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PubMed1998

Transforming growth factor-beta1 in sarcoidosis.

Transforming growth factor-beta (TGF-beta) is a cytokine that promotes extracellular matrix accumulation and inhibits matrix degradation. Although the natural course of sarcoidosis is usually favourable, granuloma healing in the lung may result in pulmonary fibrosis and respiratory impairment in some patients. In this study TGF-beta1 was evaluated in bronchoalveolar lavage (BAL) fluid and culture supernatants of alveolar macrophages (AM) from 73 patients with biopsy-proven sarcoidosis. Disease activity was defined when patients recently developed or increased symptoms (cough, dyspnoea, systemic symptoms) and/or demonstrated increasing opacities on chest radiography. Pulmonary function tests were performed in all patients including forced expiratory volume in one second (FEV1), forced vital capacity (FVC), total lung capacity (TLC) and the diffusing capacity of the lung for carbon monoxide (DL,CO). Fourteen patients with idiopathic pulmonary fibrosis (IPF) and 14 healthy subjects were investigated as a control group. Immunohistochemistry was used to evaluate the cell distribution of TGF-beta1 on lung specimens. TGF-beta1 levels in BAL and in AM supernatants were not different between sarcoidosis and healthy subjects, whereas they were markedly increased in IPF. However, the TGF-beta1 level was significantly increased in BAL fluid but not in AM supernatants from sarcoidosis with altered lung function, compared with patients with normal lung function. The TGF-beta1 level in BAL was increased in active sarcoidosis but this increased level was mainly related to the higher level observed in patients with altered lung function. TGF-beta1 levels in BAL correlated significantly with the lymphocyte percentage. TGF-beta1 staining assessed by immunohistochemistry was intense in epithelioid histiocytes comprising non-necrotizing granuloma and in bronchiolar epithelial cells, in hyperplastic type II pneumocytes and occasionally in AM. This study supports the hypothesis that overproduction of transforming growth factor-beta1 is associated with functional impairment in patients with pulmonary sarcoidosis.

Adult↗
PubMed2006

Technetium 99m-diethylene triamine penta-acetic acid aerosol clearance in the evaluation of pulmonary involvement in sickle cell disease.

BACKGROUND: Pulmonary clearance of inhaled technetium (Tc) 99m-labeled diethylene triamine penta-acetic acid (DTPA) aerosol is a sensitive non-invasive marker of alveolar permeability and patients with interstitial lung diseases show enhanced clearance. However, a previous study in adult patients with diabetes mellitus showed delayed clearance. OBJECTIVES: To investigate DTPA clearance in steady-state, otherwise healthy adult sickle cell disease (SCD) patients and correlate it with pulmonary function tests (PFTs), hematologic and clinical parameters. MATERIALS AND METHODS: The subjects were randomly selected from the Hematology Clinic of Mubarak Hospital, Kuwait. Hematologic and pulmonary function data were collected with standard methods. DTPA radio-aerosol clearance studies were performed using ultrafine nebulizer containing 35 mCi (1295 MBq) of Tc 99m-DTPA in its reservoir and t(1/2) clearance in minutes was determined. Average values for both lungs were calculated and compared with normal values for our population. RESULTS: Forty-three subjects (24 SS and 19 S-beta(0)thal) aged between 16 and 45 yr (mean of 27.1 +/- 9.7) were studied. Twenty-two subjects (51.2%) had delayed, while only 10 (23.3%) showed enhanced DTPA clearance. Patients with enhanced clearance showed better PFTs than those with normal or delayed clearance. There was significant negative correlation of DTPA clearance with forced expiratory volume in 1 s, forced vital capacity and total lung capacity and significant positive correlation with age. CONCLUSIONS: Majority of adult SCD patients have delayed DTPA clearance unlike in inflammatory lung diseases, but similar to diabetes mellitus. DTPA clearance may be a useful modality for monitoring pulmonary involvement in SCD.

Adolescent↗
PubMed1979

Radiographic comparison of human lung shape during normal gravity and weightlessness.

