title: Effectiveness of breathing through nasal and oral routes in unconscious apneic adult human subjects: a prospective randomized crossover trial.
abstract: BACKGROUND
  The authors hypothesized that mouth ventilation by a resuscitator via the nasal route ensures a more patent airway and more effective ventilation than does ventilation via the oral route and therefore would be the optimal manner to ventilate adult patients in emergencies, such as during cardiopulmonary resuscitation. They tested the hypothesis by comparing the effectiveness of mouth-to-nose breathing (MNB) and mouth-to-mouth breathing (MMB) in anesthetized, apneic, adult subjects without muscle paralysis.
  
  
  METHODS
  Twenty subjects under general anesthesia randomly received MMB and MNB with their heads placed first in a neutral position and then an extended position. A single operator performed MNB and MMB at the target breathing rate of 10 breaths/min, inspiratory:expiratory ratio 1:2 and peak inspiratory airway pressure 24 cm H₂O. A plethysmograph was used to measure the amplitude change during MMB and MNB. The inspiratory and expiratory tidal volumes during MMB and MNB were calculated retrospectively using the calibration curve.
  
  
  RESULTS
  All data are presented as medians (interquartile ranges). The rates of effective ventilation (expired volume > estimated anatomic dead space) during MNB and MMB were 91.1% (42.4-100%) and 43.1% (42.5-100%) (P < 0.001), and expired tidal volume with MMB 130.5 ml (44.0-372.8 ml) was significantly lower than with MNB 324.5 ml (140.8-509.0 ml), regardless of the head position (P < 0.001).
  
  
  CONCLUSIONS
  Direct mouth ventilation delivered exclusively via the nose is significantly more effective than that delivered via the mouth in anesthetized, apneic adult subjects without muscle paralysis. Additional studies are needed to establish whether using this breathing technique during emergency situations will improve patient outcomes.
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: Yandong
authors.initials: Y
authors.lastname: Jiang
authors.forename: Fang Ping
authors.initials: FP
authors.lastname: Bao
authors.forename: Yafen
authors.initials: Y
authors.lastname: Liang
authors.forename: William R
authors.initials: WR
authors.lastname: Kimball
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Liu
authors.forename: Warren M
authors.initials: WM
authors.lastname: Zapol
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kacmarek
mesh_terms: D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General; D001049:Apnea / Q000503:physiopathology*; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D018592:Cross-Over Studies; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity; D007442:Intubation, Intratracheal; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000502:physiology; D009296:Nasal Cavity / Q000502:physiology; D010991:Plethysmography; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult