Respiratory arrest

Cessation of gas exchange in the lungs (respiratory arrest) lasting more than 5 minutes can cause damage to vital organs, especially the brain.

Almost always, cardiac arrest follows if respiratory function cannot be immediately restored.

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Causes respiratory arrests

Respiratory arrest can be caused by airway obstruction, respiratory depression due to neurological and muscular disorders, or drug overdose.

Upper or lower airway obstruction may occur. Children under 3 months of age are usually nasal breathers. Therefore, they may develop upper airway obstruction if their nasal breathing is impaired. At any age, loss of muscle tone due to impaired consciousness may lead to upper airway obstruction due to tongue retraction. Other causes of upper airway obstruction may include blood, mucus, vomit, or a foreign body; spasm or swelling of the vocal cords; inflammation of the laryngopharynx, trachea; tumor or trauma. Patients with congenital developmental disorders often have abnormally developed upper airways that are easily obstructed.

Lower airway obstruction can occur with aspiration, bronchospasm, pneumonia, pulmonary edema, pulmonary hemorrhage, and drowning.

Weakened respiratory pattern due to central nervous system (CNS) disorders may result from drug overdose, carbon monoxide or cyanide poisoning, CNS infection, brainstem infarction or hemorrhage, and intracranial hypertension. Weakness of respiratory muscles may be secondary to spinal cord injury, neuromuscular diseases (myasthenia gravis, botulism, poliomyelitis, Guillain-Barre syndrome), use of drugs that cause neuromuscular block; and metabolic disorders.

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Symptoms respiratory arrests

When breathing stops, the patient's consciousness is impaired, the skin becomes cyanotic (if there is no severe anemia). In the absence of assistance, cardiac arrest occurs within a few minutes after the onset of hypoxia.

Until breathing ceases completely, patients without neurological disorders may be agitated, confused, and struggling to breathe. Tachycardia and sweating may occur; retraction of the intercostal spaces and sternoclavicular joint may be observed. Patients with CNS disease or respiratory muscle weakness may have weak, labored, irregular, or paradoxical breathing. Patients with a foreign body in the airway may cough, choke, and point to their neck.

In infants, especially under 3 months of age, apnea can develop acutely without any alarming prerequisites, as a result of the development of an infectious process, metabolic disorders or high respiratory rate.

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Treatment respiratory arrests

Respiratory arrest does not cause diagnostic difficulties; treatment begins simultaneously with its diagnosis. The most important task is to detect a foreign body that caused the obstruction of the airways. If it is present, mouth-to-mouth or bag-mask breathing will not be effective. A foreign object can be detected during laryngoscopy during tracheal intubation.

Treatment involves removing the foreign body from the respiratory tract, ensuring its patency by any means, and performing artificial ventilation.

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Ensuring and monitoring airway patency

The upper airway should be cleared and air circulation maintained with a mechanical device and/or assisted breaths. There are many indications for airway management. In most situations, a mask can provide adequate ventilation temporarily. If performed correctly, mouth-to-mouth (or mouth-to-mouth-and-nose in infants) ventilation can also be effective.

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Sanitation and maintenance of upper respiratory tract patency

Obstruction due to weakness of the soft tissues of the oropharynx may be temporarily relieved by neck extension (head tilt) and jaw thrust; these maneuvers elevate the tissues of the anterior neck and free up the space between the tongue and the posterior pharyngeal wall. Obstruction of the oropharynx by a denture or other foreign body (blood, secretions) may be relieved by fingers or aspiration, but be aware of the danger of their displacement into the depths (this is more likely in infants and young children, for whom this maneuver “blindly” with a finger is contraindicated). Material that has penetrated deeper may be removed with Magill forceps during laryngoscopy.

Heimlich method. The Heimlich method (manual push in the epigastric region, in pregnant and obese people - on the chest) is a method of controlling the patency of the airways in patients in a conscious, shocked or unconscious state, when other methods have failed.

An unconscious adult is placed on his back. The operator sits on top of the patient's knees. To avoid damage to the liver and chest organs, the hand should never be placed on the xiphoid process or the lower costal arch. The thenar and hypothenar of the palm are located in the epigastrium below the xiphoid process. The second hand is placed on top of the first and a strong push is applied in an upward direction. For chest thrusts, the hands are positioned as for closed cardiac massage. With both methods, 6 to 10 quick, strong thrusts may be required to remove the foreign body.

