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

Evaluation of Pulmonary Functions in Children with Type 1 Diabetes Mellitus: A Case-Control Study

Type 1 diabetes mellitus (T1DM) is one of the most prevalent chronic diseases in children and adolescents with the risk of development and progression of chronic complications. This study evaluates the pulmonary functions with spirometry in children with T1DM in relation with glycemic control. Ninety-six children with T1DM were matched with 102 healthy controls. All the spirometry parameters including FVC, FEV1, FEV1/FVC, PEFR, and MMFR were significantly reduced (p = < 0.001) in T1DM patients when compared with the controls. Compared to the children with fair glycemic control, the children with poor glycemic control were seen to have a significant decrease in FEV1 (p = 0.001) and FVC (p = 0.001) with no significant change in FEV1/FVC ratio (p = 0.9), PEFR (p = 0.4) and MMFR (p = 0.1). Restrictive lung pattern was the most common pulmonary dysfunction in children with T1DM and it worsened with poor glycemic control. This necessitates the need for adequate glycemic control and periodic lung function assessment.

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.

When kidneys and lungs suffer together

A significant interaction between kidneys and lungs has been shown in physiological and pathological conditions. The two organs can both be targets of the same systemic disease (eg., some vasculitides). Moreover, loss of normal function of either of them can induce direct and indirect dysregulation of the other one. Subjects suffering from COPD may have systemic inflammation, hypoxemia, endothelial dysfunction, increased sympathetic activation and increased aortic stiffness. As well as the exposure to nicotine, all the foresaid factors can induce a microvascular damage, albuminuria, and a worsening of renal function. Renal failure in COPD can be unrecognized since elderly and frail patients may have normal serum creatinine concentration. Lungs and kidneys participate in maintaining the acid-base balance. Compensatory role of the lungs rapidly expresses through an increase or reduction of ventilation. Renal compensation usually requires a few days as it is achieved through changes in bicarbonate reabsorption. Chronic kidney disease and end-stage renal diseases increase the risk of pneumonia. Vaccination against Streptococcus pneumonia and seasonal influenza is recommended for these patients. Vaccines against the last very virulent H1N1 influenza A strain are also available and effective. Acute lung injury and acute kidney injury are frequent complications in critical illnesses, associated with high morbidity and mortality. The concomitant failure of kidneys and lungs implies a multidisciplinary approach, both in terms of diagnostic processes and therapeutic management.

Differential Patterns of Impaired Cardiorespiratory Fitness and Cardiac Autonomic Dysfunction in Recently Diagnosed Type 1 and Type 2 Diabetes

OBJECTIVE

Both impaired cardiorespiratory fitness (CRF) and heart rate variability (HRV) are predictors of mortality, but their relative roles in recent-onset diabetes are unknown. We determined to which extent CRF and HRV are reduced and interrelated in recent-onset diabetes.

RESEARCH DESIGN AND METHODS

Participants from the German Diabetes Study with type 1 (n = 163) or type 2 (n = 188) diabetes with known diabetes duration <1 year and two age-matched glucose-tolerant control groups (n = 40 each) underwent spiroergometry and HRV assessment during a hyperinsulinemic-euglycemic clamp.

RESULTS

Compared with control subjects, patients with type 2 diabetes showed reduced VO_2max (median [1st-3rd quartiles] 19.3 [16.5-22.9] vs. 25.6 [20.7-29.9] mL/kg body weight/min; P < 0.05), diminished VCO_2max (23.0 [19.1-26.8] vs. 30.9 [24.5-34.4] mL/kg body weight/min; P < 0.05), blunted heart rate recovery after 2 min (-29.0 [-35.0 to -23.0] vs. -36.0 [-42.8 to -28.0] beats/min; P < 0.05), and reduced HRV in four of nine indices, whereas patients with type 1 diabetes had unaltered CRF but reduced HRV in three of nine indices (P < 0.05), indicating diminished vagal and sympathetic HRV modulation. HRV measures correlated with VO_2max in patients with type 1 diabetes (r >0.34; P < 0.05) but not in those with type 2 diabetes.

