Airflow effects on amplitude and spectral content of normal breath sounds.

Even though it is well known that breath-sound amplitude (BSA) increases with airflow, the exact quantitative relationships and their distribution within the relevant frequency range have not yet been determined. To evaluate these relationships, the spectral content of tracheal and chest wall breath sounds was measured during breath hold, inspiration, and expiration in six normal men. Average spectra were measured at six flow rates from 0.5 to 3.0 l/s. The areas under the spectral curves of the breath sounds minus the corresponding areas under the breath-hold spectra (BSA) were found to have power relationships with flow (F), best modeled as BSA = k.F alpha, where k and alpha are constants. The overall mean +/- SD value of the power (alpha) was 1.66 +/- 0.35, significantly less than the previously reported second power. Isoflow inspiratory chest wall sound amplitudes were 1.99 +/- 0.70- to 2.43 +/- 0.65-fold larger than the amplitudes of the corresponding expiratory sounds, whereas tracheal sound amplitudes were not dependent on respiratory phase. Isoflow breath sounds from the left posterior base were 32% louder than those from the right lung base (P < 0.01). BSA-F relationships were not frequency dependent during expiration but were significantly stronger in higher than in lower frequencies during inspiration over both posterior bases. These data are compatible with sound generation by turbulent flow in a bifurcating network with 1) flow separation, 2) downstream movement of eddies, and 3) collision of fast-moving cores of the inflowing air with carinas, all occurring during inspiration but not during expiration.

Spectral characteristics of chest wall breath sounds in normal subjects.

BACKGROUND: This study was carried out to establish a reliable bank of information on the spectral characteristics of chest wall breath sounds from healthy men and women, both non-smokers and smokers. METHODS: Chest wall breath sounds from 272 men and 81 women were measured using contact acoustic sensors, amplifiers, and fast Fourier transform (FFT) based spectral analysis software. Inspiratory and expiratory sounds were picked up at three standard locations on the chest wall during breathing at flows of 1-2 l/s and analysed breath by breath in real time. RESULTS: The amplitude spectrum of normal chest wall breath sounds has two linear parts in the log-log plane--low and high frequency segments--that are best characterised by their corresponding regression lines. Four parameters are needed and are sufficient for complete quantitative representation of each of the spectra: the slopes of the two regression lines plus the amplitude and frequency coordinates of their intersection. The range of slopes of the high frequency lines was -12.7 to -15.2 dB/oct during inspiration and -13.4 to -20.3 dB/oct during expiration. The frequency at which this line crossed the zero dB level--that is, the amplitude resolution threshold of the system--was designated as the maximal frequency (Fmax) which varied from 736 to 999 Hz during inspiration and from 426 to 796 Hz during expiration with higher values in women than in men. The mean (SD) regression coefficient of the high frequency line was 0.89 (0.05). CONCLUSIONS: These data define the boundaries of normal chest wall breath sounds and may be used as reference for comparison with abnormal sounds.

COPD in the elderly. A reversible cause of functional impairment.

OBJECTIVES: To determine the frequency of referral of patients age 69 years and older to the pulmonary function laboratory at a tertiary-care hospital for airflow limitation studies; to determine the point prevalence of a significant reversible component in patients with COPD as an age-related function; and to determine the proportion of patients who were prescribed bronchodilators following a pulmonary function test (PFT) demonstrating significant reversibility. DESIGN: A retrospective review of pulmonary function tests of patients 69 years and older within calendar year 1990 was performed. Chart review of those showing significant reversibility to bronchodilators during a PFT was performed to determine level of follow-up. SETTING: Referral-based pulmonary division in a tertiary-care hospital. PATIENTS: Men and women 69 years and older who had interpretable PFTs at Northwestern Memorial Hospital (NMH) during the calendar year 1990 (n = 405). Patients whose PFTs were uninterpretable due to poor effort (n = 10) were excluded from the study. INTERVENTIONS: No specific interventions were performed as a part of the study. Referring physicians may have requested a PFT with postbronchodilator (albuterol by nebulizer) testing and may have subsequently prescribed bronchodilators for their patients. MEASUREMENTS: We studied the effect of age, gender, smoking history, and degree of airflow obstruction on changes in spirometry values and reversibility status after bronchodilator (if applicable) as determined by a PFT. MAIN RESULTS: Of the 405 consecutive elderly patients studied, 193 (47.7%) received bronchodilators and 60 (31.1%) of these patients had significant improvement as judged by the criteria listed in the Methods section. The improvement occurred equally across all age groups (p > 0.05) and the percent responding to bronchodilators increased as the degree of obstruction increased (p < 0.001). Those who had never smoked were twice as likely to respond than were current or former smokers; men were more likely to respond than women. Most patients (84%) who responded were subsequently prescribed bronchodilators. CONCLUSIONS: Responses to inhaled bronchodilators occur at all ages. Older patients showed greater reversibility as the degree of obstruction increased, while a smoking history reduced the likelihood of a bronchodilator response. COPD in the elderly may differ from the traditional form of the disease.

