Adult Respiratory Distress Syndrome

Pulmonology

Clinicals - History

Fact Explanation
Introduction Adult respiratory distress syndrome(ARDS) is a condition characterized by acute inflammation of the lungs triggered by a pulmonary or an extrapulmonary insult. This cause bilateral and diffuse damage to the lung vascular endothelium and alveolar epithelium, causing a protein rich pulmonary edema, hyaline membrane formation, reduced lung compliance, difficult air exchange and acute respiratory failure. These occur in the absence of cardiac failure. Introduction
Adult respiratory distress syndrome(ARDS) is a condition characterized by acute inflammation of the lungs triggered by a pulmonary or an extrapulmonary insult. This cause bilateral and diffuse damage to the lung vascular endothelium and alveolar epithelium, causing a protein rich pulmonary edema, hyaline membrane formation, reduced lung compliance, difficult air exchange and acute respiratory failure. These occur in the absence of cardiac failure.
History of a predisposing event The conditions that could predispose to (or associated with development of ARDS) could be either by direct lung injury or by indirect or extra pulmonary injury. Direct injury may result from pneumonia, inhalation injury, aspiration, pulmonary vasculitis, pulmonary contusion and drugs(e.g. bleomycin, opiates, salicylates) or oxygen toxicity. Indirect injury could occur by septic shock,amniotic/eat embolism, massive hemorrhage, massive burns, major trauma, acute pancreatitis etc. History of a predisposing event
The conditions that could predispose to (or associated with development of ARDS) could be either by direct lung injury or by indirect or extra pulmonary injury. Direct injury may result from pneumonia, inhalation injury, aspiration, pulmonary vasculitis, pulmonary contusion and drugs(e.g. bleomycin, opiates, salicylates) or oxygen toxicity. Indirect injury could occur by septic shock,amniotic/eat embolism, massive hemorrhage, massive burns, major trauma, acute pancreatitis etc.
Progressive shortness of breath Acute onset rapidly progressive dyspnea associated with significant hypoxemia are diagnostic features of ARDS. Progressive shortness of breath
Acute onset rapidly progressive dyspnea associated with significant hypoxemia are diagnostic features of ARDS.
Multi-organ failure ARDS is often associated with multi-organ failure. Multi-organ failure
ARDS is often associated with multi-organ failure.

Clinicals - Examination

Fact Explanation
General examination Patient will appear dyspnoeic. Can have elevated or reduced body temperature. Cyanosis may be seen in the lips, tongue and nail beds. Look for features of a predisposing cause. For e.g. Features of sepsis such as hypotension (refractory to resuscitation), warm peripheries, bounding peripheral pulse etc. and a site of infection, intravascular lines, drain sites, surgical wounds, signs of lung consolidation, features of suggestive of acute abdomen. General examination
Patient will appear dyspnoeic. Can have elevated or reduced body temperature. Cyanosis may be seen in the lips, tongue and nail beds. Look for features of a predisposing cause. For e.g. Features of sepsis such as hypotension (refractory to resuscitation), warm peripheries, bounding peripheral pulse etc. and a site of infection, intravascular lines, drain sites, surgical wounds, signs of lung consolidation, features of suggestive of acute abdomen.
Examination of respiratory system Patient will have tachypnea. Auscultation of lungs will elicit bilateral lung crackles due to pulmonary edema. If there is decreased breath sounds over one lung in a ventilated patient, look for pneumothorax or wrong placement of the endotracheal tube in the right main bronchus. Presence of subcutaneous air may suggest barotrauma. Examination of respiratory system
Patient will have tachypnea. Auscultation of lungs will elicit bilateral lung crackles due to pulmonary edema. If there is decreased breath sounds over one lung in a ventilated patient, look for pneumothorax or wrong placement of the endotracheal tube in the right main bronchus. Presence of subcutaneous air may suggest barotrauma.
Examination of cardiovascular system Patient will have tachycardia. SIgns of congestive heart failure or that of intravascular volume overload, such as elevated jugular venous pressure, cardiac murmurs and gallops, peripheral edema etc. because these should be excluded as the cause for pulmonary edema. Examination of cardiovascular system
Patient will have tachycardia. SIgns of congestive heart failure or that of intravascular volume overload, such as elevated jugular venous pressure, cardiac murmurs and gallops, peripheral edema etc. because these should be excluded as the cause for pulmonary edema.
Examination of abdomen Look for features of acute abdomen such as abdominal distension,tenderness, guarding or rigidity etc. which may lead to the diagnosis of an intra-abdominal pathology which may have lead to the development of ARDS. Examination of abdomen
Look for features of acute abdomen such as abdominal distension,tenderness, guarding or rigidity etc. which may lead to the diagnosis of an intra-abdominal pathology which may have lead to the development of ARDS.

