The effect of aerosol distribution on airway responsiveness to inhaled methacholine in patients with asthma

Imaging Aerosol Deposition with Two-Dimensional Gamma Scintigraphy

Several imaging modalities have been employed to quantify lung dose and the distribution of the dose of orally inhaled aerosols in vivo. Two-dimensional (2D, or planar) imaging using gamma scintigraphy is the most widely used of these modalities. Two-dimensional gamma scintigraphy studies are accomplished using a single- or dual-headed gamma camera. The formulation to be tested is admixed with the gamma emitting radioisotope ^99mtechnetium, which serves as a surrogate for the drug. This article provides details as to how 2D gamma scintigraphy images should be acquired and analyzed using recently standardized methods. Based on the new guidelines, the investigator should confirm that the drug formulation is unchanged with the addition of the radioisotope, determine the amount of radioactivity needed for inhalation to obtain appropriate radioactivity counts in the lungs, perform quality control procedures for the gamma camera, identify the lung borders of the study subject using a reference image such as an X-ray computed tomography scan, a ventilation scan, or a transmission scan, acquire a lung transmission image to correct for attenuation of radioactivity by lung tissue, instruct the subject how to inhale the radiolabel-drug mixture and record associated breathing parameters, acquire anterior and/or posterior views of the lungs and any other regions of interest (i.e., oropharynx, stomach) and assess the acquired images for total and regional dose to the lungs. Total dose should be assessed after identification of the right lung border and appropriate correction for tissue attenuation. Regional dose should be quantified as a normalized outer/inner deposition ratio (O/I) and expressed as the penetration index (PI). Mass balance should be performed as needed. By following the standardized methods, 2D gamma scintigraphy data from studies in different laboratories may be compared and combined, leading to multi-center studies and more rapid development of new medications and devices for inhaled therapies.

Is "Slow Inhalation" Always Suitable for Pressurized Metered Dose Inhaler?

To achieve adequate inhalation therapy, a proper inhalation technique is needed in clinical practice. However, there is limited information on proper inhalation flow patterns of commercial inhalers. Here, we quantitatively estimated airway deposition of two commercial pressurized metered dose inhalers (pMDIs) to determine their optimal inhalation patterns. Sultanol^® inhaler (drug particles suspended in a propellant, suspension-pMDI) and QVAR™ (drug dissolved in a propellant with ethanol, solution-pMDI) were used as model pMDIs. Aerodynamic properties of the two pMDIs were determined using an Andersen cascade impactor with human inhalation flow simulator developed by our laboratory. As indices of peripheral-airway drug deposition, fine particle fractions (FPF_PA) at different inhalation flow rates were calculated. The time-dependent particle diameters of sprayed drug particles were determined by laser diffraction. On aerodynamic testing, FPF_PA of suspension-pMDI significantly decreased depending on the increasing inhalation flow rate, while solution-pMDI achieved higher and constant FPF_PA in the range of the tested inhalation flow rates. The particle diameter of solution-pMDI markedly decreased from 5 to 3 μm in a time-dependent manner. Conversely, that of suspension-pMDI remained at 4 μm during the spraying time. Although "slow inhalation" is recommended for pMDIs, airway drug deposition via solution-pMDI (extra-fine particles) is independent of patients' inhalation flow pattern. Clinical studies should be performed to validate instruction for use of pMDIs for each inhaler for the optimization of inhalation therapy.

Mucociliary Clearance in Former Tobacco Smokers with Both Chronic Obstructive Pulmonary Disease and Chronic Bronchitis and the Effect of Roflumilast

Background: Little is known of the repeatability and reliability of mucociliary clearance (MCC) in former tobacco smokers who have both chronic obstructive pulmonary disease (COPD) and chronic bronchitis (CB). Less is known of the effect of roflumilast, a selective inhibitor of PDE4, on MCC in these patients. Methods: Former tobacco smokers with COPD and CB were treated for 4 weeks with either roflumilast, or placebo, in a randomized, crossover trial. The following were measured on two baseline and two posttreatment visits: MCC values through 90 minutes, following inhalation of ^99mtechnetium sulfur colloid and gamma camera imaging; outer:inner (O:I) deposition ratio; forced expiratory volume in 1 second (FEV₁); and symptom scores. Comparisons included: MCC measures through 30 minutes (MCC30), 60 minutes (MCC60), and 90 minutes (MCC90) on the two baseline visits (n = 9) and mean change [(roflumilast - baseline)-(placebo - baseline)] for MCC30, MCC60, MCC90, and FEV₁ (n = 8). Associations between MCC measurements, FEV₁ and O:I ratio with symptom scores were also examined. Results: Pearson correlation tests indicated good repeatability for baseline measures of MCC30, MCC60, and MCC90 and intraclass correlation coefficients indicated good reliability. Only FEV₁ (percent predicted) improved significantly following roflumilast treatment. There were no statistically significant correlations between MCC measures and symptom scores. Lower FEV₁ values were significantly associated with increased shortness of breath (dyspnea), and lower O:I ratios (more inner region deposition) were significantly associated with increased cough and sputum. Conclusions: Measurements of MCC30, MCC60, and MCC90 are repeatable and reliable in former tobacco smokers with both COPD and CB. One month of treatment with roflumilast did not improve MCC in this limited study. Airway narrowing in the larger, central airways of these subjects could lead to decreased FEV₁, increased inner region deposition of the radiolabeled particles, and the associated increase in symptoms of dyspnea, cough, and sputum.

Pulmonary PET imaging confirms preferential lung target occupancy of an inhaled bronchodilator

BACKGROUND

Positron emission tomography (PET) is a non-invasive molecular imaging technique that traces the distribution of radiolabeled molecules in experimental animals and human subjects. We hypothesized that PET could be used to visualize the binding of the bronchodilator drug ipratropium to muscarinic receptors (MR) in the lungs of living non-human primates (NHP). The objectives of this study were two-fold: (i) to develop a methodology for quantitative imaging of muscarinic receptors in NHP lung and (ii) to estimate and compare ipratropium-induced MR occupancy following drug administration via intravenous injection and inhalation, respectively.

