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Results for “Closing Volume”

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At least 19 recordsLinked to original sources
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↗
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↗
PubMed1976

Closing volume in coal miners.

Closing volume and closing capacity were determined in 82 working Appalachian coal miners and in a comparable group of control subjects. Abnormalities of closing volume and closing capacity were related to other measurements of pulmonary function. The relationship of smoking history, dust exposure, and presence of pneumoconiosis and bronchitis to elevations of closing volume and closing capacity was determined. It was shown that nonsmoking miners had elevated closing volume and closing capacity when compared to control subjects. Miners who were smokers or ex-smokers also had elevated closing capacity when compared to control subjects. Neither bronchitic symptoms nor the radiographic presence of pneumoconiosis were associated with an elevation of closing volume or closing capacity.

Bronchitis↗
PubMed1976

Epidemiological limitations of the nitrogen closing volume test.

Closing volume was measured in 216 men aged 46-68 years. They were divided in 5 age groups and classified as either symptomatic or asymptomatic according to answer to standardized interviews. In 3 of 5 age groups mean value for closing volume percent (CV%) for symptomatic persons was lower than the mean value for asymptomatic persons. CV% is not considered useful as the dependent variable in a multiple regression analysis. In all 5 age groups the mean value of slope of alveolar plateau was higher for symptomatic than for asymptomatic persons. Slope af alveolar plateau is considered useful as dependent variable in a multiple regression analysis. One of the reasons for the false negative CV%-values is believed to be influence of increased uneven and sequential ventilation of the lungs, expressed in the slope of alveolar plateau.

Aged↗
PubMed1977

Difference between the He bolus and N2 technique for measuring closing volume.

We measured closing volume in sixteen healthy subjects simultaneously and separately with a bolus of He (using a rapid catharaometer) and with the N2 technique. In another group of 35 active workers (some with airway obstruction), closing volume was measured separately with those two methods. In both groups the He closing volume was significantly higher than the N2 closing volume. We attribute this difference to a less marked vertical N2 concentration gradient, leading to a less clearly defined separation between phase III and IV and resulting in an underestimation of the N2 closing volume. Indeed, increasing the N2 gradient in the lung, by inspiring O2 from a higher than residual volume level, increased the N2 closing volume which became comparable to the He closing volume. We also found, for both He and N2 tracings, a significant between-observers difference in reading of the closing volume. However, the difference in reading of ts difference in reading of the closing volume. However, the difference was less important for He closing volumes. We conclude that the bolus method improves the resolution of closing volume and decreases the interobserver variability.

Adult↗
PubMed1978

Effect of the slope of the alveolar plateau on determination of closing volume.

Repeated closing volume (CV) determinations were obtained simultaneously with the nitrogen method (CV-N2) and with a helium bolus method (CV-He) in 19 selected subjects with normal routine spirometry. Ten subjects had normal slopes of phase III and nine had abnormally steep slopes of phase III obtained with the nitrogen method. No systematic difference was found between CV-N2 and CV-He irrespective of the steepness of phase III, which seems to indicate that at least in spirometrically normal subjects airway closure is adequately assessed by the nitrogen method - even in the presence of a steep slope of phase III.

Closing Volume↗