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.

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.

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.

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.

Improved pulmonary distribution of recombinant human Cu/Zn superoxide dismutase, using a modified ultrasonic nebulizer.

Prophylactic, intratracheal instillation of recombinant human Cu/Zn superoxide dismutase (rhSOD) has been shown to lessen lung injury produced by 48 h of hyperoxia and mechanical ventilation in neonatal piglets. However, instillation of small volumes of rhSOD intratracheally would not be expected to result in uniform pulmonary distribution. Aerosolization is a technique that may improve pulmonary distribution of drugs, but is limited by the poor efficiency of most nebulizers. A newly modified ultrasonic nebulizer was tested to assess pulmonary distribution of rhSOD compared to that achieved by intratracheal instillation. rhSOD was dual-labeled with technetium-99m (99mTc) and a fluorescent analog (permitting quantitative and qualitative assessments of pulmonary distribution), and administered to neonatal piglets by intratracheal instillation or by aerosolization. Intratracheal instillation of rhSOD to piglets when supine resulted in nonuniform distribution, with most of the drug being found in the right caudal lobe, and localized in airways. Placing animals in 30 degrees of Trendelenburg and administering half the dose in the left and half in the right lateral decubitus positions improved distribution, but alveolar deposition remained patchy. Aerosolization using a modified ultrasonic nebulizer uniformly delivered 45.8 +/- 3.8% of the rhSOD to the lungs that had been placed in the nebulizer. The rhSOD was still active and present in airways and alveoli in a homogeneous fashion. We conclude that intratracheal instillation of rhSOD in small volumes results in nonuniform pulmonary distribution, while aerosolization enhances rhSOD distribution and alveolar deposition. This has important implications for ongoing clinical trials of rhSOD for the prevention of acute and chronic lung injury in premature neonates.

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)

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.

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.

Effects of milrinone on left ventricular remodeling after acute myocardial infarction.

BACKGROUND: Left ventricular remodeling after an acute myocardial infarction may result in progressive left ventricular dilation that may be associated with increased mortality. We studied the effects of the phosphodiesterase inhibitor milrinone on left ventricular remodeling after acute myocardial infarction. METHODS AND RESULTS: Rats (n = 90) were randomized to undergo either left coronary artery ligation or sham operation. Three weeks after surgery, rats received either no treatment or milrinone, which was continued until 2 days before the rats were killed. Ninety days after the initial surgery, hemodynamic measurements were made before and after volume loading. The rats were killed, the hearts were removed, and passive pressure-volume curves were obtained. The hearts were fixed at a constant pressure and analyzed morphometrically. Compared with untreated infarcted rats, milrinone-treated infarcted rats had a lower left ventricular end-diastolic pressure (1.7 +/- 0.4 versus 4.3 +/- 1.4 mm Hg, p less than 0.05), a lower left ventricular volume (1.25 +/- 0.20 versus 2.37 +/- 0.30 ml/kg, p less than 0.001) and a lower left ventricular wall stress index (1.3 +/- 0.2 versus 1.7 +/- 0.1, p less than 0.05). Left ventricular chamber stiffness was higher in milrinone-treated infarcted rats than in untreated infarcted rats. Milrinone had no cardiac effect on uninfarcted animals. CONCLUSION: Chronic milrinone therapy after acute myocardial infarction improves cardiac hemodynamic indexes and attenuates progressive left ventricular dilation.

Aerosolized surfactant improves pulmonary function in endotoxin-induced lung injury.

Surfactant dysfunction is a primary pathophysiologic component in patients with adult respiratory distress syndrome (ARDS). In this study we tested the efficacy of aerosolized surfactant (Sf ) replacement in a severe lung injury model of endotoxin-induced ARDS. Twenty-one certified healthy pigs were anesthetized, surgically prepared for measurement of hemodynamic and lung function, then randomized into one of four groups: (1) control (n = 5), surgical instrumentation only; (2) lipopolysaccharide (LPS) (n = 6), infused with Escherichia coli LPS (100 microgram/kg) without positive end- expiratory pressure (PEEP) and ventilated with a nonhumidified gas mixture of 50% N2O and 50% O2; (3) LPS + PEEP (n = 4), infused with LPS, placed on PEEP (7.5 cm H2O), and ventilated with a humidified gas mixture; and (4) LPS + PEEP + Sf (n = 6), infused with LPS, placed on PEEP, and ventilated with aerosolized Sf (Infasurf, ONY, Inc.). All animals were studied for 6 h. Arterial PO2 significantly decreased in both the LPS and LPS + PEEP groups (LPS + PEEP = 74 +/- 19 mm Hg; LPS = 74 +/- 19 mm Hg, p < 0.05) while venous admixture (Q S/Q T) increased in these groups (LPS + PEEP = 43.3 +/- 3.9%; LPS = 47.7 +/- 11%, p < 0.05) as compared with the control group. PEEP + Sf reduced the fall in PO2 (142 +/- 20 mm Hg) and rise in Q S/Q T (15.1 +/- 3.6%) caused by LPS. Delayed induction of PEEP (2 h following LPS) did not significantly improve any parameter over the LPS group without PEEP in this ARDS model. LPS without PEEP (3.4 +/- 0.2 cells/6,400 micrometer2) caused a marked increase in the total number of sequestered leukocytes in the pulmonary parenchyma as compared with the control group (1.3 +/- 0.1 cells/6,400 micrometer2). LPS + PEEP + Sf (2.3 +/- 0.2 cells/6,400 micrometer2) significantly decreased while LPS + PEEP significantly increased (4.0 +/- 0.2 cells/6,400 micrometer2) the total number of sequestered leukocytes as compared with the LPS without PEEP group. In summary, aerosolized surfactant replacement decreased leukocyte sequestration and improved oxygenation in our porcine model of endotoxin-induced lung injury.