METHODS

A series of PET measurements (n = 18) was performed after intravenous injection of the selective muscarinic radioligand ¹¹C-VC-002 in NHP (n = 5). The lungs and pituitary gland (both rich in MR) were kept in the field of view. Each PET measurement was followed by a PET measurement preceded by treatment with ipratropium (intravenous or inhaled).

RESULTS

Radioligand binding was quantified using the Logan graphical analysis method providing the total volume of distribution (V_T). Ipratropium reduced the V_T in the lung and pituitary in a dose-dependent fashion. At similar plasma ipratropium concentrations, administration by inhalation produced larger reductions in V_T for the lungs. The plasma-derived apparent affinity for ipratropium binding in the lung was one order of magnitude higher after inhalation (K_iih = 1.01 nM) than after intravenous infusion (K_iiv = 10.84 nM).

CONCLUSION

Quantitative muscarinic receptor occupancy imaging by PET articulates and quantifies the therapeutic advantage of the inhaled route of delivery and provides a tool for future developments of improved inhaled drugs.

The spatial pattern of methacholine bronchoconstriction recurs when supine, independently of posture during provocation, but does not recur between postures

The location of lung regions with compromised ventilation (often called ventilation defects) during a bronchoconstriction event may be influenced by posture. We aimed to determine the effect of prone vs. supine posture on the spatial pattern of methacholine-induced bronchoconstriction in six healthy adults (ages 21-41, three females) using specific ventilation imaging. Three postural conditions were chosen to assign the effect of posture to the drug administration and/or imaging phase of the experiment - supine methacholine administration followed by supine imaging, prone methacholine administration followed by supine imaging, and prone methacholine administration followed by prone imaging. The two conditions in which imaging was performed supine had similar spatial patterns of bronchoconstriction despite a change in posture during methacholine administration; the odds ratio for recurrent constriction was mean (SD) = 7.4 (3.9). Conversely, dissimilar spatial patterns of bronchoconstriction emerged when posture during imaging was changed; the odds ratio for recurrent constriction between the prone methacholine/supine imaging condition and the prone methacholine/prone imaging condition was 1.2 (0.9). Logistic regression showed that height above the dependent lung border was a significant negative predictor of constriction in the two supine imaging conditions (p<0.001 for each), but not in the prone imaging condition (p=0.20). These results show that the spatial pattern of methacholine bronchoconstriction is recurrent in the supine posture, regardless of whether methacholine is given prone or supine, but that prone posture during imaging eliminates that recurrent pattern and reduces its dependence on gravitational height.

Assessment of inhalation flow patterns of soft mist inhaler co-prescribed with dry powder inhaler using inspiratory flow meter for multi inhalation devices

The patients’ inhalation flow pattern is one of the significant determinants for clinical performance of inhalation therapy. However, the development of inhalation flow meters for various inhalation devices has been unable to keep up with the increasing number of newly launched inhalation devices. In the present study, we developed simple attachment orifices for the inhalation flow pattern monitoring system, which are suitable for all commercial inhalers, and investigated the efficacy of the system on the clinical inhalation instruction for patients co-prescribed dry powder inhaler (DPI) and soft mist inhaler (SMI). First, we constructed simple attachment orifices that were adjusted for 13 commercial inhalers, and examined the correlation between orifice and inhalation device. Second, the inhalation flow patterns (peak inspiratory flow rate, PIFR; inhalation duration time, DT) of patients prescribed a combination of DPI and SMI were monitored before and after inhalation instruction. The inhalation resistance of commercial inhalers are listed in the following order; Twincaps^® > Handihaler^® > Swinghaler^® = Clickhaler^® > Twisthaler^® > Turbuhaler^® > Jenuair^® > Diskus^® = Ellipta^® > Diskhaler^® > Breezhaler^® > Respimat^® = pMDI. The pressure drop via orifice was significantly correlated with that via the commercial inhaler. For the confirmation, all participants achieved the DPI criterion of PIFR. On the other hand, 4 participants (6 clinical visits) of 10 experimented participants could not achieve the essential criterion of DT (> 1.5 sec) for SMI, but all participants improved their duration time after inhalation instruction by pharmacists (P<0.05). In the present study, we successfully developed simple attachment orifice suitable for 13 commercial inhalation devices. These data suggested that our simple attachment orifices for the inhalation flow pattern monitoring system can detect patients with inadequate inhalation patterns via SMI.

[Mechanisms of non-specific airway hyperresponsiveness: Methacholine-induced alterations in airway architecture]

Multiple mechanisms drive non-specific airway hyperresponsiveness in asthma. At the organ level, methacholine inhalation induces a complex bronchomotor response involving both bronchoconstriction and, to some extent, paradoxical bronchodilatation. This response is heterogeneous both serially, along a single bronchial axis, and in parallel, among lung regions. The bronchomotor response to methacholine induces contraction of distal airways as well as focal airway closure in select lung territories, leading to anatomically defined ventilation defects and decreased vital capacity. In addition, loss of the bronchoprotector and bronchodilator effects of deep inspirations is a key contributor to airway hyperresponsiveness in asthma.

Ventilation inhomogeneities in children with congenital thoracic malformations

Background

Congenital thoracic malformations (CTM) are rare lung lesions that are managed with surgical resection or active surveillance.

The objective of this study was to comprehensively assess large and small airway function in children with CTM who underwent lobectomy in early life.

We hypothesise that sensitive measures of lung function will demonstrate residual impairments in CTM compared to healthy children.

