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Biomedical subjects

R O Crapo

Publications and source records attributed to R O Crapo.

At least 91 records · Page 5Linked to original sources
PubMed1983

Comparison of total lung diffusion capacity and the membrane component of diffusion capacity as determined by physiologic and morphometric techniques.

Morphometric estimates of diffusion capacity have traditionally been calculated for oxygen (DLO2) while physiologic techniques have been used to determine diffusion capacity for carbon monoxide (DLCO). Morphometric estimates of DLCO and Dm were determined for carbon monoxide so that the results can be directly compared to those obtained using physiologic techniques. Multiple gas rebreathing techniques were used to measure total lung diffusion capacity (DLCO), membrane component of diffusion capacity (Dm) and pulmonary capillary blood volume (Vc) in five anesthetized dogs. After the rebreathing measurements were made, the lungs were inflation fixed with glutaraldehyde and subjected to morphometric analysis. The morphometric estimate of diffusion capacity was three times higher than the physiologic estimate. The major components of diffusion capacity, Dm and theta Vc were found to be of approximately equal size when measured physiologically (Dm = 34 and theta Vc = 27 ml X min-1 X mm Hg-1). In contrast, the morphometric estimate of Dm was about six times higher than the morphometric estimate of theta Vc. The widely different ratios of the two major subcomponents of the total lung diffusion capacity as measured by these two different techniques suggest that the same lung function is not being accurately measured by at least one of these two techniques. Differences in results for DLCO cannot be explained by differences in the physiologic state of the animal at the time the measurement was made. Morphometric analysis predicts that Vc is the major term affecting the value of DLCO whereas the physiologic techniques predict that both Dm and Vc contribute substantially to the value of DLCO.

Animals↗
PubMed1983

The effect of ventilation on the accuracy of pulmonary artery and wedge pressure measurements.

A comparison was made of automated versus manual measurement of pulmonary artery (PA) and wedge (WP) pressures. The manual pressure measurements were taken at end-expiration whereas the automated measurements were taken using existing monitor and computer algorithms. A total of 40 critical care patients were divided into groups according to the ventilatory mode used (spontaneous, intermittent mandatory ventilation [IMV], or assist/control). In patients who were breathing spontaneously, the automated method underestimated mean PA pressure (MPAP) (p less than 0.01), WP (p less than 0.001), and PA diastolic (p less than 0.001) pressure but not PA systolic pressure. In patients on IMV, the automated method underestimated MPAP (p less than 0.05), WP (p less than 0.001), and PA diastolic (p less than 0.001) pressure and overestimated PA systolic pressure (p less than 0.05). In patients on assist/control, the automated method overestimated WP (p less than 0.001) and PA systolic (p less than 0.005) pressure pressure, underestimated PA diastolic (p less than 0.001) pressure and did not affect MPAP. The error was not affected by respiratory rate, thoracic compliance, or level of PEEP. The errors in automated pressure measurements believed to be clinically important varied with the ventilatory mode used. Patients breathing spontaneously had the largest measurement error, with 42% of these patients having a clinically important error in WP and 99% having a clinically important error in PA diastolic pressure. Patients on assist/control had the fewest errors in automated pressure measurements. In all ventilatory modes used, automated measurement of PA diastolic pressure had the largest amount of error.

Automation↗
PubMed1983

Pulmonary complications following abdominal lipectomy.

Previous reports underestimate the morbidity of a lipectomy, having focused on mortality statistics. Alterations of respiratory kinetics leading to complications do not always correlate with the usual signs and symptoms of respiratory failure. Patients at increased risk, namely, those with obesity, a smoking history, or lung disease, deserve special attention, including appropriate pulmonary function studies in the preoperative and postoperative phase. The following studies are indicated in the preoperative assessment of the high-risk patient: (1) vital capacity, (2) arterial blood gases, and (3) chest radiograph.

Abdomen↗
PubMed1983

"Anaerobic threshold": problems of determination and validation.

Despite the popularity of the concept of "anaerobic threshold" (AT), the noninvasive detection criteria remain subjective, and invasive validations of AT have been based on lactate data of arterial, mixed venous, venous, and capillary blood samples without any concern for the possible lactate differences from these sources. Eight normal subjects underwent two exercise tests on a bicycle ergometer. The protocol consisted of 3 min of rest, 3 min of 0 work load, and a 20 W/min ramp (1 W/3 s) until exhaustion. Simultaneous arterial and venous blood samples were drawn during the second test. Noninvasive gas response data were measured using a computerized breath-by-breath stress test system. Threshold phenomenon of the lactate accumulation was not found. The arterial lactate levels increased continuously after the start of the exercise ramp. The rise in venous lactate lagged behind the rise of the arterial lactate by about 1.5 min, and therefore venous lactate was not considered suitable for AT detection. Four independent exercise physiologists determined AT from the gas response data. The reviewer variability (avg range 16%) of AT for a given subject was representative of AT values reported for untrained and trained individuals (40-70% maximum O2 consumption). We concluded that 1) AT is not detectable using invasive methods (arterial and venous lactates); and 2) the noninvasive gas response determination has such a large range of reviewer variability that it is unsuitable for clinical use.

