Cardiorespiratory Variables Research Articles

Influence of Live High Train High on Physiological Training Adaptations and Athletic Performance in Trained Runners: An Observational Cohort Case Study

Introduction: Live high-train high (LHTH) is suggested to improve performance, especially maximal aerobic capacity through the hypoxic adaptation responses. The present study aims to determine the impact of LHTH protocol on cardio-respiratory variables, lactate response, iron profile indices, and lung function capacities to the performance enhancement of middle-long distance (MLD) runners. Methods: Seven MLD runners were trained LHTH for six weeks at 8000ft altitude. Cardio-respiratory variables (V̇O2max, VO2/HR, VEmax, HR response), lactate response, iron profile indices (Hb, iron, UIBC, TIBC, transferrin, EPO, ferritin), and lung function parameters (FVC, FEV1, FEV1/FVC, PEF, and VC) were measured via standard protocols. Result: Hemoglobin (Hb, 7.8%), iron concentration (36.7%), and TIBC (8.2%) were found to be significantly increased after LHTH. On the other hand, V̇O2max (6.4%) and PEF (10.7%) were found to be significantly (p < 0.05) increased after camp. But HRrest (1.8%), HRrec (5min and 10min with 2.3% and 4.7% respectively), and lactate peak (7.9%) significantly decreased after LHTH condition. Discussion: All participating athletes improved performances after LHTH (overall group improved by 1.7%, individual increase up to 2.6%). Specific training load with hypoxic stress at high altitude induces peripheral chemoreceptor activation and stimulates sympathetic drive to initiate adaptive cascade leading to V̇O2max improvement (improved group mean 6.4%, individually up to 16.7%) which might be supported by enhanced erythropoiesis, iron metabolism, Hb concentrations, peak expiratory flow, glycolytic enzyme activity, enhanced oxidative capacity, improved resting and recovery HR response and peak lactate tolerance.

O estimulador de nervo periférico melhora a eficácia do bloqueio paravertebral proximal paravertebral proximal em ovelhas

ABSTRACT The purpose of this study was to compare the efficacy of proximal paravertebral anesthesia in sheep using a peripheral nerve stimulator and compare it to the Cambridge technique. Eight Santa Inês sheep, five females and three males aged 2 years and weighing 13kg were enrolled in the study. Right proximal paravertebral anesthesia was carried out using 2% lidocaine without vasoconstrictor, injected in the spaces between T13-L1, L1-L2 and L2-L3, with and without the aid of a peripheral nerve stimulator in two procedures with an interval of 7 days between treatments, which comprised: ST (stimulator treatment: 3mg kg-1 of lidocaine 2%) and CT (Cambridge control treatment, 6mg kg-1 of lidocaine 2%). Cardiorespiratory variables were recorded before the treatment (baseline, TB) and then at 15, 30, 45 and 60 minutes (T15, T30, T45 and T60, respectively) following local anesthesia. Effectiveness of the regional anesthesia was assessed by means of mechanical skin clamping at a point between the iliac crest and the lowest border of the last rib. Data were tested for normal distribution using the Shapiro-Wilk test and compared using Kruskal-Wallis followed by Dunn post-hoc test. Duration of the blockade was analyzed using a Kaplan-Meyer survival curve. Analyses were performed under 5% significance. ST took significantly longer and had greater success and greater duration. Positive response to skin clamping in CT was obtained in seven animals at T15 and one at T45, whereas in ST, one animal responded to skin clamping at T15, two at T30, four at T45 and one at T60. Duration was significantly longer in ST compared to CT according to the Kaplan-Meyer analysis. No changes were seen in cardiorespiratory variables throughout the study. In conclusion, the peripheral nerve stimulator increases the success of proximal paravertebral anesthesia using a lower dose of 2% lidocaine in healthy sheep.

Cardiorespiratory effects of intramuscular alfaxalone combined with low-dose medetomidine and butorphanol in dogs anesthetized with sevoflurane

Background: The intramuscular (IM) administration of 7.5–10 mg/kg of alfaxalone produces anesthetic effects that enabled endotracheal intubation with mild cardiorespiratory depression in dogs. However, the effects of IM co-administration of medetomidine, butorphanol, and alfaxalone on cardiorespiratory function under inhalation anesthesia have not been studied. Aim: To assess the cardiorespiratory function following the IM co-administration of 5 μg/kg of medetomidine, 0.3 mg/kg of butorphanol, and 2.5 mg/kg of alfaxalone (MBA) in dogs anesthetized with sevoflurane. Methods: Seven intact healthy Beagles (three males and four females, aged 3–6 years old and weighing 10.0–18.1 kg) anesthetized with a predetermined minimum alveolar concentration (MAC) of sevoflurane were included in this study. The baseline cardiorespiratory variable values were recorded using the thermodilution method with a pulmonary artery catheter after stabilization for 15 min at 1.3 times their individual sevoflurane MAC. The cardiorespiratory variables were measured again following the IM administration of MBA. Data are expressed as median [interquartile range] and compared with the corresponding baseline values using the Friedman test and Sheff’s method. A P < 0.05 was considered statistically significant. Results: The intramuscular administration of MBA transiently decreased the cardiac index (baseline: 3.46 [3.18–3.69], 5 min: 1.67 [1.57–1.75] L/min/m2 : P < 0.001), respiratory frequency, and arterial pH. In contrast, it increased the systemic vascular resistance index (baseline: 5,367 [3,589–6,617], 5 min:10,197 [9,955–15,005] dynes sec/cm5/m2 : P = 0.0092), mean pulmonary arterial pressure, and arterial partial pressure of carbon dioxide. Conclusion: The intramuscular administration of MBA in dogs anesthetized with sevoflurane transiently decreased cardiac output due to vasoconstriction. Although spontaneous breathing was maintained, MBA administration resulted in respiratory acidosis due to hypoventilation. Thus, it is important to administer MBA with caution to dogs with insufficient cardiovascular function. In addition, ventilatory support is recommended.

Cardiorespiratory dynamics of type 2 diabetes mellitus: An extensive view of breathing and fitness challenges in a diabetes prevalent population.

Diabetes mellitus (DM) is well known for related micro and macrovascular complications. Uncontrolled hyperglycemia in diabetes mellitus leads to endothelial dysfunction, inflammation, microvascular impairment, myocardial dysfunction, and skeletal muscle changes which affect multiple organ systems. This study was designed to take an extensive view of cardiorespiratory dynamics in patients with type 2 DM. One hundred healthy controls (HC) and 100 DM patients were enrolled. We measured and compared the breathing patterns (spirometry), VO2 max levels (heart rate ratio method) and self-reported fitness level (international fitness scale) of individuals with and without diabetes. Data was analyzed in SPSS v.22 and GraphPad Prism v8.0. We observed restrictive spirometry patterns (FVC <80%) in 22% of DM as compared to 2% in HC (p = 0.021). There was low mean VO2 max in DM as compared to HC(32.03 ± 5.36 vs 41.91 ± 7.98 ml/kg/min; p value <0.001). When evaluating physical fitness on self-reported IFiS scale, 90% of the HC report average, good, or very good fitness levels. In contrast, only 45% of the DM shared this pattern, with a 53% proportion perceiving their fitness as poor or very poor (p = <0.05). Restrictive respiratory pattern, low VO2 max and fitness level were significantly associated with HbA1c and long-standing DM. This study shows decreased pulmonary functions, decreased cardiorespiratory fitness (VO2 max) and IFiS scale variables in diabetic population as compared to healthy controls which are also associated with glycemic levels and long-standing DM. Screening for pulmonary functions can aid optimum management in this population.

