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At least 433 records · Page 24Linked to original sources
PubMed1978

Pressure-volume relationships in the lung during laparoscopy.

Pressure-volume relationships for the total respiratory system and for the lung were recorded in anaesthetized and paralysed patients, during deflation from an airway pressure of 3 kPa to FRC at a rate of 2 litre min-1. Pleural pressure was estimated by means of an oesophageal balloon. A group of nine female patients (mean age 32.7 yr) about to undergo laparoscopy were each studied in four successive states: supine, 15 degrees head down tilt, tilt and lithotomy position, and again in this position after abdominal inflation with nitrous oxide to a pressure of 0.8(-1) kPa. Compliance values were calculated from the curves. Mean total compliance was increased significantly by moving to the lithotomy position, and reduced markedly after inflation of the abdomen, because of a large reduction in thoracic compliance. Mean lung compliance was unaltered, except for a slight but statistically significant increase on moving from the supine to the Trendelenburg position. Measurement of FRC by helium dilution in a group of seven patients showed that abdominal inflation caused a mean decrease of 19%. Airway closure manoeuvres were carried out using a helium bolus technique from FRC in five patients, but closing volume could be measured in only one patient, in the supine position. The absence of an inflexion in the slope of the pressure-volume curves for the other patients supported this negative finding.

Adult↗
PubMed1988

Canine model of chronic bronchial injury. Lung mechanics and pathologic changes.

Bronchial injury was induced in 7 dogs by exposure to nebulized 1% nitric acid 3 days per week for 4 weeks. Lung mechanics were measured prior to exposure, at the completion of exposure, and at 1, 3, and 5 months postexposure. Airway obstruction persisted unabated throughout the postexposure period, with significant reductions in maximal expiratory flows. Pulmonary resistance, the slope of phase III, and the volume of isoflow were increased. Hyperresponsiveness to histamine developed between 3 and 5 months. Histologically, there was minimal damage to the cartilaginous airways. Widespread chronic inflammation with minimal fibrosis was seen in the membranous bronchi and respiratory bronchioles. Pathology scores for cartilaginous and noncartilaginous (small) airways were developed and correlated with tests of airway function. Small airways pathology scores correlated with flows at 50 and 25% of the vital capacity and with pulmonary resistance. Density dependence of maximal expiratory flow, closing volume, and closing capacity failed to correlate with either the airway obstruction or the small airways pathology scores.

Animals↗
PubMed1984

The single-breath N2-test and spirometry in healthy non-smoking males.

Healthy males (aged 30-70), who had never smoked, were studied. The 178 subjects were selected by systematic sampling from an urban population. Using the single-breath N2-washout test we measured the closing volume (CV) and the slope of the alveolar plateau (delta N2). A prediction equation for CV was produced by simple regression on age. delta N2 showed an accelerated increase with age above the age of 50. A curvilinear equation was established: delta N2 (%/1) = 0.85 + e0.0929 x A( yrs ) -6.302. Reference equations were also established for vital capacity (VC), forced expiratory volume in one second (FEV1) and FEV1 in per cent VC (FEV%) by means of linear multiple regression on age and height. The distribution of delta N2 was not homogenous throughout the age-range. As an upper limit of the reference range, we suggest 180% of the predicted value.

Adult↗
PubMedDate not supplied

[Influence of sequential breath-holding on the slope of phase III (author's transl)].

Many factors contribute to the slope of phase III of the single-breath nitrogen test (SB-N2). By its effect of nitrogen concentrations, alveolar oxygen exchange may be responsible for a fraction of this slope. In fact, the slope of phase III is steeper when expiratory time is prolonged. We studied the effect of two sequential breath-holding periods of 20 seconds each with ten healthy young male volunteers, by SB-N2 and a reverse technique (SB-R). We observed a sudden increase (mean 1.27%) in the expired nitrogen concentration after each breath-holding period. Closing volume remained the same in all tests, but the slope of phase IV decreased by 44% in SB-N2A (SB-N2 with breath-holding) and increased by 55% in SB-RA. Expiratory vital capacity was significantly less after breath-holding. These data suggest that gas exchange during expiration is partly responsible for the slope of phase III.

