Acute Effect of E-Cigarette Inhalation on Mucociliary Clearance in E-Cigarette Users

Background: Recent studies show e-cigarette (EC) users have increased rates of chronic bronchitic symptoms that may be associated with depressed mucociliary clearance (MCC). Little is known about the acute or chronic effects of EC inhalation on in vivo MCC. Methods: In vivo MCC was measured in young adult vapers (n = 5 males, mean age = 21) after controlled inhalation of a radiolabeled (Tc99m sulfur colloid) aerosol. Whole-lung clearance of radiolabeled deposited particles was measured over a 90-minute period for baseline MCC and associated with controlled periodic vaping over the first 60 minutes of MCC measurements. The vaping challenge was administered from a fourth generation box mod EC containing unflavored e-liquid (65% propylene glycol/35% vegetable glycerin, 3 mg/mL freebase nicotine). The challenge was administered at the start of each 10-minute interval of MCC measurements and consisted of 1 puff every 30 seconds for 5 minutes (i.e., 10 puffs for each 10-minute period for a total of 60 puffs during the initial 60 minutes of MCC measurements). Results: Compared with baseline, peripheral lung average clearance (%) over the 90 minutes of MCC measures was enhanced, associated with EC challenge, 12 (±6) versus 24 (±6), respectively (p < 0.05 by Wilcoxon signed-rank test). Conclusions: Acute enhancement of in vivo MCC during EC challenge is contrary to recent studies showing nicotine-associated slowing of ciliary beat and mucus transport at higher nicotine levels than those used here. However, our findings are consistent with an acute increase in fluid volume and mucin secretion to the bronchial airway surface that is likely short lived. Research reported in this publication was supported by the National Institutes of Health R01HL139369 and registered with ClinicalTrials.gov (NCT03700892).

A novel method for the quantitative assessment of the fitted containment efficiency of face coverings

BACKGROUND

Face masks reduce disease transmission by protecting the wearer from inhaled pathogens and reducing the emission of infectious aerosols. Although methods quantifying efficiency for wearer protection are established, current methods for assessing face mask containment efficiency rely on measurement of a low concentration of aerosols emitted from an infected or noninfected individual.

METHODS

A small port enabled the introduction of 0.05 µm sodium chloride particles at a constant rate behind the mask worn by a study participant. A condensation particle counter monitored ambient particle numbers 60 cm in front of the participant over 3-minute periods of rest, speaking, and coughing. The containment efficiency (%) for each mask and procedure was calculated as follows: 100 × (1 - average ambient concentration with face covering worn/average ambient concentration with a sham face covering in place). The protection efficiency (%) was also measured using previously published methods. The probability of transmission (%) from infected to uninfected (a function of both the containment efficiency and the protection efficiency) was calculated as follows: {1 - (containment efficiency/100)}×{1 - (protection efficiency/100)}×100.

RESULTS

The average containment efficiencies for each mask over all procedures and repeated measures were 94.6%, 60.9%, 38.8%, and 43.2%, respectively, for the N95 mask, the KN95 mask, the procedure face mask, and the gaiter. The corresponding protection efficiencies for each mask were 99.0%, 63.7%, 45.3%, and 24.2%, respectively. For example, the transmission probability for 1 infected and 1 uninfected individual in close proximity was ∼14.2% for KN95 masks, compared to 36%-39% when only 1 individual wore a KN95 mask.

CONCLUSION

Overall, we detected a good correlation between the protection and containment that a face covering afforded to a wearer.

Respiratory Tract Deposition of E-Cigarette Particles

Total and regional deposition of inhaled electronic cigarette (E-cig) particles in the respiratory tract (RT) depends on both physical properties of the inhaled particles and biological factors of users, for example, breathing pattern or puff profile, airway anatomy, and regional ventilation. Accurate particle sizing of E-cig aerosols is essential for predicting particle deposition in the RT. Studies using a variety of sizing methods have shown mass median aerodynamic diameters ranging from 0.2 to 1.2 um and secondary count diameters in the ultrafine range (<0.1 μm). Incorporating these particle sizes into a multiple-path particle dosimetry (MPPD) model shows 10% to 45% total lung deposition by mass and 30% to 80% for ultrafine particles depending on the breathing patterns. These predictions are consistent with experimental measures of deposition fraction of submicron and ultrafine particles. While box-mod-type E-cig devices allow for full "direct-lung" inhalations of aerosol, the more recent pod-based, and disposable E-cigs (e.g., JUUL, Puff Bar, Stig) deliver the aerosol as a "mouth-to-lung" puff, or bolus, that is inhaled early in the breath followed to various degrees by further inhalation of ambient air. Measurement of realistic ventilation patterns associated with these various devices may further improve deposition predictions. Finally, while in vivo measures of RT deposition present a challenge, a recent methodology to radiolabel E-cig particles may allow for such measurements by gamma scintigraphy. Supported by NIH/NHLBI R01HL139369. © 2022 American Physiological Society. Compr Physiol 12: 1-10, year.

Assessing the effect of beard hair lengths on face masks used as personal protective equipment during the COVID-19 pandemic

BACKGROUND

Globally, a large percentage of men keep a beard at least occasionally. Workplace regulations prohibit beards with N95 respirators, but there is little information on the effect of beards with face masks worn by the public for protection against SARS-CoV-2.

METHODS AND FINDINGS

We examined the fitted filtration efficiency (FFE) of five commonly worn protective face masks as a function of beard length following the US Occupational Safety and Health Administration Quantitative Fit Test: N95 (respirator), KF94 and KN95, surgical/procedure, and cloth masks. A comparison using N95 respirators was carried out in shaven and bearded men. A detailed examination was conducted for beard lengths between 0 and 10 mm (0.5 mm increments). The effect of an exercise band covering the beard on FFE was also tested. Although N95 respirators showed considerable variability among bearded men, they had the highest FFE for beard lengths up to 10 mm. KF94 and KN95 masks lost up to 40% of their FFE. Procedure and cotton masks had poor performance even on bare skin (10-30% FFE) that did not change appreciably with beard length. Marked performance improvements were observed with an exercise band worn over the beard.

