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Biomedical subjects

H J Colebatch

Publications and source records attributed to H J Colebatch.

At least 37 records · Page 2Linked to original sources
PubMed1983

Alveolar size as a determinant of pulmonary distensibility in mammalian lungs.

Pulmonary distensibility depends on surface tension and tissue elastic forces, but the relative contribution of each to total lung recoil remains incompletely defined. By applying an exponential analysis to static pressure-volume curves obtained from the excised lungs of cats, dogs, and rats with air and saline filling, the exponential constant K (an index of lung distensibility) was related to the mean linear intercept Lm (a morphometric estimate of the mean size of peripheral air spaces at maximal inflation). K for air filling (Ka) was unrelated to K for saline filling (Ks), and Ks was unrelated to Lm, but similar highly significant regressions of Ka on Lm were found in each species, and the common regression was similar to that described previously for human lungs. Approximately 86% of the variance in lung distensibility (Ka) within and between species was explained by Lm. Because Lm determines the size of air spaces, and therefore the alveolar surface-to-volume ratio, the findings indicate that the density of surface forces is the major determinant of lung distensibility in the air-filled state.

Animals↗
PubMed1981

A possible role for corticosteroids in the treatment of influenzal pneumonia.

A 52-year-old woman with severe influenzal pneumonia developed increasing hypoxaemia on the sixth and seventh hospital days. Hydrocortisone (250 mg intravenously) was given on the seventh day and the arterial oxygen tension increased within two hours. Clinical improvement continued with further steroid therapy. Corticosteroids were ceased after three weeks, but were recommenced three weeks later when the vital capacity (VC) remained about half of the expected normal value. Although the VC had not altered for two weeks, the reintroduction of a steroid was followed within a week by an increase in VC which continued for a further eight weeks. Sequential measurements of the mechanical properties of the lungs during this recovery period showed that atelectatic areas had reinflated. Instability of lung units accompanied the increase in lung volume, suggesting a partial deficiency of surfactant in the recruited units. Eighteen months after presentation, lung volumes remained mildly decreased but the elastic behaviour, airway conductance, and gas exchanging properties of the lungs were normal. Although some alveoli had been permanently lost, there was no evidence of diffuse lung fibrosis and the remaining lung units functioned normally.

Female↗
PubMed1980

Elastic behavior and structure of normal and emphysematous lungs post mortem.

To examine the relationship between lung structure and function, static deflation pressure-volume curves were measured post mortem in 14 normal and 7 emphysematous lungs, and the results were compared to morphometric measurements of lung. Elastic behavior was described satisfactorily by an exponential function: V = A -Be-KP, where V is lung volume, P is static recoil pressure, and A, B, and K are constants. The constant K, an index of pulmonary elasticity, was closely related to a morphometric measurement of mean alveolar size. In normal lungs the decrease in pulmonary elasticity with age was quantified by an increase in K. When emphysema was present, K was invariably increased by more than 2 SD above the mean predicted value for age, reflecting the abnormally increased distensibility of alveoli in this disorder. The present findings indicate that a similar analysis of pressure-volume measurements obtained during life will reliably detect the presence of pulmonary emphysema in patients with chronic airflow limitation.

Adolescent↗
PubMed1979

Use of an exponential function for elastic recoil.

To improve the quantitative representation of elastic recoil, an exponential function (V = A - B exp (-KP), where V is the lung volume, P is the recoil pressure, and A, B, and K are constants), has been fitted to static pressure-volume (PV) data by a least-squares technique using a digital computer. The PV points below about 50% total lung capacity (TLC) usually deviate from an exponential expression. Increasing the lower volume limit to which the exponential was fitted from 40 to 75% of TLC in 20 subjects, increased K and B/A significantly. Residual variance was lowest (approx 1.0 +/- 0.5%) when the lower volume limit was between 50 and 60% TLC. The PV points in the lower volume range deviated significantly less from exponential in a group of older subjects than for young subjects. The coefficient of variation of K and B/A for duplicate studies in 10 subjects was 9 and 14%, respectively. For inflation PV data, K was significantly lower and A significantly higher than for deflation. For PV data obtained after a submaximal inspiration, K did not change significantly. From this exponential function, the PV curve above 50% TLC can be satisfactorily described by K, B/A, and recoil pressure at TLC; other conventional parameters may be derived.

Adult↗
PubMed1979

Exponential analysis of elastic recoil and aging in healthy males and females.

To examine the effects of aging on the elasticity of the lungs a single exponential function (V = A - B exp (-KP)), where V is lung volume, P is recoil pressure, and A, B, and K are constants) and a fourth-order polynomial were fitted to the static pressure-volume data from 124 healthy nonsmokers (83 males). K, the index of compliance, was independent of sex and increased with age. B/A and recoil pressures at various lung volumes were higher in males than females, but decreases with age were similar in both sexes. Static compliance (expressed as percent of total lung capacity/cmH2O), derived from the polynomial expression, was the same in males and females and increased with age. The results show that the lungs of males and females have the same intrinsic elasticity, and differences in recoil pressure depend on differences in lung size and in maximum distending forces. Loss of elasticity with age is consistent with an increase in the unstressed dimensions of alveoli and a decrease in their elastic fibers.

Adolescent↗
PubMed1978

Computerized measurement of pulmonary conductance and elastic recoil.

A system devloped for on-line measurement of transpulmonary pressure, gas flow at the mouth, change in expired volume and plethysmograph volume uses a minicomputer to control a multiplexed analog to digital converter. The computer identified samples as static or dynamic values by monitoring a voltage activating a solenoid valve, used to close the airway. Analysis of these samples by other task-specific programs yielded the static deflation pressure-volume (PV) curve, the conductance-recoil pressure, GL-Pst(L), relationship and the maximum expiratory flow-volume (MEFV) curve; the MEF-Pst(L) curve and conductance upstream from the equal pressure point were derived. The PV relationship was represented by a fourth-order polynomial and the GL-Pst(L) relationship by linear regression. In 11 subjects the results obtained using on-line data collection, compared with manual analysis of oscillograph recordings, showed small differences in static compliance and in the maximum Pst(L); but overall the two methods showed excellent agreement. Besides advantages of speed and objectivity, this system facilitates a more rigorous analytical treatment of elastic recoil and conductance.

Asthma↗
PubMed1976

Increased elastic recoil as a determinant of pulmonary barotrauma in divers.

The elastic and conductive behaviour of the lungs were studied in sixteen divers during an interrupted deflation from total lung capacity (TLC.) The results in six divers, who had suffered pulmonary barotrauma (PBT) during shallow water diving, were compared with the findings in a control group of divers. Conductive behaviour and mean lung volumes were similar in the two groups. Compared with the control group, the PBT group had higher maximum transpulmonary pressures and a lower static pulmonary compliance, and deflated their lungs earlier. In relatively stiff lungs, an even distribution of elastance may increase susceptibility to barotrauma, because the more compliant zones are subjected to a greater strain. Pulmonary barotrauma appears to select from the total population of healthy divers those with lungs of decreased distensibility.

Diving↗