Atelectasis, ARDS, Pulmonary edema Flashcards
In relation to Neonates, what is Atelectasis ?
Neonatal Atelectasis an incomplete explanation of the lungs
Acquired Atelectasis is defined as?
A collapse of previously inflated lungs, resulting in areas of relatively airless pulmonary parenchyma.
Acquired atelectasis occurs commonly in ?
Adults
List the different types of acquired atelectasis ?
- Resorption or obstruction Atelectasis
- Compression Atelectasis
- Contraction Atelectasis
In 6 steps, what’s occurs in resorption atelectasis?
- This occurs from complete obstruction of an airway
- Overtime, Air (oxygen) trapped in dependent alveoli (distal alveoli) is resorbed.
- resorption occurs without impairment of blood flow through the affected alveoli walls
- Because the lung volume is diminished, the mediastinum shifts TOWARDS the atelectatic lungs
Causes of resorption atelectasis
- Excessive secretions (Mucus plugs)
-
Exudates within smaller bronchi. This is seen in conditions like?
- Bronchial Asthma
- Chronic Bronchitis
- Bronchiectasis
- Postoperative states
- Foreign body aspiration
- Bronchial neoplasms (intrabrochiaL-tumors)
Compression atelectasis ?
This results from the accumulation of a significant volume of
- Fluid( exudate, Transudafe)
- Air (Pneumothorax, Tension pneumothorax)
- Blood
- Tumor
Accumulate in the pleural cavity
Mediastinum shifts away from the affected lung
Contraction atelectasis ?
- This occurs when focal or generalized pulmonary or pleural fibrosis prevent full lung expansion
Atelectasis is a reversible disorder except in?
Contraction Atelectasis
Significant atelectasis complications?
- Leads to reduced oxygenation
- Predisposes to infection
Pulmonary edema Definition?
Pulmonary Edema is defined as an abnormal increase in the interstitial fluid within lung parenchyma
Etiology of pulmonary Edema can be classified into?
- hemodynamic disorders
- Microvascular injury
Hemodynamic pulmonary edema is further classified into?
1) increased hydrostatic pressure - increased pulmonary Venous pressure
2) Decreased oncotic pressure
3) lymphatic obstruction (rare)
Causes of increased hydrostatic pressure includes?
- Left sided heart failure
- volume overload
- pulmonary vein obstruction
Causes of decreased oncotic pressure ?
- Hypoalbuminemia
- nephrotic syndrome
- liver diease
- protein losing Enteropathies (PLE)
Classification of edema due to microvascular injury (alveolar injury)
Primary injury to the vascular endothelium
- infection; pneumonia, septicemia
- inhaled gases; oxygen, smoke
- liquid aspiration; gastric contents, near drowning
- Radiation
- Lung trauma
Indirect injury
- systemic inflammatory response syndrome (Sepsis, extensive trauma, burns, pancreatitis)
- Blood transfusion related
- Drugs and chemicals; chemotherapeutic agents (bleomycin), amphotericin B, heroine, cocaine, Paraquat, kerosine
What can cause Edema of undetermined origin?
- Neurogenic edema- CNS trauma
- High altitude
The commonest hemodynamic cause of pulmonary edema is ?
Increased hydrostatic pressure (as seen in left-sided heart failure )
Gross description of pulmonary edema
Clinically there’s pulmonary congestion and edema is evident by
- wet lungs
- Heavy lungs
What’s dependent edema ?
Edema accumulates initially in the basal regions of the lower lobes because hydrostatic pressure is greatest in these sites.
Histological features of pulmonary edema?
- Engorgement of the alveolar capillaries
- The presence of finely granular pale pink precipitate in the intra-alveolar space
- Presence of alveolar microhemorrhages
- Presence of hemosiderin-laiden macrophages (heart failure cells)
Histological features of long standing pulmonary congestion ?
As seen in mitral stenosis
1) Abundant hemosiderin-Laiden macrophages
2) fibrosis and thickening of the alveoli walls
3) soggy lungs become firm with brown induration
Edema in microvascular injury occurs as a result of?
1) Primary injury to vascular endothelium
2) Damage to alveolar epithelial cells
- Results in fluids and protein leakage into the interstitial space and then into the alveoli
Injury-related alveolar edema is an important feature of which condition ?
