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Acute Respiratory Distress Syndrome

ARDS

Acute respiratory distress syndrome (ARDS) is a potentially life-threatening condition in which there is profound respiratory failure. It usually occurs in critically ill and is diagnosed clinically. 


Presentation

ARDS is mostly prevalent in critically ill hospitalized patients. The initial presentation of ARDS includes acute onset of dyspnea, tachypnea, hyperventilation, low oxygen saturation, cyanosis, and anxiety. A cough with frothy sputum may also be seen. The underlying cause will most likely exhibit signs and symptoms as well such as in the cases with pneumonia. Ominous signs are hypotension, tachycardia, confusion, and fatigue which are indicative of inadequate oxygen perfusion of organs. 

Hospitalized patients with ARDS are susceptible to other medical conditions such as pneumonia. Ventilation is also a risk factor for pneumonia. In addition to infection, there are other complications. One of them is pneumothorax, in which ventilated air pressure enters the space around the lungs causing subsequent collapse in one or both. In addition, lung scarring inhibits its ability to expand. Another major and potentially fatal complication is clot formation. Thromboembolism can occur due to prolonged immobility and other pathological mechanisms.

Hypoxemia
  • A 30 year-old Hispanic man with no significant previous medical history presented with refractory hypoxemia after flu-like symptoms.[ncbi.nlm.nih.gov]
  • Refractory hypoxemia, defined as Pa O 2 less than 60 mm Hg on Fi O 2 of 1.0, occurred in 138 (21%) patients. At onset of refractory hypoxemia, mean Vt was 7.1 (SD   2.0) ml/kg (n   124); 95 patients (77%) received Vt greater than 6 ml/kg.[ncbi.nlm.nih.gov]
  • Nitric oxide does not reduce mortality in adults or children with acute respiratory distress syndrome, regardless of the degree of hypoxemia.[ncbi.nlm.nih.gov]
  • The four markers independently associated with DAD were (1) duration of evolution (OR 3.29 [1.95-5.55] for patients with ARDS   3 days, p CONCLUSIONS: In addition to severe hypoxemia, diffuse opacities involving the four quadrants were a strong marker[ncbi.nlm.nih.gov]
Fever
  • The diseases generally present as undifferentiated fever, but thrombocytopenia, leucopenia, and transaminitis are important laboratory features.[ncbi.nlm.nih.gov]
  • A 35-year-old woman presented with fever, headache, cough, and body aches. Seizures, altered consciousness, and dyspnea occurred later. A nasopharyngeal swab revealed a positive reaction for the influenza A antigen.[ncbi.nlm.nih.gov]
  • He developed a fever of 39 C with respiratory distress and was transported by ambulance to his usual doctor. Since his respiratory state was very severe, he was transferred to our hospital.[ncbi.nlm.nih.gov]
  • […] treated with ECMO: a 21 years old Caucasian female with congenital HIV infection presented with Pneumocystis jirovecii pneumonia (PJP); a 38 years old Caucasian female with HIV-HCV infection and L. pneumophila pneumonia; a 24 years old Caucasian male with fever[ncbi.nlm.nih.gov]
  • The patient then developed fever, chills, a biological inflammatory syndrome, and an acute respiratory disease syndrome. Full workup excluded an infection and we concluded that ruxolitinib withdrawal syndrome was the likely cause.[ncbi.nlm.nih.gov]
Fatigue
  • Twenty four hours later she had worsening dyspnoea, fatigue, and hypotension, and was transferred to the intensive care unit for vasopressor infusion and invasive ventilation. The ventilation was weaned at 3 weeks, but rehabilitation was slow.[bmj.com]
  • Trouble doing day-to-day activities because of weakness and fatigue. Depression. Problems focusing on tasks and trouble with memory. ARDS is a serious condition, and getting better is hard work. Your life may be changed in important ways.[cigna.com]
  • Extreme fatigue and confusion. Low blood pressure. How is acute respiratory distress syndrome diagnosed? You may need any of the following tests: Blood tests may show if you have an infection. They may also show how your body is working.[northmemorial.com]
  • Medically Qualifying with ARDS The immediate symptoms of ARDS include severe breathing difficulties, low blood pressure, extreme fatigue, and confusion.[disability-benefits-help.org]
Hypothermia
  • Early evidence suggests that therapeutic hypothermia (TH) could be a viable treatment for acute respiratory failure.[ncbi.nlm.nih.gov]
  • Management of Pediatric Hypothermia and Peripheral Cold Injuries in the Emergency Department - 49.00 Appropriate management of cold injuries depends on their severity.[ebmedicine.net]
Multiple Organ Dysfunction Syndrome
  • All patients had influenza A (H1N1) viral pneumonia (confirmed with RT-PCR) complicated by ARDS and septic shock with multiple organ dysfunction syndrome. None of the patients received seasonal influenza vaccines.[ncbi.nlm.nih.gov]
  • View Article PubMed Google Scholar Vincent JL, Zambon M: Why do patients who have acute lung injury/acute respiratory distress syndrome die from multiple organ dysfunction syndrome? Implications for management.[doi.org]
Respiratory Distress
  • PATIENTS: Mechanically ventilated children with acute respiratory distress syndrome. INTERVENTIONS: Blood collection within 24 hours of acute respiratory distress syndrome onset and biomarker measurements.[ncbi.nlm.nih.gov]
  • The failure rate of noninvasive ventilation in cases of acute respiratory distress syndrome is approximately 52% and is associated with higher mortality.[ncbi.nlm.nih.gov]
  • Abstract Acute respiratory distress syndrome is a challenging entity for the intensivist.[ncbi.nlm.nih.gov]
  • Our objective was to determine whether nitric oxide reduces hospital mortality in patients with severe acute respiratory distress syndrome (PaO2/FIO2 100 mm Hg) but not in patients with mild-moderate acute respiratory distress syndrome (100 PaO2/FIO2[ncbi.nlm.nih.gov]
  • What is Acute Respiratory Distress Syndrome (ARDS, Acute Alveolar Injury, Traumatic Wet Lungs) Statistics on Acute Respiratory Distress Syndrome (ARDS, Acute Alveolar Injury, Traumatic Wet Lungs) Risk Factors for Acute Respiratory Distress Syndrome (ARDS[myvmc.com]
Dyspnea
  • Seizures, altered consciousness, and dyspnea occurred later. A nasopharyngeal swab revealed a positive reaction for the influenza A antigen.[ncbi.nlm.nih.gov]
  • A 43-year-old man was transferred to the emergency department because of accidental chlorine inhalation and rapidly progressive dyspnea. The patient was diagnosed with acute respiratory distress syndrome due to chlorine gas exposure.[ncbi.nlm.nih.gov]
  • The symptoms include dyspnea, hypotension and multovisceral failure. The disease is characterized by bilateral pulmonary infiltrates and severe hypoxemia due to increased alveolar-capillary permeability.[orpha.net]
  • In this article we underlined the key elements of the new definition of ARDS, diagnostic criteria and the importance of early diagnosis in prehospital period following clinical feature and course (a presence of severe dyspnea) by adding chest x-ray and[ncbi.nlm.nih.gov]
  • An 81-year-old previously healthy Korean man presented with cough, dyspnea, and febrile sensation. He had hypoxemia with diffuse ground glass opacity evident on chest radiography, which progressed and required mechanical ventilation.[ncbi.nlm.nih.gov]
Cough
  • A 35-year-old woman presented with fever, headache, cough, and body aches. Seizures, altered consciousness, and dyspnea occurred later. A nasopharyngeal swab revealed a positive reaction for the influenza A antigen.[ncbi.nlm.nih.gov]
  • An 81-year-old previously healthy Korean man presented with cough, dyspnea, and febrile sensation. He had hypoxemia with diffuse ground glass opacity evident on chest radiography, which progressed and required mechanical ventilation.[ncbi.nlm.nih.gov]
  • ECMO: a 21 years old Caucasian female with congenital HIV infection presented with Pneumocystis jirovecii pneumonia (PJP); a 38 years old Caucasian female with HIV-HCV infection and L. pneumophila pneumonia; a 24 years old Caucasian male with fever, cough[ncbi.nlm.nih.gov]
  • We present a Case Report of a previously healthy 18-year-old woman who presented with dyspnea, cough, and pleuritic chest pain after e-cigarette use.[ncbi.nlm.nih.gov]
Tachypnea
  • On arrival to the emergency department (ED) the patient was noted to be febrile with tachycardia, tachypnea, and hypoxia and was intubated for respiratory failure.[ncbi.nlm.nih.gov]
  • Tachypnea, hypoxia, and respiratory alkalosis are typical early clinical manifestations, and they are usually followed by the appearance of diffuse pulmonary infiltrates and respiratory failure within 48 hours.[ncbi.nlm.nih.gov]
  • The symptoms usually appear shortly after birth and may include tachypnea, tachycardia, chest wall retractions (recession), expiratory grunting, nasal flaring and cyanosis during breathing efforts.[orpha.net]
  • Clinical signs include respiratory distress characterized by tachypnea and dyspnea, and affected cattle may be found dead if clinical signs are unobserved.[merckvetmanual.com]
Abnormal Breathing
  • Symptoms can include any of the following: Shortness of breath Fast heartbeat Low blood pressure and organ failure Rapid breathing Listening to the chest with a stethoscope ( auscultation ) reveals abnormal breath sounds, such as crackles, which may be[nlm.nih.gov]
