Editing Respiratory failure

{{Short description|Inadequate gas exchange by the respiratory system}}
{{Distinguish|respiratory arrest}}
{{Infobox medical condition
| name = Respiratory failure
| image = Respiratory failure.jpg
| caption = Anatomy and causes of respiratory failure
| field = [[Pulmonology]], [[Intensive care medicine]] 
| symptoms = [[Shortness of breath]], [[cyanosis]], [[tachycardia]], [[tachypnea]], [[arrhythmia]], [[headache]], [[hypertension]]
| complications = [[seizure]], [[fainting]], [[panic attack]], [[infection]]s, [[coma]]
| types = Type 1–4
| causes = [[Stroke]], [[cystic fibrosis]], [[COPD]], [[ARDS]], [[pneumonia]], [[pulmonary embolism]], [[neuromuscular disease]]s like [[ALS]]
| diagnosis = [[Arterial blood gas test]]
| differential = [[ARDS]], [[aspiration pneumonia]]
| treatment = Treatment of underlying cause, [[non-invasive ventilation]]
| frequency = 10–80 per 100,000
}}

'''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 in arterial [[carbon dioxide]] levels is called [[hypercapnia]]. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes [[tachypnea|increased respiratory rate]], abnormal blood gases (hypoxemia, hypercapnia, or both), and evidence of increased work of breathing. Respiratory failure causes an [[altered state of consciousness]] due to [[Brain ischemia|ischemia in the brain]].

The typical [[partial pressure]] reference values are oxygen [[Blood gas tension|Pa]] [[Oxygen|{{chem|O|2}}]] more than 80 mmHg (11 kPa) and carbon dioxide [[Blood gas tension|Pa]] [[Carbon dioxide|{{CO2}}]] less than 45 mmHg (6.0 kPa).<ref name=mirabile/>

== Cause ==
A variety of conditions that can potentially result in respiratory failure.<ref name="mirabile">{{Citation |last=Mirabile |first=Vincent S. |title=Respiratory Failure |date=2023 |url=http://www.ncbi.nlm.nih.gov/books/NBK526127/ |work=StatPearls |access-date=2023-11-15 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=30252383 |last2=Shebl |first2=Eman |last3=Sankari |first3=Abdulghani |last4=Burns |first4=Bracken}}</ref> The etiologies of each type of respiratory failure (see below) may differ, as well. Different types of conditions may cause respiratory failure:
* Conditions that reduce the flow of air into and out of the lungs, including physical obstruction by foreign bodies or masses and reduced breathing due to drugs or changes to the chest.<ref name=mirabile/>
*Conditions that impair the lungs' blood supply. These include [[Thromboembolism|thromboembolic conditions]] and conditions that reduce the output of the [[right heart]], such as [[right heart failure]] and some [[myocardial infarction]]s.
* Conditions that limit the ability of the lung tissue to [[Gas exchange|exchange]] oxygen and carbon dioxide between the blood and the air within the lungs. Any disease which can damage the lung tissue can fit into this category. The most common causes are (in no particular order) [[Lower respiratory tract infection|infections]], [[interstitial lung disease]], and [[pulmonary edema]].
[[File:Respiratory failure.jpg|center|thumb|Causes of respiratory failure]]

==Types==
Respiratory failure is generally organized into 4 types.{{citation needed|date=February 2024}} Below is a diagram that provides a general overview of the 4 types of respiratory failure, their distinguishing characteristics, and major causes of each.[[File:RespiratoryFailureTypes.png|center|thumb|700x700px]]

===Type 1===
Type 1 respiratory failure is characterized by a [[Hypoxemia|low level of oxygen in the blood (hypoxemia)]] (PaO2) < 60 mmHg with a normal (normocapnia) or low (hypocapnia) level of carbon dioxide (PaCO2) in the blood.<ref name=mirabile/>

The fundamental defect in type 1 respiratory failure is a failure of oxygenation characterized by:

