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PubMed1996

In vitro hydrodynamic characteristics of DE-T2 biological heart valve prosthesis.

Our goal was to evaluate the DE-T2 biological heart valve prosthesis in our own pulse duplicator system. Pressure drop measurements were made across DE-T2 biological aortic valve size 21. All the pulsatile flow experiments were conducted in the Marmara Research Center pulse duplicator system. The pulsatile flow pressures were measured with Motorola MPX5100DP 9306 transducers, interfaced to Vishay 4270A, 4280, 4290, bridge amplifiers and Motorola System 4000. The valve DE-T2 had a vitellium ring with a central bar. The sewing ring was covered with bovine pericardium that continued to form the leaflets. A special incision was made in the pericardium at a 90 degrees angle to the central bar for the formation of two non-anatomical leaflets. The biological aortic valve prosthesis DE-T2 is similar to the natural aortic valve in systolic function. The closing volume is a little higher than the natural valve. Studies are continuing with the aim of diminishing the closing volume and searching for the ideal preservation solution for the pericardium.

Animals↗
PubMed1976

The effect of smoking cessation and modification on lung function.

The purpose of this study was to obtain more information about the effect on lung function of stopping smoking or of modifying the smoking habit and to determine the time course of change. We followed a group of 75 cigarette smokers who attended a smoking cessation clinic in May 1973, using a respiratory symptom questionnaire, spirometry, closing volumes, and the slope of the alveolar plateau of the single-breath nitrogen test. Subjects were tested before stopping smoking and at 1, 3, 6, and 12 months after the initial testing. We found a significant (P less than 0.05) improvement in closing volume as a percentage of vital capacity and closing capacity as a percentage of total lung capacity at 6 and 12 months and in the slope of the alveolar plateau at 1, 6, and 12 months in those who stopped smoking. There was also a dramatic decrease in respiratory symptoms in those who stopped smoking, a moderate decrease in those who reduced their consumption by at least 25 per cent, and very little change in those who did not appreciably modify their smoking consumption.

Adult↗
PubMed1977

The effects of posture on venous admixture and respiratory dead space in health.

Alveolar-arterial PO2 difference ([A-a]PO2), venous admixture, and physiologic dead space were measured in 24 healthy men and women 23 to 72 years of age in the sitting and supine positions, breathing air, breathing O2, and breathing O2 in deep breaths. In the supine (but not the sitting) position, (A-a)PO2 and venous admixture, breathing both air and O2, were more highly correlated with the difference between closing volume and expiratory reserve volume than with age. The change in (A-a)PO2 and venous admixture from sitting to lying was related to the change in closing volume minus expiratory reserve volume, during both air and O2 breathing. These results confirm previous work on the contribution of gravity-dependent airway closure to the air-breathing venous admixture. They further indicate that the same mechanism is important when O2 is breathed, and it may account for most of the alveoli that close during O2 breathing because of critically low ventilation perfusion ratios. Physiologic dead space in the supine position may be predicted by subtracting 12.5% from the normal sitting value for the same tidal volume and respiratory frequency.

Adult↗
PubMed2005

Hydrofluoroalkane-134A beclomethasone or chlorofluorocarbon fluticasone: effect on small airways in poorly controlled asthma.

Inflammation in asthma extends into the small airways (< 2 mm diameter). Most inhaled corticosteroids are suspensions with a particle size > 2 mm. Therefore, inflammation in the small airways of patients with asthma may not be adequately treated with these preparations. Some inhaled corticosteroids, on the other hand, are compounded with alcohol, resulting in a solution producing an aerosol that has a mean particle diameter of < 2 mm. This study was designed to compare the addition of equivalent amounts of two inhaled corticosteroids (one a suspension and one a solution) to the treatment of patients with asthma, which was uncontrolled despite treatment with moderate to high doses of inhaled corticosteroids and usually additional controller medications. The study was performed with 30 patients, > or = 18 years of age. Subjects were randomized in a single-blind fashion to receive, in addition to their current asthma therapy, either CFC-FP 220 microg each morning and 110 microg each evening (n = 10) or HFA-BDP 160 mcg twice daily (n = 20). Pre- and postbronchodilator spirometry, single breath nitrogen washout for closing volume and residual volume by plethysmography were assessed before and after 3 months of therapy. In the subjects who received HFA-BDP, the ratio of closing volume (CV) to vital capacity (VC) and residual volume (RV) decreased significantly (p = 0.0214 and 0.0433, respectively), whereas forced expiratory flow over 25-75% of the vital capacity (FEF25-75%), forced expiratory volume in 1 second (FEV1), and morning peak flow improved significantly (p = 0.0014, 0.0184, and 0.0321). Improvements from baseline of CV, CV/VC, and postbronchodilator FEF25-75%, were statistically significant in the HFA-BDP group compared with the CFC-FP group (p = 0.0049, 0.0194, and 0.0355, respectively). These preliminary findings suggest that the addition of HFA-BDP, compared with CFC-FP in patients with poorly controlled asthma despite receiving moderate to high doses of inhaled steroids, has a greater effect on parameters reflecting small airway patency presumably secondary to reduction in inflammation.

