WEBVTT

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This is an experiment in rescue breathing designed to study the influence of curare

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and other relaxant drugs on the selection of method of expired air resuscitation.

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We shall illustrate.

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Volunteers were anesthetized with barbiturates, belladonna, and opiates by vein and nitrous

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oxide by mask.

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The intravenous drugs were given to stop breathing by purposely elevating the volunteers carbon

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dioxide threshold.

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Resuscitations were tried with and then without the flaxid paralysis of curare or succinyl

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choline.

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To safeguard the condition of the anesthetized volunteer, mechanical ventilation with 40%

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oxygen was used before resuscitation trials.

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Hypoxia was avoided by limiting trials to two minutes.

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This is a new pickup devised for continuous measurements of tracheal airflow and gas

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concentrations.

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A standard tracheal tube was cut away so as to leave only its cuffed tip in which was

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built a flow meter.

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Fine polyethylene tubes lead to a mass spectrometer for oxygen measurements, a Liston-Becker

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analyzer for carbon dioxide, a Harvard transducer for flow, and a strain gauge for pressure.

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These determinations were recorded continuously on a Sanborn polyviso.

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Watch the right side of the tracing for the arrows.

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This tracing shows in order from above downward the respired oxygen and carbon dioxide concentrations,

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the airflow, and the pressure in the trachea.

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Now look at the upper left hand corner.

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With each respiratory cycle, the oxygen concentration falls from 43% in the inspired air to 40%

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in the alveolar air.

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The alveolar carbon dioxide concentration is shown with each breath, and during this

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brief period of hyperventilation falls from 6.5 to 5.5%.

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Peak air flow as produced by the mechanical ventilator is over 60 liters per minute during

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each inspiration.

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Endotracheal peak pressure here is 15 centimeters of water.

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The carbon dioxide and oxygen traces lag 6 tenths and 10 seconds respectively behind

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flow and pressure because of travel time in the catheters.

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The middle part of the tracing is recorded at slower chart speed than the two ends, one

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millimeter instead of 10 millimeters per second.

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Here is a model showing the tracheal pickup placed between the larynx and the carina after

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topical anesthesia with lidocaine.

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An ordinary tracheal tube, the white one, rests with its tip just through the vocal

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cords prior to the resuscitation trials.

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The tracheal pickup imposes minimal distortion in the upper airway.

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It avoids the pitfall of a guaranteed open airway provided by a tracheal tube.

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Unlike a mask or a mouthpiece, it can be secured in place without encumbering the jaw.

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Removal of the conventional tube leaves the tracheal pickup in place and the upper airway

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unsupported and undistorted.

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Three flexible plastic catheters about two millimeters in diameter traverse the upper

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airway.

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These catheters are tied to a narrow strip of the tracheal tube.

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150 cc of gas per minute are aspirated from the trachea for carbon dioxide analysis and

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an aliquot for oxygen analysis.

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The other two catheters are used for flow and pressure measurements.

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While the volunteer is still paralyzed by succinylcholine, the white tracheal tube is

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removed, leaving only the catheters from the tracheal pickup within the upper airway.

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Extubation must be cautious to avoid disturbing the tracheal pickup.

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As soon as ventilation with 40% oxygen is stopped, the interval timer is set for two minutes.

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Now for a trial of mouth-to-mouth breathing.

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Note how relaxed and mobile the volunteer's jaw remains during succinylcholine infusion.

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It is easy to open the mouth and pull the jaw forward.

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The thorax is very compliant, permitting high peak flows with low pressures.

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Note the good chest expansion, typical of the relaxed volunteer.

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In fact, ventilation is so efficient that the reserve oxygen supply in the patient's lung is washed out within eight breaths.

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This oxygen washout down to 20% is illustrated in the top tracing.

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Note in the second tracing that the rescuer's alveolar carbon dioxide value appears as the shoulder just preceding the victim's alveolar plateau value.

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During this sequence, the rescuer's carbon dioxide concentration was 4.5%, while that of the paralyzed volunteer was 6.3%.

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The peak flows here are about 90 liters per minute during inspiration, requiring 15 to 20 centimeters of water pressure.

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Similarly, in the subject receiving relaxant drugs, it is easy to insert an S-tube like this one.

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Either end may be used, depending upon the size of the victim.

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Again, the rescuer encounters little difficulty inflating large volumes at low pressure.

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Even when leakage occurs around the tube, adequate ventilation is achieved.

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The record confirms the delivery of satisfactory tidal volumes.

