A. Aloy et al., FLOW PATTERN OF RESPIRATORY GASES DURING SUPERIMPOSED HIGH-FREQUENCY JET VENTILATION (SHFJV) VIA THE JET LARYNGOSCOPE, Anasthesist, 44(8), 1995, pp. 558-565
High-frequency ventilation techniques have been applied for a number o
f years for laryngeal surgery in order to ventilate patients without e
ndotracheal tubes or catheters. A further development of high-frequenc
y jet ventilation (HFJV) is the technique of superimposed HFJV (SHFJV)
, which was achieved by combining low- and high-frequency jet streams.
Although good clinical results were observed, which have been publish
ed in the past, the clinical details of development of SHFJV have not
been previously published. Methods. In order to understand and study t
he mechanism of superimposition of a high-frequency jet stream, extens
ive experiments on a lung simulator at defined measuring points, which
represented the operating field in microlaryngeal surgery and the tra
chea, were conducted prior to the clinical application of SHFJV. Resul
ts. The measurements demonstrated that superposition of the two jet st
reams led to greater velocity during inspiration, and therefore produc
ed an increase in tidal volume and entrainment of inspiratory gas. Thi
s demonstrates that it is possible to apply a HFJV technique in patien
ts even with an open system. During expiration, the velocity of the lo
w-frequency gas stream is decreased by the opposing flow of the high-f
requency jet stream, leading to the buildup of positive end-expiratory
pressure. The pulsations of the high-frequency jet stream induce cont
inuous alveolar ventilation. The positioning of the jet nozzles in the
jet laryngoscopy has the result that the velocities are already decre
ased at the tip of the laryngoscope and decrease further with distance
from the nozzles. This prevents possible damage to the laryngeal muco
sa.