The aim of the study is to evaluate the effect of opioids administered during sedation on patients' respiratory activity (ventilation) and comfort of the operator and patient during the endoscopic procedure. A common side effect of sedation is the effect on patients' ventilation, resulting from a combination of attenuation of respiratory centre activity and loss of patent airways. Shallow sedation will reduce these risks, but in addition to patient discomfort, it also increases the difficulty or impossibility of the endoscopist to perform the procedure. Choosing the appropriate method of sedation thus fundamentally affects the course of the procedure from the point of view of both the patient and the endoscopist. The aim is to prove that sedation with propofol alone compared to sedation with propofol and fentanyl premedication leads to the need for higher cumulative doses of administered propofol, higher risk of respiratory depression and lower patient and operator comfort. In addition, the non-invasive respiratory volume monitor (ExSpiron 2Xi) will be used for standard patient monitoring during the procedure, which assesses the lung tidal volume and respiratory rate by measuring the electrical impedance of the chest. This measurement captures inadequate ventilation before saturation drops, allowing even slight differences between selected drugs to be compared.

The aim of the study is to evaluate the effect of opioids administered during sedation on patients' respiratory activity (ventilation) and comfort of the operator and patient during the endoscopic procedure. A common side effect of sedation is the effect on patients' ventilation, resulting from a combination of attenuation of respiratory centre activity and loss of patent airways. Shallow sedation will reduce these risks, but in addition to patient discomfort, it also increases the difficulty or impossibility of the endoscopist to perform the procedure. Choosing the appropriate method of sedation thus fundamentally affects the course of the procedure from the point of view of both the patient and the endoscopist. The aim is to prove that sedation with propofol alone compared to sedation with propofol and fentanyl premedication leads to the need for higher cumulative doses of administered propofol, higher risk of respiratory depression and lower patient and operator comfort. Standard monitoring during endoscopic procedures using sedation includes continual recording of ECG and respiratory rate (using the same electrodes), measurement of arterial blood oxygen saturation using a pulse oximeter and blood pressure measurement. Extended monitoring of spontaneous ventilation during sedation includes analysis of the concentration of exhaled carbon dioxide or analysis of the arterial blood gases.However, these methods have limitations and often critically reduced respiratory activity is diagnosed too late. Impedance monitoring of ventilation is now being introduced into clinical practice. In addition, the non-invasive respiratory volume monitor (ExSpiron 2Xi) will be used for standard patient monitoring during the procedure, which assesses the lung tidal volume and respiratory rate by measuring the electrical impedance of the chest. This measurement captures inadequate ventilation before saturation drops, allowing even slight differences between selected drugs to be compared.

Inclusion Criteria:

• Scheduled therapeutic or diagnostic colonoscopy with sedation
• Supine or lateral decubitus position
• Age 18-65
• American Society of Anesthesiologists (ASA) physical status classification system 1-2
• Informed consent signed

Exclusion Criteria:

• Planned frequent use of electrocoagulation
• Contact allergy for adhesive pads, excessive thoracic hair or other problem with pads
• contraindication of using Propofol or Fentanyl
• Incapability to understand the informed consent

The endoscopist performing the procedure will not be informed which group the patient belongs to.