Increased respiratory drive relates to severity of dyspnea in systemic sclerosis.
BACKGROUND
Dyspnea may be a presenting symptom in progressive systemic sclerosis (SSc). Respiratory drive (mouth occlusion pressure, MOP, at rest and during CO2 rebreathing, 7% CO2, 93% O2) is a major determinant of dyspnea and may relate to the magnitude of dyspnea.


METHODS
In a prospective design, MOP at 0.1 sec (P0.1) was measured in 73 SSc patients while breathing room air and during CO2 rebreathing. An abnormal V'E/P0.1 is defined as < 8 L/min/cm H2O. Dyspnea scores were assessed by a shortness of breath questionnaire (UCSD dyspnea scale).


RESULTS
Mean P0.1 in patients with normal V'E/P0.1 (n = 45) was 1.1 ± 0.04 and 1.6 ± 0.08 cm H2O in patients with abnormal V'E/P0.1 (n = 28), p <0.001. ∆P0.1/∆PetCO2 differed significantly between these groups (0.45 versus 0.75 cm H2O/mmHg, P < 0.001), but no significant difference was present in ∆V'E/∆PetCO2. V'E/P0.1 showed the highest significant correlation with the UCSD dyspnea score (r = -0.76, p <0.001). UCSD cut-off value for abnormal V'E/P0.1 was 8.5 (sensitivity 93%, specificity 96%, area under the curve 0.98).


CONCLUSIONS
In SSc patients an abnormal V'E/P0.1 better relates to the severity of dyspnea than traditional lung function parameters and can easily be assessed at first outpatient consultation.
Department of Pulmonology (C3), Leiden University Medical Center, PO Box 9600, Leiden 2300RC, the Netherlands. m.k.ninaber@lumc.nl.
Maarten K
MK
Ninaber
Willem B G J
WB
Hamersma
Annemie J M
AJ
Schuerwegh
Jan
J
Stolk
D004417:Dyspnea / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012595:Scleroderma, Systemic / Q000150:complications* / Q000503:physiopathology; D012720:Severity of Illness Index