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PubMed2000

Recurrent exacerbations in severe asthma are associated with enhanced airway closure during stable episodes.

Excessive airway narrowing is a cardinal feature of asthma, and results in closure of airways. Therefore, asthmatic patients in whom airway closure occurs relatively early during expiration might be prone to severe asthma attacks. To test this hypothesis, we compared closing volume (CV) and closing capacity (CC) in a group of asthmatic patients with recurrent exacerbations (more than two exacerbations in the previous year; difficult-to-control asthma), consisting of 11 males and two females, aged 20 to 51 yr, with those in a group of equally severely asthmatic controls without recurrent exacerbations (stable asthma) consisting of 13 males and two females aged 18 to 52 yr. Both groups used equivalent doses of inhaled corticosteroids and were matched for sex, age, atopy, postbronchodilator FEV(1), and provocative concentration of methacholine causing a 20% decrease in FEV(1). They were studied during a clinically stable period of their disease. The patients inhaled 400 microg salbutamol via a spacer device, after which TLC and RV were measured by multibreath helium equilibration, together with the slope of Phase 3 (dN(2)), CV, and CC, by single-breath nitrogen washout. CV and CC were expressed as ratios of VC and TLC, respectively, and all data are presented as % predicted (mean +/- SEM). There was no difference in TLC in patients with difficult-to-control asthma and those with stable asthma (106.7 +/- 4.0% predicted versus 101.7 +/- 4.3% predicted, p = 0.40), RV (113.1 +/- 7.8% predicted versus 100.9 +/- 7.1% predicted, p = 0.26), or dN(2) (142.7 +/- 16.3% predicted versus 116.0 +/- 20.2% predicted, p = 0.23). In contrast, CV and CC were increased in the patients with difficult-to-control asthma as compared with the group with stable asthma (CV: 159.5 +/- 26.8% predicted versus 98.8 +/- 12.5% predicted, p = 0.024; CC: 114.0 +/- 6.4% predicted versus 99.9 +/- 3. 6% predicted, p = 0.030). These findings show that asthmatic individuals with recurrent exacerbations have increased CV and CC as compared with equally severely asthmatic but stable controls, even after bronchodilation during well-controlled episodes. The findings imply that airway closure at relatively high lung volumes under clinically stable conditions might be a risk factor for severe exacerbations in asthmatic patients.

Adolescent↗
PubMedDate not supplied

[Effects of body posture on mechanical lung function in the obese patient].

The pulmonary mechanics of twelve obese patients were studied: the static and dynamic compliance, the maximum pressure of elastic recoil, and the expiratory flow curves breathing room air and a mixture of He-O2. Also analyzed were the closing capacity, the closing volume and the slope of the alveolar plateau (phase III), in the erect and supine positions. Our data confirm that the tests that explore the small airways are abnormal in the obese patients. The results obtained, allow us to assure that the pulmonary mechanics in the obese patients are affected by the change of position, as is shown by the closing volume and closing capacity when assuming the supine position when compared to orthostatism, as well as the decrease in vital capacity. These alterations were not found in non-obese patients which were used as controls.

Adult↗
PubMed1977

[Influence of body position on human gas exchanges. Role of age (author's transl)].

We measured blood gases, steady state diffusing lung capacity, global and partial lung ductances in 16 subjects aged from 20 to 63 in supine and seated position. We obtained three types of response. In group I, (n = 6) blood gases and TLCO increased probably chiefly due to an increase of perfusion of lung apices and a more even distribution of regional VA/Q (all these subjects are young and thin). In group II, (n = 4) blood gases and TLCO decreased probably due to a ventilation at closing volume level with a decrease of ventilation in the dependent parts of the lung (2 subjects with abdominal obesity and a third who is the oldest one). In group III (n = 7), PaO2 decreased but DLCO increased. Probably ventilation took a slight place in closing volume. The increase of the exchange surface area is likely to be unable to compensate the arterial hypoxemia induced by the low VA/Q in the dependent parts of the lung. Influence of body position seems to be a function of age which increases closing volume.

Adult↗
PubMed1994

Mechanisms of reduced pulmonary function after a saturation dive.