ALTERAÇÕES DA VE/VCO2 E OUES DURANTE EXERCÍCIO PROGRESSIVO EM PACIENTES COM INSUFICIÊNCIA CARDÍACA

Introduction: Heart failure originates from several etiologies resulting in cardiorespiratory impairment during physical effort. Objective: To compare the behavior of cardiorespiratory variables, slope of oxygen uptake efficiency slope and the relationship between pulmonary ventilation and carbon dioxide production between individuals with heart failure and healthy individuals. Methods: 61 male individuals (61.2 ± 7.8 years) were evaluated, who were separated into two groups: Group CI - Patients with Cardiac Insufficiency (n = 40) and Group C - Control (n = 21). The volunteers performed assessments of the following parameters: age, height, body mass and body mass index. The ergospirometry test was also performed, consisting of performing a graded exercise testing on a treadmill with direct analysis of the respiratory gases: VE/VCO2, VO2peak, PetCO2, OUES and the hemodynamic variables: maximum heart rate, recovery heart rate after the 1st minute and the echocardiogram. The Kolmorovsminoff test for normality was performed, the data were expressed as mean and standard error and the inferential analysis performed with the Anova and Post-Hoc Tests of Scheffé, considering p≤0.05. Results: The anthropometric, hemodynamic and respiratory variables results for the CI and C groups, respectively, were: age =61,0±8,2 vs. 61,5±7,4 years (p&gt;0,05), height= 1,72±5,8 vs. 1,72±6,8m (p&gt;0,05), body mass = 77,3±9,9 vs. 78,3±9,0kg (p&gt;0,05), IMC = 26,5±3,0 vs. 26,2±2,8 kg/m2 (p&gt;0,05), ejection fraction = 31,2±4,1 vs. 64,7±3,9mL (p&lt;0,001), maximum cardio frequency = 128,6±22,9 vs. 143,6±15,5bpm (p&lt;0,02), recovery heart rate after the 1st minute = -17,4±5,4 vs. -25,0±4,9bpm (p&lt;0,05), VE/VCO2slope = 38,8±5,6 vs. 28,2±3,9L/min (p&lt;0,003), VO2peak = 20,0±4,0 vs. 36,7±5,5ml/kg/min (p&lt;0,05), PetCO2 = 29,5±3,0 vs. 31,7±2,4mmHg (p&lt;0,05) and OUES = 1,81±0,4 vs. 2,3±0,3 (p&lt;0,05). Conclusion: Patients with heart failure showed high values of VE/VCO2 and low values of OUES, which limits functional capacity and leads to the early onset of metabolic acidosis. Level of Evidence I; High-Quality Prospective Study.

Dose–response effect of pre-exercise carbohydrates under muscle glycogen unavailability: Insights from McArdle disease

BackgroundThis study aimed to determine the effect of different carbohydrate (CHO) doses on exercise capacity in patients with McArdle disease—the paradigm of “exercise intolerance”, characterized by complete muscle glycogen unavailability—and to determine whether higher exogenous glucose levels affect metabolic responses at the McArdle muscle cell (in vitro) level. MethodsPatients with McArdle disease (n = 8) and healthy controls (n = 9) underwent a 12-min submaximal cycling constant-load bout followed by a maximal ramp test 15 min after ingesting a non-caloric placebo. In a randomized, double-blinded, cross-over design, patients repeated the tests after consuming either 75 g or 150 g of CHO (glucose:fructose = 2:1). Cardiorespiratory, biochemical, perceptual, and electromyographic (EMG) variables were assessed. Additionally, glucose uptake and lactate appearance were studied in vitro in wild-type and McArdle mouse myotubes cultured with increasing glucose concentrations (0.35, 1.00, 4.50, and 10.00 g/L). ResultsCompared with controls, patients showed the “classical” second-wind phenomenon (after prior disproportionate tachycardia, myalgia, and excess electromyographic activity during submaximal exercise, all p < 0.05) and an impaired endurance exercise capacity (–51% ventilatory threshold and –55% peak power output, both p < 0.001). Regardless of the CHO dose (p < 0.05 for both doses compared with the placebo), CHO intake increased blood glucose and lactate levels, decreased fat oxidation rates, and attenuated the second wind in the patients. However, only the higher dose increased ventilatory threshold (+27%, p = 0.010) and peak power output (+18%, p = 0.007). In vitro analyses revealed no differences in lactate levels across glucose concentrations in wild-type myotubes, whereas a dose–response effect was observed in McArdle myotubes. ConclusionCHO intake exerts beneficial effects on exercise capacity in McArdle disease, a condition associated with total muscle glycogen unavailability. Some of these benefits are dose dependent.

Fourteen-Days Spirulina Supplementation Increases Hemoglobin, but Does Not Provide Ergogenic Benefit in Recreationally Active Cyclists: A Double-Blinded Randomized Crossover Trial

Spirulina supplementation has been reported to increase hemoglobin concentration as well as a variety of cardiorespiratory and lactate-based performance parameters during maximal and submaximal states of exercise. This study investigates the efficacy of supplementing a 6 g/day dosage of spirulina for 14-days in recreationally active individuals, analyzing cardiorespiratory parameters during maximal and submaximal cycling as well as the potential mechanistic role of hemoglobin augmentation. 17 recreationally active individuals (Male = 14, Female = 3, Age 23 ± 5 years, V̇O2max 43.3 ± 8.6 ml/min·kg) ingested 6 g/day of spirulina or placebo for 14-days in a double-blinded randomized crossover study, with a 14-day washout period between trials. Participants completed a 20-min submaximal cycle at 40% maximal power output (WRmax), followed by a V̇O2max test. Hemoglobin (g/L), WRmax (watts), time to fatigue (seconds), heart rate (bpm), oxygen uptake (ml/min·kg), RER and blood lactate response (mmol/L) were measured and compared between conditions. Cardiorespiratory variables were recorded at 5-min intervals and lactate was measured at 10-min intervals during the submaximal exercise. There was a significant 3.4% increase in hemoglobin concentration after spirulina supplementation in comparison to placebo (150.4 ± 9.5 g/L Vs 145.6 ± 9.4 g/L, p = 0.047). No significant differences existed between either condition in both testing protocols for V̇O2max, WRmax, time to fatigue, heart rate, oxygen uptake, RER and blood lactate response (p > 0.05). 14-days of spirulina supplementation significantly improved hemoglobin concentration but did not lead to any considerable ergogenic improvements during maximal or submaximal exercise at a 6 g/day dosage in recreationally active individuals whilst cycling.

Sedation Quality and Cardiorespiratory, Echocardiographic, Radiographic and Electrocardiographic Effects of Intramuscular Alfaxalone and Butorphanol in Spanish Greyhound Dogs.

The quality of sedation and changes in cardiorespiratory variables after the intramuscular administration of alfaxalone and butorphanol in Spanish greyhound dogs were evaluated. Twenty-one adult dogs were included. The dogs received alfaxalone (2 mg/kg) and butorphanol (0.2 mg/kg) intramuscularly. Sedation scoring, cardiorespiratory parameters (including blood gas analysis), echocardiography, thoracic radiography and electrocardiography were performed before sedation and 30 min after drug administration. Moderate sedation was observed, and side effects, such as tremors, nystagmus and auditory hyperesthesia, were noticed. Statistically significant changes in heart rate, invasive blood pressure, pH, arterial saturation of O2 and partial pressure of O2 and CO2 were found. Echocardiographic variables, including end-diastolic volume, left ventricular diameter in diastole, aortic and pulmonic flow, diastolic transmitral flow and left atrial/aortic ratio, and electrocardiography parameters, including PQ interval and QT interval, showed statistically significant changes. In conclusion, the intramuscular administration of alfaxalone and butorphanol to healthy dogs produced moderate sedation with mild cardiorespiratory, echocardiographic and electrocardiographic changes, without alterations in cardiac size on radiographic images.

Determinants of the maximal functional reserve during repeated supramaximal exercise by humans: The roles of Nrf2/Keap1, antioxidant proteins, muscle phenotype and oxygenation

When high-intensity exercise is performed until exhaustion a “functional reserve” (FR) or capacity to produce power at the same level or higher than reached at exhaustion exists at task failure, which could be related to reactive oxygen and nitrogen species (RONS)-sensing and counteracting mechanisms. Nonetheless, the magnitude of this FR remains unknown. Repeated bouts of supramaximal exercise at 120% of VO2max interspaced with 20s recovery periods with full ischaemia were used to determine the maximal FR. Then, we determined which muscle phenotypic features could account for the variability in functional reserve in humans. Exercise performance, cardiorespiratory variables, oxygen deficit, and brain and muscle oxygenation (near-infrared spectroscopy) were measured, and resting muscle biopsies were obtained from 43 young healthy adults (30 males). Males and females had similar aerobic (VO2max per kg of lower extremities lean mass (LLM): 166.7 ± 17.1 and 166.1 ± 15.6 ml kg LLM−1.min−1, P = 0.84) and anaerobic fitness (similar performance in the Wingate test and maximal accumulated oxygen deficit when normalized to LLM). The maximal FR was similar in males and females when normalized to LLM (1.84 ± 0.50 and 2.05 ± 0.59 kJ kg LLM−1, in males and females, respectively, P = 0.218). This FR depends on an obligatory component relying on a reserve in glycolytic capacity and a putative component generated by oxidative phosphorylation. The aerobic component depends on brain oxygenation and phenotypic features of the skeletal muscles implicated in calcium handling (SERCA1 and 2 protein expression), oxygen transport and diffusion (myoglobin) and redox regulation (Keap1). The glycolytic component can be predicted by the protein expression levels of pSer40-Nrf2, the maximal accumulated oxygen deficit and the protein expression levels of SOD1. Thus, an increased capacity to modulate the expression of antioxidant proteins involved in RONS handling and calcium homeostasis may be critical for performance during high-intensity exercise in humans.

Ventilation and perceived exertion are sensitive to changes in exercise tolerance: arm+leg cycling vs. leg cycling.

