Visual, vestibular and somatosensory contributions to balance control in the older adult

Age- and pathology-related changes in the relative contributions of visual and somatosensory inputs to dynamic balance control were evaluated. Young adults (mean age = 25, SD = 4) were compared to older adults (mean age = 68, SD = 5). Electromyographic responses were collected when subjects' balance was perturbed on a movable platform. The amounts of visual information and of somatosensory input at the ankle were manipulated. Muscle response latencies, losses of balance, and muscle sequencing were analyzed. Muscle response latencies did not differ across age groups. Loss of balance data indicated that older adults were less stable under conditions in which peripheral vision was occluded and ankle somatosensation was limited (only foveal vision and vestibular input remaining). Older adults showed more antagonist muscle activation and used muscle sequences not seen in young adults (e.g., hip strategy). These effects were exaggerated among subjects in whom borderline pathology had been diagnosed.     

Sensory organization for balance: specific deficits in Alzheimer's but not in Parkinson's disease

BACKGROUND: The cause of frequent falling in patients with dementia of the Alzheimer type (AD) is not well understood. Distraction from incongruent visual stimuli may be an important factor as suggested by their poor performance in tests of shifting visual attention in other studies. The purpose of this study was to determine whether AD patients have difficulty maintaining upright balance under absent and/or incongruent visual and other sensory conditions compared to nondemented healthy elderly persons and individuals with Parkinson's disease (PD). METHODS: Seventeen healthy older adults, 15 medicated PD subjects, and 11 AD subjects underwent the Sensory Organization Test protocol. The incidence of loss of balance ("falls"), and the peak-to-peak amplitude of body center of mass sway during stance in the six sensory conditions were used to infer the ability to use visual, somatosensory, and vestibular signals when they provided useful information for balance, and to suppress them when they were incongruent as an orientation reference. Vestibular reflex tests were conducted to ensure normal vestibular function in the subjects. RESULTS: AD subjects had normal vestibular function but had trouble using it in condition 6, where they had to concurrently suppress both incongruent visual and somatosensory inputs. All 11 AD subjects fell in the first trial of this condition. With repeated trials, only three AD subjects were able to stay balanced. AD subjects were able to keep their balance when only somatosensory input was incongruent. In this condition, all AD subjects were able to maintain balance whereas some falls occurred in the other groups. In all conditions, when AD subjects did not fall, they were able to control as large a sway as the healthy controls, except when standing with eyes closed in condition 2: AD subjects did not increase their sway whereas the other groups did. In the PD group, the total fall incidence was similar to the AD group, but the distribution was generalized across more sensory conditions. PD subjects were also able to improve with repeated trials in condition 6. CONCLUSION: Patients with dementia of the Alzheimer type have decreased ability to suppress incongruent visual stimuli when trying to maintain balance. However, they did not seem to be dependent on vision for balance because they did not increase their sway when vision was absent. Parkinsonian patients have a more general balance control problem in the sensory organization test, possibly related to difficulty changing set.     

A novel method for continuous online glucose monitoring in humans: the comparative microdialysis technique

The aim of this study was to prove the feasibility of continuous subcutaneous glucose monitoring in humans using the comparative microdialysis technique (CMT). The performance of the CMT was determined by comparing tissue glucose values with venous or capillary blood glucose values in healthy volunteers and type 1 diabetic subjects. The CMT is a microdialysis-based system for continuous online glucose monitoring in humans. This technique does not require calibration by the patient. Physiological saline with glucose (5.5 mM) is pumped in a stop-flow mode through a microdialysis probe inserted into the abdominal s.c. tissue. Tissue glucose concentration is calculated by comparing the dialysate and perfusate glucose concentrations. The time delay due to the measurement process is 9 min. We tested the CMT on six healthy volunteers and six type 1 diabetic patients for 24 h in our clinical setting. Comparisons were made to HemoCue analyzer (Angelholm, Sweden) capillary blood glucose measurements (healthy volunteers) and to venous blood glucose concentration determined with a Hitachi analyzer (diabetic patients). The mean absolute relative error of the CMT glucose values from the blood glucose values was 17.8+/-15.5% (n = 167) for the healthy volunteers and 11.0+/-10.8% (n = 425) for the diabetic patients. The mean difference was 0.42+/-1.06 mM (healthy volunteers) and -0.17+/-1.22 mM (diabetic patients). Error grid analysis for the values obtained in diabetic patients demonstrated that 99% of CMT glucose values were within clinically acceptable regions (regions A and B of the Clarke Error Grid). The study results show that the CMT is an accurate technique for continuous online glucose monitoring.     