  • Symptoms can include any of the following: Shortness of breath Fast heartbeat Low blood pressure and organ failure Rapid breathing Exams and Tests Listening to the chest with a stethoscope ( auscultation ) reveals abnormal breath sounds, such as crackles[umms.org]
  • Physical Exam ARDS may cause abnormal breathing sounds, such as crackling. Your doctor will listen to your lungs with a stethoscope to hear these sounds.[medicinenet.com]
Hypotension
  • It is feasible that severe acidosis, hypotension, azotemia, hypoalbuminemia and the superimposed aggressive intravenous fluid administration were important risk factors for the development of cerebral edema and ARDS in the index patient.[ncbi.nlm.nih.gov]
  • A 54-year-old woman presented with fever, hypotension, and pancytopenia, with peripheral smear diagnostic of ehrlichiosis. She was started on doxycycline therapy following which she developed ARDS which resolved with methylprednisone.[ncbi.nlm.nih.gov]
  • The symptoms include dyspnea, hypotension and multovisceral failure. The disease is characterized by bilateral pulmonary infiltrates and severe hypoxemia due to increased alveolar-capillary permeability.[orpha.net]
  • Twenty four hours later she had worsening dyspnoea, fatigue, and hypotension, and was transferred to the intensive care unit for vasopressor infusion and invasive ventilation. The ventilation was weaned at 3 weeks, but rehabilitation was slow.[bmj.com]
  • Per EMS, the patient was hypotensive on their arrival, with initial blood pressure of 80/40 mm Hg, but it rapidly improved with 2 L of crystalloid given in the field. A second large-bore IV is placed and labs are drawn.[web.archive.org]
Cyanosis
  • The symptoms usually appear shortly after birth and may include tachypnea, tachycardia, chest wall retractions (recession), expiratory grunting, nasal flaring and cyanosis during breathing efforts.[orpha.net]
  • The person has shortness of breath, usually with rapid, shallow breathing, the skin may become mottled or blue (cyanosis), and other organs such as the heart and brain may malfunction.[merckmanuals.com]
  • Patients initially present with acute onset cyanosis, dyspnea, and tachypnea.[amboss.com]
  • You may also notice your lips and tongue turning blue (central cyanosis). Your doctor will take a brief history to determine if you have any of the predisposing conditions and find out what symptoms you may be having.[myvmc.com]
Tachycardia
  • On arrival to the emergency department (ED) the patient was noted to be febrile with tachycardia, tachypnea, and hypoxia and was intubated for respiratory failure.[ncbi.nlm.nih.gov]
  • The symptoms usually appear shortly after birth and may include tachypnea, tachycardia, chest wall retractions (recession), expiratory grunting, nasal flaring and cyanosis during breathing efforts.[orpha.net]
  • Signs : cyanosis (reflecting hypoxia refractory to oxygen therapy), tachypnoea, tachycardia, peripheral vasodilatation, bilateral fine inspiratory crackles. Investigations FBC, U&E, LFTs, amylase, clotting, CRP, blood cultures, ABG.[patient.info]
Confusion
  • Symptoms of ARDS Symptoms of ARDS can include: severe shortness of breath rapid, shallow breathing tiredness, drowsiness or confusion feeling faint When to get urgent medical help Although most people develop ARDS when they're already in hospital, this[nhs.uk]
  • There may also be signs, such as confusion or low blood pressure, that the vital organs aren't getting enough oxygen.[columbiasurgery.org]
  • The main common signs and symptoms are shortness of breath, difficulty breathing, fast and shallow breathing, blue colored skin, and other signs showing brain (confusion, lethargy) and heart dysfunction.[symptoma.com]
  • Other signs of ARDS include: Low blood pressure Unusually fast breathing Confusion and exhaustion Blue-tinted lips or nails from lack of oxygen in the blood Dizziness Lots of sweating While many people are already in a hospital when they get ARDS, you[webmd.com]
  • Extreme fatigue and confusion. Low blood pressure. How is acute respiratory distress syndrome diagnosed? You may need any of the following tests: Blood tests may show if you have an infection. They may also show how your body is working.[northmemorial.com]
Agitation
  • This often leads to restlessness and patient agitation, which can lead to high pressures in the lung or even cause oxygen levels to drop even further.[foundation.chestnet.org]
  • This rapidly progresses to severe dyspnea at rest, tachypnea, anxiety, agitation, and the need for increasingly high concentrations of inspired oxygen.[emedicine.medscape.com]
Difficulty Concentrating
  • Common problems in people recovering from ARDS include: memory problems, such as difficulty recalling certain words or remembering people's names difficulty concentrating low attention span problems doing complex mental tasks, such as mental arithmetic[hse.ie]

