Clinical correlates of respiratory disorders in patients with severe multiple sclerosis: A cross-sectional cohort

BACKGROUND

Respiratory disorders remain incompletely described in multiple sclerosis (MS), even though they are a frequent cause of death.

METHODS

The objective was to describe respiratory disorders in MS patients with Expanded Disability Status Score (EDSS) ⩾ 6.5. Diaphragm dysfunction was defined by at least two of the seven criteria: clinical signs, inspiratory recruitment of neck muscles during wakefulness, reduced upright vital capacity (VC) < 80%, upright-to-supine VC ⩾ 15% of upright VC, decrease in Maximal Inspiratory Pressure < 60%, phasic activation of inspiratory neck muscles during sleep, and opposition of thoracic and abdominal movements during sleep. Cough weakness was defined by a peak cough flow < 270 L/min and/or need for cough assist. Sleep apnea syndrome was defined by an apnea-hypopnea index ⩾ 15.

RESULTS

Notably, 71 MS patients were included: median age 54 [48, 61] years; median disease duration 21.4 [16.0, 31.4] years. Of these, 52 patients had one or more respiratory disorders; diaphragm dysfunction was the most frequent (n = 34). Patients with diaphragm dysfunction and cough weakness were more disabled. The fatigue score and the cognitive evaluations did not differ between the groups. Five patients required non-invasive ventilation.

CONCLUSION

Respiratory disorders are frequent in severe MS, mostly diaphragm dysfunction. Of interest, instrumental interventions are available to address these disorders.

Increasing sweep gas flow reduces respiratory drive and dyspnea in non-intubated veno-arterial ECMO patients - a pilot study

BACKGROUND.

Data on assessment and management of dyspnea in patients on veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for cardiogenic shock are lacking. We hypothesized that increasing sweep gas flow through the VA-ECMO oxygenator may decrease dyspnea in non-intubated VA-ECMO patients exhibiting clinically significant dyspnea, with a parallel reduction in respiratory drive.

METHODS.

Non-intubated, spontaneously breathing, supine patients on VA-ECMO for cardiogenic shock who presented with a visual analog dyspnea scale (dyspnea-VAS) ≥ 40/100 mm were included. Sweep gas flow was increased up to +6 L/min by three steps of +2 L/min each. Dyspnea was assessed with dyspnea-VAS and Multidimensional Dyspnea Profile. The respiratory drive was assessed by the electromyographic activity of the alae nasi and parasternal muscles.

RESULTS.

We included 21 patients. On inclusion, median dyspnea-VAS was 50 ([interquartile range] 45-60) mm and sweep gas flow was 1.0 L/min (0.5-2.0). An increase in sweep gas flow significantly decreased dyspnea-VAS (50[45-60] at baseline vs 20[10-30] at 6L/min; p<0.001). The decrease in dyspnea was greater for the sensory component of dyspnea (-50%[43-75]) than for the affective and emotional components (-17%[0-25] and -12%[0-17], p<0.001). An increase in sweep gas flow significantly decreased electromyographic activity of the alae nasi and parasternal muscles (-23%[36-10] and -20[41-0], p<0.001). There was a significant correlation between the sweep gas flow and the dyspnea-VAS (r=-0.91 95%CI[-0.94, -0.87]), between the respiratory drive and the sensory component of dyspnea (r=0.29 95%CI[0.13, 0.44]), between the respiratory drive and the affective component of dyspnea (r=0.29 95%CI[0.02, 0.54]) and between the sweep gas flow and the alae nasi and parasternal (r=-0.31 95%CI[-0.44, -0.22] and r=-0.25 95%CI[-0.44, -0.16]).

CONCLUSION.

In critically ill patients with VA-ECMO, an increase in sweep gas flow through the oxygenation membrane decreases dyspnea, possibly mediated by a decrease in respiratory drive.

Defective exercise-related expiratory muscle recruitment in patients with PHOX2B mutations: A clue to neural determinants of the congenital central hypoventilation syndrome

INTRODUCTION AND OBJECTIVES

The human congenital central hypoventilation syndrome (CCHS) is caused by mutations in the PHOX2B (paired-like homeobox 2B) gene. Genetically engineered PHOX2B rodents exhibit defective development of the brainstem retrotrapezoid nucleus (RTN), a carbon dioxide sensitive structure that critically controls expiratory muscle recruitment. This has been linked to a blunted exercise ventilatory response. Whether this can be extrapolated to human CCHS is unknown and represents the objective of this study.

MATERIALS AND METHODS

Thirteen adult CCHS patients and 13 healthy participants performed an incremental symptom-limited cycle cardiopulmonary exercise test. Responses were analyzed using guideline approaches (ventilation V'E, tidal volume VT, breathing frequency, oxygen consumption, carbon dioxide production) complemented by a breathing pattern analysis (i.e. expiratory and inspiratory reserve volume, ERV and IRV).

RESULTS

A ventilatory response occurred in both study groups, as follows: V'E and VT increased in CCHS patients until 40 W and then decreased, which was not observed in the healthy participants (p<0.001). In the latter, exercise-related ERV and IRV decreases attested to concomitant expiratory and inspiratory recruitment. In the CCHS patients, inspiratory recruitment occurred but there was no evidence of expiratory recruitment (absence of any ERV decrease, p<0.001).

CONCLUSIONS

Assuming a similar organization of respiratory rhythmogenesis in humans and rodents, the lack of exercise-related expiratory recruitment observed in our CCHS patients is compatible with a PHOX2B-related defect of a neural structure that would be analogous to the rodents' RTN. Provided corroboration, ERV recruitment could serve as a physiological outcome in studies aiming at correcting breathing control in CCHS.

"In their own words": delineating the contours of dyspnea invisibility in patients with advanced chronic obstructive pulmonary disease from quantitative discourse analysis

BACKGROUND

Dyspnea conveys an upsetting or distressing experience of breathing awareness. It heavily weighs on chronic respiratory disease patients, particularly when it persists despite maximal treatment of causative abnormalities. The physical, psychological and social impacts of persistent dyspnea are ill-appreciated by others. This invisibility constitutes a social barrier and impedes access to care. This study aimed to better understand dyspnea invisibility in patients with chronic obstructive pulmonary disease (COPD) through quantitative discourse analysis.

METHODS

We conducted a lexicometric analysis (lemmatization, descending hierarchical classification, multicomponent analysis, similarity analysis) of 11 patients' discourses (6 men, severe COPD; immediate postexacerbation rehabilitation) to identify semantic classes and communities, which we then confronted with themes previously identified using interpretative phenomenological analysis (IPA).

