Abstract
Objective. The mechanical properties of the respiratory system (i.e., elastance and resistance) depend on the frequency, tidal volume, and shape of the flow waveform used for forcing. We developed a system to facilitate accurate measurements of elastance and resistance in laboratory and clinical settings at the frequencies and tidal volumes in the physiologic range of breathing.Methods. A personal computer (PC) is used to drive a common clinically used ventilator while simultaneously collecting measurements of airway flow, airway pressure, and esophageal pressure from the experimental subject or animal at different frequencies and tidal volumes. Analysis analogous to discrete Fourier transform at the fundamental frequency (i.e., ventilator setting) is used to calculate elastances and resistances of the total respiratory system and its components, the lungs and the chest wall. We have shown that this analysis is independent of the high-frequency harmonics that are present in the waveform from clinical ventilators.Results. The system has been used successfully to make measurements in anesthetized/paralyzed dogs and awake or anesthetized human volunteers in the laboratory, and in anesthetized humans in the operating room and intensive care unit. Elastances and resistances obtained with this approach are the same as those obtained during more controlled conditions, e.g., sinusoidal forcing. Conclusions. Accurate, standardized measurements of lung and chest wall properties can be obtained in many settings with relative ease with the system described. These properties, and their frequency and tidal volume dependences in the physiologic range, provide important information to aid in the understanding of changes in respiratory function caused by day-to-day conditions, clinical intervention and pathologies.
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Barnas GM, Campbell DN, Mackenzie CF, et al. Lung, chest wall and total respiratory system resistances and elastances in the normal range of breathing. Am Rev Respir Dis 1992; 145: 110–113
Barnas GM, Harinath P, Green MD, et al. Influence of waveform and analysis technique in lung and chest wall properties. Respir Physiol 1994; 96: 331–344
Barnas GM, Heglund N, Yager D, et al. Impedance of the chest wall during sustained respiratory muscle contraction. J Appl Physiol 1989; 66: 360–369
Barnas GM, Ho G, Green MD, et al. Effects of analysis method and forcing waveform on measurement of respiratory system mechanics. Respir Physiol 1992; 89: 273–285
Barnas GM, Stamenovic D, Lutchen KR. Lung and chest wall impedances in the dog in normal range of breathing: Effects of pulmonary edema. J Appl Physiol 1992; 73: 1040–1046
Barnas GM, Stamenovic D, Lutchen KR, Mackenzie CF. Lung and chest wall impedances in the dog: Effects of frequency and tidal volume. J Appl Physiol 1992; 72: 8793
Barnas GM, Watson RJ, Green MD, et al. Lung and chest wall mechanical properties before and after cardiac surgery with cardiopulmonary bypass. J Appl Physiol 1994; 76:166–175
Navajas D, Farre R, Rotger M, Canet J. Recording pressure at the distal end of the endobronchial tube to measure respiratory impedance. Eur Respir J 1988; 2: 178–184
Baydur A, Behrakis PK, Zin WA, et al. A simple method for assessing the validity of the esophageal balloon technique. Am Rev Respir Dis 1982; 126: 788–791
Otis AB, McKerrow CB, Bartlett RA, et al. Mechanical factors in distribution of pulmonary ventilation. J Appl Physiol 1956; 8: 427–443
Pride MB, Macklem PT. Lung mechanics in disease. In: Macklem PT, Mead J, eds. Handbook of physiology. Section 3: The respiratory system, vol III, part 1. Bethesda, MD: American Physiological Society, 1986: 659–692
Rossi A, Gottfried SB, Zocchi L, et al. Measurement of static compliance of the total respiratory system in patients with acute respiratory failure during mechanical ventilation. Am Rev Respir Dis 1985; 131: 672–677
Barnas GM, Sprung J, Craft TM, et al. Effect of lung volume on lung resistance and elastance in awake subjects measured during sinusoidal forcing. Anesthesiology 1993; 78: 1082–1090
Dosman J, Bode F, Urbanetti J, et al. Role of inertia in the measurement of dynamic compliance. J Appl Physiol 1975; 38: 64–69
Douglas NJ, Wraith PK, Brash HM, et al. Computer measurement of dynamic compliance: technique and reproducibility in man. J Appl Physiol 1980 48: 903–910
Barnas GM, Green MD, Mackenzie CF, et al. Effect of posture on lung and regional chest wall mechanics. Anesthesiology 1993; 78: 251–259
Barnas GM, Mills PJ, Mackenzie CF, et al. Effect of tidal volume on respiratory system elastance and resistance during anesthesia and paralysis. Am Rev Respir Dis 1992; 145: 522–526
Fahy B, Njoku M, Agarwal M, Barnas GM. Lung and chest wall properties in mechanically ventilated patients. Crit Care Med 1995; 23: A125
Peslin R, Fredberg JJ. Oscillation mechanics of the respiratory system. In: Macklem PT, Mead J, eds. Handbook of physiology. Section 3: The respiratory system, vol III, part 1. Bethesda, MD: American Physiological Society, 1986: 145–178
Suki B, Hantos Z, Daroczy B, et al. Nonlinearity and harmonic distortion in dog lungs measured by low-frequency forced oscillations. J Appl Physiol 1991; 71: 69–75
Milic-Emili J, Robatto FM, Bates JH. Respiratory mechanics in anaesthesia. Br j Anesth 1990; 65: 4–12
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The authors thank Colin Mackenzie for his suggestions throughout the experiments.
This work was supported by the National Heart, Lung, and Blood Institute grants HL-33009 and HL-44128.
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Green, M.D., Ho, G., Polu, H. et al. Automated system for detailed measurement of respiratory mechanics. J Clin Monitor Comput 12, 61–67 (1996). https://doi.org/10.1007/BF02025312
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DOI: https://doi.org/10.1007/BF02025312