Methods

Nitrogen lung clearance index (LCI), reactance and resistance (X5Hz and R5Hz), forced expiratory volume in 1 s and forced vital capacity (FEV1 and FVC) were prospectively measured in 10 children with CTM (mean age/SD: 7.6/1.3) who had undergone surgical resection in early life and in 17 healthy children (mean age/SD: 4.8/0.4). Total lung capacity (TLC) was also conducted in children older than 7 years of age with CTM (n = 8).

Results

Mean LCI was 8.0 (95% CI 7.5 to 8.5) in the CTM group and 7.3 (95% CI 7.0 to 7.6) in healthy children (p = 0.016). Mean X5Hz was −0.44kPa/l/s (95% CI −0.58 to −0.31) in the CTM group and −0.31kPa/l/s (95% CI −0.35 to −0.27) in healthy children (p = 0.02). Mean Z score for X5Hz was −2.11 (95% CI −3.59 to −0.63) in the CTM group and −0.11 (95% CI −0.55 to 0.33) in healthy children (p = 0.0008). Mean FEV1 was 1.21 L (95% CI 0.97 to 1.45) in the CTM group and 1.02 L (95% CI 0.90 to 1.15) in healthy children (p = 0.22). Mean % predicted FEV1 was 83% (95% CI 74 to 92) in the CTM group and 97% (95% CI 87 to 107) in healthy children (p < 0.05). Mean % predicted TLC in CTM children was 121.3% (95% CI 88.45 to 154.1). Mean LCI was inversely correlated with height z-scores in the CTM group (rs = −0.88, p = 0.002) but not in healthy children (rs = 0.22, p = 0.4).

Conclusions

Children with CTM have impaired lung function as demonstrated by the significant differences in LCI, reactance and FEV1 but not FVC, resistance and TLC. These findings may be of clinical relevance as ventilation inhomogeneities are closely correlated with somatic growth in this study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-015-0023-1) contains supplementary material, which is available to authorized users.

Nitrogen dioxide exposure and airway responsiveness in individuals with asthma

Controlled human exposure studies evaluating the effect of inhaled nitrogen dioxide (NO2) on the inherent responsiveness of the airways to challenge by broncho-constricting agents have had mixed results. In general, existing meta-analyses show statistically significant effects of NO2 on the airway responsiveness of individuals with asthma. However, no meta-analysis has provided a comprehensive assessment of the clinical relevance of changes in airway responsiveness, the potential for methodological biases in the original papers, and the distribution of responses. This paper provides analyses showing that a statistically significant fraction (i.e. 70% of individuals with asthma exposed to NO2 at rest) experience increases in airway responsiveness following 30-min exposures to NO2 in the range of 200 to 300 ppb and following 60-min exposures to 100 ppb. The distribution of changes in airway responsiveness is log-normally distributed with a median change of 0.75 (provocative dose following NO2 divided by provocative dose following filtered air exposure) and geometric standard deviation of 1.88. About a quarter of the exposed individuals experience a clinically relevant reduction in their provocative dose due to NO2 relative to air exposure. The fraction experiencing an increase in responsiveness was statistically significant and robust to exclusion of individual studies. Results showed minimal change in airway responsiveness for individuals exposed to NO2 during exercise.

Bronchoprotective effect of simulated deep inspirations in tracheal smooth muscle

Deep inspirations (DIs) taken before an inhaled challenge with a spasmogen limit airway responsiveness in nonasthmatic subjects. This phenomenon is called bronchoprotection and is severely impaired in asthmatic subjects. The ability of DIs to prevent a decrease in forced expiratory volume in 1 s (FEV1) was initially attributed to inhibition of airway narrowing. However, DIs taken before methacholine challenge limit airway responsiveness only when a test of lung function requiring a DI is used (FEV1). Therefore, it has been suggested that prior DIs enhance the compliance of the airways or airway smooth muscle (ASM). This would increase the strain the airway wall undergoes during the subsequent DI, which is part of the FEV1 maneuver. To investigate this phenomenon, we used ovine tracheal smooth muscle strips that were subjected to shortening elicited by acetylcholine with or without prior strain mimicking two DIs. The compliance of the shortened strip was then measured in response to a stress mimicking one DI. Our results show that the presence of "DIs" before acetylcholine-induced shortening resulted in 11% greater relengthening in response to the third DI, compared with the prior DIs. This effect, although small, is shown to be potentially important for the reopening of closed airways. The effect of prior DIs was abolished by the adaptation of ASM to either shorter or longer lengths or to a low baseline tone. These results suggest that DIs confer bronchoprotection because they increase the compliance of ASM, which, consequently, promotes greater strain from subsequent DI and fosters the reopening of closed airways.

Mucus removal is impaired in children with cystic fibrosis who have been infected by Pseudomonas aeruginosa

OBJECTIVE

To determine if mucus removal is impaired in children with cystic fibrosis (CF) who have been recently infected with Pseudomonas aeruginosa.

STUDY DESIGN

We compared mucociliary clearance (MCC), cough clearance (CC), lung morphology, and forced expiratory volume in 1 second (FEV1) in 7- to 14-year-old children with CF and mild lung disease (FEV1 ≥ 80%). Children were either P. aeruginosa negative (n = 8), or P. aeruginosa positive (P. aeruginosa obtained from at least 1 airway culture in the preceding 18 months) (n = 10). MCC and CC were quantified from gamma camera imaging of the right lung immediately after inhalation of (99m)technetium sulfur-colloid (time 0), over the next 60 minutes (average percent clearance over the first 60 minutes [AveMCC60]), 60-90 minutes (average percent clearance between 70 and 90 minutes [AveMCC/CC90]), and after 24 hours (percent clearance after 24 hours [MCC24hrs]). Children coughed 30 times between 60 and 90 minutes. Lung morphology was assessed by high resolution computed tomography (HRCT) scores of both lungs (total score) and of the right lung, using the Brody scale. Percent AveMCC60, AveMCC/CC90, MCC24hrs, FEV1, and HRCT scores were compared across the 2 groups using unpaired t tests. Associations were assessed using Spearman correlation.