Administration, Inhalation↗
PubMed1991

[The effect of PEEP-ventilation on gas exchange and airway closure in experimental pulmonary emphysema].

The benefits of mechanical ventilation with positive end-expiratory pressure (PEEP) are well documented, especially for patients with acute respiratory failure. PEEP increases functional residual capacity (FRC) and reduces closing volume (CV) and ventilation-perfusion mismatching. Little is known about the effects of PEEP in patients with chronic obstructive pulmonary disease, where closing volume and ventilation-perfusion mismatching are increased. We investigated the effects of PEEP in a canine model of panlobular emphysema (PLE). METHODS. After completion of control-period measurements, PLE was induced in eight dogs by intratracheal application of 20 ml aerosolized 16% papain solution. Three weeks later the effects of continuous positive-pressure ventilation (CPPV, PEEP 10 cmH2O) on gas exchange, FRC, and CV were investigated. Conventional intermittent positive-pressure ventilation (IPPV) served as reference. Measurements of CV were done using both the foreign gas bolus method and the single-breath oxygen test. FRC was determined by the nitrogen dilution technique. RESULTS. The papain-induced emphysema produced a deteriation in oxygenation, enlargement of FRC and CV, and an increase in quasi-static lung compliance. CPPV led to a further increase of FRC, but gas exchange was not improved nor was CV reduced. In the PLE period, mean pulmonary arterial pressures (MPAP) were higher during both modes of ventilation. CPPV tended to increase MPAP and pulmonary capillary wedge pressure when compared with IPPV. Systemic hemodynamic conditions were stable throughout the experiment. CONCLUSIONS. The application of PEEP to emphysematous lungs seemed to enlarge FRC, predominantly in the nondependent rather than in the dependent lung regions, which are prone to airway closure. In patients with emphysema, ventilation with PEEP may further deteriorate the impaired distribution of ventilation and thus counteract any improvement of gas exchange.

Animals↗
PubMedDate not supplied

Influence of external resistance and minor flow variations on single breath nitrogen test and residual volume.

Inspiratory and expiratory flow are known to influence parameters obtained from the single breath nitrogen test. We assessed the influence of two different flow rates (0.3 and 0.5 1.s-1) with and without the use of an external resistor during inspiration and/or expiration on the indices of the single breath nitrogen test in eight healthy subjects. We found that when an external resistance was used during expiration residual volume was larger and the height of phase IV smaller, because the resistance interferes with complete lung emptying. When applied only during inspiration the resistance did not affect any of the measurements. The height of phase IV was greater at a flow of 0.3 1.s-1 than at 0.5 1.s-1; also residual volume was greater at the lower flow rate. The effect of flow rate can be accounted for by continuous gas exchange during the manoeuvers. The slope of the alveolar plateau and closing volume are not influenced by the resistance or by minor changes in flow rate. We conclude that for commonly used indices (slope of phase III, closing volume) the use of a resistance does not affect the results and is helpful for the subject; residual volumes are affected by both the resistance and the flow rate, but these effects are small.

Adult↗
PubMed1977

The influence of atropine and cromolyn on human bronchial hyperreactivity to aerosolized prostaglandin F2 alpha.

The mechanism of prostaglandin F2 alpha(PGF2alpha)-induced airway constriction was explored by determining the influence of atropine and cromolyn on the bronchoconstrictive properties of PGF2alpha. Increasing doses of aerosolized PGF2alpha were given (150, 300, 600, 1200 microgram) and the response of subjects was determined by measurements of spirometry, specific airway conductance (SGaw), and closing volumes. In normal subjects, PGF2alpha induced small but significant decreases of SGaw and spirometric parameters (FVC, FEV1), whereas there was no effect on the closing volumes. In contrast, in asthmatics, PGF2 alpha induced large decreases of SGaw and spirometric parameters. Asthmatics experienced severe and prolonged shortness of breath and wheezing, whereas normal controls experienced neither. Neither atropine nor atropine plus cromolyn was capable of preventing or substantially reversing the PGF2alpha-induced symptoms and airway constriction. The data suggest that reflex bronchoconstriction via irritant receptors is not a major mechanism of PGF2alpha-induced airway constriction. Although a minor vagally mediated reflex component may participate in the PGF2alpha-induced bronchoconstriction, it is masked by an overwhelming non-reflex mechanism that is probably a direct constricting effect of airways smooth muscle that is exquisitely sensitive to PGF2alpha.