Workup

The diagnosis of ARDS is clinical and should be considered in ill patients presenting with acute respiratory failure. The Berlin definition guides the clinician in terms of timing of the onset, chest X-ray findings (opacities not consistent with effusion, atelectasis, or nodules) and oxygenation criteria per the Berlin definition [2].

In addition to the above, a full history and physical is key. The clinician should investigate and ascertain any underlying conditions. One should be highly suspicious for sepsis, which is associated with the highest rate of mortality. Examination of patient involves lung exam and determination of basilar or diffuse rales [11]. Also another critical finding is the requirement of high oxygenation and/or PEEP to maintain saturation greater than 90%. Workup is comprised of the following tests:

  1. Arterial blood gas analysis provides values to calculate the PaO2/FIO2 ratio per the Berlin definition.
  2. Chest X-ray will show any opacities indicative of pulmonary edema.
  3. Brain natriuretic protein (BNP) can determine the etiology of pulmonary edema. BNP<100 picograms/mL suggest non cardiac causes while BNP> 500 picograms/mL are suggestive of cardiac etiology.
  4. Echocardiogram is performed to assess cardiac function if BNP and other findings are inconclusive.
  5. Pulmonary artery catheterization measures estimation of left ventricular end diastolic pressure. This is used to differentiate cardiogenic versus noncardiogenic etiology of pulmonary edema if BNP levels, echocardiogram and findings from history and physical are inconclusive. This is not a routine procedure. 
  6. Other significant laboratory tests include cultures of blood, urine, and sputum to assess for infection. Lipase and liver functions tests are helpful to detect pancreatitis
  7. Bronchoalveolar lavage (BAL) or endotracheal aspiration provides samples for culture and Gram stain are done to confirm suspected pneumonia [12]. There is a high mortality risk associated with these procedures. Therefore, the risks and benefits have to be weighed.
  8. CT of chest is more sensitive than a chest X-ray and is useful in diagnosing pneumonia and underlying lung processes [13].
Atelectasis
  • However, the predicted body weight approach is imperfect in patients with ARDS because the amount of aerated lung varies considerably due to differences in inflammation, consolidation, flooding, and atelectasis.[ncbi.nlm.nih.gov]
  • The Berlin definition guides the clinician in terms of timing of the onset, chest X-ray findings (opacities not consistent with effusion, atelectasis, or nodules) and oxygenation criteria per the Berlin definition.[symptoma.com]
  • Alveolar protective ventilation utilizing appropriate positive-end expiratory pressure (PEEP) minimizes atelectasis and shearing injury.[hamilton-medical.com]
  • […] alveolar spaces bronchial dilatation within areas of ground-glass opacification some publications also report pulmonary cysts in the early phase 11 Postulated reason for inhomogeneity of appearances: increased weight of overlying lung causing compressive atelectasis[radiopaedia.org]
  • This leads to reduced lung compliance, alveolar instability and ultimately, areas of atelectasis. Consequently, intrapulmonary shunting and hypoxemia occur, and the work of breathing increases, leading to dyspnea .[lecturio.com]
Pulmonary Infiltrate
  • It is characterized by the acute onset of diffuse, bilateral pulmonary infiltrates secondary to noncardiogenic pulmonary edema, refractory hypoxia, and decreased lung compliance.[ncbi.nlm.nih.gov]
  • The disease is characterized by bilateral pulmonary infiltrates and severe hypoxemia due to increased alveolar-capillary permeability. The severity depends on the degree of alveolar epithelial injury, with a mortality rate of 30-50%.[orpha.net]
