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PubMed2003

Helium-3 MRI diffusion coefficient: correlation to morphometry in a model of mild emphysema.

Hyperpolarised gases have been most recently used in magnetic resonance imaging to demonstrate new image-derived pulmonary function parameters. One of these parameters is the apparent diffusion coefficient, which reflects the sizes of the structures that compartmentalise gas within the lung (i.e. alveolar space). In the present study, noninvasive parameters were compared to microscopic measurements (mean linear intercept and mean alveolar internal area). Nonselective helium-3 gas density coronal ex vivo images and apparent diffusion maps were acquired in control and elastase-induced panacinar emphysema rats. Total lung capacity was considered the reference for both imaging experiments and lung fixation. A mild degree of emphysema was found based on mean linear intercept (134 +/- 25 microm) versus control (85 +/- 14 microm). The apparent diffusion coefficients were significantly different between the two groups (0.18 +/- 0.02 and 0.15 +/- 0.01 cm2 x s(-1) for elastase and control, respectively). A significant correlation between the apparent diffusion coefficient and corresponding morphometric parameters in mild emphysema was demonstrated for the first time. This study opens the possibility of estimating absolute airspace size using noninvasive techniques.

Animals↗
PubMed1995

Asbestos-induced visceral pleural fibrosis reduces pulmonary compliance.

To determine the nature of respiratory functional impairment caused by asbestos-induced visceral pleural fibrosis (VPF) and to discover which pulmonary physiological variable best reveals it, we examined 59 asbestos-exposed construction workers having asbestos-related changes on chest radiographs. Computed tomography scans of the thorax were also performed. Visceral pleural fibrosis was diagnosed in 29 subjects: seven had only VPF, 17 had VPF and pleural plaques, and five had VPF, plaques, and asbestosis. In subjects without VPF, 23 had plaques, six had plaques and asbestosis, and one had only minor fibrotic parenchymal changes insufficient for a diagnosis of asbestosis. Flow-volume spirometry, body plethysmography, static and dynamic compliance, and pulmonary diffusing capacity for carbon monoxide were measured. The subjects with VPF had significantly lower static (p = 0.005) and dynamic (p = 0.007) compliance values than those without. Other respiratory function variables failed to show any significant differences. We conclude that the measurement of static and dynamic compliance is a useful method in assessing pulmonary function impairment caused by visceral pleural fibrosis.

Adult↗
PubMed2000

Higher arterial oxygen saturation during submaximal exercise in Bolivian Aymara compared to European sojourners and Europeans born and raised at high altitude.

Arterial oxygen saturation (SaO(2)) was measured at 3,600-3,850 m by pulse oximetry at rest and during submaximal exercise in three study groups: 1) highland Aymara natives of the Bolivian altiplano (n = 25); 2) lowland European/North American sojourners to the highlands with at least 2 months of acclimatization time to 3,600 m (n = 27); and 3) subjects of European ancestry born and raised at 3,600 m (n = 22). Aymara subjects maintained approximately 1 percentage point higher SaO(2) during submaximal work up to 70% of their maximal work capacity, and showed a smaller rate of decline in SaO(2) with increasing work compared to both European study groups. The higher-exercise SaO(2) of Aymara compared to Europeans born and raised at 3,600 m suggests genetic adaptation. The two European study groups, who differed by exposure to high altitude during their growth and development period, did not show any significant difference in either resting or exercise SaO(2). This suggests that the developmental mode of adaptation is less important than the genetic mode of adaptation in determining exercise SaO(2). A weak correlation was detected (across study groups only) between the residual forced vital capacity (FVC) and the residual SaO(2) measured at the highest level of submaximal work output (P = 0.024, R = 0.26). While firm conclusions based on this correlation are problematic, it is suggested that a part of the higher SaO(2) observed in Aymara natives is due to a larger lung volume and pulmonary diffusion capacity for oxygen. Results from this study are compared to similar studies conducted with Tibetan natives, and are interpreted in light of recent quantitative genetic analyses conducted in both the Andes and Himalayas.

Adaptation, Physiological↗
PubMed1989

Scanning electron microscope study of the morphology of the reptilian lung: the Savanna monitor lizard Varanus exanthematicus and the pancake tortoise Malacochersus tornieri.

