The PAP-RES algorithm: Defining who, why and how to use positive airway pressure therapy for OSA

Obstructive sleep apnea (OSA) is a common condition that is increasing in prevalence worldwide. Untreated OSA has a negative impact on health-related quality of life and is an independent risk factor for cardiovascular diseases. Despite available data suggesting that cardiovascular risk might differ according to clinical phenotypes and comorbidities, current approaches to OSA treatment usually take a "one size fits all" approach. Identification of cardiovascular vulnerability biomarkers and clinical phenotypes associated with response to positive airway pressure (PAP) therapy could help to redefine the standard treatment paradigm. The new PAP-RES (PAP-RESponsive) algorithm is based on the identification of OSA phenotypes that are likely to impact therapeutic goals and modalities. The paradigm shift is to propose a simplified approach that defines therapeutic goals based on OSA phenotype: from a predominantly "symptomatic phenotype" (individuals with high symptom burden that negatively impacts on daily life and/or accident risk or clinically significant insomnia) to a "vulnerable cardiovascular phenotype" (individuals with comorbidities [serious cardiovascular or respiratory disease or obesity] that have a negative impact on cardiovascular prognosis or a biomarker of hypoxic burden and/or autonomic nervous system dysfunction). Each phenotype requires a different PAP therapy care pathway based on differing health issues and treatment objectives.

Seasonal changes in positive airway pressure adherence

Through their effects on sleep duration, bedroom environments, and pollen allergies, seasonal variations may impact positive airway pressure (PAP) adherence. We analyzed daily PAP telemonitoring data from 25,846 adults (median age 64 years, 67.8% male) treated with PAP for at least 4 months [mean (standard deviation, SD) duration of PAP: 5.5 years (SD 4.1)] to examine seasonal changes in PAP adherence, leaks, and residual apnea-hypopnea index. We demonstrate a significant decrease in PAP adherence in June compared to January (mean (SD): 0.37 (1.54) h/night) that achieved the minimal clinically important difference (MCID) of 30 min in 13.9% of adults. Furthermore, we provide novel data supporting the association of rising temperatures with seasonal changes in PAP use. Indeed, the most pronounced decline in PAP adherence was observed during the hottest days, while PAP adherence was only slightly reduced during the coolest days of June. Clinicians should be aware of seasonal changes in PAP adherence that are likely to be exacerbated by climate change.

Home NIV treatment quality in patients with chronic respiratory failure having participated to the French nationwide telemonitoring experimental program (The TELVENT study)

BACKGROUND

The ETAPES program is a national telemedicine experiment conducted in France between 2018 and 2023 to investigate whether home non-invasive ventilation (NIV) telemonitoring improves healthcare pathways in patients with chronic respiratory failure (CRF) and impacts healthcare organization. The program provides a combination of therapeutic education and NIV telemonitoring with data processed by an algorithm generating alerts. The TELVENT study objective was to analyze the evolution of ventilation quality in patients included in the ETAPES program.

METHODS

Multicentric cohort study on patients undergoing long-term NIV included in the ETAPES program between September 2018 and December 2020 and who did not refuse the use of their data for this research. Data were obtained from homecare provider databases. The primary endpoint was to attain successful NIV treatment, which was determined by a combination of daily NIV usage for > 4 h per day, low leaks, and a low apnea-hypopnea index (AHI) identified by the NIV device. Respiratory disability was assessed using the DIRECT questionnaire.

RESULTS

329 patients were included in the study of which 145 had COPD and 83 had started NIV and ETAPES within one-month delay. Approximately 25% of patients did not achieve the criteria for successful NIV at ETAPES entry. The proportion of patients with successful NIV treatment increased to 86.8% at six months (p = 0.003, Cochran-Armitage trend test) regardless of NIV history and continued to increase at 12 months in newly equipped NIV patients (93.8%, at month 12, p = 0.0026 for trend test). Over time, a significant increase in NIV use and compliance was observed, while AHI significantly decreased in the overall population. No significant decrease was observed for non-intentional leaks. Approximately 4.9 alerts were generated per patient per 6 months. Their number and type (low NIV use, high AHI or leaks) differed among patients based on their NIV history. Respiratory disability score decreased over time compared with baseline.

CONCLUSION

The TELVENT study highlights the importance of remote NIV monitoring to rapidly identify patients with unsuccessful ventilation. The combination of remote monitoring and therapeutic education may improve the quality of home NIV, especially in the first months of treatment.

Health trajectories before initiation of non-invasive ventilation for chronic obstructive pulmonary disease: a French nationwide database analysis

Background

Chronic obstructive pulmonary disease (COPD) is the most common indication for long-term domiciliary non-invasive ventilation (NIV) but there is uncertainty in data supporting current guidelines. This study described health trajectories before initiation of at-home NIV in people with COPD, and compared mortality outcomes between groups with different pre-NIV health trajectories.

Methods

Data were from the French national health insurance reimbursement system database for individuals with COPD aged ≥40 years and ≥1 reimbursement for NIV between 1 January 2015 and 31 December 2019. Common health trajectories were determined using time sequence analysis through K-clustering (TAK analysis).

Findings

Data from 54,545 individuals were analysed; the population was elderly (median age 70 years) with multiple comorbidities. Four clusters were generated. Cluster 1 (n = 35,975/54,545; 66%) had NIV initiated in ambulatory settings or after the first acute event/exacerbation. Cluster 2 (6653/54,545; 12%) started NIV after ≥2 severe exacerbations in the previous 6 months. Cluster 3 (11,375/54,545; 21%) started NIV after frequent severe COPD-related exacerbations in the previous year. Cluster 4 (652/54,545; 1%) started NIV after many long-lasting severe exacerbations. The four clusters differed in age, sex, comorbidities, pre-NIV investigations, and prescriber/location of NIV initiation. Mortality differed significantly between clusters: highest in Cluster 4 and lowest in Cluster 1.

Interpretation

The significant heterogeneity in clinical initiation of NIV probably reflects the current lack of strong evidence and guideline recommendations. Knowledge about the characteristics and outcomes in different clusters should be used to address inequities and facilitate more consistent and personalised use domiciliary NIV in COPD.

