Chronic obstructive pulmonary disease (COPD) is a common respiratory condition with high morbidity and mortality rates, and has become a major cause of death worldwide.1 Moreover, it is associated with significant economic and societal burdens. Persistent airflow limitation and changes in the respiratory tract caused by COPD lead to symptoms including dyspnea and cough. Acute exacerbation of COPD (AECOPD) describes the sudden worsening of symptoms, such as dyspnea, cough, or phlegm, within a short period, for which a basic medication regimen is required; nevertheless, prognosis may be poor. Respiratory failure is a common and serious complication of AECOPD that impairs effective gas exchange. Patients with type II respiratory failure and hypercapnia have a higher risk for mortality. Currently, drug therapy and respiratory support options, such as conventional oxygen therapy, high-flow nasal cannula (HFNC), noninvasive positive pressure ventilation (NPPV), and invasive positive pressure ventilation,2 are commonly used to treat patients with AECOPD.

With the assistance of accessories, such as nasal masks, mouth and nose masks, or full-face masks that connect the patient to the ventilator, NPPV can provide positive pressure-assisted ventilation without invasive procedures.3,4 For patients with AECOPD and acute respiratory failure, NPPV provides good respiratory support because it is not only beneficial for enhancing oxygenation and correcting acute respiratory acidosis, but also helpful in regulating pH and reducing the partial pressure of carbon dioxide (PaCO2) to control respiratory failure. In addition, it reduces the workload of the respiratory muscles, alleviates dyspnea, and provides assistance in COPD treatment. According to some studies, NPPV treatment has some advantages, such as decreased risks for tracheal intubation in patients with COPD, decreased rate of ventilator-associated pneumonia, and shorter hospital stays.5 However, improper setting of NPPV parameters may negatively affect its therapeutic effect. Moreover, side-effects of NPPV, such as nasal congestion, dryness in the nasal area, facial compression, and gastric emphysema, may reduce tolerance, thereby resulting in treatment failure.

HFNC continuously provides patients with regulated and relatively constant oxygen concentrations (ranging from 21% to 100%), temperature (31–37 °C), and humidity at a high flow rate (8–80 L/min) through a nasal cannula. HFNC offers good patient comfort because the high flow effectively clears nasopharyngeal dead space, increases mean airway pressure, enhances ventilation and, theoretically, improves hypoxia and hypercapnia.6 In recent years, HFNC has gained widespread acceptance in clinical practice as a new respiratory support technology, playing a pivotal role in saving patients’ lives.7 We herein present a review of the applications of NPPV and HFNC in patients with COPD.

Applications of NPPV in COPD

NPPV provides positive pressure assistance without the need for invasive endotracheal intubation or tracheotomy and connects the patient to a ventilator for positive pressure-assisted ventilation using a nasal mask, orofacial mask, full-face mask, or hood. Bi-level positive airway pressure (BiPAP) and continuous positive airway pressure (CPAP) are two common NPPV modalities.8 Throughout the breathing cycle, positive airway pressure is continuously maintained using CPAP. In contrast, BiPAP offers more positive end-expiratory and inspiratory positive airway pressures. BiPAP is widely used in the treatment of patients with COPD and respiratory failure.9 NPPV alleviates respiratory failure by partially reopening the collapsed airways through positive pressure ventilation, enhancing lung ventilation volume, and optimizing ventilation/perfusion ratios to improve oxygenation and reduce CO2 retention. In contrast to low-flow continuous oxygen administration, NPPV applies positive airway pressure at the end of expiration, further enhancing the oxygen uptake and effective tidal volume, and facilitating airway dilation and patient ventilation. Improved lung ventilation leads to an effective exchange of CO2, evident in the decreased PaCO2 and increased partial pressure of oxygen (PaO2) levels post-treatment, significantly ameliorating clinical symptoms in patients with COPD. NPPV has become an effective treatment for reducing morbidity and mortality rates in hospitalized patients with AECOPD. Elshof et al10 demonstrated that NPPV can significantly alleviate clinical symptoms, control disease progression, improve ventilation function, minimize invasive mechanical ventilation requirements, and enhance survival rates. Additionally, some studies have indicated that NPPV reduces the incidence of ventilator-associated pneumonia compared with invasive ventilation, while protecting the patient’s voluntary respiration and enhancing airway defense and swallowing function. As such, NPPV has become a preferred treatment modality for patients who do not fulfill the criteria for invasive mechanical ventilation.11,12

