The goal of this clinical trial is to learn if patients feel more comfortable while being placed on contemporary fasting principle than on conventional fasting time during flexible bronchoscopy. The main questions it aims to answer are:

To compare the thirty levels between patients with conventional fasting time (≥ 8 hours) and those with contemporary fasting principle (clear fluids for up to 2 hours before anesthesia) during flexible bronchoscopy To compare the levels of mucosal dryness between two groups of patients during flexible bronchoscopy To compare the levels of hunger between two groups of patients during flexible bronchoscopy To compare the levels of tiredness between two groups of patients during flexible bronchoscopy To compare the levels of fatigue between two groups of patients during flexible bronchoscopy To compare the levels of nausea/vomiting between two groups of patients during flexible bronchoscopy

Participants will:

Being placed on fasting either using conventional fasting time (≥ 8 hours) or with contemporary fasting principle (clear fluids for up to 2 hours before anesthesia) Being asked to respond to questions regarding thirsty, mucosal dryness, hunger, tiredness, fatigue, and nausea/vomiting in a visual analogue scale of 0 to 10

Inclusion Criteria:

• planned flexible bronchoscopy

Exclusion Criteria:

• tracheostomy or intubated
• known to be pregnant
• significant functional or structural abnormalities of the gastrointestinal tract
• oral intake prohibited and infeasible