Deep saturation diving has been shown to have prolonged effects on pulmonary function. We wanted to assess the relative contribution of various factors that could contribute to these effects. Pulmonary function was, therefore, measured before and after 17 different saturation diving operations to depths of 5-450 m of sea water, corresponding to absolute pressures of 0.15-4.6 MPa. Four to fifteen divers participated in each operation. The measurements included static and dynamic lung volumes and flows, transfer factor of the lungs for carbon monoxide (TLCO), and closing volume. The dives were characterized by the cumulative hyperoxic and hyperbaric exposures, and the load of venous gas microemboli encountered during decompression was measured in 41 divers in three dives to 0.25, 1.2 and 3.7 MPa. TLCO was reduced by 8.3 +/- 7.0% mean +/- SD after the dives, this correlated with cumulative hyperoxic exposure and load of venous gas microembolism, independently of each other. Closing volume was increased and forced mid-expiratory flow rate reduced, in correlation with cumulative hyperoxic exposure. An increase in total lung capacity correlated with cumulative hyperbaric exposure. We conclude that hyperoxia, hyperbaria, and venous gas microembolism all contribute to the changes in pulmonary function after a single saturation dive, and all may explain some of the long-term effects of diving on pulmonary function.

Adult↗
PubMed1976

Effect of modification of the smoking habit on lung function.

The effect of smoking cessation or modification on lung function was determined during a 48-week period. In a large number of the cigarette smokers, a disturbance of lung function was not revealed by conventional tests, such as the 1-sec forced expiratory volume; however, an abnormality was often demonstrable in tests that may reflect alterations in small airways, such as closing volume and Phase III of the single-breath expired N2 curve. There was no relation between the degree of abnormality of lung function and the presence of respiratory symptoms, but there appeared to be a relationship to lifetime smoking history, the heaviest smokers having the poorest function. Cessation, or more than 25 per cent decrease in the number of cigarettes smoked, was attened by improvement in the slope of Phase III of the N2 washout curve, closing volume, and closing capacity, as well as forced vital capacity, 1-sec forced expiratory volume, and peak flow. Resumption of smoking after cessation was attended by a deterioration in the slope of Phase III and closing capacity. The data suggest that the functional abnormalities in smokers are related to smoking and are at least partially reversible by cessation or significant modification of the smoking habit.

Adolescent↗
PubMed1984

The UCLA population studies of chronic obstructive respiratory disease. VIII. Effects of smoking cessation on lung function: a prospective study of a free-living population.

We evaluated effects of smoking cessation on lung function and respiratory symptoms of residents 25 to 64 yr of age from 3 communities in the Los Angeles area who completed a detailed respiratory questionnaire and measurements of forced expired volumes and flow rates, closing volume, and closing capacity at 2 times (T1 and T2) 5 yr apart. Results were analyzed in 2,401 participants who fit into 4 smoking categories: never smokers (414 males, 737 females); former smokers (294 males; 172 females); quitters between T1 and T2 (106 males, 62 females); and continuing smokers (278 males, 338 females). Covariance analysis was used to determine differences in lung function across smoking categories at T1 and T2 (adjusted for T1 values) and differences in decline in lung function between T1 and T2. Chi-square analysis was used to compare continuing smokers and quitters with respect to changes in respiratory symptoms. In this population, smoking at T1 was associated with impairment in all indexes of lung function evaluated. Smoking cessation led to significant improvement in symptoms of cough, wheeze, and phlegm production, and to significantly less decline in indexes of small airway function during 5 yr compared with measurements in continuing smokers. However, at T2, lung function still was lower among quitters compared with former and never smokers. Forced expiratory volume in one second (FEV1) was marginally improved in women who quit compared with those who continued to smoke.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1980

Nitrogen single breath test, flow-volume curves and spirometry in healthy children, 7-18 years of age.

One hundred and forty school children, 75 boys and 65 girls, aged 7-18 years, underwent the following lung function tests: closing volume, slope of the alveolar plateau, maximal expiratory and inspiratory flows at 75, 50 and 25% of vital capacity, static and dynamic lung volumes. Lung volumes and maximal flows increase with height in an exponential way, the exponents varying between 2.6 and 3.1, while closing volume in per cent of vital capacity and the slope of the alveolar plateau decrease linearily with increasing height. Regression equations are given for each sex with height as determinant.

Adolescent↗
PubMed1996

Computerized single-breath nitrogen washout: predicted values in a rural French community.

Comparative manual and computer measurements of the alveolar N2 slope and closing volumes have indicated systematic differences. When a computerized system is used in field surveys, predicted values are to be obtained under the same conditions. Therefore, we measured the alveolar nitrogen slope (phase III, PIII), closing volume (CV), and closing capacity (CC) from single-breath N2 washout maneuvers in 158 healthy subjects (68 females), ages 21 to 64 years, from a rural community living in a nonpolluted area of northeast France. PIII, the CV to vital capacity ratio (CV:VC, %), and the CC to the total lung capacity ratio (CC:TLC, %) were regressed against age, height, weight, and the body mass index (BMI, kg/m2) and prediction equations with 95% confidence intervals were computed. PIII increased with age in both sexes and tended to decrease with height in males (r = -0.19, p = .08). The CV:VC and CC:TLC ratios depended on age and, in males, increased with the BMI. Despite accepting a 15% difference between the test VC and the spirometric VC, only 46.3% of asymptomatic nonsmokers produced a valid single-breath nitrogen washout (SBN2) test. This high failure rate limits the usefulness of the test for epidemiologic purposes when older populations "naive" to pulmonary function testing are studied under field-survey conditions.

