So, what is NIV?
Type 1 RF requires CPAP type of NIV.
A BPAP machine can be used as a CPAP machine if you set EPAP=IPAP i.e. you deliver the same pressure during inspiration as well as expiration.
- Found to be more useful in reducing the need for intubation and reducing the mortality in patients with acute cardiogenic pulmonary edema.
- A fixed positive pressure is delivered throughout the respiratory cycle without any change during inspiration or expiration. The pressure required can be set on the machine and is measured in cmH2O.
- Commonly used pressures range 5-15cm of H2O. (5-8cm of H2O is a reasonable starting pressure)
- O2 can be titrated depending upon the SpO2, PaO2.
- Found more effective in acute exacerbation of COPD.
- Different pressures are used during inspiration (IPAP) and expiration (EPAP).
- The commonly used initial settings are EPAP: 3-6 and IPAP: 8-12 with supplemental oxygen of 3-5liters/min.
- The pressure can be adjusted depending upon the clinical condition of the patients and /or values of PaO2, PCO2 and SpO2.
- To treat persistent hypercapnia increase IPAP by 2cms at a time. To treat persistent hypoxia, increase IPAP and EPAP by 2cms at a time.
- The maximum EPAP/IPAP is 25/15cmH20.
- Many comparative studies have demonstrated no significant difference between two modes of NIV when used for either for pulmonary edema or COPD.
- So, just in case the nurse asks you “we do not have a BPAP machine but there’s an old CPAP machine, will that be okay?” the answer should be “Yes!” irrespective of the etiology! (Most modern machines can deliver both CPAP and BPAP)
In whom do we put it on?
- In patients with respiratory failure/respiratory distress (e.g COPD and Acute Pulmonary Edema) without any contraindications.
- Although there’s no clear consensus regarding the indications for the use of NIV, when there are no contraindications, many patients with dyspnea may be suitable candidates for NIV. (Asthma, ARDS, Neuromuscular disease, Chest trauma, Cystic Fibrosis)
- To facilitate extubation in patients with COPD who have failed weaning attempts.
- ‘Do-not-intubate (DNI) patients’
- Obstructive Sleep Apnea (OSA) – CPAP is commonly used in the night.
- Patients who require immediate endotracheal intubation.
- Decreased level of consciousness.
- Inability to fix/position the mask due to past facial surgery.
- Excessive secretions, vomiting and risk of aspiration.
- Uncooperative patient.
- Lack of staff trained/experienced in operating and monitoring the device and patient the patient on NIV.
- Hemodynamically unstable patient.
- Severe hypoxia and/or hypercapnia: PaO2/FiO2 ratio<200mmHg, PaCO2 > 60mmHg.
- Gastrointestinal bleeding.
How does it work?
How to monitor a patient on NIV? What do I look for?
- Intolerance to NIV: Restless and irritable, asynchronous breathing with ventilator.
- Increased secretions, vomiting patient.
- Altered mental status.
- Increasing dyspnea/respiratory distress despite optimum settings. (RR>35-40)
- Persistent hypoxia despite supplemental oxygen.
- Hemodynamic instability.
- Worsening blood gases.
- Explain the patient what NIV is and how air is delivered with pressure. Just forcing that nasty mask on patient’s face without explaining anything would make an already anxious patient more anxious and you will most probably end up with an uncooperative patient and failed NIV.
- Make sure that the mask is of appropriate size and well fitting. An Ill-fitting mask will result in air leak and NIV will be ineffective. – Dealing with the big mask is indeed a big deal!
- Face Mask is proffered over nasal mask in the ED.
- Use cotton over the nasal bridge/forehead (pressure points) to avoid pressure sores.
- Sitting position / Head end elevation
- Follow up with a blood gas within 30-60 minutes .
- Have an alternative plan for NIV failure. Be prepared for Intubation.
- Be very cautious if you have to use analgesics that are known to cause sedation.
- Gastric distension
- Failure of NIV
- Aspiration (rare)
- Hypotension with higher pressures (infrequent)
- Barotrauma (rare)
- Pressure ulcers over the face.
- Oral and nasal dryness à Irritation.
- Consider NIV ASAP in eligible patients (Timing is important).
- EPAP=CPAP=PEEP, IPAP > EPAP and PS = IPAP-EPAP.
- Reassure, use an appropriately sized mask .
- Have a definitive plan for failed NIV.
- Ventilation Literature Summaries http://lifeinthefastlane.com/ccc/ventilation-literature-summaries/
- EMCrit Podcast 19 – Non-Invasive Ventilation: http://emcrit.org/podcasts/niv/
- BiPAP part 1 on YouTube by David Gibson: https://www.youtube.com/watch?v=UXWa1r3hEoM
- BiPAP part 2: https://www.youtube.com/watch?v=gewxf3FopOY
- British thoracic society guidelines: https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/non-invasive-ventilation-(niv)/
- Oxford handbook of emergency medicine: Page no. 109 (section on COPD).