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PubMed1974

Relation between pulmonary gas exchange and closing volume before and after substantial weight loss in obese subjects.

Relations between expiratory reserve volume (ERV), closing volume (CV) as a percentage of vital capacity (CV/VC%), and pulmonary gas exchange have been investigated in the sitting and supine postures in eight severely obese subjects before and after substantial weight loss. CV/VC% exceeded predicted values but did not change with posture or weight loss; the increase could have been owing to the smoking habits of the subjects. Arterial oxygen pressure (PaO(2)) was significantly less in the supine than in the sitting posture and improved after weight loss in six subjects. The reduction in PaO(2) was correlated with the extent to which dependent airways were closed within the range of tidal breathing, shown by increasing negativity of ERV-CV as a percentage of VC. A good correlation was also found between PaO(2) and ERV, an easier measurement for routine use. Improvement of pulmonary gas exchange occurred only in those patients who lost weight to within 30% in excess of ideal.

Adult↗
PubMed1975

Variability of closing volume measurements in normal man.

Single breath oxygen measurements of closing volumes were performed in triplicate in 15 healthy nonsmoking young adults 3 times per day for 5 consecutive days. The purpose of the investigation was to determine the degree of variability in this test of lung function and, if possible, to specify its cause. The results demonstrated that sizable differences in the absolute volume for closing volume and for closing volume as a percentage of vital capacity can be present from trial to trial in any given person even though the technical aspects of the procedure are seemingly highly standardized. The reasons for this were found to be a combination of (1) the inherent variation in the expired volume that marked the onset of airway closure, (2) reader difficulties in detecting the onset of phase IV, and (3) variations in the expired vital capacity due to incomplete filling and/or emptying of the subject's lungs. The differences were not due to daily or diurnal rhythms or to a training effect.

Adult↗
PubMed1981

Closing volumes with variations in pulmonary capillary wedge pressure.

Increased closing volumes have been documented in patients in whom there was suspected to be early pulmonary edema due to increased pulmonary capillary wedge pressure. However, the relationship between the actual pulmonary capillary wedge pressure and closing volume has not been established. To attempt to define this relationship and to determine whether the closing volume might be a useful indicator of the onset of pulmonary edema, we measured the closing volume in dogs while sequentially increasing the pulmonary capillary wedge pressure by way of a left atrial balloon. We found a small but significant increase in closing volume (p less than 0.01) when a pulmonary capillary wedge pressure of 25 mm Hg was achieved, and it was at this pressure that pulmonary edema would hypothetically be expected to begin.

Animals↗
PubMedDate not supplied

[Closing volume and inhomogeneity of the ventilatory mechanical system (author's transl)].

The use of the closing volume (VF) to detect small airway lesions is based on physiological data : it would reflect a special and physiological distribution of the pulmonary inhomogeneity. The aim of this work is to discuss the closing volume as used to determine a pathological process or, in other words, the relationship between the observed profile of closing volume and other functional parameters, whose abnormalities are likely to reflect the inhomogeneity of the ventilatory mechanical system. In 126 patients, who represent a wide range of pathological processes, the authors calculated the closing volume and the following functional parameters : the VC/theoretical VC ratio, the RV measured by dilution method and by plethysmography, the FEV1.0/VC ratio, the expiratory total pulmonary resistance (RPTE), the efficient resistance (R), the airway resistance (Raw), the effective compliance (Ce) measured at the spontaneous respiratory frequency, and its variation in relation with respiratory frequency (f), and a distribution index of inspired gas. After discussion of the procedure and of the reproducibility of the closing volume measurements, the authors recall the significant of the lack of phase IV during the closing volume estimation and expose the reasons which allow to think that closing volume extent and inhomogeneity of the ventilatory mechanics have a parallel evolution. The increase in distribution inhomogeneity of the pulmonary time constants (shown by the slope of the Ce variation in relation with f and gas distribution index) is concomitant with an increase in closing volume. The results show that although the lack of phase IV does not have a univocal signification (and this is a limit to the utilization of the closing volume alone as a detection test) the quantification of the closing volume brings, as the Ce, f relation does, an original element, but the evaluation of Ce, f is more difficult to realize in practice.