Adolescent↗
PubMed1982

Response to the central and peripheral airways to cigarette smoking in human and rats.

The effects of tobacco smoke on the central nd peripheral airways were assessed in humans and rats by direct and indirect methods. In both species tobacco smoke affected the central and peripheral airways. In humans there were apparent decreases in the 1-second forced expiratory volume, peak expiratory flow rate and significant increases in closing volume and closing capacity (P less than 0.001). In rats significant changes were seen in specific airway resistance from the 6th week of exposure onwards. Similarly, airway luminal diameter decreased markedly in tobacco-exposed animals to subthreshold concentrations of acetylcholine (10(-8) M). This decrease was also exposure time dependent. The increased responsiveness of the respiratory system has been attributed to inter alia: (1) increased vagal activity; (2) increased mucus production leading to decreased airway lumen; (3) mucosal swelling due to changed ionic constellation; (4) disturbance of the lungs' defense mechanism; (5) imbalance in and easy accessibility to the adrenoceptors.

Adult↗
PubMed2000

Upright body position and weight loss improve respiratory mechanics and daytime oxygenation in obese patients with obstructive sleep apnoea.

To determine whether upright body position and weight loss would improve daytime gas exchange in moderately obese patients with obstructive sleep apnoea (OSAS), 13 patients with mild or moderate OSAS were studied before and after weight loss. Pulmonary function tests, arterial blood gases and respiratory gas analysis were measured prior to and after a very low calorie diet (VLCD) period of six weeks. Arterial blood gases were measured in supine and standing positions and closing volume in supine and sitting positions before and after weight loss. In the upright position, there was a significant increase in PaO2 (P<0.005) accompanied by a significant decrease in alveolar-arterial PO2 difference (P<0.005) and closing volume (P<0.05). The median weight loss was 11 kg (range 5-18). The number of desaturation episodes (four percentage units or more per hour during sleep) (ODI4) decreased (P<0.01) after weight loss. The change in PaO2 with weight loss correlated with the decrease in ODI4 (r=0.73, P<0.01). The increase in expiratory reserve volume (ERV) was closely related to the amount of weight lost (r=0.895, P<0.01). The results indicate that weight loss and upright body position improved daytime respiratory mechanics and gas exchange in obese patients with OSAS. The findings suggest that obesity plays an important role in the pathogenesis of daytime gas exchange disturbances in obese OSAS patients. The adoption of a more upright sleep posture might improve nocturnal oxygenation in obese patients with OSAS.

Adult↗
PubMed1988

High-frequency oscillatory ventilation may increase airway closure.

In five seated, normal subjects, we measured closing volumes using 133Xe boluses inhaled at residual volume. High frequency oscillatory ventilation (HFOV) (15 Hz, 2 cc/kg) was applied during either inspiration to total lung capacity or the subsequent expiration. Closing volume was increased (P less than 0.001) when HFOV was applied during the latter half of expiration, but not when HFOV was applied during inspiration or the first half of expiration. Subsequently, in seven subjects, we measured the regional distributions of 133Xe boluses delivered during open-glottis breath-hold at 14% vital capacity after equilibration with N2O. HFOV was applied during bolus delivery for about 16 sec. These distributions were compared with those achieved by intravenous injections of 133Xe in saline. Regional perfusion (injected isotope) exceeded regional N2O uptake at the lung bases and this was significantly accentuated by HFOV, compatible with increased basal closure. We conclude that in normal subjects at low lung volumes, HFOV may enhance airway closure, though other explanations are possible.

Administration, Inhalation↗
PubMed1980

Reproducibility of pulmonary function tests under laboratory and field conditions.

