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PubMed1998

Correction of single-breath helium lung volumes in patients with airflow obstruction.

STUDY OBJECTIVE: To determine whether alveolar volume (V(A)) measured during the single-breath diffusing capacity for carbon monoxide (DCO) can be used as a substitute measure for the multiple-breath total lung capacity (TLC) in subjects with and without airways obstruction. DESIGN: Retrospective review of pulmonary function test (PFT) results. SETTING: Pulmonary function laboratories at the Johns Hopkins Hospital (JHH) and the Johns Hopkins Asthma and Allergy Center (HAAC). PARTICIPANTS: Patients referred for spirometry, helium lung volumes, and Dco during a single visit between November 1993 and November 1996. RESULTS: JHAAC patients (n=2,477) were used to assess the relationship between V(A) and TLC. In patients with an FEV1/FVC > or = 0.70, there was good agreement between V(A) and TLC (V(A)/TLC=0.97 to 0.99). However, in patients with an FEV1/FVC <0.70, V(A) systematically underestimated TLC (V(A)/TLC=0.67 to 0.94). The degree of underestimation was related to the severity of airflow obstruction. To predict TLC using V(A) a regression equation was used to "correct" V(A) for the severity of obstruction. This equation was used to predict the multiple-breath TLC for JHH patients (n=2,892). Patients with an FEV1/FVC > or = 0.70 showed a high degree of correlation between V(A) and TLC (Pearson's correlation coefficient [r]=0.96 to 0.99; p<0.05). After adjusting for the severity of airflow obstruction, patients with an FEV1/FVC in the range of 0.40 to 0.70 also had a strong correlation between the corrected V(A) and the multiple-breath TLC (r=0.83 to 0.94; p<0.05). CONCLUSIONS: V(A) accurately predicts TLC in patients with mild or no airflow obstruction. For patients with moderate to severe obstruction, correcting V(A) for the severity of obstruction improves the accuracy of this relatively simple and rapid technique for measuring TLC.

Female↗
PubMedDate not supplied

Spiral CT evaluation of pulmonary emphysema using a low-dose technique.

PURPOSE: To evaluate the diagnostic accuracy and clinical acceptability of low-dose spiral CT for determining pulmonary volumes and emphysema extension in patients with pulmonary emphysema, in comparison with studies based on spiral CT at conventional dose. MATERIALS AND METHODS: We prospectively evaluated eighteen patients, current or former smokers, with a clinical diagnosis of chronic obstructive pulmonary disease. All the patients underwent: HRCT with three scans at predetermined levels; quantitative spiral CT, with two inspiratory scans, one conventional scan at 240 mA, and the second one a low-dose scan at 80 mA. We used the following parameters: 120 kV, rotation time 0.8", scan time less than 20" (single inspiratory breath-hold), layer thickness 7.5 mm, pitch 6 (high speed), interpolation algorithm at 180 degrees. A 3D reconstruction was performed, with segmentation of the lungs and automatic quantification of pulmonary volumes. We compared the volumes of absolute and percent emphysema and the ratings of the dose delivered to the patient (CTDIw and DLP) obtained with the two spiral CT scans with each other and with the respiratory function tests. RESULTS: The average total lung capacity (TLC) obtained by conventional-dose spiral CT (CTs1) was 6889.4 cc (SD +/-1813.2), and the capacity with low-dose spiral CT (CTs2) was 6929.4 cc (SD +/-1811.6). The percentage of emphysema was 39.7% (range: 2.2-63.5%; SD: +/-19.9) for the CTs1 and 41.1% (range: 2.1-66.4%; SD: +/-20). The CTDIw corresponding to CTs1 was 12.2 mGy (range: 11.9-16.4; SD: +/-1), the one corresponding to CTs2, 3.6 mGy (range: 3.6-4.9; SD: +/-0.3). The DLP corresponding to CTs1 was 391.7 mGy x cm (range: 333.3-518.9; SD: +/-46.7), the one corresponding to CTs2 was 117.8 mGy x cm (range: 100.3-156; SD: +/-14). As for the respiratory function tests, the total lung capacity (TLC) obtained by body plethysmography was 7061 cc (SD: +/-2029.7); the percent TLC was 115.9 (range: 66-165; SD: +/-27.6), the forced expiratory volume at one second (FEV1%, percentage of predicted value) was 46.7% (range: 17-123; SD: +/-27.3), residual volume (RV%) as a percentage of predicted value was 186.3 (range: 84-359; SD: +/-80.7), the Tiffeneau index (TI) was 46% (range: 25-71; SD: +/-15.7). We observed a very significant correlation between radiological and functional TLC for both CT methods. The percentage scores for emphysema obtained with the two methods correlated significantly with the functional indexes. The pixel index of CTs1 correlated with TLC% (r=0.87; p<0.0001), FEV1% (r=-0.53; p<0.02), RV% (r=0.76; p=0.004), TI (r=-0.79; p=0.0001). The pixel index of CTs2 correlated with TLC% (r=0.87; p<0.0001), FEV1% (r=-0.56; p=0.01), RV% (r=0.78; p=0.003), TI (r=-0.8; p=0.0001). The adoption of the method with low tube current entailed a highly significant reduction in the estimated dose delivered to patients (CTDIw and DLP) with r=0.9 and p < 0.0001. DISCUSSION AND CONCLUSIONS: Quantitative low-dose spiral CT is a very good method to quantify pulmonary volumes and calculate the extension of the anatomic emphysema. The reduction of mA from 240 to 80 lowers the estimated dose by 30%, without compromising the accuracy of the results. Our study achieved a highly significant correlation between the results obtained with the two spiral CT techniques and between these results and the respiratory function tests. In clinical practice, the easiest way to reduce the dose in spiral CT of the lung is to reduce the tube current. The low-dose method allows a significant reduction in radiation exposure. Further studies are required to establish to what extent the dose can be reduced without increasing in quantum noise and thereby compromising the quality of the study.

