Endoscopic grading systems for nasal polyps: are we comparing apples to oranges?

Endoscopic grading of nasal polyps (NP) is typically a coprimary endpoint in clinical trials evaluating treatments for chronic rhinosinusitis with nasal polyps (CRSwNP). However, a consensus on the most effective way to grade nasal polyps has not been reached. Different scales have been used, hampering the interpretation of data across trials. This review compares the characteristics of NP grading systems used in registration trials for approved NP treatments. These fundamental differences in grading systems make quantitative comparison of outcomes between trials inaccurate and potentially misleading. In lieu of a universal grading system, reporting the baseline distribution of polyp grades (unilateral and/or summed/total grades), as well as changes from baseline over time by baseline grade may help improve interpretability of outcomes and reduce inaccuracy when attempting cross-trial comparisons and making therapeutic decisions.

Deposition of drugs in the nose and sinuses with an exhalation delivery system vs conventional nasal spray or high-volume irrigation in Draf II/III post-surgical anatomy.

BACKGROUND: Endoscopic sinus surgery is often performed to improve delivery of topical medication into sinus cavities. Intranasal steroids are guideline recommended in post-surgical patients, and experiments with cadavers suggest that surgery improves delivery of drug into sinuses. Exhalation delivery systems (EDS) use a new mechanism for intranasal delivery and have been shown to reach superior/posterior regions of the nasal cavity better than nasal sprays in unoperated patients. METHODS: Silicone casts of the nasal cavity and sinuses from a patient after Draf II, and then Draf III, were made from high-resolution computed tomography (CT) data using 3D printing. Internal surfaces were coated with liquid-sensitive, color-changing gel. Color changes were evaluated following conventional nasal spray delivery (0.1 mL x 2) (Nasonex), EDS delivery (0.1 mL x 2) (XHANCE), and high-volume, low-flow (HVLF) delivery (80 mL) with head tilted either 45° or 90°. RESULTS: Conventional nasal spray deposited liquid only in anterior nasal segments. EDS deposited liquid throughout the nasal cavity, in surgically opened ethmoid and maxillary spaces, at entrances of the frontal sinuses in Draf II geometry, and into frontal sinuses in Draf III. Tilted 45° HVLF delivery enters the maxillary sinuses but not the frontal sinuses or the ethmoid region. At full 90° inclination, HVLF delivery reaches most of the frontal and maxillary sinuses but not the roof and posterior wall of the ethmoid region. CONCLUSIONS: HVLF and EDS produced a deep intranasal/intrasinal deposition in the silicone cast compared with conventional nasal spray delivery; both deposited liquid inside the surgically opened sinuses. HVLF offers the benefit of lavage, whereas EDS may be more efficient and convenient.

EXHANCE-3: a cohort study of the exhalation delivery system with fluticasone for chronic sinusitis with or without nasal polyps.

BACKGROUND: Inhaled nasal corticosteroid sprays (INS) are often inadequate to treat chronic rhinosinusitis (CRS). The exhalation delivery system with fluticasone (EDS-FLU; XHANCE®) may improve outcomes in CRS by increasing medication delivery to target superior/posterior anatomic sites. This study assessed safety and efficacy of EDS-FLU in a large population with moderate-to-severe CRS with or without nasal polyps (CRSwNP, CRSsNP). METHODS: Prospective, multicenter, 12-week, single-arm study of EDS-FLU 372 Â#181;g twice daily (BID) at 38 U.S. sites. Safety was assessed by adverse-event evaluations, nasal endoscopy, and ocular examinations. Efficacy was serially assessed by outcomes including nasal endoscopy (Lund-Kennedy Score, polyp grade), patient- and physician-reported outcomes (22-item Sinonasal Outcome Test [SNOT-22]), study-defined surgical indicator assessment, and Patient Global Impression of Change (PGIC). RESULTS: 705 comparatively refractory subjects were enrolled, 603 CRSsNP and 102 CRSwNP [moderate-to-severely symptomatic; baseline SNOT-22 ~43, high rates of prior INS use (92.3%) and/or prior surgery (27.5%)]. More than 90% reported improvement on treatment by PGIC. SNOT-22 scores improved substantially and similarly in patients with NP (-23.7) and without NP (-24.4). Among patients with baseline Lund-Kennedy edema scores >0, 33.3% (CRSwNP) and 54.8% (CRSsNP) had complete resolution of edema. In CRSwNP patients, 48% had polyp elimination in ?1 nostril, 63% had ?1-point improvement in polyp grade, mean bilateral polyp grade decreased from 2.9 to 1.6, and study-defined surgical eligibility decreased. EDS-FLU was generally well tolerated, with a safety profile similar to conventional INS sprays when used to treat CRS CONCLUSION: EDS-FLU 372 #181;g BID in the treatment of CRS with or without polyps was safe, well-tolerated, and produced substantial improvement across a broad range of both objective and subjective measures.

Dose-dependent social-cognitive effects of intranasal oxytocin delivered with novel Breath Powered device in adults with autism spectrum disorder: a randomized placebo-controlled double-blind crossover trial.

The neuropeptide oxytocin has shown promise as a treatment for symptoms of autism spectrum disorders (ASD). However, clinical research progress has been hampered by a poor understanding of oxytocin's dose-response and sub-optimal intranasal delivery methods. We examined two doses of oxytocin delivered using a novel Breath Powered intranasal delivery device designed to improve direct nose-to-brain activity in a double-blind, crossover, randomized, placebo-controlled trial. In a randomized sequence of single-dose sessions, 17 male adults with ASD received 8 international units (IU) oxytocin, 24IU oxytocin or placebo followed by four social-cognitive tasks. We observed an omnibus main effect of treatment on the primary outcome measure of overt emotion salience as measured by emotional ratings of faces (η2=0.18). Compared to placebo, 8IU treatment increased overt emotion salience (P=0.02, d=0.63). There was no statistically significant increase after 24IU treatment (P=0.12, d=0.4). The effects after 8IU oxytocin were observed despite no significant increase in peripheral blood plasma oxytocin concentrations. We found no significant effects for reading the mind in the eyes task performance or secondary outcome social-cognitive tasks (emotional dot probe and face-morphing). To our knowledge, this is the first trial to assess the dose-dependent effects of a single oxytocin administration in autism, with results indicating that a low dose of oxytocin can significantly modulate overt emotion salience despite minimal systemic exposure.

Low-dose oxytocin delivered intranasally with Breath Powered device affects social-cognitive behavior: a randomized four-way crossover trial with nasal cavity dimension assessment.

Despite the promise of intranasal oxytocin (OT) for modulating social behavior, recent work has provided mixed results. This may relate to suboptimal drug deposition achieved with conventional nasal sprays, inter-individual differences in nasal physiology and a poor understanding of how intranasal OT is delivered to the brain in humans. Delivering OT using a novel 'Breath Powered' nasal device previously shown to enhance deposition in intranasal sites targeted for nose-to-brain transport, we evaluated dose-dependent effects on social cognition, compared response with intravenous (IV) administration of OT, and assessed nasal cavity dimensions using acoustic rhinometry. We adopted a randomized, double-blind, double-dummy, crossover design, with 16 healthy male adults completing four single-dose treatments (intranasal 8 IU (international units) or 24 IU OT, 1 IU OT IV and placebo). The primary outcome was social cognition measured by emotional ratings of facial images. Secondary outcomes included the pharmacokinetics of OT, vasopressin and cortisol in blood and the association between nasal cavity dimensions and emotional ratings. Despite the fact that all the treatments produced similar plasma OT increases compared with placebo, there was a main effect of treatment on anger ratings of emotionally ambiguous faces. Pairwise comparisons revealed decreased ratings after 8 IU OT in comparison to both placebo and 24 IU OT. In addition, there was an inverse relationship between nasal valve dimensions and anger ratings of ambiguous faces after 8-IU OT treatment. These findings provide support for a direct nose-to-brain effect, independent of blood absorption, of low-dose OT delivered from a Breath Powered device.

