Abdominal muscle activity in sleep apnea during continuous positive airway pressure titration

Expiratory obstruction in patients with Duchenne muscular dystrophy under non-invasive ventilation: A step-by-step analysis of a new obstructive pattern

PURPOSE

Non-invasive ventilation (NIV) is the reference standard for managing chronic hypoventilation in patients with Duchenne muscular dystrophy (DMD). In these patients, upper airway obstruction under NIV may compromise efficacy and adherence. We aim to describe a novel pattern of expiratory obstructive events occurring during nocturnal barometric NIV.

METHODS

We retrospectively included all patients with DMD who underwent full-night polygraphy during NIV as part of their usual follow-up between May 2018 and July 2019.

RESULTS

We provide a step-by-step description of this previously undescribed pattern of obstruction. Expiratory obstructions lead to end-inspiratory breath-holding and impossibility to take another inspiratory breath with a barometric mode until expiration occurs. These events were observed in 4 (36%) of 11 DMD patients under barometric NIV.

CONCLUSION

Expiratory obstructions may be common in DMD patients receiving NIV and should be sought out routinely. This previously undescribed variant of obstructive event must be identified.

Upper airway resistance syndrome 2018: non-hypoxic sleep-disordered breathing

INTRODUCTION

Upper airway resistance syndrome (UARS) as obstructive sleep apnea syndrome (OSAS) has been described as abnormal breathing during sleep, based on the recording technologies and knowledge of the time. These terms have advanced the field, but are they still useful? Area Covered: Historically, the definition of UARS syndrome was aimed at recognizing pathology not covered by 'OSAS' and to prompt specialists to go further than the obvious. It aimed at pushing specialists to recognize pathologies earlier and to elicit research in the developmental features of sleep-disordered-breathing (SDB). The technology used to monitor SDB changed over-time, allowing recognition of SDB differently but not necessarily better. Expert Commentary: Currently, we have a better understanding of the development of SDB, and its evolution with aging, leading to co-morbid-OSA. However, the real issue is to recognize the problems much earlier, and to understand what can be done to prevent its development. The notions of OSA, UARS, apnea hypopnea index are only historical. There is enough knowledge to date to go beyond these definitions, to recognize problems differently and to lead to the prevention of the factors leading to SDB. The recognition of non-hypoxic sleep-disordered breathing is a step in this direction.

Esogastric pressure measurement to assist noninvasive ventilation indication and settings in infants with hypercapnic respiratory failure: A pilot study

OBJECTIVE

Noninvasive ventilation (NIV) in usually set on clinical parameters. The aim of the study was to assess the value of esophageal (P_ES ) and gastric pressure (P_GAS ) measurements for the indication and optimal settings of NIV in infants with hypercapnic respiratory failure in whom the efficacy of NIV was uncertain on clinical noninvasive parameters.

DESIGN

A retrospective study.

PATIENT-SUBJECT SELECTION

P_ES and P_GAS measurements were performed in seven infants <2 years old admitted in the Pediatric Intensive Care Unit for an acute or acute-on-chronic hypercapnic respiratory failure.

METHODOLOGY

P_ES swing and esophageal pressure time product (PTP_ES ) during spontaneous breathing, NIV set on clinical parameters (NIVclin) and on P_ES (NIVphys) were compared. According to the P_ES measurements, NIV was continued if NIV was associated with an at least 20% reduction of the P_ES swing and PTP_ES and not initiated or withdrawn in the other case.

RESULTS

In all seven patients, the P_ES and P_GAS measurements were informative and led to the decision to initiate NIV in one patient or continue NIV with different settings in three patients. In the three other patients, NIV was not initiated in one patient and withdrawn in the two last patients because of a lack of improvement in P_ES swing and PTP_ES .

CONCLUSIONS

P_ES and P_GAS measurements may be useful for the indication and optimal setting of NIV in a selected group of infants with hypercapnic respiratory failure.

