Patients with Chronic Paralytic/Restrictive Ventilatory Dysfunction: Discussion (1)
Negative-pressure body ventilators provide ventilatory assistance by increasing the gradient between atmospheric pressure and intrathoracic pressure during the patients inspiratory effort. In this way, the mechanism of air inflow is similar to and augments or replaces the tidal volumes of unassisted breathing. Inductive plethysmography can be used to detect paradoxical chest and abdominal wall motion resulting from obstructive airway phenomena. This is most frequently seen as a relative increase in chest wall circumference compared with abdominal wall circumference. Cheap Diskus Advair
The physiologic basis of plethysmography does not appear to be modified by use of a BV. It is interesting to note that we have also observed periods of obstruction to airflow in patients using IPPV via the nose or mouth during sleep. Decreased excursion of both the chest wall and the diaphragm during inductive plethysmography and decreased nasal airflow were observed during polysomnography. A sudden increase in the indicated volume ventilator pressure and dSa02 may also be observed. It occurs most likely at the level of the tongue rather than in the hypophar-ynx, the most likely site of obstruction in BV-assisted patients.