Investigations - Diagnosis

Fact Explanation
Arterial blood gas analysis(ABG) Placement of an arterial line will be needed as regular ABG analysis should be done. ABG provides level of PaO2, FiO2, PaCO2, blood pH etc. which helps in the diagnosis, assessment for the need of ventilation and for monitoring progression of ARDS. A ratio of PaO2:FiO2 <200 is one of the diagnostic features of ARDS. Patients ABG analysis will show hypoxemia with respiratory alkalosis initially but with the rise of carbondioxide, the patient develops respiratory acidosis. If the ARDS is associated with sepsis there will be metabolic acidosis with or without partial respiratory compensation. Arterial blood gas analysis(ABG)
Placement of an arterial line will be needed as regular ABG analysis should be done. ABG provides level of PaO2, FiO2, PaCO2, blood pH etc. which helps in the diagnosis, assessment for the need of ventilation and for monitoring progression of ARDS. A ratio of PaO2:FiO2 <200 is one of the diagnostic features of ARDS. Patients ABG analysis will show hypoxemia with respiratory alkalosis initially but with the rise of carbondioxide, the patient develops respiratory acidosis. If the ARDS is associated with sepsis there will be metabolic acidosis with or without partial respiratory compensation.
Complete blood count Leukopenia or leukocytosis may be seen in patients with sepsis. Complete blood count
Leukopenia or leukocytosis may be seen in patients with sepsis.
Liver function tests Done to assess presence of any liver function abnormality which may worsen the clinical state of the patient. Liver function tests
Done to assess presence of any liver function abnormality which may worsen the clinical state of the patient.
Plasma B-natriuretic peptide (BNP) Done to differentiate presence of cardiogenic pulmonary edema. BNP will be elevated in cardiogenic pulmonary edema. Plasma B-natriuretic peptide (BNP)
Done to differentiate presence of cardiogenic pulmonary edema. BNP will be elevated in cardiogenic pulmonary edema.
Chest X-ray(CXR) Will show bilateral diffuse lung infiltrates with ground glass appearance. CXR will also help to diagnose presence of pneumothorax and pneumomediastinum which can be complications of positive pressure ventilation. Chest X-ray(CXR)
Will show bilateral diffuse lung infiltrates with ground glass appearance. CXR will also help to diagnose presence of pneumothorax and pneumomediastinum which can be complications of positive pressure ventilation.
Computed tomography (CT) of chest Is indicated in some patients as it is more sensitive in detecting emphysema, pleural effusions, pneumomediastinum, lung cysts and pneumothoraces. Computed tomography (CT) of chest
Is indicated in some patients as it is more sensitive in detecting emphysema, pleural effusions, pneumomediastinum, lung cysts and pneumothoraces.
2D-echocardiography Done when there is suspicion of cardiac failure. 2D-echocardiography
Done when there is suspicion of cardiac failure.
Pulmonary artery catheter monitoring Pulmonary artery catheter enables to measure pulmonary capillary wedge pressure(PCWP). PCWP <19mmHg with normal capillary oncotic pressure is seen in ARDS. Pulmonary artery catheter monitoring
Pulmonary artery catheter enables to measure pulmonary capillary wedge pressure(PCWP). PCWP <19mmHg with normal capillary oncotic pressure is seen in ARDS.
Brochoscopy Helps to detect infection, alveolar hemorrhage, acute eosinophilic pneumonia etc. Culture material can be obtained by bronchoalveolar lavage (BAL) that can be analyzed for for for cell differential count, cytology, Gram stain, culture etc. Brochoscopy
Helps to detect infection, alveolar hemorrhage, acute eosinophilic pneumonia etc. Culture material can be obtained by bronchoalveolar lavage (BAL) that can be analyzed for for for cell differential count, cytology, Gram stain, culture etc.
Septic screen with blood/urine/sputum culture Done when there is suspicion of sepsis. Septic screen with blood/urine/sputum culture
Done when there is suspicion of sepsis.

Investigations - Management

Fact Explanation
APACHE II score This is a system devised to assess the severity of disease in patients admitted to the ICU as result of any disease. It takes a number of clinical signs and laboratory values in to count. This system can be used to assess the severity of ARDS patients admitted to the ICU. APACHE II score
This is a system devised to assess the severity of disease in patients admitted to the ICU as result of any disease. It takes a number of clinical signs and laboratory values in to count. This system can be used to assess the severity of ARDS patients admitted to the ICU.
Serum creatinine Done to assess renal function because these patients may develop acute renal failure most commonly due to acute tubular necrosis which requires renal replacement therapy. Serum creatinine
Done to assess renal function because these patients may develop acute renal failure most commonly due to acute tubular necrosis which requires renal replacement therapy.
Electrocardiogram Done to detect arrhythmia, myocardial infarction etc. which cause sudden deterioration of a patient with ARDS. Electrocardiogram
Done to detect arrhythmia, myocardial infarction etc. which cause sudden deterioration of a patient with ARDS.

