Skip to main content

Comparison of high-flow nasal cannula and conventional oxygen therapy for high-risk patients during bronchoscopy examination: protocol for a randomized controlled trial



High-flow nasal cannula (HFNC) has been proven to improve oxygenation and avoid intubation in hypoxemic patients. It has also been utilized during endoscopy examination to reduce the incidence of hypoxia. However, little is known about the effects of HFNC versus conventional oxygen therapy (COT) on oxygenation during bronchoscopy examination via nasal route; particularly, no study has compared the use of HFNC with that of COT at similar FIO2 for patients who have high-risk factors of desaturation during bronchoscopy examination.

Methods and analysis

This randomized controlled trial will be implemented in four academic centers in China. Patients who have high-risk factors including hypoxemia, hypercapnia, morbid obesity, and narrow airway will be enrolled to use HFNC or COT during bronchoscopy examination. In the HFNC group, the initial gas flow will be set at 50 L/min with a fraction of inspired oxygen (FIO2) at 0.45, if the patient tolerates, the flow can be increased to 60L/min at most, while in the COT group, oxygen flow will be set at 6 L/min via a conventional nasal cannula. After 5 min pre-oxygenation, the bronchoscope will be inserted via the nasal route. Vital signs, oxygenation (SpO2), and transcutaneous CO2 (PtCO2) will be continuously monitored. The primary outcome is the incidence of hypoxemia, defined as SpO2 < 90% for 10 s during bronchoscopy examination, and secondary outcomes include the need for treatment escalation and adverse events.


Hypoxia is a common complication of bronchoscopy, our study attempted to demonstrate that HFNC may reduce the probability of hypoxia during bronchoscopy in high-risk patients. The results will be disseminated through peer-reviewed journals and national and international conferences.

Trial registration ChiCTR2100055038. Registered on 31 December 2021.

Peer Review reports

Strengths and limitations of this study


  • ➣ This is the first study to compare the utilization of HFNC with that of conventional nasal cannula at similar FIO2 during bronchoscopy examination via nasal route for patients who have high-risk factors

  • ➣ This is the first study to report the need for treatment escalation to resolve hypoxemia during bronchoscopy examination, of which the study findings have clinically meaningful implications

  • ➣ This is the first study to demonstrate the effects of HFNC on transcutaneous CO2 during bronchoscopy examination.


  • ➣ The study enrolls patients with four different risk factors; the general conclusion might not apply to any specific group.

  • ➣ This study does not limit the procedures of bronchoscopy; the general conclusion might not apply to any specific procedure.

  • ➣ This study excludes critically ill patients, thus the findings may not apply to these patients



High-flow nasal cannula (HFNC) is an oxygen supply system that allows setting the gas flow and the fraction of inspired oxygen (FIO2) separately [1]. Because of its ability to provide high gas flow to exceed the inspiratory flow demand of patients, FIO2 is constant during HFNC treatment [2, 3]; moreover, the high flow also generates positive end-expiratory pressure [1, 4]. Therefore, HFNC has been proven to be superior to conventional oxygen therapy (COT) in improving oxygenation and avoiding intubation in hypoxemic patients [5,6,7,8,9,10,11,12,13,14]. Additionally, HFNC is also shown to reduce hypercapnia and improve ventilation in patients with chronic obstructive pulmonary disease (COPD) [15,16,17,18,19,20,21], since high-flow gas washes out the dead space [19,20,21].

In recent years, HFNC has been utilized to improve oxygenation or avoid desaturation during endoscopy examination [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37], as hypoxemia is the most common complication during endoscopy examination, particularly with sedation [31,32,33, 38, 39]. The reported incidence of hypoxemia in the RCTs varied from 28.8 to 89.7% during flexible bronchoscopy examination [22,23,24,25,26,27,28,29,30]. Patients who require bronchoscopy examination may have existing pulmonary diseases, and the insertion of bronchoscope occludes part of the airway, resulting in increased respiratory resistance. Both factors may contribute to hypoxemia and hypercapnia during bronchoscopy examination [40,41,42].

