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PubMed1983

Mechanism of relief of dyspnea after thoracocentesis in patients with large pleural effusions.

In an attempt to understand the mechanism underlying the relief of dyspnea that follows thoracocentesis in patients with large pleural effusions, we measured respiratory mechanics in nine patients before and two hours after removal of 600 to 2,750 ml (mean = 1,818 ml) of pleural fluid. Thoracocentesis resulted in only small changes in pulmonary mechanics: Mean vital capacity and functional residual capacity increased by 300 and 460 ml, respectively, lung recoil pressure slightly decreased, and mean static expiratory compliance increased by 0.021 liter/cm H2O. These changes were inconsistent and could not explain the immediate and remarkable relief of dyspnea noted by the patients. By contrast, thoracocentesis invariably resulted in a shift of the minimal (inspiratory) pleural pressure-volume curve so that the pressures generated by the inspiratory muscles were markedly more negative at any comparable lung volume. This shift was entirely due to the decrease in thoracic cage volume. We suggest that the relief of dyspnea following thoracocentesis results primarily from reduction in size of the thoracic cage, which allows the inspiratory muscles to operate on a more advantageous portion of their length-tension curve.

Aged↗

PubMed1990

The "effective dose" concept in older adults exposed to ozone.

Previous research on young adults has indicated that the magnitude of pulmonary function decrements induced by exposure to ambient ozone (O3) is related to the effective dose of O3 inhaled. The effective dose is defined as the product of O3 concentration (in ppm), mean minute ventilation (VE) and duration of exposure (min). The relative contributions of the three components of effective dose to the development of pulmonary function decrements in older adults are unknown. Twelve healthy, nonsmoking men and women (60-79 years) participated in each of four experiments: (1) a 1-h continuous exercise protocol, and (2) a 2-h intermittent exercise protocol, each performed while exposed to filtered air (FA), and to 0.45 ppm O3, resulting in different effective doses of O3. Pulmonary function (forced vital capacity, FVC, functional residual capacity, FRC, and associated calculated parameters) was measured pre- and postexposure. Ozone exposure induced significant decrements in forced expiratory volume in 0.5, 1.0 and 3.0 seconds (FEV0.5, 1.0, 3.0), regardless of the exercise protocol. There were no changes in FVC with any exposure protocol. There were significant decrements in forced expiratory flow rate at 25% and 50% of FVC (FEF25%, FEF50%) and in forced expiratory flow rate between 25% and 75% of FVC (FEF25-75%) with all four exposures, suggesting a fatigue effect. There were no differences between the decrements induced in FEV1.0 by O3 exposure under the two exercise protocols. The mean exercise VE was 25.3 l/min for the continuous exercise protocol, and was 25.2 l/min for the three exercise periods of the intermittent exercise protocol.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1990

Behavior of morphometric indices in pancreatic elastase-induced emphysema in rats.

Two morphometric indices, the destructive index (DI), a measure of alveolar wall destruction, and the proportion of destroyed alveolar attachments to the airways (AA), have been proposed as measures of early lung destruction in human smokers. The aim of this study was to compare DI and AA to the usual measure of airspace enlargement--the mean linear intercept (Lm)--in experimental emphysema. Porcine pancreatic elastase was administered intratracheally to 2 groups of Brown Norway rats (high-dose, n = 8, 1 IU/g body weight; low-dose, n = 4, 0.7 IU/g; control, n = 7). Total lung capacity (TLC), functional residual capacity (FRC) and pressure-volume curves were measured 3 weeks after administration of elastase. Lung elasticity was assessed by chord compliance (Cst). Administration of high-dose, but not low-dose, elastase led to significant increases in FRC and TLC. Cst significantly increased after high-dose elastase compared to controls (p less than 0.01). Lm increased after both low-dose and high-dose elastase compared to controls (p less than 0.01); DI and AA were increased only after high-dose elastase. Significant correlations were found between each morphometric index and Cst; the highest correlation was with AA. Behavior of the morphometric indices in this model differed from that reported in human smokers: Lm was a more sensitive measure of destruction than DI, reflecting a process marked by predominance of airspace enlargement over alveolar septal breaks. These differences from human smokers may result from a differing underlying pathogenesis of lung destruction.

