In the obtunded or unconscious patient, the upper airway may become obstructed because of relaxation of muscle groups in the upper respiratory tract.

Should upper airway obstruction by a foreign body be suspected, the airway should be cleared manually.

When respiratory effort exists, airway patency can often be obtained by a variety of simple mechanical maneuvers that involve the mouth, chin, and mandible.

When injury to the cervical spine is not present, simply tilting the head backward may be dramatically effective in opening the airway, and if so, signs of respiratory obstruction, such as stridor, may disappear.

In some patients, the insertion of an oral or a nasal airway, provided that the former does not result in gagging or vomiting, followed by bag-valve-mask (BVM) ventilation as required, may provide adequate oxygenation while the physician attends to other aspects of CPR.

In other patients with respiratory effort, the jaw thrust (which involves placing the fingers bilaterally behind the mandibular angles and displacing the mandible forward or anteriorly) or the chin lift may provide complete control of the upper airway.

The jaw thrust, which results in little or no movement of the neck, is the preferred initial maneuver in patients with possible injury to the cervical spine.

In all patients, supplemental oxygen should be administered.

Despite respiratory effort by the patient, the use of supplemental oxygen, and the application of techniques to open the airway, the patient with persistent inadequate oxygenation will require establishment of a definitive airway.

Rapid sequence endotracheal intubation is the preferred maneuver; relative contraindications include potential injury to the cervical spine, mechanical upper airway obstruction, severe restriction of cervical spine mobility, or severe perioral trauma.

In some cases, nasotracheal intubation remains a valuable technique that may safely be used in the presence of contraindications to endotracheal intubation.

Nasotracheal intubation should be avoided in patients with significant maxillofacial trauma, because intracranial penetration along fracture lines has been reported.

Because of a variety of factors, in some patients, it may not be possible to obtain an airway by endotracheal or nasotracheal intubation. In these patients, BVM ventilation using an oral or a nasal airway (during which time the adequacy of oxygenation should be ensured by continuous pulse oximetry) should occur while one considers alternative techniques for airway control, including use of the laryngeal mask airway (LMA), or needle or surgical cricothyrotomy.

The deflated LMA is inserted blindly into the hypopharynx, where cuff inflation produces an effective proximal and distal seal, with airflow then directed into the trachea. There is somewhat less airway protection from aspiration with the LMA; however, there is enthusiastic support for this device, particularly in settings associated with limited access to the patient, when possible injuries to the cervical spine preclude or complicate patient positioning for endotracheal intubation, or in situations in which early responders are untrained in endotracheal intubation. There is also significantly less risk of the “fatal error” associated with tracheal intubation (continuing to “ventilate” the patient after intubation of the esophagus).

In patients without respiratory effort, immediate intervention is required to establish an airway and provide oxygenation. This should not interrupt chest compression whenever possible.

Begin with BVM ventilation and 100% supplemental oxygen with the assistance of an oral or a nasal airway. When possible, evaluate oxygenation with pulse oximetry. Endotracheal intubation (or consideration of the alternative airway techniques, depending on the specific situation), as discussed, is then indicated, with needle or surgical cricothyrotomy considered alternatives for the patient who can be neither oxygenated nor endotracheally intubated.

Once airway patency is established, patients without adequate spontaneous respiratory effort require artificial ventilation.

When available, a BVM with an oral or a nasopharyngeal airway and supplemental oxygen (100% FiO₂) is preferred to barrier devices and mouth-to-mouth ventilation, and it is more effective.

Effective, sustained BVM ventilation is also preferable to the interrupted ventilation that can occur during multiple failed attempts at endotracheal intubation.

The adequacy of ventilation is assessed by determining that breath sounds are present bilaterally, that an inspiratory increase in chest volume occurs with each inspiration, that skin color improves, and that arterial blood gases or pulse oximetry reflect appropriate oxygenation.

It is also recommended that endotracheal tube (ET) placement be confirmed by nonphysical examination criteria such as capnography or color change CO₂ detectors.

The initial pulse check should take no longer than 10 seconds before initiating chest compressions.

Precordial thumps are no longer recommended but are not discouraged in the patient with pulseless ventricular tachycardia (VT) or ventricular fibrillation (VF).

