Rett syndrome (RTT) is an autism spectrum disorder caused by loss-of-function mutations in the methyl-CPG-binding protein 2 (Mecp2) gene. Frequent apneas and irregular breathing are prevalent in RTT, and also occur in rodent models of the disorder, including Mecp2Bird and Mecp2R168X mice. Sarizotan, a serotonin 5-HT1a and dopamine D2-like receptor agonist, reduces the incidence of apneas and irregular breathing in mouse models of RTT (Abdala et al., 2014). Targeting the 5HT1a receptor alone also improves respiration in RTT mice (Levitt et al., 2013). However, the contribution of D2-like receptors in correcting these respiratory disturbances remains untested. PAOPA, a dopamine D2-like receptor positive allosteric modulator, and quinpirole, a dopamine D2-like receptor orthosteric agonist, were used in conjunction with whole-body plethysmography to evaluate whether activation of D2-like receptors is sufficient to improve breathing disturbances in female heterozygous Mecp2Bird/+ and Mecp2R168X/+ mice. PAOPA did not significantly change apnea incidence or irregularity score in RTT mice. PAOPA also had no effect on the ventilatory response to hypercapnia (7% CO2). In contrast, quinpirole reduced apnea incidence and irregularity scores and improved the hypercapnic ventilatory response in Mecp2R168X/+ and Mecp2Bird/+ mice, while also reducing respiratory rate. These results suggest that D2-like receptors could contribute to the positive effects of sarizotan in the correction of respiratory abnormalities in Rett syndrome. However, positive allosteric modulation of D2-like receptors alone was not sufficient to evoke these effects.

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For decades spirometry has been the benchmark test for capturing lung function in children but its recognized limitations required the development of other techniques. This article introduces novel techniques in lung function assessment for pediatric patients, including multiple breath washout, impulse oscillometry, structured light plethysmography, and electrical impedance tomography, and common themes in interpreting the results. Challenges include standardization, reference data, and clinical integration of these innovative tools. Further research is ongoing to optimize these tests for clinical use, especially in diverse populations and pediatric settings.

UNASSIGNED: Blood lactate is a marker of tissue hypoxia while capillary refill time (CRT) is a surrogate of tissue perfusion. Measuring these parameters is recommended for assessing circulatory status and guiding resuscitation. However, blood lactate is not widely available in African emergency departments. Additionally, CRT assessment faces challenges related to its precision and reproducibility. This study aims to evaluate the accuracy of visual CRT(V-CRT) compared to plethysmographic CRT (P-CRT) in predicting lactate levels among septic patients.
UNASSIGNED: This prospective observational study enrolled consecutive patients with sepsis or septic shock over a 6-month period from a tertiary hospital in Marrakech, Morroco. V-CRT and P-CRT were evaluated upon admission, and simultaneous measurements of arterial lactate levels were obtained. The precision of V-CRT and P-CRT in predicting arterial lactate was assessed using ROC curve analysis.
UNASSIGNED: Forty-three patients aged of 64±15 years, of whom 70 % were male, were included in the study. Of these, 23 patients (53 %) had sepsis, and 20 patients (47 %) experienced septic shock. Both V-CRT and P-CRT demonstrated statistically significant correlations with arterial lactate, with correlation coefficients of 0.529 (p < 0.0001) and 0.517 (p = 0.001), respectively. ROC curve analysis revealed that V-CRT exhibited satisfactory accuracy in predicting arterial lactate levels >2 mmol/l, with an area under the curve (AUC) of 0.8 (95 % CI=0.65 - 0.93; p < 0.0001). The prediction ability of P-CRT was lower than V-CRT with an AUC of 0.73 (95 % CI: 0.57-0.89; p = 0.043). The optimal thresholds were determined as 3.4 s for V-CRT (sensitivity = 90 %, specificity = 58 %) and 4.1 s for P-CRT (sensitivity = 85 %, specificity = 62 %).
UNASSIGNED: These findings suggest that the plethysmographic evaluation did not improve the accuracy of CRT for predicting lactate level. However, V-CRT may still serve as a viable surrogate for lactate in septic patients in low-income settings.

