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2.
Arch Endocrinol Metab ; 63(1): 40-46, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30864630

RESUMO

OBJECTIVE: To evaluate the influence of obesity on pulmonary function and exercise tolerance in women with obstructive sleep apnea (OSA). SUBJECTS AND METHODS: A descriptive analytic cross- sectional study was carried out. Thirty-nine (39) sedentary climacteric women, aged 45 to 60 years, were evaluated and submitted to polysomnography. The participants were divided into 4 groups: a) 'eutrophic non-OSA' (n = 13); b) 'eutrophic OSA' (n = 5); c) 'obese non-OSA' (n = 6); d) 'obese OSA' (n = 15). All subjects underwent clinical and anthropometric evaluation, followed by pulmonary function tests and 6-minute walk test (6MWT). RESULTS: There was a significant difference in the predicted percentage values of FEV1/FVC when comparing 'eutrophic OSA' and 'obese OSA' (97.6% ± 6.1% vs. 105.7% ± 5.7%, respectively; p = 0.025). The other spirometric variables did not show any differences between the studied groups. There was no significant difference in the maximum distance walked when the 'eutrophic non-OSA', 'eutrophic OSA', 'obese non-OSA' and 'obese OSA' groups were compared. CONCLUSION: Considering the results of this study, OSA itself did not influence pulmonary function or functional capacity parameters compared to eutrophic women. However, not only isolated obesity but also obesity associated with OSA can negatively impact sleep quality and lung function.


Assuntos
Teste de Esforço/métodos , Tolerância ao Exercício/fisiologia , Capacidade Residual Funcional/fisiologia , Obesidade/fisiopatologia , Apneia Obstrutiva do Sono/fisiopatologia , Estudos Transversais , Feminino , Humanos , Pessoa de Meia-Idade , Polissonografia , Comportamento Sedentário , Espirometria
3.
Int J Chron Obstruct Pulmon Dis ; 13: 2551-2555, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30197511

RESUMO

Introduction: For interpretation of body plethysmographic static hyperinflation, reference values are of crucial importance. Earliest reference values have been published by the European Coal and Steel Community (ECSC) and are based on sex, body height and age as predictors. As obesity can lead to a reduction of functional residual capacity (FRC) in lung-healthy subjects, more recent approaches included body weight or body surface area. This raises the question whether these models are appropriate in patients with COPD-induced hyperinflation. Method: Several FRC prediction models and their relation to body weight were analyzed in 1513 patients with stable COPD (mean [SD] age: 64.5 [8.2] years; GOLD grades 1-4: 219/722/484/88), a subset of the multicenter COPD and Systemic Consequences - Comorbidities Network cohort. Results: Absolute values of FRC were inversely related to body mass index (p<0.001). Applying the ECSC equations to calculate predicted values, this pattern was maintained (p<0.001). By contrast, an inverted, ie, positive, relation occurred when using equations that include body weight or surface area (p<0.001). The present analysis confirmed the inverse relation of body mass and FRC in COPD, resulting from a restrictive ventilatory pattern by diaphragm elevation and decreased chest wall compliance in obesity. The weight influence in the prediction models, as obtained from lung-healthy controls, appears to lead to an overcorrection and consequently to an inappropriate overestimation of hyperinflation as indicated by FRC %predicted in COPD. Conclusion: It is concluded that models not including body weight as predictor, like the classical ECSC equations, could be superior in the interpretation of FRC in COPD.


Assuntos
Índice de Massa Corporal , Superfície Corporal , Capacidade Residual Funcional/fisiologia , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Idoso , Peso Corporal , Feminino , Volume Expiratório Forçado , Humanos , Pulmão/fisiopatologia , Medidas de Volume Pulmonar , Masculino , Pessoa de Meia-Idade , Pletismografia Total , Valores de Referência , Capacidade Vital
4.
Int J Cardiol ; 271: 54-59, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29861103

