Professor Arthur T. Johnson
IEEE Trans. Biomed. Engr. 59(8): 2355-2361 (2012)
Arthur T. Johnson
Samantha C. Jones
James J. Pan
Jafar Vossoughi
ABSTRACT
Physiologically optimized processes, such as respiration, walking, and cardiac function, usually show a range of variability about the optimized value. Airway resistance has, in the past, been noted as variable, and this variability has been connected
to pulmonary disease (e.g., asthma). A hypothesis was presented many years ago that postulated airway resistance as an optimized parameter in healthy individuals, and we have noticed that respiratory measurements made with the airflow perturbation device (APD) tend to be variable in nature. It was posited that this variability indicates that respiratory resistance is optimized similarly to other physiological processes. Fifty subjects with a wide range of demographics volunteered to have 100 measurements made of their respiratory resistances. Resistances were separated into inhalation
and exhalation phases. These were plotted and shown to have frequency distributions that were consistent with expectations for an optimized process. The frequency distributions were not quite symmetrical, being skewed slightly toward upper resistances. Comparison
between subject data and data from a mechanical respiratory analog showed that subject resistance variation is overwhelmingly from the respiratory system and not from the APD.
BioMedical Engineering OnLine 2006, 5:29
doi: 10.1186/1475-925X-5-29
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Christopher G Lausted
Arthur T Johnson
William H Scott
Monique M JohnsoX
Karen M Coyne
Derya C Coursey
ABSTRACT
Maximum pressures developed by the respiratory muscles can indicate the health of the respiratory system, help to determine maximum respiratory flow rates, and contribute to respiratory power development. Past measurements of maximum pressures have been found to be inadequate for inclusion in some exercise models involving respiration.
Maximum inspiratory and expiratory airway pressures were measured over a range of lung volumes in 29 female and 19 male adults. A commercial bell spirometry system was programmed to occlude airflow at nine target lung volumes ranging from 10% to 90% of vital capacity.
In women, maximum expiratory pressure increased with volume from 39 to 61 cmH2O and maximum inspiratory pressure decreased with volume from 66 to 28 cmH2O. In men, maximum expiratory pressure increased with volume from 63 to 97 cmH2O and maximum inspiratory pressure decreased with volume from 97 to 39 cmH2O. Equations describing pressures for both sexes are:
Pe/Pmax = 0.1426 Ln(%VC) + 0.3402 R2 = 0.95
Pi/Pmax = 0.234 Ln(100 - %VC) - 0.0828 R2 = 0.96
These results were found to be consistent with values and trends obtained by other authors. Regression equations may be suitable for respiratory mechanics models.
Can. J. Appl. Physiol. 21(3): 209-217 (1996)
Vernon Bond, Jr.
Paul Wang
Richard G. Adams
Arthur T. Johnson
Paul Vaccaro
Russell J. Tearney
Richard M. Millis
B. Don Franks
David R. Bassett, Jr.
ABSTRACT
High-intensity resistance (HIR) training has been associated with muscle hypertrophy and decreased microvascular density that might produce a blood flow limitation. The effect of HIR training on lower leg maximal blood flow and minimum vascular resistance (Rmin) during reactive hyperemia were investigated in 7 healthy males. The gastrocnemius-soleus muscles of one leg were trained using maximal isokinetic concentric contractions for 4 weeks; the nontrained leg was the control. Lower leg blood flow was measured by venous occlusion plethysmography. Lower leg muscle volume was determined using magnetic resonance imaging. Peak isokinetic torque increased in both the trained (T) and nontrained (NT) legs (p < .05). Lower leg muscle volume increased by 2% in the T leg only (p < .05). In the T leg, maximal bloodflow decreased and Rmin increased (p < .05); no hemodynamic change was detected in the NT leg. It is concluded that HIR training of the calf muscles is associated with a decrease in hyperemia-induced blood flow; thereby, indicating a blood flow limitation to the calf muscles.
Key words: Isokinetic strength training, reactive hyperemia
IEEE Transactions on Biomedical Engineering, Vol. 42, No., 3. March 1995
Arthur T. Johnson
ABSTRACT
The lung volumes from which inhalation and exhalation proceed change during exercise. There have been previous attempts to predict these lung volumes but none have been completely successful. Prediction of initial lung volume is important in the accurate calculation of respiratory power during exercise, especially when the subject is encumbered with respiratory protective apparatus and exercising above the anaerobic threshold. Although there is no direct work advantage to varying lung volumes at the beginning of inspiration or expiration, such changes appear to be dictated by the asymmetry of lung recoil pressure about the lung relaxation volume. Equalizing inspiratory and expiratory elastic pressures has been found to match available data on lung initial volume.