Diaphragmatic dysfunction in SEPN1-related myopathy

SEPN1-related myopathy (SEPN1-RM) is characterized by predominant axial muscle weakness, early scoliosis, rigid spine and severe respiratory insufficiency. The aim of the study was to characterize the mechanisms of respiratory dysfunction in SEPN1-RM patients. Breathing pattern and respiratory muscle strength were measured by means of esophageal (Pes) and gastric (Pgas) pressures. Seven patients aged 7-55 years (1 adult) at first respiratory muscle test were studied. Five patients were treated by nocturnal noninvasive ventilation (NIV)  ≥ 4 months. Mean ΔPes was within normality during tidal breathing, but the ΔPgas/ΔPes index indicated an increased contribution of the rib cage and expiratory muscles, as compared to the diaphragm, in the pediatric patients and bilateral diaphragmatic paralysis in the adult patient. Forced vital capacity (FVC) was reduced in all patients (52 ± 19%pr) with mean FVC seated-supine drop of 24 ± 7%. Global inspiratory muscle and diaphragmatic strengths were moderately reduced in 2 patients, highly reduced in 4 patients and severely reduced in the adult patient. Expiratory muscle strength was moderately reduced in 6 patients and severely reduced in the adult patient. FVC and respiratory muscle strength remained stable in 2 patients treated by nocturnal NIV within a 3-year follow-up. This study confirms that diaphragmatic dysfunction is a characteristic feature of SEPN1-RM and NIV may stabilize the decline in respiratory muscle strength.

Work of breathing as a tool to diagnose severe fixed upper airway obstruction

A 4-year-old girl with bilateral vocal fold palsy was successfully decannulated from tracheotomy after seven laryngeal procedures. But an important stridor and dyspnea recurred 13 months after decannulation. Nocturnal gas exchange was normal but her daytime work of breathing was increased by fourfold, without any beneficial effect of nasal noninvasive continuous positive airway pressure ventilation (CPAP), reflecting a severe fixed airway obstruction. Endoscopic examination confirmed the work of breathing findings showing glottic and supraglottic stenosis. This upper airway obstruction was successfully treated with a recannulation. In conclusion, the major message of this case report is that measurement of the work of breathing was able to document the "fixed" nature of the airway obstruction, by showing no improvement even with highest tolerated levels of nasal CPAP. As such, the work of breathing may be proposed as a screening tool to quantify and assess the reversibility of severe upper airway obstruction in children.

Continuous positive airway pressure titration in infants with severe upper airway obstruction or bronchopulmonary dysplasia

INTRODUCTION

Noninvasive continuous positive airway pressure (CPAP) is recognized as an effective treatment for severe airway obstruction in young children. The aim of the present study was to compare a clinical setting with a physiological setting of noninvasive CPAP in infants with nocturnal alveolar hypoventilation due to severe upper airway obstruction (UAO) or bronchopulmonary dysplasia (BPD).

METHODS

The breathing pattern and respiratory muscle output of all consecutive infants due to start CPAP in our noninvasive ventilation unit were retrospectively analysed. CPAP set on clinical noninvasive parameters (clinical CPAP) was compared to CPAP set on the normalization or the maximal reduction of the oesophageal pressure (Poes) and transdiaphragmatic pressure (Pdi) swings (physiological CPAP). Expiratory gastric pressure (Pgas) swing was measured.

RESULTS

The data of 12 infants (mean age 10 ± 8 mo) with UAO (n = 7) or BPD (n = 5) were gathered. The mean clinical CPAP (8 ± 2 cmH₂O) was associated with a significant decrease in Poes and Pdi swings. Indeed, Poes swing decreased from 31 ± 15 cmH₂O during spontaneous breathing to 21 ± 10 cmH₂O during CPAP (P < 0.05). The mean physiological CPAP level was 2 ± 2 cmH2₂O higher than the mean clinical CPAP level and was associated with a significantly greater improvement in all indices of respiratory effort (Poes swing 11 ± 5 cm H₂O; P < 0.05 compared to clinical CPAP). Expiratory abdominal activity was present during the clinical CPAP and decreased during physiological CPAP.

CONCLUSIONS

A physiological setting of noninvasive CPAP, based on the recording of Poes and Pgas, is superior to a clinical setting, based on clinical noninvasive parameters. Expiratory abdominal activity was present during spontaneous breathing and decreased in the physiological CPAP setting.

Periodic leg movement, nasal CPAP, and expiratory muscles

BACKGROUND

Periodic leg movements (PLMs) may appear during nasal CPAP titration, persisting despite the elimination of hypopneas.

