High-Flow Nasal Cannula Oxygen Supported-Transesophageal Echocardiography Under Sedation in a Respiratory Compromised Patient

High-flow nasal oxygen vs. standard oxygen therapy for patients undergoing transcatheter aortic valve replacement with conscious sedation: a randomised controlled trial

BACKGROUND

Minimally invasive surgery is becoming more common and transfemoral transcatheter aortic valve replacement is offered to older patients with multiple comorbidities. Sternotomy is not required but patients must lie flat and still for up to 2-3 h. This procedure is increasingly being performed under conscious sedation with supplementary oxygen, but hypoxia and agitation are commonly observed.

METHODS

In this randomised controlled trial, we hypothesised that high-flow nasal oxygen would provide superior oxygenation as compared with our standard practice, 2 l min^-1 oxygen by dry nasal specs. This was administered using the Optiflow THRIVE Nasal High Flow delivery system (Fisher and Paykel, Auckland, New Zealand) at a flow rate of 50 l min^-1 and FiO₂ 0.3. The primary endpoint was the change in arterial partial pressure of oxygen (pO₂) during the procedure. Secondary outcomes included the incidence of oxygen desaturation, airway interventions, the number of times the patient reached for the oxygen delivery device, incidence of cerebral desaturation, peri-operative oxygen therapy duration, hospital length of stay and patient satisfaction scores.

RESULTS

A total of 72 patients were recruited. There was no difference in change in pO₂ from baseline using high-flow compared with standard oxygen therapy: median [IQR] increase from 12.10 (10.05-15.22 [7.2-29.8]) to 13.69 (10.85-18.38 [8.5-32.3]) kPa vs. decrease from 15.45 (12.17-19.33 [9.2-22.8]) to 14.20 (11.80-19.40 [9.7-35.1]) kPa, respectively. The percentage change in pO2 after 30 min was also not significantly different between the two groups (p = 0.171). There was a lower incidence of oxygen desaturation in the high-flow group (p = 0.027). Patients in the high-flow group assigned a significantly higher comfort score to their treatment (p ≤ 0.001).

CONCLUSION

This study has demonstrated that high flow, compared with standard oxygen therapy, does not improve arterial oxygenation over the course of the procedure. There are suggestions that it may improve the secondary outcomes studied.

TRIAL REGISTRATION

International Standard Randomised Controlled Trial Number (ISRCTN) 13,804,861. Registered on 15 April 2019. https://doi.org/10.1186/ISRCTN13804861.

[The role of HFNC oxygen in pre-oxygenation prior to intubation and the practice of invasive procedures]

Over recent years, High Flow Nasal Cannula (HFNC) oxygen therapy has been more and more extensively applied in numerous medical settings, and it is now carried out in invasive procedures such as pre-oxygenation before orotracheal intubation, often leading to complications. More generally, pre-oxygenation is aimed at maintaining the highest possible oxygen saturation for extended periods of time. With this in mind, HFNC seems as effective as standard oxygen delivery with regard to hematosis in patients with mild or moderate hypoxemia, and it presents the advantage of reducing the adverse events associated with intubation. That said, during pre-oxygenation of patients with severe hypoxemia, non-invasive ventilation (NIV) is probably more effective than HFNC, especially in the prevention of respiratory events. However, in patients with little or no hypoxemia undergoing risky procedures such as bronchial endoscopy, HFNC allows better oxygen saturation than standard methods. To summarize, even though NIV remains useful in unstable patients, especially in decreasing desaturation episodes, HFNC could represent a reasonable alternative in case of poor tolerance, allowing continuous oxygenation of patients requiring digestive endoscopy or trans-esophageal ultrasound.

Nasal high flow: physiology, efficacy and safety in the acute care setting, a narrative review

Nasal high flow (NHF) is a promising novel oxygen delivery device, whose mechanisms of action offer some beneficial effects over conventional oxygen systems. It is considered to have a number of physiological effects: it improves oxygenation, dynamic lung compliance, homogeneity and end expiratory lung volume; it decreases anatomical dead space and generates a positive airway pressure that can reduce respiratory rate, the work of breathing, and enhance patient comfort. NHF has been used as a prophylactic tool or as a treatment device mostly in patients with acute hypoxemic respiratory failure such as pre-oxygenation before intubation, immunocompromised patients and acute heart failure. Moreover, there is some evidence that NHF could be used during procedural sedation. Finally, NHF was deemed to be effective in chronic obstructive pulmonary disease patients with its positive end expiratory pressure effects and dead-space washout. However, careful monitoring is crucial to maximize NHF settings aimed at maximizing patient comfort while limiting the risk of delayed intubation. The present review presents the most updated evidence for NHF use in the adult acute care setting with the goal of providing clinicians with useful insights on the physiologic effects, main clinical indications, and safety issues of NHF treatment.