title: Effect of home mechanical ventilation on inspiratory muscle strength in COPD.
abstract: BACKGROUND
  The mechanism responsible for chronic hypercapnic respiratory failure (HRF) in patients with COPD remains unclear. In this study, we tested the hypothesis that chronic HRF in patients with COPD is associated with low-frequency fatigue (LFF) of the diaphragm.
  
  
  METHODS
  To test this hypothesis, we measured the twitch transdiaphragmatic pressure (Tw Pdi) elicited by stimulation of the phrenic nerves in 25 patients with chronic HRF (mean [+/- SD] Paco(2), 55.2 +/- 5.2 mm Hg) due to COPD before and 2 months after the initiation of noninvasive mechanical ventilation (NIV) [pressure-cycled ventilation with inspiratory positive airway pressure of 19.0 +/- 2.5 cm H(2)O]. We reasoned that had LFF been present, Tw Pdi should rise after effective NIV.
  
  
  RESULTS
  The treatment compliance with NIV was good (median of machine usage was 7.1 h per night). Paco(2) decreased from 55.2 +/- 5.2 to 48.8 +/- 5.9 mm Hg (p < 0.001), and Pao(2) increased from 53.1 +/- 5.9 to 57.7 +/- 7.0 mm Hg (p = 0.007). Mean Tw Pdi at baseline was 11.1 +/- 6.6 cm H(2)O and after treatment was 11.7 +/- 7.2 cm H(2)O (not significant). Also, maximal static inspiratory mouth pressure did not change significantly (44.3 +/- 15.9 cm H(2)O vs 46.5 +/- 19.7 cm H(2)O).
  
  
  CONCLUSIONS
  LFF of the diaphragm does not accompany chronic HRF in patients with COPD.
authors.affiliation: Abteilung für Pneumologie und Internistische Intensivmedizin, Klinikum Region Hannover, Krankenhaus Oststadt-Heidehaus, Podbielskistrasse 380, 30659 Hannover, Germany. Bernd.Schoenhofer@t-online.de
authors.forename: Bernd
authors.initials: B
authors.lastname: Schönhofer
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: Stefan
authors.initials: S
authors.lastname: Suchi
authors.forename: Dieter
authors.initials: D
authors.lastname: Köhler
mesh_terms: D000368:Aged; D002245:Carbon Dioxide / Q000097:blood; D045422:Continuous Positive Airway Pressure; D003964:Diaphragm / Q000503:physiopathology*; D004558:Electric Stimulation; D005260:Female; D018575:Home Care Services, Hospital-Based; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology / Q000628:therapy; D001239:Inhalation / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D010791:Phrenic Nerve / Q000503:physiopathology; D010993:Plethysmography, Whole Body; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy*; D012131:Respiratory Insufficiency / Q000503:physiopathology* / Q000628:therapy*; D013147:Spirometry; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide