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Biomedical subjects

N B Pride

Publications and source records attributed to N B Pride.

At least 55 records · Page 3Linked to original sources
PubMed1996

A comparison of the effects of an alpha-agonist, an anti-muscarinic agent and placebo on intranasal histamine challenge in allergic rhinitis.

Autonomic receptors play a part in the physiology and pathology of the nasal mucosa. The effect of an alpha-agonist and an anti-muscarinic agent on histamine-challenge was examined on patients with perennial allergic rhinitis. Nine patients received saline, oxitropium bromide 0.075%, or xylometazoline hydrochloride 0.1% in a double-blind fashion. Sequential challenge with increasing doses of histamine were given and resistance changes, sneezes and volume and content of secretion measured. Histamine challenge produced dose-related increases in nasal resistance (P < 0.0001), lavage fluid volume (P < 0.01) and total protein (P < 0.01). Following xylometazoline, histamine produced little increase in resistance compared with saline and oxitropium bromide (P < 0.0001). The latter reduced the dose-related increase in resistance (P < 0.01) and nasal lavage fluid volume (P = 0.0007) and total protein (P = 0.023) seen with saline. These results confirm the importance of alpha-adrenergic and muscarinic receptors in the human nasal mucosa and suggest mechanisms of action for these drugs in perennial allergic rhinitis.

Adrenergic alpha-Agonists↗
PubMed1995

The effect of topical fluticasone propionate on intranasal histamine challenge in subjects with perennial allergic rhinitis.

The mechanism of action of topical intranasal steroids is obscure. To investigate this, we have studied the effects of a topical intranasal corticosteroid, fluticasone propionate on nasal airflow resistance (Rnaw), secretions, cytological smears and symptoms. Fluticasone propionate aqueous nasal spray was given to 11 patients with perennial allergic rhinitis in a double-blind, placebo-controlled study. On each day, patients were challenged with ascending doses of histamine. Rnaw, secretion volume, total protein, mucin, lysozyme and albumin were measured. Nasal smears were taken and sneezes counted. Diary card data were collected for both treatment periods. There was a significant, dose-related increase in Rnaw and sneezing on histamine challenge. A single dose of fluticasone had no effect on any parameter. After 4 weeks of treatment, resistance measurements were reduced (post-challenge g.m.2.8 cmH2O/l/s, Q1-Q3 1.6-4.8; placebo 4.2, 2.9-5.3: P < 0.0001) as were baseline secretion volumes (mean 2.4 ml/5 min, c.i.1.9-3.0; placebo 3.3, 2.8-3.8: P < 0.05). Eosinophil counts were suppressed (fluticasone 5.8%, c.i. 4.0-15.7; placebo 23.3%, 12.4-34.1: P < 0.05) and the composite symptom score reduced (P < 0.05). Fluticasone has long-term effects on the nasal response to histamine in perennial allergic rhinitis and part of this effect is likely to be vascular.

Administration, Topical↗
PubMed1995

In vivo assessment of diaphragm contraction by ultrasound in normal subjects.

BACKGROUND: Ultrasound allows observation of the thickness of the diaphragm in the zone of apposition in vivo during relaxation and maximum inspiratory efforts. METHODS: Changes of diaphragm thickness were studied by B mode (two dimensional) ultrasound in 13 healthy men aged 29-54 years in the seated position. A high resolution 7.5 MHz ultrasound transducer was held perpendicular to the chest wall in the line of a right intercostal space between the anteroaxillary and mid-axillary lines to observe the diaphragm in the zone of apposition 0.5-2 cm below the costophrenic angle. The changes of thickness were observed while breath holding at total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV). At FRC the thickness while relaxing against a closed mouthpiece and during a maximum inspiratory mouth pressure (PImax) manoeuvre was recorded. The thickening ratio (TR) was calculated as TR = thickness during PImax manoeuvre/thickness while relaxing. RESULTS: Mean (SD) thickness was 4.5 (0.9) mm at TLC, 1.7 (0.2) mm at FRC, and 1.6 (0.2) mm at RV. During the PImax manoeuvre at FRC mean thickness increased from 1.7 (0.2) mm during relaxation to 4.4 (1.4) mm, while mean PImax and TR were -104 (33) cm H2O and 2.6 (0.7), respectively. There was a high degree of correlation between TR and the pressure achieved during the maximum inspiratory manoeuvre (r = -0.82). CONCLUSIONS: Ultrasound provides a non-invasive assessment of diaphragm thickness with change of lung volume and during the PImax manoeuvre which should prove useful in assessing diaphragm mass and contraction in respiratory and muscle disease.