CONCLUSIONS

Though variable, N95 respirators offer the best respiratory protection for bearded men. While KF94 and KN95 FFE is compromised considerably by increasing beard length, they proved better options than procedure and cotton face masks. A simple exercise band improves FFE for face masks commonly used by bearded men during the COVID-19 pandemic.

A simple HEPA filtering facepiece

Shortages of efficient filtering facepiece respirators leave the public vulnerable to transmission of infectious diseases in small particle aerosols. This study demonstrates that a high-filtration-efficiency facepiece capable of filtering out >95% of 0.05μm particles while being worn can be simply produced with available materials.

Fitted Filtration Efficiency of Double Masking During the COVID-19 Pandemic

This quality improvement study compares the fitted filtration efficiency of commonly available face masks worn singly, doubled, or in combinations.

Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic

IMPORTANCE

During the coronavirus disease 2019 (COVID-19) pandemic, the general public has been advised to wear masks or improvised face coverings to limit transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, there has been considerable confusion and disagreement regarding the degree to which masks protect the wearer from airborne particles.

OBJECTIVES

To evaluate the fitted filtration efficiency (FFE) of various consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks that are intended to improve mask fit or comfort.

DESIGN, SETTING, AND PARTICIPANTS

For this study conducted in a research laboratory between June and August 2020, 7 consumer-grade masks and 5 medical procedure mask modifications were fitted on an adult male volunteer, and FFE measurements were collected during a series of repeated movements of the torso, head, and facial muscles as outlined by the US Occupational Safety and Health Administration Quantitative Fit Testing Protocol. The consumer-grade masks tested included (1) a 2-layer nylon mask with ear loops that was tested with an optional aluminum nose bridge and filter insert in place, (2) a cotton bandana folded diagonally once (ie, "bandit" style) or in a (3) multilayer rectangle according to the instructions presented by the US Surgeon General, (4) a single-layer polyester/nylon mask with ties, (5) a polypropylene mask with fixed ear loops, (6) a single-layer polyester gaiter/neck cover balaclava bandana, and (7) a 3-layer cotton mask with ear loops. Medical procedure mask modifications included (1) tying the mask's ear loops and tucking in the side pleats, (2) fastening ear loops behind the head with 3-dimensional-printed ear guards, (3) fastening ear loops behind the head with a claw-type hair clip, (4) enhancing the mask/face seal with rubber bands over the mask, and (5) enhancing the mask/face seal with a band of nylon hosiery over the fitted mask.

MAIN OUTCOMES AND MEASURES

The primary study outcome was the measured FFE of common consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks.

RESULTS

The mean (SD) FFE of consumer grade masks tested on 1 adult male with no beard ranged from 79.0% (4.3%) to 26.5% (10.5%), with the 2-layer nylon mask having the highest FFE. Unmodified medical procedure masks with ear loops had a mean (SD) FFE of 38.5% (11.2%). All modifications evaluated in this study increased procedure mask FFE (range [SD], 60.3% [11.1%] to 80.2% [3.1%]), with a nylon hosiery sleeve placed over the procedure mask producing the greatest improvement.

CONCLUSIONS AND RELEVANCE

While modifications to improve medical procedure mask fit can enhance the filtering capability and reduce inhalation of airborne particles, this study demonstrates that the FFEs of consumer-grade masks available to the public are, in many cases, nearly equivalent to or better than their non-N95 respirator medical mask counterparts.

Filtration Efficiency of Hospital Face Mask Alternatives Available for Use During the COVID-19 Pandemic

IMPORTANCE

Procuring respiratory protection for clinicians and other health care workers has become a major challenge of the coronavirus disease 2019 (COVID-19) pandemic and has resulted in nonstandard practices such as the use of expired respirators and various decontamination processes to prolong the useful life of respirators in health care settings. In addition, imported, non-National Institute for Occupational Safety and Health (NIOSH)-approved respirators have been donated or acquired by hospitals as a potential replacement for limited NIOSH-approved N95 respirators.

OBJECTIVE

To assess fitted filtration efficiencies (FFEs) for face mask alternatives used during the COVID-19 pandemic.

DESIGN, SETTING, AND PARTICIPANTS

For this quality-improvement study conducted between April and June 2020, we used the Occupational Safety and Health Administration's Quantitative Fit Testing Protocol for Filtering Facepiece Respirators in a laboratory atmosphere supplemented with sodium chloride particles to assess the FFEs of a variety of respirators worn by a male volunteer and female volunteer.

MAIN OUTCOMES AND MEASURES

The FFEs of respirators commonly worn by clinicians and other health care workers and available respirator alternatives during the COVID-19 pandemic.

RESULTS

Of the 29 different fitted face mask alternatives tested on 1 man and 1 woman, expired N95 respirators with intact elastic straps and respirators subjected to ethylene oxide and hydrogen peroxide sterilization had unchanged FFE (>95%). The performance of N95 respirators in the wrong size had slightly decreased performance (90%-95% FFE). All of the respirators not listed as approved in this evaluation (n = 6) failed to achieve 95% FFE. Neither of the 2 imported respirators authorized for use by the Centers for Disease Control and Prevention that were not NIOSH-approved tested in this study achieved 95% FFE, and the more effective of the 2 functioned at approximately 80% FFE. Surgical and procedural face masks had filtering performance that was lower relative to that of N95 respirators (98.5% overall FFE), with procedural face masks secured with elastic ear loops showing the lowest efficiency (38.1% overall FFE).

CONCLUSIONS AND RELEVANCE

This quality-improvement study evaluating 29 face mask alternatives for use by clinicians interacting with patients during the COVID-19 pandemic found that expired N95 respirators and sterilized, used N95 respirators can be used when new N95 respirators are not available. Other alternatives may provide less effective filtration.

