Respiratory and limb muscle function in lung allograft recipients

Lung transplantation recipients have reduced exercise capacity despite normal resting pulmonary and hemodynamic function. The limiting factor may be contractile dysfunction of skeletal muscle. To test this postulate, we measured limb and respiratory muscle function in nine clinically stable lung allograft recipients (six men and three women, aged 30 to 65 yr, at 5 to 102 mo after transplantation) with reduced exercise capacity. Respiratory muscle strength was tested by measuring maximal inspiratory and expiratory pressure (MIP and MEP, respectively). Ankle dorsiflexor muscle strength was measured during maximal voluntary contraction (MVC). In a subset of six recipients, we also measured contractile properties and fatigue characteristics of the tibialis anterior muscle, using electrical stimulation of the motor point. Data were compared with values from age- and sex-matched control subjects. MIP values of transplant recipients did not differ from control values; however, MEP was blunted by 30% relative to control (p < 0.05), and MVC was decreased by 39% (p < 0.05). The force-frequency relationships and fatigue characteristics of the tibialis anterior were not different between the patient and control groups. We conclude that stable lung allograft recipients experience expiratory and lower limb weakness that may contribute to exercise intolerance.

Nylon flock-associated interstitial lung disease

A work-related interstitial lung disease has been diagnosed in workers at five nylon flock facilities in three different states and a Canadian province. The National Institute for Occupational Safety and Health hosted a workshop at which consulting pulmonary pathologists reviewed lung tissue samples from all the cases for which lung biopsy material was available (15 of 20 cases known in January 1998). After independent review and scoring of these lung tissue specimens, the pathologists reached consensus that the histopathological findings revealed a characteristic lesion-a lymphocytic bronchiolitis and peribronchiolitis with lymphoid hyperplasia represented by lymphoid aggregates. The pathologists noted that the pathological findings were distinctive when compared with known lung conditions. The clinical presentation for the cases generally included cough, dyspnea, restrictive ventilatory defect with reduction in diffusing capacity, and interstitial markings on chest radiographs or high-resolution computed tomography (HRCT) scans. Six of the cases improved after removal from workplace exposure without medical treatment. Six others, who had recovered with medical treatment and removal from the workplace, had relapses in both symptoms and objective findings after attempting to return to nylon flock work. With this and other evidence supporting the existence of chronic interstitial pneumonitis associated with nylon flock processing, workshop participants recommended surveillance for early identification of affected workers and their removal from further workplace exposure.

Potential involvement of 4-hydroxynonenal in the response of human lung cells to ozone

Ozone is a photochemically generated pollutant that can cause acute pulmonary inflammation and induce cellular injury and may contribute to the development or exacerbation of chronic lung diseases. Despite much research, the mechanisms of ozone- and oxidant-induced cellular injury are still uncertain. Ozone and secondary free radicals have been reported to cause the formation of aldehydes in biological fluids. One of the most toxic aldehydes formed during oxidant-induced lipid peroxidation is 4-hydroxynonenal (HNE). HNE reacts primarily with Cys, Lys, and His amino acids, altering protein function and forming protein adducts. The purpose of this study was to determine whether HNE could account for the acute effects of ozone on lung cells. Human subjects were exposed to 0.4 parts/million ozone or air for 1 h with exercise (each subject served as his/her own control). Six hours after ozone exposure, cells obtained by airway lavage were examined for apoptotic cell injury, and cells from bronchoalveolar lavage were examined for apoptosis, presence of HNE adducts, and expression of stress proteins. Significant apoptosis was evident in airway lung cells after ozone exposure. Western analysis demonstrated an increase in a 32-kDa HNE protein adduct and a number of stress proteins, viz., 72-kDa heat shock protein and ferritin, in alveolar macrophages (AM) after ozone exposure. All of these effects could be replicated by in vitro exposure of AM to HNE. Consequently, the in vitro results and demonstration of HNE protein adducts after ozone exposure are consistent with a potential role for HNE in the cellular toxic effects of ozone.

Tolerance of volunteers to cyclosporine A-dilauroylphosphatidylcholine liposome aerosol

Cyclosporine A (CsA) in liposomes of dilauroylphosphatidylcholine (DLPC), containing 118 micrograms of CsA/L of aerosol with a particle size of 1.6 to 1.7 micron diameter, was inhaled by 10 nonsmoking, normal volunteers each for 45 min. Aerosol was administered through an Aerotech II nebulizer (CIS-US, Inc., Bedford, MA) mouthpiece. Eight of the 10 volunteers had tracheal irritation and intermittent coughing following exposure. FEV1 and FVC values were mildly reduced, but returned to normal in 1 h. Blood chemical and hematologic values were unchanged at any time point after as opposed to before inhalation. Nine of the 10 volunteers later inhaled DLPC only, administered through the nebulizer mouthpiece. There was no change in FEV1 or FVC values, and there was no coughing or tracheal irritation. Subsequently, five of the volunteers who had previously had respiratory reactions inhaled CsA-DLPC liposome aerosol for 45-min, but through a mouth-only face mask. There was no tracheal irritation, coughing, or changes in spirometric measures. Blood concentrations of CsA at 15 min after the 45-min inhalation with a face mask averaged 83 +/- 42 ng/ml (mean +/- SD). At 24 h after treatment, CsA was undetectable in blood of the initial 10 volunteers. These studies indicate that CsA-DLPC liposome aerosol can be safely explored as a treatment for patients with moderately severe asthma.

