Postural variations of pulmonary diffusing capacity in insulin-dependent diabetes mellitus

Area of Science:

• Pulmonary Medicine
• Diabetology
• Cardiovascular Research

Background:

• Insulin-dependent diabetes mellitus (IDDM) is associated with microvascular complications.
• Pulmonary abnormalities can occur in diabetic patients, but early detection methods are needed.

Purpose of the Study:

• To evaluate posture-related changes in diffusing capacity and pulmonary capillary blood volume (Vc) as early markers of pulmonary abnormalities in IDDM patients.
• To determine if variations in Vc with posture reflect lung capillary damage in diabetic microangiopathy.

Main Methods:

• Carbon monoxide diffusing capacity (DCO) was measured using the single-breath method in both sitting and supine positions.
• Pulmonary capillary blood volume (Vc) and membrane diffusing capacity were calculated and corrected for alveolar volume (VA).
• Twenty IDDM patients and 20 age- and sex-matched healthy controls were studied.

Main Results:

• IDDM patients exhibited normal pulmonary volumes and flows.
• No significant differences in DCO or Vc were found between groups in the sitting position.
• While Vc and DCO increased significantly in controls when moving from sitting to supine, this postural change was absent in IDDM patients.
• Diabetes mellitus and age were significant predictors of altered Vc postural changes.

Conclusions:

• The absence of postural increase in Vc in IDDM patients may indicate pulmonary small vessel microangiopathy.
• A posture-based test, adjusted for age, could serve as a screening tool for early pulmonary abnormalities in diabetic patients.