Effect of home mechanical ventilation on inspiratory muscle strength in COPD.
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.
Schönhofer
Bernd
B
Abteilung für Pneumologie und Internistische Intensivmedizin, Klinikum Region Hannover, Krankenhaus Oststadt-Heidehaus, Podbielskistrasse 380, 30659 Hannover, Germany. Bernd.Schoenhofer@t-online.de
Polkey
Michael I
MI
Suchi
Stefan
S
Köhler
Dieter
D
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
D002245:Carbon Dioxide