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Biomedical subjects

P M A Calverley

Publications and source records attributed to P M A Calverley.

At least 19 recordsLinked to original sources
PubMed2006

Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative.

Forced Expiratory Flow Rates↗
PubMed2006

Management of acute ventilatory failure.

Acute ventilatory failure is a challenging yet increasingly common medical emergency reflecting the growing burden of respiratory disease. It is not a diagnosis in itself but the end result of a diversity of disease processes culminating in arterial hypoxaemia and hypercapnia. This review focuses on key management issues including giving appropriate oxygen therapy, treatment of the underlying aetiology as well as any precipitant factors and provision of assisted ventilation if required. Ventilatory assistance can be provided both invasively and non-invasively and the indications for either or both forms of assisted ventilation are discussed. Further emphasis is needed regarding advanced directives of care and clinicians should be aware of ethical issues regarding assisted ventilation.

Acute Disease↗
PubMed2005

Effect of salbutamol on lung function and chest wall volumes at rest and during exercise in COPD.

BACKGROUND: Inhaled bronchodilators can increase exercise capacity in chronic obstructive pulmonary disease (COPD) by reducing dynamic hyperinflation, but treatment is not always effective. This may reflect the degree to which the abdomen allows dynamic hyperinflation to occur. METHOD: A double blind, randomised, crossover trial of the effect of 5 mg nebulised salbutamol or saline on endurance exercise time was conducted in 18 patients with COPD of mean (SD) age 67.1 (6.3) years and mean (SD) forced expiratory volume in 1 second (FEV1) of 40.6 (15.0)% predicted. Breathing pattern, metabolic variables, dyspnoea intensity, and total and regional chest wall volumes were measured non-invasively by optoelectronic plethysmography (OEP) at rest and during exercise. RESULTS: Salbutamol increased FEV1, forced vital capacity (FVC) and inspiratory capacity and reduced functional residual capacity (FRC) and residual volume significantly. OEP showed the change in resting FRC to be mainly in the abdominal compartment. Although the mean (SE) end expiratory chest wall volume was 541 (118) ml lower (p<0.001) at the end of exercise, the endurance time was unchanged by the bronchodilator. Changes in resting lung volumes were smaller when exercise duration did not improve, but FEV1 still rose significantly after active drug. After the bronchodilator these patients tried to reduce the end expiratory lung volume when exercising, while those exercising longer continued to allow end expiratory abdominal wall volume to rise. The change to a more euvolumic breathing pattern was associated with a lower oxygen pulse and a significant fall in endurance time with higher isotime levels of dyspnoea. CONCLUSIONS: Nebulised salbutamol improved forced expiratory flow in most patients with COPD, but less hyper-nflated patients tried to reduce the abdominal compartmental volume after active treatment and this reduced their exercise capacity. Identifying these patients has important therapeutic implications, as does an understanding of the mechanisms that control chest wall muscle recruitment.

Aged↗
PubMed2005

Intravenous aminophylline in patients admitted to hospital with non-acidotic exacerbations of chronic obstructive pulmonary disease: a prospective randomised controlled trial.

BACKGROUND: Intravenous aminophylline is commonly used in the treatment of exacerbations of chronic obstructive pulmonary disease (COPD), despite limited evidence for its efficacy and known risks of toxicity. We hypothesised that adding intravenous aminophylline to conventional treatment would not produce clinically important changes in the speed of spirometric or symptomatic recovery or shorten hospital stay in patients with exacerbations of COPD. METHODS: Eighty patients admitted to hospital with non-acidotic exacerbations of COPD were recruited at admission to a randomised, double blind, placebo controlled study comparing intravenous aminophylline 0.5 mg/kg/hour after an appropriate loading dose with an equivalent volume of 0.9% saline. The primary outcome was the change in post-bronchodilator forced expiratory volume in 1 second (FEV(1)) over the first 5 days of the admission. Secondary end points were changes in self-reported breathlessness, arterial blood gas tensions, forced vital capacity (FVC), and length of hospital stay. RESULTS: There was no difference in the post-bronchodilator FEV(1) over the first 5 days between the aminophylline and placebo groups. In the aminophylline group, 2 hours of treatment produced a small but significant rise in arterial pH (p = 0.001) and a fall in arterial carbon dioxide tension (p = 0.01) compared with placebo treatment. There were no differences in the severity of breathlessness, post-bronchodilator FVC, or length of hospital stay between the groups. Nausea was a more frequent side effect in the aminophylline group (46% v 22%; p<0.05), but palpitations and headache were noted equally in both groups. CONCLUSIONS: Although intravenous aminophylline produced small improvements in acid-base balance, these did not influence the subsequent clinical course. No evidence was found for any clinically important additional effect of aminophylline treatment when used with high dose nebulised bronchodilators and oral corticosteroids. Given its known toxicity, we cannot therefore recommend the use of intravenous aminophylline in the treatment of non-acidotic COPD exacerbations.

Aged↗
PubMed2005

Snoring surgery: a retrospective review.

