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• Plateau vital capacity is a better indicator for severity of disease
  John R Bach M.D.
  Published on: 22 March 2016

• Published on: 22 March 2016

  Plateau vital capacity is a better indicator for severity of disease

  • John R Bach M.D., Medical Director of the Center for Ventilator Management Alternatives at University Hospital (New Je
  • Other Contributors:
    • Ummais Khan

  We read with curiosity a consensus statement on spinal muscular atrophy type 1 (SMA1) standard of care in the UK.(1) The authors stated that "non-invasive ventilation (NIV) is ineffective and contraindicated in infants who have severe bulbar weakness, usually present in babies with severe type 1 SMA," that is, in those with "onset of symptoms before 6 months of age". Ironically, the authors interpreted studies of prolon...

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  We read with curiosity a consensus statement on spinal muscular atrophy type 1 (SMA1) standard of care in the UK.(1) The authors stated that "non-invasive ventilation (NIV) is ineffective and contraindicated in infants who have severe bulbar weakness, usually present in babies with severe type 1 SMA," that is, in those with "onset of symptoms before 6 months of age". Ironically, the authors interpreted studies of prolonged survival using NIV for continuous ventilatory support for severe SMA 1 patients, floppy at birth, unable to receive any nutrition by mouth, averbal, and permanently and continuously ventilator dependent before 6 months of age, as not severely affected. In reality SMA1 infants who are continuously NIV dependent before 1 year of age always have their "onset" before 6 months of age. Indeed, most if not all are floppy at birth and 73 of 75 in one study (2) had paradoxical breathing even though the pediatricians do not always recognize it at birth. Even children with SMA type 2 who develop the ability to sit independently can have "onset of weakness" before 6 months of age. Thus, the timing of the disease "onset" is not valid for classifying disease severity since it depends on the experience and astuteness of individual mothers and pediatricians. Maximum ever achieved (plateau) vital capacity (VC), cry VC or otherwise, is a more important indicator for severity of disease, especially since, in the UK where NIV is "contraindicated in infants with severe bulbar weakness,"these patients invariably die of respiratory failure. To determine the plateau VC, however, necessitates that the children live long enough to plateau and are often, therefore, continuously NIV dependent. In a study of 103 severe to typical SMA type 1 patients, all of whom floppy at birth with essentially no bulbar-innervated muscle function and all having respiratory failure and requiring gastrostomy tubes before the second birthday including most before 8 months of age, many are now over age 15 despite requiring continuous NIV support for over 15 years. The plateau VCs were less than 100 ml in some cases and their current VCs less than 20 ml (<0.2% of normal). Despite this, they are alive and most without tubes in their necks.(2) While this paper (2) might have been in press while the consensus was being prepared, earlier papers on identically severe, typical SMA 1 children were available to the authors.(3,4) What would have been the fate of these "mild cases" according to the UK expert consensus?

  References 1. Roper H, Quinlivan R. Implementation of "The Consensus Statement for the Standard of Care in Spinal Muscular Atrophy" when applied to infants with severe type 1 SMA in the UK. Arch Dis Child. 2009 2. Bach JR, Gupta K, Reyna M, Hon A. Spinal muscular atrophy type 1: prolongation of survival by noninvasive respiratory aids. doi:10.1089/pai.2009.0002; Pediatric Asthma, Allergy & Immunology. 2009,22(4):151-162. 3. Bach JR, Baird JS, Plosky D, Nevado J, Weaver B. Spinal muscular atrophy type 1: management and outcomes. Pediatr Pulmonol 2002;34:16-22. 4. Bach JR, Saltstein K, Sinquee D, Weaver B, Komaroff E. Long term survival in Werdnig-Hoffmann Disease. Am J Phys Med Rehabil 2007;86(5):339 -345 and Quiz 346-348, 379.

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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