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Biomedical subjects

R L Jensen

Publications and source records attributed to R L Jensen.

At least 73 records · Page 4Linked to original sources
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

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

Normal spirometric values in healthy American Indians.

Spirometric parameters were measured in 300 healthy, lifetime nonsmoking American Indians. When "best" is defined by the highest correlation coefficient and smallest residual standard deviation, the best prediction equations were linear regression equations using only age and height as the independent variables. Visual comparisons of two-dimensional graphic representations of each predictor in these equations with equations commonly used to predict spirometric variables in white persons revealed no substantial differences. However, statistical comparisons, using an analysis of covariance, with data from a previous study of white persons in our laboratory showed the forced vital capacity and forced expiratory volume in 1 second equations for Indian men to be different from the equations for white persons. No statistically significant differences were found between the prediction equations for Indian and white women. The meaning of the statistically significant differences is unclear and they may not have any clinical relevance. Until this issue is resolved we recommend that race-specific equations be used when possible.

Adult↗
PubMed1987

Diurnal variation of the diffusing capacity of the lung: is it real?

The single-breath diffusing capacity of the lung (DLCO) has been reported to decrease at a rate of 1.2 to 2.2% per hour during usual daytime hours. In an attempt to confirm these findings, we measured DLCO using both single-breath (DLCOs) and rebreathing techniques (DLCOR) in healthy, nonsmoking volunteers over the course of a day and again at different times on different days. Serial testing over a day showed a consistent fall (0.39%/h for DLCOS and 0.56%/h for DLCOR) in DLCO that was explained by increasing carboxyhemoglobin levels (COHb) and decreasing hemoglobin concentrations (Hb). When subjects were tested at different times on different days and compared using a paired t test, there was no change in DLCO over the time of day using either technique. We conclude that there is no diurnal variation in DLCO when adjusted for changes in Hb and COHb. The measurement of COHb levels and Hb concentrations for adjustment of DLCO results is important for correct interpretation of both individual and group studies of DLCO and should be performed whenever possible.

Adult↗
PubMed1987

Prediction of pulmonary function abnormalities after adult respiratory distress syndrome (ARDS).

To determine if measures of ARDS severity during the acute illness correlate with lung function after recovery from ARDS, we regressed lowest total thoracic compliance (CTH), initial intrapulmonary shunt fraction (Qsp/Qt), initial mean pulmonary artery pressure (PAP), maximal level of positive end-expiratory pressure (PEEP), time ventilated (Tvent), and time with FlO2 greater than 0.6 (TO2) against the percent of predicted FVC, TLC, and DLCO of 16 previously healthy, nonsmoking ARDS survivors. Pulmonary function tests were performed more than 1 yr after ARDS. Percent of predicted FVC correlated with CTH (r = 0.66, p less than 0.01) and PAP (r = 0.53, p less than 0.05), and percent of predicted TLC correlated with CTH (r = 0.71, p less than 0.01), PEEP (r = -0.55, p less than 0.05), and Qsp/Qt (r = -0.53, p less than 0.05). Only TO2 correlated with percent of predicted DLCO (r = -0.53, p less than 0.05). Five of 7 ARDS survivors with an abnormal DLCO were supported at FlO2 greater than 0.6 for more than 24 h, whereas all of 9 survivors with a normal DLCO received FlO2 greater than 0.6 for less than 24 h. We conclude that physiologic markers of ARDS severity during the acute illness correlate with residual pulmonary dysfunction after recovery from ARDS. Support with FlO2 greater than 0.6 for more than 24 h appears to be a sensitive and specific predictor of an abnormally reduced DLCO more than 1 yr after ARDS.

Adolescent↗
PubMed1986

Paramedic use of advanced life support procedures: experience and attitude survey.

