Sniff nasal inspiratory pressure in children with muscular, chest wall or lung disease

Sleep and sleep-related breathing disorders in patients with spinal muscular atrophy: a changing perspective from novel treatments?

Spinal Muscular Atrophy (SMA) is an inherited neuromuscular disorder characterized by progressive muscle weakness and atrophy, resulting from the degeneration of motor neurons in the spinal cord. A critical aspect of SMA is its impact on respiratory function. As the disease progresses, respiratory muscles, in particular intercostal muscles, become increasingly affected, leading to breathing difficulties and respiratory failure. Without intervention, many children with SMA type 1 die from respiratory failure before their second year of life. While assisted ventilation has improved survival, it often results in ventilator dependence. The development of new SMN-augmenting therapies has renewed optimism, but their long-term impact on respiratory function is uncertain, and non-invasive respiratory support remains an important part of SMA management. Despite the importance of respiratory support in SMA, knowledge regarding sleep disorders in this population is limited. This review aims to synthesize existing literature on sleep and sleep-related breathing disorders in patients with SMA, with a focus on SMA type 1. We summarize evidence of sleep-disordered breathing and respiratory failure in SMA, as well as outcomes and survival benefits associated with non-invasive or invasive ventilation with or without pharmacological therapies. We also discuss current knowledge regarding the effects of novel disease-modifying therapies for SMA on respiratory function and sleep. In conclusion, optimal care for children with SMA requires a multidisciplinary approach that includes neurology and respiratory specialists. This review highlights the importance of monitoring sleep and respiratory function in SMA, as well as the potential benefits and challenges associated with assisted ventilation combined with new therapies.

Reliability of maximal respiratory nasal pressure tests in healthy young adults

INTRODUCTION

Sniff nasal inspiratory (SNIP) and expiratory pressure (SNEP) may complement the assessment of respiratory muscle strength. Thus, specifying their reliability is relevant to improving the clinical consistency of both tests.

OBJECTIVE

To assess the reliability of SNIP and SNEP in healthy young adults.

METHODS

This cross-sectional study included self-reported healthy aged 18 to 29 years. SNIP was performed using a plug to occlude one nostril, while SNEP was conducted using a facemask. Participants performed 20 SNIP and SNEP maneuvers with 30-second intervals in between. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimum detectable change (MDC) assessed the reliability of SNIP and SNEP. Analyses were conducted between the highest peak pressure and the first reproducible maneuver in men and women.

RESULTS

The total sample comprised 32 participants: 16 men and 16 women. The ICC, SEM, and MDC for SNIP maneuvers were 0.994 (95%CI 0.988 to 0.997), 1.820 cmH2O, and 5.043 cmH2O, respectively. For SNEP, these parameters were 0.950 (95%CI 0.897 to 0.976), 6.03 cmH2O, and 16.716 cmH2O. The SNIP and SNEP in men showed ICC of 0.992 (95%CI 0.977 to 0.997) and 0.877 (95%CI 0.648 to 0.957), SEM of 2.07 and 7.66 cmH2O, and MDC of 5.74 and 21.23 cmH2O. In women, SNIP and SNEP presented ICC of 0.992 (95%CI 0.977 to 0.997) and 0.957 (95%CI 0.878 to 0.985), SEM of 1.15 and 6.11 cmH2O, and MDC of 3.19 and 16.95 cmH2O. Also, 60% of the highest SNIPs occurred among the 11th and 20th maneuvers in men and women. In men, 55% of the highest SNEPs occurred among the 11th and 20th maneuvers; this value was 50% in women.

CONCLUSION

SNIP and SNEP showed excellent reliability. The reliability of SNIP and SNEP in men was good and excellent, respectively, whereas both tests had excellent reliability in women. Also, women reached the highest peak pressure faster than men in both tests.

Respiratory function and sleep in children with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease in children causing sleep and respiratory disorders that are poorly described in the literature compared to adult forms. This retrospective observational study was performed at the Armand Trousseau University Hospital, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France. We retrospectively collected data from lung function tests, nocturnal gas exchange recordings, and polysomnography of 24 children with DM1. 39% of the children with DM1 reported respiratory symptoms indicative of sleep disordered breathing. Three patients (12%) presented with a restrictive respiratory pattern, 10 (42%) with a sleep apnoea syndrome, mainly of obstructive origin (2/10 with severe obstructive sleep apnea syndrome), and 11 (45%) with nocturnal alveolar hypoventilation. Non-invasive ventilation (NIV) was indicated in 9 (37.5%) children, although tolerance was poor. No significant deterioration in respiratory function or nocturnal gas exchange was observed during the NIV-free period. This study provides new and useful insights into DM1 disease evolution in children to better adapt for respiratory follow-up and management. This highlights the need for future research to better understand the origin of respiratory and sleep disorders in patients with DM1.

Short-term effect and effect on rate of lung function decline after surgery for neuromuscular or syndromic scoliosis

INTRODUCTION

Understanding the impact of scoliosis surgery on lung function is important for counseling patients about risks and benefits of surgery. We prospectively compared the trends in lung function test (LFT) results before and after scoliosis surgery in children with neuromuscular diseases or dysmorphic syndromes. We hypothesized a stabilization.

METHODS

We prospectively included children with neuromuscular or syndromic scoliosis able to perform LFTs. We studied (forced) vital capacity ([F]VC), ratio of forced expiratory volume in 1 s (FEV₁ ) and FVC, and peak expiratory flow (PEF). Preoperative LFT results were compared with results 3-4 months after surgery. The mean monthly change in LFT results up to 2 years after surgery was compared with the preoperative natural history using linear mixed-effects models.

