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Biomedical subjects

N B Pride

Publications and source records attributed to N B Pride.

At least 145 records · Page 8Linked to original sources
PubMed1976

Lung distensibility. The static pressure-volume curve of the lungs and its use in clinical assessment.

The main points of interest in the static expiratory PV curve are the changes in TLC (and to a lesser extent in RV), Pst(L) at standard volumes and particularly at TLC,and compliance (delta V/delta P) particularly close to FRC. More subtle changes in curvature may be present but have not as yet achieved any clinical or diagnostic significance. Although any presentation short of the whole PV curve inevitably conceals information a useful summary of the major changes can be obtained by considering only three points--the changes in TLC, Pst(L)max and compliance close to FRC (Fig. 22). In conditions associated with an increased TLC, four distinct patterns of change in the PV curve have been recognized resulting in different combinations of changes in Pst(L)max and compliance at FRC (Fig. 22, a, b, c, d). There are two main patterns of PV curve in restrictive lung disorders--one due to stiffening of the lung (Fig. 22, g, i, j) and the second due to extrapulmonary factors which prevent a normal distending pressure being applied to the pleural surface of the lung (Fig. 22, h). In practice it appears that lack of distending pressure leads to a secondary reduction in lung compliance. Nevertheless differences in Pst(L)max remain. The general patterns of abnormality may be summarized as follows: 1. Increases in TLC are almost always associated with a normal or increased compliance but Pst(L)max may be increased, normal or decreased. 2. Decreases in TLC are almost always associated with a decreased compliance but again Pst(L)max may be increased, normal or decreased. 3. When TLC is normal, it is theoretically possible that the whole PV curve may be displaced on the pressure axis and compliance may be altered (as in ageing) but such changes have not been identified in clinical practice.

Acromegaly↗
PubMed1976

British pilot study of exercise therapy. I. Middle-aged men.

The physiological and biochemical effects of a carefully graduated course of vigorous gymnasium training with two or three weekly exercise sessions lasting only 15 minutes have been studied in middle-aged London business men. Activity diaries and psychological questionnaires indicated that these men had a positive attitude to exercise which was probably greater than average. The gymnasium exercises caused a large oxygen debt and considerable rises in plasma catecholamines and lactate levels. A close correlation was found between the pulse rate during exercise and the Borg scale of perceived exertion, so that both could be used to ensure that short periods of exercise were sufficiently vigorous to produce a training effect, and protect against over-exertion. The acceptability of this particular exercise regime was shown by the low fall-out and injury rate. It is suggested that this exercise training programme possesses many features which are advantageous if increased physical activity is to be more widely used as a method of reducing some of the risk factors in coronary heart disease.

Adult↗
PubMed1976

Sex and age differences in pulmonary mechanics in normal nonsmoking subjects.

Maximun flow-volume, static pressure-volume, and maximum flow static recoil curves of three groups of nonsmoking, normal subjects (young men, young women, elderly women) were used to assess age and sex differences in pulmonary mechanics. No significant sex differences in maximum flow were seen but the young men showed higher lung recoil pressures at full inflation. When the influence of the inspiratory muscles and chest wall was excluded by exponential extrapolation of the pressure-volume curves to a maximum volume the bulk elastic properties of the lungs of young men and women appeared identical. Loss of maximum expiratory flow at low lung volumes and of lung recoil pressure occurred with age in nonsmoking women in whom emphysema should be minimal and therefore indicate true physiological effects of aging. The changes in pulmonary mechanics with age are consistent with an increase in unstressed dimensions and loss of elastic recoil of both alveoli and airways.

Adult↗
PubMed1975

An analysis of the physiological strain of submaximal exercise in patients with chronic obstructive bronchitis.