Till now, seven randomized controlled trials (RCTs) have compared the use of HFNC with that of COT during bronchoscopy examination and found that the incidence of hypoxia was lower in the HFNC group [22,23,24,25,26, 29, 30]. Most of the RCTs [22, 25, 26, 29, 30] were implemented with bronchoscopy via the oral route, and during the examination, HFNC was utilized with the mouth constantly open, which might cause the significant loss of the benefits of HFNC in constant FIO2 and positive end-expiratory pressure. Nasal insertion of bronchoscope would allow patients to breathe with mouth closed, which might reserve the benefits of HFNC. Besides, nasal insertion of bronchoscope is more favorable in our institutions, because it causes fewer retch reflexes and enables better control during insertion as well as additional inspection of the nasal airway [42]. Nevertheless, little evidence is available to support the utilization of HFNC during bronchoscopy via nasal insertion. Therefore, we propose an RCT to compare the use of HFNC versus that of COT during bronchoscopy examination via nasal insertion among high-risk patients. Besides hypoxemic patients, we will also enroll three other types of patients as “high-risk” patients, including (1) patients of hypercapnia with chronic pulmonary disease, who might have increased CO2 and hypoxemia during bronchoscopy [40,41,42], (2) morbidly obese patients who were reported to experience hypoxemia during endoscopy examination [32], and (3) patients of narrow airway with radiology evidence prior to bronchoscopy [42, 43]. Our hypothesis is that the incidence of hypoxemia will be lower in the HFNC group than in the COT group during nasal bronchoscopy examination for patients with high-risk factors.


This is a multi-center randomized controlled trial, which has been approved by the Ethic Committees of East Hospital (Shanghai, China) and Changhai Hospital (Shanghai, China). This trial is registered with (ChiCTR2100055038). The report of the protocol followed the SPIRIT guideline [44].

Study population

Patients who need bronchoscopy examination will be recruited from outpatient clinics or inpatient units in the four academic hospitals in China.

Inclusion criteria

Adult patients who have one of the following high-risk factors will be enrolled in the study: (1) hypoxemia with the PaO2/FIO2 ≤ 300 mmHg before bronchoscopy examination; (2) hypercapnia with PaCO2 ≥ 45 mmHg and baseline chronic pulmonary disease, including COPD, and bronchiectasis, etc.; (3) narrow trachea confirmed by radiology before bronchoscopy, which may have been caused by tracheomalacia, trachea tumor or granuloma, or aspirated foreign body, etc.; and (4) morbidly obese patients with body mass index (BMI) ≥ 30 kg/m2.

Exclusion criteria

Patients will be excluded if any of the following criteria is met: (1) refuse to participate; (2) local/general anesthesia bronchoscopy or rigid endoscopy is indicated; (3) age ≥ 90 years, or < 18 years; (4) pregnancy; (5) estimated duration of bronchoscopy is less than 10 min; (6) contraindication to using HFNC, including nasopharyngeal obstruction and blockage; (7) require oxygen flow ≥ 3L/min to maintain SpO2 at 90–97%; (8) central airway narrowness > 80%; and (9) the patient is critically ill and unsuitable for study inclusion assessed by anesthesiologists and pulmonologists.

Study procedures

See the study diagram in Fig. 1.

Fig. 1
figure 1

Study flowchart. Abbreviations: HFNC, high-flow nasal cannula; HR, heart rate; RR, respiratory rate; BP, blood pressure; SpO2, peripheral capillary oxygen saturation; PtCO2, percutaneous carbon dioxide; MV, mechanical ventilation. *For HFNC group, increase FIO2 to 1.0; For COT group, change to HFNC at 60 L/min and FIO2 0.45, if SpO2 cannot be maintained, increase FIO2 to 1.0

Recruiting and consent process

The nurse responsible for scheduling bronchoscopy examinations for patients in the bronchoscopy suite will screen the patients. The study investigator will be notified of eligible patients and will obtain informed consent from the patients. Study purposes, procedures, risks, and benefits will be discussed with the patients in a private room. Consent forms will be given to patients for full consideration before the examination day. On the examination day, arterial blood gas will be assessed for patients who are enrolled in the study due to hypoxemia and/or hypercapnia on the screen day. If the patients still meet the inclusion criteria and sign the consent form, they will be enrolled for randomization. Together with the other two types of patients (narrow airway and morbidly obese), they will be randomized to receive HFNC or COT during bronchoscopy examination after signing the consent form in the presence of the study investigator.

Randomization and treatment

An independent statistician will be responsible for generating the randomization sequence, which will be placed in a series of sequentially numbered, sealed, and opaque envelopes. After the patient signs the consent form, an envelope will be opened to assign an oxygen device for the patient.

