Non-invasive ventilation in acute respiratory failure
- British Thoracic Society Standards of Care Committee
- S Baudouin, S Blumenthal, B Cooper, C Davidson, A Davison, M Elliot, W Kinnear (Chairman), R Paton, E Sawicka, L Turner (Secretary)
- Correspondence to:
Dr W Kinnear, University Hospital, Queen's Medical Centre, Nottingham NG7 2UH, UK;
William.Kinnear{at}mail.qmcuh-tr.trent.nhs.uk
- AHRF, acute hypercapnic respiratory failure
- ARDS, acute respiratory distress syndrome
- ASB, assisted spontaneous breathing
- BMI, body mass index
- CMV, continuous mandatory ventilation
- COPD, chronic obstructive pulmonary disease
- CPAP, continuous positive airways pressure
- EPAP, expiratory positive airways pressure
- Fio2, fractionated inspired oxygen concentration
- FRC, functional residual capacity
- HDU, high dependency unit
- ICU, intensive care unit
- IE, inspiratory/expiratory
- IPAP, inspiratory positive airways pressure
- IPPV, intermittent positive pressure ventilation
- LTOT, long term oxygen therapy
- NIV, non-invasive ventilation
- OSA, obstructive sleep apnoea
- Paco2, partial pressure of arterial carbon dioxide
- Pao2, partial pressure of arterial oxygen
- PAV, proportional assist ventilation
- PEEP, positive end expiratory pressure
- PEEPi, intrinsic PEEP
- PS, pressure support
- Spo2, oxygen saturation
- SIMV, synchronised intermittent mandatory ventilation
- S/T, spontaneous/timed
- V/Q, ventilation perfusion
INTRODUCTION
Nomenclature
Non-invasive ventilation (NIV) refers to the provision of ventilatory support through the patient's upper airway using a mask or similar device. This technique is distinguished from those which bypass the upper airway with a tracheal tube, laryngeal mask, or tracheostomy and are therefore considered invasive. In this document NIV refers to non-invasive positive pressure ventilation, and other less commonly used techniques such as external negative pressure or rocking beds will not be discussed. (NIPPV is an alternative abbreviation but it is more cumbersome and involves ambiguity as to whether “N” is for “non-invasive” or “nasal”.)
Continuous positive airway pressure (CPAP) in this document refers to the non-invasive application of positive airway pressure, again using a face or nasal mask rather than in conjunction with invasive techniques. Although it might be open to debate as to whether the use of non-invasive CPAP in acute respiratory failure constitutes ventilatory support, it is included in this document because of the confusion which commonly arises between NIV and CPAP in clinical practice.
Background
One of the first descriptions of the use of NIV using nasal masks was for the treatment of hypoventilation at night in patients with neuromuscular disease.1,2 This has proved to be so successful that it has become widely accepted as the standard method of non-invasive ventilation used in patients with chronic hypercapnic respiratory failure caused by chest wall deformity, neuromuscular disease, or impaired central respiratory drive. It has largely replaced other modalities such as external negative pressure ventilation and rocking beds.
Within a few years of its introduction, NIV was starting to be used in acute hypercapnic respiratory failure and in patients with abnormal lungs rather than an impaired respiratory pump. Initial anecdotal reports were followed by larger series and then by randomised trials. Analysis of these trials has shown …
