Pulmonary edema
Encyclopedia
Pulmonary edema or oedema (British English
; both words from the Greek ), is fluid accumulation
in the air spaces and parenchyma of the lung
s. It leads to impaired gas exchange and may cause respiratory failure
. It is due to either failure of the left ventricle
of the heart
to adequately remove blood from the pulmonary circulation ("cardiogenic pulmonary edema"), see below, or an injury to the lung parenchyma
or vasculature of the lung ("noncardiogenic pulmonary edema"), see below. Whilst the range of causes are manifold the treatment options are limited, and to a large extent, the most effective therapies are used whatever the cause. Treatment is focused on three aspects, firstly improving respiratory function, secondly, treating the underlying cause, and thirdly avoiding further damage to the lung. Pulmonary edema, especially in the acute setting, can lead to respiratory failure
, cardiac arrest due to hypoxia
and death.
, anxiety
, and pale skin
. Shortness of breath can manifest as orthopnea (inability to lie down flat due to breathlessness) and/or paroxysmal nocturnal dyspnea (episodes of severe sudden breathlessness at night), indeed these are common presenting symptoms of chronic pulmonary edema due to left ventricular failure. The chronic development of pulmonary edema may be associated with symptoms and signs of "fluid overload", this is a non specific term to describe the manifestations of left ventricular failure on the rest of the body and includes peripheral edema
(swelling of the legs, in general, of the "pitting" variety, wherein the skin is slow to return to normal when pressed upon), raised jugular venous pressure
and hepatomegaly
, where the liver is enlarged and may be tender or even pulsatile. Other signs include end-inspiratory crackles (sounds heard at the end of a deep breath) on auscultation
and the presence of a third heart sound
.
Low oxygen saturation
and disturbed arterial blood gas
readings support the proposed diagnosis by suggesting a pulmonary shunt
. Chest X-ray
will show fluid in the alveolar walls, Kerley B lines
, increased vascular shadowing in a classical batwing peri-hilum pattern, upper lobe diversion (increased blood flow to the superior parts of the lung), and possibly pleural effusion
s.In contrast patchy alveolar infiltrates are more typically associated with noncardiogenic edema
Urgent echocardiography
, if available, may strengthen the diagnosis especially in cardiogenic pulmonary edema by demonstrating impaired left ventricular function, high central venous pressures
and high pulmonary artery
pressures. In certain circumstances insertion of a Swan-Ganz catheter may be required to aid diagnosis.
Blood tests are performed for electrolyte
s (sodium, potassium) and markers of renal function
(creatinine, urea). Liver enzymes, inflammatory markers (usually C-reactive protein
) and a complete blood count
as well as coagulation
studies (PT, aPTT) are typically requested. B-type natriuretic peptide
(BNP) is available in many hospitals, sometimes even as a point-of-care test. Low levels of BNP (<100 pg/ml) suggest a cardiac cause is unlikely.
and air spaces of the lungs. Classically it is cardiogenic (left ventricular
) but fluid may also accumulate due to damage to the lung. This damage may be direct injury or injury mediated by high pressures within the pulmonary circulation. When directly or indirectly caused by increased left ventricular pressure pulmonary edema may form when mean pulmonary pressure rises from the normal of 15 mmHg to above 25 mmHg. Broadly, the causes of pulmonary oedema can be divided into cardiogenic and non-cardiogenic. By convention cardiogenic refers to left ventricular causes.
-ARDS) covers many of these causes, but they may include:
There are also a range of causes of pulmonary edema which are less well characterised and arguably represent specific instances of the broader classifications above.
(CPAP) or variable positive airway pressure (VPAP)) or mechanical ventilation
and positive end-expiratory pressure
(PEEP) in very severe cases.
When circulatory causes have led to pulmonary edema, treatment with intravenous nitrates (glyceryl trinitrate), and loop diuretic
s, such as furosemide
or bumetanide
, is the mainstay of therapy. These improve both preload and afterload, and aid in improving cardiac function.
Sildenafil
is used as a preventative treatment for altitude-induced pulmonary edema and pulmonary hypertension, the mechanism of action is via phosphodiesterase inhibition which raises cGMP, resulting in pulmonary arterial vasodialtion and inhibition of smooth muscle cell proliferation. While this effect has only recently been discovered, sildenafil is already becoming an accepted treatment for this condition, in particular in situations where the standard treatment of rapid descent has been delayed for some reason.
British English
British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...