Increased 5-lipoxygenase metabolism in the lungs of human subjects exposed to ozone

The environmental pollutant ozone, at sufficiently high levels, is known to induce pulmonary inflammation with resultant airway obstruction in normal subjects. Eicosanoids comprise one group of mediators released from alveolar macrophages which are involved in the pathogenesis of inflammatory lung diseases. We compared the effects of 2-h exposures to 0.4 ppm ozone and filtered air on pulmonary function and eicosanoid levels in bronchoalveolar lavage fluid in 11 normal healthy volunteers. Subjects were exposed to a 6-fold increase in minute ventilation using an adjusted work load on a cycle ergometer. All subjects complained of cough and dyspnea, and demonstrated increased airway obstruction, and increased specific airway resistance following ozone exposure as compared to air exposure. Bronchoalveolar lavage cell count demonstrated a 9-fold increase in the number of neutrophils with a lesser reduction in the number of alveolar macrophages following ozone exposure. Notably, bronchoalveolar lavage fluid leukotriene (LT) C4 (8-fold) and to a lesser extent LTB4 (1.5-fold) levels were higher following ozone exposure compared to air control, with no change in prostaglandins. In a subset of four subjects, alveolar macrophage arachidonic acid metabolism was studied in vitro following separate in vivo exposures to both ozone and air. Alveolar macrophages obtained following ozone exposure released more 5-lipoxygenase (1.5-fold) metabolites, with no change in cyclooxygenase metabolites, than did cells obtained following air exposure. These observations document activation of the 5-lipoxygenase pathway in the lung following ozone exposure, and suggest that alveolar macrophages may participate in the generation of LT, whose actions promote airway inflammation and obstruction.

4-Hydroxynonenal mimics ozone-induced modulation of macrophage function ex vivo

Ozone is a ubiquitous pollutant that can cause acute pulmonary inflammation, cellular injury and may contribute to the development or exacerbation of chronic lung diseases. Despite much research, the effects of ozone on humans and potential cellular mechanisms of injury are still uncertain. However, ozone has been reported to increase the formation of aldehydes that could react with cellular proteins. Therefore, the purpose of these studies was to determine whether 4-hydroxynonenal (HNE), a previously unidentified aldehyde product of ozone exposure, is formed in human subjects exposed to ozone, and whether the response of human alveolar macrophages (AM) following a 1-h exposure to 0.25 ppm ozone with moderate exercise could be mimicked by in vitro incubation of AM with HNE. Western analysis demonstrated increased HNE protein adducts in airway fluid and alveolar macrophages after ozone exposure. AM were examined for endotoxin (lipopolysaccharide [LPS])-stimulated interleukin-1 beta (IL-1 beta) release and expression of heat shock protein 72 (HSP72). Immediately after ozone exposure there was no change in HSP72, but a 5-fold increase occurred 4 h after exposure. By 18 h after exposure, HSP72 levels decreased to below comparable air-exposed levels. Immediately after ozone exposure there was no effect on IL-1 beta release stimulated by LPS. However, IL-1 beta release stimulated by LPS was significantly inhibited 4 h after ozone exposure. By 18 h after ozone exposure, IL-1 beta release stimulated by LPS returned to normal. Incubation of human AM in vitro with HNE induced HSP72 and blocked LPS-stimulated IL-1 beta release possibly by inhibiting interleukin converting enzyme. Consequently, the in vitro results and demonstration of HNE protein adducts following ozone exposure are consistent with HNE being involved in this process in vivo and suggest that the cellular toxic effects of ozone could be a result of thiol reactive aldehydes produced by ozone.

Air toxics and asthma: impacts and end points

The National Urban Air Toxics Research Center (NUATRC) hosted a medical/scientific workshop focused on possible asthma/air toxics relationships, with the results of the NUATRC's first research contract with the University of Cincinnati as the point of discussion. The workshop was held at the Texas Medical Center on 4 February 1994 and featured presentations by distinguished academic, government, and industry scientists. This one-day session explored the impact of various environmental factors, including air toxics, on asthma incidence and exacerbation; an emphasis was placed on future research directions to be pursued in the asthma/air toxics area. A key research presentation on the association of air toxics and asthma, based on the study sponsored by NUATRC, was given by Dr. George Leikauf of the University of Cincinnati Medical Center. Additional presentations were made by H. A. Boushey, Jr., Cardiovascular Research Institute/University of California at San Francisco, who spoke on of the Basic Mechanisms of Asthma; K. Sexton, U.S. Environmental Protection Agency, who spoke on hazardous air pollutants: science/policy interface; and D. V. Bates, Department of Health Care and Epidemiology at the University of British Columbia, who spoke on asthma epidemiology. H. Koren, U.S. Environmental Protection Agency, and M. Yeung, of the Respiratory Division/University of British Columbia, Vancouver General Hospital, discussed occupational health impacts on asthma. Doyle Pendleton, Texas Natural Resource Conservation Commission, reviewed air quality measurements in Texas. The information presented at the workshop suggested a possible association of asthma exacerbations with ozone and particulate matter (PM10); however, direct relationships between worsening asthma and air toxic ambient levels were not established. Possible respiratory health effects associated with air toxics will require considerably more investigation, especially in the area of human exposure assessment. Two major recommendations for future research resulted from this workshop and an accompanying NUATRC Scientific Advisory Panel meeting: a need for more complete individual personal exposure assessments so that accurate determinations of actual personal exposures to various pollutants can be made; and a need for field experiments utilizing biomarkers of exposure and effect to more accurately assess the extent and variability of the biological effects, if any, of individual air toxics.