:::{| class="wikitable"
|P<sub>a</sub>O<sub>2</sub> || decreased (< {{convert|60|mmHg|kPa|abbr=on}})
|-
| P<sub>a</sub>CO<sub>2</sub> || normal or decreased (<{{convert|50|mmHg|kPa|abbr=on}})
|-
| P<sub>A-a</sub>O<sub>2</sub> || increased
|}

Type I respiratory failure is caused by conditions that affect [[Oxygenation (medical)|oxygenation]] and therefore lead to lower-than-normal oxygen in the blood. These include:

* Low ambient oxygen (e.g. at high altitude).<ref name=mirabile/>
* [[Ventilation-perfusion mismatch]] (parts of the lung receive oxygen but not enough blood to absorb it, e.g. [[pulmonary embolism]], [[Acute respiratory distress syndrome]], [[Chronic obstructive pulmonary disease]], [[Heart failure|Congestive heart failure]].<ref name=mirabile/>
* Alveolar hypoventilation (decreased [[Respiratory minute volume|minute volume]] due to reduced respiratory muscle activity, e.g. in acute [[neuromuscular disease]]); this form can also cause type 2 respiratory failure if severe.
* Diffusion problem (oxygen cannot enter the capillaries due to parenchymal disease, e.g. in [[pneumonia]] or [[Acute respiratory distress syndrome|ARDS]]).
* [[Right-to-left shunt]] (oxygenated blood mixes with non-oxygenated blood from the [[venous system]], e.g. [[Arteriovenous malformation]], Complete [[atelectasis]], Severe pneumonia, Severe pulmonary edema).

===Type 2===
[[Hypoxemia]] (PaO<sub>2</sub> <8kPa or normal) with hypercapnia (PaCO<sub>2</sub> >6.0kPa).

The basic defect in type 2 respiratory failure is characterized by:

:::{| class="wikitable"
|P<sub>a</sub>O<sub>2</sub> || decreased (< {{convert|60|mmHg|kPa|abbr=on}})or normal
|-
| P<sub>a</sub>CO<sub>2</sub> || increased (> {{convert|50|mmHg|kPa|abbr=on}})
|-
| P<sub>A-a</sub>O<sub>2</sub> || normal
|-
|pH || <7.35
|}

Type 2 respiratory failure is caused by inadequate alveolar ventilation; both oxygen and carbon dioxide are affected.  Defined as the buildup of carbon dioxide levels (P<sub>a</sub>CO<sub>2</sub>) that has been generated by the body but cannot be eliminated. The underlying causes include:
* Increased airways resistance ([[chronic obstructive pulmonary disease]], [[asthma]], suffocation)
* Reduced breathing effort (drug effects, brain stem lesion, extreme obesity)
* A decrease in the area of the lung available for gas exchange (such as in [[Bronchitis#Chronic bronchitis|chronic bronchitis]])
* Neuromuscular problems ([[Guillain–Barré syndrome]],<ref name="Burt 475–479">{{cite journal| vauthors = Arrowsmith J, Burt C |title=Respiratory failure |journal=Surgery | location = Oxford |date=1 November 2009 |volume=27 |issue=11 |pages=475–479 |doi=10.1016/j.mpsur.2009.09.007}}</ref> [[motor neuron disease]])
* Deformed ([[kyphoscoliosis]]), rigid ([[ankylosing spondylitis]]), or [[flail chest]].<ref name="Burt 475–479"/>

===Type 3===
Type 3 respiratory failure is a type of Type 1 respiratory failure, with decreased PaO2 (hypoxemia) and either normal or decreased PaCO2.<ref name=mirabile/> However, because of its prevalence, it has been given its own category. Type 3 respiratory failure is often referred to as peri-operative respiratory failure, because it is distinguished by being a Type 1 respiratory failure that is specifically associated with an operation, procedure, or surgery.<ref>{{Cite web |title=Acute respiratory failure |url=https://www.mcgill.ca/criticalcare/education/teaching/teaching-files/acute-respiratory-failure |access-date=2023-10-28 |website=Department of Critical Care |language=en}}</ref>