The morphology of the lungs of two reptilian species, Varanus exanthematicus and Malacochersus tornieri, have been studied on gross preparations, latex casts, and critical-point-dried tissues. The shape of these lungs was observed to conform with that of the body, the lung of the monitor lizard (Varanus) being long and ovoid while that of the pancake tortoise (Malacochersus) was rounded and laterally indented. With respect to the size distribution of the gas exchange compartments, the lungs were observed to be notably heterogenous. In both species these units were generally smaller in diameter in the cranial region of the lung while those in the caudal region were larger. The gas exchange compartments in the tortoise were more profusely compartmented with the primary, secondary, and tertiary septa being well developed while in the lizard only the primary and secondary septa were observed. The tertiary septa in the tortoise lung and the secondary septa in that of the monitor lizard defined the terminal gas exchange units, the faveoli. The cast impressions closely resembled the actual lung tissue and convincingly revealed the hierarchical design of the gas exchange compartments as they radiate from the air chambers and ducts, terminally giving rise to the faveoli. This stratification clearly increases the surface area available for gas exchange in these lungs. Disparate refinements of the basic reptilian lung design, as noted here, may lead to differing anatomic pulmonary diffusing capacities for oxygen to which characteristics like energetics and mode of respiration in this taxon may be attributed.

Animals↗
PubMed1992

[Evaluation of interstitial shadows by thin slice computed tomography].

We developed a method for evaluation of interstitial shadows by thin slice computed tomography (CT). We studied thirty-seven cases with interstitial shadows confirmed by thin slice CT, and 13 normal cases. Thin slice CT was scanned on 3 levels: 1) at the aortic arch, 2) about 2 cm below the carina, and 3) about 1 cm above the right diaphragm. Each level was scanned bilaterally to produce 6 regions of interest (ROI); CT numbers were recorded from each ROI. CT numbers ranging from -1000 to 100 Hounsfield units (H.U.) were classified into 4 different bands, -1000 - (-900) H.U. (low band), -900 - (-750) H.U. (medium low band), -750 - (-500) H.U. (medium high band), and -500 - 100 H.U. (high band), for cases with interstitial shadows and for normal cases. We calculated the prevalence of CT numbers in each band for both normals and subjects with interstitial shadows. Compared to the normals, subjects with interstitial shadows showed fewer pixels in the medium low band and more pixels in the medium high and high bands. Furthermore, the prevalence of CT numbers in each band correlated with %TLC, %VC, and pulmonary diffusing capacity. We conclude that thin slice CT is a useful method for evaluation of the extent and characteristics of interstitial shadows.

Alveolitis, Extrinsic Allergic↗
PubMed2001

Compromised respiratory function in postnatal lambs after placental insufficiency and intrauterine growth restriction.

Epidemiologic studies have shown persistent effects of low birth weight on respiratory function and lung health, but underlying mechanisms are not understood. Our aim was to determine the effects of intrauterine growth restriction (IUGR), a major cause of low birth weight, on postnatal respiratory function. IUGR was induced by umbilico-placental embolization during late gestation in chronically catheterized sheep. Umbilico-placental embolization was performed between 120 d of gestation and term ( approximately 146 d) during which fetuses were hypoxemic and hypoglycemic relative to controls. Umbilico-placental embolization led to a 48% reduction in birth weight compared with controls, and throughout the postnatal study period IUGR lambs (n = 8) remained lighter than controls (n = 8). Respiratory function was repeatedly studied in lambs for 8 wk after birth; during this period, IUGR lambs were mildly hypoxemic and tended to be hypercapnic compared with controls. In IUGR lambs, relative to controls, O(2) consumption (mL/min/kg) and minute ventilation (mL/kg) were increased and pulmonary diffusing capacity (adjusted for functional residual capacity) was decreased. Functional residual capacity, measured by helium dilution, and total lung capacity (measured at 30 cm H(2)O) were smaller in IUGR lambs than in controls. When adjusted for functional residual capacity, static lung compliance was reduced and chest wall compliance was increased in IUGR lambs. At 8 wk, pulmonary DNA and protein concentrations were decreased in IUGR lambs relative to controls. We conclude that restriction of fetal growth by placental insufficiency induces alterations in the lungs and chest wall that result in persistent impairments in respiratory function during early postnatal life.