RESULTS

We included 43 patients. No significant change was observed in absolute values of (F)VC, FEV₁ /FVC, and PEF before and after surgery. In 23 neuromuscular patients median standardized VC, FVC, and PEF decreased significantly after surgery from 43% to 33%, 42% to 31%, and 51% to 40%, respectively. In 20 syndromic patients, median FVC decreased from 68% to 65%. The monthly rate of change in FVC did not change significantly in both groups with a mean difference of 0.18% (95% CI: -0.27, -0.61) and -0.44% (95% CI: -1.05, 0.16).

CONCLUSION

No stabilization of lung function 3-4 months after scoliosis surgery was observed in children with neuromuscular and syndromic scoliosis with restrictive lung function disease. The effect on the rate of lung function decline remains inconclusive.

Natural history of respiratory muscle strength in spinal muscular atrophy: a prospective national cohort study

Background

Respiratory complications are the most important cause of morbidity and mortality in spinal muscular atrophy (SMA). Respiratory muscle weakness results in impaired cough, recurrent respiratory tract infections and eventually can cause respiratory failure. We assessed longitudinal patterns of respiratory muscle strength in a national cohort of treatment-naïve children and adults with SMA, hypothesizing a continued decline throughout life.

Methods

We measured maximal expiratory and inspiratory pressure (PE_max and PI_max), Sniff Nasal inspiratory pressure (SNIP), peak expiratory flow (PEF), and peak cough flow (PCF) in treatment-naïve patients with SMA. We used mixed-models to analyze natural history patterns.

Results

We included 2172 measurements of respiratory muscle function from 80 treatment-naïve patients with SMA types 1c-3b. All outcomes were lower in the more severe phenotypes. Significant differences in PEF were present between SMA types from early ages onwards. PEF decline was linear (1–2%/year). PEF reached values below 80% during early childhood in types 1c-2, and during adolescence in type 3a. PE_max and PI_max were severely lowered in most patients throughout life, with PE_max values abnormally low (i.e. < 80 cmH₂O) in virtually all patients. The PE_max/PI_max ratio was < 1 throughout life in all SMA types, indicating that expiratory muscles were most affected. All but SMA type 3b patients had a lowered PCF. Patients with types 2b and 3a had PCF levels between 160 and 270 L/min, those with type 2a around 160 L/min and patients with type 1c well below 160 L/min. Finally, SNIP was low in nearly all patients, most pronounced in more severely affected patients.

Conclusions

There are clear differences in respiratory muscle strength and its progressive decline between SMA types. We observed lower outcomes in more severe SMA types. Particularly PEF may be a suitable outcome measure for the follow-up of respiratory strength in patients with SMA. PEF declines in a rather linear pattern in all SMA types, with clear differences at baseline. These natural history data may serve as a reference for longer-term treatment efficacy assessments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02227-7.

Pulmonary function testing in neuromuscular disease

Neuromuscular disorders frequently compromize pulmonary function and effective ventilation, and a thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognostication. Since many of these disorders can be progressive, serial assessments may be necessary to best define a trajectory of impairment or improvement with therapy. Patients with neuromuscular diseases may have few respiratory symptoms and limited signs of skeletal muscle weakness, but can have significant respiratory muscle weakness. A single testing modality may fail to elucidate true respiratory compromise, and often a combination of tests is recommended to fully evaluate these patients. Common tests performed in this population include measurement of flow rates, lung volumes, maximal pressures, and airways resistance. This review covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. The majority of parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.

Effects of diaphragmatic control on multiparametric analysis of the sniff nasal inspiratory pressure test and inspiratory muscle activity in healthy subjects

BACKGROUND

We investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate, contractile properties and electrical activity of the inspiratory muscles of healthy subjects. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively.

METHODS

Twenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values were used for analysis.

RESULTS

The maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01), contraction times (CT) (p = 0.02) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles. In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes.

CONCLUSION

The diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change force velocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.

Reliability of SNIP test and optimal number of maneuvers in 6-11 years healthy children

BACKGROUND AND PURPOSE

Sniff nasal inspiratory pressure (SNIP) is a voluntary inspiratory maneuver measured through a plug occluding one nostril. The investigation of the number of maneuvers necessary to reach the highest peak of SNIP in pediatric populations has been inconsistent. Thus, this study aimed to assess the reliability of SNIP in healthy children aged 6 to 11 years according to sex and age group, and to determine the optimal number of SNIP maneuvers for this age group.

METHODS

This cross-sectional study included healthy children with normal pulmonary function. We performed 12 to 20 SNIP maneuvers, with a 30 s rest between each maneuver. The reliability was tested using the intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimal detectable change (MDC), and Bland-Altman analysis for agreement.

RESULTS

A total of 121 healthy children (62 girls [51%]) were included in this study. The ICC and corresponding confidence interval (CI) between the highest measure and the first reproducible maneuver were 0.752 (0.656-0.824), SEM = 10.37 cmH2O, and MDC = 28.74 cmH2O. For children aged 6 to 7 years, the ICC was 0.669 (0.427-0.822), SEM = 10.76 cmH2O and MDC = 29.82 cmH2O; for children aged 8 to 11 years, the ICC was 0.774 (0.662-0.852), SEM = 9.74 cmH2O, and MDC = 26.05 cmH2O. For girls, the ICC was 0.817 (0.706-0.889), SEM = 9.40 cmH2O and MDC = 26.05 cmH2O; for boys, the ICC was 0.671 (0.487-0.798), SEM = 11.51 cmH2O, and MDC = 31.90 cmH2O. Approximately 80% of the total sample reached the highest SNIP before the 10th maneuver.

