Noninvasive ventilation (NIV) is an important treatment that can be used in many cases of acute respiratory impairment and provides good results when properly indicated and performed. Its use should always be considered in eligible candidates since it has the potential to reduce the need for invasive mechanical ventilation and its complications.
Most patients that have a reasonable level of consciousness and are suffering respiratory distress that does not require emergent intubation can try noninvasive ventilation. These situations include:
Acute hypoxemic respiratory failure.
Cardiogenic pulmonary edema.
Exacerbation of COPD with hypercarbia and respiratory acidosis (pH < 7.35 and PCO2 >45 mmHg).
Extubation with a high risk of post-extubation respiratory failure.
Even though NIV can be tried in all these cases, some factors can help to predict a better outcome. These factors include but are not limited to: good neurologic status, younger age, low APACHE score, and small amount of air leaking.
NIV should be avoided in patients with:
Facial burns, trauma, deformity or recent surgery of the upper airway or esophagus
Copious, unmanageable respiratory secretions
High aspiration risk
Inability to protect own airway (altered mental status)
Hemodynamic instability or unstable cardiac arrhythmia
Respiratory or cardiac arrest
INTERFACE AND MODES TO USE:
Since most patients will be breathing through the mouth, a full face mask, an oronasal mask or a helmet are preferred instead of a nasal device.
Regarding the mode of ventilation, the Pressure support ventilation (PSV) is a good choice for those who want to facilitate synchrony. Assist control mode (AC) is the choice for those who wants to have a minimal minute ventilation. CPAP (continuous positive airway pressure), on the other hand, may be preferred in patients with pulmonary edema from cardiac origin.
The ventilator settings should be adjusted to provide the lowest inspiratory pressures or volumes needed to produce improved patient comfort (a decrease in respiratory rate and respiratory muscle unloading) and gas exchange. Typical initial settings used include: spontaneous mode, EPAP 4-5 cm H2O, IPAP 12-15cm H2O (may be increased as tolerated to 20cm H2O), back up rate of 15 bpm, back up I:E ratio 1:3
SOURCES & FURTHER READING:
- International Consensus Conferences in Intensive Care Medicine: Noninvasive Positive Pressure Ventilation in Acute Respiratory Failure. AJRCCM Vol. 163, No. 1 | Jan 01, 2001.
- Non-invasive ventilation in acute respiratory failure Thorax 2002;57:192-211.
- Keenan SP et al. Clinical practice guidelines for the use of noninvasive positive-pressure ventilation and noninvasive continuous positive airway pressure in the acute care setting. CMAJ. 2011 Feb 22; 183(3): E195–E214.
- Sanchez D, Smith G, Piper A and Rolls K (2014) Non–invasive Ventilation Guidelines for Adult patients with Acute Respiratory Failure: a clinical practice guideline. Agency for Clinical Innovation NSW government Version 1, Chatswood NSW, ISBN 978-1-74187-954-4
- Garpestad E et al.Noninvasive Ventilation for Critical Care. Chest. 2007;132(2):711-720.
- Dhar R, Ghosh D, Krishnan S. Noninvasive ventilation in hypoxemic respiratory failure. J Assoc Chest Physicians 2016;4:50-5.
- Windisch W et al. Guidelines for Non-Invasive and Invasive Mechanical Ventilation for Treatment of Chronic Respiratory Failure. Pneumologie 2010; 64: 640–652.
- Krishna B et al. The role of non-invasive positive pressure ventilation in post-extubation respiratory failure: An evaluation using meta-analytic techniques. Indian J Crit Care Med. 2013 Jul-Aug; 17(4): 253–261.