CONCLUSIONS

CRF is reduced in recently diagnosed type 2 diabetes but preserved in type 1 diabetes, whereas cardiac autonomic function is reduced in both diabetes types but is strongly associated with CRF only in type 1 diabetes. These results support the therapeutic concept of promoting physical fitness in the early course of diabetes.

Type 1 Diabetes Duration Decreases Pulmonary Diffusing Capacity during Exercise

BACKGROUND

Diabetes damages peripheral tissues; however, its effects on the lung are less known. Lung diffusing capacity (DLCO) is influenced by alveolar-capillary membrane conductance (DM) and pulmonary capillary blood volume (VC), both of which are reduced in adults with type 1 diabetes (T1D).

OBJECTIVE

We sought to determine if diabetes duration affects DLCO, DM, VC, and cardiac output (Q).

METHODS

24 T1D patients (10.7-52.8 years) and 24 non-diabetic controls were recruited and had DLCO, DM, VC, and Q measured at rest and during exercise (40, 70 and 90% VO2max).

RESULTS

When stratified into two groups based on age (young, <20.6 years old), there were no significant differences in DLCO, DM, VC, or Q (all of which were normalized to body surface area [BSA]) in the young group or in the old group. When stratified by diabetes duration (short duration, 0.33-8.9 years vs. long duration, 9.6-28 years), the T1D patients in the long duration group had lower DLCO/BSA and DM/BSA compared to the controls (p < 0.05). There were no differences in any of the variables in the short duration group.

CONCLUSIONS

This study has shown that duration of diabetes is associated with decrements in diffusing capacity and its components.

Subsequent mortality after hyperglycemic crisis episode in the non-elderly: a national population-based cohort study

Hyperglycemic crisis episodes (HCEs)-diabetic ketoacidosis and the hyperosmolar hyperglycemic state-are the most serious acute metabolic complications of diabetes. We aimed to investigate the subsequent mortality after HCE in the non-elderly diabetic which is still unclear. This retrospective national population-based cohort study reviewed, in Taiwan's National Health Insurance Research Database, data from 23,079 non-elder patients (≤65 years) with new-onset diabetes between 2000 and 2002: 7693 patients with HCE and 15,386 patients without HCE (1:2). Both groups were compared, and follow-up prognoses were done until 2011. One thousand eighty-five (14.1%) patients with HCE and 725 (4.71%) patients without HCE died (P < 0.0001) during follow-up. Incidence rate ratios (IRR) of mortality were 3.24 times higher in patients with HCE than in patients without HCE (P < 0.0001). Individual analysis of diabetic ketoacidosis and hyperosmolar hyperglycemic state also showed the similar result with combination of both. After stratification by age, mortality was significant higher in the middle age (40-64 years) [IRR 3.29; 95% confidence interval (CI) 2.98-3.64] and young adult (18-39 years) (IRR 3.91; 95% CI 3.28-4.66), but not in the pediatric subgroup (<18 years) (IRR 1.28; 95% CI 0.21-7.64). The mortality risk was highest in the first month (IRR 54.43; 95% CI 27.98-105.89), and still high after 8 years (IRR 2.05; 95% CI 1.55-2.71). After adjusting for age, gender, and selected comorbidities, the mortality hazard ratio for patients with HCE was still four times higher than for patients without HCE. Moreover, older age, male gender, stroke, cancer, chronic obstructive pulmonary disease, congestive heart failure, and liver disease were independent mortality predictors. HCE significantly increases the subsequent mortality risk in the non-elderly with diabetes. Strategies for prevention and control of comorbidities are needed as soon as possible.

Type 2 diabetes affects sleep quality by disrupting the respiratory function

BACKGROUND

The effects of diabetes on the respiratory system were investigated with arterial blood gas, sleep quality index and respiratory functions tests.