The reproducibility of pulmonary function tests in the laboratory and in a mobile field survey vehicle has been studied. Groups of laboratory workers were studied at base and a random sample of 38 coalminers was examined in the mobile laboratory. The intra-subject variability of some newer tests of lung function, including closing volume and maximum flow at low lung volumes, has been compared with that of well-established tests, such as lung volumes and forced expiratory volume from two measurements made more than one day apart. Most measurements were slightly less reproducible in the study of coalminers than in the laboratory personnel. Conventional tests, such as forced expiratory volume in one second, lung volumes, single breath CO transfer factor, and exercise ventilation were very reproducible, the coefficients of variation (cov) being generally between 5% and 10%. The closing volume test, maximum expiratory flow at low lung volumes, and the single breath N2 index were less reproducible: cov between 15% and 39% in the miners. The forced expired time and volume of isoflow, measured only on laboratory workers, however, exhibited greater reproducibility than previously reported (cov = 10% and 15% respectively). It is suggested that, when assessing the repeatability of lung function tests, account should be taken of the circumstances in which the intra-subject variability was measured.

Adolescent↗
PubMed1992

The influence of obesity and underweightness on respiratory function of geriatric patients undergoing surgery.

We investigated the influence of obesity and underweightness on the respiratory function of 228 patients over 65 ys. old undergoing elective surgery. The parameters we studied were preoperative Pa(O)(2) (Pa(O)(2)-pre), Pa(O)(2) under general anesthesia (Pa(O)(2)-op) and preoperative spirometric values including data from flow-volume curves and closing volumes. Triceps skinfold thickness (TSF), body mass index (BMI), Broca's index (BI) and Onodera's prognostic nutritional index (PNI) were measured or calculated. Respiratory parameters were compared between 3 groups; overweight (BMI >23), normal weight (BMI 20-22), underweight (BMI <19). Single and multiple correlations were analyzed between 3 nutritional parameters (BMI, TSF, PNI) and respiratory values. As a result, Pa(O)(2)-pre and Pa(O)(2)-op in overweight group were lower than those in the other groups. None of other parameters showed significant differences between the 3 groups. In multiple regression analysis, BMI correlated with Pa(O)(2)-pre (r = -0.24), Pa(O)(2)-op (r = -0.43), %VC (r = 0.18), peak flow rate (PFR, r = 0.17) and V(50)/HT (r = 0.18). TSF correlated with Pa(O)(2)-pre (r = -0.22), %MVV (r = -0.28) and RV/TLC (r = 0.28). PNI correlated with PFR (r = 0.23). We concluded that overweightness has greater influence on respiratory function of elderly patients than underweightness and that arterial blood gas analysis is essential in preoperative assessment of obese geriatric patients.

Journal Article↗
PubMed1977

New lung functions and pregnancy.

Newer lung function tests (e.g., flow volume-loops and closing volume), as well as standard pulmonary function tests, were performed on 19 healthy individuals in the third trimester and after delivery. We found that the flow characteristics, manifested in the FVL, and the CV remained unaltered during pregnancy. In regard to the standard pulmonary function tests, we found no statistically significant change except for a decrease in the ERV and in the FRC during pregnancy.

Adolescent↗
PubMed1980

Response of the lung airway to exercise testing in asthma and rhinitis.

The reactivity of the large and small airways of the lung in a group of ten atopic subjects with rhinitis was compared with that in ten non-atopic control subjects and in 17 with atopic asthma. Atopic state was assessed by skin prick testing with 22 common allergens and by measurement of total serum immunoglobulin E (IgE) antibody. The atopic state of the rhinitis and asthma patients was similar. Exercise provocation tests were performed on each subject and changes in airway function were measured by peak expiratory flow rate, forced expiratory volume in one second, vital capacity, maximal expiratory flow volume curves and closing volume. There were no statistically significant differences between the changes in lung function after exercise in the rhinitis patients compared with the controls. There were, however, statistically significant changes in all the measurements of respiratory function in those with asthma compared with the other two groups. The falls in forced expiratory flow rates in the asthmatic subjects were greater at lower lung volumes than near the total lung capacity, perhaps indicating that narrowing of small, as well as large, airways was occurring. No correlation was found between the magnitude of the airway response to exercise and either the total serum IgE antibody or the mean weal diameter of positive skin tests in each subject. Atopic subjects with rhinitis but not asthma showed no evidence of bronchial hyper-reactivity on exercise testing. It is therefore suggested that single exercise provocation test can discriminate subjects with atopic asthma from those with other atopic disorders.

Adult↗
PubMed1983

The lung sounds phase angle test for detection of small airway disease.