Management - Supportive

Fact Explanation
Education of the patient/family Education regarding the nature of the disease, prognosis, available treatment options, importance of physiotherapy and pulmonary rehabilitation etc. should be done. Education of the patient/family Education
regarding the nature of the disease, prognosis, available treatment options, importance of physiotherapy and pulmonary rehabilitation etc. should be done.
Fluid Management/Cardiovascular support This is important in order to optimize oxygen delivery to tissues. Most patients with ARDS wil be hemodynamically compromised due to underlying causes. These patients benefit from fluid resuscitation. The aim should be to maintain a low normal intravascular volume whilst maintaining the mean arterial pressure and cardiac index. This is done to prevent worsening of capillary leakage due to over resuscitation which will further compromise oxygenation. Inotrope/ vasopressor treatment may be required depending on the patient's condition. Fluid Management/Cardiovascular support
This is important in order to optimize oxygen delivery to tissues. Most patients with ARDS wil be hemodynamically compromised due to underlying causes. These patients benefit from fluid resuscitation. The aim should be to maintain a low normal intravascular volume whilst maintaining the mean arterial pressure and cardiac index. This is done to prevent worsening of capillary leakage due to over resuscitation which will further compromise oxygenation. Inotrope/ vasopressor treatment may be required depending on the patient's condition.
Nutrition support Enteral feeding should be encouraged always. This is because when compared to parenteral feeding, it helps to maintain the integrity of the gut mucosa and is associated with lower risk of systemic sepsis. If the patient has been on prolonged ventilation or has multi-organ failure gastric stress ulcer prophylaxis with H2 receptor blockers should be considered. Delayed gastric emptying and reduced gut motility will respond to prokinetic drugs or may require nasojejunal feeding. Nutritional supplementation with initial total parenteral nutrition will be needed in severe cases of ARDS. Nutrition support
Enteral feeding should be encouraged always. This is because when compared to parenteral feeding, it helps to maintain the integrity of the gut mucosa and is associated with lower risk of systemic sepsis. If the patient has been on prolonged ventilation or has multi-organ failure gastric stress ulcer prophylaxis with H2 receptor blockers should be considered. Delayed gastric emptying and reduced gut motility will respond to prokinetic drugs or may require nasojejunal feeding. Nutritional supplementation with initial total parenteral nutrition will be needed in severe cases of ARDS.
Prophylaxis for venous thromboembolism Prolong immobilization leads to deep vein thrombosis and pulmonary thromboembolism. These patients may require prophylactic treatment to prevent these complications. There are methods of mechanical prophylaxis such as
anti-embolism stockings , foot impulse devices, intermittent pneumatic compression devices or pharmacological prophylaxis with fondaparinux sodium, low molecular weight heparin(LMWH), unfractionated heparin (UFH) can be employed. These should be continue until the patient is no longer at increased risk of venous thromboembolism.
Prophylaxis for venous thromboembolism
Prolong immobilization leads to deep vein thrombosis and pulmonary thromboembolism. These patients may require prophylactic treatment to prevent these complications. There are methods of mechanical prophylaxis such as
anti-embolism stockings , foot impulse devices, intermittent pneumatic compression devices or pharmacological prophylaxis with fondaparinux sodium, low molecular weight heparin(LMWH), unfractionated heparin (UFH) can be employed. These should be continue until the patient is no longer at increased risk of venous thromboembolism.
Physiotherapy and lung function improvement Survivors of ARDS may have persistent functional disability after discharge from ICU. These may be of limitation to lung function and also extrapulmonary such as muscle wasting and weakness. Follow up of these patients with physiotherapy and pulmonary rehabilitation will help to improve their quality of life and also to recover with minimal residual limitations. Physiotherapy and lung function improvement
Survivors of ARDS may have persistent functional disability after discharge from ICU. These may be of limitation to lung function and also extrapulmonary such as muscle wasting and weakness. Follow up of these patients with physiotherapy and pulmonary rehabilitation will help to improve their quality of life and also to recover with minimal residual limitations.
Intubation/Tracheostomy Will be required if the patient needs prolonged mechanical ventilation. Both methods allow to establish a more stable airway which allows mobilization. If patient requires ventilation for a longer period or has difficulty weaning from the ventilator, tracheostomy can be considered. Intubation/Tracheostomy
Will be required if the patient needs prolonged mechanical ventilation. Both methods allow to establish a more stable airway which allows mobilization. If patient requires ventilation for a longer period or has difficulty weaning from the ventilator, tracheostomy can be considered.
Treat underlying cause The main goal of treatment is to identify and treat the underlying cause while providing optimal support for organ failure. Treat underlying cause
The main goal of treatment is to identify and treat the underlying cause while providing optimal support for organ failure.
Corticosteroid treatment Treatment with low dose steroids has shown benefit for some patients in the acute stage. This is particularly seen in patients with ARDS due to sepsis. The value of this treatment is still under study. Corticosteroid treatment
Treatment with low dose steroids has shown benefit for some patients in the acute stage. This is particularly seen in patients with ARDS due to sepsis. The value of this treatment is still under study.