; both words from the Greek ), is fluid accumulation
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
in the air spaces and parenchyma of the lung
Human lung
The human lungs are the organs of respiration in humans. Humans have two lungs, with the left being divided into two lobes and the right into three lobes. Together, the lungs contain approximately of airways and 300 to 500 million alveoli, having a total surface area of about in...
s. It leads to impaired gas exchange and may cause respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...
. It is due to either failure of the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
to adequately remove blood from the pulmonary circulation ("cardiogenic pulmonary edema"), see below, or an injury to the lung parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
or vasculature of the lung ("noncardiogenic pulmonary edema"), see below. Whilst the range of causes are manifold the treatment options are limited, and to a large extent, the most effective therapies are used whatever the cause. Treatment is focused on three aspects, firstly improving respiratory function, secondly, treating the underlying cause, and thirdly avoiding further damage to the lung. Pulmonary edema, especially in the acute setting, can lead to respiratory failure
Respiratory distress
Respiratory distress may refer to either/both:* Labored breathing, the physical presentation of respiratory distress*Shortness of breath or dyspnea - a sensation of respiratory distress-See also:*List of terms of lung size and activity...
, cardiac arrest due to hypoxia
Hypoxia
Hypoxia may refer to:* Hypoxia , reduced dissolved oxygen content of a body of water detrimental to aerobic organisms* Hypoxia , a pathological condition in which the body as a whole or region of the body is deprived of adequate oxygen supply-Popular culture:* "Hypoxia" , a 2008 ambient song*...
and death.
Symptoms and signs
The overwhelming symptom of pulmonary edema is difficulty breathing, but may also include coughing up blood (classically seen as pink, frothy sputum), excessive sweatingDiaphoresis
Diaphoresis is excessive sweating commonly associated with shock and other medical emergency conditions.Diaphoretic is the state of perspiring profusely, or something that has the power to cause increased perspiration....
, anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
, and pale skin
Pallor
Pallor is a reduced amount of oxyhaemoglobin in skin or mucous membrane, a pale color which can be caused by illness, emotional shock or stress, stimulant use, lack of exposure to sunlight, anaemia or genetics....
. Shortness of breath can manifest as orthopnea (inability to lie down flat due to breathlessness) and/or paroxysmal nocturnal dyspnea (episodes of severe sudden breathlessness at night), indeed these are common presenting symptoms of chronic pulmonary edema due to left ventricular failure. The chronic development of pulmonary edema may be associated with symptoms and signs of "fluid overload", this is a non specific term to describe the manifestations of left ventricular failure on the rest of the body and includes peripheral edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
(swelling of the legs, in general, of the "pitting" variety, wherein the skin is slow to return to normal when pressed upon), raised jugular venous pressure
Jugular venous pressure
The jugular venous pressure is the indirectly observed pressure over the venous system...
and hepatomegaly
Hepatomegaly
Hepatomegaly is the condition of having an enlarged liver. It is a nonspecific medical sign having many causes, which can broadly be broken down into infection, direct toxicity, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdominal mass...
, where the liver is enlarged and may be tender or even pulsatile. Other signs include end-inspiratory crackles (sounds heard at the end of a deep breath) on auscultation
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
and the presence of a third heart sound
Third heart sound
The third heart sound or S3 is a rare extra heart sound that occurs soon after the normal two "lub-dub" heart sounds .-Physiology:It occurs at the beginning of diastole approximately 0.12 to 0.18 seconds after S2...
.
Diagnosis
There is no one single test which confirms that breathlessness is caused by pulmonary edema, indeed in many cases the causes of shortness of breath are probably multifactorial.Low oxygen saturation
Oxygen saturation
Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...
and disturbed arterial blood gas
Arterial blood gas
An arterial blood gas is a blood test that is performed using blood from an artery. It involves puncturing an artery with a thin needle and syringe and drawing a small volume of blood. The most common puncture site is the radial artery at the wrist, but sometimes the femoral artery in the groin or...
readings support the proposed diagnosis by suggesting a pulmonary shunt
Pulmonary shunt
A pulmonary shunt is a physiological condition which results when the alveoli of the lung are perfused with blood as normal, but ventilation fails to supply the perfused region. In other words, the ventilation/perfusion ratio is zero...
. Chest X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
will show fluid in the alveolar walls, Kerley B lines
Kerley B lines
Kerley lines are a sign seen on chest radiographs with interstitial pulmonary edema. They are thin linear pulmonary opacities caused by fluid or cellular infiltration into the interstitium of the lungs...
