Lung function in patients with diabetes mellitus

Respiratory function in uncomplicated type 1 diabetes: Blunted during exercise even though normal at rest!

AIMS

Type 1 diabetes is associated with a substantially increased risk of impaired lung function, which may impair aerobic fitness. We therefore aimed to examine the ventilatory response during maximal exercise and the pulmonary diffusion capacity function at rest in individuals with uncomplicated type 1 diabetes.

METHODS

In all, 17 adults with type 1 diabetes free from micro-macrovascular complications (glycated haemoglobin: 8.0 ± 1.3%), and 17 non-diabetic adults, carefully matched to the type 1 diabetes group according to gender, age, level of physical activity and body composition, participated in our study. Lung function was assessed by spirometry and measurements of the combined diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) at rest. Subjects performed a maximal exercise test during which the respiratory parameters were measured.

RESULTS

At rest, DLCO (30.4 ± 6.1 ml min^-1  mmHg^-1 vs. 31.4 ± 5.7 ml min^-1 mmHg^-1 , respectively, p = 0.2), its determinants Dm (membrane diffusion capacity) and Vc (pulmonary capillary volume) were comparable among type 1 diabetes and control groups, respectively. Nevertheless, spirometry parameters (forced vital capacity = 4.9 ± 1.0 L vs. 5.5 ± 1.0 L, p < 0.05; forced expiratory volume 1 = 4.0 ± 0.7 L vs. 4.3 ± 0.7 L, p < 0.05) were lower in individuals with type 1 diabetes, although in the predicted normal range. During exercise, ventilatory response to exercise was different between the two groups: tidal volume was lower in type 1 diabetes vs. individuals without diabetes (p < 0.05). Type 1 diabetes showed a reduced VO_2max (34.7 ± 6.8 vs. 37.9 ± 6.3, respectively, p = 0.04) in comparison to healthy subjects.

CONCLUSIONS

Individuals with uncomplicated type 1 diabetes display normal alveolar-capillary diffusion capacity and at rest, while their forced vital capacity, tidal volumes and VO₂ are reduced during maximal exercise.

Hyperoxia increases arterial oxygen pressure during exercise in type 2 diabetes patients: a feasibility study

Objective

The study investigated the feasibility and potential outcome measures during acute hyperoxia in type 2 diabetes patients (DM2).

Methods

Eleven DM2 patients (7 men and 4 women) were included in the study. The patients cycled (30 min at 20 % W_max) whilst breathing three different supplemental oxygen flows (SOF, 5, 10, 15 L min⁻¹). During hyperoxic exercise, arterial blood gases and intra-arterial blood pressure measurements were obtained.

Results

Arterial pO₂ levels increased significantly (ANOVA, p < 0.05) with SOF: 13.9 ± 1.2 (0 L min⁻¹); 18.5 ± 1.5 (5 L min⁻¹); 21.7 ± 1.7 (10 L min⁻¹); 24.0 ± 2.3 (15 L min⁻¹). Heart rate (HR) and pH increased significantly after terminating administration of hyperoxic air.

Conclusions

An SOF of 15 L min⁻¹ appears to be more effective than 5 or 10 L min⁻¹. Moreover, HR, blood pressure, blood lactate and pH are not recommended as primary outcome measures.

Prolonged postoperative respiratory support after proximal thoracic aortic surgery: Is deep hypothermic circulatory arrest a risk factor?

PURPOSE

In addition to the pulmonary risks associated with cardiopulmonary bypass, thoracic aortic surgery using deep hypothermic circulatory arrest (DHCA) may subject the lungs to further injury. However, this topic has received little investigation to date.

MATERIALS AND METHODS

A prospective cohort review was performed on all patients undergoing proximal thoracic aortic surgery with (n = 478) and without (n = 135) DHCA between July 2005 and February 2013 at a single institution. The primary outcome was prolonged postoperative respiratory support (PPRS), defined as any of the following: >1 day of mechanical ventilation at either fraction of inspired oxygen >0.4 and/or positive end-expiratory pressure >5 mm Hg, >2 days of supplemental O2 requirement of at least 2.5 L/min, or discharge with new O2 requirement. Independent risk factors for PPRS were identified using multivariable logistic regression.

