Changes in lung volume, lung density, and distribution of ventilation during hypobaric decompression.
Explore the source record for details and available documents.
Adaptation, Physiological↗
SEARCH · PubMed Health
Results for “Lung volume”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Ventilation, lung volumes and lung mechanics of young adult and old Syrian hamsters.
The breathing pattern, subdivisions of lung volume and quasistatic pressure-volume relationships of 15 and 65 week old hamsters (Mesocricetus auratus) anesthetized with halothane were measured by plethysmography. Body weights, tidal volumes and minute volumes of the younger and older groups were nearly identical. All lung volumes were larger in the older hamsters but there were no significant age-related differences in the relative proportions of lung volume subdivisions. Quasistatic lung compliance was greater in the older group but differences in pressure-volume relationships were not significant when volume was expressed as percent of total lung capacity. It appears that hamster lungs undergo significant volume changes with age during adulthood, but the pattern of change is different from that observed in man and dogs.
Age Factors↗
Acute changes of lung volumes and lung mechanics in asthma and in normal subjects.
Lung volumes, pulmonary mechanics, and specific airway conductance (sGaw) were studied before and 15 minutes after 200 microgram of aerosol salbutamol in nine asthmatics undergoing mild spontaneous exacerbations of their disease and in five normal subjects. In addition, three of the normal subjects were studied after voluntarily breathing at high lung volumes for one minute. The normal subjects and four of the asthmatics showed no overall changes in lung volumes or pressure-volume (PV) curves after salbutamol, even though airway dilatation was produced in the asthmatic subjects. In another five asthmatics, salbutamol induced a significant fall in the total lung capacity (TLC) in three, and in the residual volume and functional residual capacity in all five. There was a significant displacement of the PV curve downwards and to the right in all five, with increased lung compliance (Cl stat) in two. The fall in TLC could be accounted for by the increase in lung elasticity. There is reason to believe that this change in lung mechanics could be due to the reversal of asthma-induced stress relaxation. Sustained breathing at high lung volume is known to cause stress relaxation of the lung. However, this breathing pattern did not alter the PV curve or TLC in two of three normal subjects, which is consistent with stress relaxation being rapidly reversible. The other normal subject had an acute shift of the PV curve upwards and to the left after breathing at high lung volume. It has been concluded that stress relaxation is usually rapidly reversed but that in some individuals it may only be slowly reversed. This more persistent form of stress relaxation may contribute to the acute changes of TLC found in some asthmatics.
Adult↗
Effect of breathing helium-oxygen on static lung volumes and lung recoil in normal man.
Static lung volumes and static elastic recoil pressure (Pel) were measured in normal subjects breathing air and 80% helium plus 20% oxygen (He+O2). In 22 subjects, He+O2 produced small but significant increases in total lung capacity (TLC) (mean 0.11 liter, P less than 0.001) and residual volume (mean 0.10 liter, P less than 0.01) without change in vital capacity or functional residual capacity. The mechanisms for this change are obscure. In 10 subjects, breathing He+O2 had no significant effect on Pel (paired t-test) at any lung volume measured (50-80% TLC). In one subject, Pel at 70 and 80% TLC was significantly higher on air than on He+O2 (unpaired t-test, P less than 0.05). Because changes in lung volumes and lung recoil were small, we concluded that these effects do not negate the clinical utility of He+O2 flow-volume curves.
Adult↗
Effects of continuous distending pressure on lung volumes and lung mechanics in the immediate neonatal period.
The effects of CPAP and CNEP on lung mechanics and lung volumes were investigated in a group of 12 healthy newborn infants. Both resulted in a mild suppression of respiration. The fall in TPR50 was far greater during CPAP than during CNEP. Both led to a one third fall in dynamic compliance. Approximately 50% of the distending pressure was transmitted to the mediastinal structures whether applied as CPAP or CNEP.
Airway Resistance↗
Flow-volume relationship at low lung volumes in healthy term newborn infants.
To describe the maximum expiratory flow-volume relationship in newborn infants, we simulated forced expiration by transiently applying positive pressure in a chamber surrounding the infant's body. Maximum expiratory flows were reached at any given lung volume when increases in chamber pressure failed to produce increases in flow. Maximum expiratory flows were achieved in seven of nine healthy newborn infants at lung volumes equal to functional residual capacity (FRC) andin all infants at lung volumes below FRC. The volume expired below FRC (6.4 ml/kg) was roughly equivalent to previously calculated values of expiratory reserve volume in newborn infants (7 ml/kg). The maximum expiratory flow volume curves showed that the infants were able to increase expiratory flow rates well above those achieved during tidal breathing. The convex shape of the curves at low lung volumes is compatible with flow limitation occurring in peripheral airways.
