Analyzing respiratory muscle weakness and thoracopulmonary restriction in subjects with Duchenne muscular dystrophy

OBJECTIVE

To analyze the underlying components of reduced maximal static inspiratory (MIP) and expiratory (MEP) pressures in subjects with Duchenne muscular dystrophy.

METHODS

Forty-three subjects were assessed based on routine pulmonary function tests. MIP and MEP were measured the subjects performed maximal expirations and inspirations using a snorkel mouthpiece. Lung volumes were measured using the helium dilution technique.

RESULTS

The mean age was 13 years (range, 7-20 years). Median total lung capacity (TLC) and residual volume (RV) were 78.0 (49.0-94.0) and 27.0 (19.7-30.1) of the predicted values respectively. The RV/TLC relationship was 35.3% (28.1-47.7). Thirty-five subjects had a TLC below the lower limit of normal, while 31 had an RV/TLC ratio above the upper limit of normal. The median (IQR) MIP and MEP values were -53.0 (-65.5 to -41.8) and 58.0 (41.5-74.8) cmH2O respectively. MIP and MEP in percent of the predicted values (predicted TLC and RV) were 42.6 (33.3-50.8) and 33.7 (23.9-44.5). MIP in percent of the RV reached for Group A (7-11 years old) was higher (p 0.025) while MEP in percent of the TLC reached for Group B (12-16 years) and C (17-20 years) were higher too (0.031).

CONCLUSIONS

In subjects with Duchenne muscular dystrophy, the intrinsic weakness of respiratory muscles and mechanical disadvantage lead to inadequate maximal static pressure generation. Maximal static pressures should be interpreted cautiously as they overestimate respiratory muscle weakness when compared to predicted values obtained at TLC and RV. Our results provide additional data supporting absolute values use rather than predicted values.

[Peer review, preprints and predatory journals. Publication ethics versus publicity applied to medical science]

The publication of medical articles has become increasingly complex, linked to multiple factors. It poses difficult problems for both authors and journals themselves. This Editorial addresses current and controversial issues: peer review, preprints as a new way of disseminating knowledge, the growing number of publications without peer review and its variants, and the risks of predatory publications. The article proposes future guidelines as an editorial policy of MEDICINA. The controversy continues, and surely the passage of time will place our proposal in a changing scientific world like knowledge itself.

Compartmental nutritional status and respiratory muscle function assessment in subjects with neuromuscular diseases

There are few data devoted to the combined assessment of the nutritional and respiratory status of subjects with neuromuscular diseases. The objective was to establish correlations between compartmental nutritional variables and respiratory variables to identify respiratory muscle weakness determinants of patients with amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD). Cross-sectional study with ALS and DMD patients included in an Institutional Registry of Neuromuscular diseases. Nutritional status was assessed through body mass index (BMI), expected weight for zero muscle mass (ZMM%) and creatinine-height index (CHI%). Respiratory indices evaluated were spirometry, maximal static inspiratory and expiratory pressures at the mouth (MIP and MEP), and peak cough flow (PCF). A total of 36 ALS and 34 DMD patients were included. Both groups showed a decrease in the body muscle mass and an excess in body fat (p < 0.001). Only in the ALS group was there a weak uphill relationship between body mass index (BMI) and the respiratory variables. In both groups, the ZMM% index did not correlate with any respiratory variable. The CHI% showed the strongest (r > 0.700) positive linear relationship with FVC%, MIP%, MEP%, and PCF% in both ALS and DMD patients (p < 0.001).In this study our patients, BMI did not accurately reflect body composition and underestimated excess fat. This study puts into perspective the relevance of compartmental evaluation to assess respiratory muscle function and establishes that body muscle mass is the most relevant nutritional parameter in relation to respiratory muscle strength.

[When should and when should not use oxygen in neuromuscular diseases?]