Human lung shape was measured during zero gravity (0 G) to decide whether the normal vertical regional differences in ventilation are due directly to distortion of the elastic lung by its own weight, or instead, due indirectly to the effect of gravity on the shape of the rib cage and diaphragm. This was important because we previously established that weightlessness virtually abolishes the normal topographical inequality of ventilation (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 45: 987-998, 1978). Chest radiographs were made after 10 s of a weightless flight trajectory aboard a NASA-Ames Research Center Learjet in both posterior-anterior and left lateral projections on five seated volunteers at residual volume, functional residual capacity, and total lung capacity. Lung shape was assessed by measuring lung heights and widths in upper, middle, and lower lung regions. We found no significant differences between any of the normal gravity (1 G) and o G measurements, although there was a slight tendency for the lung to become shorter and wider at o G (mean changes generally less than 3% or about 0.5 cm). By contrast, Grassino et al. (J. Appl. Physiol. 39: 997-1003, 1975) found no change in the vertical distribution of ventilation after voluntarily changing lung dimensions by more than 1 cm by moving the abdomen in or out. We conclude that gravity produces the topographical distribution of ventilation in the upright human lung by distorting the elastic lung tissue within the chest rather than by altering the shape of the rib cage and diaphragm.

Humans↗
PubMed1999

Angiotensin-converting enzyme inhibition facilitates alveolar-capillary gas transfer and improves ventilation-perfusion coupling in patients with left ventricular dysfunction.

OBJECTIVE: The backward effects of left ventricular dysfunction include alterations in alveolar-capillary gas transfer and ventilation-perfusion coupling. Because the angiotensin-converting enzyme (ACE) is highly concentrated in the vascular endothelium of the lungs, we examined whether ACE inhibitors may influence the pulmonary function in patients with congestive heart failure. METHODS: In 20 patients with idiopathic cardiomyopathy, pulmonary function and exercise capacity were evaluated at baseline and 6 and 12 months after treatment with enalapril (10 mg twice a day) was started. The study also included 19 age- and sex-matched control subjects with mild primary hypertension and normal left ventricular function who were given enalapril as a standard treatment of high blood pressure. RESULTS: In congestive heart failure, forced expiratory volume in 1 second, vital capacity, and total lung capacity did not vary significantly with enalapril; alveolar-capillary diffusion of carbon monoxide (DL(CO)) increased toward normal; exercise tolerance time, peak exercise oxygen uptake (peak VO2), minute ventilation and tidal volume (peak VT) also increased; and the ratio of volume of dead space (VD) to VT (peak VD/VT) at peak exercise reduced. Changes in peak VO2 showed a direct correlation with those in DL(CO) and an inverse correlation with those in peak VD/VT. Results at 6 and 12 months were comparable. Enalapril did not affect these variables in the control population. CONCLUSIONS: In patients with idiopathic cardiomyopathy heart failure, but not in control subjects, gas transfer and ventilation-perfusion improved with ACE inhibition. These pulmonary changes may contribute to the associated increase in exercise tolerance.

Adult↗
PubMed1978

Pulmonary function abnormalities in asymptomatic children after hydrocarbon pneumonitis.

To assess the effect of hydrocarbon pneumonitis on the developing lung, we studied the pulmonary function of 17 asymptomatic children, 8 to 14 years after the initial insult. Fourteen of the 17 subjects (82%) had one or more pulmonary function abnormalities, the most frequent being a high volume of isoflow. Volume of isoflow, ratio residual volume to total lung capacity, slope of phase III, flow rates at 50% and 25% of vital capacity and 60% of the total lung capacity, one-second forced expiratory volume, and maximum midexpiratory flow rate differed significantly (P less than .05) from values in control groups. Closing volume and closing capacity were not significantly different. Residual abnormalities present in children after hydrocarbon pneumonitis can be explained on the basis of small airway obstruction and/or loss of elastic recoil. These children may be at risk for the development of chronic lung disease as adults when they are exposed to exogenous factors such as air pollution or smoking.