CONCLUSIONS

SNIP demonstrated moderate reliability between the maneuvers in children aged 6 to 11 years; older children and girls reached the SNIP peak faster. Finally, results indicated that 12 maneuvers were sufficient for healthy children aged 6 to 11 years to achieve the highest SNIP peak.

Assessment of respiratory muscles and motor function in children with SMA treated by nusinersen

INTRODUCTION

Nusinersen is associated with an improvement in motor function in children with spinal muscular atrophy (SMA) but data on respiratory muscles strength are scarce. Respiratory muscles performance and lung function were evaluated in children with SMA 1c and 2 after six injections of nusinersen (M14). Results from patients with SMA2 were compared with data of age-matched historical controls. Motor function tests (MFM and HINE-2) were assessed at baseline and M14 in the treated patients.

RESULTS

Sixteen children (2 SMA Type 1c and 14 SMA Type 2), mean age 9.4 ± 2.3 years, were included. The data of 14 historical SMA 2 controls (mean age 9.3 ± 1.9 years) were gathered. The strength of the global inspiratory muscles of SMA 2 treated with nusinersen, assessed on maximal static inspiratory pressure, forced vital capacity, and esophageal pressure during a maximal sniff was significantly better compared with historical controls (p < .05). A significant improvement in MFM and HINE-2 was observed in the patients with 16 SMA treated with nusinersen after 14 months as compared with baseline.

CONCLUSION

In children with SMA Type 2, respiratory muscle performance was significantly better after six injections of nusinersen as compared with age-matched SMA Type 2 historical controls.

Respiratory management of children with spinal muscular atrophy (SMA)

Spinal muscular atrophy (SMA) causes a predominantly bilateral proximal muscle weakness and atrophy. The respiratory muscles are also involved with a weakness of the intercostal muscles and a relatively spared diaphragm. This respiratory muscle weakness translates into a cough impairment, resulting in poor clearance of airway secretions and recurrent pulmonary infections, restrictive lung disease due to a poor or insufficient chest wall and lung growth, nocturnal hypoventilation and, finally, respiratory failure. Systematic and regular monitoring of respiratory muscle performance is necessary in children with SMA in order to anticipate respiratory complications, such as acute and chronic respiratory failure, and guide clinical care. This monitoring is based in clinical practice on volitional and noninvasive tests, such as vital capacity, sniff nasal inspiratory pressure, maximal static pressures, peak expiratory flow and peak cough flow because of their simplicity, availability and ease. In young children, those with poor cooperation or severe respiratory muscle weakness, other, mostly invasive, tests may be required to evaluate respiratory muscle performance. A sleep study, or at least overnight monitoring of nocturnal gas exchange is mandatory for detecting nocturnal alveolar hypoventilation. Training for patients and caregivers in cough-assisted techniques is recommended when respiratory muscle strength falls below 50% of predicted or in case of recurrent or severe respiratory infections. Noninvasive ventilation (NIV) should be initiated in case of isolated nocturnal hypoventilation and followed by a pediatric respiratory team with expertise in NIV. Multidisciplinary (neurology and respiratory) pediatric management is crucial for optimal care of children with SMA. © 2020 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Reference values of sniff nasal inspiratory pressure in healthy children

OBJECTIVE

To determine reference values of sniff nasal inspiratory pressure (SNIP) in healthy children.

METHODS

This cross-sectional observational study included healthy children aged 6 to 11 years of both sexes. The volunteers underwent a pulmonary function test to rule out respiratory disorders. Respiratory muscle strength was measured using maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), respectively, with MIP close to functional residual capacity (FRC) and residual volume, while MEP to total lung capacity. SNIP was performed through the nostril contralateral to the occlusion, close to FRC. Two 6-minute walk tests were performed to assess functional exercise capacity.

RESULTS

The sample comprised 121 healthy children (62 girls); 54% presented body mass index (BMI) percentile less than 85th and 46% more than equal to 85th percentile, higher than expected. SNIP values were similar between sexes (91.1 ± 21.0 cmH₂ O in girls and 87.7 ± 19.4 cmH₂ O in boys; P = .36) as well as the means of lower limits of normal (56.88 cmH₂ O for girls and 56.66 cmH₂ O for boys). Girls presented SNIP measurements larger than those of the MIP of FRC (P < .0001), while boys presented similar mean values for both. We found a positive correlation between SNIP and BMI percentile (r = .25, P = .04) in girls, unlike boys, in whom no correlation was observed.

CONCLUSIONS

SNIP reference values and mean lower limits of normal were defined for healthy children aged 6 to 11. BMI percentile seems to positively influence the inspiratory muscle strength measured by SNIP in girls only.

Cough, sniff and maximal static pressure patterns in spinal muscular atrophy

In spinal muscular atrophy (SMA), respiratory muscles are heterogeneously involved with a weakness of the intercostal muscles, possibly of the abdominal wall muscles, and a relatively spared diaphragm, resulting in cough impairment. An abnormal inspiratory cough phase pattern has been reported in SMA II and III. This short communication analyzed the esogastric pressures during voluntary cough in 49 SMA II and III patients. Four different patterns of coughing, reflecting an increasing degree of respiratory muscle weakness, were identified. The "mild weakness" profile was observed mainly in SMA III, while the "severe weakness" profile, which seems to correspond to the absence of abdominal muscle activity, was observed only in a few patients with SMA II. The cough profiles of 6 patients are presented together with their sniff and maximal static pressures measurements. Different esogastric pressure patterns were observed during these forceful maneuvers, suggesting variable involvement of the intercostal and abdominal muscles, and diaphragm during the evolution of SMA II and III.

