Discussion
In this study we evaluated the benefits of nCPAP use for Oxygenation during EBUS-TBNA. Several studies about the effectiveness of noninvasive ventilation (NIV) in improving oxygenation during bronchoscopy in intensive care units have been reported. Antonelli M et al. [10] found that noninvasive positive-pressure ventilation (NPPV) that was delivered through a full-face mask was superior to Oxygen supplementation alone in improving gas exchange during and after diagnostic bronchoscopy in patients with severe hypoxemia. According to Murgu et al. [11] NPPV was an alternative to endotracheal intubation for flexible bronchoscopy in many patients with severe refractory hypoxemia, severe COPD, postoperative respiratory failure, severe obstructive sleep apnea and obesity hypoventilation syndrome. Our patients did not have any hypoxemia, and we applied Oxygen with nasal CPAP mask under sedation. In our study, all patients tolerated EBUS-TBNA procedure well and the practitioner satisfaction level was higher than Oxygen supplementation through a mask. The mean desaturation time was significantly shorter and the lowest saturation was significantly higher in nCPAP+Oxygen group. However, NIV may not be a good choice when patients are intolerant or have too much respiratory secretions.
Miyagi et al. [12] reported the usefulness of high flow nasal cannula (HFNC) during bronchoalveolar lavage in patients with acute respiratory failure. However Simon et al. [13] showed that NIV was better than HFN with regard to Oxygenation during bronchoscopy in patients with moderate to severe hypoxemia. HFNC could be a suitable device to deliver Oxygen during bronchoscopy when patients had mild or moderate hypoxemia. Takakuwa et al. [14] assessed the Oxygenation during EBUS-TBNA under midazolam sedation with using HFNC in their study and they suggested that HFNC was useful for preventing hypoxemia during the procedure. The mean age of the patients and the duration of procedure are similar to our study, but comorbidities and patient numbers are higher in our study. In Takakuwa et al.’s study, the pre and post SpO2, lowest SpO2, and the mean desaturation time were lower than our findings.
CO2 elevation is also a possible risk in bronchoscopy under intravenous sedation, [15]. Studies about the effects of flexible bronchoscopy have focused on the temporary alterations of gas exchange occurring during the procedure. The risk of hypoxaemia and hypercapnia caused by alveolar hypoventilation, by an increased ventilation–perfusion mismatch and metabolic demands, as reflected by increasing cardiac output and Oxygen consumption [16]. CPAP improves Oxygenation by reducing intrapulmonary shunting and work of breathing [17,18]. HFNC provides a low-level positive pressure (2–8 cmH2O). This effect could help to lung recruitment and open the upper airways similar to CPAP [19]. It has been shown that there was less carbon dioxide retention in HFNC when compared with the nasal Oxygen supply [20]. Unfortunately, we could not perform blood gas analysis and could not measure partial pressure of carbon dioxide (pCO2) levels. This is one of the limiting factors of our study. Further studies are needed on this subject. It is not clear how to define the CPAP pressure should be applied to the patients. We gave it by titration, starting with 6 mBar and rising to maximum pressure by 14 mBar. Since the procedure is administered orally, the risk of air leakage from the mouth may reduce the effectiveness. If the nasal airflow rate exceeds the inspiratory flow rate, the patient can breathe spontaneously from the nasal cavity. In our study, we did not specifically exclude patients with high obstructive sleep apnea (OSA) risk. We thought that the risk of desaturation would be higher in OSA patients and CPAP would be effective especially in these patients. We can not advise the use of nCPAP during EBUS-TBNA under intravenous sedation to all patients. We suggest that the patients with high Mallampati score will benefit from nCPAP.