In the absence of appropriate medical care, exposure to organophosphorus nerve agents, such as VX, can lead to respiratory failure, and potentially death by asphyxiation. Despite the critical role of respiratory disturbances in organophosphorus-induced toxicity, the nature and underlying mechanisms of respiratory failure remain poorly understood. This study aimed to characterize respiratory alterations by determining their type and duration in mice exposed to a subcutaneous sublethal dose of VX. Respiratory ventilation in Swiss mice was monitored using dual-chamber plethysmography for up to 7 days post-exposure. Cholinesterase activity was assessed via spectrophotometry, and levels of inflammatory biomarkers were quantified using Luminex technology in blood and tissues involved in respiration (diaphragm, lung, and medulla oblongata). Additionally, a histological study was conducted on these tissues to ensure their structural integrity. Ventilatory alterations appeared 20-25 minutes after the injection of 0.9 LD50 VX and increased until the end of the recording, i.e., 40 minutes after intoxication. Concurrent with the occurrence of apnea, increased inspiratory and expiratory times resulted in a significant decrease in respiratory rate in exposed mice compared to controls. Ventilatory amplitude and, consequently, minute volume were reduced, while specific airway resistance significantly increased, indicating bronchoconstriction. These ventilatory effects persisted up to 24 or even 72 hours post-intoxication, resolving on the 7th day. They were correlated with a decrease in acetylcholinesterase activity in the diaphragm, which persisted for up to 72 hours, and with the triggering of an inflammatory reaction in the same tissue. No significant histologic lesions were observed in the examined tissues. The ventilatory alterations observed up to 72 hours post-VX exposure appear to result from a functional failure of the respiratory system rather than tissue damage. This comprehensive characterization contributes to a better understanding of the respiratory effects induced by VX exposure, which is crucial for developing specific medical countermeasures.

Objective.In patients with suspected thoracic outlet syndrome (TOS), diagnosing inter-scalene compression could lead to minimally invasive treatments. During photo-plethysmography, completing a 30 s 90° abduction, external rotation (\'surrender\' position) by addition of a 15 s 90° antepulsion \'prayer\' position, allows quantitative bilateral analysis of both arterial (A-PPG) and venous (V-PPG) results. We aimed at determining the proportion of isolated arterial compression with photo-plethysmography in TOS-suspected patients.Approach.We studied 116 subjects recruited over 4 months (43.3 ± 11.8 years old, 69% females). Fingertip A-PPG and forearm V-PPG were recorded on both sides at 125 Hz and 4 Hz respectively. A-PPG was converted to PPG amplitude and expressed as percentage of resting amplitude (% rest). V-PPG was expressed as percentage of the maximal value (% max) observed during the \'Surrender-Prayer\' maneuver. Impairment of arterial inflow during the surrender (As+) or prayer (Ap+) phases were defined as a pulse-amplitude either <5% rest, or <25% rest. Incomplete venous emptying during the surrender (Vs+) or prayer (Vp+) phases were defined as V-PPG values either <70% max, or <87% max.Main results.Of the 16 possible associations of encodings, As - Vs - Ap - Vp- was the most frequent observation assumed to be a normal response. Isolated arterial inflow without venous outflow (As + Vs-) impairment in the surrender position was observed in 10.3% (95%CI: 6.7%-15.0%) to 15.1% (95%CI: 10.7%-20.4%) of limbs.Significance.Simultaneous A-PPG and V-PPG can discriminate arterial from venous compression and then potentially inter-scalene from other levels of compressions. As such, it opens new perspectives in evaluation and treatment of TOS.

OBJECTIVE: Micronized purified flavonoid fraction (MPFF) is the most widely prescribed and well-studied venoactive drug available for the treatment of chronic venous disease (CVD). Photoplethysmography (PPG) is used to quantitatively measure venous haemodynamics and provide information about the overall function of the venous system. The aim of this study was to use digital PPG to evaluate the effects of MPFF on venous haemodynamics in patients with CVD.
METHODS: Patients diagnosed with CVD at an outpatient clinic in Bursa, Turkey between February 2018 and July 2020 were assessed for inclusion in this retrospective analysis. Patients who complied with the advised treatment strategy (MPFF 1000 mg tablets taken orally once daily and compression garments) and attended follow-up visits were included in the analysis. Digital PPG was used to measure venous refilling time (VRT) and venous pumping capacity (VPC) at diagnosis and 6 months of follow-up. The Venous Clinical Severity Score (VCSS) was also obtained at these visits, and patients completed the 20-item Chronic Venous Insufficiency Quality of life Questionnaire (CIVIQ-20).
RESULTS: In total, 721 patients (mean age 52 years) with C0-C4 CVD were included in the study. PPG showed that VRT and VPC increased significantly from 19.0 sec and 2.0%, respectively, at diagnosis to 27.4 and 4.9%, respectively, at 6 months (both p<0.05). Mean VCSS improved significantly from 7.9 at diagnosis to 3.1 at 6 months (p<0.05). Mean CIVIQ-20 score also improved significantly at the 6-month follow up (20.1 vs 38.6 at diagnosis; p<0.01).
CONCLUSIONS: In patients with C0-C4 CVD, 6 months of MPFF treatment plus the wearing of compression garments was associated with statistically significant improvements in venous haemodynamic parameters measured by PPG, as well as measures of clinical severity and quality of life.

