January 3, 2002 -- Bethesda, MD -- The nose warms and humidifies air. Previous research efforts have led to an ability to measure how the nose conditions cold, dry air (CDA). The consensus is that the two most important predicting parameters of the nasal air-conditioning process are the blood temperature distribution along the airway walls, or the nasal mucosal temperature, and the volume, or perimeter, of the nasal cavity.
An increase in nasal mucosal temperature by feet warming has been previously shown to enhance the ability of the nose to warm and humidify air. How altering the other important parameter, nasal volume, affects nasal conditioning is the subject of this research.
Background
Assuming a supine position (lying face-up) has been consistently shown to increase nasal airway resistance and decrease nasal volume secondary to an increase in the volume of the capacitance vessels of the nose. Although actual blood volume in the cavernous sinusoids has not been measured in the upright and supine positions, an increase in nasal blood volume is the explanation given for the consistent changes in nasal air cavity volume and nasal airway resistance.
The only other structures within that region are the nasal mucosa with its cavernous sinusoids. Sinusoids are considered the variable responsible for the change in nasal cavity volume on changing from the upright to the supine position. Because the nasal cavity has defined anatomic limits, an increase in blood volume will lead to a reciprocal decrease in nasal cavity volume and vice versa. Supporting this notion is the effect of topical intranasal decongestants, which decrease nasal blood volume and increase nasal cavity volume.
A team of Chicago physiologists have hypothesized that decreasing nasal volume by placing subjects in the supine position would increase the ability of the nose to warm and humidify air compared with unaltered nasal volume in the upright position.
The authors of the study, “Supine Position Decreases the Ability of the Nose to Warm and Humidify Air” are Paraya Assanasen, Fuad M. Baroody, Edward Naureckas, Julian Solway, and Robert M. Naclerio, all from The Pritzker School of Medicine, University of Chicago, Chicago, Illinois. The study and its findings appeared in the December 2001 edition of the Journal of Applied Physiology.
Methodology
Six healthy volunteers with no history of allergic rhinitis (5 men and 1 woman; ages 19 to 31 years, mean, 24 years) were recruited to participate in this study. Their nonallergic status was confirmed by negative skin puncture testing with a panel of common allergens in the Chicago area. No subjects were taking medications within two weeks of the evaluation, and none had other medical problems.
A randomized, two-way crossover study comparing the effects of placing subjects in the upright and supine position on the ability of the nose to warm and humidify air was performed. Subjects were brought to the laboratory on two separate occasions, acclimatizing for 15 minutes before treatment was initiated. On each visit, subjects underwent nasal conditioning measurement in both positions, but the order of the positions was assigned by a predetermined randomization code. At least 48 hours separated the visits to eliminate any potential crossover effect of one CDA challenge on the other.
Blood pressure and pulse were measured. The volume of both nasal cavities was measured by acoustic rhinometry. The more patent or open side was chosen for probe insertion because the less patent side has been shown to be affected most by postural change. Nasal mucosal temperature was measured on the less patent side.
The more exposed nostril was sprayed with three puffs of 0.05 percent oxymetazoline hydrochloride, followed by three puffs (0.3 ml) of four percent topical lidocaine hydrochloride. Five minutes later, a probe containing a temperature sensor was inserted through the nose along the floor of the nasal cavity so that the tip touched the posterior nasopharyngeal wall, and the sensor was suspended in the airstream facing the opposite nostril. Flexible nasopharyngoscopy was then performed to verify the position of the probe. The nostril containing the probe was then occluded anteriorly with a wax plug. After that, a second series of baseline measurements was obtained that included blood pressure, pulse, nasal volume, and nasal mucosal temperature on the less exposed side. The ability of the nose to condition CDA was then measured.
At the end of CDA exposure, before removal of the mask, nasal mucosal temperature was measured in duplicate while the subjects were still wearing the mask. After that, the mask was removed, and measurements of blood pressure, pulse, nasal volume, and nasal mucosal temperature were repeated. The probe was left in the nasal cavity, and nasal volume measurement was performed on the other side was measured every five minutes until the volume returned to the baseline value. Preliminary experiments showed that nasal volume returned to baseline within 30 minutes. After completion of these measurements, nasal conditioning was measured in the other (supine or upright) position. On the other visit, the order of positions during nasal conditioning measurement was reversed.
For example, if the first visit was upright followed by supine position, the second visit would start with supine followed by upright position.
Results
In both positions, increasing the CDA flow rate progressively increased the WG (water gradient across the nose, which represents the amount of water evaporated by the nose to condition air). In the supine position, WG values obtained at all flow rates as well as the total WG were less than those obtained in upright position. For all flow rates, the WG per one volume unit of air was still significantly less in supine position compared with upright position. Other findings included the following:
- Within each position, increasing the CDA flow rate progressively decreased the WG per unit of air, regardless of position.
- When subjects were placed in the supine position, the nasal volume decreased significantly compared with that in the upright position. After nasal conditioning measurement, nasal volume decreased significantly in both positions, and the nasal volume after CDA exposure in the supine position was significantly less than that in the upright position. However, there were no significant differences in net change of CDA-induced decrease in nasal volume between both positions.
- The nasal mucosal temperature in the supine position was not significantly different compared with that in the upright position at baseline. There were statistically significant decreases in nasal mucosal temperature during CDA exposure in both positions. The nasal mucosal temperature during CDA exposure in the supine position was significantly less than that in the upright position.
Conclusions
The research has demonstrated that subjects in the supine position reveal a reduced ability of the nose to condition air. The mechanics of the process remains to be established.
Specifically, nasal mucosal temperature decreased significantly during inhalation of CDA in both positions. Nasal mucosal temperature was significantly less at the end of exposure, and the magnitude of CDA-induced reduction in nasal mucosal temperature was greater in the supine position, compared with the upright position.
Additional Research Ramifications Possible
There may be other ramifications from these research results. Nocturnal worsening of arterial saturation, which appeared to be a body position-related phenomenon, has been reported in patients with congenital heart disease and Eisenmenger's syndrome (cardiac failure with significant right to left shunt producing cyanosis due to higher pressure on the right side of the shunt). Alveolar oxygen pressure and oxygen saturation were significantly decreased in the supine position compared with the sitting position. Because both of these parameters could be corrected with nasal oxygen, a ventilation-perfusion distribution abnormality and/or a diffusion limitation phenomenon rather than an increase in true shunt may be the mechanisms responsible for this finding.
Source
December 2001 edition of the Journal of Applied Physiology.
The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.
Journal
Journal of Applied Physiology