METHODS

Fifty-three patients with type II diabetes and 41 healthy cases were included. Their biochemical data, demographic characteristics, anthropometric measurements and echocardiographic findings were collected from polyclinic records. Respiratory function tests were performed for all subjects and Pittsburgh Sleep Quality Index questionnaire was conducted. Aforementioned data were compared between these two groups.

RESULTS

The age, body weight and body mass index were similar but oxygen pressure, oxygen saturation, forced vital capacity (FVC; %), and sleep quality were decreased in patients with diabetes. Sleep quality was correlated with the presence of diabetes and hypertension, duration of diabetes, fasting and postprandial blood glucose levels, homeostasis model of assessment-insulin resistance, Glycosylated hemoglobin levels, and FVC. Half of the diabetic patients exhibited respiratory failure during sleep. Especially diabetic patients with autonomic neuropathy, experienced a more severe and prolonged decrease in oxygen saturation.

CONCLUSIONS

Blood gas, respiratory functions and sleep quality, which need to be evaluated as a whole, were affected in patients with diabetes. Assessment of sleep and its quality requires special attention in patients with diabetes.

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.

The role of 8-oxoguanine DNA glycosylase-1 in inflammation

Many, if not all, environmental pollutants/chemicals and infectious agents increase intracellular levels of reactive oxygen species (ROS) at the site of exposure. ROS not only function as intracellular signaling entities, but also induce damage to cellular molecules including DNA. Among the several dozen ROS-induced DNA base lesions generated in the genome, 8-oxo-7,8-dihydroguanine (8-oxoG) is one of the most abundant because of guanine’s lowest redox potential among DNA bases. In mammalian cells, 8-oxoG is repaired by the 8-oxoguanine DNA glycosylase-1 (OGG1)-initiated DNA base excision repair pathway (OGG1–BER). Accumulation of 8-oxoG in DNA has traditionally been associated with mutagenesis, as well as various human diseases and aging processes, while the free 8-oxoG base in body fluids is one of the best biomarkers of ongoing pathophysiological processes. In this review, we discuss the biological significance of the 8-oxoG base and particularly the role of OGG1–BER in the activation of small GTPases and changes in gene expression, including those that regulate pro-inflammatory chemokines/cytokines and cause inflammation.

Phrenic neuropathy in diabetic and prediabetic patients without neuromuscular complaint

Neuropathy, one of the major reasons of morbidity in diabetes mellitus (DM), is associated with prediabetic conditions as well as DM. The present study aims to compare phrenic and peripheral nerves in prediabetic, diabetic patients and healthy controls. A total of 37 diabetic, 40 prediabetic patients and 18 healthy controls were enrolled in the study. All subjects underwent conventional sensory and motor nerve conduction studies. Bilateral phrenic and peripheric nerve conduction studies were performed. In both right and left phrenic nerves, the amplitudes were lower in prediabetic and diabetic patients than control subjects, respectively (p: 0.005 and p: 0.001). Both of the phrenic nerve conductions were altered similarly. The results of our study demonstrate that phrenic nerves are affected like peripheric nerves in prediabetic and diabetic patients. We suggest reminding phrenic neuropathy in newly onset respiratory failure in diabetic and prediabetic patients.

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.

The diabetic lung--a new target organ?

Several abnormalities of the respiratory function have been reported in patients with type 1 and type 2 diabetes. These abnormalities concern lung volume, pulmonary diffusing capacity, control of ventilation, bronchomotor tone, and neuroadrenergic bronchial innervation. Many hypotheses have emerged, and characteristic histological changes have been described in the "diabetic lung", which could explain this abnormal respiratory function. Given the specific abnormalities in diabetic patients, the lung could thus be considered as a target organ in diabetes. Although the practical implications of these functional changes are mild, the presence of an associated acute or chronic pulmonary and/or cardiac disease could determine severe respiratory derangements in diabetic patients. Another clinical consequence of the pulmonary involvement in diabetes is the accelerated decline in respiratory function. The rate of decline in respiratory function in diabetics has been found to be two-to-three times faster than in normal non-smoking subjects, as reported in longitudinal studies. This finding, together with the presence of anatomical and biological changes similar to those described in the aging lung, indicates that the "diabetic lung" could even be considered a model of accelerated aging. This review describes and analyses the current insight into the relationship of diabetes and lung disease, and suggests intensifying research into the lung as a possible target organ in diabetes.

