P. J. Rees

Immediate response to cigarette smoke.

Using an automated method of calculating airways resistance in the body plethysmograph, we have investigated changes occurring immediately after inhalation of cigarette smoke. Decreases in specific conductance occurred by the time of the first measurement seven or eight seconds after exposure to single inhalations of cigarette smoke in 12 smokers and 12 non-smokers. Less than half of the initial change was present 40 seconds after the inhalation. Initial responses were greater in the non-smokers. Responses recurred with repeated inhalations in smokers and non-smokers. Prior administration of salbutamol and ipratropium bromide significantly inhibited the response and this inhibition appeared to be greater in non-smokers. Sodium cromoglycate inhaled as a dry powder had no effect on the response.

Automated system for the measurement of airways resistance, lung volumes, and flow-volume loops.

Using a digital computer and body plethysmograph measurements of airways resistance, lung volumes, and flow-volume loops may be obtained from a single manoeuvre performed by the patient. All the measurements together with a display of the flow-volume loop are displayed within 10 seconds of the patient completing the manoeuvre. The system appears to offer considerable advantages in speed, objectivity, and reproducibility when compared with conventional methods.

Use of a single pair of magnetometer coils to monitor breathing patterns in an intensive care unit

The use of a single pair of magnetometer coils placed centrally on the trunk to record tidal volumes and breath times has been evaluated in five normal subjects in five positions. Breath times were accurate in all positions tested but tidal volumes were only reliable with the subjects lying and the backrest raised to 45° or in the supine position only for volumes up to 1000 ml. Using this system, recordings have been made in seven patients with barbiturate overdose, five with salicylate overdose, and five undergoing anaesthesia with thiopentone. The single pair of coils was satisfactory for measuring changes in the pattern of breathing in these patients. In barbiturate overdose in five patients there was initially an increase in respiratory frequency with a decrease in tidal volume. As these patients recovered the tidal volume increased and the respiratory rate slowed. In two patients who had a raised PaCO2 there was initially reduction of both tidal volume and respiratory rate, both increasing as the patients recovered. Monitoring respiratory rate appears to be a useful guide in barbiturate overdose; a slowing of the rate without recovery of consciousness warrants further investigation to assess the need for ventilatory support. The single pair of coils were also satisfactory for measuring the increased tidal volume in salicylate overdose. As after other respiratory stimuli in man, increased ventilation occurred predominantly through changes in tidal volume and expiratory time while inspiratory time changed very little.

Immediate Responses to Lung Irritants Detected by Automated Measurements of Airway Resistance and Partial Flow-Volume Curves

Automated measurements of specific conductance and partial flow-volume curves have allowed the detailed investigation of changes occurring in the first 30 seconds after inhalation of cigarette smoke. Smokers and non-smokers show transient airway narrowing which appears to be a nervously mediated reflex contraction of smooth muscle. The major part of the stimulus is produced by the particulate matter in the smoke.