RESUMO

BACKGROUND: Changes in circulatory physiology are common in Fontan patients due to suboptimal cardiac output, which may reduce the peripheral blood flow and impair the skeletal muscle. The objective of this study was to investigate the forearm blood flow (FBF), cross-sectional area (CSA) of the thigh and functional capacity in asymptomatic clinically stable patients undergoing Fontan surgery. METHODS: Thirty Fontan patients and 27 healthy subjects underwent venous occlusion plethysmography, magnetic resonance imaging of the thigh musculature and maximal cardiopulmonary exercise testing. Muscle sympathetic nerve activity (MSNA), norepinephrine measures, cardiovascular magnetic resonance, handgrip strength and 6-minute walk test were also performed. RESULTS: Fontan patients have blunted FBF (1.59 ±â€¯0.33 vs 2.17 ±â€¯0.52 mL/min/100 mL p < 0.001) and forearm vascular conductance (FVC) (1.69 ±â€¯0.04 vs 2.34 ±â€¯0.62 units p < 0.001), reduced CSA of the thigh (81.2 ±â€¯18.6 vs 116.3 ±â€¯26.4 cm2p < 0.001), lower peak VO2 (29.3 ±â€¯6 vs 41.5 ±â€¯9 mL/kg/min p < 0.001), walked distance (607 ±â€¯60 vs 701 ±â€¯58 m p < 0.001) and handgrip strength (21 ±â€¯9 vs 30 ±â€¯8 kgf p < 0.001). The MSNA (30 ±â€¯4 vs 22 ±â€¯3 bursts/min p < 0.001) and norepinephrine concentration [265 (236-344) vs 222 (147-262) pg/mL p = 0.006] were also higher in Fontan patients. Multivariate linear regression showed FVC (ß = 0.653; CI = 0.102-1.205; p = 0.022) and stroke volume (ß = 0.018; CI = 0.007-0.029; p = 0.002) to be independently associated with reduced CSA of the thigh adjusted for body mass index. The CSA of the thigh adjusted for body mass index (ß = 5.283; CI = 2.254-8.312; p = 0.001) was independently associated with reduced peak VO2. CONCLUSION: Patients with Fontan operation have underdeveloped skeletal muscle with reduced strength that is associated with suboptimal peripheral blood supply and diminished exercise capacity.


Assuntos
Tolerância ao Exercício/fisiologia , Técnica de Fontan/tendências , Força da Mão/fisiologia , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Adolescente , Adulto , Estudos Transversais , Teste de Esforço/métodos , Teste de Esforço/tendências , Feminino , Seguimentos , Técnica de Fontan/efeitos adversos , Antebraço/irrigação sanguínea , Antebraço/diagnóstico por imagem , Antebraço/fisiologia , Capacidade Residual Funcional/fisiologia , Humanos , Masculino , Músculo Esquelético/irrigação sanguínea , Adulto Jovem
5.
J Cyst Fibros ; 17(4): 511-517, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29483003

RESUMO

BACKGROUND: Different interfaces (mouthpiece/nose clip vs. facemask) are used during multiple breath washout (MBW) tests in young children. METHODS: We investigated the effect of interface choice and breathing modalities on MBW outcomes in healthy adults and preschool children. RESULTS: In adults (n = 26) facemask breathing significantly increased LCI, compared to mouthpiece use (mean difference (95% CI) 0.4 (0.2; 0.6)), with results generalizable across sites and different equipment. Exclusively nasal breathing within the facemask increased LCI, as compared to oral breathing. In preschoolers (2-6 years, n = 46), no significant inter-test difference was observed across interfaces for LCI or FRC. Feasibility and breathing stability were significantly greater with facemask (incorporating dead space volume minimization), vs. mouthpiece. This was more pronounced in subjects <4 years of age. CONCLUSION: Both nasal vs. oral breathing and mouthpiece vs. facemask affect LCI measurements in adults. This effect was minimal in preschool children, where switching between interfaces is most likely to occur.


Assuntos
Fibrose Cística/diagnóstico , Desenho de Equipamento , Face/anatomia & histologia , Máscaras , Testes de Função Respiratória , Adulto , Anatomia Regional , Testes Respiratórios/instrumentação , Testes Respiratórios/métodos , Criança , Pré-Escolar , Estudos de Viabilidade , Feminino , Capacidade Residual Funcional/fisiologia , Humanos , Masculino , Boca/anatomia & histologia , Nariz/anatomia & histologia , Respiração , Testes de Função Respiratória/instrumentação , Testes de Função Respiratória/métodos
6.
J Appl Physiol (1985) ; 124(5): 1155-1163, 2018 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-29357506

RESUMO

The multibreath nitrogen washout (MBNW) test, as it is currently practiced, provides parameters of potential physiological significance that are derived from the relationship between the volume-normalized Phase III slope of the exhaled nitrogen fraction ([Formula: see text]) vs. the cumulative change in lung volume (V). Reliable evaluation of these parameters requires, however, that the subject breathe deeply and evenly, so that Phase III can be clearly identified in every breath. This places a burden on the test subject that may prove troublesome for young children and those with lung disease. Furthermore, the determination of the slope of Phase III requires that a decision be made as to when Phase II ends and Phase III begins. In an attempt to get around these methodological limitations, we develop here an alternative method of analysis based on a multicompartment model of the lung that accounts for the entire exhaled nitrogen profile, including Phases I, II, and III. Fitting this model to [Formula: see text] and V measured during a MBNW provides an estimate of the coefficient of variation of specific ventilation, as well as functional residual capacity, dead space volume, and a parameter that reflects structural asymmetry at the acinar level in the lung. In the present study, we demonstrate the potential utility of this modeling approach to the analysis of MBNW data. NEW & NOTEWORTHY The multibreath nitrogen washout test potentially provides important physiological information about regional ventilation heterogeneity throughout the lung, but the conventional analysis requires the subject to breathe deeply and regularly, which is not always practical. We have developed a model-based analysis method that avoids this limitation and that also provides measures of functional residual capacity and dead space volume, thereby expanding the applicability and scope of the method.


