Comparative analysis of pulmonary ventilation distribution between low-cost and branded incentive spirometers using electrical impedance tomography in healthy adults: Study protocol.

BACKGROUND: The Incentive Spirometer (IS) increases lung volume and improves gas exchange by visually stimulating patients to take slow, deep breaths. It prevents respiratory complications and treats postoperative atelectasis in patients undergoing abdominal, thoracic, and neurosurgical procedures. Its effectiveness has been validated in studies that support improved lung capacities and volumes in individuals with respiratory complications, postoperative thoracic surgery, upper abdominal surgery, and bariatric surgery. The modified Pachón incentive spirometer (MPIS) is a cost-effective alternative to branded IS. It is crucial to validate whether the MPIS distributes ventilation as effectively as commercial devices do. Ventilation distribution will be measured using electrical impedance tomography. OBJECTIVE: The aim is to compare the distribution of pulmonary ventilation between the MPIS and another commercial IS in healthy adults using electrical impedance tomography. METHODS: A crossover clinical trial is proposed to evaluate the measurement of pulmonary ventilation distribution using EIT in a sample of healthy adults. All participants will use a commercial flow IS and the MPIS, with the order of assignment randomized. This research will use electrical impedance tomography to validate the operation of the MPIS. CONCLUSIONS: This study protocol will compare two incentive spirometers' impact on pulmonary ventilation, potentially endorsing the adoption of a cost-effective device to enhance accessibility for targeted populations. TRIAL REGISTRATION: The study was registered in ClinicalTrials.gov (NTC05532748).

The status and influencing factors of lung ventilation function in employees exposed to dust in enterprises of the XPCC, China.

Background: Occupational health is closely related to harmful factors in the workplace. Dust is the primary contributing factor causing impaired lung ventilation function among employees with dust exposure, and their lung ventilation function may also be influenced by other factors. We aimed at assessing the status and influencing factors of lung ventilation function among employees exposed to dust in the enterprises of the Eighth Division located in the Xinjiang Production and Construction Corps (XPCC), China. Methods: Employees exposed to dust in enterprises of the Eighth Division located in the XPCC in 2023 were selected as the subjects of this cross-sectional study. Their lung ventilation function indicators were extracted from health examination records, and an on-site electronic questionnaire survey was conducted among them. Binary logistic regression analyses were conducted to evaluate the factors influencing lung ventilation function. Results: According to the fixed value criteria, the abnormal rates of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC were 31.6, 1.4, and 0.4%, respectively. The lower limit of normal (LLN) criteria could overestimate the rate of abnormal lung ventilation function. Several factors were related to impaired lung ventilation function, including gender, age, education level, marital status, body mass index (BMI), smoking status, physical activity, the type of dust, industry, enterprise scale, occupation, length of service, working shift, monthly income, and respiratory protection. Conclusions: A relatively low abnormal rate of lung ventilation function was observed among employees exposed to dust in enterprises of the Eighth Division, XPCC, and their lung ventilation function was associated with various factors. Effective measures should be taken urgently to reduce the effects of adverse factors on lung ventilation function, thereby further protecting the health of the occupational population.

Impacto de un Programa de Recuperación Funcional en Músculos Ventilatorios y Apendiculares en Pacientes Post-ventilación Mecánica por COVID-19 / Impact of a Functional Recovery Program on Ventilatory and Appendicular Muscles in Patients Post-mechanical Ventilation for COVID-19

