Non-invasive ventilation (NIV) is the use of breathing support administered through a face mask, nasal mask, or a helmet. Air, usually with added oxygen, is given through the mask under positive pressure; generally the amount of pressure is alternated depending on whether someone is breathing in or out. It is termed "non-invasive" because it is delivered with a mask that is tightly fitted to the face or around the head, but without a need for tracheal intubation (a tube through the mouth into the windpipe). While there are similarities with regard to the interface, NIV is not the same as continuous positive airway pressure (CPAP), which applies a single level of positive airway pressure throughout the whole respiratory cycle; CPAP does not deliver ventilation but is occasionally used in conditions also treated with NIV.
Non-invasive ventilation is used in acute respiratory failure caused by a number of medical conditions, most prominently chronic obstructive pulmonary disease (COPD); numerous studies have shown that appropriate use of NIV reduces the need for invasive ventilation and its complications. Furthermore, it may be used on a long-term basis in people who cannot breathe independently as a result of a chronic condition.
Medical uses
NIV for acute respiratory failure is used particularly for severe exacerbations of chronic obstructive pulmonary disease (COPD) but also for acute decompensated heart failure and other acute conditions. NIV can be used acutely and long-term. In some people who have presented with acute respiratory failure, there is an ongoing need for long-term use of NIV at home. The risk of poorly fitting masks emitting aerosols can require full protection gear for caregivers.
COPD
The most common indication for acute non-invasive ventilation is for acute exacerbation of chronic obstructive pulmonary disease. The decision to commence NIV, usually in the emergency department, depends on the initial response to medication (bronchodilators given by nebulizer) and the results of arterial blood gas tests. If after medical therapy the lungs remain unable to clear carbon dioxide from the bloodstream (respiratory acidosis), NIV may be indicated. Many people with COPD have chronically elevated CO<sub>2</sub> levels with metabolic compensation, but NIV is only indicated if the CO<sub>2</sub> is acutely increased to the point that the acidity levels of the blood are increased (pH<7.35). There is no level of acidity above which NIV cannot be started, but more severe acidosis carries a higher risk that NIV alone is not effective and that mechanical ventilation will be required instead. Both CPAP and NIV may be used in the prehospital care setting. There is limited evidence on whether NIV is effective in this situation, which carries a high risk of requiring mechanical ventilation. Professional guidelines therefore do not give a clear recommendation, A review from 2021 demonstrated that the chronic use of non-invasive ventilation improves daytime hypercapnia. In addition, in stable chronic obstructive pulmonary disease, survival seems to be improved and there might be a short term benefit of health-related quality of life.
Home NIV may also be indicated in people with neuromuscular disease and chest wall deformity. With regards to initiation of positive pressure treatment, the ATS guidelines recommend that in people being investigated for possible obstructive sleep apnea (OSA, a related condition), measurement of arterial carbon dioxide (in high probability) or venous bicarbonate (in moderate probability) is performed to identify OHS and to determine an indication for treatment. In those with both severe OSA and OHS, initial treatment with CPAP is recommended although the quality of research supporting this over NIV is poor.
People with motor neuron disease (MND) may require home NIV in the course of their illness. Guidelines in the United Kingdom stipulate that assessment of respiratory function is part of the multidisciplinary management of MND.
Terminology
A number of terms have been used in the medical literature to describe NIV. The more formal name "non-invasive positive pressure ventilation" (NPPV or NIPPV) has been used to distinguish it from the use of the now very rare negative pressure ventilator ("iron lung"). The brand name BiPAP/BIPAP (for Bilevel Positive Airway Pressure) has also enjoyed a degree of popularity, after an early NIV machine produced by Respironics, but its use is now discouraged. The development of non-invasive ventilation in acute care settings was further advanced by clinical investigations in the late 1980s and early 1990s. Early studies demonstrated that positive pressure ventilation delivered via face mask could improve gas exchange, reduce the work of breathing, and decrease the need for endotracheal intubation in selected patients with acute respiratory failure. Subsequent randomized controlled trials in the 1990s further established its efficacy across diverse patient populations and contributed to its adoption in intensive care practice. These findings helped define early clinical protocols and informed the integration of non-invasive ventilation into routine intensive care practice.
Since 2000 acute NIV has been used widely in the treatment of acute respiratory failure, particularly in people with COPD, including on general wards rather than the intensive care unit setting. In the United Kingdom, a 2017 report by NCEPOD found that there were widespread problems in the delivery of high-quality care to patients.