Journal of applied physiology
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The pattern of respiratory movements of the vocal cords in relation to airflow and respiratory system resistance was assessed in healthy human volunteers during quiet breathing. Motion pictures of the vocal cords were obtained through a fiber-optic laryngoscope inserted transnasally under topical anesthesia. A simultaneous estimate of lung volume was obtained using either rib cage and abdominal magnetometer coils or an integrated pneumotachograph signal. ⋯ Total respiratory system resistance, assessed by the forced oscillation technique, was negatively correlated with distance between the vocal cords when measured at isoflow points in inspiration and expiration. Analysis of breath-by-breath variations in expiratory airflow and vocal cord position revealed that decreases in airflow accompanied decreases in the distance between the vocal cords. The results of this study indicate that the human larynx participates in the regulation of respiratory airflow by providing a variable, controlled resistance.
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We perfused in situ isolated left lower lung lobes at a steady flow rate in zone 3 condition. When the lobar arterial inflow was suddenly occluded, the arterial pressure (Pa) fell rapidly and then more slowly. When the lobar venous outflow was suddenly occluded, the venous pressure (Pv) rose rapidly and then continued to rise more slowly. ⋯ Under the conditions studied, the middle nonmuscular segment contributed a major fraction of the vascular compliance and less than 16% of the total resistance. The muscular arteries and veins contributed equally to the remaining resistance. We conclude that the arterial and venous occlusion method is a useful technique to describe the resistance and compliance of different segments of the pulmonary vasculature.