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Published on: July 19, 2013
Spontaneous Breathing Pattern as Respiratory Functional Outcome in Children with Spinal Muscular Atrophy (SMA)
A LoMauro1, A Aliverti1, C Mastella2
1Dipartimento di Elettronica, Informazione e Bioingegneria; Politecnico di Milano, Italy.
Insights
Respiratory muscle weakness in spinal muscular atrophy (SMA) affects breathing patterns differently across disease types. Ribcage muscle weakness is a key indicator, correlating with motor function in children with SMA.
Area of Science:
- Pediatric Pulmonology
- Neuromuscular Disorders
- Biomedical Engineering
Background:
- Spinal muscular atrophy (SMA) is a progressive neuromuscular disease characterized by significant motor and respiratory muscle weakness.
- Understanding the specific ventilatory and thoraco-abdominal patterns (VTAp) in different SMA types is crucial for effective management.
- The impact of salbutamol therapy and natural disease progression on VTAp requires further investigation.
Purpose of the Study:
- To characterize the distinct ventilatory and thoraco-abdominal patterns (VTAp) during quiet breathing (QB) in different forms of SMA.
- To evaluate the effects of salbutamol therapy and natural history (NH) on VTAp in SMA patients.
- To determine the correlation between global motor impairment severity and VTAp in children with SMA.
Main Methods:
- Opto-electronic plethysmography was employed to analyze VTAp in 32 SMA type I, 51 SMA type II, 8 SMA type III patients, and 20 healthy controls (HC).
- Spirometry, cough assessment, and motor function evaluations were conducted on a subset of patients.
- Breathing patterns were analyzed during quiet breathing (QB) in both supine and seated positions.
Main Results:
- SMA type I (SMA1) patients exhibited rapid, shallow breathing with paradoxical ribcage motion during QB.
- SMA type II (SMA2) patients showed normal ventilation in a seated position, but with increased respiratory rate and reduced tidal volume due to poor ribcage contribution (%ΔVRC,P).
- Salbutamol therapy did not significantly alter VTAp, whereas tachypnea was observed in the natural history of SMA type I. A significant linear correlation was found between motor function scales and VTAp (p<0.001).
Conclusions:
- Reduced %ΔVRC,P, indicating ribcage muscle weakness, is a hallmark of SMA type I and II from infancy.
- Quantitative assessment of %ΔVRC,P provides a non-invasive, non-volitional index of ribcage muscle function, valuable even in uncooperative children.
- Impaired motor function in SMA is closely linked to compromised respiratory function, highlighting the importance of assessing VTAp.
Introduction:
SMA is characterised by progressive motor and respiratory muscle weakness. We aimed to verify if in SMA children 1)each form is characterized by specific ventilatory and thoraco-abdominal pattern(VTAp) during quiet breathing(QB); 2)VTAp is affected by salbutamol therapy, currently suggested as standard treatment, or by the natural history(NH) of SMA; 3)the severity of global motor impairment linearly correlates with VTAp.
Materials And Methods:
VTAp was analysed on 32 SMA type I (SMA1,the most severe form), 51 type II (SMA2,the moderate), 8 type III (SMA3,the mildest) and 20 healthy (HC) using opto-electronic plethysmography. Spirometry, cough and motor function were measured in a subgroup of patients.
Results:
In SMA1, a normal ventilation is obtained in supine position by rapid and shallow breathing with paradoxical ribcage motion. In SMA2, ventilation is within a normal range in seated position due to an increased respiratory rate(p<0.05) with reduced tidal volume(p<0.05) secondary to a poor contribution of pulmonary ribcage(%ΔVRC,P, p<0.001). Salbutamol therapy had no effect on VTAp during QB(p>0.05) while tachypnea occurred in type I NH. A linear correlation(p<0.001) was found between motor function scales and VTAp.
Conclusion:
A negative or reduced %ΔVRC,P, indicative of ribcage muscle weakness, is a distinctive feature of SMA1 and SMA2 since infancy. Its quantitative assessment represents a non-invasive, non-volitional index that can be obtained in all children, even uncollaborative, and provides useful information on the action of ribcage muscles that are known to be affected by the disease.Low values of motor function scales indicate impairment of motor but also of respiratory function.
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