Funding

JLP and SB are supported by the French National Research Agency in the framework of the "Investissements d'avenir" program (ANR-15-IDEX-02) and the "e-health and integrated care and trajectories medicine and MIAI artificial intelligence (ANR-19-P3IA-0003)" Chairs of excellence from the Grenoble Alpes University Foundation. This work was supported by ResMed.

A biphasic effect of age on CPAP adherence: a cross-sectional study of 26,343 patients

BACKGROUND

As the prevalence of OSA increases in older patients, the proportion of elderly patients treated with CPAP is expected to become even higher. We studied CPAP-adherence in a real-life cohort involving a large population of elderly patients with OSA.

METHODS

eQUALISAS is a cross-sectional study of CPAP treated OSA patients for at least 4 months who received remote monitoring during 2021. CPAP adherence, device-reported residual AHI (AHICPAP) and 95th percentile non-intentional leaks were software collected during January 2021. Age and sex were also collected.

RESULTS

Data from 26,343 patients including 1656 patients aged [80-85] years and 639 patients aged ≥ 85 years were analysed. Median CPAP adherence increases from 6.3 h (< 50 years) to 7 h (75-80 years) and decreases after this age (p < 0.001). The decrease in CPAP adherence observed after the age of 80 was associated with an increase in the proportion of patients with a CPAP-adherence < 4 h/day (p < 0.001). Proportion of CPAP treated female, patients having AHICPAP mean ≥ 10 events per hour or 95th percentile non-intentional leaks mean over 24 l/min increase with aging of the population. However, for patients over 80 years old, Chi square test showed no association of adherence with gender, AHICPAP and leaks (p > 0.05).

CONCLUSION

This study demonstrates that adherence gradually increases with age until 80 years. The proportion of non-adherent patients grows with age after 80 years old. No significative relationship was found between adherence after 80 years old and gender, leaks and AHICPAP.

TRIAL REGISTRATION

The study is registered on Health Data Hub platform (No. F20220715144543).

Solitary-like and modulated wavepackets in the Couette-Taylor flow with a radial temperature gradient

We have performed numerical and experimental studies of the flow in a large aspect ratio Couette-Taylor system with a rotating inner cylinder and a fixed radial temperature gradient. The base flow state is a superposition of an azimuthal flow induced by rotation and an axial large convective cell induced by the temperature gradient. For a relatively large temperature gradient, the rotation rate of the inner cylinder destabilizes the convective cell to give rise to travelling wave pattern through a subcritical bifurcation. This wave pattern is associated with a temperature mode and it consists of helical vortices travelling in the annulus. In a small range of the rotation rate, helical vortices have longitudinal meandering leading to the formation of kinks randomly distributed, leading to spatio-temporal disordered patterns. The flow becomes regular for a large interval of rotation rate. The friction, the momentum and the heat transfer coefficients are computed and found to be independent of the heating direction. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.

Effect of switching from continuous to bilevel positive airway pressure on sleep quality in patients with obstructive sleep apnea: the prospective POP IN VAuto study

Background

Issues with tolerability and side effects can decrease continuous positive airway pressure (CPAP) device usage and the benefits of therapy. Different positive airway pressure (PAP) therapy modes providing expiratory pressure relief or using a different pressure during inspiration vs. expiration (bilevel PAP) may alleviate some of these issues. This multicenter, prospective study evaluated the effects of switching from CPAP to bilevel PAP (VAuto mode) on respiratory parameters, device usage, side effects and patient-reported outcomes in patients with obstructive sleep apnea (OSA).

Methods

Eligible OSA patients had started CPAP ≥3 months previously, had good compliance (mean 6.1±2.0 h/night) and well-controlled OSA [residual apnea-hypopnea index (AHI) 4.9±3.1/h] but had pressure tolerance issues or persistent side effects/discomfort. All were switched from CPAP to bilevel PAP (AirCurve 10 VAuto; ResMed). Effectiveness (residual AHI), sleep quality, daytime sleepiness, fatigue, therapy-related side effects, and patient satisfaction/preference were assessed after 3 months and 1 year.

Results

Forty patients were analyzed (68% male, age 64±11 years, body mass index 30.7±5.8 kg/m²). At 3 months and 1 year after switching to bilevel PAP, median [interquartile range] residual AHI was 4/h [2-5.3] and 3.7/h [1.8-5], respectively, and device usage was 7.0 [4.9-7.5] and 6.4 [4.4-7.3] h/night, respectively. Device switch was associated with significant reductions from baseline in expiratory PAP {from 12 [11-13] to 8 [7-9] cmH₂O at 3 months (P<0.001) and 9 [8-12] cmH₂O at 1 year (P=0.005)}, 95^th percentile pressure {from 14 [12-14] to 10 [9-11] and 10 [8-11] cmH2O; P<0.001 and P=0.001, respectively} and leak {from 1 [0-6] to 0 [0-1] and 0 [0-2] L/min; P=0.049 and P=0.033, respectively}. The Pittsburgh Sleep Quality Index score decreased significantly from baseline to 3 and 6 months [7.2±4.0 to 5.0±3.2 (P=0.005) and 4.5±2.7 (P<0.001), respectively]. CPAP-related mouth dryness, choking sensation and aerophagia were significantly improved one year after switching to bilevel PAP. Bilevel PAP was preferred over CPAP by 90% of patients.

Conclusions

Switching to bilevel PAP had several benefits in patients struggling with CPAP, facilitating therapy acceptance and ongoing device usage.

Factors Associated With Residual Apnea-Hypopnea Index Variability During CPAP Treatment

BACKGROUND

CPAP is the first-line therapy for OSA. A high or variable residual apnea-hypopnea index (rAHI) reflects treatment failure and potentially is triggered by exacerbation of cardiovascular comorbidities. Previous studies showed that high rAHI and large rAHI variability are associated with underlying comorbidities, OSA characteristics at diagnosis, and CPAP equipment, including mask type and settings.

RESEARCH QUESTION

What factors are associated with predefined groups with low to high rAHI variability?

STUDY DESIGN AND METHODS

This registry-based study included patients with a diagnosis of OSA who were receiving CPAP treatment with at least 90 days of CPAP remote monitoring. We applied the hidden Markov model to analyze the day-to-day trajectories of rAHI variability using telemonitoring data. An ordinal logistic regression analysis identified factors associated with a risk of having a higher and more variable rAHI with CPAP treatment.

RESULTS

The 1,126 included patients were middle-aged (median age, 66 years; interquartile range [IQR], 57-73 years), predominantly male (n = 791 [70.3%]), and obese (median BMI, 30.6 kg/m² (IQR, 26.8-35.2 kg/m²). Three distinct groups of rAHI trajectories were identified using hidden Markov modeling: low rAHI variability (n = 393 [35%]), moderate rAHI variability group (n = 420 [37%]), and high rAHI variability group (n = 313 [28%]). In multivariate analysis, factors associated with high rAHI variability were age, OSA severity at diagnosis, heart failure, opioids and alcohol consumption, mental and behavioral disorders, transient ischemic attack and stroke, an oronasal mask, and level of leaks when using CPAP.

INTERPRETATION

Identifying phenotypic traits and factors associated with high rAHI variability will allow early intervention and the development of personalized follow-up pathways for CPAP treatment.

CPAP telemonitoring can track Cheyne-Stokes respiration and detect serious cardiac events: The AlertApnée Study

BACKGROUND AND OBJECTIVE

Case reports have suggested that continuous positive airway pressure (CPAP) telemonitoring can detect the onset of acute cardiac events such as decompensated heart failure (HF) or atrial fibrillation through an increase in the apnoea-hypopnoea index (AHI) and onset of Cheyne-Stokes Respiration (CSR). This study addressed whether long-term remote CPAP treatment telemonitoring revealing CSR can help detect serious cardiac events (SCEs) in obstructive sleep apnoea (OSA) patients.

METHODS

This monocentric prospective cohort study included adults receiving CPAP therapy for OSA with daily telemonitoring. Any sudden increase in AHI generated an alert for the home healthcare provider to download CPAP data to identify CSR. A medical consultation was scheduled if CSR was detected.

RESULTS

We included 555 adults (412 men; 57% with known cardiovascular comorbidities). During the 1-year follow-up, 78 CSR episodes were detected in 74 patients (CSR+). The main conditions associated with incident CSR were HF (24 patients [30.8%]), ventilatory instability (21, 26.9%), leaks (13, 16.7%), medications inducing central apnoeas (baclofen, ticagrelor, opioids) (7, 9.0%), arrhythmias (6, 7.7%) and renal failure (2, 2.6%). Fifteen (20.3%) CSR+ patients had a confirmed SCE. In univariable analysis, a CSR episode increased the risk of an SCE by 13.8-fold (5.7-35.6) (p < 0.0001), with an adjusted OR of 5.7 (2.0-16.8) in multivariable analysis.

CONCLUSION

Long-term telemonitoring of patients on CPAP treatment can alert CSR episodes and allows early detection of SCEs in patients with or without known cardiac comorbidities.

Interrelated atrial fibrillation and leaks triggering and maintaining central sleep apnoea and periodic breathing in a CPAP-treated patient

We report the case of a 71-year-old obese continuous positive airway pressure (CPAP)-treated man who developed an acute cardiac failure (ACF) triggered by atrial fibrillation. CPAP data downloaded from the CPAP software (Rescan®) retrospectively demonstrated the progressive development of a high residual central apnoea-hypopnoea index (AHI) with Cheyne-Stokes respiration (CSR). The AHI decreased after cardioversion allowing normalization of cardiac rhythm and function. Raw data extracted from CPAP software showed a gradual decrease in the periodic breathing cycle length related to a simultaneous improvement in left ventricular ejection fraction (LVEF) after cardioversion. During this clinical period of respiratory instability in the presence of cardiac failure, CSR episodes were exacerbated by ventilation overshoots followed by micro-arousals induced by leaks. This might explain the high night to night variability of CSR occurrence in susceptible patients with impaired cardiac function. Beyond attempts to improve cardiac function, leak reduction might represent an important target for CSR management.

Respiratory support in COPD patients after acute exacerbation with monitoring the quality of support (Rescue2-monitor): an open-label, prospective randomized, controlled, superiority clinical trial comparing hospital- versus home-based acute non-invasive ventilation for patients with hypercapnic chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is expected to be the 3rd leading cause of death worldwide by 2020. Despite improvements in survival by using acute non-invasive ventilation (NIV) to treat patients with exacerbations of COPD complicated by acute hypercapnic respiratory failure (AHRF), these patients are at high risk of readmission and further life-threatening events, including death. Recent studies suggested that NIV at home can reduce readmissions, but in a small proportion of patients, and with a high level of expertise. Other studies, however, do not show any benefit of home NIV. This could be related to the fact that respiratory failure in patients with stable COPD and their response to mechanical ventilation are influenced by several pathophysiological factors which frequently coexist in the same patient to varying degrees. These pathophysiological factors might influence the success of home NIV in stable COPD, thus long-term NIV specifically adapted to a patient's "phenotype" is likely to improve prognosis, reduce readmission to hospital, and prevent death. In view of this conundrum, Rescue2-monitor (R2M), an open-label, prospective randomized, controlled study performed in patients with hypercapnic COPD post-AHRF, will investigate the impact of the quality of nocturnal NIV on the readmission-free survival. The primary objective is to show that any of 3 home NIV strategies ("rescue," "non-targeted," and "targeted") will improve readmission-free survival in comparison to no-home NIV. The "targeted" group of patients will receive a treatment with personalized (targeted) ventilation settings and extensive monitoring. Furthermore, the influence of comorbidities typical for COPD patients, such as cardiac insufficiency, OSA, or associated asthma, on ventilation outcomes will be taken into consideration and reasons for non-inclusion of patients will be recorded in order to evaluate the percentage of ventilated COPD patients that are screening failures. ClinicalTrials.gov NCT03890224 . Registered on March 26, 2019.

[Telemonitoring in continuous positive airway pressure-treated patients with obstructive sleep apnoea syndrome: An algorithm proposal]

Most of the continuous positive airway pressure (CPAP) devices currently in use allow telemonitoring of observance, leaks and the apnoea-hypopnoea index (AHI). La Société française de recherche et de médecine du sommeil (SFRMS) and La Société de pneumologie de langue française (SPLF) workgroup offer to CPAP prescribers and to home care providers a scientific document which has the following purposes: to underline the relevance of the telemonitoring of leaks and the AHI, to define alert thresholds, to describe the principal mechanisms generating excessive leaks and high AHI, and to propose a diagnostic algorithm.

