Adult respiratory distress syndrome secondary to high altitude pulmonary edema.
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Adult↗
Biomedical subjects
R O Crapo
Publications and source records attributed to R O Crapo.
Performance of computerized protocols for the management of arterial oxygenation in an intensive care unit.
Computerized protocols were created to direct the management of arterial oxygenation in critically ill ICU patients and have now been applied routinely, 24 hours a day, in the care of 80 such patients. The protocols used routine clinical information to generate specific instructions for therapy. We evaluated 21,347 instructions by measuring how many were correct and how often they were followed by the clinical staff. Instructions were followed 63.9% of the time in the first 8 patients and 92.3% in the subsequent 72 patients. Instruction accuracy improved after the initial 8 patients, increasing from 71.5% of total instructions to 92.8%. Instruction inaccuracy was primarily caused by software errors and inaccurate and untimely entry of clinical data into the computer. Software errors decreased from 7.2% in the first 8 patients to 0.8% in subsequent patients, while data entry problems decreased from 7.5% to 4.2%. We also assessed compliance with the protocols in a subset of 12 patients (2637 instructions) as a function of 1) the mode of ventilatory support, 2) whether the instruction was to increase or decrease the intensity of therapy or to wait for an interval of time and 3) whether the instruction was 'correct' or 'incorrect'. The mode of ventilatory support did not affect compliance with protocol instructions. Instructions to wait were more likely to be followed than instructions to change therapy. Ninety-seven percent of the correct instructions were followed and 27% of the incorrect instructions were followed.(ABSTRACT TRUNCATED AT 250 WORDS)
Blood Gas Analysis↗
Inspiratory lung volume achieved on routine chest films.
Posteroanterior and lateral chest radiographs were obtained in 19 healthy subjects after routine instruction. Immediately afterwards, repeat films were obtained with the subjects vigorously coaxed to maximal inhalation. Total lung capacity was measured from both sets of radiographs. Normal subjects inhale to 95.5% +/- 3.8% (SD) of total lung capacity during routine chest radiography. Routine chest radiographs will provide useful total lung capacity measurements. Old chest radiographs, in addition to frequently being a mandatory part of the clinical evaluation of patients with chest problems, may provide the only antecedent information about lung function (total lung capacity).
Humans↗
Revision of diagnostic logic using a clinical database.
Statistical pattern-recognition techniques have been frequently applied to the problem of medical diagnosis. Sequential Bayesian approaches are appealing because of the possibility of generating the underlying sensitivities, specificities, and prevalence statistics from the estimates of medical experts. The accuracy of these estimates and the consequences of inaccuracies carry implications for the future development of this type of system. In an effort to explore these subjects, the authors used statistics derived from a clinical database to revise the diagnostic logic in a Bayesian system for generating a differential diagnostic list. Substantial changes in estimated a priori probabilities, sensitivities, and specificities were made to correct for significant under- and overestimations of these values by a group of medical experts. The system based on the derived values appears to perform better than the original system. It is concluded that the statistics used in a Bayesian diagnostic system should be derived from a database representative of the patient population for which the system is designed.
Bayes Theorem↗
A modified single-breath DLCO apparatus.
A modified apparatus for measuring the single-breath carbon monoxide diffusing capacity of the lung (DLCO) is described. The modification permits simultaneous measurement of all lung volumes and capacities. In a comparison of conventional and modified devices, no significant differences for the measures of DLCO and total lung capacity were found.
Carbon Monoxide↗
High incidence of clinical and subclinical toxicity associated with amiodarone treatment of refractory tachyarrhythmias.
Amiodarone has been hailed as the most effective single antiarrhythmic drug for treatment of refractory supraventricular and ventricular arrhythmias. However, questions continue to arise about its long-term potential toxicity and true efficacy rates. We, therefore, reviewed our experience with 78 patients, mean age 59 +/- 14 years, with drug refractory tachyarrhythmias treated with amiodarone. Sixty-two patients were treated for recurrent ventricular tachycardia or ventricular fibrillation, 4 for complex ventricular ectopy and 12 for supraventricular tachyarrhythmias. Patients have been treated for a mean of 9.9 months (range, 1 day to 39.1 months); 34(55%) continued to be successfully treated for ventricular tachycardia/ventricular fibrillation, 2 (50%) for complex ventricular ectopy and 5 (42%) for supraventricular tachyarrhythmias. Amiodarone toxicity was frequent, occurring in 57/72 patients (79%) who were treated for more than one week. Adverse effects led to drug discontinuation in 15 (21%), 3 because of pulmonary toxicity (1 in combination with neuropathy and another with drug-induced hepatitis); 2 because of chemical hepatitis; 1, confusion; 6, neuropathy; 2, arrhythmia exacerbation; 2, symptomatic bradycardia; and 1 because of impotence. Of the 62 ventricular tachycardia/ventricular fibrillation patients who were treated with amiodarone, 8 (13%) expired: 4 died suddenly and 4 from documented ventricular tachycardia during treatment. In contrast, of 16 patients who had discontinued amiodarone because of initial adverse effects or drug failure and were treated with alternative antiarrhythmic medications, 5 (31%) died suddenly. In conclusion, amiodarone appears to be fairly effective in high risk patients with refractory cardiac tachyarrhythmias but results in a rather high incidence of adverse effects in long-term follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Effect of a simulated 3,048 meter altitude on the single-breath transfer factor.