The pathophysiology of type 3 respiratory failure often includes lung atelectasis, which is a term used to describe a collapsing of the functional units of the lung that allow for gas exchange. Because atelectasis occurs so commonly in the perioperative period, this form is also called  perioperative respiratory failure.  After [[General anaesthesia|general anesthesia]], decreases in functional residual capacity  leads to  collapse  of  dependent lung units.<ref name=mirabile/>

===Type 4===
Type 4 respiratory failure occurs when metabolic (oxygen) demands exceed what the cardiopulmonary system can provide.<ref name=mirabile/> It often results from [[hypoperfusion]] of respiratory muscles as in patients in [[Shock (circulatory)|shock]], such as [[cardiogenic shock]] or [[hypovolemic shock]]. Patients in shock often experience respiratory distress due to pulmonary edema (e.g., in [[cardiogenic shock]]). [[Lactic acidosis]] and [[anemia]] can also result in type 4 respiratory failure.<ref name=mirabile/> However, type 1 and 2 are the most widely accepted.<ref name=mirabile/><ref>{{cite web | vauthors = Katyal P, Gajic O | work = Mayo Clinic | location = Rochester, MN, USA | title = Critical Care Medicine, Acute respiratory failure | url = https://www.thoracic.org/professionals/clinical-resources/critical-care/clinical-education/mechanical-ventilation/respiratory-failure-mechanical-ventilation.pdf | archive-url = https://web.archive.org/web/20210409131457/https://www.thoracic.org/professionals/clinical-resources/critical-care/clinical-education/mechanical-ventilation/respiratory-failure-mechanical-ventilation.pdf | archive-date = 9 April 2021 | via = McGill University }}</ref><ref>{{cite web | vauthors = Melanson P | publisher = McGill University | work = Critical Care Medicine | title = Acute respiratory failure | url = https://www.mcgill.ca/criticalcare/teaching/files/acute }}</ref>

== Physical exam==
Physical exam findings often found in patients with respiratory failure include findings indicative of impaired oxygenation (low blood oxygen level). These include, but are not limited to, the following:

* [[Accessory muscles of breathing|Accessory muscle]] use in breathing or other signs of [[respiratory distress]]<ref name="nih">{{Cite web |date=2022-03-24 |title=Respiratory Failure - Diagnosis |url=https://www.nhlbi.nih.gov/health/respiratory-failure/diagnosis |access-date=2023-11-15 |publisher=National Heart, Lung and Blood Institute, US National Institutes of Health |language=en}}</ref>
* Altered mental status (eg. confusion, lethargy)<ref name=nih/>
* [[Nail clubbing|Clubbing]] of fingertips (see image right)<ref name=nih/>
* Peripheral [[cyanosis]] (eg. bluish color on mucosal membranes or fingers and/or toes)
* [[Tachypnea]] (faster breathing rate)<ref name=nih/>
* Pale conjunctiva<ref name=nih/>
People with respiratory failure often exhibit other signs or symptoms that are associated with the underlying cause of their respiratory failure. For instance, if respiratory failure is caused by cardiogenic shock (decreased perfusion due to heart dysfunction, symptoms of heart dysfunction (e.g., [[Edema|pitting edema]]) are also expected.[[File:Clubbing of fingers in IPF.jpg|thumb|Clubbing]]

== Diagnosis ==
[[Arterial blood gas]] (ABG) assessment is considered the gold standard diagnostic test for establishing a diagnosis of respiratory failure.<ref name=mirabile/>  This is because ABG can be used to measure blood oxygen levels (PaO2), and respiratory failure (all types) is characterized by a low blood oxygen level.<ref name=mirabile/>

Alternative or supporting diagnostic methods include the following:

