Detecting errors in blood-gas measurement by analysis with two instruments.

We performed a two-stage prospective evaluation of the error detection capabilities of duplicate analysis of blood-gas specimens. In the first stage we analyzed 1601 specimens with a Corning Model 175 blood-gas analyzer as the test instrument and a Corning Model 178 analyzer as the reference instrument, and in the second stage we analyzed 1544 specimens with two Model 178 analyzers. In each stage the designated reference instrument underwent troubleshooting whenever an analytical error was detected; the test instrument underwent troubleshooting only when error conditions were indicated by means other than duplicate analysis. An error was considered to have occurred if the difference between the duplicate analyses exceeded 0.02 (for pH), 0.53 kPa, i.e., 4 mmHg (pCO2), or 7% (pO2). The number of specimens for which errors were detected was 97 (6.1%) in the first stage, 23 (1.5%) in the second. For each analyte more errors were detected with the Model 175 analyzer (of older design) than with the newer Model 178 analyzer. Furthermore, in certain periods associated with the use of particular electrodes there were very high error rates for individual analytes: 8% for pCO2, 18% for pO2. We conclude that duplicate analysis should be considered as a possible required standard for error detection.

Effect of simple anthracite pneumoconiosis on lung mechanics.

A respiratory questionnaire was administered to 20 miners with simple anthracite coal workers' pneumoconiosis (CWP) and ten normal subjects. Lung function studies which included lung mechanics and small airways disease measurements were also performed. Seventeen of the miners admitted to having symptoms of bronchitis. No significant differences were demonstrated between the two groups for vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and three seconds (FEV3), midmaximal flow rate (FEF25-75%), and peak flow rate (PEFR). A significant decrease in the maximum expiratory flow rate at 50 percent of vital capacity (V max50%) was detected; however, this was not evident when the flow rate was corrected for lung volume. Also, there were no significant differences in lung volumes, diffusing capacity (DCO) and diffusion coefficient (DCO/TLC). The mean static expired compliance (Cstate) was significantly increased in the anthracite miners, but no difference in specific compliance (Cstate/FRC) could be demonstrated. Also, no significant differences were detected in the mean values of any of the tests of small airways disease. There is little evidence of significant alterations in lung mechanics or small airway narrowing in miners with simple anthracite pneumoconiosis.

Airway function in sarcoidosis.

Airway function was studied in 18 patients with sarcoidosis, aged 18 to 49 years. Eleven of the patients were smokers. All patients had the characteristic functional changes of restrictive lung disease: decreased lung volumes and single breath diffusing capacity, and increased static transpulmonary pressures. Abnormal airway function was demonstrated in every patient by at least one test, and nearly always by multiple tests. Specific airway conductance was abnormally low in two patients. The ratio of the 1 second forced expiratory volume to the forced vital capacity was decreased in six patients. Frequency dependence of dynamic compliance was demonstrated in eight patients. The ratio of closing volume to vital capacity was increased above age-corrected predictions in all but two patients. Upstream airway resistance was abnormally increased in 16 of the patients. These results suggest that airway dysfunction is not uncommon in sarcoidosis.

Effect of fiberoptic bronchoscopy on respiratory performance in patients with chronic airways obstruction.

Lung volumes, airway resistance, expiratory flow rates, distribution of ventilation, and arterial blood gases were measured before and after fiberoptic bronchoscopy in 13 patients with moderately severe chronic airways obstruction and in 10 healthy non-smoking controls. Arterial blood gases were also monitored serially during the procedure. Arterial oxygen tension (Pao2) fell during fiberoptic bronchoscopy in both patients and controls whereas arterial carbon dioxide tension and pH remained unchanged. Control subjects had no change in lung mechanics after fiberoptic bronchoscopy. However, the patients consistently developed increased airway obstruction after fiberoptic bronchoscopy. Within 24 hours after bronchoscopy lung function in the patients returned to baseline values, except for the residual volume which remained abnormally high. The topical application of lignocaine (Lidocaine) for local anesthesia before fiberoptic bronchoscopy produced no effect on lung mechanics in nine patients and 10 controls, but Pao2 decreased in both the patient and control groups. These results indicate that fiberoptic bronchoscopy consistently inpairs lung mechanics and gas exchange in patients with chronic airways obstruction but that the impairment is mild and reversible. Lignocaine administration as well as the intubation procedure contribute to the fall in Pao2 which occurs both in the patients and in subjects without pre-existing lung disease.