RESULTS

There were no differences between the 2 groups in AveMCC60, MCC24hrs, mean HRCT total scores, right lung HRCT scores, or mean FEV1. AveMCC/CC90 was significantly decreased in children with P. aeruginosa compared with those without (16.2% ± 11.0% vs 28.6% ± 7.8%, respectively; P = .016). There was a significant negative correlation of AveMCC60 and AveMCC/CC90 with total lung HRCT score (all P < .05) but not with FEV1.

CONCLUSIONS

Infection with P. aeruginosa is associated with a significant slowing of MCC/CC in children with mild CF and may be a more sensitive indicator of the effects of P. aeruginosa than measurements of FEV1.

Frequency dependence of capnography in anesthetized rabbits

Aspirative capnography may be of help to diagnose early childhood asthma, but clinical usefulness in young children is limited by the relatively high respiratory rate. This study aimed to characterize the [Formula: see text] time course during airway constriction in 8 anesthetized rabbits, artificially ventilated at 30, 60 and 80breaths/min. Methacholine was inhaled to double the respiratory resistance measured at 8Hz by the forced oscillation technique. The capnogram shape changed in response to both methacholine and ventilatory frequency. Slope of phase II, the peak of first-order time derivative and trough of the second-order time derivative of the [Formula: see text] signal, were significantly attenuated after methacholine compared with baseline at all breathing rates (p<0.02). Moreover, significant correlations between respiratory reactance and resistance were observed with the phase III slope and the angle described by phase II and phase III (p<0.01). It is concluded that capnography may be useful to identify acute airway changes related to bronchoconstriction, even at high breathing frequencies.

Acute inhalation of hypertonic saline does not improve mucociliary clearance in all children with cystic fibrosis

Background

Little is known of how mucociliary clearance (MCC) in children with cystic fibrosis (CF) and normal pulmonary function compares with healthy adults, or how an acute inhalation of 7% hypertonic saline (HS) aerosol affects MCC in these same children.

Methods

We compared MCC in 12 children with CF and normal pulmonary function after an acute inhalation of 0.12% saline (placebo), or HS, admixed with the radioisotope ^{99 m}technetium sulfur colloid in a double-blind, randomized, cross-over study. Mucociliary clearance on the placebo day in the children was also compared to MCC in 10 healthy, non-CF adults. Mucociliary clearance was quantified over a 90 min period, using gamma scintigraphy, and is reported as MCC at 60 min (MCC60) and 90 min (MCC90).

Results

Median [interquartile range] MCC60 and MCC90 in the children on the placebo visit were 15.4 [12.4-24.5]% and 19.3 [17.3-27.8%]%, respectively, which were similar to the adults with 17.8 [6.4-28.7]% and 29.6 [16.1-43.5]%, respectively. There was no significant improvement in MCC60 (2.2 [-6.2-11.8]%) or MCC90 (2.3 [-1.2-10.5]%) with HS, compared to placebo. In addition, 5/12 and 4/12 of the children showed a decrease in MCC60 and MCC90, respectively, after inhalation of HS. A post hoc subgroup analysis of the change in MCC90 after HS showed a significantly greater improvement in MCC in children with lower placebo MCC90 compared to those with higher placebo MCC90 (p = 0.045).

Conclusions

These data suggest that percent MCC varies significantly between children with CF lung disease and normal pulmonary functions, with some children demonstrating MCC values within the normal range and others showing MCC values that are below normal values. In addition, although MCC did not improve in all children after inhalation of HS, improvement did occur in children with relatively low MCC values after placebo. This finding suggests that acute inhalation of hypertonic saline may benefit a subset of children with low MCC values.

Trial Registration

ClinicalTrials.gov: NCT01293084

A comparison of four tests of cognition as predictors of inability to learn to use a metered dose inhaler in old age

BACKGROUND

Previous studies have shown that a Mini Mental State Examination (MMSE) score of < 24/30 and inability to copy intersecting pentagons (IP) predict inability to learn to use inhaler devices. We hypothesised that clock drawing tests (CLOX 1 and 2), being validated tests of cognitive executive function, might predict competent inhaler acquisition with a higher sensitivity and specificity than the MMSE or IP.

METHODS

We studied 80 (63 women) inhaler-naïve inpatients, mean age 83 years (range 75-97 years). All performed the MMSE, IP, CLOX 1 and 2, before receiving standardised demonstration, instruction and assessment in the use of a metered dose inhaler (MDI).

RESULTS

A total of 28/80 (35%) patients were able to acquire a satisfactory MDI technique. Using normative thresholds for impairment, the sensitivity and specificity (% with 95% confidence intervals) of the cognitive scores in predicting inability were: MMSE < 24 sensitivity 57 (42-71), specificity 76 (57-88), p = 0.04; IP sensitivity 75 (60-85), specificity 79 (59-91), p = 0.0000; CLOX1 < 10 sensitivity 83 (69-91), specificity 57 (37-75), p = 0.0004; CLOX2 < 12 sensitivity 58 (43-71), specificity 64 (44-81), p = 0.05.

CONCLUSION

CLOX tests did not perform better than MMSE and IP, to identify patients who are unlikely to be able to acquire MDI technique from a single episode of training. In clinical practice, most patients with an MMSE < 24 or negative IP will not be able to learn MDI technique. In this study, IP had the best overall predictive value.

Targeting drugs to the airways: The role of spacer devices

AIM

Spacer devices are inhalation aids of varying dimension and complexity, specifically designed to overcome problems with the use of pressurised metered dose inhalers (pMDIs). The aim of this review is to examine the current understanding about these inhalation devices and discuss their advantages and disadvantages.

