B-mode ultrasound assessment of diaphragm structure and function in patients with COPD.
BACKGROUND
Electromyographic evaluation of diaphragmatic neuromuscular disease in patients with COPD is technically difficult and potentially high risk. Defining standard values for diaphragm thickness and thickening ratio using B-mode ultrasound may provide a simpler, safer means of evaluating these patients.


METHODS
Fifty patients with a diagnosis of COPD and FEV₁ < 70% underwent B-mode ultrasound. Three images were captured both at end expiration (Tmin) and at maximal inspiration (Tmax). The thickening ratio was calculated as (Tmax/Tmin), and each set of values was averaged. Findings were compared with a database of 150 healthy control subjects.


RESULTS
There was no significant difference in diaphragm thickness or thickening ratio between sides within groups (control subjects or patients with COPD) or between groups, with the exception of the subgroup with severe air trapping (residual volume > 200%), in which the only difference was that the thickening ratio was higher on the left (P = .0045).


CONCLUSIONS
In patients with COPD presenting for evaluation of coexisting neuromuscular respiratory weakness, the same values established for healthy control subjects serve as the baseline for comparison. This knowledge expands the role of ultrasound in evaluating neuromuscular disease in patients with COPD.
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN.
Michael R
MR
Baria
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN.
Leili
L
Shahgholi
Division of Clinical Neurophysiology, Mayo Clinic and Foundation, Rochester, MN.
Eric J
EJ
Sorenson
Department of Neurology, Mayo Medical School, Mayo Clinic and Foundation, Rochester, MN.
Caitlin J
CJ
Harper
Department of Pulmonary and Critical Care Medicine, Mayo Clinic and Foundation, Rochester, MN; Division of Allergic Diseases, Mayo Clinic and Foundation, Rochester, MN.
Kaiser G
KG
Lim
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN; Division of Clinical Neurophysiology, Mayo Clinic and Foundation, Rochester, MN.
Jeffrey A
JA
Strommen
Department of Pulmonary and Critical Care Medicine, Mayo Clinic and Foundation, Rochester, MN.
Carl D
CD
Mottram
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN; Division of Clinical Neurophysiology, Mayo Clinic and Foundation, Rochester, MN. Electronic address: boon.andrea@mayo.edu.
Andrea J
AJ
Boon
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003964:Diaphragm / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000503:physiopathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D014463:Ultrasonography / Q000379:methods*