Adult↗
PubMed1999

Role of expiratory flow limitation in determining lung volumes and ventilation during exercise.

We determined the role of expiratory flow limitation (EFL) on the ventilatory response to heavy exercise in six trained male cyclists [maximal O2 uptake = 65 +/- 8 (range 55-74) ml. kg-1. min-1] with normal lung function. Each subject completed four progressive cycle ergometer tests to exhaustion in random order: two trials while breathing N2O2 (26% O2-balance N2), one with and one without added dead space, and two trials while breathing HeO2 (26% O2-balance He), one with and one without added dead space. EFL was defined by the proximity of the tidal to the maximal flow-volume loop. With N2O2 during heavy and maximal exercise, 1) EFL was present in all six subjects during heavy [19 +/- 2% of tidal volume (VT) intersected the maximal flow-volume loop] and maximal exercise (43 +/- 8% of VT), 2) the slopes of the ventilation (DeltaVE) and peak esophageal pressure responses to added dead space (e.g., DeltaVE/DeltaPETCO2, where PETCO2 is end-tidal PCO2) were reduced relative to submaximal exercise, 3) end-expiratory lung volume (EELV) increased and end-inspiratory lung volume reached a plateau at 88-91% of total lung capacity, and 4) VT reached a plateau and then fell as work rate increased. With HeO2 (compared with N2O2) breathing during heavy and maximal exercise, 1) HeO2 increased maximal flow rates (from 20 to 38%) throughout the range of vital capacity, which reduced EFL in all subjects during tidal breathing, 2) the gains of the ventilatory and inspiratory esophageal pressure responses to added dead space increased over those during room air breathing and were similar at all exercise intensities, 3) EELV was lower and end-inspiratory lung volume remained near 90% of total lung capacity, and 4) VT was increased relative to room air breathing. We conclude that EFL or even impending EFL during heavy and maximal exercise and with added dead space in fit subjects causes EELV to increase, reduces the VT, and constrains the increase in respiratory motor output and ventilation.

Adult↗
PubMed1996

Pulmonary function and exercise capacity after lung resection.

