Oxygen used in home therapy makes fires burn more readily. It doesn’t catch fire itself, but higher oxygen levels lower ignition temperatures and speed up flames, so any ignition source becomes far more dangerous in an environment with supplemental oxygen. That’s why following safety precautions is essential: no smoking or open flames near the oxygen source, keep heat sources and petroleum-based products away from the equipment, avoid wearing oils or lotions on the face or near the cannula, and ensure proper storage and handling to prevent leaks and saturation of fabrics. In short, oxygen’s fire-supporting nature is what makes safety rules so important. Oxygen is not inert, it does not explode on contact, and it does not sterilize equipment.

Nasal cannulas are designed for low-to-moderate oxygen needs, delivering gas in a flow range that patients can tolerate comfortably. The typical flow range is 1–6 L/min because within this window you get reliable, steady oxygen delivery without causing too much drying or discomfort. Below 1 L/min the delivered FiO2 can be inconsistent and insufficient for many patients. Pushing flow beyond about 6 L/min with a simple nasal cannula doesn’t significantly raise FiO2 and can increase nasal irritation; for higher oxygen needs, clinicians switch to other devices that provide higher and more controlled FiO2, such as masks or high-flow systems. Actual FiO2 also depends on breathing pattern and whether the patient breathes through the nose or mouth, with mouth breathing tending to lower the effective FiO2 from the stated flow.

The goal of ICU oxygen therapy is to improve how efficiently oxygen moves from the lungs into the blood, not merely to push the saturation up to 100% or to flood the patient with oxygen. The key measure is the P/F ratio (PaO2 divided by FiO2), which reflects the lungs’ ability to transfer oxygen for a given amount of inspired oxygen. When this ratio improves, it indicates better alveolar gas exchange and more effective oxygen delivery to tissues for the same or even less oxygen support. Chasing a normal PaO2 at any FiO2 isn’t realistic or always safe, since lung disease and ventilation–perfusion problems prevent perfect oxygen transfer. Likewise, simply maximizing FiO2 can cause oxygen toxicity and other complications without guaranteeing better tissue oxygenation. And aiming for SpO2 of 100% regardless of FiO2 can mask underlying issues and isn’t necessary for optimal outcomes. So, improving the P/F ratio best captures the intended goal: enhancing oxygen transfer efficiency through the lungs while using the minimum effective amount of inspired oxygen.

The main idea is that arterial blood gas assessment after starting oxygen should be guided by changing clinical status, not by a fixed schedule or by SpO2 alone. ABG provides direct measurements of oxygenation (PaO2), ventilation (PaCO2), and acid-base balance (pH), which are essential for deciding whether the oxygen therapy is meeting the patient’s needs and whether ventilation is adequate. When a patient’s work of breathing changes, such as increasing dyspnea, labored or tiring breathing, or new signs of respiratory muscle fatigue, an ABG helps determine if oxygen delivery is sufficient and if ventilation is appropriate. It also helps detect acid-base disturbances that might require adjustments in therapy or ventilatory support. If acid-base status changes or a suspicion of metabolic or respiratory imbalance arises, ABG analysis guides the next steps for management, including adjusting oxygen flow, devices, or considering additional support. Relying on SpO2 alone isn’t enough because SpO2 can appear normal even when PaO2 is not at the desired level or when there are issues with ventilation that ABG would reveal. ABGs provide a fuller picture, including whether CO2 is rising or falling and whether the pH is deranged, which are critical for safe and effective oxygen management. On the other hand, performing ABGs after every hour regardless of status isn’t necessary and can be burdensome; the timing should be driven by clinical changes or specific indications rather than a fixed interval. So, the best approach is to assess ABG when indicated by the patient’s clinical status—such as changes in work of breathing or acid-base balance—to guide adjustments in therapy.