Professor Arthur T. Johnson
Respiratory Care 56(7): 969-975 (2011)
Derya C. Coursey
Steven M. Scharf
Arthur T. Johnson
ABSTRACT
BACKGROUND: Expiratory isovolume pressure-flow curves allow determination of flow limitation and airway resistance, but obtaining an isovolume pressure-flow curve requires placing an esophageal balloon. The stop-flow method of obtaining isovolume pressure-flow curves is easy and noninvasive. OBJECTIVE: To compare the stop-flow and esophageal-balloon methods by measuring the differences between the pressures and flows at which flow limitation first occurs. METHODS: In 5 healthy subjects we used the esophageal-balloon method and the stop-flow method at 25%, 50%, and 75% of vital capacity (VC), and constructed isovolume pressure-flow curves showing the pressure at which the flow became limited during forced expiration. RESULTS: The mean calculated pleural pressure at flow limitation with the stop-flow method was 2.7 times and 1.6 times that via the esophageal-balloon method at 25% of VC and 50% of VC, respectively. The maximum flow at flow-limitation with the stop-flow technique was 0.7 times and 0.6 times that via the esophageal-balloon method at 25% of VC and 50% of VC, respectively. We also calculated the resistance (the inverse of the slope of the line to the point of flow limitation), but there were large variations in the resistance values, so there was no statistically significant relationship between the stop-flow and esophageal-balloon methods. CONCLUSION: The stop-flow method showed potential to noninvasively obtain isovolume pressure-flow curves.
Physiol. Meas. 26 29-38, 2005
Nischom K Silverman
Arthur T Johnson
William H Scott
Frank C Koh
ABSTRACT
Respiratory resistance (Rrs) changes during physical labor can modify the work of breathing and thus influence the time that the labor can be performed. Ideal in vivo human respiratory performance measurements should have fine temporal resolution and minimally impact the respiratory system itself. The airflow perturbation device (APD) provides respiratory resistance measurements in this manner. Pre-exercise Rrs was compared with post-exercise Rrs continuously monitored for 6 min in 12 non-asthmatic subjects. Rrs following exercise at 70-75 was below pre-exercise levels for 40 s into recovery (p < 0.05) and inhalation resistance differed more markedly than exhalation resistance. The same post-exercise Rrs decline was found when Rrs measurements were compared to those taken during flow rates comparable to those found in recovery. Results indicate that (1) Rrs indeed declines following exercise in non-asthmatic subjects, probably due to bronchial dilation, (2) Rrs changes can occur on short time scales, (3) Rrs changes are not related primarily to flow rate.
Keywords: bronchodilation, respiration, exercise, respiratory biomechanics
DECREASE OF RESISTANCE TO AIR FLOW WITH NASAL STRIPS AS MEASURED WITH THE AIRFLOW PERTURBATION DEVICE
BioMedical Engineering OnLine 2004, 3:38
Lily S Wong
Arthur T Johnson
ABSTRACT
Background
Nasal strips are used by athletes, people who snore, and asthmatics to ease the burden of breathing. Although there are some published studies that demonstrate higher flow with nasal strips, none had directly measured the effect of the strips on nasal resistance using the airflow perturbation device (APD). The APD is an inexpensive instrument that can measure respiratory resistance based on changes in mouth pressure and rate of inflow. This study tested forty-seven volunteers (14 men and 33 women), ranging in age from 17 to 51. Each volunteer was instructed to breathe normally into the APD using an oronasal mask with and without nasal strips. The APD measured respiratory resistance during inhalation, exhalation, and an average of the two. Results of a paired mean t-test comparing nasal strip against no nasal strip were statistically significant at the p = 0.05 level. The Breathe RightTM nasal dilator strips lowered nasal resistance by an average of 0.5 cm H2O/Lps from an average nasal resistance of 5.5 cm H2O/Lps. It was concluded that nasal strips reduce nasal resistance when measured with the APD. The effect is equal during exhalation and during inhalation.