  • Abstract The acute respiratory distress syndrome (ARDS) is a heterogeneous group of illnesses affecting the pulmonary parenchyma with acute onset bilateral inflammatory pulmonary infiltrates with associated hypoxemia.[vumc.org]
  • Acute respiratory distress syndrome (ARDS) is a clinical syndrome of severe dyspnea of rapid onset, hypoxemia, and diffuse pulmonary infiltrates leading to respiratory failure.[accessmedicine.mhmedical.com]
  • It is clinically defined by the presence of pulmonary infiltrates due to alveolar fluid accumulation, without evidence suggestive of a cardiogenic etiology.[lecturio.com]
Bilateral Pulmonary Infiltrate
  • The disease is characterized by bilateral pulmonary infiltrates and severe hypoxemia due to increased alveolar-capillary permeability. The severity depends on the degree of alveolar epithelial injury, with a mortality rate of 30-50%.[orpha.net]
  • It is characterized by the acute onset of diffuse, bilateral pulmonary infiltrates secondary to noncardiogenic pulmonary edema, refractory hypoxia, and decreased lung compliance.[ncbi.nlm.nih.gov]
  • Radiography ARDS is defined by the presence of bilateral pulmonary infiltrates.[emedicine.medscape.com]
  • pulmonary infiltrates normal sized heart makes CHF less likely Respiratory compliance ( Positive end-expiratory pressure ( 10cm H20) Corrected expired volume per minute ( 10L/min) Differential Cardiogenic pulmonary edema (i.e.[orthobullets.com]
Air Bronchogram
  • bronchograms 20% 20% 70% Adult Respiratory Distress Syndrome.[learningradiology.com]
  • CXR shows bilateral alveolar shadowing, often with air bronchograms. Other investigations as deemed by the clinical scenario - eg, echocardiography.[patient.info]
  • Imaging : chest x-ray Diffuse bilateral infiltrates (perihilar bat wing or butterfly distribution of infiltrates) Air bronchogram Atelectasis Pleural effusions ARDS is a likely diagnosis in the presence of both typical causes and therapy-resistant hypoxemia[amboss.com]
  • Lichtenstein D, Meziere G, Seitz J (2009) The dynamic air bronchogram. A lung ultrasound sign of alveolar consolidation ruling out atelectasis. Chest 135:1421–1425 PubMed CrossRef Google Scholar 40.[doi.org]
Kerley A Lines
  • B lines/ peribronchial cuffing 30% 30% None Pleural effusions 40% 30% 10% Air bronchograms 20% 20% 70% Adult Respiratory Distress Syndrome.[learningradiology.com]
Hypercapnia
  • A subset of patients with ARDS has mixed hypercapnia and hypoxemia despite high-level ventilator support.[ncbi.nlm.nih.gov]
  • We performed subgroup analysis by sex and assessment of arterial partial pressure of carbon dioxide (PaCO 2 ) management where hypercapnia was potentially physiologically contraindicated.[ncbi.nlm.nih.gov]
  • High ventilatory pressures were needed because of hypoxia and severe hypercapnia with respiratory acidosis, resulting in right ventricular dysfunction with impaired haemodynamic stability.[ncbi.nlm.nih.gov]
  • PEEP will be titrated individually against peripheral oxygen saturation, targeting lower tidal volumes by a permissive approach to hypercapnia.[ncbi.nlm.nih.gov]
Decreased Lung Compliance
  • Hallmarks of ARDS include hypoxemia and decreased lung compliance, increased work of breathing, and impaired gas exchange. Mortality is often accompanied by multiple organ failure.[ncbi.nlm.nih.gov]
  • It is characterized by the acute onset of diffuse, bilateral pulmonary infiltrates secondary to noncardiogenic pulmonary edema, refractory hypoxia, and decreased lung compliance.[ncbi.nlm.nih.gov]
  • [with] hypoxemia and bilateral radiographic opacities, associated with increased venous admixture, increased physiological dead space, and decreased lung compliance."[pulmccm.org]

