title: Muscle impairment in neuromuscular disease using an expiratory/inspiratory pressure ratio.
abstract: BACKGROUND
  Neuromuscular diseases (NMDs) lead to different weakness patterns, and most patients with NMDs develop respiratory failure. Inspiratory and expiratory muscle strength can be measured by maximum static inspiratory pressure (PImax) and maximum static expiratory pressure (PEmax), and the relationship between them has not been well described in healthy subjects and subjects with NMDs. Our aim was to assess expiratory/inspiratory muscle strength in NMDs and healthy subjects and calculate PEmax/PImax ratio for these groups.
  
  
  METHODS
  Seventy (35 males) subjects with NMDs (amyotrophic lateral sclerosis, myasthenia gravis, and myotonic dystrophy), and 93 (47 males) healthy individuals 20-80 y of age were evaluated for anthropometry, pulmonary function, PImax, and PEmax, respectively.
  
  
  RESULTS
  Healthy individuals showed greater values for PImax and PEmax when compared with subjects with NMDs. PEmax/PImax ratio for healthy subjects was 1.31 ± 0.26, and PEmax%/PImax% was 1.04 ± 0.05; for subjects with NMDs, PEmax/PImax ratio was 1.45 ± 0.65, and PEmax%/PImax% ratio was 1.42 ± 0.67. We found that PEmax%/PImax% for myotonic dystrophy was 0.93 ± 0.24, for myasthenia gravis 1.94 ± 0.6, and for amyotrophic lateral sclerosis 1.33 ± 0.62 when we analyzed them separately. All healthy individuals showed higher PEmax compared with PImax. For subjects with NMDs, the impairment of PEmax and PImax is different among the 3 pathologies studied (P < .001).
  
  
  CONCLUSIONS
  Healthy individuals and subjects with NMDs showed higher PEmax in comparison to PImax regarding the PEmax/PImax ratio. Based on the ratio, it is possible to state that NMDs show different patterns of respiratory muscle strength loss. PEmax/PImax ratio is a useful parameter to assess the impairment of respiratory muscles in a patient and to customize rehabilitation and treatment.
authors.affiliation: Physical Therapy Department of Universidade Federal do Rio Grande do Norte, Natal, Brazil fregonezi@ufrnet.br.
authors.forename: Guilherme
authors.initials: G
authors.lastname: Fregonezi
authors.affiliation: Physical Therapy Department of Universidade Federal do Rio Grande do Norte, Natal, Brazil.
authors.forename: Ingrid G
authors.initials: IG
authors.lastname: Azevedo
authors.affiliation: Physical Therapy Department of Universidade Federal do Rio Grande do Norte, Natal, Brazil.
authors.forename: Vanessa R
authors.initials: VR
authors.lastname: Resqueti
authors.affiliation: Physical Therapy Department of Universidade Federal de Pernambuco, Recife, Brazil.
authors.forename: Armèle D
authors.initials: AD
authors.lastname: De Andrade
authors.affiliation: Physical Therapy Department of Universidade Federal do Rio Grande do Norte, Natal, Brazil.
authors.forename: Lucien P
authors.initials: LP
authors.lastname: Gualdi
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria-Politecnico di Milano, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.affiliation: Hospital Universitário Onofre Lopes-Universidade Federal do Rio Grande do Norte, Natal, Brazil.
authors.forename: Mário Et
authors.initials: ME
authors.lastname: Dourado-Junior
authors.affiliation: Physical Therapy Department of Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Verônica F
authors.initials: VF
authors.lastname: Parreira
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D018908:Muscle Weakness / Q000503:physiopathology; D009468:Neuromuscular Diseases / Q000150:complications / Q000503:physiopathology*; D011312:Pressure; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology*; D012132:Respiratory Muscles / Q000503:physiopathology*; D055815:Young Adult
keywords: PEmax/PImax ratio; neuromuscular diseases; respiratory muscle imbalance; respiratory muscle strength; respiratory therapy