The airflow moving from mouth to the lungs, which can be measured by pulmonary function tests, may be affected by the anatomic disorders of the upper airway. Difficult airway can be considered as the anatomic disorder of the upper airway as well. Therefore, there can be a relationship between difficult airway and pulmonary function tests. The purpose of this study is to elucidate the association between the pulmonary function tests and difficult airway.

After approval of the Gaziosmanpasa University Clinical Trials Ethics Committee, patients those admitted to the anesthesiology outpatient unit will informed about the study. And pulmonary function tests by using Spirodoc® will be performed to those willing to participate in the study. Measurements of the pulmonary function tests, and measurements belong to difficult airway will be recorded.

In the operating theatre, after induction of anesthesia, the difficult intubation measurements will be recorded.

Normality and variance will be tested using One Sample Kolmogorov-Smirnov test, skewness, kurtosis and histograms for each variable. Quantitative data will present as means and standard deviation, and qualitative data as frequency and percentage. Depending on these results, Spearman's correlation analysis will perform to show the association between pulmonary function tests and difficult airway measurements. Analyses were conducted using the Statistical Package for Social Sciences program (SPSS Inc., Chicago, IL), version 20.0. Statistical significance for all analyses was set at p < 0.05.

Inclusion Criteria:

• Patients whose admitted to the Gaziosmanpasa University, Medical Faculty, Anesthesiology and Reanimation outpatient unit
• Patients whose will be planned to undertake a surgical operation under general anesthesia and those performed tracheal intubation to secure the airway.
• An American Society of Anesthesiologists score of 1 or 2

Exclusion Criteria:

• Patient whose planned to undertake a surgical operation in the departments of ear-nose-throat, cardiac and vascular surgery, plastic and reconstructive surgery
• Patients with a history of chronic obstructive lung diseases
• Patients with a history of surgery on the neck
• Patients with a history of mandibular surgery