Treatment

These patients are admitted to ICU. Treatment is divided into 3 categories: Respiratory support, cardiovascular resuscitation, and other therapies.

Respiratory support: Most patients require ventilation when: PaO2 <8.3kPa (60mm HG) despite using FIO2 60% and PaCO2 >6kPa (45mm HG). Clinicians should be aware that increased tidal volumes coupled with poor lung compliance can further increase lung damage. Lower tidal volumes have been shown to improve survival [10].

Cardiovascular support: Clinicians should remain vigilant while monitoring the cardiovascular status in these ill patients. It is critical to maintain cardiac output and oxygenation. In many cases, drugs such as dobutamine and other vasodilators are beneficial. Fluid resuscitation is carefully monitored as well. Blood transfusions may be warranted. Clinician may consider Swan-Ganz catheter placement for invasive monitoring of cardiac output and pulmonary capillary wedge pressure.

Further therapy depends on underlying diseases. It is critical to treat sepsis and the source if the organism(s) is/are known. In certain cases where organisms are not found on culture, broad spectrum renal safe antibiotics are used.  

Other supportive therapies include prophylactic drugs such as low molecular weight heparin for venous thromboembolism prophylaxis and antacids for gastric ulcer prophylactics. Also nutrition has to be maintained. 

While steroids were commonly used in ARDS patients, their use is no longer recommended. Steroids have been linked to many cases of septicemia and hyperglycemia. Results from the Late Steroid Rescue Study report the increase in the mortality rate with methylprednisolone therapy.

Prognosis

The mortality rate in patients with ARDS is 30 to 50% and increases with severity [2]. Fatality is usually secondary to multiorgan failure [5]. Furthermore, younger age is associated with better prognosis [6]. Residual lung damage may be seen in survivors [7] [8]. Post ARDS residual effects can include neuropathies, joint disorders, chronic pain, and muscle weakness [9].

Mechanical ventilation can cause lung damage and increased mortality. Furthermore, the 2000 ARDS Network Trial shows that lower tidal volumes decrease mortality from 40 to 31% [2]. This research study further demonstrates that tidal volumes at 4-6 mL/kg are protective [10].

Etiology

The etiology of ARDS is extensive. Underlying diseases serve as risk factors. Sepsis is the most common cause and can be attributed to pulmonary and nonpulmonary etiologies [4]. Direct pulmonary insults such as pneumonia, aspiration of gastric contents, inhalation injury, pulmonary contusion, transfusion-related lung injury, and cardiopulmonary bypass are risk factors for ARDS. Nondirect pulmonary insults such as acute pancreatitis, fat embolism, noncardiogenic shock, disseminated intravascular coagulationdrug overdose, and trauma also place patients at risk for this debilitating pulmonary failure [1]. Other risk factors may include previous lung disease, smoking, obesity, and alcohol abuse.

