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Biomedical subjects

R G Loudon

Publications and source records attributed to R G Loudon.

At least 19 recordsLinked to original sources
PubMed1993

Speech breathing in patients with lung disease.

Lung volumes and breathing patterns used during speech differ from those of quiet respiration and may be expected to vary with different types of lung disease. To test this possibility, 41 patients with asthma, emphysema, or sarcoidosis and 16 healthy subjects completed a speech protocol. Volumes, times, and flow rates were recorded during conversation and during a counting task. A total of 16 measured variables were derived for each breath and analyzed statistically. Alterations in speech breathing were disease and task specific. Discriminant function analysis applied to data from either speech task could correctly classify subjects with more than 50% accuracy, showing that different patterns were significantly disease specific. Compared with healthy subjects during conversation, all patients averaged a more rapid respiratory rate and increased the proportion of time spent on inspiration (Ti/Ttot). During counting, patient groups showed a variety of patterns, most commonly subordinating metabolic need to communication drive and sounding more breathless to observers. Regression analysis was used to determine how strongly changes in measured speech variables related to degree of physiologic impairment. The effect of severity of disease on speech production is distinguishable from the effect of the diagnostic category.

Adult↗
PubMed1991

Crackles in interstitial lung disease. Comparison of sarcoidosis and fibrosing alveolitis.

STUDY OBJECTIVE: Determine why crackles on chest auscultation are characteristic of most interstitial lung diseases, but may not be heard in sarcoidosis. DESIGN: All patients with sarcoidosis or cryptogenic fibrosing alveolitis seen during a four-week period were studied. In a second study to relate ausculatory findings to anatomy, patients with fibrotic changes on their chest roentgenogram were studied. SETTING: Patients were recruited from outpatient clinics. PATIENTS: In the first part, all patients seen over the course of one month were studied. In the second study, patients with pulmonary fibrosis seen on chest roentgenograms were studied. INTERVENTIONS: For the first study, two independent observers performed auscultation on five sites for crackles and reviewed four roentgenogram quadrants for changes. For the second study, patients underwent VC measurements, auscultation, and high resolution computer tomography scans. MEASUREMENTS AND RESULTS: For the first study, crackles were noted at greater than 2 sites in all 11 CFA patients, but only one of 17 SARC patients (p less than 0.001). Roentgenogram changes were seen in greater than 2 quadrants in nine of 11 CFA patients and eight of 17 SARC patients (p = ns). In the second study, the VC was similar in the two groups: SARC: 1.96 +/- .90 L (means +/- SD), 58 +/- 20.4 percent predicted; CFA: 1.81 +/- .33 L, 59 +/- 9.2 percent predicted). Only two of 14 SARC patients had crackles in greater than 1 area, while all 14 CFA patients had crackles at greater than 2 sites. The HRCT studies were read by a radiologist unaware of the diagnosis. The presence and degree (0 to 3 scale) of subpleural and peribronchial fibrosis were scored. Twelve SARC patients had peribronchial changes (mean score 1.9 +/- 1.08), while only eight had subpleural fibrosis (mean score .6 +/- .52). There was a significantly different pattern in the CFA patients, where eight had peribronchial fibrosis (mean score = .9 +/- .78, p less than 0.05) and all 14 had subpleural fibrosis (mean score = 1.6 +/- .73, p less than 0.01). CONCLUSIONS: We conclude that crackles are more frequent in fibrosing alveolitis than in sarcoidosis; this difference may be due to the distribution of parenchymal fibrosis.

Auscultation↗
PubMed1991

Bronchoscopy with bronchoalveolar lavage in tuberculosis and fungal infections.

