Pulmonary function in diabetic children with and without persistent microalbuminuria

The Diabetic Lung: Insights into Pulmonary Changes in Children and Adolescents with Type 1 Diabetes

Historically, the lung was not listed and recognized as a major target organ of diabetic injury. The first evidence of diabetic lung involvement was published fifty years ago, with a study conducted in a population of young adults affected by type 1 diabetes (T1D). In recent years, there has been mounting evidence showing that the lung is a target organ of diabetic injury since the beginning of the disease—at the pediatric age. The deeply branched vascularization of the lungs and the abundance of connective tissue, indeed, make them vulnerable to the effects of hyperglycemia, in a way similar to other organs affected by microvascular complications. In this review, we focus on pulmonary function impairment in children and adolescents affected by T1D. We also cover controversial aspects regarding available studies and future perspectives in this field.

Assessment of pulmonary function by impulse oscillometry and spirometry in children with type 1 diabetes mellitus

AIM

To assess the lung functions with impulse oscillometry (IOS) and spirometry in children with type 1 diabetes mellitus (T1DM).

METHODS

Fifty-one children with T1DM, and sex- and age-matched 53 healthy control (HC) subjects were included in this study. Demographic, clinical, and laboratory characteristics of the subjects were recorded and their pulmonary functions were analyzed by IOS and spirometry.

RESULTS

In IOS, zR5, zR10, and zR20 levels were higher in children with T1DM compared with HCs (P = .019, P = .017, and P = .002, respectively). In spirometry, zFEF75 and zFEF25-75 were lower in children with T1DM compared with HCs (P = .025, P = .001, respectively). In IOS, zR5-20 (P = .008, P = .005, respectively) and zAX (P = .013, P = .009, respectively) were significantly lower in good-controlled group compared with moderate- and poor-controlled group. In spirometry, zFEF25-75 was significantly higher in good-controlled group compared with moderate- and poor-controlled group (P = .005, P = .009, respectively). HbA1c was positively correlated with zR5-20 value (r = .339; P = .017) in male children with T1DM. The duration of the disease was positively correlated with zR5-20 (r = .290; P = .043) and zFres (r = .358; P = .010). According to the receiver operating characteristic curve analysis to estimate optimal cut-offs to discriminate good control level of T1DM (HbA1c < 7%), a zR5-20 ≤ 2.28 demonstrated a 75.0% sensitivity and 82.9% specificity, with an area under the curve of 0.805 ([confidence interval, 0.615-0.995]; P = .007).

CONCLUSIONS

This study showed subclinical impairment of lung functions which is associated with disease duration and the degree of metabolic control in children with T1DM.

Effect of Subcutaneous Insulin on Spirometric Maneuvers in Patients with Type 1 Diabetes: A Case-Control Study

In order to compare spirometric maneuvers in adults according to the presence of type 1 diabetes, a case-control study including 75 patients with type 1 diabetes and 75 controls matched by sex, age, and body mass index were designed. In addition, 75 patients with type 1 diabetes were added to examine the potential the impact of subcutaneous insulin therapy on pulmonary function. Lung function measurements were assessed according to the global initiative for chronic obstructive lung disease guidelines. Basal insulin included long-acting insulin analogues and the delivered background insulin in patients with pump therapy. Bolus insulin included rapid-acting insulin analogues and the delivered insulin to cover postprandial hyperglycemias. Patients with type 1 diabetes showed lower spirometric values in comparison to the control group, together with a higher prevalence of forced expiratory volume in the first second (FEV1) <80% (10.7% vs. 2.7%, p = 0.044) and restrictive ventilatory pattern (10.7% vs. 0%, p = 0.006) The dose of basal insulin (U/kg/day) showed a negative correlation with forced vital capacity (FVC) (r = −0.205, p = 0.012) and FEV1 (r = −0.182, p = 0.026). The optimal cut-off value for identifying patients with a restrictive spirometric pattern was 0.5 U/kg/day of basal insulin. Additionally, basal insulin (U/kg/day) independently predicted the presence of both a restrictive spirometric pattern (OR = 77.1 (3.2 to 1816.6), p = 0.007) and an abnormal FEV1 (OR = 29.9 (1.5 to 562.8), p = 0.023). In patients with type 1 diabetes, higher basal insulin dosage seems to be related with an impairment of pulmonary function.

