Search PubMed⌕ Search

Biomedical subjects

B R Wiggs

Publications and source records attributed to B R Wiggs.

At least 37 records · Page 2Linked to original sources
PubMed1994

Pulmonary vascular abnormalities and ventilation-perfusion relationships in mild chronic obstructive pulmonary disease.

Morphologic changes in pulmonary muscular arteries may modify the mechanisms that regulate the pulmonary vascular tone and contribute to maintaining an adequate ventilation-perfusion (VA/Q) matching in patients with chronic obstructive pulmonary disease (COPD). To analyze the relationships between the abnormalities of pulmonary muscular arteries and the degree of VA/Q inequality, and to assess the effect of these abnormalities on the changes in VA/Q relationships induced by oxygen breathing, we studied a group of patients with mild COPD undergoing resective lung surgery. According to the degree of airflow obstruction and the increase in VA/Q mismatch produced by 100% O2 breathing (delta logSD Q), patients were divided into three groups: (A) patients with normal lung function, (B) patients with airflow obstruction and a high response to oxygen (delta logSD Q > 0.4), and (C) patients with airflow obstruction and a low response to oxygen (delta logSD Q < 0.4). Pulmonary arteries in Groups B and C showed narrower lumens and thicker walls than in Group A. These morphologic changes were produced mainly by an enlargement of the intimal layer and were more pronounced in Group C than in Group B. The assessment of intimal area as a function of artery diameter showed that the increase in intima in Group C took place predominantly in arteries with small diameters (< 500 microns). The mean intimal area on each subject correlated with both the PaO2 value (r = -0.46, p < 0.05) and the overall index of VA/Q mismatching (r = 0.51, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1994

Mathematical coupling explains dependence of oxygen consumption on oxygen delivery in ARDS.

Because of potential for mathematical coupling of measurement errors in shared variables used to calculate oxygen consumption (FickVO2) and oxygen delivery (DO2), we asked whether determination of the FickVO2-DO2 relationship in individual patients with ARDS was statistically valid. We studied 17 clinically resuscitated patients with severe ARDS, measuring FickVO2, CalorimetricVO2 (using analysis of respiratory gases), and DO2 at regular intervals while DO2 was increased using an infusion of dobutamine. Overall, we found that DO2 (pre 482 +/- 143, post 616 +/- 170 ml O2/min.m2, p < 0.01) and FickVO2 (pre 130 +/- 23, post 147 +/- 24 ml O2/min.m2, p < 0.02) increased significantly with dobutamine infusion, but CalorimetricVO2 measured simultaneously did not change (pre 128 +/- 22, post 128 +/- 22 ml O2/min x m2, p = NS). In addition, unpooled weighted slope for FickVO2 versus DO2 (0.06) was significantly different from zero, but unpooled weighted slope for CalorimetricVO2 versus DO2 (0.01) was not significantly different from zero. Slopes of the FickVO2-DO2 relationship were significant for only three individual patients. Using methods by Stratton and colleagues to analyze the effect of mathematical coupling in the FickVO2-DO2 relationship, we found that in all patients the slope of measurement errors was greater than observed slope and that observed slope was greater than estimated true slope. Estimated true slope of the FickVO2-DO2 relationship in all individual patients was not significant. Therefore, we suggest that determination of the FickVO2-DO2 relationship in individual patients who are resuscitated and hemodynamically stable is most often not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Prediction of heart rate and oxygen uptake during incremental and maximal exercise in healthy adults.

Measurement of heart rate and oxygen uptake during incremental exercise and at maximal exercise is useful in evaluating mechanisms responsible for exercise limitation in patients with cardiopulmonary disease. Presently used prediction equations are based on relatively small groups of subjects in whom there was an uneven distribution of subjects with regard to age and sex or based on equations that were from extrapolated data. Our prediction equations are based on data from 231 men and women equally divided within decades between 20 and 80 years. Patients exercised to a symptom-limited maximum on a cycle ergometer while measurements of heart rate and oxygen uptake were recorded. The relationship between heart rate and oxygen uptake throughout exercise (HR:VO2) was determined using a statistical technique that included each data point from each subject. The HR:VO2 throughout incremental exercise was best described by separate equations for women younger than 50 years and older than 50 years and for men younger than 70 years and older than 70 years. Prediction equations for maximal heart rate (HRmax) and maximal oxygen uptake (VO2max) were developed by linear regression and were selected from all possible combinations of parameters. The HRmax was most accurately predicted by age alone for both sexes. Unlike the HR:VO2 relationship, the slope of the line relating heart rate to age was not different for the older women compared with the younger women so that a single equation was derived to predict HRmax. A single equation for the men was also sufficient since the slope of heart rate to age was the same for all ages. To most accurately predict VO2max, a separate equation was required for both the women and men that included age, height, and weight.