RESULTS

Postoperative respiratory support was required in 100 patients (20.9%) with and 30 patients (22.2%) without DHCA (P = .74). Independent predictors of PPRS after proximal aortic surgery included the following: age, diabetes, history of stroke, preoperative creatinine, American Society of Anesthesiologists class 4, redo-sternotomy, total arch replacement, and transfusion requirement. Use of DHCA was not an independent risk factor for PPRS in the entire cohort. Subanalysis of only DHCA patients revealed that longer DHCA times were independently associated with PPRS.

CONCLUSIONS

Prolonged postoperative respiratory support is common after proximal aortic surgery. The use of DHCA was not associated with this complication in the overall cohort, although longer DHCA times were predictive when only the subset of patients undergoing DHCA was analyzed. Knowledge of the risk factors for PPRS after proximal aortic surgery should improve preoperative risk stratification and postoperative management of these patients.

Evaluation of pulmonary function changes in children with type 1 diabetes mellitus in Upper Egypt

BACKGROUND

Diabetes mellitus is a leading cause of morbidity and mortality among children across the world and is responsible for a growing proportion of global healthcare expenditure. However, limited data are available on lung dysfunction in children with diabetes.

AIM

The aim of this study was to evaluate the pulmonary function changes in children with type 1 diabetes mellitus (T1DM).

METHODS

We studied 60 children with T1DM (mean age 10.5 ± 2.32 years; disease duration 2.45 ± 0.6 years, and 50 healthy control children (mean age 9.9 ± 2.5 years). Spirometry was performed for all individuals to measure forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, and peak expiratory flow rate (PEFR). Glycemic control was assessed on the basis of glycated hemoglobin (HbA1c), with HbA1c values <8% considered to indicate good glycemic control, and HbA1c values ⩾8% to indicate poor control.

RESULTS

There was significant reduction in all spirometeric parameters in diabetic children in comparison with healthy control children. Children with poor glycemic control had significant impairment in lung functions compared with those with good glycemic control.

CONCLUSIONS

T1DM in children leads to impairment of lung functions and this impairment increases with poor glycemic control.

Cardiorespiratory fitness, pulmonary function and C-reactive protein levels in nonsmoking individuals with diabetes

The objective of this study was to evaluate cardiorespiratory fitness and pulmonary function and the relationship with metabolic variables and C-reactive protein (CRP) plasma levels in individuals with diabetes mellitus (DM). Nineteen men with diabetes and 19 age- and gender-matched control subjects were studied. All individuals were given incremental cardiopulmonary exercise and pulmonary function tests. In the exercise test, maximal workload (158.3±22.3 vs 135.1±25.2, P=0.005), peak heart rate (HR_peak: 149±12 vs 139±10, P=0.009), peak oxygen uptake (VO_2peak: 24.2±3.2 vs 18.9±2.8, P<0.001), and anaerobic threshold (VO_2VT: 14.1±3.4 vs 12.2±2.2, P=0.04) were significantly lower in individuals with diabetes than in control subjects. Pulmonary function test parameters, blood pressure, lipid profile (triglycerides, HDL, LDL, and total cholesterol), and CRP plasma levels were not different in control subjects and individuals with DM. No correlations were observed between hemoglobin A1C (HbA1c), CRP and pulmonary function test and cardiopulmonary exercise test performance. In conclusion, the results demonstrate that nonsmoking individuals with DM have decreased cardiorespiratory fitness that is not correlated with resting pulmonary function parameters, HbA1c, and CRP plasma levels.

Alveolar Gas Exchange and Pulmonary Functions in Patients with Type II Diabetes Mellitus

BACKGROUND

The incidence of diabetes is increasing tremendously throughout the world especially in the developing countries. This disease affects various organs like eyes, nerves, kidneys and the heart. In this study, we investigated whether lungs are also one of the target organs of diabetes mellitus or not.

AIM

To assess the pulmonary function parameters including alveolar gas exchange in patients with Type 2 Diabetes mellitus and to find the influence of hyperglycaemia and duration of diabetes.

METHODOLOGY

This cross sectional study involved 30 type II diabetic patients of age 30-60 years attending the diabetic outpatient department of SRM Medical College & Research Centre and 30 age and sex matched non-diabetic subjects as controls. The glycated haemoglobin (HbA1c) levels, fasting and post prandial blood glucose levels, pulmonary function parameters such as Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), Forced Expiratory Volume Percentage (FEV1 /FVC), Peak Expiratory Flow Rate (PEFR), Forced Expiratory Flow (25 - 75%), Peak Inspiratory flow ( PIF), Forced Inspiratory Vital Capacity ( FIVC), Total Lung Capacity ( TLC),Diffusing capacity of lung for carbon monoxide( DLCO) were measured for all the participants using Easyone Pro computerised spirometer. DLCO was measured by single breath Carbon Monoxide (CO) diffusion test. The alveolar membrane permeability was assessed by evaluating the ratio of DLCO to Alveolar Ventilation (VA).

