Intercostal Muscles Oxygenation and Breathing Pattern during Exercise in Competitive Marathon Runners.

The study aimed to evaluate the association between the changes in ventilatory variables (tidal volume (Vt), respiratory rate (RR) and lung ventilation (V.E)) and deoxygenation of m.intescostales (∆SmO2-m.intercostales) during a maximal incremental exercise in 19 male high-level competitive marathon runners. The ventilatory variables and oxygen consumption (V.O2) were recorded breath-by-breath by exhaled gas analysis. A near-infrared spectroscopy device (MOXY®) located in the right-hemithorax allowed the recording of SmO2-m.intercostales. To explore changes in oxygen levels in muscles with high demand during exercise, a second MOXY® records SmO2-m.vastus laterallis. The triphasic model of exercise intensity was used for evaluating changes in SmO2 in both muscle groups. We found that ∆SmO2-m.intercostales correlated with V.O2-peak (r = 0.65; p = 0.002) and the increase of V.E (r = 0.78; p = 0.001), RR (r = 0.54; p = 0.001), but not Vt (p = 0.210). The interaction of factors (muscles × exercise-phases) in SmO2 expressed as an arbitrary unit (a.u) was significant (p = 0.005). At VT1 there was no difference (p = 0.177), but SmO2-m.intercostales was higher at VT2 (p < 0.001) and V.O2-peak (p < 0.001). In high-level competitive marathon runners, the m.intercostales deoxygenation during incremental exercise is directly associated with the aerobic capacity and increased lung ventilation and respiratory rate, but not tidal volume. Moreover, it shows less deoxygenation than m.vastus laterallis at intensities above the aerobic ventilatory threshold.

Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue.

Muscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

Intercostal and vastus lateralis microcirculatory response to a sympathoexcitatory manoeuvre in patients with chronic obstructive pulmonary disease.

Patients with COPD present with systemic vascular malfunctioning and their microcirculation is possibly more fragile to overcome an increase in the sympathetic vasoconstrictor outflow during sympathoexcitatory situations. To test the skeletal muscle microvascular responsiveness to sympathoexcitation, we asked patients with COPD and age- and sex-matched controls to immerse a hand in iced water [Cold Pressor Test (CPT)]. Near-infrared spectroscopy detection of the indocyanine green dye in the intercostal and vastus lateralis microcirculation provided a blood flow index (BFI). BFI divided by mean blood pressure (MBP) provided an index of microvascular conductance (BFI/MBP). The CPT decreased BFI and BFI/MBP in the intercostal (P = 0.01 and < 0.01, respectively) and vastus lateralis (P = 0.08 and 0.03, respectively) only in the COPD group, and the per cent BFI and BFI/MBP decrease was similar between muscles (P = 0.78 and 0.85, respectively). Thus, our findings support that sympathoexcitation similarly impairs intercostal and vastus lateralis microvascular regulation in patients with COPD.

Effects of acute inspiratory loading during treadmill running on cerebral, locomotor and respiratory muscle oxygenation in women soccer players.

Respiratory limitation can be a primary mechanism for exercise cessation in female athletes. This study aimed to assess the effects of inspiratory loading (IL) on intercostal muscles (IM), vastus lateralis (VL) and cerebral (Cox) muscles oxygenation in women soccer players during high-intensity dynamic exercise. Ten female soccer players were randomized to perform in order two constant-load tests on a treadmill until the exhaustion time (Tlim) (100 % of maximal oxygen uptake- V˙O2). They breathed freely or against a fixed inspiratory loading (IL) of 41 cm H2O (∼30 % of maximal inspiratory pressure). Oxygenated (Δ[OxyHb]), deoxygenated (Δ[DeoxyHb]), total hemoglobin (Δ[tHb]) and tissue saturation index (ΔTSI) were obtained by NIRs. Also, blood lactate [La-] was obtained. IL significantly reduced Tlim (224 ± 54 vs 78 ± 20; P < 0.05) and increased [La-], V˙O2, respiratory cycles and dyspnea when corrected to Tlim (P < 0.05). IL also resulted in decrease of Δ[OxyHb] of Cox and IM during exercise compared with rest condition. In addition, decrease of Δ[OxyHb] was observed on IM during exercise when contrasted with Sham (P < 0.05). Furthermore, significant higher Δ[DeoxyHb] of IM and significant lower Δ[DeoxyHb] of Cox were observed when IL was applied during exercise in contrast with Sham (P < 0.05). These results were accompanied with significant reduction of Δ[tHb] and ΔTSI of IM and VL when IL was applied (P < 0.05). High-intensity exercise with IL decreased respiratory and peripheral muscle oxygenation with negative impact on exercise performance. However, the increase in ventilatory work did not impact cerebral oxygenation in soccer players.

Tumescent anesthesia or epidural anesthesia combined with intercostal block in bitches submitted to mastectomy / Anestesia local tumescente ou anestesia epidural associada ao bloqueio intercostal em cadelas submetidas à mastectomia

The present study aimed to evaluate the use of tumescent local anesthesia or epidural anesthesia associated with an intercostal nerve block in bitches submitted to mastectomy. Fourteen bitches from the clinical routine of the Veterinary Hospital of the Federal University of Pelotas were premedicated with acepromazine (0.03 mg/kg) and morphine (0.3 mg/kg) intramuscularly, then induced with propofol (2 to 6 mg/kg/IV) and maintained with 1,4V% isoflurane (calibrated vaporizer). The patients were randomly allocated into: GALT Group (n=7), which received tumescent local anesthesia (0.16%) at the dose of 15 mL/kg, and the GEBI Group (n=7) which received epidural anesthesia with lidocaine (5 mg/kg) and morphine (0.1 mg/kg) associated with an intercostal nerve block from the 6th to 12th intercostal space with lidocaine (2 mg/kg). An increase higher than 10% in heart rate, respiratory rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure were considered as possible signs of nociception, to which fentanyl was administered intravenously as rescue analgesia. Postoperative analgesia was evaluated by means of the modified Glasgow scale at 30, 60, 120, 240 and 360 minutes. There were no differences in physiological parameters (P>0.05) in the transoperative period intra-group and inter-group the groups. The GEBI Group required more frequent transoperative rescue analgesia (9) in comparison to the GALT Group (5), but with no statistical difference. During the postoperative period, there was no need for rescue analgesia in either group. Results suggest that epidural anesthesia associated with intercostal nerve block can be used as an alternative technique in patients with restrictions against the use of local tumescent anesthesia.(AU)

O presente estudo objetivou avaliar o uso da anestesia local tumescente ou da anestesia epidural associada ao bloqueio intercostal em cadelas submetidas à mastectomia. Foram utilizadas 14 cadelas, provenientes da rotina do Hospital de Clínicas Veterinária da Universidade Federal de Pelotas, pré-medicadas com acepromazina (0,03 mg/kg) e morfina (0,3 mg/kg) intramuscular, induzidas com propofol (2 a 6 mg/Kg/IV) e mantidas com isofluorano à 1,4 V% (vaporizador calibrado). Após essa etapa, foram alocadas aleatoriamente em grupo GALT (n=7), que recebeu a anestesia local tumescente 0,16% na dose de 15 mL/Kg e em grupo GEBI (n=7), que recebeu como tratamento a anestesia epidural com lidocaína (5 mg/kg) e morfina (0,1 mg/kg) associada ao bloqueio intercostal, do 6º ao 12º espaço intercostal, com lidocaína (2mg/kg). Os parâmetros avaliados para sinais de nocicepção transcirúrgica e realização de resgates analgésicos com fentanil foram: frequência cardíaca, frequência respiratória, pressão arterial sistólica, pressão arterial diastólica e pressão arterial média. No pós-operatório avaliou-se a analgesia pela escala de Glasgow Modificada aos 30, 60, 120, 240 e 360 minutos. Não houve diferenças entre os parâmetros clínicos (p > 0,05) no período transoperatório entre e dentro dos grupos. O GEBI apresentou maior quantidade de resgates analgésicos transoperatórios (9) em relação a GALT (5), porém sem diferenças estatísticas. No pós-operatório, nenhum animal de ambos os grupos atingiu pontuação máxima para resgate analgésico. Pode-se concluir que a anestesia epidural associada ao bloqueio intercostal é uma técnica alternativa para casos em que se tenham limitações para utilização da anestesia local tumescente.