Patient work of breathing during pressure support and volume-cycled mechanical ventilation

A computer-assisted technique based on the equation of motion of the respiratory system was used to measure inspiratory work of breathing in 11 patients during pressure support ventilation (PSV) and assisted, volume-cycled mechanical ventilation (AMV). During both modes of ventilation, patient work of breathing was calculated as the difference between the total work performed on the respiratory system (as predicted by the equation of motion) and the work performed by the ventilator. Patient work of breathing during AMV was also calculated as the difference between ventilator work measured during assisted and controlled mechanical breaths. By either method of work calculation, patient work of breathing during AMV was less than previously reported. In addition, when equal tidal volumes were delivered, there was no significant difference between the work performed by the patient during AMV and PSV. Patient work of breathing during PSV was found, however, to vary inversely with the level of pressure support. We conclude that: (1) patient work of breathing during AMV and PSV can be calculated using a computer-assisted technique based on the equation of motion of the respiratory system, and (2) depending on the amount of pressure support provided, patient work of breathing during PSV may be greater than, less than, or equal to the work performed during AMV.

The role of methotrexate in the management of steroid-dependent asthma

Severe asthma often requires high-dose corticosteroid therapy. However, steroid therapy is fraught with many side effects. There are conflicting reports in the literature regarding the role of methotrexate in reducing the steroid requirements of these patients. This study examined the role of low-dose methotrexate in the management of steroid-dependent asthma. Eleven subjects with stable steroid-dependent asthma were enrolled in a placebo-controlled double-blind crossover trial. Patients received methotrexate, 15 mg/wk, or placebo each for two 12-week periods. There was significant improvement of pulmonary function and reduction of prednisone requirement in both placebo and methotrexate treatment periods. However, methotrexate was not superior to placebo. Only 3 of 11 patients responded to methotrexate. Although low-dose methotrexate therapy may have a role in a small select group of steroid-dependent asthmatics, it provided no additional benefit overall.

Ozone-induced increases in substance P and 8-epi-prostaglandin F2 alpha in the airways of human subjects

We are interested in the mechanisms of ozone-induced lung effects after short-term exposure and the relationship with subsequent pulmonary inflammation and disease. Our hypothesis is that ozone, as a powerful oxidant, will diminish the activity of neutral endopeptidase (NEP) in the airways of humans with resulting increased concentrations of neuropeptides such as substance P (SP). We have exposed seven (two women, five men) healthy, nonsmoking individuals (22 to 30 yr of age) to filtered air and ozone (0.25 ppm) for 1 h in an environmental chamber during heavy exercise. Bronchoscopy with airway lavage (AL) and bronchoalveolar lavage (BAL) was performed immediately after ozone exposure. The lavage samples were analyzed by enzyme immunoassay for SP and 8-epi-prostaglandin F2 alpha (8-epi-PGF2 alpha) (a marker for oxidative free radical reaction) and by radioimmunoassay for complement fragments. FEV1 had declined 12.4 +/- 1.9% (mean +/- SEM) as a result of ozone exposure. The AL concentration for SP and 8-epi-PGF2 alpha and BAL concentration of C3a after ozone exposure were significantly higher than after the filtered air exposure (P < 0.05). There was a significant correlation between SP and 8-epi-PGF2 alpha concentrations in the AL fluid (r2 = 0.89 and P < 0.05). There were no changes in C5a in either compartment or any of the mediators in the plasma samples. These results extend previous results from animal studies suggesting that ozone's mechanism of action is through an oxidative reaction resulting in a decreased activity of NEP in the airways with a subsequent increase in the concentration and activity of SP.

Pulmonary responses of asthmatic and normal subjects to different temperature and humidity conditions in an environmental chamber

Determining the possible adverse health effects of air pollutants can be complicated by differences in the environmental conditions of temperature and humidity. To evaluate the potentially confounding effects of differences in temperature and humidity, we exposed 8 normal male subjects and 8 male subjects with asthma to the extremes in temperature and humidity that could be maintained in an environmental chamber. We performed serial pulmonary function tests for these subjects before and during 6 hr exposure periods on 5 separate occasions: cold, dry (10 degrees C, 10% relative humidity); cold, humid (10 degrees C, 50% relative humidity); normal ambient (22 degrees C, 40% relative humidity); hot, dry (37 degrees C, 15% relative humidity); and hot, humid (37 degrees C, 60% relative humidity). The exposure period included a 12 min exercise on a cycle ergometer. We found no significant change in spirometry, airways resistance, or diffusing capacity for either group of subjects at rest alone over the 6 hr period of exposure for any exposure condition. However, there were changes in spirometry and airways resistance as a result of the 12 min period of exercise. The subjects with asthma had significant decreases in forced expiratory volume in 1 sec (FEV1) (20-21%) and increases in specific airways resistance when exercising in conditions of cold and dry, cold and humid, and hot and dry. The normal subjects had an average increase in FEV1 of approximately 6% when exercising in the hot and humid conditions. We found significant correlations for the changes in FEV1 with the water content of the exposure conditions for both groups of subjects. We also found that the work performance (expressed as the external work performed divided by the oxygen consumed) was decreased for the subjects in both groups at the conditions of the higher temperature (37 degrees C) compared with the lower temperature (10 degrees C). These results confirm that controlling for the conditions of temperature and humidity is essential in chamber studies, field studies, or epidemiologic evaluations determining the adverse effect of an air pollutant.