Animals↗
PubMed1989

Oxygen transfer kinetics of red blood cells of the turtle Pseudemys scripta elegans.

The kinetics of O2 uptake into, and release from, the red blood cells (RBC) of the turtle Pseudemys scripta elegans were determined with a stopped-flow technique at varied temperature (10-30 degrees C) and pH (7.5-7.9). The results were compared to those obtained for RBC of other vertebrates and related to morphometric and physiological data on gas/blood diffusion in turtle lungs. The O2 transfer conductance of RBC, G, for O2 release into high concentrations of dithionite, considered to represent the best estimate of true RBC transfer conductance for O2 uptake and release, averaged 0.17 +/- 0.01 at 30 degrees C, 0.13 +/- 0.01 at 20 degrees C, 0.09 +/- 0.01 at 10 degrees C (mean +/- SD, in mmol.min-1.Torr-1.(mlRBC)-1). These values are about one half the corresponding value for human RBC, and this difference may be due to the larger size of turtle RBC (volume, 327 microns 3) compared to human RBC (90 microns 3). The temperature dependence of G, Q10 = 1.3 indicates that, as in human RBC, diffusion through aqueous media is the main limiting factor for O2 exchange. Morphometric data on the lungs of Pseudemys scripta suggest that the resistance to O2 transfer by RBC is lower than that offered by the gas-blood barrier. The total apparent transfer resistance to CO, obtained from previous measurements of pulmonary diffusing capacity for CO in the same species, is much higher than that predicted from the combination of RBC O2 kinetics and morphometric data on gas-blood barrier.

Animals↗
PubMed1995

The diagnostic value of conventional X-ray examination of the lungs in comparison with high-resolution computed tomography (HRCT), isotope perfusion scintigraphy and the diffusion capacity in patients with pneumoconiosis.

A precise diagnosis of initial reticular forms of pneumoconioses is very difficult. The present study focuses on 30 patients with initial reticular forms of silicosis, asbestos induced interstitial lung fibrosis, mixed dust pneumoconioses and pneumoconioses of electrowelders. The anterior-posterior chest radiography (according to the ILO International Radiological Classification of Pneumoconioses, 1980), high-resolution computed tomography (HRCT), perfusion scintigraphy with 99mTc and the changes in the diffusion capacity were compared. The diagnostic value of these methods was assessed. The study continues by expanding the groups of patients examined and by including the membrane component of diffusion.

Adult↗
PubMed1990

Effect of percutaneous transcatheter embolization on pulmonary function, right-to-left shunt, and arterial oxygenation in patients with pulmonary arteriovenous malformations.

The effects of percutaneous transcatheter embolization on pulmonary function and exercise capacity were assessed in 15 patients with pulmonary arteriovenous malformations (PAVM). Vital capacity (VC), FEV1, DLCO, SaO2, exercise performance, and right-to-left shunt (100% oxygen method) were measured before and 2 to 6 months after treatment. Surgical correction had been attempted in 9 patients prior to referral, and 11 had associated hereditary hemorrhagic telangiectasia (HHT). Lung function tests before intervention showed normal VC and FEV1/VC ratios, reduced DLCO (mean 71% predicted, range 36 to 123%), a resting supine SaO2 of 86% (range 67 to 95%) and mean shunt fraction of 33% (range 15 to 47%). Despite further marked falls in SaO2 on exertion, exercise capacity was well preserved. Following steel coil embolization of all PAVM with a feed vessel internal diameter greater than 3 mm (one to four sessions per patient), mean shunt fraction improved from 33 to 19% and resting SaO2 from 86 to 92% with no change in VC. A consistent improvement in diffusing capacity was seen only in patients with coexisting HHT. Exercise capacity increased in the majority (unchanged in 6), and SaO2 during maximal exercise improved in all except one patient. There were no long-term complications following embolization. These findings indicate that embolization of all macroscopic PAVM, undertaken primarily to reduce the risk of paradoxical embolization, is safe and results in substantial improvements in resting and exercise SaO2 without evidence of loss of normal lung. The right-to-left shunts remaining following embolization may reflect the presence of numerous microscopic PAVM in these patients.