Los pacientes con COVID-19 subsidiarios de ventilación mecánica (VM), evolucionan con consecuencias funcionales en la musculatura ventilatoria y apendicular que no necesariamente se abordan de manera diferenciada. El objetivo de esta investigación fue evaluar el impacto de un programa de recuperación funcional en estos pacientes y determinar si las intervenciones afectan de manera diferenciada a las funciones ventilatorias y musculatura apendicular, utilizando pruebas de bajo costo. Se evaluaron 47 pacientes con COVID-19 que estuvieron en VM. Posterior a una espirometría basal se les realizó; presión inspiratoria máxima (PIMáx), fuerza de prensión palmar (FPP), prueba de pararse y sentarse (PPS) y Prueba de caminata en 6 minutos (PC6m), antes y después del plan de intervención. Este programa incluyó ejercicios aeróbicos y de fuerza supervisados por dos sesiones semanales de 60 minutos durante 3 meses. Después del programa, se observaron mejoras significativas en la capacidad vital forzada (CVF), el volumen espiratorio en el primer segundo (VEF1) y la PIMáx. Se encontraron relaciones significativas entre estas mediciones y la distancia recorrida de la PC6m, la FPP y la PPS. En conclusión, el programa de recuperación funcional en pacientes con COVID-19 que requirieron VM, beneficia tanto la función ventilatoria como la fuerza muscular apendicular. Las pruebas de fuerza muscular apendicular pueden ser útiles para evaluar la recuperación ya que pueden entregar información diferenciada de sus rendimientos. Por último, se necesita más investigación para comprender mejor la respuesta de estos pacientes a la rehabilitación.

SUMMARY: Patients with COVID-19 requiring mechanical ventilation (MV) evolve with functional consequences in the ventilatory and appendicular muscles that are not necessarily addressed in a differentiated manner. The objective of this research was to evaluate the impact of a functional recovery program in these patients and determine if the interventions differentially affect ventilatory functions and appendicular muscles, using low- cost tests. 47 patients with COVID-19 who were on MV were evaluated. After a baseline spirometry, they were performed; maximum inspiratory pressure (MIP), handgrip strength (HGS), sit to stand test (STST) and 6-minute walk test (6MWT), before and after the intervention plan. This program included supervised aerobic and strength exercises for two weekly 60-minute sessions for 3 months. After the program, significant improvements were observed in forced vital capacity (FVC), expiratory volume in the first second (FEV1) and MIP. Significant relationships were found between these measurements and the distance traveled of the 6MWT, the HGS and the STST. In conclusion, the functional recovery program in patients with COVID-19 who required MV benefits both ventilatory function and appendicular muscle strength. Appendicular muscle strength tests can be useful to evaluate recovery since they can provide differentiated information about your performances. Finally, more research is needed to better understand the response of these patients to rehabilitation.

Fractal dimension of pulmonary gas and blood distribution assessed by synchrotron K-edge subtraction imaging: effect of bronchoconstriction.

We analyzed the fractal dimension (Df) of lung gas and blood distribution imaged with synchrotron radiation K-edge subtraction (KES), in six anesthetized adult New Zealand White rabbits. KES imaging was performed in upright position during stable Xe gas (64% in O2) inhalation and iodine infusion (Iomeron, 350 mg/mL), respectively, at baseline and after induced bronchoconstriction by aerosolized methacholine (125 mg/mL, 90 s) and bronchodilator (salbutamol, 10 mg/mL, 90 s) inhalation, at two axial image levels. Lung Xe and iodine images were segmented, and maps of regional lung gas and blood fractions were computed. The Df of lung gas (DfXe) and blood (DfIodine) distribution was computed based on a log-log plot of variation coefficient as a function of region volume. DfXe decreased significantly during bronchoconstriction (P < 0.0001), and remained low after salbutamol. DfIodine depended on the axial image level (P < 0.0001), but did not change with bronchoconstriction. DfXe was significantly associated with arterial [Formula: see text] (R = 0.67, P = 0.002), and negatively associated with [Formula: see text] (R = -0.62, P = 0.006), respiratory resistance (R = -0.58, P = 0.011), and elastance (R = -0.55, P = 0.023). These data demonstrate the reduced Df of gas distribution during acute bronchoconstriction, and the association of this parameter with physiologically meaningful variables. This finding suggests a decreased complexity and space-filling properties of lung ventilation during bronchoconstriction, and could serve as a functional imaging biomarker in obstructive airway diseases.NEW & NOTEWORTHY Here, we used an energy-subtractive imaging technique to assess the fractal dimension (Df) of lung gas and blood distribution and the effect of acute bronchoconstriction. We found that Df of gas significantly decreases in bronchoconstriction. Conversely, Df of blood exhibits gravity-dependent changes only, and is not affected by acute bronchoconstriction. Our data show that the fractal dimension of lung gas detects the emergence of clustered rather than scattered loss of ventilatory units during bronchoconstriction.

