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Biomedical subjects

D C Flenley

Publications and source records attributed to D C Flenley.

At least 55 records · Page 3Linked to original sources
PubMed1985

Technical and clinical assessment of oxygen concentrators.

One membrane oxygen enricher (Oxygen Enrichment Company OE-4E) and four molecular sieve (MS) concentrators (Mountain Medical Econo2, De Vilbiss MINI DeVO2, Cryogenic Roomate III, and Mountain Medical Mini O2) have been studied to assess technical and clinical performance. During four weeks of continuous operation at a flow rate of 2 l min-1 (6 l min-1 for OE-4E) consistent oxygen levels were delivered by all machines (mean greater than 93% for MS concentrators, 36.5% for OE-4E). At flow rates of up to 21 mm-1 all four MS machines delivered oxygen concentrations greater than 92%, but at 3 l min-1 (Econo2 89.6%, MINI DeVO2 93.9%, Roomate III 92.0%, Mini O2 85.0%) and at 4 l min-1 (Econo2 78.0%, Mini DeVO2 84.7%, Roomate III 83.3%, Mini O2 69.1%) the two newer machines gave higher oxygen concentrations. In 20 hypoxic patients the mean oxygen saturation levels achieved when they were breathing oxygen from the MS concentrators at a flow rate of 2 l min-1 were similar (Econo2 92.6%, MINI DeVO2 92.5%, Roomate II 92.6%), but the level achieved when they were breathing from the OE-4E, at the equivalent flow rate of 6 l min-1, was lower (91.0%, p less than 0.005). The performance of concentrators in service (Econo2, MINI DeVO2, Mini O2) was satisfactory when judged by patients' oxygen saturation levels and delivered oxygen concentrations. The OE-4E may be indicated for a small number of patients who require oxygen with high humidification. The four MS concentrators studied are all suitable for domiciliary use, but the MINI DeVO2 and Roomate III have advantages in terms of better performance at high flow rates and reduced size and weight.

Aged↗
PubMed1985

Clinical assessment of oxygen conserving devices in chronic bronchitis and emphysema.

We have studied the efficacy of three devices designed to conserve oxygen delivered to patients with hypoxic chronic bronchitis and emphysema. Devices A and B are valve systems, which deliver oxygen only during inspiration. Device C is a modified nasal prongs system incorporating a "moustache reservoir" (Oxymizer, Chad Therapeutics Inc, Woodland Hills, California), which is claimed to produce a higher arterial oxygen saturation (SaO2) from a given flow of oxygen than does continuous delivery through nasal prongs. Devices A and B were found to give the same oxygen saturation as continuous flow oxygen, but only device B reduced the flow of oxygen significantly (p less than 0.01). The flow characteristics of device A were likely to be the cause of this failure to conserve oxygen. Device C produced a higher mean rise in SaO2 than did standard nasal prongs at all oxygen flow rates, and was able to achieve the same rise in SaO2 as standard nasal prongs with a small (25-33%) saving in oxygen delivery. There was, however, considerable variation between patients in the oxygen saving efficiency of device C, with little or no oxygen saving in seven of the 12 patients studied.

Aged↗
PubMed1985

Mechanism of transient nocturnal hypoxemia in hypoxic chronic bronchitis and emphysema.

In five patients with hypoxic chronic bronchitis and emphysema we measured ear O2 saturation (SaO2), chest movement, oronasal airflow, arterial and mixed venous gas tensions, and cardiac output during nine hypoxemic episodes (HE; SaO2 falls greater than 10%) in rapid-eye-movement (REM) sleep and during preceding periods of stable oxygenation in non-REM sleep. All nine HE occurred with recurrent short episodes of reduced chest movement, none with sleep apnea. The arterial PO2 (PaO2) fell by 6.0 +/- 1.9 (SD) Torr during the HE (P less than 0.01), but mean arterial PCO2 (PaCO2) rose by only 1.4 +/- 2.4 Torr (P greater than 0.4). The arteriovenous O2 content difference fell by 0.64 +/- 0.43 ml/100 ml of blood during the HE (P less than 0.05), but there was no significant change in cardiac output. Changes observed in PaO2 and PaCO2 during HE were similar to those in four normal subjects during 90 s of voluntary hypoventilation, when PaO2 fell by 12.3 +/- 5.6 Torr (P less than 0.05), but mean PaCO2 rose by only 2.8 +/- 2.1 Torr (P greater than 0.4). We suggest that the transient hypoxemia which occurs during REM sleep in patients with chronic bronchitis and emphysema could be explained by hypoventilation during REM sleep but that the importance of changes in distribution of ventilation-perfusion ratios cannot be assessed by presently available techniques.

