PubMed Health⌕ Search

Biomedical subjects

R G Castile

Publications and source records attributed to R G Castile.

At least 37 records · Page 2Linked to original sources
PubMed1987

Heterogeneous lung emptying during forced expiration.

Several lines of evidence suggest that the healthy mammalian lung empties homogeneously during a maximally forced deflation. Nonetheless, such behavior would appear to be implausible if for no other reason than that airway structure is known to be substantially heterogeneous among parallel pathways of gas conduction. To resolve this paradox we reexamined the degree to which lung emptying is homogeneous, and considered mechanisms that might control differential regional emptying. Twelve excised canine lungs were studied. Regional alveolar pressure relative to pleural pressure was used as an index of regional lung volume. By use of a capsule technique, alveolar pressure was measured simultaneously in each of six regions during flow-limited deflations; flow from the lung was measured plethysmographically. The standard deviation of interregional pressure differences, which was taken as an index of nonuniformity, was 0.0, 0.74, 0.64, and 0.90 cmH2O at mean recoil pressures of 30, 8.4, 4.5, and 2.1 cmH2O (0, 25, 50, and 75% expired vital capacity), indicating that interregional pressure differences increased more rapidly earlier in the deflation. When we examined the time rate of change of regional alveolar pressure as an index of regional flow, we observed an intricate pattern of differential regional behavior that was inapparent in the maximum expiratory flow-volume (MEFV) curve. The most plausible interpretation of these findings is that regions of the healthy excised canine lung empty heterogeneously to a small degree, but in an interdependent compensatory pattern that is inapparent in the configuration of the maximum expiratory flow-volume curve.

Animals↗
PubMed1987

Airway size is related to sex but not lung size in normal adults.

Within individuals, lung size as assessed by total lung capacity (TLC) or vital capacity (VC) appears to be unrelated to airway size as assessed physiologically by maximum expiratory flows (MEF). Green et al. (J. Appl. Physiol. 37: 67-74, 1974) coined the term dysanapsis (unequal growth) to express this apparent interindividual discrepancy between parenchymal and airway size. We have reexamined this discrepancy using both physiological and anatomic indexes of airway size. Airway area by acoustic reflectance (AAAR), peak expiratory flow rates (PEFR), MEF, and lung volumes were measured in 26 male and 28 female healthy nonsmoking adults. The effect of sex on these indexes of large airway size was significant when assessed in a subset of males and females whose TLC's were matched (5.0-6.5 liters). Within this subset, male AAAR was 2.79 +/- 0.45 cm2, whereas female AAAR was 1.99 +/- 0.67 cm2 (P less than 0.01). Male's PEFR and MEF after 25% of VC had been expired (MEF25) were 23% greater than those of females within this subset (P less than 0.05). For the entire group of subjects, once these sex-related differences had been accounted for, AAAR was not significantly related to TLC, whereas PEFR and MEF25 remained at best weakly related to TLC. We conclude that tracheal areas in males are significantly larger than those of females even after controlling for TLC and that after controlling for sex-related differences, tracheal size in adults is unrelated to lung size across a broad range of lung sizes.

Adult↗
PubMed1987

In vivo estimation of tracheal distensibility and hysteresis in normal adults.

We used the acoustic reflection technique to measure the cross-sectional area of tracheal and bronchial airway segments of eight healthy adults. We measured airway area during a slow continuous expiration from total lung capacity (TLC) to residual volume (RV) and during inspiration back to TLC. Lung volume and esophageal pressure were monitored continuously during this quasi-static, double vital capacity maneuver. We found that 1) the area of tracheal and bronchial segments increases with increasing lung volume and transpulmonary pressure, 2) the trachea and bronchi exhibit a variable degree of hysteresis, which may be greater or less than that of the lung parenchyma, 3) extrathoracic and intrathoracic tracheal segments behaved as if they were subjected to similar transmural pressure and had similar elastic properties, and 4) specific compliance (means +/- SE) for the intrathoracic and bronchial segments, calculated with the assumption that transmural pressure is equal to the transpulmonary pressure, was significantly (P less than 0.05) smaller for the intrathoracic segment than for the bronchial segment: (2.1 +/- 2.0) X 10(-3) cmH2O-1 vs. (9.1 +/- 2.1) X 10(-3) cmH2O-1. Direct measurements of airway area using acoustic reflections are in good agreement with previous estimates of airway distensibility in vivo, obtained by radiography or endoscopy.

