What is the meaning of NIF (Nasal Inspiratory Flow)?

From the Guidelines

High-flow nasal oxygen is recommended over noninvasive ventilation and conventional oxygen therapy for hospitalized adults with acute hypoxemic respiratory failure, as it improves patient comfort and provides physiologic advantages, such as improved oxygenation and ventilation, according to the American College of Physicians guideline published in 2021 1.

Key Points

• High-flow nasal oxygen (HFNO) therapy involves the delivery of warm and humidified oxygen via a small nasal cannula at a flow higher than the patient's inspiratory flow (up to 60 L/min) 1.
• The benefits of HFNO include improved patient comfort, improved oxygenation and ventilation, better pulmonary compliance, reduced anatomical dead space, and modest positive end-expiratory pressure 1.
• The American College of Physicians suggests using HFNO rather than noninvasive ventilation in hospitalized adults for the management of acute hypoxemic respiratory failure (conditional recommendation; low-certainty evidence) 1.
• HFNO is also recommended over conventional oxygen therapy for hospitalized adults with postextubation acute hypoxemic respiratory failure (conditional recommendation; low-certainty evidence) 1.

Clinical Considerations

• HFNO can be used as respiratory support in critically ill patients for several indications, including initial management of acute respiratory failure and postextubation respiratory failure 1.
• The patient-centered health outcomes evaluated in the guideline include all-cause mortality, hospital length of stay, 30-day hospital readmissions, hospital-acquired pneumonia, and patient comfort, among others 1.
• The guideline was developed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) method, which provides a framework for evaluating the quality of evidence and making recommendations 1.

From the Research

NIF and Persistent Pulmonary Hypertension of the Newborn

• NIF is not explicitly defined in the provided studies, however, based on the context, it can be assumed that NIF refers to Inhaled Nitric Oxide and its effects on Persistent Pulmonary Hypertension of the Newborn (PPHN).
• PPHN is a condition where the blood pressure in the lungs remains high after birth, leading to hypoxemia and potentially life-threatening complications 2.
• Inhaled nitric oxide (iNO) is a common treatment for PPHN, as it helps to relax the blood vessels in the lungs and improve oxygenation 3, 2, 4.

Effects of Inhaled Nitric Oxide on PPHN

• Studies have shown that iNO can improve oxygenation in infants with PPHN, with response rates ranging from 53% to 75% 3, 4.
• iNO has also been shown to reduce the need for extracorporeal membrane oxygenation (ECMO) in infants with PPHN 2, 4.
• However, iNO can also increase methemoglobin levels, which can reduce the delivery of oxygen to tissues 3, 5.

Methemoglobin Levels and Response to iNO

• Research suggests that the change in methemoglobin levels (ΔMHb) may predict the oxygenation response to iNO in infants with PPHN 5.
• Infants with increased ΔMHb following iNO treatment had better oxygenation responses and survival rates without ECMO compared to those without an increase in methemoglobin levels 5.
• However, the relationship between iNO exposure and elevated methemoglobin levels is complex, and further research is needed to fully understand the effects of iNO on methemoglobin levels 3, 5.