Biomedical subjects

S M Revill

Publications and source records attributed to S M Revill.

7 recordsLinked to original sources

PubMed2001

Dynamic hyperinflation and exercise intolerance in chronic obstructive pulmonary disease.

The role of dynamic hyperinflation (DH) in exercise limitation in chronic obstructive pulmonary disease (COPD) remains to be defined. We examined DH during exercise in 105 patients with COPD (FEV(1) = 37 +/- 13% predicted; mean +/- SD) and studied the relationships between resting lung volumes, DH during exercise, and peak oxygen consumption (VO(2)). Patients completed pulmonary function tests and incremental cycle exercise tests. We measured the change in inspiratory capacity (Delta IC) during exercise to reflect changes in DH. During exercise, 80% of patients showed significant DH above resting values. IC decreased 0.37 +/- 0.39 L or 14 +/- 15% predicted during exercise (p < 0.0005), but with large variation in range. Delta IC correlated best with resting IC, both expressed %predicted (r = -0.50, p < 0.0005). Peak VO(2) (%predicted maximum) correlated best with the peak tidal volume attained (VT standardized as % of predicted vital capacity) (r = 0.68, p < 0.0005), which, in turn, correlated strongly with IC at peak exercise (r = 0.79, p < 0.0005) or at rest (r = 0.75, p < 0.0005). The extent of DH during exercise in COPD correlated best with resting IC. DH curtailed the VT response to exercise. This inability to expand VT in response to increasing metabolic demand contributed importantly to exercise intolerance in COPD.

Aged↗

PubMed2000

Randomized controlled trial of ambulatory oxygen and an ambulatory ventilator on endurance exercise in COPD.

In a prospective, randomized study we examined the effect of (i) ambulatory oxygen and (ii) a portable, inspiratory pressure support (IPS) device on the endurance shuttle walk test (ESWT) in patients with severe chronic obstructive pulmonary disease (COPD). Ten outpatients [median (range) FEV1 0.60 l(0.35, 1.45)] performed the ESWT under five test conditions: baseline walk (no assistance), IPS at 14 cmH2O from a portable ventilator (the HIPPY, Friday Medical, U.K.), sham IPS (< 8 cmH2O), ambulatory oxygen at 2 l min(-1), and sham oxygen (carrying the portable oxygen cylinder and breathing air). There were significant improvements in the ESWT with ambulatory oxygen, but a negative effect with the HIPPY device [mean (SD) time: baseline 172 (48) sec; oxygen 242 (62) sec; HIPPY 84 (35) sec]. The ESWT appeared sensitive to the effect of cylinder weight although differences in endurance capacity were not significant [sham oxygen 151 (45) sec]. The ESWT was sensitive to the acute application of oxygen, demonstrating a beneficial effect on endurance performance in patients with severe COPD. The ESWT could form the basis of a standardized assessment for ambulatory oxygen.

Aged↗

PubMed2000

Biological quality control for exercise testing.

BACKGROUND: A study was undertaken to evaluate the use of a biological quality control programme for a computer controlled, breath-by-breath exercise test system over a 2.5 year period. METHODS: One healthy volunteer performed a regular progressive treadmill test with breath-by-breath measurements of oxygen uptake (VO(2)), carbon dioxide output (VCO(2)), ventilation (VE), and the ECG heart rate (HR). Following a familiarisation period, five consecutive tests were performed and the measurements at peak exercise were averaged to give baseline values. All tests were compared with these values. RESULTS: A total of 35 tests were recorded. The within subject standard deviation for measurements at peak exercise were 52 ml/min for VO(2), 74 ml/min for VCO(2), 3.1 l/min for VE, and 3 beats/min for HR. The mean (SE) percentage variation in measurements at peak exercise compared with the baseline values was +0.37 (0.30)% for VO(2), -0.10 (0.39)% for VCO(2), -0.88 (0.52)% for VE, and +1.2 (0.26)% for HR. The variability present in measurements made during high and moderate intensity exercise (73% VO(2)peak) was not significantly different (p>0.05). During the study period the quality control detected a fault on the oxygen analyser which was not apparent from the automatic calibration. CONCLUSIONS: Regular quality control using a healthy volunteer allows all components of the breath-by-breath system to be checked simultaneously and in a manner which is consistent with its clinical use. This practice can highlight faults not detected by automatic calibration.

