Size distribution of recruited alveolar volumes in airway reopening

Abstract

In 11 isolated dog lung lobes, we studied the size distribution of recruited alveolar volumes that become available for gas exchange during inflation from the collapsed state. Three catheters were wedged into 2-mm-diameter airways at total lung capacity. Small-amplitude pseudorandom pressure oscillations between 1 and 47 Hz were led into the catheters, and the input impedances of the regions subtended by the catheters were continuously recorded using a wave tube technique during inflation from -5 cm H(2)O transpulmonary pressure to total lung capacity. The impedance data were fit with a model to obtain regional tissue elastance (Eti) as a function of inflation. First, Eti was high and decreased in discrete jumps as more groups of alveoli were recruited. By assuming that the number of opened alveoli is inversely proportional to Eti, we calculated from the jumps in Eti the distribution of the discrete increments in the number of opened alveoli. This distribution was in good agreement with model simulations in which airways open in cascade or avalanches. Implications for mechanical ventilation may be found in these results.

The Estimation of Lung Mechanics Parameters in the Presence of Pathology: A Theoretical Analysis

“…This phenomenon is expected, for example, in acute lung injury. Indeed, Suki et al 24 measured Z L continuously during slow inflation of a collapsed lung to show that recruitment occurs in discrete cascades of airway openings. The present analysis, however, is the first to consider how recruitment occurring during the actual measurement of Z L might affect what is measured.…”

Crackle sounds and lung recruitment

“…The distribution of the recruited ∆Vs has been predicted to be a power law with an exponent of 2 [21] and has recently been measured indirectly [6]. Our data reflect a direct assessment of the distribution of alveolar recruited ∆Vs.…”

“…The distribution of these ∆Vs, which correspond to avalanches reaching the alveoli, should follow a power law [6,33].…”

Computer simulation of human breath-hold diving: cardiovascular adjustments

“…A slow forced expiration to RV followed by chest strapping is known to reduce lung volume below that of voluntary effort (Douglas et al 1981), demonstrating that RV is not necessarily an anatomical limitation of the lungs. Alveoli commonly reach their closing volumes during full expiration and immersion (Bondi et al 1976), collapse harmlessly, and then reopen with a deep inspiration (Salmon et al 1981;Suki et al 2000). A degree of tracheal compression can occur in some individuals under negative pressure owing to invagination of the trachealis muscle spanning the posterior wall (Lindholm and Nyrén 2005).…”