Filtration Efficiency of Hospital Face Mask Alternatives Available for Use During the COVID-19 Pandemic

IMPORTANCE

Procuring respiratory protection for clinicians and other health care workers has become a major challenge of the coronavirus disease 2019 (COVID-19) pandemic and has resulted in nonstandard practices such as the use of expired respirators and various decontamination processes to prolong the useful life of respirators in health care settings. In addition, imported, non-National Institute for Occupational Safety and Health (NIOSH)-approved respirators have been donated or acquired by hospitals as a potential replacement for limited NIOSH-approved N95 respirators.

OBJECTIVE

To assess fitted filtration efficiencies (FFEs) for face mask alternatives used during the COVID-19 pandemic.

DESIGN, SETTING, AND PARTICIPANTS

For this quality-improvement study conducted between April and June 2020, we used the Occupational Safety and Health Administration's Quantitative Fit Testing Protocol for Filtering Facepiece Respirators in a laboratory atmosphere supplemented with sodium chloride particles to assess the FFEs of a variety of respirators worn by a male volunteer and female volunteer.

MAIN OUTCOMES AND MEASURES

The FFEs of respirators commonly worn by clinicians and other health care workers and available respirator alternatives during the COVID-19 pandemic.

RESULTS

Of the 29 different fitted face mask alternatives tested on 1 man and 1 woman, expired N95 respirators with intact elastic straps and respirators subjected to ethylene oxide and hydrogen peroxide sterilization had unchanged FFE (>95%). The performance of N95 respirators in the wrong size had slightly decreased performance (90%-95% FFE). All of the respirators not listed as approved in this evaluation (n = 6) failed to achieve 95% FFE. Neither of the 2 imported respirators authorized for use by the Centers for Disease Control and Prevention that were not NIOSH-approved tested in this study achieved 95% FFE, and the more effective of the 2 functioned at approximately 80% FFE. Surgical and procedural face masks had filtering performance that was lower relative to that of N95 respirators (98.5% overall FFE), with procedural face masks secured with elastic ear loops showing the lowest efficiency (38.1% overall FFE).

CONCLUSIONS AND RELEVANCE

This quality-improvement study evaluating 29 face mask alternatives for use by clinicians interacting with patients during the COVID-19 pandemic found that expired N95 respirators and sterilized, used N95 respirators can be used when new N95 respirators are not available. Other alternatives may provide less effective filtration.

Effect of hypertonic saline on mucociliary clearance and clinical outcomes in chronic bronchitis

Background

Mucus dehydration and impaired mucus clearance are common features of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). In CF, inhaled hypertonic saline (HS) improves lung function and produces sustained increases in mucociliary clearance (MCC). We hypothesised that administration of HS (7% NaCl) twice daily for 2 weeks would improve clinical outcomes and produce sustained increases in MCC in COPD subjects with a chronic bronchitis (CB) phenotype.

Methods

Twenty-two CB subjects completed a double-blinded, crossover study comparing inhaled HS to a hypotonic control solution (0.12% saline) administered via nebuliser twice daily for 2 weeks. Treatment order was randomised. During each treatment period, symptoms and spirometry were measured. MCC was measured at baseline, shortly after initial study agent administration, and approximately 12 h after the final dose.

Results

HS was safe and well tolerated but overall produced no significant improvements in spirometry or patient-reported outcomes. CB subjects had slower baseline MCC than healthy subjects. The MCC rates over 60 min (Ave60Clr) in CB subjects following 2 weeks of HS were not different from 0.12% saline but were slower than baseline (Ave60Clr was 9.1±6.3% at baseline versus 5.3±6.9% after HS; p<0.05). Subgroup analyses determined that subjects with residual baseline central lung clearance (14 subjects) had improved spirometry and symptoms following treatment with HS, but not 0.12% saline, treatment.

Conclusions

Inhaled HS appeared to be safe in a general CB population. A specific phenotypic subgroup may benefit from HS but requires additional study.

Radiolabeling an Electronic Cigarette Aerosol Using Technetium Carbon Ultrafine Particles

BACKGROUND

Electronic cigarettes (ECIGs) are widely used, but their health effects are not well known. ECIG exposure is difficult to quantify, and a direct measurement of deposition would be beneficial to in vivo and in vitro toxicity studies. The aim of this study was to demonstrate effective radiolabeling of an ECIG.

METHODS

A technetium-99m-labeled carbon ultrafine (TCU) aerosol was generated and introduced to a fourth-generation ECIG before nucleation and aerosol formation. The aerosolized e-liquid was a commercially available strawberry flavor containing 1.2% nicotine in a 55% propylene glycol and 45% vegetable glycerine base. An ECIG power setting of 100 W was selected. Mass and radioactivity were measured on each stage within a Sierra Cascade Impactor at 14 L/min to verify the labeling technique using the calculated aerodynamic diameters. A strong positive correlation (R² > 0.95) between the percent activity and percent mass deposition on each stage provides a reliable validation of colocation.

RESULTS

Unlabeled ECIG aerosol from the chosen e-liquid produced a mass median aerodynamic diameter (MMAD) of 0.85 μm. An ECIG labeled with TCU produced an aerosol with an activity median aerodynamic diameter of 0.84 μm and an MMAD of 0.84 μm. The relative mass versus radioactivity on each plate was highly correlated (average R² = 0.973, p < 0.001).

CONCLUSION

A TCU radiolabel was generated and shown to associate with the mass of an aerosol produced by a typical commercially available ECIG. Thus, the radioactivity of the deposited aerosol may be used to determine ECIG aerosol deposition for the future in vivo and in vitro dosimetry studies of the third- and fourth-generation ECIGs.