The influence of pulmonary resection on functional capacity can be assessed in different ways. The aim of this study was to compare the effect of lobectomy and pneumonectomy on pulmonary function tests (PFT), exercise capacity and perception of symptoms. Sixty eight patients underwent functional assessment with PFT and exercise testing before (Preop), and 3 and 6 months after lung resection. In 50 (36 males and 14 females; mean age 61 yrs) a lobectomy was performed and in 18 (13 males and 5 females; mean age 59 yrs) a pneumonectomy was performed. Three months after lobectomy, forced vital capacity (FVC), forced expiratory volume in one second (FEV1), total lung capacity (TLC), transfer factor of the lungs for carbon monoxide (TL,CO) and maximal oxygen uptake (V'O2,max) were significantly lower than Preop values, increasing significantly from 3 to 6 months after resection. Three months after pneumonectomy, all parameters were significantly lower than Preop values and significantly lower than postlobectomy values and did not recover from 3 to 6 months after resection. At 6 months after resection significant deficits persisted in comparison with Preop: for FVC 7% and 36%, FEV1 9% and 34%, TLC 10% and 33% for lobectomy and pneumonectomy, respectively; and V'O2,max 20% after pneumonectomy only. Exercise was limited by leg muscle fatigue in 53% of all patients at Preop. This was not altered by lobectomy, but there was a switch to dyspnoea as the limiting factor after pneumonectomy (61% of patients at 3 months and 50% at 6 months after resection). Furthermore, pneumonectomy compared to lobectomy led to a significantly smaller breathing reserve (mean +/- SD) (28 +/- 13 vs 37 +/- 16% at 3 months; and 24 +/- 11% vs 33 +/- 12% at 6 months post resection) and lower arterial oxygen tension at peak exercise 10.1 +/- 1.5 vs 11.5 +/- 1.6 kPa (76 +/- 11 vs 86 +/- 12 mmHg) at 3 months; 10.1 +/- 1.3 vs 11.3 +/- 1.6 kPa (76 +/- 10 vs 85 +/- 12 mmHg) at 6 months postresection. We conclude that measurements of conventional pulmonary function tests alone overestimate the decrease in functional capacity after lung resection. Exercise capacity after lobectomy is unchanged, whereas pneumonectomy leads to a 20% decrease, probably due to the reduced area of gas exchange.

Adult↗
PubMed1998

Airway-parenchymal interdependence after airway contraction in rat lung explants.

The constriction of pulmonary airways is limited by the tethering effect exerted by parenchymal attachments. To characterize this tethering effect at the scale of intraparenchymal airways, we studied the pattern of parenchymal distortion due to bronchoconstriction in a rat lung explant system. First, we measured the elastic modulus under tension for 2% (wt/vol) agarose alone (37.6 +/- 1.5 kPa) and for agarose-filled lung (5.7 +/- 1.3 kPa). The latter is similar to the elastic modulus of air-filled lung at total lung capacity (4.5-6 kPa) (S. J. Lai-Fook, T. A. Wilson, R. E. Hyatt, and J. R. Rodarte. J. Appl. Physiol. 40: 508-513, 1976), suggesting that explants can be used as a model of lung tissue distortion. Subsequently, confocal microscopic images of fluorescently labeled 0.5-mm-thick explants prepared from agarose-filled rat lungs inflated to total lung capacity (48 ml/kg) were acquired. Images were taken before and after airway constriction was induced by direct application of 10 mM methacholine, and the pattern of parenchymal distortion was measured from the displacement of tissue landmarks identified in each image for 14 explants. The magnitude of the radial component of tissue displacement was calculated as a function of distance from the airway wall and characterized by a parameter, b, describing the rate at which tissue movement decreased with radial distance. The parameter b was 0.994 +/- 0.19 (SE), which is close to the prediction of b = 1 of micromechanical modeling (T. A. Wilson. J. Appl. Physiol. 33: 472-478, 1972). There was significant variability in b, however, which was correlated with the fractional reduction in airway diameter (r = 0.496). Additionally, parenchymal distortion showed significant torsion with respect to the radial direction. This torsion was similar in concentric zones around the airway, suggesting that it originates from inhomogeneity in the parenchyma rather than inhomogeneous airway constriction. Our results demonstrate the significance of the nonlinear mechanical properties of alveolar walls and the anisotropy of the parenchyma in determining the nature of airway-parenchymal interdependence.