Adult↗
PubMed1984

Airway function in stage I and stage II pulmonary sarcoidosis.

Airway function was studied in 39 patients with stage I sarcoidosis and in 20 patients with stage II sarcoidosis. All of our patients were nonsmokers. Characteristic functional changes of restrictive lung disease was observed in 4 patients with stage II sarcoidosis. Specific airway conductance and % FEV1 were abnormal in 3 patients with stage II sarcoidosis. Abnormal small airway function was demonstrated in several patients with stage I and stage II sarcoidosis, always by multiple tests. Frequency dependence of dynamic compliance was demonstrated in 40% of stage I and 50% of stage II sarcoidosis. Maximal flow (Vmax50, Vmax25) was decreased respectively in 36 and 30% of patients of stage I sarcoidosis and in 56 and 62% of patients with stage II sarcoidosis. The ratio of closing volume to vital capacity was increased above corrected predictions in 30% of stage I and 44% of stage II sarcoidosis. delta Vmax25 decreased and Visov/VC (%) increased in more than 50% of patients. Upstream airway resistance was abnormally increased in 50% of patients with stage I and in 73% with stage II sarcoidosis. These results suggest that small airway dysfunction is common in early sarcoidosis without restrictive defect.

Adult↗
PubMed1977

Ventilatory lung function following two years of tobacco abstinence.

Spirometry, maximal expiratory flows and the nitrogen closing volume test were studied in 59 subjects following their attempt to give up smoking. Seventeen subjects were tobacco abstinent for at least 5 months. This group showed significant improvement of vital capacity (VC), forced expiratory volume in 1 sec (FEV1) and the slope of phase III. Nine of these subjects remained ex-smokers for at least 24 months. However, no significant improvement of any of the measured variables could be established in this group. This may be due to the small number in the group and the circumstance that they were older and had worse lung function before smoking cessation compared with those who resumed smoking.

Adult↗
PubMed1978

The influence of bronchial smooth muscle tone on critical narrowing of dependent airways.

Critical narrowing of the dependent airways was examined in anaesthetized dogs with closed chests. Two techniques were used, (a) "closing" volume (CV), measured from the expired nitrogen plateau and (b) tantalum bronchography, to measure the calibre of airways of 3-8 mm diameter in the upper (UZ), middle (MZ) and lower (LZ) zones. The point of airway "closure" at the junction of phases III and IV of the alveolar plateau coincided with an inflection in the diameter-lung volume curve of the airways in the most basal zone of the lung. This was accompanied by a sudden large increase in the calculated resistance of the airways in LZ compared with UZ. Following stimulation of the vagi CV increased and there was increased narrowing of airways, particularly in LZ. The addition of 0.5% halothane to the anaesthetic abolished the effect of vagal stimulation on CV and on airway resistance.

Airway Resistance↗
PubMed1982

Pulmonary function after long-term exposure to trichlorophenol.

Symptoms and pulmonary function were evaluated in subjects exposed to trichlorophenol. Symptoms from upper airways and chest were more common among those exposed than in control subjects (60% and 10%, respectively) Significantly reduced forced expired flow at 75% of vital capacity [exposed: 5.721/s (5.08-6.85), mean and range; reference: 6.451/s (5.77-8.40), P less than 0.05] and increased closing volume [exposed: 25.2% (19.5-36.0), reference: 17.1% (12.0-23.5), P less than 0.01] were measured while other spirometric variables and the transfer factor of the lung for CO were normal. Increased elastic recoil pressure of the lung and signs of lung tissue engagement in X ray were noticed in two subjects. Blood and liver tests were normal. The findings suggest an irritating effect on the lung by trichlorophenol, and it cannot be excluded that long-term exposure may produce pulmonary fibrosis.

Adult↗
PubMed2005

Contributions of lower limb and abdominal compression to ventilation inhomogeneity in hypergravity.