Adolescent↗
PubMed1997

Upper abdominal surgery: does a lung function test exist to predict early severe postoperative respiratory complications?

We evaluated the capacity to predict severe respiratory complications (SRCs) following upper abdominal surgery (UAS) by using the results of a respiratory questionnaire and preoperative pulmonary function tests. Lung volumes, flows and transfer factor of the lung for carbon monoxide (TL,CO,sb) were assessed in 361 consecutive adult patients (248 males and 113 females). SRCs were diagnosed 24 h after UAS by clinical examination and chest radiography. Univariate and stepwise multiple logistic regression analyses were performed to estimate the odds ratio (OR) and 95% confidence interval (95% CI) of each single input variable, and to determine which indices best predicted outcome. These patients had a 1% mortality rate and 14% incidence of SRCs, with a male:female ratio of 0.86. The best predictors for SRCs by multiple analysis were: preoperative current hypersecretion of mucus (OR=133; p<0.0001); an increase in residual volume (RV) (OR=3.11; p=0.01); and, to a lesser extent, low percentage of predicted values both of forced expiratory volume in one second (FEV1 % pred) and TL,CO,sb. The algorithm thus obtained (logit theta) was extremely sensitive (84%), specific (99%), and accurate (95%) for preoperative prediction of SRCs. We have found that preoperative current hypersecretion of mucus and pulmonary hyperinflation, and to a lesser extent percentage predicted values both of forced expiratory volume in one second and transfer factor of the lung for carbon monoxide, have a significant predictive capacity for severe respiratory complications following upper abdominal surgery.

Abdomen↗
PubMed1988

Application of linear integration in the morphometric study of mild and severe pulmonary alveolar injury.

In this study we applied linear integration morphometry to characterize the pulmonary alveolar reaction to toxic injury and to study possible relationships between the major tissue and cell compartments of alveolar tissue, normal and injured. Acute alveolar injury of mild and severe intensity was induced in Swiss-Webster mice by the ip administration of the chemicals diquat (4 mg/kg) and butylated hydroxytoluene (BHT; 400 mg/kg). Animals were sacrificed at Days 1 and 2 after diquat treatment and at Days 1, 3, and 5 after BHT treatment. Sampling and analysis of alveolar tissue were conducted at both levels of light and electron microscopy. Thickness distributions of arithmetic and reciprocal intercepts, as well as the arithmetic (tau) and harmonic (tau h) mean thicknesses, were established for the following alveolar compartments: septum, alveolo-capillary barrier (ACB), type I and total epithelia, capillary endothelium, and interstitium. A relative measure of the pulmonary diffusion capacity and the capillary load of alveolar septa were also determined. The parameters calculated from these thickness distributions, such as their slopes, percentages of thin intercepts, and tau/tau h ratios, proved very sensitive and useful in the detection and characterization of morphological alterations in the type I epithelial and capillary endothelial cells following either mild or severe alveolar injury. The epithelial, endothelial, and interstitial layers of pulmonary septa were all characterized by their own pattern of structural changes, so that it proved impossible to relate them in a simple way to the tissue reaction, which can be easily studied at the light microscopic level. Linear integration morphometry thus proved very useful as a morphometric approach to the study of pulmonary alveolar injury and repair.

Animals↗
PubMed1996

[Pulmonary complications in diabetes mellitus].

The lung is not considered a target organ in diabetes mellitus. In English language literature there are many papers showing the opposite. Many studies demonstrated a thickened alveolar epithelial and pulmonary capillary basal lamina and a reduced lung elasticity, others showed that these histopathological alterations developed into functional abnormalities: reduced lung volumes, reduced pulmonary diffusion capacity and elastic recoil. The pathogenesis is currently thought to involve the nonenzymatic glycosylation (NEG) of tissue proteins inducing an alteration in connective tissue. In patients with diabetic autonomic neuropathy there is an abnormal basal airway tone due to an alteration in vagal pathways: these patients have a reduced bronchial reactivity and bronchodilatation. Diabetic patients have an increased propensity to acquire infections, in particular tuberculosis and pulmonary fungal diseases (coccidioidomycosis, aspergillosis and mucormycosis). The frequency of occurrence of tuberculosis is reported to be four times than in non diabetics, there is a predilection for the lower lobes and the disease is more aggressive in poorly controlled diabetes mellitus. Pulmonary mucormycosis is an infection caused by Phycomycetes, the fungus has the propensity to invade vascular structures giving hemoptysis and leading to a high mortality unless diagnosed promptly. The mechanism for the increased susceptibility to infection is due to an alteration in chemotactic, phagocytic and bactericidal activity of polymorphonuclear leukocytes.

