Greater nasal nitric oxide output during inhalation: effects on air temperature and water content.

The nose conditions the temperature and humidity of nasal air, and the nasal mucosal vasculature supplies heat and water for these processes. We hypothesize that nitric oxide (NO) modulates these processes through vasoactive effects on nasal mucosal vasculature. We measured the temperature, humidity and NO concentrations of nasal air during inhalation and exhalation across the nose and calculated net heat, water and NO output before (controls, n=7) and after inhibition of NO synthase by topical l-NAME (N=5) in healthy humans. We found that calculated NO output across the nasal passages is approximately three-fold greater during inhalation (503+/-105 nL/min) compared with exhalation (162+/-56 nL/min). Moreover, topical administration of l-NAME decreased nasal air temperature and humidity conditioning and NO output, but these effects were limited to inhalation. We conclude that nasal NO output is greater during inhalation than exhalation in humans. Our findings also support a role of nasal NO in temperature and humidity conditioning of nasal air.

Exhaled nasal nitric oxide output is reduced in humans at night during the sleep period.

The physiologic function of nasal nitric oxide (NO) release is unknown. In prior experiments, topical NG-nitro-L-arginine methyl ester (L-NAME) on nasal mucosa reduced exhaled nasal NO output and caused daytime sleepiness. We hypothesized that nasal NO output is reduced at night during the sleep period. We measured exhaled nasal NO concentration and minute ventilation and calculated nasal NO output in humans over 24 h. Daytime awake NO output was greater than NO output at night during sleep or transient wakefulness. Exhaled NO concentration decreased during sleep along with minute ventilation. A daytime voluntary reduction in minute ventilation also decreased nasal NO output but exhaled NO concentration increased. Nasal NO output was not changed by body position. We conclude that exhaled nasal NO output is decreased at night due to decreased mass flow of NO into nasal air in addition to decreased minute ventilation. Our findings suggest a role of nasal NO in sleep or in the physiologic processes accompanying sleep.

Use of a clinical pathway to manage unsuspected radiographic findings.

STUDY OBJECTIVES: To describe our 5-year experience with a clinical pathway used to ensure the timely communication and evaluation of unsuspected radiologic findings (URFs) noted on clinically requested chest imaging. DESIGN: Prospective data collection on clinical practice. SETTING: Academically affiliated Veterans Affairs medical center. PARTICIPANTS: Pulmonary physicians, nurses, and radiologists. RESULTS: Over a period of 5 years, 1,629 URFs were referred to the pathway (from chest radiographs, 1,359 [83.4%]; from CT scans, 270 [16.6%]). Most URFs (78%) were nodules, with a specific diagnosis made in one third of URFs, and with a specific diagnosis thought to be clinically significant in another one third of URFs. The most common diagnosis was neoplasm, with over two thirds of these diagnoses being lung cancer. One third of lung cancers detected were either stage 1 or 2, with 1 in 17 of all URFs being stage IA lung cancer. The cost of the pathway was estimated at 28,600 dollars per year. CONCLUSIONS: URFs noted on chest imaging are frequently clinically significant, and a systematic approach to managing URFs, such as a clinical pathway, can significantly improve care in a large teaching hospital.

Effects of Ginkgo biloba on exhaled nasal nitric oxide during normobaric hypoxia in humans.

Ginkgo biloba, an extract of the ginkgo tree, may prevent or lessen symptoms of acute mountain sickness in humans. The mechanism of this effect is poorly understood. One hypothesis is that ginkgo alters nitric oxide (NO) metabolism, possibly by scavenging NO or altering nitric oxide synthase expression and thereby lessening the vasodilatory effects of NO. To date, an effect of Ginkgo biloba on NO metabolism has not been demonstrated in humans. We measured exhaled nasal NO output in humans (n = 9) during normoxia and then during acute normobaric hypoxia (goal oxyhemoglobin saturation 75% to 85%) before and after administration of a standardized extract of Ginkgo biloba (120 mg twice daily for 5 days). Oxygen saturation, heart rate, and minute ventilation were similar before and after Ginkgo biloba administration. Exhaled nasal NO output was increased during normoxia following ginkgo (p < 0.02) and reduced during normobaric hypoxia both before (p < 0.02) and following (p < 0.003) ginkgo. Exhaled nasal NO output during normobaric hypoxia was lowest following ginkgo (p < 0.003). We conclude that Ginkgo biloba increases exhaled nasal NO output during normoxia and enhances reduced exhaled nasal NO output during normobaric hypoxia. Our results suggest that Ginkgo biloba may act to reduce AMS through an effect on NO metabolism.

Direct coextensive plethysmography for non-invasive measurement of systemic pressures and volumes.

A method for noninvasive measurement of pressures and fluid volumes of the complete systemic vascular circuit, called direct coextensive plethysmography, is proposed. This includes the pressures of the large veins, small veins, venules, capillaries, arterioles, small arteries, large arteries and nonvascular fluid compartments. It uses a conventional pressure cuff on the outside of the arm, combined with a tetrapolar bioimpedance electrode band to derive a fluid volume indication (impedance) versus pressure profile for the entire system. Determination of state changes in the residual fluid volume versus pressure profile yields physiologic information about the pressures and fluid volumes in the various segments of the vascular circuit and nonvascular fluid compartments. Advanced signal processing techniques have been applied to improve upon early slope change analysis. Initial confirmation of the correlation between the measured large vein pressure and the central venous pressure were made in a small clinical trial with intensive care unit subjects.