Preliminary efficacy of fluticasone delivered by a novel device in recalcitrant chronic rhinosinusitis.

OBJECTIVE: To assess whether delivery of fluticasone propionate using a novel bi-directional delivery device (Opt-FP) offers therapeutic benefits in patients with chronic rhinosinusitis (CRS). METHODS: A prospective, single centre, randomized, double-blind, placebo (PBO)-controlled, parallel group study was conducted in adult subjects (n=20) with CRS without nasal polyps or only cobblestoned mucosa. Subjects received Opt-FP 400 µg or placebo twice daily for 12 weeks (n=10/group). Outcome measures included symptom scores, RSOM-31, CRS VAS, nasendoscopy, peak nasal inspiratory flow (PNIF) and magnetic resonance imaging (MRI). RESULTS: Endoscopy score for oedema showed a highly significant and progressive improvement (12 weeks (median scores): Opt-FP -4.0, PBO -1.0, p=0.015). PNIF increased significantly during Opt-FP treatment compared to placebo (4 weeks: p=0.006; 8 weeks: p=0.03). After 12 weeks MRI scores in the Opt-FP group improved against baseline (p=0.039) and a non-significant trend was seen versus placebo. The nasal RSOM-31 subscale was significantly improved with Opt-FP treatment (4 weeks: p<0.009, 8 weeks: p<0.016, 12 weeks: NS). Sense of smell, nasal discomfort and combined score were all significantly improved (p<0.05). The Opt-FP was well tolerated. CONCLUSIONS: The OptiNose breath-actuated bi-directional delivery device administering fluticasone propionate (400 µg b.i.d.) is an effective and well tolerated treatment for recalcitrant CRS.

Intranasal sumatriptan powder delivered by a novel breath-actuated bi-directional device for the acute treatment of migraine: A randomised, placebo-controlled study.

INTRODUCTION: Intranasal sumatriptan is an option for the treatment of migraine; however, nasal delivery using conventional spray pumps is suboptimal. METHODS: Adult subjects (n = 117) with migraine were enrolled in a multicentre, randomised, double-blind, parallel group, placebo-controlled study. A single migraine attack was treated in-clinic with sumatriptan 10 mg, sumatriptan 20 mg or placebo administered intranasally by a novel bi-directional powder delivery device when migraine was moderate or severe. RESULTS: A greater proportion of subjects who received sumatriptan were pain-free at 120 minutes compared with those who received placebo (10 mg/20 mg sumatriptan vs. placebo = 54%/57% vs. 25%, P < .05). Significant benefits were also observed for pain relief at 120 minutes (84%/80% vs. 44%, P < .001/.01) and as early as 60 minutes (73%/74% vs. 38%, P < .01) and for 48 hours sustained pain-free (P < .05). Treatment-related adverse events were rare, with a metallic taste being the most commonly reported (10%/13%). CONCLUSIONS: Sumatriptan nasal powder administered using the new device during a migraine attack was effective and well tolerated.

A new method for the remote collection of nasal and exhaled nitric oxide.

STUDY OBJECTIVES: The present study introduces a method that has been developed to improve the remote collection and transportation of gas samples from the nose and lungs. DESIGN: Assessment of agreement between two methods of clinical measurements. SETTING: Noninvasive exhaled gas measurement at a respiratory research laboratory. PARTICIPANTS: Ten nonsmoking adult volunteers (median age, 44 years; age range, 33 to 53 years; men, 6; women, 4) were recruited. MEASUREMENTS AND RESULTS: Exhaled nitric oxide (ENO) and nasal nitric oxide (NNO) outputs were measured directly (on-line) and remotely (off-line). With the velum closed, lung air was exhaled at fixed flows (ie, 6, 8, and 10 L/min) (ENO) or room-air was aspirated through the nose in series at one fixed flow (ie, 5 to 8 L/min) (NNO). The off-line nitric oxide (NO) measurements were achieved by a gas collection tube system, which consisted of a flow control unit, a tube reservoir with one-way valves at both ends, and an interrupter valve allowing the trapping of gas inside the tube and eliminating the inclusion of "dead space." After clamping, the reservoir may store and transport the gas samples for delayed analysis. The coefficient of variation of three consecutive NO measurements was < 3% for both on-line and off-line ENO and NNO. The correlations between on-line and off-line measurements in both ENO and NNO outputs were high (r = 0.99; R(2) = 0.99), and, unlike previous studies using bag-collection, the ENO outputs for on-line and off-line measurements were in good agreement (Bland-Altman test) at all flows tested. CONCLUSIONS: The tube gas collection system eliminates the dead space and contamination during the gas sampling and permits the cost-effective and reliable off-line collection of both nasal and exhaled gas samples.

Gas and dust exposure in underground construction is associated with signs of airway inflammation.

Exposure to gases and dust may induce airway inflammation. It was hypothesized that heavy construction workers who had been exposed to dust and gases in underground construction work for 1 yr, would have early signs of upper and lower airway inflammation, as compared to outdoor workers. A study group comprising 29 nonsmoking underground concrete workers (mean +/- SD age 44+/-12 yrs), and a reference group of 26 outdoor concrete workers (39+/-12 yrs) were examined by acoustic rhinometry, nasal and exhaled nitric oxide spirometry and a questionnaire on respiratory symptoms. Exposure measurements were carried out. The underground workers had higher exposure to total and respirable dust, alpha-quartz and nitrogen dioxide than the references (p<0.001). The occurrence of respiratory symptoms was higher in the underground workers than in the references (p<0.05). Exhaled nitric oxide (NO) (geometric mean+/-SEM) was higher in the underground workers than in the references (8.4+/-1.09 versus 5.6+/-1.07 parts per billion (ppb), p = 0.001), whereas spirometric values were comparable. The underground workers had smaller nasal cross-sectional area and volume than the references, and more pronounced increases after decongestion (p<0.001). To conclude the exposure in underground construction may cause nasal mucosal swelling and increased levels of exhaled nitric oxide, indicating signs of upper and lower airway inflammation.

Accuracy of acoustic rhinometry.

OBJECTIVES: The objective of this study was to evaluate the ability of acoustic rhinometry (AR) (Rhin2100, Rhinometrics, Lynge, Denmark) to accurately determine the dimensions (cross-sectional areas and volumes) of the curved and complex slit-like geometry of the nasal airway. MATERIALS AND METHODS: A plastic model representing the replicate of a decongested nasal airway was produced by stereolithographic techniques from a 3-D MRI-scan. The exact dimensions of this model was determined from a high resolution CT-scan. Dimensions perpendicular to the curved course of the acoustic pathway were compared with dimensions inferred from parallel sections. The impact of sound loss to the paranasal sinuses and the ability to detect posterior volume changes was tested in the same model. RESULTS: The error in volume determination was < 14% for the MCA and < 8% for the volumes, whereas the error reached 52% for dimensions calculated from parallel sections in the coronal plane. The influence of the simulated maxillary sinuses depend primarily on the size of the ostia and may represent an important source of error for posterior measurements, in particular after decongestion. CONCLUSIONS: The accuracy of acoustically derived dimensions of the 3-D model depend on the orientation of the planes used to calculate the dimensions of the model. Volume estimates based on the smallest cross-sectional areas in points along the acoustic pathway correlate well with acoustically derived volumes, whereas single cross-sectional areas are more susceptible to error. Sound leakage to patent sinus ostia reduce the accuracy of posterior measurements.