Tumescent anesthesia or epidural anesthesia combined with intercostal block in bitches submitted to mastectomy / Anestesia local tumescente ou anestesia epidural associada ao bloqueio intercostal em cadelas submetidas à mastectomia

The present study aimed to evaluate the use of tumescent local anesthesia or epidural anesthesia associated with an intercostal nerve block in bitches submitted to mastectomy. Fourteen bitches from the clinical routine of the Veterinary Hospital of the Federal University of Pelotas were premedicated with acepromazine (0.03 mg/kg) and morphine (0.3 mg/kg) intramuscularly, then induced with propofol (2 to 6 mg/kg/IV) and maintained with 1,4V% isoflurane (calibrated vaporizer). The patients were randomly allocated into: GALT Group (n=7), which received tumescent local anesthesia (0.16%) at the dose of 15 mL/kg, and the GEBI Group (n=7) which received epidural anesthesia with lidocaine (5 mg/kg) and morphine (0.1 mg/kg) associated with an intercostal nerve block from the 6th to 12th intercostal space with lidocaine (2 mg/kg). An increase higher than 10% in heart rate, respiratory rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure were considered as possible signs of nociception, to which fentanyl was administered intravenously as rescue analgesia. Postoperative analgesia was evaluated by means of the modified Glasgow scale at 30, 60, 120, 240 and 360 minutes. There were no differences in physiological parameters (P>0.05) in the transoperative period intra-group and inter-group the groups. The GEBI Group required more frequent transoperative rescue analgesia (9) in comparison to the GALT Group (5), but with no statistical difference. During the postoperative period, there was no need for rescue analgesia in either group. Results suggest that epidural anesthesia associated with intercostal nerve block can be used as an alternative technique in patients with restrictions against the use of local tumescent anesthesia.

O presente estudo objetivou avaliar o uso da anestesia local tumescente ou da anestesia epidural associada ao bloqueio intercostal em cadelas submetidas à mastectomia. Foram utilizadas 14 cadelas, provenientes da rotina do Hospital de Clínicas Veterinária da Universidade Federal de Pelotas, pré-medicadas com acepromazina (0,03 mg/kg) e morfina (0,3 mg/kg) intramuscular, induzidas com propofol (2 a 6 mg/Kg/IV) e mantidas com isofluorano à 1,4 V% (vaporizador calibrado). Após essa etapa, foram alocadas aleatoriamente em grupo GALT (n=7), que recebeu a anestesia local tumescente 0,16% na dose de 15 mL/Kg e em grupo GEBI (n=7), que recebeu como tratamento a anestesia epidural com lidocaína (5 mg/kg) e morfina (0,1 mg/kg) associada ao bloqueio intercostal, do 6º ao 12º espaço intercostal, com lidocaína (2mg/kg). Os parâmetros avaliados para sinais de nocicepção transcirúrgica e realização de resgates analgésicos com fentanil foram: frequência cardíaca, frequência respiratória, pressão arterial sistólica, pressão arterial diastólica e pressão arterial média. No pós-operatório avaliou-se a analgesia pela escala de Glasgow Modificada aos 30, 60, 120, 240 e 360 minutos. Não houve diferenças entre os parâmetros clínicos (p > 0,05) no período transoperatório entre e dentro dos grupos. O GEBI apresentou maior quantidade de resgates analgésicos transoperatórios (9) em relação a GALT (5), porém sem diferenças estatísticas. No pós-operatório, nenhum animal de ambos os grupos atingiu pontuação máxima para resgate analgésico. Pode-se concluir que a anestesia epidural associada ao bloqueio intercostal é uma técnica alternativa para casos em que se tenham limitações para utilização da anestesia local tumescente.

Impact of moderate-severe persistent allergic rhinitis on thoraco-abdominal kinematics and respiratory muscle function.

Objective: To assess thoraco-abdominal kinematics, respiratory muscle strength and electromyographic activity of the diaphragm (EAdi) in moderate-severe allergic rhinitis (AR) patients. Methods: A cross-sectional study involving 40 individuals (20 in the AR group) and 20 in the control group [CG]) was conducted. Ventilatory pattern and chest wall volume distribution (optoelectronic plethysmography), respiratory muscle strength (manovacuometry and sniff nasal inspiratory pressure [SNIP]), and EAdi were assessed in both groups. Results: The AR patients had impaired thoraco-abdominal kinematics (reduced total chest wall volume) (p = 0.004), lower values of total respiratory cycle time (p = 0.014) and expiratory time (p = 0.006). They also presented an increase of percentage contribution of the abdominal rib cage (p = 0.475) and respiratory rate (p = 0.019). A positive correlation among pulmonary rib cage tidal volume and MIP (r = 0.544; p < 0.001), SNIP (r = 0.615; p < 0.001), and MEP (r = 0.604; p < 0.001) was observed. After adjusting for age, BMI and gender through multivariate analysis, the individuals with AR presented lower values ​​of MIP (ß = -24.341; p < 0.001), MEP (ß = -0.277; p < 0.001), SNIP (ß = -34.687; p < 0.001) and RMS (ß = -0.041; p = 0.017). Conclusions: The individuals with moderate-severe persistent AR had worse respiratory muscle strength, diaphragm activation and chest wall volume distribution with a higher abdominal contribution to tidal volume than the control group. These findings reinforce the notion that the upper and lower airways work in an integrated and synergistic manner.

Reliability of NIRS portable device for measuring intercostal muscles oxygenation during exercise.

This study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO2-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m-2; V̇O2-peak, 63.7 ± 5.9 mL·kg-1·min-1) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V̇O2) was assessed using the breath-by-breath method during the V̇O2-test, while SmO2 was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO2-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from -10.8% - +9.5% to -15.3% - +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO2-m.intercostales with V̇O2 (ρ = -0.64), VE (ρ = -0.73), RR (ρ = -0.70), and Vt (ρ = -0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device.

Axillary local anesthetic spread after the thoracic interfacial ultrasound block - a cadaveric and radiological evaluation / Dispersão axilar de anestésico local após bloqueio interfascial torácico guiado por ultrassom - estudo radiológico e em cadáver

Abstract Background Oral opioid analgesics have been used for management of peri- and postoperative analgesia in patients undergoing axillary dissection. The axillary region is a difficult zone to block and does not have a specific regional anesthesia technique published that offers its adequate blockade. Methods After institutional review board approval, anatomic and radiological studies were conducted to determine the deposition and spread of methylene blue and local anesthetic injected respectively into the axilla via the thoracic inter-fascial plane. Magnetic Resonance Imaging studies were then conducted in 15 of 34 patients scheduled for unilateral breast surgery that entailed any of the following: axillary clearance, sentinel node biopsy, axillary node biopsy, or supernumerary breasts, to ascertain the deposition and time course of spread of solution within the thoracic interfascial plane in vivo. Results Radiological and cadaveric studies showed that the injection of local anesthetic and methylene blue via the thoracic inter-fascial plane, using ultrasound guide technique, results in reliable deposition into the axilla. In patients, the injection of the local anesthetic produced a reliable axillary sensory block. This finding was supported by Magnetic Resonance Imaging studies that showed hyper-intense signals in the axillary region. Conclusions These findings define the anatomic characteristics of the thoracic interfascial plane nerve block in the axillary region, and underline the clinical potential of this novel nerve block.

Resumo Justificativa Os analgésicos orais à base de opioides têm sido usados para o manejo da analgesia nos períodos peri e pós-operatório de pacientes submetidos à linfadenectomia axilar. A região axilar é uma zona difícil de bloquear e não há registro de uma técnica de anestesia regional específica que ofereça o seu bloqueio adequado. Métodos Após a aprovação do Conselho de Ética institucional, estudos anatômicos e radiológicos foram feitos para determinar a deposição e disseminação de azul de metileno e anestésico local, respectivamente injetados na axila via plano interfascial torácico. Exames de ressonância magnética foram então feitos em 15 de 34 pacientes programados para cirurgia de mama unilateral que envolveria qualquer um dos seguintes procedimentos: esvaziamento axilar, biópsia de linfonodo sentinela, biópsia de linfonodo axilar ou mamas supranumerárias, para verificar a deposição e o tempo de propagação da solução dentro do plano interfascial torácico in vivo. Resultados Estudos radiológicos e em cadáveres mostraram que a injeção de anestésico local e azul de metileno via plano interfascial torácico com a técnica guiada por ultrassom resulta em deposição confiável na axila. Nos pacientes, a injeção de anestésico local produziu um bloqueio sensitivo axilar confiável. Esse achado foi corroborado por estudos de ressonância magnética que mostraram sinais hiperintensos na região axilar. Conclusões Esses achados definem as características anatômicas do bloqueio da região axilar e destacam o potencial clínico desses novos bloqueios.

[Axillary local anesthetic spread after the thoracic interfacial ultrasound block - a cadaveric and radiological evaluation]. / Dispersão axilar de anestésico local após bloqueio interfascial torácico guiado por ultrassom - estudo radiológico e em cadáver.