Epidemiology

Due to the usage of varied definitions of ARDS in older research studies, there is an inaccurate estimate regarding the actual incidence of ARDS. However, research emerging from the United States and international regions provide some insight on the incidence.

About 4 decades ago, the National Institute of Health (NIH) estimated that the incidence is 75 cases per 100,000 population. However, the ARDS Study Network suggests that the incidence is actually greater than that. The 2005 study in King County, Washington, using the outdated definition from the 1994 AECC, reports the incidence of ALI as 86.2 per 100,000 population [4]. A further statistical analysis of the data yields an estimate of 190,600 annual cases in the United States of which 74,500 result in death. Furthermore it is estimated that ALI is associated with an annual 3.5 million hospital days [4].

The same study also shows that age is directly proportional to the incidence of ALI. In the 15-19 year old range, the incidence was 16 per 100,000 while it was 306 in the age range of 75 to 84 [4]. As for gender, the incidences are similar with the exception of trauma patients in which females have a higher incidence of ARDS.

Sex distribution
Age distribution

Pathophysiology

The complex pathophysiology of ARDS is not completely clear. The early stages consist of diffuse alveolar damage and increased permeability across the alveolar capillary membrane. Capillary endothelial cells and alveolar pneumocytes (Type I and Type II) undergo necrosis and apoptosis marking an exudative inflammatory process. This involves flooding of alveolar air spaces with edema, neutrophils and activated alveolar macrophages, in addition to mediators such as cytokines and oxidants [1]. The acute onset of alveolar flooding may result in recovery due to active clearance of pulmonary edema or may progress to disease [1].

Type II cell injury and exudative flooding contribute to surfactant dysfunction. This consequently increases alveolar-arterial oxygen gradient and leads to acute hypoxemic respiratory failure. The main features of this phase include respiratory failure, high minute ventilation and low compliant lungs [1].

Severe epithelial injury can cause progression of the inflammatory phase to a fibroproliferative phase. Necrotic type I cells denude the basement membrane thereby allowing fibrin deposition. Histologically, hyaline membranes are observed. This irreversible devastating phase consists of extensive formation or fibrous and collagen deposition [1] [4].

Prevention

ARDS cannot necessarily be prevented but cessation of smoking and alcohol may help. It is also important for all individuals, especially those as risk, to comply with appropriate immunization recommendations such as flu (annual) and pneumococcal (per guidelines) vaccines. 

Summary

Acute respiratory distress syndrome (ARDS) is characterized by rapidly progressive respiratory failure. Individuals with ARDS can develop multiorgan damage and are usually at high risk for mortality [1].

The European Society of Intensive Care Medicine, the American Thoracic Society and the Society of Critical Care Medicine formulated the new criteria for ARDS in 2011. The new updated guidelines, referred to as the Berlin definition, are as follows: [2]

Timing of ARDS: Occurs within one week of clinical risk factor/insult or within one week of new or worsening respiratory condition.
Chest imaging: Bilateral opacities that are not explained by effusions, atelectasis, or nodules.
Etiology of edema: Respiratory failure not due to cardiac etiology or fluid overload.
Oxygenation: Degree of oxygenation determines the severity. 

  • Mild: PaO2/FIO2 ≤300 mmHg and >200 mmHg  with PEEP or CPAP ≥5 cmH2O
  • Moderate: PaO2/FIO2 ≤200 mmHg and >100mm Hg with PEEP ≥5 cmH2O
  • Severe: PaO2/FIO2 ≤100 mmHg with PEEP ≥5 cmH2O

The Berlin definition replaces the previous American -European Consensus Committee (AECC) definition which differentiated ARDS from other varied or lesser forms such as acute lung injury (ALI), noncardiac pulmonary edema, and increased permeability pulmonary edema [2] [3]. This AECC definition presented diagnostic limitations and therefore was updated for accuracy.

