Organizational Memory Studies

This paper provides an overview and discussion of the rapidly growing literature on organizational memory studies (OMS). We define OMS as an inquiry into the ways that remembering and forgetting shape, and are shaped by, organizations and organizing processes. The contribution of this article is threefold. We briefly review what we understand by organizational memory and explore some key debates and points of contestation in the field. Second, we identify four different perspectives that have been developed in OMS (functional, interpretive, critical and performative) and expand upon each perspective by showcasing articles published over the past decade. In particular, we examine four papers previously published in Organization Studies to show the distinctiveness of each perspective. Finally, we identify a number of areas for future research to facilitate the future development of OMS.

Developing historical consciousness in management learners

This article argues and advocates strategies for the development of historical consciousness to stimulate both first- and second-order critical reflexivity in management students with the goal of creating critical management learners. The historic turn in management and organizational studies has demonstrated that history is not the same as the past. This understanding has had implications for many areas of investigation but has not been felt as significantly as it might be in management learning and education. To make our argument, we discuss how archives can be used to stimulate the process of historical consciousness in management learners and we provide an illustrative example of how this can be done, together with a checklist to aid instructors in facilitating student use of archival material.

Analytical validation of an immunoassay for the quantification of N-terminal pro-B-type natriuretic peptide in feline blood

The measurement of N-terminal pro-B-type natriuretic peptide (NT-proBNP), a biomarker for heart stress detectable in blood, has been shown to have clinical utility in cats with heart disease. A second-generation feline enzyme-linked immunosorbent assay (Cardiopet® proBNP, IDEXX Laboratories Inc., Westbrook, Maine) was developed to measure NT-proBNP in routine feline plasma or serum samples with improved analyte stability. Results of the analytical validation for the second-generation assay are presented. Analytic sensitivity was 10 pmol/l. Accuracy of 103.5% was determined via serial dilutions of 6 plasma samples. Coefficients of variation for intra-assay, interassay, and total precision were in the ranges of 1.6-6.3%, 4.3-8.8%, and 10.1-15.1%, respectively. Repeatability across 2 lots for both serum and plasma had an average coefficient of determination (r(2)) of 0.99 and slope of 1.11. Stability of the analyte was found to be high. In serum samples held at 4°C for 24-72 hr, the mean percent recovery from time zero was ≥99%. In serum samples held at 25°C for 24 hr, the mean percent recovery from time zero was 91.9%, and for 48 hr, 85.6%. A method comparison of the first- and second-generation assays with a clinically characterized population of cats revealed no difference in the tests' ability to differentiate levels of NT-proBNP between normal cats and cats with occult cardiomyopathy (P < 0.001). Results from our study validate that the second-generation feline Cardiopet proBNP assay can measure NT-proBNP in routine feline plasma and serum samples with accuracy and precision.

Dose and pulse sequence considerations for hyperpolarized (129)Xe ventilation MRI

PURPOSE

The aim of this study was to evaluate the effect of hyperpolarized (129)Xe dose on image signal-to-noise ratio (SNR) and ventilation defect conspicuity on both multi-slice gradient echo and isotropic 3D-radially acquired ventilation MRI.

MATERIALS AND METHODS

Ten non-smoking older subjects (ages 60.8±7.9years) underwent hyperpolarized (HP) (129)Xe ventilation MRI using both GRE and 3D-radial acquisitions, each tested using a 71ml (high) and 24ml (low) dose equivalent (DE) of fully polarized, fully enriched (129)Xe. For all images SNR and ventilation defect percentage (VDP) were calculated.

RESULTS

Normalized SNR (SNRn), obtained by dividing SNR by voxel volume and dose was higher for high-DE GRE acquisitions (SNRn=1.9±0.8ml(-2)) than low-DE GRE scans (SNRn=0.8±0.2ml(-2)). Radially acquired images exhibited a more consistent, albeit lower SNRn (High-DE: SNRn=0.5±0.1ml(-2), low-DE: SNRn=0.5±0.2ml(-2)). VDP was indistinguishable across all scans.

CONCLUSIONS

These results suggest that images acquired using the high-DE GRE sequence provided the highest SNRn, which was in agreement with previous reports in the literature. 3D-radial images had lower SNRn, but have advantages for visual display, monitoring magnetization dynamics, and visualizing physiological gradients. By evaluating normalized SNR in the context of dose-equivalent formalism, it should be possible to predict (129)Xe dose requirements and quantify the benefits of more efficient transmit/receive coils, field strengths, and pulse sequences.

Mast cells mediate hyperoxia-induced airway hyper-reactivity in newborn rats

Premature infants are at increased risk of developing airway hyper-reactivity (AHR) after oxidative stress and inflammation. Mast cells contribute to AHR partly by mediator release, so we sought to determine whether blocking mast cell degranulation or recruitment prevents hyperoxia-induced AHR, mast cell accumulation, and airway smooth muscle (ASM) changes. Rats were exposed at birth to air or 60% O2 for 14 d, inducing significantly increased AHR in the latter group, induced by nebulized methacholine challenge and measured by forced oscillometry. Daily treatment (postnatal d 1-14) with intraperitoneal cromolyn prevented hyperoxia-induced AHR, as did treatment with imatinib on postnatal d 5-14, compared with vehicle treated controls. Cromolyn prevented mast cell degranulation in the trachea but not hilar airways and blocked mast cell accumulation in the hilar airways. Imatinib treatment completely blocked mast cell accumulation in tracheal/hilar airway tissues. Hyperoxia-induced AHR in neonatal rats is mediated, at least in part, via the mast cell.

Nitric oxide mediates relative airway hyporesponsiveness to lipopolysaccharide in surfactant protein A-deficient mice

Surfactant protein A (SP-A) mediates innate immune cell responses to LPS, a cell wall component of gram-negative bacteria that is found ubiquitously in the environment and is associated with adverse health effects. Inhaled LPS induces lung inflammation and increases airway responsiveness (AR). However, the role of SP-A in mediating LPS-induced AR is not well-defined. Nitric oxide (NO) is described as a potent bronchodilator, and previous studies showed that SP-A modulates the LPS-induced production of NO. Hence, we tested the hypothesis that increased AR, observed in response to aerosolized LPS exposure, would be significantly reduced in an SP-A-deficient condition. Wild-type (WT) and SP-A null (SP-A(-/-)) mice were challenged with aerosolized LPS. Results indicate that despite similar inflammatory indices, LPS-treated SP-A(-/-) mice had attenuated AR after methacholine challenge, compared with WT mice. The attenuated AR could not be attributed to inherent differences in SP-D concentrations or airway smooth muscle contractile and relaxation properties, because these measures were similar between WT and SP-A(-/-) mice. LPS-treated SP-A(-/-) mice, however, had elevated nitrite concentrations, inducible nitric oxide synthase (iNOS) expression, and NOS activity in their lungs. Moreover, the administration of the iNOS-specific inhibitor 1400W completely abrogated the attenuated AR. Thus, when exposed to aerosolized LPS, SP-A(-/-) mice demonstrate a relative airway hyporesponsiveness that appears to be mediated at least partly via an iNOS-dependent mechanism. These findings may have clinical significance, because recent studies reported associations between surfactant protein polymorphisms and a variety of lung diseases.

