What are the implications of an oxygen saturation level of 91% on room air with a supplemental oxygen flow rate of 3 liters per minute (LPM)?

From the Guidelines

A SpO2 of 91% while receiving 3 liters per minute (LPM) of supplemental oxygen indicates mild hypoxemia that requires clinical attention, and I recommend increasing the oxygen flow rate to 4-5 LPM and reassessing in 15-30 minutes to target an SpO2 of at least 94%. This oxygen saturation is below the normal range of 95-100% despite supplemental oxygen therapy. According to the BTS guideline for oxygen use in adults in healthcare and emergency settings 1, significant arterial oxygen desaturation (SpO2 <90% or fall of 4% or more) should be corrected by supplemental oxygen with the aim of achieving target oxygen saturations of 94–98%, or 88–92% in those at risk of hypercapnic respiratory failure.

Key Considerations

• If the patient has COPD, a target SpO2 of 88-92% may be appropriate to avoid carbon dioxide retention, as stated in the BTS guideline 1.
• The patient should be monitored for signs of respiratory distress including increased work of breathing, tachypnea, or altered mental status.
• If SpO2 does not improve with increased oxygen flow or if the patient's condition deteriorates, consider changing to a different oxygen delivery device such as a non-rebreather mask or high-flow nasal cannula, and obtain arterial blood gases to assess for hypercapnia, as suggested in the management of hypercapnia or respiratory acidosis due to excessive oxygen therapy 1.
• The underlying cause of hypoxemia should be investigated promptly through physical examination, chest imaging, and other relevant tests based on clinical presentation.

Oxygen Therapy Adjustments

• For patients with a significant likelihood of severe COPD or other illness that may cause hypercapnic respiratory failure, use a 24% Venturi mask at 2–3 L/min or nasal cannulae at 1–2 L/min or 28% Venturi mask at 4 L/min and aim for an oxygen saturation of 88–92% 1.
• Patients with a respiratory rate >30 breaths/min should have the flow rate from Venturi masks set above the minimum flow rate specified for the Venturi mask packaging to compensate for the patient’s increased inspiratory flow 1.

From the Research

Implications of Oxygen Saturation Level

• An oxygen saturation level of 91% on room air with a supplemental oxygen flow rate of 3 liters per minute (LPM) is below the recommended target range of 92-96% for oxygen saturation (SpO2) measured by pulse oximetry 2, 3.
• According to the study by 4, acute hypoxemic respiratory failure is defined as PaO2 < 60 mm Hg or SpO2 < 90% on room air, and supplemental oxygen should be administered to maintain SpO2 above 92% and below 98%.
• The study by 2 suggests that the target range of acute O2 therapy for ventilated patients and nonventilated patients not at risk of hypercapnia should be between 92% and 96% for oxygen saturation (SpO2) measured by pulse oximetry.
• However, the study by 5 found that lower SpO2 thresholds, such as 88%, may be potentially safe in children with respiratory distress and may reduce hospitalization rates and length of stay.

Supplemental Oxygen Therapy

• The study by 6 evaluated the ability of emergency medical technicians to use pulse oximetry measurements in determining patient oxygen requirements and found that advanced life support units increased oxygen supplementation on all desaturated patients.
• The study by 2 states that indications for high-dose O2 therapy without a target range in critical care include carbon monoxide poisoning and patients with severe respiratory distress when SpO2 cannot be derived.
• The study by 4 recommends that high-flow nasal cannula oxygen (HFNC) should be the first-line noninvasive respiratory support in patients with PaO2/FiO2 ≤ 200 mm Hg with increased respiratory rate.

Target Oxygen Saturation Range

• The study by 3 considers the rationale for the target oxygen saturation range of 92-96% for oxygen therapy in adult patients without COPD or other conditions associated with chronic respiratory failure.
• The study by 2 suggests that hyperoxemia, i.e., SpO2 values above 96%, has not improved survival in randomized trials of predominantly ventilated ICU patients.
• The study by 5 found that the current SpO2 thresholds of 90-94% in children with respiratory distress may be too high, which could lead to unnecessary hospitalizations and prolonged hospitalization duration.