Philip Cole

The site and function of the nasal valve

Previous observers have suggested that the main site of respiratory airflow resistance is localized to the vestibular region of the nose. This resistive segment of the airway was investigated using a “head‐out” body plethysmograph in subjects with anatomically normal noses (a) untreated, (b) congested and (c) decongested. In all three conditions, 2/3 of the total nasal airflow resistance was found within the bony cavum in the vicinity of the pyriform aperture and about 1/3, in the cartilaginous vestibule. As might be expected, caval resistance changed proportionately with the degree of mucosal congestion; but, more surprisingly, vestibular resistance changed similarly. This was due in part to the observed forward expansion of the anterior ends of the inferior turbinates with congestion. EMG recordings in subjects breathing through both nostrils demonstrated a gradation of inspiratory alar dilator muscle activity with increased minute ventilation and with mucosal congestion, and there was no evidence of inspiratory alar collapse. But with elevated ventilation through one nostril only, or when the alar muscles were paralyzed by lidocaine block of the VIIth nerve, alar collapse occurred.

The switching point from nasal to oronasal breathing

The switching point from nasal to oronasal breathing during incrementally graded submaximal exercise was determined in 30 (14 M, 16 F) healthy adult volunteers. Nasal airflow was measured by a pneumotachograph attached to a nasal mask. Oral airflow was determined as the difference between nasal airflow and total pulmonary airflow, the latter being measured by a head-out exercise body plethysmograph. The airflow and pressure signals were sampled every 20 msec by a micropressor, which calculated respiratory volumes and nasal work of breathing, and produced an on-line print-out. Twenty of the 30 subjects (normal augmenters) switched from nasal to oronasal breathing at submaximal exercise of 105.0 W (SD = 30.1), four subjects (mouth breathers) breathed habitually oronasally, five subjects (nose breathers) persistently breathed through the nose only, and one subject showed no consistent nose/mouth breathing pattern. In normal augmenters, the onset of oronasal breathing (VE 35.3 +/- 10.81 . min-1) was quite consistent individually, but varied considerably between inividuals without showing a significant sex difference. The factors most closely related to the switching point were rating of perceived exertion of breathing and nasal work of breathing.

Site of upper airway obstruction in patients with idiopathic obstructive sleep apnea

We developed a technique to determine the site of upper airway obstruction in patients with idiopathic obstructive sleep apnea (OSA). This technique is based on the analysis of inspiratory airflow pressures at various levels of the pharyngeal airway during sleep. Pharyngeal pressure was measured by a moveable Millar catheter pressure transducer. The catheters position in the airway was localized radiographically. Ten patients with OSA were tested: five patients were found to have upper airway obstruction at the level of the soft palate, and five had upper airway obstruction at the base of the tongue. We concluded that measuring airway pressures at multiple sites along the airway is useful in localizing the site of obstruction in patients with OSA, and may have important implications in terms of the patients response to surgical treatment.

Acoustic rhinometry in the evaluation of nasal obstruction.

Acoustic rhinometry (AR) is a recently developed objective technique for assessment of geometry of the nasal cavity. The technique is based on the analysis of sound waves reflected from the nasal cavities. It measures cross‐sectional areas and nasal volume (NV). To obtain dependable assessments of nasal resistance by rhinomanometry or cross‐sectional area measurements by AR, it is essential that the structural relations of the compliant vestibular region remain undisturbed by the measuring apparatus. The use of nozzles in making these measurements carries a great risk of direct distortion of the nasal valve. We used a nasal adapter that does not invade the nasal cavity and a chin support that stabilizes the head. In 51 healthy nasal cavities, the average minimum cross‐sectional area (MCA) was 0.62 cm2 at 2.35 cm from the nostril and 0.67 cm2 at 2 cm from the nostril, respectively, before and after topical decongestion of the nasal mucosa. The MCA and NV findings in this group were significantly higher than MCA and NV (P<0.001) in people with structural or mucosal abnormalities before mucosal decongestion. After mucosal decongestion, the MCA and NV were significantly higher in healthy nasal cavities than in nasal cavities with structural abnormalities (P<0.001) but were not higher than nasal cavities with mucosal abnormalities (MCA, P = 0.05; NV, P = 0.06). A nozzle was applied in 20 healthy nasal cavities after mucosal decongestion, and a significantly higher MCA was found compared to measurements made with the nasal adapter (P = 0.02). We conclude that the nasal adapter, which does not invade the nasal cavities, avoids the distortion of the nasal valve and gives more accurate results.

The effect of unilateral and bilateral nasal obstruction on snoring and sleep apnea

The purpose of this study was to compare apnea and snoring in patients with different patterns of nasal resistance: normal, high unilateral, and high bilateral. The authors examined 683 unselected patients referred for evaluation of snoring and possible sleep apnea. All patients had determination of nasal resistance (performed during wakefulness in the seated posture) and nocturnal polysomnography including quantitative measurement of snoring. Analysis of variance showed no significant difference in apnea and snoring indices among the three nasal resistance groups (normal, high unilateral, and high bilateral). Furthermore, there was no significant difference in the frequency of patients with different severity of apnea and snoring among the three groups. It is concluded that 1. unilateral and bilateral elevation of nasal resistance may lead to equally severe snoring or apnea; 2. there is no direct relationship between awake seated nasal resistance measurement and sleep disordered breathing; and 3. measurements of supine nasal resistance during sleep may be required to elucidate the relationship between sleep‐disordered breathing and nasal obstruction.