Lung volume dependence of respiratory function in rodent models of diabetes mellitus

Background

Diabetes mellitus causes the deterioration of smooth muscle cells and interstitial matrix proteins, including collagen. Collagen and smooth muscle cells are abundant in the lungs, but the effect of diabetes on airway function and viscoelastic respiratory tissue mechanics has not been characterized. This study investigated the impact of diabetes on respiratory function, bronchial responsiveness, and gas exchange parameters.

Methods

Rats were allocated randomly to three groups: a model of type 1 diabetes that received a high dose of streptozotocin (DM1, n = 13); a model of type 2 diabetes that received a low dose of streptozotocin with a high-fat diet (DM2, n = 14); and a control group with no treatment (C, n = 14). Forced oscillations were applied to assess airway resistance (Raw), respiratory tissue damping (G), and elastance (H). The arterial partial pressure of oxygen to the inspired oxygen fraction (PaO₂/FiO₂) and intrapulmonary shunt fraction (Qs/Qt) were determined from blood gas samples at positive end-expiratory pressures (PEEPs) of 0, 3, and 6 cmH₂O. Lung responsiveness to methacholine was also assessed. Collagen fibers in lung tissue were quantified by histology.

Results

The rats in groups DM1 and DM2 exhibited elevated Raw, G, H, and Qs/Qt, compromised PaO₂/FiO₂, and diminished airway responsiveness. The severity of adverse tissue mechanical change correlated with excessive lung collagen expression. Increased PEEP normalized the respiratory mechanics, but the gas exchange abnormalities remained.

Conclusions

These findings indicate that diabetes reduces airway and lung tissue viscoelasticity, resulting in alveolar collapsibility that can be compensated by increasing PEEP. Diabetes also induces persistent alveolo-capillary dysfunction and abnormal adaptation ability of the airways to exogenous constrictor stimuli.

Pulmonary function in children with type 1 diabetes mellitus

AIM

To assess lung function in children and adolescents with type 1 diabetes mellitus (T1DM).

PATIENTS AND METHODS

We conducted a case-control study of 100 patients with T1DM [median age 13 (10.6-14.7), 44% men, 23% prepubertal, and all nonsmokers] and 77 controls. None had evidence of lung disease or any other comorbidity. We performed pulmonary function tests, including spirometry [forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and FEV₁/FVC ratio], plethysmography [total lung capacity (TLC), residual volume (RV), RV/TLC ratio, and airway resistance (Raw)], and diffusing capacity of carbon monoxide in the lung (TLCO), alveolar volume (AV), and TLCO/AV ratio. The duration of diabetes, degree of metabolic control, insulin dose, and presence of diabetic complications were registered. The χ²-test and analysis of variance were used to compare categorical and quantitative variables, respectively.

RESULTS

The duration of diabetes was 6.2±3.8 years with a median HbA₁c of 7.08±0.4%. FEV₁/FVC ratio was found to be significantly higher in patients with TIDM than in controls. Patients with diabetes also had a nonsignificant trend towards lower FVC, FEV₁, Raw, and TLCO, and higher RV, TLC, and RV/TLC than controls. There were no differences in pulmonary function based on duration of disease or metabolic control. We found differences in pulmonary evaluation when pubertal stage was analyzed.

CONCLUSIONS

The lung is functionally involved in children with T1DM. Pubertal development stage influences the evaluation of lung function.

Impaired diffusing capacity for carbon monoxide in children with type 1 diabetes: is this the first sign of long-term complications?

