Non-specific bronchial airway hyperreactivity and the diagnosis of asthma.

In very mild and atypical cases of asthma, highly discriminative tests are needed to make the diagnosis. To demonstrate this, measurement of non-specific bronchial airway hyperreactivity by means of standardized bronchial inhalation challenge tests with histamine and methacholine were performed in 10 very mild asthmatic and nine normal control subjects; both groups included Nigerians who were temporarily resident in London at the time of the study. Bronchial reactivity was expressed as the provocative concentration of the agents causing a 20% fall in forced expiratory volume in 1 sec (PC20FEV1); higher values indicating lower levels of non-specific bronchial reactivity. The level of non-specific bronchial reactivity in these very mild asthmatics, whose baseline physiological data were not different from those in normals, was found to be 18-29 times higher than the normal control subjects. These tests very effectively discriminated between asthmatic and normal control subjects. With available resources it should be possible to study a large number of Nigerians in their own environment.

Relationship between bronchial airway responsiveness and clinical severity of asthma.

The minimum medication required to control symptoms was individually established in a systematic manner in 10 asthmatics. A scoring system for the severity of asthma was designed using the indices of initial airway calibre (a reflection of the degree of airway obstruction) and the minimum medication requirement; all the subjects were so scored. Bronchial airway responsiveness to histamine, methacholine and isocapnic hyperventilation of cold air was then measured in these subjects. The relationship between the level of bronchial responsiveness and the asthma severity score was examined. The mean airway responsiveness to histamine or methacholine for the subjects who required a combination of drugs was not significantly greater than that for those who required single medication intermittently or daily, while the airway responsiveness to cold air was significantly different between the subjects in the two treatment subgroups. Similarly, there was no correlation between the asthma severity score and airway responsiveness to methacholine and histamine (r = -0.38 and -0.48; P greater than 0.1) while a significant correlation was found with responsiveness to cold air (r = 0.72; P less than 0.02). The results suggest that there is a qualitative difference between the bronchoconstriction induced in asthmatic subjects by pharmacological constrictor substances and natural physical stimuli such as cold air.

Morning-evening changes in airway responsiveness to methacholine in normal and asthmatic subjects: analysis using partial flow-volume curves.

In eight normal and eight asthmatic subjects airway responsiveness to methacholine was measured by means of partial flow-volume loops at 0800 and 1800 hours on the same day. Airway responsiveness was lower in the evening in both normal and asthmatic subjects.

The role of fibreoptic bronchoscopy in the investigation of pleural effusion.

Published data on the role of fibreoptic bronchoscopy in the investigation of pleural effusions are sparse and conflicting. We have reviewed our experience from November 1980 to December 1986. Thirty-two patients were identified from bronchoscopy records as having undergone the procedure during the evaluation of an effusion. Fibreoptic bronchoscopy was diagnostic in 6 of the 32 cases, but less invasive procedures had given the diagnosis in 4, and in the other 2 cases radiological abnormalities other than the effusion suggested an underlying bronchial malignancy. We conclude that routine fibreoptic bronchoscopy is not justified in the evaluation of pleural effusions.

Should patients with haemoptysis and a normal chest X-ray be bronchoscoped?

A review of bronchoscopic records over a 5 year period identified 41 patients who had undergone fibreoptic bronchoscopy after presenting with haemoptysis and a normal chest X-ray. Carcinoma of the bronchus was found in 4 patients (9.7%) and the procedure yielded a diagnosis in 8 of the 20 patients in whom a specific cause of their bleeding could be identified. The diagnostic yield is sufficiently high and the morbidity of the procedure sufficiently low to justify the investigation in patients presenting with haemoptysis and a normal chest X-ray.

Comparison of domiciliary nebulized salbutamol and salbutamol from a metered-dose inhaler in stable chronic airflow limitation.

