Effect of a single 1200 Mg dose of Mucinex® on mucociliary and cough clearance during an acute respiratory tract infection

BACKGROUND

Observational studies suggest that orally administered guaifenesin (GGE) may thin lower respiratory tract secretions but none have examined its effects on mucociliary and cough clearance (MCC/CC) during a respiratory tract infection (RTI). The current study was a randomized, parallel-group, double-blind, placebo-controlled study in non-smoking adults who suffered from an acute upper RTI.

METHODS

We assessed the effects of a single dose of Mucinex(®) 1200 mg (2 × 600 mg extended release tablets) (ER GGE) on 1) MCC/CC by assessing the rate of removal from the lung of inhaled radioactive tracer particles (Tc99m-sulfur colloid), 2) sputum dynamic rheology by stress/strain creep transformation over the linear part of the curve, 3) sessile drop interfacial tension by the deNouy ring technique, and 4) subjective symptom measures. MCC was measured during the morning (period 1) and compared to that in the afternoon 4 h later (period 2) immediately following either drug (n = 19) or placebo (n = 19). For both period 1 and 2 subjects performed 60 voluntary coughs from 60 to 90 min after inhalation of radio-labeled aerosol for a measure of CC. Sputum properties were measured from subjects who expectorated sputum during the cough period post treatment (n = 8-12 for each cohort).

RESULTS

We found no effect of ER GGE on MCC or CC compared to placebo. MCC through 60 min for period 1 vs. 2 = 8.3 vs. 11.8% (placebo) and = 9.7 vs. 11.1% (drug) (NS) and CC for period 1 vs. 2 was 9.9 vs. 9.1% (placebo) and 10.8 vs. 5.6% (drug) (NS). There was no significant difference in sputum biophysical properties after administration of drug or placebo.

CONCLUSIONS

There was no significant effect of a single dose of ER GGE on MCC/CC or on sputum biophysical properties compared to placebo in this population of adult patients with an acute RTI. ClinicalTrials.gov Identifier: NCT01114581.

Duration of action of hypertonic saline on mucociliary clearance in the normal lung

Inhalation of hypertonic saline (HS) acutely enhances mucociliary clearance (MC) in both health and disease. In patients with cystic fibrosis (CF), repeated use of HS causes a sustained improvement in MC as well as clinical benefit. The pharmacodynamic duration of activity on MC may be an important determinant of its therapeutic potential in other airways diseases. Before moving toward testing the clinical benefits of HS for non-CF indications, we sought to assess the duration of pharmacodynamic effects of HS in healthy subjects by performing radiotracer clearance studies at baseline, 30-min post-HS administration, and 4-h post-HS administration. Indeed, acceleration of MC was observed when measured 30 min after HS inhalation. This acceleration was most pronounced in the first 30 min after inhaling the radiotracer in the central lung region (mean Ave30Clr = 15.5 vs. 8.6% for 30-min post-HS treatment vs. mean baseline, respectively, P < 0.005), suggesting that acute HS effects were greatest in the larger bronchial airways. In contrast, when MC was measured 4 h after HS administration, all indices of central lung region MC were slower than at baseline: Ave30Clr = 5.9% vs. 8.6% (P = 0.10); Ave90Clr = 12.4% vs. 16.8% (P < 0.05); clearance through 3 h = 29.4 vs. 43.7% (P < 0.002); and clearance through 6 h = 39.4 vs. 50.2% (P < 0.02). This apparent slowing of MC in healthy subjects 4-h post-HS administration may reflect depletion of airway mucus following acute HS administration.

Removal of sedimentation decreases relative deposition of coarse particles in the lung periphery

Lung deposition of >0.5-μm particles is strongly influenced by gravitational sedimentation, with deposition being reduced in microgravity (μG) compared with normal gravity (1G). Gravity not only affects total deposition, but may also alter regional deposition. Using gamma scintigraphy, we measured the distribution of regional deposition and retention of radiolabeled particles ((99m)Tc-labeled sulfur colloid, 5-μm diameter) in five healthy volunteers. Particles were inhaled in a controlled fashion (0.5 l/s, 15 breaths/min) during multiple periods of μG aboard the National Aeronautics and Space Administration Microgravity Research Aircraft and in 1G. In both cases, deposition scans were obtained immediately postinhalation and at 1 h 30 min, 4 h, and 22 h postinhalation. Regional deposition was characterized by the central-to-peripheral ratio and by the skew of the distribution of deposited particles on scans acquired directly postinhalation. Relative distribution of deposition between the airways and the alveolar region was derived from data acquired at the various time points. Compared with inhalation in 1G, subjects show an increase in central-to-peripheral ratio (P = 0.043), skew (P = 0.043), and tracheobronchial deposition (P < 0.001) when particles were inhaled in μG. The absence of gravity caused fewer particles to deposit in the lung periphery than in the central region where deposition occurred mainly in the airways in μG. Furthermore, the increased skew observed in μG likely illustrates the presence of localized areas of deposition, i.e., "hot spots", resulting from inertial impaction. In conclusion, gravity has a significant effect on deposition patterns of coarse particles, with most of deposition occurring in the alveolar region in 1G but in the large airways in μG.

Effect of inhaled dust mite allergen on regional particle deposition and mucociliary clearance in allergic asthmatics

BACKGROUND

Acute exacerbations in allergic asthmatics may lead to impaired ability to clear mucus from the airways, a key factor in asthma morbidity.

OBJECTIVE

The purpose of this study was to determine the effect of inhaled house dust mite challenge on the regional deposition of inhaled particles and mucociliary clearance (MCC) in allergic asthmatics.

METHODS

We used gamma scintigraphy (inhalation of (99m) Tc -sulphur colloid particles) to measure the regional particle deposition and MCC in allergic asthmatics (n=12) 4 h following an inhaled dust mite allergen challenge (Dermatophagoides farinae extract; PD(max) =fall in forced expiratory volume in 1 s of 10%) for comparison with baseline non-challenge measures.

RESULTS

In responders (n=9 PD(max) dose), lung function returned to pre-challenge values by 3 h but was significantly decreased at 6 and 24 h in three of the responders (i.e. late-phase response) and induced sputum eosinophils were increased at 24 h post-challenge (P<0.05). Responders showed enhanced bronchial airway deposition of inhaled particles (P<0.05) and slowed clearance from the central lung zone (P<0.01) at 4 h post-challenge compared with the baseline (no allergen challenge) that was predicted by the PD(max) allergen concentration (r=-0.70, P<0.05). The decline in lung function at 24 h post-challenge correlated with reduced MCC from the central lung zone (r=-0.78, P<0.02) and PD(max) . Non-responders (n=3) showed no change in lung function, regional deposition or MCC post-challenge vs. baseline.

CONCLUSIONS AND CLINICAL RELEVANCE

These data suggest that regional deposition and clearance of inhaled particles may be sensitive for detecting mild airway obstruction associated with early- and late-phase allergen-induced effects on mucus secretions. The study was listed on clinicaltrials.gov (NCT00448851).

In vivo uptake of inhaled particles by airway phagocytes is enhanced in patients with mild asthma compared with normal volunteers

BACKGROUND

The uptake of inhaled particulate matter by airway phagocytes is an important defence mechanism contributing to the clearance of potentially toxic substances, including aeroallergens, from the lung. Since airway monocytes and macrophages can also function as antigen presenting cells, their ability to engulf materials deposited on the airway surface is of particular interest in patients with allergic asthma. To determine whether airway mononuclear phagocytes of patients with allergic asthma might have enhanced phagocytic activity, the in vivo uptake of inhaled radiolabelled particles was compared in 10 patients with mild allergic asthma and 8 healthy (non-allergic) individuals.