Adult↗
PubMed1983

Morphometric characteristics of cells in the alveolar region of mammalian lungs.

Morphometric procedures have been used to study the characteristics of cells in the alveolar region of the lungs of rats, dogs, baboons, and humans. Compared with the other species, human lungs were found to contain greater numbers of macrophages and to have larger alveolar type II, endothelial, and interstitial cells. The thickness of the interstitium and the pulmonary capillary endothelium were also significantly greater in the human lungs. These differences in human lung anatomy may be due to increased exposure to airborne pollutants and to tobacco smoke. Despite the above differences and the fact that there are large variations in size and functional characteristics of the lungs of these mammals, an overall striking similarity in characteristics of individual lung cells was found. The distribution of cells in alveolar tissue was remarkably constant between species as was the average volume and surface area of most cell types. Computer-aided three-dimensional reconstruction techniques were used to determine the spatial relationship of organelles in individual alveolar type II cells from rats. A three-dimensional reconstruction of cells permits quantification of number, size, surface area, and volume of subcellular organelles and correlations of their three-dimensional spatial relationships.

Animals↗
PubMed1983

Spirometry: what paper speed?

Controversy still exists regarding the paper speed necessary for accurate measurements from records of maneuvers for forced vital capacity. Twenty-four spirometric wave forms of known characteristics were plotted by a computer at 1, 2, and 3 cm/sec and were measured in random order by 12 experienced readers. We found that all readers made a surprisingly large number of major errors. The speed of the paper was found to be an important determinant for accurately measuring the forced expiratory volume in one second and the mean forced expiratory flow during the middle half of the forced vital capacity. A minimum paper speed of at least 3 cm/sec is important if spirograms are to be accurately measured by hand. Human errors in measurement may be minimized by obtaining results from at least three acceptable curves, by making duplicate reading of curves, and by making use of validated computerized measurement systems.

Forced Expiratory Volume↗
PubMed1982

Lung tissue and capillary blood volumes by rebreathing and morphometric techniques.

Gas rebreathing measurements of lung tissue volume (Vt) and pulmonary capillary blood volume (Vc) were made in five anesthetized dogs. After the rebreathing measurements, the lungs were inflation fixed with glutaraldehyde and analyzed morphometrically. Each lung was morphometrically divided into alveolar and nonalveolar compartments and each compartment was divided into its air, tissue and blood components. Average rebreathing and morphometric measurements of Vc were 42 and 84 ml, respectively. The reasons for this difference remain unclear. The rebreathing Vt (198 ml) was 40 ml (25%) greater than the morphometric alveolar tissue and blood components (158 ml). Assuming that the rebreathing technique measures all of the alveolar compartment, the rebreathing measurement includes a significant fraction of the nonalveolar compartment.

Animals↗
PubMed1982

Lung tissue volume estimated by simultaneous radiographic and helium dilution methods.

The pulmonary total tissue volume (blood, extravascular water, and dry tissue volume) was measured by finding the difference between the radiographic displacement volume of the thorax (RDVT) and the lung gas volume. Simultaneous determinations of RDVT and gas volume were made in 10 healthy subjects sitting upright. RDVT was determined from posteroanterior and lateral chest radiographs, a computerised modification of the Barnhard method being used; and gas volume was measured by helium dilution with each radiographic exposure. At functional residual capacity pulmonary total tissue volume was 843 +/- 110 ml (1 SD). The density of the lung (ml tissue per ml tissue and gas) was 0.19 +/- 0.03 (1 SD). This method, different in principle from indicator-dilution and acetylene rebreathing studies, provides measurements of total tissue volume.

Adult↗
PubMed1982

Computerized decision-making in the pulmonary function laboratory.

