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.