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At least 379 records · Page 21Linked to original sources
PubMed1979

[Early diagnosis of small airways disease in young smokers (author's transl)].

Investigations during the past years have established that determinations of closing volume, flow-volume curves and frequency-dependent compliance are capable of detecting pathological changes in the bronchial system at a time when the customary lung function tests (FEV1.0 resistance as measured by bodyplethysmography) are still normal. These observations have been made use of to diagnose incipient damage in persons exposed to bronchial noxae. In the present investigation the effect of smoking on the airways was studied in a group of 25 persons aged 20-25 years by determining the closing volume and differences in ventilatory distribution (Thews method). The results were compared with those obtained in a group of 27 non-smokers in the same age group.

Adult↗
PubMed2002

In vitro investigation of opening behavior and hydrodynamics of bileaflet valves in the mitral position.

The performance of four 25 mm bileaflet valves of different designs was evaluated in the mitral position of our own pulse simulator. With the aid of a high-speed video camera, it was demonstrated that both the St. Jude Medical (SJM) valve (Hemodynamic Plus [HP] Series, St. Jude Medical, Inc., St. Paul, MN, U.S.A.) and the CM valve (CarboMedics, Inc., Austin, TX, U.S.A.) were able to open fully and that the CM valve fluttered much more vigorously at the fully open position than did the SJM HP valve. Conversely, neither the ATS valve (ATS Medical, Inc., Minneapolis, MN, U.S.A.) nor the On-X valve (Medical Carbon Research Institute, Austin, TX, U.S.A.) exhibited movement to a fully open configuration. The overall average opening angles of the ATS and the On-X, on 3, 4, and 5 L/min flow rate for a heart rate of 70 bpm and 5, 6, and 7 L/min for 100 bpm, were 74.8 degrees and 81.6 degrees, respectively, whereas their design opening angles were 85 degrees and 90 degrees. Pressure drops across the CM and the ATS were consistently higher than those of the On-X and the SJM HP. Closing volumes for all the valves were below 8% for a heart rate of 70 bpm. This in vitro investigation yielded the following conclusions: The ATS and On-X valves are not able to open fully in the mitral position, but this does not impair their normal function; both a larger orifice diameter and a large opening angle can decrease the pressure drop; in general, the On-X valve achieves its design goals in this experiment (i.e., it produces a lower pressure drop and lower closing volume by virtue of its large orifice and high-profile design); however, the hinge flow in the non-fully open state should be investigated further.

Heart Valve Prosthesis↗
PubMedDate not supplied

[Distribution of 1-[14C] GABA and its conjugates with nicotinate, pyridoxal phosphate and biotin in tissues of guinea pigs in closed systems].

Distribution of the total radioactive label in the blood, different parts of the brain (the whole cortex and its lobes, bulbi olfactorii, hippocamp, striopallidum, hypothalamus, thalamus, peduculi cerebri, cerebellum, pons, medulla oblongata), eye (retina, hyaloid and vascular membrane), hypophysis and liver of guinea pig males has been studied after the hypodermic injection of [14C] GABA and products of its conjugation with pyridoxal phosphate, nicotinic acid and biotin in the equimolar dose (50 nmol/g) under normal conditions and in case of action of the closed volume factors. Accumulation of the total label in the hypophysis after injection of [14C] GABA, PLP-[14C] GABA and nicotinoyl-[14C] GABA was 3.6, 3.1 and 2.7 times (respectively) as much as that in the blood. The content of the labelled compounds in the cortical structures of the telencephalon and in the diencephalon was the greatest in comparison with other parts of the brain. The permeability through a hemato-ophthalmic barrier was 3-5 times as much as that through a hemato-encephalic barrier. The closed volume factors lead to higher accumulation of the label as compared with the control after injection of [14C] GABA, PLP-[14C] GABA and biotinyl-[14C] GABA.

Animals↗
PubMed2001

Effects of water immersion on pulmonary function in asthmatics.

