Respiratory failure Flashcards
Define type 1 & type 2 respiratory failure
Type 1=hypoxic
Type 2=hypercapnic
Describe the different pathways causing respiratory failure
- ) Lung failure leading to hypoxic respiratory failure- results in hypoxic respiratory failure
- ) respiratory muscle pump failure leading to hypercapnic respiratory failure
Define Hypoxaemia
PaO2<8kPa
-refers to oxygen in the blood
What are the causes of hypoxaemia?
- Ventilation-perfusion mismatch
- Impaired diffusion
- Alveolar hypoventilation
- Low partial pressure of inspired oxygen
- Anatomical R-L shunt e.g PAVM lobar pneumonia
What should the relationship between ventilation and perfusion be?
-They should be exactly matched
-VA=Q
Normal value should be 0.8
Describe the different Va/Q scenarios and state the values of their ratios
1.)Shunt alveolar unit. Va/Q=0 Q>>Va Wasted perfusion 2.) Ideal alveolar unit Va/Q=1 Q=Va idealized matching 3.)Dead space alveolar unit Va/Q=infinity? Q<
Define hypercapnia
PaCo2>6kPa
State the equation to work out alveolar ventilation (Va)
minute ventilation(Ve) - dead space ventilation(Vd)
How do you work out minute ventilation
Tidal volume(Vt) x respiratory rate(RR)
How do you work dead space ventilation?
Dead space volume x RR
How is blood flow increased to well ventilated alveoli and decreased to poorly ventilated alveoli in the healthy lung
via reflex mechanisms
What are the two possible responses to oxygen therapy
- Patients PaCo2 and clinical state may improve or not change
- Patients PaCo2 rises(hypercapnia), becomes drowsy or unconscious
Why do some patients develop hypercapnia on oxygen therapy?
- Patients with COPD rely on their hypoxic ventilatory drive due to blunted sensitivity to Co2 and H+
- Hypercapnia results from a suppression of the hypoxic ventilatory drive causing alevolar hypoventilation
- Patients ‘stop breathing’
What are the 3 factors governing blood gas levels
- Drive (cortical, brainstem)
- Load( resistive forces)
- Capacity( spinal cord, peripheral nerves, NMJ,muscles)
What factors influence respiratory failure?
- ) Drive failure
- Cortical &brainstem lesions (incl.trauma), encephalitis, ischaemia,Haemorrhage, Cheyne-Stokes respiration (CHF)
- Drugs(sedatives,opiods)
- Metabolic alkalosis (loop diuretics) - ) Transmission failure: (spinal cord lesion, poli,MND,myasthenia gravis)
- ) Threshold (intrinsic PEEP, dynamic hyperinflation)
What are the different forms of respiratory support?
- oxygen
- Non-invasive ventilation (NIV)
- Invasive mechanical ventilation(IMV)
- Extra-corporeal membrane oxygenation(ECMO)
What are the clinical features of respiratory failure resulting from hypoxia and hypercapnia?
- Confusion
- Cyanosis
- Somnolence/drowsiness
- Dyspnoea
What are the clinical features of respiratory failure resulting from underlying clinical conditions?
- COPD
- pneumonia
- Pulmonary oedema (cardiogenic & non-cardiogenic)
- Pulmonary embolism(PE)
- Pulmonary fibrosis
- Asthma
How can we assess respiratory failure?
- Standardised approach to unwell patient ( Airways, Breathing, Circulation)
-Assess vital signs (temp, RR,HR,BP)
-Oxy-haemoglobin saturation spO2 (normal 94-99%, >92% excludes hypoxia) - Arterial blood gas (ABG) analysis
assesses for hypercapnia
What do we need to know to manage respiratory failure?
- Hypoxia kills (titrated o2, target Spo2 94-98%; 88-92% if chronic respiratory failure)
- No benefit from oxygen if not hypoxic (stroke, MI)
- oxygen may worsen hypercapnia
- oxygen isn’t ventilation
What may result from co2 retention?
- Flapping tremor
- drowsiness
- flushed face
- Headache
What signs indicate respiratory deterioration ?
- Increased RR (esp, if >30)
- decreased sp02
- increased o2 dose needed to keep spo2 in target range
- increased EWS/ trigger score
What are the characteristics of invasive ventilation?
- Greater control of ventilation
- Secure ventilatory delivery
- Level 3 support ( requires critical care bed)
- Gold standard treatment
What are the characteristics of non- invasive ventilation?
- patient remains conscious
- Maintains structural host defence system
- level 2 support
- Evidence based in COPD, immunosuppressed
Why is anticoagulation required in ECMO?
- Extra-corporeal membrane oxygenation is a form of management of severe respiratory failure
- Anticoagulation is required because blood is coming out of the body
Which diseases can alter perfusion of the lungs
PE
Which diseases can alter ventilation of the lungs
- asthma
- COPD
- pulmonary oedema
- atelectasis
- Pneumonia
- Aspiration
What is extra corporeal membrane oxygenation
- Similar to the heart and lung by-pass machine
- Also known as extracorporeal life support, is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of gas exchange or perfusion to sustain life.
