Paul P Walker

Liverpool Hope University, Liverpool, England, United Kingdom

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Publications (9)38.82 Total impact

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    ABSTRACT: COPD patients have reduced muscle glutamate which may contribute to an impaired response of oxidative metabolism to exercise. We hypothesised that prior glutamine supplementation would enhance V(O2) peak, V(O2) at lactate threshold and speed pulmonary oxygen uptake kinetics in COPD. 13 patients (9 males, age 66±5 years, mean±SD) with severe COPD (mean FEV(1) 0.88±0.23l, 33±7% predicted) performed on separate days ramp cycle-ergometry (5-10 W min(-1)) to volitional exhaustion and subsequently square-wave transitions to 80% estimated lactate threshold (LT) following consumption of either placebo (CON) or 0.125 g kg bm(-1) of glutamine (GLN) in 5 ml kg bm(-1) placebo. Oral glutamine had no effect on peak or V(O2) at LT, {V(O2) peak: CON=0.70±0.1 l min(-1) vs. GLN=0.73±0.2 l min(-1); LT: CON=0.57±0.1 l min(-1) vs. GLN=0.54±0.1 lmin(-1)} or V(O2) kinetics {tau: CON=68±22 s vs. GLN=68±16 s}. Ingestion of glutamine before exercise did not improve indices of oxidative metabolism in this patient group.
    Respiratory Physiology & Neurobiology 03/2011; 177(1):41-6. · 2.05 Impact Factor
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    Paul Walker, Peter Calverley
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    ABSTRACT: Management of chronic obstructive pulmonary disease requires a true multidisciplinary approach, and therapies with a strong evidence base can bring benefits to patients. Our Drug review considers the available treatments and their efficacy, followed by sources of further information. Copyright © 2010 Wiley Interface Ltd
    Prescriber 04/2010; 21(8):14 - 24.
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    ABSTRACT: Bronchodilator drugs produce variable improvements in forced expiratory volume in 1 s (FEV(1)), but larger changes in end-expiratory lung volume (EELV) in chronic obstructive pulmonary disease (COPD), which were suggested to be related to the presence of expiratory flow limitation (EFL) at rest. We tested this concept in 42 COPD patients (FEV(1) 42.3+/-13.8% predicted) during spontaneous breathing before and after 5 mg nebulised salbutamol. EFL was detected by within-breath changes in respiratory system reactance measured by a multifrequency forced oscillation method, while changes in EELV were assessed by inspiratory capacity (IC). Bronchodilation (BD) increased IC (from 1.8+/-0.5 to 2.1+/-0.6 L, p<0.001) and reduced inspiration resistance ((insp)) at 5 Hz (from 5.1+/-1.6 to 4.2+/-1.5 cmH(2)OxsxL(-1), p<0.001). (insp) identified BD responders with a discriminative power of 80.1%. In total, 20 patients were flow-limited before BD. They showed worse spirometry and higher residual volume, but significant improvements in IC were seen in all patients irrespective of flow limitation. Changes in (insp) were confined to flow-limited patients, as were reactance changes. BD reduced the degree of heterogeneity in the respiratory system, a change best seen with inspiratory values. BD has complex effects on lung mechanics in COPD, and EFL affects both this and the response of some respiratory variables to treatment. However, changes in EELV are consistently seen, irrespective of the presence of flow limitation at rest.
    European Respiratory Journal 01/2009; 33(6):1329-37. · 6.36 Impact Factor
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    ABSTRACT: The non-specific bronchial hyper-responsiveness reported in mild to moderate COPD is usually attributed to reduced airway calibre accentuating the effect of airway smooth muscle shortening. We hypothesized that in more severe COPD the fall in forced expiratory volume in 1 second (FEV(1)) seen during methacholine challenge would result from an increase in residual volume and decrease in vital capacity rather than an increase in airways resistance. Twenty-five subjects with moderate to severe COPD and 10 asthmatic subjects had spirometry and oscillatory mechanics measured before methacholine challenge and at a 20% fall from baseline post challenge (PC(20)FEV(1)). In the COPD subjects median PC(20) was 0.35mg/mL. Comparing baseline to PC(20) there were significant