Raymond L. H. Murphy

Visual Lung-Sound Characterization by Time-Expanded Wave-Form Analysis

To characterize lung sounds objectively, we examined, by means of time-amplitude plots, selected tape recordings of auscultatory phenomena considered by six observers to be typical of those in a standard classification. Normal lung sounds could not consistently be visually distinguished from adventitious sounds at conventional chart recorder speeds of 100 mm per second or less, but the differentiation was easily achieved when the time scale of the plots was raised to 800 mm per second. When discontinuous sounds (rales, crackles or crepitations) were heard clinically, the time-expanded wave forms showed intermittent discontinuous deflections usually less than 10 msec in duration. When continuous sounds (rhonchi or wheezes) were heard, the deflections were usually more than 250 msec. Time-expanded wave form analysis provides reproducible visual displays that allow documentation of the differentiating features of lung sounds and enhances the diagnostic utility of the sounds.

Effects of low concentrations of asbestos. Clinical, environmental, radiologic and epidemiologic observations in shipyard pipe coverers and controls.

Abstract Low-level asbestos exposure, as occurs in pipe coverers in new ship construction, has not been considered dangerous. We surveyed 101 such workers and 94 controls matched for age, duration of employment and smoking habits in a New England yard. Dust exposure, under surveillance for 20 years, had been near the then recommended threshold limit value of 5 million particles per cubic foot (mppcf). Asbestosis was defined by presence of three or more of five standardized clinical abnormalities including dyspnea, rales, finger clubbing, reduced vital capacity and x-ray shadows. The latter were judged by three observers unaware of the exposure history. Asbestosis was 11 times more common among pipe coverers than among controls; it was found first after 13 years of exposure or 60 mppcf-years, and the prevalence was 38 per cent after 20 years. This study emphasizes that low concentrations of asbestos can lead to pulmonary fibrosis and supports the need for lower threshold limit values.

Diagnosis of “asbestosis”: Observations from a longitudinal survey of shipyard pipe coverers

Abstract In 1972, to study slight manifestations of pulmonary fibrosis due to asbestos, we evaluated 101 shipyard pipe coverers and 95 control subjects whom we had examined in 1965 and in 1966. Although these workers had been exposed to low levels of asbestos, asbestosis was diagnosed in the first survey 11 times more often among pipe coverers than among control subjects. In 1972, clinical, roentgenologic and physiologic tests for monitoring workers were evaluated with respect to (1) ability to separate pipe coverers from control subjects, (2) consistency from the initial to the final survey, (3) predictive value in 1966 with respect to health in 1972 and (4) relationship to duration of exposure. Basilar rales, irregular opacities on chest film, and reduced vital and diffusing capacity were more common in pipe coverers in both surveys. These findings tended to be abnormal in 1972 in those workers in whom they were present in 1966, whereas dyspnea and clubbing were inconsistently found. The predictive value of a single abnormality was minimal, whereas the prognosis was poor in the nine pipe coverers who had three or more of these criteria in 1966. Asbestosis was considered present when three or more of the following were present: (1) bibasilar fine rales, (2) irregular x-ray opacifications (International Labour Organization, University of Cincinnati Classification [ILO/UC] 2/1 or more), (3) forced vital capacity (FVC) less than 80 per cent predicted, (4) single breath diffusing capacity (Dsb) less than 80 per cent predicted. There was only one false positive, a worker with significant heart disease. Clusters of findings appear more important for monitoring exposed workers than single findings. An incidence of 1.1 per cent/year of asbestosis, despite an 80 per cent reduction in the total quantity of asbestos used, emphasizes the importance of environment control.

Mechanism of Inspiratory and Expiratory Crackles

OBJECTIVEnAlthough crackles are frequently heard on auscultation of the chest of patients with common cardiopulmonary disorders, the mechanism of production of these sounds is inadequately understood. The goal of this research was to gain insights into the mechanism of crackle generation by systematic examination of the relationship between inspiratory and expiratory crackle characteristics.nnnMETHODSnPatients with a significant number of both inspiratory and expiratory crackles were examined using a multichannel lung sound analyzer. These patients included 37 with pneumonia, 5 with heart failure, and 13 with interstitial fibrosis. Multiple crackle characteristics were calculated for each crackle, including frequency, amplitude, crackle transmission coefficient, and crackle polarity.nnnRESULTSnSpectral, temporal, and spatial characteristics of expiratory and inspiratory crackles in these patients were found to be similar, but two characteristics were strikingly different: crackle numbers and crackle polarities. Inspiratory crackles were almost twice as numerous as expiratory crackles (n = 3,308 vs 1,841) and had predominately negative polarity (76% of inspiratory crackles vs 31% of expiratory crackles).nnnCONCLUSIONnThese observations are quantitatively consistent with the so-called stress-relaxation quadrupole hypothesis of crackle generation. This hypothesis holds that expiratory crackles are caused by sudden airway closure events that are similar in mechanism but opposite in sign and far less energetic than the explosive opening events that generate inspiratory crackles. We conclude that the most likely mechanism of crackle generation is sudden airway closing during expiration and sudden airway reopening during inspiration.

