No abstract

We have compared the symptomatic benefit of air and oxygen at rest in hypoxemic patients with chronic obstructive airway disease (COAD) or interstitial lung disease (ILD). A total of 12 severely disabled patients with COAD (mean +/- SEM, PaO2, 50.3 +/- 3.7 mm Hg) and 10 with ILD (PaO2, 48.0 +/- 3.1 mm Hg) received 28% oxygen and air by Venturi face mask, each gas on two occasions, in a double-blind randomized fashion. SaO2 increased (p less than 0.01) in both groups during oxygen breathing: COAD, 85.1 +/- 2.3% versus 93.1 +/- 1.4%; ILD, 85.5 +/- 1.7% versus 94.7 +/- 0.9%. The patients with COAD stated that air helped their breathing on 15 of 24 occasions and that oxygen helped on 22 of 24 occasions (p less than 0.05). In the patients with ILD the values were 6 of 20 and 13 of 20 occasions, respectively (p less than 0.05). In both groups of patients the severity of breathlessness recorded on a 100-mm visual analog scale was significantly (p less than 0.05) lower during oxygen breathing: COAD, 29.6 +/- 4.5 versus 45.6 +/- 6.0; ILD, 30.2 +/- 5.1 versus 48.1 +/- 4.4. Ventilation measured by magnetometers was significantly lower during oxygen breathing in the patients with COAD (8.2 +/- 1.0 versus 9.3 +/- 1.1 L/min; p less than 0.05), but the difference between oxygen and air in patients with ILD was not statistically significant (9.3 +/- 1.3 versus 11.2 +/- 1.6 L/min; p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

To determine how the presence of generalised airflow limitation due to chronic obstructive lung disease affects the recognition of simulated upper airway obstruction, a study was carried out in 12 patients (mean (SD) age 57 (7) years) with chronic obstructive lung disease (FEV, % predicted 53 (22), range 21-70) and 12 matched control subjects. Patients and control subjects performed maximal inspiratory and expiratory flow-volume curves in a variable volume plethysmograph with and without upper airway obstruction simulated at the mouth with a series of polythene washers of internal diameter 4, 6, 8, 10, and 12 mm. In patients, as in normal subjects, peak expiratory flow (PEF) and maximum inspiratory flow at 50% of vital capacity (Vimax5O) were more sensitive to upper airway obstruction than were FEV, or maximum expiratory flow at 50% VC (VEmax5o); but the reductions in all indices caused by simulated upper airway obstruction were smaller in the patients than in the controls. The fall in PEF (whether expressed in absolute units or as a percentages) consequent on severe (4 mm) upper airway obstruction became smaller with increasing severity ofchronic obstructive lung disease. The subjects also produced flow-volume curves with and without 6 mm upper airway obstruction while breathing helium and oxygen (heliox). In both groups the effects of heliox on PEF and Vimax_0 were increased when upper airway obstruction was simulated. It was confirmed that the functional recognition of upper airway obstruction is more difficult in patients with chronic obstructive lung disease than in normal subjects and this difficulty increases with severity of disease; an unusually large increase in PEF or Vimax5o while the patient is breathing heliox should raise the suspicion ofcoexisting upper airway obstruction, but such a pattern is not specific.

No abstract

We have studied the effects of chlormethiazole and diazepam given orally on the ventilatory and mouth occlusion pressure (P0.1) responses to CO2 in a placebo controlled study in 10 healthy volunteers. Diazepam 10 mg produced a significant reduction in both the ventilatory and P0.1 responses to CO2, and this was not associated with any effect on respiratory muscle power. Chlormethiazole 250 mg produced less drowsiness than diazepam 10 mg. Therefore in a subsequent study chlormethiazole 500 mg was compared with placebo. Chlormethiazole in either dose had no effect on CO2 responses or on maximum static respiratory pressures. We conclude that diazepam has a direct depressant effect on chemoreceptors and its effects on indices of ventilatory control are not due to impaired muscle function; chlormethiazole in the doses used has no such effects despite producing drowsiness.