Inhalation of an alkaline aerosol by subjects with mild asthma does not result in bronchoconstriction

Although it is recognized that inhalation of acid aerosols by subjects with asthma can cause bronchoconstriction, the effects of the inhalation of an alkaline aerosol are unknown. When supplemental inflatable restraints (automobile air bags) are deployed an alkaline aerosol is released. This aerosol is composed of particles of sodium carbonate and sodium bicarbonate with some sodium hydroxide. The mass median aerodynamic diameter (MMAD) of the aerosol is approximately 1 micron, and the pH of the aerosol is 9.8 to 10.3. A group of 14 volunteer male subjects with mild asthma inhaled increasing concentrations of this aerosol for 20-min periods of mouth-only tidal ventilation. Pulmonary function tests were performed at baseline (preexposure), after inhalation of room air alone (control), and after each period of inhalation of the aerosol. A total of 5 subjects inhaled aerosols at nominal concentrations of 10, 20, and 40 mg/m3, whereas 11 subjects inhaled aerosols concentrations of approximately 30, 60, and 120 mg/m3. The mean changes in FEV1 and specific airways resistance (SRaw) for the 11 subjects who inhaled the higher concentrations (average highest concentration 126.6 +/- 7.5 mg/m3, mean +/- SEM) were -1.4 +/- 1.9 and +17.5 +/- 8.5%, respectively. Neither change in lung function was clinically or statistically significant. We conclude that the inhalation of relatively high concentrations of this alkaline aerosol by subjects with mild asthma does not result in bronchoconstriction.

Indomethacin does not inhibit the ozone-induced increase in bronchial responsiveness in human subjects

Exposure of human subjects to sufficiently high levels of ozone can result in reversible changes in lung function (restrictive in nature) and increases in nonspecific airway responsiveness. Several studies have implicated products of cyclooxygenase metabolism in the mediation of these changes. The purpose of this study was to determine if indomethacin (a cyclooxygenase inhibitor) would alter the changes in the ozone-induced increase in responsiveness to methacholine or the ozone-induced decrease in lung function. Thirteen male subjects underwent three randomly assigned 2-h exposure to 0.4 ppm ozone with alternating 15-min periods of rest and exercise on a cycle ergometer (30 L/min/m2, body surface area). For the 4 days before each of the exposures, the subjects received either indomethacin (150 mg/day) or placebo, or no modification. Of the 13 subjects, only seven had both detectable indomethacin serum levels on the indomethacin Study Day and a significant increase in bronchial responsiveness to methacholine on the No Medication Day. For this group of seven subjects, we found that indomethacin did not alter the ozone-induced increase in bronchial responsiveness to methacholine (decrease in PC100SRaw for the different study days: no medication, -78.4 +/- 5.3% [mean +/- SEM]; placebo, -48.9 +/- 12.2%; indomethacin, -64.5 +/- 6.3%; p greater than 0.2), although indomethacin did attenuate the ozone-induced decrease in lung function. The decrease in the FEV1 for the different study days was as follows: no medication, -20.7 +/- 5.0% (mean +/- SEM); placebo, -19.2 +/- 6.3%; indomethacin, -4.8 +/- 3.7% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

An algorithm for the interpretation of cardiopulmonary exercise tests

We have developed and are using an algorithm for the interpretation of cardiopulmonary exercise tests that are performed in our Pulmonary Diagnostic Service Department. As its decision points, this algorithm uses routinely obtained measurements from the results of these exercise tests, such as VO2, VCO2, VE, SaO2, HR, and AT. Using the algorithm results in an objective determination of limitation to exercise and allows for the differentiation between pulmonary and cardiac or circulatory limitation. This straightforward technique for arriving at an interpretation of these tests has resulted in a more consistent approach to interpretation and an excellent teaching guide for physicians and technicians.

The inhaled bronchodilators ipratropium bromide and metaproterenol in adults with CF

Ten patients with CF who were more than 18 years old, participated in a double-blind, placebo-controlled study evaluating the efficacy of inhaled ipratropium bromide and metaproterenol as bronchodilators. The mean FEV1 of the group improved 17.1 percent after treatment with ipratropium bromide, 12.5 percent after metaproterenol treatment, and 16.6 percent after treatment with both of these medications together. There was no significant difference between these responses and patients who responded to one treatment tended to respond to the others. The side effects with these medications were minimal. When compared with patients in previous studies, our patients, who were much older as a group, demonstrated a greater degree of bronchodilation with ipratropium bromide and metaproterenol, as well as a greater degree of bronchoconstriction with placebo.

