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J L Clausen

Publications and source records attributed to J L Clausen.

At least 19 recordsLinked to original sources
PubMed1990

Single-breath carbon monoxide diffusing capacity prediction equations from a Mediterranean population.

Because of unanswered questions about prediction equations for the single-breath carbon monoxide diffusing capacity (DLCO) and as part of a larger collaborative project, standardized DLCO measurements were carried out in a selected sample of 361 healthy nonsmoking volunteers (194 men and 167 women) living in the Barcelona metropolitan area (Spain). Except for the test FIO2 (0.18), the study essentially followed the American Thoracic Society (ATS) and European Community for Coal and Steel (ECCS) recommendations for standardizing the methodology of measuring DLCO. Prediction equations for ages 20 through 70 were calculated separately for both sexes. Simple linear equations using age, height, and body weight as independent variables predicted the DLCO indices (DLCO, VA, and DL/VA) as well as more complex equations. In addition, a complete analysis of the residuals (predicted measured values) showed that the assumptions of the multiple regression analysis (independence, homoscedasticity and Gaussian distribution of residuals) were fulfilled using simple linear equations. Correction for the instrumental and anatomic dead spaces decreased the DLCO an average of 4.7%. The standard error of estimates was lower than those reported from other series in the literature. The predicted values from this study were lower than those reported by some investigators and were in reasonable agreement with other studies. A portion but not all of the differences could be explained on the basis of recognized differences in testing methodology. The results of this study may be of value to clinical laboratories seeking predictive equations for DLCO most appropriate for their testing methodology and patient population, and may assist in the resolution of some controversies regarding differences among predictive equations for DLCO.

Adolescent↗
PubMed1990

Gas exchange in chronic thromboembolism after pulmonary thromboendarterectomy.

Thromboendarterectomy is the treatment of choice for chronic large vessel thromboembolic pulmonary hypertension. To identify the mechanisms responsible for the improvement in gas exchange following thromboendarterectomy, we studied nine patients with chronic thromboembolic pulmonary hypertension before and eight to 18 months after surgery using the multiple inert gas elimination technique. Preoperatively, all subjects had pulmonary hypertension and were hypoxemic or had an elevated P(A-a)O2. The VA/Q distribution was widened with an elevated VD/VT and a low cardiac index. After thromboendarterectomy, significant improvement had occurred. The VA/Q distribution had narrowed to near normal, and the cardiac index increased. It was concluded that thromboendarterectomy improved gas exchange both by improving VA/Q relationships and by increasing cardiac output.

Adult↗
PubMed1990

The diagnosis of emphysema, chronic bronchitis, and asthma.

Although of some value for understanding etiologic mechanisms, the classic diagnostic categories of asthma and emphysema and especially chronic bronchitis have not served clinicians well for defining prognosis and therapeutic options. Until more useful diagnostic categories are available, the choice of diagnostic tests should be guided more by their clinical usefulness than by their sensitivity and specificity for identifying classic diagnostic categories of obstructive lung disease. A history consistent with asthma is as good evidence of asthma as that provided by most tests, especially if combined with spirometric evidence of complete reversibility of episodes of obstruction. Positive bronchial challenge studies and partial responses to bronchodilators are common in asthma but of limited diagnostic specificity. Tests of allergic function are of limited specificity for asthma, although a low IgE level is rare. Findings of reduced expiratory flows, high TLC, and low DLCO, or radiologic signs of hyperinflation, bullae, and pulmonary vascular deficiency pattern are useful for diagnosing cases of severe emphysema, but they are of limited sensitivity for the detection of mild to moderate disease. Advances in high resolution CT offer promise of earlier diagnosis of emphysema. Making a diagnosis of chronic bronchitis based on defined criteria for chronic sputum production is easy but of limited clinical value. Prospective longitudinal studies and advances in technology promise more clinically useful diagnoses in the future.

Asthma↗
PubMed1989

Prediction of normal values in pulmonary function testing.

Appropriate use of reference equations for predicting normal values is important for maximizing the clinical and research usefulness of pulmonary function testing. Because of the diversity of clinical and research uses of pulmonary function testing, predictive equations derived from different populations may be needed for specific applications. Similarly, different limits of normalcy other than the traditional 95 per cent confidence limits may be more appropriate for some applications. Unanswered questions remain about the effects of race and altitude on predicted values for many pulmonary function parameters. In order to establish confidence that the predictive equations, lower limits of normalcy, and testing methodology are appropriate for specific patient populations, it is suggested that each clinical laboratory obtain PFT measurements on 10 to 20 individuals considered free of disease and representative of their patient population and compare these results with the prediction equations selected for use. Although the testing of such a small sample of normal subjects will not assist in the selection of optimal equations if the differences between equations are minor, it will detect grossly inappropriate predictive values and limits of normalcy as well as identify problems with testing methodology.