Postural stability and associated physiological factors in a population of aged persons

A battery of 13 visual, vestibular, sensorimotor, and balance tests was administered to 95 elderly persons (mean age 82.7 years) to examine the relationships between specific sensorimotor functions and measures of postural stability. When subjects stood on a firm surface, increased body sway was associated with poor tactile sensitivity and poor joint position sense. When subjects stood on a compliant surface (which reduced peripheral sensation) with their eyes open, increased body sway was associated with poor visual acuity and contrast sensitivity, reduced vibration sense, and decreased ankle dorsiflexion strength as well as reduced joint position sense. Increased body sway with eyes closed on the compliant surface was associated with poor tactile sensation, reduced quadriceps and ankle dorsiflexion strength, and increased reaction time. Poor performance in two clinical measures of postural stability was associated with reduced sensation in the lower limbs as measured by joint position sense, tactile sensitivity and vibration sense, reduced quadriceps and ankle dorsiflexion strength, and slow reaction times. The prevalence of vestibular impairments was high in this group, but vestibular function was not significantly associated with sway under any of the test conditions. The results suggest that reduced sensation, muscle weakness in the legs, and increased reaction time are all important factors associated with postural instability. An analysis of the percentage increases in sway under conditions where visual and peripheral sensation systems are removed or diminished, compared with sway under optimal conditions, indicated that peripheral sensation is the most important sensory system in the maintenance of static postural stability.     

Urinary Cyclophilin A as a New Marker for Diabetic Nephropathy: A Cross-Sectional Analysis of Diabetes Mellitus

Type 2 diabetes mellitus (DM) is the most common single cause of end-stage renal disease. Albuminuria is the most commonly used marker to predict onset of diabetic nephropathy (DN) without enough sensitivity and specificity to detect early DN. This is the first study to identify urinary cyclophilin A (CypA) as a new biomarker for early DN.We recruited DM outpatients and healthy control subjects from January 2014 to December 2014. In this cross-sectional study, patients’ urine samples were collected to determine the expression of urinary CypA. We also treated mesangial (MES-13) and tubular (HK-2) cells with glucose or free radicals to observe the expression of secreted CypA in Western blot analysis.A total of 100 DN patients and 20 healthy control subjects were enrolled. All variables were matched. In univariate analysis, the concentration of urinary CypA correlated well with the progression of renal function. A significant increase in urinary CypA was noted in stage 2 DN and persisted in later stages. We could diagnose stage 2 DN using urinary CypA with a sensitivity of 90.0% and specificity of 72.7%. The area under curve was up to 0.85, indicating a good discriminatory power. In cellular models, MES-13 and HK-2 cells can both release CypA.Urinary CypA is a good biomarker for early DN detection in humans and it can be released from either mesangial or tubular cells. The underlying molecular mechanisms still need further clarification in cellular and animal studies.     

The Thermocross: a simple tool for rapid assessment of thermal sensation thresholds.

We have developed the Thermocross, a simple device for rapid assessment of thermal sensitivity, tested it on healthy subjects and diabetic patients and evaluated its use in identifying patients whose sensation loss may expose them to the risk of neuropathic foot injury. Thermal discrimination deteriorated with age (P less than 0.001) in healthy subjects, but all the controls could detect a temperature difference less than or equal to 10 degrees C. In diabetic patients, the deficit in thermal sensation detected by the Thermocross paralleled the decline of nerve conduction. Thermocross thermal sensation was impaired in 87% of 38 ulcerated feet of 26 diabetic patients. We conclude that the Thermocross is a suitable tool for screening for sensation loss and that diabetic patients with impaired thermal sensation are vulnerable to ulceration. The Thermocross could also serve a useful educational purpose, the implications of reduced thermal sensation probably being more meaningful to patients and health care personnel than those of a reduction in the traditionally tested vibration sensation.     

