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Anesth Analg 2001;93:4-6
© 2001 International Anesthesia Research Society

EDITORIALS

Mouth-to-Mouth Ventilation During Cardiopulmonary Resuscitation: Word of Mouth in the Street Versus Science

Volker Wenzel, MD, Volker Dörges, MD*, Karl H. Lindner, MD, and Ahamed H. Idris, MD{dagger}

Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University, Innsbruck, Austria; *Department of Anesthesiology, Medical University, Lübeck, Germany; and {dagger}Department of Emergency Medicine, University of Florida, Gainesville, Florida

Address correspondence to Volker Wenzel, MD, Leopold-Franzens-University, Department of Anesthesiology and Critical Care Medicine, Anichstrasse 35, 6020 Innsbruck, Austria. Address e-mail to volker.wenzel{at}uibk.ac.at

In this issue of Anesthesia & Analgesia, Oschatz et al. (1) report that when lay bystanders in Vienna, Austria performed mouth-to-mouth ventilation in cardiac arrest victims before professional paramedics administered advanced cardiac life support, serious ventilation-related adverse effects such as pulmonary aspiration occurred no more often than in patients who collapsed in the presence of professional paramedics, and who therefore received advanced cardiac life support only. Without a doubt, the two most interesting questions raised by this article are the following: why did lay bystander mouth-to-mouth ventilation not increase the ~15% rate of stomach inflation? And why did professional paramedics not achieve a rate of stomach inflation less than ~15%?

When the airway is unprotected, the distribution of ventilation volume between lungs and stomach depends mainly on variables such as lower esophageal sphincter pressure (2), airway resistance, and respiratory system compliance (3). Of equal importance are differences in technique applied while performing basic or advanced airway support, such as head position, tidal volume, inflation flow rate, and duration, all of which determine upper airway pressure (4). The combination of these variables determines gas distribution between the lungs and the esophagus and, subsequently, the stomach. There are several fundamental differences between these components of respiratory mechanics in a healthy, awake adult, an anesthetized supine patient, and a victim of cardiac arrest (Table 1). On the basis of these measurements, we evaluated simulated basic life support ventilation in both bench models and apneic patients and found that even experienced paramedics and anesthesiologists can cause stomach inflation when performing routine bag-valve-mask ventilation (5,6). Moreover, we found that mouth-to-mouth ventilation skills in first-year medical students (who may be somewhat comparable to lay bystanders) deteriorated within 6 mo to levels that did not ensure proper basic life support ventilation performance at all (7).


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  		Table 1. Rescuer and Patient Variables Affecting Respiratory Mechanics During Mouth-to-Mouth Ventilation and Bag-Valve-Mask Ventilation
 
Extrapolating these observations, patients who received mouth-to-mouth ventilation by lay bystanders in the city of Vienna, Austria (1), would be expected to have much more frequent rates of stomach inflation and pulmonary aspiration, especially when considering that mouth-to-mouth ventilation was performed for approximately 7 min. In fact, our bench model investigations showed severe levels of stomach inflation when basic life support ventilation was simulated in an unintubated cardiac arrest patient for this duration (8). There could be a number of explanations for this discrepancy. First, stomach inflation and/or pulmonary aspiration may have occurred without being detected on chest radiograph; second, mouth-to-mouth ventilation skills were better than we thought; and third, stomach inflation may have been self-limiting (9). None of these possibilities can be ascertained or discounted by the investigators of the present article. Moreover, the authors correctly identified the limitation that only surviving patients were examined, indicating the possibility that if lay bystanders had performed nonsurvivable basic life support maneuvers, these catastrophic complications would not have been detected as a result of the study design. Although speculative, an additional possibility may be the most likely underlying reason for the observations of Oschatz et al. (1) in Vienna. When paramedics performed bag-valve-mask ventilation, inspiratory times were ~0.5 s instead of 2 s (10), indicating that rescuers may squeeze a self-inflating bag in such a rapid and powerful manner that extremely high flow rates are produced, and subsequently, high peak airway pressures with stomach inflation are very likely. However, it seems obvious that when bystanders perform mouth-to-mouth ventilation, they have less muscle power in their cheeks than paramedics can exert with their hands during bag-valve-mask ventilation, which may result in lower inspiratory flow rates, lower peak airway pressure, and lower rates of stomach inflation. This could explain why lay bystanders did not cause more stomach inflation and/or pulmonary aspiration in the Bystander Ventilation group and why paramedics caused more stomach inflation and/or pulmonary aspiration than anticipated in the group given only advanced cardiac life support ventilation. It is surprising that, in the Early Defibrillation group, 2 of 18 patients suffered from pulmonary aspiration despite assisted ventilation not being performed and rapid defibrillation resulted in an almost immediate return of spontaneous circulation. Although a detailed medical history for these two patients was not available, a decreased lower esophageal sphincter pressure, such as in patients with regurgitation and/or hiatus hernia, may have been present.