SP-A preserves airway homeostasis during Mycoplasma pneumoniae infection in mice

The lung is constantly challenged during normal breathing by a myriad of environmental irritants and infectious insults. Pulmonary host defense mechanisms maintain homeostasis between inhibition/clearance of pathogens and regulation of inflammatory responses that could injure the airway epithelium. One component of this defense mechanism, surfactant protein-A (SP-A), exerts multifunctional roles in mediating host responses to inflammatory and infectious agents. SP-A has a bacteriostatic effect on Mycoplasma pneumoniae (Mp), which occurs by binding surface disaturated phosphatidylglycerols. SP-A can also bind the Mp membrane protein, MPN372. In this study, we investigated the role of SP-A during acute phase pulmonary infection with Mp using mice deficient in SP-A. Biologic responses, inflammation, and cellular infiltration, were much greater in Mp infected SP-A(-/-) mice than wild-type mice. Likewise, physiologic responses (airway hyperresponsiveness and lung compliance) to Mp infection were more severely affected in SP-A(-/-) mice. Both Mp-induced biologic and physiologic changes were attenuated by pharmacologic inhibition of TNF-alpha. Our findings demonstrate that SP-A is vital to preserving lung homeostasis and host defense to this clinically relevant strain of Mp by curtailing inflammatory cell recruitment and limiting an overzealous TNF-alpha response.

Organizational structure and home team performance

Purpose

The purpose of the paper is to demonstrate that organizational task interdependence has an impact on the performance of home teams in sport.

Design/methodology/approach

The paper uses a cross‐sectional research design. It tests the authors' hypothesis using a probit analysis of nine years of data from Major League Baseball and eight years of data from the National Hockey League.

Findings

The paper determines that the underlying task interdependence of a sport has a significant impact on the performance of a sport team.

Originality/value

The paper argues that sport managers need to consider organizational structure when accounting for team performance. Moreover, the structure of the sport(s) needs to be considered when making adjustments to the league(s) that might affect the competitive balance.

Chronic LPS inhalation causes emphysema-like changes in mouse lung that are associated with apoptosis

Lipopolysaccharide (LPS) is ubiquitous in the environment. Recent epidemiologic data suggest that occupational exposure to inhaled LPS can contribute to the progression of chronic obstructive pulmonary disease. To address the hypothesis that inhaled LPS can cause emphysema-like changes in mouse pulmonary parenchyma, we exposed C57BL/6 mice to aerosolized LPS daily for 4 weeks. By 3 days after the end of the 4-week exposure, LPS-exposed mice developed enlarged airspaces that persisted in the 4-week recovered mice. These architectural alterations in the lung are associated with enhanced type I, III, and IV procollagen mRNA as well as elevated levels of matrix metalloproteinase (MMP)-9 mRNA, all of which have been previously associated with human emphysema. Interestingly, MMP-9-deficient mice were not protected from the development of LPS-induced emphysema. However, we demonstrate that LPS-induced airspace enlargement was associated with apoptosis within the lung parenchyma, as shown by prominent TUNEL staining and elevated cleaved caspase 3 immunoreactivity. Antineutrophil antiserum-treated mice were partially protected from the lung destruction caused by chronic inhalation of LPS. Taken together, these findings demonstrate that inhaled LPS can cause neutrophil-dependent emphysematous changes in lung architecture that are associated with apoptosis and that these changes may be occurring through mechanisms different than those induced by cigarette smoke.

Airway smooth muscle relaxation is impaired in mice lacking the p47phox subunit of NAD(P)H oxidase

NAD(P)H oxidase is one of the critical enzymes mediating cellular production of reactive oxygen species and has a central role in airway smooth muscle (ASM) cell proliferation. Since reactive oxygen species also affect ASM contractile response, we hypothesized a regulatory role of NAD(P)H oxidase in ASM contractility. We therefore studied ASM function in wild-type mice (C57BL/6J) and mice deficient in a component (p47phox) of NAD(P)H oxidase. In histological sections of the trachea, we found that the area occupied by ASM was 17% more in p47(phox-/-) than in wild-type mice. After correcting for the difference in ASM content, we found that force generation did not vary between the two genotypes. Similarly, their ASM shortening velocity, maximal power, and sensitivity to acetylcholine, as well as airway responsiveness to methacholine in vivo, were not significantly different. The main finding of this study was a significantly reduced ASM relaxation in p47phox-/- compared with wild-type mice both during the stimulus and after the end of stimulation. The tension relaxation attained at the 20th second of electric field stimulation was, respectively, 17.6 +/- 2.4 and 9.2 +/- 2.3% in null and wild-type mice (P <0.01 by t-test). Similar significant differences were found in the rate of tension relaxation and the time required to reduce tension by one-half. Our data suggest that NAD(P)H oxidase may have a role in the structural arrangement and mechanical properties of the airway tissue. Most importantly, we report the first evidence that the p47phox subunit of NAD(P)H oxidase plays a role in ASM relaxation.

Off-the-Ice Action in the National Hockey League

Professional sports teams have become big business in North America, but sport management has received little academic attention. This interview with Scott Howson, the assistant general manager of the National Hockey League Edmonton Oilers, reveals what it is like to be a manager in professional sports. It explores strategy, human resources decision making, and innovation from the perspective of a manager.

Bronchial edema alters (99m)Tc-DTPA clearance from the airway surface in sheep

Airway wall edema, prominent in inflammatory airways disease, may alter barrier properties at the airway air-liquid interface such that normal absorption of soluble substances into the airway circulation is altered. We studied the effects of bradykinin-induced airway wall edema on the clearance of the soluble tracer technetium-99m-labeled diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) from subcarinal airways in sheep (n = 8). (99m)Tc-DTPA (6-10 microl) was delivered by a microspray nozzle inserted through a bronchoscope to a fourth-generation bronchus both before and 1 h after bradykinin (20 ml; 10(-6) M) had been infused through a cannulated and perfused bronchial artery. Airway retention (by scintigraphy) and blood levels of radiolabel were monitored for 30 min after the local deposition of (99m)Tc-DTPA. During control conditions, 85-90% of the tracer cleared from the deposition site within 30 min. The maximum blood level during that time was 17% of the total delivered tracer. However, 1 h after bradykinin infusion, there was significant retention of the marker at the deposition site with clearance within 30 min reduced to 63-70% and decreased blood levels of radiolabel (8%; both P < 0.05). These results demonstrate that moderate airway wall edema alters blood uptake and removal of soluble substances delivered to the subcarinal airways. We suggest that the interplay between vascular and mucociliary clearance routes will impact the resident time for clearance of soluble air toxins and/or therapeutic agents from the epithelial surface.

