Thoracoabdominal asynchrony associates with exercise intolerance in fibrotic interstitial lung diseases.

BACKGROUND AND OBJECTIVE: The precise coordination of respiratory muscles during exercise minimizes work of breathing and avoids exercise intolerance. Fibrotic interstitial lung disease (f-ILD) patients are exercise-intolerant. We assessed whether respiratory muscle incoordination and thoracoabdominal asynchrony (TAA) occur in f-ILD during exercise, and their relationship with pulmonary function and exercise performance. METHODS: We compared breathing pattern, respiratory mechanics, TAA and respiratory muscle recruitment in 31 f-ILD patients and 31 healthy subjects at rest and during incremental cycle exercise. TAA was defined as phase angle (PhAng) >20°. RESULTS: During exercise, when compared with controls, f-ILD patients presented increased and early recruitment of inspiratory rib cage muscle (p < 0.05), and an increase in PhAng, indicating TAA. TAA was more frequent in f-ILD patients than in controls, both at 50% of the maximum workload (42.3% vs. 10.7%, p = 0.01) and at the peak (53.8% vs. 23%, p = 0.02). Compared with f-ILD patients without TAA, f-ILD patients with TAA had lower lung volumes (forced vital capacity, p < 0.01), greater dyspnoea (Medical Research Council > 2 in 64.3%, p = 0.02), worse exercise performance (lower maximal work rate % predicted, p = 0.03; lower tidal volume, p = 0.03; greater desaturation and dyspnoea, p < 0.01) and presented higher oesophageal inspiratory pressures with lower gastric inspiratory pressures and higher recruitment of scalene (p < 0.05). CONCLUSION: Exercise induces TAA and higher recruitment of inspiratory accessory muscle in ILD patients. TAA during exercise occurred in more severely restricted ILD patients and was associated with exertional dyspnoea, desaturation and limited exercise performance.

Mechanisms of exercise limitation in patients with chronic hypersensitivity pneumonitis.

Small airway and interstitial pulmonary involvements are prominent in chronic hypersensitivity pneumonitis (cHP). However, their roles on exercise limitation and the relationship with functional lung tests have not been studied in detail. Our aim was to evaluate exercise performance and its determinants in cHP. We evaluated maximal cardiopulmonary exercise testing performance in 28 cHP patients (forced vital capacity 57±17% pred) and 18 healthy controls during cycling. Patients had reduced exercise performance with lower peak oxygen production (16.6 (12.3-19.98) mL·kg-1·min-1versus 25.1 (16.9-32.0), p=0.003), diminished breathing reserve (% maximal voluntary ventilation) (12 (6.4-34.8)% versus 41 (32.7-50.8)%, p<0.001) and hyperventilation (minute ventilation/carbon dioxide production slope 37±5 versus 31±4, p<0.001). All patients presented oxygen desaturation and augmented Borg dyspnoea scores (8 (5-10) versus 4 (1-7), p=0.004). The prevalence of dynamic hyperinflation was found in only 18% of patients. When comparing cHP patients with normal and low peak oxygen production (<84% pred, lower limit of normal), the latter exhibited a higher minute ventilation/carbon dioxide production slope (39±5.0 versus 34±3.6, p=0.004), lower tidal volume (0.84 (0.78-0.90) L versus 1.15 (0.97-1.67) L, p=0.002), and poorer physical functioning score on the Short form-36 health survey. Receiver operating characteristic curve analysis showed that reduced lung volumes (forced vital capacity %, total lung capacity % and diffusing capacity of the lung for carbon dioxide %) were high predictors of poor exercise capacity. Reduced exercise capacity was prevalent in patients because of ventilatory limitation and not due to dynamic hyperinflation. Reduced lung volumes were reliable predictors of lower performance during exercise.

Unilateral diaphragm paralysis: a dysfunction restricted not just to one hemidiaphragm.

BACKGROUND: Most patients with unilateral diaphragm paralysis (UDP) have unexplained dyspnea, exercise limitations, and reduction in inspiratory muscle capacity. We aimed to evaluate the generation of pressure in each hemidiaphragm separately and its contribution to overall inspiratory strength. METHODS: Twenty-seven patients, 9 in right paralysis group (RP) and 18 in left paralysis group (LP), with forced vital capacity (FVC) < 80% pred, and 20 healthy controls (CG), with forced expiratory volume in 1 s (FEV1) > 80% pred and FVC > 80% pred, were evaluated for lung function, maximal inspiratory (MIP) and expiratory (MEP) pressure measurements, diaphragm ultrasound, and transdiaphragmatic pressure during magnetic phrenic nerve stimulation (PdiTw). RESULTS: RP and LP had significant inspiratory muscle weakness compared to controls, detected by MIP (- 57.4 ± 16.9 for RP; - 67.1 ± 28.5 for LP and - 103.1 ± 30.4 cmH2O for CG) and also by PdiTW (5.7 ± 4 for RP; 4.8 ± 2.3 for LP and 15.3 ± 5.7 cmH2O for CG). The PdiTw was reduced even when the non-paralyzed hemidiaphragm was stimulated, mainly due to the low contribution of gastric pressure (around 30%), regardless of whether the paralysis was in the right or left hemidiaphragm. On the other hand, in CG, esophagic and gastric pressures had similar contribution to the overall Pdi (around 50%). Comparing both paralyzed and non-paralyzed hemidiaphragms, the mobility during quiet and deep breathing, and thickness at functional residual capacity (FRC) and total lung capacity (TLC), were significantly reduced in paralyzed hemidiaphragm. In addition, thickness fraction was extremely diminished when contrasted with the non-paralyzed hemidiaphragm. CONCLUSIONS: In symptomatic patients with UDP, global inspiratory strength is reduced not only due to weakness in the paralyzed hemidiaphragm but also to impairment in the pressure generated by the non-paralyzed hemidiaphragm.