Association studies between the HSD11B2 gene (encoding human 11beta-hydroxysteroid dehydrogenase type 2), type 1 diabetes mellitus and diabetic nephropathy

OBJECTIVE: Mutations in the HSD11B2 gene (encoding human 11beta-hydroxysteroid dehydrogenase type 2) explain the syndrome of apparent mineralocorticoid excess where cortisol acts as a mineralocorticoid. A microsatellite marker within the HSD11B2 gene associates with salt sensitivity and hypertension--phenotypes characterising diabetic nephropathy. Here, we evaluate the HSD11B2 gene as a susceptibility locus for diabetic nephropathy. DESIGN: 150 patients with type 1 diabetes and nephropathy (DN), 145 patients with type 1 diabetes with a long duration of non-nephropathy (LDNN) and 151 normal controls were studied. METHODS: We determined allele frequencies for the (CA)n repeat marker within intron I of the HSD11B2 gene. Duration of type 1 diabetes, diabetic status and renal function were recorded. RESULTS: 11 alleles (138-158) for the marker were observed. Allele 152 was significantly increased in controls compared with LDNN (70.5% vs 57.6%, P(c)<0.05 where P(c) is the P value corrected for multiple comparisons) but no difference was observed between DN and LDNN subjects. Allele 154 was significantly increased in the LDNN compared with the DN subjects (15.9% vs 7.0%, P(c)<0.01) but no difference was observed between DN and controls. A greater proportion of subjects carried at least 1 allele <152 in DN compared with control subjects (47.3% vs 28.5%, P(c)<0.01), but no difference was observed in LDNN compared with control and DN subjects. CONCLUSIONS: Weak associations are reported between the HSD11B2 gene, type 1 diabetes mellitus and nephropathy. The increased frequency of HSD11B2 short alleles in the diabetic groups may reflect reduced renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity and may, in part, explain the enhanced salt sensitivity observed in patients with type 1 diabetes.     

Is plantar foot sensation associated with standing balance in type 2 diabetes mellitus patients

To examine the relationship between one-leg standing balance (OLSB) and different modalities of foot sole sensation in patients with type 2 diabetes mellitus (T2DM). Forty patients diagnosed with T2DM (mean age, 53.96 ± 15.31 years) and ten healthy control subjects were included. Duration of OLSB was measured with digital chronometer. Threshold of light-touch pressure (LTP), evaluated with full Semmes-Weinstein Monofilament Test Kit, and distance of two-point discrimination (TPD), evaluated with aesthesiometer, were assessed at six different regions of the foot sole. Thresholds of the LTP at all regions were significantly correlated with duration of OLSB (p < 0.05). However, there was no relationship between TPD sensation and duration of OLSB (p > 0.05). LTP at the plantar side of the great toe was the most related area with the OLSB (r = −0.48, p < 0.05). In patients with T2DM, LTP, and TPD sensations of foot sole and duration of OLSB were decreased compared to healthy controls. In this study, there was a moderate correlation between LTP sensation and balance. Other factors that would affect the balance in patients with T2DM should be investigated.

     

Urinary Proteomics for Diagnosis and Monitoring of Diabetic Nephropathy

The last decade has seen a surge in publications describing novel biomarkers for early detection of diabetic nephropathy (DN), but as yet none have outperformed albuminuria in well-designed prospective studies. This is partially attributable to our incomplete understanding of the many complex interrelated mechanisms underlying DN development, a heterogeneous process unlikely to be captured by a single biomarker. Proteomics offers the advantage of simultaneously analysing the entire protein content of a biological sample, and the technique has gained attention as a potential tool for a more accurate diagnosis of disease at an earlier stage as well as a means by which to unravel the pathogenesis of complex diseases such as DN using an untargeted approach. This review will discuss the potential of proteomics as both a clinical and research tool, evaluating exploratory work in animal models as well as diagnostic potential in human subjects.     

Relationship between dietary macronutrient composition with weight loss after bariatric surgery: A systematic review

This systematic review evaluated the relationship between macronutrient intake and weight loss after bariatric surgery (BS). The MEDLINE/Pubmed, EMBASE, COCHRANE/CENTRAL, and SCOPUS databases were accessed in August 2021 to search for eligible articles: original publications with adults undergoing BS and indicating the relationship between macronutrients and weight loss. Titles that did not meet these criteria were excluded. The review was written according to the PRISMA guide, and the risk of bias was according to the Joanna Briggs manual. Data were extracted by one reviewer and checked by another. Eight articles with 2.378 subjects were included. The studies indicated a positive relationship between weight loss and protein intake after BS. Prioritization of protein followed by carbohydrates with a lower percentage of lipids favors weight loss and increases weight stability after BS. Among the results found, a 1% increase in protein intake raises the probability of obesity remission by 6%, and high-protein diet increase 50% weight loss success. Limitations are the methods of included studies and review process. It is concluded that high-protein intake >60 g a 90 g/day may favor weight loss and maintenance after BS, but it is relevant to balance the other macronutrients.     

