This study is a prospective randomized controlled trial, the primary aim of this study to compare the intracuff pressure which is performed by 2 inflation methods. ( study in pediatric patients 4-12 year old) Group1 : Flow -Volume Loop-guided cuff inflation Group2 : Stethoscope-guided cuff inflation Our hypothesis is Flow-Volume Loop-guided cuff pressure will be lower than Stethoscope-guided cuff pressure.

This study also collect the incidence of common post-extubation respiratory adverse events coughing, hoarseness, stridor, croup as an secondary outcomes.

Historically, pediatric anesthesiologists abstained from using cuff-endotracheal tubes in children younger than 8 year of age because of the anatomical particularises of their airway and thus the increased risk of postintubation tracheal damage especially when Nitrous oxide is used for long procedures. In addition the tube size shoud be half size reduced when cuffed endotracheal tube is used, leading to higher airway resistance and increased risk of tube obstruction.

Recently, the use of Cuffed endotracheal tube has been increasing in children younger than 8 year of age who undergoing general anesthesia. Due to several reasons as follows 1) an increasingly sophisticated understanding of developing laryngeal anatomy 2) vastly improved materials in the manufacture of endotracheal tubes 3) cuffed endotracheal tubes serve several advantages over uncuffed endotracheal tubes including fewer laryngoscopies to replace ill-fitting tubes, less contamination of operating room with anesthetic gases, reliable capnography monitoring, better protection against aspiration, adequate ventilation with a low fresh gas flow which allow using low flow anesthsia, and also they are advantageous for certain operations such as laparoscopic/ airway procedures. 4) data are plentiful supporting the equal safety of using cuffed endotracheal tubes compared with uncuffed tubes in children However, using cuffed endotracheal tubes without being careful of cuff pressure may result in damage to tracheal mucosal wall especially in pediatric patients. The intra-cuff pressure should be monitored and maintained at the level below 25 cm H2O. The intra-cuff pressure more than 30 cmH2O causes obstruction to mucosal blood flow and increasing the risk of airway mucosal injury. Cuff pressure measurement by manometer is a gold standard, nevertheless manometer is not available in every operating room. Almost of anesthetists often use either manual palpation of pilot balloon or stethoscope-guided to inflate endotracheal tube cuff.

In adult studies, they found that endotracheal tube cuff pressure estimated by palpation even with experience personals is often much higher than 25-30 cmH2O. Therefore this inflation technique should be avoided in pediatric patients.

As for, stethoscope-guided endotracheal cuff inflation which pediatric anesthesiologists usually use for children. There were several studies in adult patients, they found the median cuff pressure from this inflation technique was 20 (16-28) cmH2O which is in acceptable tracheal cuff pressure.

In routine practice of general anesthesia rarely have continuous cuff pressure monitoring. When Nitrous Oxide is used for general anesthesia, the intra-cuff pressure can increase with time. Accordingly, it will be better to keep intra-cuff pressure as low as having proper sealing.

A couple studies from adult, compared endotracheal tube cuff inflation techniques between Pressure-Volume(PV) loop guided and stethoscope-guided and the results were intra-cuff pressure from PV loop guided was less than stethoscope guided. Moreover cuff-related complications ( coughing, sorethroat) were less in PV loop group also. It seems PV loop guided can provide least cuff pressure with efficient sealing.

This study would like to compare endotracheal cuff pressure that are performed by 2 techniques between Flow-Volume(FV) loop guided and stethoscope-guided in pediatric patients Intra-cuff pressure will be the primary outcome and we will also collect postoperative respiratory complications such as coughing, stridor, hoarseness as secondary outcomes.

Inclusion Criteria:

• Patients are undergoing an operations in Ramathibodi hospital.
• American Society of Anesthesiologists physical status class 1-2
• Endotracheal tube intubation is needed for an operation
• Consent to participate in research project.

Exclusion Criteria:

• Patient who is a predicted difficult intubation
• Patient who has lung disease, airwar abnormalities
• Patient who has pulmonary aspiration risk
• Patient who has a previous sorethroat, hoarseness, respiratory tract infection in last 2 weeks
• Refused to participate in research project