Animals↗
PubMed1996

Improvement in pulmonary function and elastic recoil after lung-reduction surgery for diffuse emphysema.

BACKGROUND: Pulmonary function may improve after surgical resection of the most severely affected lung tissue (lung-reduction surgery) in patients with diffuse emphysema. The basic mechanisms responsible for the improvement, however, are not known. METHODS: We studied 20 patients with diffuse emphysema before and at least three months after either a unilateral or a bilateral lung-reduction procedure. Clinical benefit was assessed by measurement of the six-minute walking distance and the transitional-dyspnea index, which is a subjective rating of the change from base line in functional impairment and the threshold for effort- and task- dependent dyspnea. Pressure-volume relations in the lungs were measured with static expiratory esophageal-balloon techniques, and right ventricular systolic function was assessed by echocardiography. RESULTS: The patients had significant improvement in the transitional-dyspnea index after surgery (P<0.001). The mean (+/-SD) coefficient of retraction, an indicator of elastic recoil of the lung, improved (from 1.3+/-0.6 cm of water per liter before surgery to 1.8+/-0.8 after, P<0.001). Sixteen patients with increased elastic recoil had a greater increase in the distance walked in six minutes than the other four patients, in whom recoil did not increase (P=0.02). The improved lung recoil led to disproportionate decreases in residual volume as compared with total lung capacity (16 percent vs. 6 percent), but the decreases in both values were significant (P<0.001). Forced expiratory volume in one second increased (from 0.87+/-0.36 to 1.11+/-0.45 liters, P<0.001). End-expiratory esophageal pressure also decreased (P=0.002). These improvements in lung mechanics led to a decrease in arterial partial pressure of carbon dioxide form 42+/-6 to 38+/-5 mm Hg (P=0.006). Furthermore, the fractional change in right ventricular area, an indicator of systolic function, increased from 0.33+/-0.11 to 0.38+/-0.010 (P=0.02). CONCLUSIONS: Lung-reduction surgery can produce increases in the elastic recoil of the lung in patients with diffuse emphysema, leading to short-term improvement in dyspnea and exercise tolerance.

Adult↗
PubMed1995

The Hayek oscillator. Nomograms for tidal volume and minute ventilation using external high frequency oscillation.

The Hayek Oscillator is a recent development in external high frequency ventilation and is a useful mode of ventilatory support during anaesthesia, in chronic respiratory failure and weaning in intensive care. The Hayek Oscillator is new and its application is growing, as are the number of patients who have benefited from its use. However, there are no clear guidelines on how best to adjust the oscillator to achieve optimum ventilation. A simple method of predicting changes in tidal volume and minute ventilation following adjustment would make the oscillator more useful. We present nomograms for tidal volume, minute ventilation and effective alveolar ventilation when the three variables, oscillator frequency, mean chamber pressure and peak-to-trough pressure span were adjusted. The frequency-tidal volume relationship was unaffected by a mean chamber pressure of 0, -5, -10 cmH2O, but altered with changes in peak-to-trough pressure span. We have also determined the effect of increasing negative extrathoracic pressure on functional residual capacity. The relationship between tidal volume and frequency was non-linear and related to the peak-to-trough pressure span. Mean functional residual capacity significantly increased from 2.25 l (SEM 0.10) without the cuirass at rest to 2.61 l (SEM 0.14) at -10 cmH2O (p < 0.05; n = 5) and 2.47 (SEM 0.12) at -20 cmH2O of mean chamber pressure. Vital capacity was unchanged by increasing extrathoracic pressure as was total lung capacity.

Adult↗
PubMed1994

Lung volumes during sustained microgravity on Spacelab SLS-1.

