1. The regional distribution of ventilation was studied with a 133Xe wash-out technique both after rebreathing and after intravenous injection of the isotope in six patients with chronic obstructive lung disease. Measurements were performed in the sitting position during spontaneous and augmented abdominal breathing respectively. The contribution to ventilation of the rib-cage and abdomen was measured with magnetometer recordings of the respiratory variation in the antero-posterior diameters.

2. The relative contribution of the abdomen to ventilation increased from about 40% during spontaneous breathing to about 67% during augmented abdominal breathing.

3. There was no systematic difference in the ventilation distribution between the two breathing patterns.

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