ackground : Mouth occlusion pressure (P0.1) is the mouth pressure developed against a
complete occulsion at 0.1 second after beginning of inspiration from functional residual
capacity. It appears to be an objective index of central inspiratory neuromuscular drive and
effectiveness of respiratory muscles contraction. It is simple to examine and dosen'T depend
on the patients' cooperation. The occlusion itself does not produce a change in the neuronal
discharge supplied to the respiratory muscles and it bears a constant relationship to the
neuronal discharge. Furthermore, P0.1 is not affected by several factors which may have
influence on the effectiveness of respiratory muscles contraction. Consequently, it is a valid
index without being affected by patients' consciousness, autogenous reflexes, lung mechanics
such as repiratory flow-resistance or compliane, and vagal reflex for lung volume.
Methods : We did this study in sequence of arterial blood gas examination, flow-volume
curve, body plethysmography, diffusion capacity and measurement of P0.1. The subjects were
divided into 4 groups such as normal control groups below 35 years old and above 50 years
old, and the patient groups of obstructive and restrictive pulmonary diseases. P0.1 was
measured during breathing of the ambient air and, again during 6% CO2-rebreathing with
simultaneous measurement of ventilatory parameters. Here ventilatory parameters were
MV/P0.1 (minute ventilatory volume/P0.1), T1/Tt(inspiratory time/total respiratory
tiem),VT/T1 ((tidal volume/inspirtory time), and P0.1/VT/T1 (P0.1/tidal volume/inspiratory
time.)
Results : P0.1, MV/P0.1 and P0.1/VT/T1 showed a significant difference between the
control groups and patient groups, and also between the patient groups of obstructive and
restrictives diseses during breathing of the ambient air. P0.1 and P0.1/VT/T1 showed a
significant difference between the control groups and patient groups during CO2-rebreathing.
Significant correlations were found between P0.1 and MV/P0.1 and, between P0.1 and
P0.1/VT/T1 during breating of the ambient air. During CO2-rebreathing, P0.1 and
P0.1/VT/T1 correlated significantly. We did not find a difference between the patients of
normal PaO2 and those with hypoxemia. But, there was a characteristic change of P0.1 in
the hypercapnic patient group compared with the normocapnic patient group through
CO2-rebreathing.
Conclusion : As a result of above study, we think P0.1 and P0.1/VT/T1 as valid indexs of
central inspiratory neuromuscular drive and effectiveness of respiratory muscles contraction.
They are useful in the supportive measure for the diagnosis of far-advanced chronic lung
disease which is accompanied by CO2 retension.
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