Calibration↗

PubMed1999

The endurance shuttle walk: a new field test for the assessment of endurance capacity in chronic obstructive pulmonary disease.

BACKGROUND: The purpose of this study was to develop an externally controlled, constant paced field walking test to assess endurance capacity in patients with chronic obstructive pulmonary disease (COPD). There were four objectives: (1) to develop a protocol; (2) to compare treadmill and shuttle walk tests of endurance capacity; (3) to examine the repeatability of the endurance shuttle walk test; and (4) to compare the sensitivity to pulmonary rehabilitation of endurance and incremental shuttle walk tests. METHODS: The test was designed to complement the incremental shuttle walk test (ISWT) using the same 10 m shuttle course and an audio signal to control pace. The intensity of the field endurance test was related to a percentage of each patient's maximum field exercise performance assessed by the ISWT. A number of cassette tapes were pre-recorded with a range of audio signal frequencies to dictate walking speeds between 1.80 and 6.00 km/h. In the first limb of the study 10 patients with COPD (mean (SD) forced expiratory volume in one second (FEV1) 1.0 (0.36) 1, 35% predicted) performed three endurance shuttle walk tests (ESWTs) and three treadmill endurance tests. The walking speeds were calculated to elicit 75%, 85%, and 95% of each patient's maximum ISWT performance for the field tests and measured peak oxygen consumption for the treadmill tests. In a separate group of patients the repeatability of the ESWT at an intensity of 85% of the ISWT performance was evaluated. Finally, the ESWT (at the 85% intensity) and the ISWT were performed at the start of a five week control period and at the start and end of a seven week pulmonary rehabilitation programme in 21 patients with COPD (mean FEV1 0.80 (0.18) 1). RESULTS: The mean (SE) times achieved during the ESWT were 13.1 (2.3), 10.2 (2.5), and 5.3 (1.7) min for the walks at 75%, 85%, and 95% intensities, respectively. Patients tended to walk for longer on the treadmill than during the field tests at all intensities, but there were no significant differences between the end of test heart rates or Borg ratings of breathlessness or perceived exertion. Following one practice ESWT at the 85% intensity, the mean difference and limits of agreement (2SD) between tests 2 and 3 was +15 (42) s (p > 0.05). There was no significant change in performance on either test following the five week control period prior to rehabilitation. Following rehabilitation the ESWT duration increased by 160 (24)% and the ISWT distance increased by 32 (11)% (effect sizes 2.90 and 0.41, respectively). CONCLUSIONS: The ESWT was simple to perform, acceptable to all patients, and exhibited good repeatability after one practice walk. The test showed major improvement following rehabilitation and was more sensitive to change than the field test of maximal capacity.

Exercise Test↗

PubMed1998

The cardiorespiratory response to submaximal exercise in subjects with asthma following pretreatment with controlled release oral salbutamol and high-dose inhaled salmeterol.

