anti-blackout and discomfort effects of suit inflation all increase with bladder system pressure up to arterial occlusive levels resulted in the simplified G-suit used in W.W.II to the present. Recent +Gz loss of consciousness crashes indicate current straining maneuvers plus this suit are inadequate. Furthermore, because of very high pressures to maintain cerebral circulation in the sitting position, very high G suit protection is hazardous. If piloting is essential for full use of super performance fighters, the prone position with counter-weighted head support plus omni-directional surveilance is the surest strategem to obtain this advantage.

Acceleration↗
PubMed1987

Some effects of the force environment on the heart, lungs and circulation.

The data obtained in a series of human and animal experiments carried out during the last 45 years in centrifuges, specially instrumented dive bombers, and during changes in body position are the major bases for this paper. The integrated and highly effective cardiovascular reflexes which allow awake, upright humans to regain and/or maintain vision and consciousness during sustained inertial force environments several times greater than at the surface of planet Earth are particularly impressive. Multiplication of vertical gradients in interserosal pericardial, pleural, abdominal and cerebrospinal fluid pressures and/or forces in proportion, and in the resultant vectorial direction of the force environment play a critical role in this capability both in aerospace flight and everyday life on planet Earth. The differences between the near zero specific gravity of intra-alveolar gas and the (about) 1.05 value for the encompassing blood and tissue, render lung function highly susceptible to the weight determinant force environment. Creation of a womb-like environment by liquid whole-body immersion plus assisted breathing of a respirable liquid, both with specific gravities closely similar to bodily tissues, is a seemingly impractical but technologically and biologically documented expedient for allowing air breathers to endure very high sustained force and pressure environments.

Aerospace Medicine↗
PubMed1986

Contributions of aeromedical research to flight and biomedical science.

Pilot and plane capabilities to withstand high-Gz combat maneuvers are tactically important. Sustained 10-15 Gz capabilities of current and future planes outstrip safe physiologic limits in spite of the combined use of World War II-vintage straining maneuvers and relatively ineffective anti-G suits to prevent losses of vision and consciousness. However, the extreme arterial pressure increases needed to maintain cerebral blood flow (e.g. 400 mm Hg at heart level during exposures to 13.5 G when sitting upright) carry risks of anatomic damage to the circulatory system and rupture of air-containing, essentially unprotectable, lungs. These could be minimized, and incapacitating losses of consciousness avoided, by use of horizontal positions designed to eliminate heart-to-head hydrostatic gradients. Development of a prone-position cockpit with a counterweighted, forward-looking head support plus optical-electronically aided all-directional visibility is the most physiologic, safest, and surest way to achieve this goal.

Acceleration↗
PubMed1985

Cardiogenic motion of right lung parenchyma in anesthetized intact dogs.

Cardiogenic motion of the right lung parenchyma (CGLM) was measured in six morphine-pentobarbital-anesthetized dogs (11-16 kg) under conditions of varying paced and spontaneous sinus heart rates. Motion of 1-mm-diameter percutaneously implanted radiopaque lung parenchymal markers were measured using a computer-based biplane video-roentgenographic assembly. Correlation of the amplitudes and phases of marker motions to the R wave of the electrocardiogram (ECG) were determined utilizing a modified fast Fourier transform algorithm. Of initial importance was the observation that CGLM was significantly greater than the variability of repeated measurements. The total amplitudes of motion of the markers (where AT = square root A2X + A2Y + A2Z and AX, AY, AZ are the amplitudes of marker motion along the orthogonal X, Y, and Z body axes) in the right apical, cardiac, and diaphragmatic lobes were 0.025 +/- 0.005 (SE), 0.046 +/- 0.005, and 0.023 +/- 0.025 cm, respectively, (P less than 0.01, cardiac lobe vs. others). The total amplitude of motion observed in the cardiac lobe was equivalent to earlier observations of total amplitude (0.045 +/- 0.004 cm) of marker motion in response to high frequency airway oscillation at a pump stroke volume of 22-26 ml. An analysis of the higher harmonics of marker oscillation suggested that the second harmonic of CGLM is also larger than the variability of our measurements.

Anesthesia, Intravenous↗
PubMed1979

Noninvasive three-dimensional viewing of the motion and anatomical structure of the heart, lungs, and circulatory system by high speed computerized X-ray tomography.

A new generation X-ray computerized tomography system now under construction, the Dynamic Spatial Reconstructor (DSR), will record 1680 multiple view X-ray video images of the chest or other segments of the body per second. This allows com0utation of stop-action and 60-per-second instant replay motion pictures of the dynamic three-dimensional changes in shape and dimensions of the full anatomic extents of the internal and external surfaces of the heart chambers or the vascular anatomy and circulatory dynamics in any region of the body. Current commercially available scanners require one or more seconds per cross-sectional scan and lack the synchronous volumetric scanning capabilities of the DSR. These capabilities allow nondestructive mathematical selection and removal of any subvolume of interest from a reconstructed volume. The associated abilities to "zoom in" and "section" this subvolume so as to examine its structure and physiologic function in detail allow direct visualization of the internal anatomy and function of organ systems within the body. These capabilities of "noninvasive numerical biopsy" and "vivisection" have heretofore been the preserve of pathologists at autopsy or surgeons at the operating table. Possible future availability of these techniques to the practicing internist carries promise of revolutionary improvements in clinical diagnosis and treatment of the myriad of disease processes, including cancer, which may affect the heart, lungs, vascular anatomy or circulatory dynamics in any region of the body.

Blood Vessels↗
PubMed1978

Effect of force environment on regional pulmonary displacements and volumes in dogs.

Regional displacements of lung parenchyma due to respiratory movements at 1 G and 7 Gy were studied in anesthetized dogs in the left decubitus position in a water-filled respirator that provided control of respiratory volumes and rate and minimized inertial shifts in position and shape of the thorax and abdominal contents and related effects on the lungs. Inspiratory movements at 1 G were relatively uniform, although regional volume increased more in the nondependent (right) lung than in the dependent (left) lung. Regional functional residual capacity (FRC) increased in the nondependent lung and decreased in the dependent lung during exposures to 7 Gy. The greatest inspiratory increase in volume occurred near the midlung, where regional FRC changed the least during acceleration. The decrease in dependent and increase in nondependent lung volumes during acceleration are attributed to the increased weight and consequent downward displacement of the higher specific gravity mediastinal contents concomitantly with upward displacement of pulmonary gas, producing an exaggeration of the dependent-to-nondependent gradient in alveolar size.

Adaptation, Physiological↗