Nasal obstruction: an alternative to ostiomeatal complex dysfunction in sinus disease.

OBJECTIVES: Ostial patency is thought to be essential to the function of the maxillary sinus. Ostiomeatal complex dysfunction has been implicated as a major factor in the pathogenesis of sinus disease. However, recent work in our laboratory has indicated that other factors may also contribute to this process. The objective of this study was to determine the effect of nasal obstruction in maxillary sinus gas composition, independent of its effect on ostial ventilation. STUDY DESIGN: Prospective controlled animal study. METHOD: Independent models of nasal obstruction and ostial occlusion in contralateral sinuses were established. Ipsilateral models of nasal obstruction and ostial occlusion were also created. Gas samples from each of the manipulated sinuses were analyzed on a gas chromatogram and compared. RESULTS: Results revealed a dramatic and highly significant increase in antral carbon dioxide (CO2) concentrations in the sinuses ipsilateral to either an occluded ostium or an obstructed nostril, compared with the controls. These effects on CO2 concentrations were additive when ipsilateral nasal obstruction and ostial occlusion were created. Furthermore, the effect of nasal obstruction in modulation of antral CO2 levels was found to be beyond its effect on hypoventilation of the sinus and to be independent of ostial functional status. CONCLUSIONS: We have established independent models of nasal obstruction and ostial occlusion in the same animal. Our findings suggest that ostiomeatal complex dysfunction might not be the sole underlying factor in the pathogenesis of sinus disease in all individuals. Integrity of nasal airflow seems to have a significant effect on the maintenance of the aerobic antral environment, essential to the maintenance of normal sinus function. Modulation of maxillary sinus gas composition by nasal airflow, independent of ostial patency, may be explained by the possible presence of flow-sensitive receptors in the upper respiratory tract mucosa. Work to identify such receptors is currently in progress.

A potential role for nasal obstruction in development of acute sinusitis: an infection study in rabbits.

The sequence of events that predispose to the onset of sinusitis are usually attributed to pathophysiologic factors within the ostiomeatal complex. Ostial compromise or obstruction with reduced clearance of antral pathogens has been implicated as a major factor that contributes to early sinus disease. Recent work in this laboratory has indicated that other processes may also contribute to this cascade. Using an infectious model in rabbits, the role of nasal obstruction in early, acute sinusitis was studied. Unilateral nasal closure was followed by bilateral inoculation with 10(8) CFU of Streptococcus pneumoniae type 3. Antral gas composition was examined on days 1, 2, 3, 5, 7, and 14, and swabs obtained for culture. Representative rabbits underwent CT scans to evaluate changes in nasal and sinus mucosa. Results showed a significant increase in CO2 and a trend toward a decrease in O2 on the obstructed side. There was also a significant decrease in obstructed CO2 levels from postoperative days (POD) 1-14. Acute sinusitis was not observed in any animal: however, nasal obstruction gave rise to a dramatic prolongation of bacterial retention. On days 2-7 bacteria was consistently cultured from the obstructed side only. CT scans on POD 2 and POD 3 showed mucosal thickening in the sinus and infundibulum on the obstructed side, indicative of sinus pathology. These results indicate that nasal obstruction may be a key factor in the cascade of events that predispose to the onset of sinus disease.

Maxillary sinus mucosal blood flow during nasal vs tracheal respiration.

OBJECTIVE: To determine the effect of changes from nasal to tracheal respiration on maxillary sinus mucosal blood flow in rabbits with unobstructed sinus ostia. DESIGN: Animals underwent tracheotomy with a T tube and then a small window of intact maxillary sinus mucosa was exposed. Mucosal blood flow was recorded during normal nasal respiration using laser-Doppler velocimetry. At hourly intervals, respiration was changed from the nasal to the tracheal route and then back again. SUBJECTS: Ten anesthetized rabbits were used: 5 underwent single and 4 underwent multiple shifts in the respiratory route, while 1 was monitored continuously during long-term nasal breathing only. RESULTS: A significant decrease in maxillary sinus blood flow occurred on switching from nasal to tracheal respiration and a significant increase in blood flow occurred on return to nasal respiration. Where multiple switches were made, blood flow changes diminished in magnitude, but significant decreases (nasal to tracheal) or increases (tracheal to nasal) were evident in all cases. CONCLUSIONS: It is proposed that the maxillary sinus may act in an accessory capacity to the nose for humidification of inspired air via secretions liberated from the sinus ostium. Furthermore, we suggest that nasal airflow is involved with the reflex regulation of sinus blood flow, probably via stimulation of sensory receptors in the nasal cavity. Reduced maxillary sinus mucosal blood flow may thus contribute to supra-systemic levels of antral carbon dioxide. Since elevated carbon dioxide levels have been shown to reduce maxillary sinus mucociliary activity in vitro, nasal airflow compromise may contribute to the initiation of a cascade of pathophysiological events leading to acute sinusitis.