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Biomedical subjects

R O Crapo

Publications and source records attributed to R O Crapo.

At least 55 records · Page 3Linked to original sources
PubMed1989

Rate of CO uptake by canine erythrocytes as a function of PO2.

We used a continuous-flow rapid-mixing apparatus with spectroscopic analysis to measure the rate of CO uptake by canine erythrocytes at 37 degrees C at five different PO2 values from 0 to 553 Torr. Fresh blood from five different dogs was used for the experiments. PCO approximated 80 Torr. Corrections for the lower capillary PCO during a measurement of the diffusing capacity of lung CO, as made by Roughton and Forster in 1957 (J. Appl. Physiol. 11: 290-302, 1957), were not used. The regression equation for 1/theta, where theta is milliliters of CO combining for each milliliter of whole blood (capacity 0.2 ml/ml) per minute for a PCO of 1 Torr was 1/theta = 1.45 +/- 0.0042 PO2. This equation is very similar to that for human erythrocytes under the same conditions.

Animals↗
PubMed1989

Impairment after adult respiratory distress syndrome. An evaluation based on American Thoracic Society recommendations.

To test the hypothesis that impairment after the adult respiratory distress syndrome (ARDS) is uncommon, we evaluated 41 ARDS survivors using ATS standards for determination of impairment. A total of 101 trials of pulmonary function tests were obtained between 1 and 388 wk after the onset of ARDS. It was possible to evaluate impairment at 1 yr or more after ARDS in 27 subjects. Eighteen of the 27 were impaired. The percentage of ARDS survivors who were impaired on the basis of FVC, FEV1, FEV1/FVC, and DLCOsb was 50.0, 61.1, 33.3, and 82.4%, respectively. Impairment was mild in 13 (72.2%), moderate in four (22.2%), and severe in one (5.6%). Smoking status had no predictive value in determining impairment. Physiologic indices of ARDS severity (maximal pulmonary artery pressure, lowest static thoracic compliance, and maximal level of PEEP) were found to be significantly different when those impaired 1 yr or more after ARDS were compared with those not impaired. Symptoms were found to have no association with impairment. We conclude that, using ATS criteria, impairment 1 yr or more after ARDS onset is common. Patient characteristics and symptoms after ARDS have no association with impairment 1 yr or more after ARDS onset, whereas physiologic indices of severity during ARDS do.

Adult↗
PubMed1989

Comparison of blood gas analyzer biases in measuring tonometered blood and a fluorocarbon-containing, proficiency-testing material.

This study was designed to test whether the interinstrument differences (biases) in analyses of the PO2 and PCO2 of the commercial fluorocarbon-containing emulsion (FCE) proficiency-testing material abc were similar in magnitude and direction to analyses of the PO2 and PCO2 at four similar partial pressures in tonometered blood. There were large differences among the 13 individual instrumental mean values for both blood and FCE at the four levels: for PO2 (average range, 10.3 mm Hg for blood and 17.0 mm Hg for FCE) and PCO2 (average range, 9.4 mm Hg for blood and 6.2 mm Hg for FCE). Although the instrumental biases for blood and FCE were approximately the same, the biases were slightly higher for FCE in measuring PO2 and slightly higher for blood in measuring PCO2. Accuracy and precision in blood measurement and precision in FCE measurement were significantly correlated among instruments for PO2 and PCO2. The biases of the nine instrument models evaluated significantly correlated with those of the same models participating in national surveys. We suggest that differences in technique, maintenance, and instrumental design rather than inherent differences in PO2 and PCO2 electrodes probably account for the demonstrable differences between instruments. The fluorocarbon-containing emulsion used is of value in proficiency testing for PO2 and PCO2.

Blood Gas Analysis↗
PubMed1989

Heritability estimates of pulmonary function.