The role of the bronchial vasculature in soluble particle clearance

Although a role for the airway circulation in the clearance of inhaled particles is generally assumed, there is little information to confirm its importance. We studied the effects of decreased bronchial blood flow on the uptake of the soluble tracer technetium=99m-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA) from subcarinal airways in sheep (n = 7). The bronchial artery was cannulated and perfused with autologous blood at a control flow (0.6 mL/min/kg) or when the perfusion pump was stopped (no flow). (99m)Tc-DTPA (6-10 microL) was delivered by a microspray nozzle inserted through a bronchoscope to a fourth-generation bronchus both during control blood flow conditions and no-flow conditions. Airway retention (by scintigraphy) and blood uptake were monitored for 30 min after the local deposition of (99m(Tc-DTPA. During control flow conditions, 30 min after the delivery of the radiolabel, 21% of the tracer remained at the deposition site. Of the total delivered tracer, maximum blood uptake was 18% (n) = 3). When bronchial perfusion was stopped, airway retention 30 min after deposition increased to 43%, and maximum blood uptake decreased to 7% of the total delivered tracer. Although mucociliary clearance was not directly measured, radiolabel tracer was observed to move progressively from the deposition site up to larger airways and contributed to the overall removal of tracer from the site of deposition during both flow conditions. However, these results demonstrate that decreased bronchial perfusion increases airway retention by limiting vascular uptake of the soluble tracer. These results emphasize the importance of normal perfusion of the airway vasculature for uptake of therapeutic agents delivered specifically to the conducting airways.

Interdependence of bronchial circulation and clearance of 99mTc-DTPA from the airway surface

The extent to which the systemic vasculature is involved in soluble-particle uptake in the conducting airways has not been studied extensively. In anesthetized, ventilated sheep, 6-10 microl of technetium-99m-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA) was delivered through a microspray nozzle to a fourth-generation airway. Perfusion of the cannulated bronchial artery was varied between control flow (0.6 ml x min(-1) x kg(-1)), high flow (1.8 ml x min(-1) x kg(-1)) or no flow (the infusion pump was stopped). Airway retention of the radioactive tracer was monitored using gamma camera imaging, and venous blood was sampled. During control perfusion, tracer retention at the site of deposition at 30 min averaged 20 +/- 6% (n = 7). With no flow, retention was significantly elevated to 32 +/- 8% (P = 0.03). In another group of sheep (n = 5) with a control retention of 13 +/- 4%, high flow resulted in an increase in tracer (25 +/- 4%; P = 0.04). Maximum blood uptake of tracer was calculated by estimating circulating blood volume and averaged 16% of total activity during control flow. Only during high-flow conditions was 99mTc-DTPA in the blood decreased (10%; P = 0.04). Most of the tracer was cleared by mucociliary clearance as visualized by imaging. This component was substantially decreased during no flow. The results demonstrate that both decreased and increased airway perfusion limit removal of soluble tracer applied to the conducting airways.

Methodology for the measurement of mucociliary function in the mouse by scintigraphy

The objective of the study was to develop a scintigraphic method for measurement of airway mucociliary clearance in small laboratory rodents such as the mouse. Previous investigations have characterized the secretory cell types present in the mouse airway, but analysis of the mucus transport system has been limited to in vitro examination of tissue explants or invasive in vivo measures of a single airway, the trachea. Three methods were used to deposit insoluble, radioisotopic colloidal particles: oropharyngeal aspiration, intratracheal instillation, and nose-only aerosol inhalation. The initial distribution of particles within the lower respiratory tract was visualized by gamma-camera, and clearance of particles was followed intermittently over 6 h and at the conclusion, 24 h postdelivery. Subsets of mice underwent lavage for evidence of tissue inflammation, and others were restudied for reproducibility of the methods. The aspiration and instillation methods of delivery led to greater distributions of deposited activity within the lungs, i.e., approximately 60--80% of the total respiratory tract radioactivity, whereas the nose-only aerosol technique attained a distribution of 32% to the lungs. However, the aerosol technique maximized the fraction of particles that cleared the airway over a 24-h period, i.e, deposited onto airway epithelial surfaces and cleared by mucociliary function such that lung retention at 24 h averaged 57% for delivery by aerosol inhalation and > or =80% for the aspiration or intratracheal instillation techniques. Particle delivery methods did not cause lung inflammation/injury with use of inflammatory cells and chemoattractant cytokines as criteria. Scintigraphy can discern particle deposition and clearance from the lower respiratory tract in the mouse, is noninvasive and reproducible, and includes the capability for restudy and lung lavage when time course or chronic treatments are being considered.

Airflow and device effects on aerosol delivery for large animals

Aerosol delivery of medications has recently gained acceptance in large animal veterinary medicine. However, delivery of therapeutic aerosols currently relies on equipment modified from human use and delivery of medical aerosols may be adversely affected by the equipment design. In this study, we demonstrate the effect of typical large animal inspiratory flow rates on aerosol delivery characteristics. A benchtop system was assembled to simulate aerosol delivery to large animals. Phasic airflow was generated using a large animal anesthesia machine set to deliver 6 bpm (7 L/breath) at 100, 150 and 180 L/min mean inspiratory airflow. Aerosol from a DeVilbis ultrasonic nebulizer was delivered to a simulated facemask using standard 22 mm tubing and fittings. Total mass, delivery efficiency and mass median aerosol diameter (MMAD) was measured with and without an inspiratory one-way valve on the facemask. Delivered aerosol mass ranged from 0.26 to 0.08 g/min and delivery efficiency ranged from 30 to 6%. Both parameters were significantly reduced by both increasing flow rates and the presence of a one-way valve between the nebulizer and the facemask. Average MMAD was 0.7 microm and was not affected by any experimental variable. These results demonstrate that current aerosol equipment used on large animals has a substantial adverse effect on aerosol delivery. Elimination of one-way valves between the aerosol source and the patient is expected to improve delivery of the aerosol in these patients.

Bronchial reactivity of healthy subjects: 18-20 h postexposure to ozone

Exposure of humans to ambient levels of ozone (O(3)) causes inflammatory changes within lung tissues. These changes have been reported for the "initial" (1- to 3-h) and "late" (18- to 20-h) postexposure periods. We hypothesized that at the late period, when protein and cellular markers of inflammation at the airway surface remain abnormal and the integrity of the epithelial barrier is compromised, bronchial reactivity would be increased. To test this, we measured airway responsiveness to cumulative doses of methacholine (MCh) aerosol in healthy subjects 19+/-1 h after a single exposure to O(3) (130 min at ambient levels between 120 and 240 parts/billion and alternate periods of rest and moderate exercise) or filtered air. Exposures were conducted at two temperatures: mild (22 degrees C) and moderate (30 degrees C). At the late period, bronchial reactivity to MCh increased, i.e., interpolated dose of MCh leading to a 50% fall in specific airway conductance (PC(50)) was less after O(3) than after filtered air. PC(50) for O(3) at 22 degrees C was 27 mg/ml (20% less than the PC(50) after filtered air), and for O(3) at 30 degrees C it was 19 mg/ml (70% less than the PC(50) after filtered air). The forced expiratory volume in 1 s (FEV(1)) at the late time point after O(3) was slightly but significantly reduced (2.3%) from the preexposure level. There was no relationship found between the functional changes observed early after exposure to O(3) and subsequent changes in bronchial reactivity or FEV(1) at the late time point. These results suggest that bronchial reactivity is significantly altered approximately 1 day after O(3); this injury may contribute to the respiratory morbidity that is observed 1-2 days after an episode of ambient air pollution.

