Influence of abdominal muscles, mesenteric viscera and liver on respiratory mechanics

Abstract

In a group of 13 supine, anesthetized cats initial measurement was made of respiratory elastance, total resistance by sinusoidal pressure, total resistance, k1 and k2 and their ratio of change from breath to breath, the natural frequency, damping factor and mass factor or inertance, and the functional residual capacity (FRC) and tissue resistance. Comparison was then made with the value obtained by remeasurement in the same cat after a) control operation of mid-line abdominal incision; b) incisions eliminating the effects of the abdominal muscles (mid-line vertical plus transverse incision extended to back); c) evisceration of gastrointestinal tract and spleen and d) evisceration plus hepatectomy. The abdominal response was found to be mainly a surface wave response (at a speed of about 150 cm/sec.) above the natural frequency. The abdominal muscles impose a steady force, more like a weight than a spring, which decreases the FRC. The liver contributes significantly to the mass factor and natural frequency, but the viscera do not. About half the tissue resistance consists of a resistance within the abdomen to respiratory movements; since nearly half the total resistance is tissue resistance, this is nearly one fourth the total resistance to respiration. Submitted on June 2, 1958

Input respiratory impedance measured by head generator in preschool children

“…Crs calculated from high-frequency data in infants has been shown to be markedly lower than under quasistatic conditions. 24 This may express structural heterogeneities of the respiratory system, [26][27][28] or more likely, intrinsic mechanical properties of the tissues. 29,30 However, a proper model that estimated Crs was precluded in 44% of our subjects because of insufficient data points at low ; r, correlation of coefficient; SD, residual standard deviation for ln (Y).…”

Evaluation of the forced oscillation technique for the determination of resistance to breathing

“…Since the airways account for approximately two-thirds of the total respiratory resistance in normal subjects (see above), the tissue resistances must account for about one-third. Most of the latter is due to the combined resistances of the lung tissue, the thoracic wall, and the liver (22). The subjects listed in Table IV were studied in an effort to determine whether thoracic wall disease results in a significant increase of the resistance to breathing.…”

Effect of feeding on ventilation and respiratory mechanics in newborn infants.

“…From the time of Keith (1909), a number of authors have speculated on the effects of the abdominal body wall and the abdominal contents on the mechanics of respiration (Bancroft, 1955;Brody, Connolly, and Wander, 1959). Studies which contributed to the understanding of the problem were originally related to interests in the rocking method of artificial ventilation in adults (Colville, Shugg, and Ferris, 1956) and in newborn infants (Avery and O'Doherty, 1962).…”