Assuntos
Pulmão/metabolismo , Pulmão/fisiologia , Nitrogênio/metabolismo , Ventilação Pulmonar/fisiologia , Capacidade Residual Funcional/fisiologia , Humanos , Respiração , Testes de Função Respiratória/métodos , Volume de Ventilação Pulmonar/fisiologia
7.
Chest ; 153(1): 181-186, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28629919

RESUMO

BACKGROUND: Electromagnetic navigational bronchoscopy (ENB) is guided bronchoscopy to pulmonary nodules (PN) that relies on a preprocedural chest CT to create a three-dimensional (3D) virtual airway map. The CT is traditionally done at a full inspiratory breath hold (INSP), but the procedure is performed while the patient tidal breaths, when lung volumes are closer to functional residual capacity. Movement of a PN from INSP to expiration (EXP) has been shown to average 17.6 mm. Therefore, the hypothesis of this study is that preprocedural virtual maps built off a CT closer to physiological lung volumes during bronchoscopy may better represent the actual 3D location of a PN. METHODS: Consecutive patients with a PN needing a histological diagnosis were enrolled. A preprocedure INSP and EXP CT scan were obtained to create two virtual maps. During the airway inspection, the system tracked the sensor probe to collect 3D points that were reconstructed into the lumen registration map. This map is thought to best represent the patient's airways during bronchoscopy. Predicted PN location on an EXP and INSP map was compared with lumen registration. RESULTS: Twenty consecutive PN underwent ENB. The predicted PN location, compared with lumen registration, was significantly closer on EXP vs INSP (4.5 mm ± 3.3 mm vs 14.8 mm ± 9.7 mm; p < 0.0001). CONCLUSIONS: Predicted 3D nodule location using an EXP scan for ENB is significantly closer to actual nodule location when compared with an INSP scan, but whether this leads to increased yields needs to be determined.


Assuntos
Broncoscopia/métodos , Fenômenos Eletromagnéticos , Neoplasias Pulmonares/patologia , Nódulo Pulmonar Solitário/patologia , Idoso , Suspensão da Respiração , Feminino , Capacidade Residual Funcional/fisiologia , Humanos , Imagem Tridimensional , Neoplasias Pulmonares/fisiopatologia , Masculino , Estudos Prospectivos , Respiração , Nódulo Pulmonar Solitário/fisiopatologia , Interface Usuário-Computador
8.
PLoS One ; 12(10): e0185553, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29020072

RESUMO

Nitrogen excreted from body tissues impacts the calculation of multiple breath nitrogen washout (MBWN2) outcomes. The aim of this study was to determine the effect of tissue N2 on MBWN2 outcomes in both healthy subjects and patients with CF and to assess whether it is possible to correct for tissue N2. The contribution of tissue N2 to MBWN2 outcomes was estimated by comparing MBWN2-derived functional residual capacity (FRCN2) to FRC measured by body plethysmography (FRCpleth) and by comparing MBW outcome measures derived from MBWN2 and sulfur hexafluoride MBW (MBWSF6). Compared to plethysmography and MBWSF6, MBWN2 overestimated FRC and lung clearance index (LCI). Application of mathematical tissue N2 corrections reduced FRCN2 values closer to FRCpleth in health and reduced LCIN2 in both health and CF, but did not explain all of the differences observed between N2-dependent and -independent techniques. Use of earlier washout cut-offs could reduce the influence of tissue N2. Applying tissue N2 corrections to LCIN2 measurements did not significantly affect the interpretation of treatment effects reported in a previously published interventional trial. While tissue N2 excretion likely has an impact on MBWN2 outcomes, better understanding of the nature of this phenomenon is required before routine correction can be implemented into current MBWN2 protocols.


Assuntos
Testes Respiratórios/métodos , Nitrogênio/análise , Adolescente , Estudos de Casos e Controles , Fibrose Cística/diagnóstico , Fibrose Cística/fisiopatologia , Feminino , Capacidade Residual Funcional/fisiologia , Humanos , Masculino , Pletismografia
9.
Respir Care ; 62(9): 1137-1147, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28698266

RESUMO

BACKGROUND: Spirometric Z-scores from the Global Lung Initiative (GLI) rigorously account for age-related changes in lung function and are thus age-appropriate when establishing spirometric impairments, including a restrictive pattern and air-flow obstruction. However, GLI-defined spirometric impairments have not yet been evaluated regarding associations with static lung volumes (total lung capacity [TLC], functional residual capacity [FRC], and residual volume [RV]) and gas exchange (diffusing capacity). METHODS: We performed a retrospective review of pulmonary function tests in subjects ≥40 y old (mean age 64.6 y), including pre-bronchodilator measures for: spirometry (n = 2,586), static lung volumes by helium dilution with inspiratory capacity maneuver (n = 2,586), and hemoglobin-adjusted single-breath diffusing capacity (n = 2,508). Using multivariable linear regression, adjusted least-squares means (adjLSMeans) were calculated for TLC, FRC, RV, and hemoglobin-adjusted single-breath diffusing capacity. The adjLSMeans were expressed with and without height-cubed standardization and stratified by GLI-defined spirometry, including normal (n = 1,251), restrictive pattern (n = 663), and air-flow obstruction (mild, [n = 128]; moderate, [n = 150]; and severe, [n = 394]). RESULTS: Relative to normal spirometry, restrictive-pattern had lower adjLSMeans for TLC, FRC, RV, and hemoglobin-adjusted single-breath diffusing capacity (P ≤ .001). Conversely, relative to normal spirometry, mild, moderate, and severe air-flow obstruction had higher adjLSMeans for FRC and RV (P < .001). However, only mild and moderate air-flow obstruction had higher adjLSMeans for TLC (P < .001), while only moderate and severe air-flow obstruction had higher adjLSMeans for RV/TLC (P < .001) and lower adjLSMeans for hemoglobin-adjusted single-breath diffusing capacity (P < .001). Notably, TLC (calculated as FRC + inspiratory capacity) was not increased in severe air-flow obstruction (P ≥ .11) because inspiratory capacity decreased with increasing air-flow obstruction (P < .001), thus opposing the increased FRC (P < .001). Finally, P values were similar whether adjLSMeans were height-cubed standardized. CONCLUSIONS: A GLI-defined spirometric restrictive pattern is strongly associated with a restrictive ventilatory defect (decreased TLC, FRC, and RV), while GLI-defined spirometric air-flow obstruction is strongly associated with hyperinflation (increased FRC) and air trapping (increased RV and RV/TLC). Both spirometric impairments were strongly associated with impaired gas exchange (decreased hemoglobin-adjusted single-breath diffusing capacity).


Assuntos
Obstrução das Vias Respiratórias/fisiopatologia , Capacidade Residual Funcional/fisiologia , Capacidade de Difusão Pulmonar/fisiologia , Espirometria/métodos , Adulto , Idoso , Feminino , Humanos , Análise dos Mínimos Quadrados , Modelos Lineares , Pulmão/fisiopatologia , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Volume Residual/fisiologia , Estudos Retrospectivos , Capacidade Pulmonar Total/fisiologia
10.
Respirology ; 22(8): 1662-1669, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28730724

RESUMO

BACKGROUND AND OBJECTIVE: Obstructive sleep apnoea (OSA) is typically worse in the supine versus lateral sleeping position. One potential factor driving this observation is a decrease in lung volume in the supine position which is expected by theory to increase a key OSA pathogenic factor: dynamic ventilatory control instability (i.e. loop gain). We aimed to quantify dynamic loop gain in OSA patients in the lateral and supine positions, and to explore the relationship between change in dynamic loop gain and change in lung volume with position. METHODS: Data from 20 patients enrolled in previous studies on the effect of body position on OSA pathogenesis were retrospectively analysed. Dynamic loop gain was calculated from routinely collected polysomnographic signals using a previously validated mathematical model. Lung volumes were measured in the awake state with a nitrogen washout technique. RESULTS: Dynamic loop gain was significantly higher in the supine than in the lateral position (0.77 ± 0.15 vs 0.68 ± 0.14, P = 0.012). Supine functional residual capacity (FRC) was significantly lower than lateral FRC (81.0 ± 15.4% vs 87.3 ± 18.4% of the seated FRC, P = 0.021). The reduced FRC we observed on moving to the supine position was predicted by theory to increase loop gain by 10.2 (0.6, 17.1)%, a value similar to the observed increase of 8.4 (-1.5, 31.0)%. CONCLUSION: Dynamic loop gain increased by a small but statistically significant amount when moving from the lateral to supine position and this may, in part, contribute to the worsening of OSA in the supine sleeping position.


Assuntos
Pulmão/fisiopatologia , Apneia Obstrutiva do Sono/fisiopatologia , Sono/fisiologia , Adulto , Feminino , Capacidade Residual Funcional/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Teóricos , Postura , Testes de Função Respiratória/métodos , Estudos Retrospectivos , Estatística como Assunto , Decúbito Dorsal/fisiologia
11.
Resuscitation ; 117: 80-86, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28606716

RESUMO

BACKGROUND: During delivery room resuscitation of depressed newborns, provision of appropriate tidal volume (TV) with establishment of functional residual capacity (FRC) is essential for circulatory recovery. Effective positive pressure ventilation (PPV) is associated with a rapid increase in heart rate (HR). The relationship between delivery of TV and HR responses remains unclear. OBJECTIVES: The study objectives were to determine (1) the relationship between a given TV during initial PPV and HR responses of depressed newborns, and (2) the optimal delivered TV associated with a rapid increase in HR. METHODS: In a Tanzanian rural hospital, ventilation and ECG signals were recorded during neonatal resuscitation and stored in Neonatal Resuscitation Monitors. Resuscitators without positive end-expiratory pressure were used for PPV. No oxygen was used. Perinatal events were observed and recorded by research assistants. RESULTS: 215 newborns of gestational age 37.3±1.9 weeks and birth weight 3115±579g were included. There was a non-linear relationship between delivered TV and HR increase. TV of 9.3ml/kg produced the largest increase in HR during PPV. Frequent interruptions of PPV sequences to provide stimulation/suctioning occurred in all cases and were associated with further HR increases, especially for newborns with initial HR<100 beats/minute. CONCLUSIONS: There was a consistent positive relationship between HR increase and delivered TV. The unanticipated finding of a further increase in HR with PPV pauses to provide stimulation/suctioning suggests that most newborns were in primary rather than secondary apnea.


Assuntos
Frequência Cardíaca/fisiologia , Respiração com Pressão Positiva/estatística & dados numéricos , Ressuscitação/normas , Volume de Ventilação Pulmonar/fisiologia , Estudos Transversais , Capacidade Residual Funcional/fisiologia , Idade Gestacional , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Tocologia , Respiração com Pressão Positiva/métodos , Ressuscitação/métodos , Tanzânia
12.
J Appl Physiol (1985) ; 122(6): 1379-1387, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28280107

RESUMO

Multiple breath washout (MBW) and oxygen-enhanced MRI techniques use acute exposure to 100% oxygen to measure ventilation heterogeneity. Implicit is the assumption that breathing 100% oxygen does not induce changes in ventilation heterogeneity; however, this is untested. We hypothesized that ventilation heterogeneity decreases with increasing inspired oxygen concentration in healthy subjects. We performed MBW in 8 healthy subjects (4 women, 4 men; age = 43 ± 15 yr) with normal pulmonary function (FEV1 = 98 ± 6% predicted) using 10% argon as a tracer gas and oxygen concentrations of 12.5%, 21%, or 90%. MBW was performed in accordance with ERS-ATS guidelines. Subjects initially inspired air followed by a wash-in of test gas. Tests were performed in balanced order in triplicate. Gas concentrations were measured at the mouth, and argon signals rescaled to mimic a N2 washout, and analyzed to determine the distribution of specific ventilation (SV). Heterogeneity was characterized by the width of a log-Gaussian fit of the SV distribution and from Sacin and Scond indexes derived from the phase III slope. There were no significant differences in the ventilation heterogeneity due to altered inspired oxygen: histogram width (hypoxia 0.57 ± 0.11, normoxia 0.60 ± 0.08, hyperoxia 0.59 ± 0.09, P = 0.51), Scond (hypoxia 0.014 ± 0.011, normoxia 0.012 ± 0.015, hyperoxia 0.010 ± 0.011, P = 0.34), or Sacin (hypoxia 0.11 ± 0.04, normoxia 0.10 ± 0.03, hyperoxia 0.12 ± 0.03, P = 0.23). Functional residual capacity was increased in hypoxia (P = 0.04) and dead space increased in hyperoxia (P = 0.0001) compared with the other conditions. The acute use of 100% oxygen in MBW or MRI is unlikely to affect ventilation heterogeneity.NEW & NOTEWORTHY Hyperoxia is used to measure the distribution of ventilation in imaging and MBW but may alter the underlying ventilation distribution. We used MBW to evaluate the effect of inspired oxygen concentration on the ventilation distribution using 10% argon as a tracer. Short-duration exposure to hypoxia (12.5% oxygen) and hyperoxia (90% oxygen) during MBW had no significant effect on ventilation heterogeneity, suggesting that hyperoxia can be used to assess the ventilation distribution.


Assuntos
Capacidade Residual Funcional/fisiologia , Gases Nobres/metabolismo , Oxigênio/metabolismo , Adulto , Testes Respiratórios/métodos , Feminino , Humanos , Hipóxia/metabolismo , Hipóxia/fisiopatologia , Pulmão , Masculino , Pessoa de Meia-Idade , Respiração , Testes de Função Respiratória/métodos , Volume de Ventilação Pulmonar/fisiologia , Ventilação/métodos , Adulto Jovem
13.
Respir Med ; 124: 15-20, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28284316

RESUMO

INTRODUCTION: Obesity can cause hypoxemia by decreasing lung volumes to where there is closure of lung units during normal breathing. Studies describing this phenomenon are difficult to translate into clinical practice. We wanted to determine the lung volume measurements that are associated with hypoxemia in obese patients, and explore how we could use these measurements to identify them. METHODS: We collected pulmonary function test results and arterial blood gas data on 118 patients without obstruction on pulmonary function testing. We included only patients with normal chest imaging and cardiac testing within one year of the pulmonary function test, to exclude other causes of hypoxemia. RESULTS: We found that as BMI increases, the mean paO2, ERV % predicted, and ERV/TLC decrease (BMI 20-30 kg/m2: paO2=90±8 mmHg, ERV% predicted 112±50, ERV/TLC (%) 19.7±6.5; BMI 30-40 kg/m2: paO2=84±10 mmHg, ERV% predicted 84±40 ERV/TLC(%) 13.6±7.6; BMI>40 kg/m2: paO2 78 ±12 mmHg, ERV% predicted 64±27 ERV/TLC(%) 11.4±5.8, ANOVA p<0.001). The A-a gradient increases as BMI increases (r=0.42, p<0.001). This correlation was stronger in men (r=0.54) than in women (r=0.35). The paO2 is lower in patients with a low ERV than in those with a normal ERV (p<0.001). In a multivariate linear regression, only the ERV/TLC predicted (%), age, and BMI were associated with oxygenation (r2 for A-a gradient =0.28, p=0.036). CONCLUSIONS: In obese patients without cardiopulmonary disease, oxygen levels decrease as BMI increases. This effect is associated with the obesity-related reduction in ERV and is independent of hypoventilation.


Assuntos
Hipóxia/fisiopatologia , Medidas de Volume Pulmonar/métodos , Pulmão/fisiopatologia , Obesidade/complicações , Volume de Ventilação Pulmonar/fisiologia , Adulto , Gasometria/instrumentação , Índice de Massa Corporal , Volume de Reserva Expiratória/fisiologia , Feminino , Capacidade Residual Funcional/fisiologia , Humanos , Hipóxia/complicações , Pulmão/metabolismo , Masculino , Pessoa de Meia-Idade , Obesidade/etnologia , Obesidade/fisiopatologia , Oxigênio/sangue , Troca Gasosa Pulmonar/fisiologia , Respiração , Testes de Função Respiratória/métodos , Espirometria
14.
Respir Physiol Neurobiol ; 242: 12-18, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28323205

RESUMO

Routine estimation of functional residual capacity (FRC) in ventilated patients has been a long held goal, with many methods previously proposed, but none have been used in routine clinical practice. This paper proposes three models for determining FRC using the nitrous oxide concentration from the entire expired breath in order to improve the precision of the estimate. Of the three models proposed, a dead space with two mixing compartments provided the best results, reducing the mean limits of agreement with the FRC measured by whole body plethysmography by up to 41%. This moves away from traditional lung models, which do not account for mixing within the dead space. Compared to literature values for FRC, the results are similar to those obtained using helium dilution and better than the LUFU device (Dräger Medical, Lubeck, Germany), with significantly better limits of agreement compared to plethysmography.


Assuntos
Capacidade Residual Funcional , Pulmão/fisiologia , Modelos Biológicos , Espaço Morto Respiratório , Testes Respiratórios/instrumentação , Testes Respiratórios/métodos , Simulação por Computador , Feminino , Capacidade Residual Funcional/fisiologia , Hélio , Humanos , Análise dos Mínimos Quadrados , Pulmão/anatomia & histologia , Masculino , Óxido Nitroso/análise , Pletismografia Total , Análise de Regressão , Respiração , Adulto Jovem
15.
J Cyst Fibros ; 16(6): 713-718, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28188011

RESUMO

BACKGROUND: We assessed the effect of posture on ventilation distribution and the impact on associations with structural lung disease. METHODS: Multiple breath washout (MBW) was performed in seated and supine postures in 25 healthy children and 21 children with CF. Children with CF also underwent a chest CT scan. Functional residual capacity (FRC), lung clearance index (LCI) and moment ratios were calculated from the MBW test. CT scans were evaluated for CF-related structural lung disease. RESULTS: FRC was lower in the supine than in the seated posture, whereas LCI was higher in the supine than in the seated posture. In children with CF, associations between LCI and the extent of structural lung disease were stronger when performed in the supine posture. CONCLUSIONS: Body posture influences lung volumes and ventilation distribution in both healthy children and children with CF. MBW testing in the supine posture strengthened associations with structural lung damage.


Assuntos
Fibrose Cística , Capacidade Residual Funcional/fisiologia , Depuração Mucociliar/fisiologia , Postura/fisiologia , Adolescente , Fenômenos Biomecânicos/fisiologia , Criança , Fibrose Cística/diagnóstico , Fibrose Cística/fisiopatologia , Feminino , Humanos , Pulmão/fisiopatologia , Masculino , Ventilação Pulmonar/fisiologia , Testes de Função Respiratória/métodos , Tomografia Computadorizada por Raios X/métodos
16.
Pediatr Pulmonol ; 52(1): 10-13, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27273874

RESUMO

A refined software algorithm was recently proposed for the analysis of infant multiple breath washout (MBW) measurements. The proposed algorithm uses the change in end-inspiratory molar mass between the wash-in and wash-out curves (EIMM-step) to define the required step response correction of the MM signal and is assumed to provide an accurate evaluation of complete washout of the tracer gas, in comparison to the current software algorithm which applies the change in end-expiratory molar mass (EEMM)-step. We aimed to evaluate the use of the EIMM-step method in a broad range of infants. We performed retrospective analyses comparing the EIMM- and EEMM-step change methods in MBW data collected from infants with cystic fibrosis (CF), infants born preterm, and healthy infants using an ultrasonic flowmeter. We found that the EIMM-step correction significantly increased LCI and functional residual capacity (FRC) in infants with CF, preterm infants, and healthy infants compared with the EEMM-step method. In addition, more than half the measurements that were technically acceptable and repeatable using the EEMM-step correction in healthy infants were excluded after using the EIMM-step correction. We found a large difference between the EIMM- and EEMM-steps in healthy infants indicating incomplete washout, suggesting the need for a longer washout time with using the EIMM-step analysis method. The data indicates that the EIMM-step analysis method may have the potential to generate false abnormal LCI values in individuals without lung disease. Revised normative data may be required if this method is universally adopted. Pediatr Pulmonol. 2017;52:10-13. © 2016 Wiley Periodicals, Inc.


Assuntos
Testes Respiratórios/métodos , Fibrose Cística/fisiopatologia , Testes de Função Respiratória/métodos , Algoritmos , Feminino , Fluxômetros , Capacidade Residual Funcional/fisiologia , Humanos , Lactente , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Respiração , Estudos Retrospectivos , Software
17.
J Appl Physiol (1985) ; 121(5): 1087-1097, 2016 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-27493195

RESUMO

Multiple-breath inert gas washout (MBW) is ideally suited for early detection and monitoring of serious lung disease, such as cystic fibrosis, in infants and young children. Validated commercial options for the MBW technique are limited, and suitability of nitrogen (N2)-based MBW is of concern given the detrimental effect of exposure to pure O2 on infant breathing pattern. We propose novel methodology using commercially available N2 MBW equipment to facilitate 4% sulfur hexafluoride (SF6) multiple-breath inert gas wash-in and washout suitable for the infant age range. CO2, O2, and sidestream molar mass sensor signals were used to accurately calculate SF6 concentrations. An improved dynamic method for synchronization of gas and respiratory flow was developed to take into account variations in sidestream sample flow during MBW measurement. In vitro validation of triplicate functional residual capacity (FRC) assessments was undertaken under dry ambient conditions using lung models ranging from 90 to 267 ml, with tidal volumes of 28-79 ml, and respiratory rates 20-60 per minute. The relative mean (SD, 95% confidence interval) error of triplicate FRC determinations by washout was -0.26 (1.84, -3.86 to +3.35)% and by wash-in was 0.57 (2.66, -4.66 to +5.79)%. The standard deviations [mean (SD)] of percentage error among FRC triplicates were 1.40 (1.14) and 1.38 (1.32) for washout and wash-in, respectively. The novel methodology presented achieved FRC accuracy as outlined by current MBW consensus recommendations (95% of measurements within 5% accuracy). Further clinical evaluation is required, but this new technique, using existing commercially available equipment, has exciting potential for research and clinical use.


Assuntos
Pulmão/metabolismo , Pulmão/fisiologia , Hexafluoreto de Enxofre/metabolismo , Testes Respiratórios/métodos , Dióxido de Carbono/metabolismo , Fibrose Cística/metabolismo , Fibrose Cística/fisiopatologia , Capacidade Residual Funcional/fisiologia , Humanos , Lactente , Masculino , Nitrogênio/metabolismo , Oxigênio/metabolismo , Taxa Respiratória/fisiologia , Volume de Ventilação Pulmonar/fisiologia
18.
Respir Physiol Neurobiol ; 232: 54-6, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27395446

RESUMO

Spinal cord stimulation (SCS, 50Hz) is a useful method to restore an effective cough in persons with spinal cord injury (SCI). However, high stimulus amplitudes and potential activation of pain fibers, significantly limits this application. It is our hypothesis that high frequency SCS (HF-SCS), with low stimulus amplitudes may provide the same level of expiratory muscle activation. In 6 dogs, the effects of SCS, with varying stimulus parameters on positive pressure (P) generation was evaluated. At any given level of stimulus current, mean P was largest at 500Hz, compared to all other stimulus frequencies. For example, with stimulation at 1mA and frequencies of 200, 500 and 600Hz, P were 25±3, 58±4, 51±6cmH2O, respectively. By comparison, P achieved with conventional SCS parameters was 61±5cmH2O. HF-SCS results in a comparable P compared to that achieved with conventional stimulus parameters but with much lower stimulus amplitudes. This method may be useful to restore cough even in subjects with intact sensation.


Assuntos
Fenômenos Biofísicos/fisiologia , Tosse/terapia , Tosse/veterinária , Estimulação da Medula Espinal/métodos , Potenciais de Ação , Animais , Pressão Positiva Contínua nas Vias Aéreas , Tosse/etiologia , Modelos Animais de Doenças , Cães , Eletromiografia , Potencial Evocado Motor/fisiologia , Capacidade Residual Funcional/fisiologia , Laminectomia , Músculos Respiratórios/fisiologia , Traumatismos da Medula Espinal/complicações
19.
Crit Care Med ; 44(9): e838-45, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27054894

RESUMO

OBJECTIVE: Lungs behave as viscoelastic polymers. Harms of mechanical ventilation could then depend on not only amplitude (strain) but also velocity (strain rate) of lung deformation. Herein, we tested this hypothesis. DESIGN: Laboratory investigation. SETTING: Animal unit. SUBJECTS: Thirty healthy piglets. INTERVENTIONS: Two groups of animals were ventilated for 54 hours with matched lung strains (ratio between tidal volume and functional residual capacity) but different lung strain rates (ratio between strain and inspiratory time). Individual strains ranged between 0.6 and 3.5 in both groups. Piglets ventilated with low strain rates had an inspiratory-to-expiratory time ratio of 1:2-1:3. Those ventilated with high strain rates had much lower inspiratory-to-expiratory time ratios (down to 1:9). Respiratory rate was always 15 breaths/min. Lung viscoelastic behavior, with ventilator setting required per protocol, was "quantified" as dynamic respiratory system hysteresis (pressure-volume loop [in Joules]) and stress relaxation (airway pressure drop during an end-inspiratory pause [in cm H2O]). Primary outcome was the occurrence of pulmonary edema within 54 hours. MEASUREMENTS AND MAIN RESULTS: On average, the two study groups were ventilated with well-matched strains (2.1 ± 0.9 vs 2.1 ± 0.9; p = 0.864) but different strain rates (1.8 ± 0.8 vs 4.6 ± 1.5 s; p < 0.001), dynamic respiratory system hysteresis (0.6 ± 0.3 vs 1.4 ± 0.8 J; p = 0.001), and stress relaxation (3.1 ± 0.9 vs 5.0 ± 2.3 cm H2O; p = 0.008). The prevalence of pulmonary edema was 20% among piglets ventilated with low strain rates and 73% among those ventilated with high strain rates (p = 0.010). CONCLUSIONS: High strain rate is a risk factor for ventilator-induced pulmonary edema, possibly because it amplifies lung viscoelastic behavior.


Assuntos
Edema Pulmonar/etiologia , Respiração Artificial/efeitos adversos , Mecânica Respiratória/fisiologia , Lesão Pulmonar Induzida por Ventilação Mecânica/etiologia , Animais , Capacidade Residual Funcional/fisiologia , Humanos , Complacência Pulmonar/fisiologia , Edema Pulmonar/fisiopatologia , Estresse Mecânico , Suínos , Volume de Ventilação Pulmonar/fisiologia , Lesão Pulmonar Induzida por Ventilação Mecânica/fisiopatologia
20.
J Appl Physiol (1985) ; 121(1): 223-32, 2016 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27103654

RESUMO

While airways have some degree of baseline tone, the level and variability of this tone is not known. It is also unclear whether there is a difference in airway tone or in the variability of airway tone between asthmatic and healthy individuals. This study examined airway tone and intraindividual airway tone heterogeneity (variance of airway tone) in vivo in 19 individuals with asthma compared with 9 healthy adults. All participants underwent spirometry, body plethysmography, and high-resolution computed tomography at baseline and after maximum bronchodilation with albuterol. Airway tone was defined as the percent difference in airway diameter after albuterol at total lung capacity compared with baseline. The amount of airway tone in each airway varied both within and between subjects. The average airway tone did not differ significantly between the two groups (P = 0.09), but the intraindividual airway tone heterogeneity did (P = 0.016). Intraindividual airway tone heterogeneity was strongly correlated with airway tone (r = 0.78, P < 0.0001). Also, it was negatively correlated with the magnitude of the distension of the airways from functional residual capacity to total lung capacity at both baseline (r = -0.49, P = 0.03) and after maximum bronchodilation (r = -0.51, P = 0.02) in the asthma, but not the healthy group. However, we did not find any relationship between intraindividual airway tone heterogeneity and conventional lung function outcomes. Intraindividual airway tone heterogeneity appears to be an important characteristic of airway pathophysiology in asthma.


Assuntos
Asma/patologia , Pulmão/patologia , Adulto , Albuterol/farmacologia , Asma/tratamento farmacológico , Broncodilatadores/farmacologia , Feminino , Capacidade Residual Funcional/efeitos dos fármacos , Capacidade Residual Funcional/fisiologia , Humanos , Pulmão/efeitos dos fármacos , Medidas de Volume Pulmonar/métodos , Masculino , Pessoa de Meia-Idade , Espirometria/métodos , Capacidade Pulmonar Total/efeitos dos fármacos , Capacidade Pulmonar Total/fisiologia , Adulto Jovem
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