If a foreign body is present in the respiratory tract of a conscious adult patient, the operator stands behind the patient, clasps the patient with his hands so that the fist is located between the navel and the xiphoid process, and the other palm clasps the fist. With both hands, push inward and upward.

In older children the Heimlich method can be used, however for children weighing less than 20 kg (usually under 5 years) very moderate force must be applied.

The Heimlich method is not used for infants under one year of age. The infant must be held head down, supporting the head with one hand, while another person delivers 5 blows to the back. Then 5 chest thrusts must be delivered, with the infant lying on his back, head down, on the rescuer's thigh. The sequence of back blows and chest thrusts is repeated until the airway is cleared.

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Airways and breathing devices

If there is no spontaneous breathing after clearing the airways and there are no devices, mouth-to-mouth or mouth-to-mouth-and-nose breathing must be performed to save the victim's life. Exhaled air contains 16 to 18% O2 and 4 to 5% CO2 - this is enough to maintain adequate levels of O2 and CO2 in the blood.

The bag-valve-mask (BVM) device has a breathing bag with a valve that prevents air recirculation. This device is not able to maintain airway patency, so patients with low muscle tone require additional devices to maintain airway patency. BVM ventilation can be continued until naso- or orotracheal intubation of the trachea is performed. Supplemental oxygen can be supplied with this device. If BVM ventilation is performed for more than 5 minutes, cricoid pressure should be applied to occlude the esophagus to prevent air from entering the stomach.

Situations requiring airway management

Critical	Urgent
Heart failure	Respiratory failure
Respiratory arrest or apnea (for example, due to CNS diseases, hypoxia, medication use) Deep coma with tongue retraction and airway obstruction Acute laryngeal edema	Need for respiratory support (e.g., acute respiratory distress syndrome, exacerbation of COPD or asthma, extensive infectious and non-infectious lung tissue lesions, neuromuscular diseases, respiratory center depression, excessive fatigue of the respiratory muscles)
Laryngospasm Foreign body in the larynx	Need for respiratory support in patients in shock, with low cardiac output or myocardial injury
Drowning Inhalation of smoke and toxic chemicals	Before gastric lavage in patients with oral drug overdose and impaired consciousness
Respiratory tract burn (thermal or chemical) Aspiration of gastric contents	With very high O2 consumption and limited respiratory reserves (peritonitis)
Upper respiratory tract injury	Before bronchoscopy in patients in serious condition
Injury to the head or upper spinal cord	When performing diagnostic radiographic procedures on patients with impaired consciousness, especially under sedation

A naeogastric tube is inserted to evacuate air from the stomach, which will inevitably enter there during MCM ventilation. Pediatric breathing bags have a valve that limits the peak pressure created in the airways (usually at a level of 35 to 45 cm H2O).

Oropharyngeal or nasal airways prevent airway obstruction caused by soft tissue. These devices facilitate ventilation with the ICM, although they may cause gagging in conscious patients. The size of the oropharyngeal airway should correspond to the distance between the angle of the mouth and the angle of the mandible.

The laryngeal mask is placed in the lower parts of the oropharynx. Some models have a channel through which an intubation tube can be passed into the trachea. This method causes minimal complications and is very popular due to the fact that it does not require laryngoscopy and can be used by minimally trained personnel.

The double-lumen tracheal esophageal tube (combitube) has a proximal and distal balloon. It is inserted blindly. It usually enters the esophagus, in which case ventilation is performed through one opening. If it enters the trachea, the patient is ventilated through the other opening. The technique for inserting this tube is very simple and requires minimal preparation. This technique is unsafe for long-term use, so it is necessary to intubate the trachea as soon as possible. This method is used only at the prehospital stage as an alternative in case of an unsuccessful attempt at tracheal intubation.

The endotracheal tube is crucial in cases of airway damage, to prevent aspiration and mechanical ventilation. It is used to sanitize the lower airways. When installing an endotracheal tube, laryngoscopy is necessary. Tracheal intubation is indicated for patients in a coma and those requiring prolonged mechanical ventilation.

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Endotracheal intubation

Before tracheal intubation, it is necessary to ensure airway patency, ventilation and oxygenation. Orotracheal intubation is preferable in severely ill patients and in cases of apnea, as it is performed more quickly than nasotracheal intubation. Nasotracheal tracheal intubation is more often used in patients with preserved consciousness, spontaneous breathing, when comfort is a priority.