Analysis of Variance↗

PubMed1988

Indomethacin and cromolyn sodium alter ozone-induced changes in lung function and plasma eicosanoid concentrations in guinea pigs.

Male Hartley guinea pigs were given either indomethacin (IN), cromolyn sodium (CS), or no drug (ND) and then exposed either to filtered air or to 1 ppm ozone (O3) for 1 hr. At 2 or 24 hr postexposure, ventilation, respiratory mechanics, lung volumes, carbon monoxide-diffusing capacity (DLCO), and alveolar volume (VA) were measured, and in separate groups of animals, plasma eicosanoids (EC) were measured. Both drugs blocked the increase in flow resistance noted at 2 hr after O3 and prevented O3-induced increases in the wet lung weight to body weight ratio seen at 2 and 24 hr in the ND group. In the ND animals O3 also decreased total lung capacity (TLC), vital capacity (VC), functional residual capacity (FRC), and residual volume (RV). IN as well as CS blocked reductions in FRC and RV at both 2 and 24 hr after O3. TLC was reduced by both drug treatments in air- and O3-exposed animals. CS treatment also decreased VC in all groups. IN blocked reductions in VA after O3 but did not prevent decreases in DLCO. CS blocked reductions in both VA and DLCO after O3, but the drug decreased DLCO in air-exposed animals. The prostaglandins PGF2 alpha and 6-keto PGF1 alpha were largely unaffected by O3 exposure or drug treatment. Prostaglandin E1 (PGE1) was not affected by O3, but both drugs significantly increased PGE1 in all exposure groups. Effects on plasma thromboxane B2 (TxB2) were variable although in most groups TxB2 was lower than in the O3-exposed ND groups. Although our findings suggest that both drugs block some effects of O3 exposure on the lungs and on plasma EC concentrations, the degree to which EC contribute to O3-induced pulmonary effects is not clearly apparent.

Animals↗

PubMed1994

Surface biophysics of the surface monolayer theory is incompatible with regional lung function.

The surface monolayer theory of Clements was tested on open surface films of calf lung surfactant extract in a leak-free vertical film surface balance in which alveolar area (A) changes in each lung zone were simulated in accordance with the theory. We found that: 1) physiologically necessary low surface tension (gamma), < 4 dyn/cm, was sustained only by continuous film compression ("expiration"); 2) compression from A equivalent to total lung capacity to functional residual capacity produced fleeting gamma reduction in all zones and quick reversal to high gamma with A changes that simulated tidal volume (VT) breathing at both 14 (adult) and 40 (neonatal) cpm; 3) phase differences between gamma and A axes of VT loops that indicate mixed surface film composition may be attributable to film inertia and viscoelasticity; 4) estimated alveolar retraction pressure due to gamma (P gamma) exceeds "net" transpulmonary pressure, i.e., favors alveolar collapse, under virtually all conditions of the theory in all zones; 5) return to transient, fleeting low gamma in successive VT cycles was determined by the inherent difference in compression and decompression rates, which results in exhaustion of available A in very few cycles; 6) the "sigh", which restores stable low gamma according to the theory, actually produced unstable high gamma during virtually all phases of the maneuver. In contrast, closed bubble films of the surfactant were structurally stable and produce stable near 0 gamma and P gamma.

Animals↗

PubMed2000

The effect of salbutamol on skeletal muscle in chronic heart failure.