Pulmonary diffusing capacity for carbon monoxide: a marker of depressed hypercapnic drive in type 1 diabetes mellitus?

AIMS

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.

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.

Pancreas transplantation prevents morphologic and ultrastructural changes in pulmonary parenchyma of alloxan-induced diabetic rats

PURPOSE

The aim of this study was to evaluate whether pancreas transplantation (PT) is a suitable method for controlling histopathologic changes in lungs of alloxan-induced diabetic rats.

METHODS

Sixty inbred male Lewis rats were randomly assigned to 3 experimental groups: NC, 20 nondiabetic control rats; DC, 20 untreated diabetic control rats; and PT, 20 diabetic rats that received syngeneic PT from normal donor Lewis rats. Each group was further divided into 2 subgroups of 10 rats each, which were killed after 4 and 12 weeks of follow-up. Clinical and laboratory parameters, fresh and fixed lung weights, and fixed lung volumes were recorded for all rats. Total number of alveoli, alveolar perimeter, alveolar surface area, and alveolar epithelial (AE) and endothelial capillary (EC) basal laminae thickening were randomly measured in 5 rats from each subgroup by using an image analyzer. For light microscopy, 250 alveoli were analyzed in each subgroup. For electron microscopy, 50 electron micrographs were examined for each subgroup.

RESULTS

The DC rats showed elevated blood glucose and glycosylated hemoglobin levels, with insulin blood levels significantly lower than the NC rats (P < .001). Fresh and fixed lung weights and fixed volumes were significantly reduced in these rats, although their proportions to body weight were increased at 12 weeks (P < .01). The total number of alveoli in diabetic rats was higher than in control rats, whereas alveolar perimeter and surface area were significantly diminished (P < .01). AE and EC basal laminae were significantly thicker in DC than in NC (P < .01). Successful PT corrected all clinical and metabolic changes in diabetic rats, with sustained normoglycemia throughout the study. Morphologic and morphometric changes observed in diabetic lungs were completely prevented in PT rats from 4 weeks after transplant.

CONCLUSION

We conclude that PT can control morphologic and ultrastructural changes in pulmonary parenchyma, suggesting a promising perspective for preventing other chronic diabetic lesions.

Glycemic status affects cardiopulmonary exercise response in athletes with type I diabetes

PURPOSE

This study aimed to (a) examine the influence of type I diabetes on the cardiopulmonary exercise response in trained subjects and (b) determine whether glycemic control affects these responses.

METHODS

The cardiopulmonary responses to maximal incremental cycle ergometry were compared in 12 Ironman triathletes with type I diabetes and 10 age- and sex-matched control subjects without diabetes. Athletes with type I diabetes were then stratified into low- (glycosylated hemoglobin (HbA1c) < 7%, n = 5) and high-HbA1c (HbA1c > 7%, n = 7) groups for comparison. Cardiac output, stroke volume, arterial blood pressure, and calculated systemic vascular resistance along with airway function were measured at rest and during steady-state exercise.

RESULTS

During peak exercise HR, stroke volume and cardiac output were not different between the groups with and without diabetes; however, forced expiratory flow at 50% of the forced vital capacity was lower in subjects with diabetes (P < 0.05). Within the group with diabetes, HbA1c was lower in the low-HbA1c versus high-HbA1c group (6.5 +/- 0.3 vs 7.8 +/- 0.4, respectively; P < 0.05), but training volume was not different. At rest, the low-HbA1c group had greater cardiac output and lower systemic vascular resistance than the high-HbA1c group, and all pulmonary function measurements were greater in the low-HbA1c group (P < 0.05). During peak exercise, the VO2, workload, HR, stroke volume, and cardiac output were greater in the low-HbA1c versus the high-HbA1c group (P < 0.05). In addition, all indices of pulmonary function were higher in the low-HbA1c group (P < 0.05). Finally, within the subjects with diabetes, there was a weak inverse correlation between HbA1c and exercise training volume (r2 = -0.352) and stroke volume (r2 = -0.339). These data suggest that highly trained individuals with type I diabetes can achieve the same cardiopulmonary exercise responses as trained subjects without diabetes, but these responses are reduced by poor glycemic control.

