Relationship to Changes in Breathing Pattern and Pco2 during Acute Increase in Airway Resistance in Patients with Chronic Obstructive Pulmonary Disease1•2

for magnitude production of pressure was Inversely relatad to changes in tidal volume during both modes of Increases in airway resistance (r = -0.61, P < 0.01 for both bronchoconstriction and exter· nal resistive loads). Patients with the highest exponents for pressure changes (highest slopes) demon· strated the greatest decreases In tidal volume. Consequently, a direct relationship was found be­ tween the magnitude of the exponent and the magnitude of CO2 retention during loaded breathing and bronchoconstrlction (r = 0.81, P < 0.01). These findings suggest that the intensity of respiratory sensations can affect load compensation. The respiratory responses to Increases in airway resls· tance may be Influenced by a need to minimize discomfort level, Involving compromise between a need to reduce the conscious awareness of inspiratory pressure changes and the drive to Intensify respiration to maintain eucapnla. AM REV RESPIR DIS 1985; 132:1214-1218 determinants of the pattern of breath­ ing and the level of ventilation adopted by patients with lung disease. Moreover, since the magnitude of CO2 retention in patients with COPD is related to the size of the tidal volume (11-14), modulation of the pattern of breathing may have an important effect on the severity of respi­ ratory failure when lung mechanics are disturbed. In the present study, we evaluated the