Homogeneity of Aerosol Deposition and Mucociliary Clearance are Improved Following Ivacaftor Treatment in Cystic Fibrosis

BACKGROUND

Using planar gamma scintigraphy of inhaled radioaerosols, we have developed new analytical methods for assessing homogeneity of aerosol deposition and time-dependent particle clearance on a pixel-by-pixel basis, and applied them to a therapeutic cystic fibrosis (CF) study.

METHODS

At baseline and 1 month after beginning treatment with ivacaftor, a cystic fibrosis transmembrane regulator modulator for CF patients with at least one copy of the G551D mutation (n = 13), initial deposition and subsequent mucociliary clearance (MCC) of radiolabeled particles (^99mTechnetium-sulfur colloid, 5 μm mass median aerodynamic diameter) inhaled under controlled breathing conditions were measured.

RESULTS

Improved homogeneity of deposition, that is, decreased areas of higher and lower particle deposition in the lungs, was observed following ivacaftor treatment. The mean number ratio (NR) of pixels with higher deposition, relative to lung size, decreased from 0.14 to 0.09 (p = 0.003) and mean NR of colder pixels decreased from 0.23 to 0.19 (p = 0.004). Particle clearance was also improved following treatment, with mean MCC through 60 minutes equal to 12% versus 24%, without and with treatment, respectively (p = 0.010). Pixel-level analysis of MCC showed that (1) the fraction of pixels clearing >30% at 60 minutes was increased from 0.13 to 0.32 (p = 0.007); and (2) the fraction of pixels clearing <5% at 60 minutes was decreased from 0.54 to 0.37 (p = 0.014), indicating an overall recruitment of more fast-clearing lung regions with ivacaftor treatment.

CONCLUSION

These detailed pixel analyses of deposition and clearance homogeneity may supplement traditional methods that use large regions of interest for assessing efficacy and mechanisms of therapeutic intervention in patients with airways disease.

Regional Ventilation Is the Main Determinant of Alveolar Deposition of Coarse Particles in the Supine Healthy Human Lung During Tidal Breathing

BACKGROUND

To quantify the relationship between regional lung ventilation and coarse aerosol deposition in the supine healthy human lung, we used oxygen-enhanced magnetic resonance imaging and planar gamma scintigraphy in seven subjects.

METHODS

Regional ventilation was measured in the supine posture in a 15 mm sagittal slice of the right lung. Deposition was measured by using planar gamma scintigraphy (coronal scans, 40 cm FOV) immediately postdeposition, 1 hour 30 minutes and 22 hours after deposition of ^99mTc-labeled particles (4.9 μm MMAD, GSD 2.5), inhaled in the supine posture (flow 0.5 L/s, 15 breaths/min). The distribution of retained particles at different times was used to infer deposition in different airway regions, with 22 hours representing alveolar deposition. The fraction of total slice ventilation per quartile of lung height from the lung apex to the dome of the diaphragm at functional residual capacity was computed, and co-registered with deposition data-apices aligned-using a transmission scan as reference. The ratio of fractional alveolar deposition to fractional ventilation of each quartile (r) was used to evaluate ventilation and deposition matching (r > 1, regional aerosol deposition fraction larger than regional ventilation fraction).

RESULTS

r was not significantly different from 1 for all regions (1.04 ± 0.25, 1.08 ± 0.22, 1.03 ± 0.17, 0.92 ± 0.13, apex to diaphragm, p > 0.40) at the alveolar level (r_22h). For retention times r_0h and r_1h30, only the diaphragmatic region at r_1h30 differed significantly from 1.

CONCLUSIONS

These results support the hypothesis that alveolar deposition is directly proportional to ventilation for ∼5 μm particles that are inhaled in the supine posture and are consistent with previous simulation predictions that show that convective flow is the main determinant of aerosol transport to the lung periphery.

A Trans-Nasal Aerosol Delivery Device for Efficient Pulmonary Deposition

BACKGROUND

Efficient delivery of aerosols to the lungs via the nasal route has been difficult to achieve, but it may offer benefits over the traditional oral route for a range of patient populations. Because slow, continuous delivery of short-acting agents could improve safety, tolerability, compliance, and efficacy when compared with the rapid, intermittent aerosol treatments delivered by mouthpiece or mask, a novel trans-nasal pulmonary aerosol delivery (tPAD) device was developed. The tPAD incorporates an aerosol particle-size selection chamber and a custom nasal cannula that are specifically optimized for aerosol delivery to the lung via the nasal route. The tPAD device produced a steady aerosol output (∼2 mL/h) from an optimized nasal cannula with negligible rainout in the cannula for up to 8 hours. The generated aerosol particles were small enough to minimize nasal deposition [volume median diameter (VMD) = 1.4 μm].

METHODS

In this proof-of-concept study, gamma scintigraphy was used to quantitate deposition efficiency of ^99mTc-labeled DTPA in 7% NaCl (hypertonic saline) in healthy human subjects (n = 6) during a short dosing period (15 minutes). A comparison was made with a standard oral jet nebulizer in the same subjects.

RESULTS

The tPAD device achieved high pulmonary deposition (39% ± 8%), based on emitted dose, and matched that of the oral jet nebulizer (36% ± 9%). Low fractions of aerosol deposition in the head and nose region were observed for tPAD (6% ± 6%) and jet nebulizer deliver (1% ± 1%) as well.

CONCLUSIONS

A profile of high pulmonary deposition efficiency and low nasal dose may enable the sustained use of the tPAD platform with a variety of therapeutic agents for a range of pulmonary disorders.

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.

Effect of inhaled endotoxin on mucociliary clearance and airway inflammation in mild smokers and nonsmokers

BACKGROUND

In healthy nonsmokers, inhaled endotoxin [lipopolysaccharide (LPS)] challenge induces airway neutrophilia and modifies innate immune responses, but the effect on mucociliary clearance (MCC), a key host defense response, is unknown. Although smokers are chronically exposed to LPS through inhaled tobacco smoke, the acute effect of inhaled LPS on both MCC and airway inflammation is also unknown. The purpose of this study was to determine the effect of inhaled LPS on MCC in nonsmokers and mild smokers with normal pulmonary function.