Adult↗
PubMed1985

Right ventricular performance during exercise in chronic obstructive pulmonary disease. The effects of oxygen.

Radionuclide ventriculography allows non-invasive assessment of right ventricular performance. This study has confirmed that there is a modest reduction in right ventricular ejection fraction (RVEF) in patients with chronic obstructive pulmonary disease (COPD), as compared to normal subjects. However, occult right ventricular dysfunction also becomes apparent in these patients during exercise. The change in RVEF during exercise is related to the corresponding fall in arterial oxygen saturation in patients with COPD. Oxygen improves the response of the right ventricle to exercise, although the mechanism remains unclear. Long-term oxygen therapy, in patients with respiratory failure, does not appear to have any significant effect on RVEF.

Adult↗
PubMed1985

Breathing and oxygenation during sleep are similar in normal men and normal women.

Most patients with the sleep apnea syndrome are male, and it has been suggested that there is a fundamental sex difference in breathing during sleep. To explore this we measured overnight ear oxygen saturation (SaO2), breathing patterns, and electroencephalographic sleep stage in 21 healthy nonobese women (10 premenopausal, 11 postmenopausal) and in 19 healthy nonobese men of similar age. Sleep duration averaged 6 h 51 min (range 343 to 468 min). The 21 older (greater than 45 yr) subjects had more episodes of apnea and hypopnea (p less than 0.01) and became more hypoxemic (p less than 0.02) than did the 20 younger subjects, but there was no sex difference, either in the younger or older subjects, in irregular breathing or nocturnal hypoxemia. Seven subjects 51 to 68 yr of age (4 men and 3 women) had more than 30 episodes of apnea and/or hypopnea and/or SaO2 decreases below 90%, but the clinical importance of this finding is unclear, 6 of the 7 being alive and 5 asymptomatic at an average of 47 months (range 5 to 67) later. Thus, irregular breathing and hypoxemia during sleep are common in both sexes older than 50 yr of age. Previous reports of a sex difference are probably explained by poor matching of the men and women, particularly with regard to body weight.

Adult↗
PubMed1985

Almitrine improves oxygenation when both awake and asleep in patients with hypoxia and carbon dioxide retention caused by chronic bronchitis and emphysema.

Patients with chronic bronchitis and emphysema who are hypoxic when awake become more hypoxic during sleep, with a further rise in their preexisting pulmonary hypertension. Almitrine, a respiratory stimulant, improves arterial blood gas tensions in such patients when they are awake. We have used a double-blind, placebo-controlled, cross-over study to compare the effects of 50 mg almitrine given orally twice a day for 14 days on oxygen saturation (SaO2), respiratory movements, and sleep quality in 9 patients with hypoxic chronic bronchitis and emphysema (FEV1, 0.4 to 1.0 L; PaO2, 51 +/- (SEM) 2 mmHg; PaCO2, 49 +/- 1 mmHg). Almitrine improved arterial blood gas tensions when awake, mean PaO2 rising by 8 mmHg (p less than 0.001) and PaCO2 falling by 4 mmHg (p less than 0.01). Almitrine improved nocturnal oxygenation, mean SaO2 when awake rising from 83 +/- 4% to 89 +/- 3% (p less than 0.01), and the lowest SaO2 during sleep rising on average from 65 +/- 6% to 77 +/- 3% (p less than 0.02). The number of hypoxemic episodes (SaO2 falling by greater than or equal to 10% from the preceding stable baseline during sleep) and the time when SaO2 was below 80% (135 +/- 53 versus 46 +/- 35 min; p less than 0.01) also improved. Almitrine did not improve sleep quality. We conclude that almitrine improves arterial gas tensions when awake and reduces the frequency and severity of nocturnal hypoxemia without impairing sleep quality in patients with chronic bronchitis and emphysema who are both hypoxemic and hypercapnic when awake.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Sleep in chronic obstructive lung disease.