Dichotomous physiological effects of nocturnal external nasal dilation in heavy snorers: the answer to a rhinologic controversy?

The purpose of this article was to study the impact of external dilation on nasal airway dimensions, sleep architecture, and snoring. Eighteen heavy snorers without severe obstructive sleep apnea syndrome (mean apnea-hypopnea index (AHI) 9.3) reporting nocturnal nasal obstruction were enrolled in a randomized (controlled) cross-over study, evaluating subjective and objective effects of external nasal dilation (Breathe Right, 3M). The active dilator was also worn during a one-week pretrial run-in period. Polysomnography, recording of snoring sounds, and repeated acoustic rhinometry were performed on two consecutive nights, one with the active dilator and one with a placebo strip. The significant subjective improvement reported during the run-in period compared to the preceding period without dilator (p < 0.01), remained only for nasal patency (p < 0.05) when comparing the two nights in the sleep laboratory. The nasal dimensions increased significantly (p < 0.001) with the active dilator compared to placebo, both in the evening and the next morning. In a subgroup (n = 6) of habitual snorers (AHI < 10) with severe morning obstruction (combined minimal cross-sectional area < 0.6 cm2), external dilation significantly improved the mean sleep PaSO2 (92.4 --> 96.7) and the percentage of sleep with a PaSO2 < 95% (49.9% --> 4.9%) (p < 0.05). In this subgroup there was a trend toward reduction in (7.4 --> 5.4) (p = 0.06), whereas the AHI increased significantly in the group of 12 with larger nocturnal nasal dimensions (p < 0.05). Duration and intensity of snoring remained unchanged regardless of the subgrouping. Objective beneficial effects were restricted to nocturnal oxygen saturation and AHI in a subgroup of habitual heavy snorers identified by repeated acoustic rhinometry, in whom external dilation objectively relieved marked nocturnal nasal obstruction. This finding may provide a logical explanation for the conflicting results of medical, surgical, and mechanical expansion of the nasal dimensions on snoring and sleep disturbances. (American

Nitric oxide in the nasal airway: a new dimension in otorhinolaryngology.

The discovery that the gas nitric oxide (NO) is an important signaling molecule in the cardiovascular system earned its Nobel prize in 1998. NO has since been found to play important roles in a variety of physiologic and pathophysiologic processes in the body including vasoregulation, hemostasis, neurotransmission, immune defense, and respiration. The surprisingly high concentrations of NO in the nasal airway and paranasal sinuses has important implications for the field of otorhinolaryngology. NO provides a first-line defense against micro-organisms through its antiviral and antimicrobial activity and by its upregulation of ciliary motility. Nasal treatments such as polypectomy, sinus surgery, removal of hypertrophic adenoids and tonsils, and treatment of allergic rhinitis may alter NO output and, therefore, the microbial colonization of the upper airways. Nasal surgery aimed at relieving nasal obstruction may do the same but would also be expected to improve pulmonary function in patients with asthma and upper airway obstruction. NO output rises in a number of conditions associated with chronic airway inflammation, but not all of them. Concentrations are increased in asthma, allergic rhinitis, and viral respiratory infections, but reduced in sinusitis, cystic fibrosis, primary ciliary dysfunction, chronic cough, and after exposure to tobacco and alcohol. Therefore, NO, similar to several other inflammatory mediators, probably subserves different functions as local conditions dictate. At present, it seems that the measurement of NO in the upper airway may prove valuable as a simple, noninvasive diagnostic marker of airway pathologies. The objective of this review is to highlight some aspects of the origin, physiology, and functions of upper airway NO, and to discuss the particular methodological problems that result from the complex anatomy.

Unilateral nasal nitric oxide measurement after nasal surgery.