METHODS

The pertinent literature concerning the characteristics and effects of spacers on delivery and lung deposition of inhaled medications, as well as their clinical efficacy in patients with reversible airway obstruction, is examined.

RESULTS

Spacers minimise problems of poor inhalation technique with pMDI, reduce oropharyngeal deposition and increase lung deposition. Spacers improve the clinical effect of inhaled medications, especially in patients unable to use a pMDI properly. Compared to both pMDIs and dry-powder inhalers, spacers may increase the response to beta-adrenergic bronchodilators, even in patients with correct inhalation technique. A pMDI plus spacer has proven to be viable lower cost alternative to the use of a nebuliser for delivering large bronchodilator doses in patients with severe acute asthma or chronic obstructive pulmonary disease. The use of large-volume spacers is recommended for delivering high doses of inhaled corticosteroids, and may permit a lower maintenance dose to be used.

CONCLUSION

pMDIs may be routinely fitted with a spacer, especially in situations where correct pMDI use is unlikely.

Bronchial challenge test in asthmatics sensitized to mites: role of particle size in bronchial response

Although major house dust mite allergen (Der p 1) is carried mainly on large particles (>10 microm), standard bronchial challenge tests (BCT) use nebulizers that deliver smaller particles (sizes from 1 to 5 microm) and may therefore not reflect actual domestic exposure. The objective of this study was to evaluate the influence of particle size of Dermatophagoides pteronyssinus extract on bronchial response. Specific BCT were performed with different mass median aerodynamic diameters (MMAD): 1.1, 5.6, and 9.7 microm. Each of the 19 mite-sensitized patients underwent mite BCT three times, once with each nebulizer. IL-5 levels were assessed in induced sputum and blood samples. The PD(20) for Der p 1 differed substantially with particle size, with less Der p 1 (11.2 ng) needed to produce a PD(20) with the largest particles (9.7 microm), compared to 18.1 ng for the 5.6 microm particles and 142.5 ng for the 1.1 microm particles (p < 0.0001). Large particles also induced an early phase response significantly more often than small particles (100% vs. 63%). Although the late phase reaction (LPR) frequency was similar with all three particle sizes, lower mean oral corticosteroid doses were needed to treat LPR with the largest particles (23 mg), compared to the smaller particles, with 34 mg for the 5.6 microm particles and 51 mg for the 1.1 microm. The 1.1 microm particles produced a significantly greater increase in IL-5 concentrations in sputum and blood compared to the larger particles. Large particles clearly play a role in the immediate bronchial response in asthmatics sensitized to mites and, therefore, should be included in pharmacological studies in humans.

Lidocaine exerts its effect on induced bronchospasm by mitigating reflexes, rather than by attenuation of smooth muscle contraction

BACKGROUND

Lidocaine inhalation attenuates histamine-induced bronchoconstriction, as well as bronchoconstriction elicited by mechanical irritation. This effect could be mediated by direct effects on smooth muscle or by reflex attenuation. Therefore, we evaluated whether lidocaine attenuated the bronchial response of direct smooth muscle stimulation with methacholine.

METHODS

In 15 volunteers with bronchial hyperreactivity, a methacholine challenge was performed following the inhalation of lidocaine, dyclonine (which does not attenuate bronchial reactivity) or saline on three different days in a randomized, double-blind fashion. Lung function, response to methacholine, and lidocaine and dyclonine plasma concentrations were measured.

RESULTS

The inhaled methacholine concentration (PC20) necessary for a 20% decrease in the forced expiratory volume in 1 s (FEV1) was 8.8 +/- 6.1 mg/ml at the screening evaluation. The sensitivity to methacholine challenge (PC20) remained unchanged regardless of which solution was inhaled (9.1 +/- 7.5 mg/ml for lidocaine, 10.2 +/- 9.0 mg/ml for dyclonine and 9.8 +/- 8.3 mg/ml for saline; P = 0.58, means +/- standard deviation). Furthermore, the inhalation of all three solutions caused a significant decrease in FEV1 from baseline (P = 0.0007), with a significantly larger effect for dyclonine than lidocaine (P = 0.0153).

CONCLUSIONS

Although both inhaled and intravenous lidocaine attenuates histamine-evoked bronchoconstriction, it does not alter the response to methacholine. Therefore, the attenuation of bronchial reactivity by lidocaine appears to be related solely to neurally mediated reflex attenuation, rather than to the attenuation of direct constriction of airway smooth muscle.

Albuterol Improves Impaired Mucociliary Clearance After Lung Transplantation

BACKGROUND

Previous studies have shown that mucociliary clearance (MCC) is diminished after lung transplantation. However, it is unknown how early this deficit occurs after transplantation, or whether the abnormality can be improved by pharmacologic means. We hypothesized that impairment of MCC is evident soon after lung transplantation and that the defect in MCC can be improved by inhaled beta(2)-adrenergic receptor agonists.

METHODS

MCC and cough clearance (CC) were quantified in seven patients at 76 +/- 48 days (mean +/- standard deviation) after lung transplantation (baseline visit) and again 1 week later after an acute inhalation of albuterol. MCC was also determined once in four healthy subjects. To measure MCC, volunteers inhaled 99m-technetium-sulfur colloid aerosol, followed by gamma-camera imaging of their lungs for 76 minutes.

RESULTS

Baseline MCC was significantly reduced in transplant patients, compared with healthy subjects, averaging 8.9 +/- 7.3% and 20.9 +/- 15.1%, respectively (p = 0.05). CC was not affected by transplantation. Acute inhalation of albuterol significantly improved MCC in transplant patients (31.9 +/- 21.9%) compared with baseline values (p < 0.05).