RESULTS

Class#1 ("experience and need for better understanding"; 38.9% of semantic forms, 50% of patients) illustrates the gap that patients perceive between their experience and what others see, confirming the importance of dyspnea invisibility in patients' concerns. Class#2 ("limitations"; 28.7% of forms) and Class#3 (management"; 13.1% of forms) point to the weight of daily limitations in performing basic activities, of the need to accept or adapt to the constraints of the disease. These three classes matched previously identified IPA-derived themes. Class#4 ("hospitalization"; 18.2% of forms) points to the importance of interactions with the hospital, especially during exacerbations, which constitutes novel information.

CONCLUSIONS

Lexicometry confirms the importance of dyspnea invisibility as a burden to COPD patients.

Sensory interventions to relieve dyspnoea in critically ill mechanically ventilated patients

BACKGROUND

In critically ill patients receiving mechanical ventilation, dyspnoea is frequent, severe and associated with an increased risk of neuropsychological sequelae. We evaluated the efficacy of sensory interventions targeting the brain rather than the respiratory system to relieve dyspnoea in mechanically ventilated patients.

METHODS

Patients receiving mechanical ventilation for ≥48 h and reporting dyspnoea (unidimensional dyspnoea visual analogue scale (Dyspnoea-VAS)) first underwent increased pressure support and then, in random order, auditory stimulation (relaxing music versus pink noise) and air flux stimulation (facial versus lower limb). Treatment responses were assessed using Dyspnoea-VAS, the Multidimensional Dyspnea Profile and measures of the neural drive to breathe (airway occlusion pressure (P 0.1) and electromyography of inspiratory muscles).

RESULTS

We included 46 patients (tracheotomy or intubation n=37; noninvasive ventilation n=9). Increasing pressure support decreased Dyspnoea-VAS by median 40 mm (p<0.001). Exposure to music decreased Dyspnoea-VAS compared with exposure to pink noise by median 40 mm (p<0.001). Exposure to facial air flux decreased Dyspnoea-VAS compared with limb air flux by median 30 mm (p<0.001). Increasing pressure support, but not music exposure and facial air flux, reduced P 0.1 by median 3.3 cmH2O (p<0.001).

CONCLUSIONS

In mechanically ventilated patients, sensory interventions can modulate the processing of respiratory signals by the brain irrespective of the intensity of the neural drive to breathe. It should therefore be possible to alleviate dyspnoea without resorting to pharmacological interventions or having to infringe the constraints of mechanical ventilation lung protection strategies by increasing ventilatory support.

Dyspnoea relief as an inherent benefit of high flow nasal cannula therapy: A laboratory randomized trial in healthy humans

BACKGROUND AND OBJECTIVE

Persistent dyspnoea is a public health issue for which the therapeutic arsenal is limited. This study tested high-flow nasal cannula therapy (HFNT) as a means to alleviate experimental dyspnoea.

METHODS

Thirty-two healthy subjects underwent an experimental dyspnoea induced by thoracoabdominal elastic loading. HFNT was administered with alternately FiO2 of 100% (HFNT100) or 21% (HFNT21). The sensory (S-VAS) and affective (A-VAS) components of dyspnoea, transcutaneous CO2 pressure (PtcCO2 ), pulse-oximetry oxygen saturation (SpO2 ), heart rate, respiratory rate and skin galvanometry were monitored continuously. Three experimental sessions of 8 min were conducted: the first session consisted in familiarization with the experimental dyspnoea and the next two sessions tested the effects of HFNT100 and HFNT21 alternatively in a randomized order.

RESULTS

HFNT21 and HFNT100 significantly reduced dyspnoea, respectively of ∆A-VAS = 0.80 cm [-0.02-1.5]; p = 0.007 and ∆A-VAS = 1.00 cm [0.08-1.75]; p < 0.0001; ∆S-VAS = 0.70 cm [-0.15-1.98]), p < 0.0001 and ∆S-VAS = 0.70 cm [0.08-1.95]), p = 0.0002) with no significant difference between HFNT21 and HFNT100. HFNT did not significantly alter the respiratory rate or the heart rate, reduced PtcCO2 only on room air and GSR under both experimental conditions.

CONCLUSION

HFNT was associated with a statistically significant reduction in the intensity of the sensory and affective components of dyspnoea, independent of oxygen addition. This relief of laboratory dyspnoea could result from a reduction of afferent-reafferent mismatch.

Short-term cognitive loading deteriorates breathing pattern and gas exchange in adult patients with congenital central hypoventilation syndrome

Question

Human PHOX2B mutations result in life-threatening sleep-related hypoventilation (congenital central hypoventilation syndrome, CCHS). Most patients retain ventilatory activity when awake through a respiratory-related cortical network. We hypothesised that this need to mobilise cortical resources to breathe would lead to breathing-cognition interferences during cognitive loading.

Patients and methods

Seven adult CCHS patients (five women; median age 21) performed standard neuropsychological tests (paced auditory serial addition test - calculation capacity, working memory, sustained and divided attention; trail making test - visuospatial exploration capacity, cognitive processing speed, attentional flexibility; Corsi block-tapping test - visuospatial memory, short-term memory, working memory) during unassisted breathing and under ventilatory support. Ventilatory variables and transcutaneous haemoglobin oxygen saturation were recorded. Cortical connectivity changes between unassisted breathing and ventilatory support were assessed using electroencephalographic recordings (EEG).

Results

Baseline performances were lower than expected in individuals of this age. During unassisted breathing, cognitive loading coincided with increased breathing variability, and decreases in oxygen saturation inversely correlated with an increasing number of apnoeic cycles per minute (rho -0.46, 95% CI -0.76 to -0.06, p=0.01). During ventilatory support, cognitive tasks did not disrupt breathing pattern and were not associated with decreased oxygen saturation. Ventilatory support was associated with changes in EEG cortical connectivity but not with improved test performances.

Conclusions

Acute cognitive loads induce oxygen desaturation in adult CCHS patients during unassisted breathing, but not under ventilatory support. This justifies considering the use of ventilatory support during mental tasks in CCHS patients to avoid repeated episodes of hypoxia.

'Involve me and I learn': an experiential teaching approach to improve dyspnea awareness in medical residents

BACKGROUND

Dyspnea is a frightening and debilitating experience. It attracts less attention than pain ('dyspnea invisibility'), possibly because of its non-universal nature. We tested the impact of self-induced experimental dyspnea on medical residents.

MATERIALS AND METHODS

During a teaching session following the principles of experiential learning, emergency medicine residents were taught about dyspnea theoretically, observed experimental dyspnea in their teacher, and personally experienced self-induced dyspnea. The corresponding psychophysiological reactions were described. Immediate and 1-year evaluations were conducted to assess course satisfaction (overall 0-20 grade) and the effect on the understanding of what dyspnea represents for patients.