In patients with stable COPD and obstructive sleep apnea, CPAP significantly reduces the risk for AECOPD, COPD-related hospitalization, and mortality.13 A multicenter study focusing on patients with AECOPD and persistent hypercapnia 2–4 weeks after hospital discharge compared the effect of home noninvasive ventilation combined with oxygen therapy versus oxygen therapy alone on the time to rehospitalization and mortality. The results revealed that in patients with persistent hypercapnia in AECOPD, the combination of home noninvasive ventilation and oxygen therapy significantly prolonged the time to rehospitalization and mortality over a 12-month period.14 The efficacy of NPPV in patients with COPD and prolonged hypercapnia following acute respiratory failure remains uncertain. One study demonstrated improved transcutaneous partial PaCO2 with NPPV compared with conventional home oxygen therapy; however, there was no significant difference in the number of exacerbations, lung function, emotional state, level of daily activity, or dyspnea among patients with COPD.15 Casanova et al16 demonstrated that NPPV had no significant effect or only a marginal benefit on the natural course of COPD up to 1 year in patients with stable disease. In contrast, a meta-analysis suggested that home NPPV significantly reduced all-cause hospitalization, risk for intubation, and mortality compared with non-NPPV-treated patients with COPD and hypercapnia, albeit without a significant difference in quality of life.17 Because the optimal implementation of NPPV requires the selection of appropriate patients and improvement of treatment compliance, healthcare professionals also need to customize respiratory parameters to ensure effective ventilation because inappropriate NPPV treatment settings potentially compromise patient outcomes and survival.18 Therefore, enhancing healthcare professionals’ and patients’ awareness of NPPV usage in clinical settings could further improve patient prognosis.

Applications of HFNC in COPD

HFNC is a novel oxygen therapy that directly delivers a specific concentration of air-oxygen at a high flow rate through a specially designed nasal cannula. It uses an air-oxygen mixer connected to a flow meter, turbine, or ventilator with a heated humidifier for gas compression, delivering a continuous stream of heated and humidified gas with oxygen concentrations up to 100% through a nasal interface.19 HFNC provides heated and humidified airflow to the patient that maintains airway function, facilitates clearance of airway secretions and pathogens, improves oxygenation, generates positive end-expiratory pressure, and increases functional residual capacity.20 Compared with standard oxygen therapy, HFNC reduces patient inspiratory effort, and respiratory work and rate, resulting in improved comfort and oxygenation.

HFNC exerts multiple physiological effects on the respiratory system. The mucosal cilia transport system acts as a mechanical defense system by transporting pollutants out of the airways, extending from the fine bronchioles to the nasopharynx. Respiratory epithelial cilia are highly sensitive to changes in respiratory temperature and pressure, and function best at core body temperature and 100% relative humidity. In the traditional oxygen delivery method, cool and dry gases cause bronchoconstriction by altering the viscosity of secretions in the respiratory tract, which reduces the frequency of ciliary peristalsis and decreases the rate of mucus clearance by the cilia. Impaired mucus ciliary clearance reduces lung compliance and increases airway resistance and breathing. It also increases the risks for mucus plugging, alveolar shedding, and infection. HFNC optimizes respiratory epithelial function and improves ciliary mucus clearance by warming and humidifying the air-oxygen mixture.21 Patients with respiratory failure often exhibit an increased respiratory rate, and the gas flow rate of conventional oxygen therapy is insufficient to meet their needs. The air stream delivered by HFNC effectively flushes exhaled gases from the upper airway, maintains stable oxygen concentrations, reduces rebreathing of CO2, and enhances pulmonary ventilation. A crossover study found that in patients with COPD undergoing long-term oxygen therapy, HFNC improved respiratory rate and respiratory work within a specific period, increased tidal volume and end-expiratory volume, improved lung ventilation, and reduced CO2 levels and respiratory muscle work.22

Positive end-expiratory pressure resulting from high-flow gas has the potential to offset intrinsic positive end-expiratory pressure. In addition, HFNC can enhance ventilatory efficiency and CO2 elimination by causing a washout effect in the nasopharyngeal dead space.23,24 Airway pressure can be affected by changes in the expansion and contraction of the nasopharynx. One study found that patients treated with HFNC at a rate of 60 L/min reached a nasopharyngeal pressure of 6.8 cmH2O with the mouth closed and 0.8 cmH2O with the mouth open. Mouth closure results in a positive nasopharyngeal pressure proportional to the flow rate and an increase in expiratory resistance, which is significantly reduced with open-mouth breathing.25