Patient Information

Acute respiratory distress Syndrome (ARDS) is a condition in which respiratory failure occurs. The most common cause is sepsis, which is an overwhelming response of the body to an infection. Other causes are acute pancreatitis, fat embolism, aspiration, inhalation injury, acute pancreatitis, disseminated intravascular coagulation, drug overdose, and trauma.

In ARDS, fluid accumulates in the lungs and makes it very difficult to expand and facilitate oxygen exchange. Therefore, there are low oxygen blood levels in the body which can lead to damage of organs. The main common signs and symptoms are shortness of breath, difficulty breathing, fast and shallow breathing, blue colored skin, and other signs showing brain (confusion, lethargy) and heart dysfunction.

In patients with suspected ARDS, a chest X-ray is done to evaluate for any fluid in the lungs. Also, a blood test is done to determine the levels of oxygen. Other laboratory tests may be important to determine the exact cause. Also an ultrasound of the heart may be done to look for any cardiac problems. Individuals with ARDS are likely very ill from other diseases as well. Patients with ARDS are admitted to the intensive care unit for special care. Since the lungs are not working properly and oxygen is low in the body, most patients require mechanical ventilation to help deliver oxygen to the organs. These patients are monitored closely to make sure their heart, lungs, kidneys, and other organs are receiving adequate oxygen. Other treatments are for prevention of blood clots, stomach ulcers and nutritional care.

References

Article

  1. Ware LB, Matthay MA. The acute respiratory distress syndrome. New England Journal of Medicine. 2000;342(18):1334-1349.
  2. Ranieri VM, Rubenfeld GD, Thompson BT, et al. Acute respiratory distress syndrome: the Berlin Definition. Journal of American Medical Association. 2012;307(23):2526-2533. doi:10.1001/jama.2012.5669.
  3. Tsushima K, King LS, Aggarwal NR, De Gorordo A, D’Alessio FR, Kubo K. Acute Lung Injury Review. Internal Medicine. 2009;48(9):621-630. 
  4. Rubenfeld GD, Caldwell E, Peabody E, et al. Incidence and outcomes of acute lung injury. New England Journal of Medicine. 2005;353(16):1685-1693.
  5. Montgomery AB, Stager MA, Carrico CJ, Hudson LD. Causes of mortality in patients with the adult respiratory distress syndrome. The American Review of Respiratory Disease. 1985;132(3):485-489.
  6. Ely EW, Wheeler AP, Thompson BT, Ancukiewicz M, Steinberg KP, Bernard GR. Recovery rate and prognosis in older persons who develop acute lung injury and the acute respiratory distress syndrome. Annals of Internal Medicine. 2002;136(1):25-36.
  7. Neff TA, Stocker R, Frey HR, Stein S, Russi EW. Long-term assessment of lung function in survivors of severe ARDS. Chest. 2003;123(3):845-853. doi:10.1378/chest.123.3.845.
  8. Orme J, Romney JS, Hopkins RO, et al. Pulmonary function and health-related quality of life in survivors of acute respiratory distress syndrome. American Journal of Respiratory Critical Care Medicine. 2003;167(5):690-694.
  9. Herridge MS, Cheung AM, Tansey CM, et al. One-year outcomes in survivors of the Acute Respiratory Distress Syndrome. New England Journal of Medicine New England Journal of Medicine. 2003;348(8):683–693.
  10. The Acute Respiratory Distress Syndrome Network. Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome. New England Journal of Medicine. 2000;342(18):1301–1308.
  11. Leaver SK ET. Acute Respiratory Distress Syndrome. The British Medical Journal. 2007;335(7616):389-394.
  12. Schwarz MI AR. “Imitators” of the ARDS: implications for diagnosis and treatment. Chest. 2004;125(4):1530-1535.
  13. Gattinoni L, Caironi P, Pelosi P, Goodman LR. What has computed tomography taught us about the acute respiratory distress syndrome? American Journal of Respiratory Critical Care Medicine. 2001;164(9):1701-1711. 

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Last updated: 2019-07-11 20:01