We assessed the presence of lung dysfunction in children with type 1 diabetes, evaluated as reduced diffusing capacity of the lung for carbon monoxide (DLCO), and its components: membrane diffusing capacity (DM) and pulmonary capillary blood volume (Vc). A total of 42 children, aged 15.6 ± 3.8 years, with type 1 diabetes for 8.3 ± 5.5 years, and 30 healthy age and sex-matched peers were recruited for the study. Lung volumes and spirometric dynamic parameters were assessed by plethysmography. Single-breath DLCO was measured according to international recommendation. DM and Vc volume were calculated. Lung volumes were significantly reduced in young patients with type 1 diabetes when compared to controls. Moreover, DLCO was reduced in patients compared to controls (78% ± 16% vs. 120% ± 1%, P = 0.0001). However, when differentiating DM and Vc compartments, we observed a significant impairment only about Vc (34 ± 20 ml vs. 88 ± 18 ml; P = 0.0001), while no difference was observed about DM compartment (23 ± 4 vs. 26 ± 3 ml/min/mmHg, P = 0.798). Whether this might be seen as the "first" sign of microangiopathic involvement in patients with type 1 diabetes has to be confirmed on larger groups but is still fascinating. Meanwhile, we suggest to screen DLCO in all patients with type 1 diabetes.

Pulmonary fibrosis: a possible diabetic complication

Diabetic complications affect many organs in diabetic patients. Emerging evidence indicates that diabetes can increase the risk of pulmonary dysfunction. Early epidemiological studies from different populations on whether diabetes was an independent risk for pulmonary dysfunction were inconclusive. Recent epidemiological studies and systematic reviews clearly indicate that diabetes is an independent risk factor for pulmonary dysfunction. Given that pulmonary fibrosis is an important predictor of mortality in people with this chronic disease, whether diabetes directly causes pulmonary fibrosis is an important unresolved clinical question. This review combines recent epidemiological data with findings from basic research to indicate that diabetes induces pulmonary fibrosis. We then discuss the possible underlying mechanisms for the histological and biochemical pathology. At the end of this review, we emphasize that diabetic pulmonary fibrosis as a potential diabetic complication warrants more attention.

Diffusing capacity for carbon monoxide in children with type 1 diabetes

AIMS/HYPOTHESIS

Few data are available on lung dysfunction in children with diabetes. We studied the association of pulmonary function variables (flows, volumes and alveolar capillary diffusion) with disease-related variables in children with type 1 diabetes mellitus.

METHODS

We studied 39 children with type 1 diabetes (mean age 10.9+/-2.6 years, disease duration 3.6+/-2.4 years, insulin.kg(-1).day(-1) 0.77+/-0.31) and 30 healthy control children (mean age 10.4+/-3.0 years). Pulmonary function tests included spirometry, N(2) wash-out and the single-breath diffusing capacity for carbon monoxide (DL(CO)) corrected for the alveolar volume (DL(CO)/V(A)). Glycaemic control was assessed on the basis of HbA(1)c, with HbA(1)c values of 8% or less considered to indicate good glycaemic control, and HbA(1)c values of 8% or more considered to indicate poor control.

RESULTS

Children with poor glycaemic control had comparable percentage values for predicted flows and volumes but lower DL(CO)/V(A) values than children with good glycaemic control and healthy control children (86.7+/-12.6 vs 99.8+/-18.4 and 102.0+/-15.7; p<0.05). The predicted DL(CO)/V(A) percentages correlated with HbA(1)c levels (r=-0.39, p=0.013). A multiple regression analysis (stepwise model) controlling for HbA(1)c levels and other disease-related variables (age of disease onset, disease duration, daily insulin dose/kg, sex) identified HbA(1)c levels as the sole predictor of DL(CO)/V(A) in percent.

CONCLUSIONS/INTERPRETATION

In children with type 1 diabetes, the diffusing capacity diminishes early in childhood and is associated with poor metabolic control. Although low DL(CO)/V(A) levels in these children probably reflect pulmonary microangiopathy induced by type 1 diabetes, other factors presumably influencing CO diffusion capacity measurements (e.g. a left shift in HbA(1)c resulting in high O(2) binding and low CO binding) could explain the apparent capillary and alveolar basal membrane dysfunction.