OBJECTIVE: To undertake a retrospective, questionnaire review of surgery for heavy snoring, to ascertain patients' perception of the procedure and its effect on their snoring. PATIENTS AND METHODS: A specifically designed postal questionnaire was sent to 261 patients who underwent snoring surgery at University Hospital Aintree, Liverpool, UK, between April 1993 and March 2000. One hundred ninety-three patients responded (73.9%), including 151 men and 42 women. Mean age was 49.0 years (range, 24-74 yrs). RESULTS: Twenty-two patients had a uvulopalatopharyngoplasty, 53 a traditional laser palatoplasty and uvulectomy, and 118 an uvulopalatal elevation palatoplasty. There was a 26% patient-reported postoperative infection rate. Morbidity regarding postoperative swallowing, pharyngeal sensation or voice change appeared minimal. Seventy-six percent scored postoperative pain as "moderate" or "severe," irrespective of the operation performed (P = 0.989). Thirty-seven percent of patients perceived an improvement in postoperative sleep quality. Twenty-four percent of patients reported no improvement in snoring after surgery. Forty-three percent reported an initial improvement that was not sustained for 2 years, whereas 34% of patients benefited from an improvement sustained for longer than 2 years, irrespective of the operation performed (P = 0.143). Only 47%, with hindsight, would have undergone surgery. CONCLUSION: These data highlight that snoring surgery has a high postoperative morbidity rate and a high failure rate. Research endeavors should be directed to the development of a strategy which enables reliable preoperative identification of patients' who enjoy sustained benefit postoperatively.

Adult↗
PubMed2005

Flow limitation and dynamic hyperinflation: key concepts in modern respiratory physiology.

Fashions in ideas, like clothes, come and go. From approximately 1950-1980, physiological research was seen as the key discipline in understanding lung disease and was at the cutting edge of pulmonary science. Subsequently, its importance has been down played amid a widely accepted but unfounded assumption that we now have a perfect working understanding of the physiological behaviour of the respiratory system in health and disease. Although it seems improbable that completely new disciplines within respiratory physiology will emerge with fundamentally different ways of describing the mechanical or gas exchanging function of the lung, advances in computing and new observations in disease have highlighted previously unsuspected physiological abnormalities that have changed the way we view lung disease and the interface between disordered lung mechanics, symptomatology and disability. This is especially true for the two related physiological concepts of expiratory flow limitation and dynamic hyperinflation, which are now being taken from the physiological laboratory to the bedside with dramatic effect. Each arises from well-established theoretical and practical observations first made 40 yrs ago and now adapted to a range of settings, particularly in the field of obstructive lung disease. This review focuses on how these conditions are defined and assessed and what evidence there is that they might be important in lung disease.

Airway Resistance↗
PubMed2005

Acoustic analysis of snoring before and after palatal surgery.

To investigate the effectiveness of palatal surgery for nonapnoeic snoring, 35 patients were block randomised to undergo one of two different palatoplasty procedures. Patients were admitted pre-operatively for audio recording of snoring sound and video recording of sleeping position, and between 1.0 and 4.1 months (mean 2.5) and between 5.9 and 17.5 months (mean 9.7) post-operatively. Sound files, comprising the inspiratory sound of the first 100 snores whilst sleeping in a supine position, were analysed using specifically designed software. Snore duration (s), loudness (dBA), periodicity (%) and energy ratios for the frequency bands 0-200 Hz, 0-250 Hz and 0-400 Hz were calculated. Subjective outcomes were noted. Operation type, body mass index, age, peak nasal inspiratory flow rate, Epworth sleep score and alcohol intake were considered as confounding variables. No patient was cured from snoring. Paired t-test analysis demonstrated statistically significant changes between pre- and early post-operative recordings for snore periodicity and energy ratios in the frequency ranges 0-200 Hz, 0-250 Hz and 0-400 Hz. In conclusion, only the 0-250-Hz energy ratio measurements maintained a statistically significant improvement at the time of the late post-operative recording, despite an obvious drift back to pre-operative levels. No confounding variables were identified. The subjective and objective results correlated poorly. Post-operative changes in the acoustic parameters of snoring sound, following palatal surgery, are demonstrable but short-lived.

Acoustics↗
PubMed2004

Cough in chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) most commonly complain of cough, production of phlegm and breathlessness. The cough reflex sensitivity is heightened compared with that in healthy volunteers and is similar to that in subjects with asthma. The degree of airflow obstruction does not predict cough reflex sensitivity or objective cough counts, implying an independent process. Objective cough rates seem to be relatively low in COPD, despite frequent reporting of the symptom by patients. The relative contribution of cough to disability in COPD seems to be small, if assessed by subjective reporting. Effective treatments for cough in COPD have not yet been identified. Improved outcome measures of cough, a better understanding of the mechanisms underlying cough, and the importance of cough to patients is required to progress in this field.

Clinical Trials as Topic↗
PubMed2004

Regional chest wall volumes during exercise in chronic obstructive pulmonary disease.