Treatment for exercise induced asthma (EIA) in sporting competition is controlled to prevent the use of agents which might enhance physical performance. There is little information concerning the effects of the long-acting inhaled, and oral, sustained release type bronchodilators on the cardiorespiratory effects of submaximal exercise. The aim of this study was to compare the cardiorespiratory effects of submaximal exercise in patients with EIA before and after pretreatment with high-dose inhaled salmeterol xinafoate (SX) and controlled release oral salbutamol (CR). Patients were treated with SX (100 micrograms b.d.) and CR (8 mg b.d.) for > or = 3 days in a double-blind randomized cross-over design, with a 5-14 day washout period between treatments. A submaximal exercise test (total exercise time 6 min, final 3 min at 60% of VEpeak) was performed prior to each treatment period, and repeated at 1, 6, and 12 h postdose at the end of the treatment period. Two subjects were withdrawn from the study. Three subjects required relief medication after 1 h (CR) and one subject after 6 h (SX) and they did not perform further exercise tests. Both treatments increased baseline FEV1, with SX producing significantly greater pre-exercise bronchodilation than CR (P = 0.04). Following CR, there were no significant differences from the pretreatment values for VO2, VE, respiratory exchange ratio, heart rate, ventilatory equivalents for VO2, and oxygen pulse during the submaximal exercise challenge. Following SX, there were no significant differences for any of the exercise variables except for VE at 6 and 12 h (mean increase 4.27 l min-1 at 6 h, P < 0.01 and 4.69 l min-1 at 12 h, P = 0.05). The changes in ventilation following SX did not have an effect on oxygen consumption, and the ventilatory efficiency (VE/VO2) remained unchanged. The findings from this study demonstrate that, despite exercising from a higher baseline FEV1, short pretreatment periods with controlled release oral salbutamol and with inhaled salmeterol do not confer any cardiorespiratory advantage during submaximal exercise in subjects with EIA.

Adrenergic beta-Agonists↗

PubMed1996

The effect of a time delay on the measurement of capillary blood gases.

Patients using domiciliary nasal ventilation, or long-term oxygen, require regular assessment which could be carried out in the home. Blood gas analysis may be regarded as an essential part of the assessment. The present study investigated the effect of a 1-h time delay on the measurement of capillary blood gases. Four samples of arterialized earlobe blood were collected from 15 outpatients. One sample was analysed immediately, the other three were stored on crushed ice and analysed at intervals of 30, 45, and 60 min post-collection. In order to examine any range effect, a wide range of PaO2 values were examined. The delay, at all levels, resulted in minor changes in the measurement of PaO2, which would be unlikely to alter clinical management. The technique might be used for the reliable assessment of patients in the home.

Blood Gas Analysis↗

PubMed1995

Comparison of peak oxygen consumption during cycle and treadmill exercise in severe chronic obstructive pulmonary disease.

BACKGROUND: In normal subjects treadmill exercise usually produces the greatest maximal oxygen consumption (VO2max). This may not be true for patients with severe chronic obstructive pulmonary disease (COPD) in whom bicycle exercise, which offers support for the shoulder girdle, may produce a higher oxygen consumption than treadmill exercise. The aim of this study was to determine which mode of exercise produced the greatest oxygen consumption in patients with severe COPD. METHODS: Eight patients with severe COPD (forced expiratory volume in one second (FEV1) more than three standardised residuals below predicted) exercised to a symptom limited maximum on a bicycle and on a treadmill on separate days. The workload on the bicycle wa increased by 10 watts each minute, and the treadmill gradient was increased by 2.5% alternate minutes whilst the speed remained constant. Measurements of oxygen consumption (VO2), ventilation (VE), heart rate, and oxygen saturation were made, and capillary blood gases were measured before and immediately after exercise. Lactate concentration was measured before and four minutes after exercise. RESULTS: There were no differences at peak exercise between the two forms of exercise for VO2 (median 11.7 and 12.2 ml/min/kg for bicycle and treadmill, respectively), for VE (median 26.6 and 25.0 l/min, respectively), and for heart rate (median 119 and 115 beats/min, respectively). The median lactate levels after bicycle exercise were higher than those after the treadmill (2.42 v 0.94 mmol/l). CONCLUSIONS: Although only a small number of patients was studied and individual variability was large, there was no clear difference between the two forms of exercise. Regular bicycle exercise was unfamiliar to this group of patients and generated the greatest lactate response. The results do not support the hypothesis that bicycle exercise will produce a better performance in patients with severe COPD, but the two modes of exercise cannot be used interchangeably.

Aged↗