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.

Patients diagnosed with diabetes are at increased risk for asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and pneumonia but not lung cancer

OBJECTIVE

There are limited data on the risk of pulmonary disease in patients with diabetes. The aim of this study was to evaluate and compare the incidence of asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, pneumonia, and lung cancer in patients with and without a diagnosis of diabetes.

RESEARCH DESIGN AND METHODS

We conducted a retrospective, longitudinal cohort study using the electronic records of a large health plan in northern California. Age and sex data were available for all cohort members (n = 1,811,228). Data on confounders were available for a subcohort that responded to surveys (n = 121,886), among whom Cox proportional hazards regression models were fit.

RESULTS

Age- and sex-adjusted incidence rates and 95% CIs were calculated for members with and without diabetes in the full cohort and the subcohort. No difference was observed for lung cancer, but the incidence of asthma, COPD, fibrosis, and pneumonia was significantly higher in those members with a diagnosis of diabetes. These differences remained significant in regression models adjusted for age, sex, race/ethnicity, smoking, BMI, education, alcohol consumption, and outpatient visits (asthma hazard ratio [HR] 1.08 [95% CI 1.03-1.12], COPD HR 1.22 [1.15-1.28], pulmonary fibrosis HR 1.54 [1.31-1.81], and pneumonia HR 1.92 [1.84-1.99]). The risk of pneumonia and COPD increased significantly with increasing A1C.

CONCLUSIONS

Individuals with diabetes are at increased risk of several pulmonary conditions (asthma, COPD, fibrosis, and pneumonia) but not lung cancer. This increased risk may be a consequence of declining lung function in patients with diabetes.

The assessment of pulmonary diffusing capacity in diabetes mellitus with regard to microalbuminuria

OBJECTIVE

The current study was conducted to determine whether or not the lung is one of the target organs in the development of vascular complications in diabetic patients. We also investigated the relationship between pulmonary diffusing capacity and microalbuminuria.

MATERIALS AND METHODS

A total of 68 patients with type 2 diabetes and 44 with type 1 diabetes (male/female [M/F] n=19/49 and 15/29; age: 52.4+/-8.8 and 32.5+/-11 years;) and 80 healthy controls (M/F=22/58; age=40.1+/-12.4 years) were recruited for the study. All of the participants were evaluated with simple spirometric tests and a simple breath carbon monoxide (CO) diffusion test. CO lung diffusion capacity (DLCO) and the ratio of DLCO value to the alveolar volume (VA) were used to assess alveolar membrane permeability (DLCO/VA). Urinary albumin excretion (UAE) per day of the participants was also evaluated.

RESULTS

DLCO, DLCO% and DLCO/VA% values were significantly lower in diabetics than in the control group (p=0.006; p=0.039; p=0.003, respectively). UAE was inversely correlated with DLCO, DLCO/VA, DLCO/VA% and DLCO% (p=0.050; p=<0.001; p=0.001; p=0.004, respectively).

CONCLUSION

This study demonstrated that alveolar gas exchange capacity is significantly decreased in diabetic patients. Microalbuminuria may be one of the predictors of this decline.

