Breath by breath analysis of breathing pattern in health and disease: a potential outcome measure for breathing retraining?

摘要

Analysis of breathing pattern can quantify parameters of breathing such as rate, volume, timing and regularity/rhythmicity. This information can be useful to compare breathing patterns in those healthy and with disease, under different experiment conditions (such as rest versus activity) and to monitor changes over time. In this research, respiratory inductive plethysmography (RIP) was used to record breathing patterns in a group of healthy subjects and a group of severe asthma patients. RIP is a leading technology for ambulatory monitoring of breathing, but traditional RIP devices suffered from poor signal quality under such conditions due to movement of the sensor. Several authors have also raised doubts about the existing calibration methods for RIP which can lead to inaccurate estimation of breathing parameters. During the first phase of the programme, an instrumented garment (LifeShirt®) which had RIP embedded within was tested for its validity in comparison to a pneumotachograph (PT). The first study sought to validate the measurements obtained from the LifeShirt ®against PT when calibrated with a published but yet to be tested method for breath by breath analysis and to address the limitations of existing calibration methods. Eleven healthy individuals took part in this first study. Breathing patterns were simultaneously monitored by the LifeShirt ® and the PT during thirty minutes of rest and twenty minutes of exercise. Parameters of tidal volume, expiration time and tidal volume variability were recorded and compared between devices. The analysis from the first study demonstrated that RIP recorded proportionate changes of tidal volume and expiration duration relative to PT during quiet breathing and exercise. Mean tidal volume and expiration duration between devices was strongly correlated for rest and exercise. No statistical difference in tidal volume variability was observed between devices during either period. Significant differences in expiration duration between devices were observed in all participants at rest but not during exercise. Results of this first study demonstrated that valid breath by breath analysis using RIP without PT was feasible. This is clinically advantageous due to simplicity of set-up for RIP.In the second phase, measurement of breathing patterns was made in severe asthma patients with the LifeShirt® alone during thirty minutes of rest. It intended to add new knowledge with regards to the breathing patterns within this small population as compared to the healthy population. Ten healthy individuals and ten patients diagnosed with severe asthma took part in the second study. Breathing parameters of tidal volume, inspiration time, expiration time, end tidal carbon dioxide levels, tidal volume variability and end tidal carbon dioxide levels variability were recorded by the LifeShirt®. The analysis of the second phase shown no evidence that breathing pattern parameters could differentiate between the severe asthma patients and healthy volunteers in our small study. The symptoms of hyperventilation found more commonly in the severe asthma group were not associated with differences in breathing pattern parameters. However, considerable differences were found between individuals. This suggests the existence of individuality in breathing patterns between individuals. Such findings raised doubts as to whether there is a group ‘pattern’ that is common within the severe asthma population or within the healthy population. This programme calls for a change in paradigm to consider breathing patterns as an unique individual ‘trait’ rather than as a group characteristic.