METHODS

We performed an open-label inhalational challenge with 20,000 endotoxin units in healthy adult nonsmokers (n=18) and young adult, mild smokers (n=12). At 4 hr post LPS challenge, we measured MCC over a period of 2 hr, followed by sputum induction to assess markers of airway inflammation.

RESULTS

No significant changes in spirometry occurred in either group following LPS challenge. Following LPS, MCC was significantly (p<0.05) slowed in nonsmokers, but not in smokers [MCC=10±9% (challenge) vs. 15±8% (baseline), MCC=14±9% (challenge) vs. 16±10% (baseline), respectively]. Both groups showed a significant (p<0.05) increase in sputum neutrophils 6 hr post LPS challenge versus baseline. Although there was no correlation between the increased neutrophilia and depressed MCC post LPS in the nonsmokers, baseline neutrophil concentration predicted the LPS-induced decrease in MCC in the nonsmokers, i.e., lower baseline neutrophil concentration was associated with greater depression in MCC with LPS challenge (p<0.05).

CONCLUSIONS

These data show that a mild exposure to endotoxin acutely slows MCC in healthy nonsmokers. MCC in mild smokers is unaffected by mild endotoxin challenge, likely due to preexisting effects of cigarette smoke on their airway epithelium.

The Relationship of Mucus Concentration (Hydration) to Mucus Osmotic Pressure and Transport in Chronic Bronchitis

RATIONALE

Chronic bronchitis (CB) is characterized by persistent cough and sputum production. Studies were performed to test whether mucus hyperconcentration and increased partial osmotic pressure, in part caused by abnormal purine nucleotide regulation of ion transport, contribute to the pathogenesis of CB.

OBJECTIVES

We tested the hypothesis that CB is characterized by mucus hyperconcentration, increased mucus partial osmotic pressures, and reduced mucus clearance.

METHODS

We measured in subjects with CB as compared with normal and asymptomatic smoking control subjects indices of mucus concentration (hydration; i.e., percentage solids) and sputum adenine nucleotide/nucleoside concentrations. In addition, sputum partial osmotic pressures and mucus transport rates were measured in subjects with CB.

MEASUREMENTS AND RESULTS

CB secretions were hyperconcentrated as indexed by an increase in percentage solids and total mucins, in part reflecting decreased extracellular nucleotide/nucleoside concentrations. CB mucus generated concentration-dependent increases in partial osmotic pressures into ranges predicted to reduce mucus transport. Mucociliary clearance (MCC) in subjects with CB was negatively correlated with mucus concentration (percentage solids). As a test of relationships between mucus concentration and disease, mucus concentrations and MCC were compared with FEV1, and both were significantly correlated.

CONCLUSIONS

Abnormal regulation of airway surface hydration may slow MCC in CB and contribute to disease pathogenesis.

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.

Comparison of 133 xenon ventilation equilibrium scan (XV) and 99m technetium transmission (TT) scan for use in regional lung analysis by 2D gamma scintigraphy in healthy and cystic fibrosis lungs

BACKGROUND

Quantification of particle deposition in the lung by gamma scintigraphy requires a reference image for location of regions of interest (ROIs) and normalization to lung thickness. In various laboratories, the reference image is made by a transmission scan ((57)Co or (99m)Tc) or gas ventilation scan ((133)Xe or (81)Kr). There has not been a direct comparison of measures from the two methods.

METHODS

We compared (99m)Tc transmission scans to (133)Xe equilibrium ventilation scans as reference images for 38 healthy subjects and 14 cystic fibrosis (CF) patients for their effects on measures of regional particle deposition: the central-to-peripheral ratio of lung counts (C/P); and ROI area versus forced vital capacity. Whole right lung ROI was based on either an isocontour threshold of three times the soft tissue transmission (TT) or a threshold of 20% of peak xenon ventilation counts (XV). We used a central ROI drawn to 50% of height and of width of the whole right lung ROI and placed along the left lung margin and centered vertically.

RESULTS

In general, the correlation of normalized C/P (nC/P) between the two methods was strong. However, the value of nC/P was significantly smaller for the XV method than the TT method. Regression equations for the relationship of nC/P between the two methods were, for healthy subjects, y=0.75x+0.61, R(2)=0.64 using rectangular ROIs and y=0.76x+0.45, R(2)=0.66 using isocontour ROIs; and for CF patients, y=0.94x+0.46, R(2)=0.43 and y=0.85x+0.42, R(2)=0.41, respectively.

CONCLUSIONS

(1) A transmission scan with an isocontour outline in combination with a rectangular central region to define the lung borders may be more useful than a ventilation scan. (2) Close correlation of nC/Ps measured by transmission or gas ventilation should allow confident comparison of values determined by the two methods.

Cigarette smoke exposure induces CFTR internalization and insolubility, leading to airway surface liquid dehydration

Cigarette smoke (CS) exposure induces mucus obstruction and the development of chronic bronchitis (CB). While many of these responses are determined genetically, little is known about the effects CS can exert on pulmonary epithelia at the protein level. We, therefore, tested the hypothesis that CS exerts direct effects on the CFTR protein, which could impair airway hydration, leading to the mucus stasis characteristic of both cystic fibrosis and CB. In vivo and in vitro studies demonstrated that CS rapidly decreased CFTR activity, leading to airway surface liquid (ASL) volume depletion (i.e., dehydration). Further studies revealed that CS induced internalization of CFTR. Surprisingly, CS-internalized CFTR did not colocalize with lysosomal proteins. Instead, the bulk of CFTR shifted to a detergent-resistant fraction within the cell and colocalized with the intermediate filament vimentin, suggesting that CS induced CFTR movement into an aggresome-like, perinuclear compartment. To test whether airway dehydration could be reversed, we used hypertonic saline (HS) as an osmolyte to rehydrate ASL. HS restored ASL height in CS-exposed, dehydrated airway cultures. Similarly, inhaled HS restored mucus transport and increased clearance in patients with CB. Thus, we propose that CS exposure rapidly impairs CFTR function by internalizing CFTR, leading to ASL dehydration, which promotes mucus stasis and a failure of mucus clearance, leaving smokers at risk for developing CB. Furthermore, our data suggest that strategies to rehydrate airway surfaces may provide a novel form of therapy for patients with CB.