STUDY OBJECTIVE: To determine the utility of bronchoscopy with bronchoalveolar lavage for diagnosing M tuberculosis and fungal infections. DESIGN: Retrospective review of patients over a six-year period. SETTING: In- and outpatients of one University hospital and affiliated Veterans Administration Medical Center. PATIENTS: Those who were subsequently found to have either M tuberculosis or fungal infections. INTERVENTIONS: Bronchoscopy with bronchoalveolar lavage specimens were compared to prebronchoscopy sputum, when available. Specimens were sent for smear and culture for both acid-fast bacilli and fungi. In the case of lavage, an aliquot also was studied for cellular differential. MEASUREMENTS AND RESULTS: For TB, sputum was smear-positive in 6/47 (34 percent) and culture positive in 24/47 (51 percent), while bronchoscopy was smear positive in 34/50 (68 percent) and culture positive in 46/50 (92 percent). For fungal infections, no sputum was smear-positive and only 1/22 (5 percent) was sputum culture-positive, while bronchoscopy was smear-positive in 14/41 (34 percent) and culture positive in 35/41 (85 percent). Bronchoscopy washings and BAL provided complementary specimens. Eighty-three patients had adequate lavages and the cellularity was significantly different from controls (lymphocytes: TB 18 +/- 11.2 percent [mean +/- SD]; fungal: 13 +/- 11.1 percent; controls 6 +/- 3.1 percent; p less than 0.001; neutrophils: TB 9 +/- 11.5 percent; fungal: 6 +/- 9.1 percent controls: 2 +/- 1.5 percent, p less than 0.01); however, there was overlap and no pattern was characteristic for TB or fungal infections. CONCLUSION: Bronchoscopy with BAL is useful in diagnosing tuberculosis and fungal infections.

Bronchoalveolar Lavage Fluid↗
PubMed1990

Measuring crackles.

Crackles heard on auscultation can be represented graphically as a time-amplitude plot of the associated waveform. To assess the relative merits of several measures which might be considered for machine implementation in diagnostic instruments, we compared the reproducibility of those based on the initial voltage deflection which begins a crackle with those based on the largest deflection. The latter group showed less interobserver and less intraobserver variability when the same crackles were measured twice by each of two observers. Crackles from a teaching tape, categorized as fine and coarse, were used in this study. The ability of the various measures tested to distinguish between fine and coarse crackles on an individual basis was assessed and found to favor the measures based on the largest deflection. They showed an average of 9.96 percent incorrectly classified crackles, as opposed to 19.53 percent for the two measures based on the initial deflection.

Auscultation↗
PubMed1990

Continuous adventitious lung sounds.

Recent research has increased the still limited understanding about the generation of continuous adventitious lung sounds. These sounds all have a definite pitch, such as in stridor and wheezing. With the use of waveform analysis, one can examine more closely the relationship between what is heard and the pathophysiology causing the sound. Clinical examples are given to show the utility and limitations of current lung sounds analysis techniques.

Acoustics↗
PubMed1989

Stridor: differentiation from asthma or upper airway noise.

Stridor, a musical, continuous sound often attributed to upper airway narrowing, may be encountered in the recently extubated patient. Recently extubated patients and patients with documented upper airway obstruction were studied. Sounds were recorded from the neck and chest. The sound signal of patients with stridor was compared to that made by asthmatics and extubated patients with no airway obstruction. The frequency spectrum of segments of the sound signal was determined using the fast fourier transform technique. The sound signal associated with stridor had a similar frequency to that found with asthma. However, the signal was more intense over the neck than over the chest, whereas in asthmatics the reverse was true. The musical sounds in patients with stridor occurred during inspiration, whereas in those patients with asthma, they were predominantly expiratory. The major difference between stridor and asthma was the timing of the sound and the prominence of the sound over the neck.

Asthma↗
PubMed1988

Speech segment durations produced by healthy and asthmatic subjects.

Speech segment durations of various lengths were measured to study the effect of asthma. Subjects produced 5 min of conversation and a monologue and counted at a rate of two numbers per second at two loudness levels. The number of syllables per breath was determined for all tasks. Average sound pressure level, individual segments such as voice onset time, word duration, pause time, and total duration of the activity were compared between groups for the counting tasks. Results revealed that asthmatic speakers met the sound level requirements of loud counting and generally produced speech segment durations similar to healthy subjects. Asthmatic subjects increased pause time between speech segments, produced fewer syllables per breath, and spent a larger percentage of time in nonspeech ventilatory activity than the healthy subjects, presumably to meet metabolic needs.