An expert panel on cardiopulmonary resuscitation (CPR) questioned the need for ventilation during the initial management of human cardiac arrest in 1992 and again in 1997 (11,12). This is an important issue to be resolved because many people, including health care professionals, have become fearful of giving mouth-to-mouth ventilation because of the threat of transmissible disease (13). Transmissions of Helicobacter pylori, salmonella, and herpes simplex virus during mouth-to-mouth ventilation have been described in case reports. However, the true reason for omitting mouth-to-mouth ventilation may be a fear of infection with tuberculosis, immunodeficiency virus, or hepatitis, esthetic reasons, or the fear of doing harm.

The new international CPR guidelines of both the American Heart Association and the European Resuscitation Council state that mouth-to-mouth ventilation is a safe and effective technique that has saved many lives (14,15). In one recent clinical study, the outcome after CPR in adults with chest compression alone was similar to that after chest compressions with mouth-to-mouth ventilation; the authors concluded that chest compressions alone may be the preferred approach for bystanders inexperienced in CPR (16). This point of view rapidly gained the attention of the general public worldwide and even conservative newspapers, such as the Frankfurt General in Germany, suggested in their science sections that mouth-to-mouth ventilation performed by lay bystanders during CPR could possibly be omitted (17). In the aforementioned study of Hallstrom et al. (16), wherein mouth-to-mouth ventilation performed by bystanders was assessed by emergency medical service dispatchers only and not investigators at the scene, airway patency was unclear and primary respiratory arrests were excluded; these limitations warrant cautious interpretation of these results. Thus, these results can simply not challenge the recommendation that bystander mouth-to-mouth ventilation should be performed in cardiac arrest victims whenever possible. It is both surprising and disappointing that immediate efforts of the resuscitation community to clarify this issue were not printed by the Frankfurt General Newspaper, therefore giving the public a skewed impression of how to perform lifesaving maneuvers correctly. This is even more disappointing in view of the fact that lay bystanders in Vienna did not cause more pulmonary aspiration than experienced professional paramedics (1). Thus, lay rescuers should be confident in the knowledge that mouth-to-mouth ventilation is safe and may well be lifesaving. Furthermore, reluctance to perform mouth-to-mouth ventilation is not an important issue in most cases because most cardiac arrests of cardiac etiology occur at home in the presence of family or friends. Lack of training and confidence, poor retention of skills and knowledge, and questionable teaching methods and recommendations may be the main causes of the disappointingly low rates of bystander CPR worldwide. This situation cannot necessarily be improved by simply eliminating a life-saving component of CPR–ventilation and oxygenation (18).

Acknowledgments

Supported, in part, by the Austrian Science Foundation Grant P14169-MED, Vienna, Austria; and a Founder’s Grant of the Society of Critical Care Medicine, Anaheim, California.