Adolescent↗
PubMed2002

In vitro hydrodynamics of a decellularized pulmonary porcine valve, compared with a glutaraldehyde and polyurethane heart valve.

BACKGROUND: Hydrodynamic performance of a decellularized pulmonary porcine valve was evaluated with a computer versatile pulse duplicator and compared to glutaraldehyde fixated stentless porcine bioprosthesis and a polyurethane heart valve. METHODS: Decellularized pulmonary porcine matrices (Group I, n = 5) were treated chemically to become cell-free collagen matrices. The findings of this heart valve were compared with aortic glutaraldehyde treated porcine prostheses (Group II, n = 5) and polyurethane three leaflet valve prostheses (Group III, n = 1). Measurements were performed in 0.9% saline test fluid at room temperature. Measurements compared were closing time, closing volume, systemic pressure difference and energy losses. Each valve was measured 6 times with 70 beats/minute, a stroke volume of 70 ml corresponds to a cardiac output of 4.9 L/minute. RESULTS: Group I and group III showed no significant differences between parameters. The measured closing time was significantly different (p < 0.001) between group I and II, respectively 24.333 and 53.600 ms and group II and III respectively 53.600 and 24.000. Difference in closing volume was significant (p < 0.05) between groups II and I respectively 3.67 and 0.68 ms and group II and III respectively 3.67 and 0.71. Systolic mean pressure gradient was 18.25 +/- 1.04 mm Hg in group II which was significantly different (p < 0.001) from groups I and III, respectively 10.65 +/- 0.29 mm Hg and 7.70 +/- 0.30 mm Hg. CONCLUSIONS: Decellularized pulmonary porcine valves showed the same excellent performance as polyurethane valve prosthesis, which are superior to the investigated glutaraldehyde fixed xenograft.

Animals↗
PubMed1979

Effect of inspired volume on airway closure in relation to age.

Closing volume (CV) was measured in 64 healthy subjects aged 18--76 years, in supine position, with a bolus (helium) technique in two ways: following a maximal (CV100) and a submaximal (=50% VC; CV50) inspiration from residual volume. With increasing age CV50 increased less than CV100 according to the equation CV100(%VC)-CV50(%VC)=0.13Xage-0.6(r=0.46, P less than 0.001), e.g. at 70 years of age CV100=32(%VC) and CV50=24(%VC). Therefore, during normal breathing elderly subjects to not presumably close airways at as high a lung volume as predicted from conventional CV-measurements. A strong correlation between CV50 and CV100 was found, CV50(%VC)=0.55XCV100(%VC)+5.3(r=0.90; P less than 0.001), thus allowing a more accurate prediction of CV50 from CV100 than from age. Neither smoking habits nor body position affected the decrease of CV with reduced inspired volume.

Adolescent↗
PubMedDate not supplied

Our experience with the early detection of small respiratory diseases.

In order to establish which method of examining pulmonic is appropriate for early diagnosis of small respiratory airway diseases, we made examinations of several groups by using different apparatuses and different tests. The first group consisted of 1517 young men. We examined them by MMFR and FEV1 and established that MMFR 25-75/FVC had discovered double number with lessened values than FEV1. In the fourth group a hundred men, aged 50, were examined by plethysmography and measurement of closing volume and we established the results of MEF 25 and MEF 50 as the best, as well as IGV while Rt and Rs did not show sufficient susceptibility for small respiratory airway diseases, as for closing volume it showed increasing for all, especially for smokers.

Adult↗
PubMed1985

Lung function measurements over 21 days shiftwork in steelworkers from a strandcasting department.

