- Noninvasive Ventilation: Rationale and Definitions
- Heart–Lung Interactions during Noninvasive Ventilation
- Ventilators for Noninvasive Ventilation: Critical Care versus Noninvasive Home Ventilators
- Modes of Ventilation for Noninvasive Ventilation Including Newer Modes
- Noninvasive Ventilation Interfaces
- Noninvasive Ventilation: Adjuvant Therapies (Oxygenation, Humidification, Aerosol Therapies including Nebulization)
- Noninvasive Ventilation: Indications, Contraindications, and Complications
- Application of Noninvasive Ventilation: Algorithmic Approach (Initiation, Customization, and Troubleshooting)
- Physiology of Type I and Type II Respiratory Failure
INTRODUCTION
The use of noninvasive ventilation (NIV) has expanded to a number of diseases and situations with an aim to provide benefit to the patient and to prevent the complications associated with invasive mechanical ventilation (MV).1 Positive pressure ventilation (whether provided invasively or noninvasively) has benefits like reducing work of breathing, increasing delivery of higher concentration of oxygen to the alveoli, and preventing closure of upper airways. Specific benefits of providing mechanical ventilation noninvasively are that it saves cost, allows patient to take breaks from treatment for eating and other daily activities, and is better tolerated and may be more convenient. The evidence for these benefits is overwhelming for a few diseases [cardiogenic pulmonary edema, hypercapnic respiratory failure due to acute exacerbation of chronic obstructive pulmonary diseases (COPD) and other causes, weaning from MV for COPD patients, etc.] while it is not so robust for some of the conditions in which NIV has been used [acute respiratory failure (ARF) due to severe bronchial asthma, viral pneumonias, de novo hypoxemic nonhypercapnic ARF, etc.].1-4
DEFINITIONS
Noninvasive ventilation: It is defined as mechanical ventilation provided without the use of invasive airway. It may be provided with positive or negative pressure. The most common and widely utilized method is providing NIV by positive pressure and for all practical purposes, when the term NIV is used, it denotes noninvasive positive pressure ventilation.1
Patient–ventilator interfaces: As NIV avoids the use of endotracheal intubation (ETI), it mandates the use of face masks, oronasal face masks, or helmets through which compressed gas is supplied to the patient by the ventilator. These devices are known as interfaces.
Inspiratory positive airway pressure (IPAP): It denotes peak inspiratory pressure during the phase of inspiration.
Expiratory positive airway pressure (EPAP): It denotes the pressure at the end of expiration. The EPAP is referred to as continuous positive airway pressure (CPAP) when IPAP = EPAP, and is denoted as PEEP when IPAP > EPAP.
Positive end-expiratory pressure (PEEP): It denotes the pressure maintained at the end of expiration.4
Rise time: It is the time taken to reach the set pressure or the speed at which pressure rises to reach the set pressure. Flow of air depends on the rise time. Shorter the rise time more rapid is the flow.
ADVANTAGES OF NONINVASIVE VENTILATION
Noninvasive ventilation has the following advantages over invasive MV with respect to application for use, complications (infective or local), and advantages to the patient.
- Increased patient comfort due to reduced work of breathing
- Prevention of localized trauma to the upper airways
- Reduction of ventilator-associated pneumonia
- Reduction in sedation and its attendant complications
- Reduces length of ICU and hospital stay in some patients
- Preserves airway clearance of secretions
RATIONALE FOR THE USE OF NONINVASIVE VENTILATION5
Noninvasive ventilation results in the unloading of the respiratory muscles, improves the gas exchange at the alveolar level, and increases alveolar ventilation. The decreased load on the respiratory muscles decreases respiratory muscle fatigue. Increased alveolar ventilation decreases CO2 levels and respiratory acidosis.
CONCLUSION
Noninvasive ventilation is used for beneficial effects in a variety of critically ill patients in various clinical scenarios. It has some advantages over invasive mechanical ventilation. It improves respiratory physiology and facilitates gas exchange.
REFERENCES
- Nava S, Hill N. Non-invasive ventilation in acute respiratory failure. Lancet. 2009;374(9685):250–9.
- Rochwerg B, Brochard L, Elliott MW, Hess D, Hill NS, Nava S, et al. Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure. Eur Respir J. 2017;50(2): pii: 1602426.
- Pisani L, Corcione N, Nava S. Management of acute hypercapnic respiratory failure. Curr Opin Crit Care. 2016;22(1):45–52.
- Brochard L, Lefebvre JC, Cordioli RL, Akoumianaki E, Richard JC. Noninvasive ventilation for patients with hypoxemic acute respiratory failure. Semin Respir Crit Care Med. 2014;35(4):492–500.
- Tobin MJ. Advances in mechanical ventilation. N Engl J Med. 2001;344(26):1986–96.