falls in forced vital capacity (FVC) (2.91 vs. 2.2L; p<0.001), slow vital capacity (3.22 vs. 2.58L; p<0.001) and IC (2.21 vs. 1.75L; p<0.001) without change in FEV(1)/FVC ratio (0.52 vs. 0.52; not significant) or in total lung capacity where this was measured. Total respiratory system resistance (R(5)) was unchanged (0.66 vs. 0.68; not significant) but total respiratory system reactance decreased significantly (-0.33 vs. -0.44; p<0.001). In contrast, the asthmatics became more obstructed and showed a proportionally smaller fall in lung volume with increase in R(5) (0.43 vs. 0.64; p<0.01). In moderate to severe COPD the fall in FEV(1) with methacholine is mainly due to increases in residual volume, which may represent airway closure and new-onset expiratory flow limitation.
    Respiratory medicine 12/2008; 103(4):535-41. · 2.33 Impact Factor
  • Paul P Walker, Peter M A Calverley
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    ABSTRACT: A significant proportion of patients with COPD show post-bronchodilator improvement in lung volume even though this response is rarely considered when classifying subjects as having reversible or irreversible airway disease. We studied 266 patients with a clinical and physiological diagnosis of COPD who underwent pulmonary function testing and had their spirometric response to 5 mg salbutamol assessed. After the bronchodilator 125 (47%) patients increased their forced vital capacity by more than the known variability of the test while 60 (23%) showed only a volume response without improvement in expiratory flow. These 'volume responders' had greater degrees of airflow obstruction-lower FEV(1) (p < 0.001) and FEV(1)/FVC (p < 0.05)-and a higher residual volume at rest (p = 0.005) with similar degrees of emphysema measured by K(CO). Subjects with evidence of greater dynamic airway collapse, assessed by the ratio of early to mid expiratory flow, were less likely to have a flow response but more likely to have a volume response after salbutamol (p < 0.005). This would be compatible with volume response being commoner in patients who exhibit tidal expiratory flow limitation. We suggest that post-bronchodilator absolute change in FVC provides important additional physiological information when interpreting bronchodilator reversibility testing.
    COPD Journal of Chronic Obstructive Pulmonary Disease 07/2008; 5(3):147-52. · 2.31 Impact Factor
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    ABSTRACT: Patients with chronic obstructive pulmonary disease (COPD) walk less than healthy older people and their self-reported activity predicts exacerbation risk. The relationship between lower limb activity and total daily activity is not known, nor are there any data which relate objectively assessed daily activity to laboratory assessments made before and after rehabilitation. Lower limb activity was measured by leg actigraphy over 3 days in 45 patients with moderate to severe COPD and 18 controls of similar age. Thirty-three patients with COPD entered an 8-week rehabilitation programme in which the change in leg activity was measured and related to other outcomes. In patients with COPD the mean level of activity measured by whole body and leg activity monitors was closely related (r = 0.92; p<0.001), but leg activity was consistently reduced compared with controls of similar age (p = 0.001). Mean leg activity, mean intensity of leg activity and the time that patients spent mobile at home were all related to forced expiratory volume in 1 s (FEV(1)) (r = 0.57, p = 0.001; r = 0.5, p = 0.003; and r = 0.51, p = 0.002, respectively), but intensity of activity and time spent mobile were not related. Subjects completing pulmonary rehabilitation showed significant improvements in mean activity (p = 0.001) and spent more time moving (p = 0.014). These changes were unrelated to improvement in muscle strength or walking distance but correlated with baseline FEV(1) (r = 0.8, p<0.001). Total daily activity in patients with COPD is closely related to leg activity which is reduced compared with controls of similar age. Individuals differ in the time spent mobile during the day, but subjective and objectively assessed activity improves after rehabilitation and is predicted by FEV(1). The change in activity is unrelated to improvements in corridor walking and health status.