Physiol. Meas. 25 (June 2004) 679-690
Arthur T Johnson
Manjit S Sahota
ABSTRACT
The airflow perturbation device (APD) is a recently redesigned instrument to measure resistance in the respiratory system. The APD is small and easy to use, gives rapid resistance measurements, and can easily separate inhalation from exhalation components. It also possesses some operational characteristics similar to forced oscillation (FO). Excised sheep lungs within a respiratory chamber were used to determine the effective resistance domain of the APD. Retrograde catheters were installed in the airways, alveolar capsules were used to measure alveolar pressures, and chamber pressure was used as pleural pressure. FO measurements were made to compare with the APD. The APD was found to give a resistance measurement about 1.7 to 1.9 times airway resistance. FO gave a resistance measurement 1.4 times airway resistance. Resistance values differed depending on analysis procedure and frequency of oscillation. Both devices were found to produce oscillations beyond the pleural surface of the lungs. It was concluded that the APD and FO measure similar respiratory resistances.
Keywords: respiration, respiratory resistance, pulmonary function, respiratory biomechanics, lungs, sheep
Physiol. Meas. 20 (1999) 21-35. Printed in the UK.
Christopher G Lausted
Arthur T Johnson
ABSTRACT
The airflow perturbation device (APD) is an instrument for the measurement of respiratory resistance. The APD is small, lightweight, fast and requires no special breathing manoeuvres. Airflow perturbation determines resistance by superimposing a periodic signal onto spontaneous breathing with a variable resistance device. Respiratory impedance is the ratio of magnitude of pressure perturbation to magnitude of flow perturbation, and respiratory resistance is the in-phase portion of respiratory impedance. The APD was tested to determine its responses to repeated resistance measurements and to changes in resistance. A mechanical model test showed that the APD could detect increased resistance levels, but overestimated resistance when resistance increased with flow. Tests with human subjects showed that the APD gave results consistent from day to day, was able to detect added resistances, and gave resistance values correlated with airway resistance values obtained by body plethysmography. Accelerometers placed on the chests of the subjects showed that perturbations extend to the chest surface. Thus, the APD must measure total respiratory resistance.
Keywords: respiration, resistance
Elsevier Computer Methods and Programs in Biomedicine 57 (1998) 161-166
Arthur T. Johnson
Cathryn R. Dooly
Christopher R. Simpson
ABSTRACT
The Snellen Chart is the eye chart that is commonly used to measure visual acuity. The chart has combinations of nine different letters in eleven different lines, each smaller than the one above. Repeated measures of visual acuity may result in chart memorization and false information. Thus, a computer program was written to produce randomized multiple versions of Snellen eye charts. The chart may be changed at some distance from the computer in order to hear subject letter identifications during exercise testing. Different sized letters can also be produced so that the distance from the subject to the chart can vary.
Keywords: Vision; Eye chart; Exercise testing
Transactions of the ASAE, Vol. 39(5): 1863-1868. 1996 American Society of Agricultural Engineers
K. M. Coyne
A. T. Johnson
L. R. Soma
ABSTRACT
Exercise-induced pulmonary hemorrhage (EIPH) occurs in many race horses after maximal exercise. Because of its widespread occurrence, it is considered one of the most important issues in horse racing today. Recent modeling results have shown that low alveolar pressure and high airway resistance can possibly induce EIPH. To investigate these results physically, a system capable of altering inhaled gas densities and thus the airways' resistance was needed.
A closed-circuit rebreathing system controlled by a proportional-derivative regulator control system was designed to test horses exercising on a treadmill. The objective of the system was to challenge the animals with exotic gas mixtures while supplying normal levels of oxygen and removing metabolic carbon dioxide.
The running horse's physiology and interaction with the rebreathing system were considered in designing the system. The system supplied up to 60 L/min of oxygen while removing up to 60 L/min of metabolic carbon dioxide. To reduce the physiological burden imposed on the horse, resistance to breathing was minimized by using high flow rates (up to 7200 L/min) and large diameter tubing (20 cm).
Tests demonstrated that the rebreathing system permitted the horse to exercise to a maximal level while breathing from the closed circuit. The rebreathing system replaced oxygen metabolized by the horse, mixed and recirculated the inhalation gases, compensated for resistance, removed carbon dioxide, and prevented rebreathing of exhaled carbon dioxide.
Keywords. Computer-controlled, Horses, Breathing, Recirculating system, Exercise.
SYSTEM TO OBTAIN EXERCISE RESPIRATORY FLOW WAVEFORMS
Computer Methods and Programs in Biomedicine 42 (1994) 27-32
Arthur T. Johnson
Cathryn R. Dooly
ABSTRACT
A system for obtaining respiratory flow rate waveforms, tidal volume, minute volume, respiration rate, inhalation time and exhalation time is described. The system is based on a microcomputer with analog-to-digital converter board. System software allows calibration, data acquisition and data analysis. Data can be obtained automatically at fixed time intervals. The system is inexpensive and reliable.