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in nonhuman primates

Dopaminergic neuronal cell death, associated with intracellular α-synuclein (α-syn)-rich protein aggregates [termed "Lewy bodies" (LBs)], is a well-established characteristic of Parkinson's disease (PD). Much evidence, accumulated from multiple experimental models, has suggested that α-syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here, we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct α-syn pathogenic structures derived from patients with PD. Unexpectedly, our results show that, in nonhuman primates, a small amount of singular α-syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD, as multiple causes can induce a similar outcome regarding dopaminergic neurodegeneration.

A large thermal turbulent Taylor-Couette (THETACO) facility for investigation of turbulence induced by simultaneous action of rotation and radial temperature gradient

A thermal turbulent Taylor-Couette facility has been designed to investigate turbulent flows generated by differential rotation and radial temperature gradient. It consists of a cylindrical annulus with a rotating inner cylinder and a fixed outer cylinder. The electric heating system is installed inside the inner cylinder, and the annulus is immersed in a large cylindrical container filled with cooling fluid. Temperature regulators independently control the temperature of the inner surface of the inner cylinder and that of the cooling fluid. The facility allows us to reach values of the Reynolds number (Re ∼ 5 × 10⁵) and of the Rayleigh number (Ra ∼ 3 × 10⁶) for water as the working fluid. The facility provides torque measurements, a full optical access at the side and from the bottom for velocity measurements using particle image velocimetry (2D, stereoscopic, and tomographic). Temperature measurements in the flow can be performed by thermochromic liquid crystals or laser induced fluorescence.

Marital quality, partner's engagement and continuous positive airway pressure adherence in obstructive sleep apnea

BACKGROUND

Continuous positive airway pressure (CPAP) is the first line therapy for obstructive sleep apnea (OSA) but its effectiveness requires high adherence. We aimed to assess the impacts of the spouse's/partner's involvement and the quality of the couple's relationship on CPAP adherence.

METHODS

In a multicenter prospective study conducted in France, patients reported their subjective views regarding their partner's engagement in their CPAP treatment and the quality of their marital relationship using the Quality of Marriage Index. A hierarchical linear model was built to assess the predictors of CPAP adherence at day 120. Structural equation modeling was performed to evaluate the direct and indirect effects of the spouse's/partner's engagement and the quality of the couple's relationship on CPAP adherence.

RESULTS

The 290 OSA patients were predominantly male (77%), with a median age of 53 years IQR: [46; 62], median BMI: 32 kg/m² [28.6; 35.9] and median apnea + hypopnea index: 43/per hour [33; 58]. Independent factors for CPAP adherence at day 120 were the partner's encouragement of CPAP usage and a stable relationship exceeding 30 years, although emotional support or collaboration were not associated with CPAP adherence. Structural equation modeling demonstrated that spouse's/partner's engagement is directly related to CPAP adherence and improvement of symptoms, and that CPAP adherence is a mediator of disease-specific health-related quality of life. Marital quality was a significant moderator of these interactions meaning that a spouse's/partner's engagement improved adherence only when the quality of marriage index was high.

CONCLUSION

Future research and integrated OSA management should systematically include and document the role of the spouse/partner in CPAP adherence.

Efficacy of the Addition of a Cervical Collar in the Treatment of Persistent Obstructive Apneas Despite Continuous Positive Airway Pressure

ABSTRACT

Continuous positive airway pressure (CPAP) is currently the reference treatment for obstructive sleep apnea (OSA). The use of a face mask, although sometimes necessary, is often associated with increased airway obstruction due to mandibular retrusion. We report a small group of patients in whom addition of a cervical collar to a face mask allowed correction of obstructive events.

Mutations in the SPG3A gene encoding the GTPase atlastin interfere with vesicle trafficking in the ER/Golgi interface and Golgi morphogenesis

Mutations in SPG3A causing autosomal dominant pure spastic paraplegia led to identification of atlastin, a new dynamin-like large GTPase. Atlastin is localized in the endoplasmic reticulum, the Golgi, neurites and growth cones and has been implicated in neurite outgrowth. To investigate whether it exerts its activity in the early secretory system, we expressed normal and mutant atlastin in cell culture. Pathogenic mutations in the GTPase domain interfered with the maturation of Golgi complexes by preventing the budding of vesicles from the endoplasmic reticulum, whereas mutations in other regions of the protein disrupted fission of endoplasmic reticulum-derived vesicles or their migration to their Golgi target. Atlastin, therefore, plays a role in vesicle trafficking in the ER/Golgi interface. Furthermore, atlastin partially co-localized with proteins of the p24/emp/gp25L family that regulate vesicle budding and trafficking in the early secretory pathway, and co-immunoprecipitated p24, suggesting a functional relationship that should be further explored.

In vivo upregulation of endogenous NGF in the rat brain by the alpha2-adrenoreceptor antagonist dexefaroxan: potential role in the protection of the basalocortical cholinergic system during neurodegeneration

We have previously reported that the alpha2-adrenoceptor antagonist dexefaroxan protects against the degeneration of nucleus basalis magnocellularis (NbM) cholinergic neurons following cortical devascularization in the adult rat. Since nerve growth factor (NGF) is critical to the survival of NbM cholinergic neurons in the adult brain and its synthesis is known to be regulated by noradrenergic mechanisms, we examined whether the protective effect of dexefaroxan in the devascularization model was associated with regional induction of NGF biosynthesis. Dexefaroxan or vehicle was administered to rats via subcutaneous minipumps for 28 days following devascularization or sham operation procedures. In vehicle-treated devascularized rats, NGF protein levels in the cortex were increased at 5 days but had normalized by 2 weeks postoperation; NGF levels in NbM remained unchanged during this time. In dexefaroxan-treated devascularized rats, increases in NGF protein levels (2-fold) and immunoreactivity were maintained in both the cortex and NbM over the entire 28-day postoperation period; these increases were coincident with changes in functional markers characteristic of NGF's actions, including increases in choline acetyltransferase (ChAT), p75 and TrkA immunoreactivities, and a preservation of NbM cholinergic cell numbers. Dexefaroxan also increased NGF protein levels in sham-operated rats, but without any significant consequence to the otherwise normal NbM cholinergic phenotype in these animals. Results indicate that activation of endogenous NGF systems could contribute to the cholinergic protective effect of dexefaroxan in the cortical devascularization model, and provide further support for a potential therapeutic utility of dexefaroxan in neurodegenerative diseases where central cholinergic function is progressively compromised.

