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At least 343 records · Page 19Linked to original sources
PubMed1998

Effects of nasal continuous positive airway pressure therapy on respiratory parameters of upper airway patency in patients with obstructive sleep apnea syndrome.

OBJECTIVES: To assess whether an initial treatment with nasal continuous positive airway pressure (NCPAP) therapy, applied for one night, had any effect on airway patency. METHODS: In 18 patients with obstructive sleep apnea syndrome (OSAS), we measured the total resistance of the respiratory system (Rrs) and their relevant lung functions before and after polysomnography, with and without NCPAP therapy. The Rrs was measured at 3 Hz with the forced oscillation technique. The overnight changes in the specific respiratory conductance (SGrs=reciprocal of the Rrs per unit lung volume) was also calculated in the sitting position. Since many reports have suggested that obesity, through fat deposits around the pharynx, can affect the mechanical and neuromuscular properties of the upper airway, we also investigated if the degree of obesity was related to the magnitude of improvement in these parameters. RESULTS: After the first night of NCPAP therapy, the Rrs decreased (sitting: 4.8+/-0.4 vs 4.3+/-0.4 cm H20/L/s, p < 0.05; lying: 6.5+/-0.4 vs 5.6+/-0.4 cm H20/L/s, p < 0.05) and the maximal voluntary ventilation increased in the morning (sitting: 101.6+/-5.8% vs 106.4+/-4.5%, p < 0.05; lying: 91.2+/-5.4% vs 97.9+/-4.7%, p < 0.05). The overnight difference in the SGrs showed a significant improvement after the initial treatment with NCPAP therapy (p < 0.05). However, the lung volume, flow volume loop, and closing volume in the morning did not change significantly after the therapy. An overnight decrease in the Rrs following NCPAP therapy is significantly correlated with the body mass index (sitting: r=0.54, p < 0.05; lying: r=0.61, p < 0.01). CONCLUSION: The improvements in Rrs without changes in spirometry may reflect improved upper airway patency after NCPAP therapy. The degree of obesity is suggested to be associated with the treatment effect on upper airway in patients with OSAS.

Adult↗
PubMed1976

Attenuated influenza virus in normal adults: role of pulmonary function studies in vaccine trials.

A live attenuated virus, influenza A/Hong Kong/68(H3N2)-ts-1[E], was administered to 10 normal volunteers. Infection resulted in minor upper respiratory tract symptoms in one volunteer. An isolate from one volunteer contained a presumed revertant wild-type virus, but no clinical significance could be ascribed to this infection. Since infection with natural influenza A virus adversely affects airway dynamics, serial tests of pulmonary function were performed, including measurements of forced expiratory flow rates, lung volumes, diffusing capacity, closing volume, and total pulmonary resistance at various frequencies by the oscillometric technique. All tests performed before and on days 3, 30, and 60 after administration of virus yielded normal results throughout the study; these results suggested that there was no inflammatory response to the candidate vaccine in either the large or the small airways. Determination of total pulmonary resistance by the oscillometric technique proved to be a simple and acceptable procedure and may be useful in large-scale epidemiologic studies.

Adult↗
PubMed1976

Pulmonary function evaluation during the Skylab and Apollo-Soyuz missions.

Previous experience during Apollo postflight exercise testing indicated no major changes in pulmonary function. Pulmonary function has been studied in detail following exposure to hypoxic and hyperoxic normal gravity environments, but no previous study has reported on men exposed to an environment that was both normoxic at 258 torr total pressure and at null gravity as encountered in Skylab. Forced vital capacity (FVC) was measured during the preflight and postflight periods of the Skylab 2 mission. Inflight measurements of vital capacity (VC) were obtained during the last 2 weeks of the second manned mission (Skylab 3). More detailed pulmonary function screening was accomplished during the Skylab 4 mission. The primary measurements made during Skylab 4 testing included residual volume determination (RV), closing volume (CV), VC, FVC and its derivatives. In addition, VC was measured in flight at regular intervals during the Skylab 4 mission. Vital capacity was decreased slightly (-10%) in flight in all Skylab 4 crewmen. No major preflight-to-postflight changes were observed. The Apollo-Soyuz Test Project (ASTP) crewmen were studied using equipment and procedures similar to those employed during Skylab 4. Postflight evaluation of the ASTP crewmen was complicated by their inadvertent exposure to nitrogen tetroxide gas fumes upon reentry.

Aerospace Medicine↗
PubMed1991

[Studies on wedged hepatic venous pressure, hemodynamics and pulmonary function in patients with chronic liver disease, with reference to the differences between liver cirrhosis with chronic hepatitis].