, increased vascular shadowing in a classical batwing peri-hilum pattern, upper lobe diversion (increased blood flow to the superior parts of the lung), and possibly pleural effusion
Pleural effusion
Pleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation.-Pathophysiology:...
s.In contrast patchy alveolar infiltrates are more typically associated with noncardiogenic edema
Urgent echocardiography
Echocardiography
An echocardiogram, often referred to in the medical community as a cardiac ECHO or simply an ECHO, is a sonogram of the heart . Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart...
, if available, may strengthen the diagnosis especially in cardiogenic pulmonary edema by demonstrating impaired left ventricular function, high central venous pressures
Central venous pressure
Central venous pressure describes the pressure of blood in the thoracic vena cava, near the right atrium of the heart...
and high pulmonary artery
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
pressures. In certain circumstances insertion of a Swan-Ganz catheter may be required to aid diagnosis.
Blood tests are performed for electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
s (sodium, potassium) and markers of renal function
Renal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...
(creatinine, urea). Liver enzymes, inflammatory markers (usually C-reactive protein
C-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
) and a complete blood count
Complete blood count
A complete blood count , also known as full blood count or full blood exam or blood panel, is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood...
as well as coagulation
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
studies (PT, aPTT) are typically requested. B-type natriuretic peptide
Brain natriuretic peptide
Brain natriuretic peptide , now known as B-type natriuretic peptide or GC-B, is a 32 amino acid polypeptide secreted by the ventricles of the heart in response to excessive stretching of heart muscle cells...
(BNP) is available in many hospitals, sometimes even as a point-of-care test. Low levels of BNP (<100 pg/ml) suggest a cardiac cause is unlikely.
Causes
Pulmonary edema is an accumulation of fluid within the parenchymaParenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
and air spaces of the lungs. Classically it is cardiogenic (left ventricular
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
) but fluid may also accumulate due to damage to the lung. This damage may be direct injury or injury mediated by high pressures within the pulmonary circulation. When directly or indirectly caused by increased left ventricular pressure pulmonary edema may form when mean pulmonary pressure rises from the normal of 15 mmHg to above 25 mmHg. Broadly, the causes of pulmonary oedema can be divided into cardiogenic and non-cardiogenic. By convention cardiogenic refers to left ventricular causes.
Cardiogenic
- Left ventricular failure which may be termed Congestive heart failureCongestive heart failureHeart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
and may be due to a heart attackMyocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
leading to left ventricular failure, arrhythmias (tachycardiaTachycardiaTachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
/fast heartbeat or bradycardiaBradycardiaBradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
/slow heartbeat) and fluid overload, e.g., from kidney failureRenal failureRenal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
or intravenous therapyIntravenous therapyIntravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
which may cause dilatation and failure of the left ventricle or may cause pulmonary edema in the absence of heart failure.
Non-cardiogenic
- Hypertensive crisis. The cause of pulmonary edema in the presence of a hypertensive crisis is probably due to a combination of increased pressures in the right ventricle and pulmonary circulation and also increased systemic vascular resistance and left ventricle contractilityContractilityMyocardial contractility is the intrinsic ability of the heart to contract independent of preload and afterload. Changes in the ability to produce force during contraction result from different degrees of binding between myosin and actin filaments...
increasing the hydrostatic pressure within the pulmonary capillaries leading to extravasationExtravasationExtravasation is the accidental administration of intravenously infused medicinal drugs into the surrounding tissue, either by leakage , or direct exposure...
of fluid and edema. - Upper airway obstruction (negative pressure pulmonary edema )
- Neurogenic causes (seizures, head trauma, strangulation, electrocution).
Other/unknown
Injury to the lung may also cause pulmonary oedema through injury to the vasculature and parenchyma of the lung. The acute lung injury-adult respiratory distress syndrome (ALIAcute lung injury
Acute lung injury is a diffuse heterogeneous lung injury characterized by hypoxemia, non cardiogenic pulmonary edema, low lung compliance and widespread capillary leakage...
-ARDS) covers many of these causes, but they may include:
- Inhalation of hot or toxic gases
- Pulmonary contusionPulmonary contusionA pulmonary contusion is a contusion of the lung, caused by chest trauma. As a result of damage to capillaries, blood and other fluids accumulate in the lung tissue. The excess fluid interferes with gas exchange, potentially leading to inadequate oxygen levels...
, i.e., high-energy trauma - AspirationPulmonary aspirationPulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...
, e.g., gastric fluid - Reexpansion, i.e. post large volume thoracentesisThoracentesisThoracentesis , also known as thoracocentesis or pleural tap, is an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes. A cannula, or hollow needle, is carefully introduced into the thorax, generally after administration of local anesthesia...