Child, Preschool↗
PubMed1998

Effect on lung function of methotrexate and non-steroid anti-inflammatory drugs in children with juvenile rheumatoid arthritis.

We evaluated lung function in a group of patients affected by juvenile rheumatoid arthritis (JRA), without clinical and/or radiological signs of respiratory involvement. We compared the effects on pulmonary function of methotrexate (MTX) therapy combined with non-steroid anti-inflammatory drugs (NSAIDs) to those of NSAIDs alone and correlated lung function to subtype onset, disease duration and disease activity. Our patients were 27 JRA children, subdivided into two groups according to the therapy (group A = 14 patients, treated with a low dose of MTX and NSAIDs; group B = 13 patients, treated with NSAIDs alone). Clinical evaluation, haematological data and pulmonary function tests (PFTs) were obtained in each group at baseline (time 0) and at 1 year (time 1). At time 0 and time 1 PFTs were altered in 51.8% of JRA patients. The restrictive pattern (reduced forced vital capacity, FVC) was the most frequent feature, observed in 22.2% of patients. In group A the mean values of FVC, FEV1 (forced expiratory flow in 1 s), FRC (functional residual capacity), TLC (total lung capacity) and DLCO (diffusing lung capacity of carbon monoxide) were significantly lower compared to those of group B, at time 0 and at time 1. No functional parameter was correlated to subtype, duration or activity of the disease. Our study confirms that abnormalities in PFTs may be detected in JRA patients, even in the absence of clinical and/or radiological signs of lung disease; MTX in combination with NSAIDs does not seem to affect lung function at 1 year more than NSAIDs alone.

Adolescent↗
PubMed1986

Reference values of regional ventilation, lung volumes and perfusion assessed by using an automated multidetector 133-Xe radiospirometer.

The distributions of ventilation, lung volumes and perfusion were studied in 56 healthy non-smoking Finnish adults to get reference values for a computerized 133-Xe radiospirometer with 16 detectors and moveable designed collimators (Valmet BI 1200). The age of the subjects ranged from 20 to 60 (mean 36.5, SD 9.1) years. Thirty-one of them were men. In addition, the reproducibility of the method was tested in 13 patients with pulmonary diseases. The measurements were made with the subjects in supine position. The studied variables showed no correlation with sex or age. The interpulmonary and intrapulmonary percentage distributions between 16 pulmonary subareas were calculated for the following variables: ventilation (V) (assessed from wash-in curves), functional residual capacity (FRC), vital capacity (VC), total lung capacity (TLC), wash-out time during tidal breathing (T1/2 V), perfusion (Q) (at TLC level), wash-out time after breath-holding during the perfusion study (T1/2 Q), specific ventilation (V/FRC), specific perfusion (Q/TLC), and V/Q ratio. The percentage proportion (mean and SD) in the right lung of V was 50.5 (2.6), of FRC 51.7 (2.1), of VC 51.0 (1.8), of TLC 51.1 (1.7), and of Q 50.8 (3.0). Apical parts of the lungs showed smaller functional proportions than the other parts. There was a significant tendency to increasing basal and decreasing apical proportions of V, VC, TLC and FRC with increasing height and weight. Coefficients of variation (CoV) of the distribution indices for the whole lung varied between 1.9 and 5.0%. We suggest that the distribution data obtained here are helpful in clinical work when evaluating the distributions in patients studied with the Valmet BI 1200 radiospirometer.

Adult↗
PubMed1983

Radiographic evaluation of regional pulmonary dimensions and volumes: effect of age.

On chest radiographs performed at spirometrically controlled residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC), several distances were measured in 8 young and 7 elderly male subjects. Regional volumes above and below the minor fissure were calculated using Barnhard's method for thoracic gas volume determination. When the volumes above and below the fissure were expressed as a percentage of their volume at TLC, and related to overall lung volumes (in percent of TLC), graphs similar to the ones obtained in scintigraphic studies were obtained. This illustrates that the present radiographic method may provide information on regional pulmonary volumes. Regional TLC of the upper zone was larger in elderly subjects than in young ones, while the opposite was true for regional TLC of the lower zone, indicating that maximal regional expansion changes with age. For the upper zone, the changes in diameters between RV and TLC were largest in antero-posterior direction and smallest in cranio-caudal direction. For the lower zone, changes were largest in cranio-caudal direction. This suggests an anisotropic expansion of the upper and lower zone. This anisotropy was more pronounced in the young than in the elderly subjects.

