Inspiratory Strength Research Articles

Respiratory mechanics in supine subjects during progressive partial curarization.

Respiratory mechanics were studied in six supine conscious volunteers during progressive muscle weakness produced by infusion of d-tubocurarine. Partial curarization was carried out to the point of abolishing head lift ability and handgrip strength. At all levels of partial paralysis, expiratory muscle strength was significantly more impaired than inspiratory strength. Despite this, subjects maintained relatively normal maximal expiratory flow rates, whereas inspiratory flows decreased significantly. The diminished inspiratory flows are not fully explained by decreased driving pressures during force inspiration, since inspiratory resistance increased significantly with the decreased flow. Inspiratory flow patterns suggest a variable extrathoracic obstruction most likely due to the absence of normal airway abductor activity during inspiration. Maximal respiratory muscle weakness decreased forced vital capacity by 29% and total lung capacity by 15%. The decreased level of lung inflation did not alter lung elastic recoil. Functional residual capacity was unchanged, but inspiratory capacity decreased by 25% and residual volume increased by 38%. These changes are in accord with predictions based on the decreased muscle strength and normal respiratory system recoil.

PULMONARY PHYSIOLOGY IN CHILDREN

Measurements of lung volumes, compliance and resistance, and effective respiratory muscle strength have been carried out in a series of patients with idiopathic scoliosis, scoliosis secondary to poliomyelitis and scoliosis secondary to abnormalities of the vertebral column. The patients with idiopathic scoliosis showed, in general, moderate reductions in vital capacity, while those with poliomyelitis and associated paralysis showed more marked decreases. Residual volume on the average was essentially unchanged in both groups. Compliance was only moderately but consistently reduced in both groups while flow-resistance was only slightly to moderately increased. In the group of patients with idiopathic scoliosis, effective respiratory muscle strength was normal for given lung volumes but inspiratory strength was subnormal. Serial studies show that after fusion, the patients tended to have a further decrease both in respiratory muscle function and in lung volumes. The frequently serious pulmonary dysfunction accompanying the scoliosis secondary to vertebral abnormalities is illustrated.