Acute respiratory distress syndrome (ARDS)
What’s the underlying pathology in Acute lung injury and ARDS
Pulmonary inflammation with epithelial and endothelial cell injury
Definition of Acute Lung injury ?
Characterized by an abrupt onset of significant hypoxemia and diffuse pulmonary infiltrates in the absence of cardiac failure
Bilateral pulmonary edema (non-Cardiogenic pulmonary edema)
ARDS is defined as?
This is a manifestation of severe Acute lung injury.
Histological manifestation of ALI and ADRS?
Diffuse alveolar Damage
Acute interstitial pneumonia is defined as ?
Acute lung injury occurring in the absence of any trigger, or any etiology
Etiology of ALI?
Complication from direct lung injuries or systemic disorder
1) Infections;
2) Physical injury
3) inhaled irritants
4) chemical injury
5) hematological conditions
6) uremia
7) pancreatitis
8) hypersensitivity reactions (organic solvents and drugs)
Examples of infections cause ALI?
- sepsis
- Diffuse pulmonary infection
- viral infection
- mycoplasma
- Pneumocystis pneumonia
- Miliary tuberculosis
- Gastric aspiration
Examples of physical injury causing ALI?
- Head injuries
- Pulmonary contusions
- Near drowning
- Fractures with fat embolism
- Burns
- Ionizing radiation
Examples of inhaled irritants causing ALI?
- Oxygen toxicity
- Smoke
- Irritant gases and chemicals
Examples of chemical injury causing ALI?
- Heroin or methadone overdose
- Acetyl salicylic acid
- Barbiturate overdose
- Paraquat
examples of Hematological conditions that can cause secretion
- Multiple transfusions
- Disseminated intravascular coagulation
In the pathogenesis of ARDS, what’s is the root cause (pathogenesis )
An imbalance between pro-inflammatory and anti-inflammatory conditions
Following an acute lung injury? What happens in ADRS?
- Macrophages activate and increase synthesis of IL8, IL1 and TNF
IL8 - is a potent neutrophil chemotactic.
Functions of IL8 and TNF ?
- IL8 causes activation of neutrophils
- TNF aids activated neutrophils to bind their ligands on activated endothelial cells by up-regulating the expression of adhesion molecules
Stiff neutrophils that are trapped in lung capillary bed secret what?
Inflammatory substances like
- protease
- Oxidants
- platelet activating factors
- leukotrienes
Loss of surfactant causes ?
Endothelial and epithelial injury leads to loss of surfactant and inability of the alveoli unit to expand
Dysregulation of coagulation system in ARDS ?
Yes,
- the protein C and anticoagulant levels are decreased in plasma and Bronchoalveloar lavage fluid
- Tissue factor levels are increased
Clinical features of ARDS?
- Increasing Cyanosis
- Increasing Hypoxemia
- Profound Dyspenea
- Profound tachypnea
- Respiratory acidosis
- Respiratory failure
Gross description of ALI in acute phase?
Lungs may be
- Heavy
- Red
- Boggy
- Firm
Histological features of ARDS/ ALI?
- interstitial and intra-alveolar edema
- congestion
- fibrin deposition
- Diffuse alveolar damage
- alveolar walls become lined with waxy hyaline membranes
Chronic histological features of ARDS/ALI
- Proliferation of type 2 pneumocytes
- Granulation tissue seen in the alveolar spaces
- Fibrotic thickening of the alveolar septa and walls due to interstitial cells proliferation and collagen deposit
Summarized pathogens is of ALI, ARDS
- Endothelial activation
- Adhesion and extravasation of neutrophils.
- Accumulation of intra-alveolar fluid and formation of hyaline membranes
- Resolution of injury
Damage to endothelial and alveolar epithelial cells and secondary inflammation are the key initiating events and the basis of lung damage.
Radiological findings in ARDS?
Diffuse bilateral Lung infiltrate
Treatment of ARDS
- Treat the underlying cause - sepsi etc
- Mechanical ventilation
- Supportive care
Investigations to be carried out for this patient?
Sepsis work up
FBC
E/U/Cr
Complications of ARDS?
- Bronchopneumonia
- Sepsis
- Multi organ failure
- Diffuse alveolar damage
