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1.
Undersea Hyperb Med ; 48(2): 107-117, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33975401

RESUMO

Introduction: Pre-dive altitude exposure may increase respiratory fatigue and subsequently augment exercise ventilation at depth. This study examined pre-dive altitude exposure and the efficacy of resistance respiratory muscle training (RMT) on respiratory fatigue while diving at altitude. Methods: Ten men (26±5 years; VO2peak: 39.8±3.3 mL• kg-1•min-1) performed three dives; one control (ground level) and two simulated altitude dives (3,658 m) to 17 msw, relative to ground level, before and after four weeks of resistance RMT. Subjects performed pulmonary function testing (e.g., inspiratory [PI] and expiratory [PE] pressure testing) pre- and post-RMT and during dive visits. During each dive, subjects exercised for 18 minutes at 55% VO2peak, and ventilation (VE), breathing frequency (ƒb,), tidal volume (VT) and rating of perceived exertion (RPE) were measured. Results: Pre-dive altitude exposure reduced PI before diving (p=0.03), but had no effect on exercise VE, ƒb, or VT at depth. At the end of the dive in the pre-RMT condition, RPE was lower (p=0.01) compared to control. RMT increased PI and PE (p<0.01). PE was reduced from baseline after diving at altitude (p<0.03) and this was abated after RMT. RMT did not improve VE or VT at depth, but decreased ƒb (p=0.01) and RPE (p=0.048) during the final minutes of exercise. Conclusion: Acute altitude exposure pre- and post-dive induces decrements in PI and PE before and after diving, but does not seem to influence ventilation at depth. RMT reduced ƒb and RPE during exercise at depth, and may be useful to reduce work of breathing and respiratory fatigue during dives at altitude.


Assuntos
Altitude , Exercícios Respiratórios/métodos , Mergulho/fisiologia , Exercício Físico/fisiologia , Fadiga Muscular/fisiologia , Trabalho Respiratório/fisiologia , Adulto , Análise de Variância , Exposição Ambiental , Expiração/fisiologia , Frequência Cardíaca , Humanos , Inalação/fisiologia , Masculino , Oxigênio/sangue , Consumo de Oxigênio/fisiologia , Esforço Físico/fisiologia , Treinamento de Força/métodos , Testes de Função Respiratória , Volume de Ventilação Pulmonar/fisiologia , Fatores de Tempo
2.
Crit Care ; 24(1): 494, 2020 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778136

RESUMO

Deterioration of lung function during the first week of COVID-19 has been observed when patients remain with insufficient respiratory support. Patient self-inflicted lung injury (P-SILI) is theorized as the responsible, but there is not robust experimental and clinical data to support it. Given the limited understanding of P-SILI, we describe the physiological basis of P-SILI and we show experimental data to comprehend the role of regional strain and heterogeneity in lung injury due to increased work of breathing.In addition, we discuss the current approach to respiratory support for COVID-19 under this point of view.


Assuntos
Infecções por Coronavirus/fisiopatologia , Progressão da Doença , Lesão Pulmonar/fisiopatologia , Pneumonia Viral/fisiopatologia , Trabalho Respiratório/fisiologia , Infecções por Coronavirus/terapia , Cuidados Críticos , Humanos , Lesão Pulmonar/etiologia , Pandemias , Pneumonia Viral/terapia , Ensaios Clínicos Controlados Aleatórios como Assunto , Respiração Artificial
4.
Arch Dis Child Fetal Neonatal Ed ; 105(6): 669-671, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32669360

RESUMO

BACKGROUND: The COVID-19 pandemic has raised concern for healthcare workers getting infected via aerosol from non-invasive respiratory support of infants. Attaching filters that remove viral particles in air from the expiratory limb of continuous positive airway pressure (CPAP) devices should theoretically decrease the risk. However, adding filters to the expiratory limb could add to expiratory resistance and thereby increase the imposed work of breathing (WOB). OBJECTIVE: To evaluate the effects on imposed WOB when attaching filters to the expiratory limb of CPAP devices. METHODS: Two filters were tested on three CPAP systems at two levels of CPAP in a mechanical lung model. Main outcome was imposed WOB. RESULTS: There was a minor increase in imposed WOB when attaching the filters. The differences between the two filters were small. CONCLUSION: To minimise contaminated aerosol generation during CPAP treatment, filters can be attached to expiratory tubing with only a minimal increase in imposed WOB in a non-humidified environment. Care has to be taken to avoid filter obstruction and replace filters as recommended.


Assuntos
Pressão Positiva Contínua nas Vias Aéreas/instrumentação , Infecções por Coronavirus/prevenção & controle , Filtração/instrumentação , Controle de Infecções/instrumentação , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Betacoronavirus , Expiração/fisiologia , Humanos , Recém-Nascido , Unidades de Terapia Intensiva Neonatal , Modelos Anatômicos , Trabalho Respiratório/fisiologia
5.
Br J Anaesth ; 125(1): e148-e157, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32386831

RESUMO

BACKGROUND: Bedside measures of patient effort are essential to properly titrate the level of pressure support ventilation. We investigated whether the tidal swing in oesophageal (ΔPes) and transdiaphragmatic pressure (ΔPdi), and ultrasonographic changes in diaphragm (TFdi) and parasternal intercostal (TFic) thickening are reliable estimates of respiratory effort. The effect of diaphragm dysfunction was also considered. METHODS: Twenty-one critically ill patients were enrolled: age 73 (14) yr, BMI 27 (7) kg m-2, and Pao2/Fio2 33.3 (9.2) kPa. A three-level pressure support trial was performed: baseline, 25% (PS-medium), and 50% reduction (PS-low). We recorded the oesophageal and transdiaphragmatic pressure-time products (PTPs), work of breathing (WOB), and diaphragm and intercostal ultrasonography. Diaphragm dysfunction was defined by the Gilbert index. RESULTS: Pressure support was 9.0 (1.6) cm H2O at baseline, 6.7 (1.3) (PS-medium), and 4.4 (1.0) (PS-low). ΔPes was significantly associated with the oesophageal PTP (R2=0.868; P<0.001) and the WOB (R2=0.683; P<0.001). ΔPdi was significantly associated with the transdiaphragmatic PTP (R2=0.820; P<0.001). TFdi was only weakly correlated with the oesophageal PTP (R2=0.326; P<0.001), and the correlation improved after excluding patients with diaphragm dysfunction (R2=0.887; P<0.001). TFdi was higher and TFic lower in patients without diaphragm dysfunction: 33.6 (18.2)% vs 13.2 (9.2)% and 2.1 (1.7)% vs 12.7 (9.1)%; P<0.0001. CONCLUSIONS: ΔPes and ΔPdi are adequate estimates of inspiratory effort. Diaphragm ultrasonography is a reliable indicator of inspiratory effort in the absence of diaphragm dysfunction. Additional measurement of parasternal intercostal thickening may discriminate a low inspiratory effort or a high effort in the presence of a dysfunctional diaphragm.


Assuntos
Esôfago/fisiologia , Respiração com Pressão Positiva/métodos , Músculos Respiratórios/fisiologia , Ultrassonografia/métodos , Trabalho Respiratório/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Cuidados Críticos/métodos , Estado Terminal , Diafragma/fisiologia , Esôfago/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Músculos Respiratórios/diagnóstico por imagem
7.
Sci Rep ; 10(1): 3755, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-32111935

