Flow dependence of gas distribution and the pattern of inspiratory muscle contraction

Abstract

We measured regional distribution of xenon-133 boli at 0.25, 0.75, and 1.5 l/s in four normal seated subjects during inspirations performed predominantly with intercostal and accessory muscles (IC) or with the diaphragm, accompanied by outward abdominal motion (Ab). In six additional subjects we inferred the topographical distribution of helium boli during similar breaths and flow rates from the slope of the alveolar plateau recorded during a slow expiration (less than 0.5 l/s). Distribution of the helium boli was studied during natural as well as IC and Ab inspirations. At each of the flow rates IC breaths distributed relatively more of the inspired bolus to upper lung regions than did Ab inspirations. Natural breaths at 0.25 l/s resulted in distributions similar to those of Ab inspirations, whereas at 1.5 l/s the distribution approached that of IC inspirations. A three-compartment model, representing upper, middle, and lower lung regions, was used to simulate bolus distribution. The experimental data showed substantial departure from predictions based on regional time constants alone. However, additional small differences in applied pressure (less than 0.50 cmH2O) between the regions satisfactorily accounted for the gas distribution.

Respiratory Function after Paralysis of the Right Hemidiaphragm1

“…Flow dependence of gas distribution, as we measured it, is partly due to different patterns of inspiratory muscle recruitment with high flow maneuvers using rib cage muscles more than low flow maneuvers (24). Therefore in our patient the lack of flow dependence suggested that the pattern of recruitment, emphasizing nondiaphragmatic muscles normally employed at high flow rates, was already operative on the paralyzed side at low flow rates, and persisted without change as flow increased.…”

Distribution of Inspired Gas to Each Lung in Anesthetized Human Subjects

“…1967) and (c) tidal pleural pressure variation (BAKEet a]. , FIXLEY et al 1978. The influence of each of these factors will be discussed in the following paragraphs.…”

Breathing exercises: influence on breathing patterns and thoracoabdominal motion in healthy subjects

“…Next, the participants learned the following breathing exercises which were randomized (computer program): diaphragmatic breathing - the participants had to perform a slow and deep nasal inspiration emphasizing the anterior displacement of the abdomen and avoiding RC displacement 4 , 22 ; inspiratory sighs - short, successive, and slow nasal inspirations until the inspiratory capacity was reached 7 ; sustained maximal inspiration - a slow nasal maximal inspiratory effort to reach the inspiratory capacity, followed by a 3-second post-inspiratory pause 23 ; and intercostal breathing - nasal inspiration emphasizing the displacement of the upper portion of the thorax 9 . For the diaphragmatic breathing, inspiratory sighs, and maximal inspiration, the subjects were instructed to perform a smooth and controlled pursed lip expiration.…”

“…inspiratory sighs) or maximal inspiratory effort 7 , 8 . In addition, the intercostal breathing exercise emphasizes rib cage (RC) compartment muscles, promoting greater displacement of this compartment 8 , 9 . Cuello et al 8 was the first to propose the use of inspiratory sighs and intercostal breathing exercises 8 .…”