Effects of a sigh on the respiratory mechanical properties in ali patients.
OBJECTIVE
The application of sighs during baseline ventilation was found to improve alveolar recruitment and oxygenation in patients with acute respiratory distress syndrome (ARDS). The present investigation evaluates if respiratory mechanics can be modified by a sigh.


METHODS
Ten consecutive patients with acute lung injury (ALI) admitted to the University Hospital Intensive Care Unit the were studied during mechanical ventilation. Three sighs were administered to sedated-paralyzed patients during the measurement period. Respiratory mechanics were studied in regular breaths immediately before and after a sigh provided that a steady-state had been reached and by the airway pressure-time curve profile to evaluate the lung recruitment. Viscoelastic constants (elastic, resistive, and time), as well as elastance and resistances, were determined by the single breath method. Arterial blood gases were also determined pre- and post-sigh.


RESULTS
Elastic and resistive components of viscoelasticity decreased after a sigh (20 and 21%, respectively). As a result, the pressure required to overcome viscoelasticity and mechanical inhomogeneities also decreased in these patients (17%). The mechanical changes were associated with alterations in PaO(2).


CONCLUSIONS
The sigh is useful to diminish viscoelastic impedance in ALI patients, thus allowing a smaller inflation pressure. Under the present experimental conditions it seems that viscoelastic mechanical alterations precede their elastic and resistive counterparts.
Antonaglia
Vittorio
V
Istituto di Anestesia, Rianimazione e Terapia Antalgica, Laboratorio di Biomeccanica Respiratoria, Università degli Studi di Trieste, Trieste, Italy. v.antonaglia@libero.it
Pascotto
Sara
S
Simoni
Loredana De
LD
Zin
Walter A
WA
D000328:Adult; D000368:Aged; D004548:Elasticity; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics; D016896:Treatment Outcome