Humans↗
PubMed1987

Closing volume after inspiratory resistive loading to fatigue.

Closing volume was measured by the single breath nitrogen washout test in six normal subjects both before and after inspiratory resistive loading to fatigue. Subjects breathed through an inspiratory resistance until they could no longer maintain the required mouth pressure throughout inspiration. There was electromyographic evidence of diaphragmatic fatigue in all experiments. Closing volume (expressed as a percentage of vital capacity) after resistive loading to fatigue (10.1 +/- 1.9%) was not significantly different from that before resistive loading (10.5 +/- 1.7%). Because pulmonary edema increases closing volume, this study suggests that the very negative intrathoracic pressures generated during resistive loading do not cause pulmonary edema. Therefore, the rapid shallow breathing following inspiratory resistive loading to fatigue is not due to pulmonary edema but is probably a direct consequence of fatigue.

Adult↗
PubMedDate not supplied

Nitrogen and bolus closing volumes: the effect of beta-agonist bronchodilator aerosol.

Studies of the effect of beta-agonist bronchodilators on closing volume in normal subjects have produced conflicting results. We studied the possibility that these differences might be due to the different methods of measuring closing volume. We measured closing volume by both the nitrogen washout and the bolus techniques in 19 healthy nonsmoking adults before and after inhalation of salbutamol aerosol. Prior to salbutamol, closing volume measured by the nitrogen method (N2 CV) was significantly smaller (p less than 0.02) than the closing volume measured by the bolus method (bolus CV). After salbutamol inhalation, N2 CV increased significantly (p less than 0.05); however, bolus CV did not change, so that following inhalation of salbutamol there was no significant difference between N2 CV and bolus CV. The increase in N2 CV after salbutamol inhalation was associated with an increase in the slope of phase IV (p less than 0.05). We suggest that beta-agonist bronchodilator aerosol has no effect on closing volume in normal individuals and the apparent increase in N2 CV after bronchodilator is probably an artefact.

Adrenergic beta-Agonists↗
PubMed1976

Closing volumes in man immersed to the neck in water.

Closing volumes (CV), along with residual volume (RV), vital capacity (VC), along with residual volume (RV), vital capacity (VC), and expiratory reserve volume (ERV) were determined in 10 subjects in the dry and while immersed to the neck in water. Closing volumes during immersion increased 41.3% (P less than 0.001) over dry values while RV decreased 9.35% (P less than 0.001) and VC decreased 9.94% (P less than 0.001). The large decrease of 71.3% (P less than 0.001) in ERV resulted in the impingement of closing capacity (CV + RV) on the tidal volume in 9 out of 10 subjects. We interpret this to mean that airway closure occurs during tidal ventilation in immersed subjects and may result in impaired gas exchange. When tourniquets were applied to all four limbs during immersion closing volumes increased only 32.1%, but increased to 64.3% when they were removed. If engorgement of peribronchial vessels predisposes airways to collapse, a reduction of plasma volume during an extended period of immersion might lessen this possibility. In a series of long term (2.5-h) immersion experiments where moderate reductions (-10 to -7%y in plasma volume were observed, we found, however, no correlative changes in closing volume.

Adult↗
PubMed1975

Appraisal of a new test: Between-technician variation in the measurement of closing volume.

To determine the between-technician variation in the measurement of closing volume, 24 subjects were divided into 3 blocks of 8 subjects each. Each block was then tested by a pair of technicians. Each of the 3 technicians involved in the study tested 16 subjects. It was later necessary to reject the tracings of 2 subjects in one of the 3 blocks, leaving 22 for analysis. The N2 method of determining closing volume was used. The statistical analysis was performed separately on the following measures derived from the tracings: expired vital capacity, planimetry of the area under the curve, total lung capacity, closing volume as a per cent of expired vital capacity, and closing capacity as a per cent of total lung capacity. All tracings were assessed by each technician. Two separate analyses of variance were then carried out to determine, respectively, the components of variance in the administration of the test and in the interpretation of the tracings. Because different persons were able to administer the test the same way, it seems that closing volume poses no problem in administration, provided that instructions as to how to perform the test are closely followed. In the interpretation of the tracings, significant differences were found for all measures, except planimetry; however, not all of these have the same practical implications. Some tracings were found "difficult" to interpret and contributed more to the over-all variation than did others. When making use of a new test in a population study, the between-technician variation should be determined before the study is begun.