Foot Technology, Part 1 of 2: Assessing Postural Control and Postural Control Strategy in Diabetes Patients Using Innovative and Wearable Technology

Introduction

Currently, diagnosis of patients with postural instability relies on a rudimentary clinical examination. This article suggests an innovative, portable, and cost-effective prototype to evaluate balance control objectively.

Methods

The proposed system uses low-cost, microelectromechanical sensor, body-worn sensors (BalanSens™) to measure the motion of ankle and hip joints in three dimensions. We also integrated resulting data into a two-link biomechanical model of the human body for estimating the two-dimensional sway of the center of mass (COM) in anterior–posterior (AP) and medial–lateral (ML) directions. A new reciprocal compensatory index (RCI) was defined to quantify postural compensatory strategy (PCS) performance. To validate the accuracy of our algorithms in assessing balance, we investigated the two-dimensional sway of COM and RCI in 21 healthy subjects and 17 patients with diabetic peripheral neuropathic (DPN) complications using the system just explained. Two different conditions were examined: eyes open (EO) and eyes closed (EC) for duration of at least 30 seconds. Results were compared with center of pressure sway (COP) as measured by a pressure platform (Emed-x system, Novel Inc., Germany). To further investigate the contribution of the somatosensory (SOM) feedback to balance control, healthy subjects performed EO and EC trials while standing on both a rigid and a foam surface.

Results

A relatively high correlation was observed between COM measured using BalanSens and COP measured using the pressure platform (r = 0.92). Results demonstrated that DPN patients exhibit significantly greater COM sway than healthy subjects for both EO and EC conditions (p < 0.005). The difference becomes highly pronounced while eyes are closed (197 ± 44 cm² vs 68 ± 56 cm²). Furthermore, results showed that PCS assessed using RCI is significantly better in healthy subjects compared to DPN subjects for both EO and EC conditions, as well as in both ML and AP directions (p < 0.05). Alteration in SOM feedback in healthy subjects resulted in diminished RCI values that were similar to those seen in DPN subjects (p > 0.05).

Discussion/Conclusion

This study suggested an innovative system that enables the investigation of COM as well as postural control compensatory strategy in humans. Results suggest that neuropathy significantly impacts PCS.     

锰超氧化物歧化酶基因V(16)A多态性与糖尿病肾病的相关性研究

目的探讨锰超氧化物歧化酶(MnSOD)基因V(16)A多态性与糖尿病肾病(DN)的关系。方法应用PCR-RFLP法在昆明地区汉族人中检测97例健康对照者和187例2型糖尿病(T2DM)患者[根据尿白蛋白(UAlb)定量分为DN0(UAlb<30mg/24h)、DN1(30mg/24h≤UAlb<300mg/24h)和DN2(UAlb>300mg/24h)]的MnSOD基因V(16)A多态性,比较各组间基因型分布和等位基因频率。结果DN组(DN1 DN2)VV基因型和V等位基因频率显著高于不伴肾病的DN0组(P<0·05)。MnSOD基因多态性与DN显著相关。结论MnSOD基因V(16)A多态性是中国昆明地区汉族T2DM发生DN的遗传危险因素。     

Effect of facilitation of sensation from plantar foot-surface boundaries on postural stabilization in young and older adults.

BACKGROUND: One of the more pervasive effects of aging is loss of cutaneous sensation, which appears to correlate with impaired postural control and increased risk of falling. This study examined the potential for compensating for the destabilizing effects of reduced cutaneous sensitivity by placing a raised edge underneath the perimeter of the plantar foot surface, so as to facilitate sensation from the stability boundaries of the base of support. METHODS: The main experiment involved 14 healthy older adults (aged 65-73) selected because they were known, from a previous study, to have moderate plantar cutaneous insensitivity. We also report results of an initial experiment involving 7 healthy young adults (aged 23-31). In both experiments, we studied effects of the plantar facilitation on control of rapid stepping reactions evoked by unpredictable postural perturbation, applied via sudden platform movement in forward, backward, and lateral directions. We also studied effects on "feet-in-place" responses evoked by continuous pseudorandom platform motion in mediolateral and anteroposterior directions. Subjects were blindfolded in all tests. RESULTS: Plantar facilitation reduced the incidence of "extra" limb movements, beyond the initial step, during forward-step reactions in the older adults. There also appeared to be an improved ability to control feet-in-place reactions: young subjects were better able to recover balance without stepping when falling backward (given instructions to "try not to step"), and both young and older subjects reduced the extent to which the center of foot pressure approached the posterior foot boundary during continuous anteroposterior platform motion. CONCLUSIONS: This study provides evidence that mechanical facilitation of sensation from the boundaries of the plantar surface of the foot can improve the efficacy of certain types of stabilizing reactions evoked by unpredictable postural perturbation. The results may be directly transferable to the design of special footwear insoles to reduce instability and risk of falling in older adults.     