Acoustics↗
PubMed1987

Assessment of the usefulness of helium-oxygen maximal expiratory flow curves in epidemiologic studies of lung disease in children.

Density dependence of maximal expiratory air flow (DD) has been used in adults as a test of early obstructive airway disease (OAD). Whether DD is useful as an epidemiologic tool to identify childhood risk factors for OAD is not known. In a population-based sample of 133 children 8 to 23 yr of age, we calculated density dependence at 50 and 25% of vital capacity (DD50 and DD25) (the ratios between maximal expiratory flow rates breathing helium-oxygen and air gas mixtures at each of these lung volumes), and the volume of isoflow (VisoV) (the lung volume, expressed as a percentage of vital capacity, at which maximal flow rates when breathing each gas mixture are equal), measured airway responsiveness using eucapnic hyperventilation with cold air, and obtained health and household information with questionnaires. Mean levels (+/- SD) of DD50, DD25, and VisoV were: 1.49 +/- 0.14, 1.37 +/- 0.18, and 10.7 +/- 10%. The DD50 significantly increased with age in these growing children (p less than 0.05), but DD50 was found to be significantly lower (1.42 +/- 0.14 versus 1.52 +/- 0.13; p less than 0.01) among children with nonspecific bronchial hyperresponsiveness. The DD50 also was significantly reduced among children with a history of a recent upper respiratory tract illness (URI) (p less than 0.01). There were no significant associations of DD with history of asthma, personal smoking, parental smoking, or respiratory illness during infancy. The reproducibility of DD50 was assessed on a subsample of 90 subjects in whom DD was measured during 2 surveys 1 yr apart.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Density dependence of maximal expiratory flow before and during tracheal constriction in dogs.

The effect of carbachol-induced central bronchoconstriction on density dependence of maximal expiratory flow (MEF) was assessed in five dogs. MEFs were measured on air and an 80% He-20% O2 mixture before and after local application of carbachol to the trachea. Airway pressures were measured using a pitot-static probe, from which central airway areas were estimated. At lower concentrations of carbachol the flow-limiting site remained in the trachea over most of the vital capacity (VC), and tracheal area and compliance decreased in all five dogs. In four dogs, decreases in choke point area predominated and produced decreases in flows. In one dog the increase in airway "stiffness" apparently offset the fall in area to account for an increase in MEF. Density dependence measured as the ratio of MEF on HeO2 to MEF on air at 50% of VC increased in all five dogs. Increases in density dependence appeared to be related to increases in airway stiffness at the choke point rather than decreases in gas-related airway pressure differences. Lower concentrations produced a localized decrease in tracheal area and extended the plateau of the flow-volume curve to lower lung volumes. Higher concentrations caused further reductions in tracheal area and greater longitudinal extension of bronchoconstriction, resulting in upstream movement of the site of flow limitation at higher lung volumes. Density dependence increased if the flow-limiting sites remained in the trachea at mid-VC but fell if the flow-limiting site had moved upstream by that volume.

Air↗
PubMed1986

Changes in flow-volume curve configuration with bronchoconstriction and bronchodilation.

Changes in the configuration of maximum expiratory flow-volume (MEFV) curves following mild degrees of bronchodilation or bronchoconstriction were studied in five normal and five asthmatic subjects. In a volume-displacement plethysmograph, MEFV curves were performed before and after inhalation of aerosolized isoproterenol (I) or histamine (H). Five filtered MEFV curves were averaged, and slope ratio vs. volume (SR-V) plots were obtained from averaged curves. Following I, maximal flows at 75% of the vital capacity (VC) were decreased in asthmatics but not in normal subjects. Flows at 50 and 25% of the VC increased in normal subjects and asthmatics, whereas VC's were unchanged. In asthmatics, sudden large decreases in flow (bumps) occurred at lower lung volumes following I. H reduced flows over the entire VC, with greater reductions occurring in asthmatics than in normals, particularly at low lung volumes. In asthmatics, VC was slightly reduced, and bumps in MEFV curve configuration occurred at higher lung volumes or were abolished entirely following H. A reduction in the amount of configurational detail appreciable in MEFV curves following histamine in asthmatics was best seen in SR-V plots. Following H, SR's decreased regularly with decreasing lung volume in all the asthmatics but in none of the normals. This was the single most striking finding of this study. Mild I- and H-induced perturbations of airway bronchomotor tone produced small but consistent changes in MEFV curve configuration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Nonhomogeneity of lung response to inhaled histamine assessed with alveolar capsules.

To assess the homogeneity of airway responses to inhaled histamine we examined regional alveolar pressure excursions (PA) arising from small-amplitude oscillations applied at the airway opening (Pao). In five anesthetized and vagotomized dogs the sternum was split and the anterior right lung field exposed. PA was sampled using four capsules affixed to the right apical and middle lobes while lung impedance (ZL) and airway impedances (Zaw) were measured during conventional tidal breathing and during forced oscillations (2-60 HZ at 10 cmH2O distending pressure). During tidal breathing after exposure to aerosol histamine regional PA's could be separated into three groups by plotting Lissajous figures of PA vs. Pao: PA in phase with Pao (no looping), PA lagging Pao (moderate looping), and PA decreasing while Pao was increasing and vice versa (paradoxical looping), suggesting unresponsive, responsive, and closed pathways, respectively, between the airway opening and specific alveolar zones. During high-frequency oscillation the corresponding PA spectra were markedly different from control spectra and revealed resonant amplification, overdamped resonance, and marked attenuation, respectively. With induced bronchospasm resonant amplification of PA was damped on average. However, the more obstructed and closed pathways were protected from resonant amplification, and the more open (nonlooping) pathways were subjected to resonant amplification greater than in the control state. In spite of this markedly nonhomogeneous behavior, frequency dependence of ZL was consistent with the model by Mead (J. Appl. Physiol. 26: 670-673, 1969), which ignores nonhomogeneity of peripheral compartments. These data demonstrate that the response of airways to inhaled histamine is nonhomogeneous but that frequency dependence of ZL above 2 Hz is not sufficient to characterize this nonhomogeneity.

Aerosols↗
PubMed1984

Reproducibility and accuracy of airway area by acoustic reflection.

To determine the accuracy and reproducibility of measurements of airway area by acoustic reflection (AAAR) we made repeated measurements of tracheal areas in human volunteers, glass airway models, and excised canine tracheae. In 10 adult males, the mean ratio of tracheal AAAR to tracheal areas determined roentgenographically was not significantly different from one (1.06 +/- 0.13 SD). Within-run variability was 10 +/- 4% (CV), mean intrasubject day-to-day variability was 9 +/- 4% (CV). A custom-made mouthpiece is necessary for accurate measurements of AAAR. Mean variability related to differences in mouthpiece construction was 7 +/- 6% (CV). The effect of variations in upper airway and glottic sizes on tracheal AAAR measurements was investigated using glass airway models. In model studies, tracheal AAAR measurements were found to be independent of changes in proximal airway size for glottic apertures greater than or equal to 1 cm2 and upper airway areas less than or equal to 8 cm2. Tracheal area was, however, overestimated by 20% in the rigid-walled glass models. The effects of airway wall rigidity were qualitatively investigated by comparing acoustic and roentgenographic measurements of excised canine tracheae surrounded by either air or petroleum jelly. Differences in the accuracy of measurements of AAAR in vitro and in vivo are probably due to differences in airway wall inertance. These studies suggest that the measurement of AAAR yields an accurate and reproducible result that may be clinically useful for the noninvasive detection of changes in central airway geometry.

Acoustics↗
PubMed1984

Alveolar pressure nonhomogeneity during small-amplitude high-frequency oscillation.

In six excised canine lungs, regional alveolar pressures (PA) were measured during small-amplitude high-frequency oscillations applied at the airway opening. Both the regional distribution of PA's and their relationship to pressure excursions at the airway opening (Pao) were assessed in terms of amplitude and phase. PA was sampled in several capsules glued to the pleural surface and communicating with alveolar gas via pleural punctures. Pao and PA were measured over the frequency (f) range 1-60 Hz, at transpulmonary pressures (PL) of 5, 10, and 25 cmH2O. The amplitude of PA excursions substantially exceeded Pao excursions at frequencies near the resonant frequency. At resonance the ratio [PA/Pao] was 1.9, 2.9, and 4.8 at PL's of 5, 10, and 25 cmH2O, respectively. Both spatial homogeneity and temporal synchrony of PA's between sampled lung regions decreased with f and increased with PL. Interregional variability of airway impedance [(Pao - PA)/Vao] and tissue impedance (PA/Vao) tended to be larger than differences due to changing PL but not as large as between-dog variability. These data define the baseline nonhomogeneity of the normal canine lung and also suggest that there may be some advantage in applying high-frequency ventilation at frequencies at least as high as lung resonant frequency.

Airway Resistance↗
PubMed1983

Density dependence of maximal flow in dogs with central and peripheral obstruction.

In 12 anesthetized, tracheotomized, vagotomized, open-chested, mongrel dogs we measured end and side hole airway pressures during forced expiration using a Pitot static probe. Volume was obtained as the integral of flow from a dog plethysmograph with frequency response adequate to 20 Hz. Equal pressure points (EPPs) and choke points (CPs) were located with dogs breathing air or a mixture of 80% helium-20% oxygen (HeO2) before and after partial obstruction of the trachea and intravenous histamine and propranolol. At 50% of vital capacity (VC) the CP was in the trachea in 11 of 12 dogs. Partial obstruction of the trachea decreased flow during the plateau of the maximum expiratory flow-volume curve (MEFVC) with the CP remaining in the trachea. The MEFVC plateau was extended to a lower lung volume. At 50% of VC the EPP moved downstream and density dependence remained high. Histamine and propranolol caused EPPs and CPs to move towards the periphery and density dependence to decrease. The shape of the MEFVC changed as the plateau was shortened and, in some instances, abolished. A plateau on the MEFVC could be regenerated by partial obstruction of the trachea. This was accompanied by return of the CP to the trachea and an increase in density dependence. Changes in density dependence were found to be a result of both the relocation of sites of flow limitation and differences in local CP areas with HeO2 and air.

Airway Obstruction↗
PubMed1982

Density dependence of maximum expiratory flow in the dog.

Airway lateral and impaction pressures were measured during expiratory flow limitation in six anesthetized, vagotomized, tracheally intubated, open-chest dogs with the lungs filled with air or a mixture of 80% helium-20% oxygen (HeO2). Pressures were measured in the vicinity of equal pressure points (EPP) and choke points (CP). Maximum flow (Vmax) was ensured by demonstrating no increase in flow with a 50% increase of driving pressure. At 50% vital capacity, mean density dependence (VmaxHeO2/Vmaxair) was 1.58, which was less than 1.69 predicted for fully density-dependent flow. Transmural pressure and airway area at CP and EPP (located on air) were significantly less with HeO2 than with air. Frictional losses between the alveoli and CP were 40% greater with HeO2 than with air. These enhanced losses were mostly peripheral to the EPP. Frictional loss upstream from the EPP was 47% of the total pressure loss on air and increased to 70% on HeO2. The data at 50% VC suggest that these higher frictional losses with HeO2 resulted in decreased density dependence of Vmax due to different pressure distribution along the airway with a lower transmural pressure and smaller area at the CP.

