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1.
Pneumologie ; 74(3): 137-148, 2020 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-31918445

RESUMO

Nasal high-flow provides a stable oxygenation in acute hypoxemic respiratory failure, modifies breathing patterns, reduces work of breathing and can decrease hypercapnia. Thereby NHF provides more features than low-flow oxygen and acts as a ventilatory support device. Different studies show benefits of NHF compared to NIV. For these reasons we will discuss the capabilities of NHF and NIV in selected settings.


Assuntos
Pulmão/fisiopatologia , Ventilação não Invasiva/métodos , Oxigenoterapia/métodos , Oxigênio/administração & dosagem , Respiração com Pressão Positiva/métodos , Insuficiência Respiratória/terapia , Trabalho Respiratório/fisiologia , Humanos , Hipercapnia/prevenção & controle , Resultado do Tratamento
2.
J Sports Sci ; 37(23): 2653-2659, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31419921

RESUMO

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.


Assuntos
Exercício Físico/fisiologia , Músculos Intercostais/fisiologia , Consumo de Oxigênio/fisiologia , Espectroscopia de Luz Próxima ao Infravermelho/instrumentação , Trabalho Respiratório/fisiologia , Adulto , Desempenho Atlético/fisiologia , Teste de Esforço/métodos , Humanos , Masculino , Reprodutibilidade dos Testes , Taxa Respiratória/fisiologia , Corrida/fisiologia , Volume de Ventilação Pulmonar/fisiologia , Adulto Jovem
3.
Eur J Pediatr ; 178(8): 1237-1242, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31187264

RESUMO

Heated, humidified, high-flow nasal cannula (HHHFNC) is increasingly being used, but there is a paucity of evidence as to the optimum flow rates in prematurely born infants. We have determined the impact of three flow rates on the work of breathing (WOB) assessed by transcutaneous diaphragm electromyography (EMG) amplitude in infants with respiratory distress or bronchopulmonary dysplasia (BPD). Flow rates of 4, 6 and 8 L/min were delivered in random order. The mean amplitude of the EMG trace and mean area under the EMG curve (AEMGC) were calculated and the occurrence of bradycardias and desaturations recorded. Eighteen infants were studied with a median gestational age of 27.8 (range 23.9-33.5) weeks and postnatal age of 54 (range 3-122) days. The median flow rate prior to the study was 5 (range 3-8) L/min and the fraction of inspired oxygen (FiO2) was 0.29 (range 0.21-0.50). There were no significant differences between the mean amplitude of the diaphragm EMG and the AEGMC and the number of bradycardias or desaturations between the three flow rates.Conclusions: In infants with respiratory distress or BPD, there was no advantage of using high (8 L/min) compared with lower flow rates (4 or 6 L/min) during support by HHHFNC. What is known: • Humidified high flow nasal cannulae (HHHFNC) is increasingly being used as a non-invasive form of respiratory support for prematurely born infants. • There is a paucity of evidence regarding the optimum flow rate with 1 to 8 L/min being used. What is new: • We have assessed the work of breathing using the amplitude of the electromyogram of the diaphragm at three HHHFNC flow rates in infants with respiratory distress or BPD. • No significant differences were found in the EMG amplitude results or the numbers of bradycardias or desaturations at 4, 6 and 8 L/min.


Assuntos
Displasia Broncopulmonar/terapia , Diafragma/fisiologia , Eletromiografia , Ventilação não Invasiva/métodos , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Trabalho Respiratório/fisiologia , Displasia Broncopulmonar/fisiopatologia , Cânula , Estudos Cross-Over , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Ventilação não Invasiva/instrumentação , Síndrome do Desconforto Respiratório do Recém-Nascido/fisiopatologia , Resultado do Tratamento
5.
Med Sci Sports Exerc ; 51(8): 1727-1735, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30817718

RESUMO

PURPOSE: The physiological consequences of freely chosen cadence during cycling remains poorly understood. We sought to determine the effect of cadence on the respiratory and hemodynamic response to cycling exercise. METHODS: Eleven cyclists (10 males, 1 female; age, 27 ± 6 yr; V˙O2max = 60.8 ± 3.7 mL·kg·min) completed four, 6-min constant-load cycling trials at 10% below their previously determined gas exchange threshold (i.e., 63% ± 5% peak power) while pedaling at 60, 90, and 120 rpm, and a freely chosen cadence (94.3 ± 6.9 rpm) in randomized order. Standard cardiorespiratory parameters were measured and an esophageal electrode balloon catheter was used to assess electromyography of the diaphragm (EMGdi) and the work of breathing (Wb). Leg blood flow index (BFI) was determined on four muscles using near-infrared spectroscopy with indocyanine green dye injections. RESULTS: Oxygen uptake (V˙O2) increased as a function of increasing cadence (all pairwise comparisons, P < 0.05). The EMGdi and Wb were significantly greater at 120 rpm compared with all other conditions (all P < 0.01). Vastus medialis and semitendinosus BFI were significantly greater at 120 rpm compared with 60 and 90 rpm (all P < 0.05). Gastrocnemius BFI was higher at 120 rpm compared with all other cadences (all P < 0.01). No difference in BFI was found in the vastus lateralis (P = 0.06). Blood flow index was significantly correlated with the increase in V˙O2 with increasing cadence in the medial gastrocnemius (P < 0.001) and approached significance in the vastus lateralis (P = 0.09), vastus medialis (P = 0.06), and semitendinosus (P = 0.09). There was no effect of cadence on Borg 0-10 breathing or leg discomfort ratings (P > 0.05). CONCLUSIONS: High cadence cycling at submaximal exercise intensities is metabolically inefficient and increases EMGdi, Wb, and leg muscle blood flow relative to slower cadences.


Assuntos
Ciclismo/fisiologia , Hemodinâmica/fisiologia , Perna (Membro)/irrigação sanguínea , Músculo Esquelético/irrigação sanguínea , Trabalho Respiratório/fisiologia , Adulto , Fenômenos Biomecânicos , Diafragma/fisiologia , Eletromiografia , Feminino , Humanos , Masculino , Microcirculação , Percepção/fisiologia , Esforço Físico/fisiologia , Fluxo Sanguíneo Regional , Adulto Jovem
6.
Med Sci Sports Exerc ; 51(7): 1467-1476, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30649105

RESUMO

The thorax undergoes unique conditions while swimming. Hydrostatic pressure from water immersion places an external load on the thorax and increases airway resistance, and the horizontal body position results in central venous engorgement and an associated reduction in lung compliance. The aforementioned factors likely increase the work of breathing (Wb); however, this hypothesis remains untested. PURPOSE: This study aimed to compare Wb during freestyle swimming relative to cycling and to characterize the differences in the cardiorespiratory responses to swimming relative to cycling in the same individuals. METHODS: Eight collegiate swimmers (four men and four women, age = 22 ± 2 yr) performed an incremental swim test while tethered to a resistance apparatus. On a separate day, subjects performed an incremental cycle test. During swimming and cycling, metabolic and ventilatory parameters were measured using a customized metabolic cart, and inspired Wb was quantified using an esophageal balloon catheter. RESULTS: Swimming and cycling elicited statistically similar levels of peak oxygen uptake (3.87 ± 0.92 vs 4.20 ± 0.83 L·min, P = 0.143). However, peak minute ventilation (V˙E) (118 ± 3 vs 154 ± 25 L·min) and heart rate (164 ± 19 vs 183 ± 8 bpm) were significantly lower during swimming relative to cycling (both P < 0.05). Inspired Wb was higher at a V˙E of 50 L·min (+27 ± 16 J·min), 75 L·min (+56 ± 23 J·min), and 100 L·min (+53 ± 22 J·min) during swimming compared with cycling (all P < 0.05). Periods of interbreath apnea were observed while swimming (duration = 0.13-2.07 s). CONCLUSION: We interpret our findings to mean that the horizontal body position and hydrostatic pressure on the chest wall requires swimmers to generate greater inspiratory pressures to sustain adequate V˙E during exercise.


Assuntos
Postura/fisiologia , Mecânica Respiratória/fisiologia , Natação/fisiologia , Ciclismo/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Pressão Hidrostática , Medidas de Volume Pulmonar , Masculino , Consumo de Oxigênio/fisiologia , Tórax/fisiologia , Trabalho Respiratório/fisiologia , Adulto Jovem
7.
Eur J Pediatr ; 178(1): 105-110, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30374754