Key words.- Respiration; Exercise; Airflow waveforms; Pneumotach
Computers and Electronics in Agriculture, 7 (1992) 121-132
A.T. Johnson
T. Holly
ABSTRACT
TERPS is a computer program package written for IBM XT/AT compatibles to assist in design of erosion control terraces. The program package contains seven program modules that assist terrace design from initial topographic survey to storage basin design. The programs are written in GWBASIC. Each program module features user-friendliness and the integration of terrace system layout with contour maps and hydrologic units superimposed upon land use zones.
Environmental Technology, Vol. 11. pp. 1107-1111, 1990
M. J. Krones
A. T. Johnson
O. J. Hao
ABSTRACT
A numerical technique coupled with automatic data acquisition was developed for the rapid and accurate evaluation of the bioluminescence ATP assay using the luciferin-luciferase reaction. An exponential decay equation is fitted to the light emission curve of a sample containing ATP. The integral of the curve was found to be a reliable indicator of the amount of ATP in a sample regardless of the overall shape of the curve, peak height, or rate of initial rise. This method is useful for analyzing extracts from environmental samples containing contaminating colloids and molecular species which tend to alter the light emission curve.
MICROCOMPUTER PROGRAMS FOR INSTRUMENTATION AND DATA ANALYSIS
Computers in Education Division of ASEE 7(2):37, 1987
Arthur T. Johnson
ABSTRACT
Four microcomputer programs for instrumentation and data analysis have been written for IBM PC compatible machines. Each of these can be useful in classroom situations to illustrate and teach data analysis techniques.
HortScience 22(3):501-503, June 1987
Michael J. Krones
John C. Sager
Arthur T. Johnson
ABSTRACT
This paper describes a closed-loop control system for controlling the irradiance and spectral quality generated by fluorescent lamps in a controlled environment chamber. The 400 to 800 nm irradiance and the ratio of the red waveband (600 to 700 nm) to the far-red waveband (700 to 800 nm) were independently controlled and varied as functions of time. A suggested application is to investigate the possibility of synergistic effects of changing irradiance levels and changing spectral distributions on photoperiodism and photomorphogenesis.
IEEE Transactions on Biomedical Engineering, Vol. BME-34, No. 3, March 1987
Arthur T. Johnson
Joel M. Milano
ABSTRACT
A previous communication presented a procedure to convert perturbational airways resistance to plethysmographic resistance. While working with this procedure, we discovered that one of the unknown exhalation parameters must be set to a value of 1.0, and another represents the inverse of the respiratory system time constant. This simplifies the conversion procedure and makes it easier to apply.
IEEE Transactions on Biomedical Engineering, Vol. BME-33, No. 8, August 1986
Arthur T. Johnson
ABSTRACT
Equations were developed for airway pressure-flow characteristics which were then used to illustrate differences between airflow perturbation device measurements and body plethysmographic airways resistance measurements. The general conclusions indicate that perturbational resistances may be able to be reformulated as plethysmographic resistances, yielding information where the body plethysmograph itself is not well suited.
Innov. Tech. Biol. Med.; Vol. 6, no 4, 1985
C.-S. Lin
A. T. Johnson
M. Yarmanoglu
ABSTRACT
The airflow perturbation device (APD) is proposed as a new instrument for noninvasive measurement of respiratory airways resistance. Consisting of flow and mouth pressure measuring devices with a rotating screen, the APD is supposed to measure airways resistance from flow and pressure perturbations. To test this concept, as well as determine effects of screen resistance and rotation rate, a three compartment lumped parameter model of the human respiratory system was programmed using the MIMIC computer language. By adding to the model a section representing the APD, the effects of the device upon respiratory system were studied. The results indicate that the APD can be a useful measurement tool and agrees well with experimental results except that the model indicates higher APD resistance values than are experimentally obtained.
Computer Methods and Programs in Biomedicine 21 (1985) 203-210
Arthur T. Johnson
ABSTRACT
The program presented here is intended to be a design device and learning tool for digital filters. Digital filters designed with the program can be implemented by incorporation within the data analysis programs of the user. The program is written in BASIC for use with the IBM-PC, is intended to be user-friendly, and includes a great deal of filter assistance not found in other programs. An example of program use shows how one filter can be used to remove noise from respiratory waveform data.
