The association between blood oxygen saturation and baroreflex sensitivity in adults with type 1 diabetes with and without albuminuria.

BACKGROUND: Low baroreflex sensitivity is an indicator of early cardiovascular autonomic neuropathy. We explored the association between baroreflex sensivity and blood oxygen saturation (SpO2) in type 1 diabetes and various degrees of microvascular disease. METHODS: In this Danish-Finnish cross-sectional multicentre study, baroreflex sensivity and SpO2 (pulse oximetry) were examined in persons with type 1 diabetes and normoalbuminuria (n = 98), microalbuminuria (n = 28), or macroalbuminuria (n = 43), and in non-diabetic controls (n = 54). Associations and differences between groups were analysed using regression models and adjustment included age, sex, smoking, HbA1c, blood haemoglobin, urine albumin creatinine ratio, body mass index, and estimated glomerular filtration rate. RESULTS: In type 1 diabetes, higher baroreflex sensitivity was associated with higher SpO2 before adjustment (% increase per one % increase in SpO2 = 20 % (95%CI: 11-30); p < 0.001) and the association remained significant after adjustment (p = 0.02). Baroreflex sensitivity was not different between non-diabetic controls and persons with type 1 diabetes and normoalbuminuria (p = 0.052). Compared with type 1 diabetes and normoalbuminuria, baroreflex sensitivity was lower in micro- (p < 0.001) and macroalbuminuria (p < 0.001). SpO2 was lower in persons with type 1 diabetes and normoalbuminuria compared with non-diabetic controls (p < 0.01). Within the participants with type 1 diabetes, SpO2 was not different in micro- or macroalbuminuria compared with normoalbuminuria (p-values > 0.05), but lower in macro-compared with microalbuminuria (p < 0.01). CONCLUSIONS: Lower baroreflex sensitivity was associated with lower SpO2 in type 1 diabetes. The present study support the hypothesis that hypoxia could be a therapeutic target in persons with type 1 diabetes.

Persons with type 1 diabetes have low blood oxygen levels in the supine and standing body positions.

INTRODUCTION: Blood oxygen saturation is low compared with healthy controls (CONs) in the supine body position in individuals with type 1 diabetes (T1D) and has been associated with complications. Since most of daily life occurs in the upright position, it is of interest if this also applies in the standing body position. In addition, tissue oxygenation in other anatomical sites could show different patterns in T1D. Therefore, we investigated blood, arm and forehead oxygen levels in the supine and standing body positions in individuals with T1D (n=129) and CONs (n=55). RESEARCH DESIGN AND METHODS: Blood oxygen saturation was measured with pulse oximetry. Arm and forehead mixed tissue oxygen levels were measured with near-infrared spectroscopy sensors applied on the skin. RESULTS: Data are presented as least squares means±SEM and differences (95% CIs). Overall blood oxygen saturation was lower in T1D (CON: 97.6%±0.2%; T1D: 97.0%±0.1%; difference: -0.5% (95% CI -0.9% to -0.0%); p=0.034). In all participants, blood oxygen saturation increased after standing up (supine: 97.1%±0.1%; standing: 97.6%±0.2%; difference: +0.6% (95% CI 0.4% to 0.8%); p<0.001). However, the increase was smaller in T1D compared with CON (CON supine: 97.3%±0.2%; CON standing: 98.0%±0.2%; T1D supine: 96.9%±0.2%; T1D standing: 97.2%±0.1%; difference between groups in the change: -0.4% (95% CI -0.6% to -0.2%); p<0.001). Arm oxygen saturation decreased in both groups after standing and more in those with T1D. Forehead oxygen saturation decreased in both groups after standing and there were no differences between the changes when comparing the groups. CONCLUSION: Compared with CON, individuals with T1D exhibit possible detrimental patterns of tissue oxygen adaptation to standing, with preserved adaptation of forehead oxygenation. Further studies are needed to explore the consequences of these differences.

Retracted articles in rehabilitation: just the tip of the iceberg? A bibliometric analysis.

BACKGROUND AND AIM: The volume of withdrawn publications in scholarly disciplines has grown steadily, but there is little awareness about this issue in rehabilitation. The aim of this study was to analyze the extent of retracted articles pertaining to rehabilitation. METHODS: Retracted articles were searched in 4 different bibliographic databases from their inception to April 2020: PubMed, Web of Science, WikiLetters and Retraction Watch. Three independent reviewers assessed the relevance of the retrieved articles to the rehabilitation area. RESULTS: Of 280 rehabilitation-related publications retracted between 1984 and 2020, 83 (29.6%) were published in 55 full open access journals and 197 (70.4%) were published in 147 traditional, non-open access or hybrid journals. In the last 10 years (2009-2018) there was a significant steady increase in both the total number of retractions (p < 0.005; r = 0.856; R2 = 0.733) and retraction rate per year (p < 0.05; r = 0.751; R2 = 0.564). However, the number of retractions represents a very small percentage (~ 0.1%) of the overall volume of publications in rehabilitation. CONCLUSIONS: Our data indicate that the number of retracted articles in rehabilitation is increasing, although the phenomenon is still limited. However, the true prevalence of misconduct may go unnoticed due to the large number of low-quality journals not indexed in the searched databases. Physiotherapists should be aware of the danger of misleading information originating from withdrawn publications.

Acute fall and long-term rise in oxygen saturation in response to meditation.

The effects of meditation on arterial and tissue oxygenation are unknown and difficult to assess because respiration is often altered, directly or indirectly, during meditation practice. Thus, changes in respiration may affect cardiovascular responses independently from meditation. In this study, we aim to isolate the specific effect of meditation on arterial and tissue oxygenation and other cardiorespiratory indexes while systematically controlling for the role of respiration. Furthermore, we aim to clarify to what extent prior expertise in meditation practice is needed to observe reliable changes. Eighty participants, half with and half without prior meditation experience, were tested while pacing breathing at predetermined rates, in the presence or absence of mantra meditation instructions, and in a body scan meditation that did not involve controlled breathing. Continuous recordings were acquired for arterial and brain oxygenation, respiratory excursion, electrocardiogram, skin vasomotion, and blood pressure. In both groups, meditation acutely decreased arterial and cerebral oxygen saturation, reduced chemoreflex sensitivity, and prolonged the RR interval, independently of respiration. Conversely, slow breathing improved heart rate variability, independently of concurrent meditation. In addition to the immediate effects of meditation, the individuals with long-term practice of meditation had overall higher arterial and cerebral oxygen saturation, overall lower blood pressure, and slower baseline respiration. Meditation acutely lowers arterial and tissue oxygenation. A repeated exposure to this condition may lead to long-term adaptation and, through increased ventilatory efficiency and improved gas exchanges, to an increase in baseline oxygenation. Meditation induces favorable changes in cardiovascular and respiratory end points of clinical interest.

Oxygen-induced impairment in arterial function is corrected by slow breathing in patients with type 1 diabetes.

Hyperoxia and slow breathing acutely improve autonomic function in type-1 diabetes. However, their effects on arterial function may reveal different mechanisms, perhaps potentially useful. To test the effects of oxygen and slow breathing we measured arterial function (augmentation index, pulse wave velocity), baroreflex sensitivity (BRS) and oxygen saturation (SAT), during spontaneous and slow breathing (6 breaths/min), in normoxia and hyperoxia (5 L/min oxygen) in 91 type-1 diabetic and 40 age-matched control participants. During normoxic spontaneous breathing diabetic subjects had lower BRS and SAT, and worse arterial function. Hyperoxia and slow breathing increased BRS and SAT. Hyperoxia increased blood pressure and worsened arterial function. Slow breathing improved arterial function and diastolic blood pressure. Combined administration prevented the hyperoxia-induced arterial pressure and function worsening. Control subjects showed a similar pattern, but with lesser or no statistical significance. Oxygen-driven autonomic improvement could depend on transient arterial stiffening and hypertension (well-known irritative effect of free-radicals on endothelium), inducing reflex increase in BRS. Slow breathing-induced improvement in BRS may result from improved SAT, reduced sympathetic activity and improved vascular function, and/or parasympathetic-driven antioxidant effect. Lower oxidative stress could explain blunted effects in controls. Slow breathing could be a simple beneficial intervention in diabetes.