Computers are now in widespread use in pulmonary function laboratories, where they have made an important contribution by assisting with complex and repetitive tasks. They can be used to acquire data from testing instruments, make measurements and calculations, and prepare reports. At LDS Hospital in Salt Lake City, we use the HELP (Health Evaluation through Logical Processing) Computer System for medical decision-making. As a result of our experience with this system, we have found six definable steps between data acquisition and data interpretation: (1) establish quality instrumentation, (2) establish adequate procedures for test performance, (3) standardize measurement and computational techniques, (4) determine the adequacy and reproducibility of results and apply a test selection, (5) identify the measurements to be used for interpretation, and (6) apply strategies that lead to consistent interpretation of results. Because spirometry and blood gas tests account for the major activities of our pulmonary function laboratory, we have applied these six steps necessary for computer decision-making to these two two tests; however, they are equally applicable to other tests in the pulmonary function laboratory.

Blood Gas Analysis↗
PubMed1981

Standardized single breath normal values for carbon monoxide diffusing capacity.

Prediction equations for DLCO and diffusing capacity per unit of lung volume (DL/VA) were generated from 245 normal subjects (122 women and 123 men) using a standardized technique for measuring DLCO. Measurements were made at an altitude of 1,400 meters. Multiple linear regressions were made using standard and robust regression techniques. The resultant equations predicted values for DLCO and DL/VA that were higher than most previously reported values. The use of robust regressions did not add to the predictability of standard linear regressions.

Adolescent↗
PubMed1981

Reference spirometric values using techniques and equipment that meet ATS recommendations.

Forced expiratory volumes and flows were measured in 251 healthy nonsmoking men and women using techniques and equipment that meet American Thoracic Society (ATS) recommendations. Linear regression equations using height and age alone predict spirometric parameters as well as more complex equations using additional variables. Single values for 95% confidence intervals are acceptable and should replace the commonly used method of subtracting 20% to determine the lower limit of normal for a predicted value. Our study produced predicted values for forced vital capacity and forced expiratory volume in one second that were almost identical to those predicted by Morris and associates (1) when the data from their study were modified to be compatible with the back extrapolation technique recommended by the ATS. The study of Morris and colleagues was performed at sea level in rural subjects, whereas ours was performed at an altitude of 1,400 m in urban subjects. Either the present study or the study of Morris and co-workers, modified to back extrapolation, could be recommended for predicting normal values.

Adolescent↗
PubMed1981

Dung lung: a report of toxic exposure to liquid manure.

The use of liquid manure storage facilities poses several serious threats: toxic gas inhalation, asphyxiation, aspiration of liquid manure, and infection. Hydrogen sulfide poisoning in a manure storage pit resulted in three deaths. Two of the persons who died had massive aspiration of liquid manure; the third had severe pulmonary edema but had not aspirated manure. The clinical course of the patient who survived was complicated by hemodynamic instability, adult respiratory distress syndrome, and infection. These accidents can be prevented by the use of a self-contained breathing apparatus and a safety line, as well as the presence of a second person for rescue if necessary. Recommendations for treatment are mainly supportive, including cardiopulmonary resuscitation, mechanical ventilation, oxygen, and positive end-expiratory pressure. Nitrites may speed recovery but in excess can cause other complications.

Adult↗
PubMed1980

Pulmonary tissue volume in isolated perfused dog lungs.

Lung tissue volume (Vt) and pulmonary capillary blood flow (Qc) were measured with an acetylene rebreathing technique in intact and isolated perfused dog lungs. Qc (1.73 +/- 0.17 l/min) was consistently greater than pump flow (0.87 +/- 0.10 l/min) in isolated perfused lungs because acetylene disappearance from the lung was increased by diffusion across the pleura into the room. In spite of the increased acetylene loss, Vt can be measured in isolated lungs with reproducibility similar to that in intact animals (Vt intact = 207 +/- 63 ml, Vt isolated perfused = 208 +/- 61 ml).

Animals↗
PubMed1980

Selection of the best spirometric values for interpretation.

Selection of spirometric test values for reporting and interpretation has recently received considerable attention. In 1977, the American Thoracic Society (ATS) Snowbird Workshop on Standardization of Spirometry recommended that the maximal values for FVC and FEV1 be used for clinical interpretation, even if they came from different spirometric tracings. The Intermountain Thoracic Society (ITS) had recommended in 1975 that FVC and FEV1, be reported from the single tracings, using the largest sum of FVC plus FEV1 (best test). We evaluated the results of 1,853 spirometric test sessions in 1,101 subjects (923 hospital patients and 178 normal volunteers). The mean difference between the 2 test selection methods cited above was 5.8 ml for FVC and 8.4 ml for FEV1. In 98.4% of the FVC comparisons and 95.7% of the FEV1 comparisons, the differences were within the minimal instrument accuracy standard (+/- 50 ml or +/- 3% of the reading) suggested by the ATS. Differences between maximal and best test FVC and FEV1 were small. The selection of values for interpretation from the best test did not compromise accuracy, and was a simpler and more practical method for reporting clinical spirometric results.

Adult↗