BACKGROUND: Oral opioid analgesics have been used for management of peri- and postoperative analgesia in patients undergoing axillary dissection. The axillary region is a difficult zone to block and does not have a specific regional anesthesia technique published that offers its adequate blockade. METHODS: After institutional review board approval, anatomic and radiological studies were conducted to determine the deposition and spread of methylene blue and local anesthetic injected respectively into the axilla via the thoracic inter-fascial plane. Magnetic Resonance Imaging studies were then conducted in 15 of 34 patients scheduled for unilateral breast surgery that entailed any of the following: axillary clearance, sentinel node biopsy, axillary node biopsy, or supernumerary breasts, to ascertain the deposition and time course of spread of solution within the thoracic interfascial plane in vivo. RESULTS: Radiological and cadaveric studies showed that the injection of local anesthetic and methylene blue via the thoracic inter-fascial plane, using ultrasound guide technique, results in reliable deposition into the axilla. In patients, the injection of the local anesthetic produced a reliable axillary sensory block. This finding was supported by Magnetic Resonance Imaging studies that showed hyper-intense signals in the axillary region. CONCLUSIONS: These findings define the anatomic characteristics of the thoracic interfascial plane nerve block in the axillary region, and underline the clinical potential of this novel nerve block.

Inspiratory Muscle Training Improves Intercostal and Forearm Muscle Oxygenation in Patients With Chronic Heart Failure: Evidence of the Origin of the Respiratory Metaboreflex.

BACKGROUND: The impact of inspiratory muscle training (IMT) on respiratory and peripheral muscle oxygenation and perfusion during inspiratory muscle fatigue in patients with chronic heart failure (HF) has not been established. METHODS AND RESULTS: Twenty-six patients with chronic HF were randomly assigned to either 8 weeks of IMT or a control group. Inspiratory fatigue was induced by means of a progressive inspiratory resistive loading protocol until there was an inability to sustain inspiratory pressure, when the inspiratory muscle metaboreflex should be activated. The main outcomes were intercostal and forearm muscle oxygen saturation and deoxygenation as measured by means of near-infrared spectroscopy (NIRS) and blood lactate levels. Inspiratory muscle strength was increased by 78% (P <.001) after 8 weeks of participation in the IMT group. IMT attenuated the reduction of oxygen saturation in intercostal and forearm muscles and the increase in blood lactate during respiratory fatigue (P <.001 and P <.05, respectively). These changes were different from the control group (P <.01, P <.05, and P <.05, respectively). After 8 weeks, similar increases in oxygen consumption, mean arterial pressure, heart rate, stroke volume, and cardiac output were observed in both groups during respiratory fatigue. CONCLUSIONS: This randomized controlled clinical trial demonstrates that IMT attenuates the respiratory muscle oxygen demand-delivery mismatch during respiratory fatigue in patients with chronic HF.

Effects of breathing type on electromyographic activity of respiratory muscles at different body positions.

AIM: To compare the effect of breathing type on the activity of respiratory muscles at different body positions. METHODOLOGY: Two groups of 20 subjects each, one with upper costal and the other with costodiaphragmatic breathing, were studied. Electromyographic activity of sternocleidomastoid (SCM), diaphragm (DIA), external intercostal (EIC), and latissimus dorsi (LAT) muscles was recorded at standing and lateral decubitus positions during swallowing and maximal voluntary clenching. RESULTS: All muscles showed higher activity during standing in upper costal breathing subjects except the SCM muscle. EIC activity was higher during standing in the costodiaphragmatic breathing group. Subjects with upper costal breathing showed higher DIA activity than subjects with costodiaphragmatic breathing at both body positions and higher SCM activity at lateral decubitus position, whereas, EIC activity was only higher during swallowing. CONCLUSIONS: Subjects with upper costal breathing presented higher respiratory effort than subjects with costodiaphragmatic breathing, being most prominent at the lateral decubitus position.