The effect of orexin on the hypoxic ventilatory response of female rats is greatest in the active phase during diestrus.

We recently showed that in male rats, orexin contributes to the hypoxic ventilatory response (HVR), with a stronger effect in the active phase. The effect of orexin on the HVR in females has not been investigated. As estrogen can inhibit orexin neurons, here we hypothesized that orexin neurons are activated by hypoxia and facilitate the HVR only in diestrus, when estrogen is low. We exposed female rats (n = 10) to near-isocapnic hypoxia ([Formula: see text] from 0.21 to 0.09) over ∼5 min, after vehicle and again after suvorexant (a dual OxR antagonist; 20 mg/kg ip), with ventilation measured using whole body plethysmography. Each rat was tested in proestrus or estrus (p/estrus), and again in diestrus, during both inactive and active phases. We also performed immunohistochemistry (IHC) to determine the proportion of orexin neurons activated by acute hypoxia during diestrus (n = 6) or proestrus/estrus (n = 6) in the active phase. In the inactive phase, the HVR was unaffected by OxR blockade, irrespective of estrus stage. In the active phase, the effect of OxR blockade depended on stage: the slope of the HVR was significantly reduced by OxR blockade only during diestrus. IHC revealed that hypoxia activated more orexin neurons during diestrus compared with p/estrus. We conclude that in females, orexin neurons are activated by hypoxia and contribute to the HVR only in diestrus when estrogen levels are low. Stage of the estrus cycle should be considered when examining the physiological function of orexin neurons in females.NEW & NOTEWORTHY We previously showed that orexin facilitates the hypoxic ventilatory response (HVR) of adult male rats during the active phase. Others have shown that estrogen inhibits orexin neurons. Here we show that orexin neurons are activated by hypoxia and facilitate the HVR of adult female rats during the active phase, but only in diestrus. These data suggest that orexin neurons facilitate the HVR in females when they are free from the inhibitory effects of estrogen.

Regional ventilation distribution in patients with scoliosis assessed by electrical impedance tomography: Is individual thorax shape required?

BACKGROUND: Electrical impedance tomography (EIT) is a non-invasive non-radiological regional lung function measurement. The aim of the study was to examine the feasibility of assessing ventilation distribution with EIT in scoliosis patients using generic and individual thorax shape. METHODS: Eight subjects were measured with EIT before scoliosis surgery. Reconstructions with two different forward models were compared: the generic shape and the individual thorax shapes. Three EIT-based parameters measuring ventilation distribution were calculated: left lung to overall ratio, center of ventilation (CoV), global inhomogeneity index. RESULTS: EIT measurements were successfully conducted in all subjects. No statistical differences were found in the EIT-based parameters using the different reconstruction models. CoV based on the generic shape was significantly correlated to the main Cobb angle (r=-0.84, p < 0.01). CONCLUSION: It was feasible to monitor regional ventilation distribution in scoliosis patients with EIT. Individual thorax shapes might not be required for reliable patient assessment in a clinical setting.

Impact of bronchial wall thickness on airflow obstruction in bronchiectasis.

The association between airflow obstruction and bronchial dilation has been researched in bronchiectasis. However, the impact of bronchial wall thickening on airflow obstruction has not been thoroughly investigated. This study assessed the underlying mechanism of airflow obstruction in bronchiectasis due to abnormal bronchial wall thickening using oscillometry. A total of 98 patients with bronchiectasis were retrospectively reviewed. At the time of diagnosis, spirometric and oscillometric parameters, high-resolution computed tomography scores, and clinical characteristics were collected. The bronchial diameter, bronchial wall thickness, and extent of emphysema were evaluated semi-quantitatively. Correlations between patient data and characteristics were analyzed. Thirty-three patients with airflow obstruction showed higher respiratory resistance, more negative respiratory reactance (Xrs) at 5 Hz (X5), and higher bronchial wall thickness score than those without airflow obstruction. The bronchial wall thickness score negatively affected forced expiration volume in 1 s /forced vital capacity and X5. Abnormal bronchial wall thickening might make Xrs more negative and progress airflow obstruction in bronchiectasis.