Respiratory impairment in workers exposed to "safe" levels of toluene diisocyanate (TDI).

Workers in a factory producing polyurethane foam have been studied at six-month intervals for a period of 18 months. On each of the four surveys the forced expiratory volume in one second (FEV1) was determined on Monday morning and afternoon. The concentration of toluene diisocyanate (TDI) in air did not exceed 0.014 ppm on any occasion (multiple samples during each survey in all parts of the factory were taken). The exposed workers had reduction of ventilatory capacity at the afternoon measurement; the acute changes were not reversed overnight; cumulative changes exceeding those associated with aging occurred in these workers over 6, 12, and 18 months; symptomatic workers showed a greater response to TDI than asymptomatic ones; and a substantial positive correlation existed between the acute and cumulative changes in FEV1.

Pulmonary function in shipyard welders.

Sixty-one welders were studied at a shipyard by means of questionnaire, partial physical examination, x-ray films, and comprehensive tests of pulmonary function. Extensive air sampling was accomplished. The results were compared with 63 pipefitters similarly studied. There were no significant differences noted. St was noted, however, that both groups revealed evidence of depressed values of pulmonary function. By comparing welders to a third group (pipecoverers exposed to asbestos), evidence for the development of obstructive lung disease in welders and restrictive lung disease in pipecoverers arose, although nonsmoking welders appeared to have normal pulmonary function. When the shipyard groups were compared to pipefitters with no asbestos and no welding exposures, all shipyard groups were abnormal. Based on other prediction formulas, this finding remained consistent. It would thus appear that all three shipyard groups have depressed pulmonary function.

Low exposure to asbestos. Gas exchange in ship pipe coverers and controls.

In a previous survey of shipyard pipe coverers and controls, clinical criteria were used to define pulmonary asbestosis. This second survey focused on physiologic abnormalities. Pipe coverers had significantly reduced vital capacities (FVC) as well as single breath (DlSB) and exercise steady stale (DlSS-Ex) diffusing capacities. Resting steady state diffusing capacity (DlSS-R), fraction carbon monoxide removed (Fco), and the diffusing constant (K) differed from selected normals but not from all controls. Airways resistance, specific conductance, minute ventilation, arterial carbon dioxide pressure (Pco 2) and dead space were not significantly abnormal. Obstructive disease was equally common in both groups. All workers with clinical “asbestosls” also had severely reduced Dl and Fco. The significance of isolated reduction of Dlrequires further study. However, In a third survey three years later, Dl in exposed workers had deteriorated more rapidly than FVC; some with initially isolated reduction of Dl had de...

Ventilatory function in workers exposed to low levels of toluene diisocyanate: a six-month follow-up

Peters, John M., Murphy, Raymond L. H., and Ferris, Benjamin, G., Jr. (1969).Brit. J. industr. Med.,26, 115-120. Ventilatory function in workers exposed to low levels of toluene diisocyanate: a six-month follow-up. Thirty-four workers exposed to toluene diisocyanate during production of polyurethane foam were examined with a respiratory questionnaire and tests of ventilatory capacity. The tests of pulmonary function were conducted on Monday morning and afternoon and on Tuesday morning and afternoon. Twenty-eight of these 34 workers had been examined with the same tests six months earlier. On Monday a mean change in the one-second forced expiratory volume (F.E.V.1·0) of –0·16 l. occurred that did not return to the baseline value (Monday a.m.) on Tuesday morning. A statistically significant decrease in all the measurements of ventilatory capacity except the forced vital capacity occurred over the six months in the 28 workers. The F.E.V.1·0 fell an average of 0·14 l. and flow rates at 75%, 50%, 25%, and 10% of vital capacity also decreased significantly. There was a highly significant correlation coefficient (r = 0·72) between one-day changes in F.E.V.1·0 (measured six months earlier) and six-month changes in F.E.V.1·0. Workers with respiratory symptoms (cough and/or phlegm) demonstrated greater falls in F.E.V.1·0 than did asymptomatic workers. All air concentrations of toluene diisocyanate measured during this study were below the threshold limit value (0·02 p.p.m.).

Pulmonary Toxicity of Isocyanates

Excerpt In our plastic world polyurethanes have achieved great commercial importance. The production of polyurethane involves the combination of chemicals containing two highly reactive isocyanate ...

Carbon Monoxide Exposures from Snow Melting Machines

Snow melting machines are coming into wide usage in cities and airports. Large units are capable of melting 50 tons of ice per hour by burning 125 gallons of fuel oil per hour in immersion-type burners that discharge hot combustion gases through the melting pool to extract the maximum quantity of heat. When improperly designed or operated, the flame can impinge on snow or icewater before combustion is completed with the resulting formation of large amounts of carbon monoxide. Following the death of one person and serious CO poisoning of another, measurements were made at an operators station of one large machine where CO concentrations were found to be in excess of 2,000u2009ppm. Renovation of the burners in these units resulted in a reduction of CO concentrations to less than 50u2009ppm, the TLV.