Regional clearance of solute from peripheral airway epithelia: recovery after sublobar exposure to ozone

The influence of local exposure to ozone (O3) on respiratory epithelial permeability of sublobar lung segments was studied by using aerosolized 99mTc-diethylenetriamine pentaacetic acid (DTPA; mol wt, 492). Two bronchoscopes were inserted through an endotracheal tube in anesthetized, mechanically ventilated, mixed breed dogs and were wedged into sublobar bronchi located in the right and left lower lobes, respectively. Segments were ventilated via the bronchoscope with 5% CO2 in air delivered at 200 ml/min, and an aerosol of 99mTc-DTPA was generated and delivered through the scope and into the sublobar segment over a 30-s period. Clearance of 99mTc-DTPA was measured simultaneously from right and left lower lung segments at baseline and 1, 7, and 14 days after a 6-h sublobar exposure to filtered air or 400 parts per billion O3. O3 treatment significantly decreased the clearance halftime (t50) of 99mTc-DTPA by 50% from the baseline mean of 32.3 to 16.0 min at 1 day postexposure. After 7 days of recovery, t50 was still reduced by 28. 8%; however, by 14 days postexposure, clearance of 99mTc-DTPA had recovered, and the t50 had a mean value of 30.0 min. 99mTc-DTPA clearance was not altered by exposure to filtered air, and t50 values were comparable to baseline at 1, 7, and 14 days postexposure. These results reveal that a single local exposure to O3 increases transepithelial clearance, but only for epithelia directly exposed to O3, and that 7-14 days of recovery are required before permeability to small-molecular-weight solutes returns to normal.

Retention of soluble 99mTc-DTPA in the human lung: 24-h postdeposition

Clearance of low-molecular-weight solutes, e.g., radiolabeled chelate diethylenetriaminepentaacetate (DTPA), across epithelial surfaces of distal airways and the lung parenchyma is a broadly used technique to assess epithelial integrity. It has been generally assumed that clearance of solute follows a simple first-order process and that DTPA clearance through the respiratory epithelium and into blood and lymphatic channels is complete within a few hours. Using gamma-camera imaging and a radiolabeled aerosol of 99mTc-labeled DTPA, we observed in eight healthy subjects lung retention of radioisotope approximately 24 h postdeposition of the 99mTc-DTPA. Residual lung retention at the 24-h end point averaged 6.0 +/- 1.8 (SD)% of the amount of radioisotope initially deposited in the lung. This suggests that for normal healthy subjects a small amount of the 99mTc radioisotope, either in a dissociated or chelated form, is nonpermeable or slowly cleared from respiratory tisssues.

Importance of airway blood flow on particle clearance from the lung

The role of the airway circulation in supporting mucociliary function has been essentially unstudied. We evaluated the airway clearance of inert, insoluble particles in anesthetized ventilated sheep (n = 8), in which bronchial perfusion was controlled, to determine whether airway mucosal blood flow is essential for maintaining surface transport of particles through airways. The bronchial branch of the bronchoesophageal artery was cannulated and perfused with autologous blood at control flow (0.6 ml.min-1.kg-1) or perfusion was stopped. With the sheep in a supine position and after a steady-state 133Xe ventilation scan for designation of lung zones of interest, an inert 99mTc-labeled sulfur colloid aerosol (2.1-microns diameter) was deposited in the lung. The clearance kinetics of the radiolabeled particles were determined from the activity-time data obtained for right and left lung zones. At 60 min postdeposition of aerosol, average airway particle retention for control bronchial blood flow conditions was 57 +/- 7 (SE)% for the right and 53 +/- 8% for the left lung zones. Clearance of particles was significantly impaired when bronchial blood flow was stopped, e.g., right and left lung zones averaged 77 +/- 6 and 76 +/- 7% at 60 min, respectively (P < 0.05). These data demonstrate a significant influence of the bronchial circulation on mucociliary transport of insoluble particles. Potential mechanisms that may account for these results include the importance of the bronchial circulation for nutrient flow, maintenance of airway wall temperature and humidity, and release of mediators and sequelae associated with tissue ischemia.

Intravenous lidocaine and oral mexiletine block reflex bronchoconstriction in asthmatic subjects

Stimulation of the airways of asthmatic individuals causes severe bronchoconstriction, which is in part neurally mediated via the vagus nerve. Local anesthetics are commonly administered to prevent this reflex-induced bronchoconstriction. Therefore, in a double-blind, placebo-controlled prospective study, we tested the effectiveness of oral mexiletine and intravenous lidocaine at blocking histamine-induced reflex bronchoconstriction. Fifteen subjects with mild asthma were selected (for whom the provocative concentration of histamine aerosol causing a 20% decrease in FEV1 (PC20) was less than 18 mg/ml). Subsequently, the subjects were pretreated with oral mexiletine, intravenous lidocaine, or placebo, and the histamine challenges were repeated. The baseline PC20 for histamine was 8.8 +/- 1.8 mg/ml. Mexiletine and lidocaine at therapeutic serum concentrations blocked reflex bronchoconstriction. Oral mexiletine increased the PC20 to 21.1 +/- 5.0 mg/ml (serum concentration: 0.7 +/- 0.05 microg/ml). Likewise, intravenous lidocaine increased the PC20 to 24.5 +/- 4.9 mg/ml (serum concentration: 2.6 +/- 0.15 microg/ml). Oral mexiletine and intravenous lidocaine block reflex-induced bronchoconstriction. Furthermore, mexiletine may have additional airway benefits when selected for the treatment of dysrhythmias or chronic pain in patients with coexisting lung diseases.

Regional clearance of solute from the respiratory epithelia: 18-20 h postexposure to ozone

Exposure of humans to ambient levels of ozone causes inflammatory changes within lung tissues. These changes have been reported for the "initial" (1- to 3-h) and "late" (18- to 20-h) postexposure periods. We hypothesized that at the late period when protein and cellular markers of inflammation in bronchoalveolar lavage remain abnormal, permeability of respiratory epithelia would be altered. To test this, we measured by gamma-camera imagery the clearance kinetics in healthy subjects (n = 9) of 99mTc-labeled solute [diethylenetriaminepentaacetic acid (DTPA)] that was deposited by aerosol onto epithelial surfaces 19 +/- 1 h after a single exposure to ozone (O3; 130 min at ambient levels between 150 and 350 parts per billion and alternate periods of rest and moderate exercise) or filtered air. At the late period, the lung clearance of 99mTc-DTPA over a 120-min period was significantly increased, i.e., 0.732%/min for O3 exposures compared with 0.661%/min for filtered-air exposures (P < 0.05). Regional analysis demonstrated that 99mTc-DTPA clearance from the periphery (excluding the lung hilum) and lung apexes were significantly increased by O3 but changes in clearance for the base of the lung were not significant. The forced expiratory volume in 1 s at the late time after O3 was slightly but significantly reduced (-2.1%) from preexposure levels. There was no relationship between the functional changes observed acutely after exposure to O3 and subsequent changes in 99mTc-DTPA clearance or forced expiratory volume in 1 s observed at the late period. These results suggest that epithelial permeability of the lung is altered 18-20 h post-O3; this injury is regional, and the lung base appears to have a different time course of response or is in an adapted state with respect to O3 exposure.