RESUMO

Our aim was to compare the work of breathing (WOB) during synchronised nasal intermittent positive pressure ventilation (SNIPPV) and heated humidified high flow nasal cannula (HHHFNC) when used as post-extubation support in preterm infants. A randomised crossover study was undertaken of nine infants with a median gestational age of 27 (range 24-31) weeks and post-natal age of 7 (range 2-50) days. Infants were randomised to either SNIPPV or HHHFNC immediately following extubation. They were studied for 2 h on one mode and then switched to the other modality and studied for a further 2-h period. The work of breathing, assessed by measuring the pressure time product of the diaphragm (PTPdi), and thoracoabdominal asynchrony (TAA) were determined at the end of each 2-h period. The infants' inspired oxygen requirement, oxygen saturation, heart rate and respiratory rate were also recorded. The median PTPdi was lower on SNIPPV than on HHHFNC (232 (range 130-352) versus 365 (range 136-449) cmH2O s/min, p = 0.0077), and there was less thoracoabdominal asynchrony (13.4 (range 8.5-41.6) versus 36.1 (range 4.3-50.4) degrees, p = 0.038).Conclusion: In prematurely born infants, SNIPPV compared to HHHFNC post-extubation reduced the work of breathing and thoracoabdominal asynchrony. What is Known: • The work of breathing and extubation failure are not significantly different in prematurely-born infants supported by HHHFNC or nCPAP. • SNIPPV reduces inspiratory effort and increases tidal volume and carbon dioxide exchange compared to nCPAP in prematurely born infants. What is New: • SNIPPV, as compared to HHHFNC, reduced the work of breathing in prematurely-born infants studied post-extubation. • SNIPPV, as compared to HHHFNC, reduced thoracoabdominal asynchrony in prematurely born infants studied post-extubation.


Assuntos
Extubação/métodos , Ventilação com Pressão Positiva Intermitente/métodos , Ventilação não Invasiva/métodos , Trabalho Respiratório/fisiologia , Gasometria , Cânula , Estudos Cross-Over , Feminino , Frequência Cardíaca/fisiologia , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Taxa Respiratória/fisiologia
8.
Med Sci Sports Exerc ; 51(2): 361-371, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30216239

RESUMO

INTRODUCTION: Recently a novel, time-saving respiratory muscle sprint-interval training (RMSIT) was developed. To test the extent to which RMSIT improves respiratory muscle performance compared with a conventional respiratory muscle endurance training (RMET), a novel incremental respiratory muscle test (IncRMT), loading inspiratory and expiratory muscles, was designed to assess performance changes associated with respiratory muscle training (RMT). METHODS: Healthy, moderately trained males and females (age: 26 ± 5 yr, V˙O2peak: 47 ± 12 mL·min·kg) were randomized and balanced to three groups (RMSIT 5m/5f; RMET 6m/6f; PLAT 5m/6f). Lung function, respiratory muscle strength, and IncRMT performance were tested before and after 1 month of RMT. During the IncRMT, muscle activity and muscle deoxygenation were assessed via surface EMG and near-infrared spectroscopy of sternocleidomastoid (STERNO), intercostal (INTER), and abdominal (ABDO) muscles. RESULTS: Two-way ANOVA revealed a main effect of training for increased maximal voluntary ventilation (P = 0.001) and maximal inspiratory pressure (P = 0.017). Both RMT groups increased work of breathing during training sessions to the same extent (RMSIT: +17.4 ± 8.9 kJ; RMET: +26.2 ± 16.1 kJ; P = 0.143) with a larger increase in average mouth pressure in RMSIT (RMSIT: +20.0 ± 15.0 cm H2O; RMET: +3.3 ± 1.5 cm H2O; P = 0.001). After training, IncRMT duration increased in both RMT groups compared with PLAT (RMSIT: +5.6 ± 2.1 min, P = 0.0006 vs PLAT; RMET: +3.8 ± 4.2 min, P = 0.020 vs PLAT). At similar work, only INTER activity during inspiration increased after RMET. Higher performance after RMSIT was associated with higher activity in STERNO and ABDO, but after RMET, STERNO, INTER, and ABDO showed higher activity. CONCLUSION: One month of RMSIT and RMET shows similar improvements in respiratory muscle performance despite different duration of training sessions. Also, muscular adaptations might differ.


Assuntos
Exercícios Respiratórios/métodos , Treino Aeróbico/métodos , Treinamento Intervalado de Alta Intensidade/métodos , Pulmão/fisiologia , Músculos Respiratórios/fisiologia , Adaptação Fisiológica , Adulto , Eletromiografia , Feminino , Humanos , Masculino , Força Muscular/fisiologia , Trabalho Respiratório/fisiologia , Adulto Jovem
9.
Respir Physiol Neurobiol ; 260: 131-136, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30471435

RESUMO

PURPOSE: While dyspnea on exertion (DOE) is a common complaint in otherwise healthy obese women, less is known about feelings of unpleasantness and/or negative emotions provoked by DOE. We examined whether ratings of perceived breathlessness (RPB) during exercise were associated with ratings of unpleasantness and negative emotions (depression, anxiety, frustration, anger, and fear) in obese women. METHODS: Seventy-four women (34 ± 7 yrs, 36 ± 4 kg/m2, 46 ± 5% body fat) performed 6 min of constant-load cycling (60 W); RPB (0-10 scale), and unpleasantness and negative emotions (visual analog scales, 10 cm) were assessed at the end. RESULTS: RPB were significantly correlated with unpleasantness and negative emotions (p < 0.05). The strongest correlations were between RPB and unpleasantness (r = 0.61, p < 0.001), and RPB and anxiety (r = 0.50, p < 0.001). CONCLUSIONS: DOE can significantly provoke unpleasantness and negative emotions during exercise in obese women. This may affect their willingness to engage in regular physical activity.