Adult↗
PubMed1993

Identification of the critical oxygen delivery for anaerobic metabolism in critically ill septic and nonseptic humans.

OBJECTIVES: To determine the critical oxygen delivery threshold for anaerobic metabolism and to compare its value between septic and nonseptic critically ill patients. DESIGN: Cohort analytic study, consecutive sample. SETTING: Two tertiary care medical and surgical intensive care units in university hospitals. PATIENTS: Nine septic and nine nonseptic critically ill humans. A diagnosis of sepsis was established by the presence of sepsis syndrome, positive cultures obtained within 48 hours of study, and autopsy evidence of a source of infection. METHODS AND INTERVENTIONS: The O2 consumption (determined by indirect calorimetry), O2 delivery (calculated from the Fick equation), and concentration of arterial plasma lactate were simultaneously determined at 5- to 20-minute intervals while life support was discontinued. MAIN OUTCOME MEASURES: Critical O2 delivery, critical O2 extraction ratio, and maximal O2 extraction ratio. RESULTS: In all septic and eight nonseptic patients, O2 delivery and O2 consumption displayed a biphasic relationship over the range of O2 delivery studied. There were no differences in critical O2 delivery threshold (3.8 +/- 1.5 vs 4.5 +/- 1.3 mL.min-1 x kg-1; P > .28), critical O2 extraction ratio (0.61 +/- 0.05 vs 0.59 +/- 0.16; P > .64), and maximal O2 extraction ratio (0.74 +/- 0.08 vs 0.80 +/- 0.11; P > .29) between septic and nonseptic patients. These data have greater than 90% power to detect a difference of 2 mL.min-1 x kg-1 in the critical O2 delivery and 0.1 in the critical and maximal O2 extraction ratios between the septic and nonseptic groups. CONCLUSIONS: The critical O2 delivery for anaerobic metabolism was identified from the biphasic relationship between O2 delivery and O2 consumption in individual humans. The critical O2 delivery is considerably lower than previously reported in humans with the use of pooled group data. Sepsis does not alter the critical O2 delivery for anaerobic metabolism or tissue O2 extraction ability. Interventions to increase O2 delivery to supranormal levels in critically ill humans in the hope of increasing O2 consumption may be inappropriate.

Adult↗
PubMed1993

Circadian rhythm of glycogen in the hamster diaphragm.

The purpose of this study was to determine the diurnal fluctuation of glycogen stores for the whole hemidiaphragm and within a specific myofibrillar ATPase (M-ATPase) fibre type and diaphragmatic region. Fifty-six golden Syrian hamsters were randomly divided into six groups according to the time of sampling biopsies from the diaphragm: 03:00, 07:00, 11:00, 15:00, 19:00, and 23:00. The right hemidiaphragm was quick frozen and biochemically assayed for glycogen levels. Biopsies from the left hemidiaphragm of the same animal were cut from the anterior costal and crural regions, and stained with periodic acid--Schiff (PAS) and for M-ATPase. Optical density measures of PAS-stained fibres were determined to quantitate glycogen in different M-ATPase fibre types and diaphragmatic regions. Biochemical assay of the entire hemidiaphragm showed slightly greater glycogen content of biopsies taken at 11:00 and 15:00 than at 03:00, 19:00, and 23:00 (range of differences: 6.4-10.0%). However, glycogen levels within a specific M-ATPase fibre type and diaphragm region were not different in biopsies sampled at different times. Because the hamster has a small diurnal variation of glycogen in the diaphragm, which is similar to the small diurnal variation of glycogen in human skeletal muscle, this species may be a good animal model for metabolic studies of the diaphragm that could be affected by diurnal glycogen variability.

Adenosine Triphosphatases↗
PubMed1993

Airway smooth muscle shortening in excised canine lung lobes.

