ARDS + Respiratory Failure Flashcards
What is adult respiratory distress syndrome
Fluid accumulation in alveoli due to increased permeability caused by inflammation
Non cardiac pulmonary oedema
What are pulmonary causes of adult respiratory distress
Pneumonia Direct lung injury Smoke inhalation Vasculitis Aspiration
What are other causes of RDS
Sepsis Shock Massive haemorrhage Blood transfusion - within 6 hours usually known as TRALI Trauma Head injury = sympathetic = pulmonary hypertension DIC Pancreatitis Ovarain hyperstimulation Liver failure Bypass Drugs / toxins
What are symptoms of RDS
Acute + severe SOB Tachycardia Tachypnoea Cyanosis Bilateral crackles - fine Low sats Hyperaemia Type 1 resp failure as gas exchangedoesnt occur in inflamed lung CO2 normal as can compensate by tachypnoea Multi-organ failure Signs of hypercapnia if rises
What are symptoms if on ventilatory
Rising ventilatory pressure
Normal capillary wedge pressure excludes cardiac cause
What is the criteria for diagnosing RDS
Within 1 week of trigger
Pulmonary oedema on CXR (not explained by collapse or effusion)
Non-cardiogenic cause
PaO2 <40kPa
How do you treat RDS
ITU Oxygen Negative fluid balance - diuretic / haemodialysis Ventilation - low TV CPAP but most need ventilation Organ support Vasopressor to maintain CO Nutrition Treat cause
What are complications of RDS
Scarring
Decreased lung function
What causes atelectasis (collapse)
Post-op
Obstructed airway - COPD / asthma
When should you consider atelectasis post op
72 hours
What are the symptoms
SOB Hypoxaemia Resp difficulty Decreased expansion Decreased breath sounds NO FEVER - more likely infection
How do you treat
Chest physio
What is type 1 respiratory failure
PaO2 <8
PaCo2 normal
What causes type 1 respiratory failure
V/Q mismatch
Abnormal diffusion
R-L shunt
Hypoventilation = type 2
What can cause a V/Q mismatch (poor perfusion due to barrier to gas exchange)
Pneumonia Pulmonary oedema PE Asthma Emphysema RDS
What are the symptoms of type 1
Features of cause Features of hypoxia Restless SOB Agitated Confusion Cyanosis
What happens in long standing type 1
Polycythaemia
Pulmonary hypertension
Cor pulmonale
How do you Dx respiratory failure
FBC, U+E, CRP ABG CXR PFT Sputum and blood Spirometry - restrictive
How do you treat type 1
Treat cause Oxygen Monitor O2 with ABG and increase if CO2 stable Assisted ventilation if PaO2 <8 CPAP
Why do you want to control O2 delivery even in type 1
As want to be able to see if condition worsens and sats drop
Why is CPAP only indicated in type 1
Decreases ventilation as no pressure differenece
Can’t be used in type 2 which is due to decreased ventilation
Useful for pulmonary oedema as pushes fluid out
What does CPAP do
Stops lungs collapsing as keeps alveoli open so increases O2 delivery
Can be delivered through high flow nasal cannula - 40l
What is O2 a good marker of
Diffusion i.e. in oedema / infection
What is CO2 a good marker of
Poor ventilation
Very soluble so shouldn’t be affected by diffusion issues
What is type 2 resp failure
PaO2 <8
PaCO2 >6
What causes type 2 respiratory failure
Alveolar hypoventilation with or without V/Q mismatch Ventilation issue Asthma COPD OSA Fibrosis Drugs CNS tumour Trauma Neuromuscular Thoracic wall disease
How does type 2 present
Hypercapnia Headache Peripheral vasodilation Tachycardia Bounding pulse Tremor Papilloedema Confusion Drowsy Coma
How do you treat type 2
Treat underlying cause Beware of hypoxic drive Controlled O2 Check ABG regularly Consider NIPPV if CO2 rising Bipap (2 diff pressures) Intubation if this fails ECMO
Consequences
Acidosis
Indications for non-invasive ventilation
COPD with pH 7.25-7.35
Type 2 res failure
Cardiopulmonary oedema resistant to CPAP
Weaning from tracheostomy
What excludes cardiac cause for ARDS
Normal capillary wedge pressure
When is ventilation indicated
pH <7.25
What is CPAP
Continuous +Ve airway pressure
Keeps airway expanded so air can move in and out
What are indications for CPAP
Type 1 resp failure
OSA
CCF
Acute pulmonary oedema as push fluid out
What is BiPAP
Bilevel +Ve airway pressure Involves high or low pressures to correspond to ventilation Can give - Nasal - Full face mask - Hood
When is it used
Type 2 resp failure
Usually due to COPD
If pH <7.35 despite medical therapy
What should you always do if on NIV
ABG
What causes obstructive pattern on PFT
COPD
Asthma
Bronchiectasis
Bronchiolitis obliterans
What is an obstructive pattern
FEV1 = significantly reduced FVC = reduced or normal RAtio = reduced
What causes restrictive pattern on PFT
Pulmonary fibrosis Asbestosis Sarcoidosis ARDS Infant respiratory distress Kyphoscoliosis e.g. AS Neuromuscular Severe obesity
What is a restrictive pattern
FEV1 = reduced FVC = significantly reduce Ratio= normal or increased
ABG
OK
What suggests chronic resp acidosis e.g. due to COPD
Elevated bicarb (as compensating)