Bloodborne markers in humans during multiday exposure to ozone

Intermittent exposure of the human lung to ambient levels of ozone (O3) was assayed in systemic fluids by using serum alpha-tocopherol (ST) as a gauge of oxidative stress and the blastogenic activity of peripheral blood monocytes as an index of immune function. Healthy men (n = 10) were evaluated over 3 consecutive days (130 min/day) of chamber exposure to O3 and filtered air (FA); subjects alternated between rest and light treadmill exercise during exposures. For O3, the level was varied at 20-min intervals, i.e., 250, 350, 450, 450, 350, and 250 parts/billion, and concluded with 10 min at 250 parts/billion. ST was quantitated by high-performance liquid chromatography techniques, and T-lymphocyte blastogenesis was measured in cell cultures of peripheral blood monocytes by comparing [3H]thymidine incorporation in mitogen-stimulated (concanavalin A) and nonstimulated cells. After the third day of O3 at 20 h postexposure, ST levels were reduced significantly compared with the FA control subjects (down 14%; -0.96 mumol/l). Mitogen-activated T lymphocytes exhibited a 61% increase in blastogenic activity after 3 days of O3 exposure, significant compared with the proliferative activity of activated T lymphocytes collected after FA or before O3. Acute airway function was impaired by O3, e.g., on day 1, the forced vital capacity and forced expiratory volume in 1 s were decreased 8% (-0.92 liter) and 14% (-0.86 l/s), respectively, from preexposure values, and full recovery was delayed beyond 24 h. Effects of O3 exposure on cellular and biochemical markers increased in magnitude after each exposure and did not parallel the apparent adaptability of bronchial sensitivity to O3.

Breath isoprene: temporal changes in respiratory output after exposure to ozone

Isoprene is a major hydrocarbon found in human breath. This study was conducted to evaluate whether respiratory isoprene output could serve as a monitor for ozone exposure. Healthy young adult subjects (n = 10) underwent chamber exposure on separate days to filtered air and to a variable concentration of ozone. Exposures had durations of 130 min that included alternate periods of rest and light treadmill exercise; breath was sampled pre- and postexposure. For six subjects, breath was resampled 19 +/- 1 h postexposure. Breath samples were concentrated cryogenically and analyzed by capillary gas chromatography. Isoprene output immediately postexposure was significantly reduced by ozone or filtered air (17 and 19%, respectively). These results suggest that exercise alone reduces isoprene levels in breath without an additive ozone effect. However, in the six subjects restudied 19 +/- 1 h postexposure to ozone, breath isoprene concentrations were now increased above the preexposure output by 99% (P < 0.01) and exceeded the 51% increase in output of isoprene at this time point after filtered-air exposure (P < 0.01). Therefore, breath isoprene is proposed as a noninvasive marker of a physiological response to oxidant-induced injury to epithelial membranes and fluid linings of the lower respiratory tract by ozone.

Evidence for ozone-induced small-airway dysfunction: lack of menstrual-cycle and gender effects

Recently, we analyzed FEF25-75 isovolumetrically to assess the acute effects of ozone (O3) on small-airway function: the reduction in isovolumetric (isoV) FEF25-75 at end exposure progressed during the next 25 min even as FVC was recovering. To evaluate this effect over a longer period, we measured isovolumetric FEFs, helium-oxygen (He-O2) volume of isoflow (VisoV), the multiple breath nitrogen washout (MBNW) curve, FRC, and RV in 24 subjects 24 h after a 130-min exposure to filtered air (FA) and O3 (0.35 ppm). Men and women were studied to test for gender-based differences in response, after first determining that menstrual-cycle phase did not itself influence response. Isovolumetric FEF25-75, Vmax50, and Vmax75 were reduced about equally at 25 min after O3 exposure (p < or = 0.02) and showed no recovery at 24 h. FVC and FEV1, although still depressed after 24 h (p < 0.05), showed substantial recovery (p < 0.01). FRC, RV, and VisoV showed no effect of O3 exposure. No gender differences in O3 responsiveness were found. In summary, O3-induced reductions in isovolumetric flow rates, suggestive of small-airway dysfunction, may persist for 24 h following acute exposure to O3, a time-course consistent with inflammation.

Breath ethane generation during clinical total body irradiation as a marker of oxygen-free-radical-mediated lipid peroxidation: a case study

Total body irradiation (TBI) is used therapeutically for treatment of leukemias and other malignancies of the hemopoietic system. Ionizing radiation produces oxygen free radicals that contribute to cytotoxicity. Breath collected from one patient undergoing therapeutic TBI showed measurable changes in levels of ethane during treatment. Breath ethane is a marker of lipid peroxidation of n-3 fatty acids. The TBI treatment involved 4 days of irradiation. The largest changes in breath ethane occurred on Day 2. The increased levels of breath ethane on Day 2 were correlated to clinical manifestations of toxicity. The correlation of the onset of gastrointestinal side effects with higher levels of breath ethane suggests that breath ethane may be a clinically useful measure of the toxicity of various TBI fractionation treatment protocols currently in use at different medical centers. The levels of breath ethane on the other days of treatment were lower, suggesting that the oxidative-antioxidative balance of the patient may be important in protection against free radical mediated injury. These results for a single patient suggest that breath ethane may be a promising approach to elucidate the role of antioxidants in clinical TBI and should be extended for verification to a larger volunteer patient population.

