Effects of airway anesthesia on pattern of breathing and blood gases in patients with chronic obstructive pulmonary disease during acute respiratory failure.

To assess the role played by airway receptors in the genesis of rapid and shallow breathing of patients with chronic obstructive pulmonary disease (COPD), we studied the effects of airway anesthesia in 14 patients with COPD during acute respiratory failure. Airway anesthesia was performed by fiberoptic xylocaine administration from the larynx to the subsegmental bronchi, all patients being intubated or tracheostomized. A small decrease in minute ventilation of 6 +/- 1% of the control values occurred after airway anesthesia. This was due to a decrease (p less than 0.01) in respiratory frequency (f) (14.5 +/- 1%). The latter resulted from an increase (p less than 0.0005) in the expiratory time, whereas the inspiratory time did not change significantly. On the other hand, tidal volume increased (p less than 0.02) by 10.1 +/- 0.6%. In all patients, these modifications were accompanied by arterial blood gas deterioration, mean PaO2 and PaCO2 of 42 +/- 3 mmHg and 62 +/- 3 mmHg, respectively, 15 min after xylocaine administration, as compared with 48 +/- 2 mmHg and 54 +/- 2 mmHg, respectively, during the control period. No correlation was found between the changes in minute ventilation and PaO2 or PaCO2. We conclude that (1) activation of airway receptors are involved in the determination of the rapid and shallow breathing observed in patients with COPD during acute respiratory failure, and (2) airway xylocaine anesthesia that worsens arterial blood gases is contraindicated in these patients.