METHODS

Systematic recordings of expiratory abdominal muscles on the right and left sides with surface electromyographic (EMG) electrodes lateral to navel, and close from the lateral side of abdomen, were added during nasal CPAP titration for treatment of obstructive sleep apnea (OSA). Positive airway pressure was titrated during nocturnal polysomnography, based on analysis of the flow curve derived from the CPAP equipment and EEG analysis, including persistence of phases A2 and A3 of the cyclic alternating pattern (CAP). The requirement was to eliminate American Association of Sleep Medicine (AASM)-defined hypopnea and also flow limitation and abnormal EEG patterns. When CPAP reached valid results, it was lowered at the time of awakening by 2 or 3 cm H(2)O, and titration was performed again. Data collected during a 7-month period on adults with a prior diagnosis of OSA who had received treatment with nasal CPAP regardless of age and sex were rendered anonymous and were retrospectively rescored by a blinded investigator.

RESULTS

Eighty-one successively seen patients with PLMs during CPAP titration were investigated. Elimination of AASM-defined hypopnea was not sufficient to eliminate the PLMs observed during the titration; higher CPAP eliminated flow limitation and CAP phases A2 and A3 and persisting PLMs. PLMs were associated with simultaneous EMG bursts in expiratory abdominal muscles.

CONCLUSIONS

The presence of PLMs during CPAP titration indicates the persistence of sleep-disordered breathing. PLMs during CPAP titration are related to the presence of abdominal expiratory muscle activity.

The human genioglossus response to negative airway pressure: stimulus timing and route of delivery

The genioglossus reflex response to sudden onset pulses of negative airway pressure (NAP) in humans is reported to occur more commonly at end rather than onset of expiration when delivered via a mouthpiece. We examined whether this response was modulated by the route of stimulus delivery throughout the respiratory cycle. The genioglossus surface EMG (GGsEMG) response to NAP delivered randomly throughout the respiratory cycle was measured in a set of experiments: (i) 40 stimuli of NAP at -5, -7.5 and -10 cmH2O applied to eight healthy, awake, supine males via nose-mask; and (ii) 60 stimuli of -7.5 cmH2O NAP applied to 15 subjects via both nose-mask and mouthpiece in random order. Despite similar pressure changes being detected in the epiglottis during both routes of stimulus delivery, far lower pressure changes were measured at the nasal choanae during mouthpiece compared with nose-mask delivery. There were no significant differences between the responses during any phase of respiration, nor when NAP was delivered via nose-mask or mouthpiece. We conclude that the sensitivity of the GGsEMG response to NAP in humans does not vary significantly with phase of respiration or route of breathing.

Modulation of upper airway collapsibility during sleep: influence of respiratory phase and flow regimen

We hypothesized that upper airway collapsibility is modulated dynamically throughout the respiratory cycle in sleeping humans by alterations in respiratory phase and/or airflow regimen. To test this hypothesis, critical pressures were derived from upper airway pressure-flow relationships in six tracheostomized patients with obstructive sleep apnea. Pressure-flow relationships were generated by varying the pressure at the trachea and nose during tracheostomy (inspiration and expiration) (comparison A) and nasal (inspiration only) breathing (comparison B), respectively. When a constant airflow regimen was maintained throughout the respiratory cycle (tracheostomy breathing), a small yet significant decrease in critical pressure was found at the inspiratory vs. end- and peak-expiratory time point [7.1 +/- 1.6 (SE) to 6.6 +/- 1.9 to 6.1 +/- 1.9 cmH(2)O, respectively; P < 0.05], indicating that phasic factors exerted only a modest influence on upper airway collapsibility. In contrast, we found that the inspiratory critical pressure fell markedly during nasal vs. tracheostomy breathing [1.1 +/- 1.5 (SE) vs. 6.1 +/- 1.9 cmH(2)O; P < 0.01], indicating that upper airway collapsibility is markedly influenced by differences in airflow regimen. Tracheostomy breathing was also associated with a reduction in both phasic and tonic genioglossal muscle activity during sleep. Our findings indicate that both phasic factors and airflow regimen modulate upper airway collapsibility dynamically and suggest that neuromuscular responses to alterations in airflow regimen can markedly lower upper airway collapsibility during inspiration.