RESULTS

The pulmonary function parameters FVC, FEV1, PEFR, PIF, FIVC, TLC , DLCO and DLCO/VA were significantly low (p<0.05) in patients with type II diabetes mellitus when compared to control group. The DLCO and DLCO/VA were significantly lower (p<0.05) in patients with poor glycemic control(HbA1c > 7).

CONCLUSION

We conclude that the pulmonary function parameters like FVC, FEV1, PEFR, PIF, FIVC, TLC and alveolar gas exchange were significantly reduced in patients with type II diabetes. The patients with Type II diabetes mellitus had a restrictive pattern of respiratory abnormality. The patients with poor glycaemic control( HbA1c > 7) had reduced alveolar diffusion which was not dependent on the duration of diabetes. The impaired respiratory function may give way for the development of pulmonary complications. Spirometry can be used as a screening tool among diabetics as an early preventive measure.

Chronic obstructive pulmonary disease and glucose metabolism: a bitter sweet symphony

Chronic obstructive pulmonary disease, metabolic syndrome and diabetes mellitus are common and underdiagnosed medical conditions. It was predicted that chronic obstructive pulmonary disease will be the third leading cause of death worldwide by 2020. The healthcare burden of this disease is even greater if we consider the significant impact of chronic obstructive pulmonary disease on the cardiovascular morbidity and mortality. Chronic obstructive pulmonary disease may be considered as a novel risk factor for new onset type 2 diabetes mellitus via multiple pathophysiological alterations such as: inflammation and oxidative stress, insulin resistance, weight gain and alterations in metabolism of adipokines. On the other hand, diabetes may act as an independent factor, negatively affecting pulmonary structure and function. Diabetes is associated with an increased risk of pulmonary infections, disease exacerbations and worsened COPD outcomes. On the top of that, coexistent OSA may increase the risk for type 2 DM in some individuals. The current scientific data necessitate a greater outlook on chronic obstructive pulmonary disease and chronic obstructive pulmonary disease may be viewed as a risk factor for the new onset type 2 diabetes mellitus. Conversely, both types of diabetes mellitus should be viewed as strong contributing factors for the development of obstructive lung disease. Such approach can potentially improve the outcomes and medical control for both conditions, and, thus, decrease the healthcare burden of these major medical problems.

Pulmonary functions in patients with diabetes mellitus

Background:

A reduction in lung capacity has been reported previously among diabetics. According to WHO estimates, Pakistan is currently eighth in the prevalence of diabetes mellitus (DM) and will become fourth by the year 2025 with over 15 million individuals. This study was designed to see the impairment of lung functions on spirometry in DM patients.

Objective:

Our aim was to investigate the pulmonary functions tests of Pakistani patients with DM.

Materials and Methods:

Between January to July 2004, 128 subjects who were never-smokers and had no acute or chronic pulmonary disease were recruited. Sixty-four of these subjects had DM and 64 were healthy matched controls. All underwent screening with detailed history, anthropometry, lipid profile, and spirometric measurements at the Aga Khan University Hospital, Karachi, Pakistan.

Results:

The mean age of diabetics and matched control were 54.3±9 and 54.0±8 (P<0.87) years, respectively. Diabetes patients showed a significant reduction in the forced vital capacity (FVC) [mean difference (95% CI) – 0.36 (–0.64, –0.07) P<0.01], forced expiratory volume in one second (FEV₁) [– 0.25(–0.50, –0.003) P<0.04], and slow vital capacity (SVC) [– 0.28(–0.54, –0.01) P<0.04], relative to nondiabetic controls. There was no significant difference noted in the forced expiratory ratio and maximum mid-expiratory flow between the groups. There was also a significant higher level of triglycerides noted among diabetics (P<0.001).

Conclusion:

Diabetic patients showed impaired lung function independent of smoking. This reduced lung function is likely to be a chronic complication of diabetes mellitus.