Gravito-inertial load in the head-to-foot direction (Gz) and compression of the lower body half by an anti-G suit (AGS) are both known to influence ventilation distribution in the lungs. To study the interaction of Gz and AGS and to asses the separate contributions from lower limbs and abdominal compressions to large and small-scale ventilation inhomogeneities nine males performed SF6/He vital capacity (VC) single-breath washouts at 1, 2, and 3 Gz in a centrifuge, with abdominal and/or lower limbs compressions. SF6/He and (SF6-He) phase III slopes were used for determination of overall and small-scale ventilation inhomogeneity. Closing volume and phase IV height were used as measures of large-scale inhomogeneity. VC decreased marginally with G-load but markedly with lower limbs compression. Small-scale ventilation inhomogeneity increased slightly with G-load, but substantially with AGS pressurization. Small-scale ventilation inhomogeneity increased with AGS pressurization. Large-scale inhomogeneity increased markedly with G-load. Translocation of blood to the lungs might be the key determinant for changes in small-scale ventilation inhomogeneity when pressurizing an AGS.

Abdomen↗
PubMed1990

Exponential gradient maker using a disposable syringe.

With a simple modification, any disposable syringe can become a reliable and easy to use exponential gradient maker. The modification consists of two notches, made with a razor blade, in the borders of the rubber sealing tip of the plunger. A clamp in the tube connected to the syringe allows control over solution flow. With the clamp prohibiting drainage, the body of the syringe is filled with the desired volume of starting solution I. A magnetic stir bar, small enough to spin inside the syringe is included. The notched plunger is introduced until no air space remains. This forms the fixed volume, closed mixing chamber, while the rest of the volume of the syringe forms the open chamber. The two chambers are connected through the notches in the plunger. The ending solution II is poured after the introduction of the plunger. Opening the clamp allows solution I in the closed chamber to flow out, and the solution II in the open chamber flows through the notches and mixes with solution I. This exponential gradient maker can be reused many times, but the low cost of the components makes it potentially disposable. This feature is especially useful when using toxic chemicals, or when pouring polyacrylamide gradient gels, since the apparatus may be disposed of after contamination or eventual polymerization.

Chemistry Techniques, Analytical↗
PubMed1982

The role of gas exchange in phase IV of the single-breath nitrogen test.

Because at the end of a prolonged expiration the respiratory quotient is less than 1, ongoing gas exchange could add to the rising N2 concentration in phase IV of the single-breath nitrogen (SB-N2) test. To verify this, 7 normal subjects performed SB-N2 and reversed gradients (SB-R) tests with and without a 20-s apnea at the onset of closing volume. In the SB-R test, the residual gas is 100% O2 and the final VC inspiration is room air. This gives a downward slope of phase IV (delta N2IV). Apnea, by prolonging total expiratory time, should increase the contribution of gas exchange and therefore increase the delta N2IV in the SB-N2 test and decrease it in the SB-R test. In the SB-N2 test, the delta N2IV increased, with the apnea, from 5.58 +/- 1.35 to 8.12 +/- 1.52 (mean +/- SD, p less than 0.01). In the SB-R test, the delta N2IV decreased from 4.31 +/- 1.65 to 1.43 +/- 1.45 (p less than 0.01). These results suggest that 10% of the N2 changes in the delta N2IV in the normal SB-N2 test may be related to gas exchange.

Adult↗
PubMedDate not supplied

Small airway testing and smoking in predicting risk in surgical patients.

A prospective study was performed on 185 surgical patients without overt respiratory disease to determine whether three sensitive tests for early airway obstruction or cigarette smoking at the time of hospitalization were useful in identifying the patient at risk for a postoperative pulmonary complication. Subjects were evaluated by questionnaire. Pulmonary function testing consisted of the single breath nitrogen test (SBN2) to determine the closing volume (CV) and slope of the alveolar plateau, and a maximum expiratory flow volume curve (MEFV) to determine expiratory flow at low lung volumes. Fifty-five patients had upper abdominal surgery and 130 a major surgical procedure under general or spinal anesthesia upon another part of the body. Ninety-six (52%) of the 185 patients were smokers. Seventy-nine patients (43%) had one or more abnormal function parameters. The CV was abnormal in 59, alveolar plateau in 18, and MEFV in 12. Fifty-four percent of smokers and 30 percent of nonsmokers had abnormal small airway tests. Sixteen of 185 patients (8.6%) developed a postoperative respiratory complication determined by review of the hospital record. Eleven were in the 96 smokers, but 13 were in the 79 patients with abnormal small airway tests. The incidence was highest (38%) in smokers with an abnormal alveolar plateau who underwent upper abdominal surgery. Identification of the patient at risk was better served by tests of small airway abnormality than by smoking history alone.