Acute sarcoid myositis with respiratory muscle involvement. Case report and review of the literature.

A 61-year-old woman with a history of sarcoidosis presented with acute sarcoid myositis affecting the respiratory muscles. The patient responded to prednisone therapy with improved pulmonary function test results and resolution of her symptoms. Acute myositis is a rare manifestation of sarcoidosis and should be treated with steroids.

Respiratory health screening using pulmonary function tests and lung sound analysis.

Lung sounds (LS) analysis is a potential source of additional objective, noninvasive and quantitative information on the status of the pulmonary system. We have examined the hypothesis that the addition of lung sounds analysis to spirometry increases the sensitivity of objective population screening, as compared to the use of spirometry alone. Questionnaires, spirometry and lung sounds were obtained in 493 active workers. Lung sounds analysis consisted of the averaged power spectra of breath sounds, measured separately during inspiration and expiration at four standard locations over the trachea and the chest-wall. Of the 493 subjects, 91 had an obstructive lung disease, including 27 with chronic bronchitis identified by a history of prolonged cough and sputum production but with normal spirometry. Twelve additional workers had a restrictive lung disease. Abnormal spirometric results were found in 74 of the patients. Abnormal lung sounds analyses were found in 54 patients, including 14 of the chronic bronchitis cases, so that the overall sensitivity of objective screening tests increased from 71% to 87% by combining the two tests. Thirty three of the subjects considered normal by evaluation of their questionnaire and spirometry had abnormal lung sounds. Of the twenty four who were re-evaluated 12-18 months after the first tests, three had developed a lung or heart disease. We conclude that the combination of spirometry and lung sounds analysis significantly increased the sensitivity of detection of pulmonary diseases by objective tests, and provided an early sign of lung disease that was not detected by spirometry alone.

Evaluation of a worker with possible formaldehyde-induced asthma.

BACKGROUND: We describe the evaluation of a worker with clinical symptoms compatible with bronchospasm caused by formaldehyde exposure. METHODS: The worker was evaluated by means of enzyme-linked immunosorbent assay, cutaneous tests, and methacholine and formaldehyde inhalation challenges. The worker's serum was injected intradermally into the skin of a normal rhesus monkey to determine whether hypersensitivity could be transferred from human to primate. RESULTS: An enzyme-linked immunosorbent assay showed that the worker had positive IgE and IgG titers to formaldehyde-human serum albumin. The worker had a positive cutaneous test for formaldehyde-human serum albumin, and this cutaneous reactivity was transferred to a rhesus monkey through the worker's serum. The worker had a negative methacholine challenge at 25 mg/ml and negative formaldehyde inhalation challenges at 0.3, 1, 3, and 5 ppm for 20 minutes. It is possible that the worker would have had a positive result if a higher concentration of F were used for the challenge, but it is more probable that the worker's symptoms were not caused by immunologically mediated asthma. We have studied individuals exposed to formaldehyde, their clinical syndromes, and serologic results for a decade. This worker is the one subject with the most compatible history and immunology, but the worker had a negative challenge. CONCLUSION: Immunologically mediated asthma caused by formaldehyde is extremely rare, if it exists at all.

The hard metal diseases.

Hard metal is a mixture of tungsten carbide and cobalt, to which small amounts of other metals may be added. It is widely used for industrial purposes whenever extreme hardness and high temperature resistance are needed, such as for cutting tools, oil well drilling bits, and jet engine exhaust ports. Cobalt is the component of hard metal that can be a health hazard. Respiratory diseases occur in workers exposed to cobalt--either in the production of hard metal, from machining hard metal parts, or from other sources. Adverse pulmonary reactions include asthma, hypersensitivity pneumonitis, and interstitial fibrosis. A peculiar, almost unique form of lung fibrosis, giant cell interstitial pneumonia, is closely linked with cobalt exposure.