Rationale and Clinical Use of Bronchodilators in Adults with Bronchiectasis.

Currently, there is much controversy surrounding the therapeutic approach to pulmonary function abnormalities in patients with bronchiectasis and, consequently, whether and when to use bronchodilators in these patients. National and international guidelines on the treatment of bronchiectasis in adults do not recommend the routine use of bronchodilators because there is no evidence that a significant response to a bronchodilator or the presence or hyperresponsiveness of the airway are good predictors of future effective clinical response. However, some guidelines recommend them in the presence of airway obstruction and/or special conditions, which vary according to the guideline in question, although there are no recommendations on optimal dosing and bronchodilator treatment combined with or without inhaled corticosteroids. Nonetheless, in contrast with guideline recommendations, bronchodilators are overused in real-world patients with bronchiectasis even in the absence of airway obstruction, as demonstrated by analysis of national and international registries. This overuse can be explained by the awareness of the existence of a solid pharmacological rationale that supports the use of bronchodilators in the presence of chronic airway obstruction independent of its aetiology. We performed a systematic review of the literature and were able to verify that there are no randomised controlled trials (apart from a small study with methodological limitations and a very recent trial involving a not-very-large number of patients), or any long-term observational studies on the short- or long-term effect of bronchodilators in patients with bronchiectasis. Therefore, we believe that it is essential and even urgent to evaluate the effects of bronchodilators in these patients with appropriately designed studies.

Use of High-Rate Ventilation Results in Enhanced Recellularization of Bioengineered Lung Scaffolds.

While transplantation is a viable treatment option for end-stage lung diseases, this option is highly constrained by the availability of organs and postoperative complications. A potential solution is the use of bioengineered lungs generated from repopulated acellular scaffolds. Effective recellularization, however, remains a challenge. In this proof-of-concept study, mice lung scaffolds were decellurized and recellurized using human bronchial epithelial cells (BEAS2B). We present a novel liquid ventilation protocol enabling control over tidal volume and high rates of ventilation. The use of a physiological tidal volume (300 µL) for mice and a higher ventilation rate (40 breaths per minute vs. 1 breath per minute) resulted in higher cell numbers and enhanced cell surface coverage in mouse lung scaffolds as determined via histological evaluation, genomic polymerase chain reaction (PCR) analysis, and immunohistochemistry. A biomimetic lung bioreactor system was designed to include the new ventilation protocol and allow for simultaneous vascular perfusion. We compared the lungs cultured in our dual system to lungs cultured with a bioreactor allowing vascular perfusion only and showed that our system significantly enhances cell numbers and surface coverage. In summary, our results demonstrate the importance of the physical environment and forces for lung recellularization. Impact statement New bioreactor systems are required to further enhance the regeneration process of bioengineered lungs. This proof-of-concept study describes a novel ventilation protocol that allows for control over ventilation parameters such as rate and tidal volume. Our data show that a higher rate of ventilation is correlated with higher cell numbers and increased surface coverage. We designed a new biomimetic bioreactor system that allows for ventilation and simultaneous perfusion. Compared to a traditional perfusion only system, recellularization was enhanced in lungs recellularized with our new biomimetic bioreactor.

Ventilatory responses during and following hypercapnic gas challenge are impaired in male but not female endothelial NOS knock-out mice.

The roles of endothelial nitric oxide synthase (eNOS) in the ventilatory responses during and after a hypercapnic gas challenge (HCC, 5% CO2, 21% O2, 74% N2) were assessed in freely-moving female and male wild-type (WT) C57BL6 mice and eNOS knock-out (eNOS-/-) mice of C57BL6 background using whole body plethysmography. HCC elicited an array of ventilatory responses that were similar in male and female WT mice, such as increases in breathing frequency (with falls in inspiratory and expiratory times), and increases in tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives. eNOS-/- male mice had smaller increases in minute ventilation, peak inspiratory flow and inspiratory drive, and smaller decreases in inspiratory time than WT males. Ventilatory responses in female eNOS-/- mice were similar to those in female WT mice. The ventilatory excitatory phase upon return to room-air was similar in both male and female WT mice. However, the post-HCC increases in frequency of breathing (with decreases in inspiratory times), and increases in tidal volume, minute ventilation, inspiratory drive (i.e., tidal volume/inspiratory time) and expiratory drive (i.e., tidal volume/expiratory time), and peak inspiratory and expiratory flows in male eNOS-/- mice were smaller than in male WT mice. In contrast, the post-HCC responses in female eNOS-/- mice were equal to those of the female WT mice. These findings provide the first evidence that the loss of eNOS affects the ventilatory responses during and after HCC in male C57BL6 mice, whereas female C57BL6 mice can compensate for the loss of eNOS, at least in respect to triggering ventilatory responses to HCC.