Lung function in children with diabetes mellitus

A cross-sectional study design was undertaken to assess pulmonary function in children with insulin-dependent diabetes mellitus (IDDM), and to establish if there is any relationship with diabetic factors and complications. Thirty-eight children (10 +/- 1.8 years) with IDDM and without clinical or radiological evidence of lung involvement, and 41 healthy age-matched reference subjects, underwent a pulmonary function study. Thirteen (34%) of 38 subjects with IDDM were studied at the onset of their disease. Adjusted values expressed as SD score of forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV(1)), and the transfer factor for carbon monoxide (TLCO) were found to be significantly lower than in controls (-0.54 +/- 0.87 vs. 0.40 +/- 1.10, P = 0.0008; -0.11 +/- 0.96 vs. 0.52 +/- 1.07, P = 0.01; -1.60 +/- 1.07 vs. -0.57 +/- 1.28, P = 0.001, respectively). These differences also existed in the group investigated at onset of diabetes. Residual volume (RV) and RV/total lung capacity ratio (RV/TLC) were significantly higher in the whole group of patients with IDDM than in controls (-0.20 +/- 0.83 vs. -0.80 +/- 0.88, P = 0.003; and 26 +/- 6.2 vs. 21 +/- 5.0, P = 0.0002, respectively). Seventeen patients (45%) had abnormal pulmonary function (SD score, less than -1.64): 16 subjects had reduced TLCO, 4 had reduced FVC, and in 3 of the 17, both functional indices were abnormal. There was no significant relationship between pulmonary function indices and diabetic factors or complications. The only significant association was between abnormal TLCO and females (P = 0.03), suggesting that sex may be a predisposing factor for the development of pulmonary complications. This study supports the view that the lung is functionally involved in children with IDDM early on in the course of the disease.

Lung function abnormalities in children with type I diabetes

Recent developments in intrabronchial administration of insulin raise lung function in patients with type I diabetes as important issue. Several studies in adults report abnormalities of lung function of these patients. The aim of this study was to investigate lung function in children with type I diabetes. Twenty-seven children with type I diabetes performed measurement of airway obstruction (forced flow-volume curves), lung volumes and airway resistance (bodyplethysmography) and of pulmonary carbon monoxide diffusion capacity Mean age (+/- SD) of the children was 12.8 +/- 5 years. Mean time between the detection of type I diabetes and the lung function tests was 5.5 years with a variation from I to 17 years. The total airway resistance (Raw) was significantly higher compared to the reference values (P < 0.001). The other lung function parameters were not significantly different from reference values (P > 0.05). In this relatively small study no relationship between lung function abnormalities and age, the duration of disease or level of HbA1c was observed. Our data show that increase of airway resistance do occur in children withtype I diabetes. Progressive abnormalities in lung function might interfere with the promising results of treatment with intrabronchial administration of insulin.

Diabetes mellitus vs. Raynaud disease: different lung vascular bed disorders

BACKGROUND

In type II diabetes mellitus there are few data concerning pulmonary function abnormalities. In normal subjects and in patients with primary Raynaud phenomenon, cold pressor test induces a decrease in carbon monoxide single-breath diffusing capacity (DL,co) but not in secondary Raynaud phenomenon. Our objective was to assess evaluation of lung diffusion capacity postural changes in diabetes mellitus and in secondary Raynaud phenomenon, two diseases with different pulmonary capillaries functional disorders.

METHODS

Twenty-five patients with type II diabetes mellitus (mean age 52.24 years), 17 patients with secondary Raynaud phenomenon (mean age 47.06 years), non-smokers without pulmonary or heart disease, and 26 healthy matched subjects (mean age 47.50 years) underwent lung diffusion capacity measurements by single-breath method also corrected by alveolar volume (DL,co) in sitting and supine positions.