Compared with NPPV, HFNC offers a more comfortable alternative without facial compression, minimizing adverse effects such as facial pressure sores. In addition, humidified gas delivery through HFNC reduces mucosal dryness and airway mucosal damage associated with traditional oxygen therapy. It effectively promotes sputum discharge, reduces airway resistance, and improves ventilation and oxygenation. Accordingly, HFNC has recently been recommended as the primary respiratory support for patients with acute respiratory distress and hypoxemia to yield significant improvements in dyspnea and oxygenation indices and reduce the risk for endotracheal intubation compared with conventional oxygen therapy.26

The long-term efficacy of HFNC in treating COPD-induced chronic hypercapnic respiratory failure remains unclear. Studies have compared the efficacy of long-term HFNC oxygen therapy with that of oxygen therapy alone in patients with hypercapnic COPD. HFNC significantly reduced the incidence of moderate-to-severe AECOPD and prolonged the duration of non-acute exacerbations. Health-related quality of life, peripheral oxygen saturation, and lung function of patients in the HFNC group significantly improved.27 However, limitations of HFNC have been noted. In severe cases of COPD, the positive airway pressure provided by HFNC cannot meet patient needs and the respiratory rate cannot be improved. The patient then opens the mouth to breathe, resulting in increased leakage and a decrease in airway pressure. This condition undermines the effectiveness of ventilation by reducing the pressure necessary for an effective respiratory effort. A study demonstrated that HFNC is not appropriate in patients with a respiratory rate of >35 breaths/min.28 Furthermore, the elasticity of lung tissues decreases in some patients who experience repeated COPD because the lungs are in a state of hyperinflation, leading to ventilation dysfunction, resulting in CO2 retention and, ultimately, chronic hypercapnia. Owing to the increased tolerance to CO2 retention and elevated airway resistance, HFNC therapy may not offer sufficient respiratory support to effectively eliminate CO2 from the body. Consequently, this inadequacy can result in poor clinical outcomes. Lu et al29 found that while HFNC may be beneficial for specific patients with AECOPD, the presence of B-type natriuretic peptide levels ≥ 280 ng/L and arterial blood pH ≤ 7.30 before treatment initiation often indicates that a single HFNC session may be ineffective. In such cases, close monitoring is recommended and prompt consideration should be given to transitioning to NPPV or invasive mechanical ventilation if necessary.29

Differences Between NPPV and HFNC in Applications for COPD

Patients with AECOPD often experience acute respiratory symptoms and hypercapnia, and some require admission to the intensive care unit (ICU). Conventional drug therapies may not achieve the desired outcomes in these patients. NPPV improves respiratory symptoms, enhances alveolar ventilation, corrects hypercapnia, reduces the length of ICU stay, and lowers mortality rates. Therefore, NPPV is recommended as a routine treatment for AECOPD accompanied by hypercapnia. However, the effectiveness of NPPV is closely linked to factors including parameter settings, patient comfort, and the level of collaboration between the patient and the device.

HFNC therapy delivers heated and humidified constant airflow to generate positive pressure ventilation, which helps increase end-expiratory lung volume, promotes the clearance of tracheobronchial secretions, and reduces respiratory effort, thereby improving respiratory function. Cortegiani et al30 demonstrated that HFNC therapy is effective in treating patients with COPD and mild-to-moderate hypercapnia and respiratory failure. This treatment was found to significantly decrease blood CO2 levels, with efficacy comparable with NPPV, while offering high comfort levels and person–device cooperation. In contrast, in patients with COPD complicated by moderate to severe hypercapnic respiratory failure, there is no significant difference in treatment failure rates between HFNC and NPPV. However, HFNC is associated with fewer complications, reduced need for airway care interventions, and lower risk for breakdown of the facial skin.31 Further research has shown that in patients having mild-to-moderate AECOPD with similar treatment failure rates between HFNC and NPPV, there is comparable effectiveness in avoiding tracheal intubation.32 Additionally, the HFNC group exhibited a lower incidence of complications and a reduced risk for barotrauma compared with the NPPV group.33 During the stable phase and recovery period of AECOPD, HFNC demonstrates effectiveness in reducing respiratory work, lowering respiratory rate, and maintaining adequate gas exchange, and also facilitates superior compliance and adaptability compared with NPPV.34