Assuntos
Ansiedade/fisiopatologia , Dispneia/fisiopatologia , Emoções/fisiologia , Exercício Físico/fisiologia , Obesidade/complicações , Obesidade/psicologia , Ventilação Pulmonar/fisiologia , Trabalho Respiratório/fisiologia , Adulto , Análise de Variância , Composição Corporal , Feminino , Humanos , Medidas de Volume Pulmonar , Consumo de Oxigênio
10.
Physiother Res Int ; 24(1): e1750, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30251299

RESUMO

OBJECTIVES: Faster recovery of postexertional dyspnea might enable chronic obstructive pulmonary disease (COPD) patients to undertake more physical activity. The purpose of this study was to determine whether breathing with a positive expiratory load to reduce dynamic hyperinflation (DH) would hasten recovery. METHODS: Thirteen male COPD patients (59 ± 7 years; Global Initiative for Obstructive Lung Disease Stages II and III) took part in a randomized cross-over trial in which they exercised by self-paced spot marching. Interventions at the end of exercise consisted of six breaths against either a 5-cm H2 O expiratory load (positive expiratory pressure [PEP]) or no load (Sham), with 3-hr rest between interventions. Recovery was followed for the next 10 min. Primary outcome measures were dyspnea during recovery and inspiratory capacity (IC), measured at rest, at the end of exercise and after the intervention; oxygen saturation, end-tidal CO2 , heart rate, and breathing frequency were also monitored. RESULTS: Patients exercised for 5 min reaching a heart rate of 70% age-predicted maximum and developed dyspnea of 3-4 on the Modified Borg CR10 scale. Dyspnea recovered significantly faster after the PEP intervention in all patients, taking 2.8 ± 0.4 min to return to baseline compared with 5.1 ± 0.6 min for Sham (p < 0.01). IC declined at the end of exercise and was improved by PEP (+270 220-460 ml, median, interquartile range) more than Sham (+100, 40-160 ml). However, PEP was equally effective in reducing dyspnea in all patients irrespective of the degree of DH. Changes in oxygen saturation, end-tidal CO2 , heart rate, and breathing frequency were similar in PEP and Sham. CONCLUSIONS: Positive expiratory pressure breathing is an effective means of reducing postexercise dyspnea and DH in COPD. The benefits were not limited to patients with high DH suggesting PEP may be used to speed recovery and increase the volume of exercise during pulmonary rehabilitation sessions and physical activity at home or work.


Assuntos
Dispneia/terapia , Respiração com Pressão Positiva , Doença Pulmonar Obstrutiva Crônica/terapia , Trabalho Respiratório/fisiologia , Idoso , Estudos Cross-Over , Dispneia/fisiopatologia , Teste de Esforço , Tolerância ao Exercício/fisiologia , Feminino , Humanos , Capacidade Inspiratória , Masculino , Pessoa de Meia-Idade , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Músculos Respiratórios/fisiologia
11.
Exp Physiol ; 104(2): 180-188, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30462876

RESUMO

NEW FINDINGS: What is the central question of this study? Increased respiratory muscle activation is associated with neural and cardiovascular consequences via the respiratory muscle metaboreflex. Does increased sympathetic vasoconstriction originating from the respiratory musculature elicit a reduction in blood flow to an inactive limb in order to maintain blood flow to an active limb? What is the main finding and its importance? Arm blood flow was reduced whereas leg blood flow was preserved during mild leg exercise with inspiratory resistance. Blood flow to the active limb is maintained via sympathetic control of blood flow redistribution when the respiratory muscle-induced metaboreflex is activated. ABSTRACT: The purpose of this study was to elucidate the effect of increasing inspiratory muscle work on blood flow to inactive and active limbs. Healthy young men (n = 10, 20 ± 2 years of age) performed two bilateral dynamic knee-extension and knee-flexion exercise tests at 40% peak oxygen uptake for 10 min. The trials consisted of spontaneous breathing for 5 min followed by voluntary hyperventilation either with or without inspiratory resistance for 5 min (40% of maximal inspiratory mouth pressure, inspiratory duty cycle of 50% and a breathing frequency of 40 breaths min-1 ). Mean arterial blood pressure was acquired using finger photoplethysmography. Blood flow in the brachial artery (inactive limb) and in the femoral artery (active limb) were monitored using Doppler ultrasound. Mean arterial blood pressure during exercise was higher (P < 0.05) with inspiratory resistance (121 ± 7 mmHg) than without resistance (99 ± 5 mmHg). Brachial artery blood flow increased during exercise without inspiratory resistance (120 ± 31 ml min-1 ) compared with the resting level, whereas it was attenuated with inspiratory resistance (65 ± 43 ml min-1 ). Femoral artery blood flow increased at the onset of exercise and was maintained throughout exercise without inspiratory resistance (2576 ± 640 ml min-1 ) and was unchanged when inspiratory resistance was added (2634 ± 659 ml min-1 ; P > 0.05). These results suggest that sympathetic control of blood redistribution to active limbs is facilitated, in part, by the respiratory muscle-induced metaboreflex.