Air↗
PubMed1982

Symptomatic pectus deformities of the chest.

Aspects of pulmonary mechanics and exercise tolerance were investigated in 8 young male patients with pectus deformities, 5 of whom presented with the chief complaint of exercise limitation. Results of pulmonary mechanics studies did not adequately explain patient symptoms. Lung volumes were only mildly reduced. There was no evidence of airway obstruction. Measures of lung compliance were normal in 6 patients studied. Results of exercise studies did reveal significant abnormalities in symptomatic and asymptomatic patients; tidal volume at maximal effort expressed as a percentage of vital capacity was diminished, suggesting restriction of ventilation. Oxygen uptakes in the 4 symptomatic patients were normal at lesser work loads but progressively exceeded predicted values at greater work loads, suggesting an abnormally elevated work of breathing during vigorous exertion. Three asymptomatic patients demonstrated a normal linear pattern of increase in oxygen uptake with increasing work load. Respiratory symptoms in some patients with pectus deformities appear to have a physiologic basis. Our data suggest a dynamic restrictive pulmonary process as an explanation for these symptoms.

Adolescent↗
PubMed1980

Determinants of maximal expiratory flow and density dependence in normal humans.

There is a large variability in maximal expiratory flow (V) and density dependence (DD) in normal humans. Lung mechanics and flow-volume curves were obtained in 40 normal males while they breathed air or helium-oxygen (80%-20%). Static lung recoil (Pst) at 50% vital capacity, total lung capacity, and pulmonary resistance each correlated (P < 0.05) with airflow at 50% vital capacity. The relationship of V and Pst was described by Pst = 1/2 p V2/A2 + RV, where p is gas density, A is the critical area at the flow-limiting site, and R is peripheral resistance. At constant Pst and R, this simplified equation predicts an inverse relation between DD and airflow, which was found at recoil pressures of 8 and 7 cmH2O (P < 0.05). If peripheral losses are small, subjects with smaller flow-limiting airways would have lower airflows but higher DD than subjects with larger airways. Our findings are consistent with concept of dysanaptic growth and suggest that the central airways play a significant role in determining V and DD in normal humans.

Adult↗
PubMed1980

Implementation and operation of a hospital pediatric satellite pharmacy.

The planning, implementation, operation, and evaluation of a hospital pediatric satellite pharmacy are described. An initial three-month project involving establishment of a pediatric satellite pharmacy that provided unit dose drug distribution, intravenous admixtures, and a few clinical services was completed and evaluated. Positive evaluations by the medical and nursing staffs resulted in continuation of the satellite as a permanent program. Clinical services initially provided by the pediatric pharmacist were expanded to include acquisition of admission drug histories, instruction on discharge medication, participation on pediatric medical rounds and on the pediatric cardiopulmonary arrest team, operation of the poison control center, distribution of pediatric drug information, preparation of chemotherapy and monitoring of investigational protocols, and provision of pediatric nursing inservice education and community education. A five-year evaluation of the services provided by the pediatric satellite pharmacy was completed by 71 pediatric nurses and 27 Mayo Clinic physicians, all of whom had worked with the system regularly. The tabulated results are presented. Responses to overall services of the pediatric pharmacy were designated good to excellent by 100% of the physicians and by 98.6% of the nurses, indicating that the pediatric satellite pharmacy is a successful and beneficial program at this institution.

Child↗
PubMed1975

Vitamin D deficiency rickets. Two cases with faulty infant feeding practices.

Two cases of vitamin D deficiency rickets verify the occurrence of deficiency rickets in the United States in 1973. The two cases demonstrate the need for periodic reviews of feeding practices, especically when the possibility of so-called milk allergy is postulated. This may lead to avoidance of milk products. Fortification of various kinds of food with vitamin D does not ensure the protection from nutritional rickets of all children with peculiar feeding habits.

Alkaline Phosphatase↗