Hernia pulmonar espontánea secundaria a acceso de tos: reparación por técnica asistida por video / Spontaneous lung hernia secondary to coughing fit: repair by video assisted technique

La hernia pulmonar es la protrusión del tejido pulmonar a través de una de las estructuras que lo contienen. Generalmente, son secundarias a traumatismos o a un procedimiento quirúrgico; con menos frecuencia, pueden ser espontáneas posteriores a accesos de tos. El diagnóstico se hace por el cuadro clínico y debe confirmarse con radiografía o tomografía, con las cuales se puede ver la protrusión del tejido pulmonar a través de los espacios intercostales. Pueden tratarse de manera conservadora si son asintomáticas, pero el tratamiento más común es el quirúrgico, con técnica abierta o asistida por video. Se presenta una revisión bibliográfica y el reporte de un caso manejado con técnica asistida por video.

Lung hernia is the protrusion of lung tissue through one of its bounding structures. Usually it develops as the result of thoracic trauma or after a surgical procedure; less frequently it can be spontaneous after a coughing fit. Diagnosis is made on the basis of the clinical findings and should be confirmed by X-ray imaging or computed tomography, which evidence the protrusion of the lung through the intercostal spaces. Treatment of lung hernia may be conservative when the patient is asymptomatic, but surgical intervention is most commonly performed, which can be by the open technique or by the video assisted technique. We present a literature review and report a case that was managed by the video assisted surgical technique.

Intercostal and forearm muscle deoxygenation during respiratory fatigue in patients with heart failure: potential role of a respiratory muscle metaboreflex

The purpose of this study was to determine the effect of respiratory muscle fatigue on intercostal and forearm muscle perfusion and oxygenation in patients with heart failure. Five clinically stable heart failure patients with respiratory muscle weakness (age, 66±12 years; left ventricle ejection fraction, 34±3%) and nine matched healthy controls underwent a respiratory muscle fatigue protocol, breathing against a fixed resistance at 60% of their maximal inspiratory pressure for as long as they could sustain the predetermined inspiratory pressure. Intercostal and forearm muscle blood volume and oxygenation were continuously monitored by near-infrared spectroscopy with transducers placed on the seventh left intercostal space and the left forearm. Data were compared by two-way ANOVA and Bonferroni correction. Respiratory fatigue occurred at 5.1±1.3 min in heart failure patients and at 9.3±1.4 min in controls (P<0.05), but perceived effort, changes in heart rate, and in systolic blood pressure were similar between groups (P>0.05). Respiratory fatigue in heart failure reduced intercostal and forearm muscle blood volume (P<0.05) along with decreased tissue oxygenation both in intercostal (heart failure, -2.6±1.6%; controls, +1.6±0.5%; P<0.05) and in forearm muscles (heart failure, -4.5±0.5%; controls, +0.5±0.8%; P<0.05). These results suggest that respiratory fatigue in patients with heart failure causes an oxygen demand/delivery mismatch in respiratory muscles, probably leading to a reflex reduction in peripheral limb muscle perfusion, featuring a respiratory metaboreflex.

Intercostal and forearm muscle deoxygenation during respiratory fatigue in patients with heart failure: potential role of a respiratory muscle metaboreflex.

The purpose of this study was to determine the effect of respiratory muscle fatigue on intercostal and forearm muscle perfusion and oxygenation in patients with heart failure. Five clinically stable heart failure patients with respiratory muscle weakness (age, 66 ± 12 years; left ventricle ejection fraction, 34 ± 3%) and nine matched healthy controls underwent a respiratory muscle fatigue protocol, breathing against a fixed resistance at 60% of their maximal inspiratory pressure for as long as they could sustain the predetermined inspiratory pressure. Intercostal and forearm muscle blood volume and oxygenation were continuously monitored by near-infrared spectroscopy with transducers placed on the seventh left intercostal space and the left forearm. Data were compared by two-way ANOVA and Bonferroni correction. Respiratory fatigue occurred at 5.1 ± 1.3 min in heart failure patients and at 9.3 ± 1.4 min in controls (P<0.05), but perceived effort, changes in heart rate, and in systolic blood pressure were similar between groups (P>0.05). Respiratory fatigue in heart failure reduced intercostal and forearm muscle blood volume (P<0.05) along with decreased tissue oxygenation both in intercostal (heart failure, -2.6 ± 1.6%; controls, +1.6 ± 0.5%; P<0.05) and in forearm muscles (heart failure, -4.5 ± 0.5%; controls, +0.5 ± 0.8%; P<0.05). These results suggest that respiratory fatigue in patients with heart failure causes an oxygen demand/delivery mismatch in respiratory muscles, probably leading to a reflex reduction in peripheral limb muscle perfusion, featuring a respiratory metaboreflex.