Swallowing and swallowing-breathing interaction as predictors of intubation in Guillain-Barré syndrome.

BACKGROUND: Bulbar weakness and respiratory impairment have been associated with increased morbidity in retrospective studies of Guillain-Barré syndrome (GBS) patients. The aim of this study was to prospectively explore the relationship between subclinical swallowing impairment, respiratory function parameters, the necessity to intubate patients and the development of early postintubation pneumonia in patients with GBS in the intensive care unit (ICU). METHODS: Respiratory, swallowing, and tongue strength parameters were measured in 30 consecutive adults (51.7 ± 18.1 years old), hospitalized for GBS in the ICU of a teaching hospital. Twenty healthy volunteers were recruited as a control group. The primary outcomes were intubation and pneumonia during the ICU stay. RESULTS: Nineteen patients (65.5%) had piecemeal swallowing, and 19 (65.5%) had impaired breathing-swallowing interaction, of which, respectively, 47.4% and 52.6% had a clinically apparent swallowing impairment. Swallowing impairment was associated with lower values of respiratory function, but not with peripheral motor weakness. Tongue protrusion strength was correlated with respiratory parameters and swallowing impairment. Ten patients were intubated and six developed pneumonia. Age, BMI, severe axial involvement, respiratory parameters (vital capacity and respiratory muscle strength), tongue protrusion strength, and clinical swallowing impairment were predictors of intubation. CONCLUSIONS: Swallowing impairment was present early after ICU admission in over 80% of patients and was an important predictor of intubation. A systematic clinical evaluation of swallowing should be carried out, eventually combined with an evaluation of tongue protrusion strength, along with the usual assessment of neurological and respiratory function, to determine the severity of the GBS.

Noninvasive Mechanical Ventilation Improves Breathing-Swallowing Interaction of Ventilator Dependent Neuromuscular Patients: A Prospective Crossover Study.

BACKGROUND: Respiratory involvement in neuromuscular disorders may contribute to impaired breathing-swallowing interactions, swallowing disorders and malnutrition. We investigated whether the use of non-invasive ventilation (NIV) controlled by the patient could improve swallowing performances in a population of neuromuscular patients requiring daytime NIV. METHODS: Ten neuromuscular patients with severe respiratory failure requiring extensive NIV use were studied while swallowing without and with NIV (while ventilated with a modified ventilator allowing the patient to withhold ventilation as desired). Breathing-swallowing interactions were investigated by chin electromyography, cervical piezoelectric sensor, nasal flow recording and inductive plethysmography. Two water-bolus sizes (5 and 10ml) and a textured yogurt bolus were tested in a random order. RESULTS: NIV use significantly improved swallowing fragmentation (defined as the number of respiratory interruption of the swallowing of a single bolus) (p = 0.003) and breathing-swallowing synchronization (with a significant increase of swallows followed by an expiration) (p <0.0001). Patient exhibited piecemeal swallowing which was not influenced by NIV use (p = 0.07). NIV use also significantly reduced dyspnea during swallowing (p = 0.04) while preserving swallowing comfort, regardless of bolus type. CONCLUSION: The use of patient controlled NIV improves swallowing parameters in patients with severe neuromuscular respiratory failure requiring daytime NIV, without impairing swallowing comfort. TRIAL REGISTRATION: ClinicalTrials.gov NCT01519388.

Physiological comparison of breathing patterns with neurally adjusted ventilatory assist (NAVA) and pressure-support ventilation to improve NAVA settings.