An increasing work rate was performed by 40 patients with chronic obstructive bronchitis, split into two groups according to FEV1 (group M, mean FEV1 1-451. and group S, mean FEV1 0-621.), and by 20 normal, non-athletic men of similar age to the patients. Values for cardiac frequency and ventilation were interpolated to standard oxygen uptakes of 0-75, 1-0, and, where possible, 1-5 min-1. The tidal volume at a ventilation of 20 and 30 1 min-1 was also determined. The cardiac frequencies at oxygen uptake of 0-75 and 1-01 min-1 were significantly higher in the patient groups than in the normal men, and were highest in patient group S. The cardiac output when related to the oxygen uptake was in the normal range in all three groups of subjects, so that the patients had smaller stroke volumes than the normal men. Ventilation at oxygen uptakes of 0-75 and 1-01 min-1 was significantly higher in both patient groups than in the normal subjects; there were no significant differences between the two patient groups, Values for dead space/tidal volume ration, alveolar-arterial oxygen gradient, and the percent venous admixture measured during a constant work rate test were significantly greater than normal in the patient groups. Possible factors limiting exercise tolerance in these patients were assessed by extending the increasing work rate test from submaximum to maximum exercise. Changes in blood gas tensions and blood lactate concentrations from resting levels were small, and probably did not limit exercise performance. Measurements at maximum exercise did not add appreciably to the analysis of the disturbed cardiopulmonary function. This study has shown that major disturbances in cardiopulmonary function can be demonstrated without the need for stressing a patient to the limit of his effort tolerance.

Aged↗
PubMed1975

Changes in lung mechanics during asthma induced by exercise.

Pulmonary and airway mechanics were assessed in seven asthmatic patients in remission, when asthma was induced by exercise and again after spontaneous recovery or bronchodilator treatment. After exercise there was a sustained fall in forced expiratory volume in 1 s (FEV 1.0) in all patients, varying from 30 to 80 percent of the initial value. Total lung capacity (TLC) increased significantly in four of the seven patients. In one of the four patients the increase in TLC was associated with an increase in static transpulmonary pressure at full inflation but in the remaining three patients it was associated with a parallel shift of the pressure-volume curve of the lung without change in its slope. In all patients residual volume increased, regardless of change in TLC; both pressure-volume and maximum expiratory flow-volume curves suggested that widespread airway closure (or virtual closure) occurred at positive transpulmonary pressures when asthma was induced. Loss of lung recoli pressure sometimes contributed to the reduction in maximum expiratory flow but diffuse airway narrowing was probably the dominant abnormality. When air-flow obstruction became more severe the ratio of expiratory to inspiratory time was increased and although expiratory flow limitation was present excessive expiratory pressures were not generated.

Adolescent↗
PubMed1973

Contributions of loss of lung recoil and of enhanced airways collapsibility to the airflow obstruction of chronic bronchitis and emphysema.

We investigated the contributions of intrinsic disease of the airways, loss of lung recoil and enhanced airway collapsibility to the airflow obstruction of 17 patients with chronic bronchitis and emphysema. Airways conductance at low flow (G(aw)), maximum expiratory flow (V(E, MAX)) and static lung recoil pressure [P(st) (l)] were measured at different lung volumes, and conductance-static recoil pressure and maximum flow-static recoil pressure curves constructed. Low values of DeltaG(aw)/DeltaP(st) (l) and DeltaV(E), max/DeltaP(st) (l) were attributed to intrinsic airways disease. Airway collapsibility was assessed by comparing G(aw) with upstream conductance on forced expiration and by the intercept of the maximum flow-static recoil curve on the static recoil pressure axis (P(tm)'). All patients had reduced G(aw) at all volumes but in seven DeltaG(aw)/DeltaP(st) (l) was normal. On forced expiration, maximum flow in all patients was reduced more than could be accounted for by loss of lung recoil. DeltaV(E, MAX)/DeltaP(st) (l) was reduced in the patients in whom DeltaG(aw)/P(st) (l) was low. In contrast DeltaV(E, MAX)/DeltaP(st) (l) was normal in three and only slightly reduced in another three of the seven patients with normal DeltaG(aw)/DeltaP(st) (l). In these patients G(aw) greatly exceeded upstream conductance and P(tm)' was increased.We conclude that loss of lung recoil could account for the reduction in resting airways dimensions in 7 of the 17 patients. Enhanced airway collapsibility commonly contributed to reduction in maximum flow. In three patients the airflow obstruction could be entirely accounted for by loss of lung recoil and enhanced airway collapsibility.

Adult↗