Age-related differences in walking stability

BACKGROUND: a large proportion of falls in older people occur when walking; however the mechanisms underlying impaired balance during gait are poorly understood. OBJECTIVE: to evaluate acceleration patterns at the head and pelvis in young and older subjects when walking on a level and an irregular walking surface, in order to develop an understanding of how ageing affects postural responses to challenging walking conditions. METHODS: temporo-spatial gait parameters and variables derived from acceleration signals were recorded in 30 young people aged 22-39 years (mean 29.0, SD 4.3), and 30 older people with a low risk of falling aged 75-85 years (mean 79.0, SD 3.0) while walking on a level and an irregular walking surface. Subjects also underwent tests of vision, sensation, strength, reaction time and balance. RESULTS: older subjects exhibited a more conservative gait pattern, characterised by reduced velocity, shorter step length and increased step timing variability. These differences were particularly pronounced when walking on the irregular surface. The magnitude of accelerations at the head and pelvis were generally smaller in older subjects; however the smoothness of the acceleration signals did not differ between the two groups. Older subjects performed worse on tests of vision, peripheral sensation, strength, reaction time and balance. CONCLUSION: the adoption of a more conservative basic gait pattern by older people with a low risk of falling reduces the magnitude of accelerations experienced by the head and pelvis when walking, which is likely to be a compensatory strategy to maintain balance in the presence of age-related deficits in physiological function, particularly reduced lower limb strength.     

Footwear for the neuropathic patient: offloading and stability

Diabetic neuropathy is related to plantar ulceration through a variety of factors of which increased plantar pressures and loss of protective sensation are the most important. Loss of sensation in the lower limbs is also related to postural instability and an increased risk of falling. Ankle and foot proprioception play an important role in postural control and this sensory function is also affected by neuropathy. It is conceivable that footwear, orthotics, casts and braces used for treatment or prevention of plantar ulceration through offloading of the injured or at-risk foot area can exacerbate the postural instability and risk of falling. This has, however, received very limited attention in the literature. There are studies that have demonstrated that footwear adjustments can influence balance and stability in healthy, elderly subjects. The adjustments made to footwear for the diabetic foot are generally more dramatic and, therefore, are expected to have a greater influence on postural stability. Furthermore, casts and braces tend to deviate even more from normal footwear. This may seriously interfere with normal gait and posture and, therefore, stability. So far the evidence suggests that patients wearing such devices demonstrate markedly reduced activity levels. This reduced activity could add to the effect of offloading. This could also be interpreted to indicate problems with stability. This presentation will review the different types of offloading interventions frequently used for ulcer treatment and prevention and will consider the mechanical effect of these interventions on stability.     

Facts about the kock continent ileostomy

A great number of publications on the results obtained by different techniques employed for construction of the continent ileostomy have been published over the years. Unfortunately, many reports are incomplete or presented in such a way that they do not allow for proper interpretation or mutual comparison. Analysis of the collective results obtained from studies where the different techniques employed are accurately described and complications properly specified demonstrates more clearly what measures may improve the success rate and which factors have to be taken into account for anyone who is going to adopt the method. Maintaining a continuing flow of appropriate material for this section is impossible, at least currently. Nevertheless, from time to time, we do receive unsolicited review articles that furnish concise, up-to-date information on specific subjects, and they will appear in this section. Subjects covered, obviously, will depend upon our contributors.     

Silent Aspiration: What Do We Know?