Humans↗
PubMed1988

The lung volume at which shunting occurs with inhalation anesthesia.

The relationship between functional residual capacity (FRC) and shunt development with halothane anesthesia in 18 nonobese surgical patients (age, 21-34 yr) was studied. FRC was measured by helium dilution, and intrapulmonary shunt was distinguished from ventilation-perfusion inequality by multiple tracer inert gas elimination analysis. Awake supine FRC was 34.6 +/- 6.6% (mean +/- SD) of total lung capacity (TLC), and closing capacity (CC) was 29.8 +/- 5.3% of TLC. Anesthesia, muscle paralysis, tracheal intubation, and mechanical ventilation produced an average 14.6 +/- 13.3% FRC reduction to an average anesthesia FRC 29.8% of TLC (P = 0.002). Shunt increased from 1.2% +/- 1.5% awake to 8.6 +/- 8.3% during anesthesia (P = 0.005). A nonlinear relationship was found between shunt and FRC/TLC so that anesthetized subjects with an FRC less than awake CC had an average 11.4 +/- 8.3% shunt, whereas subjects with an FRC greater than CC had a 2.4 +/- 2.8% shunt (P = 0.025). Nonsmokers developed shunt only if FRC was less than CC. Smokers showed a significantly higher shunt for a given (FRC-CC)/TLC compared to nonsmokers (P less than 0.001). The slope of the regression of shunt on BMI (body mass index = weight/height2) showed a significant increase during anesthesia (P = 0.005), and smokers had a significantly higher slope compared to nonsmokers (P = 0.001). These findings suggest a gravity-dependent mechanism for intrapulmonary shunting during anesthesia. Therefore, shunting was due to dependent regional lung volume reduction associated with an FRC decrease to less than closing capacity. The enhanced intrapulmonary shunting in smokers may have been related to the increased dependent regional residual volume associated with smoking.

Adult↗
PubMed1988

Pulmonary function tests cannot predict exercise-induced hypoxemia in chronic obstructive pulmonary disease.

We studied 40 patients with chronic obstructive pulmonary disease (COPD) to determine whether measurements of pulmonary function could predict a fall in arterial oxygen pressure (PaO2) with exercise. The PaO2 fell more than 3 mm Hg in 21 patients (group 1), did not change (+/- 3 mm Hg) in nine patients (group 2), and increased more than 3 mm Hg in ten patients (group 3). Group 3 had significantly less severe expiratory obstruction than groups 1 and 2. The most significant variables in predicting a change in PaO2 with exercise were the ratio of the forced expiratory volume in one second over the forced vital capacity (FEV1/FVC) and the single-breath carbon monoxide diffusing capacity (Dsb). Measurements of FEV1/FVC of 0.50 or more and Dsb of 20 ml/min/mm Hg or more were 100 percent predictive in excluding a fall in PaO2 with exercise. Measurements below these thresholds could not be used reliably to predict which patients would develop worsening hypoxemia with exercise. Because of wide variability in reference values from eight different published studies for diffusing capacity, recommended criteria based on the percent predicted Dsb should be used with caution. We conclude that pulmonary function measurements cannot be used to predict exercise-induced hypoxemia in patients with COPD; however, the measurements may be useful in identifying patients whose condition is less severe who are unlikely to develop worsening hypoxemia with exercise.

Carbon Dioxide↗
PubMed1988

The use of cutaneous oximetry in the prescription of long-term oxygen therapy.

Using current Medicare guidelines for the prescription of long-term oxygen therapy, we studied the impact on decision-making of substituting cutaneous oxyhemoglobin saturation measurements (SaO2) for direct arterial oxygen tension measurements (PaO2). Fifty-five patients with chronic lung disease and resting hypoxemia were studied. More than 80 percent of patients with a resting PaO2 of 7.33 kPa (55 mm Hg) or less had a cutaneous oximetry SaO2 greater than 85 percent. These patients would not have met the guidelines for long-term oxygen therapy if the cutaneous oximetry measurements were used instead of direct PaO2 measurements. Substituting a threshold criterion of 88 percent instead of 85 percent resulted in fewer patients being denied oxygen therapy but also included patients with PaO2 values greater than 7.33 kPa (55 mm Hg). We conclude that cutaneous oximetry cannot be substituted equivalently for PaO2 measurements in prescribing long-term oxygen therapy.