If patients do not achieve satisfactory therapeutic outcomes after NPPV, timely invasive ventilatory support may be necessary. However, invasive ventilation may lead to complications such as ventilator-associated pneumonia. Therefore, in recent years, invasive-noninvasive sequential treatment has been proposed in the clinic. More specifically, endotracheal extubation is performed before meeting the extubation criteria, followed by continued oxygen therapy using noninvasive methods.35–37 Nevertheless, owing to poor tolerance and contraindications, some patients may require reintubation. Studies have reported HFNC therapy to demonstrate favorable clinical efficacy in preventing reintubation in patients with respiratory failure after extubation.24,38,39 Jing et al40 compared the outcomes of invasive-HFNC sequential therapy and invasive-NPPV sequential therapy in patients with COPD and severe respiratory failure, finding that they were equally effective in improving pulmonary oxygenation function; however, invasive-HFNC sequential therapy demonstrated superior tolerance.

Summary

Due to factors such as the aging population in China, the incidence of COPD, especially respiratory failure, is gradually increasing, which significantly affects patient health and quality of life. Owing to its simplicity of operation, NPPV has become an important treatment option. NPPV treatment not only enhances therapeutic effects and reduces the risks associated with tracheal intubation and incision, but also helps to improve lung function. However, it is essential to tailor ventilation modes and parameters according to individual patient conditions to ensure treatment effectiveness and safety. HFNC can actively improve oxygenation and clinical outcomes in patients with respiratory failure, and can be used as a frontline treatment for acute hypoxemic respiratory failure. Nevertheless, while studies have indicated that HFNC can enhance oxygenation and ventilation, reduce hypercapnia, prolong the time until the next moderate acute exacerbation, and improve health-related quality of life scores in patients with AECOPD, acute hypercapnic respiratory failure, and stable hypercapnic COPD receiving long-term oxygen therapy, the overall assessment of the utility of HFNC in this patient population is currently limited by factors such as small sample sizes, heterogeneity of patient groups, and short follow-up durations. As such, further research and clinical analyses are warranted to better evaluate the value of HFNC in such patients.

Funding

The study was supported by a grant (JDY2022015) from medical education collaborative innovation funding of Jiangsu University.

Disclosure

Yuting Wang and Yan Liu are co-first authors for this study. The authors report no conflicts of interest in this work.

References

1. Global Strategy for Prevention, Diagnosis and Management of COPD: 2024 Report. Global Initiative for Chronic Obstructive Lung Disease; 2024. Available from: https://goldcopd.org/2024-gold-report/. Accessed May20, 2024.

2. Cai BQ. The current situation and existing problems of diagnosis and treatment of chronic obstructive pulmonary disease in China. Zhonghua Yi Xue Za Zhi. 2017;97(40):3124–3127. doi:10.3760/cma.j.issn.0376-2491.2017.40.002

3. Arnal J-M, Texereau J, Garnero A. Practical insight to monitor home NIV in COPD patients. COPD. 2017;14(4):401–410. doi:10.1080/15412555.2017.1298583

4. Nava S, Ceriana P. Causes of failure of noninvasive mechanical ventilation. Respir Care. 2004;49(3):295–303.

5. Plant PK, Owen JL, Elliott MW. Early use of non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentre randomised controlled trial. Lancet. 2000;355(9219):1931–1935. doi:10.1016/s0140-6736(00)02323-0

6. Rochwerg B, Einav S, Chaudhuri D, 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):2226–2237. doi:10.1007/s00134-020-06312-y

7. Roca O, Caralt B, Messika J, et al. An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy. Am J Respir Crit Care Med. 2019;199(11):1368–1376. doi:10.1164/rccm.201803-0589OC

8. Papalski W, Siedler J, Callaway DW. Airway management with noninvasive positive pressure ventilation. J Spec Oper Med. 2022;22(2):93–96. doi:10.55460/URGL-D2X1

9. Renston JP, DiMarco AF, Supinski GS. Respiratory muscle rest using nasal BiPAP ventilation in patients with stable severe COPD. Chest. 1994;105(4):1053–1060. doi:10.1378/chest.105.4.1053

10. Elshof J, Vonk JM, Pouw A, et al. Clinical practice of non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease. Respir Res. 2023;24(1):208. doi:10.1186/s12931-023-02507-1

11. Zhang JH, Luo Q, Zhang HJ, et al. Effects of different levels of non-invasive proportional assist ventilation and pressure support ventilation on respiratory work in patients with chronic obstructive pulmonary disease. Zhonghua Jie He He Hu Xi Za Zhi. 2017;40(6):450–456. doi:10.3760/cma.j.issn.1001-0939.2017.06.011

12. Williams JW Jr, Cox CE, Hargett CW. Et Al. Noninvasive Positive-Pressure Ventilation (NPPV) for Acute Respiratory Failure. Rockville (MD): Agency for Healthcare Research and Quality (US); 2012.

13. Srivali N, Thongprayoon C, Tangpanithandee S, et al. The use of continuous positive airway pressure in COPD-OSA overlap syndrome: a systematic review. Sleep Med. 2023;108:55–60. doi:10.1016/j.sleep.2023.05.025

14. Murphy PB, Rehal S, Arbane G, et al. Effect of home noninvasive ventilation with oxygen therapy vs oxygen therapy alone on hospital readmission or death after an acute COPD exacerbation: a randomized clinical trial. JAMA. 2017;317(21):2177–2186. doi:10.1001/jama.2017.4451

15. Struik FM, Sprooten RT, Kerstjens HA, et al. Nocturnal non-invasive ventilation in COPD patients with prolonged hypercapnia after ventilatory support for acute respiratory failure: a randomised, controlled, parallel-group study. Thorax. 2014;69(9):826–834. doi:10.1136/thoraxjnl-2014-205126

16. Casanova C, Celli BR, Tost L, et al. Long-term controlled trial of nocturnal nasal positive pressure ventilation in patients with severe COPD. Chest. 2000;118(6):1582–1590. doi:10.1378/chest.118.6.158

17. Wilson ME, Dobler CC, Morrow AS, et al. Association of home noninvasive positive pressure ventilation with clinical outcomes in chronic obstructive pulmonary disease: a systematic review and meta-analysis. JAMA. 2020;323(5):455–465. doi:10.1001/jama.2019.22343

18. Kohnlein T, Windisch W, Kohler D, et al. Non-invasive positive pressure ventilation for the treatment of severe stable chronic obstructive pulmonary disease: a prospective, multicentre, randomised, controlled clinical trial. Lancet Respir Med. 2014;2(9):698–705. doi:10.1016/s2213-2600(14)70153-5

19. Ricard J-D, Roca O, Lemiale V, et al. Use of nasal high flow oxygen during acute respiratory failure. Intens Care Med. 2020;46(12):2238–2247. doi:10.1007/s00134-020-06228-7

20. Nishimura M. High-flow nasal cannula oxygen therapy devices. Respir Care. 2019;64(6):735–742. doi:10.4187/respcare.06718

21. Crimi C, Noto A, Cortegiani A, et al. High flow nasal therapy use in patients with acute exacerbation of COPD and bronchiectasis: a feasibility study. J Chronic Obst Pulm Dis. 2020;17(2):184–190. doi:10.1080/15412555.2020.1728736

22. Fraser JF, Spooner AJ, Dunster KR, et al. Nasal high flow oxygen therapy in patients with COPD reduces respiratory rate and tissue carbon dioxide while increasing tidal and end-expiratory lung volumes: a randomized crossover trial. Thorax. 2016;71(8):759–761. doi:10.1136/thoraxjnl-2015-207962

23. Di Mussi R, Spadaro S, Stripoli T, et al. High-flow nasal cannula oxygen therapy decreases postextubation neuroventilatory drive and work of breathing in patients with chronic obstructive pulmonary disease. Crit Care. 2018;22(1):180. doi:10.1186/s13054-018-2107-9

24. Tan D, Wang B, Cao P, et al. High flow nasal cannula oxygen therapy versus non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease with acute-moderate hypercapnic respiratory failure: a randomized controlled non-inferiority trial. Crit Care. 2024;28(1):250. doi:10.1186/s13054-024-05040-9

25. Vieira F, Bezerra FS, Coudroy R, et al. High-flow nasal cannula compared with continuous positive airway pressure: a bench and physiological study. J Appl Physiol. 2022;132(6):1580–1590. doi:10.1152/japplphysiol.00416.2021