Glycemic control influences lung membrane diffusion and oxygen saturation in exercise-trained subjects with type 1 diabetes: alveolar-capillary membrane conductance in type 1 diabetes

Lung diffusing capacity (DLCO) is influenced by alveolar-capillary membrane conductance (D (M)) and pulmonary capillary blood volume (V (C)), both of which can be impaired in sedentary type 1 diabetes mellitus (T1DM) subjects due to hyperglycemia. We sought to determine if T1DM, and glycemic control, affected DLNO, DLCO, D (M), V (C) and SaO(2) during maximal exercise in aerobically fit T1DM subjects. We recruited 12 T1DM subjects and 18 non-diabetic subjects measuring DLNO, DLCO, D (M), and V (C) along with SaO(2) and cardiac output (Q) at peak exercise. The T1DM subjects had significantly lower DLCO/Q and D (M)/Q with no difference in Q, DLNO, DLCO, D (M), or V (C) (DLCO/Q = 2.1 ± 0.4 vs. 1.7 ± 0.3, D (M)/Q = 2.8 ± 0.6 vs. 2.4 ± 0.5, non-diabetic and T1DM, p < 0.05). In addition, when considering all subjects there was a relationship between DLCO/Q and SaO(2) at peak exercise (r = 0.46, p = 0.01). Within the T1DM group, the optimal glycemic control group (HbA1c <7%, n = 6) had higher DLNO, DLCO, and D (M)/Q than the poor glycemic control subjects (HbA1c ≥ 7%, n = 6) at peak exercise (DLCO = 38.3 ± 8.0 vs. 28.5 ± 6.9 ml/min/mmHg, DLNO = 120.3 ± 24.3 vs. 89.1 ± 21.0 ml/min/mmHg, D (M)/Q = 3.8 ± 0.8 vs. 2.7 ± 0.2, optimal vs. poor control, p < 0.05). There was a negative correlation between HbA1c with DLCO, D (M) and D (M)/Q at peak exercise (DLCO: r = -0.70, p = 0.01; D (M): r = -0.70, p = 0.01; D (M)/Q: r = -0.68, p = 0.02). These results demonstrate that there is a reduction in lung diffusing capacity in aerobically fit athletes with T1DM at peak exercise, but suggests that maintaining near-normoglycemia potentially averts lung diffusion impairments.

Alveolar gas diffusion abnormalities in heart failure

In heart failure (HF), development of pressure or volume overload of the lung microcirculation elicits a series of structural adaptations, whose functional correlate is an increased resistance to gas transfer across the alveolar-capillary membrane. Acutely, hydrostatic mechanical injury causes endothelial and alveolar cell breaks, impairment of the cellular pathways involved in fluid filtration and reabsorption, and resistance to gas transfer. This process, which is reminiscent of the so-called alveolar-capillary stress failure, is generally reversible. When the alveolar membrane is chronically challenged, tissue alterations are sustained and a typical remodeling process may take place that is characterized by fixed extracellular matrix collagen proliferation and reexpression of fetal genes. Remodeling leads to a persistent reduction in alveolar-capillary membrane conductance and lung diffusion capacity. Changes in gas transfer not only reflect the underlying lung tissue damage but also bring independent prognostic information and may play a role in the pathogenesis of exercise limitation and ventilatory abnormalities. They are not responsive to fluid withdrawal by ultrafiltration and tend to be refractory even to heart transplantation. Some drugs can be effective that modulate lung remodeling (eg, angiotensin-converting enzyme inhibitors, whose impact on the natural course of cardiac remodeling is well known) or that increase nitric oxide availability and nitric oxide-mediated pulmonary vasodilation (eg, type 5 phosphodiesterase inhibitors). This review focuses on the current knowledge of these topics.

Pulmonary complications in diabetes mellitus

Clear decrements in lung function have been reported in patients with diabetes over the past two decades, and many reports have suggested plausible pathophysiological mechanisms. However, there are no reports of functional limitations of activities of daily living ascribable to pulmonary disease in patients with diabetes. This review attempts to summarize the available information from the present literature, to describe the nature of the lung dysfunction in diabetes and the emerging clinical implications of such dysfunction.

