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)
• Additional methods for respiratory support

  1. Chest physiotherapy

  2. 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 or trauma
• Acute Respiratory Distress Syndrome

  • Collapse of the alveoli and lung tissue (atelectasis)
  • Pulmonary oedema (not related to heart failure or fluid overload)
  • Decreased lung compliance
  • Fibrosis of the lung tissue (typically after 10 days or more)
  • Acute respiratory distress
  • Hypoxia with an inadequate response to oxygen therapy
  • Bilateral infiltrates on a chest x-ray
• Management of ARDS


  1. Respiratory support

  2. Prone positioning (lying on their front)

  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
• Lung protective ventilation


  • Low volumes and pressures are used during mechanical ventilation to avoid over-inflating the small functional portion of the lungs
• Positive end-expiratory pressure (PEEP)


  • Used to prevent the lungs from collapsing further
• Benefits of prone positioning

  • Reducing compression of the lungs by other organs
  • Improving blood flow to the lungs, particularly the well-ventilated areas
  • Improving clearance of secretions
  • Improving overall oxygenation
  • Reducing the required assistance from mechanical ventilation
• Methods for delivering oxygen

  Oxygen therapy
• Benefits of Oxygen Therapy


  1. Improving clearance of secretions

  2. Improving overall oxygenation

  3. Reducing the required assistance from mechanical ventilation
• Methods of delivering oxygen

  • Nasal cannula
  • Simple face mask
  • Venturi masks
  • Face mask with reservoir (non-rebreather mask)
• Oxygen flow rates and FiO2 levels for different delivery methods

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


  1. Refers to the pressure that remains in the airways at the end of exhalation

  2. Additional pressure in the airways at the end of exhalation helps prevent airways from collapsing and improves ventilation

  3. Forms of respiratory support that add PEEP help keep the airways from collapsing, reduce atelectasis, improve ventilation of the alveoli, open more areas for gas exchange, and decrease the effort of breathing
• Methods of adding Positive End-Expiratory Pressure

  • High-flow nasal cannula
  • Non-invasive ventilation
  • Mechanical ventilation
• High-Flow Nasal Cannula


  1. Allows for controlled flow rates of up to 60 L/min of humidified and warmed oxygen

  2. Reduces the amount of room air inhaled alongside supplementary oxygen, increasing the concentration of oxygen inhaled

  3. Adds positive end-expiratory pressure to help prevent airways from collapsing at the end of exhalation

  4. Effectively clears dead space air and replaces it with oxygen, improving patient oxygenation
• Continuous Positive Airway Pressure (CPAP)


  1. Involves adding constant pressure to the lungs to keep the airways expanded

  2. Used to maintain airways in conditions where they are likely to collapse, for example, in obstructive sleep apnoea
• Non-Invasive Ventilation (NIV)


  1. Involves using a full face mask, hood, or tight-fitting nasal mask to blow air forcefully into the lungs and ventilate them

  2. 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) is the pressure during inspiration
• 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 airways from collapsing
• Mechanical Ventilation


  1. Used when other forms of respiratory support are inadequate or contraindicated

  2. A ventilator machine is used to move air into and out of the lungs

  3. Patients generally require sedation while on a ventilator

  4. Mechanical ventilation has several adverse effects and is used for the shortest time necessary

  5. An endotracheal tube (ETT) or tracheostomy is required to connect the ventilator to the lungs

  6. No leaks in the circuit are allowed to enable the ventilator 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 (ratio of time spent in inspiration and expiration)
  • Peak flow rate (maximum rate of air flow during inspiration)
  • Peak inspiratory pressure (maximum pressure during inspiration)
  • Positive end-expiratory pressure (positive pressure applied at the end of expiration to prevent airway collapse)
• Modes of mechanical ventilation

  • Volume controlled ventilation (VC)
  • Pressure controlled ventilation (PC)
  • Assist control (AC)
  • Continuous positive airway pressure (CPAP)
• Extracorporeal Membrane Oxygenation


  1. Most extreme form of respiratory support used where respiratory failure is not adequately managed by intubation and ventilation

  2. Blood is removed from the body, passed through a machine where oxygen is added and carbon dioxide is removed, then pumped back into the body

  3. Similar to haemodialysis but for respiratory support

  4. ECMO is only used short-term with a potentially reversible cause of respiratory failure

  5. Provided in specialist ECMO centres and not available in most intensive care units

  6. Patients need to be transferred to a specialist centre for ECMO
• Last updated


  August 2021