METHODS

Phagocyte function was assessed by quantifying the proportion of radioactivity associated with cellular and supernatant fractions of induced sputum 2 h after inhalation of radiolabelled sulfur colloid particles. All subjects were pretreated with albuterol before sputum induction. A standardised breathing pattern was used to target aerosol deposition in the bronchial airways.

RESULTS

In vivo particle uptake by airway cells was significantly greater in patients with asthma than in healthy volunteers (57.2% (95% CI 46.5% to 67.9%) vs 22.3% (95% CI 4.9% to 39.6%), p<0.01), as was in vitro phagocytosis of opsonised zymosan-A bioparticles. There was also a significant correlation (r = 0.85, p<0.01) between the percentage of sputum mononuclear phagocytes and the percentage uptake of particles in the patients with asthma but not in the control subjects.

CONCLUSIONS

In vivo particle uptake by airway macrophages is enhanced in persons with mild asthma. Enhanced uptake and processing of particulate antigens could contribute to the pathogenesis and progression of allergic airways disease and may contribute to the increased risk of disease exacerbation associated with particulate exposure.

Regional deposition of coarse particles and ventilation distribution in healthy subjects and patients with cystic fibrosis

The efficacy of inhaled pharmaceuticals depends, in part, on their site of respiratory deposition. Markedly nonuniform ventilation distribution may occur in persons with obstructive airways diseases and may affect particle deposition. We studied the relationship between regional deposition (RDep) and regional ventilation (RVent) in a group of 12 cystic fibrosis (CF) patients with mild to moderate airway obstruction (63 +/- 8% predicted FEV1) and 11 healthy nonsmoking volunteers (104 +/- 13% predicted FEV1) using planar scintigraphic methods. RDep was assessed from initial deposition and 24-h retention images for monodisperse technetium-99m-labeled iron oxide particles (5-microm MMAD). Regional volumes and RVent were assessed from xenon-133 equilibrium and washout, respectively. Six regions of interest per lung were established by dividing each lung into thirds by height and approximately half by width. The two lower regions of the left lung were not analyzed due to activity in the stomach. Remaining regions were categorized as central (two interior-most regions) and peripheral (eight exterior regions). RDep and RVent were computed for the eight peripheral regions. Tracheobronchial (TB) deposition was estimated for each of the peripheral regions as the difference between initial activity and decay-corrected 24-h retention or parenchymal deposition. RDep was computed as the fraction of material within a region normalized to regional volume. RVent for each region was determined by normalizing the xenon washout rate for that region by the total washout rate for the eight peripheral regions. Significant linear associations were found between RDep and RVent in both the healthy subjects and CF patients. In healthy subjects, RDep in the TB airways was positively associated with RVent (p = 0.03). In CF patients, RDep in the TB airways was negatively associated with RVent (p = 0.04) and RDep in the parenchyma was positively associated with RVent (p < 0.001). The initial pattern of RDep in the lung was not significantly associated with RVent in either group. These data suggest that significant coarse particle deposition may occur in the TB airways of poorly ventilated lung regions in CF patients, whereas, particle deposition in the TB airways of the healthy subjects follows ventilation.

Effects of inhaled iron oxide particles on alveolar epithelial permeability in normal subjects

Pulmonary inflammation secondary to oxidant generation catalyzed by transition metals associated with inhaled particles is one factor postulated to underlie the acute health effects of particulate air pollution. We postulated that inhaled iron oxide particles with associated amounts of soluble iron should induce mild pulmonary inflammation and lead to altered alveolar epithelial integrity and altered gas exchange. To test this hypothesis we examined the effects of inhaled iron oxide particles on alveolar epithelial permeability. Sixteen healthy subjects inhaled aerosols of iron oxide particles (1.5 microm mass median aerodynamic diameter) having either high or low water-soluble iron content [3.26 +/- 0.25 (SE) and 0.14 +/- 0.04 microg soluble iron/mg of particles, respectively] for 30 min at an average mass concentration of 12.7 mg/m(3). Alveolar epithelial permeability was assessed by measuring the pulmonary clearance of an inhaled radiolabeled tracer molecule ((99m)Tc-DTPA, diethylene triamine pentaacetic acid) using a gamma camera at 1/2 h and 24 h post particle exposure. Carbon monoxide lung diffusing capacity (DL(CO)) and spirometry were also performed before and after breathing the iron oxide. As a control, on a separate day, the procedures were duplicated except that the subject breathed particle-free air. For those subjects breathing aerosols with high soluble iron, we found no significant difference in DTPA clearance half-times after breathing particles versus particle-free air either at 1/2 h (97.4 +/- 15.4 vs. 116.1 +/- 15.5 min, respectively) or 24 h postinhalation (105.1 +/- 13.8 vs. 106.9 +/- 12.9 min, respectively). Likewise, for those subjects breathing aerosols with low soluble iron content we found no significant difference in DTPA clearance half-times after breathing particles versus particle-free air either at 1/2 h (108.6 +/- 31.9 vs. 95.6 +/- 10.8 min, respectively) or 24 h postinhalation (130.0 +/- 18.0 vs. 105.8 +/- 13.7 min, respectively). We found no significant differences in DL(CO) between particle exposures and air exposures. Minor differences in spirometric measurements were noted but were not statistically significant. We conclude that inhalation of iron oxide particles did not cause an appreciable alteration of alveolar epithelial permeability, lung diffusing capacity, or pulmonary function in healthy subjects under the studied conditions.

Induced sputum derives from the central airways: confirmation using a radiolabeled aerosol bolus delivery technique

Indirect evidence suggests that induced sputum derives from the surfaces of the bronchial airways. To confirm this experimentally, we employed a radiolabeled aerosol bolus delivery technique that preferentially deposits aerosol in the central airways in humans. We hypothesized that there would be significantly more radioactivity recovered in an induced sputum sample, and greater airways clearance of radiolabeled particles, immediately after a central versus peripheral airways deposition. Ten healthy volunteers underwent radiolabeled aerosol deposition ((99m)Tc sulfur colloid particles) to the central and peripheral airways on separate occasions followed immediately by induced sputum or no sputum (control), while seated in front of a gamma camera. Radioactivity was measured in the selected sputum sample, processed cell pellet, and supernatant fraction. Significantly more radioactivity was present in all portions of the sputum sample after central versus peripheral airways deposition (i.e., selected sample: 15,607 counts +/- 2,985 versus 943 counts +/- 298, p = 0.001). Clearance from the whole lung was significantly greater 40 min after central versus peripheral airways deposition (48 +/- 3% versus 5 +/- 1%, p = 0.0001). Compared with control, induced sputum greatly enhanced clearance after central deposition (48 +/- 3% versus 11 +/- 6%, p = 0.0001), but not after peripheral deposition (5 +/- 1% versus 3 +/- 0.8%). These results provide direct evidence that induced sputum derives from the central airways with little or no contribution from the peripheral airways.

Effect of aerosolized uridine 5'-triphosphate on mucociliary clearance in mild chronic bronchitis

Previous studies show that uridine 5'-triphosphate (UTP), a P2Y(2) receptor agonist, is effective at acutely enhancing mucociliary clearance in healthy, nonsmoking adults. UTP solution for inhalation is being developed by Inspire Pharmaceuticals under the compound number INS316. In a double-blind, randomized, crossover, placebo-controlled study we tested the single-dose effect of UTP in chronic smokers with mild chronic bronchitis (n = 15) by measuring the clearance of (99m)Tc-Fe(2)O(3) particles (4.0 microm mass median aerodynamic diameter [MMAD]) after inhalation of nebulized placebo (0.9% saline) and two doses of UTP (20 and 100 mg in the nebulizer). On each study day, gamma camera scanning was performed over a 2-h period. After an initial deposition scan, subjects inhaled placebo or UTP during the first 20 min of scanning. Analysis of whole lung clearance showed that the retention-time curves for each day were biphasic and that the earliest break point in the average curves occurred at 50 min. Mean particle clearance rate (Clr in %/min) through 50 min for placebo treatment was Clr = 0.65 +/- 0.27 whereas treatment with UTP showed Clr significantly increased to 0.95 +/- 0.48 and 0.93 +/- 0.44 for the 20-mg and 100-mg dose respectively, p < 0.005 for both as compared with placebo. These data show that mucociliary clearance associated with mild chronic bronchitis is acutely improved with minimal doses of aerosolized UTP, presumably because of its stimulation of ciliary beating and hydration of airway secretions.

Prolonged airway retention of insoluble particles in cystic fibrosis versus primary ciliary dyskinesia

Patients with cystic fibrosis (CF) and primary ciliary dyskinesia (PCD) have been shown to have impaired large airway clearance of radiolabelled particles as measured by external gamma camera scanning up to 6 hours post deposition. Recent studies suggest that 24-hour retention of particles may reflect some airway retention in addition to alveolar retention. In a retrospective study, we analyzed the relationship between the deposition pattern and 24-hour retention (Ret24 hr) of technetium 99-radiolabelled iron oxide (99Tc-Fe2O3) particles in 20 patients with CF, 12 patients with PCD, and 17 normal subjects. By gamma camera analysis, initial aerosol deposition was analyzed in terms of central-peripheral (C/P) activity within the lungs. Gamma camera scanning was performed immediately following deposition and again at 24 hours to assess residual retention (Ret24 hr) as a percent of initial deposition. C/P analysis was also performed on the 24-hour scan (C/P24). For all subjects, initial deposition pattern (C/P) was inversely related to lung function (forced expiratory volume in 1 second [FEV1]%pred vs. C/P, r = -.54). Ret24 hr was also inversely related to initial deposition pattern for all subjects (Ret24 hr vs. C/P ratio, r = -.42). Analysis of covariance showed that for a given C/P ratio, CF patients had significantly greater Ret24 hr compared to normal subjects (9.8 +/- 2.8 [SE]%). In addition, the CF patients had similar C/P24 as the normal subjects (1.35 +/- 0.40 [SD] vs. 1.10 +/- 0.39, respectively). These results suggest that small airway clearance is compromised in CF patients compared to normal subjects. On the other hand, PCD patients had C/P24 similar to their initial deposition C/P ratios (2.78 +/- 1.72 vs. 2.45 +/- 0.87, respectively), significantly greater than 1.0, and significantly greater than CF or normal subjects, suggesting that PCD patients have prolonged particle retention associated with their large bronchial airways.

In vivo characterization of the transitional bronchioles by aerosol-derived airway morphometry

Effective airway dimensions (EADs) were determined in vivo by aerosol-derived airway morphometry as a function of volumetric lung depth (VLD) to identify and characterize, noninvasively, the caliber of the transitional bronchiole region of the human lung and to compare the EADs by age, gender, and disease. By logarithmically plotting EAD vs. VLD, two distinct regions of the lung emerged that were identified by characteristic line slopes. The intersection of proximal and distal segments was defined as VLD(trans) and associated EAD(trans). In our normal subjects (n = 20), VLD(trans) [345 +/- 83 (SD) ml] correlated significantly with anatomic dead space (224 +/- 34 ml) and end of phase II of single-breath nitrogen washout (360 +/- 53 ml). The corresponding EAD(trans) was 0.42 +/- 0. 07 mm, in agreement with other ex vivo measurements of the transitional bronchioles. VLD(trans) was smaller (216 +/- 64 ml) and EAD(trans) was larger (0.83 +/- 0.04 mm) in our patients with chronic obstructive pulmonary disease (n = 13). VLD(trans) increased with age for children (age 8-18 yr; P = 0.006, n = 26) and with total lung capacity for age 8-81 yr (P < 0.001, n = 61). This study extends the usefulness of aerosol-derived airway morphometry to in vivo measurements of the transitional bronchioles.

Effect of aerosolized uridine-5'-triphosphate on airway clearance with cough in patients with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a genetic disease characterized by abnormal ciliary structure and function and impaired mucociliary clearance. Because patients with PCD use cough clearance as an airway defense mechanism, we tested the hypothesis that aerosolized uridine-5'-triphosphate (UTP) would improve clearance during cough by its actions to stimulate Cl- secretion and mucin release by goblet cells. We measured clearance during cough in 12 patients with PCD (ages 14 to 71 yr, FEV1 43% to 89% predicted) in a double blind, randomized, crossover study after aerosolization of a single dose of UTP (5 mg/ml, 3.5 ml) or vehicle (0.12% saline, 3.5 ml). Clearance during cough (whole lung) was quantified during and after a series of controlled coughs by measuring the clearance of [99mTc]Fe2O3 particles via gamma camera scanning over 120 min. Safety parameters were recorded during and after drug delivery. Aerosolized UTP improved whole-lung clearance during cough as compared with vehicle (from 0 to 60 min: 0.40 +/- 0.07%/min [UTP] versus 0.26 +/- 0. 04%/min [vehicle] [mean +/- SEM], p = 0.01), and from 0 to 120 min: 0.38 +/- 0.05%/min [UTP] versus 0.25 +/- 0.04%/ min [vehicle], p = 0. 02). Aerosolized UTP is safe, with no serious adverse effects. Whole-lung clearance during cough in patients with defective ciliary function is enhanced after inhalation of UTP.

Combinatorial Libraries by Portioning and Mixing

Abstract:

Combinatorial chemistry - due to its radically new synthetic methods - can be considered a forerunner of chemistry in the next century. One of the most important methods is the portioning-mixing (split-mix) synthesis which embodies the combinatorial principle. It is easily realized. Both manual and automatic devices have been described. Some features that contribute to its popularity include: it produces all possible structural combinations of the monomers, it has outstanding productivity, it leads to the formation of individual compounds in nearly equimolar quantities (affected by statistics and incomplete reactions), and it can be applied to all classes of organic compounds. Since an enormously large number of compounds can be produced in principle in a relatively short time, some practical considerations are discussed that can be useful in library design. Encoding organic libraries by peptide or nucleotide sequences or with binary tags are also described together with methods for tagging macroscopic support units with electronic chips, two dimensional bar codes or colored resin and capsule caps. Among the deconvolution strategies, the iteration method, positional scanning, omission libraries, the Selectide and the Pharmacopeia methods are mentioned. A collection of libraries prepared by portioning-mixing is also included in graphical format.

Cellular and biochemical response of the human lung after intrapulmonary instillation of ferric oxide particles

Bronchoalveolar lavage (BAL) was used to sample lung cells and biochemical components in the lung air spaces at various times from 1 to 91 d after intrapulmonary instillation of 2.6 microm-diameter iron oxide particles in human subjects. The instillation of particles induced transient acute inflammation during the first day post instillation (PI), characterized by increased numbers of neutrophils and alveolar macrophages as well as increased amounts of protein, lactate dehydrogenase, and interleukin-8 in BAL fluids. This response was subclinical and was resolved within 4 d PI. A similar dose-dependent response was seen in rats 1 d after intratracheal instillation of the same particles. The particles contained small amounts of soluble iron (240 ng/mg) and possessed the capacity to catalyze oxidant generation in vitro. Our findings indicate that the acute inflammation after particle exposure may, at least partially, be the result of oxidant generation catalyzed by the presence of residual amounts of ferric ion, ferric hydroxides, or oxyhydroxides associated with the particles. These findings may have relevance to the acute health effects associated with increased levels of ambient particulate air pollutants.