Adult↗
PubMed1995

Continuous nasal positive airway pressure with a mouth leak: effect on nasal mucosal blood flux and nasal geometry.

BACKGROUND: Obstructive sleep apnoea is a common condition. Treatment with nasal continuous positive airway pressure (CPAP), while effective and safe, causes nasal congestion and stuffiness in some patients. The hypothesis that this study aimed to test was that nasal CPAP with a mouth leak and subsequent unidirectional airflow across the nasal mucosa causes an increase in nasal mucosal blood flux and a fall in both nasal volume and minimal cross sectional area. A secondary aim was to study if this could be prevented by humidifying the air inspired with nasal CPAP. METHODS: Nasal CPAP was applied to eight normal subjects who kept their mouths open until they had expired 500 litres. The effect of this on nasal mucosal blood flux and nasal geometry was studied with and without humidification using a laser Doppler blood flowmeter and acoustic rhinometer. In addition, nasal mucosal blood flux was measured in four of the eight subjects before and after nasal CPAP with the mouth closed. RESULTS: Nasal CPAP using room air with the mouth closed did not result in any change in nasal mucosal blood flux; with a mouth leak nasal CPAP using room air was associated with a 65% increase in nasal mucosal blood flux. There was no change in nasal geometry. Nasal CPAP using humidified air with a mouth leak did not cause any change in nasal mucosal blood flux or nasal geometry. CONCLUSION: Nasal CPAP used with an open mouth leads to an increase in nasal mucosal blood flux. This can be prevented by humidifying the air inspired with nasal CPAP.

Adult↗
PubMed1995

Comparison of four methods of assessing airflow resistance before and after induced airway narrowing in normal subjects.

Four methods for assessing airflow resistance were compared in seven normal adults at baseline and after inducing airway narrowing with inhaled methacholine. Airway resistance (Raw) was measured during panting at 1-2 Hz within a body plethysmograph; total lung resistance was measured by using an esophageal balloon during quiet breathing (RLq) and with doubling of frequency while maintaining the original tidal volume; total respiratory resistance (Rrs) was measured at 6 Hz during forced oscillation applied at the airway opening, and interruption resistance (Rint) was measured at midtidal expiratory flow. Three methods of obtaining Rint after airflow interruption were compared [smooth curve fit of mouth pressure (Pm) back extrapolated to valve closure; two-point linear fit of Pm back extrapolated to 15 ms after closure; and Pm at 100 ms after valve closure]. We found similar basal median values (cmH2O.l-1.s) of Raw (1.3), RLq (1.4), RL of double resting frequency (1.9), Rrs (1.7), and smooth curve fit of Pm back extrapolated to valve closure (1.5); basal values of two-point linear fit of Pm back extrapolated to 15 ms after closure (2.4) and Pm at 100 ms after valve closure (4.4) were considerably larger. After induced airway narrowing, all methods of measuring resistance showed significant increases; these were largest with RLq (median %change of 265) and smallest with the three Rint methods (median %change of 62-72). Rint and Rrs methods had poorer sensitivity for detecting bronchoconstriction than lung resistance of Raw. Of the Rint methods, end interruption pressure was the most sensitive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Effects of posture on respiratory mechanics in obesity.

Increased abdominal mass in obesity should enhance normal gravitational effects on supine respiratory mechanics. We have examined respiratory impedance (forced oscillation over 4-26 Hz applied at the mouth during tidal breathing), maximum inspiratory and expiratory mouth pressures (MIP and MEP), and maximum effort flow-volume curves seated and supine in seven obese subjects (O) (mean age 51 yr, body mass index 43.6 kg/m2) and seven control subjects (C) (mean age 50 yr, body mass index 21.8 kg/m2). Seated mean total lung capacity was smaller in O than in C (82 vs. 100% of predicted); ratio of functional residual capacity (FRC) to total lung capacity averaged 43% in O and 61% in C (P < 0.01). Total respiratory resistance (Rrs) at 6 Hz seated was higher in O (4.6 cmH2O.l-1.s) than in C (2.2 cmH2O.l-1.s; P < 0.001); total respiratory reactance (Xrs) at 6 Hz was lower in O than in C. In C, on changing to the supine posture, mean Rrs at 6 Hz rose to 2.9 cmH2O.l-1.s, FRC fell by 0.68 liter, and Xrs at 6 Hz showed a small fall. In O, despite no further fall in FRC, supine Rrs at 6 Hz increased to 7.3 cmH2O.l-1.s, and marked frequency dependency of Rrs and falls in Xrs developed. Seated, MIP and MEP in C and O were similar; supine there were small falls in MEP and maximum expiratory flow in O. The site and mechanism of the increase in supine Rrs and reduction in supine Xrs and the mechanism maintaining supine FRC in obesity all need further investigation.