Serum IgE and IgG to formaldehyde-human serum albumin: lack of relation to gaseous formaldehyde exposure and symptoms.

Fifty-five subjects were studied to determine if the presence of IgE or IgG antibodies to formaldehyde (F)-human serum albumin (HSA) was associated with exposure to gaseous F or with respiratory or conjunctival symptoms from such exposure. The study population included cohorts exposed to F in the workplace, smokers, and normal subjects. IgE antibody specific for F-HSA was detected by ELISA in three subjects; immediate-type skin testing was negative in two of these subjects, and not interpretable because of dermatographism in one subject. One of these subjects had a history of respiratory symptoms when the subject was working in a histology laboratory that contained ambient F and xylene; a respiratory challenge with F at concentrations of up to 2 ppm failed to produce respiratory symptoms or significant changes in pulmonary function. Serum from the three subjects with IgE to F-HSA by ELISA failed to passively transfer skin reactivity to F-HSA to rhesus monkey recipients. These three subjects and two other subjects had IgG to F-HSA by ELISA, although this was of generally low titer. We could not define a relationship between the presence of antibodies and (1) a history of F exposure or (2) a history of adverse respiratory or conjunctival symptoms from F. This study is a continuum of 5 years of study in our laboratory attempting to define allergy to gaseous F, and the current study does not support an immunologic basis for respiratory or conjunctival symptoms from gaseous F exposure. Based on the findings of this and our other studies, it is possible that clinical IgE-mediated allergy to gaseous F does not exist, or if it does exist, it is extremely rare.

[A respiratory health questionnaire for occupational screening].

A Hebrew pulmonary health questionnaire was designed for occupational screening, based on the American Thoracic Society questionnaire but adjusted to conditions in Israel. It was designed for assisted completion using a computer, but can easily be modified to become self-administered. We propose that it be used here as the standard, occupational, pulmonary health questionnaire and as the basis for a standard, general purpose, respiratory health questionnaire.

The respiratory effects of cobalt.

We studied seven subjects with certain manifestations of cobalt-induced lung disease. All worked with cobalt and were involved in either the production or use of hard metal. The mode of presentation varied from an acute hypersensitivity pneumonitis that cleared completely when exposure ceased to progressive severe interstitial fibrosis of the lungs. In one subject reexposure was followed by a recurrence of the symptoms. All subjects showed restrictive ventilatory impairment and a reduction of their diffusing capacity. The radiologic appearances varied greatly. While two subjects had clear roentgenograms with small lung volumes, others had a micronodular pattern or small blotchy nodular infiltrates, and one had diffuse reticulonodulation as is seen in cryptogenic fibrosing alveolitis. The pathologic appearances varied between desquamative interstitial pneumonia and overt mural fibrosis of the alveoli. Six of the seven patients had multinucleated giant cells in their biopsy specimens or bronchoalveolar lavage fluid.

Wideband acoustic transmission of human lungs.

The measurement of sound transmission in human lungs has shown promise to reveal, by noninvasive methods, information about the structure of peripheral airways and lung tissue. The paper gives a detailed explanation of the instrumentation and testing methods developed to measure sound transmission through human lungs and thoracic structures in the 5-20 kHz frequency range and describes in detail experiments comparing the acoustic lung transmission patterns of four different subject groups. The experimental results are compared with those predicted by an acoustical model of sound transmission through lung parenchyma.

Flutter in flow-limited collapsible tubes: a mechanism for generation of wheezes.

We studied flutter in collapsible tubes as a possible mechanism for the generation of respiratory wheezes. The pressure-flow relationships and the wall oscillations of thick-walled [wall thickness (h)-to-lumen radius (r) ratio 1:1.7 to 1.3] self-supporting latex and Silastic tubes mounted between rigid pipes were measured. A high-impedance vacuum pump was connected to the downstream end. Upstream and downstream valves were used to control corresponding resistances. We found loud honking sounds and tube wall oscillations that occurred only when the tubes were buckled and flow limiting, i.e., when the flow became constant and independent of downstream driving pressure. The overall range of oscillatory frequencies was 260-750 Hz for airflow, presenting as sharp peaks of power on the frequency spectrum. The oscillatory frequencies (f) were higher at higher fluid velocities (u) and with narrower distance between opposing flattened walls (2b), resulting from increasing downstream suction pressure and the transmural pressure becoming more negative. The effect of u and b on f for a latex tube (h-to-r ratio 1:1.7) were found to be f = 228 + 0.021 (u/b). These relationships were valid throughout the range of oscillations in this tube (283-720 Hz) and with flow rates of 12-64 l/min. The experimental data were compared with predictions of the fluid dynamic flutter theory and the vortex-induced wall vibrations mechanism. We conclude that viscid flutter in soft tubes is the more probable mechanism for the generation of oscillations in the soft tube model and is a possible mechanism for the generation of respiratory wheezes.