, resolution of pneumothorax, post decortication, removal of endobronchial obstruction, effectively a form of negative pressure pulmonary oedema. - Reperfusion injury, i.e. postpulmonary thromboendartectomy or lung transplantationLung transplantationLung transplantation, or pulmonary transplantation is a surgical procedure in which a patient's diseased lungs are partially or totally replaced by lungs which come from a donor...
- Immersion pulmonary edema
- Multiple blood transfusionBlood transfusionBlood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...
s - Severe infectionInfectionAn infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
or inflammationInflammationInflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
which may be local or systemic. This is the classical form of ALIAcute lung injuryAcute lung injury is a diffuse heterogeneous lung injury characterized by hypoxemia, non cardiogenic pulmonary edema, low lung compliance and widespread capillary leakage...
-ARDS.
There are also a range of causes of pulmonary edema which are less well characterised and arguably represent specific instances of the broader classifications above.
- Arteriovenous malformationArteriovenous malformationArteriovenous malformation or AVM is an abnormal connection between veins and arteries, usually congenital. This pathology is widely known because of its occurrence in the central nervous system, but can appear in any location. An arteriovenous malformation is a vascular anomaly. It is a...
- HantavirusHantavirusHantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...
pulmonary syndrome - High altitude pulmonary edemaHigh Altitude Pulmonary EdemaHigh altitude pulmonary edema is a life-threatening form of non-cardiogenic pulmonary edema that occurs in otherwise healthy mountaineers at altitudes typically above ....
(HAPE), probably a manifestation of neurogenic pulmonary edema - EnvenomationEnvenomationEnvenomation is the process by which venom is injected into some animal by the bite of a venomous animal. Many kinds of animals, including mammals , reptiles , spiders , insects , employ venom for hunting and for self defense...
, such as with the venom of Atrax robustus
Management
Focus is initially on maintaining adequate oxygenation. The patient is given high-flow oxygen, noninvasive ventilation (either continuous positive airway pressureContinuous positive airway pressure
Positive airway pressure is a mode of respiratory ventilation used primarily in the treatment of sleep apnea, for which it was first developed. PAP ventilation is also commonly used for those who are critically ill in hospital with respiratory failure, and in newborn infants...
(CPAP) or variable positive airway pressure (VPAP)) or mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
and positive end-expiratory pressure
Positive end-expiratory pressure
Positive end-expiratory pressure is the pressure in the lungs above atmospheric pressure that exists at the end of expiration...
(PEEP) in very severe cases.
When circulatory causes have led to pulmonary edema, treatment with intravenous nitrates (glyceryl trinitrate), and loop diuretic
Loop diuretic
Loop diuretics are diuretics that act on the ascending loop of Henle in the kidney. They are primarily used in medicine to treat hypertension and edema often due to congestive heart failure or renal insufficiency...
s, such as furosemide
Furosemide
Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...
or bumetanide
Bumetanide
Bumetanide is a loop diuretic of the sulfamyl category to treat heart failure. It is often used in people in whom high doses of furosemide are ineffective. It is marketed by Hoffmann-La Roche. The main difference between the two substances is in bioavailability and pharmacodynamic potency...
, is the mainstay of therapy. These improve both preload and afterload, and aid in improving cardiac function.
Sildenafil
Sildenafil
Sildenafil citrate, sold as Viagra, Revatio and under various other trade names, is a drug used to treat erectile dysfunction and pulmonary arterial hypertension . It was originally developed by British scientists and then brought to market by the US-based pharmaceutical company Pfizer...
is used as a preventative treatment for altitude-induced pulmonary edema and pulmonary hypertension, the mechanism of action is via phosphodiesterase inhibition which raises cGMP, resulting in pulmonary arterial vasodialtion and inhibition of smooth muscle cell proliferation. While this effect has only recently been discovered, sildenafil is already becoming an accepted treatment for this condition, in particular in situations where the standard treatment of rapid descent has been delayed for some reason.
See also
- High Altitude Pulmonary EdemaHigh Altitude Pulmonary EdemaHigh altitude pulmonary edema is a life-threatening form of non-cardiogenic pulmonary edema that occurs in otherwise healthy mountaineers at altitudes typically above ....
- Flash pulmonary edemaFlash pulmonary edemaIn medicine, flash pulmonary edema , is rapid onset pulmonary edema. It is most often precipitated by acute myocardial infarction or mitral regurgitation, but can be caused by aortic regurgitation, heart failure, or almost any cause of elevated left ventricular filling pressures...
- Swimming Induced Pulmonary Edema
External links
- HeartFailureMatters.org Animation showing How Heart Failure causes Fluid Accumulation - Created by the European Heart Failure Association