    Thorax 05/2008; 63(8):683-9. · 8.38 Impact Factor
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    Paul Walker, Peter Calverley
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    ABSTRACT: Treatment for chronic obstructive pulmonary disease is now focussed on both evidence based therapies and a patient-centred approach. Our Drug review considers the current approach to recommended management, followed by sources of further information and the Datafile. Copyright © 2007 Wiley Interface Ltd
    Prescriber 09/2007; 18(11):50 - 63.
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    ABSTRACT: Primary-care spirometry has been promoted as a method of facilitating accurate diagnosis of chronic obstructive pulmonary disease (COPD). The present study examined whether improving rates of diagnosis lead to improvements in pharmacological and nonpharmacological management. From 1999 to 2003, the current authors provided an open-access spirometry and reversibility service to a local primary-care area, to which 1,508 subjects were referred. A total of 797 (53%) had pre-bronchodilator airflow obstruction (AFO). Of the subjects who underwent reversibility testing, 19.3% were no longer obstructed post-bronchodilator. The results and records of a subgroup of 235 subjects with post-bronchodilator AFO were examined. Of the 235 subjects, 130 received a new diagnosis, most commonly COPD. The patients with COPD were significantly undertreated before spirometry and testing led to a significant increase in the use of anticholinergics (37 versus 18%), long-acting beta-agonists (25 versus 8%) and inhaled steroids (71 versus 52%). More than three quarters of smokers received smoking cessation advice but very few were referred for pulmonary rehabilitation. In conclusion, primary-care spirometry not only increases rates of chronic obstructive pulmonary disease diagnosis, but it also leads to improvements in chronic obstructive pulmonary disease treatment. The use of bronchodilator reversibility testing in this setting may be important to avoid misdiagnosis.
    European Respiratory Journal 12/2006; 28(5):945-52. · 6.36 Impact Factor
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    ABSTRACT: Exacerbation of chronic obstructive pulmonary disease commonly causes hospitalization. The change in lung mechanics during exacerbation and its relationship to symptoms in spontaneously breathing individuals has not been described. We hypothesized that changes in both airflow and lung volumes would occur during an exacerbation, but that only volume change would relate to symptomatic improvement. Lung mechanics and resting dyspnea were recorded in 22 hospitalized patients during recovery from exacerbation. Spirometry, inspiratory capacity, respiratory system resistance and reactance, tidal breathing patterns, and expiratory flow limitation were recorded after nebulized bronchodilator therapy on the first 3 d after admission, at discharge, and 6 wk postadmission (Day 42). Prebronchodilator measurements were taken on Day 2, at discharge, and on Day 42. Postbronchodilator inspiratory capacity increased 0.23 +/- 0.07 L by discharge and 0.42 +/- 0.1 L by Day 42, FEV1 rose 0.09 +/- 0.04 and 0.2 +/- 0.05 L at discharge and Day 42, respectively, and FVC increased 0.21 +/- 0.08 and 0.47 +/- 0.09 L at discharge and Day 42 (all p < 0.05). Consistent reduction in dyspnea was seen as the exacerbation resolved. Respiratory system resistance, FEV1/FVC, and expiratory flow limitation were unchanged throughout, indicating that changes in lung volume rather than airflow resistance predominated. Improvement in operating lung volumes is the principal change seen as a chronic obstructive pulmonary disease exacerbation resolves and increase in inspiratory capacity is a useful guide to a reduction in dyspnea.
    American Journal of Respiratory and Critical Care Medicine 12/2005; 172(12):1510-6. · 11.04 Impact Factor

Publication Stats

234 Citations
38.82 Total Impact Points

Institutions

  • 2011
    • Liverpool Hope University
      Liverpool, England, United Kingdom
  • 2006–2011
    • University of Liverpool
      • Department of Clinical Sciences
      Liverpool, England, United Kingdom
  • 2005
    • Aintree University Hospital NHS Foundation Trust
      Liverpool, England, United Kingdom