* '''[[Capnography|Capnometry]]:''' measures the amount of carbon dioxide in exhaled air.<ref name=mirabile/>
* '''[[Pulse oximetry|Pulse Oximetry]]''': measures the fraction of hemoglobin saturated with oxygen (SpO2).<ref name=mirabile/>

Imaging (eg. ultrasonography, radiography) may be used to assist in the diagnostic workup. For example, it may be utilized to determine the etiology of a person's respiratory failure. 
[[File:Arterial blood gas device.jpg|thumb|Arterial blood gas analyzer]]

==Treatment==
[[Image:VIP Bird2.jpg|thumb|right|140 px|Mechanical ventilator]]
Treatment of the underlying cause is required, if possible. The treatment of acute respiratory failure may involve medication such as [[bronchodilator]]s (for airways disease),<ref>{{cite journal | vauthors = Artigas A, Camprubí-Rimblas M, Tantinyà N, Bringué J, Guillamat-Prats R, Matthay MA | title = Inhalation therapies in acute respiratory distress syndrome | journal = Annals of Translational Medicine | volume = 5 | issue = 14 | pages = 293 | date = July 2017 | pmid = 28828368 | pmc = 5537120 | doi = 10.21037/atm.2017.07.21 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Budinger GR, Mutlu GM | title = β2-agonists and acute respiratory distress syndrome | journal = American Journal of Respiratory and Critical Care Medicine | volume = 189 | issue = 6 | pages = 624–5 | date = March 2014 | pmid = 24628310 | pmc = 3983843 | doi = 10.1164/rccm.201401-0170ED }}</ref> [[antibiotic]]s (for infections), [[glucocorticoid]]s (for numerous causes), [[diuretic]]s (for pulmonary oedema), amongst others.<ref name=mirabile/><ref>{{cite journal | vauthors = Yin J, Bai CX | title = Pharmacotherapy for Adult Patients with Acute Respiratory Distress Syndrome | journal = Chinese Medical Journal | volume = 131 | issue = 10 | pages = 1138–1141 | date = May 2018 | pmid = 29722332 | pmc = 5956763 | doi = 10.4103/0366-6999.231520 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Lewis SR, Pritchard MW, Thomas CM, Smith AF | collaboration = | title = Pharmacological agents for adults with acute respiratory distress syndrome. | journal = Cochrane Database of Systematic Reviews | date = 2019 | volume = 7| issue = 7 | pages = CD004477| id = CD004477 | doi = 10.1002/14651858.CD004477.pub3 | pmid = 31334568| pmc = 6646953}}</ref> Respiratory failure resulting from an [[overdose]] of [[opioid]]s may be treated with the antidote [[naloxone]]. In contrast, most [[benzodiazepine overdose]] does not benefit from its antidote, [[flumazenil]].<ref>{{cite journal | vauthors = Sivilotti ML | title = Flumazenil, naloxone and the 'coma cocktail' | journal = British Journal of Clinical Pharmacology | volume = 81 | issue = 3 | pages = 428–36 | date = March 2016 | pmid = 26469689 | pmc = 4767210 | doi = 10.1111/bcp.12731 }}</ref> [[Respiratory therapist|Respiratory therapy]]/respiratory [[physiotherapy]] may be beneficial in some cases of respiratory failure.<ref name = "Wong_2000">{{cite journal | vauthors = Wong WP | title = Physical therapy for a patient in acute respiratory failure | journal = Physical Therapy | volume = 80 | issue = 7 | pages = 662–70 | date = July 2000 | pmid = 10869128 | doi = 10.1093/ptj/80.7.662 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Gai L, Tong Y, Yan B | title = The Effects of Pulmonary Physical Therapy on the Patients with Respiratory Failure | journal = Iranian Journal of Public Health | volume = 47 | issue = 7 | pages = 1001–1006 | date = July 2018 | pmid = 30181999 | pmc = 6119578 }}</ref>