Diabetes Complications↗
PubMed1999

Respiratory function in lambs after in utero treatment of lung hypoplasia by tracheal obstruction.

Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is little knowledge of subsequent postnatal respiratory function. We have determined the effectiveness of TO in fetal sheep with existing lung hypoplasia in restoring postnatal respiratory function. Lung hypoplasia was induced by lung liquid drainage from 112 days of gestation to term ( approximately 148 days). We used an untreated group (ULH), a treated group (TLH) in which the trachea was obstructed for 10 days, and a control group. ULH lambs died within 4 h of birth. TLH lambs were hypoxic for the first week and were hypercapic at 2 days. Pulmonary diffusing capacity, gas volumes, and respiratory compliances were not different between control and TLH lambs. Minute ventilation was not different between the two groups; however, tidal volumes were lower and respiratory frequencies were higher in TLH lambs than in controls for 2 wk after birth. We conclude that 10 days of TO in the presence of initial lung hypoplasia prevents death at birth and returns most aspects of pulmonary function to normal by 1-2 wk after birth.

Aging↗
PubMed1998

Fixed maximal stroke index in patients after pneumonectomy.

Patients who have undergone pneumonectomy (PNX) show limited exercise capacity, partly attributable to an impaired stroke index (SI). To determine whether this limitation is due to deconditioning, we assessed exercise performance and cardiopulmonary function in seven patients after PNX (age: 59 +/- 2 yr, mean +/- SEM) and eight normal, healthy nonsmokers (52 +/- 3 yr) before and after an ergometer exercise training program for 30 min per day, 5 d per week, for 8 wk at 65% of measured maximal O2 uptake. Lung volume, diffusing capacity of carbon dioxide (DL(CO)) and cardiac index (CI) were determined during steady-state exercise by a rebreathing method. Exercise endurance was measured at 80% of maximal power. As compared with normal subjects, patients who had had PNX showed diminished maximal oxygen uptake (VO2max), as well as diminished lung volumes, ventilatory capacities, and maximal cardiac and stroke indexes. After training, VO2max, endurance, and peripheral O2 extraction improved in both groups. However, maximal cardiac and stroke indexes increased only in normal subjects and not in patients. We conclude that an irreversibly fixed maximal SI is a major source of exercise limitation after PNX, probably because of pulmonary arterial hypertension and/or mechanical distortion of the cardiac fossa. Ventilatory impairment after PNX did not prevent a training-induced increase in VO2max. Exercise training confers significant functional benefit on postpneumonectomy patients by enhancing peripheral O2 extraction.

Adult↗
PubMed1986

High-dose intravenous methylprednisolone pulse therapy as initial treatment in cryptogenic fibrosing alveolitis. A pilot study.

Ten patients with fibrosing alveolitis were treated in a simple random design initially with either a high dose of methylprednisolone (5 patients) or a conventional dose of prednisolone (5 patients) followed by a maintenance dose of 30 mg prednisolone daily. The patients were followed for 6 weeks. No significant (p greater than 0.05) differences were observed between patients with high and low initial dose of glucocorticosteroids, as regards forced vital capacity, transfer factor for carbon monoxide or symptom scores after 3 and 6 weeks of treatment. After 6 weeks the dyspnoea score and the 67Ga uptake decreased, on average, by 74 and 85%, respectively, while forced vital capacity and transfer factor increased by 15 and 29%.

Adult↗
PubMed1994

Mechanisms of increased epithelial lung clearance of DTPA in diffuse fibrosing alveolitis.