Airway Resistance↗
PubMed1995

Abnormal intraepithelial airway nerves in persistent unexplained cough?

Idiopathic persistent nonproductive cough (PNPC) is characterized by enhanced cough sensitivity to inhaled capsaicin, suggesting that capsaicin-sensitive afferent airway nerves are either present in increased numbers or functionally upregulated. In 16 patients with idiopathic PNPC and eight healthy control subjects, we measured cough sensitivity to inhaled capsaicin and the anatomic density in bronchial epithelium of nerves immunoreactive for the general nerve-marker protein gene product (PGP)-9.5 and the sensory neuropeptides calcitonin-gene-related-peptide (CGRP) and substance-P (SP). The log concentrations of capsaicin required to elicit at least two (C2) and five (C5) coughs were significantly lower in patients (P) than in control subjects (C) (median [range] log C2, P = 0.3 [-0.3 to 1.2] microM; C = 1.5 [0.9 to 2.1], p < 0.0005; log C5, P = 0.8 [-0.3 to 2.1]; C = 2.6 [1.8 to 3.0], p < 0.0005). In bronchial epithelium taken from the carina of the right upper lobe (RUL) and a subsegmental carina of the right lower lobe (RLL), total nerve density (PGP-9.5 immunoreactivity) was greater in P than C, although this was not significant. CGRP-immunoreactive nerve density was significantly higher in P than in C in the RUL (median [range] P = 1.05% [0.13 to 5.08]; C = 0.02% [0 to 0.24], p = 0.001) and RLL (P = 0.59% [0.04 to 3.14]; C = 0% [0 to 0.50], p < 0.02). SP-immunoreactive nerves were not significantly different in the two groups. Abnormal intraepithelial airway nerves containing increased quantities of CGRP are present in patients with idiopathic PNPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Effect of induced bronchoconstriction on nasal airflow resistance in patients with asthma.

1. Reflex bronchial changes have been demonstrated after nasal stimulation in both man and experimental animals. The existence of a pulmonary-nasal reflex is less established. We have examined whether induced narrowing of the intrathoracic airways leads to increases in nasal airflow resistance (Rnaw) in patients with asthma. 2. We have used a non-invasive forced oscillation method to measure total respiratory resistance (Rrs) at 8 Hz during tidal breathing sequentially via the nose (Rrs, na) and via the mouth (Rrs, mo) and derived Rnaw by subtracting Rrs, mo from Rrs, na. We examined whether changes in Rnaw occurred when increases in Rrs, mo were induced by inhaling histamine aerosol via the mouth with the nose occluded in 11 patients with stable, mild asthma (six males, age 28.1 +/- 2.1 years, forced expiratory volume in 1 s 97 +/- 6% of predicted, means +/- SEM). Six of the patients had a history of rhinitis. The patients were first challenged with doubling concentrations of histamine via a dosimeter to establish the dose which reduced the forced expiratory volume in 1 s by > or = 20%. Two hours later when the forced expiratory volume in 1 s had returned to baseline, they were challenged with saline and again 2 h later with the concentration of histamine that had earlier caused a > or = 20% fall in the forced expiratory volume is 1 s. 3. Between 0.5 and 10 min after histamine inhalation, a sustained increase in Rrs, mo was achieved with mean increases averaging 68-77% above baseline over this period (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The effect of topical sodium cromoglycate on intranasal histamine challenge in allergic rhinitis.