Profound transient nocturnal hypoxemia is common during REM sleep in "blue bloaters" with chronic obstructive lung disease, these patients having hypoxemia and CO2 retention when awake, when breathing air. These hypoxemic episodes appear to be due to a combination of reduced ventilation in REM sleep with a possible increase in the maldistribution of ventilation to perfusion within the alveoli at that time, and a reduction in functional residual capacity. The episodes are associated with exacerbations of pulmonary vasoconstriction, which can be reversed by oxygen therapy throughout sleep. Cardiac arrhythmias and alterations in ST segments are also found in these patients during sleep when breathing air. It is probable that the severity of hypoxemia in REM sleep can be predicted from knowledge of the arterial PO2 when breathing air when awake in patients with COPD. If so, expensive sleep studies are not essential to indicate the presence of hypoxemia in sleep in these patients, but such studies may be required in obese patients, in those who snore, or those who complain of headache following nocturnal oxygen therapy to demonstrate the presence of the overlap syndrome, in which obstructive sleep apnea is combined with chronic obstructive lung disease in the same patient. Nocturnal oxygen therapy may be dangerous in such patients with the overlap syndrome but appears to cause little rise in PCO2, in patients with COPD and REM-associated hypoxemia alone. Hypoxemia and sleep quality can probably be improved by oxygen therapy in "blue bloaters," and this treatment can also reverse pulmonary hypertension in REM sleep. The new ventilatory stimulant almitrine can also correct hypoxemia, without disturbing sleep quality, but the effects of this drug on pulmonary vasoconstriction during REM sleep are as yet unknown.

Arrhythmias, Cardiac↗
PubMed1985

Breathing during sleep.

Hypoxaemia during the rapid eye movement phase of sleep is common in older healthy normal subjects over 55 years of age; the sleep apnoea syndromes--such as obstructive sleep apnoea, where oro-nasal airflow ceases for more than 10 seconds on many separate occasions throughout the night, due to failure of contraction of the genio-glossus muscle; "blue and bloated" patients with chronic bronchitis and emphysema, where profound nocturnal hypoxaemia is common in REM sleep, and is associated with further elevation of pulmonary arterial pressure; the overlap syndrome--where "blue and bloated" chronic bronchitis is associated with an obstructive sleep apnoea syndrome; and bronchial asthma, where hypoxaemia is associated with irregular breathing and possibly nocturnal bronchoconstriction. Although absolute recognition depends upon all night sleep studies, monitoring of ear oxygen saturation, breathing patterns, and EEG, the clinical features when awake can lead to suspicion of sleep hypoxaemia--as, for example, obesity and obstructive sleep apnoea with loud snoring and restlessness in sleep, hypoxaemia during wakefulness in the overlap syndrome, and nocturnal awakening with wheeze in bronchial asthma. Treatment depends on the cause, and may vary from weight loss and nasal continuous positive airway pressure in obstructive sleep apnoea, to nocturnal oxygen in "blue bloaters", a combination of these two in the overlap syndrome, and long acting bronchodilators such as slow release theophyllines in nocturnal asthma. Recognition and appropriate treatment of nocturnal hypoxaemia is an important new development in respiratory medicine.

Age Factors↗
PubMed1984

Diagnosis of pulmonary emphysema by computerised tomography.

Eleven patients with peripheral bronchial carcinoma had computerised tomographic (CT) scans before operation. The resected specimens from six of these patients showed mild centri-acinar emphysema. Preoperatively the two groups had not differed significantly in spirometric findings or lung volumes. The frequency distribution curves of EMI numbers within the lung fields of patients who proved to have centri-acinar emphysema differed significantly from those of the group who did not, there being more pixels in the EMI range -450 to -500 in the emphysematous group (p less than 0.001). Detailed assessment of lung density by CT scanning may be useful in the diagnosis of emphysema in life.