Combinatorial libraries by portioning and mixing

Combinatorial chemistry--due to its radically new synthetic methods--can be considered a forerunner of chemistry in the next century. One of the most important methods is the portioning-mixing (split-mix) synthesis which embodies the combinatorial principle. It is easily realized. Both manual and automatic devices have been described. Some features that contribute to its popularity include: it produces all possible structural combinations of the monomers, it has outstanding productivity, it leads to the formation of individual compounds in nearly equimolar quantities (affected by statistics and incomplete reactions), and it can be applied to all classes of organic compounds. Since an enormously large number of compounds can be produced in principle in a relatively short time, some practical considerations are discussed that can be useful in library design. Encoding organic libraries by peptide or nucleotide sequences or with binary tags are also described together with methods for tagging macroscopic support units with electronic chips, two dimensional bar codes or colored resin and capsule caps. Among the deconvolution strategies, the iteration method, positional scanning, omission libraries, the Selectide and the Pharmacopeia methods are mentioned. A collection of libraries prepared by portioning-mixing is also included in graphical format.

Regional deposition and retention of particles in shallow, inhaled boluses: effect of lung volume

The regional deposition of particles in boluses delivered to shallow lung depths and their subsequent retention in the airways may depend on the lung volume at which the boluses are delivered. To evaluate the effect of end-inspiratory lung volume on aerosol bolus delivery, we had healthy subjects inhale radiolabeled, monodisperse aerosol (99mTc-iron oxide, 3.5-microm mass median aerodynamic diameter) boluses (40 ml) to a volumetric front depth of 70 ml into the lung at lung volumes of 50, 70, and 85% of total lung capacity (TLC) end inhalation. By gamma camera analysis, we found significantly greater deposition in the left (L) vs. right (R) lungs at the 70 and 85% TLC end inhalation; ratio of deposition in L to R lung, normalized to L-to-R ratio of lung volume (mean L/R), was 1.60 +/- 0.45 (SD) and 1. 96 +/- 0.72, respectively (P < 0.001 for comparison to 1.0) for posterior images. However, at 50% TLC, L/R was 1.23 +/- 0.37, not significantly different from 1.0. These data suggest that the L and R lungs may be expanding nonuniformly at higher lung volumes. On the other hand, subsequent retention of deposited particles at 2 and 24 h postdeposition was independent of L/R at the various lung volumes. Thus asymmetric bolus ventilation for these very shallow boluses does not lead to significant increases in peripheral alveolar deposition. These data may prove useful for 1) designing aerosol delivery techniques to target bronchial airways and 2) understanding airway retention of inhaled particles.

Effect of ventilation distribution on aerosol bolus dispersion and recovery

It has been speculated that convective ventilatory inhomogeneities are an important factor influencing aerosol bolus behavior in the compromised lung. Multiple-breath 133Xe washout (MBWXe) is a commonly accepted test of ventilation distribution. By comparing aerosol bolus parameters to MBWXe in 9 healthy subjects and 14 cystic fibrosis patients with mild-to-moderate airway obstruction, we have attempted to discern the effect of altered ventilation distribution on aerosol bolus dispersion and recovery. Aerosol boluses (150-ml width) were delivered to the volumetric penetrations of 250 and 500 ml. Similar tidal volumes (approximately 1.25 liters) and flow rates (0.4 l/s) were used for aerosol bolus and MBWXe maneuvers. Associations between bolus parameters and ventilation distribution were only observed in the cystic fibrosis patients. We conclude that aerosol bolus dispersion and recovery are both influenced by convective ventilatory inhomogeneities induced by airway obstruction in these patients.

Bronchial airway deposition and retention of particles in inhaled boluses: effect of anatomic dead space

The fractional deposition of particles in boluses delivered to shallow lung depths and their subsequent retention in the airways may depend on the relative volume and size of an individual's airways. To evaluate the effect of variable anatomic dead space (ADS) on aerosol bolus delivery we had healthy subjects inhale radiolabeled, monodisperse aerosol (99mTc-iron oxide, 3.5 micron mean mondispersed aerosol diameter) boluses (40 ml) to a volumetric front depth of 70 ml into the lung at a lung volume of 70% total lung capacity end inhalation. By using filter techniques, aerosol photometry, and gamma camera analysis, we estimated the fraction of the inhaled boluses deposited in intrathoracic airways (IDF). ADS by single-breath N2 washout was also measured from 70% total lung capacity. Results showed that among all subjects IDF was variable (range = 0.04-0.43, coefficient of variation = 0.54) and increased with decreasing ADS (r = -0.76, P = 0.001, n = 16). We found significantly greater deposition in the left (L) vs. right (R) lungs; mean L/R (ratio of deposition in L lung to R lung, normalized to ratio of L-to-R lung volume) was 1.58 +/- 0.42 (SD; P < 0.001 for comparison with 1.0). Retention of deposited particles at 2 h was independent of ADS or IDF. There was significant retention of particles at 24 h postdeposition (0.27 +/- 0.05) and slow clearance of these particles continued through 48 h postdeposition. Finally, analysis of central-to-peripheral ratios of initial deposition and 24-h-retention gamma-camera images suggest significant retention of insoluble particles in large bronchial airways at 24 h postdeposition (i.e., 24 h central-to-peripheral ratio = 1.40 +/- 0. 44 and 1.82 +/- 0.54 in the R and L lung, respectively; P < 0.02 for comparison with 1.0). These data may prove useful for 1) designing aerosol delivery techniques to target bronchial airways and 2) understanding airway retention of inhaled particles.

Retention and intracellular distribution of instilled iron oxide particles in human alveolar macrophages

Bronchoalveolar lavage (BAL) was used to sample retention of particles within the alveolar macrophage (AM) compartment at various times from 1 to 91 d following intrapulmonary instillation of 2. 6-microm-diameter iron oxide (Fe2O3) particles in human subjects. Particles were cleared from the lavagable AM compartment in a biphasic pattern, with a rapid-phase clearance half-time of 0.5 d and long-term clearance half-time of 110 d, comparable to retention kinetics determined by more traditional methods. The intracellular distribution of particles within lavaged AMs was similar in bronchial and alveolar BAL fractions. AMs with high intracellular particle burdens disappeared from the lavagable phagocytic AM population disproportionately more rapidly (shorter clearance half-time) than did AMs with lower particle burdens, consistent with the occurrence of a particle redistribution phenomenon as previously described in similar studies in rats. The rates of AM disappearance from the various particle burden categories was generally slightly slower in bronchial fractions than in alveolar fractions. The instillation of particles induced a transient acute inflammatory response at 24 h postinstillation (PI), characterized by increased numbers of neutrophils and alveolar macrophages in BAL fluids. This response was subclinical and was resolved within 4 d PI.

Acute safety and effects on mucociliary clearance of aerosolized uridine 5'-triphosphate +/- amiloride in normal human adults

Impaired mucociliary clearance contributes to the pathophysiology of several airways diseases including cystic fibrosis, asthma, and chronic bronchitis. Extracellular triphosphate nucleotides (adenosine 5'-triphosphate [ATP], uridine 5'-triphosphate [UTP]) activate several components of the mucociliary escalator, suggesting they may have potential as therapeutic agents for airways diseases. We conducted initial (Phase I) studies of acute safety and efficacy of aerosolized UTP alone and in combination with aerosolized amiloride, the sodium channel blocker, in normal human volunteers. Safety was assessed by measurement of pulmonary function. Neither UTP alone nor in combination with amiloride caused any clinically significant adverse effects on airway mechanics, (subdivisions of) lung volumes, or gas exchange. Acute efficacy of UTP and amiloride alone and in combination, was assessed by measuring changes in the clearance of inhaled radiolabeled particles. A 2.5-fold increase in mucociliary clearance was seen in response to UTP alone and in combination with amiloride. We conclude that aerosolized UTP +/- amiloride clearly enhances mucociliary clearance without acute adverse effects in normal adults, and may have therapeutic potential to enhance airways clearance in diseases characterized by retained airways secretions.