Nineteen normal subjects and fifteen smokers with minimal symptoms were studied. All subjects performed spirograms, maximal expiratory flow volume (MEFV) maneuvers both breathing air and 80% He and 20% O2 mixture, pressure-volume maneuvers, and single breath N2 washout curves with preceding thoracic gas volume, from which closing capacity (CC), closing volume (CV), and slope of phase III (delta N2) were computed. Pulmonary resistances (RL) and compliances (CL) at various breathing frequencies were also measured. The sequence of breath sounds during the inspiratory phase of tidal breathing as assessed by lung sounds (lung sounds ventilation sequence indices (theta) was measured between two positions from various parts of the right lung in the same horizontal level. None of the normal subjects had a mean theta larger than 5 degrees. Eleven out of 15 smokers had a mean theta greater than 5 degrees. The mean theta correlated significantly with CLdyn/CLst, but not with CC, CV, delta Vmax50, delta N2 and FEF25-75. It is concluded that theta is an index of intraregional inhomogeneity of time constants.

Adult↗
PubMed2004

Small aortic annulus: the hydrodynamic performances of 5 commercially available bileaflet mechanical valves.

OBJECTIVE: Hemodynamic performances of mechanical valve prostheses in patients with aortic valve stenosis and a small aortic annulus are crucial. We analyzed the in vitro hydrodynamics of 5 currently available bileaflet mechanical prostheses that fitted a 21-mm-diameter valve holder of a Sheffield pulse duplicator. METHODS: Three samples of 5 high-performance production-quality prostheses, including the sewing ring cuffs, were tested in the aortic chamber of a Sheffield pulse duplicator. Sizes of the prostheses fitting the 21-mm valve holder were as follows: 18-mm ATS, 19-mm SJM Regent, 19-mm Sorin Bicarbon Slimline, 19-mm On-X, and 21-mm Carbomedics Top Hat. The tests were carried out at a fixed pulse rate (70 beats/min) and at increasing cardiac outputs of 2, 4, 5, and 7 L/min. Each valve was tested 10 times for each different cardiac output. This resulted in a total of 40 tests for each valve and 120 tests for each valve model. The aortic pressure was set at 120/80 mm Hg (mean pressure, 100 mm Hg) throughout the experiment for all cardiac outputs. Forward flow pressure decrease, total regurgitant volume, closing and leakage volumes, effective orifice area, and stroke work loss were recorded while the valve operated under each cardiac output. RESULTS: The SJM Regent valve and the Sorin Bicarbon Slimline prosthesis showed the lowest mean and peak gradients at increasing cardiac outputs. The closure volume was higher for the SJM Regent and Sorin Bicarbon Slimline prostheses, unlike with the ATS prosthesis at 7 L/min of cardiac output. The ATS and SJM Regent prostheses showed the largest regurgitant volume, whereas the Sorin Bicarbon Slimline prosthesis showed the lowest regurgitant volume. The calculated effective orifice area and stroke work loss were significantly better with the SJM Regent and Sorin Bicarbon Slimline prostheses. CONCLUSION: Assuming that the 21-mm valve holder in which all the tested prostheses were accommodated is comparable with a defined aortic valve size, this hydrodynamic evaluation model allowed us to compare the efficiency of currently available valve prostheses, and among these, the SJM Regent and the Sorin Bicarbon Slimline exhibited the best performances.

Aortic Valve↗
PubMed2006

Do changes in lung function predict high-altitude pulmonary edema at an early stage?

PURPOSE: Ascent to high altitude is associated with alterations in lung function. The mechanisms of these changes and whether they reflect early stages of high-altitude pulmonary edema (HAPE) has been debated. Therefore, we investigated the time course of pulmonary function in relation to hemodynamics and clinical symptoms in mountaineers ascending rapidly to high altitude. METHODS: In 26 unacclimatized subjects we assessed spirometry, single-breath nitrogen washout, diffusing capacity (DLCO), and Doppler echocardiography in Zurich, 490 m, after climbing within 24 h to Monte Rosa, 4559 m, and after one night at 4559 m. RESULTS: Mean (+/- SD) FVC fell from 103 +/- 9% predicted in Zurich to 96 +/- 10% predicted at 4559 m, FEV1/FVC increased from 0.82 +/- 0.06 to 0.84 +/- 0.08, and closing volume increased from 0.35 +/- 0.14 to 0.44 +/- 0.11 L above residual volume (P < 0.05, all changes). On the following day at 4559 m, closing volume remained elevated in 9 of 21 subjects who had a lower DLCO but similar pulmonary artery systolic pressures compared with the remaining 12 subjects (40 +/- 8 vs 43 +/- 7 mm Hg, P = NS). None of the subjects had overt HAPE. CONCLUSION: We conclude that changes in pulmonary function after rapid ascent to high altitude were consistent with interstitial fluid accumulation, but they were not related to changes in pulmonary artery pressure. Individual lung function responses to high-altitude exposure varied largely and did not predict subsequent HAPE.

Adolescent↗