Ultrasonic nebulized in comparison with instilled surfactant treatment of preterm lambs.

To evaluate the efficiency and distribution of ultrasonic nebulized versus instilled surfactant in the treatment of surfactant deficiency at varying degrees of maturation, twin or triplet lamb fetuses were delivered at 125 to 137 d gestational age and received nebulized natural surfactant (Neb Only), instilled surfactant followed by a second instilled dose (Inst/Inst), instilled surfactant followed by nebulized surfactant (Inst/Neb), or no surfactant (Control). The lambs were ventilated for 6 h. Twenty-eight lambs were categorized into two groups (low compliance versus moderate compliance) based on initial physiologic lung characteristics. Efficiency of deposition of nebulized surfactant directly correlated with the compliances and ventilatory efficiency indices measured at 15 min of age. The low-compliance group (Low Comp) had significantly lower efficiency of surfactant deposition (7.6 +/- 1.6%) than did the moderate-compliance group (Mod Comp) (23.4 +/- 2.5%) (p < 0.01). Overall, instilled surfactant had a reasonably homogeneous distribution, whereas nebulized surfactant had a less homogeneous distribution, except for the Low Comp, Inst/Neb group, which had a distribution pattern similar to that for instilled surfactant. The potential for nebulized surfactant therapy for respiratory distress syndrome (RDS) may be limited by the nonhomogeneous nature of ventilation in the preterm lung.

Localization and activity of recombinant human CuZn superoxide dismutase after intratracheal administration.

Hyperoxia and mechanical ventilation cause acute lung injury which may be mitigated by prophylactic intratracheal (IT) administration of recombinant human CuZn superoxide dismutase (rhSOD). However, little is known about the localization, activity, and metabolism of rhSOD after IT administration by instillation or nebulization. Twenty-six newborn piglets were intubated, mechanically ventilated, and given either saline or fluorescently labeled rhSOD (5 mg/kg IT) by instillation or nebulization. Animals were killed 1, 6, or 12 h later. Intact rhSOD (% total fluorescence still associated with macromolecules) and total SOD activity in lung tissue were then determined. Results indicate that, after 1 and 6 h of administration, the majority of rhSOD present in the lung was still associated with the fluorescent label. By 12 h, most of the rhSOD was no longer fluorescently labeled. At 1 h, lung SOD activity increased by 100% compared with untreated control values, with activity remaining elevated at 6 and 12 h. Laser confocal microscopy of lung tissue showed that at 1 h, labeled rhSOD was found throughout the lung, inside a variety of cell types of airways, respiratory bronchioles, and alveoli. Deposition was more homogeneous after nebulization. Negative controls had minimal background fluorescence. These data indicate that after IT administration, rhSOD is rapidly incorporated into cells in the lung and significantly increases lung SOD activity. These observations have important implications for the clinical use of rhSOD in human trials.

Effects of pH and dose on nasal absorption of scopolamine hydrobromide in human subjects.

PURPOSE: The present study was conducted to evaluate the effects of formulation pH and dose on nasal absorption of scopolamine hydrobromide, the single most effective drug available for the prevention of nausea and vomiting induced by motion sickness. METHODS: Human subjects received scopolamine nasally at a dose of 0.2 mg/0.05 mL or 0.4 mg/0.10 mL, blood samples were collected at different time points, and plasma scopolamine concentrations were determined by LC-MS/MS. RESULTS: Following administration of a 0.2 mg dose, the average Cmax values were found to be 262+/-118, 419+/-161, and 488+/-331 pg/ mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At the 0.4 mg dose the average Cmax values were found to be 503+/-199, 933+/-449, and 1,308+/-473 pg/mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At a 0.2 mg dose, the AUC values were found to be 23,208+/-6,824, 29,145+/-9,225, and 25,721+/-5,294 pg x min/mL for formulation pH 4.0, 7.0, and 9.0, respectively. At a 0.4 mg dose, the average AUC value was found to be high for pH 9.0 formulation (70,740+/-29,381 pg x min/mL) as compared to those of pH 4.0 (59,573+/-13,700 pg x min/mL) and pH 7.0 (55,298+/-17,305 pg x min/mL) formulations. Both the Cmax and AUC values were almost doubled with doubling the dose. On the other hand, the average Tmax, values decreased linearly with a decrease in formulation pH at both doses. For example, at a 0.4 mg dose, the average Tmax values were 26.7+/-5.8, 15.0+/-10.0, and 8.8+/-2.5 minutes at formulation pH 4.0, 7.0, and 9.0, respectively. CONCLUSIONS: Nasal absorption of scopolamine hydrobromide in human subjects increased substantially with increases in formulation pH and dose.