Neurally adjusted ventilator assist (NAVA) assists spontaneous breathing in proportion to diaphragmatic electrical activity (EAdi). Here, we evaluate the effects of various levels of NAVA and PSV on the breathing pattern and, thereby, on [Formula: see text] homeostasis in 10 healthy volunteers. For each ventilation mode, four levels of support (delivered pressure 0 i.e. baseline, 5, 8, and 10cmH2O) were tested in random order. EAdi, flow, and airway pressure were recorded. Optoelectronic plethysmography was used to study lung volume distribution. During both PSV and NAVA, EAdi decreased with the level of assistance (P<0.01). Tidal volume (VT) increased and [Formula: see text] decreased with increased levels of PSV (P=0.044 and P=0.0004; respectively) while no change was observed with NAVA. Subject-ventilator synchronization was better with NAVA than with PSV. NAVA and PSV similarly decreased the abdominal contribution to VT. No airflow profile similarities were observed between baseline and mechanical ventilation. Diaphragmatic activity can decrease during NAVA without any change in VT and [Formula: see text] . This suggests that NAVA adjustment cannot be based solely on VT and [Formula: see text] criteria. Registered by Frédéric Lofaso and Nicolas Terzi on ClinicalTrials.gov, #NCT01614873.

An open-source software for automatic calculation of respiratory parameters based on esophageal pressure.

PURPOSE: We have developed a software that automatically calculates respiratory effort indices, including intrinsic end expiratory pressure (PEEPi) and esophageal pressure-time product (PTPeso). MATERIALS AND METHODS: The software first identifies respiratory periods. Clean signals are averaged to provide a reference mean cycle from which respiratory parameters are extracted. The onset of the inspiratory effort is detected automatically by looking backward from the onset of inspiratory flow to the first point where the esophageal pressure derivative is equal to zero (inflection point). PEEPi is derived from this point. Twenty-three recordings from 16 patients were analyzed with the algorithm and compared with experts' manual analysis of signals: 15 recordings were performed during spontaneous breathing, 1 during non-invasive mechanical ventilation, and 7 under both conditions. RESULTS: For all values, the coefficients of determinations (r(2)) exceeded 0.94 (p<0.001). The bias (mean difference) between PEEPi calculated by hand and automatically was -0.26±0.52cmH2O during spontaneous breathing and the precisions (standard deviations of the differences) was 0.52cmH2O with limits of agreement of 0.78 and -1.30cmH2O. The mean difference between PTPeso calculated by hand and automatically was -0.38±1.42cmH2Os/cycle with limits of agreement of 2.46 and -3.22cmH2Os/cycle. CONCLUSIONS: Our program provides a reliable method for the automatic calculation of PEEPi and respiratory effort indices, which may facilitate the use of these variables in clinical practice. The software is open source and can be improved with the development and validation of new respiratory parameters.

Patient-controlled positive end-expiratory pressure with neuromuscular disease: effect on speech in patients with tracheostomy and mechanical ventilation support.

OBJECTIVE: Communication is a major issue for patients with tracheostomy who are supported by mechanical ventilation. The use of positive end-expiratory pressure (PEEP) may restore speech during expiration; however, the optimal PEEP level for speech may vary individually. We aimed to improve speech quality with an individually adjusted PEEP level delivered under the patient's control to ensure optimal respiratory comfort. METHODS: Optimal PEEP level (PEEPeff), defined as the PEEP level that allows complete expiration through the upper airways, was determined for 12 patients with neuromuscular disease who are supported by mechanical ventilation. Speech and respiratory parameters were studied without PEEP, with PEEPeff, and for an intermediate PEEP level. Flow and airway pressure were measured. Microphone speech recordings were subjected to both quantitative and qualitative assessments of speech, including an intelligibility score, a perceptual score, and an evaluation of prosody determined by two speech therapists blinded to PEEP condition. RESULTS: Text reading time, phonation flow, use of the respiratory cycle for phonation, and speech comfort significantly improved with increasing PEEP, whereas qualitative parameters remained unchanged. This resulted mostly from the increase of the expiratory volume through the upper airways available for speech for all patients combined, with a rise in respiratory rate for nine patients. Respiratory comfort remained stable despite high levels of PEEPeff (median, 10.0 cm H2O; interquartile range, 9.5-12.0 cm H2O). CONCLUSIONS: Patient-controlled PEEP allowed for the use of high levels of PEEP with good respiratory tolerance and significant improvement in speech (enabling phonation during the entire respiratory cycle in most patients). The device studied could be implemented in home ventilators to improve speech and, therefore, autonomy of patients with tracheostomy. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01479959; URL: clinicaltrials.gov.

Effect of a tracheostomy speaking valve on breathing-swallowing interaction.

