Correspondence

Bag and Mask Ventilation

N Engl J Med 2007; 357:2090-2092November 15, 2007

Article

To the Editor:

The video and accompanying text by Ortega et al. on positive-pressure ventilation with a face mask and a bag-valve device (July 26 issue)1 identify the tongue as the most common cause of airway obstruction. Although this concept is commonly accepted, it is probably inaccurate. Using plain radiographs, Safar et al. identified airway obstruction by the tongue and other soft tissues just above the laryngeal entrance in spontaneously breathing, anesthetized patients.2 Obstruction of the nasopharynx by the soft palate was also noted. More recent studies suggest that the soft palate and epiglottis are actually the most common sources of airway obstruction. Nandi et al.3 studied 18 patients with the use of plain-film radiographs. After induction of anesthesia with thiopentone, airway obstruction was caused by the palate in 17 of the 18 patients and by the epiglottis in 4 of the 18 patients. Although the tongue was displaced posteriorly, it did not cause obstruction. Other studies, with the use of magnetic resonance imaging, have shown that decreases in the pharyngeal anterior–posterior diameter occur mainly at the level of the soft palate4,5 and epiglottis,4 not at the level of the tongue.

Lawrence J. Caruso, M.D.
Murat Sungur, M.D.
University of Florida College of Medicine, Gainesville, FL 32610-0254

5 References

1. 1

   Ortega R, Mehio AK, Woo A, Hafez DH. Positive-pressure ventilation with a face mask and a bag-valve device. N Engl J Med 2007;357:e4.
   

2. 2

   Safar P, Escarraga LA, Chang F. Upper airway obstruction in the unconscious patient. J Appl Physiol 1959;14:760-764
   Web of Science | Medline

3. 3

   Nandi PR, Charlesworth CH, Taylor SJ, Nunn JF, Dore CJ. Effect of general anaesthesia on the pharynx. Br J Anaesth 1991;66:157-162
   CrossRef | Web of Science | Medline

4. 4

   Shorten GD, Opie NJ, Graziotti P, Morris I, Khangure M. Assessment of upper airway anatomy in awake, sedated and anaesthetised patients using magnetic resonance imaging. Anaesth Intensive Care 1994;22:165-169
   Web of Science | Medline

5. 5

   Mathru M, Esch O, Lang J, et al. Magnetic resonance imaging of the upper airway: effects of propofol anesthesia and nasal continuous positive airway pressure in humans. Anesthesiology 1996;84:273-279
   CrossRef | Web of Science | Medline

To the Editor:

Ortega et al. have provided an informative primer on mask ventilation. However, since the primary audience for this report is presumably composed of non-anesthesiologists, there are several omissions that we believe must be addressed. The authors do not mention that it is difficult to provide ventilation with a mask in 2 to 5% of patients, even by experienced anesthesiologists, and that 21% of patients will require an adjunct oral or nasopharyngeal airway.1,2

Furthermore, although the video describes some risk factors, it omits several important predictors of difficulty with mask ventilation, including oropharyngeal malproportion (Mallampati class III or IV), advanced age, limited jaw protrusion, and a history of snoring. As the prevalence of conscious sedation supervised by non-anesthesiologists rises, these risk factors should be considered. Data suggest that at least 5% of patients undergoing elective conscious sedation require active airway management by a non-anesthesiologist.3

Finally, the video recommends the removal of the patient's dentures to prevent aspiration. However, this classically held tenet should be reconsidered. Recent data show that leaving dentures in place during mask ventilation not only is safe but also reduces the incidence of difficulty with mask ventilation from 16% to 4% among patients in this high-risk group.4

Sachin Kheterpal, M.D., M.B.A.
Kevin K. Tremper, M.D., Ph.D.
George A. Mashour, M.D., Ph.D.
University of Michigan, Ann Arbor, MI 48109
sachinkh@med.umich.edu

4 References

1. 1

   Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006;105:885-891
   CrossRef | Web of Science | Medline

2. 2

   Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology 2000;92:1229-1236
   CrossRef | Web of Science | Medline

3. 3

   Arepally A, Oechsle D, Kirkwood S, Savader SJ. Safety of conscious sedation in interventional radiology. Cardiovasc Intervent Radiol 2001;24:185-190
   CrossRef | Web of Science | Medline

4. 4

   Conlon NP, Sullivan RP, Herbison PG, Zacharias M, Buggy DJ. The effect of leaving dentures in place on bag-mask ventilation at induction of general anesthesia. Anesth Analg 2007;105:370-373
   CrossRef | Web of Science | Medline

To the Editor:

As a practicing anesthesiologist who administers anesthesia with a face mask and bag-valve device in about 1000 patients per year, I wonder why the video by Ortega et al. does not emphasize the adequate establishment of face-mask ventilation as the crucial event in the difficult-airway algorithm of the American Society of Anesthesiologists. Adequate face-mask ventilation is the condition for the nonemergency pathway of the algorithm.1 The practitioner who masters this skill has time to collect and assemble more specialized airway equipment and to summon more expert help when necessary, since gas exchange is adequate to support metabolic functions.

Another value of face-mask ventilation, as compared with direct laryngoscopy and endotracheal intubation, is the low incidence of upper-airway damage from a nonexpert operator — a great benefit when an expert is called to establish a more permanent airway.

Finally, elevating the head of the bed between 15 and 40 degrees may help to improve the airway compliance to mask ventilation in large patients.

Andrea Torri, M.D.
Massachusetts General Hospital, Boston, MA 02114

1 References

1. 1

   Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98:1269-1277[Erratum, Anesthesiology 2004;101:565.]
   CrossRef | Web of Science | Medline

Author/Editor Response

Considering the complexity of airway management and the time allotted for this video, we struggled in deciding what to include and what to omit.

With regard to the comments by Caruso and Sungur, upper-airway obstruction in unconscious patients is a multifactorial phenomenon that may involve several structures, including the tongue, soft palate, and epiglottis. The majority of texts describe the tongue as the most common cause of airway obstruction. However, data suggest that under certain circumstances, such as during anesthesia with propofol in infants, other mechanisms are involved.1

Kheterpal and colleagues comment on the removal of dentures. To emphasize the role of the tongue, the video illustrates how the application of pressure to the submandibular soft tissues may push the tongue against the palate, leading to airway obstruction. This situation is worsened in edentulous patients and can be minimized, as described in the video, by leaving full dentures in place. The video also illustrates how an inappropriately small oral airway may push the tongue against the pharynx, causing or worsening airway obstruction. Further studies are needed to elucidate the extent of the tongue's contribution in airway obstruction in a variety of clinical situations.

With regard to the comments by Torri, the American Society of Anesthesiologists difficult-airway algorithm is a valuable strategy.2 Our video is in concert with the algorithm's recommendations and stresses the importance of face-mask ventilation as a potentially lifesaving and temporizing maneuver. Finally, the video demonstrates how raising the head of a bed may facilitate the delivery of adequate tidal volumes.

Rafael Ortega, M.D.
Abdel K. Mehio, M.D.
Albert Woo, M.D.
Boston University Medical Center, Boston, MA 02118

2 References

1. 1

   Crawford MW, Rohan D, Macgowan CK, Yoo SJ, Macpherson BA. Effect of propofol anesthesia and continuous positive airway pressure on upper airway size and configuration in infants. Anesthesiology 2006;105:45-50
   CrossRef | Web of Science | Medline

2. 2

   Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98:1269-1277[Erratum, Anesthesiology 2004;101:565.]
   CrossRef | Web of Science | Medline