Posts Tagged ‘airway

Thus, the ventilatory pattern adopted by these asthmatic subjects in response to bronchoconstriction is probably optimal under the circumstances. The ventilatory pattern response to inhaled histamine is believed to be neurally mediated via airway irritant receptors; hypoxemia itself increases respiratory frequency but usually without any decrease in Vt. The ventilatory pattern changes observed after bronchoconstriction […]

In theory, there could be several possible effects of induced bronchoconstriction on the dead space. Firstly, narrowing of the airways could be predicted to decrease airway volume and hence, the anatomic dead space. The present results show that this does not occur: absolute VDan did not alter significantly (Table 1). The reason for this may […]

The present study shows that bronchoconstriction in these mildly asthmatic subjects resulted in a significant increase in P(A-a)02 and the VDphys/VT ratio which, in the absence of an increase in overall ventilation, resulted in a marked fall in Pa02. An increase in the VDphys/VT relationship, as derived in the present study by the Enghoff modification […]

However, while studies of the acute effects of bronchodilation on arterial blood gases and V/Q relationships in asthma have been reported, there are, to our knowledge, no published reports specifically examining the effects of histamine-induced bronchoconstriction on V/Q relationships. In a study primarily concerned with the pulmonary vasodilator actions of nifedipine, Ballester et al found […]

Mean baseline values (Table 1) for Rint were moderately increased, the upper limit for Rint in normal subjects in our laboratory being 2.5 cm H20/L/s. Minute ventilation and arterial blood gas values were within normal limits, although the subjects displayed a mild degree of hyperventilation. Following histamine inhalation, all of the subjects noticed a tightness […]

Each subject returned on a separate day for the subsequent study. An arterial catheter was inserted into the radial artery of the nondominant arm using an aseptic technique. Spirometric measurements including FRC were measured as described above. In addition, measurements of Rint, minute ventilation (Ve), tidal volume (Vt), respiratory frequency (f), and the anatomic and […]

Pulmonary airway challenge has become an accepted method for assessment of airway reactivity. These assessments focus almost exclusively on measurements of resistance to airflow. However, spontaneous bronchoconstriction in asthma is associated not only with increased resistance to airflow, but also with marked changes in ventilation/perfusion relationships. Whether similar changes occur during induced bronchoconstriction has not […]