Ozone-induced changes in pulmonary function and bronchial responsiveness in asthmatics

To compare the responses of asthmatic and normal subjects to high effective doses of ozone, nine asthmatic and nine normal subjects underwent two randomly assigned 2-h exposures to filtered, purified air and 0.4 ppm ozone with alternating 15-min periods of rest and exercise on a cycle ergometer (minute ventilation = 30 l.min-1.m-2). Before and after each exposure, pulmonary function and bronchial responsiveness to methacholine were measured and symptoms were recorded. Ozone exposure was associated with a statistically significant decrease in forced vital capacity (FVC), forced expired volume in 1 s (FEV1), percent FEV1 (FEV1%), and forced expired flow at 25-75% FVC (FEF25-75) in both normal and asthmatic subjects. However, comparing the response of asthmatic and normal subjects to ozone revealed a significantly greater percent decrease in FEV1, FEV1%, and FEF25-75 in the asthmatic subjects. The effect of ozone on FVC and symptom scores did not differ between the two groups. In both normal and asthmatic subjects, exposure to ozone was accompanied by a significant increase in bronchial responsiveness. We conclude that exposure to a high effective ozone dose produces 1) increased bronchial responsiveness in both normal and asthmatic subjects, 2) greater airways obstruction in asthmatic than in normal subjects, and 3) similar symptoms and changes in lung volumes in the two groups.

Arachidonic acid metabolism in cultured alveolar macrophages from normal, atopic, and asthmatic subjects

In order to test the hypothesis that alveolar macrophages (AM) from asthmatics might manifest abnormalities in the amounts, spectrum, or glucocorticoid regulation of eicosanoid synthesis, we compared arachidonic acid (AA) metabolism under resting and ionophore A23187-stimulated conditions in cultured AM obtained by bronchoalveolar lavage from 10 asthmatic, nine atopic, and 10 nonatopic normal subjects. [14C]AA-prelabeled AM constitutively released free [14C]AA and release increased significantly with A23187 incubation. Under resting conditions, unlabeled cells produced small amounts of immunoreactive thromboxane B2 (TxB2), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4). With A23187 stimulation there were significant increases in the synthesis of all immunoreactive metabolites, which were produced in the following relative amounts: LTB4 much greater than TxB2 greater than PGD2 greater than leukotriene C4 greater than PGE2. High performance liquid chromatographic separation of radiolabeled eicosanoids produced by prelabeled cells confirmed the radioimmunoassay results and further indicated the production of relatively large amounts of 5-hydroxyeicosatetraenoic acid and 12-hydroxyheptadecatrienoic acid. Pretreatment (16 h) with 1 microM methylprednisolone inhibited A23187-induced synthesis of immunoreactive cyclooxygenase products to a greater extent than immunoreactive leukotrienes. We identified no significant differences among the three study groups in the quantities or profiles of eicosanoids synthesized either constitutively or with A23187 stimulation, nor in their regulation by methylprednisolone.

The physiology of spontaneous and mechanical ventilation

This article provides both an overview of normal ventilation and gas exchange during spontaneous breathing and a review of the alterations of pulmonary physiology that occur with the institution of mechanical ventilation.

Mediator release in an isolated airway segment in subjects with asthma

To determine if mediator release would occur in the airways of human subjects after exposure to a hyperosmolar stimulus, we challenged isolated airway segments in vivo with 900 mosmol sodium chloride using a specially designed double-balloon catheter. In order to determine if differences in mediator concentrations correlated with airway responsiveness or with atopy, we studied 3 separate groups: 6 atopic, asthmatic subjects; 6 atopic, nonasthmatic subjects; and 6 nonatopic, nonasthmatic normal subjects. In addition, to determine if the presence of the catheter itself was a stimulus, we studied 6 atopic, asthmatic subjects after exposure to isotonic sodium chloride alone (sham exposure). Lavage specimens were assayed for PGD2, PGF2 alpha, PGE2, TxB2, LTC4, and LTB4 by radioimmunoassay and for histamine by the modified single isotope enzymatic assay. The histamine concentration of the baseline lavage samples (bronchoalveolar lavage and isolated airway segment lavage) for the subjects with asthma were significantly greater than for the atopic or normal subjects (p less than 0.05). There was a significant negative correlation between histamine concentration in the lavage samples and the airway responsiveness of the subjects (r = -0.53, p less than 0.0001). There was a marked correlation among the concentrations of histamine, PGD2, PGF2 alpha, and TxB2 in all the lavage fluids for the subjects with asthma (p less than 0.03 for all comparisons and p less than 0.0001 for overall concordance). As a result of hyperosmolar challenge, there was a significant increase in the concentration of histamine, PGD2, and PGF2 alpha in the subjects with asthma.(ABSTRACT TRUNCATED AT 250 WORDS)

Effectiveness of a heat and moisture exchanger in preventing hyperpnoea induced bronchoconstriction in subjects with asthma

The effect of a heat and moisture exchanger, a device with hygroscopic material for conditioning inspired air, on hyperpnoea induced bronchoconstriction was studied in nine non-smoking volunteers with asthma, aged 19-32 years. Each had previously shown an increase of at least 100% in specific airways resistance (sRaw) to isocapnic hyperpnoea with dry air. On two separate days the subject performed isocapnic hyperpnoea with dry air at 60-70 l min-1 for five minutes. Before, immediately after, and five minutes after completion of a test sRaw measurements were made. Heat and moisture exchangers were placed in the breathing circuit on one of the two days. All subjects had an increase in sRaw of 100% or more without the heat and moisture exchangers (average increase 300%) but were protected from bronchoconstriction with the devices in place (average increase 7%) (p less than 0.005). The exchanger's resistance to airflow was less than 1 cm H2O for flow rates of 100 l min-1. A heat and moisture exchanger designed as a facemask or mouthpiece may allow a person with asthma to exercise without the need for prophylactic drugs.