Diaphragm sniff ultrasound: Normal values, relationship with sniff nasal pressure and accuracy for predicting respiratory involvement in patients with neuromuscular disorders

Background

In patients with neuromuscular disorders, assessment of respiratory function relies on forced vital capacity (FVC) measurements. Providing complementary respiratory outcomes may be useful for clinical trials. Diaphragm sniff ultrasound (US) is a noninvasive technique that can assess diaphragm function that may be affected in patients with neuromuscular disorders.

Purpose

We aimed to provide normal values of sniff diaphragm ultrasound, to assess the relationship between sniff diaphragm US, vital capacity (VC) and sniff nasal pressure. Additionally, we aimed to evaluate the diagnostic accuracy of sniff diaphragm US for predicting restrictive pulmonary insufficiency.

Materials and methods

We included patients with neuromuscular disorders that had been tested with a sniff diaphragm US and functional respiratory tests. Healthy subjects were also included to obtain normal diaphragm sniff ultrasound. We performed diaphragm tissue Doppler imaging (TDI) and time movement (TM) diaphragm echography combined with sniff maneuver.

Results

A total of 89 patients with neuromuscular diseases and 27 healthy subjects were included in our study. In patients, the median age was 32 years [25; 50] and the median FVC was 34% of predicted [18; 55]. Sniff diaphragm motion using TM ultrasound was significantly associated with sniff nasal pressure, both for the right hemidiaphragm (r = 0.6 p <0.0001) and the left hemidiaphragm (r = 0.63 p = 0.0008). Right sniff peak TDI velocity was also significantly associated with FVC (r = 0.72, p<0.0001) and with sniff nasal pressure (r = 0.66 p<0.0001). Sniff diaphragm ultrasound using either TM mode or TDI displayed significant accuracy for predicting FVC<60% with an area under curve (AUC) reaching 0.93 (p<0.0001) for the right sniff diaphragm ultrasound in TM mode and 0.86 (p<0.001) for right peak diaphragm TDI velocity.

Conclusion

Sniff diaphragm TM and TDI measures were significantly associated with sniff nasal pressure. Sniff diaphragm TM and TDI had a high level of accuracy to reveal respiratory involvement in patients with neuromuscular disorders. This technique is useful to assess and follow up diaphragm function in patients with neuromuscular disorders. It may be used as a respiratory outcome for clinical trials.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

Pulmonary Function Testing in Neuromuscular and Chest Wall Disorders

Neuromuscular and chest wall disorders frequently compromise pulmonary function, and thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognosis. Because many of these disorders can be progressive, serial assessments are necessary to best define a trajectory of impairment (or improvement with therapy). This article covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. Most parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.

Impact of moderate-severe persistent allergic rhinitis on thoraco-abdominal kinematics and respiratory muscle function

Objective: To assess thoraco-abdominal kinematics, respiratory muscle strength and electromyographic activity of the diaphragm (EAdi) in moderate-severe allergic rhinitis (AR) patients. Methods: A cross-sectional study involving 40 individuals (20 in the AR group) and 20 in the control group [CG]) was conducted. Ventilatory pattern and chest wall volume distribution (optoelectronic plethysmography), respiratory muscle strength (manovacuometry and sniff nasal inspiratory pressure [SNIP]), and EAdi were assessed in both groups. Results: The AR patients had impaired thoraco-abdominal kinematics (reduced total chest wall volume) (p = 0.004), lower values of total respiratory cycle time (p = 0.014) and expiratory time (p = 0.006). They also presented an increase of percentage contribution of the abdominal rib cage (p = 0.475) and respiratory rate (p = 0.019). A positive correlation among pulmonary rib cage tidal volume and MIP (r = 0.544; p < 0.001), SNIP (r = 0.615; p < 0.001), and MEP (r = 0.604; p < 0.001) was observed. After adjusting for age, BMI and gender through multivariate analysis, the individuals with AR presented lower values ​​of MIP (β = -24.341; p < 0.001), MEP (β = -0.277; p < 0.001), SNIP (β = -34.687; p < 0.001) and RMS (β = -0.041; p = 0.017). Conclusions: The individuals with moderate-severe persistent AR had worse respiratory muscle strength, diaphragm activation and chest wall volume distribution with a higher abdominal contribution to tidal volume than the control group. These findings reinforce the notion that the upper and lower airways work in an integrated and synergistic manner.

Diaphragm: Pathophysiology and Ultrasound Imaging in Neuromuscular Disorders

Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive respiratory pattern. The diaphragm is the main respiratory muscle involved during inspiration. Ultrasound imaging is a noninvasive, radiation-free, accurate and safe technique allowing assessment of diaphragm anatomy and function. The authors review the pathophysiology of diaphragm in neuromuscular disorders, the methodology and indications of diaphragm ultrasound imaging as well as possible pitfalls in the interpretation of results.

The assessment of sniff nasal inspiratory pressure in patients with Duchenne muscular dystrophy in China

OBJECTIVE

Progressive weakness of respiratory muscles remains one of the leading causes of death among patients with Duchenne muscular dystrophy (DMD). Currently, there are few pulmonary function data among Chinese DMD patients. This study was carried out to evaluate the sniff nasal inspiratory pressure (SNIP) change among a group of Chinese DMD patients, and compare it with the SNIP value of patients with neuromuscular disorders in other countries.