Exposure to ozone alters regional function and particle dosimetry in the human lung

Effects of experimental exposure to O3 (0.33 ppm) or filtered air on regional lung function were assessed in nine healthy male subjects. Immediately after 2-h chamber exposures, regional ventilation and particle dosimetry were measured by gamma camera imaging. The vertical distributions of a radiolabeled gas (133Xe) and aerosol (3.5-microns-diam insoluble 99mTc-tagged Fe2O3 particles) were quantitated for upper, middle, and lower lung regions; distribution data were corrected for regional differences in lung volume and tissue attenuation. Indexes of mechanical function, inspiratory capacity, and mid-maximal expiratory flow rates were significantly reduced after O3, but functional residual capacity remained unchanged. Exposure to O3 significantly enhanced the fraction of respired aerosol retained by the lung and altered the distribution pattern of deposited aerosol by increasing particle deposition to the middle lung region (P < 0.05). Aerosol penetration indexes, i.e., ratio of particle deposition in central lung regions to that in peripheral lung regions, and particle retention 24 h postinhalation (an index of aerosol deposition within alveoli and slowly clearing bronchioles) indicated that particle filtration efficiency had increased for tracheobronchial and parenchymal lung regions. For seven of the nine subjects, regional ventilation after O3 was reduced by 14% to the lung base and enhanced by 8 and 6% to the upper and middle lung regions, respectively; these changes were significant (P < 0.02) compared with ventilation after filtered air.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional impairment of mucociliary clearance in chronic obstructive pulmonary disease

Asthmatic subjects with tidal expiratory flow limitation have mucociliary clearance (MC) impairment in central airways. Because tidal flow limitation develops in COPD, it is possible that regional MC in these patients also may be affected. We tested this hypothesis by measuring MC in the presence or absence of flow limitations. Patients with COPD and chronic flow limitation were compared with non-flow-limited normal volunteers. Deposition was normalized for regional lung volume and expressed as the specific central to peripheral (sC/P) ratio. In COPD subjects, clearance from the whole lung and central airways was significantly different from that of normal subjects after 20 min of observation. In the peripheral airways, there were no significant differences between COPD and normal subjects. An alternative analysis of regional MC indicated patients retained particles in central airways while normal subjects, with intact MC, emptied central airways. Thus, COPD subjects with tidal expiratory flow limitation have impaired MC in their central airways.

Aerosolized lidocaine reduces dose of topical anesthetic for bronchoscopy

Conventional aerosol techniques were used to determine if inhalation of lidocaine can supplement topical anesthesia applied during bronchoscopy. Aerosols of either saline or lidocaine (50 mg at either 2 or 4% concentrations) were generated by jet nebulizer and administered with or without intermittent positive-pressure breathing. Patients (n = 38) after aerosol inhalation were administered 2% lidocaine (atomized and instilled) for suppression of the gag reflex, control of cough, and airway anesthesia. For five of the patients, prior to bronchoscopy, additional studies with radioaerosols and scintillation scans were accomplished with the same aerosol methodology to demonstrate lung distribution of deposited aerosol. For five patients who received 2% lidocaine aerosol prior to bronchoscopy, the subsequent topical dose of anesthetic required for the procedure was 186 +/- 34 (SEM) mg lidocaine. Nine patients in a control group received saline aerosol and required significantly more anesthetic, i.e., 308 +/- 26 mg; procedures were completed on average within 50 min. The largest difference was in the amount delivered to the upper airway (naris, pharynx, epiglottis, and larynx), i.e., 144 +/- 26 mg for saline control versus 48 +/- 16 mg for lidocaine aerosol protocol. Airways distal to the cords required less anesthesia also, on average, 77 mg for the saline control versus 46 mg for the lidocaine aerosol protocol (p < 0.05). Topical anesthetic dosage data were replicated in 12 additional patients studied by a different bronchoscopist. No additional benefit was afforded by premedication with 4% lidocaine aerosol rather than the 2% aerosol (n = 12). We conclude that aerosol modalities can supplement topical anesthesia during bronchoscopy, primarily by reducing the dose required to anesthetize the upper airway.

Improvement in pulmonary function following smoking cessation

This study investigated improvement in pulmonary function following smoking cessation. It employed three indices of lung function that are sensitive to improvement following smoking cessation and that can be easily assessed within a clinical setting: maximum mid-expiratory flow (MMF), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). Smoking status was verified by saliva thiocyanate analysis. Significant improvement in MMF was evident after 3 months of cessation and was maintained at the 6-month follow-up. This study demonstrates that significant improvement in at least one parameter of lung function occurs within the time span typically used in smoking cessation programs.

Aerosolized atropine sulfate: influence of inhalation pattern on effective blockade of vagal airway tone

The influence of aerosolized atropine sulfate on airway tone was evaluated in nine healthy adult subjects using three modes of inhalation and a dosimeter to deliver equal doses of aerosol. For six of the subjects additional studies with radioaerosols and scintillation scans were accomplished to qualify lung distributions of deposited aerosol. The three breathing patterns, identified as Tidal, IC, and VC, had average inspiratory volumes of 0.66 +/- 0.1, 2.10 +/- 0.4, and 4.31 +/- 0.9 (SD) L and were initiated from the rest position of the lung for the first two patterns, and residual volume for the third pattern. Total nebulization time and concentration inhaled were identical for each pattern at an atropine dose of 0.025 mg/kg body weight. Average inspiratory flow rates had means of 0.40 +/- 0.1, 0.64 +/- 0.2, and 0.82 +/- 0.2 (SD) L/s for the respective inhalations. Functional indices of FEV1, MMF, and Vmax50 and anticholinergic side effects were assessed for a 4-h period after aerosol administration. Functional improvement and duration of effect were maximal with the IC pattern. Within the first hour, absolute increases in FEV1 averaged 240 ml above baseline (6.2% increase). Increases for MMF and Vmax50 were on average greater than 23% above baseline (airflow benefit exceeded baseline by 0.91 +/- 0.4 L/s for MMF and 1.14 +/- 0.4 L/s for Vmax50). Except for xerostomia, which was present after all patterns, systemic side effects (tachycardia, blurred vision, and urinary retention) occurred only with VC pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of inhaled atropine on lung mucociliary function in humans

The influence of aerosolized atropine sulfate on lung airway mucus clearance was investigated in healthy human subjects who were nonsmokers. Mucus transport was measured with radiolabeled insoluble particles inhaled by mouth and deposited onto mucosal surfaces; subsequent retention of radiolabel was quantitated over a 4- to 5-h period by a noninvasive, posteriorly aligned, gamma camera. Placebo and atropine clearance tests were matched in a given subject for initial and for final (24-h postinhalation) deposition pattern of labeled aerosol at the onset and conclusion, respectively, of tracheobronchial particle clearance. In seven subjects mucociliary function was delayed after inhalation of 0.025 mg/kg body weight atropine sulfate as compared with placebo (0.9% NaCl). On the basis of the area under the activity versus time curves, retention times during atropine exceeded placebo times by more than 30% (p less than 0.01). At 90 min postatropine inhalation, the Vmax50 exceeded baseline values by 21% (p less than 0.01). Urine retention was present in one subject and xerostomia was present in all subjects after atropine. These data suggest that a single dose of atropine sulfate delivered topically to the airway surfaces delays the continuous flow of airway mucus in healthy subjects and that basal autonomic tone is an inherent factor for optimal secretion and/or removal of tracheobronchial secretions.

