The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

EFFICACY OF VENTILATION VIA THE NASAL ROUTE VS. THE ORAL ROUTE  IN PATIENTS UNDER GENERAL ANESTHESIA

YAFEN LIANG, MD; MOHAMED HELMY, MD; WILLIAM R. KIMBALL, MD; I. DAVID TODRES, MD; WARREN M. ZAPOL, MD; YANDONG JIANG, MD, PhD; ROBERT M. KACMAREK, PhD, RRT. Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts

Background: Mouth to mouth breathing has been used in CPR for over half a century. However, recent studies demonstrate that mouth-to-mouth breathing plus chest compression during CPR does not produce better outcome for patients receiving CPR than chest compression alone. We hypothesized that mouth-to-mouth breathing adversely affects upper airway obstruction and does not provide adequate ventilation. We questioned if nasal route ventilation is more effective than oral route ventilation in non-paralyzed adult patients under general anesthesia.

Methods: 7 adult ASA I-II patients requiring general anesthesia were studied using separate oral and nasal masks. Ventilation was provided via both masks together then randomly by each mask separately. Airway flow, airway pressure, tidal volume and other respiratory parameters during positive pressure ventilation was recorded with 2 NICO monitors (Respironics Corp).

Results: As shown in the following table, patients had significantly higher peak inspiratory pressure (PIP) during oral ventilation and higher peak inspiratroy flow/PIP (PIF/PIP) during nasal ventilation. Furthermore, during combined nasal and oral ventilation, 6 patients had higher PIF via the nasal route than oral route at the same PIP. During separate nasal and oral ventilation, all patients had higher PIP during oral ventilation than during nasal ventilation. Five patients had higher exhaled tidal volumes via the nasal route than the oral route.

                                            Combined          Nasal                 Oral                ANOVA 
                                            ventilation        ventilation         ventilation

 Peak (i) Flow(L/min)       33.34±14.88      29.81±4.96        27.07±8.17           NS
 Exhaled tidal  vol (mL)  149.20±195.31   155.88±80.09    99.86±247.79        NS

 PIP (cm H2O)                    1.80±4.80        16.04±4.50        30.73±6.48       P=0.001*  

 PIF/PIP(L/(min·cmH2O))  1.56±0.59          2.05±0.83         0.93±0.44        P=0.01*     

Conclusions: Nasal ventilation provides better ventilation with lower airway pressure than oral ventilation or combined oral/nasal ventilation in non-paralyzed patients under general anesthesia. Nasal ventilation may prevent or reduce upper airway obstruction by forcing the tongue and soft palate forward and establishing an open airway.


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