OH-70C (micomme, HuNan, China) will be used to provide HFNC, with initial flow of 50 L/min and FIO2 at 0.45. The temperature will be set at 37° C. Nasal cannula will be chosen based on the patient’s prong size: the nasal cannula size should be less than 50% of the nasal prong size. Similarly, in the group with COT, a double-prong nasal cannula (Healthcare Medical Supplies Co., Ltd. Hangzhou, China) will be used, and oxygen flow will be set at the maximum setting of 6 L/min, in which FIO2 is calculated to be 0.45. Before using the assigned device, pre-oxygenation will last for 5 min to maintain SpO2 98–100% by using an anesthetic mask, due to the need for adjusting the sedation dose. Duration of pre-oxygenation, patient SpO2, PtCO2, and vital signs including heart rate, respiratory rates, and blood pressure before and after pre-oxygenation will be recorded (Fig. 1).

Bronchoscopy examination and hypoxemia management

Topical anesthesia will be provided prior to bronchoscopy as routine treatment. Sedation and/or anesthesia will be utilized by an anesthesiologist at the bedside. The depth of sedation will be assessed using the Modified Observer’s Assessment of Alertness/Sedation Scale(MOAA/S), and the score will be maintained at 2 ~ 3 throughout the examination process. The timing to use, the name, and the dose of sedation will be recorded. Bronchoscopy examination will be performed by experienced pulmonologists in the bronchoscopy suite. SpO2, PtCO2, and vital signs will be continuously monitored while FIO2 for HFNC and oxygen flow for COT will be maintained until the patients experience the first desaturation, defined as SpO2 ≤ 90% for 10 s. The timing and the lowest SpO2 in the first desaturation will be recorded (Fig. 1). Once desaturation occurs, jaw thrust maneuvers and/or suspension of bronchoscopy examination will be implemented to improve oxygenation. If desaturation persists, FIO2 will be increased to 1.0 in the HFNC group while in the COT group, COT will be changed to HFNC with flow at 60 L/min and initial FIO2 at 0.45, FIO2 will be increased to 1.0 if hypoxia remains. All the management will be recorded as treatment escalation. If SpO2 is still below the safe range, advanced airways, including nasopharyngeal airway, oropharyngeal airway, laryngeal mask, or tracheal intubation, will be inserted depending on patient situation (Fig. 1). The process, the duration, and the reason for the suspension of bronchoscopy examination will be recorded. After the recovery, whether bronchoscopy will be resumed or not will be determined by pulmonologists based on the clinical situation. Notably, besides desaturation, other adverse events may also cause the examination to be suspended, such as tachycardia, severe hypertension, arrhythmia, etc. These events will also be recorded in detail. The duration of the bronchoscopy examination refers to the time from the first entry into the nasal cavity to the end of the examination, as well as the time of per interruption will be precisely documented.

Termination criteria

Bronchoscopy examination will be terminated if any of the criteria is met: (1) any of the adverse events, including hemodynamic instability, cardiac arrest, massive bleeding, and pneumothorax is observed or reported, and (2) despite maximal oxygen delivery, SpO2 cannot be maintained at a level ≥ 90%.

All the rescue treatments and resuscitation equipment are prepared in the bronchoscopy suite. Any patient who experiences adverse events will be rested and monitored in the general unit, until the patient recovers.

Post bronchoscopy monitoring

After bronchoscopy, SpO2, PtCO2, and vital signs will be continuously monitored until the patients return to pre-bronchoscopy status or are stable. The recovery time and postoperative adverse reactions will be recorded as well. After the patients recover, patient comfort will be assessed. Lastly, we will also survey the anesthesiologists and pulmonologists on their satisfaction with the bronchoscopy examination.


The primary outcome is to compare the incidence of desaturation which is defined as SpO2 < 90% between patients using HFNC and those using COT. The secondary outcomes include the timing of the appearance of the first desaturation (namely desaturation time), the lowest SpO2 and the highest PtCO2 during the entire bronchoscopy examination, the need for treatment escalation and airway management, the number and duration of bronchoscopy suspensions, the incidence of adverse events, and the recovery time between the two groups. A post hoc analysis will be performed to explore the risk factors of desaturations during bronchoscopy examination among high-risk patients.

Sample size calculation (

This study is a superiority study. While in the study [26] with a patient population close to our study during bronchoscopy examination, the incidence of desaturation of HFNC vs COT group was 13.3 vs 33.3%, respectively. However, this previous study only included hypoxemic patients while we will enroll other types of patients, so the incidence of hypoxemia in the HFNC group in their study might be higher than the incidence in ours. Thus, we assumed that when the maximal concentration of oxygen is provided by the two assigned devices, that is, when FIO2 is set at 1.0 for HFNC and oxygen flow at 6 L/min for COT, the probability of desaturation is 10% in the HFNC group and 30% in the COT group, respectively. According to statistical calculation, the sample size should be 124, with a confidence level (α) of 95%, power (1-ß) of 80%, and margin (Δ) of 0.2. Assuming a 20% dropout rate during the study, we set the final sample size to be 148. An interim analysis will be conducted once 50% of the sample size is reached.

