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Respiratory arrest is a sickness caused by
apnea Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there ma ...
(cessation of breathing) or respiratory dysfunction severe enough it will not sustain the body (such as
agonal breathing Agonal respiration, gasping respiration or agonal breathing is a distinct abnormal pattern of breathing and brainstem reflex characterized by gasping, labored breathing, accompanied by strange vocalizations and myoclonus. Possible causes include ...
). Prolonged apnea refers to a patient who has stopped breathing for a long period of time. If the heart muscle contraction is intact, the condition is known as respiratory arrest. An abrupt stop of pulmonary
gas exchange Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a ...
lasting for more than five minutes may permanently damage vital organs, especially the
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
. Lack of
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
to the brain causes loss of
consciousness Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...
. Brain injury is likely if respiratory arrest goes untreated for more than three minutes, and
death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
is almost certain if more than five minutes. Damage may be reversible if treated early enough. Respiratory arrest is a life-threatening
medical emergency A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified ...
that requires immediate medical attention and management. To save a patient in respiratory arrest, the goal is to restore adequate ventilation and prevent further damage. Management interventions include supplying oxygen, opening the
airway The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose t ...
, and means of artificial ventilation. In some instances, an impending respiratory arrest could be predetermined by signs the patient is showing, such as the increased work of breathing. Respiratory arrest will ensue once the patient depletes their oxygen reserves and loses the effort to breathe. Respiratory arrest should be distinguished from respiratory failure. The former refers to the complete cessation of breathing, while respiratory failure is the inability to provide adequate ventilation for the body's requirements. Without intervention, both may lead to decreased oxygen in the blood ( hypoxemia), elevated carbon dioxide level in the blood (
hypercapnia Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous p ...
), inadequate oxygen perfusion to tissue ( hypoxia), and may be fatal. Respiratory arrest is also different from
cardiac arrest Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possi ...
, the failure of heart muscle contraction. If untreated, one may lead to the other.


Signs and symptoms

One common symptom of respiratory arrest is
cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...
, a bluish discoloration of the skin resulting from an inadequate amount of oxygen in the blood. If respiratory arrest remains without any treatment, cardiac arrest will occur within minutes of hypoxemia,
hypercapnia Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous p ...
or both. At this point, patients will be unconscious or about to become unconscious. Symptoms of respiratory compromise can differ with each patient. Complications from respiratory compromise are increasing rapidly across the clinical spectrum, partly due to expanded use of
opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...
s combined with the lack of standardized guidelines among medical specialties. While respiratory compromise creates problems that are often serious and potentially life-threatening, they may be prevented with the proper tools and approach. Appropriate patient monitoring and therapeutic strategies are necessary for early recognition, intervention and treatment.


Causes

*
Airway obstruction Airway obstruction is a blockage of respiration in the airway that hinders the free flow of air. It can be broadly classified into being either in the upper airway (UPA) or lower airway (LOA). Airway obstruction is a life-threatening condition ...
: Obstruction may occur in the upper and lower airway. **Upper airway: Obstruction of the upper airway is common in infants less than 3 months old because they are nose breathers. Nasal blockage may easily lead to upper airway obstruction in infants. For other ages, upper airway obstruction may occur from a foreign body or
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
of the pharynx, larynx, or trachea. In cases of decreased or total loss of consciousness, the tongue can lose muscle tone and obstruct the upper airway. Other potential causes of obstruction include tumors of the upper respiratory tract ( oral cavity,
pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
,
larynx The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
), bodily fluids (blood, mucus, vomit), and trauma to the upper airway. The most common type of tumor of upper respiratory tract is squamous cell carcinoma, with the greatest risk factors for this condition being alcohol and tobacco use, with
HPV Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...
(genotype 16) being another important risk factor. An epidemiological study of over 5 million cases of head and neck trauma in the United States resulting in visits to the emergency department found that the majority occur due to falls or blunt force, with foreign body injuries being more common in the pediatric population. **Lower airway: may occur from bronchospasm, drowning, or airspace filling disorders (e.g.
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severit ...
,
pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is due ...
,
pulmonary hemorrhage Pulmonary hemorrhage (or pulmonary haemorrhage) is an acute bleeding from the lung, from the upper respiratory tract and the trachea, and the pulmonary alveoli. When evident clinically, the condition is usually massive.
). Obstructive conditions of the lower airway, including severe
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...
or COPD episodes, can also lead to respiratory arrest. During these episodes, known as exacerbations, airway resistance is increased due to inflammatory changes in the lungs. This leads to increased work of breathing and decreased oxygen delivery to tissue. In asthma, this involves bronchiolar constriction whereas in COPD this involves small airway collapse during expiration and subsequent air-trapping. One of the ways the body attempts to compensate for these increased respiratory demands is by increasing respiratory rate, which in turn worsens respiratory muscle fatigue of the diaphragm and can eventually lead to respiratory arrest and death without timely medical intervention. *Decreased respiratory effort: Central nervous system impairment leads to decreased respiratory effort. The respiratory center of the brain is located in the pons and medulla and is primarily driven by elevated carbon dioxide levels in the blood (
hypercapnia Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous p ...
) with decreased oxygen levels ( hypoxemia) serving as a less potent stimulus. Central nervous system disorders, such as
stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...
and tumors, may cause hypoventilation. Drugs may decrease respiratory effort as well, such as opioids, sedative-hypnotics, and alcohol. These lower respiratory drive by blunting the response of the respiratory center of the brain to hypercapnia.
Metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter t ...
s could also decrease respiratory effort.
Hypoglycemia Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose bel ...
and
hypotension Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the di ...
depress the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
and compromise the respiratory system. *Respiratory muscle weakness: Neuromuscular disorders may lead to respiratory muscle weakness, such as
spinal cord injury A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...
,
neuromuscular disease A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and wea ...
s, and neuromuscular blocking drugs. Respiratory muscle fatigue can also lead to respiratory muscle weakness if patients breathe over 70% of their maximum voluntary ventilation. Breathing over an extended period of time near maximum capacity can cause metabolic acidosis or hypoxemia, ultimately leading to respiratory muscle weakness.


