Reappraisal of mouth-to-mouth ventilation during bystander-initiated CPR

An Anesthesiologist's Perspective on the History of Basic Airway Management: The "Modern" Era, 1960 to Present

This fourth and last installment of my history of basic airway management discusses the current (i.e., "modern") era of anesthesia and resuscitation, from 1960 to the present. These years were notable for the implementation of intermittent positive pressure ventilation inside and outside the operating room. Basic airway management in cardiopulmonary resuscitation (i.e., expired air ventilation) was de-emphasized, as the "A-B-C" (airway-breathing-circulation) protocol was replaced with the "C-A-B" (circulation-airway-breathing) intervention sequence. Basic airway management in the operating room (i.e., face-mask ventilation) lost its predominant position to advanced airway management, as balanced anesthesia replaced inhalation anesthesia. The one-hand, generic face-mask ventilation technique was inherited from the progressive era. In the new context of providing intermittent positive pressure ventilation, the generic technique generated an underpowered grip with a less effective seal and an unspecified airway maneuver. The significant advancement that had been made in understanding the pathophysiology of upper airway obstruction was thus poorly translated into practice. In contrast to consistent progress in advanced airway management, progress in basic airway techniques and devices stagnated.

Should unobstructed gasping be facilitated and confirmed before administering adrenaline, otherwise, give titrated vasopressin?

A recent commentary, "Resuscitation That's (Un)Shockable: Time to Get the Adrenaline Flowing", published in the New England Journal of Medicine Journal Watch called attention to a relatively recent study showing that a large and increasing percentage of patients with in-hospital cardiac arrests exhibit initial nonshockable rhythms (asystole or pulseless electrical activity [PEA]; 82% in 2009 vs 69% in 2000) and a most recent study that concluded that neurologically intact survival to hospital discharge after in-hospital cardiac arrest was significantly more likely after earlier epinephrine administration. It was found that delayed administration of epinephrine was associated significantly with lower chance for survival to hospital discharge, in stepwise fashion (12%, 10%, 8%, and 7% survival, respectively, for patients receiving their first epinephrine dose≤3, 4-6, 7-9, and >9 minutes after arrest). Although early use of epinephrine to manage patients with nonshockable rhythms lacks strong evidence to support efficacy, focus on time to epinephrine administration-in addition to high-quality chest compressions-might be the best early intervention. However, evidence may strongly support the recommendation that adrenaline needs to be used very early because without effective-depth cardiopulmonary resuscitation (CPR) with complete recoil, epinephrine may only be effective when gasping is present, which is a time-limited phenomenon. However, because very few rescuers can perform effective-depth chest compressions with complete recoil, gasping is critically necessary for adequate ventilation and generation of adequate coronary and cerebral perfusion. However, under acidemic conditions and high catecholamine levels and/or absence of gasping, vasopressin should be administered instead.

Pneumothorax During CPR Training: Case Report and Review of the CPR Literature

Cardiopulmonary resuscitation is taught widely to both lay persons and health care oworkers. It is a challenging psychomotor skill. Concerns about its safety to the rescuer have centered around the risk of infectious disease exposure. A young nursing assistant developed a minimally symptomatic pneumothorax during CPR training. This case is the first reported example of this complication for a CPR trainee or provider. The literature is reviewed for complications for CPR provider and recipient and the relevant issues regarding the current status and future direction of this intervention.

The need for head rotation and abdominal compressions during bystander cardiopulmonary resuscitation

The current AHA-ECC guidelines for basic life support focus on the provision of good chest compressions with minimal interruptions for patients with presumed out-of-hospital cardiac arrest. Moreover, international consensus guidelines now support the use of chest compression-only cardiopulmonary resuscitation (CPR) instructions for dispatcher-assisted CPR given over the phone to untrained bystanders. However, evidence that strongly challenge these recommendations have been overlooked. A review of this evidence argues for the need for head rotation (a hands-free method of airway control) and abdominal compressions during bystander CPR.

Clinical and hemodynamic comparison of 15:2 and 30:2 compression-to-ventilation ratios for cardiopulmonary resuscitation*

OBJECTIVE

To compare cardiopulmonary resuscitation (CPR) with a compression to ventilation (C:V) ratio of 15:2 vs. 30:2, with and without use of an impedance threshold device (ITD).

DESIGN

Prospective randomized animal and manikin study.

SETTING

Animal laboratory and emergency medical technician training facilities.

SUBJECTS

Twenty female pigs and 20 Basic Life Support (BLS)-certified rescuers.