Adult↗
PubMed1984

Fitness facilitates sleep.

Eight army recruits were studied at the start, middle, and end of their initial 18-week training programme. At each point the subjects were studied for four consecutive nights in the sleep laboratory. Their sleep was characterized by the means of the recordings on the last two nights. Within 2 days of the sleep recordings (but never on the same day) each subject spent 2 non-consecutive days in the exercise laboratory. On the 1st day a maximum oxygen consumption (VO2 max) measurement was performed on a treadmill and on the 2nd day a 24-min progressive exercise bicycle ergometer test was carried out with simultaneous venous sampling (for lactic acid measurements) and oxygen consumption recordings from which the lactate turn point (LTP) was calculated. LTP was used as a measure of fitness. Approximately 1 week after the above measures lean muscle mass as calculated by total body potassium estimation was obtained for each subject. Slow wave sleep (SWS) as a percentage of total sleep time increased significantly between the start and the measurements at 9 and 18 weeks, being 21.9%, 29.9%, and 28.5% respectively. Anaerobic threshold increased significantly (P less than 0.05) over the first 9 weeks and continued to increase to the end of the training period (P less than 0.001) using VO2 when lactate level was 2 mmol/l as a percentage of VO2 max. With increase in fitness, sleep onset latency and wake time during sleep decreased and sleep efficiency improved. The results suggest that as fitness increases sleep quality improves.

Adolescent↗
PubMed1984

Nocturnal cough in patients with chronic bronchitis and emphysema.

Patients with respiratory disease commonly report that their sleep is disrupted by nocturnal cough. We have recorded cough during the night in 10 patients with severe chronic bronchitis and emphysema (forced expiratory volume in one second, 1.0 +/- SEM 0.1/L) who complained of nocturnal cough and correlated cough with electroencephalographic sleep stage and arterial oxygenation. Cough was recorded using a directional microphone and an auto-editing tape recorder system. Each cough was subsequently verified by a listener. There was a mean of 14.6 +/- 4.5 bouts of coughing per patient per night, each bout lasting on average 3.9 +/- 0.2 s. Eighty-five percent of coughing bouts occurred during electroencephalographically confirmed wakefulness (p less than 0.02 versus sleep), and coughs during true sleep were rare, with only 1 patient coughing during rapid eye movement sleep and none during Stages 3 and 4 sleep. Cough was only once followed by arousal. There was no correlation between cough and either apneas or hypoxemia during sleep. We conclude that spontaneous cough is suppressed during sleep and only rarely awakens patients.

Adult↗
PubMed1983

Effects of pirbuterol and sodium nitroprusside on pulmonary haemodynamics in hypoxic cor pulmonale.

The acute haemodynamic effects of oral pirbuterol (a beta-agonist) were contrasted with those of sodium nitroprusside, a vasodilator, in six patients with hypoxic chronic bronchitis and emphysema. Sodium nitroprusside (1-5 mg/kg intravenously) reduced mean pulmonary arterial pressure and total pulmonary vascular resistance significantly (p less than 0.01) without change in cardiac output or right ventricular ejection fraction, measured by radionuclide ventriculography. Oral pirbuterol (22.5 mg) produced a greater reduction in total pulmonary vascular resistance than sodium nitroprusside, largely as a result of increasing cardiac output. Right ventricular ejection fraction also increased significantly after pirbuterol (p less than 0.01). Pirbuterol in a lower dosage (15 mg by mouth) in six further patients with hypoxic chronic bronchitis and emphysema produced similar changes in total pulmonary vascular resistance and right ventricular ejection fraction. Nine of the patients who were studied acutely thereafter received pirbuterol 15 mg thrice daily for six weeks, which produced a significant fall in systolic pulmonary arterial pressure and a rise in right ventricular ejection fraction (p less than 0.01), without a significant fall in arterial oxygen tension. Pirbuterol acts as a vasodilator on the pulmonary circulation in these patients and may in addition improve right ventricular performance by an inotropic action.

Adrenergic beta-Agonists↗