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A method for measuring total respiratory resistance (RT) using a forced oscillation technique was applied to children between 3 and 12 years of age. RT at midinspiration was higher than airway resistance (Raw) measured on the same children by total body plethysmography. Normal RT values were compared with results in children with asthma and cystic fibrosis. It is suggested that the technique could have a wider application in the assessment of airway obstruction in children.

As a step toward improvement of the calculation of lateral motion (sway, yaw and roll) of a ship in waves, the coefficients of equations of motion were determined by the forced oscillation technique. Experiments made it possible to know the effects of frequency, advance speed and bilge keels on ship motions. The experimental values were compared with the calculated values by the strip method. For the main terms of sway, yaw or roll, except roll damping term, the results show a fairly good agreement. For the coupling terms of sway-yaw, yaw-roll or roll-sway, there are fair correspondences. For the prediction of the roll damping term, a proper method of approximation which includes the effects of viscous damping, advance speed, bilge keels and frequency of motion should be developed.

Total respiratory resistance (R(T)) was measured by the application of a sine wave of airflow to the mouth at the resonant frequency of the respiratory system. The mean respiratory resistance of 42 normal subjects, measured at a mean functional residual capacity of 3.3 liters, was 2.3, SD +/- 0.5, cm H(2)O/liter per sec, and the resonant frequency was between 5 and 8 cycle/sec. The airway resistance measured in these same subjects with the body plethysmograph at a mean panting thoracic gas volume of 3.5 liters was 1.3, SD +/- 0.3, cm H(2)O/liter per sec. Total respiratory resistance was found to vary inversely with lung volume (V) measured plethysmographically; prediction formulae for normal subjects based on this relationship are: R(T) (mean) = 7.1/V, R(T) (range) = 4.0/V to 11.6/V where V is in liters and R(T) is in cm H(2)O/liter per sec. When these criteria were applied to subjects with thoracic disease the following results were obtained: 17 subjects with obstructive lung disease all had elevated total respiratory resistance; 9 subjects with diffuse lung disease without airway obstruction all had normal respiratory resistance; all but 1 of 5 obese subjects and all but 2 of a heterogeneous group of 9 subjects without airway obstruction had normal respiratory resistance. Failure to take lung volume into account resulted in a considerable decrease in the ability to discriminate between obstructive and nonobstructive lung disease on the basis of the forced oscillation test. The resonant frequency of the respiratory system of patients with obesity or nonobstructive lung disease was similar to that obtained in the normal group; accurate evaluation of resonant frequency in subjects with obstructive lung disease was frequently not possible. The combined resistances of lung, thoracic wall and abdominal tissues were found to account for less than 43% of the total respiratory resistance in normal subjects and were only slightly increased by the presence of obesity, restrictive diseases of the thoracic wall, and hyperinflation of the thorax. The forced oscillation method is potentially of value in the study of resistance to breathing of patients who cannot undergo body plethysmography, such as acutely ill, anesthetized, or unconscious subjects. Accurate evaluation of R(T) requires an independent measure of lung volume as well as careful attention during measurements to the airflow rate, phase of respiration, and the adequacy of cheek compression and laryngeal relaxation.

An automated system for obtaining a direct measurement of total respiratory resistance (RT) is presented. A polygraph and digital computer are used to filter and quantify the pressure and flow outputs of a forced oscillatory device to determine RT. Functional descriptions of the complete hardware system and of the computer software are included. The measurement of RT is viewed as providing a sensitive and relatively unobtrusive means for investigation of psychophysiological precipitants of subclinical variations in bronchial tone in normal Ss and in Ss suffering from obstructive bronchial disorders such as bronchial asthma. In addition, augmented sensory feedback of RT can be utilized in investigations of S's ability to attain voluntary control of RT.

Publisher Summary This chapter presents a survey of flight flutter testing techniques. There is a requirement for flight flutter testing to satisfy the need for positive proof of the acceptability of a prototype aircraft and specifically to cope with vibration or flutter difficulties encountered during the development stage of an aircraft. The continuously forced oscillation technique is generally considered to have certain advantages but it is more complicated than the transient oscillation technique. In cases where the equipment can be installed, the first technique is considered the best presently available. Phased inertia exciters provide a further refinement of this technique. In other cases, transient excitation by means of rockets is the best alternative. In flight flutter testing of modern aircraft, it is very important to be able to lean on results of preflight flutter calculations or wind tunnel flutter tests, to reduce the danger inherent in this type of testing. From this point of view, it is desirable that methods for flutter calculations be improved.

Small-amplitude forced oscillation technique for determining damping and oscillatory stability in roll, pitch, and yaw in free flight