Diagnosis

Diagnosis requires clinical evaluation, as detailed below.


Initial assessment

After determining the scene is safe, approach the patient and attempt to converse with him or her. If the patient responds verbally, you have established that there is at least a partially patent airway and that the patient is breathing (therefore not currently in respiratory arrest). If the patient is unresponsive, look for chest rise, which is an indicator of active breathing. A sternal rub is sometimes used to further assess for responsiveness. Initial assessment also involves checking for a pulse, by placing two fingers against the
carotid artery Carotid artery may refer to: * Common carotid artery, often "carotids" or "carotid", an artery on each side of the neck which divides into the external carotid artery and internal carotid artery * External carotid artery, an artery on each side of ...
,
radial artery In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm. Structure The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of the f ...
, or
femoral artery The femoral artery is a large artery in the thigh and the main arterial supply to the thigh and leg. The femoral artery gives off the deep femoral artery or profunda femoris artery and descends along the anteromedial part of the thigh in the f ...
to ensure this is purely respiratory arrest and not cardiopulmonary arrest. Checking a pulse after encountering an unresponsive patient is no longer recommended for non-medically trained personnel. Once one has determined that the patient is in respiratory arrest, the steps below can help to further identify the cause of the arrest.


Clearing and opening the upper airway

The first step to determining the cause of arrest is to clear and open the upper airway with correct head and neck positioning. The practitioner must lengthen and elevate the patient's neck until the
external auditory meatus The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter. Str ...
is in the same plane as the sternum. The face should be facing the ceiling. The mandible should be positioned upwards by lifting the lower jaw and pushing the mandible upward. These steps are known as head tilt, chin lift, and jaw thrust, respectively. If a neck or spinal injury is suspected, the provider should avoid performing this maneuver as further nervous system damage may occur. The cervical spine should be stabilized, if possible, by using either manual stabilization of the head and neck by a provider or applying a C-collar. The C-collar can make ventilatory support more challenging and can increase intracranial pressure, therefore is less preferable than manual stabilization. If a foreign body can be detected, the practitioner may remove it with a finger sweep of the oropharynx and suction. It is important that the practitioner does not cause the foreign body to be lodged even deeper into the patient's body. Foreign bodies that are deeper into the patient's body can be removed with Magill forceps or by suction. A
Heimlich maneuver Abdominal thrusts, also known as the Heimlich maneuver or Heimlich manoeuvre, is a first aid procedure used to treat upper airway obstructions (or choking) by foreign objects. American doctor Henry Heimlich is often credited for its creation. ...
can also be used to dislodge the foreign body. The Heimlich maneuver consists of manual thrusts to the upper abdomen until the airway is clear. In conscious adults, the practitioner will stand behind the patient with arms around the patient's midsection. One fist will be in a clenched formation while the other hand grabs the fist. Together, both hands will thrust inward and upward by pulling up with both arms.