We performed a randomised placebo-controlled trial to investigate the effects of the anabolic drug salbutamol on skeletal muscle and exercise capacity in chronic heart failure. Twelve patients received salbutamol slow-release 8 mg twice daily or placebo for 3 weeks. We assessed the effect of treatment on exercise capacity, quadriceps muscle bulk, maximal isometric strength and fatigue, respiratory muscle strength, spirometry and 24-h ECG (electrocardiogram). There was no significant change in the muscle indices, exercise time or peak oxygen consumption. The frequency of ventricular arrhythmias and spirometric measurements were also unchanged. Maximal expiratory mouth pressure, measured at total lung capacity and functional residual capacity, increased significantly (+29.7+/-10.6 vs. -0. 5+/-7.5 cm H(2)O [mean+/-S.E.M., change over 3 weeks treatment salbutamol vs. placebo] and +31.2+/-5.4 vs. +0.2+/-4.0 cm H(2)O both P<0.05). Maximal inspiratory pressures showed a trend towards increasing with treatment when measured from either lung volume (-22. 8+/-9.5 vs. -6.2+/-3.6 cm H(2)O, P=0.14 and -21.5+/-7.5 vs. -3.5+/-3. 4 cm H(2)O, P=0.054). Treatment with 3 weeks of salbutamol increases respiratory muscle strength in chronic heart failure but does not improve quadriceps abnormalities or exercise capacity. Salbutamol is unlikely to have a role in treating the muscle abnormalities in chronic heart failure.

Albuterol↗

PubMed1986

Reduction of lung elasticity due to training and expiratory flow limitation during exercise in competitive female rowers.

Lung elasticity and lung volumes at rest were measured in 22 female rowers, in 14 women who just started with rowing, in 21 female cyclists, and in 9 male rowers. The female rowers had a higher specific static and dynamic lung compliance (P less than 0.01) and a lower recoil pressure at functional residual capacity (P less than 0.05) as compared to the other three groups. According to their age, height, and fat-free mass, the female rowers had a normal vital capacity. The residual volume, the functional residual capacity, and the fast expiratory volume in 1 s were also normal. During an increased load test till exhaustion on a bicycle ergometer, the transpulmonary pressure and the expiratory flow were measured. While the expiratory transpulmonary pressure at exhaustion in the female rowers was not markedly lower than in the other groups, expiratory flow did not increase linearly with decreasing expiratory transpulmonary pressure in most of the female rowers. In the other three groups, there was a linear relation between expiratory flow and pressure. The higher lung compliance and lower elastic recoil in the female rowers caused the flow-limiting pressure to be reached at a lower level. The difference in lung elasticity between the male and female rowers showed that the physical stress on the lungs during rowing is not alike in women and men. We assume that the typical female physique requires extra fixation of the trunk during the pull phase of the rowing stroke, which could lead to loss of lung elasticity in female rowers.

Adolescent↗

PubMed1978

Reversible pulmonary oxygen toxicity in the primate.

In order to investigate the effects of high concentrations of oxygen on the lung, experiments were performed on 18 baboons exposed to a humidified environment of 95% oxygen for five days. Open lung biopsies for biochemical assay, histologic and electron microscopic analysis and measurement of tissue respiration were performed before and after oxygen exposure. Pulmonary function was evaluated by measurement of arterial blood gases, compliance, closing capacity (CC), functional residual capacity (FRC), total lung capacity (TLC), residual volume (RV) and vital capacity (VC) before and after exposure and then at seven and 14 days in the animals which recovered. Six baboons removed from the oxygen environment after 96--110 hours and exposed to room air died within three to 20 hours of profound hypoxemia (PaO2 40 +/- 6). The remaining 12 baboons were successfully weaned to room air over a three day period with a return of ABGs to control values (PaO2 89+/- 2). Electron microscopic analysis of alveolar membranes exposed to 120 hours of hyperoxia demonstrated endothelial cell swelling, interstitial alveolar membrane edema, and an increased predominance of Type II pneumocytes. Lung volume measurements showed significant decreases in TLC (25%), VC (34%), CC/TLC (28%) and dynamic compliance (47%). Biochemical studies indicated a shift toward anaerobic metabolism with a decrese in tissue oxygen consumption, reduced cytochrome oxidase activity, and increased lung lactic acid production. These changes were all found to be reversible in the 12 baboons slowly weaned back to room air.

Animals↗

PubMed1983

Pre- and postoperative lung function in sitting and supine position related to postoperative chest X-ray abnormalities and arterial hypoxaemia.