The relationship between nitric oxide and leptin in the lung of rat with streptozotocin-induced diabetes

Lung structural changes and immunoreactivity of endothelial (eNOS)- and inducible nitric oxide synthase (iNOS) were investigated by light microscopy in lungs of treated and untreated diabetic rats. Diabetes was induced by a single intraperitoneal (i.p.) injection of 65 mg kg(-1) streptozotocin (STZ) in Wistar albino male rats. Diabetic rats received daily i.p. doses of dexamethasone (2 mg kg(-1)), leptin (0.5 microg kg(-1)) and intramuscular insulin (20 U kg(-1)) or a combination of these drugs for 1 week starting 4 weeks after the STZ injections. After treatment, the blood levels of glucose, leptin, insulin and nitrate/nitrite (NO(3) (-)/NO(2) (-)) were measured. Dilatation of alveoli and alveolar ducts, partial alveolar wall thickening and increased eNOS- and iNOS characterized the diabetic rat lungs. High blood glucose and nitrate/nitrite levels as well as low insulin and leptin levels were also present. Treatment with insulin, dexamethasone and a combination of these drugs resulted in improvement of the structural and immunohistochemical abnormalities. The most effective treatment was insulin therapy. Leptin administration resulted in increased relative amounts of extracellular material, which led to noticeable respiratory efficiency in the diabetic rat lungs. All treatments except leptin lowered blood glucose levels. The combination of insulin and dexamethasone increased blood leptin and insulin, while the remaining diabetic rats had blood with low leptin and insulin concentrations. These results suggest that therapy with insulin plus dexamethasone but not therapy with leptin is beneficial for diabetics.

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.

Effect of duration of disease on ventilatory function in an ethnic Saudi group of diabetic patients

BACKGROUND

Diabetes mellitus is a leading cause of illness and death across the world and is responsible for a growing proportion of global health care expenditures. The present study was designed to observe the effect of diabetes mellitus on lung function in patients with diabetes belonging to a specific ethnic group, namely Saudis.

METHOD

In this study, a group of 47 apparently healthy volunteer male Saudi patients with diabetes was randomly selected. Their ages ranged from 20 to 70 years. The patients were matched with another group of 50 healthy male control subjects in terms of age, height, weight, ethnicity, and socioeconomic status. Both groups met exclusion criteria as per standard. Spirometry was performed with an electronic spirometer (Schiller AT-2 Plus, Switzerland), and results were compared by a Student's t test.

RESULTS

Subjects with diabetes showed a significant reduction in forced vital capacity (FVC) and forced expiratory volume in the first second (FEV(1)) relative to their matched controls. However, there were no significant differences in the forced expiratory ratio (FEV(1)/FVC%) and the middle half of the FVC (FEF(25-75%)) between the groups. We observed a significantly negative correlation between duration of disease and pulmonary function, as measured by FEV(1) (r = 0.258, p = 0.04), FVC (r = 0.282, p = 0.28), and the middle half of the FVC (FEF(25-75%)) (r = 0.321, p = 0.014).

CONCLUSIONS

Pulmonary function in a specific ethnic group of patients with diabetes was impaired as evidenced by a decrease in FVC and FEV(1) compared to pulmonary function in matched controls. Stratification of results by years of disease revealed a significant correlation between duration of disease and a decline in pulmonary function.

Pulmonary Function in Patients With Type 1 Diabetes Before and After Simultaneous Pancreas and Kidney Transplantation

INTRODUCTION

Pulmonary function is impaired in type 1 diabetes mellitus and is associated with the quality of metabolic control. Correction of chronic hyperglycemia by pancreas transplantation may ameliorate pulmonary function.

METHODS

Lung volume and diffusing capacity were measured in 75 uremic patients with type 1 diabetes and a long diabetes duration waiting for a simultaneous kidney and pancreas transplantation (SPK). In addition 85 patients after SPK and 20 patients after kidney transplantation alone (KA) were investigated. In a subgroup of 30 patients, data before and after SPK were available for prospective analysis.

RESULTS

Reduced lung volume and diffusing capacity were found in type 1 diabetic patients before transplantation. Nearly all parameters of pulmonary function improved after SPK and KA. A significant change was found for forced expiratory volume at 1 sec (FEV1) and FEV1/forced vital capacity (FVC) (Tiffenau index). A significant amelioration of diffusing capacity was only found in the SPK group but not in the KA group. The prospective investigation revealed significant improvements of pulmonary function after SPK: FEV1 (P=0.001), FVC, (P=0,006), Tiffenau index (P=0.03), and Hb-corrected diffusing capacity (carbon monoxide transfer factor, TCO), P=0.03; transfer coefficient (KCO=TCO corrected for alveolar volume), P=0.01.

