Evaluating Forced Oscillation Technique (FOT) in Abolishing Flow Limitation

Evaluating Forced Oscillation Technique (FOT) in Abolishing Flow Limitation in Patients With Stable Chronic Pulmonary Disease (COPD)

To validate the capability of the Respironics Synchrony ventilator to properly detect Expiratory Flow Limitation (EFL) as compared to the gold standard method of detecting EFL via the Mead and Wittenberger technique.

Positive end expiratory pressure (PEEP) is used in COPD patients to counteract the intrinsic PEEP (PEEPi), which represents the end expiratory recoil pressure of the total respiratory system due to the presence of dynamic hyperinflation (DH).

DH commonly occurs in COPD, where the presence of expiratory flow-limitation (EFL) requires the patient to breath at higher lung volumes to produce the necessary after appropriate leak correction, showed a sensitivity and specificity in detecting EFL expiratory flow. To be effective, the PEEP level applied to the patient should be equal to PEEPi.

The continuous monitoring of EFL could be a useful tool to select the minimum PEEP level required to abolish it.

EFL can be detected using the forced oscillation technique (FOT) by an index which quantifies, for each breath, the within-breath variations of respiratory reactance (delta Xrs) at 5Hz.

Inclusion Criteria

1. Age < 80 years
2. Moderate - Severe COPD diagnosed by spirometry (according to the GOLD criteria - Global Initiative for Chronic Obstructive Lung Disease criteria)
3. Free from any exacerbation in the 6 weeks preceding the study

Exclusion Criteria

1. Any co-existing cardio-pulmonary conditions which may result in a picture of ventilatory failure such as congestive cardiac failure, chest wall or neuromuscular disease, bronchopneumonia, pulmonary fibrosis, bronchiectasis, cystic fibrosis or obesity-hypoventilation syndrome
2. Clinically unstable; exacerbation within the preceding 6 weeks
3. The presence of pulmonary or extra-pulmonary neoplasia that is still active
4. The presence of a bleeding diathesis
5. Unstable coronary artery disease
6. Presence of tuberculosis, current infection or potentially infectious pathogen
7. Inability to provide informed consent to the study