Chest compressions should begin simultaneously with the establishment of an airway and the initiation of ventilation.

Interruptions in chest compressions should be minimized at all costs.

With the patient placed in a supine position on a hard surface, external cardiac compressions are initiated by placing the heel of one hand over the lower half of the sternum and the heel of the second hand on top of the first hand.

Pressure over the xiphoid process should be avoided.

With the elbows extended, rhythmic compressions should be provided by depressing the sternum 1.5 to 2.0 inches posteriorly in adults.

Compressions should be smooth and should be performed at the rate of approximately 100/min.

The efficacy of external compressions can be checked by palpating the carotid or femoral pulse.

CPR cycles of 30 compressions to 2 breaths via a BVM should continue until the patient is connected to the defibrillator and an advanced airway is established.

Ventilations should be given at a rate of 8 to 10/min during chest compressions once an advanced airway is established.

Initial venous access should be sought in a peripheral vein if possible (e.g., using veins in the antecubital fossa, generally the most accessible peripheral veins).

Intraosseous (IO) access is an increasingly utilized modality in adults and should be considered in any patient in whom large bore peripheral venous access is difficult. This approach involves the use of a specially designed IO needle that is inserted into the proximal anterior tibial bone marrow; the distal femur, the proximal humerus, and distal tibia can also be used. If rapid volume expansion is needed, then fluids can be administered under pump pressure. The major complications of this procedure are tibial fractures, lower extremity compartment syndromes in the case of dislodged needles, and osteomyelitis.

Central venous sites are avoided because of the increased time associated with their placement and the unavoidable interruption of CPR; hand and wrist peripheral IV

sites are also less useful, as is femoral venous catheterization. One must remember that 1 to 2 minutes is required for medications administered at a peripheral site to reach the heart; this is true even when CPR is adequate.

Drugs should be administered by rapid bolus and followed by a 20-mL bolus of fluid.

When venous access is unobtainable, the following medications can be administered via ET tube: lidocaine, epinephrine, atropine, and narcan (LEAN), which are administered in approximately 2- to 2.5-times the recommended dose, first diluted in 10 mL of normal saline and then injected by passing a catheter beyond the tip of the ET.

After injecting the medication, three to four forceful ventilations are provided.

In the past, the use of sodium bicarbonate was encouraged to treat acidosis associated with cardiac arrest; the use of sodium bicarbonate is now discouraged in routine CPR. The rationale for this change involves the lack of evidence supporting the use of this alkali in changing the outcome of routine CPR as well as a number of factors suggesting a negative effect. For example, bicarbonate (1) does not facilitate defibrillation or improve survival in laboratory animals in VF; (2) shifts the oxyhemoglobin saturation curve to the left, inhibiting the release of oxygen to the tissues; (3) produces a paradoxical acidosis in cells, which results from the ability of carbon dioxide, released from sodium bicarbonate, to diffuse freely into cells, depressing cellular function; (4) may inactivate administered catecholamines; and (5) induces a number of other adverse effects caused by systemic alkalosis produced from overvigorous administration. Bicarbonate is therefore not recommended in routine CPR.

In certain specific circumstances, bicarbonate may be of use, but only when the diagnosis on which such therapy is based has been clearly defined. For example, patients with pronounced systemic acidosis associated with renal failure, patients with tricyclic antidepressant overdose, and patients with hyperkalemia documented before arrest may benefit from the prompt administration of bicarbonate.

Bicarbonate can also be considered in patients with prolonged resuscitations, provided tracheal intubation and adequate ventilation have been provided (the administration of bicarbonate to patients with hypercarbic acidosis is harmful), and in patients with restoration of normal circulation after prolonged arrests.

The routine administration of bicarbonate should otherwise, however, be avoided.

Calcium should be used only in arrests associated with hyperkalemia, hypocalcemia, or calcium channel blocker toxicity.

If possible, particularly in profoundly hypotensive patients who have regained pulses, bedside US may provide a clue as to the etiology of the shock (i.e., cardiac tamponade, free fluid in the abdomen suggesting intraabdominal aneurysm rupture, etc.).