CONCLUSIONS

MCC is diminished within a few months after transplantation. However, the response to albuterol suggests that the deficit is not static and can be improved with inhalation of a beta(2)-adrenergic receptor agonist.

Chronic inhalation of nebulized levalbuterol does not increase mucociliary clearance in healthy subjects

Acute inhalations of beta 2-adrenergic receptor agonists increase mucociliary clearance (MCC). Less is known about the effect of long-term inhalations of these agents on MCC, or cough clearance (CC). We hypothesized that chronic inhalations of nebulized levalbuterol, the R-isomer of albuterol, would enhance MCC and/or CC in healthy subjects, compared to albuterol or placebo. This was a randomized, double-blind, placebo-controlled trial in ten healthy, adult subjects who inhaled nebulized levalbuterol (1.25mg), albuterol (2.5mg), or placebo for 7 days, three times daily. MCC and CC were measured 6-7h after the last dose of drug on the 7th day of treatment. These were quantified from gamma camera images of the lungs following inhalation of an aerosol containing the isotope (99m)technetium. Levalbuterol did not improve MCC or CC. MCC averaged (+/-SD) 12.3+/-8.3%, 9.2+/-4.7% and 10.0+/-9.6% with placebo, albuterol and levalbuterol, respectively. CC averaged 3.9+/-6.8%, 4.9+/-4.3% and 3.8+/-6.4% with placebo, albuterol and levalbuterol, respectively. These results indicate that chronic inhalations of nebulized levalbuterol for 1 week do not increase MCC or CC in healthy subjects, compared to albuterol or placebo.

Allergen challenge and deposition of nedocromil sodium in asthma

We examined whether the acute protective effect of nedocromil sodium aerosol could be enhanced by increasing the deposition uniformity of the drug in the lungs of adult patients with allergic asthma. Ten patients with mild-to-moderate asthma were challenged with the same doses of allergen on two occasions in a randomized manner. Thirty minutes before these challenges, patients inhaled 4 mg nedocromil sodium, admixed with the radioisotope (99m)technetium. Radiolabeled drug was inhaled during slow (25.4 +/- 4.6 L/min) and faster (58.0 +/- 7.3 L/min) inhalations from a 700 ml holding chamber. Percent changes in FEV(1) at the same top dose of allergen on the two treatment visits were compared. Lung deposition fraction (LDF) and indices of distribution uniformity, quantified from gamma camera images, were also compared. Acute protection against allergen challenge was similar and complete after slow or faster inspiration of nedocromil sodium. Mean (+/- SD) allergen-induced changes in FEV(1) were -1.05 +/- 2.78% and -0.39 +/- 2.80%, respectively, compared to -26.30 +/- 8.49% on a screening challenge (no drug). Mean LDF was also similar on the two visits, averaging 16.4 +/- 4.6% and 16.1 +/- 7.2% of administered drug, respectively. Distribution of nedocromil sodium was most uniform after slow inspiration, but increased uniformity was not related to enhanced protection. Complete protection against acute bronchoconstriction induced by inhaled allergen can be obtained with 4 mg of nedocromil sodium aerosol, inhaled from a large volume holding chamber, 30 min before the exposure, and at inspiratory flow rates between approximately 20-60 L/min. Protection does not appear to be enhanced by increased uniformity of drug distribution within the lungs.

Factors affecting the deposition of aerosolized insulin

The inhalation of insulin for absorption into the bloodstream via the lung seems to be a promising technique for the treatment of diabetes mellitus. A fundamental issue to be resolved in the development of such insulin aerosol delivery systems is their efficiency (measured, for example, in terms of the amount of insulin absorbed in the blood compared to the total amount loaded into an inhalation device). A primary factor that could cause inefficiency of insulin absorption is deposition in the nonalveolated airways with subsequent removal from the lung via mucociliary clearance. Thus, a better understanding of the spatial distribution of insulin particle deposition in the lung can give guidance to the optimization of inhalation therapy. A mathematical model was used to study factors affecting the disposition of aerosolized insulin. The model calculates the trajectories of inhaled particles in the lung and has been validated by data from human subject experiments. Computer simulations were performed describing a wide range of patient breathing maneuvers. The results indicate significant variations in particle deposition patterns within lungs for different tidal volumes, inspiratory flow rates, and breath hold times. These findings indicate that particle sizes and ventilatory parameters are significant factors determining locations of particle deposition within human lungs, and thus the absorption of insulin into the blood stream via alveloated airways. Mathematical modeling is a valuable technique to complement clinical studies in the targeted delivery of inhaled insulin.

Combined lidocaine and salbutamol inhalation for airway anesthesia markedly protects against reflex bronchoconstriction

BACKGROUND

Lidocaine inhalation, in subjects with bronchial hyperreactivity, attenuates evoked bronchoconstriction but also irritates airways. Whether salbutamol pretreatment can mitigate airway irritation and whether combined treatment offers more protection than treatment with either drug alone is unknown. Therefore, we evaluated the effects of the inhalation of lidocaine, salbutamol, lidocaine and salbutamol combined, and placebo on an inhalational histamine challenge.

METHODS

Fifteen patients with mild asthma were selected by a screening procedure (ie, a provocative concentration of a substance [histamine aerosol of < 18 mg/mL] causing a 20% fall in FEV(1) [PC(20)]). On 4 different days after pretreatment with the inhalation of lidocaine (5 mg/kg), inhalation of salbutamol (1.5 mg), combined treatment, or placebo, the histamine challenge was repeated.

RESULTS

The baseline FEV(1) after lidocaine inhalation but prior to the histamine challenge decreased by > 5% in 7 of 15 volunteers, with a mean (+/- SD) decrease from 3.82 +/- 0.90 to 3.54 +/- 0.86 L (p = 0.0054). The baseline PC(20) for histamine was 6.4 +/- 4.3 mg/mL. Both lidocaine and salbutamol inhalation significantly increased PC(20) more than twofold (14.9 +/- 13.7 and 16.8 +/- 10.9 mg/mL, respectively; p = 0, 0007) at a lidocaine plasma concentration of 0.7 +/- 0.3 microg/mL. Combined treatment quadrupled the PC(20) to 29.7 +/- 20.3 mg/mL (vs lidocaine, p = 0.002; vs salbutamol, p = 0.003).