Data collection

The parameters that are continuously monitored by the bedside monitor before, during, and after bronchoscopy examination, including vital signs, SpO2, and PtCO2, and the incidence of desaturation and bronchoscopy suspension/termination will be observed and recorded by an independent investigator. Meanwhile, the anesthesia information and procedures under bronchoscopy such as bronchoalveolar lavage, EBUS, and biopsy, as well as bleeding volume and the adverse events during the examination, will be collected. Demographic information of patients (age, gender, height, weight, BMI, race, smoking and drinking history, diagnosis, comorbidity, current medication, and reason for bronchoscopy examination) and laboratory results such as coagulation and chest CT will also be collected.

Statistical analysis

Categorical variables, including the incidence of desaturation, treatment escalation, suspension or termination of bronchoscopy, etc., will be presented as percentages and analyzed by chi-square test. Continuous variables, including the desaturation time, recovery time, the lowest SpO2, the highest PtCO2, etc., will be presented as mean ± standard derivation (SD) or median and interquartile rage (IQR) and compared by independent t-test or Mann Whitney test, depending on the normality of distribution, which will be tested by the Kolmogorov–Smirnov test. A two-sided P-value of < 0.05 will be regarded as statistically significant for all tests. Data analysis will be conducted with SPSS software (SPSS 23.0; Chicago, IL).

Patient and public involvement

Patients and/or the public were not involved in the study design.


This is the first study to compare HFNC vs COT during bronchoscopy via nasal route among high-risk patients. The benefit of using the nasal route is that it allows for better control of the bronchoscope [42]. More importantly, because the patient’s mouth is mainly closed during the examination, the placement of HFNC may help generate and maintain the positive end-expiratory pressure, resulting in better oxygenation during HFNC. Even though NIV has been shown to be more effective in improving oxygenation during bronchoscopy examination, the complications of NIV, particularly gastric overdistension, are concerning [45], since in this process the bronchoscope is inserted via the oral route. In patients who receive positive pressure ventilation with the mouth constantly open and a bronchoscope is inserted via the bite block, the closure of vocal cords and the function of swallow will be substantially affected, and the risk of aspirating gas from positive pressure ventilation might be higher than in HFNC. Therefore, although we will not compare HFNC with NIV in this study, when HFNC is placed in two prongs at the same flow with the mouse closed, the nasal route may generate positive pressure comparable to that in NIV and produce similar washing-out effects [46, 47].

We only enroll patients with high-risk factors, due to the consideration of cost-effectiveness and clinical implication. For the general patient population, the incidence of desaturation during endoscopy examinations is low. Even when hypoxemia occurs during bronchoscopy examination, most can be easily resolved by increasing oxygen flows through the conventional nasal cannula. More importantly, since a general bronchoscopy examination usually lasts 10–15 min, using a new set of HFNC circuits and nasal cannula might not be worthwhile, especially considering the high cost of HFNC, which is 200–400-fold of conventional nasal cannula. As such, using HFNC to assist bronchoscopy examination for patients with high-risk factors might be more reasonable [48].

Moreover, Riccio et al. compared nasal cannula with HFNC at similar FIO2 during colonoscopy examination in morbidly obese patients and did not find a significant difference between the two groups, which implies the FIO2 other than high-flow setting is essential to the maintenance of oxygenation during endoscopy [32]. However, Yilmazel Ucar E et al. [25] compared the use of HFNC with that of COT at the same FIO2 during the endobronchial ultrasonography (EBUS) procedure among 170 patients and found a lower incidence of desaturation with HFNC. They did not enroll any patients with high-risk factors, so the exact effect of flow settings on oxygenation during bronchoscopy for patients with high-risk factors is still unclear. More importantly, in our study, we plan to compare HFNC and COT at similar FIO2 (~ 0.45), which is the maximum FIO2 setting for the COT group. If patients in the COT group continue to desaturate, they will be switched to HFNC with FIO2 at 1.0. Advanced airways will be inserted if the oxygenation still cannot be maintained. This management of hypoxemia and the study findings have an important clinical implication, as the consequences of bronchoscopy suspension or the need to switch to a different oxygen device is more meaningful than the incidence of desaturation, which might be easily resolved by simply increasing the oxygen flow with a standard nasal cannula, especially in the studies using low flow (2–3 L/min) oxygen in the COT group [23, 24, 29].