Adult↗
PubMed1980

Prostaglandin F-2 alpha functions as a local hormone on human airways.

Vasoactive hormones may be classified either as 'local' or as 'circulating', depending on whether they are or are not removed by the pulmonary circulation. Prostaglandin F-2 alpha is partially removed by the human pulmonary circulation. We examined the hypothesis that, with respect to the human lung, PGF-2 alpha functions as a local mediator. Prostaglandin F-2 alpha was given to normal and asthmatic subjects via both intravenous and aerosolized routes, and we measured specific airway conductance, spirometry, functional residual capacity, and closing volume. Aerosolized PGF-2 alpha induced significant changes of all measured parameters in both normals and asthmatics, while intravenous PGF-2 alpha-induced changes were limited to the FVC in both normals and asthmatics. The data suggest that intravenous PGF-2 alpha induced constriction of peripheral lung units. The greater sensitivity of the peripheral lung units of asthmatics versus normals to PGF-2 alpha, suggest that the increased sensitivity of airway smooth muscle of asthmatics versus normals to PGF-2 alpha is not restricted to the conducting airways, but extends to the smooth muscle of the peripheral lung units. The data is consistent with the hypothesis that, with respect to the lung, PGF-2 alpha functions as a local hormone, but, furthermore, suggest that, possibly of greater importance than the definition of a hormone as 'local' or 'circulating', is the definition of the intrinsic properties of the muscles on which the hormone is exerting its effects.

Adolescent↗
PubMed1981

Bronchial obstruction after oesophageal acid perfusion in asthmatics.

Fifteen patients with the combination of bronchial asthma and symptoms of gastro-esophageal reflux reproduced at endo-oesophageal acid perfusion (group 1) were investigated to detect bronchial obstruction, reflexly elicited from the distal oesophagus. Five patients with bronchial asthma but without symptoms of gastro-oesophageal reflux (group 2) and five patients with symptoms of gastro-oesophageal reflux but without respiratory symptoms (group 3) served as controls. The vital capacity (VC), the slope of the alveolar plateau (delta N2) and the closing volume (CV) were measured with the single breath nitrogen test before and after acid perfusion of the oesophagus, and again after antacid and glucose perfusion of the oesophagus. In group 1 a significant decrease of VC by 0.21 (P less than 0.001) and a significant increase of delta N2 by 0.9% (P less than 0.05) was seen while no change in CV was found. There was no change after acid perfusion in groups 2 or 3. After glucose and antacid the VC increased significantly in group 1 while no significant change was seen in delta N2 or CV. These findings were taken as indirect evidence of bronchial obstruction induced by the acid infusion. Since the changes were provoked in the sitting position and only in asthmatics with a positive acid perfusion test and since no patient complained of acid taste in the mouth it is unlikely that the bronchial obstruction was due to aspiration. A neural oesophago-bronchial reflex mechanism is suggested.

Adult↗
PubMed2000

Reduction in turgid water volume in jack pine, white spruce and black spruce in response to drought and paclobutrazol.

Significant reductions in needle water content were observed in white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill) B.S.P.), and jack pine (Pinus banksiana Lamb.) seedlings in response to a 10-day drought, although turgor was apparently maintained. When the seedlings were re-watered after the drought, jack pine needles regained their original saturated volume, whereas white spruce and black spruce needles did not. Significant drought-induced reductions in turgor-loss volume (i.e., tissue volume at the point of turgor loss) were observed in shoots of all three species, especially jack pine. Repeated exposure to 7 days of drought or treatment with the cytochrome P(450) inhibitor, paclobutrazol ((2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol), reduced seedling height relative to that of untreated controls in all three species. The reductions in saturated and turgor-loss needle volumes in the paclobutrazol-treated seedlings were comparable with those of seedlings subjected to a 10-day drought. The treatment-induced reductions in shoot and needle water contents enabled seedlings to maintain turgor with tissue volumes close to, or below, the turgor-loss volume of untreated seedlings. Paclobutrazol-treated seedlings subsequently survived drought treatments that were lethal to untreated seedlings.

