High-flow nasal cannula oxygen therapy as an emerging option for respiratory failure: the present and the future

Abstract

Conventional oxygen therapy (COT) and noninvasive ventilation (NIV) have been considered for decades as frontline treatment for acute or chronic respiratory failure. However, COT can be insufficient in severe hypoxaemia whereas NIV, although highly effective, is poorly tolerated by patients and its use requires a specific expertise. High-flow nasal cannula (HFNC) is an emerging technique, designed to provide oxygen at high flows with an optimal degree of heat and humidification, which is well tolerated and easy to use in all clinical settings. Physiologically, HFNC reduces the anatomical dead space and improves carbon dioxide wash-out, reduces the work of breathing, and generates a positive end-expiratory pressure and a constant fraction of inspired oxygen. Clinically, HFNC effectively reduces dyspnoea and improves oxygenation in respiratory failure from a variety of aetiologies, thus avoiding escalation to more invasive supports. In recent years it has been adopted to treat de novo hypoxaemic respiratory failure, exacerbation of chronic obstructive pulmonary disease (COPD), postintubation hypoxaemia and used for palliative respiratory care. While the use of HFNC in acute respiratory failure is now routine as an alternative to COT and sometimes NIV, new potential applications in patients with chronic respiratory diseases (e.g. domiciliary treatment of patients with stable COPD), are currently under evaluation and will become a topic of great interest in the coming years.

Physiological Effects of High-Flow Nasal Cannula Therapy and Its Use in Acute Cardiogenic Pulmonary Edema

“…Dry airways increase airway resistance and work of breathing. HFNC not only provides high flow but also contains an active heated humidifier which warms and humidifies air before delivering it to the airways [ 12 ]. A study by Chikata et al found that 100% humidification can be maintained at high flow (20-50 L/min) at normal body temperature (37˚C) [ 13 ].…”

“…Anatomical dead space is defined as “the segments of the respiratory tract responsible for conducting air to the alveoli and respiratory bronchioles which does not take part in gas exchange” [ 12 ]. Studies have shown high flow produced by HFNC reduces respiratory rate in patient with moderate-to-severe respiratory distress, which in turn decreases minute ventilation (respiratory rate × tidal volume), while partial pressure of carbon dioxide remains steady or even decreases.…”

“…Inspiration is an active process whereas expiration is a passive process. Respiratory muscles consume energy during inspiration which is also known as work of breathing [ 12 ]. One of the main functions of NIPPV is to assist respiratory muscles by reducing work of breathing.…”

“…However, in fact, HFNC can be an alternative when NIPPV is contraindicated, for example, in patients with claustrophobia and intolerance towards tight interface contact. Although HFNC can cause abdominal distention and barotrauma as other NIPPV, the incidence is very rare [ 12 ]. There is no guideline for when to escalate respiratory therapy from HFNC to the invasive form.…”

Oldest-old Covid-19 patients: Lessons learnt in a geriatric intermediate care unit

“…Recrutability by positive pressure seems effective in most of the case. Hypercarbia is rare, excepted among COPD patients Thus, for oldest-old patients not eligible for intubation, an admission in an intermediate care unit (IMCU) for non-invasive therapy such as High Flow Nasal Cannula (HFNC) and Continuous Positive Airway Pressure (CPAP) could be an alternative [ 3 , 4 , 5 , 6 ].…”