Background

"Preoxygenation prior to induction of general anesthesia is intended to increase the oxygen reserve in the lungs. This technique delays the onset of hypoxemia during the placement of the tracheal tube."

Objective

"To observe the benefits of oxygen through nasal cannula when used as an adjunct during preoxygenation."

Methods

"We enrolled 30 healthy volunteers and conducted a sequence of six preoxygenation tests. These included 3-minute tidal volume breathing and 8 vital capacity breaths, with and without oxygen flowing through the nasal cannula as an adjunct. Subjects were kept at a supine position with a face mask on their faces. Their baseline vitals were measured and end-tidal O2 (ETO2) was recorded at the end of each test. The comfort of each technique was also assessed."

Results

"When comparing the efficacy of the two preoxygenation methods, we found that the addition of oxygen through the nasal cannula improved the efficacy of preoxygenation with both the 3-minute tidal volume breathing method and the 8 vital capacity method (p < 0.001). The three-minute tidal volume breathing technique had higher end-tidal oxygen when compared to the eight vital capacity breaths."

Conclusions

"The administration of oxygen through a nasal cannula during preoxygenation improves the efficacy of preoxygenation in healthy volunteers. Tidal volume breathing for three minutes achieves a higher end-tidal oxygen concentration compared to eight vital capacity breaths over one minute."

Excerpts

The effectiveness of preoxygenation is primarily based on two measurable factors, namely, efficacy and efficiency. The efficacy of preoxygenation is measured based on the increase in the fraction of alveolar O2 (FAO2), the reduction in alveolar nitrogen (FAN2), and the increase in alveolar tension (PaO2), while efficiency is measured by the decrease in saturation (SaO2) during apnea [1]. Effective preoxygenation can be confirmed by an increase in end-tidal O2 (ETO2) more than 90% or an end-tidal nitrogen concentration of 5% [2]

using nasal cannula as an adjunct improved the end-tidal oxygen concentration, irrespective of the preoxygenation technique used (3-minute tidal volume respiration and 8 vital capacity breaths over 1 minute)

Effective preoxygenation improves the safety of patients during airway manipulation by increasing the safe apneic time [12]. This is especially evident in certain subset of patients such as pediatric, pregnant women, obesity, and full stomach and patients with a difficult airway. The prevalence of unanticipated difficult airway is 0.9–1.9% [13]. The pediatric population is particularly susceptible to hypoxia during general anesthesia and sedation due to greater oxygen consumption and diminished functional residual capacity. It is reported that over 50% of critical events during the perioperative period in children are respiratory related [14].

we ensured leak was minimal by adjusting the mask seal to minimize distortion in the continuous capnography waveforms. We were able to achieve similar ETO2 values (82%) in our study to those achieved by the former authors (79% and 84%) with a tight-fitting bag mask valve device and no leak, possibly demonstrating that a good mask seal can be achieved even with a nasal cannula in place.

We found that 3-minute TV breathing was better than 8 VC breaths over one minute as a preoxygenation technique, and the use of nasal cannula as an adjunct improved the ETO2 in both 3-minute TV and 8VC technique

The use of nasal cannula as adjunct to the standard preoxygenation technique is an ingenious way to achieve the benefits of using a high flow nasal oxygen device in low resource settings. The addition of oxygen via nasal cannula as an adjunct to standard mask preoxygenation increases the overall oxygen flow (10–20 l/min),

A flow of 5 L/min was found to provide a balance between tolerability and effective preoxygenation

Preoxygenation with 5 L/min oxygen through the nasal cannula may be sufficient to overcome any possible leaks imposed by the presence of the nasal cannula when a reasonably tight fit of the mask can be ensured. The nasal cannula can be left in place throughout airway management, providing an extra margin of safety.

Citation

Joel M, Podder S, Nagesh SK, Aithal R, Devalla AR, Mathew S. Use of a Nasal Cannula as a Preoxygenation Adjunct: A Randomized Crossover Study. Anesthesiol Res Pract. 2024 Sep 5;2024:7873142. doi: 10.1155/2024/7873142. PMID: 39267881; PMCID: PMC11392575.

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