PURPOSE: Expiratory flow towards the upper airway after swallowing serves to expel liquid or food particles misdirected towards the trachea during swallowing. However, expiration may not occur consistently after swallowing in tracheostomised patients with an open tracheostomy tube. We investigated the effect of a speaking valve (SV) on breathing-swallowing interactions and on the volume expelled through the upper airway after swallowing. METHODS: Eight tracheostomised neuromuscular patients who were able to breathe spontaneously were studied with and without an SV. Breathing-swallowing interactions were investigated by chin electromyography, cervical piezoelectric sensor, and nasal and tracheal flow recording. Three water-bolus sizes (5, 10, and 15 mL) were tested in random order. RESULTS: Swallowing characteristics and breathing-swallowing synchronisation were not influenced by SV use. However, expiratory flow towards the upper airway after swallowing was negligible without the SV and was restored by adding the SV. CONCLUSION: In tracheostomised patients, protective expiration towards the upper airway after swallowing is restored by the use of an SV.

Speech effects of a speaking valve versus external PEEP in tracheostomized ventilator-dependent neuromuscular patients.

PURPOSE: Many patients with respiratory failure related to neuromuscular disease receive chronic invasive ventilation through a tracheostomy. Improving quality of life, of which speech is an important component, is a major goal in these patients. We compared the effects on breathing and speech of low-level positive end-expiratory pressure (PEEP, 5 cmH(2)O) and of a Passy-Muir speaking valve (PMV) during assist-control ventilation. METHODS: We studied ten patients with neuromuscular disorders, between December 2008 and April 2009. Flow was measured using a pneumotachograph. Microphone speech recordings were subjected to both quantitative measurements and qualitative assessments; the latter consisted of both an intelligibility score (using a French adaptation of the Frenchay Dysarthria Assessment) and a perceptual score determined by two speech therapists. RESULTS: Text reading time, perceptive score, intelligibility score, speech comfort, and respiratory comfort were similar with PEEP and PMV. During speech with 5 cmH(2)O PEEP, six of the ten patients had no return of expiratory gas to the expiratory line and, therefore, had the entire insufflated volume available for speech, a condition met during PMV use in all patients. During speech, the respiratory rate increased by at least 3 cycles/min above the backup rate in seven patients with PEEP and in none of the patients with PMV. CONCLUSIONS: Low-level PEEP is as effective as PMV in ensuring good speech quality, which might be explained by sealed expiratory line with low-level PEEP and/or respiratory rate increase during speech with PEEP observed in most of the patients.

Impact of tracheostomy on swallowing performance in Duchenne muscular dystrophy.

Mechanical ventilation has improved survival in patients with Duchenne muscular dystrophy (DMD). Over time, these patients experience upper airway dysfunction, swallowing impairments, and dependency on the ventilator that may require invasive mechanical ventilation via a tracheostomy. Tracheostomy is traditionally believed to further impair swallowing. We assessed swallowing performance and breathing-swallowing interactions before and after tracheostomy in 7 consecutive wheelchair-bound DMD patients, aged 25+/-4 years, over a 4-year period. Chin electromyography, laryngeal motion, and inductive respiratory plethysmography recordings were obtained during swallowing of three water-bolus sizes in random order. Piecemeal deglutition occurred in all patients over several breathing cycles. Half the swallows were followed by inspiration before tracheostomy. Total bolus swallowing time was significantly shorter (P=0.009), and the number of swallows per bolus significantly smaller (P=0.01), after than before tracheostomy. Invasive ventilation via a tracheostomy may improve swallowing.

Sniff and Muller manoeuvres to measure diaphragmatic muscle strength.

We hypothesized that peak values of oesophageal (Poes) and transdiaphragmatic pressure (Pdi) swings during a maximal sniff manoeuvre and a maximal static inspiratory manoeuvre (Muller manoeuvre) are comparable or give complementary information for assessing diaphragmatic and global inspiratory muscle strength. We studied 98 patients with suspected diaphragmatic dysfunction. Poes and Pdi swings were measured during maximal sniff manoeuvres (sniff), maximal Muller manoeuvres (max), and cervical magnetic phrenic nerve stimulation (cervical Tw). Eighty eight patients were able to perform both volitional manoeuvres. Among them, mean Poes sniff was significantly higher than mean Poes max (48.7+/-28.7 cm H(2)O vs. 42.9+/-27.4 cm H(2)O, p<0.05) and mean Pdi sniff was higher than mean Pdi max (49.2+/-35.1cm H(2)O vs. 42.9+/-33.3 cm H(2)O, respectively, p=0.05). Cervical Pdi Tw correlated better with Pdi sniff (p<0.0001, r=0.62) than with Pdi max (p<0.0001, r=0.44). Poes and Pdi swings were greatest during the sniff manoeuvre in 42 patients (48%) and during the Muller manoeuvre in 29 patients (33%). Among the 17 remaining patients, nine had the greatest Poes swing during a maximal sniff manoeuvre and the greatest Pdi swing during a maximal static inspiratory manoeuvre; the opposite occurred in the other eight patients. The combination of Muller manoeuvre and sniff manoeuvre increased the diagnosis of normal diaphragmatic strength from 18 patients (20%) to 21 patients (24%), and the additional analysis of cervical Pdi Tw further increased the diagnosis of normal diaphragmatic strength to 27 patients (31%). In conclusion, though sniff manoeuvre gave significantly higher values than Muller manoeuvre, both volitional manoeuvres and cervical Pdi Tw are complementary and should be used in combination to evaluate diaphragmatic muscle strength.

Breathing-swallowing interaction in neuromuscular patients: a physiological evaluation.

RATIONALE: Malnutrition and aspiration are major problems in patients with neuromuscular disease. Because impaired swallowing contributes to malnutrition, means of improving swallowing are needed. OBJECTIVES: To investigate interactions between breathing and swallowing in neuromuscular disorders and to evaluate the impact of mechanical ventilation (MV) on swallowing in tracheostomized patients. METHODS: We studied 10 healthy individuals and 29 patients with neuromuscular disease and chronic respiratory failure (including 19 with tracheostomy). The tracheostomized patients who could breathe spontaneously were recorded during spontaneous breathing (SB) and with MV, in random order. MEASUREMENTS AND MAIN RESULTS: Breathing-swallowing interactions were investigated by chin electromyography and inductive respiratory plethysmography, using three water-bolus sizes (5, 10, and 15 ml) in random order. In contrast to healthy individuals, neuromuscular patients showed piecemeal deglutition with several swallows over several breathing cycles for each bolus. The percentage of swallows followed by expiration was about 50% in the patients compared with nearly 100% in the control subjects. The number of swallows and total swallowing time per bolus correlated significantly to maximal inspiratory pressure. In the 10 tracheostomized patients who were recorded both in SB and MV, the number of swallows and total swallowing time per bolus were significantly reduced during MV compared with SB. CONCLUSION: Neuromuscular patients showed abnormal breathing-swallowing interactions, which correlated to maximal inspiratory pressure. Moreover, MV improved the swallowing parameters in tracheostomized patients who were able to breathe spontaneously.

Oxygen consumption during machine-assisted and unassisted walking: a pilot study in hemiplegic and healthy humans.