Adult↗
PubMed1998

Lung diffusing capacity and exercise in subjects with previous high altitude pulmonary oedema.

Subjects with a history of high-altitude pulmonary oedema (HAPE) have increased pulmonary artery pressure and more ventilation-perfusion (V'A/Q') inhomogeneity with hypoxia and exercise. We used noninvasive methods to determine whether there are differences in the pulmonary diffusing capacity for carbon monoxide (DL,CO) and cardiac output (Q') during exercise, indicative of a more restricted pulmonary vascular bed in subjects with a history of HAPE. Eight subjects with radiographically documented HAPE and five controls with good altitude tolerance had standard pulmonary function testing and were studied during exercise at 30 and 50% of normoxic maximal oxygen consumption (V'O2) at an inspiratory oxygen fraction of 0.14 and 0.21. DL,CO and Q' were measured by CO and acetylene rebreathing techniques. HAPE-resistant subjects had 35% greater functional residual capacity than HAPE-susceptible subjects. Vital capacity and total lung capacity were also 7-10% greater. There were no differences in airflow rates or resting diffusing capacity. However, DL,CO in HAPE-susceptible subjects was lower in hypoxia and with exercise, and showed less increase (32 versus 49%) with the combined stimulus of hypoxic exercise. HAPE-susceptible subjects had smaller increases in stroke volume, Q', and ventilation during exercise. The findings are consistent with lower pulmonary vasoconstriction, greater vascular capacitance and greater ventilatory responsiveness during exercise in subjects who are resistant to high-altitude pulmonary oedema. Their larger lung volumes suggest a constitutional difference in pulmonary parenchyma or vasculature, which may be a determinant of high-altitude pulmonary oedema resistance.

Adult↗
PubMed1988

Functional characteristics of canine costal and crural diaphragm.

We estimated the in situ force-generating capacity of the costal and crural portions of the canine diaphragm by relating in vitro contractile properties and diaphragmatic dimensions to in situ lengths. Piezoelectric crystals were implanted on right costal and left crural diaphragms of anesthetized dogs, via midline laparatomy. With the abdomen reclosed, diaphragm lengths were recorded at five lung volumes. Contractile properties of excised muscle bundles were then measured. In vitro force-frequency and length-tension characteristics of the costal and crural diaphragms were virtually identical; their optimal force values were 2.15 and 2.22 kg/cm2, respectively. In situ, at residual volume, functional residual capacity (FRC), and total lung capacity the costal diaphragm lay at 102, 95, and 60% of optimal length (Lo), whereas the crural diaphragm lay at 88, 84, and 66% of Lo. Muscle cross-sectional area was 40% greater in costal than in crural diaphragms. Considering in situ lengths, cross-sectional areas, and in vitro length-tension characteristics at FRC, the costal diaphragm could exert 60% more force than the crural diaphragm.

Animals↗
PubMed2003

Study of Clara cell 16, KL-6, and surfactant protein-D in serum as disease markers in pulmonary sarcoidosis.