Adult↗
PubMed1988

Volumes and breathing patterns during speech in healthy and asthmatic subjects.

The lung volumes and ventilatory patterns used by 10 healthy subjects and 14 patients with varying degrees of asthma were studied. The protocol included conversation, monologue, and counting at two loudness levels. Lung-volume changes were measured with a Respitrace and recorded with associated speech sounds. Volumes, durations, and flows were analyzed for sequences of respiratory cycles. Asthmatics used a greater percentage of their reduced vital capacity. Their inspiratory flow rates were slower, and expiratory rates faster. Asthmatics spent a greater proportion of the total respiratory cycle time on inspiration, and expired a greater volume of gas without sound. Patterns of ventilation suggested that asthmatics favored respiratory over communication needs to a greater extent than healthy subjects. Activities that forced priority to communication needs (counting to a metronome) were inadequate for gas exchange in asthmatics and could be sustained for only a limited period of time.

Asthma↗
PubMed1988

Factors influencing the production of wheezes during expiratory maneuvers in normal subjects.

We recorded wheezes, pleural pressure, plethysmographic lung volumes and mouth flow rates in 6 healthy subjects during maximal expiratory maneuvers breathing air and a mixture of 80% He-20% O2 (He) before and after methacholine inhalation. During expiratory flow maneuvers a critical pleural pressure was needed before wheezes occurred. All but one wheeze occurred in the last two thirds of vital capacity during forced exhalation where flow limitation existed. At a flow rate of 2 liters/s, the critical pleural pressure breathing air was 21 +/- 5.8 cm H2O (mean +/- SD), whereas that of breathing He was higher: 32 +/- 7.8 cm H2O (p less than 0.02). In addition the wheezes occurred at lower lung volumes (associated with small airway diameters) when He was breathed instead of air. This was seen both before (p less than 0.02) and after (p less than 0.01) methacholine. These findings suggested that for a given flow rate a lighter gas such as He had to acquire a higher linear velocity so that the convective acceleration was sufficient to produce wheezes. This was achieved by either an increase in the driving critical pleural pressure or narrowing of bronchi by a larger compressing pleural pressure or smaller lung volumes.

Adult↗
PubMed1988

The utility of a long-acting sympathomimetic agent, procaterol, for nocturnal asthma.

Patients with nocturnal asthma have their lowest pulmonary function and lowest serum epinephrine level at 4 to 6 AM. We studied a new long-acting beta-adrenergic agonist, procaterol, in ten patients with nocturnal asthma. The patients received 0.1 mg of procaterol one night and a placebo the other night in random order. Pulmonary function tests were performed every two hours from 10 PM to 8 AM. Pulmonary sounds were recorded using a modified stethoscope and were subsequently analyzed to estimate the proportion of time occupied by wheezing (est Tw/Ttot). The forced expiratory volume in one second (FEV1) while receiving the placebo and procaterol were similar at 10 PM (placebo, 1.35 +/- 0.18 L [mean +/- SE]; procaterol, 1.48 +/- 0.20 L); however, by 4 AM, the FEV1 had dropped significantly lower on the night with the placebo (1.01 +/- 0.14 L) than the night with procaterol (1.30 +/- 0.19 L; p less than 0.05). The est Tw/Ttot was similar at 12 AM for both nights, but at 4 AM, there was a significant increase in the est Tw/Ttot for the group with placebo but not the group with procaterol. The use of a long-acting beta-adrenergic sympathomimetic agent reversed the obstruction of the airways seen with nocturnal asthma.

Asthma↗
PubMed1987

The lung exam.

Accurate diagnosis is essential for effective treatment. After history-taking, the physical examination is second in importance in assessing a pulmonary patient. The time-honored sequence of inspection, palpation, percussion, and auscultation is appropriate. Diagnostic tests are becoming more complex, more expensive, and more inclined to separate the patient and physician. The stethoscope is still the more commonly used diagnostic medical instrument, but it is not always used to best advantage. It is familiar, harmless, portable, and inexpensive. Its appropriate use improves medical practice and reduces costs. Improvements in sound recording and analysis techniques have spurred a renewed interest in lung sounds and their meaning. This is likely to lead to better understanding of what we hear, and perhaps to the development of new noninvasive diagnostic and monitoring techniques.

Auscultation↗
PubMed1986

Cerebrospinal fluid ions in metabolic acidosis in dogs: effects of acetazolamide.

We hypothesized that, during isosmotic isonatremic HCl acidosis with maintained isocapnia in cisternal cerebrospinal fluid (CSF), acetazolamide, by inhibiting carbonic anhydrase (CA) in the central nervous system (CNS), should produce an isonatric hyperchloric metabolic acidosis in CSF. Blood and CSF ions and acid-base variables were measured in two groups of anesthetized and paralyzed dogs with bilateral ligation of renal pedicles during 5 h of HCl acidosis (plasma [HCO3-] = 11 meq/l). Mechanical ventilation was regulated such that arterial PCO2 dropped and CSF Pco2 remained relatively constant. In group I (control group, n = 6), CSF [Na+] remained unchanged, [HCO3-] and strong ions difference (SID) fell, respectively, 6.1 and 5 meq/l, and [Cl-] rose 3.5 meq/l after 5 h of acidosis. In acetazolamide-treated animals, (group II, n = 7), CSF [Na+] remained unchanged, [HCO3-], and SID fell 11 and 7.1 meq/l, respectively, and [Cl-] rose 7.1 meq/l. We conclude that during HCl acidosis inhibition of CNS CA by acetazolamide induces an isonatric hyperchloric metabolic acidosis in CSF, which is more severe than that observed in controls.

Acetazolamide↗
PubMed1986

Sound spectral analysis of voice-transmitted sound.

There is a change in voice-generated sound heard over an area of pulmonary consolidation described as the "e" to "a" change. The lung may act as a low pass filter with properties that are changed by consolidation. We studied 5 patients with pneumonia. Using an electronic stethoscope, we recorded the voice-generated sounds "e" and "9-9-9." Sound spectral analysis using the fast Fourier transformation technique was used to characterize the frequency spectrum of the recorded sound. This technique allowed us to evaluate the filter properties of the normal and consolidated lung. We found that the normal lung allowed transmission of sound as high as 250 Hz with a gradual cutoff by 400 Hz. The consolidated lung allowed transmission of sound of a higher frequency; however, there was no significant transmission of sound with a frequency higher than 1,000 Hz.

Auscultation↗
PubMed1985

Lung sound analysis for continuous evaluation of airflow obstruction in asthma.

We developed a system for monitoring airflow obstruction noninvasively, based on the principle that the proportion of the breath cycle occupied by wheezing (Tw/Ttot) in any one subject corresponds to the severity of airways obstruction. Lung sounds were recorded continuously from the chest wall. Fifty 250 ms sound segments were randomly chosen from five-minute periods and analyzed for the presence or absence of wheezes. The proportion with wheezes was used as an estimate of Tw/Ttot (Est Tw/Ttot). For 12 wheezy patients, there was a good correlation between the Est Tw/Ttot and the forced expiratory volume in one second (r = 0.893, p less than 0.001). The system was used to evaluate nocturnal asthma. Five subjects were studied over eight nights. It was found that there was more wheezing from 4:00 to 4:30 AM than from midnight to 12:30 AM (p less than 0.05). This technique may prove useful in continuous, noninvasive monitoring of wheezy patients.

Adult↗
PubMed1984

Quantitation of wheezing in acute asthma.

Pulmonary sounds were recorded before and after bronchodilator treatment in 20 patients with acute attacks of asthma. Analysis of the sounds showed that improvement in the forced expiratory volume in one second was associated with the following two changes in the sound signal: (1) the proportion of the respiratory cycle occupied by wheeze (Tw/Ttot ratio) was reduced from 86 percent to 31 percent on average; and (2) the sound frequency of the highest pitched wheeze was also reduced, from a mean of 440 Hz to 298 Hz.

Acute Disease↗