CONCLUSION

Simultaneous pancreas and kidney transplantation is able to attain long-term normoglycemia and to improve pulmonary function in uremic type 1 diabetic patients.

The challenges of chronic obstructive pulmonary diseases (COPD)--a perspective

Chronic Obstructive Pulmonary Disease (COPD) is an inflammatory disease, primarily caused by cigarette smoke, which will soon become the third leading cause of death globally. Despite the importance of the problem, our real understanding of the biological underpinnings of COPD remains incomplete. Consequently, our first-line therapies, while helpful, are not yet as effective as they need to be. In this review, we will focus on these challenges and more, including the role of impaired tissue repair and adaptive immunity in disease pathogenesis, determining who may be at risk, describing COPD phenotypes and potential biomarkers. New ideas for chronic disease management and prevention of exacerbations will also be discussed. While much remains to be accomplished, meeting these challenges will bring rewards because what we learn will have implications for the understanding and treatment of chronic inflammatory diseases beyond COPD.

Dissociation of Lung Function Changes with Humoral Immunity during Inhaled Human Insulin Therapy

RATIONALE

Inhaled human insulin (INH; Exubera [human insulin (recombinant DNA origin) Inhalation Powder]) causes small changes in pulmonary function and increases in insulin antibodies compared with subcutaneous (SC) insulin.

OBJECTIVES

To investigate the relationship between changes in pulmonary function and insulin antibodies and acute effects of INH on lung function.

METHODS

In a 24-wk multicenter study, 226 patients with type 1 diabetes were randomized to receive daily premeal INH or SC insulin for 12 wk (comparative phase), followed by SC insulin for 12 wk (washout phase).

MEASUREMENTS

Spirometry tests were conducted and insulin antibody levels were measured throughout the study. Acute insulin-induced changes in lung function were calculated as the difference between FEV1 before, and 10 and 60 min after, insulin.

MAIN RESULTS

There was a temporal dissociation between pulmonary function changes and insulin antibody generation. Small treatment group differences in changes in FEV1 from baseline, favoring SC insulin, were fully manifest by 2 wk of INH therapy, did not increase during the remainder of the comparative phase, and resolved within 2 wk of INH discontinuation. By contrast, insulin antibody levels remained low for the first 2 wk with INH, increased during Weeks 2 to 12, and gradually declined during washout. There was no evidence of acute insulin-induced alterations in lung function 10 and 60 min postinhalation.

CONCLUSION

The small lung function changes observed with INH therapy are not mediated by the humoral immune response, or associated with acute decrements in lung function immediately after insulin inhalation.

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.

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.

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.

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.

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.

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.

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.

Impairment of ventilatory response to metabolic acidosis in insulin-dependent diabetic patients with advanced nephropathy

Sudden cardiopulmonary arrest due to a defective respiratory reflex is observed in diabetic patients. Impaired ventilatory response in diabetic patients to acute hypoxia or hypercapnia induced by the inhalation of an artificial gas has been reported. Little is known regarding the respiratory compensatory ability for mild to moderate metabolic acidosis due to renal failure in insulin-dependent diabetic subjects. Arterial blood pH, HCO3-, PaCO2 and PaO2 were measured in 13 insulin-dependent diabetic subjects with advanced nephropathy and in 33 non-diabetic subjects with end-stage renal failure. The diabetic group consisted of six predialysis patients and seven on regular hemodialysis (HD) and the non-diabetic group, ten predialysis patients and 23 on HD. Differences between measured partial arterial pressure of carbon dioxide (PaCO2) and predicted PaCO2 determined from HCO3- were examined. PaCO2 was significantly higher in the diabetic than in non-diabetic group (40.0 +/- 7.4 versus 31.1 +/- 5.1 mmHg, p < 0.05 in predialysis, 42.0 +/- 6.4 versus 36.0 +/- 2.6 mmHg, p < 0.05 in HD), though plasma pH was essentially the same for either. Differences in measured PaCO2 and predicted PaCO2 were significantly larger in the diabetic group than in non-diabetic group. Ventilatory response to uremic acidosis may thus be considered impaired in subjects with advanced diabetic nephropathy.