Humans↗
PubMed1976

Added apparatus dead space in the N2-closing volume test: - a refinement or a bias.

14 subjects without symptoms of cardiopulmonary disease underwent paired closing volume determinations by the modified single breath nitrogen test. Measurements were performed with an apparatus dead space of approximately 40 ml and approximately 350 ml. A rise in closing volume percent for all subjects was found in measurements with dead space of 350 ml. This Difference was statistically significant at the 0.001 level for the group as a whole. No change in the accuracy of the method, expressed as the standard deviation of each subjects values with and without added dead space cojld be demonstrated. Linear regression analysis of the closing volume percent values measured with added dead space as a function of closing volume percent values measured without added dead space showed the expected highly significant positive correlation. However the regression line was not parallel to line of identity, indicating that the higher the initial value of closing volume percent the higher rise after addition of apparatus dead space. With reference to characterizing a person as normal or abnormal this could be considered a refinement of the method.

Adult↗
PubMed1975

[Comparison between the closing volume comportments and the Vmax/V curve in patients with obstruction of the small airways].

Three groups of patients with obstruction of the small airways and normal main airways were submitted to study by determining the closing volume and the V max/V curve. In the first group (beginning chronic bronchitis) was noted an alteration of the curve with normal closing volume in almost all the cases; in the second group (asthma in the remission phase) the closing volume was increased and the curve normal in a part of the patients, -while in the other part the closing volume was normal and the curve altered; in the third group (recent heart infarct), a significative increase in the closing volume was noted with a slightly altered curve: improvement of the tests was obtained after administration of diuretics, the improvement being far more noticeable for the closing volume than for the V max/V curve. The closing volume is therefore an extremely sensitive test of the obstruction of the small airways when the obstruction interests before all the basal zones of the lungs. When the resistances of the small airways are irregularly distributed, the determination of the V max/V curve is, conversely, more useful.

Asthma↗
PubMed2000

Closing volume influences the postural effect on oxygenation in unilateral lung disease.

In normal adults, both blood flow and ventilation are distributed preferentially to the dependent lung zones. In adults with unilateral lung disease, arterial oxygenation improves when they are positioned with their good lung down because of improved matching of ventilation and perfusion. When the closing volume is increased, dependent airways are closed during tidal breathing, so that reduced ventilation-perfusion ratio and hypoxia develops and ventilation is preferentially distributed to the upper lung zones. We undertook an observational study on the effects of lateral recumbency on arterial oxygenation in adult patients with unilateral lung disease and tested the hypothesis that oxygenation in lateral recumbency might be influenced by an increase in closing volume. Arterial blood gases were analyzed in the supine, right and left lateral decubitus positions and the AaPO(2) was calculated in 44 randomly selected patients 49.9 +/- 18.7 yr of age with unilateral pneumonia (23 cases) or pulmonary tuberculosis (21 cases). In 26 patients, individual Pa(O(2)) with the normal lung in the dependent position was higher than that with the diseased lung; the opposite was true for 18 patients. The difference in Pa(O(2)) and AaPO(2) between the two positions was statistically significant in both groups. In 16 patients (10 men and six women 49.2 +/- 18.2 yr of age), we measured closing volume and determined the fractional ventilation to each lung by (133)Xe lung scan in the three positions. In these 16 patients, the difference in Pa(O(2)) between the normal and the diseased lung in the dependent position was related significantly to the difference in the fractional ventilation going to the normal lung between the dependent and the supine position (r = 0.642, p = 0. 007). The latter was related significantly to the % predicted closing volume (CV/VC) (r = -0.597, p = 0.015). This study has shown that closing volume, as well as posture, might be involved in determining oxygenation in lateral recumbency in patients with unilateral lung disease.