METHODS

SNIP data were collected in three research groups that consists of 581 subjects: 125 DMD boys who have taken steroid (Age 5.0-13.3, DMD-steroid group), 145 DMD steroid-naive boys (Age 5.0-13.9, DMD-nonsteroid group), and 311 healthy controls (Age 5.0-14.0, Control group).

RESULTS

The SNIP for DMD-nonsteroid group, DMD-steroid group and Control group were: 56.5 (±14.3) cm H₂O,66.4 (±15.5) cm H₂O and 78.9 (±21.5) respectively. The SNIP in the DMD-nonsteroid group became significantly different from that of the healthy controls since age 7.0-8.9. The significant difference of SNIP between DMD-steroid group and DMD-nonsteroid group at age 7.0-10.9. The peak value of SNIP in the DMD-nonsteroid group appeared at age 8.7, and decreased dramatically thereafter, while in DMD-steroid group and the Control group peaked at 10.2 years and 12.2 years respectively. There was a bit difference between SNIP in this group and that in previous researches which may be due to geographical distribution and ethnic backgrounds.

CONCLUSION

This study strengthens the previous findings that SNIP can be used to evaluate respiratory dysfunction during the early stage of young patients with neuromuscular disorders, and demonstrates that steroid is effective in slowing the decrease of SNIP in this group of Chinese DMD boys.

Effects of diaphragmatic control on the assessment of sniff nasal inspiratory pressure and maximum relaxation rate

OBJECTIVE:

To assess the influence of diaphragmatic activation control (diaphC) on Sniff Nasal-Inspiratory Pressure (SNIP) and Maximum Relaxation Rate of inspiratory muscles (MRR) in healthy subjects.

METHOD:

Twenty subjects (9 male; age: 23 (SD=2.9) years; BMI: 23.8 (SD=3) kg/m²; FEV₁/FVC: 0.9 (SD=0.1)] performed 5 sniff maneuvers in two different moments: with or without instruction on diaphC. Before the first maneuver, a brief explanation was given to the subjects on how to perform the sniff test. For sniff test with diaphC, subjects were instructed to perform intense diaphragm activation. The best SNIP and MRR values were used for analysis. MRR was calculated as the ratio of first derivative of pressure over time (dP/dt_max) and were normalized by dividing it by peak pressure (SNIP) from the same maneuver.

RESULTS:

SNIP values were significantly different in maneuvers with and without diaphC [without diaphC: -100 (SD=27.1) cmH₂O/ with diaphC: -72.8 (SD=22.3) cmH₂O; p<0.0001], normalized MRR values were not statistically different [without diaphC: -9.7 (SD=2.6); with diaphC: -8.9 (SD=1.5); p=0.19]. Without diaphC, 40% of the sample did not reach the appropriate sniff criteria found in the literature.

CONCLUSION:

Diaphragmatic control performed during SNIP test influences obtained inspiratory pressure, being lower when diaphC is performed. However, there was no influence on normalized MRR.

Assessment and management of respiratory function in patients with Duchenne muscular dystrophy: current and emerging options

Duchenne muscular dystrophy (DMD) is an X-linked myopathy resulting in progressive weakness and wasting of all the striated muscles including the respiratory muscles. The consequences are loss of ambulation before teen ages, cardiac involvement and breathing difficulties, the main cause of death. A cure for DMD is not currently available. In the last decades the survival of patients with DMD has improved because the natural history of the disease can be changed thanks to a more comprehensive therapeutic approach. This comprises interventions targeted to the manifestations and complications of the disease, particularly in the respiratory care. These include: 1) pharmacological intervention, namely corticosteroids and idebenone that significantly reduce the decline of spirometric parameters; 2) rehabilitative intervention, namely lung volume recruitment techniques that help prevent atelectasis and slows the rate of decline of pulmonary function; 3) scoliosis treatment, namely steroid therapy that is used to reduce muscle inflammation/degeneration and prolong ambulation in order to delay the onset of scoliosis, being an additional contribution to the restrictive lung pattern; 4) cough assisted devices that improve airway clearance thus reducing the risk of pulmonary infections; and 5) non-invasive mechanical ventilation that is essential to treat nocturnal hypoventilation, sleep disordered breathing, and ultimately respiratory failure. Without any intervention death occurs within the first 2 decades, however, thanks to this multidisciplinary therapeutic approach life expectancy of a newborn with DMD nowadays can be significantly prolonged up to his fourth decade. This review is aimed at providing state-of-the-art methods and techniques for the assessment and management of respiratory function in DMD patients.

Can daytime measures of lung function predict respiratory failure in children with neuromuscular disease?

Neuromuscular disorders in children are a heterogeneous group of conditions with a variable age of presentation and overlapping clinical manifestations, many of which have progressive respiratory morbidity. Respiratory insufficiency occurs as a consequence of an imbalance between demands on the respiratory system and respiratory muscle capacity. Daytime measures of pulmonary function are used routinely in these children to assess respiratory status and monitor the consequences of the progression of muscle weakness. This review describes the current evidence for daytime pulmonary function tests and their ability to predict imminent respiratory morbidity.

Thoraco-abdominal asymmetry and asynchrony in congenital diaphragmatic hernia

OBJECTIVE

Congenital diaphragmatic hernia (CDH) consists of an incomplete formation of the diaphragm and the subsequent herniation of abdominal bowels. Diaphragmatic defect can be repaired by primary closure or placing a patch. Respiratory follow up usually focuses on spirometric and clinical evaluation. The aim of the study was to assess thoraco-abdominal volumes in CDH patients and to verify whether the action of the diaphragm on the chest wall is altered leading to an asymmetric and asynchronous expansion of the different thoracoabdominal compartments.