One may concern about hypercapnia during bronchoscopy [46], due to the partial occlusion of the airway and the side effects of sedation, so our study will continuously monitor PtCO2 before, during, and after bronchoscopy, which is also the first clinical study reporting the effects of HFNC on PtCO2 during bronchoscopy examination.

The major limitation of this study is the difficulty of excluding the impact of the length of examination and procedures on hypoxemia. Special operations under bronchoscope (such as EBUS), long operation time, or more than 3 biopsies under bronchoscope may cause hypoxia. Even though the patients will be randomized, those factors might be balanced into two groups, and the post hoc analysis will be performed, the conclusion from this study still might not apply to any specific type of procedure during bronchoscopy examination. Additionally, it is an open-label study, as the intervention (HFNC) is a unique device, which is largely different from the conventional nasal cannula, thus blinding the participants or investigators is impossible.

Trial status

We originally planned to start enrolling patients on June 1, 2022, and end the study within 1 year, but due to the COVID-19 outbreak in China, it may be delayed.

Availability of data and materials

Data will be sourced from forced expiratory capacity test results, electronic medical records, and monitors. Data will be de-identified and entered into a secure, web-based electronic database. Only the investigators will have access to the final dataset. Individual participant data after de-identification that underlie the reports reported in this article can be obtained by contacting the corresponding author. Data will be available immediately following publication and ending in 5 years.



High-flow nasal cannula


Conventional oxygen therapy

FIO2 :

Fraction of inspired oxygen

PtCO2 :

Transcutaneous CO2


Chronic obstructive pulmonary disease


Endoscopic retrograde cholangiopancreatography


Body mass index


Endobronchial ultrasonography


  1. Li J, Jing GQ, Scott JB. Year in review 2019: High-flow nasal cannula (HFNC) oxygen therapy for adult patients. Respir Care. 2020;65(4):545–57.

    Article  Google Scholar 

  2. Ritchie JE, Williams AB, Gerard C, Hockey H. Evaluation of a humidified nasal high-flow oxygen system, using oxygraphy, capnography and measurement of upper airway pressures. Anaesth Intensive Care. 2011;39(6):1103–10.

    Article  CAS  Google Scholar 

  3. Li J, Scott JB, Fink JB, Reed B, Roca O, Dhand R. Optimizing high-flow nasal cannula flow settings in adult hypoxemic patients based on peak inspiratory flow during tidal breathing. Ann Intensive Care. 2021;11(1):164.

    Article  Google Scholar 

  4. Nishimura M. High-flow nasal cannula oxygen therapy in adults: Physiological benefits, indication, clinical benefits, and adverse effects. Respir Care. 2016;61(4):529–41.

    Article  Google Scholar 

  5. Rochwerg B, Granton D, Wang DX, Helviz Y, Einav S, Frat JP, et al. High flow nasal cannula compared with conventional oxygen therapy for acute hypoxemic respiratory failure: A systematic review and meta-analysis. Intensive Care Med. 2019;45(5):563–72.

    Article  CAS  Google Scholar 

  6. Lu Z, Chang W, Meng SS, Zhang X, Xie J, Xu JY, et al. Effect of high-flow nasal cannula oxygen therapy compared with conventional oxygen therapy in postoperative patients: A systematic review and meta-analysis. BMJ Open. 2019;9(8):e027523.

    Article  Google Scholar 

  7. Rochwerg B, Einav S, Chaudhuri D, Mancebo J, Mauri T, Helviz Y, et al. The role for high flow nasal cannula as a respiratory support strategy in adults: a clinical practice guideline. Intensive Care Med. 2020;46(12):2226–37.

    Article  Google Scholar 

  8. Agarwal A, Basmaji J, Muttalib F, Granton D, Chaudhuri D, Chetan D, et al. High-flow nasal cannula for acute hypoxemic respiratory failure in patients with COVID-19: systematic reviews of effectiveness and its risks of aerosolization, dispersion, and infection transmission. Can J Anaesth. 2020;67(9):1217–48.

    Article  CAS  Google Scholar 

  9. Liu Q, Zhu C, Lan C, Chen R. High-flow nasal cannula versus conventional oxygen therapy in patients with dyspnea and hypoxemia before hospitalization. Expert Rev Respir Med. 2020;14(4):425–33.