RESULTS

Patients with diabetes mellitus exhibited lower values of DL,co and DL,co/VA measurements in comparison with subjects with Raynaud phenomenon and control group (p <0.01). Additionally, they had a significant decrease in DL,co in supine compared to sitting position (83.88 +/- 16.53 vs. 89.68 +/- 18.03, p = 0.023). To the contrary, supine position in secondary Raynaud phenomenon and in control group after cold pressor test showed a significant increase in DL,co/VA (120.93 vs. 109.78 in Raynaud and 114.36 vs. 99.47 in control group, p <0.001).

CONCLUSIONS

Postural changes of lung diffusion capacity could be used as a simple, non-invasive method to detect vascular disease resulting from different pathophysiologic mechanisms such as diabetes mellitus and Raynaud phenomenon.

Pulmonary function in patients with diabetes mellitus

BACKGROUND

Pulmonary complications of diabetes mellitus have been poorly characterized. Although some authors have reported normal pulmonary function, others found abnormalities in lung volumes, pulmonary mechanics, and diffusing capacity.

SUBJECTS AND METHODS

We studied pulmonary function in a group of patients with diabetes using a combined cardiopulmonary exercise test. Twenty-seven patients with diabetes aged 48 +/- 13 years participated in the study.

RESULTS

Overall, forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow, midexpiratory phase, were within the predicted values, but the residual volume/total lung capacity ratio was slightly elevated. Comparison by diabetes type showed nonsignificant differences in forced expiratory volume in 1 second and forced expiratory flow, midexpiratory phase. Residual volume/total lung capacity ratio was significantly elevated in type 1 patients compared with type 2. Carbon monoxide diffusion capacity (DLCO) was normal in both groups. There was no correlation between the results on pulmonary function test and duration of disease, presence of microangiopathy, or glycemic control. The DLCO was significantly lower in patients with microangiopathic changes, but not when DLCO was corrected for alveolar volume. On the cardiopulmonary exercise test, maximal workload, maximum oxygen uptake, and maximal heart rate were less than predicted, whereas anaerobic threshold and ventilatory reserve were normal. No significant differences were noted in diabetes type, and there was no correlation between parameters of cardiopulmonary exercise test and the other variables.

CONCLUSION

Spirometric values are preserved in patients with diabetes mellitus, and there are no defects in diffusing capacity. Cardiovascular factors may account for impaired physical performance. There is no need for routine screening of pulmonary function among diabetic patients.

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

STUDY OBJECTIVE

To assess whether posture-related changes of diffusing capacity could be considered as an early sensitive marker of pulmonary abnormalities in patients with insulin-dependent diabetes mellitus (IDDM) and whether the postural variations of pulmonary capillary blood volume (Vc) could reflect the lung capillary damage that characterizes the diabetic microangiopathy.

DESIGN

Carbon monoxide diffusing capacity (DCO) was measured by the single-breath method. Four DCO measurements, two in sitting and two in supine position, were performed in each subject using gas mixtures containing different oxygen concentrations. Membrane and capillary volume components of the diffusion capacity were calculated and both were expressed as absolute value and corrected by alveolar volume (VA).

PATIENTS

Twenty IDDM patients and 20 normal subjects matched for age and sex were studied.

MEASUREMENTS AND RESULTS

The IDDM patients showed normal pulmonary volumes and flows. No significant differences between the two groups were found for DCO, coefficient of diffusion, Vc, and pulmonary capillary blood volume corrected by alveolar volume in sitting position. All these indexes significantly increased in normal subjects but not in diabetics, by changing the posture of the subject from sitting to supine position. In a multivariate analysis, the presence of diabetes mellitus and the age of the subjects were the only significant predictors of Vc postural changes.

CONCLUSIONS

This postural test, adjusted for age, could be included in a screening diagnostic procedure for an early assessment of pulmonary abnormalities in diabetic patients. The lack of Vc postural increase in diabetics could reflect the presence of a microangiopathy involving the pulmonary small vessels.