Treatment

Treatment varies depending on the cause of respiratory arrest. In many cases, it is necessary to establish an alternate airway and providing artificial ventilation that can include modes of mechanical ventilation. There are many ways to provide an airway and to deliver breathing support. The list below includes several options.


Opioid-overdose

Opioid overdose remains a major cause of death with an increase in rate of death by 12% in the United States from 2016 to 2017. In cases of overdose leading to respiratory arrest, the recommended treatment according to the 2015 American Heart Association guidelines is to administer intramuscular or intranasal naloxone at an initial dose of 0.04-0.4 mg. Dosing may be repeated up to 2 mg if initial dose is ineffective. Special consideration must be taken in individuals with opioid dependency as naloxone administration can induce severe opioid withdrawal, hence the recommended starting doses above. Goal of naloxone therapy is to restore respiratory drive in the individual, however mechanical ventilation may still be necessary during initial resuscitation.


Bag-valve-mask (BVM) ventilation devices

Resistance to
bag valve mask A bag valve mask (BVM), sometimes known by the proprietary name Ambu bag or generically as a manual resuscitator or "self-inflating bag", is a hand-held device commonly used to provide positive pressure ventilation to patients who are not breathin ...
may suggest presence of a foreign body that is obstructing airways and commonly used as a diagnostic tool and treatment for respiratory arrest. The bag-valve-mask device has a self-inflating bag with a soft mask that rests on the face. When the bag is connected to an oxygen supply, the patient will receive 60 to 100% of inspired oxygen. The purpose of bag-valve-mask is to provide adequate temporary ventilation and allow the body to achieve airway control by itself. However, if the bag-valve-mask is left on for more than five minutes, air may be introduced into the stomach. At that point, a nasogastric tube should be inserted to take the accumulated air out. During this process, practitioners must carefully position and maneuver the bag-valve-mask in order to keep airways open. To ensure an adequate seal when using the bag valve mask to ventilate, specific hand positioning is typically used. The provider places his or her thumb and index finger in a 'C' shape on top of the mask and grips the jaw under the mask with the other three fingers, creating an 'E' shape. The thumb and index finger provide downward pressure on the mask while the remaining fingers maintain head tilt and jaw thrust. The free hand can then be used to provide ventilation via the bag. For children, pediatric bags can be used. Pediatric bags have a valve that limits peak airway pressures to around 35–40 cm of water. Practitioners must tweak valve settings to accurately determine each of their patients to avoid hypoventilation or hyperventilation. When applying ventilation with the bag valve mask, the provider should apply just enough pressure to bag to see a chest rise. Providing excessive bag pressure can actually impair the blood flow to the heart and brain, so during
CPR Cardiopulmonary resuscitation (CPR) is an emergency procedure consisting of chest compressions often combined with artificial ventilation in an effort to manually preserve intact brain function until further measures are taken to restore spont ...
extra caution should be taken to limit size of
tidal volume Tidal volume (symbol VT or TV) is the volume of air moved into or out of the lungs during a normal breath. In a healthy, young human adult, tidal volume is approximately 500 ml per inspiration or 7 ml/kg of body mass. Mechanical vent ...
. The rate of manual ventilation should not exceed 12 times per minute, or one ventilation every 5 seconds as to avoid hyperventilation.


Airway patency devices

An
oropharyngeal The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struct ...
or
nasopharyngeal airway In medicine, a nasopharyngeal airway, also known as an NPA, nasal trumpet (because of its flared end), or nose hose, is a type of ''airway adjunct'', a tube that is designed to be inserted through the nasal passage down into the posterior pharynx ...
is used during bag-valve-mask ventilation to prevent soft tissues from blocking the airway. An oropharyngeal airway may cause gagging and vomiting. Therefore, an oropharyngeal airway must be sized appropriately. An airway that is incorrectly sized can worsen the airway obstruction. The distance measured should be from the corner of the patient's mouth to the angle of the jaw or earlobe.


Laryngeal mask airways

The laryngeal mask airway (LMA) is a tube with an inflatable cuff. A laryngeal mask airway can be positioned in the lower oropharynx to prevent airway obstruction by soft tissues and to create a safe channel for ventilation. The laryngeal mask airway is the standard rescue ventilation when endotracheal intubation cannot be accomplished. To insert the laryngeal mask airway into the patient, the deflated mask should be pressed against the hard palate, rotated past the base of the tongue, and reaching the pharynx. Once the mask has been placed in the correct position, the mask can be inflated. Some benefits of the laryngeal mask airway include minimization of gastric inflation and protection against regurgitation. A potential problem the laryngeal mask airway poses is that over inflation will make the mask more rigid and less able to adapt to the patient's anatomy, compressing the tongue and causing tongue edema. In that case, the mask pressure should be lowered or a larger mask size should be used. If non-comatose patients are given muscle relaxants before the insertion of the laryngeal mask airway, they may gag and aspirate when the drugs are worn off. At that point, the laryngeal mask airway should be removed immediately to eliminate the gag response and buy time to start at new alternative intubation technique.