Adolescent↗
PubMed1975

Variability of the closing volume measurement in normal subjects.

The repeatablilty of the measurement of closing volume (nitrogen method) in healthy, normal subjects was investigated. At least 7 consecutive measurements at 5-min intervals were made in each of 22 subjects. The mean coefficient of variation for the absolute volume of phase IV was 36.1 per cent and for the percentage ratio of phase IV to vital capacity, 36.1 per cent. Repeated measurements by the same observer of the same records on various days did not differ significantly (P greater than 0.5). There was a significant difference (P less than 0.05) between 2 observers measuring the same records, but there was no significant difference between the two observers in the variance of the closing variability in the same subject, it may be necessary to perform several closing volume maneuvers in each subject to establish his or her range before changes in the closing volume can be interpreted.

Adult↗
PubMedDate not supplied

Diurnal variations and reproducibility of the N2 closing volume test in healthy subjects.

To assess the diurnal variation of closing volume measurements, 11 non-smokers and 10 somkers, all healthy, were tested with the single-breath nitrogen test. In each subject, 3 satisfactory tracings were recorded at 9:a.m., 11:a.m., 1:p.m., 3:p.m. and 5:p.m. on each of two consecutive days. Duplicate copies of the tracings were read in radom order by two independent observers. The "best+ and the mean values of closing volume to vital capacity ratio (CV/VC or phase 4/VC) and of the slppe of phase 3 were calculated. The study shows that: (1) the time of the day may be a source of variation of the closing volume measurements. Meals and cigarette smoke did not appear to be responsible for this diurnal variation, (2) values obtained with the "best" tracing method can, at least in some readers, give systematic differences with the mean of several traces, (3) individual variations in CV/VC and in the slope of phase 3 are the highest with the "best" trace analysis, and (4) the vlaues obtained by two independent readers may significantly differ. The differences observed between hours, although significant, were nevertheless small in magnitude and did not explain most of the variation of the measurements. Variations in trace aspect were small in some subjects. The reproducibility of the test was remarkable in them, at least when the junction of phase 4 with phase 3 was well defined. In other subjects, the coefficient of variation was high mainly because of varying curve shape and/or poorly defined departure of phase 4. This explains for a great part the intra-and interreader variations observed in this study.

Adult↗
PubMed1975

Nitrogen and bolus closing volumes: differences after histamine-induced bronchoconstriction.

Studies in normal subjects have shown that there is little difference in the size of the closing volume when measured by either the nitrogen methods or a bolus method. In this study we have examined the changes in closing volume following histamine-induced bronchoconstriction. In five normal subjects histamine resulted in a reduction in the vital capacity, an increase in the residual volume, and an increase in the airway resistance. The size of the closing volume measured by a bolus method increased after induced bronchoconstriction (0.52 +/- 0.15 1 to 0.74 +/- 0.17 1). With the nitrogen method the closing volume became smaller (0.51 +/- 0.19 1 to 0.17 +/- 0.17 1). Similar differences between the two methods are demonstrated in patients with asthma. The suggested explanation for these differences lies in the different methods used to establish a concentration gradient of gas in the lung. If there is "air trapping" the nitrogen method may fail to establish a concentration gradient.

Adult↗
PubMed1991

[Comparative methodologic studies of closing volume and increase in airway resistance volumes].

The early recognition of obstructive lung diseases plays an important role in the subsequent therapy; the closing volume, determined by means of single-breath oxygen test has been established as a suitable parameter. This technique, however, has not succeeded as a routine method due to prohibitive costs. In a clinical study the closing volume and the easier estimatable so-called flow-resistance elevation volume (Ros-volume-curve parameter obtained from oscilloresistometry/volumetry) were compared and a correlation sought. It could be concluded, that for characterization of small airways diseases the closing volume is a more suitable parameter than the flow-resistance elevation volume.

Adolescent↗