Smoking cessation and acute airway response to ozone

Pulmonary function and symptom responses of asymptomatic smokers were measured during chamber exposures to ozone or filtered air. Subjects were evaluated while habituated to smoking and after 6 mo of smoking abstinence. At the onset of treatment, subjects (n = 18) who had a history of smoking 33.4 +/- 15.6 packs/y and who had almost normal pulmonary function (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV1.0], and mid-maximal flow [MMF] were greater than 82% of predicted) were unresponsive to ozone exposure (0.4 ppm for 2 h). A matched group of control smokers (n = 16) did not respond to filtered air exposure. After 6 mo of smoking cessation, baseline MMF rates improved significantly (p less than .02); exsmokers (n = 15) raised this index from 3.32 to 4.11 l/s. All 9 subjects who abstained from smoking cigarettes for 6 mo and who were re-exposed to 0.4 ppm ozone had significant (p less than .01) reductions in MMF (from a mean of 3.86 +/- 1.32 [standard deviation] to 2.99 +/- 0.94 l/s, i.e., 22.5% reduction) and marginally significant reductions in comfort, as evidenced by an increase in the incidence of dry cough (p less than .10). The FVC was not reduced during ozone exposure. Control exsmokers (n = 6) remained unresponsive to filtered air exposure. The exsmokers' responses to ozone and their improved MMF during the period of smoking abstinence were correlated (coefficient = .88), i.e., subjects with the largest baseline gains in MMF after withdrawal experienced the largest acute decrements in MMF during ozone exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

T3 preserves respiratory function in sepsis

Sepsis produces profound hypothyroidism. This hypothyroid state is associated with altered lung metabolism and structural integrity. We studied the respiratory function of rats during sepsis-induced hypothyroidism with or without T3 treatment. Forty-four male Holtzman rats underwent cecal ligation and puncture (CLP). Treatment was administered at six hours after surgery consisting of intraperitoneal injection of T3 (15 micrograms/kg, n = 19) or saline (n = 25). At 20 hours (Group A) or 30 hours (Group B) following CLP, respiratory drive was assessed by serial occlusion pressure technique (P0.1). The rats were killed and static elastance determined by serial air inflation to 10 cc. The lungs were excised for weight determination. The P0.1 values were significantly greater in T3-treated animals over controls in Group A (9.3 +/- 0.7 vs. 6.6 +/- 2.2, p less than 0.05 by t test); elastance was significantly improved by T3 treatment in Group B (p less than 0.05 by two-way ANOVA). Lung weight, pH, pO2, pCO2, respiratory rate (RR), and mortality were not significantly different between groups. Control animals were hypothyroid by 20 hours after CLP (T3 less than 12.5 ng/dL) whereas T3-treated animals were euthyroid (T3 = 145 +/- 43 ng/dL). Pulmonary dysfunction frequently accompanies sepsis; the euthyroid state appears protective. We found a significantly improved respiratory drive in septic animals with T3 treatment. Lung elastance was similarly improved in late sepsis with T3 treatment. The data suggest that T3 treatment preserves respiratory function in septic rats as evidenced by respiratory drive and compliance.

Large and small airway responses to bronchoconstrictors in the guinea pig and ferret

In the isolated, perfused lung lobe of the ferret we evaluated the bronchoconstrictor response of its airways to methacholine and histamine, pharmacologic agents associated with the asthmatic state. The bronchus of excised lobes was cannulated and needle scarifications were made on the pleural surface to allow perfusate to exit. Lung airways were perfused at constant flow with equilibrated 95% O2/5% CO2, warmed Krebs-Ringers solution. Perfusion pressure was measured as a gauge of airway resistance. A concentration-dependent smooth muscle contraction of the ferret lung lobes was observed to methacholine and histamine. The ED50's of methacholine and histamine were 6.41 x 10(-6) M +/- 1.38 x 10(-6) (SEM) and 6.41 x 10(-6) M +/- 1.38 x 10(-6) (SEM) and 2.39 x 10(-6) M +/- 0.53 x 10(-6) (SEM), respectively. The maximum level of bronchoconstriction developed in the ferret (2.42 mmHg/ml/min +/- 0.28 SEM (resistance units] in response to methacholine, was six times greater than that found for histamine (0.42 mmHg/ml/min +/- 0.05 SEM). Responses to both agonists were less pronounced in the ferret lung preparation than those in a similar lung preparation of guinea pig. Compliance changes in both animals were also evaluated. The ferret did not demonstrate a compliance change in response to histamine as was seen for methacholine, suggesting that resistance changes precede compliance changes, or that the ferret airways are particularly resistant to histamine. Despite a lesser contractile response, the ferret has the advantage of a relatively large lung and long trachea that allow study in several preparations obtained from a single animal. It should prove a useful animal model for study of pulmonary pharmacology.

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.

Supramicron-sized particle clearance from alveoli: route and kinetics

Particles inhaled and deposited in the alveoli of the lung, i.e., distal to the tracheobronchial mucociliary escalator, may theoretically be cleared by several routes, including solubilization, lymphatic drainage, and the mucociliary pathway. We studied the clearance routes and kinetics of an inert insoluble carbonized polystyrene particle of supramicron size (2.85 micron count median diameter) tagged with 57Co (half-life 270 days) in the adult unanesthetized sheep. The rate of particle clearance, assessed by gamma scintillation camera of the whole lung, showed a three-exponential function, comprising a rapid initial phase in the first 44 h of clearance for tracheobronchial deposition followed by a slower phase of mostly alveolar clearance in the next 30 days and a final phase of very slow relatively pure alveolar clearance. A balance study of particle route during clearance and autopsy of regional thoracic lymph nodes, blood, liver, and spleen demonstrated that this supramicron-sized particle cleared from alveoli predominantly via the mucociliary escalator of the tracheobronchial tree. Whole-lung lavage studies showed particle and macrophage recovery rates suggesting a sequestered state for alveolar-deposited particles, which may partly account for their slow clearance rates. The failure to find interstitial penetration by alveolar-deposited particles indicates that the macrophages engulfing these particles, at low particle burdens, travel normally in only one direction, i.e., from interstitium to alveolus and then to the mucociliary escalator.

Determining deposition sites of inhaled lung particles and their effect on clearance

An essential component of lung defense is clearance of particulates and infectious vectors from the mucus membrane of the tracheobronchial tree and the alveolar regions of the lung. To partition clearance between these areas we determined the bronchial branching pattern, the anatomical sites of particle deposition, and subsequent clearance in the same animal. Using a 2.85-microns particle tagged with 57Co for inhalation and deposition in the sheep lung, we followed clearance via a series of computer-stored gamma-scintillation lung images. The same sheep was reinhaled, and the particle distributions for both inhalations were compared. After the animals were killed, the bronchial branching pattern and length of the bronchial tree were documented. The number of particles depositing in all bronchi down to 1 mm diam was determined by scintillation counting, and the number in respiratory bronchioles and alveoli was microscopically counted. We conclude that particles deposited in bronchi greater than or equal to 1 mm diam clear in 2-4 h postdeposition. Bronchi distal to 1-mm-diam bronchi and alveoli clear evenly over 72 h, and the number of particles equal to the tracheobronchial deposition cleared after 45 h.