Gravity is known to influence the mechanical behavior of the lung and chest wall. However, the effect of sustained microgravity (mu G) on lung volumes has not been reported. Pulmonary function tests were performed by four subjects before, during, and after 9 days of mu G exposure. Ground measurements were made in standing and supine postures. Tests were performed using a bag-in-box-and-flowmeter system and a respiratory mass spectrometer. Measurements included functional residual capacity (FRC), expiratory reserve volume (ERV), residual volume (RV), inspiratory and expiratory vital capacities (IVC and EVC), and tidal volume (VT). Total lung capacity (TLC) was derived from the measured EVC and RV values. With preflight standing values as a comparison, FRC was significantly reduced by 15% (approximately 500 ml) in mu G and 32% in the supine posture. ERV was reduced by 10-20% in mu G and decreased by 64% in the supine posture. RV was significantly reduced by 18% (310 ml) in mu G but did not significantly change in the supine posture compared with standing. IVC and EVC were slightly reduced during the first 24 h of mu G but returned to 1-G standing values within 72 h of mu G exposure. IVC and EVC in the supine posture were significantly reduced by 12% compared with standing. During mu G, VT decreased by 15% (approximately 90 ml), but supine VT was unchanged compared with preflight standing values. TLC decreased by approximately 8% during mu G and in the supine posture compared with preflight standing. The reductions in FRC, ERV, and RV during mu G are probably due to the cranial shift of the diaphragm, an increase in intrathoracic blood volume, and more uniform alveolar expansion.

Adult↗
PubMed1976

Abnormal lung elasticity in juvenile diabetes mellitus.

Static lung pressure-volume curves, lung volumes, spirometry, diffusing capacity for CO, and airway and total pulmonary resistance were determined in 11 young men with juvenile-onset diabetes mellitus who were not cigarette smokers. Twelve nonsmoking men of similar age without diabetes served as control subjects. Elastic recoil at low lung volumes was significantly less in the diabetics than in the control group. Total lung capacity was also decreased in the diabetics. There were no significant differences between the 2 groups in the other parameters of pulmonary function measured. It is postulated that the abnormalities in lung elastic behavior are manifestations of the widespread elastin and collagen abnormalities that have been demonstrated in diabetes and are, in some respects, similar to those that occur during normal aging. Loss of elastic recoil at low lung volumes may cause more significant decreases in flows and gas transport as the juvenile diabetics age.

Adult↗
PubMed1991

Difficulties of attribution of effect in workers exposed to fiberglass and asbestos.

Man-made mineral fibers have many properties of asbestos that raise concern about their safety. We studied 175 fiberglass production workers, using chest radiographs, measurement of total lung capacity, chest examinations, and occupational and medical histories. Pulmonary volumes and flows were calculated as percent of predicted, adjusted for height, age, ethnicity, and cigarette smoking. Thirty-one men with radiographically evident small irregular opacities of profusion of 1/0 or greater and/or pleural abnormalities were observed. Eight of 38 men with such changes said they had been exposed only to fiberglass; the other 23 with radiologically detectable pleural and/or pulmonary changes were among the 137 whose histories indicated that they had been exposed to asbestos and to fiberglass. Pulmonary function measurements as group means were reduced in the 175: FVC was 94.8% predicted, FEV1 was 91.3% predicted, FEF25-75 was 80.7% predicted, FEF75-85 was 73.1% predicted and FEV1/FVC was 0.73. Total lung capacity (TLC) was elevated to 114.2% predicted (mean) and RV/TLC (mean 0.46) was also elevated. Although only 78% of fiberglass production workers gave histories of asbestos exposure, all had shared the air in a manufacturing plant where ovens insulated with asbestos were continuously cleaned, repaired, dismantled, and rebuilt. It appears that attribution of the effects of their exposure to fiberglass could not be estimated independently of the effects of asbestos exposure.

Adult↗
PubMed1992

Bronchoalveolar lavage cell count and differential are not reliable indicators of amiodarone-induced pneumonitis.