To estimate the importance of lung parenchymal airway interdependence in attenuating airway narrowing, airway smooth muscle shortening in response to nebulized carbachol was measured in excised canine lung lobes and compared with the calculated load applied by lung elastic recoil. Pulmonary resistance of matched right and left upper lobes of five dogs was measured in a pressure-compensated volume plethysmograph by forced oscillation (6 Hz) before and after administration of an aerosol of carbachol (250 mg/ml) or saline. Matched lobes were studied at transpulmonary pressures (PL) of 5, 7, 10, 12, and 15 cmH2O. The lungs were then fixed at that PL by pulmonary arterial perfusion with formaldehyde, and cross sections of multiple airways from each lobe (n = 275) were examined by use of morphometric techniques to measure luminal area and smooth muscle length. By use of the saline lobe as a control, percentage of muscle shortening and decrease in airway lumen area caused by carbachol could be calculated. Passive and active smooth muscle stresses in each airway were calculated from PL and the calculated change in peribronchial pressure for a given change in airway diameter. The increase in pulmonary resistance and average smooth muscle shortening after administration of carbachol was greater in lobes held at lower PL. There was marked variation in narrowing between airways within a lobe: smooth muscle shortening ranged between 0 and 65% but averaged < 45% at all levels of PL.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1993

Effect of positive end-expiratory pressure on leukocyte transit in rabbit lungs.

Previous experiments in humans and animals have shown that neutrophils (PMN) are delayed in the lung by the inhalation of cigarette smoke. Others have shown that cigarette smoking raises airway resistance, and it follows that this will increase the expiratory time constant of the airways. When the expiratory time constant of the airways exceeds that of the chest wall, alveolar pressure will rise and compress alveolar capillaries. To determine the effect of alveolar compression on PMN retention, we measured the arteriovenous (A-V) difference for leukocytes across the lung and determined the retention of 51Cr-labeled PMN in the lungs of anesthetized ventilated rabbits. The results show that the application of positive end-expiratory airway pressure (PEEP) produced an immediate difference for PMN across the lung, which disappeared in approximately 3 min when PEEP was continuously applied. This effect was attributed to alveolar compression rather than reduced cardiac output, because a similar A-V difference for PMN was observed in separate experiments in which cardiac output was maintained by vascular expansion during PEEP. The results also show that, when PEEP was continuously applied for approximately 30 min, it failed to increase the percent retention of either inactivated (PEEP = 14 +/- 2% vs. non-PEEP 16 +/- 3%) or activated (PEEP = 62 +/- 7% vs. non-PEEP 63 +/- 6%) 51Cr-PMN. We conclude that the application of PEEP traps PMN in compressed alveolar capillaries, creating an immediate A-V difference that disappears as blood flow is redistributed to vessels that are not compressed by PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Functional significance of increased airway smooth muscle in asthma and COPD.

Using a computational model, we investigated the effect of the morphologically determined increased airway smooth muscle mass, adventitial mass, and submucosal mass observed in patients with asthma and chronic obstructive pulmonary disease (COPD) on the increase in airway resistance in response to a bronchoconstricting stimulus. The computational model of Wiggs et al. (J. Appl. Physiol. 69: 849-860, 1990) was modified in such a way that smooth muscle shortening was limited by the maximal stress that the muscle could develop at the constricted length. Increased adventitial thickness was found to increase constriction by reducing parenchymal interdependence. Increased submucosal thickness led to greater luminal occlusion for any degree of smooth muscle shortening. Increased muscle thickness allowed greater smooth muscle shortening against the elastic loads provided by parenchymal interdependence and airway wall stiffness. We found that for constant airway mechanics, as reflected by the passive area-pressure curves of the airways, the increased muscle mass is likely to be the most important abnormality responsible for the increased resistance observed in response to bronchoconstricting stimuli in asthma and COPD. For a given maximal muscle stress, greater muscle thickness allows the development of greater tension and thus more constriction of the lumen.

Adult↗
PubMed1993

Regional myocardial capillary erythrocyte transit time in the normal resting heart.

