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Changes in lung function and tidal airflow patterns after increasing extrathoracic airway resistance
M Jocelyn Morris1, E Mark Williams, Richard Madgwick
1Osler Chest Unit, Churchill Hospital, Oxford, UK. jocelyn_morris@yahoo.co.uk
Respirology (Carlton, Vic.)
|December 23, 2004
Summary
Adding external resistance to breathing in patients with chronic obstructive pulmonary disease (COPD) altered their expiratory flow patterns, making them similar to those of healthy individuals.
Area of Science:
- Respiratory Physiology
- Pulmonary Medicine
- Biomedical Engineering
Background:
- Tidal expiratory flow patterns are crucial for assessing respiratory function.
- Extrathoracic resistance can significantly influence breathing mechanics.
Purpose of the Study:
- To investigate the impact of added extrathoracic expiratory resistance (EER) on tidal expiratory flow patterns.
- To compare these changes in individuals with normal lung function and those with chronic obstructive pulmonary disease (COPD).
Main Methods:
- 16 healthy subjects and 15 COPD patients participated.
- Measurements included expiratory time, frequency, tidal expiratory flow, and respiratory system time constant before and after adding EER.
- Expiratory flow profiles were analyzed, categorizing them as convex, linear, or concave.
Main Results:
- Adding EER decreased tidal maximum expiratory flow and increased the respiratory system time constant in both groups.
- The expiratory time to maximum flow/total expiratory time ratio increased in COPD patients with EER, but not in controls.
- COPD patients showed an increase in the percentage of convex expiratory flow profiles after EER addition.
Conclusions:
- The addition of extrathoracic expiratory resistance during tidal breathing normalized expiratory flow patterns in COPD patients.
- This suggests that EER can be a useful tool for evaluating respiratory mechanics in COPD.