Non Invasive Ventilation in copd Sarah Davey Specialist Registrar Emergency Medicine. Pinderfields General Hospital.
Introduction • NIV is the provision of ventilatory support through the patient’s upper airway using a mask or similar device. • NIV is patient triggered and air/oxygen is delivered under preset pressure. • NIV used in treatment for hypercapnic respiratory failure, particularly in those patients with COPD. • NIV may avoid intubation and avoid ICU/HDU admission.
Terminology • IPAP – Inspiratory Positive Airways Pressure. - Pressure set during inspiration. - Cm of H2O above atmospheric. - Increases Tidal volume, reduces work of breathing and increases alveolar ventilation, reducing pCO2. * usually set at 10-14 cmH2O and gradually increased as tolerated to a max. 20 cmH2O.
Terminology Cont. • EPAP – Expiratory Positive Airways Pressure. - Pressure set during expiration. - Recruits under ventilated lung. - Offsets intrinsic PEEP, aids triggering. - Reduces perceived effort. - Serves to vent exhaled gas thru the exhaust port and reduce rebreathing. * Set at 4-5 cmH2O.
Terminology Cont. • BPM – Breaths Per Minute. - Back-up breath rate. - Machine will automatically deliver a breath to the patient if the resp. rate falls below the set value. - Usually set to 12-14 if available.
Terminology Cont. • Rise Time. - Controls the rate of pressure change during transition from EPAP to IPAP phase of ventilation. - i.e. Time taken to reach IPAP pressure. - Intended for patient comfort. - If respiratory rate is high then a faster rise time is required.
Indications In COPD. • Considered in all patients with acute exacerbation of COPD in whom a respiratory acidosis persist despite maximal medical treatment with controlled oxygen therapy. • Respiratory acidosis – pH 7.25-7.35. • Able to protect airway. • Conscious and cooperative. • Haemodynamically stable. • No excessive respiratory secretions • No contraindications.
Contraindications. • Facial trauma/Burns. • Recent facial, upper airway or upper GI surgery * • Fixed obstruction of upper airway. • Inability to protect airway.* • Life threatening hypoxia.* • Haemodynamic instability.* • Severe co-morbidity.* • Impaired consciousness.* • Confusion/agitation.* • Vomiting. • Bowel Obstruction.* • Copious respiratory secretions.* • Focal consolidation on CXR.* • Undrained pneumothorax.
Predictions of Success. • pH 7.25-7.35. • Improvement of pH at 1hr. • Good level of consciousness. • Poor outcome associated with: - Co-existing pneumonia. - Copious resp. secretions. - Edentulous. - Poor nutritional state. - Confusion.
How To Perform. • Practical Time!
Equipment Needed. • BiPAP machine. • Disposable circuit (tubing, filter & expiration port). • Appropriate mask. • Green Oxygen tubing. • SaO2 Monitor.
How To Set Up NIV. • Obtain baseline obs. • Check for contraindications. • Explain procedure to patient and the reasons for use. • Select mask of appropriate size to fit patient. • Set up circuit. • Set ventilator settings. • Commence NIV and apply mask. • Reassess after a few mins. • Add oxygen if sats <85%. (aim sats 90%). • Adjust settings as required. • Request repeat ABG at 1hr adjusting BiPAP accordingly.
Typical Initial Settings. • IPAP – 10-14 cmH2O. • EPAP – 4-5 cmH2O. • Oxygen – 2-4 l/min. • BPM - 12-14/min. • I:E – 1:3
Treatment Failure. • Is Medical management optimal? • Developed complications? • PaCO2 remains high? • PaO2 remains low with PaCO2 improving?
PaCO2 Remains High. • Too much oxygen? - adjust O2 to maintain sats of 85-90%. • Excessive Leak? - check mask fit. • Re-breathing occurring? - check exhaust valve. - consider increasing EPAP. • Poor synchronising with ventilator? - observe patient. - consider inc. EPAP or adjust rate. • Inadequate ventilation? - increase IPAP. - Consider increasing inspiratory time.
PaCO2 improves but PaO2 remains low. • Increased inspired O2. • Consider increasing EPAP.
Summary • NIV effect therapy when used in appropriate patients. • Use local protocols. • Know your own equipment. • Seek senior help early.