Functional Residual Capacity↗
[Method of determining residual lung volume by vital lung capacity and age].
Explore the source record for details and available documents.
Age Factors↗
Trapped gas at maximum lung volume in intact isolated rat lungs.
Excised rat lungs were ventilated with air in a liquid filled plethysmograph that was enclosed in a large pressure chamber, C(B). The lungs were inflated then deflated by removing or adding saline to the plethysmograph while the trachea was attached to a cannula extending through the plethysmograph base. In this system, tracheal pressure, Pao, was equal to gas pressure inside C(B). The gas pressure was held constant at either ambient pressure (Pamb), Pamb + 350 Torr, or Pamb - 350 Torr. When excised lungs were ventilated slowly from their atelectatic state for 10 inflation-deflation cycles with Pao equal to any one of the three pressures, an equivalent amount of gas was trapped in the lungs. If after 10 cycles, however, lungs containing trapped gas were inflated and held at maximum lung volume, the trapped gas spaces could be made to expand in response to rarefaction or compression of the tracheal gas. The amount of expansion and contraction of the trapped gas spaces demonstrates that trapped gas is likely trapped between menisci of a foam that occlude the alveoli or small airways.
Animals↗
The influence of lung volume on expiratory flow rates in diffuse interstitial lung disease.
This study evaluated maximum expiratory flow rates with respect to lung volume and maximum recoil pressure in selected patients with diffuse interstitial lung disease who had normal large airway function by standard technique. Coefficient of retraction was normal or greater than normal in all. Peak flow varied directly with lung volume as in normals. At 50% vital capacity (VC) and 25% VC, the absolute flow rates varied from higher to lower than normal. However, when flow was adjusted to volume, the flow/volume ratio was normal or high in all. Flow/volume ratio at mid-lung volume appeared to increase with increase in coefficient of retraction. Patients with frequency dependence of compliance had lower flow/volume ratios at 25% VC than those without, although still within normal range. Thus, despite recognized wide variations in normals, the flow/volume ratio is pertinent to the evaluation of reduced air flow rates in in interstitial lung disease to distinguish abnormal upstream airway resistance from volume-dependent reduction of flow rate. An effort-independent flow rate that yields a supernormal flow/volume ratio suggests increased recoil properties of the respiratory system.
Adult↗
Measurement of lung volumes from supine portable chest radiographs.
Lung volumes in supine nonambulatory patients are physiological parameters often difficult to measure with current techniques (plethysmograph, gas dilution). Existing radiographic methods for measuring lung volumes require standard upright chest radiographs. Accordingly, in 31 normal supine adults, we determined helium-dilution functional residual and total lung capacities and measured planimetric lung field areas (LFA) from corresponding portable anteroposterior and lateral radiographs. Low radiation dose methods, which delivered less than 10% of that from standard portable X-ray technique, were utilized. Correlation between lung volume and radiographic LFA was highly significant (r = 0.96, SEE = 10.6%). Multiple-step regressions using height and chest diameter correction factors reduced variance, but weight and radiographic magnification factors did not. In 17 additional subjects studied for validation, the regression equations accurately predicted radiographic lung volume. Thus, this technique can provide accurate and rapid measurement of lung volume in studies involving supine patients.
Adult↗
[Closing volume and resistance-lung-volume-relationship in simple coal worker's pneumoconiosis (author's transl)].
Explore the source record for details and available documents.
Adult↗
Rabbit lung plasma and erythrocyte volumes. Lung hematocrit in relation to total body hematocrit.
The total body hematocrit has been reported to be 85--90% of packed cell volume (PCV) in several species. We have found similar values in rabbits. An "extra" plasma volume must exist somewhere in the vascular bed to explain this observation. We have looked for such an extra plasma volume in the pulmonary vasculature. The dynamic hematocrit was estimated in isolated, perfused rabbit lungs from distribution volumes for plasma and erythrocyte tracers. Estimation was also obtained from indicator-dilution curves using bolus-injections of such tracers avoiding their recirculation. It was thus possible to calculate mean transit times for the tracers from their dilution curves directly or applying monoexponential extrapolation from the first part of the downslope of the curves. The dynamic hematocrit of the lung vessels was about 94% of perfusate PCV and there was no difference between the results obtained by the different methods. We concluded that in the rabbit only a very small part of the extra plasma volume is located in the lung vessels. The lung plasma volume is not underestimated by the indicator-dilution technique.
Animals↗
Lung volumes and arterial blood gases in obesity.
