To determine whether asthma alone can cause irreversible airflow obstruction 42 men and 47 women with chronic asthma (mean duration 22 (SD 13) years) without evidence of other disease likely to cause irreversible airflow obstruction were treated with theophylline orally and a beta agonist both orally and by inhalation for four weeks. After two weeks of treatment the FEV, was less than 85% of the predicted normal value (%P) in 48 patients and these individuals then received prednisolone 0*6 mg/kg/day for two weeks. Duration and severity of asthma and smoking history were quantified by questionnaire; 38 patients were current smokers or ex-smokers. FEV1 was measured at 0, 2, and 4 weeks. The mean difference between the best FEV1 during the study and the predicted normal value was 0-29 1 (p < 0.001); FEVy %P decreased with age (r = -030, p < 0.01) and with the duration (r = -0 47, p < 0.001) and severity (r = -0*55, p < 0.001) of asthma. Similar findings were noted when the results for non-smokers and those whose asthma started in adult life were analysed separately. We conclude that asthma alone can cause irreversible airflow obstruction and that the degree of obstruction is a function of the duration and severity of previous asthma. The results suggest the possibility that irreversible airflow obstruction in asthma may be preventable by minimising the degree of persistent asthma.

No abstract

Snoring and obstructive sleep apnea (OSA) are related to narrowing of the upper airway. A mandibular advancement splint (MAS) could improve both conditions by increasing oropharyngeal and hypopharyngeal dimensions. The effects of a MAS on snoring and OSA was evaluated 3.5 +/- 2.1 (mean +/- SD) mo after issue in 57 subjects with habitual loud snoring, 39 of whom had an apnea-hypopnea index (AHI) > or = 10. Assessment was by questionnaire (all subjects) and polysomnography (51 subjects, 47 male) including measurement of sound intensity. Use of the MAS was randomized to first or second half of study. Snores were scored where inspiratory noise was greater than 5 dB above background. Total sleep time, sleep efficiency, % REM sleep, and % sleep spent supine were similar (p > 0.05) with and without the MAS. Snores per sleep minute, corrected for time in apnea, and sound intensity of snores (% snores > or = 50 dB) decreased with the MAS from 11.0 +/- 5.8 and 42.0 +/- 25.0% to 9.0 +/- 6.0 (p < 0.01) and 26.2 +/- 25.2% (p < 0.01), respectively. Using the MAS significantly improved OSA: AHI decreased from 32.2 +/- 28.5 to 17.5 +/- 22.7 (p < 0.01) and arousal index decreased from 31.4 +/- 20.6 to 19.0 +/- 14.6 (p < 0.01). AHI decreased to < 20 with the MAS in 12 of 17 subjects where untreated AHI was between 20 and 60, and in 2 of 9 subjects where untreated AHI was > 60. Forty-five patients continued to use the MAS regularly.(ABSTRACT TRUNCATED AT 250 WORDS)

To refine the functional guidelines for operability for lung resection, we prospectively studied 55 consecutive patients with suspected lung malignancy thought to be surgically resectable. Lung function and exercise capacity were measured preoperatively and at 3 and 12 months postoperatively. Preoperative pulmonary scintigraphy was used to calculate the contribution to overall function by the affected lung or lobe and to predict postoperative lung function. Pneumonectomy was performed in 18 patients, lobectomy in 29, and thoracotomy without resection in six. No surgery was attempted in two patients who were considered functionally inoperable. Cardiopulmonary complications developed in 16 patients within 30 days of surgery, including three deaths. The predictions of postoperative function correlated well with the measured values at 3 months. For FEV1, r = 0.51 in pneumonectomy (p less than 0.05) and 0.89 in lobectomy (p less than 0.001). Predicted postoperative FEV1 (FEV1-ppo), diffusing capacity (DLCO), predicted postoperative DLCO (DLCO-ppo) and exercise-induced arterial O2 desaturation (delta SaO2) were predictive of postoperative complications including death and respiratory failure. In patients who underwent pneumonectomy, the best predictor of death was FEV1-ppo. The predictions were enhanced by expressing the value as a percentage of the predicted normal value (% pred) rather than in absolute units. For the entire surgical group a FEV1-ppo greater than or equal to 40% pred was associated with no postoperative mortality (n = 47), whereas a value less than 40% pred was associated with a 50% mortality (n = 6), suggesting that resection is feasible when FEV1-ppo is greater than or equal to 40% pred.(ABSTRACT TRUNCATED AT 250 WORDS)

To examine respiratory muscle recruitment pattern during inspiratory loading and role of fatigue in limiting endurance, we studied seven normal subjects on 17 +/- 6 days during breathing against progressive inspiratory threshold load. Threshold pressure (Pth) was progressively increased 14 +/- 5 cmH2O every 2 min until voluntary cessation (task failure). Subjects could adopt any breathing pattern. Tidal volume (VT), chest wall motion, end-tidal PCO2, and arterial O2 saturation were measured. At moderate loads [50-75% of maximum Pth (Pthmax)], inspiratory time (TI) decreased and VT/TI and expiratory time increased, increasing time for recovery of muscles between inspirations. At high loads (> 75% Pthmax), VT/TI decreased, which, with progressive decrease in end-expiratory lung volume (EELV) throughout, increased potential for inspiratory force development. Progressive hypoxia and hypercapnia occurred at higher work loads. Immediately after task failure all subjects could recover at high loads and still reachieve initial Pthmax on reimposition of progressive loading. Respiratory pressures were measured in subgroup of three subjects: transdiaphragmatic pressure response to 0.1-ms bilateral supramaximal phrenic nerve stimulation at end expiration initially increased with increasing load/decreasing EELV, consistent with increasing mechanical advantage of diaphragm, but decreased at highest loads, suggesting diaphragm fatigue. Full recovery had not occurred at 30 min after task failure. We demonstrated that progressive threshold loading is associated with systematic changes in breathing pattern that act to optimize muscle strength and increase endurance. Task failure occurred when these compensatory mechanisms were maximal. Inspiratory muscles appeared relatively resistant to fatigue, which was late but persistent.