Journal of applied physiology
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We studied the action of the costal and crural (vertebral) parts of the diaphragm on the lower rib cage in normal supine dogs. The two parts of the diaphragm were separately stimulated by electrodes directly implanted in the muscle or via the different phrenic nerve roots in the neck. The results of the experiments indicate the following. 1) The costal and crural parts of the diaphragm have a different segmental innervation and a different mechanical action on the rib cage. 2) The costal diaphragm expands the lower rib cage when it contracts. ⋯ In the intact animal at functional residual capacity, these two opposite effects cancel each other. 4) The inflationary action of both parts on the rib cage decreases progressively as lung volume increases. The findings also suggest that the rise in abdominal pressure which occurs when the diaphragm contracts expands the lower rib cage by acting through the area of apposition of the diaphragm to the rib cage. These findings also strengthen the idea that the diaphragm actually consists of two muscles.
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We examined the effects of quantity and physical properties of mucus on resistance to steady and oscillatory flows in a circular tube. Gels with similar rheological properties to canine tracheal mucus were prepared from hog gastric mucin or locust bean gum cross-linked with Na2B4O7. A horizontal straight tube (D 1.85 cm) was lined with these mucus simulants to depths ranging from 0.3 to 1.0 mm. ⋯ Recrit, which corresponded to the onset of wave formation in the lining layer, was insensitive to changes in gel depth. However, gel cross-link density did affect the onset of wave formation: in oscillatory flow Recrit was shifted to higher Re, and the rise in f in steady flow was blunted with high degrees of cross-linking. The existence of Recrit and its association with wave formation are consistent with predictions based on two-phase flow theory.
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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.
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The indirect measurement of pleural pressure in neonates is obtained from measurements of esophageal pressure (Pes) with either a liquid-filled catheter or an esophageal balloon-catheter system. The purpose of this investigation was to assess the validity of the water-filled esophageal catheter by comparing the simultaneous changes in Pes and airway opening pressure (Pao) during occluded respiratory efforts. ⋯ During occlusions, changes in Pes and Pao were almost identical in magnitude and timing in each body position studied (right lateral, prone, and supine). We conclude that the water-filled 8-FG esophageal catheter gives an accurate measurement of pleural pressure changes in healthy neonates.