First approved inhaled insulin therapy for diabetes mellitus

The long-term benefits of tight glycemic control in preventing microvascular and macrovascular complications are well established in both Type 1 diabetes mellitus (Type 1 DM) and Type 2 diabetes mellitus (Type 2 DM). Nonetheless, achievement of recommended haemoglobin A1c (HbA(1c)) goals (< or = 6.5 - 7.0%) has remained elusive, especially in patients with diabetes who require insulin therapy. Delayed/suboptimal titration of insulin is partly related to poor acceptance of multiple injection regimen by both physicians and patients. EXUBERA (human insulin [rDNA origin]; Pfizer), the first approved inhaled insulin for the treatment of diabetic patients, has been shown to be safe and as effective as regular/rapidly acting insulin in improving glycemic control. In addition to controlling postprandial glucose excursions, EXUBERA exerts a major action to reduce fasting plasma glucose (FPG) concentration. Thus, it has the potential to be used as a monotherapy in Type 2 DM, as well as in combination with an insulin sensitizer in Type 2 DM or in combination with long-acting insulin in both Type 2 DM and Type 1 DM.

Evaluation of pulmonary alveolo-capillary permeability in Type 2 diabetes mellitus: using technetium 99mTc-DTPA aerosol scintigraphy and carbon monoxide diffusion capacity

The thickening of alveolar basement membrane is found in autopsies, along with microvascular pathologies, in Type 1 and 2 diabetes mellitus (DM). To detect the function and permeability of alveolar basement membrane, carbon monoxide diffusion capacity (DLCO) and technetium 99m-diethyltriaminepentaaceticacid ((99m)Tc-DTPA) aerosol scintigraphy methods can be used. The aim of this study was to determine alveolar basement membrane damage using these two methods. Nineteen women and 6 men, nonsmoking, Type 2 DM cases, without any lung and/or heart disease and who had neither anemia nor obesity, made up the patient group. They were compared with six female and nine male healthy cases who had the same characteristics with the diabetes cases. All of the cases DLCO were measured by single-breath method and (99m)Tc-DTPA aerosol scintigraphy was performed. DLCO showed no difference between the two groups. Aerosol scintigraphy was significantly decreased in the diabetic group (P=.01). In cases with >5 years of diabetic duration (P<.01), in cases with glycolized hemoglobin (HbA(1c)) </=8% (P<.05) and >8% (P<.05), and in microangiopathic cases (P<.01), alveolo-capillary permeability was significantly decreased than in the control group. Among the same groups, no significant difference could be detected for DLCO. The permeability of alveolar basement membrane can reduce in respect to diabetes duration and poor metabolic control. According to our investigation, (99m)Tc-DTPA aerosol scintigraphy method is more sensitive than DLCO method for determining these pathologies.

Lung function and glucose metabolism: an analysis of data from the Third National Health and Nutrition Examination Survey

Although people with diabetes have decreased lung function, the dose-response relation between measures of glucose control and lung function in nondiabetic people is not known. The authors used data from the Third National Health and Nutrition Examination Survey (1988-1994) to investigate the relation between glucose tolerance test response and other measures of glucose homeostasis and lung function in an adult population without a clinical diagnosis of diabetes. Plasma glucose level 2 hours after oral administration of 75 g of glucose was inversely related to forced expiratory volume in 1 second (FEV(1)), with a difference of -144.7 ml (95% confidence interval: -231.9, -57.4) for persons in the highest quintile of postchallenge glucose compared with the lowest. Similar inverse associations with FEV(1) were found for other measures of glucose autoregulation. Lung function did not appear to be related to fasting glucose level. Similar associations were seen for forced vital capacity (FVC) but not for the FEV(1):FVC ratio. In the total study population, persons with previously diagnosed diabetes had an FEV(1) 119.1 ml (95% confidence interval: -161.5, -76.6) lower than persons without diabetes. This effect was greater in those with poorly controlled diabetes. These findings suggest that impaired glucose autoregulation is associated with impaired lung function.

The diabetic lung: relevance of alveolar microangiopathy for the use of inhaled insulin

The alveolar-capillary network receives the entire cardiac output and constitutes the largest microvascular organ in the body, making it highly susceptible to systemic microangiopathy. Owing to its large reserves, symptoms and disability develop later in the lung than in smaller microvasculature such as the kidney or retina despite a comparable severity of anatomic involvement. Hence, pulmonary impairment in diabetes mellitus is under-recognized. Nonetheless, respiratory autonomic neuropathy and structural derangement of the thorax and lung parenchyma develop in many asymptomatic diabetic patients; the pathophysiology parallels that in other target organs. Even subclinical loss of alveolar microvascular reserves can be quantified noninvasively from lung diffusing capacity and its components (membrane diffusing capacity and alveolar-capillary blood volume) measured at a given cardiac output at rest or during exercise. The alveolar diffusion-perfusion relation tracks the recruitment of microvascular reserves in a manner independent of physical fitness. This article addresses the importance and pathophysiologic basis of diabetic pulmonary involvement, the assessment of diabetic alveolar microangiopathy, and the relevance of this understanding for the emerging use of inhaled insulin.