This study was designed to validate and standardize a method for unilateral nasal nitric oxide (NO) measurement. Fourteen healthy volunteers and 11 patients who had undergone unilateral medial maxillectomy were enrolled. Nasal NO was measured unilaterally by means of a dual pump system, and bilateral nasal NO was measured by aspirating air through the nasal airway in series. The median unilateral NO output was 195 nL/min on the surgical side and 291 nL/min on the contralateral, surgically untreated side (p = .006). The NO output was not significantly different between nostrils in the control group (p = .82). With the bilateral technique, there was no significant difference between the surgery group and the healthy-subjects group (p = .72). The unilateral nasal NO technique is sensitive in determining unilateral differences in nasal NO production. The NO outputs from the nostrils were similar in normal subjects regardless of the nasal cycle, but were significantly lower on the operated side in the unilateral nasal surgery group.

Computational simulation of accumulation of expired air in the infant cot.

Accumulation and re-breathing of CO2 in expired air has been suggested as one possible explanation for the strong association between prone sleeping position and sudden infant death syndrome (SIDS). This preliminary study applying a modern computational fluid dynamics (CFD) program to simulate the aerodynamics in an infant cot supports the idea that accumulation of expired air may occur in the prone position. The literature dealing with the potential association between re-breathing of accumulated CO2 and SIDS is briefly reviewed.

Necrotizing fascitis of the head and neck--report of three cases and review of the literature.

Necrotizing fasciitis (NF) of the head and neck is a rare but potentially life-threatening soft tissue infection primarily affecting the superficial fascial planes. It is caused by group A streptococci or by a synergistic combination of aerobe and anaerobe micro-organisms. If proper treatment is delayed, the infection may cause extensive necrosis of overlying skin, extend to deeper planes and produce severe systemic toxicity. Recent reviews suggest that cervical and facial NF should be considered separate clinical entities with different clinical features and prognosis. In both, early diagnosis with prompt, aggressive surgical and medical treatment is essential to a successful outcome. Three cases of NF of the neck secondary to peritonsillar/parapharyngeal infections are presented and the main characteristics of 117 well-characterized cases of cervical and facial NF are reviewed.

[Nitric oxide in the nose and paranasal sinuses--respiratory tract physiology in a new perspective]. / Nitrogenmonoksid i nese og bihuler--luftveienes fysiologi i et nytt perspektiv.

Nitric oxide (NO) has important functions in a variety of physiological and pathophysiological processes in the body, including vasoregulation, haemostasis, neurotransmission, immunity and respiration. The discovery of surprisingly high concentrations of NO in the nasal airway and paranasal sinuses has important implications for the understanding of airway physiology. The high NO levels in the nasal and paranasal airways contribute to the first line defence against microorganisms. Furthermore, autoinhalation of nasal NO may improve pulmonary function and other remote physiological processes. This airborne messenger system represents a new physiological concept of potential clinical importance. However, NO, like several other mediators, has a dualistic function. Airway NO levels are increased in airway inflammations, such as asthma and allergic rhinitis, but is reduced in cystic fibrosis and other conditions with ciliary dysfunction, sinusitis and after exposure to tobacco and alcohol. Consequently, NO may prove valuable as a non-invasive marker in the diagnosis and monitoring of airway pathologies.

Acoustic rhinometry: a study of transient and continuous noise techniques with nasal models.