Effects of different levels of hypoxia and hypercarbia on ventilation and gas exchange in Boa constrictor amaralis and Crotalus durissus (Squamata: Serpentes).

Ventilation and gas exchange have been studied in relatively few species of snakes, especially regarding their response to environmental hypoxia or hypercarbia. We exposed Crotalus durissus (N = 6) and Boa constrictor (N = 6) to decreasing levels of oxygen (12, 9, 6, 3 % O2) and increasing levels of carbon dioxide (1.5, 3.0, 4.5, 6.0 % CO2) and analyzed the effect of the different gas mixtures on ventilation and gas exchange using open-flow respirometry. Neither hypoxia nor hypercarbia significantly altered the duration of expiration or inspiration, nor their proportions. Both hypoxia and hypercarbia increased minute ventilation, but the decrease in oxygen had a less pronounced effect on ventilation. Gas exchange under normoxic conditions was low and was not significantly affected by hypoxia, but hypercarbia decreased gas exchange significantly in both species. While B. constrictor maintained its respiratory exchange ratio (RER) under hypercarbia between 0.5 and 1.0, C. durissus showed a RER above 1.0 during hypercarbia, due to a significantly greater CO2 excretion. The overall responses of both species to hypercarbia and especially to hypoxia were very similar, which could be associated to similar lifestyles as ambush hunting sit-and-wait predators that are able to ingest large prey items. The observed differences in gas exchange could be related to respiratory systems with macroscopically different structures, possessing only a tracheal lung in C. durissus, but two functional lungs in B. constrictor.

Menstrual phase does not influence ventilatory responses to group III/IV afferent signaling in eumenorrheic young females.

Estrogen can reduce sympathetic activity, but its effects on minute ventilation (VE) with group III/IV afferent activation remain unclear. This study examined the influence of estrogen on VE during lower-extremity exercise with group III/IV activation. Females completed two identical visits in follicular and ovulatory menstrual phases. Nine participants (age 25 ± 4 years) performed three minutes of baseline steady-state cycle ergometry and then group III/IV afferents were further activated with proximal thigh cuffs inflated to 20, 60, and 100 mmHg (randomized) for two minutes and five minutes of cycling between each occlusion. Metaboreflex was isolated by post-exercise circulatory occlusion. Ventilation was measured continuously and rating of perceived exertion (RPE) was recorded for each stage. During rest and exercise, VE (p < 0.001) and tidal volume (VT) (p = 0.033) were higher in the follicular than ovulatory phase. Minute ventilation, VT, and respiratory rate (RR) with ergoreflex and metaboreflex activation were similar across phases. With cuff occlusion of 100 mmHg, VE increased from baseline by 26.3 ± 7.0 L/min in the follicular phase (p < 0.001) and by 25.3±7.7 L/min in the ovulatory phase (p < 0.001), with no difference between phases (p> 0.05); RR and VT increased similarly with occlusion, also with no phase differences. In eumenorrheic females, menstrual phase influences ventilation but not ventilatory responses to group III/IV isolation.

Flow Simulation in the Upper Respiratory Tract of Two Obstructive Sleep Apnea Patients with Successful and Failed Surgery.

