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A case report of a patient in which exercise and cough induced asthmatic attacks is presented. Besides exercise, maximal voluntary hyperventilation, and repeated forced expirograms yielded each time an asthmatic attack. Coughing, spontaneously or imposed, precipitated also an asthmatic attack. A high flow rate is considered to be responsible for triggering asthmatic attacks through stimulation of airway receptors.

Lung volumes, maximal expiratory flows, pulmonary resistance and static recoil pressure-volume curves were measured before and after inhalation of isoprenaline in four groups of subjects: heqlthy patients with mild and severe chronic bronchitis and asthmatics. The observed changes were qualitatively similar in the four groups. Whereas total lung capacity and dynamic compliance were not influenced, there was an increase in vital capacity (not in healthy subjects and mild bronchitics), in FEV1, in maximal expiratory flows and a decrease in pulmonary resistance. The static recoil pressure-volume relationship was shifted to the left over its ascending part. The effect of isoprenaline tended to be larger in patients. Among the latter, the increase of vital capacity was especially pronounced in the severe bronchitics, whereas the maximal flows increased most in asthmatics. We suggest that the influence of isoprenaline on maximal flows results from a bronchodilation, associated with an increased collapsibility of the central intrathoracic airways, whereas the influence of VC might reflect a delayed onset of small airway closure.

The usefulness of flow-volume curves for the assessment of upper airway function is emphasized. The different behaviour of intra- and extra-thoracic airways, submitted to different transmural pressures, results in the reduction of maximum expiratory flows in cases of variable intrathoracic airways stenosis, whereas in the presence of an extrathoracic stenosis, the inspiratory maximum flows are mainly affected. Sleep apnea syndrome and "asthma-like" syndromes with a glottic origin are further examples of the potentials of flow-volume loops in the assessment of upper airway function.

To clarify whether the radiographic estimate of total lung capacity (TLC) using the method of Barnhard et al., as modified by Loyd et al., yields accurate values, we measured TLC in 20 young healthy subjects with the above technique (Vb). We compared it to the more sophisticated radiologic method of Pierce et al. (Vp) and to plethysmographic measurements (Vbox). Plethysmographic results, 7.38 +/- 0.94 l (mean +/- SD) or 101.7% of predicted, were significantly higher than Vb (mean difference 0.53 +/- 0.68 l; p less than 0.005 by paired t test), but were not significantly different from Vp (mean difference 0.13 +/- 0.52 l). Based on these and previous data, we conclude that the Pierce et al. approach yields more accurate results than the Barnhard and Loyd method, although individual data, in both methods, should be interpreted cautiously.

A 49 yr old poliomyelitic patient had been under cuirass-type nocturnal negative pressure ventilation for more than 20 yrs. He had a severe restrictive ventilatory impairment, and normal awake blood gases at rest and during light exercise. He was offered a trial of intermittent positive pressure ventilation applied through the nose (nIPPV). Two daytime studies and one night study were carried out under nIPPV, and one night study was performed under negative pressure ventilation. Tidal volume, respiratory frequency (Respitrace), blood gases and electromyogram (EMG) of the diaphragm (DEMG, oesophageal electrode) and/or sternocleidomastoid (ScEMG, surface electrodes) were measured. During daytime studies under nIPPV, the DEMG (and/or the ScEMG) did not decrease by more than 25% (p less than 0.005). However, when the patient was encouraged to relax, the DEMG decreased by 62% (p less than 0.001). Tidal volume and ventilation significantly increased during daytime nIPPV (p less than 0.025), whereas blood gases were kept at physiological levels. At night, the ScEMG was present and prominent until sleep onset. Thereafter it disappeared and remained silent, including periods of wakefulness during sleep time, until final awakening in the morning. This was true for both negative pressure ventilation and nIPPV. Snoring was present throughout sleep under negative pressure ventilation but not under nIPPV. We conclude that the behavioural response of the subject may determine the electrical activity of respiratory muscles during assisted ventilation.