PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Closing 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.

At least 19 recordsLinked to original sources
PubMed1982

Lung volume, closing volume, and gas exchange.

The effect of a voluntary reduction in lung volume on arterial O2 saturation (SaO2) was studied in 10 normal subjects aged 19-63 yr. SaO2 was measured by ear oximetry first during tidal breathing at functional residual capacity, and then during tidal breathing at 380 ml above residual volume. Tidal volume and breathing frequency were kept constant, and end-tidal CO2 partial pressure remained stable or fell in 9 out of 10 subjects. When lung volume was reduced, SaO2 fell by a mean of 1.5% (range 0-3%). Closing volume (CV) was measured by the N2-washout method (mean 0.89 liter, range 0.41-1.44). There was a close correlation between CV and the fall in SaO2 (r = 0.867, P = 0.001). Arterial and mixed venous CO2 were measured in one subject; the results indicated some fall in cardiac output following the lung volume change, but this accounted for less than half of the fall in SaO2. The relationship between CV and the lung volume at which tidal breathing occurs is an important determinant of pulmonary gas exchange through its effect on the matching of ventilation to perfusion.

Adult↗
PubMed1974

Effects of age and posture on closing volume.

Closing volume and closing capacity increased linearly with age. In the seated position, the closing volume exceeded the expiratory reserve volume in subjects older than about 65 years, while in the supine position, as the expiratory reserve volume is markedly reduced, this occurred at about 44 years. Above these two "critical ages", ventilation to the dependent parts of the lungs is reduced during the normal tidal volume breathing. Thus, in seated subjects older than 65 years and in supine individuals older than 44 years there is significant impairment of ventilation distribution to the dependent lung zones, which necessiarly causes impaired gas exchange within the lungs.

Adolescent↗
PubMed1976

Effect of inspired volume on closing volume.

Closing volume (CV) was ?EASURED WITH THE RESIDENT GAS TECHNIQUE IN 12 HEALTHY SEATED SUBJECTS AGE 22-70 YR, AND IN 8 SUBJECTS WITH THE BOLUS TECHNIQUE. Various volumes were inspired (Vi range: 20-100% vital capacity) from residual volume and CV was assessed on the subsequent recording of expired volume versus gas concentration. The results indicate that the resident gas technique may erroneously underestimate CV at reduced Vi in conformity with calculations which predict that during expiration, after a certain reduced VI, the nitrogen concentration is identical in the most basal lung region and at the mouth. CV obtained with the bolus technique decreased linearly with reduced Vi and the effect appeared to be age dependent according to the equation CV50/CV100=0.0078 X age +1.18, where CV50 and CV100 denote the bolus CV corresponding to Vi=50% and 100% of vital capacity. Therefore, in older subjects, during tidal breathing, airways appear to close at substantially lower lung volume than previously considered.

Adult↗
PubMed1977

Comparison of flow-volume and closing volume variables in a random population.

Data obtained from results of single-breath N2, or closing volume, tests were compared with maximal expiratory flow-volume parameters in 725 subjects, 25 to 54 years of age, from a random, stratified, cluster sample of the population of Tucson, Arizona. Results of the 2 tests showed poor concordance. A greater proportion of abnormalities was revealed by maximal expiratory flow-volume measurements than by the single-breath N2 test in population subgroups defined as other than "normal". Among the 114 subjects reporting physician-confirmed asthma, chronic bronchitis, or emphysema, less than one half of those with maximal expiratory flow-volume abnormalities also had an abnormality in the single-breath N2 test. Results of this comparison do not indicate that the closing volume test, when applied to a general population, consistently reveals abnormalities of clinical significance.

Adult↗
PubMed1975

Intraindividual variability in maximal expiratory flow-volume and closing volume in asymptomatic subjects.

The variability of the parameters derived from analysis of the forced vital capacity and the expired nitrogen trace after a vital capacity inhalation of oxygen (closing volume) within a day, from day to day, and from week to week, has been determined. Effort-dependent tests as vital capacity and peak expiratory flow showed the least variability. The greatest variability was seen in effort-independent tests of function such as the maximal expiratory flow rate at 25 per cent (75 per cent of expired vital capacity) and 50 per cent of vital capacity, as well as closing volume. The degree of variability in the tests used was uninfluenced by the periodicity of the tests or the age or smoking habits of the subjects tested. It is suggested that variability of tests of respiratory function should be taken into account in their interpretation.

Adolescent↗
PubMed1975

Effect of preinspiratory lung volume on closing volume determination by nitrogen method.

The effect of preinspiratory lung volume on the N2 closing volume (CV) was studied in simulated CV determination in a lung model. The model analysis supports our hypothesis that inspiration of O2 initiated at the "closing capacity" (CC = CV ;V) will improve the resolution of the inflection point between phases III and IV. It further indicates that if the inflection point is located by extrapolating the terminal portion of phase IV, then the original N2 method could underestimate CV systematically as much as 5% VC because of the relatively small initial rise in N2 concentration. Conversely, the CV obtained by the modified method should be closer to the value obtained by the "bolus method." In practice, the modification can be done simply by adding a dead space (DS) with its capacity equal to CV (600-700 ml in male adults). The theoretical lung model analysis was confirmed by the experimental study, which showed that CV with DS was consistently larger than CV without DS (a mean difference of 4.7% VC).

