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1.  Quadriceps muscle strength in scoliosis 
The European respiratory journal  2009;34(6):1429-1435.
Quadriceps muscle weakness is an important component of chronic obstructive pulmonary disease (COPD). We hypothesised that quadriceps weakness would also be a feature of restrictive lung disease due to scoliosis.
We studied 10 patients with severe scoliosis (median (interquartile range (IQR)) forced expiratory volume in 1 s (FEV1) 35.3 (11)% predicted), 10 patients with severe COPD (FEV1 26.5 (9.0)% pred) and 10 healthy age-matched adults. We measured quadriceps strength, exercise capacity and analysed quadriceps muscle biopsies for myosin heavy-chain (MyHC) isoform expression and the presence of oxidative stress.
Both groups exhibited quadriceps weakness with median (IQR) maximal voluntary contraction force being 46.0 (17.0) kg, 21.5 (21.0) kg and 31.5 (11.0) kg, respectively (p=0.02 and 0.04, respectively, for each patient group against controls). Oxidative stress was significantly greater in the quadriceps of both restrictive and COPD patients. The scoliosis patients exhibited a decrease in the proportion of MyHC type I compared with controls; median (IQR) 35.3 (18.5)% compared with 47.7 (9.3)%, p=0.028. The scoliosis patients also showed an increase in MyHC IIx (26.3 (15.5)% compared with 11.3 (13.0)%, p=0.01.
Quadriceps weakness is a feature of severe scoliosis; the similarities between patients with scoliosis and patients with COPD suggest a common aetiology to quadriceps weakness in both conditions.
doi:10.1183/09031936.00074008
PMCID: PMC3073323  PMID: 19443534
Chronic obstructive pulmonary disease; extrapulmonary restrictive lung disease; oxidative stress; quadriceps muscle weakness
2.  Expiratory muscle endurance in chronic obstructive pulmonary disease 
Thorax  2002;57(2):132-136.
Background: A reduction in expiratory muscle (ExM) endurance in patients with chronic obstructive pulmonary disease (COPD) may have clinically relevant implications. This study was carried out to evaluate ExM endurance in patients with COPD.
Methods: Twenty three patients with COPD (FEV1 35 (14)% predicted) and 14 matched controls were studied. ExM endurance was assessed using a method based on the use of an expiratory threshold valve which includes two steps. In step 1 the load is progressively increased (50 g every 2 minutes) until task failure is reached, and the pressure generated against the highest tolerated load is defined as the maximal expiratory sustainable pressure (Pthmax). In step 2 subjects breathe against a submaximal constant load (80% of Pthmax) and the time elapsed until task failure is termed the expiratory endurance time (Tth80). In addition, the strength of peripheral muscles (handgrip, HGS) and respiratory muscles (maximal inspiratory and expiratory pressures, PImax and PEmax, respectively) was evaluated.
Results: Patients with COPD had lower ExM strength and endurance than controls: PEmax 64 (19)% predicted v 84 (14)% predicted (mean difference 20%; 95% confidence intervals (CI) 14 to 39); Pthmax 52 (27) v 151 (46) cm H2O (mean difference 99, 95% CI 74 to 123); and Tth80 9.4 (6.3) v 14.2 (7.4) min (mean difference 4.8, 95% CI 1.0 to 10.4; p<0.01 for all). Interestingly, ExM endurance directly correlated with both the severity of airways obstruction (Pthmax with FEV1, r=0.794, p<0.01) and the reduction in strength observed in different muscle groups (Pthmax with HG, PImax or PEmax, r=0.550, p<0.05; r=0.583, p<0.001; and r=0.584, p<0.001, respectively).
Conclusions: ExM endurance is decreased in patients with COPD. This impairment is proportional to the severity of the disease and is associated with lower strength in different muscle groups. This suggests that systemic effects are implicated in the impairment observed in ExM function.
doi:10.1136/thorax.57.2.132
PMCID: PMC1746253  PMID: 11828042
3.  Methacholine induced headache. 
Thorax  1995;50(3):319.
A lung function technician developed episodes of headache, probably related to the use of methacholine. The headache disappeared with breathing 100% oxygen. Cholinergic agents are known to induce headaches but the mechanism remains unclear. Vascular factors could be implicated.
PMCID: PMC1021203  PMID: 7660351
4.  AUTHORS' REPLY 
Thorax  1994;49(7):729.
PMCID: PMC475073
5.  Simplified exercise test for the initial differential diagnosis of Pneumocystis carinii pneumonia in HIV antibody positive patients. 
Thorax  1994;49(2):112-114.
BACKGROUND--This study was designed to evaluate the usefulness of a simplified exercise test in the differential diagnosis of Pneumocystis carinii pneumonia (PCP). METHODS--Forty five subjects with antibodies against the human immunodeficiency virus (HIV) and pneumonia were included and divided into two groups: those with PCP and those with "other pneumonias" (non-PCP). The test involved pedalling for two minutes on a stretcher bed and was considered positive if SaO2 decreased by at least 3%. RESULTS--During the exercise the mean(SE) SaO2 fell in patients with PCP from 88(4)% to 84(3)%, p < 0.01, whilst it improved slightly in subjects with non-PCP from 91(1)% to 93(3)%, p < 0.05. Sensitivity was 77% and specificity 91%. CONCLUSIONS--This simple test seems potentially useful for the initial investigation of HIV antibody positive patients with pneumonia.
PMCID: PMC474319  PMID: 8128398

Results 1-5 (5)