Animal models of Parkinson's disease in rodents induced by toxins: an update

The development of animal models of Parkinson's disease is of great importance in order to test substitutive or neuroprotective strategies for Parkinson's disease. Such models should reproduce the main characteristics of the disease, such as a selective lesion of dopaminergic neurons that evolves over time and the presence of neuronal inclusions known as Lewy bodies. Optimally, such models should also reproduce the lesion of non-dopaminergic neurons observed in a great majority of patients with Parkinson's disease. From a behavioral point of view, a parkinsonian syndrome should be observed, ideally with akinesia, rigidity and rest tremor. These symptoms should be alleviated by dopamine replacement therapy, which may in turn lead to side effects such as dyskinesia. In this review, we analyze the main characteristics of experimental models of Parkinson's disease induced by neurotoxic compounds such as 6-hydroxydopamine, MPTP and rotenone. We show that, whereas MPTP and 6-hydroxydopamine induce a selective loss of catecholaminergic neurons that in most cases evolves over a short period of time, rotenone infusion by osmotic pumps can induce a chronically progressive degeneration of dopaminergic neurons and also of non-dopaminergic neurons in both the basal ganglia and the brainstem.

The basics of renal imaging and function studies

Many radiotracers are available for kidney studies. They are classified into glomerular tracers (DTPA, EDTA), tubular tracers (OIH, MAG3) and cortical tracers (DMSA, GHA). Renal function is best assessed by glomerular filtration rate. Camera studies provide a relative function assessment, whereas clearance techniques provide a precise and reliable assessment of absolute renal function. The combination of both therefore gives a comprehensive study of glomerular function. Attempts to assess absolute function from camera studies only resulted in gross inaccuracy. Tubular tracers have a higher extraction rate. This could be used to estimate renal plasma flow (by assessing the effective renal plasma flow), or to determine relative function when renal function is low, or to study the urine flow in the urinary tract. Cortical tracers provide a high imaging quality. They are more adapted to infection assessment and relative function measurements. This paper reviews the most commonly used tracers and their relationship with renal physiology. Techniques for camera static and dynamic studies and plasma and urinary clearances are detailed. Procedures follow the recommendations of the most recent international consensus conferences on the topics.

Large-scale finite-wavelength modulation within turbulent shear flows

We show that turbulent "spirals" and "spots" observed in Taylor-Couette and plane Couette flow correspond to a turbulence-intensity modulated finite-wavelength pattern which in every respect fits the phenomenology of coupled noisy Ginzburg-Landau (amplitude) equations with noise. This suggests the existence of a long-wavelength instability of the homogeneous turbulence regime.

[SPECT-identified hypoperfusion of the left temporomesial structures in a Kleine-Levin syndrome]

A 13-year-old boy developed typical features of Kleine-Levin syndrome. Routine investigations and MRI were normal. SPECT, performed both during an attack and during a symptom-fee period, demonstrated clear hypoperfusion of the left mesiotemporal structures. The possible implications of this finding are discussed.

Clinical impact of (18)F-FDG PET in thyroid carcinoma patients with elevated thyroglobulin levels and negative (131)I scanning results after therapy

18F-FDG PET has been shown to effectively detect differentiated thyroid carcinoma (DTC) metastases with impaired iodine-trapping ability. This article evaluates the potential contribution of FDG PET in the follow-up of patients with differentiated thyroid carcinoma, elevated thyroglobulin (Tg) levels, and negative whole-body scan results obtained after high doses of (131)I.

METHODS

We prospectively assessed the ability of FDG to detect metastases in 37 DTC patients who had undergone total thyroidectomy and radioactive ablation and presented with persistent disease, as assessed from elevated Tg levels and negative results of whole-body scans performed after therapeutic doses of (131)I. Additional conventional imaging procedures were performed to detect residual disease, and the patients were divided into 2 groups: group 1, with positive conventional imaging findings (n = 10), and group 2, with negative conventional imaging findings (n = 27).

RESULTS

FDG PET showed positive findings in 28 patients and accurately localized tumor sites in 89% of them. In group 1, FDG PET confirmed 17 of 18 previously known tumor sites and detected 11 additional sites. In group 2, FDG PET findings were positive in 19 of 27 patients with no previously detected metastases. PET was effective for both low- and high-stage tumors. The FDG data led to a change in the clinical management of 29 of 37 patients with further surgical resection in 23 patients, 14 of whom achieved disease-free status, and external radiation therapy in 4 patients.

CONCLUSION

FDG PET is able to detect metastases undetected by (131)I posttherapy whole-body scanning in patients with elevated Tg levels. It should be proposed as a first-line investigation in patients with persistent disease but negative findings on (131)I whole-body scans after treatment.

[Respiratory bronchiolitis with diffuse interstitial lung disease]

Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) is a disease that exclusively affects cigarette smokers. Long-term prognosis is good with cessation of smoking, in combination or not with corticosteroid therapy. We report here the case of a 50-year-old patient with RB-IL diagnosed on lung biopsy. Despite corticosteroid and cyclophosphamide therapy, no functional or radiological improvement was obtained. In contrast, cessation of smoking was associated with the disappearance of the infiltrative opacities. Clinical and radiological parameters remained stable during follow-up (13 years) while a moderate obstructive pattern appeared.

Can dimercaptosuccinic acid renal scintigraphy be used to assess global renal function?

Use of dimercaptosuccinic acid (DMSA) has been proposed for the assessment of both relative and absolute renal function. Our aim was to test whether the renal absolute DMSA uptake (ADU) can reflect the absolute renal function from a theoretical point of view. A simple model was used to compute the ADU in the case of injury to one kidney. It was found that the assumption that ADU correctly reflects the absolute renal function may lead to a more than 50% overestimation of the function of both the normal and the impaired kidney. The later the measurement is made and the more impaired is the kidney, the more important is the error. Although DMSA can reliably quantify the relative renal function, it should not be used to assess absolute renal function lest major overestimation should occur.