RESUMO

This study's objective was the generation of a standardized geometry of the healthy nasal cavity. An average geometry of the healthy nasal cavity was generated using a statistical shape model based on 25 symptom-free subjects. Airflow within the average geometry and these geometries was calculated using fluid simulations. Integral measures of the nasal resistance, wall shear stresses (WSS) and velocities were calculated as well as cross-sectional areas (CSA). Furthermore, individual WSS and static pressure distributions were mapped onto the average geometry. The average geometry featured an overall more regular shape that resulted in less resistance, reduced WSS and velocities compared to the median of the 25 geometries. Spatial distributions of WSS and pressure of the average geometry agreed well compared to the average distributions of all individual geometries. The minimal CSA of the average geometry was larger than the median of all individual geometries (83.4 vs. 74.7 mm²). The airflow observed within the average geometry of the healthy nasal cavity did not equal the average airflow of the individual geometries. While differences observed for integral measures were notable, the calculated values for the average geometry lay within the distributions of the individual parameters. Spatially resolved parameters differed less prominently.


Assuntos
Algoritmos , Modelos Biológicos , Cavidade Nasal , Tomografia Computadorizada por Raios X , Trabalho Respiratório/fisiologia , Adulto , Feminino , Humanos , Masculino , Cavidade Nasal/diagnóstico por imagem , Cavidade Nasal/fisiologia , Estudos Retrospectivos
8.
Am J Respir Crit Care Med ; 201(9): 1086-1098, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32097569

RESUMO

Rationale: Monitoring and controlling respiratory drive and effort may help to minimize lung and diaphragm injury. Airway occlusion pressure (P0.1) is a noninvasive measure of respiratory drive.Objectives: To determine 1) the validity of "ventilator" P0.1 (P0.1vent) displayed on the screen as a measure of drive, 2) the ability of P0.1 to detect potentially injurious levels of effort, and 3) how P0.1vent displayed by different ventilators compares to a "reference" P0.1 (P0.1ref) measured from airway pressure recording during an occlusion.Methods: Analysis of three studies in patients, one in healthy subjects, under assisted ventilation, and a bench study with six ventilators. P0.1vent was validated against measures of drive (electrical activity of the diaphragm and muscular pressure over time) and P0.1ref. Performance of P0.1ref and P0.1vent to detect predefined potentially injurious effort was tested using derivation and validation datasets using esophageal pressure-time product as the reference standard.Measurements and Main Results: P0.1vent correlated well with measures of drive and with the esophageal pressure-time product (within-subjects R2 = 0.8). P0.1ref >3.5 cm H2O was 80% sensitive and 77% specific for detecting high effort (≥200 cm H2O ⋅ s ⋅ min-1); P0.1ref ≤1.0 cm H2O was 100% sensitive and 92% specific for low effort (≤50 cm H2O ⋅ s ⋅ min-1). The area under the receiver operating characteristics curve for P0.1vent to detect potentially high and low effort were 0.81 and 0.92, respectively. Bench experiments showed a low mean bias for P0.1vent compared with P0.1ref for most ventilators but precision varied; in patients, precision was lower. Ventilators estimating P0.1vent without occlusions could underestimate P0.1ref.Conclusions: P0.1 is a reliable bedside tool to assess respiratory drive and detect potentially injurious inspiratory effort.


Assuntos
Pressão do Ar , Monitoramento Biológico/normas , Inalação/fisiologia , Respiração com Pressão Positiva/normas , Guias de Prática Clínica como Assunto , Respiração Artificial/normas , Trabalho Respiratório/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes
9.
Arch Dis Child Fetal Neonatal Ed ; 105(5): 550-554, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32047029

RESUMO

BACKGROUND: The original bubble continuous positive airway pressure (bCPAP) design has wide-bore tubing and a low-resistance interface. This creates a stable airway pressure that is reflected by the submersion depth of the expiratory tubing. Several systems with alterations to the original bCPAP design are now available. Most of these are aimed for use in low-income and middle-income countries and have not been compared with the original design. OBJECTIVE: We identified three major alterations to the original bCPAP design: (1) resistance of nasal interface, (2) volume of dead space and (3) diameter of expiratory tubing. Our aim was to study the effect of these alterations on CPAP delivery and work of breathing in a mechanical lung model. Dead space should always be avoided and was not further tested. METHODS: The effect of nasal interface resistance and expiratory tubing diameter was evaluated with simulated breathing in a mechanical lung model without interface leakage. The main outcome was delivered CPAP and imposed work of breathing. RESULTS: High-resistance interfaces and narrow expiratory tubing increased the work of breathing. Additionally, narrow expiratory tubing resulted in higher CPAP levels than indicated by the submersion depth. CONCLUSION: Our study shows the significant effect on CPAP delivery and imposed work of breathing when using high-resistance interfaces and narrow expiratory tubing in bCPAP systems. New systems should include low-resistance interfaces and wide-bore tubing and be compared with the original bCPAP. Referring to all systems that bubble as bCPAP is misleading and potentially hazardous.


Assuntos
Pressão Positiva Contínua nas Vias Aéreas/instrumentação , Pressão Positiva Contínua nas Vias Aéreas/métodos , Trabalho Respiratório/fisiologia , Resistência das Vias Respiratórias/fisiologia , Humanos , Recém-Nascido , Modelos Biológicos
10.
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
11.
Eur J Appl Physiol ; 120(2): 381-390, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31813046

RESUMO

PURPOSE: To quantify the mechanical work of breathing (Wb) during an indoor rowing test in men and women. Additionally, to compare sex-based differences in the Wb and its components through a rowing test. METHODS: Fifteen collegiate rowers were recruited (8 women/7 men) and performed a 2000 m rowing test on a rowing ergometer. Esophageal pressure was measured during exercise via balloon catheterization, after which pressure-volume curves were used to calculate total, inspiratory resistive and elastic, and total expiratory Wb. RESULTS: Men had significantly higher values of instantaneous and cumulative total Wb at and beyond 37.5% (430.4 ± 42.5 vs. 282.1 ± 45.1 J min-1, P < 0.05) and 62.5% (1946.8 ± 150.9 vs. 1360.1 ± 197.2 J, P < 0.05) total exercise time, respectively. However, when compared at the same minute ventilation, women had higher values of total (at and above ~ 140 L min-1), inspiratory resistive (at and above ~ 120 L min-1), and inspiratory elastic (at and above ~ 135 L min-1) Wb, whereas men presented higher total expiratory Wb compared to women at any ventilation. CONCLUSION: Although female rowers present higher relative values of inspiratory resistive and elastic Wb, their male counterparts develop greater ventilatory efforts during a 2000 m rowing test, resulting in a larger total mechanical Wb. We interpret these findings to mean that the Wb reflects both anatomical (i.e., airways and lung sizes) and respiratory (i.e., minute ventilation) sex differences during rowing.


Assuntos
Exercício Físico , Esportes Aquáticos , Trabalho Respiratório/fisiologia , Adolescente , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
12.
Exerc Sport Sci Rev ; 48(1): 11-19, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31453845

RESUMO

We propose that abnormalities of the pulmonary system contribute significantly to the exertional dyspnea and exercise intolerance observed in patients with chronic heart failure. Interventions designed to address the deleterious pulmonary manifestations of heart failure may, therefore, yield promising improvements in exercise tolerance in this population.


Assuntos
Tolerância ao Exercício/fisiologia , Insuficiência Cardíaca/fisiopatologia , Hemodinâmica/fisiologia , Pulmão/fisiopatologia , Pressão Sanguínea/fisiologia , Brônquios/irrigação sanguínea , Doença Crônica , Dispneia/fisiopatologia , Humanos , Hipertensão Pulmonar/fisiopatologia , Pulmão/irrigação sanguínea , Músculo Esquelético/fisiopatologia , Consumo de Oxigênio/fisiologia , Prognóstico , Capacidade de Difusão Pulmonar , Troca Gasosa Pulmonar , Relação Ventilação-Perfusão , Trabalho Respiratório/fisiologia
13.
Crit Care ; 23(1): 346, 2019 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-31694692

RESUMO

BACKGROUND: Excessive respiratory muscle effort during mechanical ventilation may cause patient self-inflicted lung injury and load-induced diaphragm myotrauma, but there are no non-invasive methods to reliably detect elevated transpulmonary driving pressure and elevated respiratory muscle effort during assisted ventilation. We hypothesized that the swing in airway pressure generated by respiratory muscle effort under assisted ventilation when the airway is briefly occluded (ΔPocc) could be used as a highly feasible non-invasive technique to screen for these conditions. METHODS: Respiratory muscle pressure (Pmus), dynamic transpulmonary driving pressure (ΔPL,dyn, the difference between peak and end-expiratory transpulmonary pressure), and ΔPocc were measured daily in mechanically ventilated patients in two ICUs in Toronto, Canada. A conversion factor to predict ΔPL,dyn and Pmus from ΔPocc was derived and validated using cross-validation. External validity was assessed in an independent cohort (Nanjing, China). RESULTS: Fifty-two daily recordings were collected in 16 patients. In this sample, Pmus and ΔPL were frequently excessively high: Pmus exceeded 10 cm H2O on 84% of study days and ΔPL,dyn exceeded 15 cm H2O on 53% of study days. ΔPocc measurements accurately detected Pmus > 10 cm H2O (AUROC 0.92, 95% CI 0.83-0.97) and ΔPL,dyn > 15 cm H2O (AUROC 0.93, 95% CI 0.86-0.99). In the external validation cohort (n = 12), estimating Pmus and ΔPL,dyn from ΔPocc measurements detected excessively high Pmus and ΔPL,dyn with similar accuracy (AUROC ≥ 0.94). CONCLUSIONS: Measuring ΔPocc enables accurate non-invasive detection of elevated respiratory muscle pressure and transpulmonary driving pressure. Excessive respiratory effort and transpulmonary driving pressure may be frequent in spontaneously breathing ventilated patients.


Assuntos
Ventilação não Invasiva/métodos , Pressão , Pesos e Medidas/instrumentação , Trabalho Respiratório/fisiologia , Lesão Pulmonar Aguda/fisiopatologia , Lesão Pulmonar Aguda/prevenção & controle , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Monitorização Fisiológica/métodos , Respiração Artificial/métodos , Músculos Respiratórios/lesões , Músculos Respiratórios/fisiopatologia , Pesos e Medidas/normas
14.
Exp Physiol ; 104(11): 1737-1745, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31408911

RESUMO

NEW FINDINGS: What is the central question of this study? What is the effect of age and sex on the resistive and viscoelastic components of work of breathing (Wb ) during exercise? What is the main finding and its importance? The resistive and viscoelastic components of Wb were higher in older adults, regardless of sex. The resistive, but not viscoelastic, component of Wb was higher in females than in males, regardless of age. These findings contribute to improving our understanding of the effects of ageing and sex on the mechanical ventilatory response to exercise. ABSTRACT: Healthy ageing and biological sex each affect the work of breathing (Wb ) for a given minute ventilation ( V ̇ E ). Age-related structural changes to the respiratory system lead to an increase in both the resistive and viscoelastic components of Wb ; however, it is unclear whether healthy ageing differentially alters the mechanics of breathing in males and females. We analysed data from 22 older (60-80 years, n = 12 females) and 22 younger (20-30 years, n = 11 females) males and females that underwent an incremental cycle exercise test to exhaustion. V ̇ E and Wb were assessed at rest and throughout exercise. Wb - V ̇ E data for each participant were fitted to a non-linear equation (i.e. Wb  = a V ̇ E 3 + b V ̇ E 2 ) that partitions Wb into resistive (i.e. a V ̇ E 3 ) and viscoelastic (i.e. b V ̇ E 2 ) components. We then modelled the effects of healthy ageing and biological sex on each component of Wb . Overall, the model fit was excellent (r2 : 0.99 ± 0.01). There was a significant main effect of age and sex on the resistive component of Wb (both P < 0.05), and a significant main effect of age (P < 0.001), but not sex (P = 0.309), on the viscoelastic component of Wb . No significant interactions between age and sex on a V ̇ E 3 or b V ̇ E 2 were noted (both P > 0.05). Our findings indicate that during exercise: (i) the higher total Wb in females relative to males is due to a higher resistive, but not viscoelastic, component of Wb , and (ii) regardless of sex, the higher Wb in older adults relative to younger adults is due to higher resistive and viscoelastic components of Wb .


Assuntos
Exercício Físico/fisiologia , Mecânica Respiratória/fisiologia , Trabalho Respiratório/fisiologia , Idoso , Idoso de 80 Anos ou mais , Teste de Esforço/métodos , Feminino , Humanos , Pulmão/fisiologia , Masculino , Pessoa de Meia-Idade , Ventilação Pulmonar/fisiologia , Respiração
15.
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
16.
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
17.
Intensive Care Med ; 45(8): 1061-1071, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31236639

RESUMO

INTRODUCTION: This narrative review summarizes current knowledge on the physiology and pathophysiology of expiratory muscle function in ICU patients, as shared by academic professionals from multidisciplinary, multinational backgrounds, who include clinicians, clinical physiologists and basic physiologists. RESULTS: The expiratory muscles, which include the abdominal wall muscles and some of the rib cage muscles, are an important component of the respiratory muscle pump and are recruited in the presence of high respiratory load or low inspiratory muscle capacity. Recruitment of the expiratory muscles may have beneficial effects, including reduction in end-expiratory lung volume, reduction in transpulmonary pressure and increased inspiratory muscle capacity. However, severe weakness of the expiratory muscles may develop in ICU patients and is associated with worse outcomes, including difficult ventilator weaning and impaired airway clearance. Several techniques are available to assess expiratory muscle function in the critically ill patient, including gastric pressure and ultrasound. CONCLUSION: The expiratory muscles are the "neglected component" of the respiratory muscle pump. Expiratory muscles are frequently recruited in critically ill ventilated patients, but a fundamental understanding of expiratory muscle function is still lacking in these patients.


Assuntos
Expiração/fisiologia , Doenças Musculares/fisiopatologia , Músculos Respiratórios/fisiopatologia , Estado Terminal , Humanos , Músculos Respiratórios/anormalidades , Músculos Respiratórios/efeitos dos fármacos , Trabalho Respiratório/fisiologia
18.
Am J Phys Med Rehabil ; 98(9): 835-838, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-30973517

RESUMO

Mechanical insufflation-exsufflation, or "cough assist," is a commonly used method of clearing tracheal and pulmonary secretions in patients with respiratory insufficiency secondary to spinal cord injury. This report presents a novel technique termed the pharyngeal clearance maneuver, which uses a modified application of the mechanical insufflation-exsufflation device to mobilize "secretion burden" at the portion of the trachea above the tracheostomy cuff during cuff deflation. Utilization of this strategy may reduce the risk of aspiration, infection, and respiratory compromise for patients with high cervical spinal cord injury in the acute rehabilitation setting. It is of particular benefit for those whose cuffs are being deflated for the first time and who may have large secretion volumes above the cuff. It can be further used as needed before speaking trials and swallow therapies. We anticipate that the pharyngeal clearance maneuver may be used in other populations with impaired cough and need for invasive ventilator support because of ventilator pump failure (eg, spinal muscular atrophy, congenital myopathies, obesity hypoventilation, amyotrophic lateral sclerosis, muscular dystrophy, and acute inflammatory demyelinating polyneuropathy).


Assuntos
Tosse , Insuflação/métodos , Quadriplegia/complicações , Insuficiência Respiratória/terapia , Sucção/métodos , Traqueostomia/métodos , Humanos , Quadriplegia/terapia , Sucção/instrumentação , Traqueostomia/instrumentação , Trabalho Respiratório/fisiologia
20.
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
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