On the assumption that short term changes in lung function may reflect the potential for a long term decline the evolution of lung function indices in 25 steelworkers from a strandcasting department and in 11 comparable steelworkers not exposed to dust was investigated over an almost uninterrupted 21 day working period and over three different workshifts. The mean total dust level in the strandcasting department, assessed by personal sampling, was 11.8 mg/m3. All subjects were examined at the beginning, in the middle, and at the end of their first (day 1) morning shift (0600 to 1400), their last (day 14) afternoon shift (1400 to 2200), and their last (day 21) night shift (2200 to 0600). Indices measured were vital capacity (VC), forced expiratory volume in one second (FEV1) and in three seconds (FEV3), forced expiratory flow over the middle half of the forced vital capacity (FEF25-75), peak expiratory flow rate (PEFR), the slope of the N2 plateau (delta N2) and the closing volume (CV) of the single breath oxygen test. Differences in indices between initial values (0600 on day 1) and final values (0500 on day 21) were not significant in the control group (except delta N2 which became lower); in the casting group there were significant (p less than 0.05) decreases in FEF25-75 and FEV3, but these decreases were not significantly greater than in the control group. Lung function changes were not significant in either group over the morning shift. During the afternoon there were significant decreases in spirometric indices in the casting group, with no significant decreases in the control group, but the interactions between exposure and time were generally not significant. During the night shift, however, the decreases in FEV1 and FEF25-75 observed in the strandcasting group were significantly more pronounced than in the control group. The single breath test, which many subjects failed to perform correctly on each occasion, showed no significant changes in closing volumes, and an "improvement" of delta N2 over the morning and the night shift in the control but not the exposed subjects needs to be interpreted with caution. The more pronounced decrease in spirometric indices, suggestive of slight airways obstruction, found over the night shift in the strandcasting workers is attributed to their working environment.

Belgium↗
PubMed1974

Measurement of regional lung function in the early detection of chronic obstructive pulmonary disease.

Radioisotopic regional lung function measurements using both 99mTc-labeled albumin microspheres and inhaled 133Xe were compared to measurements of total lung function in a population of 30 participants in an epidemiological study of the causative factors of obstructive pulmonary disease. Five of the 8 asymptomatic subjects who had no evidence of obstruction by the tests of total function had abnormal regional lung function measurements. The closing volume was abnormal in three of these five, suggesting the presence of small airways disease. Regional lung function was abnormal in all subjects who were symptomatic, who had a FEV1/FVC less than 75%, or who had an elevated closing volume or residual volume. The data indicate that the measurement of regional lung function may be a highly sensitive test for the early diagnosis of chronic obstructive pulmonary disease.

Adolescent↗
PubMed1982

Effect of elastase or histamine on single-breath N2 washouts in the rat.

A method for performing single-breath N2 washouts (SBNW) in rats was developed and the test's usefulness was studied using two experimentally induced models of lung disease. Rats were anesthetized, intubated with oral tracheal and esophageal catheters, and tested by plethysmography. The SBNW expirogram was recorded during exhalation after inhaling 100% O2 from residual volume. The slope of phase III (slope III), closing volume (CV), and closing capacity (CC) were calculated. Changes in the SBNW expirogram were compared with changes in breathing pattern, dynamic and quasistatic lung mechanics, lung volumes, and forced expiratory indices. Pre- and postinstillation tests were performed on rats treated with elastase or histamine and on untreated controls. The SBNW indices were altered at significant levels equal to those of other indices of lung function, and different patterns of change were induced by the two disease models. Elastase increased CV and CC, but slope III was unchanged. Other tests suggested loss of elastic recoil and expiratory flow limitation. Histamine increased slope III, but CV and CC were unchanged. Other tests suggested large airway constriction. These results suggested the usefulness of the SBNW in rats, but the relationships between SBNW changes and underlying physiological phenomena remain to be defined.

Animals↗
PubMed1979

Influence of immersion to the neck in water on airway closure and distribution of perfusion in man.

We measured closing volume (CV), expiratory reserve volume (ERV) regional distribution of lung volume (Vr) and perfusion in 7 normal subjects in air and during immersion to the neck in water. In four subjects immersion resulted in a CV greater than ERV and the normal perfusion distribution became inverted. In the other subjects, ERV remained larger than CV and perfusion distribution during immersion was uniform, not inverted. In 5 subjects closing volume increased and in 3 of them, the ratio of apical/basal Vr increased significantly during immersion. One subject had nomeasurable CV and in the other it was not measured. The data suggest: (1) that when CV is greater than ERV during immersion there is an inversion of the normal perfusion distribution, caused by hypoxia and/or an increase in mean alveolar pressure in the alveoli beyond the closed airways, and (2) that an increase in pleural pressure gradient during immersion may contribute to the increase in C.V.

Adolescent↗
PubMed2005

In vitro hydrodynamics, cusp-bending deformation, and root distensibility for different types of aortic valve-sparing operations: remodeling, sinus prosthesis, and reimplantation.