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The small excursions in the initial oxygen and carbon dioxide traces during apnea are not related to artificial respiration, but rather to the heartbeat.

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In the last respiratory cycle, alveolar oxygen is 20% and alveolar carbon dioxide is 6%.

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Now we will shut off the succinylcholine infusion, and all subsequent resuscitation will be attempted without the benefit of relaxant drugs.

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Now apnea will be sustained by the prolonged effect of opiate and barbiturate drugs, and oxygenation will be assured by repeated ventilation with 40% oxygen or higher.

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The effects of succinylcholine were allowed to wear off for 30 minutes, while oxygenation was ensured with a mechanical ventilator.

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Excessive ventilation was avoided, maintaining the volunteer's carbon dioxide at levels consistent with mild asphyxia.

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Now that the volunteer is no longer flexed, the foregoing maneuvers will be repeated.

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The first step of opening the volunteer's mouth or insertion of the thumb fails.

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His lips are mobile, but he promptly clenches his teeth.

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Now airway insertion is no longer possible in a non-paralyzed volunteer.

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When the teeth are clenched, the rescuer can't blow through the mouth because the tongue blocks it.

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Even when the thumb can be forcibly inserted, injury by sharp teeth is a possible hazard.

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During such a period of apnea, the cardiac effects are again noted, and with the first breath by the ventilator,

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the alveolar oxygen concentration was over 40%, more than twice normal,

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but the alveolar carbon dioxide had reached an early asphyxia level of 7.2% in 25 seconds.

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Here we have hypercapnea without hypoxia.

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Now another rescuer will try the mouth-to-mouth method, but the teeth are clenched because the jaw muscles are still contracted.

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One alternative for mouth-to-mouth breathing is to hold the mandible in this manner,

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to open the jaw and lips, and then to blow through the mouth.

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But the mouth-to-mouth method, or the use of an S-tube, depend on a patent oral air passage.

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If jaw muscles are contracted and the teeth cannot be separated, it becomes impossible to insert a tube.

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Time for the ventilator again. The next trial will utilize the nose.

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Although the jaw muscles are contracted, the head can still be tilted back,

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and the mandible can be elevated sufficiently to prevent blockage by the tongue in the posterior pharynx.

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Bilateral lifting at the angles of the jaw can be effectively applied even when neither thumb nor an airway can be inserted between the teeth.

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In this and in other volunteers, mouth-to-nose breathing has consistently yielded satisfactory results.

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In every instance in which excessive muscle tone prevented access to the mouth for ventilation, mouth-to-nose breathing was successful.

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Airway obstruction was easily overcome by lifting the jaw when the nasal passages were used in this manner in 20 anesthetized patients.

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Here is the record. Pulmonary ventilation by mouth-to-nose equals or exceeds that by procedures tried so far.

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After eight breaths, the oxygen washout reached 20 percent. The carbon dioxide fell from 7 to 6.5 percent.

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Peak flows reached 50 liters per minute, but required pressures approaching 30 centimeters of water.

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These higher pressures are correlated with the reduced compliance of the non-paralyzed volunteers thorax.

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But the simple mouth-to-nose procedure must be one alternative in any teaching of expired air resuscitation.

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Note the diminished expansion of the chest since succinylcholine has worn off.

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Exaggerated lift of the chest is routinely observed when these studies utilize a paralyzed volunteer.

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Mouth-to-nose breathing does not actually require direct contact.

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The use of a handkerchief has been suggested for practice purposes upon conscious volunteers.

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Dr. Ralph Waters described this version 15 years ago.

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For some, the barrier may make the procedure more acceptable.

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It is important for the rescuer to blow with his mouth widely opened.

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An auronasal mask is equally suited to the challenge of the clenched jaw.

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This soft vinyl folding resuscitation mask covers the nose and mouth of a child or adult

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and thereby makes use of the nasal air passage or the oral air passage or both.

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Watch the chest. No tube is in the mouth.

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It is imperative under these circumstances that the jaw be lifted and the head tilted back as in the mouth-to-nose technique.

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A snug fit of the mask is usually obtained by thumbs and forefingers held along the sides of the mask.

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As in all methods of expired air resuscitation, air may be blown into the stomach.

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Be sure to watch for regurgitation of stomach contents during its decompression.

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In our series with non-flaxid victims, excessive gastric dilatation has not been a problem.

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It should be emphasized that the mask using the nasal passage sometimes works when an S-tube cannot be inserted.

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Either a mask or an S-tube enables the rescuer to see the chest rise.

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The S-tube is a non-flaxid victim.

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