RESULTS

Overall, 55 emergency medicine residents participated in the study (26 men, median age 26 years). They were moderately satisfied with previous dyspnea teaching (6 [5-7] on a 0-10 numerical rating scale [NRS]) and expressed a desire for an improvement in the teaching (8 [7-9]). Immediately after the course they reported improved understanding of patients' experience (7 [6-8]), which persisted at 1 year (8 [7-9], 28 respondents). Overall course grade was 17/20 [15-18], and there were significant correlations with experimental dyspnea ratings (intensity: r = 0.318 [0.001-0.576], p = 0.043; unpleasantness: r = 0.492 [0.208-0.699], p = 0.001). In multivariate analysis, the only factor independently associated with the overall course grade was 'experiential understanding' (the experimental dyspnea-related improvement in the understanding of dyspneic patients' experience). A separate similar experiment conducted in 50 respiratory medicine residents yielded identical results.

CONCLUSIONS

This study suggests that, in advanced medical residents, the personal discovery of dyspnea can have a positive impact on the understanding of what dyspnea represents for patients. This could help fight dyspnea invisibility.

'You can't feel what we feel': Multifaceted dyspnoea invisibility in advanced chronic obstructive pulmonary disease examined through interpretative phenomenological analysis

BACKGROUND

More than a symptom, dyspnoea is an existential experience shaping the lives of those afflicted, particularly when its persistence despite maximal pathophysiological treatments makes it pervasive. It is, however, insufficiently appreciated by concerned people themselves, family members, healthcare professionals and the public (dyspnoea invisibility), limiting access to appropriate care and support.

AIM

To provide a better understanding of dyspnoea experiences and its invisibility.

DESIGN

Interpretative phenomenological analysis of data collected prospectively through in-depth semi-structured interviews.

SETTING/PARTICIPANTS

Pulmonary rehabilitation facility of a tertiary care university hospital; 11 people (six men, five women) with severe chronic obstructive pulmonary disease (stages 3 and 4 of the 4-stage international GOLD classification) admitted for immediate post-exacerbation rehabilitation.

RESULTS

We identified several types of dyspnoea invisibility depending on temporality and interlocutors: (1) invisibility as a symptom to oneself; (2) invisibility as a symptom to others; (3) invisibility as an experience that cannot be shared; (4) invisibility as an experience detached from objective measurements; (5) invisibility as an experience that does not generate empathic concern. The notion of invisibility was present in all the identified experiential dimensions of dyspnoea. It was seen as worsening the burden of the disease and as self-aggravating through self-isolation and self-censorship.

CONCLUSIONS

The study confirmed that dyspnoea invisibility is a reality for people with advanced chronic obstructive pulmonary disease. It shows dyspnoea invisibility to be a multifaceted burden. Future research should aim at identifying individual and collective measures to overcome dyspnoea invisibility.

Prognostic Value of the Intensive Care Respiratory Distress Observation Scale on ICU Admission

BACKGROUND

The association between dyspnea and mortality has not been demonstrated in the ICU setting. We tested the hypothesis that dyspnea (self-reported respiratory discomfort) or its observational correlates (5-item intensive care Respiratory Distress Observation Scale [IC-RDOS]) assessed on ICU admission would be associated with ICU mortality.

METHODS

Ancillary analysis of single-center data prospectively collected from 220 communicative ICU subjects allocated to a derivation cohort of 120 subjects and a separate validation cohort of 100 subjects. Dyspnea was assessed dichotomously (yes/no), with a dyspnea visual analog scale (measured in mm), and IC-RDOS was calculated. Multivariate logistic regression was used to identify factors associated with ICU and hospital mortality.

RESULTS

Dyspnea was reported by 69 (58%; median 45 [interquartile range [IQR] 32-60] mm) and 47 (47%; 38 [IQR 26-48] mm) subjects in the derivation and validation cohorts, respectively. IC-RDOS was 2.3 (1.2-3.1) and 2.4 (1.3-2.8), respectively. IC-RDOS values were higher in subjects with dyspnea than in subjects without dyspnea in both the derivation cohort (2.6 [2.2-4.6] vs 1.4 [0.9-2.4], P < .001) and the validation cohort (2.6 [2.3-4.4] vs 2.2 [1.0-2.8], P < .001). On multivariate analysis of the derivation cohort, admission for hemorrhagic shock (odds ratio 13.98), IC-RDOS (odds ratio 1.77), and Simplified Acute Physiology Score II (odds ratio 1.10) was associated with ICU mortality. Areas under the receiving operating characteristic curve of IC-RDOS to predict ICU mortality were 0.785 and 0.794 in the derivation and validation cohorts, respectively.

CONCLUSIONS

IC-RDOS, an observational correlate of dyspnea, but not dyspnea itself, was associated with higher mortality in ICU subjects.

Respiratory distress observation scales to predict weaning outcome

Background

Whether dyspnea is present before starting a spontaneous breathing trial (SBT) and whether it may affect the outcome of the SBT is unknown. Mechanical Ventilation—Respiratory Distress Observation Scale (MV-RDOS) has been proposed as a reliable surrogate of dyspnea in non-communicative intubated patients. In the present study, we sought (1) to describe the evolution of the MV-RDOS during a SBT and (2) to investigate whether MV-RDOS can predict the outcome of the SBT.

Methods

Prospective, single-center study in a twenty-two bed ICU in a tertiary center. Patients intubated since more 48 h who had failed a first SBT were eligible if they meet classical readiness to wean criteria. The MV-RDOS was assessed before, at 2-min, 15-min and 30-min (end) of the SBT. The presence of clinically important dyspnea was inferred by a MV-RDOS value ≥  2.6.

Results

Fifty-eight patients (age 63 [51–70], SAPS II 66 [51–76]; med [IQR]) were included. Thirty-three (57%) patients failed the SBT, whose 18 (55%) failed before 15-min. Twenty-five (43%) patients successfully passed the SBT. A MV-RDOS ≥ 2.6 was present in ten (17%) patients before to start the SBT. All these ten patients subsequently failed the SBT. A MV-RDOS ≥ 2.6 at 2-min predicted a SBT failure with a 51% sensibility and a 88% specificity (AUC 0.741 95% confidence interval [CI] 0.616–0.866, p = 0.002). Best cut-off value at 2-min was 4.3 and predicted SBT failure with a 27% sensibility and a 96% specificity.

Conclusion

Despite patients met classical readiness to wean criteria, respiratory distress assessed with the MV-RDOS was frequent at the beginning of SBT. Measuring MV-RDOS before to initiate a SBT could avoid undue procedure and reduce patient’s exposure to unnecessary mechanical ventilation weaning failure and distress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04028-7.