Purpose: Growing evidence suggests that respiratory frequency (f R) is a marker of physical effort and a variable sensitive to changes in exercise tolerance. The comparison between arm+leg cycling (Arm+leg) and leg cycling (Leg) has the potential to further test this notion because a greater exercise tolerance is expected in the Arm+leg modality. We systematically compared Arm+leg vs. Leg using different performance tests. Methods: Twelve males underwent six performance tests in separate, randomized visits. Three tests were performed in each of the two exercise modalities, i.e. an incremental test and two time-to-exhaustion (TTE) tests performed at 90% or 75% of the peak power output reached in the Leg incremental test (PPOLeg). Exercise tolerance, perceived exertion, and cardiorespiratory variables were recorded during all the tests. Results: A greater exercise tolerance (p < 0.001) was found for Arm+leg in the incremental test (337 ± 32W vs. 292 ± 28W), in the TTE test at 90% of PPOLeg (638 ± 154s vs. 307 ± 67s), and in the TTE test at 75% of PPOLeg (1,675 ± 525s vs. 880 ± 363s). Unlike O2 and heart rate, both f R and minute ventilation were lower (p < 0.003) at isotime in all the Arm+leg tests vs. Leg tests. Furthermore, a lower perceived exertion was observed in the Arm+leg tests, especially during the TTE tests (p < 0.001). Conclusion: Minute ventilation, f R and perceived exertion are sensitive to the improvements in exercise tolerance observed when comparing Arm+leg vs. Leg, unlike O2 and heart rate.

Cardiorespiratory Effects and Desflurane Requirement in Dogs Undergoing Ovariectomy after Administration Maropitant or Methadone.

General anesthesia for ovariectomy in dogs is based on a balanced anesthesia protocol such as using analgesics along with an inhalant agent. While opioids such as fentanyl and methadone are commonly used for their analgesic potency, other drugs can also have analgesic effects. Maropitant, an antiemetic for dogs and cats, has also been shown to exert analgesic effects, especially on visceral pain. The aim of this study was to compare the cardiorespiratory effects and analgesic properties of maropitant and methadone combined with desflurane in dogs undergoing ovariectomy. Two groups of 20 healthy mixed-breeds bitches undergoing elective ovariectomy received intravenous either maropitant at antiemetic dose of 1 mg kg-1 or methadone at the dose of 0.3 mg kg-1. Cardiorespiratory variables were collected before premedication, 10 min after sedation and during surgery. Recovery quality and postoperative pain were evaluated 15, 30, 60, 120, 240 and 360 min postoperatively. Results showed that maropitant produced analgesia and reduced the requirement of desflurane in amounts similar to those determined by methadone (5.39 ± 0.20% and 4.91 ± 0.26%, respectively) without significant difference, while maintaining heart rate, arterial blood pressure, respiratory rate and carbon dioxide end-tidal partial pressure even at a more satisfactory level. Therefore, maropitant may be recommended as an analgesic drug for abdominal surgery not only in healthy dogs but also in those with reduced cardiorespiratory compensatory capacities or at risk of hypotension, especially when combined with a sedative such as dexmedetomidine.

Effects of propofol alone or in combination with ketamine on intraocular pressure in unpremedicated dogs.

To determine the effects of propofol (P) alone and in combination with ketamine (KP) at ratios of 1:1, 1:2, and 1:3 on intraocular pressure (IOP) in unpremedicated dogs. A total of 28 cross-bred healthy dogs. Dogs were randomly assigned to one of four groups (n = 7 per group) to receive intravenous P or KP at 1:1, 1:2, and 1:3 ratios, respectively. The infusion was administered at 0.6 mg/kg/min for 60 min. IOP, cardiorespiratory variables, rectal temperature (RT), and pedal reflex were recorded every 5 min for 60 min, starting from baseline (BL). There was a statistically significant increase in IOP in all groups: P (p = .011), KP 1:1 (p = .003), KP 1:2 (p = .023), and KP 1:3 (p = .008). The IOP increase was less pronounced in the KP 1:2 group and was only significant (p = .023) at T45 compared with BL. A significant correlation was observed between IOP and SpO2 in P (r = -.215, p = .02), KP 1:2 (r = -.579, p < .01), and KP 1:3 (r = -.402, p < .01) groups. IOP significantly increased due to decreased SpO2 below 86.5% (p < .05). Propofol alone and in combination with ketamine may increase preexisting IOP in unpremedicated dogs. SpO2 levels below 86.5% may trigger an increase in IOP. Administering KP in a 1:2 ratio at an infusion rate of 0.6 mg/kg/min does not significantly alter IOP for under 45 min in unpremedicated dogs with sufficient oxygenation.