To test the hypothesis that there is genetic control of pulmonary function parameters independent of that influencing height, we evaluated 74 pairs of asymptomatic, nonsmoking twins. FVC, FEV1, FEF25-75%, TLCsb, RVsb, Dsb, and D/VA were measured. Pulmonary function indices were adjusted for height using simple linear regression. Mean intrapair differences (unadjusted and adjusted for height) were compared using t tests of independent samples. Within pair, Holzinger's, and Falconer's heritability estimates were calculated using height-adjusted residual values. When total variances of a function parameter were statistically different between monozygotes and dizygotes, the among component heritability estimate was calculated and used as the best indicator of heritability. Following adjustment for height, no measure of pulmonary function which satisfied the requirements of the analysis was found to be significantly heritable.

Adult↗
PubMed1989

Carbon monoxide diffusing capacity.

Before measuring single-breath DLCO it is important to: (1) standardize carefully test technique and computation using current ATS guidelines; (2) confirm that computerized systems correctly perform the calculations; and (3) confirm that the reference values selected are consistent with the data produced by the device in the laboratory by comparing measured values with predicted values in several healthy subjects. Interpretation of the test should begin with the following steps: (1) confirmation that the test was properly performed; (2) identification of "noise" factors that may interfere with the interpretation (these may include age, body size, ethnic factors, Hb concentration, COHb, smoking, lung volume, PaO2, exercise, and hormonal effects); and (3) correlation of abnormal findings with clinical data to ensure that they are consistent with the clinical diagnosis.

Carbon Dioxide↗
PubMed1989

Spirometry and flow-volume curves.

Spirometry is the best and most widely used pulmonary function test. Equipment recommendations are made and performance information about different types of spirometers is given. Methods for obtaining clinically applicable spirometric results for use in making diagnostic and treatment decisions are presented. Selection and use of reference or "normal" values and interpretive strategies are discussed.

Forced Expiratory Flow Rates↗
PubMed1989

Pulmonary function testing: sources of error in measurement and interpretation.

Valid pulmonary function data require that attention be paid to issues that can lead to errors in measurement or in interpretation. Routine procedures designed to reduce errors should be established. Among the most important of these are (1) assuring the accurate measurement and calculation of lung function parameters, which requires attention to accuracy when an instrument is brought into service in a laboratory and again when it is updated; (2) selecting reference equations and lower limits of normal appropriate for the patients being studied and for the equipment being used; (3) avoiding the errors introduced by using an excessive number of measurements in generating an interpretation; and (4) avoiding interpretation of results without considering the clinical setting and the pertinent elements of a complete data base.

Equipment Failure↗
PubMed1988

Evaluation of lung diffusing capacity by physiological and morphometric techniques.

Determinations of pulmonary diffusing capacity for CO (DLCO) by physiological and morphometric techniques have resulted in substantially different values for both DLCO and its major components. To evaluate the differences in these methods of measurement of DLCO, measurements were made under controlled conditions on isolated perfused dog lungs. Multiple gas-rebreathing techniques were used to measure DLCO, the membrane component of the diffusing capacity for CO (DmCO), and pulmonary capillary blood volume (Vc) in both anesthetized dogs and after isolation and perfusion of their lungs. The isolated perfused lungs were than perfusion fixed for morphometric analysis of the components of DLCO. The values obtained morphometrically for Vc were similar to those measured by physiological techniques. Perfusion fixation did not substantially alter the morphometric estimate of DmCO when compared with previous values obtained on inflation fixed lungs. However, the morphometric estimate of DmCO was over 10 times higher than that estimated physiologically. Analysis of the potential errors in the techniques suggests that the correct value for DmCO is substantially higher than that commonly estimated by use of physiological techniques and that the explanation for the difference is due to a number of factors that can influence the binding of CO to hemoglobin under in vivo conditions. The net effect of these factors can be represented by an unknown in each component of the Roughton-Forster relationship so that 1/DL = 1/(U1.Dm) + 1/(U2.theta Vc), where theta is the binding rate for CO to hemoglobin. Because the magnitudes of the unknown terms (U1 and U2) in the Roughton-Forster relationship are likely to be large, this relationship cannot be reliably used to determine Dm and Vc.

Animals↗
PubMed1988

Pulmonary veno-occlusive disease associated with severe reduction of single-breath carbon monoxide diffusing capacity.