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).

Targeting aerosolized drugs to the conducting airways using very large particles and extremely slow inhalations

BACKGROUND

The site of deposition in the respiratory tract for aerosolized, inhaled therapeutic drugs depends on both the particles' aerodynamic size and the patient's breathing pattern.

METHODS

In 21 healthy subjects with normal lung function, we evaluated an extremely slow inhalation of a large 9.5-μm MMAD particle aerosol (ESI-9) for its ability to enhance the delivery of radiolabeled particles ((99m)Tc-labeled sulfur colloid) to the conducting airways. The regional deposition of the large particles (modified Pari-Boy jet nebulizer), inhaled at the extremely low rate of 0.080 Lps for 10 sec, was compared to the deposition of 5-μm MMAD particles inhaled during cyclic resting tidal breathing (TVB-5-) (mean 0.44 L and 0.46 Lps). Gamma scintigraphy gave an estimate of conducting airway deposition (% CAD) as a fraction of all deposited particles by multiplying the percent of activity in both lungs immediately postdeposition relative to the total deposition (i.e., lungs + mouth + esophagus + stomach) times the percent of activity cleared from the lungs over 24 h.

RESULTS

% CAD for healthy subjects for the ESI-9 and TVB-5 maneuvers was 35% (±8%) and 27% (±11%), respectively, p = 0.004). The amount deposited within the oropharynx was 26% (±7%) and 37% (±11%), respectively, p < 0.001.

CONCLUSIONS

Higher therapeutic value of a medication delivered to the conducting airways where the primary defect is associated with many diseases, and with fewer losses to the extrathoracic surfaces, may be obtained by using an "extremely slow inhalation and large particle" routine when compared to a normal tidal volume breathing associated with typical nebulizers.

Noninvasive real-time measurement of nasal mucociliary clearance in mice by pinhole gamma scintigraphy

Mucociliary clearance (MCC) is the key defense mechanism in the upper airways, as the removal of debris-laden mucus in the sinuses completely depends on MCC. So far, how the nasal MCC is regulated remains unknown. Recently, mice deficient in genes encoding the components of MCC apparatus have been generated, which will allow investigators to conduct more in-depth nasal MCC studies. However, the methodology necessary to comprehensively evaluate the nasal MCC in this species is not well established. We therefore developed a novel method to measure nasal MCC in live mice using pinhole gamma camera. Insoluble radiolabeled particles were delivered into the noses of lightly anesthetized mice. The nasal clearance of these particles was measured continuously in a real-time manner. The effect of three different anesthetics-avertin, pentobarbital, and isoflurane-on nasal MCC was also determined. In mice anesthetized by 1.1% isoflurane, radiolabeled particles were immediately moved into the oropharynx, which was significantly accelerated by the treatment of hypertonic but not isotonic saline. According to the clearance rate, the mouse nasal MCC presented two distinct phases: a rapid phase and a slow phase. In addition, we found that isoflurane had a very small inhibitory effect on nasal MCC vs. both avertin and pentobarbital. This was further supported by its dose response. Collectively, we have developed a noninvasive method to monitor the real-time nasal MCC in live mice under physiological conditions. It provides more comprehensive evaluation on nasal MCC rather than assessing a single component of the MCC apparatus in isolation.

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.

Nasal contribution to breathing and fine particle deposition in children versus adults

Both the route of breathing, nasal versus oral, and the effectiveness of the nose to filter inhaled, fine particles may differ between children and adults. This study compared (1) the nasal contribution to breathing at rest and during mild to moderate exercise in children (age 6-10 yr) versus young adults and (2) the nasal deposition efficiency (NDE) of fine particles (1 and 2 microm MMAD, GSD < 1.2) under resting and light exercise breathing conditions in the same children and adults. Nasal contribution to breathing was assessed by respiratory inductance plethysmography and a nasal mask with flow meter during incremental exercise on a bicycle ergometer. Fine particle deposition fractions for nasal and oral breathing were assessed by inhalation of monodisperse carnauba wax particles and laser photometry to determine inhaled/exhaled concentrations. There was a trend for children to have a lesser nasal contribution to breathing at rest and during exercise, but the differences from adults were not statistically significant. Children did, however, have significantly decreased NDE for 2-microm particles under light exercise breathing conditions compared to adults, suggesting less efficient nasal filtering for larger particles and higher flow conditions. These results suggest that the lungs of children may be exposed to higher concentrations of inhaled, ambient particles than adults.

Mucus clearance and lung function in cystic fibrosis with hypertonic saline

BACKGROUND

Abnormal homeostasis of the volume of airway surface liquid in patients with cystic fibrosis is thought to produce defects in mucus clearance and airway defense. Through osmotic forces, hypertonic saline may increase the volume of airway surface liquid, restore mucus clearance, and improve lung function.

METHODS

A total of 24 patients with cystic fibrosis were randomly assigned to receive treatment with inhaled hypertonic saline (5 ml of 7 percent sodium chloride) four times daily with or without pretreatment with amiloride. Mucus clearance and lung function were measured during 14-day baseline and treatment periods.