Assuntos
Exercício Físico/fisiologia , Extremidades/fisiologia , Músculo Esquelético/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Músculos Respiratórios/fisiologia , Trabalho Respiratório/fisiologia , Adulto , Pressão Arterial/fisiologia , Teste de Esforço/métodos , Artéria Femoral/metabolismo , Artéria Femoral/fisiologia , Humanos , Inalação/fisiologia , Joelho/fisiologia , Masculino , Fadiga Muscular/fisiologia , Músculo Esquelético/metabolismo , Oxigênio/metabolismo , Reflexo/fisiologia , Respiração , Músculos Respiratórios/metabolismo , Descanso/fisiologia , Sistema Nervoso Simpático/metabolismo , Sistema Nervoso Simpático/fisiologia , Resistência Vascular/fisiologia , Adulto Jovem
12.
Arch Dis Child Fetal Neonatal Ed ; 104(1): F46-F49, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29305407

RESUMO

OBJECTIVES: To assess the work of breathing at different levels of volume targeting in prematurely born infants with evolving or established bronchopulmonary dysplasia (BPD). DESIGN: Randomised crossover study. SETTING: Tertiary neonatal intensive care unit. PATIENTS: Eighteen infants born at <32 weeks gestation who remained ventilated at or beyond 1 week after birth, that is, they had evolving or established BPD. INTERVENTIONS: Infants received ventilation at volume targeting levels of 4, 5, 6 and 7 mL/kg each for 20 minutes, the levels were delivered in random order. Baseline ventilation (without volume targeting) was delivered for 20 minutes between each epoch of volume-targeting. MAIN OUTCOME MEASURES: Pressure-time product of the diaphragm (PTPdi), a measure of the work of breathing, at different levels of volume targeting. RESULTS: The 18 infants had a median gestational age of 26 (range 24-30) weeks and were studied at a median of 18 (range 7-60) days. The mean PTPdi was higher at 4 mL/kg than at baseline, 5 mL/kg, 6 mL/kg and 7 mL/kg (all P≤0.001). The mean PTPdi was higher at 5 mL/kg than at 6 mL/kg (P=0.008) and 7 mL/kg (P<0.001) and higher at 6 mL/kg than 7 mL/kg (P=0.003). Only at 7 mL/kg was the PTPdi significantly lower than at baseline (P=0.001). CONCLUSIONS: Only a tidal volume target of 7 mL/kg reduced the work of breathing below the baseline and may be more appropriate for infants with evolving or established BPD who remained ventilator dependent at or beyond 7 days of age.


Assuntos
Displasia Broncopulmonar/fisiopatologia , Displasia Broncopulmonar/terapia , Recém-Nascido Prematuro , Respiração Artificial/métodos , Trabalho Respiratório/fisiologia , Estudos Cross-Over , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Unidades de Terapia Intensiva Neonatal , Masculino , Centros de Atenção Terciária , Volume de Ventilação Pulmonar
14.
Crit Care ; 22(1): 238, 2018 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-30261920

RESUMO

BACKGROUND: Diaphragm dysfunction develops frequently in ventilated intensive care unit (ICU) patients. Both disuse atrophy (ventilator over-assist) and high respiratory muscle effort (ventilator under-assist) seem to be involved. A strong rationale exists to monitor diaphragm effort and titrate support to maintain respiratory muscle activity within physiological limits. Diaphragm electromyography is used to quantify breathing effort and has been correlated with transdiaphragmatic pressure and esophageal pressure. The neuromuscular efficiency index (NME) can be used to estimate inspiratory effort, however its repeatability has not been investigated yet. Our goal is to evaluate NME repeatability during an end-expiratory occlusion (NMEoccl) and its use to estimate the pressure generated by the inspiratory muscles (Pmus). METHODS: This is a prospective cohort study, performed in a medical-surgical ICU. A total of 31 adult patients were included, all ventilated in neurally adjusted ventilator assist (NAVA) mode with an electrical activity of the diaphragm (EAdi) catheter in situ. At four time points within 72 h five repeated end-expiratory occlusion maneuvers were performed. NMEoccl was calculated by delta airway pressure (ΔPaw)/ΔEAdi and was used to estimate Pmus. The repeatability coefficient (RC) was calculated to investigate the NMEoccl variability. RESULTS: A total number of 459 maneuvers were obtained. At time T = 0 mean NMEoccl was 1.22 ± 0.86 cmH2O/µV with a RC of 82.6%. This implies that when NMEoccl is 1.22 cmH2O/µV, it is expected with a probability of 95% that the subsequent measured NMEoccl will be between 2.22 and 0.22 cmH2O/µV. Additional EAdi waveform analysis to correct for non-physiological appearing waveforms, did not improve NMEoccl variability. Selecting three out of five occlusions with the lowest variability reduced the RC to 29.8%. CONCLUSIONS: Repeated measurements of NMEoccl exhibit high variability, limiting the ability of a single NMEoccl maneuver to estimate neuromuscular efficiency and therefore the pressure generated by the inspiratory muscles based on EAdi.


Assuntos
Estado Terminal/terapia , Diafragma/fisiopatologia , Eficiência/fisiologia , Estatística como Assunto/normas , Idoso , Estudos de Coortes , Eletromiografia/métodos , Feminino , Humanos , Unidades de Terapia Intensiva/organização & administração , Suporte Ventilatório Interativo/métodos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Respiração Artificial/métodos , Índice de Gravidade de Doença , Estatística como Assunto/métodos , Trabalho Respiratório/fisiologia
15.
Crit Care ; 22(1): 180, 2018 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-30071876

RESUMO

BACKGROUND: The physiological effects of high-flow nasal cannula O2 therapy (HFNC) have been evaluated mainly in patients with hypoxemic respiratory failure. In this study, we compared the effects of HFNC and conventional low-flow O2 therapy on the neuroventilatory drive and work of breathing postextubation in patients with a background of chronic obstructive pulmonary disease (COPD) who had received mechanical ventilation for hypercapnic respiratory failure. METHODS: This was a single center, unblinded, cross-over study on 14 postextubation COPD patients who were recovering from an episode of acute hypercapnic respiratory failure of various etiologies. After extubation, each patient received two 1-h periods of HFNC (HFNC1 and HFNC2) alternated with 1 h of conventional low-flow O2 therapy via a face mask. The inspiratory fraction of oxygen was titrated to achieve an arterial O2 saturation target of 88-92%. Gas exchange, breathing pattern, neuroventilatory drive (electrical diaphragmatic activity (EAdi)) and work of breathing (inspiratory trans-diaphragmatic pressure-time product per minute (PTPDI/min)) were recorded. RESULTS: EAdi peak increased from a mean (±SD) of 15.4 ± 6.4 to 23.6 ± 10.5 µV switching from HFNC1 to conventional O2, and then returned to 15.2 ± 6.4 µV during HFNC2 (conventional O2: p < 0.05 versus HFNC1 and HFNC2). Similarly, the PTPDI/min increased from 135 ± 60 to 211 ± 70 cmH2O/s/min, and then decreased again during HFNC2 to 132 ± 56 (conventional O2: p < 0.05 versus HFNC1 and HFNC2). CONCLUSIONS: In patients with COPD, the application of HFNC postextubation significantly decreased the neuroventilatory drive and work of breathing compared with conventional O2 therapy.


Assuntos
Extubação/métodos , Cânula/normas , Oxigenoterapia/métodos , Doença Pulmonar Obstrutiva Crônica/terapia , Trabalho Respiratório/fisiologia , Idoso , Idoso de 80 Anos ou mais , Extubação/normas , Análise de Variância , Cânula/tendências , Estudos Cross-Over , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ventilação não Invasiva/métodos , Ventilação não Invasiva/normas , Oxigenoterapia/normas , Desmame do Respirador/métodos , Desmame do Respirador/normas
16.
Paediatr Anaesth ; 28(9): 780-787, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30004614

RESUMO

BACKGROUND: Over the last decade, cuffed endotracheal tubes are increasingly used in pediatric anesthesia and also in pediatric intensive care. However, the smaller inner diameter of cuffed endotracheal tubes and, implicitly, the increased endotracheal tube resistance is still a matter of debate. AIMS: This in vitro study investigated work of breathing and inspiratory airway pressures in cuffed and uncuffed endotracheal tubes and the impact of pressure support ventilation and automatic tube compensation. METHODS: In 5 simulated neonatal and pediatric lung models, the Active Servo Lung 5000 and an intensive care ventilator were used to quantify the differences in work of breathing under spontaneous breathing (with and without pressure support ventilation and automatic tube compensation) between cuffed and uncuffed endotracheal tubes. Additionally, differences in inspiratory airway pressures, measured either proximal or distal of the endotracheal tube, between cuffed and uncuffed endotracheal tubes under mechanical ventilation were investigated. RESULTS: Work of breathing was overall 10.27% [95% confidence interval 9.01-11.94] higher with cuffed than with uncuffed endotracheal tubes and was dramatically reduced by 34.19% [95% confidence interval 31.61-35.25] with the application of pressure support. Automatic tube compensation almost diminished work of breathing differences between the 2 endotracheal tube types in nearly all pediatric lung models. Peak inspiratory and mean airway pressures measured at the proximal endotracheal tube end revealed significantly higher values in cuffed than in uncuffed endotracheal tubes. However, these differences measured at the distal end of the endotracheal tube became minimal. CONCLUSION: This in vitro study confirmed significant differences in work of breathing and inspiratory pressures between cuffed and uncuffed endotracheal tubes. Work of breathing, however, is almost neutralized by pressure support ventilation with automatic tube compensation and distal inspiratory airway pressures that, from a clinical perspective, are not significantly increased.


Assuntos
Intubação Intratraqueal/instrumentação , Pulmão/fisiologia , Modelos Biológicos , Respiração com Pressão Positiva/instrumentação , Trabalho Respiratório/fisiologia , Resistência das Vias Respiratórias , Criança , Desenho de Equipamento , Humanos , Pulmão/anatomia & histologia , Volume de Ventilação Pulmonar , Ventiladores Mecânicos
17.
Respir Care ; 63(7): 865-872, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29895701

RESUMO

BACKGROUND: Sensitive flow or pressure triggers are usually applied to improve ventilator response time. Conversely, too sensitive triggers can incur risk of auto-triggering, a type of asynchrony in which a breath is triggered without inspiratory muscle activity. A frequent cause of auto-triggering is cardiogenic oscillations, characterized by cyclical variations in pressure and flow waveforms caused by cardiac contractions. Our goal was to test trigger performance and capacity to abolish auto-triggering in 5 different ICU ventilators using different simulated levels of cardiogenic oscillations. METHODS: A mechanical breathing simulator was used to test 5 different ICU ventilators' trigger response time and capacity to minimize auto-triggering in conditions with 0, 0.25, 0.5, and 1 cm H2O cardiogenic oscillation. Each ventilator was evaluated until an ideal trigger was found (the most sensitive that abolished auto-triggering). When the least sensitive flow trigger was unable to avoid auto-triggering, a pressure trigger was used. We compared time delay, airway pressure drop until triggering, and work of breathing before each trigger, all at the ideal trigger level for each cardiogenic oscillation amplitude. We also assessed the proportion of auto-triggered breaths in the whole range of trigger levels tested. RESULTS: Larger cardiogenic oscillations were associated with more frequent auto-triggering. To avoid auto-triggering, less sensitive triggers were required (+2.51 L/min per 1 cm H2O increase in cardiogenic oscillation; 95% CI 2.26-2.76, P < .001). Time delay increased with larger cardiogenic oscillations, because less sensitive trigger levels were required to abolish auto-triggering (4.79-ms increase per 1 L/min increment on flow trigger). CONCLUSIONS: More sensitive triggers led to faster ventilator response, but also to more frequent auto-triggering. To avoid auto-triggering, less sensitive triggers were required, with consequent slower trigger response. To compare trigger performance in a scenario that more closely represents clinical practice, evaluation of the tradeoff between time delay and frequency of auto-triggering should be considered.


Assuntos
Falha de Equipamento , Hemodinâmica , Respiração com Pressão Positiva/instrumentação , Mecânica Respiratória , Ventiladores Mecânicos , Simulação por Computador , Coração/fisiopatologia , Humanos , Oscilometria , Tempo de Reação , Trabalho Respiratório/fisiologia
18.
Respir Care ; 63(7): 849-858, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29765004

RESUMO

BACKGROUND: Faster inspiratory pressurization can improve patient-ventilator synchrony and reduce the patient's work of breathing during pressure controlled continuous mandatory (PC-CMV) ventilation. The characteristics of the pressurization ramp settings are not standardized across ventilators from different manufacturers. We performed a bench test of 5 models of ICU ventilators to examine the effects of pressurization ramp settings on the actual pressurization. METHODS: A twin-bellows lung model was used, in which one bellow simulates inspiratory muscle activity and the other simulates an adult normal lung model. We made the inspiratory effort by changing the tidal volume of the inspiratory muscle bellow. The effect of pressurization ramp settings on the performance of each ventilator was examined at 3 inspiratory effort levels (ie, none, ordinary, and strong). The pressurization ramp was set at 4 or 5 evenly divided steps from the minimum to maximum for each ventilator. The following parameters were measured: tidal volume, mean airway pressure, maximal inspiratory flow, time to maximal flow, and pressure-time products at 0.3 s (PTP0.3) and 0.5 s (PTP0.5) from the beginning of inspiration. PTP0.3 and PTP0.5 indicated levels of inspiratory pressurization. RESULTS: A proportional increase in PTP0.3 and PTP0.5 was observed with an increase in the pressurization ramp settings of the recent models of ventilators. PTP0.3 and PTP0.5 at ordinary and strong effort levels were similar in the recent models of ventilators. The actual adjustable ranges of PTP0.3 and PTP0.5 associated with change in the pressurization ramp settings differed between the 5 ventilators. CONCLUSIONS: The adjustable ranges of the pressurization were largely different among the different types of ventilators. The actual absolute inspiratory pressurization during PC-CMV varied between the different ventilators even at similar pressurization ramp settings. Users should be mindful of the differences in the pressurization ramp settings.


Assuntos
Ventilação com Pressão Positiva Intermitente/instrumentação , Ventiladores Mecânicos , Adulto , Humanos , Inalação/fisiologia , Unidades de Terapia Intensiva , Pulmão/fisiopatologia , Modelos Anatômicos , Pressão , Trabalho Respiratório/fisiologia
19.
J Appl Physiol (1985) ; 125(1): 190-197, 2018 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-29672228

RESUMO

It is unknown whether the greater total work of breathing (WOB) with aging is due to greater elastic and/or resistive WOB. We hypothesized that older compared with younger adults would exhibit a greater total WOB at matched ventilations (V̇e) during graded exercise, secondary to greater inspiratory resistive and elastic as well as expiratory resistive WOB. Older (OA: 60 ± 8 yr; n = 9) and younger (YA: 38 ± 7 yr; n = 9) adults performed an incremental cycling test to volitional fatigue. Esophageal pressure, inspiratory (IRV) and expiratory reserve volumes (ERV), expiratory flow limitation (EFL), and ventilatory variables were measured at matched V̇e (i.e., 25, 50, and 75 l/min) during exercise. The inspiratory resistive and elastic as well as expiratory resistive WOB were quantified using the Otis method. At V̇e of 75 l/min, older adults had greater %EFL and larger tidal volumes to inspiratory capacity but smaller relative IRV ( P ≤ 0.03) than younger adults. Older compared with younger adults had greater total WOB at V̇E of 50 and 75 l/min (OA: 90 ± 43 vs. YA: 49 ± 21 J/min; P < 0.04 for both). At V̇e of 75 l/min, older adults had greater inspiratory elastic and resistive WOB (OA: 44 ± 27 vs. YA: 24 ± 22 and OA: 23 ± 15 vs. YA: 11 ± 3 J/min, respectively, P < 0.03 for both) and expiratory resistive WOB (OA: 23 ± 19 vs. YA: 14 ± 9 J/min, P = 0.02) than younger adults. These data demonstrate that aging-induced pulmonary alterations result in greater inspiratory elastic and resistive as well as expiratory resistive WOB, which may have implications for the integrated response during exercise. NEW & NOTEWORTHY Aging-induced changes to the pulmonary system result in increased work of breathing (WOB) during exercise. However, it is not known whether this higher WOB with aging is due to differences in elastic and/or resistive WOB. Herein, we demonstrate that older adults exhibited greater inspiratory elastic and resistive as well as expiratory resistive WOB during exercise.


Assuntos
Exercício Físico/fisiologia , Expiração/fisiologia , Trabalho Respiratório/fisiologia , Adulto , Estudos Transversais , Feminino , Humanos , Pulmão/fisiologia , Medidas de Volume Pulmonar/métodos , Masculino , Pessoa de Meia-Idade , Músculos Respiratórios/fisiologia , Volume de Ventilação Pulmonar/fisiologia
20.
Heart Surg Forum ; 21(2): E070-E071, 2018 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-29658860

RESUMO

Because of the risks associated with extended mechanical ventilation, it is desirable to extubate patients as early as possible. However, weaning patients from mechanical ventilation too early has risks associated with it as well. Thus, it is important to note that in the two cases presented here, pressure-supported breaths were falsely triggered by a patient's a Syncardia® total artificial heart (TAH), influencing decisions about weaning the patient from mechanical ventilation.


Assuntos
Insuficiência Cardíaca/cirurgia , Coração Artificial , Ventilação não Invasiva/métodos , Respiração com Pressão Positiva/métodos , Insuficiência Respiratória/terapia , Trabalho Respiratório/fisiologia , Adulto , Feminino , Insuficiência Cardíaca/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Insuficiência Respiratória/etiologia , Insuficiência Respiratória/fisiopatologia
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