A 49-year-old woman presented with pulmonary hypertension, profound arterial hypoxemia, and a single-breath carbon monoxide diffusing capacity (DLCO) which was 17% of predicted. History, physical examination, and chest roentgenograms did not suggest the presence of parenchymal pulmonary disease. Spirometry and lung volume measurements were within normal limits. Pulmonary veno-occlusive disease was diagnosed by lung biopsy. This case illustrates the severe reduction of DLCO which can be associated with pulmonary veno-occlusive disease.

Carbon Monoxide↗
PubMed1988

Maximum respiratory pressures in morbidly obese subjects.

Maximum inspiratory and expiratory pressures were measured at residual volume, total lung capacity, and functional residual capacity in 45 morbidly obese patients who on average weighed 183% of their predicted weights. The pressures were compared to determinations made in 25 subjects of similar age whose mean weight was 99% of predicted. For both men and women, pressures generated by control subjects tended to be higher than those produced by obese patients but the differences were not statistically significant. The mean vital capacity and total lung capacity were also similar in the 2 subject groups. The results indicate that despite working constantly against a less compliant chest wall, obese patients do not increase their capacity to generate maximal respiratory pressures.

Adult↗
PubMed1988

Longitudinal pulmonary function changes in pigeon breeders.

We studied 15 subjects (14 men and one woman; seven symptomatic and eight asymptomatic) at three- to four-year intervals from 1967 through 1985 (18 years) to determine if continued pigeon antigen exposure in these groups was associated with a decline in pulmonary function greater than expected in healthy individuals. We collected immunologic studies at the initial visit, performed sequential pulmonary function studies and obtained chest radiographs. After compensating for the normal changes expected with increasing age, we found the declines in FVC, FEV1, and Dsb in the symptomatic group were nearly four times greater than expected. There was no significant difference in the decline of pulmonary function between asymptomatic subjects and the normal predicted declines with increasing age. We conclude that, if an individual has episodes of acute hypersensitivity pneumonitis, long-term exposure to pigeon antigens will result in an accelerated decline in pulmonary function.

Adult↗
PubMed1988

Upper airway obstruction following adult respiratory distress syndrome. An analysis of 30 survivors.

To evaluate the effects of current supportive care measures for the adult respiratory distress syndrome (ARDS) upon the upper airway, we studied 30 survivors of ARDS. All patients were interviewed and examined and performed inspiratory and expiratory maximal flow-volume curves more than six months after the onset of ARDS. Three women had developed symptomatic upper airway obstruction due to laryngotracheal stenosis 4 to 12 months after discharge from the hospital. Potential etiologic factors included difficult orotracheal intubation (one) and high tracheal cuff pressures (one). The three survivors who developed laryngotracheal stenoses did not differ from the 27 survivors of ARDS without symptomatic upper airway obstruction with respect to age, duration of tracheal intubation, or maximum level of positive end-expiratory pressure. Each patient with upper airway obstruction required more than one operation for laryngotracheal reconstruction. Although corrective surgery improved airflow, two survivors of ARDS had upper airway obstruction and exertional dyspnea more than five years after the ARDS. We conclude that upper airway obstruction is an important cause of dyspnea and impairment following ARDS. Exertional dyspnea weeks to months following treatment for ARDS suggests the possibility of laryngotracheal stenosis.

Adolescent↗
PubMed1988

Variability of the single-breath carbon monoxide transfer factor as a function of inspired oxygen pressure.

We measured single-breath CO transfer factor (TLCO) and alveolar oxygen partial pressure (PAO2) six times at each of three fractions of inspired oxygen (FIO2) (0.17, 0.21, 0.26) in twelve healthy subjects, to determine whether one FIO2 would have the advantage of producing less variable TLCO results than the others. Measured TLCO was adjusted for the increase in carboxyhaemoglobin during the tests. We found no significant differences in intra- or interindividual variance as a function of test FIO2.

Carbon Monoxide↗
PubMed1988

Smoke inhalation.

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Acute Disease↗