Obstructive sleep apnea (OSA) is a common disorder which may need to be treated by the upper respiratory tract (URT) surgery. To increase the success rate of the URT surgery, it is crucial to understand the flow features in the URT models. In this work, the turbulent flow characteristics in four 3D anatomically accurate URT models reconstructed from two OSA subjects with successful and failed surgery are numerically studied by the large-eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS). The features of velocity fields, pressure fields, and wall shear stress fields as well as the spectral analysis of wall shear stress between successful and failed surgery are explored. The results indicate that LES is capable of capturing flow patterns and flow oscillation and is effective for OSA surgery prediction. Even if the unsteady RANS can obtain the correct pressure drop across the airways, it may not be appropriate to be used for surgery prediction. Moreover, it is found that the quality of oscillating signal of wall shear stress is a key factor in surgery prediction. In a successful surgery, the wall shear stress oscillation is always strong, and the oscillating signal can perform a dominant frequency near 3~5 Hz, while in a failed surgery it does not show this clear intrinsic property. The results not only will gain new insights in the URT surgical planning but also will improve the prediction of surgical outcome for OSA patients.

Pulmonary volume-feedback and ventilatory pattern after bilateral lung transplantation using neurally adjusted ventilatory assist ventilation.

BACKGROUND: Bilateral lung transplantation results in pulmonary vagal denervation, which potentially alters respiratory drive, volume-feedback, and ventilatory pattern. We hypothesised that Neurally Adjusted Ventilatory Assist (NAVA) ventilation, which is driven by diaphragm electrical activity (EAdi), would reveal whether vagally mediated pulmonary-volume feedback is preserved in the early phases after bilateral lung transplantation. METHODS: We prospectively studied bilateral lung transplant recipients within 48 h of surgery. Subjects were ventilated with NAVA and randomised to receive 3 ventilatory modes (baseline NAVA, 50%, and 150% of baseline NAVA values) and 2 PEEP levels (6 and 12 cm H2O). We recorded airway pressure, flow, and EAdi. RESULTS: We studied 30 subjects (37% female; age: 37 (27-56) yr), of whom 19 (63%) had stable EAdi. The baseline NAVA level was 0.6 (0.2-1.0) cm H2O µV-1. Tripling NAVA level increased the ventilatory peak pressure over PEEP by 6.3 (1.8), 7.6 (2.4), and 8.7 (3.2) cm H2O, at 50%, 100%, and 150% of baseline NAVA level, respectively (P<0.001). EAdi peak decreased by 10.1 (9.0), 9.5 (9.4) and 8.8 µV (8.7) (P<0.001), accompanied by small increases in tidal volume, 8.3 (3.0), 8.7 (3.6), and 8.9 (3.3) ml kg-1 donor's predicted body weight at 50%, 100%, and 150% of baseline NAVA levels, respectively (P<0.001). Doubling PEEP did not affect tidal volume. CONCLUSIONS: NAVA ventilation was feasible in the majority of patients during the early postoperative period after bilateral lung transplantation. Despite surgical vagotomy distal to the bronchial anastomoses, bilateral lung transplant recipients maintained an unmodified respiratory pattern in response to variations in ventilatory assistance and PEEP. CLINICAL TRIAL REGISTRATION: NCT03367221.

A new ventilatory efficiency index and accuracy for early lung diffusion impairment in non-COPD smokers.

In smokers without manifest airway obstruction, early emphysema and endothelial dysfunction has been related to minute-ventilation/carbon dioxide output ratio (V'E/V'CO2). Thus, smokers with reduced lung carbon monoxide diffusion capacity (DLco) have a heightened V'E/V'CO2 ratio. We hypothesized that ventilatory inefficiency could contribute to the suspicion of impaired diffusive capacity in the absence of significant airway obstruction. Thus, 15 smokers with impaired DLco were compared to 15 smokers with normal DLco. Accuracy through sensibility and specificity for V'E/V'CO2 slope and nadir was compared with a new index for ventilatory efficiency (ηV'E,%), to uncover early diffusive changes in smokers without COPD.