Large endotracheal tubes have high-volume, low-pressure cuffs that minimize the risk of aspiration. Cuffed tubes are used in adults and children over 8 years of age, although they may be used in infants and young children in some cases. For most adults, tubes with an internal diameter equal to or greater than 8 mm are suitable and are preferable to smaller diameter tubes. They have lower resistance to airflow, allow passage of a bronchoscope, and facilitate weaning from mechanical ventilation. The cuff is inflated with a 10 ml syringe, and then the cuff pressure is set with a manometer to be less than 30 cm H2O. For children under 6 months, the tube diameter is 3.0-3.5 mm; from 6 months to 1 year - 3.5-4.0 mm. For children over 1 year, the tube size is calculated by the formula (age in years + 16)/4.

Before intubation, the uniform inflation of the cuff and the absence of air leaks are checked. For conscious patients, lidocaine inhalation makes the procedure more comfortable. Sedation, vagolytic drugs, and muscle relaxants are used in both adults and children. A straight or curved laryngoscope blade can be used. A straight blade is preferable for children under 8 years of age. The technique for visualizing the glottis is slightly different for each blade, but in any case it should allow for its clear visualization, otherwise esophageal intubation is likely. To facilitate visualization of the glottis, pressure on the cricoid cartilage is recommended. In pediatric practice, it is always recommended to use a removable guidewire for the endotracheal tube. After orotracheal intubation, the guidewire is removed, the cuff is inflated, a mouthpiece is installed, and the tube is fixed with a plaster to the corner of the mouth and upper lip. An adapter is used to connect the tube to a breathing bag, T-shaped humidifier, oxygen source, or ventilator.

With correct placement of the endotracheal tube, the chest should rise evenly during manual ventilation, breathing should be symmetrical on both sides during auscultation of the lungs, and there should be no extraneous noise in the epigastrium. The most reliable way to determine the correct position of the tube is to measure the concentration of CO2 in the exhaled air; its absence in a patient with preserved blood circulation indicates esophageal intubation. In this case, it is necessary to intubate the trachea with a new tube, after which the previously installed tube is removed from the esophagus (this reduces the likelihood of aspiration when removing the tube and the occurrence of regurgitation). If breathing is weakened or absent above the surface of the lungs (usually the left), the cuff is deflated and the tube is pulled by 1-2 cm (0.5-1 cm in thoracic patients) under constant auscultatory control. With correct placement of the endotracheal tube, the centimeter mark at the level of the incisors or gums should correspond to three times the size of the internal diameter of the tube. X-ray examination after intubation confirms the correct position of the tube. The end of the tube should be 2 cm below the vocal cords but above the bifurcation of the trachea. Regular auscultation of both lungs is recommended to prevent tube displacement.

Additional devices can facilitate intubation in severe situations (cervical spine injury, massive facial trauma, respiratory tract malformations). Sometimes a lighted guide is used; when the tube is positioned correctly, the skin above the larynx begins to light up. Another method is retrograde passage of a guide through the skin and cricothyroid membrane into the mouth. Then, an endotracheal tube is inserted into the trachea along this guide. Another method is tracheal intubation using a fiberscope, which is passed through the mouth or nose into the trachea, and then an intubation tube slides down it into the trachea.

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Nasotracheal intubation

Nasotracheal intubation can be performed in a patient with preserved spontaneous breathing without laryngoscopy, which may be necessary in a patient with a cervical spine injury. After local anesthesia of the nasal mucosa and through it, a tube is slowly advanced to a position above the larynx. On inspiration, the vocal cords are separated and the tube is quickly advanced into the trachea. However, due to anatomical differences in the airways, this method is not generally recommended.

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Surgical methods for restoring airway patency

If a foreign body or massive trauma has caused obstruction of the upper airway or ventilation has not been restored by other means, surgical methods must be used to restore airway patency.

Cricothyrotomy should be used only in emergency situations. The patient lies supine, a bolster is placed under the shoulders, and the neck is extended. After treating the skin with antiseptics, the larynx is held with one hand, an incision is made in the skin, subcutaneous tissues, and cricothyroid membrane with a blade exactly along the midline to the entrance to the trachea. A tracheostomy tube of the appropriate size is passed through the opening into the trachea. In outpatient settings, in case of a life-threatening situation, any suitable hollow tube can be used to restore air passage. If other equipment is unavailable, a 12G or 14G intravenous catheter can be used. While holding the larynx with your hand, the catheter is passed through the cricothyroid membrane along the midline. An aspiration test can reveal damage to large vessels; when conducting an aspiration test into the lumen of the trachea, one must remember about the possibility of perforation of the posterior wall of the trachea. The correct position of the catheter is confirmed by aspiration of air through it.