A major determinant of oxygen transport to the myocardium is the time spent by the erythrocytes (red blood cells [RBCs]) traversing the microcirculation. Although it has been shown that the myocardium has regional differences in blood volume, blood flow, metabolism, and sensitivity to ischemic injury, the regional distribution of RBC transit times through the myocardial capillaries has not been previously measured. The present study was designed to measure the regional myocardial capillary RBC transit time by a new technique to determine whether there are regional differences in the capillary RBC transit time in the normal resting heart. Anesthetized open-chest male New Zealand White rabbits (3.0-3.7 kg, n = 8) were studied. Regional myocardial blood volume was determined using chromium-51-labeled RBCs, and regional blood flow was measured using a reference flow technique and a left atrial injection of 15-microns-radiolabeled (gadolinium-153, 10-20 muCi) microspheres. Capillary blood volume was determined by multiplying the regional blood volume by the histologically determined fraction of the total blood volume that was in the capillaries. Capillary RBC transit time was calculated as the quotient of capillary blood volume and blood flow. The myocardial capillary blood volume was the same in the endocardium and the epicardium (4.67 +/- 0.67 ml/100 g for endocardium versus 4.52 +/- 0.70 ml/100 g for epicardium, p = NS), whereas myocardial blood flow tended to be greater in the endocardium (6.09 +/- 0.73 ml/sec per 100 g for endocardium versus 5.47 +/- 0.75 ml/sec per 100 g for epicardium), although this was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Oxygen consumption is independent of increases in oxygen delivery by dobutamine in septic patients who have normal or increased plasma lactate.

We asked whether the relationship between oxygen delivery and oxygen consumption is different between patients who have sepsis and normal (n = 6) or increased (n = 8) concentrations of plasma lactate. We determined oxygen consumption using analysis of respiratory gases while increasing oxygen delivery using a dobutamine infusion. The relationship between oxygen delivery and consumption was y = 124 + 0.043 * x in the normal lactate group and y = 131 - 0.003 * x in the high lactate group (95% CI for differences in slopes, -0.003 to 0.096; p < or = 0.05 for slope, normal versus high lactate). In the normal lactate group, direct oxygen consumption increased by only 8 +/- 6 ml/min/m2 after dobutamine infusion (from 144 +/- 26 to 153 +/- 22 ml/min/m2, p < or = 0.02) despite an average increase of 220 +/- 80 ml/min/m2 in oxygen delivery (from 446 +/- 91 to 666 +/- 90 ml/min/m2, p < or = 0.01). The oxygen extraction ratio fell from 0.27 +/- 0.03 to 0.21 +/- 0.02 after dobutamine (p < or = 0.017). In the high lactate group, direct oxygen consumption decreased by 1 +/- 6 ml/min/m2 after dobutamine (from 131 +/- 33 to 130 +/- 35 ml/min/m2, p > 0.60) despite an average increase of 168 +/- 138 ml/min/m2 in oxygen delivery (from 467 +/- 194 to 635 +/- 300 ml/min/m2, p < or = 0.01). The oxygen extraction ratio fell from 0.30 +/- 0.14 to 0.26 +/- 0.12 after dobutamine (p < or = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Small airways dimensions in asthma and in chronic obstructive pulmonary disease.

The purpose of this study was to compare the dimensions of the peripheral airways in fatal asthma with those from patients with nonfatal asthma, mild COPD, and normal lung function. Lung specimens from eight individuals who had fatal asthmatic attacks were obtained at postmortem and compared with similar specimens from three asthmatic patients who died of an unrelated cause and four specimens obtained from known asthmatic patients who required lung resection for tumor. These 15 asthmatic lungs were also compared with lungs resected for peripheral neoplasms from 15 patients with normal airway function (FEV1, % of predicted > 85) and 15 patients with mild chronic airflow obstruction (FEV1, % of predicted < 85). All membranous airways with a long-short diameter ratio of 3:1 or less were examined. The smooth muscle and the tissue areas external and internal to the muscle layer were traced using a Bioquant BQ System 4. The same system was used to evaluate the fraction of the submucosa and adventitia taken up by blood vessels. The adventitial, submucosal, and muscle area of the asthmatic airways were greater than those of COPD and control (p < 0.01), and the muscle area was greater in COPD than in control lungs (p < 0.05). These parameters were also greater in the 8 patients with fatal asthma compared with the 7 patients with nonfatal asthma (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Airway narrowing in excised canine lungs measured by high-resolution computed tomography.

