Negative Pressure Ventilation
attempts to mimic normal action of respiratory muscles to allow breathing through normal physiological mechanisms
when applied to the thoracic cage, pressure is transmitted across the chest wall, into the pleural space, and into the intraalveolar space
Negative Pressure Ventilation
intraalveolar space becomes increasingly more negative in relation to pressure at the mouth
pressure gradient allows movement of air into the lungs
expiration occurs when the pressure is removed
normal recoil allows passive exhalation
Drinker and Shaw
1928, Harvard Medical School
had the first successful attempt with negative pressure ventilator
the chamber enclosed the patients body while the head remained out
rubber collar around the neck sealed the chamber
difficult to manage a patient
originally us
Chest Cuirass Ventilator
negative pressure ventilator that covered the thorax and sometimes the abdomen
has been ventilating patients with chronic paralytic disorders for as long as 25-30 years
Polio
first appeared in 1952 in Copenhagen
first application of ventilatory techniques:
1) cuffed trach tubes
2) manual artificial ventilation
3) sigh breaths
4) weaning by decreasing the number of assisted breaths
5) IPPB
Advantages of Negative Pressure Ventilation
no need to intubate
patient can talk and eat
less physiological disadvantages than positive pressure ventilation
good for home care patients requiring ventilation (polio, ALS)
Disadvantages of Negative Pressure Ventilation
pooling of blood in the abdomen
decreased venous return to the heart, especially with hypovolemic patients (tank shock)
poor patient access
air leakage