Type 1 respiratory failure may require oxygen therapy to achieve adequate oxygen saturation.<ref>{{cite journal | vauthors = O'Driscoll BR, Howard LS, Earis J, Mak V | title = British Thoracic Society Guideline for oxygen use in adults in healthcare and emergency settings | journal = BMJ Open Respiratory Research | volume = 4 | issue = 1 | pages = e000170 | date = May 2017 | pmid = 28883921 | pmc = 5531304 | doi = 10.1136/bmjresp-2016-000170 }}</ref> Lack of oxygen response may indicate other modalities such as [[heated humidified high-flow therapy]], [[continuous positive airway pressure]] or (if severe) [[endotracheal intubation]] and [[mechanical ventilation]]. .{{Citation needed|date=September 2019}}

Type 2 respiratory failure often requires [[non-invasive ventilation]] (NIV) unless medical therapy can improve the situation.<ref name=":0">{{cite journal | vauthors = Rochwerg B, Brochard L, Elliott MW, Hess D, Hill NS, Nava S, Navalesi P, Antonelli M, Brozek J, Conti G, Ferrer M, Guntupalli K, Jaber S, Keenan S, Mancebo J, Mehta S, Raoof S | display-authors = 6 | title = Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure | journal = The European Respiratory Journal | volume = 50 | issue = 2 | pages = 1602426 | date = August 2017 | pmid = 28860265 | doi = 10.1183/13993003.02426-2016 | doi-access = free | pmc = 5593345 }}</ref> Mechanical ventilation is sometimes indicated immediately or otherwise if NIV fails.<ref name=":0" /> [[Respiratory stimulant]]s such as [[doxapram]] are now rarely used.<ref>{{cite journal | vauthors = Greenstone M, Lasserson TJ | title = Doxapram for ventilatory failure due to exacerbations of chronic obstructive pulmonary disease | journal = The Cochrane Database of Systematic Reviews | issue = 1 | pages = CD000223 | date = 2003 | pmid = 12535393 | doi = 10.1002/14651858.CD000223 }}</ref>

There is tentative evidence that in those with respiratory failure identified before arrival in hospital, [[continuous positive airway pressure]] can be helpful when started before conveying to hospital.<ref>{{cite journal | vauthors = Bakke SA, Botker MT, Riddervold IS, Kirkegaard H, Christensen EF | title = Continuous positive airway pressure and noninvasive ventilation in prehospital treatment of patients with acute respiratory failure: a systematic review of controlled studies | journal = Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine | volume = 22 | issue = 1 | pages = 69 | date = November 2014 | pmid = 25416493 | pmc = 4251922 | doi = 10.1186/s13049-014-0069-8 | doi-access = free }}</ref>

== Prognosis ==
Prognosis is highly variable and dependent on etiology and availability of appropriate treatment and management.<ref name="cc">{{Cite web |title=Respiratory failure |url=https://my.clevelandclinic.org/health/diseases/24835-respiratory-failure|publisher=Cleveland Clinic|date=15 March 2023|accessdate=15 November 2023}}</ref> One of three hospitalized cases of acute respiratory failure is fatal.<ref name=cc/>

== See also ==
* [[Ventilation/perfusion ratio]]
* [[Pulmonary shunt]]

== References ==
{{Reflist}}

== External links ==
* [https://www.medlineplus.gov/respiratoryfailure.html MedlinePlus: Respiratory Failure]

{{Medical resources
| DiseasesDB      = 6623
| ICD10           = {{ICD10|J|96||j|95}}
| ICD9            = {{ICD9|518.81}}
| MedlinePlus     =
| eMedicineSubj   = med
| eMedicineTopic  = 2011
| MeshID          = D012131
| SNOMED CT       = 409622000
}}
{{Respiratory pathology}}
{{Organ failure}}
{{Authority control}}

[[Category:Intensive care medicine]]
[[Category:Medical emergencies]]
[[Category:Organ failure]]
[[Category:Respiratory diseases]]
[[Category:Causes of death]]