Effect of uridine 5'-triphosphate plus amiloride on mucociliary clearance in adult cystic fibrosis

Cystic fibrosis (CF) is characterized by abnormal airway epithelial electrolyte transport leading to viscous airway secretions that are difficult to clear. By enhancing Cl- secretion onto and blocking Na+ absorption from the airway surface, treatment with aerosolized uridine 5'-triphosphate (UTP) plus amiloride may improve the rheology of airway secretions and enhance mucociliary clearance in patients with CF. After performing safety studies of aerosolized UTP/amiloride in adult patients with CF, we investigated the effects of inhaled vehicle and UTP/amiloride on mucociliary clearance of [99mTc] iron oxide particles from the airways of adult patients with CF (n = 14). We found no clinically significant adverse effects from inhalation of therapeutic doses of UTP/amiloride. Mean baseline peripheral clearance rates during the first 40 min of clearance measurements were significantly less in patients with CF than in normal subjects (mean +/- SE: 0.30 +/- 0.05 versus 0.54 +/- 0.07%/min, respectively; p = 0.01). Aerosolized UTP and amiloride in combination improved mucociliary clearance from the peripheral airways of the CF lungs to near normal values (0.51 +/- 0.09%/min; p = 0.04) during this period. These data support the concept for the use of UTP in combination with amiloride as therapy to improve clearance of secretions from the lungs of patients with CF.

Variability of fine particle deposition in healthy adults: effect of age and gender

Recent epidemiologic studies suggest increased mortality among the elderly in association with particulate air pollution. We investigated the variability in fractional deposition (DF) of inhaled particles (2 microns mass median aerodynamic diameter [MMAD]) in 62 subjects with normal lung function, aged 18 to 80 yr. Each subject inhaled 2-microns monodisperse carnauba wax particles while following a breathing pattern previously determined by respiratory inductance plethysmography in that subject (i.e., particles inhaled) was determined by laser aerosol photometry and pneumotachometry at the mouth. DF (mean DF = 0.29 +/- 0.06 (ages 18 to 40 yr), 0.29 +/- 0.07 (ages 41 to 60 yr), and 0.26 +/- 0.06 (age over 60 yr) was independent of age. There was a tendency toward greater DF in female than in male subjects; DF = 0.30 +/- 0.07 (females) and 0.27 +/- 0.06 (males) (p = 0.06); however, because the males had 45% higher minute ventilations than the females, the deposition rate (Drate), or particles depositing per unit of time, was 30% greater in males than in females (p = 0.004). Multiple regression analysis showed that among all subjects, the variability in DF was best predicted by variability in the breathing period (T) associated with the pattern used to breathe the particles, and by the subject's specific airway resistance (sRAW). These results may prove useful in determining age- and gender-relative risks that may be associated with the inhalation of pollutant particles in ambient air.

Measuring alveolar dimensions at total lung capacity by aerosol-derived airway morphometry

A technique based on particle sedimentation, aerosol-derived airway morphometry (ADAM), was modified to investigate the morphometry of human lung airspaces at full inflation in 54 subjects with normal lung function, ages 18 to 69 years. The technique compares the recovered concentrations of monodisperse aerosol particles after gravitational settling during breath holds to determine effective airspace diameters (EADs) as a function of volumetric lung depth. The method is simple and non-invasive, requiring only several inhalations of aerosol to total lung capacity, breath holds at end inhalation and exhalation to residual volume (RV). The method is sensitive enough to detect differences in the smallest observed airspaces (EADmin) due to normal aging of healthy lungs when older subjects are compared to younger subjects. The average EADmin was larger (p = 0.009) for the oldest adults (293 +/- 54 um, s.d., 50-70 years, n = 13) at the deepest volumetric lung depth (near 40% of TLC into the lung) when compared to the youngest adults (250 +/- 38 um, s.d., 18-40 years, n = 22). The two groups had similar EADs at a depth of 5% of TLC. No gender difference in EADmin was found when comparing all males and females. No correlation was found between EADs and TLC implying number of alveolar airspaces rather than airspace size determines lung volume. The effects of changing the aerosol inhalation volume to TLC ratio was also investigated. Compared to the dichotomous Weibel morphometric model, the average EADs of 22 18-40 year old subjects were found to be equivalent near 1% TLC and 40% TLC, but were larger in size than the model between those extremes with a maximum difference occurring at approximately 3% TLC. This method appears to be extremely sensitive to in vivo changes in airspace dimensions and may prove useful in determining changes in these dimensions associated with normal lung development and early disease states.

Retention of insoluble particles after local intrabronchial deposition in dogs

Recent studies have challenged the generally accepted hypothesis that bronchial particle clearance is complete within 24-48 h postdeposition. We studied bronchial retention of inert particles using a bronchoscope and microspray nozzle to localize deposition in a bronchus while avoiding alveolar deposition. Six-microliter aliquots (444 kBq) of submicrometer (number mean diameter = 0.22 microns, geometric standard deviation = 1.75) technetium-99m-labeled (99mTc) sulfur colloid (SC) particles (n = 6) or the unbound radiolabel 99mTc-pertechnetate (99mTcO4-; n = 3) were sprayed onto a 5-mm-diam bronchus in halothane-anesthetized dogs. Radioactivity at the deposition site and clearance pathway was monitored externally with a gamma camera beginning immediately postspray. Bronchial retention of SC was 8.5 +/- 2.4 and 1.5 +/- 0.7% at 3 and 24 h postspray, respectively. Tracheal mucus velocity was measured at 10.4 +/- 2.2 mm/min. For comparison, clearance of inhaled submicrometer SC particles was also measured in the same dogs. Retention of inhaled aerosolized SC (peripheral lung deposition) was 98.1 +/- 1.1 and 76.3 +/- 1.8% at 3 and 24 h, respectively. 99mTcO4- cleared from the bronchi slightly more rapidly than did SC. Radioactivity was readily detected in the blood after deposition of 99mTcO4- but not of SC. Thus SC cleared by mucociliary transport, whereas 99mTcO4- cleared predominantly by transepithelial absorption. We conclude that clearance of submicrometer particles from a 5-mm conducting airway is very nearly complete by 24 h, with approximately 92% of the clearance occurring within the first 3 h postdeposition.

Dispersion of aerosol boluses in the human lung: dependence on lung volume, bolus volume, and gender

The dispersion of aerosol boluses in the human lungs has been studied in health and disease, usually as a means of investigating convective mixing. However, there are limited data on the roles of critical factors, such as the volume of inhaled boluses, lung inflation, and gender on dispersion. To examine these factors, we measured the difference in volume variance between exhaled and inhaled boluses (sigma 2V) of a 0.5-micron aerosol in 11 healthy male and 12 healthy female subjects as a function of tidal volume (VT = 1,000 and 1,500 ml in females and 1,000 and 2,000 ml in males), bolus penetration volume (Vi at 250-ml increments over each VT), and bolus volume (target VBol = 75, 150, and 300 ml). Analysis of variance showed marginally significant gender effects (P = 0.073) on sigma 2V, with sigma 2V greater in males than in females. There was also a significant effect of VBol on sigma 2V (P < 0.001). A Vi-dependent mean volume shift between inhaled and exhaled boluses (delta V) was observed at all Vi except 500 ml. The observation of gender and VBol effects and the existence of a nonzero delta V suggest that convective mixing mechanisms other than longitudinal dispersion alone occur in the healthy lung. The lack of VT dependence suggests a minimal role of lung inflation above functional residual capacity on dispersion. The dependence of sigma 2V on Vi2 up to 1,750 ml and minimal VBol effects demonstrates that convective mixing processes continue far into the gas exchange regions of the lung and support a significant role for axial streaming.