The single-breath transfer factor (TLCO) was measured in ten healthy subjects at sea level and at a simulated altitude of 3,048 m. Measurements were made at sea level using 21% oxygen and at altitude using both 21% and 31% oxygen in the test gas. At 3,048 m altitude (PB = 69.7 kPa), the mean TLCO increased 14% or about 2.3% per kPa (0.3% per mmHg) decrease in inspired oxygen pressure. Our data also suggests that altering the test gas oxygen concentration to account for the change in PAO2 due to altitude results in a TLCO equivalent to that obtained at sea level.
Adult↗
Standardization of computation of single-breath transfer factor.
The transfer factor (TLCOsb) is currently widely used as a lung function test. Although the test maneuver itself is well described and uniformly approached by most workers, the computation technique varies considerably. Significant changes in the TLCOsb are induced by correcting for: blood hemoglobin concentration [Hb], apparatus and anatomic dead space (VD), alveolar gas sample dead space (VDbag), carboxyhemoglobin concentration (COHb), alveolar carbon dioxide fraction (FACO2), initial inspired gas (VI) conditions, and breath-hold time (t). The quantitative impact upon TLCOsb of the presence or absence of corrections was calculated using TLCOsb measurements from 245 normal subjects. The average change (%) in computed TLCOsb induced by correcting for the above variables is: Hb (+8%); VD (-8%); VDbag (-0.3 to -6%); COHb (+X% for X% COHb); FACO2 (+5%); VI (+4%); t (+7%). Since corrections are made by some laboratories and not by others and since no uniformity exists concerning the corrections to be made, it is possible for two laboratories to choose their computation routines in such a way that they would compute, from the same test results, TLCOsb values which differ by 41%. Standardization of the TLCOsb computation technique is needed.
Carboxyhemoglobin↗
Exercise performance of subjects with ankylosing spondylitis and limited chest expansion.
To examine the mechanism of exercise limitation associated with chest wall restriction (CWR), we compared the ramp (1 W/3 s) exercise performance of six untrained subjects with ankylosing spondylitis (AS) and six healthy subjects matched for age and body size. Subjects with AS had CWR (maximum rib cage expansion : 1.4 +/- 0.2 cm; means +/- sem). The maximum oxygen uptake (VO2max) of AS subjects (2.15 +/- 0.2 1-stpd) was less than their predicted VO2max (2.68 +/- 0.13 1-stpd; p less than 0.03) and the measured VO2max of matched healthy subjects (2.78 +/- 0.22 1-stpd; p less than 0.03). Subjects with AS achieved 95 percent of predicted maximum heart rate, and their maximum voluntary ventilation exceeded their maximum exercise ventilation by at least 15 l X min-1 unless parenchymal pulmonary disease was present. We conclude that maximum ramp exercise performance of AS subjects with CWR is decreased. Deconditioning or cardiovascular impairment rather than ventilatory impairment appears responsible for the observed reduction of VO2max.
Adult↗
False positive rates of multiple pulmonary function tests in healthy subjects.
Spirometry, diffusing capacity and lung volume tests were performed on 251 healthy, nonsmoking volunteers in order to determine the rate of false positive results of multiple pulmonary function tests. Each test had an approximately 5% false positive rate, defined here as the percentage of normal subjects classified as abnormal by the tests. The percentage of subjects with at least one abnormal test rose substantially as the number of tests performed increased. When simple spirometry (FVC, FEV1, FEV1/FVC) was performed, 10% had at least one abnormal test; this rose to 24% when a complete battery of 14 tests was performed.
False Positive Reactions↗
Reference values for pulmonary tissue volume, membrane diffusing capacity, and pulmonary capillary blood volume.
Pulmonary tissue volume (Vti), carbon monoxide diffusing capacity, membrane diffusing capacity, pulmonary capillary blood flow and pulmonary capillary blood volume were measured in ninety (54 men and 36 women) healthy lifetime nonsmokers using an inert gas rebreathing technique. Prediction equations were generated using multiple linear regressions with height and age as the independent variables. Normalizing the data by dividing by functional residual capacity eliminated all sex differences. In contrast to the other variables, normalized pulmonary tissue volume did not correlate with any of the independent variables tested. Therefore, an average normalized Vti value can be recommended as a reference value
Adult↗
Lung volumes in healthy nonsmoking adults.
Total lung capacity (TLC), functional residual capacity, residual volume, and corresponding 95% confidence intervals were measured in 245 healthy nonsmoking person (122 women, 123 men) using a single-breath helium technique. Prediction equations for lung volumes were generated by multiple linear regression. The resultant equations are similar to previously published equations using multiple-breath gas equilibration techniques. Measured 95% confidence intervals can be closely approximated by using two times the standard error of the estimate for each equation, but cannot be approximated by using +/- 20% of the predicted value. Radiographic TLC was not significantly different from the helium dilution TLC.
Adult↗