A technique for isolated airway segment lavage

A novel technique has been developed for the isolation and lavaging of a central airway segment in humans. The procedure uses a double-balloon airway-sampling catheter that is placed into the airways with fiberoptic bronchoscopic guidance. A protocol using this technique was attempted in 32 subjects (18 normal subjects and 14 subjects with mild asthma), and 27 of the subjects were able to complete all phases of the protocol, including bronchoalveolar lavage and lavage of an isolated airway segment. There was no significant complication in any subject. Cellular composition of the lavages demonstrated differences in cell differential and total cell counts for the two different sampled regions (central airway vs alveolar spaces). We believe that this technique of lavage of an isolated airway segment is safe and has potential usefulness in many areas of pulmonary research.

Effects of esmolol on airway function in patients with asthma

In a double-blind, randomized, crossover study in ten patients with asthma, the effects on specific airway resistance of esmolol, a new ultra-short-acting beta 1-selective adrenoceptor blocker, were compared with those of placebo. Specific airway resistance was measured during increasing doses of esmolol infusion, during dry air provocation tests, and following isoproterenol inhalation. These same studies were later carried out on six of ten patients following intravenous propranolol infusion. All patients were able to tolerate the maximum dose of esmolol (300 micrograms/kg/min); treatment differences between esmolol and placebo were not found. In contrast, intravenous propranolol produced marked symptomatic bronchoconstriction after the lowest dose (1 mg) in two of six patients. Esmolol produced slight but statistically significant enhancement of patients' sensitivity to dry air provocation. Similarly, a slight but significant inhibition of bronchomotor sensitivity to isoproterenol was noted during esmolol infusion. After infusion of 5 mg of intravenous propranolol, one of four patients had a clinically significant increase in sensitivity to dry air. It is concluded that esmolol, because of its short duration of action and relative lack of effect on airway resistance, may be preferred over propranolol in patients with asthma who require treatment with an intravenous beta-blocking agent.

Respiratory heat loss is not the sole stimulus for bronchoconstriction induced by isocapnic hyperpnea with dry air

It is uncertain if respiratory heat loss or respiratory water loss is the stimulus for bronchoconstriction induced by isocapnic hyperpnea or exercise with dry air in subjects with asthma. We partially separated these 2 stimuli by having 18 subjects with asthma breathe dry air (0 mg/L water content) at increasing ventilations by isocapnic hyperpnea while we measured the increase in specific airway resistance (SRaw). The study was divided into 2 phases. In Phase 1, we used an apparatus with a single respiratory valve and evaluated the subjects' responses at 3 different inspired temperatures (-8.4, 20.5, and 39.4 degrees C). Seven of the subjects had esophageal catheters with 2 thermocouples in place to measure retrocardiac and retrotracheal temperatures. In this phase, we found that there were no significant differences in the ventilation required to cause a 100% increase in SRaw among the 3 different inspired temperatures (48.4 L/min, cold; 47.5 L/min, room temperature; 44.2 L/min, hot), even though the retrotracheal temperature fell more when the subjects breathed cold air at 40 L/min (2.1 degrees C) than when they breathed hot air (1.2 degrees C), suggesting greater airway cooling with the cold air. In Phase 2, in order to accurately measure inspired and exhaled temperatures and exhaled water content, we used 2 separate systems for delivering the inspired air and collecting the exhaled air at 2 different inspired temperatures (-21.4 and 38.9 degrees C). Again, we found that there was no significant difference in the ventilation required to cause a 100% increase in SRaw between the 2 different inspired temperatures (28.3 L/min, cold; 33.6 L/min, hot). When the subjects inhaled cold air, exhaled temperature was warmer than previously reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated concentrations of leukotriene D4 in pulmonary edema fluid of patients with the adult respiratory distress syndrome

The possible contribution of metabolites of arachidonic acid to the increased permeability of the alveolar-capillary barrier in the adult respiratory distress syndrome was examined by quantifying the pulmonary edema fluid concentrations of lipoxygenase and cyclooxygenase products. The concentration of leukotriene D4 in pulmonary edema fluid of 10 patients with the adult respiratory distress syndrome (18.5 +/- 6.8 pmol/ml; mean +/- SD), assessed by specific radioimmunoassay after isolation of the mediator, was significantly higher (P less than 0.001) than that of five patients with cardiogenic pulmonary edema (4.4 +/- 1.1 pmol/ml). The concentrations of leukotrienes B4 and C4, prostaglandin E2, and thromboxane B2 in edema fluid were not significantly different in the adult respiratory distress syndrome patients than in the other subjects with pulmonary edema. The edema fluid concentration of leukotriene D4 correlated with the ratio of edema fluid to plasma concentrations of albumin (r = 0.64). Leukotriene D4 thus may contribute to the permeability defect which allows an accumulation of protein-rich alveolar fluid in the adult respiratory distress syndrome.