The exact site of airway narrowing in asthma and chronic obstructive pulmonary disease is unknown. High-resolution computed tomography (HRCT) is a sensitive noninvasive imaging technique that can be used to measure airway dimensions. After determining the optimal computed tomographic parameters using a phantom, we measured lobe volume and airway dimensions of isolated canine lung lobes at a transpulmonary pressure of 25 cmH2O. These measurements were repeated after deflation and administration of aerosolized saline and carbachol (256 mg/ml). Lobe volume decreased with all treatments. The maximal lobar volume change was 26% at 6 cmH2O after carbachol. Average airway lumen area decreased with all treatments. After carbachol, at transpulmonary pressures of 25, 15, 10, 8, and 6 cmH2O, lumen area decreased by 7.3 +/- 4.1, 62.0 +/- 4.9, 77.5 +/- 3.0, 31.9 +/- 9.0, and 95.2 +/- 1.0% (SE), respectively. When the airways were divided into four categories on the basis of initial lumen diameter (less than 2, 2-4, 4-6, and greater than 6 mm), the greatest decreases in luminal area after carbachol were seen in intermediate-sized airways (2-4 mm, 56 +/- 4%; 4-6 mm, 59 +/- 3%). HRCT can be used to make accurate measurements of airway dimensions and airway narrowing in excised lungs. HRCT may allow measurement of airway wall thickness and determination of the site of airway narrowing in asthma.

Administration, Inhalation↗
PubMed1992

A model of airway narrowing in asthma and in chronic obstructive pulmonary disease.

We have examined the effect of airway wall thickening, loss of lung recoil, and airway smooth muscle shortening on the increase in airway resistance using a model of the human tracheobronchial tree. The values for airway wall thickening were determined morphometrically on the postmortem or surgically resected lungs of normal subjects, patients with moderate chronic obstructive pulmonary disease, and patients with severe asthma. Loss of recoil was simulated by deflating airways along their pressure-area curves by 1 to 3 cm H2O. Values of smooth muscle shortening between 20 and 40% were used in the model to generate sigmoidal-shaped "dose-response" curves. The analysis shows that moderate amounts of airway wall thickening, which have little effect on baseline resistance, can profoundly affect the airway narrowing caused by smooth muscle shortening--especially if the wall thickening is localized in peripheral airways. The combination of a loss of recoil and airway wall thickening are more than additive in their effect on simulated airway responsiveness. We conclude that airway wall thickening and a loss of lung recoil can partially explain the airway hyperresponsiveness observed in patients with chronic obstructive lung disease and asthma.

Airway Resistance↗
PubMed1992

Fiber type and regional differences in oxidative capacity and glycogen content in the hamster diaphragm.

The purpose of this study was to define variability of the oxidative capacity and glycogen content between different fiber types and regions of the hamster diaphragm. Using histochemical and microphotometric techniques, the oxidative capacity (identified by nicotinamide-adenine dinucleotide tetrazolium reductase reaction end product) and glycogen levels (identified by the periodic acid-Schiff stain test) were examined in three myofibrillar ATPase (M-ATPase) fiber types and four diaphragmatic regions: sternal, anterior costal, thoracic surface of the crural (thor/crur), and abdominal surface of the crural (abd/crur). Most regional differences were found between the crus and the rest of the diaphragm. There were no differences in the oxidative capacity between diaphragmatic regions in the types 1 and 2a fibers, but the type 2b fibers in the thor/crur region had the greatest oxidative capacity and the 2b fiber in the sternal region had the lowest oxidative capacity. There were differences in glycogen content between diaphragmatic regions for all of the three M-ATPase fiber types. Variability in oxidative capacity between fiber types was demonstrated in all regions except the thor/crur region. Variation in glycogen content between fiber types was only demonstrated in the two surfaces of the crus. The type 2b fiber demonstrated the most differences from types 1 and 2a fibers in oxidative capacity and glycogen content in the different diaphragmatic regions, whereas the types 1 and 2a fibers demonstrated few differences from each other in these features across the different diaphragmatic regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminosalicylic Acid↗
PubMed1991

Direct injury to the bronchial vasculature in anesthetized sheep.