Spirometry in both sitting and supine position was performed before and 3-5 days after elective upper abdominal surgery in 53 men, aged 41-72 years. The results were related to postoperative respiratory complications as defined by chest radiography and to measurements of the arterial oxygen tension. Preoperative total lung capacity (TLC), functional residual capacity (FRC) and wash-out volume (WOV) were lower in both positions among patients who were to develop major chest X-ray abnormalities than among patients with normal chest radiographs postoperatively. All patients who developed major chest X-ray abnormalities had a negative value for FRC - closing capacity (CC) in the supine position preoperatively, indicating 'airway closure' during tidal breathing. Preoperative WOV and lung clearance index (LCI) were higher in both sitting and supine positions in patients who developed postoperative hypoxaemia than in patients who did not. The postoperative decrease in TLC, FRC and WOV in the sitting position was greater among patients with major X-ray abnormalities and/or arterial hypoxemia postoperatively than among patients without these complications. According to our results, conventional spirometry in the supine position is not superior to conventional spirometry in the sitting position as part of pre- or post-operative assessment of patients. On the other hand, both preoperative 'airway closure' and arterial oxygen tension, measured in the supine position, showed a correlation with postoperative chest X-ray abnormalities.

Adult↗

PubMed1980

Lung mechanics after cardiac valve replacement.

Fourteen patients undergoing single aortic or mitral valve replacement had measurements made of lung volumes, static pressure-volume (P-V) relationships, and conductance-pressure relationships during deflation before operation and again between one and two years later. At follow-up, total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), and static tidal compliance (slope of static P-V deflation line for one litre above FRC) had increased significantly, in association with a decrease in heart size. There was a change in the shape and position of some P-V curves both in the aortic and mitral patients. In the patients with aortic disease P-V deflation curves shifted to the left after operation. In the patients with mitral disease the P-V deflation curves before operation crossed those measured after operation, so that at high lung volumes recoil became less after operation, but at low lung volumes recoil increased. Conductance had increased at high lung volumes. The data suggest that in longstanding pulmonary congestion, airways are more rigid making them less distensible at high and less compressible at low transpulmonary pressures than after operation when congestion has been at least partly relieved.

Adult↗

PubMed1986

Measurement of abdominal wall compliance in normal subjects and tetraplegic patients.

On inspiration descent of the diaphragm is opposed by the passive properties of the abdominal wall, the tone of its muscles, and the inertia of the abdominal contents. As a result, intra-abdominal pressure rises and promotes rib cage expansion. In patients with high spinal injury the diaphragm is the most important muscle of inspiration and abdominal wall displacement is more evident than in normal subjects. Abdominal wall compliance has been measured by relating gastric pressure to abdominal wall displacement, which was determined by means of an optical contour mapping system. Six normal subjects and six tetraplegic patients were studied in the supine posture, during passive expiration from total lung capacity to functional residual capacity. Over this lung volume range the normal subjects partitioned an average of 31% of expired volume to the abdominal compartment, while the corresponding average figure in the patients was 77% of expired volume. Since the range of gastric pressure was similar in the two groups, it is concluded that abdominal wall compliance is greater in tetraplegic patients. This high compliance could have a detrimental effect on lower rib cage expansion.

Abdominal Muscles↗

PubMed1980

Single-breath diffusing capacity and lung volumes in small laboratory mammals.

We measured the single-breath diffusing capacity for carbon monoxide (DLCO), total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV) in anesthetized male hamsters, rats, guinea pigs, and rabbits whose weights varied from 40 to 3,500 g. TLC (defined as an airway pressure of 25 cmH2O) was calculated by neon dilution. The DLCO was estimated by a modification of the single-breath method. There was a high correlation between body weight and our measurement of both the diffusing capacity and the lung volumes. No significant difference in DLCO was observed in rats when measured in different body positions, at airway pressures of 10 or 20 cmH2O, from FRC or RV, in male or female rats, or following hyperventilation.

Animals↗

PubMed1982

Mechanical properties of the lungs during acclimatization to altitude.