Although the references warn about the adverse effects of adding O2 without ventilatory assistance in patients with neuromuscular diseases (NMD), patients are still to be admitted to intensive care units with severe hypercapnia and CO2 narcosis. It seems that the problem is rediscovered as the years and generations go by. Unfortunately, many patients and their network of formal and informal caregivers are unaware of this risk, leading to significant worsening of symptoms, acute events, hospital admissions, and, in some cases, cause death. This article focuses on the dangers of O2 administration as well as its precise indications in people with NMD. The central problem is that the administration of O2 can remove the hypoxic impulse to ventilate, however, other mechanisms could be involved, but. The complete withdrawal of oxygen therapy is an even greater mistake if it is not supported by ventilatory assistance. It is possible to supply O2 and control CO2 safely. Oxygen should never be administered without constantly monitoring the CO2 level. Bi-level non-invasive ventilation (BiPAP) through a buccal, nasal interface or mouthpiece is the primary measure to reverse hypoventilation and achieve a decrease in PaCO2. The indications for oxygen therapy in people with NMD have been agreed upon and are reserved for specific situations. To improve the care of those with NMD and avoid iatrogenic interventions, education of the health team and support in the patient's environment is required.

Bilateral diaphragmatic paralysis and Lyme neuroborreliosis. Ten years of follow-up

Borrelia burgdorferi infection (Lyme disease) is one of the few identifiable causes of neuralgic amyotrophy. Bilateral diaphragmatic paralysis is considered rare in borreliosis, and the pattern of long-term recovery of diaphragm function is also uncertain. Transdiaphragmatic pressure is the gold standard for diagnosis of bilateral diaphragmatic paralysis, a study that has been reported on few occasions. We present a case of neuralgic amyotrophy associated with Borrelia infection and bilateral diaphragmatic paralysis that provides a detailed follow-up of the spirometric evolution, of the maximum static pressures in the mouth and of transdiaphragmatic pressure from the onset of symptoms and the long term. This case allows us to know one of the possible evolutionary profiles of diaphragmatic dysfunction in neuralgic amyotrophy due to borreliosis.

[Diffusing capacity for carbon monoxide, guidelines for interpretation]

The diffusing capacity for carbon monoxide (DLCO) is, after spirometry the standard and noninvasive pulmonary function test of greater clinical use. However, there are substantial errors in the interpretation of the physiological significance of the DLCO, its derived measures and, therefore the clinical significance of its alterations. In addition to the use of different nomenclatures, other sources of confusion have contributed to some negative view of the test. The technical aspects of the DLCO test have the advantage of being well standardized. But unlike what happens with other pulmonary function tests where we have reference values which allow us to determine their "normality or abnormality", it is difficult to apply this route of analysis in the case of DLCO. The central fact in the analysis of DLCO, transference factor for CO (KCO), and alveolar volume (VA) is that for a correct interpretation it is necessary to think about the mechanism by which the pathology induces change. A KCO of 100% can be considered normal in some circumstances or pathological in others and, for the moment, the automated study report cannot discriminate. This article will address the principles of the DLCO test; present different models of analysis submit concrete examples and provide guidelines for their correct interpretation. It is considered essential to carry out an integrated analysis of the DLCO test in relation to other functional tests and clinical data.

[Analysis of the results of a palliative care quality program for the last days of life. Ten years of experience]

The integrated care pathways for the last days of life propose quality standards optimizing the care of patients and families. The Pallium Multidisciplinary Assistance Program (PAMPA ©) was implemented based on standards of the International Collaborative for Best Care for the Dying Person in 4 phases: induction, implementation, dissemination and sustainability, in five health centres in Argentina, between 2008 and 2018. A total of 1237 adult patients in the last days of life were included and cared for by palliative care teams trained in PAMPA©. An audit was conducted before and after the implementation of the Program, which is still going on. The median range of follow up into five centres from the beginning of the pathway until death varied from 16 to 178 hours. Care goals were compared: symptom control, communication, multidimensional needs, hydration and nutrition, documentation of interventions and post-mortem care. The overall analysis showed an improvement in the number of records (p = 0.001). The goal of communication on care plan to the patient showed no difference (p = 0.173). Continuous training, support and permanent teams supervision were carried out and perceptions and impact of the implementation were registered. The main emerging items of the qualitative analysis were: attitudes towards the program, fundamental contributions, strengths, weaknesses and subjective definition of the program, recognition of institutional cultural singularities and its influence on care. PAMPA© demonstrated its feasibility as a model of end of life care for patients and families, based on international quality standards.

[Argentine consensus on late-onset Pompe's disease]

Pompe's disease (PD) is an infrequent metabolic autosomic recessive disorder produced by the lack or deficiency of the acid alpha-glucosidase lysosomal enzyme in tissues of involved individuals. Delayed-onset PD is considered whenever symptoms onset start after one year of age. We present an update of the recommendations for the management of delayed-onset PD, taking as reference the guidelines from the Argentine Consensus for diagnosis, treatment and follow-up of PD published in 2013. The present consensus gathered several experts in PD in the areas of internal medicine, laboratory diagnosis, neuropathology, pulmonology, nutrition, neurology, metabolic and neuromuscular disorders as well as rehabilitation to perform an update of the literature of delayed-onset PD, with special attention on relevant information published within the last 4 years. The entire working group approved the final version of the consensus. Each participant provided a declaration of conflict of interest. As a result, it is an update of the previous Argentine PD Consensus with focus on the delayed-onset presentation of the disease. Being such infrequent disorder, available data were rather limited and thus, the recommendations represent expert opinions.

[Argentina enacts first law on medical use of the cannabis plant. History and perspectives]

In the last few years, great expectations have risen in the society concerning the eventual therapeutic usefulness of compounds derived from the cannabis plant. It is well known that these compounds are being used in treating certain health conditions, either through medical prescription or self-administration. Extreme opinions range from believing that it is a harmful and dangerous drug to sustaining that it is a panacea. However, the sheer existence of an endocannabinoid system in the brain compels us to study its dimensions and derivations thoroughly. It is expected that controversies and knowledge gaps will be clarified within the framework of this new law. Prohibitionism should not be a category of analysis. Regardless of the therapeutic effects of cannabinoid compounds, demonstrated or to be demonstrated, there are already severe restrictions on their use, which mirror the still existing restrictions to the use of opioids (drugs of definite utility but on which a huge taboo persists). This review presents the first Argentine law on the medical use of cannabis. Milestones in the history of marijuana at the national level are pointed out, which are inextricably linked to world trends either in favor or against prohibition. The current status of the use of cannabis oil in the country and evidences for its therapeutic value are also analyzed. Evidences on its therapeutic value are also analyzed as well as the current status of the use of cannabis oil in our country.

[Medicine at the "edge of chaos". Life, entropy and complexity]

The aim of this paper is to help physicians and health professionals, who constantly seek to improve their knowledge for the benefit of the ill, to incorporate new conceptual and methodological tools to understand the complexity inherent to the field of medicine. This article contains notions that are unfamiliar to these professionals and are intended to foster reflection and learning. It poses the need to define life from a thermodynamic point of view, linking it closely to complex systems, nonlinear dynamics and chaotic behavior, as well as to redefine conventional physiological control mechanisms based on the concept of homeostasis, and to travel the path that starts with the search for extraterrestrial life up to exposing medicine "near the edge of chaos". Complexity transcends the biological aspects; it includes a subjective and symbolic/social dimension. Viewing disease as a heterogeneous and multi-causal phenomenon can give rise to new approaches for the sick.

[Thymic neuroendocrine carcinoma with Pompe's disease of the adult]

Pompe disease (glycogenosis type II) is an inherited autosomal recessive lysosomal storage disease caused by a deficiency of acid alpha-glucosidase. Thymic neuroendocrine tumors, are primary thymic neoplasms with neuroendocrine differentiation that generally present as a mass within the anterior mediastinum. Both diseases are considered rare. To our knowledge the co-existence of Pompe disease and thymic neuroendocrine tumor in the same patient has not been previously reported. We could not find biological plausibility between both diseases. Further studies are needed to confirm the finding and to further increase our understanding of this association. Clinical data from epidemiological studies, case reports, case series and small formal open or controlled clinical trials may define both clinical plausibility and causality between the two conditions.

[Analysis of factors associated with chronic hypercapnia in patients with myotonic dystrophy]

Myotonic dystrophy (DM) is the most common dystrophy in adults. Several factors may explain the chronic CO2 retention. The selection of patients, different clinical stages and evaluation forms may explain the differing results obtained. Our objectives were to characterize respiratory function and to evaluate factors associated with chronic retention of CO2 in DM. We included 27 consecutive ambulatory and stable patients who were allocated into normocapnic and hypercapnic groups (PaCO2 ≥ 43 mmHg). Forced vital capacity (FVC), maximum static pressure, voluntary apnea time, Epworth scale and arterial blood gases were measured. The CO2 chemosensitivity was assessed using CO2 rebreathing (Read method). The slope ΔP0.1/ΔPCO2 expressed the CO2 chemosensitivity. A 59.3% (16/27) presented hypercapnia. FVC and respiratory muscle strength were normal or showed mild to moderate decrease. No significant differences in these variables were found in both groups. Inadequate response to CO2 (slope ΔP0.1/ΔPCO2 low (< 0.1 cm H2O/mmHg) or flat) was associated with hypercapnia (p < 0.005). Chronic retention of CO2 represented 11.56 times higher risk of inadequate response to CO2. The group with low-flat slope ΔP0.1/ΔPCO2 showed higher PaCO2 (p = 0.0017) and more prolonged voluntary apnea time (p = 0.002). We conclude that in our patients with DM, chronic CO2 retention was associated with the presence of abnormalities of the central control of breathing. Our results allow explaining previous reports describing the striking frequency of postoperative respiratory failure and difficulties in the process of weaning from mechanical ventilation.

The use of full-setting non-invasive ventilation in the home care of people with amyotrophic lateral sclerosis-motor neuron disease with end-stage respiratory muscle failure: a case series

Introduction

Little has been written about the use of non-invasive ventilation in the home care of amyotrophic lateral sclerosis-motor neuron disease patients with end-stage respiratory muscle failure. Nocturnal use of non-invasive ventilation has been reported to improve daytime blood gases but continuous non-invasive ventilation dependence has not been studied in this regard. There continues to be great variation by country, economics, physician interest and experience, local concepts of palliation, hospice requirements, and resources available for home care. We report a case series of home-based amyotrophic lateral sclerosis-motor neuron disease patients who refused tracheostomy and advanced non-invasive ventilation to full-setting, while maintaining normal alveolar ventilation and oxygenation in the course of the disease. Since this topic has been presented in only one center in the United States and nowhere else, it is appropriate to demonstrate that this can be done in other countries as well.

Case presentation

We present here the cases of three Caucasian patients (a 51-year-old Caucasian man, a 45-year-old Caucasian woman and a 57-year-old Caucasian woman) with amyotrophic lateral sclerosis who developed continuous non-invasive ventilation dependence for 15 to 27 months without major complications and were able to maintain normal CO₂ and pulse oxyhemoglobin saturation despite a non-measurable vital capacity. All patients were wheelchair-dependent and receiving riluzole 50 mg twice a day. Patient one developed mild-to-moderate bulbar-innervated muscle weakness. He refused tracheostomy but accepted percutaneous gastrostomy. Patient two had two lung infections, acute bronchitis and pneumonia, which were treated with antibiotics and cough assistance at home. Patient three had three chest infections (bronchitis and pneumonias) and asthmatic episodes treated with antibiotics, bronchodilators and cough assistance at home. All patients had normal speech while receiving positive pressure; they died suddenly and with normal oxygen saturation.

Conclusions

Although warned that prognosis was poor as vital capacity diminished, our patients survived without invasive airway tubes and despite non-measurable vital capacity. No patient opted for tracheostomy. Our patients demonstrate the feasibility of resorting to full-setting non-invasive management to prolong survival, optimizing wellness and management at home, and the chance to die peacefully.

[Study of diaphragmatic muscle function during abdominal weight in normal subjects]

The effects of the abdominal weight with the intention of producing training of the diaphragm, have not been sufficiently evaluated. We studied the function of the diaphragm during the abdominal weight training and during associated changes in the respiratory pattern. Six normal volunteers were studied. Flow at the mouth at functional residual capacity (FRC) was obtained as well as gastric pressure (Pga), esophageal pressure (Pes), thoracic and abdominal movements, maximal inspiratory pressure and mean and maximal transdiaphragmatic pressure (Pdi and Pdi max). Pdi/Pdimax and the diaphragm tension-time index (TTdi) were calculated. Studied steps: normal pattern (NP), abdominal pattern (AP) and weight of 1, 2, 4 and 6 kg with NP and AP as well. We found 1) The AP was facilitated by the abdominal weight, 2) Only with 6 kg (NP and AP) the Pga at FRC increased significantly (p 0.001), 3) the Pdi followed the variations of the Pga and increased with all the AP (p < 0.001), 4) The index TTdi load reached a value of 0.05 ± 0.02 (p < 0.001). The charges did not increase this rate more than did the AP alone. Our findings suggest abdominal weight increases propioception related to the respiratory movements and descent of the diaphragm. The loads on the abdomen produce minor changes in mechanics of the diaphragm (1/3 of the load required to develop fatigue in normal subjects). Al least in normal subjects these changes appear to be insufficient to produce respiratory muscle training.

Making it possible to measure knowledge, experience and intuition in diagnosing lung injury severity: a fuzzy logic vision based on the Murray score

BACKGROUND

Murray score is the result of an equation that gives all its variables the same linear contribution and weight and makes use of consented cut-offs. Everyday physicians' vocabulary is full of terms (adjectives) like: little, small, low, high, etc. that they handle in an intuitive and not always linear way to make therapeutic decisions. The purpose of this paper is to develop a fuzzy logic (FL) vision of Murray's score variables to enable the measurement of physicians' knowledge, experience and intuition in diagnosing lung injury and test if they followed Murray's equation predictions.

METHODS

For a prospective survey carried out among a team of professionals (aged 29 to 53) in a University Hospital Intensive Care Unit, twelve physicians filled in two questionnaires. In the first one they had to define the ranks which should be categorized as normal, moderate and severe for three of four Murray variables. In another questionnaire, which represented all probable combinations of those categories, they had to tick the pulmonary condition as: no injury, mild, moderate, and ARDS. This procedure gave rise to a Fuzzy Inference System designed to provide the degree of severity as sensed by the group.

RESULTS

The survey showed fuzzy frontiers for the categories and fuzzy diagnosis. In all, 45% of the hypothetical patients (n 18,013) were equally diagnosed by the survey and Murray's equation, whereas another 51% was overestimated in one level by the survey. Physicians agreed with 96.5% of ARDS cases according to Murray's test but only 11.6% of its mild cases were equally diagnosed by the survey. Nonlinearity of the survey reasoning (high relevance to gas exchange and chest film) was apparent.

CONCLUSIONS

The contiguous categories of the variables confirm the existence of fuzzy frontiers. An overestimation was found in the surveyed group's interpretation of severity. This overestimation was mainly due to the different weight assigned to PO2/FiO2 and chest film variables. The FL approach made it possible to measure knowledge, experience and intuition as they appear in physicians' thinking. FL methodology could overcome a series of restrictions that current tests have due to cut-offs.

[Respiratory domain of revised amyotrophic lateral sclerosis. Functional Rating Scale]

Virtually all patients with amyotrophic lateral sclerosis will complain of dyspnea, which is perhaps the most distressing symptom of this devastating disease. The objective was to correlate respiratory domain of ALSFRS-R with forced vital capacity and maximal static pressures in the mouth. We designed a prospective study in 20 consecutive patients without dyspnea during 24 months. The global decline of ALSFRS-R was from 34.3 +/- 10.3 to 22.1 +/- 8.0 (p = 0.0325), the contribution of respiratory domain was irrelevant. Those who referred dyspnea (n: 12), forced vital capacity fell 41 +/- 21% of the initial value but with similar value of fall (46 +/- 23%) 8 patients did not referred dyspnea. Total score of ALSFRS-R correlated with forced vital capacity (litres), r: 0.73, p = 0.0016 and maximal inspiratory pressure (cm H2O), r: 0.84, p = 0.0038, but the fall of the forced vital capacity (%) did not correlate with dyspnea (r(s): 0.23, p = 0.1400). There was a moderate correlation between dyspnea and maximal inspiratory pressure (%), r(s): 0.58, p = 0.0300 and between dyspnea and maximal expiratory pressure (%), r(s): 0.49, p = 0.0400. We concluded that the respiratory functional deterioration could not be predicted using respiratory domain of ALSFRS-R. This suggests that respiratory domain of this scale does not replace to respiratory function testing measurements and, due to the respiratory insufficiency could not be clinically evident; performing pulmonary function tests provides an objective view and permit to make anticipatory actions.

[Variability of breathing pattern during inspiratory elastic load]

In humans, lung ventilation exhibits breath-to-breath variability and dynamics that are nonlinear, complex and chaotic. Our objective was to characterize the breathing pattern variational activity in anesthetized dogs (n: 8) breathing through threshold inspiratory elastic load (7 to 50 cm H2O). Starting from flow signal and tracheal and esophageal pressures, we analyzed inspiratory time (Ti), timing (expiratory time, Te; total time, Ttot; and Ti/Ttot) and central drive (Vt/Ti) and variables related to it (tidal volume, Vt and pulmonary ventilation, Ve). We measured gross variability (variances), low frequency oscillations (spectral analysis), and short term memory (autocorrelation analysis). Loading decreased variance of the mean values of Te, Ttot, Vt and Vt/Ti (p < 0.05); the mean of variances for Ti/Ttot increased (p < 0.005) while it decreased for Vt and Vt/Ti (p < 0.05). In general, percent of data recordings with low frequency oscillations (OB%) decreased (p < 0.02). During heavy load, timing parameters percent of data recordings with autocorrelations (AU%) did not change, but Vt and its related parameters decreased their AU% (p < 0.005). There was a positive correlation (r: 0.955, p < 0.001) between the existence of low frequency oscillations and autocorrelations for Vt and its related parameters, while timing variables did not show such a correlation. In conclusion, threshold elastic load induced a monotonous respiratory pattern. The short term memory decreased during inspiratory stage while increased during expiratory stage. These changes occurred during anesthesia suggesting that certain suprapontine structures may not be obligatory to induce them.

[Functional respiratory evolution in two patients with emphysema and pulmonary fibrosis]

Combined pulmonary fibrosis and emphysema (CPFE) is a frequently under-diagnosed condition. Isolated pulmonary function tests (PFT) can give rise to misinterpretations. We have found no reports on these patients' spirometric progression. We describe two cases of CPFE, showing long-term functional evolution to have a more accurate understanding of current spirometric values. The most relevant findings are: 1) spirometry with discrete functional alterations in the presence of a marked dyspnea and the need, in one patient, for chronic oxygen therapy; and 2) functional evolution reflecting "pseudonormalisation" of the initial obstructive spirometric pattern, possibly as a result of fibrosis development. A mild obstructive defect in a patient with chronic airflow limitation and marked impairment of his/her clinical status and functional class should alert on the possibility of associated pulmonary fibrosis. A computed tomography (CT) and previous PFTs will allow a better understanding of this condition.

[Relationship between Hoover sign, functional and variables, and curvature radius in patients with obstructive pulmonary disease]

The purpose of the present study was: 1) to relate the Hoover sign -SH (+)- with several functional (spirometry and lung volumes) and radiographic (AP x-ray) parameters, 2) to characterize the changes in diaphragmatic curvature radius and the efficiency and to establish some relationships with the functional and radiographic parameters. Fifteen patients with COPD (SH (+), n: 8) were studied. The radius was determined in the right hemidiaphragm after maximal inspired and expired x-ray. The SH (+) was found in more severely obstructed patients (FEV1%, p 0.005%) and with high degree of air trapping (RV/TLC %, p 0.01). The expiratory radius (Re) was higher (p 0.05), and their efficiency (1/Re), was minor (p 0.05). The FEV1% correlated with the degree of hyperinflation according to TLC % (r -0.58, p 0.022) and with air trapping according to RV % (r -0.77, p 0.0008). The patients with low FEV1% showed high Re (r -0.61, p 0.015) and decreased diaphragmatic efficiency during expiration (1/Re) according to 1/Re = 0.093 cm-1 + 0.0012 cm-1* FEV1% (r 0.688, p 0.0054). The FEV1 correlated with the diaphragmatic movement (r 0.71, p 0.003). The PaCO2 correlated with the TLC % (r 0.534, p 0.04), the RV% (r 0.62, p 0.014) and with the radiographic parameters of hyperinflation (r 0.546, p 0.035) and air trapping (r 0.528, p 0.043). The presence of Hoover sign suggest severe bronchial obstruction, diaphragmatic flattening, increase of curvature radius, decrease of mobility and efficiency.