Quantitation in planar renal scintigraphy: which mu value should be used?

The attenuation coefficient value mu used by different authors for quantitation in planar renal scintigraphy varies greatly, from the theoretical value of 0.153 cm-1 (appropriate for scatter-free data) down to 0.099 cm-1 (empirical value assumed to compensate for both scatter and attenuation). For a 6-cm-deep kidney, such variations introduce up to 30% differences in absolute measurement of kidney activity. Using technetium-99m phantom studies, we determined the mu values that would yield accurate kidney activity quantitation for different energy windows corresponding to different amounts of scatter, and when using different image analysis approaches similar to those used in renal quantitation. With the 20% energy window, it was found that the mu value was strongly dependent on the size of the region of interest (ROI) and on whether background subtraction was performed: the mu value thus varied from 0.119 cm-1 (loose ROI, no background subtraction) to 0.150 cm-1 (kidney ROI and background subtraction). When using data from an energy window that could be considered scatter-free, the mu value became almost independent of the image analysis scheme. It is concluded that: (1) when performing background subtraction, which implicitly reduces the effect of scatter, the mu value to be used for accurate quantitation is close to the theoretical mu value; (2) if the acquired data were initially corrected for scatter, the appropriate mu value would then be the theoretical mu value, whatever the image analysis scheme.

Concordance between dobutamine Doppler tissue imaging echocardiography and rest reinjection thallium-201 tomography in dysfunctional hypoperfused myocardium

OBJECTIVE

To evaluate the efficiency of the new technique colour Doppler tissue imaging (DTI) by studying the concordance between dobutamine DTI, standard grey scale echocardiography (SE), and rest-reinjection TI-201 tomography (TI) in dysfunctional myocardium.

PATIENTS

23 patients with chronic wall motion abnormalities and proven coronary artery disease (> 70% diameter stenosis of at least one major coronary artery at angiogram).

METHODS

The contractile reserve and the resting perfusion characteristics of dysfunctional myocardial segments were assessed with low dose dobutamine SE and/or DTI (2.5 up to 20 gamma/kg/min) and TI on a semiquantitative basis. The DTI or SE data were separately compared with TI, on the basis of a 13 segment ventricular model. The resulting score of combined DTI and SE was also compared with TI. Finally the results obtained from DTI were compared with SE.

RESULTS

A total of 142 severely hypokinetic or akinetic segments were visualised. The viability study was feasible in 127 (89%) and 121 (85%) segments with DTI and SE, respectively. TI detected viability more frequently than DTI (84 v 61, p < 0.001) and SE (80 v 50, p < 0.001). However, as many viable segments were detected with combined DTI and SE as with TI (78 v 84, NS). The kappa values between TI and SE, DTI or combined SE and DTI were 0.38, 0.45, and 0.57, respectively, and increased to 0.52 and 0.76, respectively, for SE and DTI versus TI when mid-anterior and mid-inferior segments only were considered. The kappa value between SE and DTI was 0.34.

CONCLUSIONS

DTI is a helpful adjunct to SE, when using low dose dobutamine. This combination revealed as many viable segments as TI and showed a better agreement than DTI or SE alone for the assessment of myocardial viable segments evidenced by TI.

Consensus report on quality control of quantitative measurements of renal function obtained from the renogram: International Consensus Committee from the Scientific Committee of Radionuclides in Nephrourology

Among all the physiological indices that can be quantified using renography, measurement of renal function is the most basic. These measurements are used to make critical clinical management decisions and, as such, their reliability needs to be quality assured. This article seeks to address each aspect of the renography procedure, with particular emphasis on the effect on measurement of relative renal function. Estimation of individual kidney function is mentioned, but only briefly. A consensus approach was adopted, overseen, and directed by a chairman appointed by the Scientific Committee of the International Radionuclides in Nephro-Urology Group. The chairman selected the panel of experts from eight different countries based on their practical experience in the field. Where evidence exists to support the various recommendations it is given. Otherwise, the stated guidance represents the considered opinion of a body of experts, based on long experience and unpublished data. Some necessary compromises were made to account for the fact that renography is seldom performed solely with the purpose of measuring relative renal function. The technicalities of renography have always been a source of debate in nuclear medicine, which is reflected by the fact that a consensus could simply not be reached on a small number of issues. The structure of the report ensures that these are clearly indicated. This should serve to highlight gaps in our current knowledge, thus helping to direct future research. It is envisaged that the recommendations will be revised on a 2-year cycle to ensure that they remain up to date. An "open" process will be used to encourage participation and ownership. It is hoped that promotion of these guidelines, suitably complemented by audit processes, will raise standards in the practice of gamma camera renography.

Distribution of semaphorin IV in adult human brain

The semaphorins comprise a family of secreted and membrane bound proteins that influence development of the nervous system as well as non-neural organs. H.SemaIV was originally isolated from a homozygously deleted region involving a subset of small cell lung cancers, a neuroendocrine derived neoplasm. To investigate H.SemaIV expression, specific polyclonal antibodies directed against a unique polypeptide (amino acids 758-773) were developed and their specificity confirmed. In cell lines, H.SemaIV staining was observed in cytoplasmic granules. In the normal adult human brain, we noted three general characteristics of H.SemaIV expression. H.SemaIV was strongly present in specific nuclei or in neuronal regions arranged in defined subnuclear structures. It was also present in neurons but not glial cells or ependymocytes. Lastly, H.SemaIV was not present in cell bodies, but rather in fibers and nerve terminals. Interestingly, an altered pattern of staining was detected in brains of three patients with Alzheimer's disease.