Lack of bronchomotor response to up to 3 ppm formaldehyde in subjects with asthma

A study was undertaken to determine whether exposure to concentrations of formaldehyde occasionally encountered in polluted indoor air would cause bronchoconstriction in subjects with mild asthma. In seven subjects the increase in specific airways resistance (SRaw) caused by inhalation of 1 ppm formaldehyde for 10 min was compared with the response caused by inhalation of formaldehyde-free air. Also, the increase in SRaw caused by inhalation of 1 and 3 ppm formaldehyde during moderate exercise for 10 min was compared with the response caused by inhalation of formaldehyde-free air during exercise for 10 min. Inhalation of formaldehyde at rest and during exercise did not cause a significant increase in SRaw in the subjects. It is concluded that brief exposure to these concentrations of formaldehyde, even in association with moderate exercise, is unlikely by itself to cause significant bronchoconstriction in most subjects with mild asthma.

Morphine sulfate inhibits bronchoconstriction in subjects with mild asthma whose responses are inhibited by atropine

To determine whether morphine sulfate alters the bronchoconstrictive response to inhalation of distilled water, we gave 13 subjects with mild asthma 0.15 mg/kg morphine sulfate or normal saline intravenously, after which they inhaled increasing volumes of nebulized distilled water from an ultrasonic nebulizer. We constructed stimulus-response curves, and by interpolation determined the provocative output of the nebulizer that resulted in a 50% increase in SRaw from baseline (PO50). On a separate day the subjects inhaled 2.0 mg of atropine sulfate 30 min before they inhaled distilled water. We compared the bronchoconstrictive response after morphine and after atropine with the bronchoconstrictive response after saline by determining the ratio of the PO50 values. Atropine was considered effective in inhibiting bronchoconstriction in 7 of the 13 subjects in whom the ratio of PO50 after atropine to the PO50 after saline was greater than 2.0. By similar criteria, morphine was also considered effective in 5 of these 7 subjects. Neither atropine nor morphine was effective in the remaining 6 subjects. By chi-square analysis, we found a positive correlation between the inhibitory effects of morphine and those of atropine (p less than 0.05). In the 5 subjects in whom morphine was effective, naloxone reversed the inhibitory effect of morphine. Atropine caused significant baseline bronchodilation when compared with placebo (normal saline), whereas morphine did not. We conclude that opiate receptor stimulation by morphine causes inhibition of the vagally mediated component of water-induced bronchoconstriction.

Magnitude of the interaction between the bronchomotor effects of sulfur dioxide and those of dry (cold) air

We studied the interaction between airway drying (cooling) and inhalation of sulfur dioxide (SO2) causing bronchoconstriction in 8 subjects with mild asthma. On 3 separate days, we measured specific airway resistance (SRaw) before and after the subject performed voluntary eucapnic hyperpnea at a constant minute ventilation (30 to 40 L/min) for successive 3-min periods with doubling concentrations of SO2 in dry cold air (-20 degrees C, 0% relative humidity), in dry warm air (22 degrees C, 0% relative humidity), and in partially humidified warm air (22 degrees C, 70% relative humidity). On another day, we measured SRaw before and after the subject performed each of 6 successive 3-min periods of voluntary eucapnic hyperpnea at the same minute ventilation breathing dry cold air without SO2. The concentration of SO2 that caused a 100% increase in SRaw was significantly lower in dry cold air and in dry warm air than it was in humidified warm air. Repeated hyperpnea with dry cold air without SO2 at the same ventilation had no effect on SRaw. We then had the same subjects perform voluntary eucapnic hyperpnea at successively increasing levels of ventilation on 3 different days with dry air alone, dry air with 0.1 ppm SO2, or dry air with 0.25 ppm SO2. The minute ventilation that caused an 80% increase in SRaw was significantly lower for hyperpnea with 0.1 and with 0.25 ppm SO2 than for dry air without SO2, but these differences were small.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory water loss as a stimulus to exercise-induced bronchoconstriction

Exercise and the resultant hyperpnea increase the magnitude of many stimuli delivered to the airways. Thus clinical "exercise-induced" bronchoconstriction can probably be initiated by a number of stimuli including, for example, sulfur dioxide, which is present in polluted air. In the laboratory, when subjects perform exercise breathing clean air, the water content of the inspired air is a major determinant of the bronchoconstriction induced, whereas in our hands, the temperature of the inspired air is of little or no importance, even over a range associated with significant differences in airway cooling. These observations support the view that water loss is an important stimulus to exercise-induced bronchoconstriction, perhaps as a result of a transient increase in the osmolarity of airway surface liquid.