Pharmacologic treatment of abnormal ion transport in the airway epithelium in cystic fibrosis

Cystic fibrosis (CF) is a recessive genetic disease reflecting mutations in the gene coding for the CF transmembrane regulator (CFTR) protein, which normally functions as a cyclic adenosine monophosphate (cAMP)-regulated chloride (Cl-) channel. Functional abnormalities include thick airway secretions resulting from defective cAMP-mediated Cl- (liquid) secretion and a related defect, excessive sodium (Na+) (liquid) absorption. Novel pharmacologic agents are being tested as therapy for these ion transport defects. Aerosolized amiloride inhibits excessive Na+ absorption, and pilot studies in adult patients with CF show slowing of the disease-associated decline in lung function. Clinical trials of amiloride are currently underway in adults and adolescents, and short-term safety studies have been initiated in children. Aerosolized uridine triphosphate (UTP) induces Cl- (and liquid) secretion in CF airway epithelia via non-CFTR Cl- channels. Short-term aerosolized UTP is well tolerated by normal subjects and patients with CF, and pilot studies in normal subjects show that aerosolized UTP is an effective stimulator of mucociliary clearance. Pharmacotherapy that modifies airway epithelial ion transport may provide new opportunities for treatment of CF lung disease.

Effect of enhanced supramaximal flows on cough clearance

Efficiency of cough for clearing mucus from the lungs is believed to be a function of peak airflow velocities in the airways. Initial transient supramaximal flows are characteristic of cough, and these peak flow rates can be enhanced by placing a triggered shutter at the mouth, serving the role of the epiglottis. Using radiolabeled monodispersed aerosols (99mTc-iron oxide) and gamma camera analysis, we measured over a 2-h period the efficacy of 60 voluntary vs. shutter coughs for clearing mucus from the airways of patients (n = 15) with chronic airway obstruction (mean ratio of forced expired volume in 1 s to forced vital capacity = 0.55). In a subset of patients (n = 9), we also measured the efficacy of forced expirations, or huffs, without glottis closure. Peak flow rate was greater for shutter than voluntary coughs [9.4 +/- 2.0 (SD) vs. 4.1 +/- 1.9 l/s; P < 0.001]. Retention at 60 min (as a fraction of initial deposition) was significantly different for the 3 study days (control, 0.83 +/- 0.17; voluntary cough, 0.69 +/- 0.18; shutter cough, 0.75 +/- 0.19; P = 0.01), but only control vs. voluntary cough values were significantly different from each other (P = 0.01). In contrast, retention at 120 min was significantly different for the 3 days, but both voluntary and shutter coughs were significantly different from control (P = 0.01 and P = 0.02, respectively) (control, 0.73 +/- 0.16; voluntary cough, 0.61 +/- 0.20; shutter cough, 0.65 +/- 0.20). Patients studied with buffs showed a clearance rate faster than control and similar to that associated with voluntary cough.(ABSTRACT TRUNCATED AT 250 WORDS)

Mucociliary clearance of inhaled particles measured at 2 h after ozone exposure in humans

Acute exposure of humans to ozone is known to acutely cause pulmonary function decrements, inflammation, and increased permeability of pulmonary epithelium. A single study in humans has also shown that mucociliary transport increases during acute ozone exposure. Because different responses have shown a different time course of recovery after exposure, it was important to examine mucociliary transport at a different time after the cessation of ozone exposure. We exposed 15 healthy male and female nonsmoking subjects, on different occasions, to clean air and 0.4 ppm ozone for 1 h while they exercised continuously. Pulmonary function was measured immediately before and after exposure and 90 min and 24 h after exposure. Between 2 and 5 h after each exposure, retention of inhaled 5-microns mass median aerodynamic diameter 99mTc-labeled Fe2O3 particles was measured. Each subject returned the next day for a final particle retention measurement. Despite significant changes in pulmonary function, there was no difference in mean whole lung retention time of particles between clean air [77.9 +/- 0.8 (SE) min] and ozone (78.0 +/- 0.8 min) exposures, indicating that mucociliary transport is unaffected by ozone exposure when it is measured 2 h after exposure.

The acute effect of ipratropium bromide bronchodilator therapy on cough clearance in COPD

Using radiolabeled, monodispersed aerosols (99mTc-iron oxide) and gamma camera analysis, we measured the efficacy of cough for clearing mucus from the airways of the lung following inhalation of the bronchodilator ipratropium bromide (IB) (Atrovent, Boehringer Ingelheim, Inc), a drug that has been shown to have no effect on mucociliary clearance in COPD. Clearance of radiolabeled aerosol was studied over a 2.5-h period on three separate days, a control day with no coughing, and two study days during which the patient performed controlled cough maneuvers over the course of clearance measurements following IB or placebo therapy (double blind, crossover). Fifteen patients, age > 45 years, with stable moderate-to-severe airway obstruction (mean FEV1/FVC = 0.45) were studied. IB diminished the effectiveness of cough for clearing the radiolabeled particles from the airways. This effect of IB on cough clearance may be due to (1) changes in the airflow dynamics induced by bronchodilation or (2) altered rheology or depth of airway secretions.

Ineffectiveness of cough for enhancing mucus clearance in asymptomatic smokers

Using monodisperse aerosols radiolabeled with 99mTc, we studied the effectiveness of cough and rapid inhalations for clearing mucus in ten asymptomatic smokers. On three separate study days, each subject breathed 5 microns (MMAD) 99mTc-iron oxide particles under controlled breathing conditions. While seated in front of a gamma camera, retention (R) of lung activity (measured as a percent of initial activity) was measured over the initial 2 h and again at 24 h following particle inhalation. On the control day the subject sat quietly in front of the camera, while on the cough day each subject performed 60 controlled coughs during the first hour of retention measurements, and on the rapid inhalation study day each subject performed 90 rapid inhalations during the first hour of retention measurements. Because breathing patterns were controlled during particle inhalation, initial lung deposition patterns were matched on control, cough, and rapid inhalation study days. By paired analysis, retentions at both 1 and 2 h (R1 and R2) for the cough and rapid inhalation measurements were not significantly different from control (mean control R1 = 69 percent; mean cough R1 = 66 percent; mean rapid inhalation R1 = 66 percent, NS; and mean control R2 = 59 percent, mean cough R2 = 55 percent; mean rapid inhalation R2 = 54 percent, NS). Retention at 24 h (R24) was not significantly different between cough, rapid inhalation, and control measurements (mean cough R24 = 15 percent, mean rapid inhalation R24 = 14 percent, mean control R24 = 17 percent). In other words, these young smokers with normal pulmonary function were unable to enhance their rate of mucus clearance by coughing. The inability of these young smokers to enhance their mucus clearance by cough suggests a change in the mucociliary apparatus from normal.

Aerosolized drug delivery: fractional deposition of inhaled particles

Delivery of drugs by aerosol is increasingly used as a means of providing therapy to both the lungs and to the rest of the body through absorption into the pulmonary circulation. The techniques, definitions, and terminology for aerosol delivery are not standardized or necessarily understood by the increasing number of clinicians and clinical investigators involved in these studies. This paper attempts to establish some definitions and guidelines for defining and characterizing deposition of aerosols in the respiratory tract. Some of the parameters that affect deposition are discussed (e.g., particle size, breathing pattern, airway caliber). It is suggested that these parameters be controlled or measured when characterizing new aerosol delivery systems for clinical investigations. These recommendations were discussed and agreed upon during an expert meeting on definitions and standards related to aerosols in medicine at the 8th Congress of ISAM.