STUDY OBJECTIVES: To determine the discriminative value of serum Clara cell 16 (CC16), KL-6, and surfactant protein (SP)-D as markers of interstitial lung diseases, and their ability to reflect pulmonary disease severity and prognosis in sarcoidosis. SUBJECTS: Seventy-nine patients with sarcoidosis and 38 control subjects. MEASUREMENTS: Serum CC16, KL-6, and SP-D concentrations at disease presentation were measured. Pulmonary function tests and chest radiographs were analyzed at presentation and 2-year follow-up. RESULTS: All markers co-correlated, and a significant difference was found between CC16, KL-6 (Krebs von den Lungen-6), and SP-D levels in patients with sarcoidosis and control subjects (p < 0.0001). Receiver operating characteristic curve analysis revealed largest area under the curve for KL-6. Significantly higher levels of CC16 and KL-6 were found in patients with parenchymal infiltration (stage II, III) compared to patients without parenchymal infiltration (stage I). In concordance, CC16 and KL-6 levels inversely correlated with diffusion capacity and total lung capacity, and KL-6 also with inspiratory vital capacity. Moreover, higher KL-6 levels were weakly but significantly associated with persistence or progression of parenchymal infiltrates at 2-year follow-up. CONCLUSION: In this study, KL-6 appears to be the best discriminative marker in differentiating patients with sarcoidosis from healthy control subjects; however, as it is not a specific marker for this condition, this quality is unlikely to be useful as a diagnostic tool. Both CC16 and KL-6 may be of value in reflecting disease severity, and KL-6 tends to associate with pulmonary disease outcome.

Adult↗
PubMed2002

Inflammation, infection, and pulmonary function in infants and young children with cystic fibrosis.

Our aim was to study the effect of lower airway infection on clinical parameters, pulmonary function tests, and inflammation in clinically stable infants and young children with cystic fibrosis (CF). To accomplish this goal, a prospective cohort of screened CF patients under 4 years of age were studied, using elective anesthesia and intubation for: passive respiratory mechanics (single breath occlusion passive deflation) and lung volumes (nitrogen washout), under neuromuscular blockade; and bronchoalveolar lavage (BAL) of 3 main bronchi for cytology, cytokine interleukin (IL)-8, and quantitative microbiology. There were 22 children studied, with a mean age of 23.2 months (6.7-44 months). A greater relative risk of lower airway pathogens was associated with prior respiratory admission (3.60, 95% confidence interval [CI] 2.87-4.51), history of asthma (1.75, 95% CI 1.52-2.03), and chronic symptoms (1.50, 95% CI 1.23-1.83), especially wheeze (1.88, 95% CI 1.61-2.19). Lower respiratory pathogens (> or = 10 cfu/ml BAL) were found in 14 out of 22, and greater than 10(5) cfu/ml in 8 out of 22 subjects. The level of pathogens in BAL (log10 cfu/ml) explained 78% of the variability in percent neutrophils and 34% of the variability in IL-8 levels. Pathogen level also correlated with pulmonary function tests of specific respiratory system compliance (r -0.49, p = 0.02) and functional residual capacity over total lung capacity (r 0.49, p = 0.03). We conclude that the presence of pathogens in the lower airways correlated with levels of inflammation, respiratory system compliance, and degree of air trapping.

Bronchoalveolar Lavage Fluid↗
PubMed2001

Pulmonary (99m)Tc-DTPA aerosol clearance and survival in usual interstitial pneumonia (UIP).

BACKGROUND: Clearance of inhaled technetium 99m-labelled diethylenetriamine penta-acetic acid ((99m)Tc-DTPA) from the lungs is a potential indicator of disease progression in patients with idiopathic pulmonary fibrosis (IPF). METHODS: We prospectively analysed the usefulness of this technique for predicting survival in 106 non-smoking patients with usual interstitial pneumonia (UIP) pattern IPF diagnosed by high resolution CT (HRCT) scanning or histological examination (M/F 65/41, mean (SD) age 61 (11) years). DTPA clearance was analysed according to both mono-exponential and bi-exponential models. Half times for the fast (t(0.5)F) and slow (t(0.5)S) components of clearance, the percentage contribution of the fast component (fF), and half time for mono-exponential approximation to the early part of the clearance curve (t(0.5)) were calculated. RESULTS: The patients had substantially faster t(0.5) (mean 23.9 (9.6) minutes) than normal values (>45 minutes). Thirty seven patients (35%) died during follow up (median 15 months). Univariate Cox regression analysis identified significant predictors of survival as age, forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), total lung capacity (TLC), % predicted TLC, carbon monoxide transfer factor (TLCO), % predicted TLCO, arterial oxygen tension (PaO(2)), oxygen saturation, t(0.5)F, and HRCT fibrosis score. Multiple stepwise Cox regression analysis identified t(0.5)F (p=0.03, hazard ratio 0.747, 95% CI 0.578 to 0.964), % predicted TLC (p=0.02, hazard ratio 0.976, 95% CI 0.956 to 0.995), % predicted TLCO (p=0.003, hazard ratio 0.960, 95% CI 0.935 to 0.986), and age (p=0.003, hazard ratio 1.062, 95% CI 1.021 to 1.104) as independent predictors of survival. CONCLUSION: These data suggest that (99m)Tc-DTPA clearance t(0.5)F measurement may predict survival in patients with UIP pattern IPF.