To gather information about paramedic use of 11 advanced life-support (ALS) procedures, 74 emergency physicians and 171 paramedics practicing in Utah were surveyed. Response was 66% and 65%, respectively. Performance difficulty, frequency of use, and success rate were evaluated. The willingness of physicians to order, and paramedics to perform each procedure were compared. Physicians' and paramedics' difficulty ratings were significantly different (P less than .001) for only 3 of the 11 procedures. During the study period, paramedics successfully performed 455 procedures; 229 were performed by 15 (13%) of the responding paramedics. The reported success rate for all attempted procedures was 82% (455/557). The number of attempts and the success rate was significantly higher (P less than .05) for paramedics with secondary medically affiliated employment. Paramedics were significantly more willing to perform 7 of the 11 procedures (P less than .001) than physicians were willing to order. We conclude that paramedic and physician difficulty ratings were generally similar, that many types of ALS procedures are rarely performed, that a small percentage of paramedics perform the largest number of ALS procedures, that secondary employment increases paramedics' procedural attempts and improves success rates, and that they are more willing to perform ALS procedures than physicians are to order them.

Allied Health Personnel↗
PubMed1986

Ear oximetry to detect apnea and differentiate rapid eye movement (REM) and non-REM (NREM) sleep. Screening for the sleep apnea syndrome.

Ear oximetry is commonly employed in screening patients for the sleep apnea syndrome, but the lack of objective information regarding the duration of sleep, including the presence of rapid-eye-movement (REM) sleep, is a major limitation. Based on the premise that both apnea and sleep-state-dependent changes in ventilation give rise to distinctive patterns in the arterial oxygen saturation, we developed a systematic technique to analyze ear oximetric tracings for wakefulness, REM sleep, and non-REM (NREM) sleep. Fifty-four patients were studied by both all-night polysomnography and ear oximetry. A careful comparison of ear oximetric data for sleep states and apnea was then made, using polysomnography as the correct classification to determine sensitivity, specificity, predictive value positive, and predictive value negative of the ear oximetric tracings. When classification of sleep state was compared, ear oximetry correctly classified 280.5 (82 percent) of 340.9 hours of sleep that was either REM or NREM sleep. The sensitivity for classifying NREM sleep was 0.85, for REM sleep was 0.70, and for wakefulness was 0.49. The sensitivity by ear oximetry for apnea was 0.80, with a predictive value negative of 0.87. We conclude that although polysomnography must be performed for definitive evaluation, ear oximetry is a valuable screening test for sleep apnea because the presence or absence of apnea can be determined, total duration of sleep can be estimated, and NREM vs REM sleep can be differentiated.

Adult↗
PubMed1985

Hypoxemia after gastric bypass surgery for morbid obesity.

Fifty-six patients who underwent Roux-en-Y gastrojejunostomy for morbid obesity had arterial blood gas analysis before surgery and during the first five postoperative days. Preoperatively, seven subjects were hypoxemic and three were hypercapneic. Twenty-four hours after gastric bypass, 75% of the patients had an arterial oxygen pressure (Pao2) less than 60 mm Hg. Compared with preoperative measurements, blood gas values on the first postoperative day showed a 13.7-mm Hg decrease in the mean arterial Pao2 and a 5.0-mm Hg increase in the mean arterial carbon dioxide pressure. Arterial Pao2 determinations on the third, fourth, and fifth postoperative days returned toward, but remained significantly less than, paired values obtained before surgery. Patients with hypoxemia after gastrojejunostomy were significantly older and had significantly lower preoperative arterial Pao2 measurements than patients who were not hypoxemic after surgery. Weight, body mass index, and preoperative spirometric measurements did not distinguish between those patients who did and did not become hypoxemic postoperatively. We conclude that hypoxemia commonly follows gastric bypass for morbid obesity, and thus we recommend that all patients undergoing this procedure be treated with supplemental oxygen for at least the first three postoperative days.

Adolescent↗
PubMed1985

Effect of intravenous aminophylline upon the incremental exercise performance of healthy men.

Aminophylline increases the contractile force of fatiguing muscles. The effects of aminophylline upon maximal exercise performance are not defined. 6 healthy men performed incremental bicycle ergometry before and after receiving intravenous aminophylline (6 mg/kg). Maximal oxygen uptake, maximum work rate, and maximum minute ventilation were unchanged following aminophylline. Heart rate measured at rest and at 50-watt increments of work rate was significantly increased following aminophylline (p less than 0.03). The heart rate response to incremental exercise (delta HR/delta VO2) was unchanged by aminophylline. We conclude that aminophylline does not increase maximal exercise performance of healthy men.

