1995 OPEN FORUM Abstracts
EFFECT OF VENTILATOR ADJUSTMENTS DURING CLOSED INLINE SUCTIONING WITH HFOV.
Dale Gerstmann MD, Ron Haskill RRT, Larry Cooper RRT, Gordon Lassen RRT. Neonatology and Respiratory Therapy, Utah Valley Reg Med Cen, Provo, UT.
Introduction: We evaluated the effect of changes in HFOV frequency (Freq) and pressure amplitude (PAmp) on mean tracheal airway pressure (PTr) and real-time oxygenation (P_aO_2) during suctioning with closed in-line catheters. Method: Ten white rabbits (2.2-2.8 kg) underwent sedation, analgesia, tracheostomy, intubation, paralysis and 21 suctioning episodes prior to and after saline lavage (Total episodes = 420). ABGs were normalized by adjusting mean airway pressure, F_iO_2, and PAmp at Freq=10Hz. Various ETT (2.0, 2.5, 3.0mm) and catheter (CATH) sizes (5.0, 6.0, 8.0F) were used. Suction pressures (PSxn) of -70, -90, -110 mmHg were tested with ETT=2.0 + CATH=5.0, otherwise PSxn=-90 mmHg. Suctioning episodes were performed with random adjustments of Freq (6, 10, 15 Hz) and PAmp (PAmp=0, PAmp+0, PAmp+10 cmH_2O). PTr was measured with a small monitoring tube 2cm below the tip of the ETT. Real-time P_aO_2 was measured with an electrode catheter in the right carotid artery at the level of the aortic arch. Each suction episode was divided into 5 segments based on PTr: pre-baseline, ready, suction, recovery, and post-baseline. Segment interval time, PTr, and P_aO_2 were measured and recorded.
Results: Average ready, suction, recovery and total interval durations were 5.8±0.1, 4.3±0.1, 2.7±0.1, and 13.4±0.2 secs (mean±se). PSxn had no effect as tested. Lavage caused lower PTr in the ready interval (p=0.003) and lower P_aO_2 in the suction interval (p < 0.001). Increasing PAmp decreased the drop in PTr in the ready interval (p < 0.001) and decreased the drop of P_aO_2 during suctioning (p=0.018) and at post-baseline (p < 0.001). Decreasing Freq had the same effect on P_aO_2 during suctioning (p < 0.001) and at post-baseline (p < 0.001). Post-baseline PTr was not different from pre-baseline values, 7.1±0.1 vs 7.1±0.1 cmH_2O.
Conclusions: Ventilator adjustments, eg. increased PAmp and decreased Freq, that yield larger HFOV tidal volume output appear to retard drops in PTr before suctioning (as the catheter enters the ETT) and preserve P_aO_2 during and after suctioning. Turning PAmp off appears less beneficial than leaving it on or increasing it. Inadvertant PEEP (increase in PTr) was not seen in this study. (Funded by a grant from Ballard Medical Products, Draper, UT.)