    Article  CAS  Google Scholar 

  10. Wang Y, Ni Y, Sun J, Liang Z. Use of High-Flow Nasal Cannula for Immunocompromise and Acute Respiratory Failure: A Systematic Review and Meta-Analysis. J Emerg Med. 2020;58(3):413–23.

    Article  Google Scholar 

  11. Theologou S, Ischaki E, Zakynthinos SG, Charitos C, Michopanou N, Patsatzis S, et al. High Flow Oxygen Therapy at Two Initial Flow Settings versus Conventional Oxygen Therapy in Cardiac Surgery Patients with Postextubation Hypoxemia: A Single-Center, Unblinded, Randomized, Controlled Trial. J Clin Med. 2021;10(10):2079.

    Article  CAS  Google Scholar 

  12. Xiang GL, Wu QH, Xie L, Song JQ, Wu X, Hao SY, et al. High flow nasal cannula versus conventional oxygen therapy in postoperative patients at high risk for pulmonary complications: A systematic review and meta-analysis. Int J Clin Pract. 2021;75(3):e13828.

    Article  CAS  Google Scholar 

  13. Chaudhuri D, Granton D, Wang DX, Burns KEA, Helviz Y, Einav S, et al. High-Flow Nasal Cannula in the Immediate Postoperative Period: A Systematic Review and Meta-analysis. Chest. 2020;158(5):1934–46.

    Article  Google Scholar 

  14. Fong KM, Au SY, Ng GWY. Preoxygenation before intubation in adult patients with acute hypoxemic respiratory failure: a network meta-analysis of randomized trials. Crit Care. 2019;23(1):319.

    Article  Google Scholar 

  15. Jing GQ, Li J, Hao D, Wang T, Sun Y, Tian H, Fu Z, Zhang Y, Wang X. Comparison of high flow nasal cannula with noninvasive ventilation in chronic obstructive pulmonary disease patients with hypercapnia in preventing post extubation respiratory failure: A pilot randomized controlled trial. Res Nurs Health. 2019;42(3):217–25.

    Article  Google Scholar 

  16. Yang PL, Yu JQ, Chen HB. High-flow nasal cannula for acute exacerbation of chronic obstructive pulmonary disease: A systematic review and meta-analysis. Heart Lung. 2021;50(2):252–61.

    Article  Google Scholar 

  17. Li XY, Tang X, Wang R, Yuan X, Zhao Y, Wang L, Li HC, et al. High-Flow Nasal Cannula for Chronic Obstructive Pulmonary Disease with Acute Compensated Hypercapnic Respiratory Failure: A Randomized, Controlled Trial. Int J Chron Obstruct Pulmon Dis. 2020;15:3051–61.

    Article  CAS  Google Scholar 

  18. Huang X, Du Y, Ma Z, Zhang H, Jun L, Wang Z, et al. High-flow nasal cannula oxygen versus conventional oxygen for hypercapnic chronic obstructive pulmonary disease: A meta-analysis of randomized controlled trials. Clin Respir J. 2021;15(4):437–44.

    Article  CAS  Google Scholar 

  19. Pilcher J, Eastlake L, Richards M, Power S, Cripps T, Bibby S, et al. Physiological effects of titrated oxygen via nasal high-flow cannula in COPD exacerbations: A randomized controlled cross-over trial. Respirology. 2017;22(6):1149–55.

    Article  Google Scholar 

  20. Biselli P, Fricke K, Grote L, Braun AT, Kirkness J, Smith P, et al. Reductions in dead space ventilation with nasal high flow depend on physiological dead space volume: Metabolic hood measurements during sleep in patients with COPD and controls. Eur Respir J. 2018;51(5):1702251.

    Article  CAS  Google Scholar 

  21. Xu Z, Zhu L, Zhan J, Liu L. The efficacy and safety of high-flow nasal cannula therapy in patients with COPD and type II respiratory failure: a meta-analysis and systematic review. Eur J Med Res. 2021;26(1):122.

    Article  Google Scholar 

  22. Ben-Menachem E, McKenzie J, O’Sullivan C, Havryk AP. High-flow nasal oxygen versus standard oxygen during flexible bronchoscopy in lung transplant patients: A randomized controlled trial. J Bronchology Interv Pulmonol. 2020;27(4):259–65.

    Article  Google Scholar 

  23. Wang R, Li HC, Li XY, Tang X, Chu HW, Yuan X, et al. Modified high-flow nasal cannula oxygen therapy versus conventional oxygen therapy in patients undergoing bronchoscopy: a randomized clinical trial. BMC Pulm Med. 2021;21(1):367.