Oxigenación de músculos respiratorios y locomotores durante el test cardiopulmonar en pacientes con circulación de fontan: serie de casos / Patients with fontan: oxygen consumption in respiratory and Locomotor muscles during excersie testing

Resumen: Antecedentes: Los pacientes con circulación de Fontan (PCF) presentan limitación cardíaca durante el esfuerzo máximo lo que repercute en menor capacidad de ejercicio (VO2-peak). La rehabilitación cardiovascular (RC) revierte este desacondicionamiento, al aumentar el gasto cardíaco y diferencia arteriovenosa de oxígeno, aspectos evaluados con monitorización invasiva y gases exhalados. La valoración no invasiva de la saturación muscular de oxígeno (SmO2) es un método de reciente aplicación para evaluar la limitación muscular al ejercicio. En PCF esta limitación puede atribuirse a la mayor acción de músculos respiratorios (cambios ventilatorios) y/o locomotores (carga periférica). Objetivo: Evaluar el trabajo de músculos respiratorios y locomotores durante el ejercicio físico máximo e incremental mediante los cambios en la SmO2. Métodos: A seis PCF (5 hombres; 13.8±2.9 años; 158±9cm; 49.8±13.3 kg) se les valoró el VO2-peak (23.0±4.5mL·kg-1·min-1) mediante ciclo-ergoespirometría sincrónicamente con SmO2 en músculos respiratorios (SmO2-m.Intercostales) y locomotores (SmO2-m.Vastus-Laterallis) mediante espectroscopía cercana al rango infrarrojo durante el test cardiopulmonar. Resultados: SmO2-m.Intercostales disminuyó desde el 60% del VO2-peak (p<0.05), mientras que SmO2-m.Vastus-Laterallis no cambió. La ventilación pulmonar (VE) aumentó progresivamente, siendo significativo a partir del 60% VO2-peak (p<0.05). La mayor desoxigenación de SmO2-m.Intercostales (∆SmO2) se asoció con los máximos cambios en ventilación pulmonar (∆VE) en ejercicio (rho=0.80; p=0.05). Conclusiones: Durante un protocolo de esfuerzo, los pacientes con circulación de Fontan presentan mayor trabajo muscular respiratorio que locomotor. Los cambios en la ventilación pulmonar se asocian a mayor extracción de oxígeno en la musculatura respiratoria, reforzando la necesidad de incorporar el entrenamiento respiratorio en la rehabilitación cardiovascular.

Abstract: Background: During a maximum incremental exercise patients with Fontan circulation (PFC) show cardiac limitation reducing aerobic exercise capacity (VO2-peak). Cardiovascular rehabilitation (CR) reverses this deconditioning by increasing cardiac output and arteriovenous oxygen difference, aspects that can be evaluated by invasive methods and analyzing the exhaled gases. Non-invasive assessment of muscle oxygen saturation (SmO2) is a novel method for recording local oxygen levels. By this technology, it is possible to evaluate the muscle limitation to exercise. In PFC, that limitation could be attributed to higher contractions of respiratory (ventilatory changes) and/ or locomotor muscles (peripheral load). Objective: To evaluate in PFC the changes at SmO2 of respiratory and locomotor muscles during a maximum and incremental exercise protocol (cardiopulmonary test, VO2-peak). Methods: Six PFC (5 men; 13.8±2.9 years; 158±9 cm; 49.8±13.3 kg) were assessed during the VO2peak test (23.0±4.5mL·kg-1·min-1) by cyclo-ergospirometry synchronously with SmO2 at respiratory (SmO2-m.Intercostales) and locomotor (SmO2-m. Vastus-Laterallis) muscles by Near-Infrared Spectroscopy (NIRS). Results: SmO2-m.Intercostales decreased from 60% of VO2-peak (p<0.05), while SmO2-m.Vastus-Laterallis did not change. Minute ventilation (VE) increased progressively, showing changes to rest at 60% of VO2-peak (p<0.05). The higher deoxygenation of SmO2-m.Intercostales (∆SmO2) correlated to maximum changes of lung ventilation (∆VE) (rho=0.80; p=0.05). Conclusions: During an incremental and maximum exercise protocol, patients with Fontan circulation have more work at respiratory than locomotor muscles. Changes in VE are direct associated with greater extraction of oxygen at respiratory muscles, reinforcing the incorporation of respiratory muscle training in cardiovascular rehabilitation.

The effects of sinusoidal linear drifts on the estimation of cardiorespiratory dynamic parameters during sinusoidal workload forcing: a simulation study.