Immersion induces air trapping in the lungs, as does asthma. Consequently, when using diving apparatus, asthmatics may face greater risk than non-asthmatics of pulmonary barotrauma (PBT) during ascent. We studied the pulmonary airflows and closing capacities (CC = closing volume + residual volume) in subjects with exercise-induced asthma (A, n = 12) and in healthy controls (C, n = 11) under four conditions: dry and immersed, both before and after exercise (treadmill running, non-immersed). Immersed, both C and A had significant and equivalent reductions in vital capacity, FEV1, FEV1/FVC, and FEF25%-75%. Post-exercise and immersed, pulmonary airflows deteriorated further in A but were better in C: FEV1 (A, 3.6 +/- 0.8 liter vs. 3.3 +/- 0.8 liter, P = 0.001; C, 3.9 +/- 0.5 liter vs. 4.1 +/- 0.6 liter, P = 0.006), FEF25-75% (A, 3.5 +/- 1.0 liter x s(-1) vs. 3.0 +/- 0.8 liter x s(-1). P < 0.05; C, 4.0 +/- 0.9 liter x s(-1) vs. 4.3 +/- 0.9 liter x s(-1), P < 0.05). Therefore, in contrast to C, A subjects had reduced pulmonary airflows during immersion after exercise. Furthermore, A subjects more often had no closing volume phase IV when immersed after exercise than C (P = 0.005). Interpreting the absence of phase IV as indicative of more air trapping in the asthmatics during immersion after exercise would be consistent with the reductions in airflow.

Adult↗
PubMed1990

Tracheal dead space influences regional ventilation measurement in dogs.

The lung volume at which airway closure begins during expiration (closing volume, CV) can be measured 1) with a radioactive bolus inspired at residual volume (RV) and 2) with the single-breath N2 elimination test. In previous studies in dogs, we observed that N2 CV was systematically larger than 133Xe bolus CV (Xe CV) [N2 CV %vital capacity (VC) = 35 +/- 2.3 (SE) vs. Xe CV %VC = 24 +/- 2.2, P less than 0.01]. Because the regional RV in the dog is evenly distributed throughout the lung and all airways closed at RV, N2 CV is related to the regional distribution of the tracheal N2; differences between N2 and Xe CV could then be related to the size of the inhaled dead space. Simultaneous measurements of Xe and N2 CV were performed at various sites of Xe bolus injection while the regional distribution of the bolus was measured. Injections at the level of the carina increased Xe CV to a value (30 +/- 1.4%VC) near simultaneous N2 CV (32 +/- 1.5%VC) and increased the unevenness of regional distribution of the Xe bolus. The difference between N2 and Xe CV is then the result of the size of the inspired tracheal dead space. Moreover, comparisons between different values of Xe CV require injections of the boluses at the same distance from the carina.

Animals↗
PubMed1994

[Respiratory symptoms and function of coal miners presenting radiological pulmonary abnormalities].

Respiratory symptoms and lung function of 80 coal workers suspected of pneumoconiosis (pulmonary X-rays classified 0/1 or 1/0 according to International Labour Organisation classification) who worked for at least 10 years at face work (Ts) were studied in comparison with two control groups matched by age (+/- 2 years), height (+/- 5 cm), weight (+/- 10 kg) and smoking habits: the Tn group constituted by 80 coal workers who worked for at least 10 years at face work with normal pulmonary X-rays, and the HTn group constituted by 80 underground miners who worked mainly out of face work with normal pulmonary X-rays. The frequencies of cough, expectoration, chronic bronchitis or dyspnoea were significantly higher in Ts group than in the two others. The one-second forced expiratory volume to vital capacity ratio (FEV1/VC) was lower, closing volume to vital capacity (CV/VC) or to total lung capacity ratios (CV/TLC) were higher in Ts group than in the control groups. Unexpectedly, vital capacity (VC), one-second forced expiratory volume (FEV1), total lung capacity (TLC), compliance, diffusing capacity (DLCO) referred to alveolar volume (VA) were higher. In Ts group, the small rounded opacities were noted in the top part of the lung (56.9%), the irregular ones were distributed on the entire lung (65.5%). There were no relation between the category of small opacities and respiratory symptoms or lung function.

