Emergent technologies have provided a wide variety of noninvasive ventilation (NIV) devices and modes to deliver treatment for respiratory failure through a mask or tracheotomy, both in the acute care setting and at home. An in-depth understanding of NIV indications, modes, and settings is crucial to guarantee delivery of effective therapy. However, knowledge gaps exist in most practitioners regarding matching advanced NIV modes and settings to a patient’s unique respiratory failure pathophysiology. In this chapter we review the principles of NIV devices and modes, assess indications for its use (e.g., neuromuscular and chest wall disease, obstructive airway diseases, obesity-related respiratory failure), and review the most recent published literature, including guidelines in the application (and adjustment) of these devices during hospitalization and at home. For additional information, the reader is referred to Chapters 98, 99, and 142, in which the use of noninvasive ventilation in management of sleep-disordered breathing and the pathogenesis of hypoventilatory disorders are discussed.
PRINCIPLES OF PRESSURE-TARGETED NONINVASIVE VENTILATION
Before considering the details of a noninvasive mechanical ventilator circuit and important underlying physiologic principles, we provide a brief review of the history of the modality.
Brief Historic Perspective of Noninvasive Positive Airway Pressure Modes
In 1981, Sullivan published his seminal paper describing a novel therapeutic modality to successfully treat obstructive sleep apnea (OSA). By applying a mask (“soft plastic tubes shaped to fit each naris”), hoses, and a “vacuum cleaner–blower motor with variable speed control,” he was able to deliver pressurized air to a patient’s upper airway. He coined the term continuous positive airway pressure (CPAP) to describe the delivery of constant pressure throughout the respiratory cycle.1 Today, CPAP is a commonly prescribed noninvasive positive airway pressure mode that provides a pneumatic splint to the pharyngeal airway (preventing it from collapsing during sleep), along with improvement in end-expiratory lung volumes and oxygenation (improvement of ventilation–perfusion matching). However, by providing the same single (constant) pressure during inhalation and exhalation, CPAP does not support or augment a patient’s tidal volume and, therefore, minute ventilation (Fig. 148-1A).
Differences between CPAP and NIV in respiratory support. A. CPAP versus NIV in respiratory support. B. Types of positive airway pressure modes: BPAP, bilevel positive airway pressure; CPAP, continuous positive airway pressure; FRC, functional residual capacity; NIV, noninvasive ventilation; RR, respiration rate; ST, spontaneous-timed; UA, upper airway; Vt, tidal volume.
In 1990, almost 10 years after the introduction of CPAP, Sanders and Kern published a novel research article describing the treatment of OSA by “independently adjusted inspiratory and expiratory positive airway pressures” via a nasal mask.2 By installing a flow sensor (input), the device was able to correctly detect (and differentiate) the patient’s breath phase to deliver a different therapeutic pressure during inhalation—inspiratory positive airway pressure ...