A novel perspective on the use of intraoperative high-flow oxygen delivery systems

High-flow nasal oxygen (HFNO) has been demonstrated to improve respiratory mechanics and oxygenation by enhancing functional residual capacity through increased pulmonary airway pressures.[1,2] High-flow nasal oxygen provides a continuous positive airway pressure ranging from 2.7 to 7.4 cm H₂O, which facilitates the clearance of nasopharyngeal dead space, decreases nasopharyngeal resistance, improves alveolar recruitment, reduces the work of breathing, and helps prevent atelectasis and bronchospasm.[3]

The use of high-flow oxygen delivery systems during surgery has gained significant attention in recent years, particularly for their ability to optimise oxygenation and improve patient outcomes. By delivering oxygen at higher flow rates, the system helps maintain positive end-expiratory pressure, thereby stabilising alveoli and improving lung compliance. This is particularly beneficial in patients with pre-existing respiratory conditions or those undergoing thoracic or abdominal surgeries, where lung collapse is more likely. HFNO has emerged as a transformative modality in perioperative respiratory management, offering significant advantages over traditional oxygen delivery systems. By delivering heated and humidified oxygen at flow rates up to 120 L/min, HFNO ensures a consistent and precise fraction of inspired oxygen, thereby enhancing patient outcomes during surgical procedures. Furthermore, the integration of high-flow oxygen delivery with advanced monitoring technologies, such as continuous capnography and oxygen reserve index, provides real-time feedback on the patient’s respiratory status.[4] This enables timely interventions, reducing the likelihood of complications and improving overall surgical safety.

The integration of HFNO into intraoperative care represents a significant advancement in anaesthetic management. Its ability to reduce the work of breathing, and enhance patient comfort underscores its value as a critical tool in modern anaesthesia practice. As evidence continues to support its efficacy, HFNO is poised to become a standard component of perioperative respiratory support.

Recently, a novel perspective on the use of high-flow tracheal oxygenation (HFTO) was defined for critically ill patients with tracheostomy.[5] Unlike HFNO, HFTO operates with an open-circuit system using a T-piece Mapleson setup, where one end remains open to allow exhalation. HFTO enhances oxygenation and produces modest levels of positive airway pressure. This method provides several key benefits. Firstly, by delivering inspiratory flow directly into the trachea, the oropharyngeal dead space is bypassed, significantly reducing its influence. Secondly, the tracheal tube eliminates glottic closure, which is a critical factor in maintaining PEEP. In tracheostomised patients, the impact of dead space washout is expected to be lower due to a reduction in anatomical dead space.[6]

Natalini et al.[7] concluded that high-flow tracheal oxygenation leads to a modest, flow-dependent enhancement in oxygenation and a rise in tracheal expiratory pressure. In comparison to conventional oxygen therapy, a minimum flow rate of 50 L/min is necessary during HFOT to improve oxygenation, increase expiratory pressure, stabilise fluctuations in inspiratory airway pressure, and lower the respiratory rate. In a bench study, Cour et al.[8] conducted a comparison between high-flow nasal cannula and HFTO. They observed a significant reduction in the total work of breathing per breath. Both the resistive and elastic components of work of breathing were automatically analysed on a breath-by-breath basis.

Outside the critical care setting, HFTO was first introduced for intraoperative apnoeic oxygenation during robotic flexible ureteroscopy procedures.[9] During roboflex surgery, apnoeic oxygenation was sustained in 10-minute intervals. The absence of diaphragmatic movement kept the kidney immobile, providing optimal surgical conditions and maintaining a clear and unobstructed operative field. To conduct an outcome analysis, the authors carried out a clinical comparative study involving a large patient cohort. When administered via an endotracheal tube, these systems offer a unique advantage in maintaining precise control over oxygen delivery, especially in procedures requiring general anaesthesia. This approach ensures a consistent and high fraction of inspired oxygen, which is critical in preventing hypoxemia and supporting tissue perfusion during prolonged or complex surgeries.

One key benefit of intraoperative high-flow oxygen delivery via endotracheal tube is its ability to reduce the risk of atelectasis, a common complication during mechanical ventilation. High-flow endotracheal oxygenation is a method of delivering oxygen at high flow rates through an endotracheal tube or a tracheostomy tube to improve oxygenation in patients with respiratory failure, during airway management, or in specific medical procedures. There are several methods to apply. High-flow insufflation via tracheal tube can be provided through a catheter using the wall oxygen or a ventilator. High-flow oxygen can be also applied through a jet ventilator to deliver short bursts of high-pressure oxygen. This technique is often used in airway surgery or during bronchoscopy. Finally, high-flow oxygen can be directly connected. A specialised tracheostomy tube interface enables the delivery of humidified and warmed gas flow at rates ranging from 10 to 60 L/min.[10] A T-piece connector is used for the tracheal tube connection.[9]

Precautions should be carefully observed throughout the procedure. The PEEP effect may cause barotrauma, particularly at high oxygen flow rates. However, patients experience low pressure when the T-piece is utilised.[11] The use of HFTO allows for better management of carbon dioxide levels. The system’s ability to provide consistent gas exchange minimises the risk of hypercapnia, which can be detrimental in patients with compromised respiratory function. This is especially relevant in surgeries where prolonged periods of apnoea or reduced ventilation are anticipated. However, if ventilation is not adequately managed, carbon dioxide may accumulate, leading to hypercapnia and respiratory acidosis. High-flow oxygenation should not be considered for patients with complete or near-complete airway obstruction. In surgical settings, high oxygen concentrations increase the risk of combustion and airway fire, especially during electrocautery or laser procedures.[12] Moreover, high-pressure oxygen delivery may worsen bleeding or disrupt healing in airway injuries.

Another innovative aspect of this approach is its potential to enhance surgical precision. By ensuring optimal oxygenation, HFTO systems can reduce the need for frequent adjustments to ventilator settings, allowing anaesthesiologists to focus more on monitoring the patient’s overall condition. This stability is particularly advantageous in minimally invasive surgeries, where even minor fluctuations in ventilation can impact the surgical field.

In conclusion, the use of intraoperative high-flow oxygen delivery systems via endotracheal tube represents a significant advancement in perioperative care. By enhancing oxygenation, reducing atelectasis, and improving carbon dioxide management, this approach not only supports better patient outcomes but also contributes to the efficiency and precision of surgical procedures. As technology continues to evolve, further research and clinical trials will be essential to fully explore the potential of this innovative method in diverse surgical settings.