Amiodarone-induced interstitial pneumonitis is a serious, frequently fatal untoward effect of a commonly used antiarrhythmic agent. Recent reports suggest that bronchoalveolar lavage (BAL) fluid cellular analysis might be used to diagnose amiodarone-induced pneumonitis. The purpose of this study was to determine if the diagnosis of amiodarone-induced pneumonitis could be made by patient history, pulmonary function evaluation, and examination of BAL fluid. We studied five groups of patients. Three of the five groups received amiodarone: patients receiving amiodarone without evident lung toxic reaction, patients with amiodarone-induced pneumonitis, and amiodarone-treated patients diagnosed as having other pathologic processes involving the lung. The two other groups examined were healthy volunteers and patients with interstitial lung disease from causes other than amiodarone. Pulmonary function tests included vital capacity (FVC), first second forced exhaled volume (FEV1), total lung capacity (TLC), and diffusing capacity for carbon monoxide (DCO). BAL fluid analysis included total and differential cell counts. We found that amiodarone-induced interstitial pneumonitis was not associated with an alteration in pulmonary function or BAL cellular composition which could permit its distinction from amiodarone-treated patients diagnosed as having an unrelated pulmonary process or patients with interstitial lung disease from other causes. The most frequent abnormality encountered in patients with amiodarone toxicity was a reduction in the percentage of macrophages in the differential cell count. The sensitivity, specificity, and predictive value of this finding was 82 percent, 69 percent, and 69 percent, respectively. The sensitivity, specificity, and predictive value of a > or = 15 percent reduction in DCO was 44 percent, 50 percent, and 36 percent, respectively. We conclude that amiodarone-induced interstitial pneumonitis remains a diagnosis of exclusion, and the role of BAL fluid analysis is to narrow the differential diagnosis through microbiologic culture and cytologic examination.

Aged↗
PubMed1993

The contribution of respiratory function tests to clinical diagnosis.

The purpose of this study was to investigate the amount of diagnostic information contained in a set of routine lung function studies and to attempt to determine which tests could be omitted without significant loss of discrimination. Cluster analysis was performed on a set of physiological and questionnaire data, collected prospectively in 1,542 male patients, referred consecutively for measurement of forced expired volumes, static lung volumes and measurements of the transfer factor for carbon monoxide. A respiratory questionnaire was completed for each patient. A physician assigned the patients to a rigorously defined diagnostic category, based on supporting clinical information, as well as pulmonary function, apart from 241 patients with unusual diagnoses and those in whom the criteria did not apply satisfactorily. This diagnosis was never included as a classification variable. Basing the classification on three independent measurements, total lung capacity, the ratio of forced expiratory volume in one second (FEV1) to vital capacity, and the transfer factor for carbon monoxide, the computer generated six groups: one normal, one showing an isolated gas exchange defect, and four with varying degrees of restriction and obstruction. This classification performed well in separating the patients with the clinical diagnoses of chronic airflow obstruction, bronchial asthma and interstitial lung disease from those with ischaemic and valvular heart disease and other miscellaneous disorders. Omitting total lung capacity resulted in some loss of specificity, but valid information was still obtained. The inclusion of all the static and dynamic lung volumes and of carbon monoxide transfer coefficient made little difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Cluster Analysis↗
PubMed2002

Long-term results of lung volume reduction surgery.