Accuracy of Invasive and Noninvasive Parameters for Diagnosing Ventilatory Overassistance During Pressure Support Ventilation.

OBJECTIVE: Evaluate the accuracy of criteria for diagnosing pressure overassistance during pressure support ventilation. DESIGN: Prospective clinical study. SETTING: Medical-surgical ICU. PATIENTS: Adults under mechanical ventilation for 48 hours or more using pressure support ventilation and without any sedative for 6 hours or more. Overassistance was defined as the occurrence of work of breathing less than 0.3 J/L or 10% or more of ineffective inspiratory effort. Two alternative overassistance definitions were based on the occurrence of inspiratory esophageal pressure-time product of less than 50 cm H2O s/min or esophageal occlusion pressure of less than 1.5 cm H2O. INTERVENTIONS: The pressure support was set to 20 cm H2O and decreased in 3-cm H2O steps down to 2 cm H2O. MEASUREMENTS AND MAIN RESULTS: The following parameters were evaluated to diagnose overassistance: respiratory rate, tidal volume, minute ventilation, peripheral arterial oxygen saturation, rapid shallow breathing index, heart rate, mean arterial pressure, change in esophageal pressure during inspiration, and esophageal and airway occlusion pressure. In all definitions, the respiratory rate had the greatest accuracy for diagnosing overassistance (receiver operating characteristic area = 0.92; 0.91 and 0.76 for work of breathing, pressure-time product and esophageal occlusion pressure in definition, respectively) and always with a cutoff of 17 incursions per minute. In all definitions, a respiratory rate of less than or equal to 12 confirmed overassistance (100% specificity), whereas a respiratory rate of greater than or equal to 30 excluded overassistance (100% sensitivity). CONCLUSION: A respiratory rate of 17 breaths/min is the parameter with the greatest accuracy for diagnosing overassistance. Respiratory rates of less than or equal to 12 or greater than or equal to 30 are useful clinical references to confirm or exclude pressure support overassistance.

Thoracoabdominal asynchrony: Two methods in healthy, COPD, and interstitial lung disease patients.

BACKGROUND: Thoracoabdominal asynchrony is the nonparallel motion of the ribcage and abdomen. It is estimated by using respiratory inductive plethysmography and, recently, using optoelectronic plethysmography; however the agreement of measurements between these 2 techniques is unknown. Therefore, the present study compared respiratory inductive plethysmography with optoelectronic plethysmography for measuring thoracoabdominal asynchrony to see if the measurements were similar or different. METHODS: 27 individuals (9 healthy subjects, 9 patients with interstitial lung disease, and 9 with chronic obstructive pulmonary disease performed 2 cycle ergometer tests with respiratory inductive plethysmography or optoelectronic plethysmography in a random order. Thoracoabdominal asynchrony was evaluated at rest, and at 50% and 75% of maximal workload between the superior ribcage and abdomen using a phase angle. RESULTS: Thoracoabdominal asynchrony values were very similar in both approaches not only at rest but also with exercise, with no statistical difference. There was a good correlation between the methods and the Phase angle values were within the limits of agreement in the Bland-Altman analysis. CONCLUSION: Thoracoabdominal asynchrony measured by optoelectronic plethysmography and respiratory inductive plethysmography results in similar values and has a satisfactory agreement at rest and even for different exercise intensities in these groups.

Diagnostic methods to assess inspiratory and expiratory muscle strength.

Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength.

Diagnostic methods to assess inspiratory and expiratory muscle strength / Métodos diagnósticos para avaliação da força muscular inspiratória e expiratória

Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength.

O acometimento da musculatura ventilatória (inspiratória e expiratória) é um achado clínico frequente, não somente nos pacientes com doenças neuromusculares, mas também nos pacientes com doenças primárias do parênquima pulmonar ou das vias aéreas. Embora esse acometimento seja frequente, seu reconhecimento costuma ser demorado porque seus sinais e sintomas são inespecíficos e tardios. Esse reconhecimento tardio, ou mesmo a falta de reconhecimento, é acentuado porque os exames diagnósticos usados para a avaliação da musculatura respiratória não são plenamente conhecidos e disponíveis. Usando diferentes métodos, a avaliação da força muscular ventilatória é feita para a fase inspiratória e expiratória. Os métodos usados dividem-se em volitivos (que exigem compreensão e colaboração do paciente) e não volitivos. Os volitivos, como a medida da pressão inspiratória e expiratória máximas, são os mais empregados por serem facilmente disponíveis. Os não volitivos dependem da estimulação magnética do nervo frênico associada a medida da pressão inspiratória na boca, no esôfago ou transdiafragmática. Finalmente, outro método que vem se tornando frequente é a ultrassonografia diafragmática. Acreditamos que o pneumologista envolvido nos cuidados a pacientes com doenças respiratórias deve conhecer os exames usados na avaliação da musculatura ventilatória. Por isso, o objetivo do presente artigo é descrever as vantagens, desvantagens, procedimentos de mensuração e aplicabilidade clínica dos principais exames utilizados para avaliação da força muscular ventilatória.