Topical sodium cromoglycate is used to treat allergic diseases of the upper and lower airways. To investigate its mechanisms of action, intranasal histamine challenge was used in nine subjects with perennial allergic rhinitis. After a preliminary day where subjects' reactivity thresholds (D100) for histamine were determined, intranasal sodium cromoglycate was administered in a double-blind, placebo-controlled fashion. Graded (D100/3, D100, D100X3), sequential challenges were performed on days 1 and 21 of each course, and responses measured by changes in nasal airway resistance, sneezes, secretion volume and secretion content: total protein, lysozyme and mucin. After a single dose of sodium cromoglycate, there was no change in resistance, but secretion volumes fell significantly (3.12 ml/5 min c.i. 2.83-3.4; placebo 3.61, c.i. 3.32-3.90: P = 0.026). After a 3-week-course, there was a significant fall in resistance (4.29 cm H2O/l/s, c.i. 3.85-4.72; placebo 5.45, c.i. 5.01-5.88: P < 0.0001). No change in other parameters was observed. Thus, in perennial allergic rhinitis, intranasal sodium cromoglycate has both short- and long-term effects on nasal reactivity to histamine challenge. Acutely, there is a reduction in nasal lavage fluid volume which may be the result of reduced irritant receptor activity. After a 3-week course, there is a reduction in nasal resistance responses, a possible anti-inflammatory effect.

Administration, Intranasal↗
PubMed1994

Effect of clonidine on induced cough and bronchoconstriction in guinea pigs and healthy humans.

We examined the effects of the alpha 2-receptor agonist clonidine, administered orally and by inhalation, on citric acid- and capsaicin-induced reflexes in guinea pigs and healthy human subjects. In groups (n = 8-10) of conscious guinea pigs, oral clonidine (10 and 100 micrograms/kg) was without effects, whereas inhaled clonidine (10-1,000 microM) caused a concentration-dependent inhibition of citric acid-induced cough (coughs during 3 min: control, 6.5 +/- 0.9; 1,000 microM clonidine, 1.7 +/- 1.0; P < 0.05) and reflex bronchoconstriction (time to onset of bronchoconstriction: control, 191 +/- 24 s; 1,000 microM clonidine, 317 +/- 33 s; P < 0.05). The inhibitory effect of inhaled clonidine on both reflexes was completely reversed by pretreatment with yohimbine but not with prazosin. In 12 healthy human volunteers, oral clonidine (150 mg) caused a significant fall in supine and erect systolic blood pressure and a significant increase in drowsiness as measured on a visual analogue scale 1 and 2 h after administration. Despite these effects, oral clonidine had no effect on capsaicin-induced cough or reflex bronchoconstriction in humans. In contrast to the effects in guinea pigs, inhaled clonidine (281 microM) had no effect on capsaicin-induced cough or reflex bronchoconstriction in humans. These data suggest that peripheral alpha 2-receptors exert an inhibitory effect on sensory neurotransmission in the guinea pig but not in the healthy human airway, indicating an important difference between the two species.

Administration, Inhalation↗
PubMed1994

Capsaicin cough sensitivity decreases with successful treatment of chronic cough.

To assess the role of enhanced cough sensitivity in the pathogenesis of cough, we measured cough severity on a visual analogue scale (VAS) and capsaicin cough sensitivity (the concentration required to elicit two [C2] and five [C5] coughs) in 87 consecutive patients referred with chronic cough. Measurements were repeated after complete investigation and treatment, when patients were entered into one of four study groups: (1) treatment success (primary cause of cough successfully treated with elimination of the cough, n = 48); (2) primary treatment failure (treatment of potential primary cause of cough unsuccessful, n = 12); (3) cough treatment failure subgroup A (potential primary cause of cough identified and successfully treated but no improvement in cough, n = 8); and (4) cough treatment failure subgroup B (no potential primary cause of cough identified, n = 19). All patients in groups 3 and 4 were nonsmokers, had normal chest radiography and negative histamine challenge test, and failed to respond to intensive empirical treatment for rhinitis and gastroesophageal reflux. The VAS cough severity was lower and log C2 and C5 higher after treatment compared with initial values in the treatment success group but not in the other three groups. Enhanced sensitivity of airway nerves that mediate cough is important in the pathogenesis of nonproductive cough, and successful treatment is associated with a reduction in cough sensitivity. While enhanced sensitivity of airway nerves is usually present in patients with identifiable causes of chronic nonproductive cough, it is also found in other patients in whom the cause of cough is unknown.

Adult↗
PubMed1993

Effects of correcting arterial hypoxaemia on respiratory resistance in patients with chronic obstructive pulmonary disease.