Comparison of incisional, transverse abdominis plane, and rectus sheath blocks in dogs undergoing ovariohysterectomy.

To compare the analgesia provided by incisional (Incisional), transverse abdominis plane (TAP), and rectus sheath (RS) blocks in dogs submitted for ovariohysterectomy (OHE). 22 female mixed-breed dogs were allocated into 3 treatments of Incisional (n = 7), TAP (n = 7), and RS (n = 8) and underwent OHE from April 4 to December 6, 2022. After premedication with acepromazine (0.05 mg/kg) and morphine (0.5 mg/kg), anesthesia was induced (6 mg/kg) and maintained (0.4 mg/kg/min) with propofol. Each dog randomly received either an incisional (blind technique), TAP, or RS (ultrasound-guided) block. Intraoperative analgesia was assessed using cardiorespiratory variables. Postoperative analgesia was evaluated up to 6 hours after the operation with a Short Form of Glasgow Pain Scale (SF-GCPS) and Visual Analog Scale (VAS). Fentanyl was administered as a rescue analgesic when needed. During surgery, all data remained within normal limits without any significant differences. Fentanyl was administered to 1 dog in the Incisional and 1 in the TAP. Post-operatively, a single dose of fentanyl was given to 1 dog in the TAP and 1 in the RS. Four dogs in the Incisional and 3 in the RS received both doses of fentanyl. There was no significant difference regarding postoperative rescue analgesia among treatments. All 3 techniques demonstrated acceptable intra- and post-operative analgesia efficacy in dogs undergoing OHE. Further studies are warranted to confirm these findings.

Do poles really "save the legs" during uphill pole walking at different intensities?

In sky- and trail-running competitions, many athletes use poles. The aims of this study were to investigate whether the use of poles affects the force exerted on the ground at the feet (Ffoot), cardiorespiratory variables and maximal performance during uphill walking. Fifteen male trail runners completed four testing sessions on different days. On the first two days, they performed two incremental uphill treadmill walking tests to exhaustion with (PWincr) and without poles (Wincr). On the following days, they performed submaximal and maximal tests with (PW80 and PWmax) and without (W80 and Wmax) poles on an outdoor trail course. We measured cardiorespiratory parameters, the rating of perceived exertion, the axial poling force and Ffoot. When walking on the treadmill, we found that poles reduced maximum Ffoot (- 2.8 ± 6.4%, p = 0.03) and average Ffoot (- 2.4 ± 3.3%, p = 0.0089). However, when outdoors, we found pole effect only for average Ffoot (p = 0.0051), which was lower when walking with poles (- 2.6 ± 3.9%, p = 0.0306 during submaximal trial and - 5.21 ± 5.51%, p = 0.0096 during maximal trial). We found no effects of poles on cardiorespiratory parameters across all tested conditions. Performance was faster in PWmax than in Wmax (+ 2.5 ± 3.4%, p = 0.025). The use of poles reduces the foot force both on the treadmill and outdoors at submaximal and maximal intensities. It is, therefore, reasonable to conclude that the use of poles "saves the legs" during uphill without affecting the metabolic cost.

COMPARISON OF KETAMINE-MIDAZOLAM AND KETAMINE-MIDAZOLAM-BUTORPHANOL PREMEDICATION PRIOR TO SEVOFLURANE ANESTHESIA IN WOODCHUCKS (MARMOTA MONAX).

Cardiovascular disease is a frequent cause of death in the critically endangered Vancouver Island marmots (Marmota vancouverensis). This warrants the use of anesthetic protocols with minimal cardiovascular adverse effects. In this study, 12 adult male woodchucks (Marmota monax) were used as models for Vancouver Island marmots. The objective was to compare the physiological effects of two premedication protocols during induction and maintenance of anesthesia with sevoflurane. The two premedications were ketamine 10 mg/kg and midazolam 0.5 mg/kg (KM) or ketamine 10 mg/kg, midazolam 0.5 mg/kg, and butorphanol 1.0 mg/kg (KMB), administered intramuscularly prior to mask induction. Each marmot underwent three anesthetic events and protocols were assigned using a blinded randomized crossover design. Heart rate, respiratory rate, oxygen saturation, and body temperature were recorded throughout, and blood gases were assessed following induction. Resistance to induction was scored and time to induction was recorded. Although mask induction with sevoflurane was successful in all events (mean induction time of 2.1 min), KMB premedication resulted in a faster induction (mean induction time reduced by 1.2 ± 0.3 min) and lower resistance scores. Both protocols resulted in significant cardiovascular and respiratory depression; however, animals that received KMB were more hypercapnic than KM by 8.8 ± 2.8 mm Hg (P = 0.03) (mean venous partial pressure of carbon dioxide [PvCO2] for all: 79.9 mm Hg). In conclusion, if shorter induction times are desired, KMB premedication is preferred. However, cardiorespiratory variables including blood pressure should be monitored, and endotracheal intubation is recommended to allow for ETCO2 monitoring and provision of intermittent positive pressure ventilation.