OBJECTIVE: To determine whether a gait-training (GT) machine influenced walking time duration and oxygen consumption in hemiplegic patients. DESIGN: Repeated measures with comparison of 2 groups. SETTING: Physiology laboratories in a rehabilitation hospital. PARTICIPANTS: Seven patients with stroke-related hemiplegia (2 men, 5 women; age, 46+/-11y; time since stroke, 12+/-9wk) and 7 healthy subjects (3 men, 4 women; age, 30+/-7y). INTERVENTIONS: Floor walking (FW) and GT-assisted walking with and without 50% body-weight support (BWS). MAIN OUTCOME MEASURES: Walking time duration, oxygen consumption (Vo(2)), minute ventilation (V(E)), and heart rate. RESULTS: When the condition effect was analyzed independently from the group, mean Vo(2) was higher during FW than during the GT tests (post hoc analysis: FW vs GT, P=.017; FW vs GT+BWS, P<.002). When the groups were compared independently of the condition, the group with hemiplegia had a significantly shorter walking time duration (analysis of variance [ANOVA], P<.001) and a significantly higher Vo(2) as a percentage of baseline (ANOVA, P=.03), compared with the controls. Walking time duration was influenced by walking condition (ANOVA, P<.001; post hoc analysis: FW vs GT, P<.001; FW vs GT+BWS, P<.001). Ve was influenced by walking condition (ANOVA, P=.043; not significant in the post hoc analysis) and was higher in the group with hemiplegia (ANOVA, P=.02). Heart rate was not influenced by walking condition (P=.11). A group effect was found with heart rate in cycles per minute (P=.035) but not as a percentage of baseline. No interaction was found between the ANOVA group-effect factor and the ANOVA walking-condition effect factor. CONCLUSIONS: Compared with FW, GT assistance increased walking time duration and reduced Vo(2) in patients with severe hemiplegia.

Is forced oscillation technique useful in the diagnosis of occupational asthma?

OBJECTIVE: The aim of the study was to determine whether the forced oscillation technique (FOT), which does not require active cooperation, may be useful to assess bronchial responsiveness in patients with suspected occupational asthma (OA). METHODS: Changes in resistances evaluated by FOT, and DeltaFEV1 measured during methacholine challenge test were compared in 77 adults referred for suspected OA. Spearman correlations and ROC curves were used. RESULTS: R0 at the final dose of methacholine (R0hmd) and DeltaR0 were strongly correlated with DeltaFEV1 (p < 0.001). The ROC curves showed that R0hmd >or= 240% predicted was the best cut-off value to discriminate subjects with OA from nonasthmatic subjects (sensitivity: 80%, specificity: 76%). CONCLUSION: FOT can be proposed as an alternative method for the assessment of bronchial responsiveness in subjects with suspected OA, unable to correctly perform forced expiratory maneuvers.

Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury.

OBJECTIVE: To determine whether a custom girdle, designed to provide truncal stability and abdominal support, will improve pulmonary function, enhance inspiratory muscle activity, and reduce the sensation of respiratory effort in patients with spinal cord injury (SCI). DESIGN: Pulmonary function, transdiaphragmatic pressure time product (PTP di ), twitch (Tw Pdi) and maximal transdiaphragmatic pressures (Pdi), and perception of respiratory effort (Borg Rating of Perceived Exertion score) were measured with and without an abdominal girdle in a seated position. SETTING: Rehabilitation hospital. PARTICIPANTS: Ten patients with posttrauma SCI (injury level, C5-T6). INTERVENTION: Application of the abdominal girdle. MAIN OUTCOME MEASURES: Borg score and measures of lung volumes, dynamic abdominal compliance, and Tw Pdi and maximal Pdi. RESULTS: Wearing of the girdle was associated with a lower Borg score (P = .002) and reduced functional residual capacity (P = .006) but increased inspiratory capacity (P = .02) and forced vital capacity (P = .02). Although there was a decrease in dynamic abdominal compliance (P < .001) and an increase in PTP di (P = .02), this was accompanied by an increase in both Tw Pdi (P = .02) and maximal Pdi (P = .03). CONCLUSIONS The custom girdle reduced the sensation of respiratory effort in patients with SCI by optimizing the operating lung volumes and decreasing abdominal compliance, which enhanced diaphragm performance.

Cough determinants in patients with neuromuscular disease.

Neuromuscular disease leads to cough impairment. Cough augmentation can be achieved by mechanical insufflation (MI) or manually assisted coughing (MAC). Many studies have compared these two methods, but few have evaluated them in combination. In 155 neuromuscular patients, we assessed determinants of peak cough flow (PCF) using stepwise correlation. Maximal inspiratory capacity contributed 44% of the variance (p<0.001), expiratory reserve volume 13%, and maximal expiratory pressure 2%. Thus, augmenting inspiration seems crucial. However, parameters dependent on expiratory muscles independently influence PCF. We measured vital capacity and PCF in 10 neuromuscular patients during cough augmentation by MI, MAC, or both. MI or MAC significantly improved VC and PCF (p<0.01) as compared to the basal condition and VC and PCF were higher during MI plus MAC than during MAC or MI alone (p<0.01). In conclusion, combining MAC and MI is useful for improving cough in neuromuscular patients.

Upper airway calibre and impedance in patients with Steinert's myotonic dystrophy.

Myotonic dystrophy (MD) can be responsible for increased inspiratory muscle loading, the origin of which is debated, with some authors incriminating distal lesions and others central abnormalities. Using a recent non-invasive method based on single transient pressure-wave reflection analysis, we measured central airway calibre from the mouth to the carina and respiratory impedance in a group of adults with MD, a group of patients with sleep apnoea syndrome (SAS) but no neuromuscular disease, and a group of normal controls. All participants were awake during the measurements. We found no reduction in central airway calibre in the patients with the adult form of MD, as compared to the normal controls. These data suggest that MD may be associated with peripheral airway obstruction related to alterations in the elastic properties of the lung.

Perceived inspiratory difficulty in neuromuscular patients with primary muscle disorders.

Intensity of perceived inspiratory difficulty was investigated in 17 patients with severe respiratory insufficiency due to muscle disease, compared with healthy matched controls. Subjects breathed through a threshold valve generating a constant inspiratory negative pressure proportional to their maximal inspiratory pressure. Four load levels ranging from 10 to 40% of the maximal inspiratory pressure were applied in random order. Patients had significantly less perceived inspiratory difficulty than controls at each load level expressed as a percentage of maximal inspiratory pressure P < 0.001. However, when the load was expressed as the absolute value, the slope of the Borg scale score versus mouth pressure was similar in the two groups (P = 0.11). The ventilatory pattern remained unchanged in each group as the load increased. We conclude that in patients with myopathy, loads leading to respiratory muscle fatigue (40% of maximal inspiratory pressure) may fail to produce perceived inspiratory difficulty.

Assessing inspiratory muscle strength by sniff nasal inspiratory pressure.

The sniff nasal inspiratory pressure (SNIP) consists in the measurement of pressure through an occluded nostril during sniffs performed through the controlateral nostril. It is an accurate and noninvasive approximation of esophageal pressure swing during sniff maneuvers. However SNIP can underestimate esophageal pressure swing in subjects with nasal obstruction, patients with chronic obstructive pulmonary disease and severe neuromuscular patients. Nevertheless, since SNIP maneuver has predicted normal values, is noninvasive and is easier to perform than maximal inspiratory pressure (MIP) maneuver, it could be considered as the first simple test to use in order to assess inspiratory muscle weakness. In addition, because it is as reproducible as MIP, it can be suitable to follow inspiratory muscle function in chronic neuromuscular patients. Because, of the important limit of agreement between SNIP and MIP, these two methods are not interchangeable but complementary.

Comparative effects of two ventilatory modes on speech in tracheostomized patients with neuromuscular disease.

Many patients with respiratory failure related to neuromuscular disease receive chronic invasive ventilation through a tracheostomy. Improving quality of life, of which speech is an important component, is a major goal in these patients. We compared the effects on breathing and speech production of assist-control ventilation (ACV) and bilevel positive-pressure ventilation (BPPV) in nine patients with neuromuscular disease. Ventilator-delivered flow was measured using a pneumotachograph, and respiratory rate, inspiratory time, and ventilator-delivered volume were measured on this flow signal. Gas exchange was assessed using oxygen saturation and end-tidal carbon dioxide measurement. Microphone speech recordings were subjected to quantitative analysis. At rest, ventilatory parameters were similar with both modes. Speech induced an increase in inspiratory time during BPPV, with a greater increase in the volume released by the ventilator during speech as compared with ACV (172 +/- 194 versus 26 +/- 31 ml). Consequently, speech duration was longer during inspiration with BPPV. Moreover, BPPV allowed speech production to extend into expiration, and three patients could speak continuously during several respiratory cycles while receiving BPPV. Blood gas exchange was not modified by speech with BPPV or ACV. This study shows that BPPV provides better speech duration than ACV with no detectable short-term deleterious effects.