Management - Specific

Fact Explanation
Intensive care unit(ICU)/ High dependency unit(HDU) care Almost all patients with ARDS will require admission to ICU/HDU. Make arrangement for this early. Intensive care unit(ICU)/ High dependency unit(HDU) care
Almost all patients with ARDS will require admission to ICU/HDU. Make arrangement for this early.
Ventilation These patients require respiratory support to improve gas exchange and correct hypoxia. Patients with ARDS will require a high oxygen concentration (provided with non-rebreather mask) and with reservoir FiO2 of 60-80% or continuous positive airway pressure. Non invasive Positive Pressure Ventilation (NIPPV) is prefered than mechanical ventilation due to the complications owing to intubation & other related procedures. NIPPV employs usage of different interfaces such as mouth piece or nasal, face, or helmet mask and different ventilatory modes such as volume support pressure support, bilevel positive airway pressure [BiPAP] , proportional-assist ventilation [PAV], continuous positive airway pressure [CPAP]. The patient with ARDS will require high FiO2, Low Vte (Tidal Volume) and high PEEP, which can be achived by CPAP. CPAP provides constant positive pressure through out the respiratory cycle and allows a higher FiO2, approaching 80-100%. It acts by opening the collapsing alveoli filled with fluid, increases the functional residual capacity and compliance so that the work of breathing is reduced and gas exchange is increased. Depending on the severity, mechanical or invasive ventilation methods will be adopted. Indications for mechanical ventilation include inadequate oxygenation with PaO2< 8kPa or FiO2> 0.6, PaCO2 level>6kPa, clinical signs of incipient respiratory/cardiovascular failure. Prolong high FiO2 (>65%) can cause further damage to lungs due to O2 radicals. Other preventable complication of mechanical ventilation include volutrauma and barotrauma. Volutrauma is damage caused to alveoli by the overdistention during mechanical ventilation with a ventilator set for an excessively high tidal volume. Barotrauma as the mane implies, refers to alveolar injury caused by increased alveolar pressure. These can be prevented in ARDS patients by using a low Vte and moderate/high PEEP during mechanical ventilation. Ventilation
These patients require respiratory support to improve gas exchange and correct hypoxia. Patients with ARDS will require a high oxygen concentration (provided with non-rebreather mask) and with reservoir FiO2 of 60-80% or continuous positive airway pressure. Non invasive Positive Pressure Ventilation (NIPPV) is prefered than mechanical ventilation due to the complications owing to intubation & other related procedures. NIPPV employs usage of different interfaces such as mouth piece or nasal, face, or helmet mask and different ventilatory modes such as volume support pressure support, bilevel positive airway pressure [BiPAP] , proportional-assist ventilation [PAV], continuous positive airway pressure [CPAP]. The patient with ARDS will require high FiO2, Low Vte (Tidal Volume) and high PEEP, which can be achived by CPAP. CPAP provides constant positive pressure through out the respiratory cycle and allows a higher FiO2, approaching 80-100%. It acts by opening the collapsing alveoli filled with fluid, increases the functional residual capacity and compliance so that the work of breathing is reduced and gas exchange is increased. Depending on the severity, mechanical or invasive ventilation methods will be adopted. Indications for mechanical ventilation include inadequate oxygenation with PaO2< 8kPa or FiO2> 0.6, PaCO2 level>6kPa, clinical signs of incipient respiratory/cardiovascular failure. Prolong high FiO2 (>65%) can cause further damage to lungs due to O2 radicals. Other preventable complication of mechanical ventilation include volutrauma and barotrauma. Volutrauma is damage caused to alveoli by the overdistention during mechanical ventilation with a ventilator set for an excessively high tidal volume. Barotrauma as the mane implies, refers to alveolar injury caused by increased alveolar pressure. These can be prevented in ARDS patients by using a low Vte and moderate/high PEEP during mechanical ventilation.

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