Journal of the ISRP, Vol. 2, Issue 4, October-December 1984
Arthur T. Johnson
John N. Hochheimer
Jolynn Windle
ABSTRACT
The Airflow Perturbation Device (APD) is presented as a means of routinely and noninvasively measuring airways resistance of humans for the purpose of respirator research and medical surveillance. The theoretical basis of the APD is presented, APD construction is outlined, and some preliminary experimental results are described. Results thus far have been consistent with expectations and can be used as the basis for further development.
IEEE Transactions on Biomedical Engineering, Vol. BME-31, No. 9, September 1984
Arthur T. Johnson
Chin-Shing Lin
John N. Hochheimer
ABSTRACT
This communication introduces the airflow perturbation device (APD) as a means for measuring airways resistance in humans and animals. The APD uses a rotating screen to perturb airflow during spontaneous breathing. The resultant mouth pressure perturbation amplitudes are divided by flow rate perturbation amplitudes to give airways resistance. Data shown for both humans and swine demonstrate values to be in the correct magnitude range, and to reflect changes in flow rate and direction.
Transactions of the ASAE, Vol. 26, No. 2, pp. 503-506, 1983
Arthur T. Johnson
Chin-Shing Lin
ABSTRACT
The APD as a device for measuring airway resistance of livestock and other animals is suitable for use with unanesthetized subjects. It is lightweight, portable, simple, and easy to use. Its use can become important for diagnosis and prognosis of animal respiratory disorders and for assessing respiratory effects of airborne contaminants.
Transactions of the ASAE, Vol. 25, No. 5, pp. 1282-1283 & 1289, 1982
Robert L. Kort
Arthur T. Johnson
James E. Ayars
Allen D. Schlosser
ABSTRACT
Research to study the nature and extent of non-point sources of pollution from surface water runoff, including agricultural operations, requires instrumentation that records intermittent runoff water levels and activates sampling equipment (Johnson et al., 1978). Acquisition and analysis of hydrologic data using current techniques is a time consuming and expensive process which demands better data collection and reduction procedures.
Transactions of the ASAE 1981, Vol. 24, no. 2, Mar-Apr 1981
Arthur T. Johnson
G. Douglas Kirk
ABSTRACT
Botsball and WBGT sensors are two ways currently used to measure environmental heat stress. Thermodynamic and heat transfer relations are developed for these sensors in order to obtain basic understanding of the way these two measurements are related. Slight modifications of our equations were accomplished to match published natural wet bulb and Botsball data. An analysis such as this enables standard WBGT information to be determined from nonstandard, but more convenient, means of measurement.
Fire Technology 16(3) 181-191, August 1980
Arthur T. Johnson
Allen D. Schlosser
G. Douglas Kirk
Gerry L. Long
ABSTRACT
An electronic circuit has been designed and tested which can automatically determine ignition temperatures of shredded combustible materials.
CORRELATION OF WBGT AND BOTSBALL SENSORS
American Industrial Hygiene Association JOURNAL (41) 5/80
Arthur T. Johnson
G. Douglas Kirk
ABSTRACT
The standard method for measuring human environmental heat stress is the WBGT. The WBGT apparatus is cumbersome and difficult to relate to standard psychrometric parameters or to other environmental measures such as the Botsball. The work presented in this paper was derived from thermodynamic and heat transfer considerations with corrections applied to be consistent with published experimental results.
Instruments & Control Systems: March 1980, Vol. 53 No. 3
Arthur T. Johnson
Allen D. Schlosser
ABSTRACT
One digital panel meter can be made to display several stored input voltage values being held by a voltage hold signal.
AgriculturalEengineering, December 1979
Arthur T. Johnson
James E. Ayars
ABSTRACT
An inexpensive wristwatch was utilized to extend timekeeping capabilities of a Stevens Type F Water Stage Recorder.
Agricultural Engineering, September 1978 59(9):22-23
Arthur T. Johnson
Robert Kort
James E. Ayars
ABSTRACT
The Stevens Type F Water Stage Recorder, frequently used in watershed hydrology, can be modified to start the recorder chart drive whenever the water stage reaches a preset level and to coordinate an event marker between the recorder chart and a water sampler. This modification is practical and economical in runoff studies and steam monitoring at a remote site with intermittent flow. This modification allows more efficient use of electricity, chart paper, and manpower that is possible with continuous monitoring.