Nineteen patients (12 men) mean age, 63.4 years (range, 32 to 78), with stable chronic airflow limitation, mean FEV, 0.55 L (range, 0.3 to 1.05 L), completed an eight-week, double-blind, double cross-over study comparing nebulized salbutamol and salbutamol from a metered-dose inhaler (MDI). Salbutamol from both delivery systems produced bronchodilation. The doses of salbutamol inhaled via the nebulizer and MDI producing maximal bronchodilation were established by cumulative dose-response curves. The contents of the nebulizer and MDI were inhaled four times a day, one system containing salbutamol and the other a placebo. Cross-over of salbutamol from one system to the other occurred every two weeks. There was no significant difference between the two delivery methods in daily peak expiratory flow rate (PEFR), severity of symptoms, or extra bronchodilator usage. Two weekly laboratory assessments of spirometry, PEFR, and exercise tolerance also showed no significant differences. Careful assessment is recommended before the provision of domiciliary nebulizers.

Transcutaneous oxygen tension during exercise in patients with pulmonary emphysema.

Transcutaneous PO2 (tcPO2) and arterial PO2 (PaO2) were compared during exercise in six patients with pulmonary emphysema. For calibration purposes, the tcPO2 electrode was first attached to the skin and after stabilisation its reading was adjusted to correspond to the PO2 of an initial arterial blood sample. It was shown that tcPO2 measurement could follow accurately the rapid changes in PaO2 occurring during exercise. Sixty-eight paired comparisons of PaO2 and tcPO2 were available and the regression equation was given by: tcPO2 (mmHg) = 0.98 PaO2 + 0.7 (correlation coefficient, 0.985; 95% confidence limits, 5.7 mmHg).

In vivo calibration of a transcutaneous oxygen electrode in adult patients.

Transcutaneous oxygen tension (tcPO2) has been compared with arterial oxygen tension (PaO2 in 14 haemodynamically stable patients in an intensive care unit. Two calibration methods have been compared: (1) "In vitro" calibration, a two point calibration procedure carried out before attachment to the skin. (2) "In vivo" calibration, calibration using a single arterial sample, to recalibrate the upper point after attachment of the electrode to the skin and stabilisation of the electrical output. After "in vitro" calibration the regression equation was given by tcPO2 (mmHg) = 0.58 PaO2 + 13.4 (95% confidence limits +/- 19.6). After "in vivo" calibration, the regression equation for 55 comparisons over the range 50 to 120 mmHg was given by: tcPO2 (mmHg) = 0.98 PaO2 + 1.6 (95% confidence limits +/- 6.6). The "in vivo" calibration method therefore allows a close estimate of PaO2 to be made from tcPO2 values in adult patients providing strict operating criteria observed.

Cold air as a bronchial provocation technique. Reproducibility and comparison with histamine and methacholine inhalation.

Bronchial provocation testing with cold air was carried out on 36 asthmatic and 13 normal subjects in order to assess the reproducibility and clinical relevance of the technique as a test of airways reactivity. Sixteen subjects underwent repeat testing after an interval of two to three weeks. Using a least squares linear regression analysis, the technique was highly reproducible, with a correlation of r = 0.93 (p less than 0.001). The 21 asthmatic subjects who had exercise-provoked symptoms required a significantly lower level of ventilation of cold air to produce a 35 percent drop in specific airways conductance (PD35) than did those who had no exercise-induced asthma (33.9 L min-1 vs 45.8 L min-1; p less than 0.02). Subjects requiring no regular treatment for their asthma had a geometric mean PD35 of 62.6 L min-1, significantly higher than those requiring inhaled therapy (44.9 L min-1; p less than 0.005). Subjects requiring oral in addition to inhaled treatment had the lowest PD35 (23.6 L min-1; p less than 0.02). Atopic status did not appear to influence the response. There was a strong correlation between the PD35 to cold air and to histamine (r = 0.92; p less than 0.001) and between the PD35 to cold air and to methacholine (r = 0.86; p less than 0.001). The three techniques of assessing bronchial reactivity were equally successful in separating the normal and asthmatic groups. The results indicate that cold air provocation may be reliably and reproducibly used to assess bronchial reactivity. The use of a naturally-occurring stimulus of asthma in all subjects has great potential as an investigational technique.