The effect of ozone exposure on the dispersion of inhaled aerosol boluses in healthy human subjects

Acute exposure of humans to low levels of ozone are known to cause decreases in FVC and increases in SRaw. These alterations in lung function do not, however, elucidate the potential for acute small airway responses. In this study we employed a test of aerosol dispersion to examine the potential effects of ozone on small airways in humans. Twenty-two healthy nonsmoking male volunteers were exposed to 0.4 ppm ozone for 1 h while exercising at 20 L/min/m2 body surface area. Before and immediately after exposure, tests of spirometry (FVC, FEV1, and FEF25-75) and plethysmography (Raw and SRaw) were performed. Subjects also performed an aerosol dispersion test before and after exposure. Each test involved a subject inhaling five to seven breaths of a 300-ml bolus of a 0.5 micron triphenyl phosphate aerosol injected into a 2-L tidal volume. The bolus was injected into the tidal breath at three different depths: at Depth A the bolus was injected after 1.6 L of clean air were inhaled from FRC, at Depth B after 1.2 L, and at Depth C after 1.2 L but with inhalation beginning from RV. The primary measure of bolus dispersion was the expired half-width (HW). Secondary measures were the ratio (expressed as percent) of peak exhaled aerosol concentration to peak inhaled concentration (PR), shift in the median bolus volume between inspiration and expiration (VS), and percent of total aerosol recovered (RC). Changes in pulmonary function after ozone exposure were consistent with previous findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Cough-enhanced mucus clearance in the normal lung

We studied the effectiveness of cough for clearing mucus in 12 nonsmoking subjects with normal lung function. On 2 separate study days, each subject breathed 6-microns Mass Median Aerodynamic Diameter 99mTc-labeled iron oxide particles under controlled breathing conditions while they were seated in front of a gamma camera. Retention (R) of lung activity was measured over the initial 2 h and again at 24 h after particle inhalation. On the control day the subject sat quietly in front of the camera, while on the cough day each subject performed 60 controlled coughs during the 1st h of retention measurements. By paired analysis, retentions at both 1 and 2 h (R1 and R2, respectively) for the cough measurements were significantly less than control (mean control R1 = 85% vs. mean cough R1 = 72%, P less than 0.002; mean control R2 = 75% vs. mean cough R2 = 65%, P less than 0.02). Retention at 24 h (R24) was not significantly different between cough and control measurements (mean cough R24 = 35% and mean control R24 = 32%). Thus coughing increased the rate at which the radiolabeled particles were cleared from the bronchial airways in these individuals. Follow-up experiments with subjects performing rapid inhalations rather than cough showed similar enhanced particle clearance to that seen with cough. These results suggest that the observed enhancement of mucus clearance by cough (and rapid inhalation) in the normal lung may be due to a stimulation of the mucociliary apparatus rather than via a two-phase gas-liquid flow mechanism.

Relationship between tracheobronchial particle clearance rates and sites of initial deposition in man

Mucociliary clearance was compared in three groups of normal subjects; each group inhaled a different type of aerosol (sebecate, iron oxide, and aqueous) labelled with 99Tc, to determine the relationship between deposition pattern and the subsequent total lung clearance. Standardization for deposition was accomplished by measuring a central to peripheral ratio (C/P) of deposited radioactivity in the thorax. Lung particle retention at 30, 60, 90, 120 min, and 24 h was measured, and compared at each time period to the C/P ratio. A linear relationship between the retention of aerosol at each time period and the C/P ratio was seen among all aerosols, e.g., aerosol with high C/P ratios had less retention of aerosol at a given time period than aerosols with more diffuse deposition patterns and lower C/P ratios. Furthermore, the relationship was similar to that of the more traditional measurement of regional deposition, the 24-h percentage retention. Lung particle retention was compared among aerosols, using analysis of covariance to standardize for C/P ratio. The intersubject variability was similar among all three aerosol groups. Thus, mucociliary clearance can be standardized in healthy subjects by using an initial deposition index, the C/P ratio, with similar accuracy to the 24-h percentage retention, as an index of aerosol deposition. The use of the C/P ratio, however, has distinct advantages over the 24-h retention, in that studies can be conveniently shortened, used with short lived isotopes, and be adapted to techniques investigating lung permeability instead of tracheobronchial clearance. An unexpected finding was the more rapid clearance of sebecate particles, compared with iron oxide or aqueous particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual pathway clearance of 99mTc-DTPA from the bronchial mucosa

Many studies have reported clearance rates of 99mTc-DTPA from the alveolar epithelial surface, but few have measured clearance of this solute from the bronchial mucosa. Those that have attempted such measurements have discounted the possibility that 99mTc-DTPA may be removed from the bronchial airways by mucocilliary transport as well as by absorption through the epithelium. This study was designed to better approximate the rate of 99mTc-DTPA absorption across the bronchial epithelium by correcting the measurements of total 99mTc-DTPA clearance for mucus transport. On two separate study days, each normal, nonsmoking subject (n = 8) breathed an aqueous aerosol (2.0 microns MMAD, sigma g = 2.0) containing 99mTc bound to DTPA or human serum ablumin (HSA) (a relatively nonpermeable solute that is cleared only by mucus transport over the period of measured clearance) while seated in front of a gamma camera. Breathing pattern was standardized to produce a similar central deposition of particles on both study days. From measurements of retention versus time over a 1-h period, exponential rate constants (Ktot and Km) were determined for the clearance of 99mTc-DTPA and 99mTc-HSA, respectively. By modeling the airways as a single compartment with two possible routes of clearance, we determined the permeability rate constant, Kp, as Ktot minus Km. Results showed that mucus clearance (Km) accounted for two thirds of the total rate of 99mTc-DTPA clearance (Ktot) (mean Ktot = 0.00985, Km = 0.00698, and Kp = 0.00287/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Permeability of the bronchial mucosa to 99mTc-DTPA in asthma

Previous investigators, using 99mTc-DTPA aerosol as a marker to assess epithelial permeability in asthma, did not find an increased permeability in this group. However, they either failed to deliver the aerosol to the optimal site (bronchial mucosa, not alveoli) or failed to account for mucociliary clearance in analyzing their results. We studied 10 asthmatics and eight age-matched control subjects using a dosimeter (Spira-Elektra 2) and a carefully controlled breathing pattern to deliver aerosol to the subjects' airways. Two aerosols were delivered on separate days in each patient; 99mTc-DTPA aerosol, and 99mTc-HSA (human serum albumin), using similar breathing patterns to ensure reproducibility of the deposition pattern with the two aerosols. From measurements of retention versus time over a 1-h period, rate constants Ktot and Km were determined for the clearance of 99mTc-DTPA and 99mTc-HSA, respectively. By modelling the airways as a single compartment with two possible routes of clearance, we determined the permeability rate constant, Kp, as Ktot minus Km. There was no significant difference between Ktot in normal subjects and asthmatics; however, because of the slower mucociliary clearance in the asthmatic group, and the relative importance of mucociliary clearance in determining the washout of 99mTc-DTPA aerosol, there was a significant difference in airway permeability between the normal subjects and the asthmatics (t1/2 = 296 min +/- 141 SD and 126 min +/- 58, p less than 0.01, in normal subjects and asthmatics, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

How we marketed drug abuse testing

Careful laboratory planning, a commitment to quality, and extensive documentation are ingredients of a successful drug testing program.

