No abstract

Patients with infantile spinal muscular atrophy develop pectus excavatum along with a severe restrictive syndrome as a result of failure to expand the upper chest wall and lungs because of intercostal muscle weakness. By using an automatic motion analyzer to provide three-dimensional computer analyses of images sampled at 25 Hz, 9 spinal muscular atrophy Type II patients and 13 controls underwent kinematic analysis of thoracoabdominal movements partitioned into the upper thorax, lower thorax, and abdominal volume compartments. The analyses were performed during spontaneous breathing for the controls and during spontaneous breathing and while using mechanically assisted ventilation for the patients. Vital capacity, maximum inspiratory pressures, and nocturnal oxyhemoglobin saturation and transcutaneous carbon dioxide tensions were also measured for the patients. The kinematic data demonstrated a paradoxical ventilatory pattern for the spontaneously breathing SMA patients with the following inspiratory volume changes: upper thorax, -6.4+/-9.6%; lower thorax, 7.3+/-15.8%; abdominal, 99.1+/-21.3%. During mechanical ventilation, the compartmental volume changes were as follows: upper thorax, 13.5+/-6%; lower thorax, 13.7+/-7.9%; abdominal, 72.7+/-9.3%. This kinematic pattern is comparable with that seen in spontaneously breathing normal subjects. We conclude that mechanical ventilation can normalize kinematic volume changes during alveolar ventilation and that this might help deter loss of thoracic compliance caused by the chronic hypoventilation of the upper thoracic compartments. Kinematic analysis may be helpful for choosing the ventilation parameters to optimize therapeutic benefits.

Twelve children with spinal muscular atrophy (SMA) type 2 and 13 children without physical disability underwent kinematic analysis of thoracoabdominal volume changes when breathing spontaneously and when breathing deeply. A very accurate optical method of kinematic analysis was used. Volumes were partitioned into upper thoracic, lower thoracic, and abdominal compartments. Abdominal volume increases accounted for 96% of the normal tidal volumes and 87% of the deep breathing volumes for the patients, but only 74 and 41% of the volumes, respectively, for the controls. For the patients the upper thoracic contribution to breathing volumes was --1.7% for normal tidal volumes and 0.3% for deep breathing volumes. Patients with less upper thoracic kinematic reserve were also found to be more likely to have chronic nocturnal hypoventilation. We conclude that kinematic analysis can be helpful in determining differences in regional lung mobility and risk for nocturnal ventilatory dysfunction for children with SMA. Therapeutic interventions need to be addressed to maintain thoracic kinematic reserve and lung compliance and, thereby, to facilitate more normal lung growth and the ability to cough.