Adult↗
PubMed1984

Association between early graft patency and late outcome for patients undergoing artery bypass graft surgery.

For a group of 658 patients who received coronary artery bypass graft surgery, we investigated the correlation between the degree of early (6 months) graft patency and recurrence of anginal symptoms, late myocardial infarction, and postoperative coronary-related death. The patients were grouped according to the number of surgically placed grafts, and each group was further subgrouped on the basis of the number of grafts functioning at the early postsurgical follow-up examination. The patients were observed over a period as long as 13 years. The frequency with which angina returned correlated significantly with the degree of patency within each of the groups (one, two, three, or four grafts); patients with a higher percentage of patent grafts experienced longer periods of freedom from angina. On the average, patients with all of their multiple grafts patent experienced at least 7 more years of symptomatic relief than their counterparts with all grafts occluded. Most surprisingly, the rate of the return of angina for those patients who had all grafts patent and were completely revascularized was independent of the number of diseased vessels or the number of grafts placed. The findings for coronary death and postoperative infarction showed similar trends.

Aged↗
PubMed1983

Prolonged mechanical ventilation for respiratory failure: a cost-benefit analysis.

To define the costs and benefits associated with prolonged mechanical ventilation, we studied retrospectively the records of 137 consecutive patients who required at least 48 h of ventilator support. The patients were physiologically unstable and required intensive care. Causes of respiratory failure included pulmonary diseases, post-operative complications, neuromuscular diseases, cardiac dysfunction, and GI disease. Forty-nine (36%) patients survived the hospitalization, and 38 (28%) patients were alive 3 yr after receiving prolonged mechanical ventilation. The mean total hospital cost was +16,930/patient (U.S. dollars, 1976-1977). The cost-benefit averaged +1826/yr of extended life. These costs varied from +460/yr of extended life for patients with respiratory failure complicating asthma to +8026/yr for patients with cardiac dysfunction. The cost-benefit ratio increased sharply for men older than 56 yr and for women older than 75 yr. These data document the importance of the basic disease process and the patient's age in the cost-benefit relationship.

Age Factors↗
PubMed1982

Quantitative analysis of segmental wall motion throughout systole and diastole in the normal human left ventricle.

We traced left ventricular contours, frame-by-frame throughout systole and diastole, of normal sinus beats from 30 degrees right anterior oblique ventriculograms from 32 normal patients. We separated both systole and diastole into 19 equal time intervals each and calculated regional lengths (R), normalized by both end-diastole length and relative time interval (T) in systole and diastole and diastole, for the middle inferior wall, distal inferior wall, apex, distal anterior wall, middle anterior wall, and proximal anterior wall. We also computed the relative velocities of R, delta R/ delta T, over each quarter of systole and diastole. Comparing systole with diastole, we found significant differences between paired values of R at all regions except the distal inferior wall, but these differences were not the same between regions. Between regions, mean R and delta R/ delta T values were significantly different as early as the first quarter of systole. Within a region, there were significant differences between mean R and delta R/ delta T values over intervals as short as one-fourth of systole or diastole. Thus, there is no homogeneity between regions in normal wall motion in both systole and diastole. This normal lack of homogeneity has important clinical implications for identifying abnormal wall motion in individual patients from ventriculographic measurements, and for using the information present in the diastole portion of the ventriculogram to characterize normal segmental function.

Age Factors↗
PubMed1982

Relationship between graft patency, postoperative work status, and symptomatic relief.

In 405 men under the age of 65 requiring coronary bypass, in whom 6 month postoperative arteriograms were performed, we compared graft patency to postoperative work status and recurrent symptoms. We divided the population into subgroups of patients with varying degrees of patency. When these subgroups were tested, no significant dependence was found between the degree of graft patency and the percentages of patients who were working after operation, unless certain subgroups were removed from the population. When relief of angina was examined in the same manner as the postoperative work, we found a significant dependence between the graft patency and the percentage of patients who reported either short or long-term relief of angina in all groups. Because the rate of rehabilitation was high, even in patients with occluded grafts, and because older patients were less likely to return to work than younger patients despite successful revascularization, we conclude that physician emphasis on work rehabilitation and patient age, as well as graft patency, are all important factors which influence postoperative work status.

Age Factors↗