Pulmonary Edema - causes, symptoms, diagnosis, treatment, pathology

Aug 26, 2023

Pulmonary Edema - causes, symptoms, diagnosis, treatment, pathology

What is pulmonary edema? Pulmonary edema describes having excess fluid in the lungs. Find more videos at http://osms.it/more.

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Content

3.179 -> Pulmonary edema refers to the buildup of fluid in the lungs including the airways like the

7.95 -> alveoli - which are the tiny air sacs - as well as in the interstitium, which is the

13.049 -> lung tissue that’s sandwiched between the alveoli and the capillaries.

18.56 -> This space is mostly full of proteins, and when it starts filling up with fluid, it can

23.47 -> make it hard for oxygen to cross over from the alveoli into the capillary, leaving the

28.039 -> body hypoxic - or deprived of oxygen.

33.96 -> To understand pulmonary edema, let’s first talk about the three main factors that determine

38.14 -> how fluid moves between the capillaries and interstitial fluid, which are the hydrostatic

43.12 -> pressure, oncotic pressure and capillary permeability.

49.44 -> Hydrostatic pressure refers to the pressure felt by fluid in a confined space, pushing

54.26 -> the fluid out of that space.

58.57 -> In the interstitial space, it’s the same thing as the blood pressure in the pulmonary

62 -> capillaries, and because the pulmonary circulation is a low pressure system, the hydrostatic

67.27 -> pressure is pretty low.

68.58 -> But it’s still higher than the hydrostatic pressure exerted by the interstitial fluid

72.56 -> of the lungs - which is almost zero.

75.28 -> So, to be clear, if hydrostatic pressure was the only factor involved, a lot of fluid would

81.14 -> be continuously leaking out of the pulmonary capillaries into the lung’s interstitial

85.159 -> space.

86.9 -> The next factor, though, is oncotic pressure; which is a type of osmotic pressure exerted

93.17 -> by cells and proteins that can’t cross the capillary membrane and therefore tend to attract

98.33 -> fluid.

100.61 -> The oncotic pressure is higher in the pulmonary capillaries than in the interstitial fluid,

105.18 -> so it opposes the hydrostatic pressure.

108.34 -> Finally, there’s capillary permeability or leakiness which affects how easily fluid

115.829 -> is actually able to get through.

118.49 -> When taking these three factors together, the net result is that a very small amount

123.869 -> of fluid leaks into the interstitial space, and that fluid is normally whisked away by

128.45 -> the lymphatic channels in the lungs, which keeps the lungs free of excess fluid.

133.959 -> Now, the underlying cause of pulmonary edema can be cardiogenic - meaning that it develops

140.12 -> as a result of a heart disease, or can be non-cardiogenic which typically involves damage

145.12 -> to the pulmonary capillaries or alveoli.

148.209 -> The most common cardiogenic cause is left-sided heart-failure, and in left-sided heart failure,

154.59 -> the left ventricle becomes unhealthy and can’t pump effectively, which means that blood starts

159.329 -> to backup in the left atrium, and then the pulmonary veins and pulmonary capillaries.

166.69 -> The extra blood in the pulmonary capillaries causes pulmonary hypertension - which is an

171.299 -> increase in the hydrostatic pressure of the pulmonary blood vessels, and this pushes more

175.97 -> fluid into the interstitial space of the lungs which leads to pulmonary edema.

182.76 -> Another cardiogenic cause is severe systemic hypertension - specifically a blood pressure

187.489 -> that is greater than 180 systolic or 110 diastolic.

192.589 -> In this situation, the left ventricle is healthy but simply can’t effectively pump blood

196.439 -> in a system with such high afterload - in other words, under conditions with such high

201.18 -> systemic pressures.

203.7 -> Once again, blood starts to back up in the left atrium, pulmonary veins, and pulmonary

208.689 -> capillaries, ultimately leading to pulmonary hypertension and pulmonary edema.

217.049 -> Noncardiogenic causes of pulmonary edema include things like pulmonary infections, inhalation

221.199 -> of toxic substances, and trauma to the chest.

224.9 -> All of these can cause direct injury to the alveoli, and when this happens there is usually

229 -> an inflammatory process that makes nearby capillaries more permeable.

234.26 -> As a result, proteins and fluid enter the interstitial space.

238.799 -> Another cause is sepsis, and the key difference is that in sepsis the inflammatory process

243.409 -> happens throughout the body rather than just in the lungs, so in addition to pulmonary

248.339 -> edema, sepsis can cause extra fluid in the interstitial space of tissues throughout the

252.709 -> body.

254.939 -> Another category of non-cardiogenic causes is having low oncotic pressure.

259.17 -> And this could result from not making enough proteins like albumin due to malnutrition

264.49 -> or from liver failure.

267.2 -> Alternatively it could be due to losing protein too quickly like in nephrotic syndrome.

273.05 -> Regardless of the cause, low oncotic pressure leads to fluid moving from the capillary and

277.41 -> into the interstitial space throughout the body, and in the lungs that results in pulmonary

281.96 -> edema.

285.669 -> Pulmonary edema can develop in a few ways and often develops through a combination of

290.99 -> mechanisms.

291.99 -> Pulmonary edema makes gas exchange difficult because oxygen and carbon dioxide have to

296.07 -> diffuse through a wide layer of interstitial fluid, to get from the alveoli to the pulmonary

301.59 -> capillary and vice versa.

304.16 -> That journey can take too long relative to how quickly blood moves through the lungs,

308.419 -> and that makes it hard to fully oxygenate the blood.

313.979 -> Pulmonary edema can lead to severe shortness of breath, and in left-sided heart failure,

318.199 -> it can lead to orthopnea which is when there’s worse shortness of breath while lying flat.

323.53 -> This happens because there’s increased pulmonary congestion while lying down, and in left-sided

328.169 -> ventricular heart failure, the pulmonary circulation is already overloaded.

332.96 -> As a result, the extra blood can’t be pumped out efficiently, and it causes shortness of

336.78 -> breath.

338.16 -> This pulmonary congestion and shortness of breath decreases when a person sits up.

343.31 -> The diagnosis of pulmonary edema is usually made with a chest x-ray or chest CT scan that

348.84 -> shows fluid in the interstitial space.

353.28 -> Treatment for pulmonary edema typically involves giving supplemental oxygen.

357.18 -> Other treatments are dependent on the underlying cause - if the cause is cardiogenic in nature,

362.36 -> medications aimed at boosting the heart’s performance or lowering the blood pressure

366.11 -> can be helpful.

367.59 -> If the cause is related to inflammation or low oncotic pressure, then managing that illness

373.06 -> will help resolve the pulmonary edema.

375.65 -> Alright, as a quick recap, pulmonary edema refers to fluid accumulation in the interstitial

381.469 -> space of the lungs which can be seen on a chest Xray or chest CT scan.

387.53 -> Common cardiogenic causes include left sided heart failure and hypertension, both of which

392.28 -> lead to increased hydrostatic pressure in the pulmonary capillaries.

396.889 -> Common non-cardiogenic causes include inflammation in the lungs or system-wide inflammation which

402.4 -> causes the pulmonary capillaries to be more permeable.

406.65 -> Other causes include a low oncotic pressure which can be from malnutrition, liver failure,

411.949 -> and nephrotic syndrome.

414.55 -> Regardless of the cause, pulmonary edema interferes with gas exchange and results in shortness

418.78 -> of breath.

Source: https://www.youtube.com/watch?v=oRDOUv6dEpE