References

  1. Oschatz E, Wunderbaldinger P, Sterz F, et al. Bystanders do not increase cardiopulmonary resuscitation associated adverse effects assessed by chest radiography. Anesth Analg 2001; 93: 128–33.[Abstract/Free Full Text]
  2. Bowman FP, Menegazzi JJ, Check BD, Duckett TM. The lower esophageal sphincter pressure during prolonged cardiac arrest and resuscitation. Ann Emerg Med 1995; 26: 216–9.[Web of Science][Medline]
  3. Wenzel V, Idris AH. The current status of ventilation strategies during cardiopulmonary resuscitation. Curr Opin Crit Care 1997; 3: 206–13.
  4. Wenzel V, Idris AH, Dörges V, et al. The respiratory system during resuscitation: a review of the history, risk of infection during assisted ventilation, respiratory mechanics, and ventilation strategies for patients with an unprotected airway. Resuscitation 2001; 49: 123–36.[Web of Science][Medline]
  5. Ocker H, Wenzel V, Schmucker P, Dörges V. Effectiveness of various airway management techniques in a bench model simulating a cardiac arrest patient. J Emerg Med 2001; 20: 7–12.[Web of Science][Medline]
  6. Wenzel V, Keller C, Idris AH, et al. Effects of smaller tidal volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk? Resuscitation 1999; 43: 25–9.[Web of Science][Medline]
  7. Wenzel V, Lehmkuhl P, Kubilis PS, et al. Poor correlation of mouth-to-mouth ventilation skills after basic life support training and six months later. Resuscitation 1997; 35: 129–34.[Web of Science][Medline]
  8. Dörges V, Sauer C, Ocker H, et al. Smaller tidal volumes during cardio-pulmonary resuscitation: comparison of adult and pediatric size self-inflatable bags with three different ventilatory devices. Resuscitation 1999; 43: 31–7.[Web of Science][Medline]
  9. Safar P. Ventilatory efficacy of mouth-to-mouth artificial respiration: airway obstruction during manual and mouth-to-mouth artificial respiration. JAMA 1958; 167: 335–41.
  10. Wenzel V, Idris AH, Banner MJ, et al. The influence of tidal volume on the distribution of gas between the lungs and stomach in the unintubated patient receiving positive pressure ventilation. Crit Care Med 1998; 26: 364–8.[Web of Science][Medline]
  11. Cobb LA, Eliastam M, Kerber RE, et al. Report of the American Heart Association task force on the future of cardiopulmonary resuscitation. Circulation 1992; 85: 2346–55.[Free Full Text]
  12. Becker LB, Berg RA, Pepe PE, et al. A reappraisal of mouth-to-mouth ventilation during bystander-initiated cardiopulmonary resuscitation: a statement for healthcare professionals from the Ventilation Working Group of the Basic Life Support and Pediatric Life Support Subcommittees, American Heart Association. Circulation 1997; 96: 2102–12.[Free Full Text]
  13. Locke CJ, Berg RA, Sanders AB, et al. Bystander cardiopulmonary resuscitation: concerns about mouth-to-mouth contact. Arch Intern Med 1995; 155: 938–43.[Abstract/Free Full Text]
  14. Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care: international consensus on science. Circulation 2000; 102 (suppl): 384.
  15. Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care: international consensus on science. Resuscitation 2000; 46: 1–447.[Medline]
  16. Hallstrom A, Cobb L, Johnson E, Copass M. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. N Engl J Med 2000; 342: 1546–53.[Abstract/Free Full Text]
  17. Sahm S. A new ABC of cardiopulmonary resuscitation [in German]? Frankfurter Allgemeine Zeitung 2000; 131: N1.
  18. Dick WF, Brambrink AM, Kern T. "Topless" cardiopulmonary resuscitation: should heart-lung resuscitation be preformed without artificial resuscitation [in German]? Anaesthesist 1999; 48: 290–300.[Web of Science][Medline]
Accepted for publication March 9, 2001.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins and Stanford University Libraries' HighWire Press®. Copyright 2001 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press