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Biomedical subjects

J B Forrest

Publications and source records attributed to J B Forrest.

85 records · Page 5Linked to original sources
PubMed1977

Acute pulmonary toxicity of a commercial fluorocarbon--lipid aerosol.

The death of an adolescent after deliberate inhalation of the domestic fluorocarbon--lipid spray, PAM, triggered an investigation of the effects of this product on mammalian lung. Some of its constituents are known to destroy the lung-surfactant system, but death from its inhalation by earlier victims was usually attributed to the fluorocarbon's cardiac arrhythmogenic properties. In the present study, we applied methods and experimental models not previously used to study the effects of this aerosol material on the lung surfactant. We found morphological and functional acute disintegration of normal alveolar surfactant, leading to extensive alveolar collapse, with sustained and elevated surface tensions in vitro. This could result in fatal hypoxaemia at inspired concentrations of fluorocarbons insufficient to cause cardiac arrhythmias, and may explain at least partly the large number of deaths associated with inhalation of such product.

Aerosol Propellants↗
PubMed1976

An unusual complication after stellate ganglion block by the paratracheal approach: a case report.

A case is presented of repeated stellate ganglion block using the paratracheal approach at the level of C6 and using the low dose method. Subarachnoid spread of local anaesthetic resulted in total spinal block below the level of C4. The potential hazards of this techinque of stellate ganglion block and methods of avoiding them are discussed, together with the possible mechanism in this case.

Autonomic Nerve Block↗
PubMed1976

Lung tissue plasticity: morphometric analysis of anisotropic strain in liquid filled lungs.

Lungs of rats were fixed at different inflation pressures (Ptp) during liquid filling with the pulmonary vessels tied to prevent vascular volume change after fixation had begun. Morphometric analysis showed that alveolar surface varied as a alveolar volume (Va) to the power 0.82, while the arithmetic mean tissue thickness varied as Va-0.2. This is interpreted as evidence for anisotropic expansion. Capillary volume (Vc) was found to increase from zero Ptp to a maximum at Ptp = 2 cm H2O then decrease as Va increased. Morphometric diffusion capacity of the membrane component increased as Va0.59 while that for whole lung (DL)paralleled the change in Vc. Alveolar capillary tissue unfolding is described as the main factor accounting for anistropic expansion of alveolar surface and for capillary configuration. The absolute values of Vc and DL were lower by 60% and 50%, respectively, compared with values obtained by standard instillation fixation methods and this is suggested could account for previous discrepancres between morphometric and physiologic estimates of DL.

Animals↗
PubMed1975

Morphometric estimation of pulmonary diffusion capacity. VII. The normal Guinea pig lung.

A study of 15 normal adult guinea pig lungs fixed by instillation of fixatives via the airways is described. The morphological appearance of the guinea pig lung is similar to that of other mammals apart from quantitative differences in the mass of connective tissue in the alveolar-capillary barrier whose mean thickness was estimated at 1.59 mum. Lung volume, alveolar volume, capillary volume and the surface areas of alveoli and capillaries are shown to be linearly related to body weight. Analysis of the morphometric diffusion capacities of the alveolar-capillary membrane and of the lung shows that these are also linearly related to body weight. For a mean body weight of 429 g the lung volume was 13 ml, the alveolar surface 0.91 m2, the capillary volume 1.5 ml, the harmonic mean barrier thickness 0.42 mum, and DL 2.13 ml/min.mm Hg. These parameters are compared with those of other mammalian species and discussed in the context of normal activity levels as a probable important adaptive factor determining the size of the gas exchange apparatus.

Animals↗
PubMed1970

The effect of changes in lung volume on the size and shape of alveoli.

1. A technique is described by which living anaesthetized guinea-pigs were artificially ventilated with a positive and negative pressure cycle, and rapidly frozen at the instant of cessation of ventilation at a preselected point on the respiratory cycle.2. The dimensions of alveoli and alveolar ducts were measured by histological morphometric methods, and related to the degree of lung inflation at the instant of freezing.3. The alveolar volume fraction increased from 0.52 at low lung volumes, up to 0.62 at lung volumes in the mid-inflation range, then decreased to 0.51 at high lung volumes. The alveolar duct volumetric fraction remained constant at all lung volumes.4. The total volume of alveoli increased linearly with increase in lung volume. The total alveolar duct volume increased little until the lungs were 40% inflated, above which it increased steeply.5. The total number of alveoli was linearly related to the body weight.6. The total alveolar surface area increased steeply between lungs of low lung volume and those which were up to 50% inflated, above which the increase levelled off. The absolute values of total alveolar surface depended on the body weight as well as the degree of lung inflation.7. The mean alveolar duct diameter was 40% greater, and the mean alveolar mouth diameter 35% greater in lungs which were fully inflated than in lungs which were nearly collapsed. The average geometrical shape of alveoli was not related to the degree of lung inflation.8. The harmonic mean thickness of the air-blood barrier was 33% less in lungs which were fully inflated than in lungs which were nearly collapsed. The alveolar surface membrane was smooth whether the lungs were fully inflated or collapsed.

Animals↗