The Effect of Pulmonary Secretions on Respiratory Mechanics in Intubated Patients

Abstract

Background

The effect of airway secretions on respiratory mechanics in adult, mechanically ventilated patients has not been reported. We sought to determine whether such an effect existed using a prospective, nonrandomized cohort of medical- and surgical-intensive-care-unit patients.

Methods

Thirty mechanically ventilated patients with increased airways resistance (R_aw ≥ 15 cm H₂O · s · L⁻¹) were enrolled. Peak (P_peak) and end-expiratory pressures (P_pause) were recorded before and after routine standardized endotracheal suctioning was performed (vacuum = -120 torr and 2 passes of the suction catheter separated by 1 minute). Raw and respiratory system compliance (C_rs) were calculated. Mean R_aw and mean C_rs were compared before and after suctioning using paired t tests.

Results

Suctioning reduced Raw in 27 of 30 patients from a mean (SD) of 24.8 (7.9) to 22.1 (5.5) cm H₂O s L⁻¹, p < 0.01). Of 30 patients, 11 experienced ≤ 1 cm H₂O.s. L_-1 reduction in Raw after suctioning and, when a single patient who had an unusually high reduction in resistive pressure is excluded, Raw decreased in the remaining patients from 23.5 (5.0) to 21.6 (5.2) cm H₂O s L⁻¹ (p = 0.15). There was no significant change in Crs following suctioning.

Conclusion

Airway secretions are a relatively small component of increased Raw in our critically ill patients. However, some patients may experience marked reduction in Raw with endotracheal suctioning. Further studies may help identify patients who are most likely to benefit from this therapy.