OBJECTIVE: Lung volume reduction surgery (LVRS) is effective in the short and intermediate term for the improvement of pulmonary function and subjective symptoms in selected patients with advanced emphysema. The purpose of this study was to examine the long-term functional results of LVRS and to investigate which subgroups would benefit in terms of long-term survival. METHODS: All records of the patients who underwent LVRS between 1994 and, 1998 at our hospital were reviewed. RESULTS: Eighty-eight consecutive patients underwent LVRS during the period. There were 62 men and 26 women with an average age of 56.1 years (range 34-72 years). Eleven patients with alpha1-antitrypsin deficiency were included. The perioperative mortality rate (<90 days) was 2.3% (n=2). Total lung capacity (7.5+/-0.3 l) and residual volume (4.8+/-0.3 l) at 3 years remained lower than baseline (9.2+/-0.2 l, 6.5+/-0.2 l, each) (P<0.001). The mean forced expiratory volume in 1 s (FEV(1)) at 3 years (0.86+/-0.08 l) was higher than baseline (0.78+/-0.02 l), but the difference did not reach statistical significance. The FEV(1) of the patients with alpha1-antitrypsin deficiency and of those with respiratory bronchiolitis returned to baseline at one year after LVRS and showed further deterioration. Overall survival rate at 5 years was 71.0% with the mean length of follow-up of 54.2 months. The survival difference was statistically significant between patients with preoperative FEV(1) >or=28.5% and those with FEV(1)<28.5% (P=0.0152). CONCLUSIONS: The improvement of total lung capacity and residual volume persisted long after the operation. Patients with alpha1-antitrypsin deficiency and those with bronchiolitis showed early deterioration of the lung function. Patients with higher preoperative FEV(1) had a survival benefit. The favorable long-term survival might justify LVRS for the treatment of selected patients with severe emphysema.

Bronchiolitis↗
PubMed2002

Effects of lung volume and chemoreceptor activity on blood pressure and R-R interval during the Valsalva maneuver.

STUDY OBJECTIVES: The purpose of the present investigation was to examine the effect of lung volume and inspiration of 100% oxygen on blood pressure and R-R interval responses during the Valsalva maneuver. DESIGN AND PARTICIPANTS: Fourteen healthy subjects completed eight Valsalva maneuvers. Four of the maneuvers were completed after inspiring to total lung capacity while the remaining maneuvers were completed at end-expiratory lung volume. Two maneuvers completed at a given lung volume were performed under hyperoxic conditions while the remaining maneuvers were completed under normoxic conditions. RESULTS: Overall, a significant increase in blood pressure and decrease in R-R interval occurred throughout phases I-IV of the Valsalva maneuvers that were initiated from end-expiratory lung volume as compared to total lung capacity. These changes were accompanied by a concomitant increase in baroreflex sensitivity during phase IV. Furthermore, independent of lung volume the baroreflex response was attenuated under hyperoxic conditions. CONCLUSIONS: We conclude that the lung volume that exists prior to the onset of the maneuver alters the blood pressure and R-R interval response during phases I-IV of the Valsalva maneuver. Furthermore, we suggest that these responses are mediated in part by changes in chemoreceptor activity since the baroreflex was reset and the sensitivity was reduced under hyperoxic conditions. Given these findings, we recommend that lung volume be controlled when patients are completing a Valsalva maneuver to obtain reliable and reproducible measures of blood pressure, R-R interval duration and baroreflex sensitivity.

Administration, Inhalation↗
PubMed2006

Pulmonary function in renal transplant recipients and end-stage renal disease patients undergoing maintenance dialysis.

The aim of this study was to reveal the pulmonary function status of renal transplant recipients and chronic renal failure patients on hemodialysis or continuous ambulatory peritoneal dialysis. The study involved 73 subjects, including 49 patients who were either on peritoneal dialysis (n = 22) or hemodialysis (n = 27), and 24 renal transplant recipients. The spirometry results revealed significantly higher residual volume and total lung capacity in the hemodialysis and peritoneal dialysis groups than in the transplantation group. Forced expiratory flow between 25% and 75% of vital capacity was slightly below normal in the dialysis patients. Preservation of diffusion capacity of the lung for carbon monoxide was noted in the hemodialysis group (112.4%). Inspiratory and expiratory muscle strength was reduced in all groups. Only type of dialysis was correlated with this reduction. Inspiratory muscle strength in the peritoneal dialysis group (49.9%) was significantly lower than in the transplantation and hemodialysis groups (54.7% and 66.5%, respectively). The spirometry findings suggest that small-airway disease causes increased residual volume and total lung capacity (hyperinflation) in hemodialysis and peritoneal dialysis patients and that this airway obstruction subsides after renal transplantation. Preserved diffusion capacity in the hemodialysis group was attributed to the use of biocompatible dialyzer membranes. Renal failure complications may be the main explanation for global respiratory muscle weakness in dialysis patients, whereas corticosteroid therapy might be the primary cause in kidney graft recipients. Significantly lower inspiratory muscle strength in the peritoneal dialysis group suggests that presence of intra-abdominal dialysate might interfere with diaphragmatic contraction.