CONCLUSIONS

Thus, histamine-evoked bronchoconstriction, as a model of reflex bronchoconstriction, can be significantly attenuated by salbutamol or lidocaine inhalation. However, lidocaine inhalation causes significant initial bronchoconstriction. The combined inhalation of salbutamol and lidocaine prevents the initial bronchoconstriction observed with lidocaine alone and offers even more protection to a histamine challenge than either lidocaine or salbutamol alone. Therefore, the combined inhalation of lidocaine and salbutamol can be recommended to mitigate bronchoconstriction when airway instrumentation is required.

Both intravenous and inhaled lidocaine attenuate reflex bronchoconstriction but at different plasma concentrations

Intravenous lidocaine can attenuate bronchial hyperreactivity. However, lidocaine inhalation might yield the same or better results at higher airway and lower lidocaine plasma concentrations. Therefore, we tested in awake volunteers with bronchial hyperreactivity the effect of lidocaine on histamine-induced bronchoconstriction administered either intravenously or as an aerosol. After approval of the local ethics committee, 15 volunteers were enrolled in this placebo-controlled, double-blinded, randomized study. Volunteers were selected by showing a decrease in FEV1 greater than 20% of baseline (PC20) in response to histamine inhalation. On three different days the challenge was repeated after pretreatment with either intravenous lidocaine, inhaled lidocaine, or placebo. Blood samples for determination of lidocaine plasma concentration were drawn. Comparisons were made using the Friedman and Wilcoxon signed-rank tests. Baseline PC20 was 6.4 +/- 1.1 mg. ml-1. Both inhalation of lidocaine and intravenous administration significantly increased PC20 to 14.8 +/- 3.5 mg. ml-1 and 14.2 +/- 2. 5 mg. ml-1, respectively (p = 0.0007). Peak plasma lidocaine concentrations at the end of challenges were 0.7 +/- 0.1 microg. ml-1 (inhaled) and 2.2 +/- 0.1 microg. ml-1 (i.v.). However, 7 of 15 subjects showed an initial decrease of FEV1 greater than 5% following lidocaine inhalation. While both intravenous as well as inhaled lidocaine attenuate reflex bronchoconstriction significantly, lidocaine plasma concentrations are significantly lower after inhalation. However, the high incidence of initial bronchoconstriction to lidocaine inhalation may limit its use in patients with asthma and thus offers therapeutic advantages for intravenous lidocaine.

Rapid reversibility of the allergen-induced pulmonary late-phase reaction by an intravenous beta2-agonist

This study was performed to determine the degree to which beta2-adrenergic receptor agonists can reverse the allergen-induced late reduction in lung function. On two occasions, seven asthmatic subjects were administered terbutaline or its vehicle by intravenous infusion 7 h after inhaled allergen, at which point the forced expiratory volume in 1 s was 57% of baseline. On another occasion, terbutaline was infused at baseline to determine maximal attainable bronchodilation. After allergen challenge, terbutaline rapidly improved lung function. At the end of terbutaline infusion, the forced expiratory volume in 1 s reached 100 +/- 1.3% of baseline and 84.2 +/- 4.3% of maximal attainable value, but the bronchodilating effect of the beta-agonist did not plateau. The values for forced vital capacity were 102 +/- 1.3% of baseline and 95.1 +/- 3% of maximal attainable value. The kinetics of the terbutaline effect, when it was infused at baseline, were similar to those in the late phase. Because the late-phase reduction in lung function is rapidly reversible by beta2-adrenergic agonists, we conclude that it is caused mainly by bronchial smooth muscle spasm.

The efficacy of slow versus faster inhalation of cromolyn sodium in protecting against allergen challenge in patients with asthma

BACKGROUND

Approximately one third of patients with allergy-induced asthma who are treated with aerosolized cromolyn sodium (CS) fail to achieve a full therapeutic effect. This lack of effectiveness could involve nonhomogeneous distribution of drug in the lung as a result of high inspiratory flow rates.

OBJECTIVE

We sought to determine the efficacy of slow versus faster inhalation of CS in protecting against allergen challenge in patients with asthma.

METHODS

Eight patients with asthma underwent two allergen challenges 30 minutes after pretreatment with CS that was inhaled from a large holding chamber at approximately 30 L/min or approximately 70 L/min. Percent decreases in FEV1 at a common dose of allergen on the two challenge days were compared. Values of skew (an indicator of aerosol distribution homogeneity) obtained from gamma camera lung images after slow and faster inhalation of radiolabeled CS were also compared.

RESULTS

Mean (+/- SD) allergen-induced decrease in FEV1 was 5.4% +/- 4.2% after slow inspiration of CS, which was significantly less than the allergen-induced decrease in FEV1 after faster inhalation of CS with 12.6% +/- 11% (p < 0.05). Mean skew values were also significantly decreased after slow inspiration of CS, and differences in decreases in allergen FEV1 and skew values for the two breathing maneuvers were significantly correlated.

CONCLUSION

These data indicate that protection against allergen-induced asthma can be optimized by slowly inspiring CS from a large holding chamber compared with faster inhalation of the drug. These results appear to be related to enhanced distribution homogeneity of CS within the lungs.