Adult↗
PubMed1980

Abnormalities in maximum flow volume curve and closing volume in patients with hepatic cirrhosis.

Pulmonary functions were measured in 53 patients with hepatic cirrhosis in whom there was no clinical or radiographic evidence of pulmonary involvement. Spirometric tests such as total lung capacity, vital capacity, functional residual capacity, residual volume and forced expiratory volume during one second were within normal ranges, in all subjects. Flow volume curve and closing volume tests, however, were abnormal in the majority. The maximal expiratory flow at 50 per cent of vital capacity was not altered but the maximal expiratory flow at 25 percent of vital capacity was decreased significantly in patients with hepatic cirrhosis. The closing volume in patients with hepatic cirrhosis was also significantly increased. The abnormalities in flow volume curve and closing volume curve were also demonstrated in non-smokers, and at any age, in cases of hepatic cirrhosis. These results suggested that the narrowing or closure in small airways may occur in patients with hepatic cirrhosis. These changes may be due to mechanical compression of small airways but interstitial edema which was induced by presence in the circulating blood of vasoactive substances and endotoxins.

Adult↗
PubMed1975

[Measurement of "flow-volume" curves and "closing volume" in occupational medicine. Normal findings in healthy subjects (author's transl)].

A method is described for measuring, by a single test, some functional respiratory indexes, such as lung volumes, dynamic tests (flow-volume curve included), rapid He and CO2 curves, "closing volume". The normal values of "closing volume" and of forced expiratory flows obtained in 114 healthy subjects (65 men and 49 women) are then reported. Such values are comparable to those obtained by other authors. An equipment is used by the authors which is easily transportable to the workplace; their method can therefore be used for surveys of workers exposed to occupational respiratory risk during a working shift. The described respiratory index should be able to detect in a pre-clinical stage the early functional changes in chronic bronchitis.

Adult↗
PubMed1975

Comparison of maximal mid-expiratory flow, flow volume curves, and nitrogen closing volumes in patients with mild airway obstruction.

Maximal mid-expiratory flow (MMEF), maximal expiratory flow volume (MEFV) curves obtained with a wedge spirometer, and nitrogen closing volumes were determined in 38 patients with mild airway obstruction. Seventeen patients had asthma in remission and 21 had bronchitis. In all of them the forced expiratory volume in one second was within the normal range. Results were compared with predicted data in the literature and with a group of normal control subjects. In the patients with asthma, compared to predicted flow rates, MMEF was abnormal in 5, MEFV curves were abnormal in at least 8; closing volume was abnormally increased in only one patient, and an abnormal slope of the alveolar plateau was present in 4 additional patients. In the patients with bronchitis, compared to predicted flow rates, -MEF was reduced in 5, MEFV curves were abnormal in at least 7; increased closing volumes were present in 6, and the slope of the alveolar plateau was abnormal in 3 other patients. When flow rates were compared with those of normal control subjects, MMEF was about as frequently abnormal as MEFV curves, suggesting that the discrepancy between abnormal MMEF AND MEFV curves was due to variability of the predicted data. The results indicated that flow rates can be abnormal in subjects with normal closing volumes and a normal slope of the alveolar plateau, and that MEFV curves can be more sensitive than closing volume in detecting abnormalities in patients with mild airway obstruction. The results suggested that the use of both MEFV curves and the closing volume test for screening would defect functional abnormalities more frequently than either test alone.

Adult↗
PubMed1978

Influence of lung volume history on closing volume measurement during anaesthesia.

Airway closure measurements were made with the bolus technique on eight healthy subjects, who were in a supine position prior to and during anaesthesia. Measurements were made on an expiration following vital capacity (VC) and 30% VC. Closing volume (CV) was calculated prior to anaesthesia, and closing capacity (CC)--functional residual capacity (FRC) was estimated during anaesthesia. When measured from VC, CV was 703 +/- 20 ml (s.e. mean) and from 30% VC it was 440 +/- 51 ml (s.e. mean) (P less than 0.005) prior to anaesthesia. When measured from VC, CC--FRC was 370 +/- 34 ml (s.e. mean), and from 30% VC it was 343 +/- 37 (s.e. mean) (P greater than 0.05) during anaesthesia. It is concluded that volume history has little effect on CC measurement during anaesthesia and artificial ventilation, but a major influence on CC measurement in the conscious patient. Hence, it is suggested that CC, within the tidal range, is increased during anaesthesia.

Aged↗
PubMed1975

Inflection point on transpulmonary pressure-volume curves and closing volume.

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express "airway closure," their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

Adult↗