ackground : Lung distensibility or elastic recoil is generally evaluated by lung compliance
which is defined as rhe ratio of the change in lung volume to a change in transpulmonary
pressure in the absence of airflow, that is to say, the slope of the pressure-volume curve
(P-V curve). Pulmonary compliance is usually of more clinical interest than chest wall
compliance because the majority of diseases affect the lungs rather than chest wall.
Pulmonary compliance is not constant over the entire range of vital capacity and plotting P-V
relationships results in a curve rather than a straight line. But if it is taken at a particular
volume range, conventionally from functional residual capacity (FRC) to (FRC+0.5 L), the
curve becomes almost nearly linear with consisrent and reproducible slope and because of
the absence of a forced expiration, airway and extrapulmonary factors are not involved.
Dynamic compliance is reduced not only by stiffening of the lung parenchyme but also by
relatively minor change in the airways, and therefore, it is a reliable measure of the
peripheral airway disease rather than lung elasticity.
Methods : Subjects were divided into four groups; normal control groups below 35 years
old and above 50 years old, and patient groups of obstructive and restrictive pulmonary
diseases. We did this study in sequence of arterial blood gas measurement, flow-volume
curve, body plethysmography, diffusion capacity and measurement of lungcompliance.
Esophageal ballon volumes were restricted to less than 0.5 cc and location was confined to
the lower 1/3 of the esophagus. We measured the dynamic compliance about 10 times
during the tidal breathing. After then, to obtain the static expiratory P-V curves, the subjects
performed a sequence of full inflation up to the level of total lung capacity (TLC), where the
breath should be held for two or three seconds at TLC to obtain a near-pleteau of pressure.
The subsequent expiration was then interrupted by obstruction at the mouthpiece after
successive small decrements of volume with 1∼2 seconds pause at each volume. As a result
of smoking the above examination about five times, we obtained the average values of satic
lung comlpiance. Specific compliance, maximal static rscoil pressure, and coefficient of
rstraction were also calculated.
Results : Static compliance was significantly reduced in patient groups of obstructive lung
diseases other than emphysema and restrictive lung diseases. Specific compliance also showed
similar results. Maximal static recoil pressure showed characteristic findings such as the
reduction in extrapulmonary restrictions and elevation in parenchymal restrictions.
Coefficient of retraction was increased only in the cases of restrictive pulmonary diseases.
Results on dynamic compliance by the hypoxia and static compliance by the hypercapnia
showed significant differences and specific compliance results showed significant difference
both by the hypoxia and hypercapnia.
Conclusion : Static compliance and specific compliance were significantly decreased in
pulmonary disease groups and they were thought to be useful indexes for lung elasticity.
Maximal static recoil pressure was useful for differential diagnosis between parenchymal and
extrapulmonary restrictions. Coefficient of retraction was characteristically elevated in
restrictive pulmonary diseases and useful in differential diagnosis between restrictive lung
diseases and normal or obstructive lung diseases. Dynamic compliance was affected by airway
resistance as well as lung volume.
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