PATIENTS AND METHODS

Total and compartmental chest wall volumes and asynchronies were measured by Opto-Electronic Plethysmography in 14 CDH patients (7 M/7F, age 5 ± 2 years, 12 left side operated) and in 9 age matched healthy subjects during quiet spontaneous breathing in supine position. Patients were divided in two groups: five patients with suture (group S) and nine patients with diaphragmatic patch (group P). Pulmonary function was assessed by spirometry and spirometric parameters were expressed as Z-score.

RESULTS

In group P abdominal contribution to tidal volume was lower than healthy controls and group S. Unlike controls, in both CDH groups the right side of pulmonary rib cage moved inward with a correspondent left side expansion during inspiration. In group S, thoraco-abdominal asynchronies were higher than in group P and controls, especially in the right side. Five patients belonging to group P had a spirometric obstructive pattern.

CONCLUSIONS

In overall CDH patients a reduced action of the treated (left) hemi-diaphragm is evident. In patients treated by primary suture, a compensatory action of the right side allows to reach a normal total diaphragmatic displacement and a proper contribution of the whole diaphragm to tidal volume. In patients treated by diaphragmatic patch, instead, thoraco-abdominal asynchronies are prevented.

The value of respiratory muscle testing in children with neuromuscular disease

Routine lung function and respiratory muscle testing are recommended in children with neuromuscular disease (NMD), but these tests are based on noninvasive volitional maneuvers, such as the measurement of lung volumes and maximal static pressures, that young children may not always be able to perform. The realization of simple natural maneuvers such as a sniff or a cough, and the measurement of esophageal and gastric pressures during spontaneous breathing can add valuable information about the strength and endurance of the respiratory muscles in young children. Monitoring respiratory muscles in children with NMD may improve understanding of the natural history of NMD and the evaluation of disease severity. It may assist and guide clinical management and it may help the identification and selection of optimal end points, as well as the most informative parameters and patients for clinical trials.

Determinants of respiratory pump function in patients with cystic fibrosis

Respiratory failure constitutes the major cause of morbidity and mortality in patients with Cystic Fibrosis (CF). Respiratory failure could either be due to lung parenchyma damage or to insufficiency of the respiratory pump which consists of the respiratory muscles, the rib cage and the neuromuscular transmission pathways. Airway obstruction, hyperinflation and malnutrition have been historically recognised as the major determinants of respiratory pump dysfunction in CF. Recent research has identified chronic infection, genetic predisposition, dietary and pharmaceutical interventions as possible additional determinants of this impairment. Furthermore, new methodological approaches in assessing respiratory pump function have led to a better understanding of the pathogenesis of respiratory pump failure in CF. Finally, respiratory muscle function could be partially preserved in CF patients with structured interventions such as aerobic exercise, inspiratory muscle training and non-invasive ventilation and CF patients could consequently be relatively protected from respiratory fatigue and respiratory failure.

Normal values for inspiratory muscle function in children

Assessment of inspiratory muscle function (IMF) is limited in children with neuromuscular disorders, because respiratory muscle tests are poorly standardized and valid normative data are unavailable. We investigated maximum inspiratory pressure after exhalation to residual volume (MIP), mouth occlusion pressure (P0.1) and time of inspiration during quiet breathing and derived inspiratory muscle load (P0.1/MIP), and tension time index (TTI) in 301 healthy schoolchildren 6-16 years old. Gender-specific and age-dependent percentile curves for MIP were drawn with the median, 5%, 10%, 25%, 75% and 95% percentile. P0.1 was equal in boys and girls (0.23  ±  0.11 kPa), while MIP was significantly higher in boys (6.8  ±  2.2 versus 5.8  ±  2.4 kPa). Consequently, P0.1/MIP (4.8% ± 3.2% versus 4.0% ± 3.1%) and TTI (0.2  ±  0.14 versus 0.16  ±  0.14) were significantly higher in girls. MIP was 2.90 + 0.36 × age (kPa) and 3.19 + 0.24 × age (kPa) in boys and girls, respectively. The 95% confidence intervals for boys and girls, respectively, were MIP, 6.3-7.3 kPA and 5.4-6.2 kPa; P0.1/MIP, 3.5%-4.5% and 4.3%-5.3%; TTI, 0.14-0.18 and 0.18-0.22; and P0.1, 0.20-0.24 kPa for both. IMF in children has a wide interindividual variability; however percentile curves facilitate a longitudinal assessment of individual patients. Furthermore, narrow confidence intervals allow for comparisons of study populations, making IMF an appropriate endpoint for clinical trials.

Respiratory muscle decline in Duchenne muscular dystrophy

OBJECTIVES

Duchenne muscular dystrophy (DMD) causes progressive respiratory muscle weakness. The aim of the study was to analyze the trend of a large number of respiratory parameters to gain further information on the course of the disease.

STUDY DESIGN

Retrospective study.

SUBJECT SELECTION

48 boys with DMD, age range between 6 and 19 year old, who were followed in our multidisciplinary neuromuscular clinic between 2001 and 2011.

METHODOLOGY

Lung function, blood gases, respiratory mechanics, and muscle strength were measured during routine follow-up over a 10-year period. Only data from patients with at least two measurements were retained.

RESULTS

The data of 28 patients were considered for analysis. Four parameters showed an important decline with age. Gastric pressure during cough (Pgas cough) was below normal in all patients with a mean decline of 5.7 ± 3.8 cmH2 O/year. Sniff nasal inspiratory pressure (SNIP) tended to increase first followed by a rapid decline (mean decrease 4.8 ± 4.9 cmH2 O; 5.2 ± 4.4% predicted/year). Absolute forced vital capacity (FVC) values peaked around the age of 13-14 years and remained mainly over 1 L but predicted values showed a mean 4.1 ± 4.4% decline/year. Diaphragmatic tension-time index (TTdi) increased above normal values after the age of 14 years with a mean increase of 0.04 ± 0.04 point/year.

