Effect of Co2 Inhalation on Ventilation and Mechanics of Breathing in Mitral Disease

Respiratory effects of intravenous lobeline in normal subjects and in patients with mitral stenosis.

“…These results resemble the diminished respiratory response of patients with mitral stenosis following CO2 breathing (Pauli et al, 1960;Bruderman et al, 1965). While CO2 breathing induces hyperventilation by a combined stimulatory effect on the respiratory centre and the peripheral chemoreceptors (Heymans et al, 1930), lobeline in small doses, as used in our experiments, produces hyperventilation through stimulation of the peripheral chemoreceptors only (Liljestrand, 1951).…”

“…The different response in TLR to CO2 breathing and to lobeline in patients with mitral stenosis is noteworthy. As previously reported (Bruderman et al, 1965), no change in TLR occurred in these patients following CO2 inhalation, while there was a marked rise in normal subjects; whereas, in the present study, after lobeline the increase in TLR in patients with mitral stenosis was of almost the same magnitude as in the healthy subjects. This difference may be due to different pathways of action of lobeline and CO2 on the bronchial smooth muscle.…”

“…This makes a reduced concentration of the drug reaching the chemoreceptors unlikely. We assume, therefore, that the chemoreceptor cells might have reduced sensitivity in these patients, though a change in the mechanical properties of the lungs of such patients might also play a part (White, Butler, and Donald, 1958;Bruderman et al, 1965). The causative factor leading to decreased sensitivity could not be identified by us.…”

“…Reduced responsiveness of the respiratory centre (Pauli, Noe, and Coates, 1960) and/or altered mechnical properties of the lungs are assumed to be responsible for this change (Bruderman, Braun, and Rogel, 1965). The ventilatory response to CO2 inhalation is mediated partly through peripheral chemoreceptors (Heymans, Bouckaert, and Dautrebande, 1930), and the possibility of decreased activity of these receptors in the presence of mitral stenosis has not been investigated.…”