In 17 compensated liver cirrhosis and 8 chronic hepatitis cases (no histories of cardiac or pulmonary disease), wedged hepatic venous pressure (WHVP), hemodynamics, and pulmonary function were measured and their clinical significance and interrelations evaluated. Both diseases were comparatively analyzed. WHVP was determined by wedging a catheter from the right femoral vein into the right hepatic vein. Hemodynamics was measured with a Swan-Ganz catheter. Spirography, flow-volume curve, closing-volume curve and pulmonary diffusion capacity were measured and aortic blood gas analyzed to assess pulmonary function. Esophageal endoscopy was used to diagnose the presence or absence of esophageal varices. The results showed that the group of liver cirrhosis patients featured elevated WHVP and a hyperhemodynamic pattern and a positive correlation between WHVP on the one hand and cardiac index and right left ventricle stroke work indexes on the other; there was a negative correlation between WHVP and the systemic vascular resistance and pulmonary vascular resistance indexes. The results showed an increase in oxygen consumption in the group of patients with esophageal varices. In all chronic hepatitis cases, findings were normal. Pulmonary function was characterized by abnormal %VC, PaO2, and pulmonary diffusion capacity in both groups along with abnormal PaCO2 in the liver cirrhosis group; no significant differences were noted between the two groups. These results indicate that liver cirrhosis elevates intarahepatic pressure, affecting systemic hemodynamics and resulting in a circulatory distribution disorder, leading to right and left ventricle overload and a decline in potential cardiac function. The results also indicated that mild pulmonary function disorder can occur as early in a state of chronic hepatitis.

Adult↗
PubMed1987

[Comparative study of mechanical heart valves for implantation in mitral position].

For hydrodynamic comparison of mechanical heart valves, three tilting disc valves (Björk-Shiley SD, Björk-Shiley CCD, Björk-Shiley Monostrut) and two bileaflet valves (St. Jude Medical, Duromedics) with annulus diameter dA = 31 mm were perfused in a mock circulation in mitral position. Flow, pressure, and orifice area were measured during pulsatile flow. Insufficiency, maximal orifice area, mean orifice area, performance index and efficiency index were calculated. The tilting disc valves show distinctly lower orifice areas than the bileaflet valves. The mean value of maximal orifice area Amax of the Björk-Shiley prostheses varies between 227.82 +/- 7.77 mm2 and 243.21 +/- 6.21 mm2. The mean value of Amax of the Duromedics prosthesis is 295.45 +/- 7.76 mm2 and that of the St. Jude Medical prosthesis is 477.43 +/- 11.32 mm2. The calculated mean orifice areas A of the bileaflet valves are also higher than those of the tilting disc valves. The mean values of A are: Björk-Shiley SD: 183.55 +/- 10.03 mm2; Björk-Shiley CCD: 206.30 +/- 8.62 mm2; Björk-Shiley Monostrut: 210.12 +/- 4.74 mm2; St. Jude Medical: 398.69 +/- 19.55 mm2; Duromedics: 262.90 +/- 6.84 mm2. The performance index PI is qualitatively identical with the values of the mean orifice area A because in this study only heart valves of the same size were investigated. For calculation of insufficiency I the entire reflux volume VR including closing volume VS and leakage volume VL was used, thus, insufficiency was also determined in intact prostheses. The values of insufficiency of the mechanical valves investigated are higher for the bileaflet valves than for the tilting disc valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗
PubMed1976

[Early changes of respiratory function in mitral valve stenosis].

In order to detect early changes of respiratory function in patients affects by pure mitral valve stenosis, the authors selected 12 patients-non smokers, without symptoms of respiratory disease, of I and II NYHA class. In all subjects right and left cardiac catheterization and conventional spirometric measurements were performed. Then maximal mid-expiratory flow (MMEF), maximal expiratory flow at 50% of vital capacity (MEF 50%), maximal expiratory flow at 25% of vital capacity (MEF 25%), closing volume (CV) and closing capacity (CC) were determined, to find a small airways (bronchi of caliber inferior to 2 mm) disease. Whereas conventional spirometric measurements showed normal values, the small airways disease was proved by MEF 50% and MEF 25% measurements. The small airways obstruction observed by the authors may be due to: a) dilatation of pulmonary vessels because of venous congestion resulting in the compression of adjacent small airways; b) partial bronchiolar obstruction because of congestion of submucous venous plexus; c) interstitial oedema due to increase of extravascular pulmonary water because of pulmonary venous congestion.

Adult↗
PubMed1989

Role of lung volumes in sleep apnoea-related oxygen desaturation.