1. We have re-examined the effects of breathing 100% O2 on airflow resistance in hypoxaemic patients with chronic obstructive pulmonary disease. We measured arterial O2 saturation with an ear oximeter and total respiratory resistance by imposing forced oscillations at the mouth over the range 6-26 Hz during tidal breathing. Six normal subjects (mean age, 27.3 years; forced expiratory volume in 1 s, 3.82 litres) and 18 patients with severe chronic obstructive pulmonary disease and hypoxaemia (mean age, 66.6 years; forced expiratory volume in 1 s, 0.61 litres; O2 saturation breathing air, 88.4%) were examined in the sitting position breathing air and 100% O2. Eleven of the patients with chronic obstructive pulmonary disease were also studied before and after treatment with nebulized salbutamol (2.5 mg). 2. In normal subjects total respiratory resistance at 8 Hz breathing air was 2.35 (0.16) cmH2O l-1 s [mean (SEM)]; after salbutamol there was a small decrease in total respiratory resistance to 1.99 (0.12) cmH2O l-1 s. Breathing 100% O2 had no effect on total respiratory resistance either before or after salbutamol treatment. 3. In the patients with chronic obstructive pulmonary disease, values of total respiratory resistance fell with increasing frequency of oscillation; at 8 Hz, total respiratory resistance was 4.53 (0.35) cmH2O l-1 s breathing air and 3.73 (0.28) cmH2O l-1 s breathing 100% O2 (paired t-test, P = 0.001). The reduction in total respiratory resistance with O2 breathing varied between patients but was not related to the severity of hypoxaemia breathing air. Inhaled salbutamol had no significant effect on total respiratory resistance breathing air or 100% O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Changes in nasal mucosal blood flux and air-flow resistance on unilateral histamine challenge.

To investigate reflex vascular control in the nose, we challenged each side of the nose with 0.9% saline and histamine (0.3 mg aqueous) and observed changes in unilateral nasal airway resistance (Rnaw) and laser doppler flux (LDF) in response to contra-lateral and ipsilateral challenge in eight normal subjects. Preliminary studies demonstrated that the preferred site for observation of LDF was the nasal septum (same-day concordance 0.920; inferior turbinate 0.307). Ipsilateral contra-lateral saline induced no significant change to either parameter. Ipsilateral histamine produced a highly significant rise in LDF (757 arbitrary units SEM 94 at 3 min; baseline 489 SEM 75: P < 0.05) and Rnaw (baseline: 3.10, SEM 0.52; 5 min: 8.81, SEM 2.09 cmH2O/l/s: P < 0.01). Contra-lateral histamine produced a significant P < 0.05) fall in both (LDF 317, SEM 24 at 3 min; Rnaw 2.67, SEM 0.78 cm H2O/l/s at 6 min). This previously unrecorded observation suggests a neural reflex that increases the patency of the contra-lateral nostril after unilateral obstruction is provoked.

Adult↗
PubMed1993

Effect of topical beclomethasone on histamine-induced increases in nasal airflow resistance and secretion in perennial rhinitis.

The effects of topical beclomethasone dipropionate on changes in nasal resistance and secretion induced by topical histamine were studied in eight patients with perennial rhinitis. Patients were studied at enrollment, after 3 weeks of beclomethasone (100 micrograms spray to each nasal cavity twice daily), and after 3 weeks of placebo (saline) treatment administered in a double-blind cross-over trial. Nasal airflow resistance (Rnaw) and total protein, albumin, lysozyme and glycoconjugate secretion in nasal lavage fluids were measured after topical application of histamine to the nasal mucosa. Resistance measurements and secretory parameters were similar for the initial study and after placebo treatment. In those studies, histamine (1 and 10 mg) increased both nasal resistance and secretion of total protein, albumin and glycoconjugates. After beclomethasone treatment the rise in respiratory resistance in response to histamine was significantly attenuated (delta Rnaw, +11.57 cm H2O/l/s with placebo, +5.80 with beclomethasone, P < 0.05). Beclomethasone had no effect on histamine-induced secretion. Because nasal resistance is determined mainly by vascular processes, beclomethasone treatment appears to have a prominent action on the vascular bed to reduce mediator-induced vasodilatation in perennial rhinitis.

Administration, Intranasal↗
PubMed1993

Influence of smoking habits on change in carbon monoxide transfer factor over 10 years in middle aged men.