    Article  CAS  Google Scholar 

  24. Longhini F, Pelaia C, Garofalo E, Bruni A, Placida R, Iaquinta C, et al. High-flow nasal cannula oxygen therapy for outpatients undergoing flexible bronchoscopy: a randomised controlled trial. Thorax. 2022;77(1):58–64.

    Article  Google Scholar 

  25. Yilmazel Ucar E, Araz Ö, Kerget B, Akgun M, Saglam L. Comparison of high-flow and conventional nasal cannula oxygen in patients undergoing endobronchial ultrasonography. Intern Med J. 2021;51(11):1935–9.

    Article  CAS  Google Scholar 

  26. Douglas N, Ng I, Nazeem F, Lee K, Mezzavia P, Krieser R, et al. A randomised controlled trial comparing high-flow nasal oxygen with standard management for conscious sedation during bronchoscopy. Anaesthesia. 2018;73(2):169–76.

    Article  CAS  Google Scholar 

  27. Simon M, Braune S, Frings D, Wiontzek AK, Klose H, Kluge S. High-flow nasal cannula oxygen versus non-invasive ventilation in patients with acute hypoxaemic respiratory failure undergoing flexible bronchoscopy–a prospective randomised trial. Crit Care. 2014;18(6):712.

    Article  Google Scholar 

  28. Saksitthichok B, Petnak T, So-Ngern A, Boonsarngsuk V. A prospective randomized comparative study of high-flow nasal cannula oxygen and non-invasive ventilation in hypoxemic patients undergoing diagnostic flexible bronchoscopy. J Thorac Dis. 2019;11(5):1929–39.

    Article  Google Scholar 

  29. Irfan M, Ahmed M, Breen D. Assessment of High Flow Nasal Cannula Oxygenation in Endobronchial Ultrasound Bronchoscopy: A Randomized Controlled Trial. J Bronchology Interv Pulmonol. 2021;28(2):130–7.

    Article  Google Scholar 

  30. Lucangelo U, Vassallo FG, Marras E, Ferluga M, Beziza E, Comuzzi L, et al. High-flow nasal interface improves oxygenation in patients undergoing bronchoscopy. Crit Care Res Pract. 2012;2012:506382.

    Article  Google Scholar 

  31. Lin Y, Zhang X, Li L, Wei M, Zhao B, Wang X, et al. High-flow nasal cannula oxygen therapy and hypoxia during gastroscopy with propofol sedation: A randomized multicenter clinical trial. Gastrointest Endosc. 2019;90(4):591–601.

    Article  Google Scholar 

  32. Riccio CA, Sarmiento S, Minhajuddin A, Nasir D, Fox AA. High-flow versus standard nasal cannula in morbidly obese patients during colonoscopy: A prospective, randomized clinical trial. J Clin Anesth. 2019;54:19–24.

    Article  Google Scholar 

  33. Teng WN, Ting CK, Wang YT, Hou MC, Chang WK, Tsou MY, et al. High-flow nasal cannula and mandibular advancement bite block decrease hypoxic events during sedative esophagogastroduodenoscopy: A randomized clinical trial. Biomed Res Int. 2019;2019:4206795.

    Article  CAS  Google Scholar 

  34. Kim SH, Bang S, Lee KY, Park SW, Park JY, Lee HS, et al. Comparison of high flow nasal oxygen and conventional nasal cannula during gastrointestinal endoscopic sedation in the prone position: a randomized trial. Can J Anaesth. 2021;68(4):460–6.

    Article  CAS  Google Scholar 

  35. Gamal M, Kamal MA, Abuelazm M, Yousaf A, Abdelazeem B. Meta-analysis comparing the efficiency of high-flow nasal cannula versus low-flow nasal cannula in patients undergoing endoscopic retrograde cholangiopancreatography. Proc (Bayl Univ Med Cent). 2022;35(4):485–91.

    Article  Google Scholar 

  36. Mazzeffi MA, Petrick KM, Magder L, Greenwald BD, Darwin P, Goldberg EM, et al. High-Flow Nasal Cannula Oxygen in Patients Having Anesthesia for Advanced Esophagogastroduodenoscopy: HIFLOW-ENDO, a Randomized Clinical Trial. Anesth Analg. 2021;132(3):743–51.

