title: Pulmonary diffusing capacity for carbon monoxide: a marker of depressed hypercapnic drive in type 1 diabetes mellitus?
abstract: OBJECTIVE
  Decreased chemosensitivity to hypercapnia, a common finding in Type 1 diabetes mellitus, seems related to autonomic neuropathy. We proposed to verify whether simple neuroautonomic cardiovascular tests or indexes of severity of diabetes and respiratory impairment can identify patients with such a dysfunction, but no clinical evidence of autonomic neuropathy.
  
  
  METHODS
  Forty patients with Type 1 diabetes, 20 with autonomic neuropathy according to the results of a standardized test battery, were studied and compared with 40 normal subjects matched by age and sex. Spirometry and pulmonary diffusing capacity for carbon monoxide were performed. The chemosensitivity to hypercapnia was tested by the rebreathing method.
  
  
  RESULTS
  There was no significant difference between patients with and without autonomic neuropathy in chemosensitivity to hypercapnia, as expressed by the ventilation response to increasing end-tidal pressure of carbon dioxide; however, it was lower in the whole group of patients with diabetes than in control subjects (1.71 ± 0.80 vs. 2.45 ± 1.11 l⁻¹ min⁻¹ mmHg, respectively, P=0.002). No significant correlation was found between ventilation response to increasing end-tidal pressure of carbon dioxide and the results of autonomic tests. In patients with diabetes mellitus, the ventilatory response to hypercapnia significantly correlated with pulmonary diffusing capacity for carbon monoxide (Spearman's rho=0.387, P=0.013) and this was the only variable significantly associated with ventilation response to increasing end-tidal pressure of carbon dioxide in a multiple regression model.
  
  
  CONCLUSIONS
  Chemosensitivity to hypercapnia was depressed in patients with diabetes mellitus, irrespective of autonomic neuropathy, in comparison with control subjects. The correlation with pulmonary diffusing capacity for carbon monoxide suggests that microcirculatory damage might contribute to depress the central chemosensitivity.
authors: Respiratory Disease Unit, Catholic University, Italy.
authors: L
authors: L
authors: Fuso
authors: L
authors: L
authors: Paladini
authors: D
authors: D
authors: Pitocco
authors: T
authors: T
authors: Musella
authors: C
authors: C
authors: Contu
authors: L
authors: L
authors: Maugeri
authors: A P
authors: AP
authors: Santamaria
authors: F
authors: F
authors: Varone
authors: G
authors: G
authors: Ghirlanda
authors: R
authors: R
authors: Antonelli Incalzi
mesh_terms: D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000209:etiology / Q000378:metabolism*; D002248:Carbon Monoxide / Q000009:adverse effects / Q000378:metabolism*; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000378:metabolism*; D003929:Diabetic Neuropathies / Q000209:etiology / Q000378:metabolism*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000150:complications / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011653:Pulmonary Diffusing Capacity; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests
chemical_list: D002248:Carbon Monoxide