Respiratory muscle function and hypoxic ventilatory control in patients with type I diabetes

STUDY OBJECTIVES

The interaction among pulmonary mechanics, respiratory muscle performance, and ventilatory control in subjects with insulin-dependent diabetes mellitus has so far received little attention. We therefore decided to assess the role of central factors and peripheral factors on the ventilatory response to a hypoxic stimulus in type I diabetic patients.

SUBJECTS

Eight patients in stable condition aged 19 to 48 years old, with insulin-dependent diabetes mellitus (duration of the disease, 36 to 240 months) and no history of smoking, cardiopulmonary involvement, or autonomic neuropathy; and an age- and gender-matched control group.

MEASUREMENTS

In each patient, we measured the following: pulmonary volumes; diffusing capacity of the lung for carbon monoxide (D(LCO)); time and volume components of ventilation (tidal volume [V(T)] and respiratory frequency); static compliance (Clstat) and dynamic compliance (Cldyn); swings in pleural pressure (Pes) and gastric pressure (Pg); and transdiaphragmatic pressure (Pdi), obtained by subtracting Pes from Pg. Maximal inspiratory Pes and Pdi during a maximal sniff maneuver were also measured. Swings in Pes and Pdi during V(T) as a percentage of Pes and Pdi during the maximal sniff maneuver [Pessw(%Pessn) and Pdisw(%Pdisn), respectively] were both considered as a measure of central respiratory output, and the Pessw(%Pessn)/V(T) ratio was considered as an index of neuroventilatory dissociation (NVD) of the inspiratory pump. Subjects were studied at baseline and during hypoxic rebreathing.

RESULTS

Pulmonary volumes and D(LCO) were normal or slightly reduced. A lower Cldyn, higher central respiratory output, and NVD were found. During hypoxic rebreathing, patients had lower V(T), similar central respiratory output, and greater NVD per unit change in arterial oxygen saturation compared with values in control subjects. An increase in dynamic elastance, computed as 1/Cldyn, during hypoxia was found in patients, but not in normal subjects, and was directly related to concurrent changes in NVD.

CONCLUSIONS

We have shown that the assessment of a normal Clstat and normal routine parameters of airway obstruction does not permit the definite exclusion of the role of peripheral airway involvement in insulin-dependent diabetes mellitus. Peripheral airway involvement is likely to influence indices of hypoxic ventilator) drive by modulating a normal central motor output into a rapid and shallow pattern of ventilatory response.

Reduction of diffusion capacity for carbon monoxide in diabetic patients

Diabetes can cause the development of pulmonary complications due to collagen and elastin changes, as well as microangiopathy. This study demonstrates the relationship between pulmonary complications and other chronic complications in diabetes. Twenty-seven patients with diabetes, aged 21 to 62 years, who had had the disease from 3 to 32 years, were included in this study. The protein excretion rate (PER) and the diffusion capacity of the lung for carbon monoxide (DLCO) were included as parameters of the severity of complications. PER was determined by the Biuret method. DLCO was measured by the single-breath method and was corrected by the measurement of alveolar volume (VA). The values of DLCO as corrected by VA (DLCO/VA) were included in the statistical evaluation of the results. The variables of age, duration of diabetes, and complication parameters were included in a multiple regression model with forward, stepwise selection to assess their value in predicting DLCO/VA. The variables were found to be significant predictors of DLCO/VA (R2 = 0.46, adjusted R2 = 0.32, p < 0.022). However, proteinuria was the only significant independent predictor of DLCO/VA. This finding indicates that both renal and pulmonary complications of diabetes share a similar microangiopathic background.