Adult↗
PubMed1979

Single-breath nitrogen washout; effects of alterations of lung volumes and elastic recoil.

Strapping of the chest causes decreased lung volumes and increased elastic recoil pressure. Such strapping was used in conjunction with single-breath nitrogen washout to study the effects of changes in these factors on the dynamics of the small airways. Studies consisted of simultaneous measurements of the quasistatic lung pressure-volume curve and single-breath nitrogen washout. Strapping caused significant reductions in all lung volumes and in lung compliance at 50 percent of the total lung capacity (TLC). The volume of phase 4 was not changed; however, the ratio of closing capacity to control TLC decreased from 29.9 +/- 6 percent to 24.2 +/- 4 percent with strapping (P less than 0.02). This observation indicates that the onset of closing volumes occurred at a lower absolute lung volume during strapping, compared with control. The closing pressure of 2.1 +/- 0.8 cm H2O was not altered by strapping of the chest. The slope of phase 3 of the single-breath nitrogen-washout test and the average alveolar concentration of nitrogen were increased during strapping. A similar phenomenon occurred in three subjects who performed the single-breath nitrogen-washout test following partial vital capacities. A reduction of the onset of closure of the airways without a change in closing pressure suggests that restrictions of the chest wall caused no change in mechanical properties of the small airways. Elevation of the slope of the alveolar plateau is probably due to exaggeration of the apex-to-base nitrogen difference consequent to the strapping-associated decreased lung and alveolar compliance.

Adult↗
PubMed1977

New tests for the detection of obstructive pulmonary disease.

Abnormalities in small airways appear to be important in the evolution of chronic obstructive pulmonary disease. Patients with these pathologic lesions may have normal values for airway resistance and forced expiratory volume in one second. Two new tests, the closing volume (CV) and the dependence of maximal flow on density, are believed to be sensitive to abnormalities in the peripheral airways. The CV test detects an increased nonuniformity of changes in volume of pulmonary units. Reduced dependence of flow on density is believed to result from an increase in the peripheral component of the losses of driving pressure which determine maximal expiratory flow. Both tests differentiate smokers with normal conventional spirometric data from age-matched nonsmokers. Although this evidence suggests that these tests can be used to detect abnormalities in small airways, there is very little pathologic confirmation of this belief. The clinical significance of abnormalities in the results of either of these tests in an otherwise normal person has not yet been determined.

Airway Resistance↗
PubMed2001

Size exclusion behavior of hydroxypropylcellulose beads with temperature-dependent porosity.

Beads prepared from a thermosensitive polymer, hydroxypropylcellulose, exhibit temperature-dependent porosity. At temperatures below 40 degrees C the beads are swollen having large pores, while at temperatures above 45 degrees C the beads are in a shrunken state having smaller pores. In the presence of 1 M NaCl the transition temperature decreased to about 30 degrees C. In a swollen state the size of pore is large enough to accommodate lysozyme (mol. mass 14400) and alpha-chymotrypsin (mol. mass 21600) but not bovine serum albumin (mol. mass 67000). When the beads are shrunken, all the proteins are eluted from the column packed with hydroxypropylcellulose beads in the volume close to the void volume of the column.

Chromatography, Gel↗
PubMed2006

Bladder reservoir function in children with monosymptomatic nocturnal enuresis and healthy controls.