Lung volumes and arterial blood gases have been studied in six severely obese patients (mean weight 143 kg), admitted for jejunoileal shunt-operation. The lung volumes were recorded on a Siemens constant volume body plethysmograph, and the arterial blood gases were measured by means of a Radiometer ABL-1 blood gas analyzer. The patients were in the seated body position. The Functional Residual Capacity (FRC) was found to be 40% (mean value) of Total Lung Capacity (TLC). Predicted normal value of FRC/TLC% in non-obese subjects of the same height, sex and age is 54%. During tidal breathing the arterial oxygen tension (PaO2) was 84 mm Hg (mean value) compared to 95 mm Hg in non-obese subjects. A positive correlation between FRC/TLC% and the PaO2 was found. A series of 5 deep breaths normalized the PaO2 which rose by 18 mm Hg to 102 mm Hg (mean value). These results confirm the generally held opinion that the main abnormality of lung function in obesity is a reduction of lung volume to such a low value that airway closure occurs during tidal breathing, causing arterial hypoxemia.
Adult↗
Lung volumes in man immersed to the neck: dilution and plethysmographic techniques.
Previous studies of lung volumes during immersion have utilized dilution techniques for residual volume. We have compared lung volumes obtained by the use of a dual inert gas dilution technique with those determined by the Boyle's law technique in a plethysmograph designed to allow measurements in air and submersed to the neck in water. Both techniques gave similar results dry, but during immersion the dilution residual volume (RV) was 0.200 liter (16%) lower than the plethysmographic value (P greater than 0.001), which suggests that there is a significant amount of gas trapping during immersion due to breathing at low lung volumes and the central shift of blood. The unchanged RV due to hydrostatic force on the chest wall is balanced by the tendency to increase RV due to vascular congestion, which increases closing volume and stiffens the lung to compression.
Adult↗
Voluntary changes of thoracoabdominal shape and regional lung volumes in humans.
We measured regional lung volumes from apex to base in humans during changes in thoracoabdominal shape which we monitored with magnetometers. In erect subjects, voluntary changes of shape at FRC did not change regional volume distribution. In supine subjects, the effect of negative pressure applied to the abdomen and a similar thoracoabdominal configuration achieved by voluntary means were studied. The distribution of regional volumes in both situations was the same as that measured during relaxation at the same overall lung volumes. We concluded that neither voluntary changes in shape nor negative abdominal pressure influenced the human pleural pressure gradient. This result, which differed from findings in animals, was probably because the human chest was relatively stiff and behaved with one degree of freedom; all parts of the human rib cage changed dimensions proportionally while negative abdominal pressure distorted the rib cage of animals.
Abdomen↗
Alterations in lung volume and pulmonary function in relation to hemodynamic changes in acute myocardial infarction.
To characterize the changes in lung volumes after acute myocardial infarction (AMI), and the relationship of these changes to other alterations in lung function which correlate with the severity of pulmonary vascular congestion, we made measurements of pulmonary hemodynamics, lung volume, closing volume, frequency dependence of total pulmonary resistance to forced oscillation, and arterial PO2 in 18 subjects with AMI. The most consistent finding was reduced lung volume which correlated with the severity of pulmonary diastolic hypertension. Frequency dependence of resistance showed a small but significant correlation with pulmonary hemodynamics. Closing volume measurements by the resident gas method in nine subjects was not related to hemodynamics. Follow-up studies at the time of hospital discharge revealed a significant return toward normal for arterial PO2, all lung volumes, and total pulmonary resistance at 9 Hz. Based on measurements in healthy subjects, the reduced lung volume after AMI may explain the changes in resistance. In acute and follow-up studies the degree of lung volume reduction and the severity of hypoxemia were strongly correlated.
Acute Disease↗
Summation of phasic lung volume reflexes between the two lungs in dogs [proceedings].
Explore the source record for details and available documents.
Animals↗
Lung volume and pleural pressure in the anesthetized hamster.
Lung volumes and respiratory pressures were measured in anesthetized male hamsters weighing an average 117 g. In 16 supine animals functional residual capacity (FRC) determined by body plethysmograph was 1.12 +/- 0.23 (SD) ml (about 20% total lung capacity, TLC) slightly and significantly larger than the FRC measured by saline displacement, 1.01 +/- 0.15 ml. Similar results were found in six prone animals. Paralysis did not significantly alter supine FRC. Contrary to published reports, pleural pressure (Ppl) estimated from esophageal pressure was negative at FRC. The fact that lung volume decreased by 0.2 ml (about 4% TLC) when the chest was opened at FRC provided additional evidence of negative Ppl at FRC. No consistent changes in the lung pressure-volume curve were found after the chest was opened. Deflation chest wall compliance just above FRC was about twice lung compliance. The vital capacity and reserve volumes in this study agreed with values reported in the literature. However, absolute lung volumes (TLC, FRC, and residual volume) were lower by about 1.4 ml, possibly because of earlier overestimates of box FRC.
Animals↗