IACFS/ME Conference –  Professor Todd Davenport study on exercise testing and ventilatory measurements

The 2^nd Virtual Scientific Conference for the International Association for Chronic Fatigue Syndrome/ Myalgia Encephalomyelitis was held on the 19^th – 21^st August 2021 (streamed on zoom). The conference promoted unpublished data and included both clinicians and biomedical researchers. 

The talks were grouped into different sections, including the longer 45 minute talks in the Professional Workshops and shorter talks covering topics of infectious diseases, immunology and clinical cases. 

We have chosen a selection of the talks which will hopefully be of interest to you, which are listed below. Here we report on our seventh talk in this series with a talk from Professor Todd Davenport who talked about his study on exercise testing and ventilatory measurements, with his presentation titled “Ventilatory Functioning During Serial Cardiopulmonary Exercise Testing in People With and Without Myalgic Encephalomyelitis/Chronic Fatigue Syndrome”. The further talks we will cover are shown below and these will be available in one report by the end of October 2021. 

Due to the format of the conference and the focus on unpublished data, no direct recordings or pictures are available freely as this may jeopardise publication. The full conference programme can be found on the IACFS/ME website here, where recorded presentations may be purchased. 

7. Ventilatory Functioning During Serial Cardiopulmonary Exercise Testing in People With and Without Myalgic Encephalomyelitis/Chronic Fatigue Syndrome  

Todd Davenport, DPT, MPH 
University of the Pacific; Stockton, CA, USA 

Professor Todd Davenport opened his presentation by briefly introducing the topic and the studies which have already been published showing that oxygen debt occurs sooner in people with ME/CFS. Professor Davenport’s study has addressed pulmonary function through cardiopulmonary exercise testing (CPET). 

Professor Davenport briefly examined some of the biology behind breathing and its relevance to lactic Acidosis. Lactic Acidosis is a chemical reaction which is always occurring to keep the hydrogen ions in balance, which produce CO₂ which diffuses out of the alveoli. CO₂ is important in blood pH regulation.  

The research study in this presentation used 37 ME/CFS patients with 38 healthy sedentary controls. The study put participants through either one or two maximal cardiopulmonary exercises and then measured a range of ventilatory measurements. The tests used were already tested in prior published research studied by the same research group. To understand the differences between the groups 3-way analysis of variance (ANOVA) was used, where statistical tests compared ME/CFS and controls, exercise events one and two, as well as three events of exercise (rest, VAT/VO₂ peak). 

The study measured and found: 

• Volume of oxygen consumed: significantly blunted rise in VO2 (onset of blood lactate accumulation) for people with ME/CFS 
• Workload: significantly lower overall workload for people with ME/CFS 

• Heart rate: significantly blunted rise in heart rate for people with ME/CFS 
• Respiratory rate: significantly blunted rise in respiratory rate for people with ME/CFS 
• Minute ventilation: significantly blunted rise in minute ventilation for people with ME/CFS 
• Tidal volume: No significant difference was found despite the increase being seen with each exercise event. 
• End of tidal oxygen: A rise was seen between test one and two, but no difference was found between people ME/CFS and healthy controls. 

• End tidal carbon dioxide: A rise was seen between test one and two and with different forms of exercise, but no difference was found between people with ME/CFS and healthy controls. 

In summary of findings, there was a significantly blunted effect seen between ME/CFS and healthy controls for VO₂, heart rate, respiratory rate and minute ventilation. ME/CFS and healthy control group results were found to be statistically similar for tidal volume, end oxygen and end carbon dioxide. 

Professor Davenport explained that these findings are important as little research has been conducted on ventilation and adds new data to the field of research. However, findings are in line with previous studies (e.g. Keller et al., 2014; Nagelkirk et al., 2003; Sisto et al., 1996). 

Furthermore, these findings were explained by Professor Davenport to be important as respiratory rate links in with findings which show autonomic problems in people with ME/CFS especially following post-exertion. The findings which showed similarities in the two groups in tidal volume suggests that the lungs and chest are not involved in these processes, suggesting findings to be more at the cellular level. Professor Davenport also extrapolated that these results therefore may not be found in long-COVID patients. 

Professor Davenport ended with talking about future research which could look into the relationship between ventilation and autonomic function during exercise, conducting these studies breath-by breath, additional measurements of blood status (eg pH and blood gas) and studying symptom severity with ventilatory results. 

Katrina Pears, Research Correspondent, ME Association