PURPOSE: We investigated bladder reservoir function in children with monosymptomatic nocturnal enuresis and in healthy controls. MATERIALS AND METHODS: A total of 18 children with monosymptomatic nocturnal enuresis and 119 controls who were 7 to 13 years old were recruited. Children completed frequency volume charts and measurements of nocturnal urine production. Mean diuresis in the period preceding each voiding was calculated. Those with enuresis were grouped according to bladder capacity and hospitalized for 4 nights, including a baseline night and 3 with an oral water load. Enuresis volumes and post-void residual volume were estimated, allowing the calculation of bladder volume at the time of enuresis. RESULTS: Nine children with monosymptomatic nocturnal enuresis were characterized as having normal bladder capacity and 9 had decreased bladder capacity. We found large intra-individual variability in daytime voided volume in all 3 groups of participants. Children with enuresis and small bladder capacity generally voided with volumes close to maximal voided volume. A total of 93 enuresis episodes were recorded. Large intra-individual variability was seen in bladder volume at enuresis and it was lower than maximal voided volume in more than 50% of episodes. Variability in bladder volume at enuresis was greatest in the patient group with decreased bladder capacity. We found a significant correlation between diuresis and bladder capacity in all groups during the day and night. CONCLUSIONS: There is a great intra-individual diurnal variability in voided volume in children with enuresis and in healthy children. Enuresis seems to occur at bladder volumes that are smaller and larger than the maximal voided volume obtained from voiding charts.

Child↗
PubMed1979

Ventilatory function in laryngectomized patients.

It is established that maximum expiratory flow-volume curve coupled with closing volume curve may give important information on obstructive impairment in the laryngectomized patients. In the patients after laryngectomy, the pattern of the flow-volume curve was similar to that found in patients with chronic bronchitis. These abnormalities of the flow-volume curve which became convexity to the volume axis can be reversed at least partially by bronchodilator drug inhalation. It is concluded that the patients after laryngectomy have abnormalities of ventilation distribution despite relatively normal results of routine pulmonary function tests and respiratory resistance.

Adult↗
PubMed1987

Small airway hyperreactivity among lifelong non-atopic non-smokers exposed to isocyanates.

The development of isocyanate asthma is little understood. To gain more knowledge in this area, a group of 20 workers occupationally exposed to isocyanates, five subjects with clinical isocyanate asthma, and a control group of 10 people not exposed to isocyanate were examined with lung function tests and a methacholine provocation test. Forced expiratory volume in one second and tests aimed at detecting small airways obstruction such as volume of trapped gas, closing volume, and wash out volume were made. To detect abnormal airway reactivity, tests were made before and after inhalation of methacholine and of salbutamol. A significant increased reactivity to methacholine in the exposed and asthma groups was seen compared with the control group as measured by volume of trapped gas. The increase was reversed by inhaling salbutamol. In neither group could a statistically significant reaction be shown in the large airways. The study group had increased small airways reactivity of the same magnitude as the group with isocyanate asthma. The subjects in the study group had no clinical symptoms or spirometric abnormalities. The volume of trapped gas in combination with methacholine seems to disclose significantly altered reactivity of the small airways in workers exposed to isocyanate with no subjective symptoms of disease.

Adult↗
PubMedDate not supplied

Altered respiratory physiology in obesity.

The major respiratory complications of obesity include a heightened demand for ventilation, elevated work of breathing, respiratory muscle inefficiency and diminished respiratory compliance. The decreased functional residual capacity and expiratory reserve volume, with a high closing volume to functional residual capacity ratio of obesity, are associated with the closure of peripheral lung units, ventilation to perfusion ratio abnormalities and hypoxemia, especially in the supine position. Conventional respiratory function tests are only mildly affected by obesity except in extreme cases. The major circulatory complications are increased total and pulmonary blood volume, high cardiac output and elevated left ventricular end-diastolic pressure. Patients with obesity commonly develop hypoventilation and sleep apnea syndromes with attenuated hypoxic and hypercapnic ventilatory responsiveness. The final result is hypoxemia, pulmonary hypertension and progressively worsening disability. Obese patients have increased dyspnea and decreased exercise capacity, which are vital to quality of life. Decreased muscle, increased joint pain and skin friction are important determinants of decreased exercise capacity, in addition to the cardiopulmonary effects of obesity. The effects of obesity on mortality in heart failure and chronic obstructive pulmonary disease have not been definitively resolved. Whether obesity contributes to asthma and airway hyper-responsiveness is uncertain. Weight reduction and physical activity are effective means of reversing the respiratory complications of obesity.

