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Biomedical subjects

M Lippmann

Publications and source records attributed to M Lippmann.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Associations of London, England, daily mortality with particulate matter, sulfur dioxide, and acidic aerosol pollution.

During the extreme pollution episodes of 1952 and 1962 in London, England, excesses in daily mortality were clearly evident. In this study, we examined daily British Smoke, sulfur dioxide, acid aerosols, and weather variables for their short-term associations with daily mortality in the more typical (nonepisodic) winters of 1965-1972. Consideration of the acid aerosol data was of special interest because this chemical component has been suspected as a causal agent in past episodes. Temporal lag structures between the variables were examined after removal of long-term components from each series in order to obtain "rational" cross-correlations. Significant associations between same-day and lagged pollution variables and mortality were found. Alternative regression models with pollution and weather variables were also developed. The coefficients obtained were applied to the 1962 pollution episode to examine the continuity of the estimated slopes. The pollution-predicted deaths fit the observed deaths well, which supports the applicability of such deviation-derived coefficients to the absolute scale. These models were also employed to estimate mean excess daily deaths attributed hypothetically to air pollution. On average, mean effect ranged from 2-7% of all deaths during the nonepisodic winters in Greater London, but the 95% confidence intervals of these estimates overlapped for all model specifications examined. This estimated pollutant mixture "effect" cannot be attributed to a particular pollutant because of a lack of quantitative information on the relative downward biases caused by both analytical errors and errors in the spatial representativeness of each respective pollution index.

Acids↗
PubMedDate not supplied

Controlled deposition of tantalum powder in a cast of the human airways: applications for aerosol bronchography.

A hollow latex cast of the human larynx and tracheobronchial tree extending to 2 mm diameter airways "inhaled" tantalum powder (mass median aero-dynamic diameter equals 9.2 mum, omicron-g equals 1.41) at 8 liters/min. Tantalum deposited within the cast as predicted by preliminary deposition calculations. These calculations predicted deposition surface densities among greater than 2 mm diam. airways to have a range of similar to 2:1, and also predicted less than 5% alveolar deposition. A deposition surface density of 8 mg/cm-2 provided good bronchographic visualization. Single rice grains located within some airways were distinctly outlined. The small amount of tantalum needed to outline the airways be a simulated voluntary inhalation indicates that tantalum may be suitable for use as a bronchographic contrast medium when administered under strictly controlled exposure conditions.

Aerosols↗
PubMedDate not supplied

Ventricular arrhythmias after epinephrine injection in enflurane and in halothane anesthesia.

The use of subcutaneous epinephrine during anesthesia is a common clinical practice for providing surgical hemostasis. In studies with 100 patients given either enflurane or halothane, with or without subcutaneous epinephrine, the incidence of ventricular ectopy in patients receiving halothane without epinephrine was 3 percent, while in those given epinephrine with halothane, the incidence was 7 percent. Those who received enflurane alone had no ectopic beats, while ventricular ectopy with enflurane and epinephrine resulted in an incidence of 1 percent. The authors conclude that enflurane anesthesia with concomitant administration of subcutaneous epinephrine is safe, provided the safeguards previously established for use of epinephrine with halothane are observed.

Adjuvants, Anesthesia↗
PubMedDate not supplied

Anesthetic management of pulmonary lavage in adults.

A 6-year experience in the anesthetic management of 34 successful whole-lung lavages on 11 adult patients with pulmonary alveolar proteinosis is described. All patients were radiographically, physiologically, and symptomatically improved after the procedures. The anesthetic protocol for lung lavage includes: (1) unilateral whole-lung lavages 2 to 4 days apart; (2) general anesthesia with the placement of a Carlens tube; (3) isotonic saline as the lavage solution; (4) mechanical chest percussion during lavage; (5) serial arterial blood-gas determination and measurement of lung compliance in the intraoperative and immediate postlavage period. The authors conclude that whole-lung lavage is a safe and effective palliative procedure in pulmonary alveolar proteinosis and in the treatment of patients with pulmonary disease, such as cystic fibrosis or asthma, in which filling of the lung acini by liquid or solid material impairs oxygenation of the pulmonary capillary blood.