The effect of gravity on the response of ventilation to abrupt change in FICO2.

Recently, Arieli and Farhi (1987) formulated a model for a previous suggestion made by their group that an increased ventilation as gravity increases is due to reduced perfusion of the respiratory center which causes an elevation of tissue PCO2. Extending the model to the dynamic response, we predict a slower ventilatory response to CO2 breathing as gravity increases. To test this prediction, ventilatory response to 5% CO2 was studied in 11 seated subjects at +1 and +2 Gz in a human centrifuge. Five of these subjects were studied at +3 Gz as well. In addition, ventilatory response to 5% CO2, using breath-by-breath analysis, was measured in three subjects in supine and upright postures. The ventilatory response (mainly through tidal volume) was faster as gravity increased from +1 to +2 and to +3 Gz, and from supine to the upright position. These findings disagree with the model prediction. Therefore, an alternative explanation is suggested based on the response of CO2 sensitive stretch receptors in the lung. Increased gravity causes increased ventilation, reduction of cardiac output and increased VA/Q mismatch; all enlarge the part of the lung with low CO2 where responsiveness of the CO2 sensitive stretch receptors is large.

Changes on radiographs of wives of workers exposed to asbestos.

Between January and March 1986, 117 wives of insulation workers exposed to asbestos were screened by means of chest radiography, pulmonary function testing, and a detailed questionnaire. The final study group included 93 women over 40 years of age. Eighteen of these (19.4%) demonstrated pleural changes consistent with asbestos exposure, including pleural plaque (88.9%), diaphragm plaque (27.8%), pleural calcification (16.6%), and diffuse pleural thickening (5.5%). In statistical correlation between the groups with normal and abnormal radiographs, the only factor that proved significant was the year of first exposure (the duration of the latent period). Finally, radiographs of the husbands were compared for 17 of the 18 wives with radiographic abnormalities. Fourteen of the husbands (82%) demonstrated more severe radiographic changes than their wives.

Clinical pharmacology and toxicology of ipratropium bromide.

Anticholinergic drugs inhibit a variety of intrapulmonary events related to airflow obstruction. When administered as an inhaled aerosol, approximately 90 percent of ipratropium bromide (as with beta-adrenergic aerosols) can be assumed to be swallowed. Peak pharmacologic effects occur prior to any detectable plasma drug concentrations. Ipratropium does not exhibit the well-known toxic effects of atropine, and doses many times those required for maximum therapeutic benefit do not produce any effects on the eye, urinary bladder, heart rate, or mucociliary function. Ipratropium seems to act primarily on large- and intermediate-size airways; beta-adrenergic agents, on the other hand, appear to act primarily on the smaller airways. The drug is a promising addition to the therapeutic armamentarium, and may be especially useful in certain groups of patients whose condition is less responsive to other agents.

Comparison of the anticholinergic bronchodilator ipratropium bromide with metaproterenol in chronic obstructive pulmonary disease. A 90-day multi-center study.

The short- and long-term efficacy and safety of an inhaled quaternary ammonium anticholinergic agent, ipratropium bromide, and a beta agonist aerosol, metaproterenol, were compared in 261 nonatopic patients with chronic obstructive pulmonary disease (COPD). The study was a randomized, double-blind, 90-day, parallel-group trial. On three test days-one, 45, and 90-mean peak responses for forced expiratory volume in one second and forced vital capacity and mean area under the time-response curve were higher for ipratropium than for metaproterenol. Clinical improvement was noted in both treatment groups, especially during the first treatment month, with persistence of improvement throughout the remainder of the study. Side effects were relatively infrequent and generally mild; tremor, a complication of beta agonists, was not reported by any subject receiving ipratropium. These results support the effectiveness and safety of long-term treatment with inhaled ipratropium in COPD.