HFNC During Bronchoscopy for Bronchoalveolar Lavage

High Flow Oxygen Therapy Through Nasal Cannula in Patients With Acute Respiratory Failure During Bronchoscopy for Bronchoalveolar Lavage

The execution of diagnostic-therapeutic investigations by bronchial endoscopy can expose the patient to acute respiratory failure (ARF). In particular, the risk of hypoxemia is greater during broncho-alveolar lavage (BAL). For this reason, oxygen therapy is administered at low or high flows during the course of bronchoscopic procedures, in order to avoid hypoxemia. Few clinical studies have demonstrated the efficacy and safety of high flow oxygen through nasal cannula (HFNC) during BAL procedures, and no study has evaluated, during bronchial endoscopy, the effects of HFNC on diaphragmatic effort (assessed with ultrasound) and aeration and ventilation of the different lung regions (assessed with electrical impedance tomography). Therefore, investigators conceived the present randomized controlled study to evaluate possible differences existing during bronchoscopy between oxygen therapy administered with HFNC and conventional (low-flow) oxygen therapy, delivered through nasal cannula.

Patients with Acute Respiratory Failure may sometimes require a bronchial endoscopy for broncho-alveolar lavage (BAL). During the procedure, hypoxemia may worsen and oxygen may be require to avoid desaturation. In the recent years, High-Flow through Nasal Cannula (HFNC) has been introduced in the clinical practice. HFNC delivers to the patient heated humidified air-oxygen mixture, with an inspiratory fraction of oxygen (FiO2) ranging from 21 to 100% and a flow up to 60 L/min through a large bore nasal cannula. HFNC has some potential advantages. First of all, HFNC provides heated (37°C) and humidified (44 mg/L) air-oxygen admixture to the patient, which avoids injuries to ciliary motion, reduces the inflammatory responses associated to dry and cold gases, epithelial cell cilia damage, and airway water loss, and keeps unmodified the water content of the bronchial secretions. Second, HFNC determines a wash out from carbon dioxide of the pharyngeal dead space. Third, HFNC generates small amount (up to 8 cmH2O) of pharyngeal pressure during expiration, which drops to zero during inspiration. Fourth, HFNC guarantees a more stable FiO2, as compared to conventional oxygen therapy. Whenever the inspiratory peak flow of a patient exceeds the flow provided by a Venturi mask, the patient inhaled also part of atmospheric air. Electrical impedance tomography (EIT) is a noninvasive imaging technique providing instantaneous monitoring of variations in overall lung volume and regional distribution of ventilation, as determined by variations over time in intrathoracic impedance, which is increased by air and reduced by fluids and cells. EIT allows determining changes in end-expiratory lung impedance (EELI), a surrogate estimate of end-expiratory lung volume, assessing global and regional distribution of Vt, and obtaining indexes of spatial distribution of ventilation. Diaphragm ultrasound is a bedside, radiation free technique to assess the contractility of the diaphragm and the respiratory effort. In this study investigators aim to evaluate possible differences existing during bronchoscopy between oxygen therapy administered with HFNC and conventional (low-flow) oxygen therapy, delivered through nasal cannula in terms of respiratory effort (as assessed through diaphragm ultrasound), lung aeration and ventilation distribution (as assessed with EIT) and arterial blood gases.

High Flow Nasal cannula is a system to deliver heated and humidified oxygen with an inspired oxygen fraction between 21 and 100% through large bore nasal cannula. The system delivers a flow up to 60 liters/min.

Conventional oxygen therapy will be administered through common nasal cannula with a flow up to 6 Liters per minute

High Flow Nasal Cannula will be set at 60 liters per minute of air/oxygen admixture to reach a peripheral oxygen saturation equal or greater than 94%

Conventional Oxygen Therapy will be administered through nasal cannula with a oxygen flow set to achieve a peripheral oxygen saturation equal or greater than 94%

The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction

The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction

The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction

The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

5 minutes before the beginning of the bronchial endoscopy, while receiving the assigned treatment, compared to baseline