We studied the influence of lung volumes on apnoea-induced desaturation in ten subjects with sleep apnoea syndrome. Lung volumes were measured by helium dilution in the sitting and supine position and closing volume with the single-breath nitrogen washout test. To characterize the severity of apnoea-induced desaturations, we determined a desaturation curve for each patient. This curve was obtained by plotting the fall in arterial oxygen saturation (SaO2) reached at the end of each apnoea against the apnoea duration. From this curve we selected two indices: 1) the SaO2 fall following 30 s of obstructive apnoea (delta SaO2 30); and 2) the desaturation surface between 10-30 s of obstructive apnoea (DS 10-30). Both the delta SaO2 30 and the DS 10-30 were significantly correlated with the expiratory reserve volume (ERV), measured in the sitting (r = 0.77 and 0.65, respectively; p less than 0.05) and the supine positions (r = 0.96 and 0.87; p less than 0.005). A strong correlation was also observed with the difference between the supine ERV and the seated closing volume CV) (r = 0.99 with delta SaO2 30 and 0.89 with DS 10-30; p less than 0.005). Obesity influenced sitting and supine ERV values. We conclude that, among lung volumes, supine ERV and supine ERV-seated CV are the best indicators of the severity of apnoea-induced desaturation.

Humans↗
PubMed1980

Respiratory status of seventy-four habitual marijuana smokers.

Previous studies of the long-term effects of habitual marijuana smoking on respiratory status and lung function have yielded conflicting results. In the present study, lung function tests obtained in 74 regular marijuana smokers (duration of smoking > two-five years; frequency of smoking three days/week to several times/day) who denied intravenous narcotic drug abuse were compared with similar tests performed in two groups of control subjects. One group consisted of individuals tested in a mobile laboratory who were computer-matched to the marijuana smokers for anthropometric characteristics and quantity and duration of tobacco smoking; the other group was comprised of 41 nonsmokers of marijuana who were tested in the same laboratory as the marijuana smokers. Paired and unpaired t analyses revealed lower values for specific airway conductance (-0.07 to -0.08 +/- 0.02; P < 0.001) in the marijuana smokers compared with either group of control subjects, but no differences in spirometric indices, closing volume or delta N2 750-1250. When non-tobacco smoking marijuana users (n = 50) were matched with either non-tobacco smoking or tobacco smoking control subjects, significant differences were again noted in specific airway conductance (P < 0.001) but not in spirometric tests, closing volume or delta N2 750-1250. These results suggest that habitual smoking of marijuana may cause mild, but significant, functional impairment predominantly involving large airways which is not detectable in individuals of the same age who regularly smoke tobacco. The clinical implications of these findings await further study.

Adult↗
PubMed1979

The UCLA population studies of chronic obstructive respiratory disease. I. Methodology and comparison of lung function in areas of high and low pollution.

The prevalence of symptoms of chronic obstructive respiratory disease and of functional respiratory impairment was determined in 3465 residents (70 per cent of enumerated) of an area historically exposed to photochemical/oxidant pollutants and 4509 residents (79 per cent of enumerated) of an area exposed to low levels of chemical pollutants. Tests administered included the NHLI questionnaire, electronic volume spirometry, whole body plethysmography, and the single-breath nitrogen test (deltaN2750-1250 and closing volume). Cough and cough with sputum were more frequently reported in the low-pollution area. Lung function was better among residents of the low-pollution area according to FEV1, FVC, maximal expiratory flow rates, closing volume fraction, thoracic gas volume, and airway resistance. Maximal mid-expiratory flow rate, considered to be a sensitive spirometric test for detection of small airways disease, was similar in residents of both areas. Mean deltaN2750-1250 was slightly worse among residents of the low-pollution area. Findings suggest that adverse effects of long-term exposure to photochemical/oxidant pollutants may occur primarily in the larger airways both among smokers and never smokers. The greatest differences between areas were observed in residents 18-59 years of age, suggesting that long-term exposure may be required to cause measurable impairment and that these differnces may be obliterated by such factors as smoking, differential out-migration and differential survival.

Adolescent↗
PubMed1975

The unreliability of the maximal midexpiratory flow as an index of acute airway changes.

This study evaluates the reliability of the maximal midexpiratory flow (MMF) as an index of acute airway changes. In a group of asthmatics, intravenous histamine induced a significant decrease in the forced vital capacity, expiratory volume in the first second, and peak flow, while increasing the respiratory system resistance and the closing volume. The studies showed narrowing of the airways, while the MMF significantly increased in all subjects, implying dilation of the airways. The increased closing volume suggested narrowing of the small airways. The data, however, suggest that the paradoxic increase of the MMF is a result of histamine-induced early small airway closure, eliminating the lung units with longer time constants. Unless the MMF is related to absolute lung volumes (as presently measured the MMF is not related to absolute lung volumes) it may be misleading, and is thus an unreliable index of acute airway changes.

