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A mathematical model is developed for the measurement of respiratory air flow, based on the phase shift of ultrasonic pulse trains. A correction is made for the velocity of found as a function of gas composition, moisture, temperature and pressure. Error estimates and calibration procedures as they relate to clinical application are discussed.

351 SPF OF1 non-immunized mice of both sexes were infected by aerosolized Pasteurella multocida. Female mice were significantly less susceptible to infection than were males of the same age (which were heavier). Males and females of equal bodyweight, but different age, showed no significant difference in susceptibility. The difference at equal ages can be explained by the lower respiratory flow of females. The consequences of these results for experimental studies on atmospheric pollutants are discussed.

An electronic sampling method is utilized to delay the respiratory flow waveform in exact accord with transport delay which is inherent in many conventional high-speed gas analyzers. The system makes it possible for analog respiratory instrumentation computers to process data more accurately and with a minimum of expense.

An alternating laminar flow in a straight tube used to simulate the respiratory flow in trachea is studied analytically. Flow characteristics are shown to be all affected by the frequency of oscillation. Some qualitative agreement between the present theory and some published experimental results has been found. It is concluded that the theories developed previously for the bronchial tree without considering the oscillatory fluid motion need to be modified.

A three-dimensional graphic representation of the mechanical aspects of pulmonary ventilation has been developed from experimental data obtained in man, in which transpulmonary pressure, respiratory flow and lung inflation have been uniquely related. The basic element of this representation is the isovolume pressure-flow curve. The behavior of a simple lung model is described to emphasize the general determinants of these isovolume pressure-flow curves. The broad inferences drawn from analysis of this model are applied to the pressure-flow-volume (P-F-V) relationship of the human lung. The three-dimensional surface representing the P-F-V relationship has had certain conceptual value. The concept of the α F-V curve evolved from consideration of this surface. This curve has been studied in man and found to have certain unique characteristics that suggest that it may become a valuable clinical tool. The α F-V curve is quite reproducible, is only moderately dependent upon effort, is essentially unaffected by wide variations in upper airway resistance, is determined by the physical properties and dimensions of the intrathoracic pulmonary system, is greatly altered in emphysematous subjects and is relatively easily obtained. In the light of this three-dimensional analysis it has been possible to evaluate a number of the commonly used indices of ventilatory mechanics. The interrelationship between these tests has been demonstrated and an understanding of their potential variability gained. Certain areas meriting further experimental exploration are suggested from considerations of the surface. It is not our intent to suggest that thorough study of ventilatory mechanics requires construction of such a surface for each person. Although certain limitations of the approach are stressed, it nevertheless has proved extremely useful in visualizing these three variables simultaneously.

Apparatus and procedures are described for measuring respiratory function in intact and unanesthetized guinea pigs during exposure to clean or contaminated air. Modification of previously reported methods enabled measurements on several animals in a single experiment. With this multi-animal test system, values for total respiratory flow resistances, respiratory rates, and tidal volumes that were obtained during inhalation of air or formaldehyde-contaminated air agreed closely with previously reported values for single-animal test methods. The method is sensitive for detecting early functional alterations during inhalation of irritants at concentrations much below acutely toxic levels, and the multi-animal test system permits rapid screening tests for respiratory effects of contaminated atmospheres.

A new oral bronchodilator, cp-12,521-1 was studied in 17 asthmatics. Respiratory flow-volume loops were obtained during an 8-week double-blind randomized crossover study. The usefulness and practicality of this technique in the evaluation of the response of patients to treatment were clearly indicated.

The method of forced oscillations was used to examine the effect of curare on respiratory flow resistance and to compare it to the effect of pancuronium. The results indicate that curare has a bronchoconstrictor effect that is significant in those with pre-existing airways obstructive disease. In contrast, pancuronium has no such effect. It is concluded that curare should be avoided in any patient with significant airways obstruction. The data suggests that pancuronium is the agent of choice.

SUMMARY The effect of the respiratory flow pattern on the fresh gas flow required to prevent rebreathing in a T-piece system was investigated using laboratory models. With a sine wave pattern slighdy less than 2½ times the minute volume was necessary. With the flow patterns produced by the ventilators studied, up to 3 times the minute volume was required. It is suggested that during artificial ventilation with certain flow patterns higher fresh gas flows may be required.

