Nasal Oxygen Insufflation: Limitations & Clinical Applicability

In the literature

Murphy ML, Hodgson DS, Bello NM. Accuracy of oxygen delivery through bubble humidifiers and nasal catheters. Vet Anaesth Analg. 2020;47(3):356-367.

The Research …

Patients with signs of respiratory distress, hypoxia, or hypoxemia often require oxygen supplementation.^1-3 Nasal insufflation catheters connected to a bubble humidifier and an oxygen source are often used to provide supplemental oxygen. Although these devices are easily manufactured in-clinic, this study highlights that the prescribed oxygen flow is often undelivered in these situations. 

The study evaluated 64 oxygen delivery assemblies manufactured in-clinic and included a flowmeter, a bubble humidifier, oxygen delivery tubing, and nasal insufflation catheters made of nasogastric feeding tubes of different sizes (3.5 Fr, 5.0 Fr, 8.0 Fr, and 10.0 Fr). Single and double nasal insufflation catheter assemblies were tested, and the oxygen flow rates varied from 0.1 to 5 L/minute. Because of leaks through the bubble humidifier’s safety pressure relief valve (PRV), which was set to open at 3 psi, most assemblies consistently delivered less oxygen relative to the specified flow setting. The authors suggested that a bubble humidifier with a PRV that opens at 6 psi may decrease the leakage, possibly resulting in a more accurate delivered flow. Small-sized catheters (eg, 3.5 Fr) were the least accurate in delivering the target oxygen flow, and assemblies with larger catheters (ie, 10.0 Fr) and higher flow rates (ie, 1 L/minute, 5 L/minute) were more accurate.  

Although the amount of oxygen reaching the patient may not match the flowmeter setting, several studies have supported nasal insufflation as a reliable way of increasing inspired fraction of oxygen (FiO₂) and partial pressure of oxygen (PaO₂) in arterial blood.^1,3-5 An estimated FiO₂ of 0.5 to 0.6 can be achieved with the recommended oxygen flow of 50 to 100 mL/kg/minute delivered via unilateral nasal cannula.^1,3-5 Bilateral nasal cannulas may be needed to decrease patient discomfort and to allow for higher oxygen flow rates (>100-200 mL/kg/minute); however, care should be taken when higher flows are used, especially for prolonged periods (>18-24 hours), due to the risk for oxygen toxicity.⁴   

The inaccuracy of oxygen flow delivered via in-clinic manufactured systems should be considered, but improvement in clinical signs should be the main guide for treatment adequacy. Response to treatment may include improved oxygen saturation (SpO₂; >96%) or Pa0₂ (>80 mm Hg) or decreased effort of breathing. Although the exact oxygen flow reaching the patient may not be accurately determined due to possible leaks in the system, nasal insufflation is an easy and economical method of oxygen delivery, requires no specialized equipment, and is well-tolerated by most patients.

… The Takeaways

Key pearls to put into practice:

• The largest catheter possible should be used to administer oxygen when nasal insufflation is attempted.

• High oxygen flow can cause discomfort and increase the risk for oxygen toxicity. The recommended oxygen flow for nasal insufflation is 50 to 100 mL/kg/minute. If higher flows are required, bilateral nasal cannulas can be considered.

• Efficacy of oxygen supplementation should be determined with close monitoring of clinical signs and variables (eg, SpO₂, PaO₂).