Adolescent↗
PubMed1987

Inter-instrument comparison of blood gas analyzers and assessment of tonometry using fresh heparinized whole human blood.

Because of limitations associated with commercial blood gas quality controls and tonometry of stored blood, fresh heparinized blood was used to compare PO2 and PCO2 performance of ten blood gas analyzers. Function of nine gas mixer/tonometer systems was evaluated. These were used to create blood samples with target values for PO2 and PCO2. All ten analyzers had high precision; this magnified small differences between observed results and target values. Grand mean results from all ten analyzers were within 0.8 mm Hg of the target for PO2 of 40.0 and 100.0 and for PCO2 of 20.0 and 70.0 mm Hg. Eight automated blood gas analyzers gave clinically indistinguishable results for PO2 and PCO2 that were sufficiently accurate for clinical purposes. Also reported is the practicality of using tonometry of fresh heparinized blood in a per shift quality control program for PO2 and PCO2.

Blood↗
PubMed1986

Pulmonary function tests in the detection of left heart failure: correlation with pulmonary artery wedge pressure.

Standard pulmonary function tests, including lung volumes measured by three fundamentally different techniques, were performed in 40 patients undergoing cardiac catheterization. These were compared with clinical and radiologic evaluations in detecting left heart failure (LHF). Patients with elevation in mean pulmonary artery wedge pressure (PAWM) greater than or equal to 20 mm Hg had significant restrictive changes with reduction in vital capacity (VC), forced expiratory volume in 1 s (FEV1.0), and total lung capacity (TLC) measured by helium dilution and body plethysmography. Radiographic TLC was not reduced in these patients or correlated with PAWM. Obstructive changes were not present. Radiologic gradings by 5 different observers were reasonably accurate in detecting LHF but varied between observers. VC and TLC measured by helium dilution and body plethysmography were slightly less sensitive but more specific in detecting PAWM elevation. Clinical classification was sensitive but nonspecific; in addition, clinical signs were not reliable indicators of elevated PAWM. We conclude that pulmonary function testing may provide objective, accurate, and useful information in the evaluation of cardiac patients for LHF. However, radiographic measurement of thoracic cage volume does not reflect the changes in lung gas volume measured by gas dilution or plethysmographic techniques in patients with chronic congestive heart failure.

Adult↗
PubMed1986

Proficiency testing materials for pH and blood gases. The California Thoracic Society experience.

The California Thoracic Society Blood Gas Proficiency Testing Program distributed ampules from three separate lots of quality control products every three months as unknowns to participating clinical (survey) laboratories and ten selected reference laboratories. For eight quarters, aqueous buffers were distributed. For each lot, PCO2 and pH measurements varied within narrow ranges between laboratories. Concurrently, the PO2 measurements varied widely between reference laboratories as well as survey laboratories, but varied minimally when repeatedly assessed on each reference laboratory machine. Change to a fluorocarbon-containing emulsion as a testing medium resulted in a significant reduction in within model and overall variability for PO2. We attribute this reduction in variability to the higher O2 content and decreased temperature sensitivity for PO2 of the fluorocarbon-containing emulsion. Because we have no evidence that the magnitude of the interinstrument differences in PO2 found with these materials would be found with fresh human blood we recommend that regulatory agencies use the results of proficiency testing for PO2 cautiously.

Blood↗
PubMed1985

Accuracy of two ear oximeters at rest and during exercise in pulmonary patients.

The accuracy of 2 ear oximeters (Hewlett-Packard 47201A and Biox IIA) was evaluated at rest and during exercise in 116 pulmonary patients. Ear oximetry measurements were compared with arterial oxygen saturation (SaO2) measured from simultaneous arterial blood samples. When used according to the manufacturer's instructions for stabilization during exercise testing, both oximeters demonstrated comparable accuracy in estimating arterial blood SaO2 both at rest and during exercise in these patients (95% confidence limits, 2 SEE = +/- 4 to 5%). The oximeters were more accurate in measuring a change in SaO2 from a previous reading (95% confidence limits, 2 SEE = +/- 2.5 to 3.5%). COHgb levels greater than 4% and dark skin pigmentation appeared to decrease the accuracy of ear oximetry measurements. Within the limitations of accuracy, both ear oximeters may be useful for clinical exercise testing in pulmonary patients.

Arteries↗