Site of airway obstruction in patients with obstructive sleep apnea before and after uvulopalatopharyngoplasty

This study describes a simple method, based on a movable catheter technique, for use during routine polysomnography to identify the site of obstruction, and this has been applied to 51 patients with suspected sleep apnea. The obstruction was found to be retropalatal in 30, retrolingual in 7, and could not be determined in 14 patients (12 had no sleep apnea, 1 did not sleep, and 1 had central sleep apnea). Twelve of these patients had uvulopalatopharyngoplasty with preoperative and postoperative polysomnograms to determine the site of obstruction. The preoperative obstruction was retropalatal in nine and retrolingual in three. Postoperatively, four patients (one with retrolingual obstruction and three with retropalatal obstruction) no longer had sleep apnea. In the remaining eight patients, the site of obstruction was unchanged from the preoperative one. Several conclusions result: 1. the movable catheter technique offers a simple way to determine the site of obstruction in patients with significant obstructive sleep apnea, 2. most such patients obstruct in the retropalatal region, and 3. preoperative localization of the site of obstruction to the retropalatal region does not seem to improve the surgical outcome of uvulopalatopharyngoplasty.

The four components of the nasal valve.

The nasal valve consists of four distinct airflow-resistive components. (i) The vestibule terminates in an airflow-resistive aperture between the septum and the caudal end of the upper lateral cartilage. Its cross-sectional area is stabilized by the cartilaginous structures and by inspiratory isometric contractions of alar dilator muscles. Its walls are devoid of erectile tissues that might otherwise affect its cross-sectional area and airflow resistance. By contrast, (ii) the bony entrance to the cavum is occupied by erectile tissues of both (iii) lateral (turbinate) and (iv) septal nasal walls that modulate the cross-sectional area of the airway and airflow resistance. The body of the cavum offers little resistance to airflow. Valve constrictions induce “orifice flow” of inspiratory air as it enters the body of the cavum, disrupting laminar characteristics and thereby enhancing exchanges with the nasal mucosa of heat, water, and contaminants. Acoustic rhinometric and rhinomanometric measurements show the sites, dimensions, and resistances of the valve constrictions and indicate that it is seldom necessary to extend septal and/or turbinate surgery far beyond the piriform aperture in the treatment of nasal obstruction.

Acoustic rhinometric assessment of the nasal valve.

The aims of this study are to assess nasal valve cross-sectional areas in healthy noses and in patients with nasal obstruction after rhinoplasty and to evaluate the effect of an external nasal dilator on both healthy and obstructive nasal valves. Subjects consisted of (i) volunteers with no nasal symptoms, nasal cavities unremarkable to rhinoscopy and normal nasal resistance and (ii) patients referred to our clinic complaining of postrhinoplasty nasal obstruction. All subjects were tested before and after topical decongestion of the nasal mucosa and with an external nasal dilator. In 79 untreated healthy nasal cavities the nasal valve area showed two constrictions: the proximal constriction averaged 0.78 cm2 cross-section and was situated 1.18 cm from the nostril, the distal constriction averaged 0.70 cm2 cross-section at 2.86 cm from the nostril. Mucosal decongestion increased cross-sectional area of the distal constriction significantly (p < 0.0001) but not the proximal. External dilation increased cross-sectional area of both constrictions significantly (p < 0.0001). In 26 post-rhinoplasty obstructed nasal cavities, only a single constriction was detected, averaging 0.34 cm2 cross-section at 2.55 cm from the nostril and 0.4 cm2 at 2.46 cm from the nostril, before and after mucosal decongestion respectively. External dilation increased the minimum cross-sectional area to 0.64 cm2 in these nasal cavities (p < 0.0001). We conclude that the nasal valve area in patients with postrhinoplasty nasal obstruction is significantly smaller than in healthy nasal cavities as shown by acoustic rhinometry. Acoustic rhinometry objectively determines the structural and mucovascular components of the nasal valve area and external dilation is an effective therapeutical approach in the management of nasal valve obstruction.

Biophysics of nasal airflow: a review.

An account is given of the constituents of the flow resistive nasal valve, their aerodynamic function, and the essential role they play in processing inspiratory air. The relatively fixed structural component and the variable mucovascular components of the lateral and medial nasal walls are described, and particular attention is drawn to the septal mucovascular component because its existence is not universally recognized. Common sources of error in subjective and objective assessments of obstruction to nasal respiratory airflow are discussed. Comments are presented advocating limitations of surgical interference in the treatment of mucosal and structural nasal airway obstruction.

Posture and the Nasal Cycle

The experiments reported in this communication show that the spontaneous nasal cycle of airflow resistances, which alternates between cavities of seated subjects, persists in healthy young adults standing, supine, and laterally recumbent. In addition, persistence of the cycle was recorded throughout 24–hour periods of unrestricted light activity, rest, and recumbency. Recumbency was found to augment amplitude of the cycle, yet resistance of the combined nasal cavities showed little change to accompany daytime activity or nocturnal sleeping postures. In subjects with normal noses, resistance remained similar to that of upright subjects in the range of 2 to 3 cm of H2O/L/s. By contrast, noses with fixed unilateral obstruction showed high cyclical resistances of the combined nasal cavities. The importance of the cycle in rhinoscopic assessment, nasal airway obstruction, and breathing disorders of sleep is discussed.