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The influence of the breathing pattern on transcutaneous blood gases was evaluated in 18 boys and 8 girls 7-18 years of age, with bronchial asthma, during bronchial provocation with histamine-HCl. Transcutaneous oxygen tension (tcPO2), carbon dioxide tension (tcPCO2) and the breathing pattern assessed by the transthoracic impedance technique were continuously monitored during the provocation. At reaction, when the fall in the forced expiratory volume in 1 s (FEV1) was 20% or more, the tcPO2 fell by 15% or more below the baseline in 22/26 and by 20% or more in 14/26 children. In some children, a marked fall in the tcPO2 was already noted after the saline inhalation and the first histamine dose steps without simultaneous changes in the FEV1. This early fall in the tcPO2 correlated to changes in the breathing pattern and was interpreted as a sign of compensatory hypoventilation secondary to the hyperventilation observed during the inhalations. We conclude that transcutaneous oxygen tension can be used as an indicator of a bronchial reaction during bronchial provocation tests in children only if one takes account of the fact that the breathing pattern during the inhalation of the challenge compound per se has an effect on the oxygen tension.

The effect of salbutamol inhalations on transcutaneous blood gases was investigated in 23 children (aged 11 months-2.5 years) with asthmatic symptoms. After one salbutamol inhalation there was a mean increase in transcutaneous PO2 (tcPO2) of 0.5 kPa (P less than 0.01); after a second dose given 30 minutes later, the mean increase was 1.2 kPa (P less than 0.001). The increase in tcPO2 after only one dose of salbutamol was significantly correlated to age (P less than 0.01). No such correlation was observed after a second dose. The overall increase in tcPO2 after two salbutamol inhalations showed a negative correlation to the duration of the current symptomatic period (P less than 0.05). We conclude that salbutamol inhalations have beneficial effects in young children with acute asthmatic symptoms, even below the age of 18 months, provided that an adequate dose reaches the lung and preferably at an early stage of obstruction.

The laryngeal chemoreflex involves bradycardia, apnea, swallowing and peripheral vasoconstriction. This reflex was studied in twelve infants, aged 5 days-28 weeks, who had sustained an apparent life-threatening event or were siblings of infants who had died of the sudden infant death syndrome. The bradycardic and apneic components of the reflex were found to be significantly, and sometimes powerfully, reinforced when elicited by pharyngeal water instillation during acute, mild hypoxia (transcutaneous PO2 4.6-8.3 kPa). Apnea duration during normoxia was 0.7-15 sec, and during hypoxia 2-30 sec. Heart rate change ranged from +26% to -21% during normoxia, as compared with -4% to -63% during hypoxia. The percentage change in heart rate was found to inversely correlate with the transcutaneous PO2-level prevailing when the reflex was elicited. The conclusion is that there is a significant reinforcement of the cardiorespiratory adjustments when the laryngeal reflex is activated during simultaneous excitation of the peripheral arterial chemoreceptors. One infant, showing a particularly strong increase of the cardiorespiratory response to laryngeal receptor stimulation during hypoxia, later died of sudden infant death syndrome.

A SIDS sibling is described who showed a normal respiratory regulation at 1.5 months but who was equipped with an apnea monitor at home on psychological indications. At 3 months he had a near-miss SIDS episode. He was then found to have developed a reaction to hypoxia with appearance of periodic breathing. With theophylline this response pattern was normalized but despite theophylline medication episodes of prolonged apnea occurred.

Regional lung function using xenon-133 was studied in 45 seated patients aged 11 to 78 years with untreated idiopathic scoliosis and angulation of curvature between 10 and 190°. Perfusion distribution was assessed by intravenous bolus injection of 133 Xe and distribution of ventilation to volume ratios by washouts after inhalation and intravenous injection. No consistent differences between the lungs on the convex and concave sides of the curvature were found. The lung bases were found to be more severely affected than the apices, perfusion and ventilation being progressively reduced with increasing deformity. There was evidence of inhomogeneity within regions and it is suggested that in younger patients the ventilation and perfusion within regions are better matched than in older patients.

Bake, B., Bjure, J. & Widimsky, J. The Effect of Sitting and Graded Exercise on the Distribution of Pulmonary Blood Flow in Healthy Subjects Studied with the 133Xenon Technique. Scand. J. clin. Lab. Invest. 22, 99-106, 1968. The distribution of pulmonary blood flow before, during and after graded exercise was studied in 13 healthy male volunteers. 133Xe was injected intravenously and the counting activity measured with 10 scintillation detectors in the sitting position at total lung capacity. At rest, the unevenness in distribution of perfusion increased with time, the apical regions receiving a progressively smaller proportion of the pulmonary blood flow and the basal regions a progressively greater proportion. During exercise this unevenness in distribution of perfusion was successively reduced with increasing work load.