Vol. 87, Issue 1, 428-437, July 1999
Physiological effects of alveolar, tracheal, and
"standard" pressure supports
Jean-Luc
Diehl1,
Daniel
Isabey1,
Gilbert
Desmarais2,
Laurent
Brochard1,
Alain
Harf1, and
Frédéric
Lofaso1
1 Service de
Physiologie-Explorations Fonctionnelles, Institut National de la
Santé et de la Recherche Médicale Unité 492,
Hôpital Henri Mondor, 94010 Créteil; and
2 École
Supérieure d'Ingénieurs en Électrotechnique et
Électronique, 93160 Noisy le Grand, France
Pressure support
(PS) is characterized by a pressure plateau, which is usually generated
at the ventilator level
(PSvent). We have built a PS
device in which the pressure plateau can be obtained at the upper
airway level (PSaw) or at the
alveolar level (PSA). The effect
of these different PS modes was evaluated in seven healthy men during
air breathing and 5% CO2
breathing. Minute ventilation during air breathing was higher with
PSA than with PSaw and lower with
PSvent (16 ± 3, 14 ± 3, and 11 ± 2 l/min, respectively). By contrast, there were
no significant differences in minute ventilation during 5%
CO2 breathing (25 ± 5, 27 ± 7, and 23 ± 5 l/min, respectively). The esophageal
pressure-time product per minute was lower with
PSA than with
PSaw and
PSvent during air breathing (29 ± 26, 44 ± 44, and 48 ± 30 cmH2O · s, respectively) and 5% CO2
breathing (97 ± 40, 145 ± 62, and 220 ± 41 cmH2O · s,
respectively). In conclusion, during PS, moving the inspiratory
pressure plateau from the ventilator to the alveolar level reduces
pressure output, particularly at high ventilation levels.
control of breathing; positive inspiratory pressure; unloading