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.

Alveolar gas exchange in patients with type 2 diabetes mellitus

The present study has been conducted to quantify and compare the capacity of gas exchange in patients with type 2 diabetes mellitus (DM) and healthy controls and also to investigate the effects of various factors on alveolar capillary permeability. A total of 37 subjects, 25 patients with DM and 12 healthy controls were recruited for the study. All the participants were evaluated with simple spirometric tests and simple breath carbonmonoxide (CO) diffusion test (DLCO). The ratio of DLCO value to the alveolar ventilation (VA) was used to assess alveolar membrane permeability. Diabetic patients were also evaluated in detail with respect to degenerative diabetic complications including the presence of microalbuminuria, advanced nephropathy, sensorial and autonomic neuropathy, retinopathy, hypertension and macrovascular disease. The results of simple spirometric tests which determined lung capacity were similar in the diabetic patients and the healthy controls. Ratio of DLCO/VA, which determines alveolar membrane permeability, revealed statistically significant decline in pulmonary gas exchange in the diabetic group (p: 0.037). Pearson correlation analysis revealed statistically significant correlation between duration of diabetes mellitus, age and urinary albumin excretion with DLCO/VA values (Pearson: -0.726, p: 0.001; Pearson: -0.438, p: 0.036; Pearson: -0.472, p: 0.023 respectively). This study demonstrated the decreased alveolar gas exchange capacity in diabetic patients compared with healthy controls. Detrimental effects of DM on alveolar capillaries were found to be correlated with age, duration of DM and urinary albumin excretion. Microalbuminuria was the only significant predictor of DLCO/VA.

Association between glycemic state and lung function: the Framingham Heart Study

Diabetes mellitus has been inconsistently associated with a reduced level of pulmonary function. To elucidate this association further, we analyzed the relationship of diabetes and of fasting blood glucose to the level of pulmonary function assessed by spirometry in the 3,254 members of the Framingham Offspring Cohort. Diabetes was defined as a fasting blood glucose of 126 mg/dl or more or pharmacologic treatment. Subjects were classified as current, former, or never smokers based on questionnaire responses. Predicted pulmonary function was determined from the coefficients of a regression of pulmonary function on age, sex, and body habitus in the 1,110 never smokers. Both the diagnosis of diabetes and a higher level of fasting blood glucose were associated with lower than predicted levels of pulmonary function. The adverse effect of diabetes and glycemic level on pulmonary function was stronger among ever smokers than never smokers, suggesting an interaction between the level of fasting glycemia and tobacco smoking.

Insulin improves alveolar-capillary membrane gas conductance in type 2 diabetes

OBJECTIVE

In type 1 diabetes, lung diffusing capacity for carbon monoxide (DL(CO)) may be impaired, and insulin has been shown to be beneficial in cases in which near-normal metabolic control is achieved. An influence of insulin, per se, on the alveolar-capillary membrane conductance is unexplored. We aimed at testing this possibility.

RESEARCH DESIGN AND METHODS

We studied 19 life-long nonsmoking, asymptomatic patients with type 2 diabetes and normal cardiac function, whose GHb averaged 6.2 +/- 0.3% with diet and hypoglycemic drugs. DL(CO) and its subcomponents (alveolar capillary membrane conductance [D(M)] and pulmonary capillary blood volume available for gas exchange [Vc]), vital capacity (VC), forced expiratory volume 1 s (FEV(1)), cardiac output (CO), ejection fraction (EF), pulmonary wedge pressure (WPP), and pulmonary arteriolar resistance (PAR) were determined before and within 60 min after infusion of 50 ml saline + 10 IU of regular insulin or after saline alone on 2 consecutive days (random block design). Glycemia was kept at baseline levels during experiments by dextrose infusion.

RESULTS

Percent of normal predicted DL(CO) averaged 84.2 +/- 7.9% and in 14 patients was <100%. Insulin infusion, not saline alone, improved (P < 0.01) DL(CO) (12%) and D(M) (14%) and raised DL(CO) to 98% of the normal predicted value. There were no variations in VC, FEV(1,) CO, EF, WPP, or PAR, suggesting that the influences of the hormone on gas transfer were not mediated by changes in spirometry, volumes, and hemodynamics of the lung.

