Respiratory Support

• Options for supporting a patient’s respiratory system

  1. Oxygen therapy

  2. High-flow nasal cannula

  3. Non-invasive ventilation

  4. Intubation and mechanical ventilation

  5. Extracorporeal membrane oxygenation (ECMO)

  6. Chest physiotherapy

  7. Suction
• Respiratory support does not fix the underlying problem. It buys time while the underlying problem is managed
• Acute respiratory distress syndrome occurs due to a severe inflammatory reaction in the lungs, often secondary to sepsis (e.g., pneumonia or covid-19) or trauma
• Acute respiratory distress syndrome symptoms

  1. Collapse of the alveoli and lung tissue (atelectasis)

  2. Pulmonary oedema

  3. Decreased lung compliance

  4. Fibrosis of the lung tissue
• Acute respiratory distress syndrome clinical presentation

  1. Acute respiratory distress

  2. Hypoxia with an inadequate response to oxygen therapy

  3. Bilateral infiltrates on a chest x-ray
• Management of ARDS


  1. Respiratory support

  2. Prone positioning

  3. Careful fluid management to avoid excess fluid collecting in the lungs
• In ARDS, only a small portion of the total lung volume is aerated and has functional alveoli. The remainder of the lungs are collapsed and non-aerated
• Mechanical ventilation in ARDS

  1. Low volumes and pressures are used to avoid over-inflating the small functional portion of the lungs (lung protective ventilation)

  2. Positive end-expiratory pressure (PEEP) is used to prevent the lungs from collapsing further
• Benefits of prone positioning in ARDS

  1. Reducing compression of the lungs by other organs

  2. Improving blood flow to the lungs

  3. Improving clearance of secretions

  4. Improving overall oxygenation

  5. Reducing the required assistance from mechanical ventilation
• Management of Oxygen Therapy

  Oxygen can be delivered by several methods
• Improving oxygenation in the lungs

  1. Improving blood flow to the lungs, particularly the well-ventilated areas

  2. Improving clearance of secretions

  3. Improving overall oxygenation

  4. Reducing the required assistance from mechanical ventilation
• Oxygen Therapy


  1. Oxygen can be delivered by several methods with varying FiO2 concentrations:

  2. Nasal cannula: 24 – 44% oxygen

  3. Simple face mask: 40 – 60% oxygen

  4. Venturi masks: 24 – 60% oxygen

  5. Face mask with reservoir (non-rebreather mask): 60 – 95% oxygen
• Oxygen delivery methods and FiO2 concentrations

  • Nasal Cannula: 1 L/min - 24%, 2 L/min - 28%, 4 L/min - 36%
  • Simple Face Mask: 5 L/min - 40%, 8 L/min - 60%
  • Face Mask With Reservoir (Non-Rebreather Mask): 8 L/min - 80%, 10 L/min - 95%
  • Venturi masks: Blue - 2 L/min - 24%, White - 4 L/min - 28%, Orange - 6 L/min - 31%, Yellow - 8 L/min - 35%, Red - 10 L/min - 40%, Green - 15 L/min - 60%
• Positive End-Expiratory Pressure (PEEP)


  Additional pressure in the airways at the end of exhalation keeps them inflated, reduces atelectasis, improves ventilation of the alveoli, opens more areas for gas exchange, and decreases the effort of breathing
• Positive end-expiratory pressure


  Helps keep the airways from collapsing and improves ventilation
• High-Flow Nasal Cannula


  Allows for controlled flow rates of up to 60 L/min of humidified and warmed oxygen, reduces the amount of room air inhaled alongside supplementary oxygen, adds positive end-expiratory pressure, and provides dead space washout
• Continuous Positive Airway Pressure (CPAP)


  Constant pressure added to the lungs to keep the airways expanded, used in conditions where airways are likely to collapse, such as obstructive sleep apnoea
• Non-Invasive Ventilation (NIV)


  Involves using a full face mask, hood, or tight-fitting nasal mask to blow air forcefully into the lungs and ventilate them, a valuable middle point between basic oxygen therapy and mechanical ventilation
• BiPAP stands for Bilevel Positive Airway Pressure
• NIV involves a cycle of high and low pressure to correspond to the patient’s inspiration and expiration: IPAP (inspiratory positive airway pressure)
• NIV


  Non-Invasive Ventilation
• IPAP


  Inspiratory Positive Airway Pressure - pressure during inspiration forcing air into the lungs
• EPAP


  Expiratory Positive Airway Pressure - pressure during expiration preventing airway collapse
• Mechanical Ventilation


  Used when other forms of respiratory support are inadequate or contraindicated, involves a ventilator machine moving air into and out of the lungs
• Patients generally require sedation while on a ventilator as it can be uncomfortable and distressing
• Mechanical ventilation has several adverse effects and is only used for the shortest time necessary
• An endotracheal tube (ETT) or tracheostomy is required to connect the ventilator to the lungs
• No leaks should be present in the circuit for mechanical ventilation
• The ventilator should be able to deliver controlled pressures and volumes into the lungs
• Basic settings for mechanical ventilation

  • FiO2 (concentration of oxygen)
  • Respiratory rate (breaths per minute)
  • Tidal volume (volume of air pushed in per breath)
  • Inspiratory: expiratory ratio
  • Peak flow rate
  • Peak inspiratory pressure
  • Positive end-expiratory pressure
• Modes of mechanical ventilation

  • Volume-controlled ventilation (VC)
  • Pressure-controlled ventilation (PC)
  • Assist control (AC)
  • Continuous positive airway pressure (CPAP)
• ECMO


  Extracorporeal Membrane Oxygenation - extreme form of respiratory support used when intubation and ventilation are insufficient
• ECMO involves removing blood from the body, adding oxygen and removing carbon dioxide, then pumping it back into the body
• ECMO is only used short-term for potentially reversible causes of respiratory failure and is not a long-term treatment
• ECMO is provided in specialist ECMO centres and is not available in most intensive care units