Measurement and Evaluation of Total Lung Capacity (TLC) in the Field of Pulmonary Functional Testing (PFT)

Inclusion Criteria: 1. Subject is at least 18 years of age. 2. Subject is cooperative and capable of following instructions. 3. Healthy subjects: 1. Never smokers. 2. No known history of respiratory, cardiovascular, hepatic, renal or metabolic disease. 3. BMI \< 35. 4. No persisting respiratory symptoms during the last 12 months. (e.g., dyspnea, chronic cough, wheezing or phlegm). 5. No history suggesting upper respiratory infection during the three weeks prior to testing. 4. Patients with known disease affecting the respiratory system, with previous documentation of obstructive, restrictive, or mixed obstructive plus restrictive ventilatory abnormality. Exclusion Criteria: 1. Subjects who are unable to satisfactorily perform routine, full lung function testing(due to non-compliance or claustrophobia). 2. Subjects unable or unwilling to give informed consent. 3. Subjects who have performed any significant physical activity during 1 hour prior to the Study. 4. Patients with a tracheostomy. 5. Pregnant women.