Measurements of flow resistance of various components of the respiratory system were measured in adult male subjects in the sitting position. Nasal resistance is the largest single component being nearly one-half the total and two-thirds of the airway resistance during nose breathing. It is highly nonlinear, and shows much variability. During mouth breathing upper airway resistance (mouth, pharynx, glottis, larynx and upper trachea) is also markedly nonlinear, and accounts for one-third the total airway resistance. Lower airway resistance is approximately linear up to flows of 2 liters/sec. Pulmonary tissue resistance is low as reported in this study. Chest wall resistance is nearly linear up to flow rates of 2 liters/sec and accounts for slightly less than half the total respiratory resistance during mouth breathing and 10–19% during nasal breathing. larynx; airways; chest wall; nose Submitted on December 16, 1963

Trans-pulmonary pressure, respiratory flow, and tidal volume of seven normal subjects were measured at rest and during treadmill exercise on the level at a speed of 1.5 mph. Pulmonary compliance remained unchanged during exercise. Nonelastic resistance showed an insignificant increase (0.9—1.4 cm H2O per liter per sec). Examination of other parameters which may affect compliance were made. Functional residual capacity decreased 120—200 ml during exercise, tidal volume doubled, and respiratory frequency increased 43.5%, yet none of these factors affected the lung compliance. The phenomenon of “second wind” was experienced by four of the subjects, and nothing was observed to explain its occurrence during exercise. exercise second wind; change in functional residual capacity during exercise; effect of functional residual capacity on compliance; effect of tidal volume on compliance during exercise; effect of respiratory frequency on compliance Submitted on January 15, 1965

For measurement of gas flow, a flowmeter consisting of a heated wire anemometer combined with a thermocouple was implanted into a dorsobronchus of the lungs in unanesthetized ducks. The direction of gas flow recorded in the dorsobronchus during spontaneous breathing and during artificial ventilation was from the mesobronchus to the parabronchi both in inspiration and expiration. This result is in accordance with the unidirectional flow hypothesis propounded by Bethe and by Hazelhoff, and is incompatible with the alternating respiratory flow hypothesis of Zeuthen.

Flow curves of tidal breathing, vital capacity and maximum breathing capacity of a group of 27 normal subjects were obtained with accurate flowmeters. The harmonic and frequency content of these th...

Regional deposition of aerosol in the human respiratory tract is estimated from experiments in which aerosol concentration and respiratory flow were measured continuously during individual breaths and from a theoretical analogy with a tubular continuous filter bed model of the respiratory tract. Since the volume of anatomic dead space is uncertain, regional distinction is made by selected boundary volumes which separate the upper tract of the selected volume from the more distal lower tract. The central feature of the estimation procedure is the determination of a combined upper tract penetration, for inspiration, pause, and expiration, derived from expired aerosol concentration corrected for aerosol mixing. The estimations indicate the particle size for maximum alveolar deposition is greater than 2 μ, equivalent diameter of a unit density sphere. This result is consistent with the calculations of Findeisen, Landahl, and Beeckmans and higher than the 1 μ value of Brown et al.

The modifications of Ayre's T-piece system can be divided into three types. In the first there is no expiratory limb, in the second the capacity of the expiratory limb is greater than the tidal volume, and in the third the capacity of the expiratory limb is less than the tidal volume. On the basis of previous mathematical and laboratory investigations by other authors, the three types are discussed with reference to the resistance to respiration and minimum fresh gas flow required to prevent rebreathing and air dilution during both spontaneous and controlled ventilation. The resistance and the fresh gas flow requirements are related to the expiratory flow rates and respiratory flow patterns which occur in children. It is suggested that the most convenient system is a T-piece of 10 mm diameter with an expiratory limb greater than the tidal volume and a bag attached to the expiratory limb. A fresh gas flow of up to 2½–3 times the minute volume is required.

SUMMARY Respiratory flow rates and tidal and minute volumes were measured by pneumotachography during routine dental anaesthesia. Peak inspiratory flow rates from 50 l./min to more than 200 l./min, tidal volumes from 300 ml to more than 3,000 ml, and inspiratory minute volumes between 11 and 50 l./min were found. It was confirmed that raising the pressure within the nosepiece does not necessarily lead to the escape of gases through the mouth. The possibility of using pneumotachography for the measurement of nitrous oxide uptake was also demonstrated qualitatively.