In vivo measurements of aerosol dose and distribution: clinical relevance

Mathematical and in vitro models, that incorporate particle diameter, normal breathing frequencies and tidal volumes, have been used to predict the deposition fraction of respirable aerosols within the lungs. Although very useful in drug development, determinations of dose and the distribution of dose based solely on such models may be less accurate than in vivo measurements, which are performed under conditions that combine the effects of all the factors that determine aerosol deposition, including the effect of disease. Gammascintigraphy provides a method for in vivo quantification of the total deposited fraction and the distribution of the dose within the lower respiratory tract. Using this technology, it has been shown that deposition fraction in the lower respiratory tract may vary between 1-30% of the dose actuated from an MDI or nebulizer. This wide range in deposited dose suggests that variations in the clinical response to inhaled aerosols may be explained by alterations in the dose delivered, especially if the aerosolized medication has a narrow therapeutic range. Alterations in the distribution of inhaled drugs within the lungs may also affect the clinical response, such that some disorders may best be treated by targeting drug to specific locations of the lung, while others may respond best to homogeneous distribution of aerosolized drug. In vivo measurements would provide confirmation of the dose deposited as well as the pattern of distribution, which should improve the therapeutic outcome of most aerosolized medications.

The bronchial response, but not the pulmonary response to inhaled methacholine is dependent on the aerosol deposition pattern

The clinical effect of inhaled radio-labeled (Technetium-99m diethylenetriamine-pentaacetic acid) methacholine was studied in two separate experiments performed in eight symptom-free asthmatics with bronchial hyperresponsiveness. Aerosols were formed by two different nebulizers, producing either mainly small aerosol particles (2-microns mass median aerodynamic diameter [MMAD]) for peripheral, or mainly large aerosol particles (9-microns MMAD) for large airway deposition. The intended site of deposition was confirmed by gamma camera recordings. Changes in specific airway conductance (sGaw) were set as an index of central airway constriction, and functional alterations in the gas exchanging parts of the lung were estimated by multiple inert gas elimination technique (MIGET) and arterial blood gas analyses. The main finding was that the responses, as measured by the changes in arterial blood gases and by MIGET, were similar in the two experiments, while the fall in sGaw was significantly larger after deposition in the main bronchi than in the peripheral airways (p < 0.05). The time courses of the abnormalities in the gas exchanging elements were much longer than those of the responses of the central airways, and the abnormalities were recorded still at the end of the experiment 2 h after challenge in most patients. A discrepancy in dose dependency and time courses suggests differences in mechanism and/or dynamics of the responses exerted by the various target organs. Interaction in the process of clearance from the lung of inhaled methacholine by the bronchial circulation may have contributed to the observed discrepancies.

Changing patterns of aerosol deposition during methacholine bronchoprovocation

During bronchoprovocation testing with methacholine, induced changes in airway geometry are known to affect sites of drug deposition. However, it is not known if changes in these sites determine measured responsiveness. We assessed the importance of sites of deposition as determinants of reactivity by comparing particle behavior in two subject groups with and without hyperresponsiveness. By administering radiolabeled aerosols of similar aerodynamic characteristics to methacholine aerosol, we measured the deposition pattern in terms of the specific central to peripheral ratio (sC/P) before and after methacholine inhalation (sC/P1 and sC/P2, respectively) and thereby quantified the changes in deposition sites that occur during the course of a typical bronchoprovocation test. Subjects whose FEV1 decreased by 20 percent or greater were classified as methacholine responsive (MR; nine subjects), and the remainder were classified as non-methacholine responsive (NMR; seven subjects). The two groups had similar baseline FEV1 percent predicted (FEV1 percent) and initial deposition patterns (sC/P1) with particles depositing primarily in peripheral airways (mean +/- SE; sC/P1 1.43 +/- 0.070 and 1.39 +/- 0.65, MR and NMR, respectively, p = NS). Following methacholine inhalation, the deposition pattern changes markedly for all subjects with particles depositing primarily in central airways (sC/P2 2.58 +/- 0.24, p = 0.001, and 2.15 +/- 0.22, p = 0.001 from baseline, p = NS between groups) By definition, the MR subjects had a significantly greater change in FEV1 than the NMR subjects. Preferential deposition in central airways occurs in all subjects during bronchoprovocation testing and does not significantly determine methacholine responsiveness.

Acute exposure to acid fog. Effects on mucociliary clearance

Submicrometric sulfuric acid (H2SO4) aerosol can affect mucociliary clearance without eliciting irritative symptoms or changes in pulmonary function. The effect of larger fog droplets containing H2SO4 on mucociliary clearance is unknown. We quantified mucociliary clearance from the trachea (n = 4) and small airways (n = 7) of young healthy male adults after an acute exposure to H2SO4 fog (MMAD = 10.3 microns; pH = 2.0; liquid water content = 481 +/- 65 mg/m3; osmolarity = 30 mOsm). Acid fog (AF) or saline fog (SF) (10.9 microns; 492 +/- 116 mg/m3; 30 mOsm) was administered for 40 min of unencumbered breathing (no mouth-piece) at rest and for 20 min of exercise sufficient to produce oronasal breathing. Fog exposures were followed by a methacholine (MCh) challenge (a measure of airway reactivity) or inhalation of technetium-99M radioaerosol (MMAD = 3.4 microns) on 2 study days each. Changes in symptoms and forced ventilatory function were also assessed. Clearance was quantified from computer-assisted analyses of gamma camera images of the lower respiratory tract in terms of %removal/min of the radiolabel from the trachea 25 min after inhalation and from the outer zone of the right lung after 1.9 to 3 h. Symptoms, forced ventilatory function, and MCh response were unaffected by either fog. Tracheal clearance was more rapid in four of four subjects after AF (0.83 +/- 1.58% removal/min) compared with that after SF (-0.54 +/- 0.85% removal/min). Outer zone clearance was more rapid in six of seven subjects after AF (0.22 +/- 0.15% removal/min) compared with that after SF (0.01 +/- 0.09% removal/min).(ABSTRACT TRUNCATED AT 250 WORDS)