Static Pressure-volume Curve Of Lungs Research Articles

Estimation of lung recruitment characteristics using the static pressure-volume curve of lungs

Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients' characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.

Effect of left pneumonectomy on lung mechanics in rabbits

Left pneumonectomy was performed in nine rabbits at 10 wk of age. Detailed pulmonary mechanics studies were performed at 14 wk of age in these rabbits and in nine littermate controls. Lung weight, total lung capacity, and static lung pressure-volume curves of the pneumonectomized rabbits were not different from those of the controls, but the forced vital capacity was smaller (P less than 0.05). Tantalum bronchograms of excised right lungs revealed no difference between controls and pneumonectomized rabbits in terms of bronchial diameter or pressure-area behavior of central or peripheral airways. Airways of pneumonectomized rabbits lengthened in accordance with the increase in lung volume. Over the midvolume range, the flow-limiting site moved from the trachea in controls to the right main bronchus in pneumonectomized rabbits. Maximal expiratory flow on air and on 80% He-20% O2 in the pneumonectomized rabbits average 70% of that in controls. This difference in flow was consistent with predictions based on the wave-speed theory of flow limitation.

Decrease in lung recoil pressure after cessation of smoking.

Tests of lung mechanics and single-breath carbon monoxide diffusing capacity (DLCO) were done in 26 apparently healthy cigarette smokers before and 2 months after cessation of smoking. There was a significant increase in vital capacity and 1-sec forced expiratory volume as well as improvement in frequency dependence of lung dynamic compliance. Slope and phase III and density dependence of maximal expiratory flow showed a borderline improvement DLCO did not change. Static lung pressure-volume curves showed a small but significant (P less than 0.01) shift toward lower pressures. We concluded that the previously reported decrease in lung recoil pressure observed in smokers is even more accentuated after cessation of smoking.

Bleomycin-induced diffuse interstitial pulmonary fibrosis in baboons.

Pulmonary fibrosis was induced in eight baboons with bleomycin; five untreated animals were controls. After 45-65 U/kg of bleomycin, lung volumes and diffusing capacity were reduced, and static lung pressure-volume curves were shifted to the right. Right middle lobes were resected at this time in five bleomycin-treated and two control animals. Compared to controls, right middle lobes from bleomycintreated animals had increased weight and contained increased amounts of total protein, collagen, elastin, and DNA; synthesis of collagen and noncollagen protein were also elevated. Occasional alveolar septae were edematous and infiltrated by mononuclear inflammatory cells; a slight increase in collagen was demonstrable histologically. Four of six treated animals died with extensive diffuse interstitial fibrosis after 95 U/kg of bleomycin. Biochemical analyses revealed significantly elevated lobar contents of dry weight, protein, elastin, and collagen. Two animals survived 95 U/kg of bleomycin and were terminated 6 mo after treatment. In these animals, physiologic studies were indicative of restrictive lung disease, but lung histology was nearly normal. Lung weight, total protein, and DNA had returned to control values, but collagen and elastin were increased in amount and concentration. Bleomycin induces an intense inflammatory response in the lung. During this inflammation, connective tissue proliferation occurs in concert with proliferation of other tissue components. Cessation of bleomycin treatment is followed by resolution of inflammation manifested by decreases in tissue mass, cellular content, and nonconnective tissue protein. Collagen and elastin deposited during inflammation are less successfully removed during resolution, leading to a stage characterized by increased concentrations of these proteins. A similar sequence of tissue alterations may occur in idiopathic diffuse interstitial fibrosis of man in response to various lung injuries.

Reduced surface tension in lungs of fetal rabbits injected with pilocarpine

After opening the maternal abdomen under methoxyflurane anesthesia, fetal rabbits 25.5-28.5 days gestation were given an intraperitoneal injection of pilocarpine (150 mg/kg) or saline through the intact uterine wall. They were delivered by hysterotomy and sacrificed without breathing 2.5 h later. Newborn rabbits 29.5 days gestation received an injection of pilocarpine or saline at birth and breathed 30-120 min. Other newborn rabbits 29.5 days gestation were alternately sacrificed at birth or after breathing 30 min. Static pressure-volume curves with air showed decreased recoil and improved air retention on deflation in fetal rabbits 25.5-27.5 days injected with pilocarpine. There was no change in the static pressure-volume curve of lungs filled with saline. The data suggest that pilocarpine reduced surface tension by producing secretion of surfactant into air spaces. No change in lung recoil occurred with pilocarpine at 28.5 days, or with pilocarpine or breathing at 29.5 days. This may mean that air spaces at 28.5-29.5 days contained optimal surfactant, so further secretion of surfactant stimulated by pilocarpine or breathing failed to reduce surface tension.

Influence of forced inflations on static pressure-volume curve of the lungs and thorax in the dog.

A study was made of the variations, under the influence of forced inspirations, of the static pressure-volume curve of lungs and thorax in dogs and of the dependence on time of these variations. The initial inflation curve, determined after a period of artificial ventilation, differs in shape from the second and following adapted curves. A progressive transformation of the pattern of the inflation curve is observed when the inflationary pressure is increased. Simultaneously, a displacement of the respiratory level occurs. Both phenomena are limited : the changes are observed only between critical lower and upper pressure values. To some degree, the variations in pattern of the inflation curve are also time-dependent. A second inflation at the same pressure produces a further adaptation but, following the second series of inflations, no further deformation can be achieved by repeating the inflations.In the interpretation of these variations, Berstein's hypothesis of the recruitment of previously closed alveoli, to explain the change in pattern of the pressure-volume curve, must be supplemented by some other mechanism producing the observed dependence on time of the observed processes.