CONCLUSIONS

This study confirms the previous findings that FVC and SNIP are among the most important parameters to monitor the evolution of DMD. Expiratory muscle strength, assessed by Pgas cough, and the endurance index, TTdi, which are reported for the first time in a large cohort, appeared to be informative too, even though measured through an invasive method.

Longitudinal course of lung function and respiratory muscle strength in spinal muscular atrophy type 2 and 3

BACKGROUND

Spinal muscular atrophy (SMA) is a common genetic disorder that causes severe hypotonia and weakness, and often fatal restrictive lung disease. The aim of the study was to describe the natural history of the respiratory involvement in patients with SMA type 2 and 3 in order to assess the relevance of the clinical classification and identify the parameters associated with the earliest and most rapid decline over time.

METHODS

Thirty-one patients aged 3-21 years were followed over a 10-year period. Lung function, blood gases, respiratory mechanics and muscle strength with recording of oesogastric pressures were measured during routine follow-up.

RESULTS

At least two measurements were available in 16 patients (seven type 2 and nine type 3). Among all the volitional and non-volitional, invasive and non-invasive tests, forced vital capacity (FVC) and sniff nasal inspiratory pressure (SNIP) were shown to be the most informative parameters, showing lower values in SMA type 2, with however a similar rate of decline in patients with SMA type 2 and 3.

CONCLUSION

Our results confirm an earlier decline in lung and respiratory muscle function in patients classified as SMA type 2 as compared with patients classified as type 3. This decline can be assessed by two simple non-invasive tests, FVC and SNIP, with the last maneuver being feasible and reliable in the youngest children, underlying its interest for the monitoring of children with SMA.

The lung is involved in juvenile dermatomyositis

BACKGROUND

Juvenile dermatomyositis (JDM) is the main cause of chronic idiopathic inflammatory myopathy of autoimmune origin in children. The aim of this multicenter prospective study was to describe respiratory status and treatment of children followed for JDM.

METHODS AND PATIENTS

Clinical manifestations, pulmonary function tests (PFT), chest high-resolution computed tomography (HRCT) scan results, and treatments and their adverse effects were analyzed in children followed for JDM.

RESULTS

Twenty-one patients (median age: 9.9 years; range: 20 months-18 years) were included. The median of disease duration at the time of the analysis was 3 years (range: 6 months-9 years 4 months). Overall 16 (76%) of 21 children presented with a respiratory involvement related to JDM including interstitial lung disease (n = 3) and/or respiratory muscle involvement (n = 7). Seven patients presented with other nonspecific manifestations. Three children had aspiration pneumonia. A chest HRCT was performed in 15 children, and abnormalities were observed in 12. PFT were performed in 20 of 21 patients. Seven showed functional abnormalities: restrictive ventilatory defect (n = 3) or obstructive ventilatory defect (n = 4). Six patients had abnormal respiratory muscle tests, including three with a restrictive ventilatory defect and one with an obstructive ventilatory defect. One other child with an acute aspiration pneumonia had a clearly muscle respiratory involvement but was too young to perform respiratory muscle tests and confirm this diagnosis. Treatment comprised systemic corticosteroid for all patients and adjuvant immunosuppressive therapy for 11. Adverse effects linked to treatment were reported in eight patients.

CONCLUSION

The frequency of lung involvement in children with JDM justifies systematic respiratory assessment with PFT including measures of respiratory muscle strength. We suggest that a chest HRCT scan is indicated in cases of respiratory symptoms and/or PFT abnormalities. Longitudinal studies are needed to assess pediatric characteristics, long-term outcomes, and responses to treatment taking into account the risk-benefit ratio.

Computed tomography measurement of rib cage morphometry in emphysema

Background

Factors determining the shape of the human rib cage are not completely understood. We aimed to quantify the contribution of anthropometric and COPD-related changes to rib cage variability in adult cigarette smokers.

Methods

Rib cage diameters and areas (calculated from the inner surface of the rib cage) in 816 smokers with or without COPD, were evaluated at three anatomical levels using computed tomography (CT). CTs were analyzed with software, which allows quantification of total emphysema (emphysema%). The relationship between rib cage measurements and anthropometric factors, lung function indices, and %emphysema were tested using linear regression models.

Results

A model that included gender, age, BMI, emphysema%, forced expiratory volume in one second (FEV₁)%, and forced vital capacity (FVC)% fit best with the rib cage measurements (R² = 64% for the rib cage area variation at the lower anatomical level). Gender had the biggest impact on rib cage diameter and area (105.3 cm²; 95% CI: 111.7 to 98.8 for male lower area). Emphysema% was responsible for an increase in size of upper and middle CT areas (up to 5.4 cm²; 95% CI: 3.0 to 7.8 for an emphysema increase of 5%). Lower rib cage areas decreased as FVC% decreased (5.1 cm²; 95% CI: 2.5 to 7.6 for 10 percentage points of FVC variation).

Conclusions

This study demonstrates that simple CT measurements can predict rib cage morphometric variability and also highlight relationships between rib cage morphometry and emphysema.