Adiposity↗
PubMed1992

In vitro pulsatile flow hemodynamics of five mechanical aortic heart valve prostheses.

In vitro measurements of velocity, turbulent shear stress, effective orifice area (EOA), and regurgitant fraction were performed on five new-generation low-profile mechanical aortic heart valve designs under pulsatile flow conditions. These were: Medtronic-Hall tilting disc, St. Jude Medical bileaflet, Björk-Shiley Monostrut tilting disc, Omni-Carbon tilting disc, and Duromedics bileaflet. In general, bileaflet valves have larger EOAs than the tilting disc design, especially in the larger sizes, due to the larger opening angles and lack of obstructive struts. The regurgitant fractions range from 8% for 21-mm valves to 13% for the 29-mm sizes. This increase was largely due to an increase in leakage volume as opposed to closing volume. Furthermore, the leakage volumes increased as the mean aortic pressures increased. The tilting disc valves generally have better regurgitant characteristics compared to the bileaflet valve designs, due to lower leakage volumes and to the smaller opening angle of the occluder providing a more rapid closure of the valve. The velocity and shear stress measurements showed that none of the current valve designs are ideal: all designs create areas of stasis and/or regions of low-velocity reverse flow and regions of elevated turbulent shear stresses capable of causing sublethal and/or lethal damage to the formed elements of blood. It is therefore unlikely that these valve designs will eliminate the problems of hemolysis, thrombosis, and thromboembolic complications.

Aortic Valve↗
PubMed1977

[Small airway function tests; techniques of measurements. Review of the literature].

It is usually agreed that obstructive lesions in small airways are the first abnormalities in patients with chronic bronchitis. Consequently, there is now a great interest in the early detection of airways obstruction. Three techniques are described: frequency dependence of compliance, flow-volume curve and closing-volume. The results obtained in healthy subjects and in patients with obstructed airways are discussed.

Airway Obstruction↗
PubMed1993

Variability of the computerized single-breath nitrogen washout test in healthy adults. Results from a field survey in a French rural area.

Within-subject (difference between paired tests, or coefficient of variation [c. var.] of three consecutive measurements) and between-subjects (standard deviation of the mean group) variability were assessed for the variables derived from the single-breath nitrogen (SBN2) test in a group of healthy, asymptomatic subjects (n = 289) aged 20-64 years, from a rural area in North-East France. Duplicate measurements in 99 subjects showed excellent agreement between the two attempts (correlation coefficients between 0.94 and 0.98) for static lung volumes and the alveolar N2 slope (PIII); closing volumes (CV) were more variable (r = 0.77 for absolute value, 0.79 for % VC) while closing capacities (CC) were in intermediate position (r = 0.86 for absolute value, and 0.88 for % TLC). The variability of three consecutive measures in 190 subjects showed the coefficients of variation to be low for static volumes and closing capacity (2.4-7.4%) and higher for PIII (15.1%) and CV or CV/VC (18.2 and 17.8%). The analysis of variance did not detect significant differences between the three sets of measurements, with the exception of a progressive increase of vital capacity (VC), and decrease in residual volume (RV) from test 1 to test 3, the total lung capacity being the same. Variability was uninfluenced by age or sex, except a higher c. var. for female VC as compared to males (2.8 vs. 2.2%, P = 0.02) and a higher variability of TLC (2.9 vs. 2.3%, P = 0.03) and VC (2.8 vs. 1.9%, P = 0.003) in people older than 40 years as opposed to those younger than 40 years.

Adolescent↗