This study aimed at investigating whether: 1) different sinusoidal linear drifts would affect the estimation of the dynamic parameters amplitude (A) and phase lag (φ) of minute ventilation (V˙E), oxygen uptake, carbon dioxide production and heart rate (HR) sinusoidal responses when the frequency analysis technique (F) is performed; 2) the Marquardt-Levenberg non-linear fitting technique (ML) would provide more precise estimations of A and φ of drifted sinusoidal responses compared to F. For each cardiorespiratory variable, fifteen responses to sinusoidal forcing of different sinusoidal periods were simulated by using a first-order dynamic linear model. A wide range of linear drifts were subsequently applied. A and φ were computed for all drifted and non-drifted responses by using both F (AF and φF) and ML (AML and φML). For non-drifted responses, no differences between AF vs AML and φF vs φML were found. Whereas AF and φF were affected by the sinusoidal linear drifts, AML and φML were not. Significant interaction effects (technique x drift) were found for A (P <  0.001; ƞP2 > 0.247) and φ (P <  0.001; ƞP2 > 0.851). Higher goodness of fit values were observed when using ML for drifted V˙E and HR responses only. The present findings suggest ML as a recommended technique to use when sinusoidal linear drifts occur during sinusoidal exercise, and provide new insights on how to analyse drifted cardiorespiratory sinusoidal responses.

Performance determinants, running energetics and spatiotemporal gait parameters during a treadmill ultramarathon.

PURPOSE: The objective of this study was to investigate the changes in metabolic variables, running energetics and spatiotemporal gait parameters during an 80.5 km treadmill ultramarathon and establish which key predictive variables best determine ultramarathon performance. METHODS: Twelve participants (9 male and 3 female, age 34 ± 7 years, and maximal oxygen uptake ([Formula: see text]O2max) 60.4 ± 5.8 ml·kg-1·min-1) completed an 80.5 km time trial on a motorised treadmill in the fastest possible time. Metabolic variables: oxygen consumption ([Formula: see text]O2), carbon dioxide production ([Formula: see text]CO2) and pulmonary ventilation ([Formula: see text]E) were measured via indirect calorimetry every 16.1 km at a controlled speed of 8 km·h-1 and used to calculate respiratory exchange ratio (RER), the energy cost of running (Cr) and fractional utilisation of [Formula: see text]O2max (F). Spatiotemporal gait parameters: stride length (SL) and cadence (SPM) were calculated via tri-axial accelerometery. RESULTS: Trial completion time was 09:00:18 ± 01:14:07 (hh:mm:ss). There were significant increases in [Formula: see text]O2, Cr, F, [Formula: see text]E and heart rate (HR) (p < 0.01); a significant decrease in RER (p < 0.01) and no change in SL and SPM (p > 0.05) across the measured timepoints. F and Cr accounted for 61% of the variance in elapsed finish time ([Formula: see text] = 0.607, p < 0.01). CONCLUSION: A treadmill ultramarathon elicits significant changes in metabolic variables, running energetics and spatiotemporal gait parameters. With F and Cr explaining 61% of variance in finish time. Therefore, those able to maintain a higher F, while adopting strategies to minimise an increase in Cr may be best placed to maximise ultramarathon performance.

Nasal cavity airflow: Comparing laser doppler anemometry and computational fluid dynamic simulations.

Objective parameters to assess the physical flow conditions of breathing are scarce and decisions for surgery, e.g. nasal septum correction, mainly rely on subjective surgeon judgment. To define decision supporting parameters, we compare laser Doppler anemometry (LDA) and numerical computational fluid dynamic simulations (CFD) of the airflow velocity vector fields in the nasal cavity, including lattice Boltzmann (LB) and finite volume methods (FVM). The simulations are based on an anonymous patient CT dataset with septal deviation. LDA measurements are preformed using a 3D printed model. Nasal airflow geometry is randomly deformed in order to approximate surgical changes. The root-mean-square velocity error near the nasal valve of laser Doppler anemometry and lattice Boltzmann simulations is 0.071. Changes in geometry similarly affect both measurement and simulation.