OBJECTIVE: Preserving aortic valve cusps during operations for aortic root pathology theoretically offers several advantages over alternative prosthetic valve-bearing conduits. Functional properties of different valve-sparing techniques under defined conditions are not well studied. METHODS: Fresh porcine aortic roots were investigated in a pulsatile flow simulator, either native root or after different types of valve-sparing procedures (remodeling, sinus prosthesis, and reimplantation). Functional parameters, such as transvalvular pressure gradient, closing volume, cusp-bending deformation, and distensibility at different levels of the root were analyzed. RESULTS: The mean pressure gradient was highest in reimplantation techniques (8.4 +/- 1.8 mm Hg) compared with sinus prostheses (7.2 +/- 0.9 mm Hg, P = .01) and remodeling techniques (6.8 +/- 1.0 mm Hg, P = .002), mirror imaging the closing volume (reimplantation, 1.5 +/- 0.4 mL; sinus prostheses, 2.3 +/- 0.7 mL [P < .001]; remodeling, 3.4 +/- 1.1 mL [P < .001]). Bending deformation indices increased significantly from remodeling (0.45 +/- 0.05) and sinus prostheses (0.58 +/- 0.06) to reimplantation techniques (0.73 +/- 0.09). Dynamic changes in area of all techniques were decreased at the sinotubular junction and the commissural and sinus levels when compared with those seen in native roots but increased at the annular level for techniques with unfixed annulus (remodeling and modified sinus prosthesis). CONCLUSIONS: In vitro the various aortic valve-sparing operations differed characteristically in their ability to spare valve function, none of them completely meeting native valve behavior. The remodeling techniques exhibited valve dynamics closest to those of the native aortic root. The more the aortic valve is fixed with noncompliant prosthetic material, the more the native root dynamics are impaired.

Animals↗
PubMed1979

Sulfur dioxide exposure in a smelter. III. Acute effects and sputum cytology.

Although acute effects from exposure to SO2 have frequently been observed at low levels in acute exposure experimental studies, it was not known whether or not such effects occur among workers chronically exposed at ranges of 0.3 to 4 ppm of SO2. Measurements of FVC, FEV1, FEF50, FEF75 and FEF50-75, and closing volume were made before and after the workshift for copper smelter workers and controls. Sputum samples for cytological examination were collected. Mean FEV1 and FVC were significantly more smelter workers had a decrease in FEV1 and FEF50 during the day than did controls. More of the smelter workers felt "chest tightness." No change in closing volumes was seen. Smelter workers tended to have a higher percentage of sputum samples with moderate and marked atypia than did controls but the difference was not statistically significant.

Acute Disease↗
PubMed1989

Long-term pulmonary sequelae of meconium aspiration syndrome.

To determine the incidence of long-term sequelae after meconium aspiration syndrome (MAS), we studied 11 children who had MAS at age 8.2 +/- 0.2 years (mean +/- SD) and nine healthy control subjects with pulmonary function and exercise stress tests. The MAS children had evidence of mild airway obstruction, hyperinflation, and increased closing volumes in comparison with control values. During graded exercise stress tests on a treadmill, MAS children achieved normal maximal oxygen consumption and anaerobic threshold without a significant fall in arterial oxygen saturation or increase in CO2 tension. Exercise-induced bronchospasm occurred in four (36%) MAS subjects but in none of the control subjects. We conclude that children surviving MAS have long-term pulmonary sequelae, including airway obstruction, hyperinflation, elevated closing volumes, and airway hyperreactivity; yet they achieve normal aerobic capacity. These findings are similar, although less severe, than those after prematurity and bronchopulmonary dysplasia.

Airway Obstruction↗
PubMed1976

Effects of rhinovirus infection of pulmonary function of healthy human volunteers.

The effects of experimentally induced rhinovirus and mycoplasmal respiratory tract infections on the pulmonary function of healthy, young, adult volunteers were investigated prospectively. Before inoculation, 12 volunteers were completely normal, whereas 9 had increased frequency dependence of compliance as their only abnormality of pulmonary function. Rhinovirus infection was induced in 8 of the completely normal volunteers, and 5 developed increased frequency dependence of compliance at the time of illness. These changes returned toward normal during the following 2 weeks and were not associated with concomitant changes in any other parameter of pulmonary function, including "closing volume". Three subjects with increased frequency dependence of compliance as their only abnormality before rhinovirus infection developed no significant change in dynamic compliance or any other abnormality in pulmonary function after infection. No changes in pulmonary function were detected in 3 volunteers with experimentally induced mycoplasmal infection. These finding suggest that although rhinovirus infections are associated primarily with upper respiratory illness, they can produce transient peripheral airway abnormalities in previously normal young adults; however, closing volumes, as well as routine pulmonary function studies, may not detect these changes.

Adult↗