Adolescent↗
PubMed1979

Effect of an inhaled atropinelike agent on normal airway function.

Ten normal subjects inhaled 80 microgram ipratropium or placebo. Body plethysmograph studies showed that ipratropium increased specific conductance (0.14-0.21 s-1.cmH2O-1) and increased flow rates during both maximal and partial forced expiratory maneuvers at all volumes from 50 to 10% vital capacity (P less than 0.01). Ipratropium produced no change in quasi-static or dynamic compliance, closing volume, or the slope of phase III of the closing volume trace, but there was an increase in the height of phase IV (P less than 0.01). Specific conductance reflects central airways caliber, whereas flow rates at low lung volumes in the absence of alteration in static recoil pressure may reflect the caliber of more peripheral airways. We conclude that inhibition of vagal tone results in dilatation of large and small airways. Analysis of the flow volume results on the equal pressure point model suggests that the bronchodilatation normally resulting from the inhalation to total lung capacity is not solely due to inhibition of vagal tone.

Adult↗
PubMed1987

Effect of verapamil on pulmonary function changes induced by fluid overloading in normal subjects.

The acute effects of the intravenous administration of 10 mg verapamil on pulmonary function changes induced by rapid saline infusion were studied in six normal subjects. Rapid intravenous fluid overloading caused on increase of closing volume (from 6.55 +/- 1.74 to 9.53 +/- 1.77%, p less than 0.05). After verapamil, the closing volume did not increase after infusion in three subjects and the mean increase was not significant (7.08 +/- 1.82 to 8.43 +/- 1.86%). These results suggest that the rapid administration of intravenous verapamil blunts respiratory function abnormalities caused by overhydration interstitial lung oedema.

Adult↗
PubMed1976

Influence of bronchomotor tone on ventilation distribution and airway closure in asymptomatic asthma.

Simultaneous washouts of nitrogen (N2) and helium (He) boluses were performed in 9 seated symptom-free asthmatic patients. Recent work has indicated a correlation between the height of Phase IV (deltaIV) of a vital capacity washout and the end-inspiratory vertical concentration gradient of the gas in the lung. The deltaIV for both He and N2 washouts increased by a factor of 2 and 1.25, respectively, after isoproterenol inhalation. In addition, the amplitude of the cardiogenic oscillations increased from a mean of 0.32 per cent to 0.51 per cent for N2 and from 0.030 per cent to 0.051 per cent for He. Closing volume measured by the He bolus method was higher than that by the N2 method in 8 of 9 subjects, by 3.7 +/- 0.7 per cent vital capacity (mean +/- 1 SE, P less than 0.001). Similarly, He closing capacity was greater than N2 closing capacity in the same 8 subjects by 2.6 +/- 1.3 per cent total lung capacity (P less than 0.001). Despite a decrease in closing volume in 8 subjects, and in closing capacity in all 9 subjects after isoproterenol, the differences between the results obtained by the 2 methods remained unchanged. The slope of Phase III in both N2 and He washouts was influenced in an inconstant fashion, probably reflecting differing contributions from topographic and intraregional inhomogeneities of ventilation in these subjects. The results suggest that in patients with asymptomatic asthma the vertical gradient of regional residual volume as well as the pattern of airway closure is more uniformly distributed between apex and base of the lung. Furthermore, the slope of Phase III in either N2 or He bolus washouts may not reflect the degree of bronchoconstriction.

Adult↗
PubMed1978

Changes in airway calibre following pulmonary venous congestion.

"Closing volume" (CV) was measured in 18 anaesthetized dogs before, during and after pulmonary vascular congestion produced by inflation of a balloon placed in the left atrium. In group A 10 dogs were anaesthetized with pentobarbitone. CV increased from 30.0 +/- 1.2 to 42 +/- 5.6% of vital capacity (P less than 0.05) when pulmonary wedge pressure was increased from 0.21 +/- 0.27 to 1.54 +/- 0.44 kPa (1.6 +/- 2.0 to 11.6 +/- 3.3 mm Hg) (P less than 0.05). In seven of these 10 dogs gas exchange was impaired after an increase of left atrial pressure. These changes in lung function during pulmonary vascular congestion were not associated with an increase in lung water. In group B, eight dogs were studied after anaesthesia with chloralose and urethane. Vagotomy or vagal cooling to 0 degrees C returned CV to baseline values in six dogs with pulmonary vascular congestion. In two dogs in which bilateral vagotomy had been performed before pulmonary vascular congestion there was no change in CV after balloon inflation. Isoprenaline abolished the effect of pulmonary vascular congestion on closing volume. This suggests that the vagus mediates the changes in lung mechanics associated with pulmonary vascular congestion.

Airway Resistance↗
PubMed1975

Evaluation of nitrogen analyzers.

Commercial N2 analyzers are in current use in tests for pulmonary closing volume. To determine whether differences between instruments might lead to inconsistencies in the measurement of closing volume, we compared the performances of 3 different N2 analyzers. The tests involved measurement of accuracy under constant and varying conditions, response to transient changes in N2 concentration, long-term stability, and an assessment of mechanical integrity. There were moderate differences in accuracy among the 3 instruments that can be essentially eliminated at N2 concentrations less than 40 per cent by changing the calibration procedure for one of the instruments. There were also moderate differences in instrument stability, dependence on environmental conditions, and mechanical quality.

Lung Volume Measurements↗
PubMed1971

Regional lung function in patients with hepatic cirrhosis.

The lung volume at which the dependent lung zones begin to trap gas as a result of airway closure (i.e., the "closing volume") was measured with (133)Xe in 10 seated patients with hepatic cirrhosis. In all of them the closing volume was increased above normal, and in eight it was greater than the functional residual capacity, indicating the presence of airway closure and gas trapping during resting tidal volume breathing. Direct measurements made with (133)Xe in five cirrhotic patients (a) confirmed the presence of increased gas trapping in the lower lung zones both at residual volume and at functional residual capacity, and (b) indicated that in liver cirrhosis the ventilation-perfusion ratio of the dependent lung zones may be very low, primarily as a result of decreased ventilation due to airway closure. It is concluded that in hepatic cirrhosis, gas trapping in the dependent lung zones may be an important cause of impaired gas exchange within the lungs. It is suggested that the premature airway closure observed in this disease may be due to mechanical compression of small airways by dilated blood vessels and/or interstitial pulmonary edema.

Adolescent↗
PubMed1988

Pulmonary limits of oxygen tolerance in man.

As part of a comprehensive study of specific organ oxygen tolerance [1-4], oxygen effects on pulmonary function were measured in normal, resting men who breathed oxygen continuously at 3.0, 2.5, 2.0, and 1.5 atmospheres absolute (ATA) for average durations of 3.4, 5.7, 9.0, and 17.7 h, respectively. Rates of development of effects of pulmonary oxygen toxicity were monitored during oxygen exposure at 2.5, 2.0, and 1.5 ATA with repeated flow-volume loops, spirometry, and symptom assessment. Additional pulmonary measurements before and after exposure included lung compliance, airway resistance, density dependence of flow, nitrogen closing volumes, carbon monoxide diffusing capacity, and alveolar-arterial oxygen differences. Of these measurements only airway resistance and closing volumes were not significantly affected at any pressure, but patterns and magnitudes of effects varied at different pressures. Overall, the data indicate that continuous oxygen exposure at 3.0 to 1.5 ATA affects pulmonary mechanical function earlier and more prominently than CO diffusing capacity. Recovery of lung mechanical function usually occurred within 12-24 h after exposure, but required more than 24 h in some individuals. No individual measure of pulmonary function was found to be uniquely satisfactory for monitoring rates of development or reversal of pulmonary oxygen poisoning. The existence of multiple pulmonary effects of oxygen toxicity and the complexity of their interactions require selective applications of individual toxicity indices to specific conditions of exposure and recovery.

Atmospheric Pressure↗
PubMed1977

In vivo gas trapping induced by nitrous oxide.

Repeated vital capacity (VC) breaths in 17 anesthetized and curarized dogs induced a small but significant increase in residual volume (RV). This trapping was greatly enhanced when a mixture of 80% N2O and 20% O2 (N2O-O2) was used instead of air. VC breaths with N2O-O2 also increased closing volume, closing capacity and closing pressure determined with 133Xe. Successive quasi-static pressure volume (PV) curves of the lung showed a shift to the right at high lung volume and to the left at low lung volume. Again these changes were more impressive with N2O-O2). The PV curve of the chest wall was unchanged. Insufflations from RV were necessary to produce the gas trapping. Increase in RV was positively related to the size of the inspired volume, to N2O concentration, and inversely related to the inspiratory flow rate. Vagotomy, intravenous isoproterenol, and intravenous propanolol did not alter the phenomena. We propose that these observations can be explained by the presence of foam in the airways and that N2O leads to an increase of foam by osmotic liquid shift into the bronchioli, and/or to an increase in bubble's size by gas diffusion.

Animals↗