In the diving setting, the management of a drowning situation often begins with witnessing a diver become unconscious underwater. Before resuscitation efforts can begin, the victim must be retrieved to the surface. Related considerations were reviewed by the Undersea and Hyperbaric Medical Society (UHMS) Diving Committee1, and their findings are outlined here.
The overarching goal of this initial phase of the rescue is to retrieve the diver to the surface as quickly as possible, even if the victim has a mouthpiece in place and appears to be breathing (which would be a most unusual circumstance). More typically, the victim is found unconscious with the mouthpiece out. No attempt should be made to replace it; however, if the mouthpiece is retained in the mouth, then the rescuer should make an attempt to hold it in place during the ascent. An ascent should be initiated immediately. If there is significant risk to the rescuer in ascending (if the rescuer has a significant decompression obligation), then making the victim buoyant and sending him or her to the surface may be the only option, depending on the degree to which the rescuer wishes to avoid endangering himself or herself.
The committee flagged one exception to the advice to surface immediately. In the situation where a diver is in the clonic phase of a seizure with the mouthpiece retained, then the mouthpiece should be held in place and ascent delayed until the seizure abates. To be clear, however, this does not apply to the more common situation of the seizing diver whose mouthpiece is out. In the latter situation, the ascent should be initiated while the diver is still seizing. This dichotomy arises because of the committee’s perception of the shifting balance of risk between pulmonary barotrauma and drowning in situations where the airway is at least partially protected or not. Thus, where the airway is completely unprotected (mouthpiece not retained), the risk of drowning outweighs the risk of barotrauma imposed by seizure-induced apposition of the glottis tissues. Where the airway is partly protected (mouthpiece retained and held in place), the opposite holds true. This matter is discussed in more detail in the committee report.
At the surface, the victim should be made positively buoyant face-up, and a trained rescuer should attempt to give two mouth-to-mouth rescue breaths. Experience has shown that this is often all that is required to stimulate the victim to breathe. Pausing to give rescue breaths will slightly delay removal from the water for definitive cardiopulmonary resuscitation (CPR) and is therefore a gamble that the victim has not yet having suffered cardiac arrest. However, given the extremely poor outcome expected if a drowning victim suffers a hypoxic cardiac arrest and the time it usually takes to remove a diver from the water, the committee determined that this was a gamble worth taking. The best chance of survival lies in preventing hypoxic cardiac arrest, and establishing oxygenation is the means of such prevention. If the diver has already had a cardiac arrest, then a small extra delay in initiating CPR imposed by performing in-water rescue breaths is not likely to alter the outcome. There is some human evidence suggesting a survival advantage for in-water rescue breathing in non-diving drowning situations2.
Once at the surface and in a situation where the surface support is not immediately to hand, a choice must be made whether to wait for rescue or initiate a tow to shore or nearest surface support. The committee determined that if surface support is less than a 5-minute tow away, then a tow should be commenced with intermittent rescue breaths administered if possible. If surface support or the shore is more than a 5-minute tow away, then the rescuer should remain in place, continuing to administer rescue breaths for 1 minute. If there is no response in this time, then a tow toward the nearest surface support should be initiated without ongoing rescue breaths. These guidelines are summarized in Figure 23.1.
It is notable that these guidelines contain no reference to in-water chest compressions. Although techniques for in-water chest compressions have been described3,4, the committee did not consider there was adequate evidence of efficacy to justify the extra difficulty and stress to the rescuer for their inclusion in the rescue protocol.
The victim should be kept horizontal as much as possible during and after removal from the water. The patient should be moved with the head in the neutral position if cervical spine injury is suspected. Scuba divers are most unlikely to have suffered cervical spine trauma. A basic life support algorithm should be initiated immediately, beginning with assessment of the airway (Figure 23.2).
Vomiting and regurgitation frequently follow a submersion incident. Foreign particulate matter causing upper airway obstruction should be removed manually or later by suction. Obstruction of the upper airway by the tongue is common in the unconscious patient.
Two methods are used to overcome the obstruction:
Head-tilt/chin-lift is accomplished by pushing firmly back on the patient’s forehead and lifting the chin forward by using two fingers under the jaw at the chin. The soft tissues under the chin should not be compressed, and unless mouth-to-nose breathing is to be employed, the mouth should not be completely closed. This technique should be avoided if cervical spine injury is suspected.