Endotracheal intubation

A
tracheal tube A tracheal tube is a catheter that is inserted into the trachea for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate exchange of oxygen and carbon dioxide. Many different types of tracheal tubes are ...
is inserted into the trachea through the mouth or nose. Endotracheal tubes contain high-volume, low-pressure balloon cuffs to minimize air leakage and the risk of aspiration. Cuffed tubes were made originally for adults and children over 8 years old, but cuffed tubes have been used in infants and younger children to prevent air leakage. Cuffed tubes can be inflated to the extent needed to prevent air leakage. The endotracheal tube is a guaranteed mechanism to secure a compromised airway, limit aspiration, and bring about mechanical ventilation in comatose patients. The endotracheal tube is a great method for patients who are comatose, have an obstructed airway, or need mechanical ventilation. The endotracheal tube also allows suctioning of the lower respiratory tract. Drugs that can be inserted through the endotracheal tube during cardiac arrest are discouraged. Before intubation, patients need correct patient positioning and ventilation with 100% oxygen. The purpose of ventilation with 100% oxygen is to denitrogenate healthy patients and prolong the safe apneic time. Tubes with an internal diameter of over 8mm are acceptable for most adults. Insertion technique includes visualizing the epiglottis, the posterior laryngeal structure, and not passing the tube unless tracheal insertion is ensured.


Surgical airway

Surgical entry is required when the upper airway is obstructed by a foreign body, massive trauma has occurred, or if ventilation cannot be accomplished by any of the aforementioned methods. The requirement of the surgical airway is commonly known as the response to failed intubation. In comparison, surgical airways require 100 seconds to complete from incision to ventilation compared to laryngeal mask airways and other devices. During emergency
cricothyrotomy A cricothyrotomy (also called cricothyroidotomy) is an incision made through the skin and cricothyroid membrane to establish a patent airway during certain life-threatening situations, such as airway obstruction by a foreign body, angioedema, or ...
, the patient lies on his back with neck extended and shoulders backward. The larynx is held in one hand by the practitioner while the other hand is holding a blade to incise the skin through the subcutaneous tissue and into the midline of the cricothyroid membrane to access the trachea. A hollow tube is used inserted into the trachea to keep the airway open. A tracheal hook is used to keep the space open and prevent retraction. Complications may include hemorrhage, subcutaneous emphysema, pneumomediastinum, and pneumothorax. Cricothyrotomy is used as emergency surgical access due to being fast and simple. Another surgical airway method is called tracheostomy. Tracheostomy is done in the operating room by a surgeon. This is the preferred method for patients requiring long-term ventilation. Tracheostomy uses skin puncture and dilators to insert the tracheostomy tube.


Drugs to aid intubation

Patients with respiratory arrest can be intubated without drugs. However, patients can be given sedating and paralytic drugs to minimize discomfort and help out with intubation. Pretreatment includes 100% oxygen, lidocaine, and atropine. 100% oxygen should be administered for 3 to 5 minutes. The time depends on pulse rate, pulmonary function, RBC count, and other metabolic factors.
Lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic of the amino amide type. It is also used to treat ventricular tachycardia. When used for local anaesthesia or in nerve blocks, lid ...
can be given in 1.5 mg/kg IV a few minutes before sedation and paralysis. The purpose of administering lidocaine is to blunt the sympathetic response of an increased heart rate, blood pressure, and intracranial pressure caused by laryngoscopy. Atropine can be given when children produce a vagal response, evidenced by bradycardia, in response to intubation. Some physicians even give out vecuronium, which is a neuromuscular blocker to prevent muscle fasciculations in patients over 4 years old. Fasciculations may result in muscle pain on awakening. Laryngoscopy and intubation are uncomfortable procedures, so etomidate may be delivered. Etomidate is a short-acting IV drug with sedative analgesic properties. The drug works well and does not cause cardiovascular depression. Ketamine is an anesthetic that may be used as well, but it may cause hallucinations or bizarre behavior upon awakening. Thiopental and methohexital may be used as well to provide sedation, but they tend to cause hypotension.