The objective of this study is to compare the properties of two of the most frequently used acoustic rhinometers: the EcoVision (Hood Laboratories, USA) using the transient technique, and the Rhin2100 (RhinoMetrics, Denmark) using the continuous wide-band technique. In the wide-band rhinometer (Rhin2100), the transient analog signals of traditional rhinometers (EcoVision), are replaced by a digitally produced continuous wide-band noise signal. Tubular models and a plastic model produced by stereolithography (SLA), representing the true replicate of the nasal anatomy, were used to compare the accuracy of the two rhinometers. The effect of increasing angling (0-50 degrees) between the sound wave tube and the cavity was evaluated in a tubular model. The curves obtained with the two rhinometers showed close similarity, and the acoustically derived volumes correlated well with the volumes of tubular (% error < 4%) as well as the complex nasal model (% error < 10.5%). Both rhinometers underestimated the minimum cross-sectional area (MCA) of the complex nasal model (mean % error complex model: Rhin2100 = -7.6%, EcoVision = -13%). The effect of increasing the angle between the nose adapter and the tubular models was small for both rhinometers (CV < 3% for MCA and CV < 1% for volumes). The similar, and in general, high accuracy of the two rhinometers evaluated, particularly in the complicated geometry of the SLA model, is an indication of the reliability of both. The small effect of changing the angle between the nose adapter and the models was unexpected and very encouraging. Nevertheless, some minor differences in performance and capabilities of the two rhinometers might influence interpretation and comparison of results. Further comparisons in a clinical setting are under current investigation.

Does nasal nitric oxide come from the sinuses?

OBJECTIVE: The purpose of this study was to assess nitric oxide (NO) output by the nose and sinuses. METHOD: In one volunteer, the osteomeatal complex and sphenoethmoidal recess were occluded to isolate the nose from the sinuses. The antrum and frontal sinus were each punctured by two catheters and irrigated with air at constant flow. Nitric oxide output and its rate of accumulation in the absence of air flow were measured in each sinus and in the adjacent nasal cavity. RESULTS: Prior to ostial occlusion, NO output in the nose was 96 nL/min. It decreased by 12% after blockage of all of the ostia. In the isolated sinuses, it was 190 nL/min (antrum) and 68 nL/min (frontal). After 5 minutes stagnation; NO concentration [NO] rose in the occluded sinuses to 24,700 nL/L in the antrum and 22,300 nL/L in the frontal sinus. In the nose, it increased to 29,000 nL/L. When the period of stagnation was prolonged in the frontal sinus, the [NO] reached a plateau. NO output and accumulation were not altered in the nose or either sinus by opening their ostia. In the antrum and frontal sinus, lidocaine reduced NO output and the rate of NO accumulation, but not in the nose. CONCLUSIONS: In this volunteer, 88% of nasal NO was derived from the nose itself. Nitric oxide exchange between the frontal sinus, antrum, and nose was negligible. In the absence of air flow, [NO] rose to a plateau in the nose and frontal sinus. Lidocaine inhibited NO output in the sinuses but not the nose.

Aerodynamic influences on nasal nitric oxide output measurements.

Nitric oxide (NO) concentration in aspirated nasal air is flow-dependent. Nasal NO outputs calculated from steady-state plateaux at flows < 1 l/min are substantially smaller than those at flows > 2 l/min. This study aimed to determine the differences in NO output as calculated from the NO concentration plateaux in aspirated nasal air, resulting from different aspiration flows. Nasal NO was determined by chemiluminescent analysis of air obtained from the nasal passages in series during velopharyngeal closure in 8 healthy adults (flows: 0.2-3.7 l/min) and 5 with symptomatic allergic rhinitis (flows: 0.2-3.7 l/min). Mean NO output in the healthy subjects was stable at approximately 315 nl/l/min at flows of 0.2-0.7 l/min, and increased to a second steady output level of approximately 400 nl/l/min (+28%, p < 0.0001) at more physiological flow rates of 2.7 l/min and higher. The symptomatic subjects had substantially higher NO output at all flows (p < 0.001) (709.3 nl/min at 3.7 l/min) than the non-allergic subjects. The flow dependency of the nasal NO output may be explained by failure at low flows for the air stream to penetrate the peripheral parts of the complex nasal passages, and by the presence of a laminar flow regime in which a marginal lamina would tend to insulate the main stream from the mucosa. Thus, previously reported NO outputs obtained at low flows may underestimate nasal NO output compared to output at higher and more physiological transnasal airflow rates, thus affecting interpretation of results.