The pulmonary diffusion capacity is also reduced in diabetics that is dependent on impaired autonomic functions that can be measured by heart rate variability (HRV) (1) In clinical trials, proinsulin C-peptide increased significantly HRV in insulin-dependent diabetes mellitus patients. (2) It is an interesting fact that COVID-19 is dangerous only to the groups e.g. elderly who have relatively low HRV. HRV is also associated with immune functions. (3) Low HRV and impaired lung functions are also associated with reduced exercise capacity in diabetics generally. (4) The susceptibility to pulmonary edema is also increased with reduced HRV. (5)

1. https://pubmed.ncbi.nlm.nih.gov/19046231/?fbclid=IwAR2sZf4rEWjsaUtn7fg4q2gR7-WI9Gsb-25ugiTiwjh6TVzsW52Z6oLpe7c
2. https://link.springer.com/article/10.1007/BF00418540
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5187961/
4. https://pubmed.ncbi.nlm.nih.gov/30606177/
5. https://pubmed.ncbi.nlm.nih.gov/26718350/?fbclid=IwAR1jhLES4b7qx9CkwBt4mMLdaqynU3D-BCr1COBYhYIR7UQLRUb-b6pWh9Y