BACKGROUND: Beat-to-beat blood pressure variability (BPV) is based on each heartbeat and represents a dynamic equilibrium process modulated by artery and cardiac involvement of pressure-receptive reflexes. To date, there remains a lack of prospective studies illustrating the clinical value of beat-to-beat BPV within 24 hours of acute ischemic stroke onset.
RESULTS: This study prospectively monitored beat-to-beat blood pressure and heart rate in patients with acute ischemic stroke within 24 hours of onset using a noninvasive plethysmograph and calculated beat-to-beat BPV, heart rate variability, and the cross-correlation baroreflex sensitivity. A modified Rankin Scale score of ≥2 at 90 days was defined as an unfavorable prognosis. Multivariate logistic regression was performed, and the nomogram model was developed by adding the beat-to-beat BPV to the traditional model for predicting prognosis. Beat-to-beat BPV increased significantly in the unfavorable outcome group (P<0.05) compared with that in the favorable outcome group, whereas no difference was observed in beat-to-beat heart rate variability and cross-correlation baroreflex sensitivity between both groups (P>0.05). Furthermore, beat-to-beat BPV within 24 hours of acute ischemic stroke onset was independently associated with unfavorable outcome at 90 days (P<0.005). The addition of beat-to-beat BPV to the traditional model for predicting prognosis enhanced the area under the receiver operating characteristic curve from 0.816 to 0.830.
CONCLUSIONS: Increased beat-to-beat BPV within 24 hours of acute ischemic stroke onset was independently associated with a poor prognosis at 90 days and may be a potential predictor for discriminating unfavorable prognosis.

Finger photo pulse plethysmography is a simple, inexpensive and non-invasive method for measurement of arterial stiffness. The objective is to assess the correlation of arterial stiffness in low back pain subjects with lumbar disc degeneration. Thirty-four back pain patients of both sexes in age group of 30-65 were included. Anthropometric measures like height, body weight, body mass index (BMI) were included. Stiffness index (SI) and reflection index (RI) were measured from the digital volume pulse waveform. There was a negative correlation between SI/RI and no correlation between SI and RI with BMI in both sexes. A significant correlation found between weight and BMI in both sexes. Arterial stiffness may not have any influence on disc degeneration. BMI showed some influence on disc degeneration and back pain.

UNASSIGNED: It has been hypothesized that compromised ocular circulation in glaucoma may be concomitant of systemic changes. The purpose of this study is to test whether systemic blood flow pulse waveform patterns differ between individuals with glaucoma (GL), glaucoma suspects (GLS), and normal healthy controls (HC).
UNASSIGNED: The study included 35 bilateral GL, 67 bilateral GLS, 29 individuals with unilateral GL who were considered GLS in the other eye, and 44 healthy controls. Systemic pulsatile blood pressure waveforms were recorded using a finger cuff. A continuous 200 Hz plethysmography recording is made to obtain a pulse waveform. Waveform parameters were extracted using custom software from an average of eight pulse cycles. These were compared between GL, GLS, and HC groups on a per-eye basis, using generalized estimating equation models to account for intereye correlations; and plotted against disease severity by visual field linearized mean deviation (MDlin) and retinal nerve fiber layer thickness (RNFLT).
UNASSIGNED: Averaged blood pressure was significantly lower in the HC group (mean ± standard deviation 91.7 ±11.7 mm Hg) than the GLS (102.4 ± 13.9) or GL (102.8 ± 13.7) groups, with P < 0.0001 (generalized estimating equation regression). Waveform parameters representing vascular resistance were higher in both GLS and GL groups than the HC group; and were correlated with RNFLT and MDlin (P ≤ 0.05).
UNASSIGNED: The shape of the systemic pulsatile waveform differs in individuals with GL/GLS suspects, compared to HC eyes. Blood pressure changes more rapidly in individuals with GL, which suggests higher arterial stiffness.