RESULTS

Long-term inhalation of hypertonic saline without pretreatment with amiloride (i.e., with placebo pretreatment) resulted in a sustained (> or =8 hours) increase in 1-hour rates of mucus clearance, as compared with those with amiloride pretreatment (14.0+/-2.0 vs. 7.0+/-1.5 percent, respectively; P=0.02) and increased 24-hour rates of mucus clearance over baseline. Furthermore, inhalation of hypertonic saline with placebo improved the forced expiratory volume in one second (FEV1) between the baseline period and the treatment period (mean difference, 6.62 percent; 95 percent confidence interval, 1.6 to 11.7; P=0.02), whereas hypertonic saline with amiloride did not improve FEV1 (mean difference, 2.9 percent; 95 percent confidence interval, -2.2 to 8.0; P=0.23). Forced vital capacity (FVC), the forced expiratory flow between 25 and 75 percent of FVC (FEF25-75), and respiratory symptoms also significantly improved in patients treated with hypertonic saline and placebo, whereas the residual volume as a proportion of total lung capacity (RV:TLC) did not change in either group. A comparison of the changes in lung function in the two groups showed no significant difference. In vitro data suggested that sustained hydration of airway surfaces was responsible for the sustained improvement in mucus clearance, whereas inhibition of osmotically driven water transport by amiloride accounted for the observed loss of clinical benefit.

CONCLUSIONS

In patients with cystic fibrosis, inhalation of hypertonic saline produced a sustained acceleration of mucus clearance and improved lung function. This treatment may protect the lung from insults that reduce mucus clearance and produce lung disease.

Growth of the small airways and alveoli from childhood to the adult lung measured by aerosol-derived airway morphometry

Understanding the human development of pulmonary air spaces is important for calculating the dose from exposure to inhaled materials as a function of age. We have measured, in vivo, the air space caliber of the small airways and alveoli at their natural full distension [total lung capacity (TLC)] by aerosol-derived airway morphometry in 53 children of age 6-22 yr and 59 adults of age 23-80 yr. Aerosol-derived airway morphometry utilizes the gravitational settling time of inhaled inert particles to infer the vertical distance necessary to produce the observed loss of particles to the airway surfaces at sequential depths into the lung. Previously, we identified anatomical features of the lung: the caliber of the transitional bronchioles [transitional effective air space dimension (EADtrans)]; the mean linear dimension of the alveoli (EADmin); and a measure of conducting airway volume [volumetric lung depth (VLDtrans)]. In the present study, we found that EADmin increased with age, from 184 microm at age 6 to 231 microm at age 22, generally accounting for the increase in TLC observed over this age range. EADtrans did not increase with TLC, averaging 572 microm, but increased with subject age and height when the entire age range of 6-80 yr is included {EADtrans (microm)=0.012[height (cm)]x[age (yr)]+508; P=0.007}. VLDtrans scaled linearly with lung volume, but VLDtrans relative to TLC did not change with age, averaging 7.04+/-1.55% of TLC. The data indicate that from childhood (age of 6 yr) to adulthood a constant number of respiratory units is maintained while both the smallest bronchioles and alveoli expand in size to produce the increased lung volume with increased age and height.

Effect of race on fine particle deposition for oral and nasal breathing

Nasal efficiency for removing fine particles from inhaled air may be affected by variations in nasal structure associated with race. In 11 African American and 11 Caucasian adults (age 18-31 yr) we measured the fractional deposition (DF) of fine particles (1 and 2 mum mass median aerodynamic diameter) (MMAD) for oral and nasal breathing using individual breathing patterns previously measured by respiratory inductance plethysmography during a graded exercise protocol. DF for both nasal and mouth breathing was measured separately by laser photometry at the same tidal volume and breathing rate for resting and light exercise (20% of maximum work load) conditions. From these DF measures, nasal deposition efficiency (NDE) was calculated for each condition. For light exercise conditions, NDE for both 1- and 2-microm particles was less in African Americans versus Caucasians, 0.15 +/- 0.07 (SD) versus 0.24 +/- 0.11 for 1-microm particles (p = .03), and 0.29 +/- 0.13 versus 0.44 +/- 0.11 for 2-microm particles (p = .006). The racial differences in NDE were associated with racial differences in nasal resistance and nostril shape. These race-dependent nasal efficiencies are dosimetric factors that should be considered in modeling and assessing particulate dose from human exposure to air pollutants.

In vivo particle uptake by airway macrophages in healthy volunteers

We combined two techniques, radiolabeled aerosol inhalation delivery and induced sputum, to examine in vivo the time course of particle uptake by airway macrophages in 10 healthy volunteers. On three separate visits, induced sputum was obtained 40, 100, and 160 min after inhalation of radiolabeled sulfur colloid (SC) aerosol (Tc99 m-SC, 0.2 microm colloid size delivered in 6-microm droplets). On a fourth visit (control) with no SC inhalation, induced sputum was obtained and SC particles were incubated (37 degrees C) in vitro with sputum cells for 40, 100, and 160 min (matching the times associated with in vivo sampling). Total and differential cell counts were recorded for each sputum sample. Compared with 40 min (6 +/- 3%), uptake in vivo was significantly elevated at 100 (31 +/- 5%) and 160 min (27 +/- 4%); both were strongly associated with the number of airway macrophages (R = 0.8 and 0.7, respectively); and the number and proportion of macrophages at 40 min were significantly (P < 0.05) elevated compared with control (1,248 +/- 256 versus 555 +/- 114 cells/mg; 76 +/- 6% versus 60 +/- 5%). Uptake in vitro increased in a linear fashion over time and was maximal at 160 min (40 min, 12 +/- 2%; 100 min, 16 +/- 4%; 160 min, 24 +/- 6%). These data suggest that airway surface macrophages in healthy subjects rapidly engulf insoluble particles. Further, macrophage recruitment and phagocytosis-modifying agents are factors in vivo that likely affect particle uptake and its time course.