Volume-cycled ventilation

The purpose of mechanical ventilators is to deliver a constant volume, constant pressure, or a combination of both with each breath. Any given volume will correspond to a specific pressure on the pressure-volume curve and vice versa in any case. Settings on each mechanical ventilator may include respiratory rate, tidal volume, trigger sensitivity, flow rate, waveform, and inspiratory/expiratory ratio. The volume-cycled ventilation includes the volume-control function and delivers a set tidal volume. The pressure is not a fixed number but it varies with resistance and
capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
of the respiratory system. The volume-cycled ventilation is the simplest and most efficient of providing ventilation to a patient's airway compared to other methods of mechanical ventilation. Each inspiratory effort that is beyond the set sensitivity threshold will be accounted for and fixed to the delivery of the corresponding tidal volume. If the patient does not breathe enough, then the volume-cycled ventilation will initiate a breath for the patient to bring up the breathing rate to the minimum respiratory rate. The synchronized intermittent mandatory ventilation (SIMV) is a similar method of mechanical ventilation that also delivers breaths at a fixed rate and volume that corresponds to the patient's breathing. Unlike the Volume-Cycled Ventilation, patient efforts above the fixed rate are unassisted in the synchronized intermittent mandatory ventilation (SIMV).


Pressure-cycled ventilation

The pressure-cycled ventilation includes pressure control ventilation and pressure support ventilation. Both methods offer a set inspiratory pressure. The
tidal volume Tidal volume (symbol VT or TV) is the volume of air moved into or out of the lungs during a normal breath. In a healthy, young human adult, tidal volume is approximately 500 ml per inspiration or 7 ml/kg of body mass. Mechanical vent ...
varies depending on the resistance and elastance of the respiratory system. Pressure-cycled ventilation can help alleviate symptoms in patients with acute respiratory distress syndrome by limiting the distending pressure of the lungs. The pressure control ventilation is specifically a pressure-cycled form of assist-control ventilators. Assist-control ventilators describe a mode of ventilation that maintains a minimum respiratory rate regardless of whether or not the patient initiates a spontaneous breath. Each inspiratory effort that is beyond the sensitivity threshold delivers full pressures support for a fixed inspiratory time. There is maintenance of a minimum respiratory rate. In the pressure support ventilation, the minimum rate is not set. Instead, all breaths are triggered by the patient. The way that the pressure support ventilation works is by assisting the patient with a constant pressure until the patient's inspiratory flow falls below a threshold. The longer, deeper inspiratory flows by the patient will result in a larger tidal volume. This method of mechanical ventilation will help patients assume more work of breathing.


Noninvasive positive pressure ventilation (NIPPV)

Noninvasive positive pressure ventilation is the delivery of positive pressure ventilation through a tight-fitting mask that covers the nose and mouth. It assists patients who can spontaneously breathe. Noninvasive positive pressure ventilation delivers end-expiratory pressure with a volume control setting. There are two ways that noninvasive positive pressure ventilation can be delivered: continuous
positive airway pressure Positive airway pressure (PAP) is a mode of respiratory ventilation used in the treatment of sleep apnea. PAP ventilation is also commonly used for those who are critically ill in hospital with respiratory failure, in newborn infants (neonates), ...
or bilevel positive airway pressure. In continuous positive airway pressure, constant pressure is maintained throughout cycles of respiration with no additional inspiratory support. In bilevel positive airway pressure, both expiratory positive airway pressure and inspiratory positive airway pressure are set by the physician. Noninvasive positive pressure ventilation should not be administered to people who are hemodynamically unstable, gastric emptying impaired, bowel obstructed or pregnant. In these circumstances, swallowing large amounts of air will result in vomiting and possibly death. If frequent arrhythmias, myocardial ischemia and shock arrhythmias occur, practitioners should change delivery to endotracheal intubation or conventional mechanical ventilation. People who should not use noninvasive positive pressure ventilation include obtunded patients or ones with secretions. Noninvasive positive pressure ventilation can be used in an outpatient setting for patients with obstructive sleep apnea.


See also

*
Crash cart A crash cart or code cart (crash trolley in UK medical jargon) or "MAX cart" is a set of trays/drawers/shelves on wheels used in hospitals for transportation and dispensing of emergency medication/equipment at site of medical/surgical emergency ...
*
Respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...


References


External links

{{Circulatory and respiratory system symptoms and signs Medical emergencies Causes of death Symptoms and signs: Respiratory system