Efeitos cardiorrespiratórios/sedativos de um peptídeo identificado no veneno crotálico comparado à acepromazina e à xilazina em equinos

ABSTRACT The purpose of this study was to investigate whether intravenous crotalphine produces significant sedation, as well as physiological changes, in healthy standing horses. Six mares, aged 8 years and weighing 415kg underwent three different treatments in a crossover design: TA (acepromazine: 50μg.kg-1), TC (crotalphine: 0.01μg.kg-1) and TX (xylazine: 1000μg.kg-1), intravenously. At various time points over 60 minutes, physiologic variables were recorded: heart rate, respiratory rate, and rectal temperature. The head height from the ground (HHG) was evaluated in centimeters. Data were analyzed using ANOVA followed by Dunnett’s test or Friedman followed by Dunn’s test, under 5% significance. Heart rate decreased significantly at M5 and M10 compared with Mb in TX (28±7, 26±6 and 40±8 beats/minute-1, respectively; p=0.0004). Respiratory rate and rectal temperature did not differ among groups or time points. The HHG significantly decreased in all groups compared with Mb at various time points (p&lt;0.0001). In conclusion, crotalphine did not produce reliable and durable sedation in healthy standing mares and did not influence cardiorespiratory variables in a clinically relevant manner.

Multi-wavelength SPAD photoplethysmography for cardio-respiratory monitoring

There is a growing interest in photoplethysmography (PPG) for the continuous monitoring of cardio-respiratory signals by portable instrumentation aimed at the early diagnosis of cardiovascular diseases. In this context, it is conceivable that PPG sensors working at different wavelengths simultaneously can optimize the identification of apneas and the quantification of the associated heart-rate changes or other parameters that depend on the PPG shape (e.g., systematic vascular resistance and pressure), when evaluating the severity of breathing disorders during sleep and in general for health monitoring. Therefore, the objective of this work is to present a novel pulse oximeter that provides synchronous data logging related to three light wavelengths (green, red, and infrared) in transmission mode to optimize both heart rate measurements and a reliable and continuous assessment of oxygen saturation. The transmission mode is considered more robust over motion artifacts than reflection mode, but current pulse oximeters cannot employ green light in transmission mode due to the high absorbance of body tissues at this wavelength. For this reason, our device is based on a Single-Photon Avalanche Diode (SPAD) with very short deadtime (less than 1 ns) to have, at the same time, the single photon sensitivity and high-count rate that allows acquiring all the wavelengths of interest on the same site and in transmission mode. Previous studies have shown that SPAD cameras can be used for measuring the heart rate through remote PPG, but oxygen saturation and heart-rate measures through contact SPAD-based PPG sensors have never been addressed so far. The results of the preliminary validation on six healthy volunteers reflect the expected physiological phenomena, providing rms errors in the Inter Beat Interval estimation smaller than 70 ms (with green light) and a maximum error in the oxygen saturation smaller than 1% during the apneas. Our prototype demonstrates the reliability of SPAD-based devices for continuous long-term monitoring of cardio-respiratory variables as an alternative to photodiodes especially when minimal area and optical power are required.

Weight loss does not affect the sit-to-stand metabolic cost in adolescents with obesity.

There is considerable interest in simple and effective methods to reduce sitting time and increase energy expenditure, and standing breaks have emerged as a realisable approach in individuals with obesity. The aim of the present study was to determine the extent to which energy expenditure in standing differs from sitting, and whether this energetic and metabolic-related responses are modified following a weight loss program in adolescents with obesity. After body composition assessment (DXA), cardiorespiratory and metabolic variables were continuously recorded (indirect calorimetry) during 10min while sitting and then during 5min standing posture before (n = 21; T1) and at the end of a multidisciplinary intervention (n = 17; T2) in adolescents with obesity. Before and after the intervention, energy expenditure and fat oxidation rates were significantly increased in standing compared with sitting. Weight loss did not change the relationship between sitting and standing energy expenditure. Sitting energy expenditure represented 1.0 and 1.1 Metabolic Equivalent of Task at T1 and T2, and increased to 1.1 and 1.2 during standing at T1 and T2, respectively. The percentage of change of android fat mass between T1 and T2 was positively associated with the percentage of change in energy expenditure from sitting to standing at T2. The vast majority of the adolescents with obesity significantly increased their energy expenditure between sitting and standing, both before and after a weight loss intervention. However, the standing posture did not allow breaking the sedentary threshold. Abdominal fat mass is associated with energic profile.

Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammals.

While basal metabolic rate (BMR) scales proportionally with body mass (Mb ), it remains unclear whether the relationship differs between mammals from aquatic and terrestrial habitats. We hypothesized that differences in BMR allometry would be reflected in similar differences in scaling of O2 delivery pathways through the cardiorespiratory system. We performed a comparative analysis of BMR across 63 mammalian species (20 aquatic, 43 terrestrial) with a Mb range from 10 kg to 5318 kg. Our results revealed elevated BMRs in small (>10 kg and <100 kg) aquatic mammals compared to small terrestrial mammals. The results demonstrated that minute ventilation, that is, tidal volume (VT )·breathing frequency (fR ), as well as cardiac output, that is, stroke volume·heart rate, do not differ between the two habitats. We found that the "aquatic breathing strategy", characterized by higher VT and lower fR resulting in a more effective gas exchange, and by elevated blood hemoglobin concentrations resulting in a higher volume of O2 for the same volume of blood, supported elevated metabolic requirements in aquatic mammals. The results from this study provide a possible explanation of how differences in gas exchange may serve energy demands in aquatic versus terrestrial mammals.

P286 IMPACT OF PERSONAL PROTECTIVE MASKS ON CARDIORESPIRATORY VARIABLES IN HEALTHY SUBJECTS AND PATIENTS WITH HEART FAILURE: AN INTERIM ANALYSIS

Abstract Background protective masks are a powerful mean to contain COVID–19. However, a general feeling that masks alter the normal dynamics of breathing may reduce its application. Patients with heart failure (HF) experience dyspnea even during daily life activities (ADLs). Aim of the study is to evaluate cardiorespiratory parameters during ADLs, cardiopulmonary exercise test (CPET) to highlight differences related to protective masks. Methods 9 healthy subjects (age 59±11, 2F) and 10 HF patients (age 64±11, 2F, EF &amp;lt;45%) underwent a set of tests twice, wearing a protective surgical mask and without it. We performed the following tests: standard spirometry; CPET; a set of tests recorded by a wearable ergospirometer (Cosmed K5), including ADLs), six–minute walking test (6MWT) and two 4–minute treadmill exercises (TREAD2 and TREAD3 at a speed of 2 km/h and 3 km/h, respectively). Results Spirometry showed a reduction of forced expiratory volume in 1s (3.29±0.75 L vs 2.65±0.57 L as for healthy subjects, p= 0.002; 2.45±0.6 L vs 1.97±0.54 L as for HF patients, p= 0.002) and forced vital capacity (4.14±0.92 L vs 3.39±0.83 L as for healthy subjects, p= 0.004; 2.93±0.76 L vs 2.59±0.73 L as for HF patients, p= 0.01) in both the groups from no mask to mask. Both healthy and HF patients showed: a trend of reduction of peak oxygen pulse (p&amp;lt;0.005 in healthy) and peak oxygen consumption (VO2); a decrease of tidal volume (Vt) at peak exercise (peak Vt: 2.283±0.449 L vs 1.864±0.359 L in healthy, p= 0.022; 1.6±0.41 L vs 1.448±0.431 L in HF, p= 0.02), with no significative variations of resting and peak ventilation (VE). HF patients experienced a statistically significative decrease of VO2 at the anaerobic threshold (AT) (794±227 vs 682±151 mL · min–1, p=0.01). Task–related VO2 was significantly reduced from no mask to mask in ALDs and 6MWT in the healthy, whereas HF patients experienced a significative reduction more physically demanding tasks. Both healthy and HF subjects showed an increase in the basal and task–related ratio of VE vs carbon dioxide production (VE/VCO2) in the two protocol conditions. Conclusions Surgical masks influences cardiorespiratory variables in healthy and HF patients at rest and during both mild and maximal physical activity. The physiological impact of the mask is far from being clinically relevant The use of masks seems to be safe both in the general population and in HF patients. These data should be confirmed in a larger group of patients.