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)

Calculating concentration of inhaled radiolabeled particles from external gamma counting: external counting efficiency and attenuation coefficient of thorax

We determined the overall external counting efficiency of radiolabeled particles deposited in the sheep lung. This efficiency permits the noninvasive calculation of the number of particles and microcuries (microCi) from gamma-scintillation lung images of the live sheep. Additionally, we have calculated the attenuation of gamma radiation (120 keV) by the posterior chest wall and the gamma-scintillation camera collection efficiency of radiation emitted from the lung. Four methods were employed in our experiments: (1) by light microscopic counting of discrete carbonized polystyrene particles with a count median diameter (CMD) of 2.85 microns and tagged with cobalt-57 (57Co), we delineated a linear relationship between the number of particles and the emitted counts per minute (cpm) detected by well scintillation counting; (2) from this conversion relationship we determined the number of particles inhaled and deposited in the lungs by scintillation counting fragments of dissected lung at autopsy; (3) we defined a linear association between the number of particles or microcuries contained in the lung and the emitted radiation as cpm detected by a gamma scintillation camera in the live sheep prior to autopsy (external counting efficiency); and (4) we compared the emitted radiation from the lungs of the live sheep to that of whole excised lungs in order to calculate the attenuation coefficient (ac) of the chest wall. The mean external counting efficiency was 4.00 X 10(4) particles/cpm (5.1 X 10(-3) microCi/cpm), the camera collection efficiency was 1 cpm/10(4) disintegrations per minute (dpm), and the ac had a mean of 0.178/cm. The external counting efficiency remained relatively constant over a range of particles and microcuries, permitting a more general use of this ratio to estimate number of particles or microcuries depositing after inhalation in a large mammalian lung if a similarly collimated gamma camera system is used.

Ozone exposure alters tracheobronchial mucociliary function in humans

Mucociliary function is a primary defense mechanism of the tracheobronchial airways, and yet the response of this system to an inhalational hazard, such as ozone, is undefined in humans. Utilizing noninvasive techniques to measure deposition and retention of insoluble radiolabeled particles on airway mucous membranes, we studied the effect on mucus transport of 0.2 and 0.4 ppm ozone compared with filtered air (FA) in seven healthy males. During 2-h chamber exposures, subjects alternated between periods of rest and light exercise with hourly spirometric measurement of lung function. Mechanical and mucociliary function responses to ozone by lung airways appeared concentration dependent. Reduction in particle retention was significant (P less than 0.005) (i.e., transport of lung mucus was increased during exposure to 0.4 ppm ozone and was coincident with impaired lung function; e.g., forced vital capacity and midmaximal flow rate fell by 12 and 16%, respectively, and forced expiratory volume at 1 s by 5%, of preexposure values). Regional analysis indicated that mucus flow from distal airways into central bronchi was significantly increased (P less than 0.025) by 0.2 ppm ozone. This peripheral effect, however, was buffered by only a marginal influence of 0.2 ppm ozone on larger bronchi, such that the resultant mucus transport for all airways of the lung in aggregate differed only slightly from FA exposures. These data may reflect differences in regional diffusion of ozone along the respiratory tract, rather than tissue sensitivity. In conclusion, mucociliary function of humans is acutely stimulated by ozone and may result from fluid additions to the mucus layer from mucosal and submucosal secretory cells and/or alteration of epithelial permeability.

Airway mucus membrane: effects of beta-adrenergic and anticholinergic stimulation

Mucus hypersecretion and non-continuous clearance of tracheobronchial mucus contribute to airflow obstruction in several pulmonary disease entities. Bronchospasm, which is frequently associated with bronchial asthma, can present simultaneously with mucus transport abnormalities. Therapy designed to dilate airways may produce secondary effects, which are deleterious to effective transport of lung mucus. Sympathomimetic agents, such as beta-adrenergic agonists, reduce the tone of bronchial smooth muscle and enhance the flow of mucus within lung airways. Parasympatholytic agents also improve airflow in the lungs, but their effects at the mucus membrane of the airways may not be beneficial. Atropine, an anticholinergic agent, apparently has dose-dependent effects on human mucociliary function and, administered orally, can reduce large airway mucus transport. However, newer anticholinergic agents, such as ipratropium bromide, are effective bronchodilators and do not exhibit unfavorable effects on lung mucus transport in either subjects with normal mucus secretion or those with hypersecretory disease entities, such as bronchitis. In mildly symptomatic asthmatic patients, aerosolized ipratropium decreased airway obstruction without consistent positive or negative influence on lung mucociliary function.

Disassociation in the mucociliary function of central and peripheral airways of asymptomatic smokers

Mucociliary function of peripheral airways in asymptomatic smokers may be impaired and contribute to the abnormal airway changes described in these subjects. Techniques using the inhalation and deposition of radioactive particles followed by gamma camera imaging were applied to healthy subjects discordant for smoking habit to determine if mucus transport of peripheral and central airways was altered by smoking. Smokers (n = 8) averaged 26 +/- 2 yr (mean +/- SEM) and less than 7.5 pack-years of smoking, with pulmonary function within normal limits; when compared with the nonsmokers (n = 8) of similar age, their expiratory volumes were similar, i.e., FEV1 as a percent of predicted averaged 94.5 +/- 4% (mean +/- SEM) in the smokers and 98.8 +/- 4% in the nonsmokers. Using 24-h particle retention and planar distribution of particles in the chest as indexes of peripheral and central deposition, the 2 groups had similar deposition patterns. Mucus clearance of particles deposited onto tracheobronchial airways was quantitated as the interval between initial deposition and the time required to attain 75, 50, and 25% retention levels. Six of the 8 smokers had 75% retention times comparable to those of the nonsmokers, but the 50 and 25% retention times differed significantly between the 2 groups (p less than 0.025). Smokers cleared lung mucus at slower rates, i.e., the intervals to attain 25 and 50% retention levels were 60 to 90% greater than the mean values observed for nonsmokers. Velocity of mucus streaming within stem bronchi was comparable for the 2 groups; beta 2-adrenergic stimulation increased mucus transport in the smokers to the baseline control rates of the nonsmokers.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory drugs influence lung mucociliary clearance in central and peripheral ciliated airways

Radiolabelling of mucus and gamma-camera imaging techniques were utilized to differentiate mucociliary function in large central and small peripheral bronchi of man. Lung mucus clearance was analyzed for the entire right lung field and a peripheral region, which was representative of mucus clearance from airways distal to lobar bronchi. On control days, healthy subjects breathed monodisperse particles, average size 4.19 micrometers, and achieved central patterns of deposition with mouth breathing at rest. Matched deposition patterns were achieved on treatment days when isoetharine or isoproterenol influence on mucus clearance was measured and compared to control. Whole and peripheral lung clearances were increased by beta-adrenergic aerosol: isoetharine/control clearance ratios for whole and peripheral lung average 1.47 and 1.50, respectively; similar results were found for isoproterenol with ratios of 1.47 and 1.23, respectively. These data indicated that in healthy subjects the peripheral bronchi have the longest turn-over times for replacement of their mucous linings, and that these airways, like the larger airways of the trachea and main bronchi, can be stimulated by beta-adrenergic agents to increase their base-line flow of mucus.