Use of aerosols to estimate mean air-space size in chronic obstructive pulmonary disease

Using in vivo measures of aerosol recovery (RC) as a function of breath-hold time (t) (Gebhart et al. J. Appl. Physiol. 51: 465-476, 1981), we estimated the mean diameter (D) of the pulmonary air spaces in subjects diagnosed with chronic obstructive pulmonary disease (COPD) (n = 8) and in subjects with normal pulmonary function (n = 10). For each subject, RC (aerosol expired/aerosol inspired) decreased exponentially with t. Based on a model of the lung as a system of randomly oriented cylindrical tubes, the half time (t1/2) (i.e., the breath-hold time to reach 50% of RC with no breath hold) is proportional to a mean diameter (D) of air spaces filled with aerosol. Subjects with normal pulmonary function had a mean t1/2 = 6.5 +/- 0.8 s, corresponding to a mean D = 0.36 +/- 0.05 mm. On the other hand, subjects with COPD had a mean t1/2 = 12.7 +/- 3.2 s, corresponding to a mean D = 0.70 +/- 0.18 mm [i.e., twice as large (P less than 0.01) as normal subjects]. Furthermore, D correlated significantly with diffusing capacity in the patients with COPD (r = -0.95, P less than 0.001 for D vs. percent predicted diffusing capacity of CO) but not with any other measure of pulmonary function. In contrast, D varied only slightly in normals and did not correlate with any measure of pulmonary function. We conclude that in vivo measures of RC vs. t, in conjunction with other pulmonary function tests, may be a useful tool for identifying actual changes in pulmonary air-space sizes associated with pulmonary disease.

Human variation in the peripheral air-space deposition of inhaled particles

Intersubject variability in both peripheral air-space dimensions and breathing pattern [tidal volume (VT) and respiratory frequency (f)] may play a role in determining intersubject variation in the fractional deposition of inhaled particles that primarily deposit in the lung periphery (i.e., distal to conducting airways). In healthy subjects breathing spontaneously at rest, we measured the deposition fraction (DF) of a 2.6-microns monodisperse aerosol by Tyndallometry while simultaneous measurement of VT and f were made. Under these conditions particle deposition occurs primarily in the peripheral air spaces of the lung. As an index of peripheral air-space size, we used measurements of aerosol recovery (RC) as a function of breath-hold time (t) (Gebhart et al. J. Appl. Physiol. 51: 465-476, 1981). In each subject, we measured RC (aerosol expired/aerosol inspired) of a 1.0-micron monodisperse aerosol as a function of breath-hold time for inspiratory capacity breaths of aerosol. The half time (t1/2) (the breath-hold time to reach 50% RC with no breath hold) is proportional to a mean diameter (D) of air spaces filled with aerosol. In the 10 subjects studied, we found a variable DF, range 0.04-0.44 [0.25 +/- 0.12 (SD)]. DF correlated most closely with 1/f, or the period of breathing (r = 0.96, P less than 0.01). There was no significant correlation between DF and t1/2 as an index of peripheral air-space size. In fact there was little deviation in t1/2 in these normal subjects [coefficient of variation (CV) = 0.12].(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo hysteresis of airspace dimensions measured by aerosol recovery

In anesthetized mongrel dogs, we made measurements of single breath aerosol recovery (RC) at equal volume points on the inflation and deflation limb of the quasi-static pressure-volume (P-V) curve of the lungs. Using a 1.2 micron monodisperse aerosol, a large aerosol tidal volume (Vt), and a breathing period of 5 sec, we found that losses of particles were primarily due to sedimentation in pulmonary airspaces distal to anatomic dead space. Thus, the RC measurements could be related to a mean radius (R) of airspaces filled with aerosol over the course of the breath. Furthermore, at a given volume, differences between inflation and deflation limb RC could be attributed to differences in R for the two measurements (i.e., RI vs RD). We found that at isovolume, RC as measured from the inflation limb was larger than that measured from the deflation limb for low lung volumes (less than 0.75 TLC). However, the recoveries were similar as lung volume approached TLC (greater than 0.75 TLC). These results implied that at the same volume, RI greater than RD expect at volumes approaching TLC, i.e. a larger mean airspace dimension on the inflation limb than on the deflation limb at equal volume. The findings of this study support a model of nonuniform changes in airspace dimensions associated with in vivo inflation and deflation of the lungs.

Effect of exercise on deposition and subsequent retention of inhaled particles

To investigate the effect of exercise and its associated increase in ventilation on the deposition and subsequent retention of inhaled particles, we measured the fractional and regional lung deposition of a radioactively tagged (99mTc) monodisperse aerosol (2.6 microns mass median aerodynamic diam) in normal human subjects at rest and while exercising on a bicycle ergometer. Breath-by-breath deposition fraction (DF) was measured throughout the aerosol exposures by Tyndallometry. Following each exposure gamma camera analysis was used to 1) determine the regional distribution of deposited particles and 2) monitor lung retention for 2.5 h and again at 24 h. We found that DF was unchanged between ventilation at rest (6-10 l/min) and exercise (32-46 l/min). Even though mouth deposition was enhanced with exercise, it was not large enough to produce a significant difference in the deposition fraction of the lung (DFL) between resting and exercise exposures. The central-to-peripheral distribution of deposited aerosol was larger for the exercise vs. resting exposure, reflecting a shift of particle deposition to more central bronchial airways. Apical-to-basal distribution was not different for the two exposures. Retention at 2.5 h and 24 h (R24) was reduced following the exercise vs. the resting exposure, consistent with greater bronchial deposition during exercise. The product of DFL and R24 gave a measure of fractional burden at 24 h (B24), i.e., the fraction of inhaled aerosol residing in the lungs 24 h after exposure. B24 was not significantly different between rest and exercise exposures.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of aerosols to measure in vivo volume-dependent changes in lung air space dimensions

Using measurements of aerosol recovery following a 5-s breath hold [NRC(5)] as indices of lung air space dimensions, we evaluated the in vivo changes in these dimensions associated with changes in lung volume (VL). In anesthetized dogs, single breaths of a 1.2-micron monodisperse aerosol were introduced into the respirator's cycle at a number of isovolume points on the inflation and deflation limb of the pressure-volume curve for the dog's lungs. At isovolume, NRC(5) measured off the inflation limb was slightly larger than NRC(5) measured off the deflation limb, implying a larger mean air space dimension for the air space configuration on the inflation vs. the deflation limb. Since a constant aerosol tidal volume (VT) was used for all VL in all dogs, the proportion of the lung filled with aerosol, VT/VL = Pn (where Pn is defined as an index of aerosol penetration into the lung periphery), varied along with VL. In all dogs, we found that, for NRC(5) measurements with Pn less than 0.33, NRC(5) steadily increased with increasing VL, which implies an increasing mean air space dimension as VL increases. However, when we account for the effect that changes in Pn with increasing VL have on NRC(5), we conclude that the observed increase in NRC(5) with VL is primarily due to decreases in Pn and not increases in the mean air space dimension as VL increases.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alkyl-lysophospholipids on phosphatidylcholine biosynthesis in leukemic cell lines

Alkyl-lysophospholipids are ether analogues of lysophospholipids that have tumoricidal activity mediated through activation of macrophages or by direct effect on tumor cells by disturbance of phospholipid metabolism. The effect of racemic 1-octadecyl-2-methyl-sn-glycero-3 phosphocholine on phosphatidylcholine synthesis was investigated in sensitive (HL-60) and resistant (K-562) human leukemic cell lines. Radiolabeled lysophosphatidyl-choline, choline, and methionine incorporation into phosphatidylcholine was measured in intact cells exposed for 24 h to varying concentrations of the compound. In HL-60 cells, marked inhibition of phosphatidylcholine synthesis was demonstrated using lysophosphatidylcholine or choline as precursors, but no effect was observed on methionine incorporation. No effects were observed in K-562 cells. These investigations suggest that alkyl-lysophospholipids inhibit phosphatidylcholine synthesis via the acyltransferase reaction and from choline, but not from methionine.