Injury to the bronchial vasculature may contribute to liquid and solute leakage into the lung during noncardiac pulmonary edema. The purpose of this study was to measure changes in hemodynamics, pulmonary mechanics, extravascular lung water, and lung morphometry after selectively injuring the bronchial vasculature in anesthetized sheep. In two groups of seven sheep, we injected oleic acid (0.1 ml/kg) or normal saline directly into the bronchoesophageal artery. We measured systemic and pulmonary arterial pressures, cardiac output, oxygen saturation, pulmonary resistance and compliance, and lung volumes before and 1 and 4 h after injection. The lungs were removed for measurement of extravascular water, histology, and morphometry. Four hours after injection of oleic acid, cardiac output decreased but pulmonary arterial pressure did not change. In addition, pulmonary resistance increased and dynamic compliance and vital capacity decreased. Extravascular lung water was slightly but significantly greater in the oleic acid group. Histological examination showed interstitial edema and leukocytes in airway walls and sloughing of bronchial epithelium but little or no alveolar edema. Morphometric analysis showed significant thickening of airway walls. We conclude that direct injury to the bronchial vasculature increases lung resistance, decreases dynamic compliance, and increases extravascular lung water by the accumulation of an inflammatory infiltrate in airway walls.

Airway Resistance↗
PubMed1990

Bicarbonate does not improve hemodynamics in critically ill patients who have lactic acidosis. A prospective, controlled clinical study.

STUDY OBJECTIVE: To determine whether correction of acidemia using bicarbonate improves hemodynamics in patients who have lactic acidosis. DESIGN: Prospective, randomized, blinded, crossover study. Each patient sequentially received sodium bicarbonate and equimolar sodium chloride. The order of the infusions was randomized. SETTING: Intensive care unit of a tertiary care hospital. PATIENTS: Fourteen patients who had metabolic acidosis (bicarbonate less than 17 mmol/L and base excess less than -10) and increased arterial lactate (mean, 7.8 mmol/L). All had pulmonary artery catheters and 13 were receiving catecholamines. MEASUREMENTS AND MAIN RESULTS: Sodium bicarbonate (2 mmol/kg body weight over 15 minutes) increased arterial pH (7.22 to 7.36, P less than 0.001), serum bicarbonate (12 to 18 mmol/L, P less than 0.001), and partial pressure of CO2 in arterial blood (PaCO2) (35 to 40 mm Hg, P less than 0.001) and decreased plasma ionized calcium (0.95 to 0.87 mmol/L, P less than 0.001). Sodium bicarbonate and sodium chloride both transiently increased pulmonary capillary wedge pressure (15 to 17 mm Hg, and 14 to 17 mm Hg, P less than 0.001) and cardiac output (18% and 16%, P less than 0.01). The mean arterial pressure was unchanged. Hemodynamic responses to sodium bicarbonate and sodium chloride were the same. These data have more than 90% power of detecting a 0.5 L/min (7%) change in mean cardiac output after administration of sodium bicarbonate compared with that after sodium chloride. Even the 7 most acidemic patients (mean pH, 7.13; range, 6.90 to 7.20) had no significant hemodynamic changes after either infusion. CONCLUSIONS: Correction of acidemia using sodium bicarbonate does not improve hemodynamics in critically ill patients who have metabolic acidosis and increased blood lactate or the cardiovascular response to infused catecholamines in these patients. Sodium bicarbonate decreases plasma ionized calcium and increases PaCO2.

Acidosis, Lactic↗
PubMed1990

Effect of raised alveolar pressure on leukocyte retention in the human lung.

To determine whether an increase in alveolar pressure delays the passage of leukocytes (WBCs) through the lung by compressing the lung capillaries, we measured the concentration of WBC across the lung in response to a forced expiratory maneuver. In 20 human subjects, blood was sampled from catheters placed in the pulmonary artery (PA) and left ventricle (LV) before, during, and after a forced expiratory maneuver held for greater than or equal to 20 s against an occluded airway. Pressures were recorded at the mouth and from both catheters. A significant fall in LV WBC (P less than 0.01) but not in PA WBC occurred during or immediately after the maneuver in 18 subjects, with a mean maximum decrease of 26 +/- 12% (SD) from base line (range 9-46%). Between 1 and 3 min after the maneuver, there was an increase in LV and PA WBC (P less than 0.01) above base line. The neutrophil and lymphocyte counts showed similar changes, but erythrocyte and platelet counts remained unchanged. The degree of fall in LV WBC correlated closely (r = 0.68, P less than 0.01) with the changes from lung zone 3 to zone 2 and 1 conditions, as determined from the pressure changes. We conclude that WBCs are retained in the lung during a forced expiratory maneuver because of alveolar capillary compression.

Adolescent↗