    Article  Google Scholar 

  37. Nay MA, Fromont L, Eugene A, Marcueyz JL, Mfam WS, Baert O, et al. High-flow nasal oxygenation or standard oxygenation for gastrointestinal endoscopy with sedation in patients at risk of hypoxaemia: a multicentre randomised controlled trial (ODEPHI trial). Br J Anaesth. 2021;127(1):133–42.

    Article  CAS  Google Scholar 

  38. Riachy M, Khayat G, Ibrahim I, Aoun Z, Dabar G, Bazarbachi T, et al. A randomized double-blind controlled trial comparing three sedation regimens during flexible bronchoscopy: Dexmedetomidine, alfentanil and lidocaine. Clin Respir J. 2018;12(4):1407–15.

    Article  CAS  Google Scholar 

  39. Hong KS, Choi EY, Park DA, Park J. Safety and Efficacy of the Moderate Sedation During Flexible Bronchoscopic Procedure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Medicine (Baltimore). 2015;94(40):e1459.

    Article  CAS  Google Scholar 

  40. Li C, Zhu T, Ma D, Chen Y, Bo L. Complications and safety analysis of diagnostic bronchoscopy in COPD: a systematic review and meta-analysis. Expert Rev Respir Med. 2022;16(5):555–65.

    Article  CAS  Google Scholar 

  41. Grendelmeier P, Tamm M, Jahn K, Pflimlin E, Stolz D. Flexible bronchoscopy with moderate sedation in COPD: a case-control study. Int J Chron Obstruct Pulmon Dis. 2017;12:177–87.

    Article  Google Scholar 

  42. de Boer GM, Türk Y, Meuleman-van Waning VH, Braunstahl GJ. Bronchoscopy: Oral or Nasal Insertion? J Bronchol Intervent Pulmonol. 2017;24(2):125–30.

    Article  Google Scholar 

  43. Jin F, Li Q, Li S, Wang H, Bai C, Zeng Y, et al. Interventional Bronchoscopy for the Treatment of Malignant Central Airway Stenosis: An Expert Recommendation for China. Respiration. 2019;97(5):484–94.

    Article  Google Scholar 

  44. Chan A-W, Tetzlaff JM, Altman DG, Laupacis A, Gøtzsche PC, Krleža-Jerić K, et al. SPIRIT 2013 Statement: Defining standard protocol items for clinical trials. Ann Intern Med. 2013;158(3):200–7.

    Article  Google Scholar 

  45. Ozyilmaz E, Ugurlu AO, Nava S. Timing of noninvasive ventilation failure: causes, risk factors, and potential remedies. BMC Pulm Med. 2014;13(14):19.

    Article  Google Scholar 

  46. Ishiwata T, Tsushima K, Terada J, Fujie M, Abe M, Ikari J, et al. Efficacy of End-Tidal Capnography Monitoring during Flexible Bronchoscopy in Nonintubated Patients under Sedation: A Randomized Controlled Study. Respiration. 2018;96(4):355–62.

    Article  Google Scholar 

  47. Bräunlich J, Mauersberger F, Wirtz H. Effectiveness of nasal high flow in hypercapnic COPD patients is flow and leakage dependent. BMC Pulm Med. 2018;18(1):14.

    Article  CAS  Google Scholar 

  48. Li J, Scott JB, Lee JH. Defining the Optimal Role of High-Flow Nasal Cannula in Pediatric Procedural Sedation. Pediatr Pulmonol. 2020;55(12):3225–7.

    Article  Google Scholar 

Download references


We thank Mr. Rongshou Zheng, MPH from National Cancer Center, China to generate the randomization sequence for us and provide statistical consultation.


This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Author information

Authors and Affiliations



J. Li conceived and designed the study and drafted and revised the manuscript. W. Zhang supervised the study and revised the manuscript. H. Qin, GQ Jing, W. Tan, YN Yin, and J. Wang contributed substantially to the treatment of patients in the study, participated in the acquisition of the data, and provided revisions to the manuscript. Rong-Zhang Chen contributed substantially to the research design, monitored and organized the study, and recruited patients to the study. The authors read and approved the final manuscript.

Corresponding authors

Correspondence to Wei Zhang or Jie Li.

Ethics declarations

Ethics approval and consent to participate

This study has been approved by the Ethic Committees of the following hospitals: East Hospital, Shanghai; Changhai Hospital, Shanghai. All patients were required to be informed before being included in the study and signed the informed consent. Written informed consent applies to all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Qin, H., Jing, GQ., Tan, W. et al. Comparison of high-flow nasal cannula and conventional oxygen therapy for high-risk patients during bronchoscopy examination: protocol for a randomized controlled trial. Trials 24, 12 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: