Chest wall configurational changes before and during acute obstructive episodes in asthma.

Area of Science:

• Respiratory physiology
• Pulmonary mechanics
• Thoracic biomechanics

Background:

• Asthma is characterized by reversible airway obstruction.
• Chest wall mechanics play a crucial role in respiratory function.
• Understanding chest wall motion during obstruction is vital for asthma management.

Purpose of the Study:

• To investigate the effects of induced bronchial obstruction on chest wall dimensions and motion in asthmatic subjects.
• To characterize the changes in rib cage and abdominal configuration during breathing with airway obstruction.
• To explore the relationship between the severity of obstruction and observed chest wall distortions.

Main Methods:

• Induced bronchial obstruction in 7 healthy asthmatic subjects.
• Measured anteroposterior (AP) and transverse diameters of the rib cage and abdomen.
• Assessed chest wall configuration changes during inspiration and expiration.

Main Results:

• Airway obstruction led to increased end-expiratory AP diameter of the upper rib cage in all subjects.
• Lower rib cage became more elliptical during inspiration in 6/7 subjects.
• A pronounced rocking motion of the sternum was observed during inspiration.
• Chest wall distortions correlated with obstruction severity and resolved as obstruction decreased.

Conclusions:

• Induced bronchial obstruction significantly alters chest wall configuration and motion in asthmatics.
• End-expiratory dimensions suggest an actively maintained increase in functional residual capacity.
• Inspiratory chest wall changes resemble responses to external resistive loading.
• Caution is advised when estimating volume changes from rib cage and abdominal measurements during obstructive episodes.