Biomedical subjects
Publications and source records attributed to A H Morris.
Nuclear magnetic resonance imaging was used to determine quantitatively the water distribution of saline-filled and normal rat lungs in both isolated lung and in situ preparations. Regional lung edema was easily detected. Studies of an isolated lung fragment indicate an accuracy of better than 1 percent and images of H2O/D2O phantoms indicate an average error of 2.7 percent.
We reviewed the hemodynamic data of 27 patients with severe adult respiratory distress syndrome (ARDS) and found significant elevations in heart rate, pulmonary artery pressure, and pulmonary vascular resistance and depressions of stroke index and left ventricular stroke work index. Altered left ventricular performance was suggested by a left ventricular stroke work index lower than expected for the level of wedge pressure in 19 patients and decreased slopes in nine of 11 ventricular function curves. Hemodynamic values in a subgroup receiving 0 to 5 cm H2O of positive end expiratory pressure (PEEP) were similar to those in the overall group (mean PEEP 12.5 +/- 7.9 cm H2O). Improvement in pulmonary and systemic hemodynamics occurred in survivors. Eight of 11 patients who underwent postmortem examination had cardiac abnormalities. The findings in this study suggest that changes in cardiovascular performance commonly occur in severe ARDS and that several mechanisms may contribute to the alterations.
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.
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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.
Quantitative values if oestradiol receptor were determined in the primary breast cancer of 526 patients, 106 of whom have so far required hormonal therapy for metastatic disease (premenopausal patients-oophorectomy; postmenopausal patients-tamoxifen 20 mg twice daily). The rate of response to treatment was significantly higher in patients with receptor-positive primary cancers, and the likelihood of response further increased in proportion to the measured receptor concentration. Preliminary data also suggest that patients with high receptor values in the primary tumour will enjoy a longer remission than those with low measured values. Assays of oestradiol receptor were also carried out on biopsy specimens of accessible metastases, largely skin and lymph-node recurrences, in 24 patients who were treated mainly with local measures. Receptor status was the same in both the primary and the secondary tumour in only 18 patients.
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.
Pulmonary function studies were performed on 13 survivors of adult respiratory distress syndrome (ARDS). Six of these 13 patients had a forced vital capacity (FVC) and total lung capacity (TLC) less than 80% of predicted within 2 months of the onset of ARDS. Seven patients followed 6 months or more showed no significant difference between measured and predicted FVC (p = 0.26) or TLC (p = 0.12). The diffusing capacity of carbon monoxide was significantly lower than predicted normal values (p less than 0.001). Although the alveolar arterial oxygen tension gradient (delta AaPO2) was within the predicted normal range for 11 nonsmokers at rest, for 7 patients who exercised (1.0 less than VO2 less than 1.5 L/min), delta AaPO2 increased. The ratio of dead space to tidal volume decreased to less than 0.25 when VCO2 exceeded 1.0 L/min. We concluded that lung mechanics return to predicted normal values within 4 to 6 months after ARDS, but abnormalities of pulmonary gas exchange persist. Pulmonary vascular obstruction does not appear to explain persistent abnormalities of gas exchange.
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.
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).
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.
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Nine medical centers collaborated in a prospective randomized study to evaluate prolonged extracorporeal membrane oxygenation (ECMO) as a therapy for severe acute respiratory failure (ARF). Ninety adult patients were selected by common criteria of arterial hypoxemia and treated with either conventional mechanical ventilation (48 patients) or mechanical ventilation supplemented with partial venoarterial bypass (42 patients). Four patients in each group survived. The majority of patients suffered acute bacterial or viral pneumonia (57%). All nine patients with pulmonary embolism and six patients with posttraumatic acute respiratory failure died. The majority of patients died of progressive reduction of transpulmonary gas exchange and decreased compliance due to diffuse pulmonary inflammation, necrosis, and fibrosis. We conclude that ECMO can support respiratory gas exchange but did not increase the probability of long-term survival in patients with severe ARF.
Three hundred and fifty-four women with primary operable breast cancer had a bone scan performed within 6 weeks of a simple mastectomy. Eight (2.3 per cent) were positive, but 7 of these patients had radiological evidence of bony metastases. Follow-up bone scans 1 year postoperatively on 278 patients showed only 12 (4.3 per cent) positive, and of these, 9 had other radiological evidence of metastatic disease. At 2 years postoperatively there were 13 (9.2 per cent) positive bone scans amongst 141 patients. Only 2 of these 13 had no other evidence of metastases. Although a bone scan is a useful investigation in patients with bone pain, there is no place for routine bone scanning in either the staging or follow-up of women with operable breast cancer.
The intermountain Respiratory Intensive Care Unit (IRICU), established in 1973 at the LDS Hospital in Salt Lake City, provides specialized care for adults and older children with severe respiratory failure in the intermountain West. Because of the large area serviced by the IRICU, a transportation system for the critically ill was developed. Our report describes the transport system, including team organization, techniques, and experiences. Of 44 attempted transports during the last three years, 43 (98%) were safely accomplished without obvious ill effect to the patient. Patients with severe respiratory failure, if their conditions are adequately stabilized, can be safely transported hundreds of kilometers by ground and air by a well-equipped and well-trained team of physicians and nurses.
Bone scans using technetium-99m phosphate complexes and a rectilinear scanner were carried out on 192 women with primary operable breast cancer four to six weeks after operation. The lymph node status of all these patients was assessed histologically from triple node biopsy specimens. Only nine patients had positive scans, although 94 patients had histological evidence that the tumour had already spread beyond the confines of the breast. Bone scanning, although accurate as a prognostic guide, is helpful only in a very few cases, and serves mainly to confirm prognostic information obtained more simply and less extensively by histological examination of lymph node biopsy specimens.
A rebreathing technique was utilized to assess changes in diffusing capacity (DCO), pulmonary capillary blood volume (Vc), pulmonary parenchymal tissue volume (Vt), and cardiac output (Qc), after infusion of 2 liters of 0.9% saline intravenously in 13-25 min in five healthy subjects. Blood hemoglobin concentration decreased an average of 17%. Vc increased strikingly in all five subjects. No significant changes in Vt, or in Vt per unit lung volume were observed. Radiographic evidence of interstitial pulmonary edema was present in four of the five subjects. Radiographic total lung capacity was reduced significantly in four of the five subjects. Significant reductions in forced vital capacity (FVC), forced expiratory volume in 1.0 and 3.0 s, and mean forced expiratory flow during the middle half of the FVC occurred in three of the five subjects. No dyspnea, cough, or physical examination abnormalities of lungs or heart occurred. This noninvasive, ventilation-limited, rebreathing technique appears capable of detecting early changes in pulmonary congestion, at a time when definitive radiographic changes and changes in the physical examination are absent. It appears capable of detecting the increase in Vc associated with hypervolemia in man.