Sniff nasal inspiratory pressure and sleep disordered breathing in childhood neuromuscular disorders

The ease of sniff nasal inspiratory pressure testing may extend application of respiratory muscle assessment to younger and cognitively-impaired children. We sought to quantify sniff nasal inspiratory pressure in childhood neuromuscular disorders, and to correlate this measure with conventional pulmonary function tests and overnight polysomnography. Thirty children (mean 9.7 ± 3.8 years, range 4.3-16.5 years) with diagnosed neuromuscular disorders (Duchenne muscular dystrophy, spinal muscular atrophy, Becker muscular dystrophy, congenital myopathy, facioscapulohumeral muscular dystrophy, myotonic dystrophy, multi-minicore disease) underwent assessment. Thirty-seven percent displayed cognitive impairment. Those with neuromuscular disorders were then compared with 32 volunteer age- and gender-matched controls (mean 10.9 ± 2.9 years, range 6.6-17.2 years) with normal respiratory function. Twenty-three children with neuromuscular disorders also underwent overnight polysomnography. Children with neuromuscular disorders demonstrated significantly impaired sniff nasal inspiratory pressure, maximal inspiratory pressure, FEV(1) and FVC (p<0.05). A positive correlation was identified between daytime sniff nasal inspiratory pressure and maximal inspiratory pressure (r=0.58), FEV(1) (r=0.55) and FVC (r=0.46), though not with polysomnography variables (respiratory disturbance index, nadir SpO(2), peak CO(2)). Moderate prevalence of nocturnal hypoxia was observed, and 32% of children demonstrated sleep disordered breathing. Sniff nasal inspiratory pressure assessment was well tolerated, representing a promising surrogate measure for assessment of respiratory function in childhood neuromuscular disorders.

Indicators for ventilator use in Duchenne muscular dystrophy

BACKGROUND

Noninvasive mechanical ventilation is being used up to continuously by patients with Duchenne muscular dystrophy (DMD). Invasive and noninvasive tests are used to assess ventilatory function but there are few reports relating them to extent of ventilator dependence for which simple and cost effective parameters are needed.

OBJECTIVE

To investigate the relative efficacy of noninvasive lung function parameters for determining extent of need for ventilator use.

MATERIALS AND METHODS

83 DMD patients were divided into three groups: no ventilator use (asymptomatic) (n = 26) [Group 1], nocturnal ventilator use (symptomatic) (n = 20) [Group 2], and full-time ventilator dependence (n = 37) [Group 3]. Tidal volume (TV), vital capacity (VC), respiratory rate (RR), inspiratory time (Ti), respiratory cycle time (Ttot), rapid shallow breathing index (RSBI [RR/TV]), breathing intolerance index (BITI), ventilator requirement index (VRI) and a new parameter RR/VC were monitored and compared. Data were analyzed with receiver-operating-characteristic curves (ROC) and the area under the curve (AUC) was calculated.

RESULTS

In group 2 and 3, patients used NIV for 3.3 ± 2.1 and 11.2 ± 4.7 years, respectively. By ROC comparison, RR/VC (RR/VC ≥ 0.024 [AUC, 0.921] and ≥0.071 [AUC, 0.935]), RR/TV (RR/TV ≥ 0.024 [AUC, 0.905] and ≥0.153 [AUC, 0.905]), and VC (VC ≤ 770 ml [AUC, 0.896] and ≤370 ml [AUC, 0.898]) represented to introduce nocturnal and continuous ventilator use, respectively. TV/VC, BITI, and VRI were either less sensitive or less specific.

CONCLUSIONS

Lung function parameters including RR/VC, RR/TV, and VC are useful and inexpensive in predicting the extent of need for ventilator use. Overall, RR/VC is the most appropriate predictor for determining extent of need for ventilator use.

Respiratory muscle pressures in non-CF bronchiectasis: Repeatability and reliability

Background: Respiratory muscle strength is used diagnostically in clinical practice and as an outcome measure in clinical trials in various chronic lung diseases. There is limited data on its repeatability in people with non-CF bronchiectasis. The aim of the present study was to assess the repeatability of maximal inspiratory (P Imax) and expiratory pressures (PEmax) in a group of patients with stable, moderate-to-severe non-CF bronchiectasis. Methods: Twenty participants with stable moderate-to-severe non-CF bronchiectasis were recruited. Respiratory muscle strength measurements (three maximal inspiratory and expiratory pressures) were made on 2 separate days. A standard protocol was used, including practice tests, before obtaining three technically acceptable and reproducible readings with a difference of 10% or less between values. Clinical trial registration number: ClinicalTrials.gov: NCT00487149. Results: The mean (SD) age of the non-CF bronchiectasis group was 63 (9) years. Maximal inspiratory pressures were repeatable with mean (SD) for highest PImax, Test 1 and Test 2, 75.90 (20) and 79.40 (19) cmH2O, and limits of agreement (mean difference ± 2SD) —3.50 ± 20 cmH2O, (p = 0.14). Maximal expiratory pressures differed significantly with mean (SD) for highest PEmax, Test 1 and Test 2, 102.25 (27) and 112.30 (32) cmH 2O, and limits of agreement (mean difference ± 2SD) —10.10 ± 35 cmH2O, (p = 0.02). The intraclass correlation coefficient (95% CI) for highest PImax and PEmax was 0.93 (95% CI 0.82 to 0.97) and 0.90 (95% CI 0.76 to 0.96), respectively. Conclusion: Maximal inspiratory pressure measurements were repeatable during a period of clinical stability in moderate-to-severe non-CF bronchiectasis, suggesting this may be a useful outcome measure in non-CF bronchiectasis. Once a baseline has been established, a second visit is not required. PEmax was not a repeatable measure and further study is necessary to ascertain how much practice testing is required to obtain an accurate value.