Control Engineering V23(3):26, March 1976
A. T. Johnson
ABSTRACT
AC loads up to 35 amperes can be controlled directly from CMOS digital circuits. The power control device uses a CMOS quad bilateral switch and a capacitative triggered triac.
Transactions of the ASAE, Vol. 18, No. 4, pp. 719-721, and 727, 1975
A. T. Johnson
John V. Wallace
James. J. Alter
ABSTRACT
A circuit has been designed, fabricated, and tested, which can be used to segmentally linearize general nonlinear data. The circuit provides for 10 individual segments with independently varied breakpoint and slope adjustments. Visual indications of adjusted segment and magnitude of input signal is provided. The circuit is relatively easy to calibrate and can provide a low distortion linearized output voltage within the limitations of adjustment accuracy, input nonlinearity, frequency, and magnitude.
IEEE Trans Biomed. Engr., BME-22(5) 420-423, September 1975
Arthur T. Johnson
ABSTRACT
Frequently in measuring physiological variables it is necessary to store an electrical signal for relatively long periods of time. The circuit presented has been designed for this purpose, and can operate with signals up to + 10 v with drift rates dependent upon the stored voltage but typically less than 7 mv/hr.
Instruments & Control Systems, November 1974
Arthur Johnson
John Wallace
ABSTRACT
A digital panel meter can be used to convert analog electrical signals into digital form for use with a desk-top calculator. Needed are an interface card and power supply shown in this article.
Electronics/February 21, 1974, Vol. 47, No. 5
Arthur Johnson
ABSTRACT
Power to an ac load can be efficiently controlled by an integrated complementary-MOS quad bilateral switch and a capacitively triggered sensitive-gate triac. The necessary gate-triggering current comes, not from the low-voltage C-MOS power supply, but from the ac line.
Medical Instrumentation 8(2), March, 1974
Arthur T. Johnson, PhD
Howard M. Berlin, MS
Spooner A. Purnell, BS
ABSTRACT
A simple device based on modification of the airflow interrupter technique has been developed. Instead of totally interrupting airflow, the device switches respiratory airflow from one known resistance to another, with the difference between resistance values as small as current measurement techniques will allow. Flow and mouth pressure can be measured under both resistance conditions. Airway resistance values are obtained independently from flow and pressure measurements. Advantages of this device are the two ways of obtaining values of airway resistance, unnoticeable change in device resistance, and minimal effects of the device on the respiratory system.
Transactions of the ASAE, Vol. 16, No. 5, pp. 926-929, and 933, 1973
A. T. Johnson
ABSTRACT
A sample-and-hold circuit for long term storage of voltage levels has been presented. Performance of less than 7 mv per hr has been demonstrated for signals up to ±10 v. Design consideration and construction precautions have been given. The circuit is capable of performance which several years ago would have been unattainable at moderate cost.
Transactions of the ASAE, Vol. 15, No. 1, pp. 14-18, and 23, 1972
N. R. Scott
A. T. Johnson
ABSTRACT
An inexpensive system for determination of heart rate of unrestrained small animals is presented. Electrode selection and placement, miniature ECG radio transmitter, unmodified hi-fi FM tuner and heart rate counter are discussed in detail with emphasis on interrelationships between functional elements and with circuit diagrams included. Data are presented to verify the operational characteristics and reliability of the system under physiological conditions. The final output d-c voltage is proportional to the frequency of heartbeat pulses (3-9v proportional to 3-9bps). Linearity is within 1 percent over a range of 3-9 pulses per second with a rapid time response (time constant about 3.5 seconds). Total system cost is less than $200 (ECG transmitter, <$10; commercial FM tuner, $50-$120; heart rate counter, <$40).
AN ANALOG SAMPLE-AND-HOLD CIRCUIT FOR CALIBRATION MONITORING
Edgewood Arsenal Technical Report EATR 4725, July 1973. Edgewood Arsenal, MD 21010
Arthur T. Johnson
ABSTRACT
Instances may arise where it is important to monitor system calibration for long periods of time. It is frequently inconvenient to recalibrate the measuring system, especially during testing. A sample-and-hold circuit which stores necessary recalibration levels for long periods of time has been designed, built, and evaluated. Depending on the operational amplifier used, the circuit is capable of less than 7 mv/hr voltage drift over the full +10 v input voltage range.