Aged↗
PubMed1999

Intravenous cyclophosphamide pulse therapy for the treatment of lung disease associated with scleroderma.

Until recently, renal crisis was the most significant cause of morbidity and mortality in patients with scleroderma (SSc). Nowadays, following the introduction of angiotensin-converting enzyme inhibitors used in renovascular hypertension, pulmonary fibrosis and pulmonary hypertension have become the most common causes of death in SSc. Consequently, the early diagnosis and treatment of pulmonary fibrosis is essential to improve morbidity and mortality in SSc patients. The aim of this study was to investigate the effect of intravenous cyclophosphamide pulse therapy in patients with SSc and evidence of active alveolitis assessed on a high resolution computed tomographic (HRCT) scan, and to compare the effect of cyclophosphamide pulse therapy with oral therapy. Sixteen consecutive patients with SSc were allocated alternately to the two treatment groups. Eight patients were treated with monthly cyclophosphamide pulse therapy (750 mg/ m2) for 12 months; the other eight patients were treated with oral cyclophosphamide (2-2.5 mg/kg/day) for the same period. All patients received concurrently prednisone (10 mg/day). Pulmonary function tests and HRCT scans were performed before therapy and at 6 and 12 months. In the oral cyclophosphamide group, three patients with a grade I pattern showed regression of disease extent. In the other five patients (one with grade II and four with grade III) the pattern and extent of disease remained stable during the study. No statistical differences were found in forced expiratory volume in 1 s, forced vital capacity and total lung capacity during the study period. The diffusing capacity for carbon monoxide increased significantly between baseline and 12 months (p = 0.043). In the cyclophosphamide pulse therapy group, seven patients with a grade I pattern showed regression of disease extent at 6 months (p = 0.018) and 12 months (p = 0.012). One patient with grade III remained stable during the study. In both groups the regression of the extent of disease estimated on HRCT was due to a decrease in the ground glass appearance. The extent of the reticular appearance remained stable throughout the study. Our results indicate that cyclophosphamide pulse therapy is effective in suppressing active alveolitis (ground glass appearance). Although in this study it is not possible to compare pulse therapy with oral therapy because of the different pattern seen on HRCT between the two groups, it seems that oral therapy is also effective in suppressing active alveolitis. Neither regimen improved pulmonary involvement when the reticular appearance predominated over the ground glass appearance on HRCT. It is concluded that either pulse or oral cyclophosphamide therapy may improve the outcome of SSc patients.

Adult↗
PubMed1980

Postural effects on lung volumes and asynchronous ventilation in anesthetized horses.

Quasi-static pressure-volume curves and single-breath nitrogen washouts were performed simultaneously on eight anesthetized horses (average body wt = 485 kg) in left lateral, right lateral, prone, and supine postures (sequence randomized). The shift from prone to lateral or supine posture decreased expiratory reserve volume (ERV), vital capacity (VC), residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC); RV and FRC expressed as %TLC were unchanged, suggesting that in the lateral and supine postures a significant portion of the lung volume was not recruited by VC maneuvers. Phase III slope increased from 0.13 %N2/l in prone horses to 0.34 %N2/l in the lateral and supine positions. The onset of phase IV was not significantly different from FRC in the prone or laterally recombent animal, but exceeded FRC in the supine horse. The sequence of body positions had no effect on any of our results indicating that all changes in lung volumes and regional asynchronous ventilation c;n be reversed by placing the horse in the prone posture. The reduction in lung volume and increased asynchronous ventilation in the lateral and supine horse suggests that impaired gas exchange in anesthetized horses is predominantly related to posture, and not general anesthesia.