Tracheostomy is a more complex procedure. It must be performed by a surgeon in the operating room. In emergency situations, tracheostomy has more complications than cricothyrotomy. If a prosthetic breathing is needed for more than 48 hours, tracheostomy is preferable. An alternative for seriously ill patients who cannot be taken to the operating room is percutaneous puncture tracheostomy. The tracheostomy tube is inserted after puncturing the skin and sequentially inserting one or more dilators.

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Complications of intubation

During tracheal intubation, the lips, teeth, tongue, epiglottis, and laryngeal tissues can be damaged. Esophageal intubation under mechanical ventilation can lead to gastric distension (rarely, rupture), regurgitation, and aspiration of gastric contents. Any endotracheal tube causes vocal cord distension. Laryngeal stenosis may develop later (usually in the 3rd or 4th week). Rare complications of tracheostomy may include bleeding, thyroid damage, pneumothorax, damage to the recurrent nerve, and major vessels.

Rare complications of intubation include hemorrhages, fistulas and tracheal stenosis. High pressure in the cuff of the endotracheal tube may cause erosions on the tracheal mucosa. Correctly selected tubes with large-volume and low-pressure cuffs and regular monitoring of cuff pressure can reduce the risk of ischemic necrosis.

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Drugs used in intubation

In cases of apnea without a pulse or consciousness, intubation can (and should) be performed without premedication. For other patients, premedication is required to facilitate intubation and minimize discomfort during the procedure.

Premedication. If the patient's condition allows, pre-oxygenation with 100% 0 ₂ for 3-5 minutes is performed; this will ensure sufficient oxygenation during apnea for 4-5 minutes.

Laryngoscopy causes sympathetic activation, with an increase in heart rate, arterial pressure, and probably intracranial pressure. To attenuate this response, lidocaine 1.5 mg/kg is given intravenously 1 to 2 minutes before sedation and myoplegia. In children and adults, a vagal response (marked bradycardia) is common during intubation, so atropine 0.02 mg/kg is given intravenously (at least 0.1 mg in infants; 0.5 mg in children and adults). Some clinicians premedicate with a small amount of a muscle relaxant, such as vecuronium 0.01 mg/kg intravenously in patients over 4 years of age, to prevent muscle fasciculations caused by the full dose of succinylcholine. Muscle pain and transient hyperkalemia may occur on awakening as a result of fasciculations.

Sedation and analgesia. Laryngoscopy and intubation cause discomfort, so short-acting sedatives or sedative-analgesics are administered intravenously immediately before the procedure. After that, the assistant presses on the cricoid cartilage (Sellick maneuver), clamps the esophagus to prevent regurgitation and aspiration.

Etomidate 0.3 mg/kg (a nonbarbiturate hypnotic, preferred) or fentanyl 5 mcg/kg (2-5 mcg/kg in children, exceeding the analgesic dose), an opioid (analgesic and sedative) that is effective without causing cardiovascular depression, may be used. However, chest rigidity may develop at high doses. Ketamine 1-2 mg/kg is an anesthetic with cardiac stimulant action. This drug may cause hallucinations or inappropriate behavior on awakening. Thiopental 3-4 mg/kg and methohexital 1-2 mg/kg are effective but cause hypotension.

Myoplegia. Relaxation of skeletal muscles significantly facilitates tracheal intubation.

Succinylcholine (1.5 mg/kg IV, 2.0 mg/kg in infants), a depolarizing muscle relaxant, has a rapid onset (30 sec to 1 min) and short duration (3 to 5 min). It is generally not used in patients with burns, muscle crush injuries (more than 1 to 2 days old), spinal cord injury, neuromuscular disease, renal failure, and possibly penetrating eye injury. Malignant hyperthermia may occur in 1/15,000 cases of succinylcholine administration. In children, succinylcholine should be used with atropine to prevent severe bradycardia.

Non-depolarizing muscle relaxants have a longer duration (more than 30 min) and a slower onset of action. These include Atracurium 0.5 mg/kg, Mivacurium 0.15 mg/kg, Rocuronium 1.0 mg/kg, Vecuronium 0.1-0.2 mg/kg, which are administered over 60 s.

Local anesthesia. Intubation of conscious patients requires anesthesia of the nasal passages and pharynx. Ready-to-use aerosols of Benzocaine, Tetracaine, Butyl Aminobenzoate, and Benzalkonium are commonly used. Alternatively, 4% lidocaine can be aerosolized through a face mask.

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