CONCLUSIONS

Several cases of type 2 diabetes present with increased impedance to gas transfer across the alveolar-capillary membrane, and hypoglycemic drugs do not prevent this inconvenience. Insulin, independently of the metabolic effects, acutely improves gas exchange, possibly through a facilitation of the alveolar-capillary interface conductance.

Diabetes worsens pulmonary diffusion in heart failure, and insulin counteracts this effect

Chronic heart failure (CHF) (hydrostatic stress) and diabetes (basal laminae thickening) share the potentiality of damaging the alveolar-capillary membrane. We investigated 15 control subjects and 3 groups of 15 patients each having type 2 diabetes (Group 1), CHF (Group 2), and diabetes and CHF (Group 3), to probe whether addition of diabetes worsens lung diffusion in CHF and whether insulin counteracts this effect. Compared with control subjects, carbon monoxide diffusing capacity (DL(CO)) and diffusing capacity of the alveolar-capillary membrane at rest were increasingly depressed from Group 1 through Group 3. DL(CO) was lower than predicted in 11 patients each in Groups 1 and 2 and in all patients in Group 3. Regular insulin (10 IU) was ineffective in CHF alone, whereas it improved DL(CO) and diffusing capacity of the alveolar-capillary membrane in diabetes; changes, however, were significantly greater in the patients with both diabetes and CHF (+17.6%, +27.3%) than in those with diabetes alone (+9.2%, +13.1%). Insulin did not affect lung spirometry, volumes, and hemodynamics. Thus, gas transfer is depressed in a number of patients with diabetes or CHF; comorbidity increases the frequency and extent of this disorder. Insulin facilitates diffusion in diabetes, through an influence on alveolar-capillary conductance, and its efficacy is greater in comorbidity; diabetes is more disturbing in patients with CHF and produces a synergistic rather than a simple additive effect.

Effect of non-insulin-dependent diabetes mellitus on pulmonary function and exercise tolerance in chronic congestive heart failure

In chronic congestive heart failure (CHF), backward effects of left ventricular dysfunction alter pulmonary volumes and gas diffusion. Some of these disorders are detected in some patients with diabetes mellitus, possibly due to a microangiopathic process and nonenzymatic glycosylation of lung tissue proteins. We explored the possibility that coexistence of non-insulin-dependent diabetes mellitus (NIDDM) may potentiate the deterioration of lung function in CHF. In 20 normoglycemic patients (group 1) and in 20 patients with NIDDM (group 2), with New York Heart Association class II to III CHF due to idiopathic or ischemic cardiac disease, and in 20 controls (groups were age- and gender-matched), we investigated cardiac function, pulmonary volumes, carbon monoxide diffusion (DL(CO)) and its alveolar-capillary membrane (D(M)) subcomponent, oxygen uptake and dead space-to-tidal volume ratio (pVD/VT) at peak exercise (individualized ramp test), and slope of ventilation-to-carbon dioxide production ratio (VE/VCO(2)) during exercise. Although, compared with reference subjects, both patient groups had similar variations in left ventricular diastolic volume, ejection fraction, and pulmonary wedge pressure; in group 2 lung volumes, DL(CO), D(M), and oxygen uptake were significantly more reduced; in this group there was no overlap of individual results of DL(CO) and D(M) with those in controls; VE/VCO(2) slope and pVD/VT also were significantly increased, and inversely correlated with D(M). Thus, coexistence of NIDDM makes pulmonary dysfunction worse in CHF, and significantly enhances exercise intolerance.

Spirometric reference equations for older adults

The objective of this study was to develop spirometric reference equations for healthy, never-smoking, older adults. It was designed as a cross-sectional observational study consisting of 1510 Seventh Day Adventists, ages 43-79 years enrolled in a study of health effects of air pollutants. Individuals were excluded from the reference group (n = 565) for a history of current respiratory illness, smoking, or chronic respiratory disease, and for a number of 'non-respiratory' conditions which were observed in these data to be related to lower values of FEV1. Gender-specific reference equations were developed for the entire reference group and for a subset above 65 years of age (n = 312). Controlling for height and age, lung function was found to be positively related to the difference between armspan and height, and in males was found to be quadratically related to age. The predicted values for this population generally fell within the range of those of other population groups containing large numbers of adults over the age of 65 years. Individuals with lung function below the 5th percentile in this sample, however, could not be reliably identified by using the lower limits of normal predictions commonly used in North America and Europe.