Jaw-thrust describes the technique of forward displacement of the lower jaw by lifting it with one hand on either side of the angle of the mandible. Unless cervical spine injury is suspected, this technique is often combined with head-tilt.
Time should not be wasted in trying to clear water from the lower airways. If airway obstruction is encountered and has not responded to normal airway management, the Heimlich manoeuvre (sub-diaphragmatic thrust) has been suggested5. This manoeuvre, which was proposed as a routine step to clear water from the airway, has not received the widespread endorsement of resuscitation councils around the world. It should be used with caution and only as a last resort because of the risks of regurgitation of gastric contents, rupture of the stomach and causing delay in initiating effective ventilation. Persistent airway obstruction may result from a foreign body, but other causes include laryngeal oedema or trauma, bronchospasm and pulmonary oedema.
Respiration can be assessed by placing one’s ear over the victim’s mouth while looking for chest movement, listening for air sounds and feeling for the flow of expired air. If breathing is detected, oxygen should be administered and the victim maintained in the ‘recovery’ position to avoid aspiration of fluid or vomitus.
If breathing is absent, mouth-to-mouth or mouth-to-nose breathing is instituted. Initially, two full breaths of air, with an inspiratory time (for the victim) of 1 to 1.5 seconds, are recommended. For adults, an adequate volume to observe chest movement is about 800 ml. If no chest movement is seen and no air is detected in the exhalation phase, then head-tilt or jaw-thrust manoeuvres should be revised. Failing that, further attempts at clearing the airway with the fingers (only if the victim is unconscious!) should be undertaken. With mouth-to-mouth respiration, the rescuer pinches the victim’s nose and closes it gently between finger and thumb. Mouth-to-nose rescue breathing may be more suitable in certain situations, such as when marked trismus is present or when it is difficult to obtain an effective seal (e.g. injury to mouth, dentures).
Paramedics or other practitioners with advanced skills are likely to use a bag-mask-reservoir device connected to an oxygen source for manual positive pressure ventilation in the field. Useful adjuncts in resolving upper airway obstruction may include a nasopharyngeal airway, oropharyngeal airway or supraglottic airway device such as a laryngeal mask. Endotracheal intubation in the field should be undertaken only by highly trained and experienced practitioners.
The rate of chest inflation should be about 12 per minute (one every 5 seconds) with increased rate and decreased volume in young children.
It must be made clear that the recent advocacy for ‘compression-only CPR’ in which rescue breathing is omitted and first responders provide only chest compressions to victims of community cardiac arrest is not relevant to CPR in the context of drowning.The cause of cardiac arrest in the community is usually some sort of cardiac disease, whereas it is hypoxia in drowning. Compression-only CPR works in community cardiac arrest because the victim is not hypoxic at the onset of cardiac standstill, and the lungs are filled with air to functional residual capacity. In contrast, hypoxia is usually the cause of cardiac arrest in drowning, and the lungs are frequently compromised by aspirated fluid and alveolar collapse. Failing to ventilate the lungs during resuscitation of a drowning victim is likely to bias against a good outcome.
The presence of a carotid or femoral pulse should be sought in the unconscious non-breathing victim. This is often difficult because the patient is usually cold and peripherally vasoconstricted. Although it is possible that external cardiac compression (ECC) could precipitate ventricular fibrillation in a hypothermic patient, if in doubt it is safer to commence ECC than not.
If no carotid pulse is detected, ECC should be commenced after two initial breaths. Higher rates of compression are now recommended, with greater outputs achieved at 100/minute compared with the traditional 60/minute standard. Controversy still exists over the mechanism of flow in external compression, with the evidence for the older ‘direct compression’ model being challenged by the ‘thoracic pump’ theory.
Cardiac compression should be performed with the patient supine on a firm surface. The legs may be elevated to improved venous return. The rescuer kneels to the side of the patient. The heel of the rescuer’s hand should be placed in line with the patient’s sternum. The lower edge of the hand should be about two fingers above the xiphisternum (i.e. compression is of the lower half of the sternum). The second hand should be placed over the first, and the compression of the sternum should be about 4 to 5 centimetres in adults in the vertical plane. To achieve this, the rescuer’s elbow should be straight, with the shoulders directly over the sternum. A single rescuer may be able to achieve rates of only 80/minute because of fatigue, but if several rescuers are present, it may be possible to maintain high rates.
Further help should be sought immediately, by a third person, if possible, without compromising resuscitation efforts.