BACKGROUND: Dynamic hyperinflation of the lungs impairs exercise performance in chronic obstructive pulmonary disease (COPD). However, it is unclear which patients are affected by dynamic hyperinflation and how the respiratory muscles respond to the change in lung volume. METHODS: Using optoelectronic plethysmography, total and regional chest wall volumes were measured non-invasively in 20 stable patients with COPD (mean (SD) forced expiratory volume in 1 second 43.6 (11.6)% predicted) and dynamic hyperinflation was tracked breath by breath to test if this was the mechanism of exercise limitation. Resting ventilation, breathing pattern, symptoms, rib cage and abdominal volumes were recorded at rest and during symptom limited cycle ergometry. Pleural, abdominal, and transdiaphragmatic pressures were measured in eight patients. RESULTS: End expiratory chest wall volume increased by a mean (SE) of 592 (80) ml in 12 patients (hyperinflators) but decreased by 462 (103) ml in eight (euvolumics). During exercise, tidal volume increased in euvolumic patients by reducing end expiratory abdominal volume while in hyperinflators tidal volume increased by increasing end inspiratory abdominal and rib cage volumes. The maximal abdominal pressure was 22.1 (9.0) cm H(2)O in euvolumic patients and 7.6 (2.6) cm H(2)O in hyperinflators. Euvolumic patients were as breathless as hyperinflators but exercised for less time and reached lower maximum workloads (p<0.05) despite having better spirometric parameters and a greater expiratory flow reserve. CONCLUSIONS: Dynamic hyperinflation is not the only mechanism limiting exercise performance in patients with stable COPD. Accurate measurement of chest wall volume can identify the different patterns of respiratory muscle activation during exercise.

Aged↗
PubMed2004

Effect of oxygen on recovery from maximal exercise in patients with chronic obstructive pulmonary disease.

BACKGROUND: The effects of oxygen on recovery from exercise in patients with chronic obstructive pulmonary disease (COPD) are not clearly known. A study was undertaken to determine whether oxygen given after maximal exercise reduced the degree of dynamic hyperinflation and so reduced the perception of breathlessness. METHODS: Eighteen patients with moderate to severe COPD performed maximal symptom limited exercise on a cycle ergometer. During recovery they received either air or oxygen at identical flow rates in a randomised, single blind, crossover design. Inspiratory capacity, breathing pattern data, dyspnoea intensity, and leg fatigue scores were collected at regular intervals during recovery. At a subsequent visit patients underwent a similar protocol but with a face mask in situ to eliminate the effects of instrumentation. RESULTS: When oxygen was given the time taken for resolution of dynamic hyperinflation was significantly shorter (mean difference between air and oxygen 6.61(1.65) minutes (95% CI 3.13 to 10.09), p = 0.001). Oxygen did not, however, reduce the perception of breathlessness during recovery nor did it affect the time taken to return to baseline dyspnoea scores in either the instrumented or non-instrumented state (mean difference 2.11 (1.41) minutes (95% CI -0.88 to 5.10), p = 0.15). CONCLUSIONS: Oxygen reduces the degree of dynamic hyperinflation during recovery from exercise but does not make patients feel less breathless than breathing air. This suggests that factors other than lung mechanics may be important during recovery from exercise, or it may reflect the cooling effect of both air and oxygen.

Adult↗
PubMed2004

Detection of expiratory flow limitation in COPD using the forced oscillation technique.

Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.

Aged↗
PubMed2004

Long-acting inhaled anticholinergic therapy improves sleeping oxygen saturation in COPD.

Oxygen desaturation occurs during sleep in severe chronic obstructive pulmonary disease (COPD), especially during rapid eye movement (REM) sleep, due to hypoventilation and ventilation-perfusion mismatching, but the possible contribution of airflow limitation is unclear. In a randomised, placebo-controlled, double-blind study of severe, stable COPD patients, the authors compared 4 weeks treatment with a long-acting inhaled anticholinergic agent (tiotropium), taken in the morning (tiotropium-AM), or in the evening (tiotropium-PM), on sleeping arterial oxygen saturation (Sa,O2) and sleep quality. Overnight polysomnography was performed at baseline and after 4 weeks treatment. A total of 95 patients with awake resting arterial oxygen tension < or = 9.98 kPa (75 mmHg) were randomised, with a mean age of 66.4 yrs and mean forced expiratory volume in one second (FEV1) of 32% predicted. A total of 80 patients completed the study, of which 56 fulfilled the polysomnographic criterion of at least 2 h sleep in both sleep study nights and represent the group analysed. Tiotropium significantly improved spirometry compared with placebo. Both tiotropium-AM and tiotropium-PM groups had higher Sa,O2 during REM than placebo (+2.41% and +2.42%, respectively, and both pooled and tiotropium-PM groups had higher Sa,O2 during total sleep time (+2.49% and +3.06%, respectively). End-of-treatment FEV1 correlated with Sa,O2 during REM sleep, however, tiotropium did not change sleep quality. Sustained anticholinergic blockade improves sleeping arterial oxygen saturation without affecting sleep quality.

Administration, Inhalation↗