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography

5 minutes before the beginning of the bronchial endoscopy, while receiving the assigned treatment, compared to baseline

change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography

change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography

Inclusion Criteria: need for bronchial endoscopy for bronchoalveolar lavage Exclusion Criteria: life-threatening cardiac aritmia or acute miocardical infarction within 6 weeks need for invasive or non invasive ventilation presence of pneumothorax or pulmonary enphisema or bullae recent (within 1 week) thoracic surgery presence of chest burns presence of tracheostomy pregnancy nasal or nasopharyngeal diseases dementia lack of consent or its withdrawal

The full protocol, datasets used and analysed during the current study will be available on reasonable request e-mailing the corresponding author

Albertini R, Harrel JH, Moser KM. Letter: Hypoxemia during fiberoptic bronchoscopy. Chest. 1974 Jan;65(1):117-8. doi: 10.1378/chest.65.1.117. No abstract available.

Randazzo GP, Wilson AR. Cardiopulmonary changes during flexible fiberoptic bronchoscopy. Respiration. 1976;33(2):143-9. doi: 10.1159/000193727.

Pirozynski M, Sliwinski P, Radwan L, Zielinski J. Bronchoalveolar lavage: comparison of three commonly used procedures. Respiration. 1991;58(2):72-6. doi: 10.1159/000195900.

Cuquemelle E, Pham T, Papon JF, Louis B, Danin PE, Brochard L. Heated and humidified high-flow oxygen therapy reduces discomfort during hypoxemic respiratory failure. Respir Care. 2012 Oct;57(10):1571-7. doi: 10.4187/respcare.01681. Epub 2012 Mar 12.

Renda T, Corrado A, Iskandar G, Pelaia G, Abdalla K, Navalesi P. High-flow nasal oxygen therapy in intensive care and anaesthesia. Br J Anaesth. 2018 Jan;120(1):18-27. doi: 10.1016/j.bja.2017.11.010. Epub 2017 Nov 21.

Matamis D, Soilemezi E, Tsagourias M, Akoumianaki E, Dimassi S, Boroli F, Richard JC, Brochard L. Sonographic evaluation of the diaphragm in critically ill patients. Technique and clinical applications. Intensive Care Med. 2013 May;39(5):801-10. doi: 10.1007/s00134-013-2823-1. Epub 2013 Jan 24.

Zambon M, Greco M, Bocchino S, Cabrini L, Beccaria PF, Zangrillo A. Assessment of diaphragmatic dysfunction in the critically ill patient with ultrasound: a systematic review. Intensive Care Med. 2017 Jan;43(1):29-38. doi: 10.1007/s00134-016-4524-z. Epub 2016 Sep 12.

Costa EL, Lima RG, Amato MB. Electrical impedance tomography. Curr Opin Crit Care. 2009 Feb;15(1):18-24. doi: 10.1097/mcc.0b013e3283220e8c.

Miyagi K, Haranaga S, Higa F, Tateyama M, Fujita J. Implementation of bronchoalveolar lavage using a high-flow nasal cannula in five cases of acute respiratory failure. Respir Investig. 2014 Sep;52(5):310-4. doi: 10.1016/j.resinv.2014.06.006. Epub 2014 Jul 25.

Kim EJ, Jung CY, Kim KC. Effectiveness and Safety of High-Flow Nasal Cannula Oxygen Delivery during Bronchoalveolar Lavage in Acute Respiratory Failure Patients. Tuberc Respir Dis (Seoul). 2018 Oct;81(4):319-329. doi: 10.4046/trd.2017.0122. Epub 2018 Jun 19.

Longhini F, Pisani L, Lungu R, Comellini V, Bruni A, Garofalo E, Laura Vega M, Cammarota G, Nava S, Navalesi P. High-Flow Oxygen Therapy After Noninvasive Ventilation Interruption in Patients Recovering From Hypercapnic Acute Respiratory Failure: A Physiological Crossover Trial. Crit Care Med. 2019 Jun;47(6):e506-e511. doi: 10.1097/CCM.0000000000003740.

Longhini F, Pelaia C, Garofalo E, Bruni A, Placida R, Iaquinta C, Arrighi E, Perri G, Procopio G, Cancelliere A, Rovida S, Marrazzo G, Pelaia G, Navalesi P. High-flow nasal cannula oxygen therapy for outpatients undergoing flexible bronchoscopy: a randomised controlled trial. Thorax. 2022 Jan;77(1):58-64. doi: 10.1136/thoraxjnl-2021-217116. Epub 2021 Apr 29.