Adult↗
PubMedDate not supplied

Particle transport through a hollow canine airway cast by high-frequency oscillatory ventilation.

High-frequency oscillatory ventilation (HFV) of the mammalian respiratory tract can maintain good respiratory ventilation, even with tidal volumes less than half of the anatomic dead space. A steady bidirectional drift is established in airways when the frequency is greater than 2 Hz, resulting in quasi-steady axial streams in the airways. Convective transport from the trachea to peripheral airways takes place in the central core of the bifurcating network of the bronchial tree. It takes place in the opposite direction in the annular regions near the airway walls. In this study, aerosol particle transport was measured in a hollow cast of a canine tracheobronchial tree that extended from the trachea to terminal bronchioles. The 0.5 micron particles, placed in the upper trachea as a bolus, were transported rapidly to the terminal airways of the cast by HFV with tidal volumes of less than one third the volume of the cast. Carrier gases of different kinematic viscosity were used to investigate the fluid dynamics of the transport. Particle transport during HFV was fastest in a gas of high kinematic viscosity (helium), and slowest in a gas of low kinematic viscosity (sulfur hexafluoride). The results are consistent with the application of lubrication theory, improve our understanding of convective processes involved in HFV, and provide new insights into particle penetration in the airways and other aspects of respiratory ventilation.

Aerosols↗
PubMedDate not supplied

Aerosol tracer study of gas convective transport to 0.1-cm airways by high-frequency ventilation in a human lung airway cast.

A cast of human tracheobronchial airways, which is complete to airways less than 0.1 cm in diameter, was employed for experimental studies of gas convective transport by high-frequency ventilation (HFV). The cast was ventilated with gases of different kinematic viscosity (He, air, and SF6) and tidal volumes of 10-60 mL. The convective transport through the cast was followed by labeling the tidal volume with 0.5-micron aerosol particles. Such particles undergo little diffusion and have a short relaxation time and, therefore, can serve as tracers of stream flow. The time of arrival of particles transported to isolated peripheral segments of the cast during HFV was measured with an optical particle counter at various oscillatory tidal volumes and frequencies. Distally directed particle transport was found to be substantial in He and air, but weak in SF6. The extent of transport increased with increasing tidal volume. These results provide evidence for a distally directed axial flow during quasi-steady-state tidal breathing of lung airways over a wide range of frequency. This superimposed distal flow along the axial core is consistent with (1) the demonstrated efficacy of O2-CO2 exchange during HFV, and (2) concentrations of particles deposited on bifurcations of alveolar ducts as observed during normal breathing in small animal inhalation studies.

Adult↗
PubMedDate not supplied

Effect of lung airway branching pattern and gas composition on particle deposition in bronchial airways: III. Experimental studies with radioactively tagged aerosol in human and canine lungs.

Particle penetration into lung airways during normal respiration is affected by the exchange of inspired air and residual gas. In this study, particle penetration during the inspiratory phase was investigated using gamma-tagged monodisperse particles (0.70, 0.90, 0.96, and 1.44 microns) suspended in various carrier gases having a wide range of kinematic viscosity. A 40-mL bolus of tagged aerosol was drawn into excised human and dog lungs at the end of a tidal breath, followed by a long breathhold to allow for complete particle deposition by sedimentation. The lungs were then fixed, sectioned, and autoradiographed to determine tidal front locations. In human lungs, particles suspended in He-O2 penetrated deeper than particles suspended in air; particles penetrated least in SF6-O2. Dog lungs, which have more asymmetrical airway branching patterns than human lungs, had no significant particle penetration differences associated with carrier gas composition. It is concluded that particle penetration during the inspiratory phase is dependent on factors that determine flow profile development, such as branching pattern and the Reynolds number of the carrier gas. The bolus front at the end of an air inspiration extended into about 10% of human lung airways of 1 mm diameter, and into about 0.1% of 0.5-mm airways. It is concluded that rapid particle penetration to 1-mm airways during high-frequency oscillatory ventilation of lung casts is due to cumulative axial core transport during multiple breathing cycles. Similarly, the dispersion of an aerosol bolus from large airways to small airways during in vivo breathholding studies appears to be due to oscillatory flow created by the heartbeat.

Aerosols↗
PubMedDate not supplied

Dispersion of aerosol particles in an airway cast of a dog.

Aerosol bolus dispersion was measured in the first branching generations of a replicate hollow cast. The cast was made from a solid cast of a beagle-dog tracheobronchial tree. The dispersion was measured after penetration of boluses into different volumetric depths, with different particle sizes and flow rates into the cast. An enhanced flow rate led to a decreasing dispersion in the cast. Particle size up to about 4 microns has no significant effect on dispersion.

Aerosols↗
PubMedDate not supplied

Effect of flow rate on aerosol bolus penetration in a hollow canine lung airway cast.

A cast of dog tracheobronchial airways, which is complete to airways of 1 mm in diameter, was used for experimental studies of the effect of flow rate on aerosol bolus penetration during a tidal breath. Aerosol boli of 35 cm3 were injected during a 1-L inhalation of air. The recoveries of aerosol particles in expired air were measured after various breathholding times. The results show that the penetration depth of an aerosol bolus increases with decreasing flow rate, especially for flow in transition from a flat profile to a parabolic profile.

Aerosols↗
PubMedDate not supplied

A multi-year study of air pollution and respiratory hospital admissions in three New York State metropolitan areas: results for 1988 and 1989 summers.

As part of a multi-year study of air pollution and respiratory hospital admissions in the Buffalo, Albany, and New York City, New York, metropolitan areas, filter samples were collected daily at suburban air monitoring sites and analyzed for their content of particulate phase aerosol strong acidity (i.e., hydrogen ion, H+) and sulfate (SO4 = ). In addition, daily hospital admissions for respiratory causes, other community air pollutant measurements (e.g., ozone, O3), and meteorological data (e.g., temperature) were also obtained for these metropolitan areas. The summer months (June-August) were selected for analysis because that is when the highest H+ (and O3) are usually experienced at these sites, and because these months are rarely complicated by other major influences (e.g., high pollen counts). Thus, any pollution-admissions relationships were expected to be most clearly discernible in this season. Prior to the health effects analysis, the summer admissions and environmental data were first detrended to eliminate long-wave autocorrelations, and day-of-week effects were removed via regression. Cross-correlations of the filtered 1988 and 1989 admissions and environmental data revealed strong associations between elevated summer haze pollution (i.e., H+, SO4 =, and O3) and increased total respiratory and asthma admissions on the same day and/or on subsequent days in Buffalo and New York City, especially during the summer of 1988 (when pollution levels were more extreme). Regression analyses indicated that the pollution-admissions associations remained significant (p < 0.05) even after the simultaneous inclusion of lagged daily maximum temperature. Mean effects calculations for these cities indicated that summertime haze can play a significant role in the occurrence of respiratory admissions in that season: accounting for an average 6 to 24% of 1988 Buffalo and NYC asthma admissions (depending on the pollutant index employed). O3 consistently had the highest mean effects estimates. Relative risk (RR) calculations indicated that the risk of admission for asthma was increased by a factor of 1.19 to 1.43 in these cities on maximum 1988 summertime pollution days, with H+ consistently having the highest RR estimates. These results are consistent with the hypothesis that ambient acid aerosol peaks (e.g., H+ > or = 100 nmol/m3) can potentiate the respiratory disease effects of O3. Associations were weaker in the less urbanized Albany metropolitan area and in the New York City (NYC) suburbs, even though the NYC suburban O3 exposures were similar to (and the H+ concentrations may even be somewhat higher than) those in the center city.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollution↗