The aim of this study was to elucidate possible mechanisms of increased epithelial lung clearance in diffuse fibrosing alveolitis (DFA). We investigated the relationships between epithelial lung clearance as assessed by the clearance of aerosolized 99mTc-diethylene-triamine-penta-acetic acid (RC-DTPA), luminal alveolitis as assessed by bronchoalveolar lavage, and pulmonary function, in 30 nonsmokers with DFA. In 14 of these patients, RC-DTPA and lung function were determined before and during therapy with prednisolone (0.5 mg.kg-1 daily). RC-DTPA was higher in patients with DFA (4.45 +/- 2.50%.min-1) than in normal subjects (1.18 +/- 0.31%.min-1). RC-DTPA did not correlate with the number of alveolar neutrophils, but correlated positively with the number of alveolar lymphocytes, and negatively with vital capacity (VC). RC-DTPA decreased from 6.1 +/- 2.8 to 3.8 +/- 1.9%.min-1 with prednisolone. RC-DTPA before prednisolone correlated positively with the prednisolone-associated improvement in VC. We conclude that in patient with DFA, RC-DTPA is increased, and decreases but does not return to normal with corticosteroid therapy. Our data suggest that in DFA the increase in RC-DTPA could be related to the recoil-induced stretch of the respiratory epithelium and to alveolar lymphocytic inflammation.

Aerosols↗
PubMed1983

Effects of obesity on respiratory function.

Obesity, because it alters the relationship between the lungs, chest wall, and diaphragm, has been expected to alter respiratory function. We studied 43 massively obese but otherwise normal, nonsmoking, young adults with spirometry, lung volume measurement by nitrogen washout, and single-breath diffusing capacity for carbon monoxide (DLCO). Changes in respiratory function were of two types, those that changed in proportion to degree of obesity--expiratory reserve volume (ERV) and DLCO--and those that changed only with extreme obesity--vital capacity, total lung capacity, and maximal voluntary ventilation. When compared with commonly used predicting equations, we found that mean values of subjects grouped by degree of obesity were very close to predicted values, except in those with extreme obesity in whom weight (kg)/height (cm) exceeded 1.0. In 29 subjects who lost a mean of 56 kg, significant increases in vital capacity, ERV, and maximal voluntary ventilation were found, along with a significant decrease in DLCO. Because most subjects fell within the generally accepted 95% confidence limits for the predicted values, we concluded that obesity does not usually preclude use of usual predictors. An abnormal pulmonary function test value should be considered as caused by intrinsic lung disease and not by obesity, except in those with extreme obesity.

Adult↗
PubMed1992

Ventilatory capacity and exercise-induced arterial desaturation of highly trained endurance athletes.

Recent evidence suggested that exercise-induced arterial O2 desaturation may occur in highly trained endurance athletes. So, Dempsey brought the hypothesis that the pulmonary capacity for oxygen transport cannot meet superior demands imposed by cardiovascular system in highly trained endurance athletes, and endurance training primarily causes adaptation in the skeletal muscles and in the systemic cardiovascular system, with little change in the pulmonary system. In the present study, we determined the propriety of the hypothesis due to measure the ventilatory capacity of endurance athletes. Sixteen highly trained endurance athletes (ET) and thirteen untrained subjects (UT) volunteered to participate in these experiments. All subjects performed the four experiments, 1) the highest oxygen uptake (peak VO2) during incremental cycle exercise and ventilation (VE), ventilatory equivalent for O2 (VE/VO2) and arterial O2 saturation (SaO2) at which peak VO2 was observed, 2) the maximal voluntary ventilation for 30 sec at rest (MVV), 3) the pulmonary diffusing capacity for CO (DLCO) and expressed per unit of alveolar lung volume (KCO) at rest by the single breath method, and 4) the ventilatory response to hypercapnia (S) at rest by rebreathing method, were measured. The peak VO2 of ET (66.7 ml.min-1.kg-1) was significantly (30.8%) higher than UT (52.4 ml.min-1.kg-1), and VE/VO2 and SaO2 of ET (29.3 and 93.7%, respectively) were significantly lower than UT (34.6 and 95.8%). There were no differences in VE, MVV, DLCO, and S between two groups.

Adult↗