Journal Article↗
PubMed1980

Alveolar gas compression in smokers and asthmatics.

To correlate the degree of alveolar gas compression with the severity of airway obstruction, we plotted separately exhaled and plethysmographic maximal-expiratory-flow-volume (MEFV) curves in each of 4 healthy nonsmokers, 4 asymptomatic smokers, and 4 asymptomatic asthmatics. Spirometry, lung volumes, single breath nitrogen plateau (Phase III), and closing volumes (Phase IV) were normal in the smokers and nonsmokers, and there were either normal or showed evidence of mild airway obstruction in the asthmatics. MEFV curves were plotted by using exhaled flow (VE) against exhaled volume (VE), and by using plethysmographic flow (VL) against plethysmographic volume (VL). These curves were utilized to construct isovolume-pressure-flow (IVPF) curves of esophageal pressure (Pes) against VE and against VL for each subject. Differences in the flow (VL minus VE) were calculated from these curves at 75% vital capacity (VC), 50% VC, and 25% VC at the same Pes in all 3 groups. At 75% VC, the mean flow difference in the asthmatic group was significantly higher than in normals (P less than 0.05); at 50% VC, it was significantly higher both in the asthmatics and the smokers (P less than 0.05); at 25% VC, there was no significant difference among the 3 groups. The mean plethysmographic forced vital capacity (FVC) exceeded exhaled FVC in all 3 groups, but the difference was significantly higher in smokers and asthmatics than in nonsmokers (P less than 0.05). These findings suggest that significant alveolar gas compression may occur at 75% VC in mild asthmatics, whereas in smokers it occurs at the middle portion of the VC.

Adult↗
PubMed1977

Airway response to short-term inhalation of tobacco smoke. Lack of racial differences.

Airway response to short-term inhalation of cigarette smoke was studied in healthy black subjects. We have measured thoracic gas volume, airway resistance, maximum expiratory flow rates, and closing volume in 12 healthy black volunteers before and after smoking a cigarette. We found a significant reduction in airway conductance and midexpiratory flow rate after smoking the cigarette. The results are similar to those previously observed in white subjects. We conclude from our study that the response to short-term inhalation of cigarette smoke is identical in both white and black subjects.

Adult↗
PubMed1975

A comparison of pulmonary function tests in detecting exercise-induced bronchoconstriction.

In an attempt to compare most of the available pulmonary function tests in detecting airway obstruction after exercise, two studies were conducted. In the first study 24 bronchodilator-dependent asthmatic boys were evaluated before treadmill exercise (baseline) and at 7 and 30 minutes afterwards. The following pulmonary function parameters were measured: forced vital capacity (FVC), forced expiratory volume in one second (FEV1), maximum mid expiratory flow (MMEF), peak expiratory flow rate, thoracic gas volume, airway resistance, specific airway conductance (SGaw), and closing volume (CV). Results showed that SGaw, MMEF, and CV were the most sensitive parameters reflecting changes in airway caliber. Less significant changes also appeared in FEV1 and in FVC. The significance of these changes and their relationships to other parameters are discussed. In an attempt to better understand the effects of airway obstruction on the maximum-expiratory flow-volume curve (MMEF curve) after exersise, a second study was conducted. Comparisons were made between "classical" parameters such as MMEF (measured by spirometry), SGaw (measured by body plethysmography), and flow-volume parameters (measured by wedge spirometer). Sixteen asthmatic subjects (9 to 12 years of age) whose airway obstruction was further exacerbated by exercise of a moderate work load on the treadmill (2 w/kg of body weight) were studied. The asthmatic subjects were tested prior to exercise and at 7 and 30 minutes after exercise. All the measurements mentioned above were done in a randomized manner. When both MMEF and SGaw were decreased in the post-exercise period, significant correlations were obtained between these "classical" parameters and all of the flow-volume parameters. However, when only one of the two was decreased, no correlation could be obtained with any of the flow-volume parameters. It was concluded that under certain conditions flow-volume curves reflect airway obstruction satisfactorily, but under other conditions they appear to be less sensitive than the "classic" parameters. These results are also discussed.

Adolescent↗