II. Definitions

  1. Negative Inspiratory Flow (NIF) or Maximal Inspiratory Pressure (MIP)
    1. Maximal inspiratory effort measured as the pressure generated against an occluded airway
    2. Maximal Inspiratory Pressure (MIP) and Negative Inspiratory Flow (NIF) represent the same measure
      1. MIP is typically reported as positive, while NIF is reported as negative

III. Indications

  1. Progressive Neuromuscular Disease (e.g. Guillain Barre Syndrome, Myasthenia Gravis)
  2. Ventilator Weaning

IV. Interpretation: Findings of Impending Respiratory Failure

  1. Physical findings
    1. Tachypnea with decreased chest excursion
    2. Hypophonia
    3. Accessory Muscle use (e.g. intercostal retractions, abdominal Muscle use)
    4. Paradoxical breathing
  2. Quantitative Tests
    1. Single Breath Counting <10 to 15
    2. Vital Capacity <15-20 ml/kg
    3. Tidal Volume <5 ml/kg
    4. Maximum expiratory force <40 cm H2O (normal may be as high as 100 cm H2O)
    5. Negative Inspiratory Flow (NIF) less negative than -20 to -30 cm H2O (normal may be < -100 cm H2O)
      1. NIF less negative than-25 cmH2O may predict Ventilator Weaning failure

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Related Studies

Ontology: Inspiratory force (C0231823)

Concepts Organ or Tissue Function (T042)
SnomedCT 64231002
English Inspiratory force, function, inspiratory force, Inspiratory force, Inspiratory force, function (observable entity), Inspiratory force (function)
Spanish esfuerzo inspiratorio (entidad observable), esfuerzo inspiratorio (función), esfuerzo inspiratorio, fuerza inspiratoria

Ontology: Respiratory muscular pressure (C0231900)

Concepts Finding (T033)
SnomedCT 24296009
English P MUS, P<sub>MUS</sub>, Respiratory muscular pressure, P>MUS<, Respiratory muscular pressure (observable entity)
Spanish presión muscular respiratoria (entidad observable), presión muscular respiratoria