Mechanical properties of the lung were studied in nine healthy lowlanders during a 6-day sojourn at an altitude of 3,457 m. In comparison to sea-level values, it was found at altitude that 1) lung volumes measured by plethysmography including total lung capacity, vital capacity, and functional residual capacity (FRC) presented small changes not exceeding 300 ml; 2) static and dynamic lung compliances were not modified but static pressure-volume curves of lungs were shifted progressively to the left (the decrease in lung elastic recoil averaged about 2 cmH2O on days 4-6); and 3) maximal midexpiratory flow, forced expiratory volume in 1 s, and maximal expiratory and inspiratory flows were increased and, conversely, airways and pulmonary flow resistances were decreased on most days at altitude. The unchanged FRC in the face of a decreased lung recoil may be explained by an increase in thoracic blood volume at altitude, but other possible mechanisms are discussed. The decrease in resistances and increase in maximal flows may be partly explained by the decreased air density at altitude, but another contributing factor such as a bronchodilatation is also suggested. It is proposed that changes in lung mechanics at altitude may account for some of the changes in the pattern of breathing and mouth occlusion pressure (P0.1) observed during acclimatization of lowlanders to altitude.

Acclimatization↗

PubMed1985

Regional lung strain in dogs during deflation from total lung capacity.

Regional lung distortion during deflation from total lung capacity to functional residual capacity (FRC) in intact supine and prone anesthetized dogs was determined from the displacement of multiple metallic markers embedded in the lung parenchyma. Distortion was expressed as strain (epsilon), which is related to fractional length changes. In the supine position, transverse strain (epsilon yy) was larger than vertical strain (epsilon xx) and cephalocaudal strain (epsilon zz) in the upper lobe. The FRC of the lower lobe was smaller than FRC of the upper lobe and all strains were larger, but epsilon zz increased most and became equal to epsilon yy. In the prone position, epsilon yy was largest in all upper lobes and in three of four lower lobes. Strains and volumes of the upper and lower lobes were similar. The upper and lower lobes rotated slightly around different axes, indicating that interpleural fissures allow additional degrees of freedom for the lungs to conform to the thoracic cavity. In the prone position, there were no consistent gradients of strain or volume. These results indicate that, in determining the regional distribution of FRC in the recumbent dog, in addition to the effect of gravity on the lung, there are important interactions between lung and thoracic cavity shapes.

Animals↗

PubMed1987

Effect of high-frequency ventilation on lung mechanics at high transpulmonary pressure.

The different tidal volumes and frequencies of high-frequency ventilation (HFV) compared with conventional mechanical ventilation (CMV) may have different effects on lung mechanics. To test this hypothesis, we compared the effects of 3 h of HFV and CMV on total lung capacity (TLC), functional residual capacity (FRC), the shape of the pressure-volume (PV) curve (%V10), and dynamic compliance (Cdyn), as well as venous admixture and alveolar-arterial O2 gradient. We studied a total of 12 dogs at lung inflations equivalent to 15 cmH2O positive end-expiratory pressure (PEEP) (group I) and 8 dogs at lung inflations equivalent to 0 cmH2O PEEP (group II). For CMV, we used a standard-volume ventilator at a mean tidal volume of 13.8 ml/kg. For HFV, we used an oscillator-type ventilator at 15 Hz and an average tidal volume of 4.3 ml/kg. Our results showed that ventilation with 3 h of PEEP raised lung volume, and lung volumes on HFV were higher than those on CMV in both groups. Specifically, in group I, the volume during ventilation rose on both CMV (150 ml) and HFV (250 ml). These volume changes persisted beyond the ventilation period, such that TLC was unchanged on CMV but had risen 200 ml on HFV. FRC also rose 200 and 300 ml after HFV and CMV, respectively. In group II, the volume during ventilation fell 100 ml on CMV and rose slightly (40 ml) on HFV. TLC and FRC both tended to fall more on CMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Determinants of transdiaphragmatic pressure in dogs.