BACKGROUND: Emphysema is associated with a reduction in carbon monoxide transfer coefficient (TLCO/VA), but little is known about the evolution of changes in TLCO/VA in middle aged smokers at risk of developing chronic airflow obstruction. METHODS: TLCO/VA (single breath method) was measured on two occasions 10 years apart in 122 middle aged men. RESULTS: Initially TLCO/VA averaged 97% predicted in never smokers (n = 42, mean age 37.2 years), 99% predicted in ex-smokers (n = 21, mean age 41.9 years), and 85% predicted in those who smoked over 15 cigarettes a day (n = 42, mean age 42.0 years). Mean rates of decrease in TLCO/VA over 10 years, however, were similar in the three groups, so that differences between smokers and non-smokers did not increase during the 10 years. Seventeen men (mean age 40.9 years) who initially were smokers became sustained ex-smokers within two years of the first measurement; in these men mean absolute values of TLCO/VA rose, averaging 89% predicted at the first assessment but 102% predicted 10 years later. CONCLUSION: By the age of about 40 years TLCO/VA was lower in smokers than in never smokers but this difference did not increase over the following 10 years. Sustained ex-smokers had values similar to those of never smokers even when TLCO/VA was known to have been reduced while they were smoking. Changes in TLCO/VA associated with stopping smoking were considerably larger than could be explained by carbon monoxide back pressure, indicating that mechanisms other than irreversible increase in the size of terminal air spaces underlie the lower values in smokers. To detect emphysema in smokers it is necessary to use reference equations that take account of current smoking.

Adult↗
PubMed1993

Effects of treatment on airway dynamics and respiratory muscle strength in Parkinson's disease.

To investigate how treatment can affect airway dynamics and respiratory muscle strength in Parkinson's disease (PD), we assessed maximum effort inspiratory and expiratory mouth pressures (MIP and MEP), oscillatory impedance, and maximum expiratory and inspiratory flow-volume curves (MEFV and MIFV) in 10 patients (8 male and 2 female; mean age 51 +/- 5.3 yr, SD) after temporary interruption of antiparkinsonian therapy (off) and during continuous subcutaneous infusion of a direct stimulant of dopamine receptors, apomorphine (on). Treatment improved neurologic scores (off 25 +/- 5, on 9 +/- 5, modified Webster scale, p < 0.001), MEP (off 45 +/- 25, on 63 +/- 29 cm H2O, p = 0.003), and peak inspiratory flow (PIF; off 3.83 +/- 1.6, on 4.37 +/- 1.7 L/s, p = 0.028). Maximum inspiratory pressure was very low off treatment (-25 +/- 16 cm H2O) and improved moderately with apomorphine (-33 +/- 17 cm H2O) (p = 0.064). Total respiratory resistance during tidal breathing was normal in 9 patients both off and on treatment despite, in some cases, dramatic changes in MEFV and MIFV curves. These results suggest that abnormalities of the flow-volume curves may be due to problems in the rapid activation and coordination of contraction of upper airways and chest wall muscles during forced maneuvers, which is improved by apomorphine treatment.

Adult↗
PubMed1993

Intranasal histamine challenge in normality and allergic rhinitis.

A series of investigations was performed in which histamine challenge was used to compare nasal responsiveness in 20 normal subjects and 20 with allergic rhinitis. There was found to be a lower threshold of reactivity (D100) to histamine in allergic subjects as measured by resistance changes (geometric mean, 0.53 mg/ml; normal subjects, 2.15: p = 0.022). This may represent increased number or sensitivity of histamine receptors on the nasal capacitance vessels. The loss of a laser Doppler response to a supramaximal histamine stimulus (normal subjects, 102% increase in flux at 3 minutes; p < 0.05) was observed in patients with allergic rhinitis and indicates either a down-regulation of the capillary system or an altered effect of histamine on superficial vessels, perhaps mediated by a shift in histamine receptor type. There was an observed increase in neutrophils at the mucosal surface under baseline conditions (rhinitis median, 49.6%; normal subjects, 32.72%: p < 0.05), which suggests an important primary role in the pathogenesis of this condition for this active cell. The observed increase in secretory volume response to histamine in allergic subjects, which persisted beyond 40 minutes after a single D100 challenge, may be related to an altered sensitivity of glandular tissue. There are important changes in nasal reactivity to histamine challenge in allergic rhinitis that may have implications for its pathogenesis.

Adult↗