Non-Invasive Ventilation



Indications for nasal or Full face NIV

Based on the 2008 BTS Guidelines: NIV in COPD

Hypercapnic respiratory failure during an acute exacerbation of COPD with:

  1. Arterial pH <7.35.
  2. Arterial PaCO2 >6kPa (if acute onset).
  3. Tachypnoea >23 breaths/min.

Uses

  1. Acute hypercapnoeic respiratory failure (e.g. in acute exacerbations of COPD).
  2. Cardiogenic pulmonary oedema.
  3. Respiratory failure in immunocompromised patients (e.g. pneumonia).
  4. Neuromuscular disorders (respiratory failure).
  5. Asthma (NB selected cases only - decision by Respiratory Physician).

Contraindications

  • Facial trauma/burns.
  • Recent facial, upper airway or upper GI tract surgery.
  • Fixed obstruction of the airways.
  • Inability to protect airways or excessive airway secretions.
  • Life threatening hypoxaemia.
  • Undrained pneumothorax.
  • Impaired consciousness or confusion/agitation.
  • Vomiting.

Assessment

  1. Full medical assessment.
  2. Arterial blood gases (ABG): pH 7.25 – 7.35; high PaCO2.
  3. Optimal medical treatment not successful.
  4. Consider commencing NIV.
  5. Have a plan for if NIV fails.
  6. Good outcome predicted if improvement in pH, PaCO2 and respiratory rate after 1hr of NIV.
  7. ?Chance of failure – high Apache score, poor nutritional status, confusion/impaired consciousness.
  8. Inform ITU of decision to commence NIV.

Setting Up (Bipap Focus)

BiPAP Focus in CUH
BiPAP Focus
  1. Consultant/Senior Decision maker to commence NIV.
  2. NIV machine (Bipap Focus in CUH) + tube + CO2 exhalation port + mask + head-cap.
  3. On the Bipap focus machine, the O2 tubing can be attached into the port on the face mask or beside the exhalation port.
  4. Set EPAP at 4 – 5 cm H2O and IPAP at 10 cm H2O.
  5. Set back-up breathing frequency to 8 – 10 breaths/minute.
  6. Select appropriate size mask (full face in preference to nasal) to fit patient.
  7. Explain procedure to patient.
  8. Hold mask in place to allow patient to familiarize themselves.
  9. Attach pulse oximeter.
  10. Commence NIV, holding mask in place initially.
  11. Secure mask in place with straps/headgear to prevent leaks – do not attach too tightly!
  12. Reassess patient after a few minutes.
  13. Check for leaks and refit mask if necessary.
  14. Add O2 to maintain SpO2 >85%.
  15. Instruct patient how to remove the mask and summon help.
  16. Increase IPAP gradually up to about 12 - 15 cmH2O over 1 hr.
  17. Clinical assessment and, if appropriate, check ABG at 1 hour.
  18. If procedure fails, institute alternative management plan.

COPD Patients in Mercy University Hospital

COAD NIV Protocol

In MUH, COPD (in contrast to LVF patients) can be non-invasively ventilated using the guidelines shown right.

Initiating NIV

  • Commence BiPAP at IPAP 10cm H20 / EPAP 4cm H20.
  • Increase FiO2 to improve O2 saturation to >90%.
  • Repeat ABG after 1 hr of NIV treatment.
  • Titrate IPAP
  • if pH<7.35, respiratory rate >25/min, PaCO2>6 kPa or persistent use of accessory muscles.
  • Titrate EPAP.
    • if persistent hypoxia.
  • Titrate in increments of 2cm H20 to peak IPAP 20 / EPAP 8.
  • Repeat ABG after 4 hrs of NIV; titrate pressures as above.
  • NIV should be used for a minimum of 16 hours / 24 hours initially, reducing to 12 hours on Day 2, and 8 hours on Day 3 as the clinical setting permits.

Full ventilation reconsidered if:

  • Arterial pH<7.2.
  • Arterial pH 7.2 - 7.25 on two occasions 1 hr apart.
  • Hypercapnic coma GCS <8 and PaCO2>8 kPa).
  • PaO2<6 kPa despite maximum tolerated FiO2.
  • Cardiorespiratory arrest.

Treatment failure

  1. Is medical treatment optimal?
  2. Is physiotherapy needed (particularly for sputum retention)?
  3. What complications have developed (beware PTX or aspiration etc.)
  4. Check the pressures actually being achieved ( visible on the screen of the Bipap Focus).
  5. If PaCO2 remains high
    • To much O2? Maintain SpO2 between 85% to 90%
    • Excessive mask leakage?
    • Is circuit set up correctly?
    • Is patient synchronising with ventilator – adjust breathing rate and/or inspiratory and/or expiratory trigger
    • Is re-breathing occurring? - Check patency of expiratory valve (if fitted). Consider increasing EPAP
    • Is ventilation adequate – ?increase IPAP (increments of 2cm H2O to alleviate resp distress)
  6. If PaCO2 improves but PaO2 remains low
    1. Increase FiO2
    2. Consider increasing EPAP by increments of 2cm H2O. NB keep difference betw. IPAP and EPAP ≥ 6 cmH2O - so you may need to also increase IPAP.

Aims of NIV

  • Deal with acute phase of respiratory failure.
  • Attempt to stabilise patient’s condition.
  • Contact ITU Registrar prior to transfer to medical ward.
  • Treatment failure warrants ITU admission.

Infection control

  • Disposable masks and exhalation ports should be disposed of.
  • Headgear should be washed in a washing machine – be careful with the Velcro straps.
  • Use a bacterial filter between the tube and the BiPaP machine to reduce contamination risk to machine.

References


Content by Dr. Íomhar O' Sullivan January 2003. Last review Dr. Gerard McCarthy, Dr. ÍOS 22/04/15.