Lower Rate of Daily Smokers With Symptomatic COVID-19: A Monocentric Self-Report of Smoking Habit Study

Background: Identification of prognostic factors in COVID-19 remains a global challenge. The role of smoking is still controversial. Methods: PCR-positive in- and outpatients with symptomatic COVID-19 from a large French University hospital were systematically interviewed for their smoking status, use of e-cigarette, and nicotinic substitutes. The rates of daily smokers in in- and outpatients were compared using the same smoking habit questionnaire to those in the 2019 French general population, after standardisation for sex and age. Results: The inpatient group was composed of 340 patients, median age of 66 years: 203 men (59.7%) and 137 women (40.3%), median age of both 66 years, with a rate of 4.1% daily smokers (CI 95% [2.3-6.9]) (5.4% of men and 2.2% of women). The outpatient group was composed of 139 patients, median age of 44 years: 62 men (44.6%, median age of 43 years) and 77 women (55.4%, median age of 44 years). The daily smoker rate was 6.1% (CI 95% [2.7-11.6], 5.1% of men and 6.8% of women). Amongst inpatients, daily smokers represented 2.2 and 3.4% of the 45 dead patients and of the 29 patients transferred to ICU, respectively. The rate of daily smokers was significantly lower in patients with symptomatic COVID-19, as compared to that in the French general population after standardisation by age and sex, with standardised incidence ratios (SIRs) of 0.24 [0.12-0.48] for outpatients and 0.24 [0.14-0.40] for inpatients. Conclusions: Daily smoker rate in patients with symptomatic COVID-19 is lower as compared to the French general population.

Lifting dyspnoea invisibility: COVID-19 face masks, the experience of breathing discomfort, and improved lung health perception - a French nationwide survey

QUESTION ADDRESSED

In contrast with pain, dyspnoea is not visible to the general public who lack the corresponding experiential baggage. We tested the hypotheses that the generalised use of face masks to fight SARS-CoV2 dissemination could change this and sensitise people to respiratory health.

METHODS

General population polling (1012-person panel demographically representative of the adult French population -quota sampling method-; 517 women, 51%). 860 (85%) answered "no" to "treated for a chronic respiratory disease" ("respiratory healthy", RH) and 152 "yes" ("respiratory disease", RD). 14% of RH respondents reported having a close family member treated for a chronic respiratory disease (RH-family+ and RH-family-). Respondents described mask-related attitudes, beliefs, inconveniencies, dyspnoea, and changes in their respiratory health vision . RESULTS: Compliance with masks was high (94.7%). Dyspnoea ranked first among mask inconveniencies (RD 79.3%, RH 67.3%, p=0.013). "Air hunger" was the main sensory dyspnoea descriptor. Mask-related dyspnoea was independently associated with belonging to RH-family+ (Odds Ratio [OR] [95% confidence interval (CI)]: 1.85 [1.16-2.98]) and removing masks to improve breathing (OR 5.21 [3.73-7.28]). It was negatively associated with considering masks effective to protect others (OR]: 0.42 [0.25-0.75]). Half the respondents were more concerned with their respiratory health since wearing masks; 41% reported better understanding patients' experiences.

ANSWER TO THE QUESTION

Wearing protective face masks leads to the mass discovery of breathing discomfort. It raises the public's awareness of what respiratory diseases involve and sensitises to the importance of breathing. These data should be used as the fulcrum of respiratory-health-oriented communication actions.

L’atteinte de structures neurologiques centrales explique-elle le défaut de perception des sensations respiratoires constaté au cours de l’infection à SARS CoV 2 ?

Introduction

Méthodes

Résultats et Conclusion

Prevalence of hyposmia and hypogeusia in 390 COVID-19 hospitalized patients and outpatients: a cross-sectional study

Anecdotal evidence rapidly accumulated during March 2020 from sites around the world that sudden hyposmia and hypogeusia are significant symptoms associated with the SARS-CoV-2 pandemic. Our objective was to describe the prevalence of hyposmia and hypogeusia and compare it in hospitalized and non-hospitalized COVID-19 patients to evaluate an association of these symptoms with disease severity. We performed a cross-sectional survey during 5 consecutive days in March 2020, within a tertiary referral center, associated outpatient clinic, and two primary care outpatient facilities in Paris. All SARS-CoV-2-positive patients hospitalized during the study period and able to be interviewed (n = 198), hospital outpatients seen during the previous month (n = 129), and all COVID-19-highly suspect patients in two primary health centers (n = 63) were included. Hospitalized patients were significantly more often male (64 vs 40%) and older (66 vs 43 years old in median) and had significantly more comorbidities than outpatients. Hyposmia and hypogeusia were reported by 33% of patients and occurred significantly less frequently in hospitalized patients (12% and 13%, respectively) than in the health centers' outpatients (33% and 43%, respectively) and in the hospital outpatients (65% and 60%, respectively). Hyposmia and hypogeusia appeared more frequently after other COVID-19 symptoms. Patients with hyposmia and/or hypogeusia were significantly younger and had significantly less respiratory severity criteria than patients without these symptoms. Olfactory and gustatory dysfunction occurs frequently in COVID-19, especially in young, non-severe patients. These symptoms might be a useful tool for initial diagnostic work-up in patients with suspected COVID-19.

Association of Clinical, Biological, and Brain Magnetic Resonance Imaging Findings With Electroencephalographic Findings for Patients With COVID-19

Importance

There is evidence of central nervous system impairments associated with coronavirus disease 2019 (COVID-19) infection, including encephalopathy. Multimodal monitoring of patients with COVID-19 may delineate the specific features of COVID-19-related encephalopathy and guide clinical management.

Objectives

To investigate clinical, biological, and brain magnetic resonance imaging (MRI) findings in association with electroencephalographic (EEG) features for patients with COVID-19, and to better refine the features of COVID-19-related encephalopathy.

Design, Setting, and Participants

This retrospective cohort study conducted in Pitié-Salpêtrière Hospital, Paris, France, enrolled 78 hospitalized adults who received a diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-Cov2) and underwent EEG between March 30 and June 11, 2020.

Exposures

Detection of SARS-CoV-2 from a nasopharyngeal specimen using a reverse transcription-polymerase chain reaction assay or, in the case of associated pneumonia, on a computed tomography scan of the chest.

Main Outcomes and Measures

Data on the clinical and paraclinical features of the 78 patients with COVID-19 were retrieved from electronic patient records.