Alteration in osmolarity of inhaled aerosols cause bronchoconstriction and cough, but absence of a permeant anion causes cough alone

To determine whether cough and bronchoconstriction result from alterations in the osmolarity or alterations in the ion concentration of inhaled aerosols and to determine if the specific ions in the aerosol are important, we had 9 subjects with mild asthma inhale various solutions while we recorded cough and measured specific airway resistance. To evaluate the effects of altering osmolarity and ion concentration separately, we administered aerosols of hypo-osmolar distilled water (0 mosm), iso-osmolar sodium chloride (308 mosm), iso-osmolar dextrose in water (308 mosm), hyperosmolar sodium chloride (1,232 mosm), and a hyperosmolar solution of dextrose and sodium chloride (1,232 mosm). To evaluate cough without bronchoconstriction, we had the subjects inhale metaproterenol before inhaling the same aerosols. To determine whether the absence of a specific ion was important in causing cough or bronchoconstriction, we had the subjects inhale iso-osmolar solutions of sodium bromide, sodium gluconate, and lysine monohydrochloride. We found that alteration in osmolarity away from iso-osmolarity of inhaled aerosols is a stimulus for bronchoconstriction in subjects with mild asthma. Absence of ions in the presence of iso-osmolarity is not a stimulus for bronchoconstriction, but the absence of a permeant anion is a stimulus for cough. Thus, we found that the responses of cough and bronchoconstriction to inhaled aerosols can be separated.

Cardiovascular effects of positive-pressure ventilation in normal subjects

In normal subjects during 15-min positive-pressure ventilation with 10 cmH2O end-expiratory pressure (PEEP), cardiac output fell 19% due to a fall in stroke volume. Transmural mean right atrial pressure rose 3.1 cmH2O and right ventricular end-diastolic diameter increased 15%. Simultaneously, left ventricular end-diastolic diameter decreased 21%, ejection time increased 11%, and velocity of circumferential fiber shortening fell 30%. Thus, right ventricular filling increased and left ventricular filling decreased. The function of the right ventricle was impaired and the function of the left ventricle may have been impaired. Cardiac output gradually increased due to a 7% increase in heart rate as PEEP was continued for 1 h and transmural mean right atrial pressure also increased further by 2.4 cmH2O. Compensation for the reduced stroke volume occurred as filling pressures and heart rate rose, but ventricular function remained impaired for the entire duration of PEEP. On resuming spontaneous breathing, cardiac output and ventricular function returned to base-line levels. We conclude that the reduced cardiac output during PEEP is not due to a direct mechanical reduction in right ventricular filling.

Reflex cardiovascular depression during unilateral lung hyperinflation in the dog

We have examined whether lung hyperinflation in the anesthetized dog reflexly depresses cardiac output, stroke volume, heart rate, and blood pressure and whether these changes persist for more than a minute. To eliminate any mechanical restriction to venous return and pulmonary blood flow during lung hyperinflation, a model was developed in which all pulmonary artery blood flow and all ventilation were directed to the right lung in dogs with widely open chest and the left lung was hyperinflated before and after left cervical vagotomy. Heart rate, stroke volume, and blood pressure decreased by 24, 20, and 27%, respectively, within 15 s of left lung inflation to 30 cm H(2)O. Heart rate increased to preinflation levels by 1 min, but stroke volume and blood pressure remained depressed during lung hyperinflation for at least 15 min. Upon deflation, stroke volume and blood pressure returned to control levels within 1 min. Division of the left vagosympathetic trunk at the neck interrupted all autonomic afferent and efferent nerves of the left lung, but left intact the right vagal sympathetic and parasympathetic afferent and efferent nerves of the heart. After left cervical vagotomy the transient fall in heart rate, stroke volume, and blood pressure during left lung hyperinflation was greatly reduced or eliminated. These results suggest that unilateral lung hyperinflation reflexly depresses heart rate and blood pressure, which are partially compensated with time, and reflexly depresses stroke volume, which persists uncompensated until the lung is deflated. These findings may explain the depressed cardiovascular function observed during regional lung overdistention especially when it occurs during positive pressure ventilation.

Respiratory muscle blood flow distribution during expiratory resistance

When work load on the respiratory system is increased the relative increase in blood flow to each of the muscles of breathing provides an index of how the augmented effort of breathing is partitioned among the different muscles. We have used a radio-active microsphere technique to measure blood flow to each of the muscles of respiration in supine dogs during unobstructed respiration and breathing against graded expiratory threshold loads. 79% of the augmented flow went to expiratory muscles; of this increased flow to expiratory muscles 74% went to abdominal wall muscles and 26% to internal intercostals. In our earlier studies of hyperventilation induced by CO(2) rebreathing where expiratory work loads were low, 44% of the increase in flow went to expiratory muscles; of this, only 39% went to abdominal wall muscles and 61% to internal intercostals. During inspiratory resistance which produced small increases in expiratory work, 27% of the increase in blood flow went to expiratory muscles; of this, only 37% went to abdominal wall muscles and 63% to internal intercostals. These results suggest that the internal intercostals are predominantly used for expiration when expiratory work loads are low, whereas the abdominal wall muscles are predominantly used when loads are high. For similar rates of pressure-volume work done on the lung, the total respiratory muscle blood flow is significantly greater during expiratory loads than during unobstructed hyperventilation or inspiratory loads. Thus, the abdominal wall muscles that are utilized for overcoming high pressure expiratory loads are relatively inefficient in converting metabolic energy into pressure-volume work.