26. Rittayamai N, Tscheikuna J, Praphruetkit N, et al. Use of high-flow nasal cannula for acute dyspnea and hypoxemia in the emergency department. Respir Care. 2015;60(10):1377–1382. doi:10.4187/respcare.03837

27. Nagata K, Horie T, Chohnabayashi N, et al. Home high-flow nasal cannula oxygen therapy for stable hypercapnic COPD: a randomized clinical trial. Am J Respir Crit Care Med. 2022;206(11):1326–1335. doi:10.1164/rccm.202201-0199OC

28. Delbove A, Foubert A, Mateos F, et al. High Flow nasal cannula oxygenation in CoVID-19 related acute respiratory distress syndrome: a safe way to avoid endotracheal intubation? Ther Adv Respir Dis. 2021;15:17534666211019555. doi:10.1177/17534666211019555

29. Lu JC, Qiu HZ, Chen LL. Analysis of risk factors for failure of nasal high-flow oxygen therapy in patients with acute exacerbation of chronic obstructive pulmonary disease complicated with respiratory failure. Lab Med Clin. 2021;18(11):1582–1586. doi:10.3969/j.issn.1672-9455.2021.11.020

30. Cortegiani A, Longhini F, Carlucci A, et al. High-flow nasal therapy versus noninvasive ventilation in COPD patients with mild-to-moderate hypercapnic acute respiratory failure: study protocol for a noninferiority randomized clinical trial. Trials. 2019;20(1):450. doi:10.1186/s13063-019-3514-1

31. Sun J, Li Y, Ling B, et al. High flow nasal cannula oxygen therapy versus non-invasive ventilation for chronic obstructive pulmonary disease with acute-moderate hypercapnic respiratory failure: an observational cohort study. Int J Chron Obstruct Pulmon Dis. 2019;14:1229–1237. doi:10.2147/copd.S206567

32. Pantazopoulos I, Daniil Z, Moylan M, et al. Nasal high flow use in COPD patients with hypercapnic respiratory failure: treatment algorithm & review of the literature. J Chronic Obst Pulm Dis. 2020;7(1):101–111. doi:10.1080/15412555.2020.1715361

33. Mauri T, Turrini C, Eronia N, et al. Physiologic effects of high-flow nasal cannula in acute hypoxemic respiratory failure. Am J Respir Crit Care Med. 2017;195(9):1207–1215. doi:10.1164/rccm.201605-0916OC

34. Bonnevie T, Elkins M, Paumier C, et al. Nasal high flow for stable patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis. J Chronic Obst Pulm Dis. 2019;16(5–6):368–377. doi:10.1080/15412555.2019.1672637

35. Messas E, IJsselmuiden A, Goudot G, et al. Feasibility and performance of noninvasive ultrasound therapy in patients with severe symptomatic aortic valve stenosis: a first-in-human study. Circulation. 2021;143(9):968–970. doi:10.1161/circulationaha.120.050672

36. Liu J, Duan J, Bai L, Zhou L. Noninvasive ventilation intolerance: characteristics, predictors, and outcomes. Respir Care. 2016;61(3):277–284. doi:10.4187/respcare.04220

37. Delclaux C, L’Her E, Alberti C, et al. Treatment of acute hypoxemic nonhypercapnic respiratory insufficiency with continuous positive airway pressure delivered by a face mask: a randomized controlled trial. JAMA. 2000;284(18):2352–2360. doi:10.1001/jama.284.18.2352

38. Abrard S, Jean L, Rineau E, et al. Safety of changes in the use of noninvasive ventilation and high flow oxygen therapy on reintubation in a surgical intensive care unit: a retrospective cohort study. PLoS One. 2021;16(3):e0249035. doi:10.1371/journal.pone.0249035

39. Jing G, Li J, Hao D, et al. Comparison of high flow nasal cannula with noninvasive ventilation in chronic obstructive pulmonary disease patients with hypercapnia in preventing postextubation respiratory failure: a pilot randomized controlled trial. Res Nurs Health. 2019;42(3):217–225. doi:10.1002/nur.21942

40. Jing S, Gao J, Li MZ. Effects of high-flow oxygen therapy and invasive-noninvasive ventilation sequential therapy on pulmonary oxygenation function and prognosis in patients with chronic obstructive pulmonary disease complicated with severe respiratory failure. J North Sichuan Med Coll. 2022;37(7):847–851. doi:10.3969/j.issn.1005-3697.2022.07.006