Results

Of 644 patients who were hospitalized for COVID-19, 78 (57 men [73%]; mean [SD] age, 61 [12] years) underwent EEG. The main indications for EEG were delirium, seizure-like events, and delayed awakening in the intensive care unit after stopping treatment with sedatives. Sixty-nine patients showed pathologic EEG findings, including metabolic-toxic encephalopathy features, frontal abnormalities, periodic discharges, and epileptic activities. Of 57 patients who underwent brain MRI, 41 showed abnormalities, including perfusion abnormalities, acute ischemic lesions, multiple microhemorrhages, and white matter-enhancing lesions. Fifty-five patients showed biological abnormalities, including dysnatremia, kidney failure, and liver dysfunction, the same day as the EEG. The results of cerebrospinal fluid analysis were negative for SARS-Cov-2 for all tested patients. Nine patients who had no identifiable cause of brain injury outside COVID-19 were further isolated; their brain injury was defined as COVID-19-related encephalopathy. They represented 1% (9 of 644) of patients with COVID-19 requiring hospitalization. Six of these 9 patients had movement disorders, 7 had frontal syndrome, 4 had brainstem impairment, 4 had periodic EEG discharges, and 3 had MRI white matter-enhancing lesions.

Conclusions and Relevance

The results from this cohort of patients hospitalized with COVID-19 suggest there are clinical, EEG, and MRI patterns that could delineate specific COVID-19-related encephalopathy and guide treatment strategy.

Continuous positive airway pressure to avoid intubation in SARS-CoV-2 pneumonia: a two-period retrospective case-control study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause severe pneumonia requiring invasive mechanical ventilation [1], in the context of atypical acute respiratory distress syndrome (ARDS) [2]. The magnitude of the epidemic places an unprecedented pressure on intensive care units (ICUs), making avoidance of intubation a critical issue.

COVID-19 pneumonia can be life-threatening. Given the unprecedented burden placed on ICU resources by the epidemic, avoiding intubation is a major issue. This study suggests that CPAP can achieve this objective.https://bit.ly/2X4Q8Zj

Intensity and quality of exertional dyspnoea in patients with stable pulmonary hypertension

Dynamic hyperinflation is observed during exercise in 60% of patients with clinically stable pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH), intensifying exertional dyspnoea. The impact of dynamic changes in respiratory mechanics during exercise on qualitative dimensions of dyspnoea in these patients has not been evaluated.

26 patients (PAH n=17; CTEPH n=9) performed an incremental symptom-limited cycle exercise test. Minute ventilation (V′E), breathing pattern, operating lung volumes and dyspnoea intensity were assessed throughout exercise. Dyspnoea quality was serially assessed during exercise using a three-item questionnaire (dyspnoea descriptors). The inflection point of tidal volume (VT) relative to V′E was determined for each incremental test. Changes in inspiratory capacity during exercise defined two groups of patients: hyperinflators (65%) and non-hyperinflators (35%). Multidimensional characterisation of dyspnoea was performed after exercise using the Multidimensional Dyspnea Profile.

In hyperinflators, inspiratory capacity decreased progressively throughout exercise by 0.36 L, while remaining stable in non-hyperinflators. The “work/effort” descriptor was most frequently selected throughout exercise in both types of patients (65% of all responses). At the VT/V′E inflection, work/effort plateaued while “unsatisfied inspiration” descriptors became selected predominantly only in hyperinflators (77% of all responses). In the affective domain, the emotion most frequently associated with dyspnoea was anxiety.

In pulmonary hypertension patients who develop hyperinflation during exercise, dyspnoea descriptors referring to unsatisfied inspiration become predominant following the VT/V′E inflection. As these descriptors are generally associated with more negative emotional experiences, delaying or preventing the VT/V′E inflection may have important implications for symptom management in patients with pulmonary hypertension.

Human diaphragm atrophy in amyotrophic lateral sclerosis is not predicted by routine respiratory measures

Amyotrophic lateral sclerosis (ALS) patients show progressive respiratory muscle weakness leading to death from respiratory failure. However, there are no data on diaphragm histological changes in ALS patients and how they correlate with routine respiratory measurements.

We collected 39 diaphragm biopsies concomitantly with laparoscopic insertion of intradiaphragmatic electrodes during a randomised controlled trial evaluating early diaphragm pacing in ALS (https://clinicaltrials.gov; NCT01583088). Myofibre type, size and distribution were evaluated by immunofluorescence microscopy and correlated with spirometry, respiratory muscle strength and phrenic nerve conduction parameters. The relationship between these variables and diaphragm atrophy was assessed using multivariate regression models.

All patients exhibited significant slow- and fast-twitch diaphragmatic atrophy. Vital capacity (VC), maximal inspiratory pressure, sniff nasal inspiratory pressure (SNIP) and twitch transdiaphragmatic pressure did not correlate with the severity of diaphragm atrophy. Inspiratory capacity (IC) correlated modestly with slow-twitch myofibre atrophy. Supine fall in VC correlated weakly with fast-twitch myofibre atrophy. Multivariate analysis showed that IC, SNIP and functional residual capacity were independent predictors of slow-twitch diaphragmatic atrophy, but not fast-twitch atrophy.

Routine respiratory tests are poor predictors of diaphragm structural changes. Improved detection of diaphragm atrophy is essential for clinical practice and for management of trials specifically targeting diaphragm muscle function.

Survival of amyotrophic lateral sclerosis patients after admission to the intensive care unit for acute respiratory failure: an observational cohort study

PURPOSE

Amyotrophic lateral sclerosis (ALS) entails a risk of acute respiratory failure (ARF). The decision to admit such patients to the intensive care unit (ICU) is difficult given the inexorable prognosis of ALS. To fuel this discussion, this study describes the ICU and post-ICU survival of ALS-related ARF.

MATERIAL AND METHODS

Retrospective cohort analysis over 10 years (university hospital setting, ALS reference center).

RESULTS

Of 90 patients (66 men, median age: 67 [IQR 59-71], median interval since ALS diagnosis: 26.5 months [14-53], ALSFRS-R: 19 [12-30], bulbar signs 73%), 48 were managed by noninvasive ventilation (NIV) only, 7 were already tracheotomized upon admission, 12 were tracheotomized during the ICU stay (advance care planning project), 18 were already intubated before admission, 5 received oxygen and physiotherapy only. Median ICU stay was 4 days [2-9] with 20% mortality. Median hospital stay was 10 days [5-22] with 33% mortality. The 3-month and one year mortality wer 46% and 71%. Hospital mortality was higher in patients with more severe respiratory acidosis and higher simplified acute physiology scores on admission.

CONCLUSIONS

The prognosis of ALS-related ARF requiring ICU admission resembles that of ARF complicating other conditions with high short-term mortality (e.g. lung cancer).

Neuroergonomic and psychometric evaluation of full-face crew oxygen masks respiratory tolerance: a proof-of-concept study

INTRODUCTION

Preventing in-flight hypoxia in pilots is typically achieved by wearing oxygen masks. These masks must be as comfortable as possible to allow prolonged and repeated use. The consequences of mask-induced facial contact pressure have been extensively studied, but little is known about mask-induced breathing discomfort. Because breathlessness is a strong distractor and engages cerebral resources, it could negatively impact flying performances.

METHODS

Seventeen volunteers (age 20-32) rated respiratory discomfort while breathing with no mask and with two models of quick-donning full-face crew oxygen masks with regulators (mask A, mask B). Electroencephalographic recordings were performed to detect a putative respiratory-related cortical activation in response to inspiratory constraint (experiment 1, n=10). Oxygen consumption was measured using indirect calorimetry (experiment 2, n=10).

RESULTS

With mask B, mild respiratory discomfort was reported significantly more frequently than with no mask or mask A (experiment 1: median respiratory discomfort on visual analogue scale 0.9 cm (0.5-1.4), experiment 1; experiment 2: 2 cm (1.7-2.9)). Respiratory-related cortical activation was present in 1/10 subjects with no mask, 1/10 with mask A and 6/10 with mask B (significantly more frequently with mask B). Breathing pattern, sigh frequency and oxygen consumption were not different.

CONCLUSIONS

In a laboratory setting, breathing through high-end aeronautical full-face crew oxygen masks can induce mild breathing discomfort and activate respiratory-related cortical networks. Whether or not this can occur in real-life conditions and have operational consequences remains to be investigated. Meanwhile, respiratory psychometric and neuroergonomic approaches could be worth integrating to masks development and evaluation processes.

Aerosol furosemide for dyspnea: Controlled delivery does not improve effectiveness

Aerosolized furosemide has been shown to relieve dyspnea; nevertheless, all published studies have shown great variability in response. This dyspnea relief is thought to result from the stimulation of slowly adapting pulmonary stretch receptors simulating larger tidal volume. We hypothesized that better control over aerosol administration would produce more consistent dyspnea relief; we used a clinical ventilator to control inspiratory flow and tidal volume. Twelve healthy volunteers inhaled furosemide (40mg) or placebo in a double blind, randomized, crossover study. Breathing Discomfort was induced by hypercapnia during constrained ventilation before and after treatment. Both treatments reduced breathing discomfort by 20% full scale. Effectiveness of aerosol furosemide treatment was weakly correlated with larger tidal volume. Response to inhaled furosemide was inversely correlated to furosemide blood level, suggesting that variation among subjects in the fate of deposited drug may determine effectiveness. We conclude that control of aerosol delivery conditions does not improve consistency of treatment effect; we cannot, however, rule out placebo effect.

Interferences between breathing, experimental dyspnoea and bodily self-consciousness

Dyspnoea, a subjective experience of breathing discomfort, is a most distressing symptom. It implicates complex cortical networks that partially overlap with those underlying bodily self-consciousness, the experience that the body is one’s own within a given location (self-identification and self-location, respectively). Breathing as an interoceptive signal contributes to bodily self-consciousness: we predicted that inducing experimental dyspnoea would modify or disrupt this contribution. We also predicted that manipulating bodily self-consciousness with respiratory-visual stimulation would possibly attenuate dyspnoea. Twenty-five healthy volunteers were exposed to synchronous and asynchronous respiratory-visual illumination of an avatar during normal breathing and mechanically loaded breathing that elicited dyspnoea. During normal breathing, synchronous respiratory-visual stimulation induced illusory self-identification with the avatar and an illusory location of the subjects’ breathing towards the avatar. This did not occur when respiratory-visual stimulation was performed during dyspnoea-inducing loaded breathing. In this condition, the affective impact of dyspnoea was attenuated by respiratory-visual stimulation, particularly when asynchronous. This study replicates and reinforces previous studies about the integration of interoceptive and exteroceptive signals in the construction of bodily self-consciousness. It confirms the existence of interferences between experimental dyspnoea and cognitive functions. It suggests that respiratory-visual stimulation should be tested as a non-pharmacological approach of dyspnoea treatment.

Fooling the brain to alleviate dyspnoea

Dyspnoea affects a multitude of patients with a multitude of diseases, and therefore concerns a multitude of physicians and other healthcare professionals. In view of the physical and psychological distress associated with dyspnoea, and in view of the pervasive impact of dyspnoea on the patient's psychological state and social life [1, 2], relieving dyspnoea should constitute a leading and universal clinical goal. Some have even proposed that failing to provide a patient with dyspnoea with “state of the art” management of this symptom would constitute an infringement of human rights [3, 4].

The application of a stream of air onto the face by a hand-held fan has a real place in the treatment of dyspnoea http://ow.ly/tKJk30dJ5Pv

Normal sleep on mechanical ventilation in adult patients with congenital central alveolar hypoventilation (Ondine's curse syndrome)

Background

The purpose of this study was to describe the sleep structure (especially slow wave sleep) in adults with congenital central hypoventilation syndrome (CCHS), a rare genetic disease due to mutations in the PHOX2B gene. Fourteen patients aged 23 (19.0; 24.8) years old (median [1^rst-3rd quartiles]) with CCHS underwent a sleep interview and night-time attended polysomnography with their ventilatory support. Their sleep variables were compared to those collected in 15 healthy control subjects matched for age, sex and body mass index.

Results

The latency to N3 sleep was shorter in patients (26.3 min [24.0; 30.1]) than in controls (49.5 min [34.3; 66.9]; P = 0.005), and sleep onset latency tended to be shorter in patients (14.0 min [7.0; 20.5]) than in controls (33.0 min [18.0; 49.0]; P = 0.052). Total sleep time, sleep stage percentages, sleep fragmentation as well as respiratory and movement index were within normal ranges and not different between groups.

Conclusions

Normal sleep in adult patients with CCHS and adequate ventilator support indicates that the PHOX2 gene mutations do not affect brain sleep networks. Consequently, any complaint of disrupted sleep should prompt clinicians to look for the usual causes of sleep disorders, primarily inadequate mechanical ventilation. Shorter N3 latency may indicate a higher need for slow wave sleep, to compensate for the abnormal respiratory-related cortical activity during awake quiet breathing observed in patients with CCH.

Bench Evaluation of Four Portable Oxygen Concentrators Under Different Conditions Representing Altitudes of 2438, 4200, and 8000 m

Bunel, Vincent, Amr Shoukri, Frederic Choin, Serge Roblin, Cindy Smith, Thomas Similowski, Capucine Morélot-Panzini, and Jésus Gonzalez. Bench evaluation of four portable oxygen concentrators under different conditions representing altitudes of 2438, 4200, and 8000 m. High Alt Med Biol. 17:370-374, 2016.-Air travel is responsible for a reduction of the partial pressure of oxygen (O₂) as a result of the decreased barometric pressure. This hypobaric hypoxia can be dangerous for passengers with respiratory diseases, requiring initiation or intensification of oxygen therapy during the flight. In-flight oxygen therapy can be provided by portable oxygen concentrators, which are less expensive and more practical than oxygen cylinders, but no study has evaluated their capacity to concentrate oxygen under simulated flight conditions. We tested four portable oxygen concentrators during a bench test study. The O₂ concentrations (FO₂) produced were measured under three different conditions: in room air at sea level, under hypoxia due to a reduction of the partial pressure of O₂ (normobaric hypoxia, which can be performed routinely), and under hypoxia due to a reduction of atmospheric pressure (hypobaric hypoxia, using a chamber manufactured by Airbus Defence and Space). The FO₂ obtained under conditions of hypobaric hypoxia (chamber) was lower than that measured in room air (0.92 [0.89-0.92] vs. 0.93 [0.92-0.94], p = 0.029), but only one portable oxygen concentrator was unable to maintain an FO₂ ≥ 0.90 (0.89 [0.89-0.89]). In contrast, under conditions of normobaric hypoxia (tent) simulating an altitude of 2438 m, none of the apparatuses tested was able to achieve an FO₂ greater than 0.76. (0.75 [0.75-0.76] vs. 0.93 [0.92-0.94], p = 0.029). Almost all portable oxygen concentrators were able to generate a sufficient quantity of O₂ at simulated altitudes of 2438 m and can therefore be used in the aircraft cabin. Unfortunately, verification of the reliability and efficacy of these devices in a patient would require a nonroutinely available technology, and no preflight test can currently be performed by using simple techniques such as hypobaric hypoxia.

Early diaphragm pacing in patients with amyotrophic lateral sclerosis (RespiStimALS): a randomised controlled triple-blind trial

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder associated with respiratory muscle weakness and respiratory failure. Non-invasive ventilation alleviates respiratory symptoms and prolongs life, but is a palliative intervention. Slowing the deterioration of diaphragm function before respiratory failure would be desirable. We aimed to assess whether early diaphragm pacing could slow down diaphragm deterioration and would therefore delay the need for non-invasive ventilation.

METHODS

We did a multicentre, randomised, controlled, triple-blind trial in patients with probable or definite ALS in 12 ALS centres in France. The main inclusion criterion was moderate respiratory involvement (forced vital capacity 60-80% predicted). Other key eligibility criteria were age older than 18 years and bilateral responses of the diaphragm to diagnostic phrenic stimulation. All patients were operated laparoscopically and received phrenic stimulators. Clinicians randomly assigned patients (1:1) to receive either active or sham stimulation with a central web-based randomisation system (computer-generated list). Investigators, patients, and an external outcome allocation committee were masked to treatment. The primary outcome was non-invasive ventilation-free survival, analysed in the intention-to-treat population. Safety outcomes were also assessed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT01583088.

FINDINGS

Between Sept 27, 2012, and July 8, 2015, 74 participants were randomly assigned to receive either active (n=37) or sham (n=37) stimulation. On July 16, 2015, an unplanned masked analysis was done after another trial showed excess mortality with diaphragm pacing in patients with hypoventilation (DiPALS, ISRCTN 53817913). In view of this finding, we analysed mortality in our study and found excess mortality (death from any cause) in our active stimulation group. We therefore terminated the study on July, 16, 2015. Median non-invasive ventilation-free survival was 6·0 months (95% CI 3·6-8·7) in the active stimulation group versus 8·8 months (4·2-not reached) in the control (sham stimulation) group (hazard ratio 1·96 [95% CI 1·08-3·56], p=0·02). Serious adverse events (mainly capnothorax or pneumothorax, acute respiratory failure, venous thromboembolism, and gastrostomy) were frequent (24 [65%] patients in the active stimulation group vs 22 [59%] patients in the control group). No treatment-related death was reported.

INTERPRETATION

Early diaphragm pacing in patients with ALS and incipient respiratory involvement did not delay non-invasive ventilation and was associated with decreased survival. Diaphragm pacing is not indicated at the early stage of the ALS-related respiratory involvement.

FUNDING

Hospital Program for Clinical Research, French Ministry of Health; French Patients' Association for ALS Research (Association pour la Recherche sur la Sclérose Latérale Amyotrophique); and Thierry de Latran Foundation.

Reduced survival in patients with ALS with upper airway obstructive events on non-invasive ventilation

INTRODUCTION

Non-invasive ventilation (NIV) is part of standard care in amyotrophic lateral sclerosis (ALS). Intolerance or unavailability of NIV, as well as the quality of correction of nocturnal hypoventilation, has a direct impact on prognosis.

OBJECTIVES

We describe the importance of NIV failure due to upper airway obstructive events, the clinical characteristics, as well as their impact on the prognosis of ALS.

METHODS

Retrospective analysis of the data of 190 patients with ALS and NIV in a single centre for the period 2011-2014. 179 patients tolerating NIV for more than 4 h per night without leaks were analysed.

RESULTS

Among the 179 patients, after correction of leaks, 73 remained inadequately ventilated at night (defined as more than 5% of the night spent at <90% of SpO2), as a result of obstructive events in 67% of cases (n=48). Patients who remained inadequately ventilated after optimal adjustment of ventilator settings presented with shorter survival than adequately ventilated patients. Unexpectedly, patients with upper airway obstructive events without nocturnal desaturation and in whom no adjustment of treatment was therefore performed also presented with shorter survival. On initiation of NIV, no difference was demonstrated between patients with and without upper airway obstructive events. In all patients, upper airway obstruction was concomitant with reduction of ventilatory drive.

CONCLUSIONS

This study shows that upper airway obstruction during NIV occurs in patients with ALS and is associated with poorer prognosis. Such events should be identified as they can be corrected by adjusting ventilator settings.

Cortical drive to breathe in amyotrophic lateral sclerosis: a dyspnoea-worsening defence?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease causing diaphragm weakness that can be partially compensated by inspiratory neck muscle recruitment. This disappears during sleep, which is compatible with a cortical contribution to the drive to breathe. We hypothesised that ALS patients with respiratory failure exhibit respiratory-related cortical activity, relieved by noninvasive ventilation (NIV) and related to dyspnoea.

We studied 14 ALS patients with respiratory failure. Electroencephalographic recordings (EEGs) and electromyographic recordings of inspiratory neck muscles were performed during spontaneous breathing and NIV. Dyspnoea was evaluated using the Multidimensional Dyspnea Profile.

Eight patients exhibited slow EEG negativities preceding inspiration (pre-inspiratory potentials) during spontaneous breathing. Pre-inspiratory potentials were attenuated during NIV (p=0.04). Patients without pre-inspiratory potentials presented more advanced forms of ALS and more severe respiratory impairment, but less severe dyspnoea. Patients with pre-inspiratory potentials had stronger inspiratory neck muscle activation and more severe dyspnoea during spontaneous breathing.

ALS-related diaphragm weakness can engage cortical resources to augment the neural drive to breathe. This might reflect a compensatory mechanism, with the intensity of dyspnoea a negative consequence. Disease progression and the corresponding neural loss could abolish this phenomenon. A putative cognitive cost should be investigated.

Real-life assessment of the multidimensional nature of dyspnoea in COPD outpatients

Dyspnoea is a prominent symptom of chronic obstructive pulmonary disease (COPD). Recent multidimensional dyspnoea questionnaires like the Multidimensional Dyspnea Profile (MDP) individualise the sensory and affective dimensions of dyspnoea. We tested the MDP in COPD outpatients based on the hypothesis that the importance of the affective dimension of dyspnoea would vary according to clinical characteristics.A multicentre, prospective, observational, real-life study was conducted in 276 patients. MDP data were compared across various categories of patients (modified Medical Research Council (mMRC) dyspnoea score, COPD Assessment Test (CAT) score, Global Initiative for Chronic Obstructive Lung Disease (GOLD) airflow obstruction categories, GOLD "ABCD" categories, and Hospital Anxiety and Depression Scale (HADS)). Univariate and multivariate regressions were conducted to explore factors influencing the affective dimension of dyspnoea. Cluster analysis was conducted to create homogeneous patient profiles.The MDP identified a more marked affective dimension of dyspnoea with more severe mMRC, CAT, 12-item Short-Form Health Survey mental component, airflow obstruction and HADS. Multivariate analysis identified airflow obstruction, depressive symptoms and physical activity as determinants of the affective dimension of dyspnoea. Patients clustered into an "elderly, ex-smoker, severe disease, no rehabilitation" group exhibited the most marked affective dimension of dyspnoea.An affective/emotional dimension of dyspnoea can be identified in routine clinical practice. It can contribute to the phenotypic description of patients. Studies are needed to determine whether targeted therapeutic interventions can be designed and whether they are useful.

When Breathing Interferes with Cognition: Experimental Inspiratory Loading Alters Timed Up-and-Go Test in Normal Humans

Human breathing stems from automatic brainstem neural processes. It can also be operated by cortico-subcortical networks, especially when breathing becomes uncomfortable because of external or internal inspiratory loads. How the “irruption of breathing into consciousness” interacts with cognition remains unclear, but a case report in a patient with defective automatic breathing (Ondine's curse syndrome) has shown that there was a cognitive cost of breathing when the respiratory cortical networks were engaged. In a pilot study of putative breathing-cognition interactions, the present study relied on a randomized design to test the hypothesis that experimentally loaded breathing in 28 young healthy subjects would have a negative impact on cognition as tested by “timed up-and-go” test (TUG) and its imagery version (iTUG). Progressive inspiratory threshold loading resulted in slower TUG and iTUG performance. Participants consistently imagined themselves faster than they actually were. However, progressive inspiratory loading slowed iTUG more than TUG, a finding that is unexpected with regard to the known effects of dual tasking on TUG and iTUG (slower TUG but stable iTUG). Insofar as the cortical networks engaged in response to inspiratory loading are also activated during complex locomotor tasks requiring cognitive inputs, we infer that competition for cortical resources may account for the breathing-cognition interference that is evidenced here.

Interactions Between Dyspnea and the Brain Processing of Nociceptive Stimuli: Experimental Air Hunger Attenuates Laser-Evoked Brain Potentials in Humans

Dyspnea and pain share several characteristics and certain neural networks and interact with each other. Dyspnea-pain counter-irritation consists of attenuation of preexisting pain by intercurrent dyspnea and has been shown to have neurophysiological correlates in the form of inhibition of the nociceptive spinal reflex RIII and laser-evoked potentials (LEPs). Experimentally induced exertional dyspnea inhibits RIII and LEPs, while “air hunger” dyspnea does not inhibit RIII despite its documented analgesic effects. We hypothesized that air hunger may act centrally and inhibit LEPs. LEPs were obtained in 12 healthy volunteers (age: 21–29) during spontaneous breathing (FB), ventilator-controlled breathing (VC) tailored to FB, after inducing air hunger by increasing the inspired fraction of carbon dioxide -FiCO₂- (VCCO₂), and during ventilator-controlled breathing recovery (VCR). VCCO₂ induced intense dyspnea (visual analog scale = 63% ± 6% of full scale, p < 0.001 vs. VC), predominantly of the air hunger type. VC alone reduced the amplitude of the N2-P2 component of LEPs (Δ = 24.0% ± 21.1%, p < 0.05, effect-size = 0.74) predominantly through a reduction in P2, and the amplitude of this inhibition was further reduced by inducting air hunger (Δ = 22.6% ± 17.9%, p < 0.05, effect-size = 0.53), predominantly through a reduction in N2. Somatosensory-evoked potentials (SEPs) were not affected by VC or VCCO₂, suggesting that the observed effects are specific to pain transmission. We conclude that air hunger interferes with the cortical mechanisms responsible for the cortical response to painful laser skin stimulation, which provides a neurophysiological substrate to the central nature of its otherwise documented analgesic effects.

Respiratory neuromodulation in patients with neurological pathologies: for whom and how?

Implanted phrenic nerve stimulation is a technique restoring spontaneous breathing in patients with respiratory control failure, leading to being dependent on mechanical ventilation. This is the case for quadriplegic patients with a high spinal cord injury level and for patients with congenital central hypoventilation syndrome. The electrophysiological diaphragm explorations permits better patient selection, confirming on the one hand a definite issue with central respiratory command and on the other hand the integrity of diaphragmatic phrenic nerves. Today there are two different phrenic stimulation techniques: the quadripolar intrathoracic stimulation and the bipolar intradiaphragmatic stimulation. Both techniques allow patients to be weaned off their mechanical ventilator, improving dramatically their quality of life. In fact, one of the systems (phrenic intradiaphragmatic stimulation) was granted social security reimbursement in 2009, and now both are reimbursed. In the future, phrenic intradiaphragmatic stimulation may find its place in the intensive care unit, for patients needing it temporarily, for example, after certain surgeries with respiratory complications as well as diaphragmatic atrophies induced by prolonged mechanical ventilation.