INTERVENTIONS, MEASUREMENTS, AND MAIN RESULTS

ANIMALS

Acid-base status, cerebral, and cardiovascular hemodynamics were evaluated in 18 pigs in cardiac arrest randomized to a C:V ratio of 15:2 or 30:2. After 6 mins of cardiac arrest and 6 mins of CPR, an ITD was added. Compared to 15:2, 30:2 significantly increased diastolic blood pressure (20 +/- 1 to 26 +/- 1; p < .01); coronary perfusion pressure (18 +/- 1 to 25 +/- 2; p = .04); cerebral perfusion pressure (16 +/- 3 to 18 +/- 3; p = .07); common carotid blood flow (48 +/- 5 to 82 +/- 5 mL/min; p < .001); end-tidal CO2 (7.7 +/- 0.9 to 15.7 +/- 2.4; p < .0001); and mixed venous oxygen saturation (26 +/- 5 to 36 +/- 5, p < .05). Hemodynamics improved further with the ITD. Oxygenation and arterial pH were similar. Only one of nine pigs had return of spontaneous circulation with 15:2, vs. six of nine with 30:2 (p < 0.03). HUMANS: Fatigue and quality of CPR performance were evaluated in 20 BLS-certified rescuers randomized to perform CPR for 5 mins at 15:2 or 30:2 on a recording CPR manikin. There were no significant differences in the quality of CPR performance or measurement of fatigue. Significantly more compressions per minute were delivered with 30:2 in both the animal and human studies.

CONCLUSIONS

These data strongly support the contention that a ratio of 30:2 is superior to 15:2 during manual CPR and that the ITD further enhances circulation with both C:V ratios.

What is the optimal chest compression-ventilation ratio?

PURPOSE OF REVIEW

Despite a more widespread knowledge of basic cardiopulmonary resuscitation maneuvers in the community, the survival rate for patients with cardiac arrest has remained essentially unchanged in the past 30 years. Over the past few decades, many different compression-ventilation ratios have been studied in terms of best coronary and cerebral oxygen delivery, restoration of spontaneous circulation, and neurologic outcome. This article summarizes the recent evidence presented at the International Consensus on Resuscitation Science in January 2005.

RECENT FINDINGS

Recent data from animal and mathematical models suggest a move to a higher compression-ventilation ratio to maximize coronary and cerebral oxygen delivery during cardiac arrest and long-term neurologic outcome. Prospective randomized human data on alternative compression-ventilation ratios are missing and new evidence seems to indicate the inadequacy of both lay and professional rescuers in providing chest compression and ventilating the victim in cardiac arrest. Finally, observational and animal studies highlight the hidden danger of inadvertent hyperventilation during advanced cardiac life support as a reduction of both coronary and perfusion pressure secondary to increased intrathoracic pressure and decreased venous return.

SUMMARY

The optimal compression-ventilation ratio is still unknown and the best tradeoff between oxygenation and organ perfusion during cardiopulmonary resuscitation is probably different for each patient and scenario. A discrepancy between what is recommended by the current guidelines and the 'real world' of cardiopulmonary resuscitation has resulted in a near flat survival rate from cardiac arrest in the past few years.

["Topless" cardiopulmonary resuscitation. Fashion or science?]

A decade after the onset of a discussion whether ventilation could be omitted from bystander basic life support (BLS) algorithms, the state of the evidence is reevaluated. Initial animal studies and a prospective randomized patient trial had suggested that omission of ventilation during the first minutes of lay cardiopulmonary resuscitation (CPR) did not impair patient outcomes. More recent studies demonstrate, however, that this may hold true only in very specific scenarios, and that the chest compression-only technique was never superior to standard BLS. Instead of calling basics of BLS training and practice into question, more and better training of lay persons and professionals appears mandatory, and targeted use of dispatcher-guided telephone CPR should be evaluated and, if it improves outcome, it should be encouraged. Future studies should focus much less on the omission but on the optimization of ventilation under the specific conditions of CPR.

Resuscitating an idea: prone CPR

Cardiopulmonary resuscitation (CPR) is widely recognized as an essential part of the medical response to cardiac arrest. Traditional ('basic') CPR has remained essentially unchanged for 40 years despite major problems with training and performance, and survival rates from out-of-hospital cardiac arrest remain disappointingly low, despite massive resources devoted to CPR training and public awareness. More than a decade ago, an article described an alternative method-prone CPR-which offered many potential advantages over traditional CPR, including much simpler training and increased likelihood of actual performance by bystanders. The article received little notice at the time; however, the method of prone CPR merits further consideration based on a number of subsequent supporting studies and case reports. Prone CPR may represent a superior alternative to traditional CPR; research into its effectiveness should be given high priority.