Enalapril plus frusemide MAG3 scintigraphy in hypertensive patients with atherosclerosis and moderate renal insufficiency

We performed a retrospective study on 26 patients with moderate renal failure (mean GFR = 51 +/- 21 ml min-1 1.73 m-2), hypertension and atherosclerosis. Apart from three patients who had completely normal renal Doppler ultrasonography, all patients underwent renal angiography. Three groups of kidneys with different atherosclerotic renal artery involvement were identified: Group 1, 24 kidneys with no renal artery stenosis (RAS); Group 2, 18 kidneys with mild (> 25% and < 50% diameter) RAS; and Group 3, 10 kidneys with moderate (> 50% diameter) RAS. We used a two-day protocol with frusemide plus enalapril 99Tcm-MAG3 scintigraphy. The mean parenchymal transit time (MPTT), time to the maximum activity (time to peak) of the renal curve (Tmax), residual activity and split renal uptake were evaluated. The measured parameters did not differ before and after enalapril in Group 1 or in Group 2. In Group 3, MPTT and residual activity differed significantly (P < 0.025) before and after enalapril. The Tmax before and after enalapril, MPTT before and after enalapril and residual activity after enalapril differed significantly (P < 0.05) between Groups 1 and 3 and between Groups 2 and 3. Threshold values were obtained to maximize diagnostic accuracy. The Tmax, MPTT and residual activity after enalapril gave satisfactory results, and MPTT performed best with a 75% positive predictive value and a 98% negative predictive value for the diagnosis of renal artery stenosis. We conclude that MPTT, measured after enalapril administration, is a useful parameter to detect renal artery stenosis in patients with hypertension, atherosclerosis and moderate renal insufficiency.

Is differential regulation of mitochondrial transcripts in Parkinson's disease related to apoptosis?

A cDNA library of substantia nigra pars compacta from a patient with Parkinson's disease (PD) was differentially screened with probes of normal and parkinsonian substantia nigra enriched in neuronal transcripts. Fifty-eight clones were isolated; 39 were subunits of mitochondrial respiratory complexes I and IV. Parallel screening of a cDNA library derived from normal substantia nigra confirmed differential representation of the transcripts in the substantia nigra pars compacta. In situ hybridization in postmortem brain from parkinsonian and control subjects, with representative complex I and complex IV probes, showed increased labeling, at the cellular level, of the complex I subunit ND1 in neurons of the lateral substantia nigra, where cell death is greatest in PD, but decreased labeling in the medial substantia nigra where fewer cells die. Expression of a complex IV subunit, COXI, increased, however, in both parts of the structure. Increased expression of ND1 and COXI was also observed in nerve growth factor-differentiated PC12 cells undergoing apoptosis induced by tumor necrosis factor-alpha, suggesting that the differential regulation of certain mitochondrial mRNAs may be associated with this form of cell death. This in vitro model of apoptosis is potentially relevant to the death of dopaminergic neurons in PD, because these cells express the tumor necrosis factor-alpha receptor, and neighboring microglial cells in patients synthesize the cytokine.

[Measurement of global and separate renal blood flow using cine-computed tomography]

EBCT flow study offer a promising new approach to measure the renal blood flow. In vitro and in vivo studies were performed to resolve methological problems such as checking the linear relation between contras concentration and Hounsfield units or determination of the Treshold used for the mapping. First measurements of renal volumes and flow performed in patients showed expected values.

Prostaglandin E2 production by uterine stromal cell line UIII: regulation by estradiol and evidence of an ethanol action

We have recently established a uterine stromal cell line (UIII). The purpose of the present study was to determine whether these cells have retained the ability to produce and release prostaglandins after several passages and whether this production was regulated. UIII cells, grown in basal conditions, released a very low amount (40.6 +/- 2.9 pg/24h/10(6) cells) of prostaglandin E2 (PGE2) though cellular content was more elevated (192 +/- 23 pg/10(6) cells). Ethanol increased the cellular content but decreased the release of PGE2, whereas estradiol 17 beta (E2) increased it in a dose-dependent manner, but had no effect on the cellular content. The PGE2 release by cells grown in medium containing 10 microM arachidonate (AA) reached 1.39 +/- 0.05 ng/24h/10(6) cells, and was further increased to 2.1 +/- 0.1 ng/24 h/10(6) cells by the addition of ethanol. Under the latter condition, E2 was ineffective. This study also showed that UIII cells expressed an immunoreactive pancreatic type 14 kD PLA2. A substantial increased 14 kD PLA2 expression was observed in ethanol-treated cells, suggesting that ethanol-effect on prostaglandin production might be partly mediated by PLA2 increase. Medium supplementation with arachidonate also resulted in a significant increase of intracellular 14 kD PLA2 expression. The present results showed that uterine stromal UIII cells have retained the enzymatic machinery to produce PGE2. Moreover these data demonstrate that ethanol and E2 affect differently uterine PGE2 production.

The diagnosis of renovascular hypertension: the role of captopril renal scintigraphy and related issues

This article reviews the screening and diagnostic tests used in the detection of significant renal artery stenosis and renovascular hypertension. After addressing the pathophysiological considerations necessary for correct diagnostic test interpretation, this review critically surveys the recent advances in, and the limitations of, relevant investigational procedures and in particular focuses on the efficacy and issues of angiotensin-converting enzyme inhibitor renal scintigraphy.

Chronic neutral phosphate supplementation induces sustained, renal metabolic alkalosis

The aim of the present study was to test whether intravenous neutral phosphate supplementation, recently shown in our laboratory to acutely stimulate proton secretion in the distal nephron, was able to induce a sustained metabolic alkalosis. Neutral Na and K phosphate supplementation for seven days, with equivalent reduction in chloride supply and unchanged intake of sodium and potassium, in ADX rats receiving fixed physiological doses of aldosterone and dexamethasone (group 1, N = 7), was responsible for a severe metabolic alkalosis (MA; delta [HCO3] 11 +/- 1.3 mM, and delta pH 0.11 +/- 0.06 unit). Metabolic alkalosis was at least in part of renal origin, since net acid excretion (NAE) transiently increased, principally due to an increment in titratable acid excretion rate. Balances were equilibrated for sodium and negative for chloride and potassium, which may have contributed to the severity of the MA. Chronic i.v. neutral Na phosphate, without change in potassium and chloride supply, in ADX rats receiving the same doses of steroids (group 2, N = 5), was responsible for a less severe MA (delta [HCO3] 7.5 +/- 0.9 mM, and delta pH 0.07 +/- 0.01 unit), also of renal origin. In this group, balances were positive for chloride and sodium and equilibrated for potassium. Finally, neutral Na and K phosphate supplementation with reduction in chloride supply in intact rats (group 3, N = 4) was also able to induce a MA (delta [HCO3] 5.5 +/- 1.8 mM, and delta pH 0.06 +/- 0.01 unit) of renal origin, with balances negative for chloride and equilibrated for potassium and sodium. In all groups, the generation and maintenance of MA probably resulted from stimulated proton secretion in the distal nephron, as suggested by the observed increase of PCO2 over HCO3 concentration ratio in the urine and a fall in urine pH despite augmented urinary buffer content throughout the phosphate infusion period. Glomerular filtration rate did not significantly vary in any group. In conclusion, chronic supplementation of neutral phosphate appears to stimulate per se proton secretion in the distal nephron, independently of sodium, chloride, and potassium balances, and adrenal steroid secretion. Thus neutral phosphate supplementation should be added to the previously known factors able to induce MA.