Adrenal Cortex Hormones↗
PubMed1981

Surfactant release in excised rat lung is stimulated by air inflation.

Because increased ventilation has been associated with an acceleration of lung surfactant turnover, we investigated the effect of fluid and air inflations on the release of surfactant into the air spaces. We found that excised rat lungs, initially lavaged three times at 23 degrees C, release approximately 40-90 micrograms of phospholipid/g wet lung wt into the air spaces in response to a further infusion of fluid into the airway equal to total lung capacity. A single air inflation to the same volume, followed by degassing and lavage, contributes approximately 230 micrograms to the yield of phospholipid. We estimated basal release of phospholipid as 112 micrograms wet lung wt-1 . h-1, which is far less than the 2,050 micrograms -1 . h-1 retrieved during a series of air and fluid inflations. The above findings are consistent with the hypothesis that air inflation to total lung capacity is a major physiological stimulus to release of lung surfactant into the alveolar space. The lung lavage process itself also causes the release of surfactant.

Air↗
PubMed1976

Site of action of inhaled 6 per cent carbon dioxide in the lungs of asthmatic subjects before and after exercise.

We studied 10 nonsmoking young adults before and after inducing asthmatic attacks by treadmill exercise. We used body plethysmography, flow-volume curves with air and a mixture of 80% helium and 20% oxygen, pressure-volume diagrams, and arterial blood gas analyses to characterize the effects of exercise and acute inhalation of 6% CO2. Even when exercise produced no change in arterial CO2 tension, inhalation of 6% CO2 relieved obstruction to airflow. It also altered the volume-pressure ralationship of the lungs so that total lung capacity was reduced within minutes, and elastic recoil was increased at fixed lung volume. A large increase in density dependence of airflow was seen in some cases, suggesting relief of obstruction in peripheral airways. Atropine sulfate did not prevent obstruction after exercise and did not prevent relief during CO2 inhalation. We concluded that CO2 inhalation can relax both central and peripheral airways in young asthmatic adults, both at rest and after exercise, and that both total lung capacity and density dependence of airflow can change acutely in these subjects.

Adolescent↗
PubMed1978

Lung function in acromegaly.

Lung function has been assessed by spirometry, body plethysmography, flow volume loops and single breath transfer factor in thirty patients with acromegaly. Having excluded eight patients with kyphosis and/or clinical or radiological evidence of pulmonary venous hypertension we have found a significant correlation between duration of acromegaly and lung size as assessed by total lung capacity. Excluding the same eight patients we have found evidence of small airways narrowing in eight patients, seven of these eight had had acromegaly for nine years or longer, and the duration of acromegaly was significantly longer in the patients with small airways narrowing than in those without. In the absence of other recognized causes it is possible that small airways narrowing in acromegaly is caused either by the increased whole blood volume with pulmonary vascular engorgement, or by increase in size of the soft tissues of the small conducting airways. Six of the eight patients with kyphosis and/or pulmonary venous hypertension also had evidence of small airways narrowing. Thus fourteen of the thirty patients with acromegaly had small airways narrowing. Five men had evidence of extra thoracic airway narrowing and in four the duration of acromegaly was ten years or longer. We conclude that the increase in total lung capacity, the incidence of small airways narrowing and the incidence of upper airway narrowing are all related to the duration of acromegaly. It seems that once duration exceeds eight years patients are very likely to develop abnormalities of lung function either primarily from the effects of acromegaly on the airways and lung or secondarily from the associated cardiovascular and thoracic skeletal abnormalities. It seems probable that the small airways and upper airway narrowing contribute to the morbidity and mortality of this disease. This study provides further evidence that acromegaly should be treated early.

Acromegaly↗