Cardiopulmonary resuscitation performed by bystanders does not increase adverse effects as assessed by chest radiography

Important adverse effects of bystander cardiopulmonary resuscitation (CPR) are well known. We describe the number of nonmedical professional CPR-related complications in patients surviving cardiac arrest, as assessed by chest radiograph. Within 2 yr, all consecutive patients admitted to the department of emergency medicine at a university hospital who had a witnessed, nontraumatic, normothermic cardiac arrest were studied. Radiologically evaluated adverse effects were compared with Mann-Whitney U-tests between patients who received bystander basic life support (Bystander group) and patients who did not receive bystander basic life support before advanced life support was started (ALS group). For assessment of bystander CPR-associated complications, chest radiographs were used. Of 224 patients, 173 were eligible. The median age was 58 yr (interquartile range, 51-71 yr), and 126 patients (73%) were men. The incidence of adverse effects associated with assisted-ventilation maneuvers and external chest compressions did not differ significantly between groups (severe gastric insufflation, 17% vs 18% between the Bystander group [n = 59] and the ALS group [n = 96], respectively; suspicion of aspiration, 22% vs 17%, respectively; soft tissue emphysema, 2% vs 1%, respectively; and serial rib fractures, 8% vs 8%, respectively). CPR administered by nonmedical personnel did not increase the number of life support-related adverse effects in patients surviving cardiac arrest as assessed by means of chest radiograph on admission.

IMPLICATIONS

Complications related to cardiopulmonary bypass (CPR) are not increased when CPR is administered by nonmedical personnel, as assessed by chest radiograph. These data may be valuable in motivating lay people to perform basic life support.

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

The fear of acquiring infectious diseases has resulted in reluctance among healthcare professionals and the lay public to perform mouth-to-mouth ventilation. However, the benefit of basic life support for a patient in cardiopulmonary or respiratory arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. The distribution of ventilation volume between lungs and stomach in the unprotected airway depends on patient variables such as lower oesophageal sphincter pressure, airway resistance and respiratory system compliance, and the technique applied while performing basic or advanced airway support, such as head position, inflation flow rate and time, which determine upper airway pressure. The combination of these variables determines gas distribution between the lungs and the oesophagus and subsequently, the stomach. During bag-valve-mask ventilation of patients in respiratory or cardiac arrest with oxygen supplementation (> or = 40% oxygen), a tidal volume of 6-7 ml kg(-1) ( approximately 500 ml) given over 1-2 s until the chest rises is recommended. For bag-valve-mask ventilation with room-air, a tidal volume of 10 ml kg(-1) (700-1000 ml) in an adult given over 2 s until the chest rises clearly is recommended. During mouth-to-mouth ventilation, a breath over 2 s sufficient to make the chest rise clearly (a tidal volume of approximately 10 ml kg(-1) approximately 700-1000 ml in an adult) is recommended.

On the future of reanimatology

This article is adapted from a presentation given at the 1999 SAEM annual meeting by Dr. Peter Safar. Dr. Safar has been involved in resuscitation research for 44 years, and is a distinguished professor and past initiating chairman of the Department of Anesthesiology and Critical Care Medicine at the University of Pittsburgh. He is the founder and director of the Safar Center for Resuscitation Research at the University of Pittsburgh, and has been the research mentor of many critical care and emergency medicine research fellows. Here he presents a brief history of past accomplishments, recent findings, and future potentials for resuscitation research. Additional advances in resuscitation, from acute terminal states and clinical death, will build upon the lessons learned from the history of reanimatology, including optimal delivery by emergency medical services of already documented cardiopulmonary cerebral resuscitation, basic-advanced-prolonged life support, and future scientific breakthroughs. Current controversies, such as how to best educate the public in life-supporting first aid, how to restore normotensive spontaneous circulation after cardiac arrest, how to rapidly induce mild hypothermia for cerebral protection, and how to minimize secondary insult after cerebral ischemia, are discussed, and must be resolved if advances are to be made. Dr. Safar also summarizes future technologies already under preliminary investigation, such as ultra-advanced life support for reversing prolonged cardiac arrest, extending the "golden hour" of shock tolerance, and suspended animation for delayed resuscitation.