We measured the transdiaphragmatic pressure (Pdi) during bilateral phrenic nerve stimulation and evaluated the determinants of its change with lung volume, chest wall geometry, and respiratory system impedance in supine dogs. Four rows of radiopaque markers were sewn onto muscle bundles of the costal and crural diaphragm between their origin on the central tendon and their insertion on the rib cage and spine. The length of the diaphragm (L) was determined from the projection images of marker rows using biplane fluoroscopy. Measurements were made at lung volumes between total lung capacity and functional residual capacity before and after the infusion of Ringer lactate solution into the abdominal cavity. In contrast to relaxation, during tetanic stimulation the active lengths of the muscle bundles were similar at all volumes, but the diaphragm assumed different shapes. Although the small differences in active muscle length with volume and liquid loads are consistent with only small changes in muscle force output, Pdi varied by a factor of greater than or equal to 5. There was no single L/Pdi curve that fitted all data during 50-Hz stimulations. We conclude that under these experimental conditions Pdi is not a unique measure of the force produced by the diaphragm and that lung volume, chest wall geometry, and respiratory system impedance are important determinants of the mechanical efficiency of the diaphragm as a pressure generator.

Action Potentials↗

PubMed1998

Chest wall mechanics in sustained microgravity.

We assessed the effects of sustained weightlessness on chest wall mechanics in five astronauts who were studied before, during, and after the 10-day Spacelab D-2 mission (n = 3) and the 180-day Euromir-95 mission (n = 2). We measured flow and pressure at the mouth and rib cage and abdominal volumes during resting breathing and during a relaxation maneuver from midinspiratory capacity to functional residual capacity. Microgravity produced marked and consistent changes (Delta) in the contribution of the abdomen to tidal volume [DeltaVab/(DeltaVab + DeltaVrc), where Vab is abdominal volume and Vrc is rib cage volume], which increased from 30.7 +/- 3. 5 (SE)% at 1 G head-to-foot acceleration to 58.3 +/- 5.7% at 0 G head-to-foot acceleration (P < 0.005). Values of DeltaVab/(DeltaVab + DeltaVrc) did not change significantly during the 180 days of the Euromir mission, but in the two subjects DeltaVab/(DeltaVab + DeltaVrc) was greater on postflight day 1 than on subsequent postflight days or preflight. In the two subjects who produced satisfactory relaxation maneuvers, the slope of the Konno-Mead plot decreased in microgravity; this decrease was entirely accounted for by an increase in abdominal compliance because rib cage compliance did not change. These alterations are similar to those previously reported during short periods of weightlessness inside aircrafts flying parabolic trajectories. They are also qualitatively similar to those observed on going from upright to supine posture; however, in contrast to microgravity, such postural change reduces rib cage compliance.

Abdomen↗

PubMed1999

Ratio of active to passive muscle shortening in the canine diaphragm.

Active and passive shortening of muscle bundles in the canine diaphragm were measured with the objective of testing a consequence of the minimal-work hypothesis: namely, that the ratio of active to passive shortening is the same for all active muscles. Lengths of six muscle bundles in the costal diaphragm and two muscle bundles in the crural diaphragm of each of four bred-for-research beagle dogs were measured by the radiopaque marker technique during the following maneuvers: a passive deflation maneuver from total lung capacity to functional residual capacity, quiet breathing, and forceful inspiratory efforts against an occluded airway at different lung volumes. Shortening per liter increase in lung volume was, on average, 70% greater during quiet breathing than during passive inflation in the prone posture and 40% greater in the supine posture. For the prone posture, the ratio of active to passive shortening was larger in the ventral and midcostal diaphragm than at the dorsal end of the costal diaphragm. For both postures, active shortening during quiet breathing was poorly correlated with passive shortening. However, shortening during forceful inspiratory efforts was highly correlated with passive shortening. The average ratios of active to passive shortening were 1.23 +/- 0.02 and 1.32 +/- 0.03 for the prone and supine postures, respectively. These data, taken together with the data reported in the companion paper (T. A. Wilson, M. Angelillo, A. Legrand, and A. De Troyer, J. Appl. Physiol. 87: 554-560, 1999), support the hypothesis that, during forceful inspiratory efforts, the inspiratory muscles drive the chest wall along the minimal-work trajectory.

Airway Obstruction↗