Effect of salmeterol on mucociliary and cough clearance in chronic bronchitis

The effect of long acting beta(2)-adrenergic bronchodilators on impaired mucociliary clearance in chronic bronchitis is unknown. Using a radiolabeled aerosol (technetium-99m-labeled sulfur colloid) and gamma camera analysis, we measured the acute effect of salmeterol vs. placebo on mucociliary and cough clearance in mild-moderate chronic bronchitics (n = 14) over a 2h period. During the 1-1(1/2) h period of observation patients performed 60 controlled coughs on each study day. Average whole lung clearance through 1 and 2h after administration of salmeterol (42 microg) or placebo via metered dose inhaler (double-blinded, crossover design study) showed no significant difference between treatments. Similarly, for the specific period when cough was added to mucociliary clearance, there was no difference on whole lung clearance between treatments. However, when clearance from the peripheral region of the lung was assessed over the entire 2h period of observation, salmeterol provided a 30% enhancement of airway clearance compared to placebo, average peripheral 2h clearance (%) = 22 +/- 9 vs. 17 +/- 10 for salmeterol vs. placebo (P = 0.05 by paired analysis). Thus, in addition to its bronchodilating effects, salmeterol acutely enhances peripheral airway clearance of secretions in mild-moderate chronic bronchitis.

Effect of body size on breathing pattern and fine-particle deposition in children

Interchild variability in breathing patterns may contribute to variability in fine particle lung deposition and morbidity in children associated with those particles. Fractional deposition (DF) of fine particles (2-microm monodisperse, carnauba wax particles) was measured in healthy children, age 6-13 yr (n = 36), while they followed a resting breathing pattern previously determined by respiratory inductance plethysmography. Interchild variation in DF, measured by photometry at the mouth, was most strongly predicted by their tidal volume (Vt) (r =0.79, P < 0.001). Multiple regression analysis further showed that, for any given height and age, Vt increased with increasing body mass index (BMI) (P < 0.001). The overweight children (> or =95th percentile BMI) (n = 8) had twice the DF of those in the lowest BMI quartile (<25th percentile) (n = 9; 0.28 +/- 0.13 vs. 0.15 +/- 0.06, respectively; P < 0.02). In the same groups, resting minute ventilation was also significantly higher in the overweight children (8.5 +/- 2.2 vs. 5.9 +/- 1.1 l/min; P < 0.01). Consequently, the rate of deposition (i.e., particles depositing/time) in the overweight children was 2.8 times that of the leanest children (P < 0.02). Among all children, the rate of deposition was significantly correlated with BMI (r = 0.46, P = 0.004). These results suggest that increased weight in children may be associated with increased risk from inhalation of pollutant particles in ambient air.

Nasal contribution to breathing with exercise: effect of race and gender

Because the nose acts as a filter to prevent penetration of toxic particles and gases to the lower respiratory tract, the route of breathing, oral vs. nasal, may be an important determinant of toxicant dose to the lungs. Using respiratory inductance plethysmography and a nasal mask fitted with flowmeter, we measured the nasal contribution to breathing at rest and during exercise (to 60% maximum workload) in healthy young adults (men/women = 11/11 and Caucasian/African-American = 11/11). We found that the nasal contribution to breathing is less during submaximal exercise in the Caucasians vs. African-Americans (e.g., at 60% maximum workload, mean nasal-to-total ventilation ratio = 0.40 +/- 0.21 and 0.65 +/- 0.24, respectively, P < 0.05). This difference is likely due to the African-Americans' ability to achieve higher maximal inspiratory flows through their nose than the Caucasians. Men also had a lesser nasal contribution to breathing during exercise compared with women. This is likely due to greater minute ventilations at any given percentage of maximum workload in men vs. women.

Ultrafine particle deposition and clearance in the healthy and obstructed lung

Numerous epidemiologic studies have shown associations between exposure to particulate air pollution and acute increases in morbidity and mortality, particularly in persons with chronic obstructive pulmonary disease. The dosimetry of ultrafine particles in the human lung is poorly characterized. We studied the deposition and clearance of an ultrafine technetium-99m-labeled aerosol in 10 patients with chronic obstructive pulmonary disease and in 9 healthy subjects. Particle retention was followed for 2 hours after inhalation and again at 24 hours by gamma scintigraphy. Central-to-peripheral ratios indexed airway deposition. Particle accumulation in the liver was examined by quantifying activity below the right lung. The dose rate for an aerosol exposure of 10 micro g/m(3) was calculated. Patients had a significantly greater dose rate than healthy subjects (2.9 +/- 1.0 versus 1.9 +/- 0.4 micro g/h, p = 0.02). Central-to-peripheral ratios were slightly greater in patients than in healthy subjects (1.11 +/- 0.10 versus 1.01 +/- 0.11, p = 0.05). Clearance did not statistically differ between health and disease. On average, 24-hour retention was 85 +/- 8% (corrected for isotope dissolution). No accumulation in the liver's vicinity was observed. Data suggest that relative to healthy subjects, patients with moderate-to-severe airways obstruction receive an increased dose from ultrafine particle exposure.

Targeting delivery of aerosols to different lung regions

With the increasing use of aerosolized drugs, there is a need to understand the means by which these drugs can most effectively be targeted to desired regions of the lung. Several attempts have been made at targeting aerosols in the lung by changing particle sizes and breathing patterns with varying degrees of success. Recent use of such techniques as shallow, aerosol bolus delivery and extremely slow inhalations of aerosols in diagnostic lung tests may also prove beneficial for targeting drug delivery to the conducting airways. This review discusses the potential for utilizing aerosol delivery techniques for selectively targeting aerosol deposition along both serial and parallel pathways in the lung. Based on a review of previous studies concerning factors that determine aerosol and gas distribution in the lung, the potential for utilizing various breathing techniques in concert with variations in particle sizes are considered. Further research on the factors that determine distribution of aerosol in the diseased lung may help in designing successful targeting strategies for the future.

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.

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.

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.

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.

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.