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.

Indications of reduced pulmonary function in type 1 (insulin-dependent) diabetes mellitus

Abnormalities of pulmonary function tests have been described in type 1 (insulin-dependent) diabetes mellitus (IDDM). To better characterise such abnormalities and to verify whether these latter are associated with the presence of diabetic microvascular disease we compared 23 non-smoking patients who had IDDM with 24 non-smoking healthy control subjects strictly matched for sex, age, and body mass index. Compared with controls, diabetic patients had a reduced forced vital capacity (FVC) (87.5 +/- 13.1% vs. 96.4 +/- 13.6% of the predicted; P = 0.03) and forced expiratory volume in 1 s (FEV1) (90.5 +/- 17.7% vs. 101.2 +/- 13.2% of the predicted; P = 0.02). While within the group of patients the presence of retinopathy and autonomic neuropathy were not associated with modifications of pulmonary function tests, those with altered urinary albumin excretion rate (AER > or = 20 micrograms/min; range 21-589) (n = 7) had a significantly lower pulmonary diffusion capacity (DLCO) than the 16 normoalbuminuric subjects (62.6 +/- 7.2% vs. 88.7 +/- 20.1% of the predicted; P = 0.01). Moreover, in the group of patients, DLCO was inversely related with AER (r = -0.43; P = 0.04). In conclusion, IDDM is characterised by reduced FVC and FEV1, while a significant decrease in DLCO may be considered as selectively associated with renal disease.

Pulmonary complications of type 1 (insulin-dependent) diabetic patients

We have investigated the influence of diabetes mellitus including the presence of late complications of the pulmonary system. To check this relationship 31 Type 1 (insulin-dependent) diabetic patients (mean age 30.6 +/- 5.32 years, mean duration of diabetes 12.9 +/- 5.05 years) were admitted into the trial and compared with 18 control subjects. Pulmonary function tests were measured including spirometric parameters, diffusing capacity, specific diffusing capacity and dynamic compliance measured at 20 and 60 breaths per min. No disturbance of the spirometric parameters was observed in the diabetic patients. Diffusing capacity in the diabetic patients with complications was significantly lower than in both the diabetic patients without complications and the control group (81.2 +/- 16.2%, 104 +/- 13.7%, 99.3 +/- 2.8%; p < 0.001, p < 0.005 respectively). Specific diffusing capacity was significantly lower in the diabetic patients than in the control subjects (80.3 +/- 13.1% vs 89.4 +/- 12.9%; p < 0.05). In the group with late complications specific diffusing capacity was lower than in the group without complications (69.7 +/- 9.17%; 87.2 +/- 10.7%, respectively; p < 0.001). Dynamic compliance at 20 breaths per min in diabetic patients was 84.06 +/- 17.08% vs 95.2 +/- 11.59% in the control subjects (p < 0.05). It was particularly low in the group with late complications 80.6 +/- 13.2% and patients with metabolic poor control, 80.3 +/- 12.02% (both p < 0.005 vs the control group). Dynamic compliance at 60 breaths per min was 60.1 +/- 15.0% as compared to 83.2 +/- 13.3% in the control group (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary gas exchange and oxygen uptake during exercise in patients with type 1 diabetes mellitus

In order to investigate pulmonary gas exchange and cardiopulmonary performance in Type 1 diabetes, 36 patients underwent a progressive incremental exercise test on a cycle ergometer. Cardiopulmonary variables were measured, and arterial blood gases determined on samples obtained from an indwelling catheter in the radial artery. The results were compared with those from 40 control subjects. In the patients, the maximum power (Wmax) and maximum oxygen uptake (VO2max) were lower than in the control subjects (Wmax 186 +/- 52 (+/- SD) vs 233 +/- 48 W, p less than 0.05; VO2max 2.56 +/- 0.71 vs 3.17 + 0.77 l min-1, p less than 0.05). At comparable levels of power output, however, no significant abnormality was observed in the difference between alveolar and arterial oxygen pressure (P(A-a)O2), and the ratio of physiological dead space to tidal volume (VD/VT ratio). These data indicate that in Type 1 diabetic patients, despite their reduced maximum oxygen uptake, gas transfer during exercise is not limited and thus does not contribute to the impairment of exercise capacity.