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Limitations of sniff nasal pressure in patients with severe neuromuscular weakness
  1. N Hart1,
  2. M I Polkey1,
  3. T Sharshar2,
  4. L Falaize3,
  5. B Fauroux4,
  6. J C Raphaël5,
  7. F Lofaso3
  1. 1Respiratory Muscle Laboratory, Royal Brompton Hospital, Fulham Road, London, UK
  2. 2Service de Réanimation Médicale, Raymond Poincaré Hôpital, Garches, France
  3. 3Service de Physiologie-Explorations Fonctionnelles, Raymond Poincaré Hôpital, Garches, France
  4. 4Paediatric Pulmonary Department, Armand Trousseau Hospital-AP-HP, Paris, France
  5. 5Service de Réanimation Medicale, Raymond Poincaré Hôpital, Garches, France
  1. Correspondence to:
 Professor F Lofaso
 Service de Physiologie-Explorations Fonctionnelles, Raymond Poincaré Hôpital, Garches 92380, France; f.lofasorpc.ap-hop-paris.fr

Abstract

Background: Inspiratory muscle strength in patients with neuromuscular disorders can be assessed using sniff inspiratory nasal pressure (Pnsn) and maximum inspiratory mouth pressure (PImax). However, the relative merits of Pnsn against PImax are not known in patients with severe neuromuscular disease.

Objective: To investigate whether severity of disease modifies the relation between Pnsn and PImax.

Methods: Vital capacity (VC), Pnsn, and PImax were measured in 258 patients with neuromuscular disorders.

Results: Data were analysed from 241 patients, 17 being unable to perform PImax or Pnsn manoeuvres. The correlation between Pnsn and PImax was +0.94 (p<0.0001), with a mean (SD) difference between Pnsn and PImax of −4.8 (21.2) cm H2O (the limits of agreement were 37.6 and –47.2 cm H2O). VC (% predicted) was positively correlated with Pnsn/PImax (r  =  +0.86; p<0.0001), with a lower Pnsn/PImax value in patients with a VC <40% of predicted than in those with a VC >40% (0.80 (0.35) v 1.04 (0.41); p<0.0001).

Conclusions: PImax is greater than Pnsn in patients with a severe restrictive ventilatory defect caused by neuromuscular disease. Pnsn may not accurately reflect inspiratory muscle strength in such patients and it is thus advisable to use both tests.

  • neuromuscular disease
  • inspiratory muscle strength
  • FRC, functional residual capacity
  • NIV, non-invasive ventilation
  • PImax, inspiratory mouth pressure
  • Pnsn, sniff inspiratory nasal pressure
  • VC, vital capacity

https://doi.org/10.1136/jnnp.74.12.1685

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    Footnotes

    • Competing interests: none declared