Although clinically evident aspiration is common in subjects with dysphagia, a significant proportion may aspirate silently, i.e., without any outward signs of swallowing difficulty. This article reviews the literature on the prevalence, etiology, and prognostic significance of silent aspiration. An electronic database search was performed using silent aspiration, aspiration, dysphagia, and stroke as search terms, together with hand-searching of articles. Silent aspiration has been described in many conditions and subgroups of patients (including normal individuals), using a number of detection methods, making comparisons a challenge. The best data are for acute stroke, in which 2%–25% of patients may aspirate silently. Mechanisms associated with silent aspiration may include central or local weakness/incoordination of the pharyngeal musculature, reduced laryngopharyngeal sensation, impaired ability to produce a reflexive cough, and low substance P or dopamine levels. In terms of prognosis, silent aspiration has been associated with increased morbidity and mortality in many but not all studies. However, some degree of silent aspiration at night may be normal in healthy individuals. The phenomenon of silent aspiration is poorly understood and further research is needed to improve methods of detection and thereby better define its prevalence and prognostic significance.     

Local anesthesia reduces the maximal skin vasodilation during iontophoresis of sodium nitroprusside and heating

AIM: To evaluate the effect of local anesthesia on the skin vasodilation induced by the iontophoresis of sodium nitroprusside and heating. METHODS: Skin vascular reactivity, in response to iontophoresis of sodium nitroprusside (SNP), was evaluated at the forearm and foot in 13 neuropathic diabetic (DN) and 11 nonneuropathic diabetic (D) patients and 9 healthy, nondiabetic subjects who served as controls (C). The direct (DI) and nerve axon reflex-related (N-V) vasodilation were measured by using two single-point laser Doppler probes. The vasodilation in response to local warming was also assessed. A topical anesthetic was applied on the contralateral forearm and foot and all the measurements were repeated. RESULTS: Dermal anesthesia resulted in a reduction of the direct vasodilation to SNP at the forearm [C: 58.1 +/- 16, D: 60.6 +/- 11%, and DN: 48.3 +/- 37% (postanesthesia percentage of reduction; mean +/- SEM), P<0.01] and at the foot in all three groups (D: 38.5 +/- 12%, P<0.01; C: 27.2 +/- 14% and DN: 11.3 +/- 17.5%, P=NS). The N-V related vasodilation was very low before and did not change after local anesthesia. The postanesthesia hyperemic response to warming was significantly reduced at low temperatures but did not change at 44 degrees C. CONCLUSION: The sodium nitroprusside-related vasodilation is reduced after local anesthesia in a similar way in healthy subjects and diabetic patients with and without neuropathy. The response to heating is also reduced at low temperatures. This indicates a stabilizing effect of local anesthesia on the smooth muscle cell.     

Sustained hypoxia depresses sensory processing of respiratory resistive loads

RATIONALE: The combination of acute hypoxia and increased respiratory load is encountered in several respiratory diseases including acute life-threatening asthma and sleep apnea. Hypoxia has been shown to inhibit respiratory load perception in healthy and asthmatic subjects, and could contribute to treatment delays and impaired function of protective reflexes. OBJECTIVES: Using respiratory-related evoked potentials (RREPs) this study aimed to determine the sensory processes mediating hypoxia-induced suppression of respiratory load sensation. METHODS: EEG was measured over the central and parietal cortical regions in 14 healthy subjects. RREPs were elicited by 500-ms midinspiratory resistive load stimuli during and after isocapnic normoxia or hypoxia (blood arterial O2 saturation approximately 80%). On a separate occasion, subjects rated the perceived magnitude of five externally applied inspiratory resistive loads (range, 8.6-43.7 cm H2O x L(-1) x s) under similar experimental conditions. In both experiments subjects voluntarily ventilated approximately 90% above baseline to match ventilatory output between gas conditions. RESULTS: RREP stimulus was matched between gas conditions in 11 subjects (minimum mask pressure -9.7 +/- 0.6 versus -9.2 +/- 0.4 cm H2O). P1 and P2 amplitudes were reduced during isocapnic hypoxia compared with normoxia (maximal at Cz: P1, 2.5 +/- 1.1 versus 3.9 +/- 1.2 microv, p = 0.03; P2, 10.0 +/- 2.2 versus 12.4 +/- 2.1 microv, p < 0.01, respectively). Perceived magnitude of externally applied resistive loads was also reduced during hypoxia compared with normoxia (17.1 +/- 1.1 versus 19.0 +/- 1.1 au, p < 0.01). CONCLUSIONS: These data confirm that isocapnic hypoxia suppresses respiratory load sensation. Decreased amplitude of the earlier (P1) RREP component suggests that this is mediated, at least in part, by suppression of respiratory afferent information before its arrival at the primary sensory cortex.