![]() Common causes of hypercapnic respiratory failure are increased lung ventilation–perfusion inequality and respiratory system load (e.g., chronic obstructive pulmonary disease), decreased respiratory drive (e.g., opioid intake), or inadequate respiratory muscle strength (e.g., neuromuscular disorders), or a combination of them. ![]() Sleep-related hypoventilation disorders (alveolar hypoventilation) are associated with hypercapnia (PaCO 2 ≥ 45 mmHg) due to ineffective ventilation (CO 2 elimination). In general, these breathing disorders can be grouped into two categories based upon their effect on partial pressure of carbon dioxide (pCO 2) balance, as reflected in arterial carbon dioxide tension (PaCO 2). Different from CPAP, these advanced modes of bilevel positive airway pressure ventilation, collectively known as noninvasive ventilation (NIV), were developed to address complex cardiorespiratory pathophysiology beyond OSA (Fig. With the introduction of digital processing of the flow signal (input), current advanced bilevel devices have developed the capability to self-modulate IPAP and/or EPAP as well as to “time” the initiation and/or termination of each breath in synchrony with patient’s breathing. By installing a flow sensor (input), the device was able to correctly detect the patient’s breath phase (inhalation vs exhalation) to deliver a different therapeutic pressure during inhalation-inspiratory positive airway pressure (IPAP)-and during exhalation-expiratory positive airway pressure (EPAP). In 1990, Sanders and Kern described the treatment of OSA by “independently adjusted inspiratory and expiratory positive airway pressures” via mask interface. ![]() CPAP provides a pneumatic splint to the pharyngeal airway preventing it from collapsing during sleep, along with improvement in lung volumes (i.e., functional residual capacity) and oxyhemoglobin saturation. Collin Sullivan introduced continuous positive airway pressure (CPAP) as a therapeutic modality to treat obstructive sleep apnea (OSA) in 1981. ![]()
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