Frontiers Med. Biol. Engng, Vol. 5, No. 4, pp. 265-287 (1993)
Arthur T. Johnson
ABSTRACT
The rate of work expended to move air in the respiratory system has been determined for five different airflow waveshapes, a non-linear respiratory model and five exercise levels. As expected, the rectangular waveshape was the most efficient. Model conditions were then changed one at a time: (i) starting lung volume was allowed to vary, (ii) exhalation flow limitation was added, (iii) respiration was considered to be a metabolic burden determining part of the ventilation requirement and (iv) a respirator mask was added. Although there is no direct work advantage to varying initial lung volume, such volume changes appear to be dictated by the asymmetry of lung recoil pressure about the lung relaxation volume; allowing the work of respiration to become a metabolic burden clearly shows why respiratory waveforms change from rest to exercise; and, adding a respirator imposes a severe respiratory burden on the wearer engaging in moderate, heavy and very heavy exercise.
Key words: respiration; work.
Frontiers Med. Biol. Engng, Vol. 4, No. 4, pp. 271-289 (1992)
Arthur T. Johnson
Lawrence R. Soma
Carmella Ferouz
ABSTRACT
Exercise-induced pulmonary hemorrhage (EIPH) affects a large portion of racing thoroughbred horses. Sites of hemorrhage and causal mechanisms remain unestablished. Our mathematical model was constructed to test the hypothesis that EIPH could be caused by a combination of respiratory and circulatory mechanical factors occurring during exercise. Various physiological data for respiration, blood circulation and exercise were incorporated into the model. Results show that inhalation pressure drops across airway resistances become great enough during exercise to cause rupture of capillaries for both bronchial and pulmonary systems.
Key words: horses; exercise; respiration; pulmonary system; capillary bursting.
Transactions of the ASAE, Vol. 26, No. 4, pp. 1150-1152, 1983
Arthur T. Johnson
Chin-Shing Lin
ABSTRACT
The Airflow Perturbation Device (APD) was used to measure airway resistance of conscious caged boars. Although the pigs resisted the measurement, sufficient data was obtained to give an average value of airway resistance of 0.97 cm H2O-s/L for the eight pigs tested. Values are in the expected range, and exhalation resistance is higher than inhalation resistance, also as expected. Plots of resistance within each breath for two different pigs apparently show the dominance in one of the flow rate effect on resistance and in the other of the lung volume effect.
Perspectives in Biomechanics, D. N. Ghista, ed., Harwood: New York, 1980
Arthur T. Johnson
ABSTRACT
Biomechanical analyses of agricultural problems have contributed greatly to the steady improvement of agricultural productivity. As the range of agricultural endeavors is broad, so is the range of problems which have been approached by agribioengineers. The objective of this chapter is to sample some biomechanical approaches to demonstrate this breadth. Accordingly, examples have been selected highlighting mechanical harvesting, flow of biological materials, plant models, product processing, thermal models, and human biomechanics.
IEEE Transactions on Biomedical Engineering, Vol., BME-23, No. 5, September 1976
Arthur T. Johnson
Ceslovas Masaitis
ABSTRACT
Using a criterion of minimization of total respiratory work during a complete respiratory cycle, an expression has been derived for prediction of the inhalation time/exhalation time ratio. Comparison of calculated results to experimental data is favorable. The expression also predicts a rectangular waveshape during exercise, and this result agrees well with experimental and theoretical findings previously published.
Transactions of the ASAE, Vol. 14, No. 5, pp. 828-836 and 840, 1971
A. T. Johnson
Norman R. Scott
ABSTRACT
Thermoreceptors are means by which humans and animals receive information about their thermal environment. A computer model based on the Hodgkin-Huxley equations was formulated to simulate thermoreceptor action. Simulated thermoreceptors can be used as a component of larger thermal models of animals.
Transactions of the ASAE, Vol. 13, No. 3, pp. 342-347, 1970
Norman R. Scott
Arthur T. Johnson
A. Van Tienhoven
ABSTRACT
Hypothalamic temperature is a key element in thermoregulation of poultry. To measure this temperature, a probe inserted into the brain was made from a 23 gage hypodermic needle containing a miniature copper-constantan thermocouple. Heart rate was obtained using a miniature FM transmitter affixed to the bird's back. Both hypothalamic temperature and heart rate were found to fluctuate over the monitoring period. They exhibited diurnal variation, and were affected by level of arousal, activity, sleep, and feeding. The maximum daily hypothalamic temperature corresponded to the time of oviposition.