Anesthesia, General↗
PubMed1982

Surface tension at low lung volumes: dependence on time and alveolar size.

We measured surface tension in individual alveoli by observing the spreading properties of fluid droplets placed by micropipette on the alveolar surfaces. The test fluids were calibrated on monolayers of dipalmitoyl phosphatidylcholine spread at the air-saline interface of a captive bubble. The air bubble was floated by buoyancy against a ceiling of 0.5% agar. The bubble surface tension could be altered by inflating or deflating the bubble, and the value of the surface tension was determined by shape analysis for the sessile drop. Test fluid droplets were placed by micropipette onto the upper, flat bubble surface and the diameters of these droplets were measured with a microscope. In cat lungs held at 40% total lung capacity and 37 degrees C the surface tension remained below 1 mN . m -1 for about 10 min, and then increased slowly in a linear fashion to 9 mN . m -1 in 70 min. During stepwise deflation from 70% to 40% total lung capacity the surface tension changed from approximately 10 mN . m -1 to less than 1 mN . m -1. At each step during deflation we compared surface tension in alveoli of differing size and location. At any given lung volume in the range between 70% and 40% total lung capacity we found equal values for the alveolar surface tension regardless of alveolar size and location.

Animals↗
PubMed1981

Comparison of lung diffusing capacity during rebreathing and during slow exhalation.

In five normal sitting subjects DLCO and Qc were measured from the disappearances of a stable isotope of carbon monoxide (C18O) and of acetylene with respect to an inert and insoluble reference gas (Helium). Measurements were made during two respiratory maneuvers: (1) during rebreathing both at functional residual capacity (FRC) and near total lung capacity (TLC); and (2) during a slow exhalation at a constant rate from TLC to FRC. Changes in gas concentration were measured at the mouth during both maneuvers with a respiratory mass spectrometer. Mean DLCO was significantly higher during rebreathing near TLC (34.6 ml . min-1 . mm Hg-1) than near FRC (28.8 ml . min-1 . mm Hg). Mean DLCO measured during slow exhalation near FRC (32.7 ml . min-1 . mm Hg) was significantly higher than DLCO measured during rebreathing over the same volume range. Measurements of Qc were not significantly different between the rebreathing and slow exhalation maneuvers. Differences in DLCO between the two methods at FRC were not due to differences in Qc.

Adult↗
PubMed1999

Respiratory function in children undergoing bone marrow transplantation.

We conducted a prospective study of respiratory function in children undergoing bone marrow transplantation (BMT) for onco-hematological disorders. Each child was evaluated before and 100 days after BMT. The investigations included clinical examination, chest X-ray, and pulmonary function tests (PFT) to determine: slow vital capacity (VC), functional residual capacity (FRC), total lung capacity (TLC), forced expiratory volume in 1 s (FEV1), carbon monoxide diffusing capacity (DLCO), ratio of residual volume (RV) to TLC, and FEV1/VC. The values obtained before and after BMT were compared to predicted values, and the post-BMT values were compared to the pre-BMT values (Student's t-test). From 1986 to 1995, 77 children underwent BMT, of whom 39 were available for testing. The pre-BMT VC (P = 0.0234) and DLCO (P < 0.0001) were lower and FRC higher (P < 0.0001) than predicted values. After BMT, the VC (P = 0.004), TLC (P = 0.044), and FEV1 (P = 0.012) were lower, and the RV/TLC ratio was higher (P = 0.043), compared with pre-BMT data. The observed respiratory abnormalities were not clinically relevant. The only identifiable risk factor for a decrease in lung function was age at BMT. This study shows that some lung dysfunction may be present before BMT and be further altered by BMT. This stresses the need for longitudinal respiratory monitoring and follow up to detect such dysfunctions and to insure an optimal treatment program for these children.

Age Factors↗