Volemic status influences the response of plasma atrial natriuretic factor to positive airway pressure.
STUDY OBJECTIVE; To evaluate interactive effects of volemic status and positive end-expiratory pressure (PEEP) on the plasma levels of atrial natriuretic factor (ANF) in assist-controlled mechanical ventilation (MV).


METHODS
Three successive protocols applied in randomized order to each participant.


METHODS
Clinical investigation laboratory.


METHODS
Twenty-one young, healthy adults.


METHODS
The three protocols were as follows: (1) MV+PEEP, normovolemia; (2) MV+PEEP, hypervolemia; and (3) spontaneous breathing (SB), hypervolemia. In protocols 1 and 2, a preliminary period of SB lasting 2 h was followed by MV alone (0.5 h), MV+20 cm H2O PEEP (1 h), and a recovery period of SB (1.5 h). Hypervolemia was induced by the continuous i.v. infusion of 3 L of 0.9% NaCl in 5 h (protocols 2 and 3).


RESULTS
Heart rate, BP, and the plasma levels of immunoreactive ANF and catecholamines were measured serially. During hypervolemia, ANF significantly decreased when PEEP was added to MV (protocol 2: from 31.1 +/- 2.7 to 20.7 +/- 1.5 fmol/mL; p < 0.01). This did not occur in normovolemia (protocol 1: from 20.0 +/- to 16.7 +/- 1.2 fmol/mL; p = NS). The different effects of MV+PEEP in normovolemia and hypervolemia were not related to differences in circulating catecholamine levels.


CONCLUSIONS
These results demonstrate for the first time (to our knowledge) that volemic status modulates the response of plasma ANF to PEEP in humans. The role of ANF in the water and salt retention induced by MV with PEEP might be limited to hypervolemic conditions.
Beuret
P
P
Institut de Physiopathologie, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland.
Feihl
F
F
Nussberger
J
J
Brunner
H R
HR
Perret
C
C
D000328:Adult; D009320:Atrial Natriuretic Factor / Q000097:blood*; D001794:Blood Pressure; D001810:Blood Volume / Q000502:physiology*; D002395:Catecholamines / Q000097:blood; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D011175:Positive-Pressure Respiration; D012016:Reference Values
D002395:Catecholamines; D009320:Atrial Natriuretic Factor