[Renal acidosis]

Normal adults with normal protein intakes have a urinary NH4 excretion of 40 to 50 mmol/24 hours and a variable urinary pH. In cases of metabolic acidosis a urinary pH less than 5.5 suggests an extra-renal origin whilst a urinary pH greater than 5.5 is in favour of renal acidosis, but there are many exceptions to this rule. On the other hand, urinary NH4 excretion is always greater than 70 mmol/24 hours in the first case and less than 40-50 mmol/24 hours in the second; and the use of the urinary anionic gap (Na + K - Cl), negative in the first case and positive in the second, enables the two situations to be distinguished. The acidosis of nephron reduction is easily recognised in cases of severe renal failure with an increase in unmeasured plasma anions whilst tubular acidoses are accompanied by a hyperchloremia. Measurement of fractional HCO3 excretion after an oral loading dose of NaHCO3, preferably by TmCHO3 with respect to GFR, distinguishes proximal tubular acidosis (low TmHCO3) from distal tubular acidosis (normal or high TmHCO3). In the latter case, the presence of hypokalemia suggests a distal tubular acidosis either due to deficiency of the H(+)-ATPase pumps (absence of increased urinary pCO2 after oral loading dose of NaHCO3) or to the inability of the kidney to maintain a normal H+ gradient (normal increase of urinary pCO2. The presence of hyperkalemia suggests diseases associated with hypoaldosteronism (low or inappropriate serum aldosterone concentrations), abnormal transepithelial voltages or with a pseudo-hypoaldosteronism syndrome (high plasma aldosterone concentration). The prevalence of distal tubular acidosis with hyperkalemia is on the increase whilst tubular acidosis with hypokalemia remains rare.

[Renal regulation of the acid-base equilibrium]

The kidney controls extracellular bicarbonate concentration and the pH of the body by modulating neat acid excretion (ammonium plus titratable acidity minus bicarbonate) according to the systemic acid-base balance. Proton, bicarbonate and phosphate transport and ammonium synthesis in the proximal tubules change in a homeostatic manner. The intercalycial A (proton secreting) and B cells (bicarbonate secreting) of the distal tubule and cortical collecting ducts have a high capacity of adaptation. The wide ascending branch of the loop of Henle also plays an important role in the bicarbonate and ammonium transport. Recent data suggest a pluri-hormonal regulation of urinary acidification. Therefore, the precision of the renal response to metabolic acidosis depends on the coordinated regulation of different segments of the nephron by the parathyroid hormone, aldosterone and the glucocorticosteroids.

Effects of glucagon on H(+)-HCO3- transport in Henle's loop, distal tubule, and collecting ducts in the rat

Paired micropuncture experiments were carried out in somatostatin-infused volume-expanded rats to examine the effects of a glucagon infusion (0.05 ng.min-1.g body wt-1) on urinary acidification and tubular handling of bicarbonate. Whole kidney and single-nephron glomerular filtration rate were not affected by glucagon. In thyroparathyroidectomized (TPTX) rats, glucagon inhibited the reabsorption of total CO2 in Henle's loop. In intact animals, however, the latter effect was not observed. In the distal tubule accessible to micropuncture, net total CO2 absorption was observed during volume expansion plus somatostatin infusion, which reversed to net total CO2 secretion during glucagon infusion in Wistar rats; thus the late distal delivery of total CO2 increased almost 80%. Marked inhibition of urinary acidification occurred in all animals as evidenced by a rise in urine pH and bicarbonate excretion. Conversely, a somatostatin infusion, which decreased the plasma glucagon concentration, stimulated net total CO2 absorption along the distal tubule and augmented final urine acidification in Wistar rats. Finally, urine-minus-blood PCO2 during alkaline diuresis was significantly reduced by glucagon infusion in bicarbonate-loaded TPTX rats. We conclude that 1) glucagon inhibits bicarbonate absorption in superficial Henle's loop in TPTX but not in intact rats, and 2) glucagon stimulates bicarbonate secretion and/or inhibits proton secretion in the distal tubule and collecting ducts, which leads to reduced urinary acidification.

Determinants of parathormone secretion in primary hyperparathyroidism

We studied the effects of acute modifications in plasma calcium on parathormone (PTH) secretion in 23 patients with primary hyperparathyroidism (PHPT). In 12 patients, PTH hypersecretion was autonomous, and basal plasma calcium concentration was positively correlated with maximal serum PTH(1-84) reached during Na2EDTA infusions. In 11 patients, PTH hypersecretion remained suppressible, but with elevated set point value, and basal plasma calcium concentration was positively correlated with set point. Thus, the degree of hypercalcemia seems mainly determined by the magnitude of maximal PTH secretion and set point error in autonomous and suppressible PHPT, respectively. We have previously suggested that high serum calcitriol levels might chronically inhibit PTH hypersecretion in PHPT. We showed that hyperparathyroid patients with renal stone presentation exhibited an abnormally high value of circulating calcitriol and a moderately elevated PTH activity, while patients with severe bone disease presentation displayed a low to normal calcitriol value and a dramatically increased PTH activity. The hypothesis was supported by a recent study from our Unit in one hyperparathyroid patient with severe bone disease and normal serum calcitriol level. Increment of serum calcitriol after daily intravenous Rocaltrol for 5 days directly suppressed PTH hypersecretion without change in plasma ionized calcium.