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Biomedical subjects

K F Whyte

Publications and source records attributed to K F Whyte.

At least 19 recordsLinked to original sources
PubMed2000

Home ventilation: the Green Lane Hospital experience.

AIMS: To describe the characteristics and outcomes of patients treated with domiciliary nocturnal support ventilation (NSV). METHODS: Case-note review of all patients treated with home NSV by Green Lane Hospital. RESULTS: 111 patients received home NSV between 1990 and 1999. 59 had respiratory failure due to obesity-hypoventilation syndrome (OHS), most of whom were Maori or Pacific Island people. Their mean BMI was 53 kg/m2. They frequently presented acutely, and often in extremis. After a median duration of 22 months treatment, 37 patients continued treatment. Four have died, but none from respiratory failure. Other causes of respiratory failure included: neuromuscular disease (26), kyphoscoliosis (19) and obstructive sleep apnoea (8). Patients who did not have OHS were mostly of New Zealand European ethnicity, required lower ventilation pressures than patients with OHS, and had better arterial blood gases on treatment. After a median follow-up of 35 months, however, fourteen have died. 33 continued on treatment. Both OHS and non-OHS patients had high deprivation scores according to NZdep96. This was most apparent for patients with OHS. CONCLUSIONS: OHS is an important cause of respiratory failure in New Zealand, particularly affecting Maori and Pacific people. The prognosis of OHS treated with NSV appears to be good despite significant co-morbidity.

Adult↗
PubMed1994

Changes in regional ventilation during histamine bronchial challenge in stable asthma.

Our objective was to examine the changes in regional ventilation during histamine-induced bronchoconstriction in stable asthma. We measured regional ventilation by a new method which measures regional distribution of inhaled 127Xe during tidal breathing by a gated method and, by simultaneously measuring 99mTc counts from labelled macroaggregates, allowed for changes in lung shape during the breathing cycle. We studied 10 asthmatic patients [forced expiratory volume in 1 s (FEV1 2.04-4.37 litres)] and measured, in addition to the regional ventilation, oxygen saturation (SaO2), minute ventilation (VE) and tidal volume (Vt) before and after inhaling enough histamine to lower FEV1 by > 20% and/or SaO2 by > 4%. Histamine inhalation reduced FEV1 by 0.44-1.15 liters and SaO2 by 0-4%. It increased VE and functional residual capacity (FRC) in 8 of the 10 patients. The FEV1 fall did not correlate with the SaO2 fall, VE or FRC changes. Histamine inhalation increased apical ventilation in most patients, but the changes in regional ventilation in the left and right lungs were asymmetrical in 17 out of the 30 lung regions studied (upper, middle and lower paired regions in 10 patients). These results demonstrate that histamine bronchial challenge causes uneven regional ventilation. Any resultant change in ventilation-perfusion balance may be the underlying mechanism of oxygen desaturation seen in this procedure and in spontaneous attacks of asthma.

Adult↗
PubMed1993

Nocturnal desaturation and serum erythropoietin: a study in patients with chronic obstructive pulmonary disease and in normal subjects.

1. To clarify the relationship between nocturnal oxygen desaturation and erythropoietin production in patients with chronic obstructive pulmonary disease, we determined arterial oxygen saturation and serum immunoreactive erythropoietin levels over 24 h in eight patients with chronic obstructive pulmonary disease and in nine normal subjects. 2. In the normal subjects, there was a significant circadian variation in serum erythropoietin levels with the highest mean deviation from the geometric mean at 22.00 hours and the nadir at 05.00 hours. 3. The three patients with chronic obstructive pulmonary disease with the most marked nocturnal desaturation (lowest arterial oxygen saturation < 57%) and most marked daytime hypoxaemia (daytime arterial partial pressure of oxygen < 6 kPa) had raised nocturnal serum erythropoietin levels. In two of these patients, the serum erythropoietin level was raised throughout the 24 h and erythrocyte mass was also raised. In the other patient, the serum erythropoietin level was not raised in five daytime samples and erythrocyte mass was normal. 4. The other five patients with chronic obstructive pulmonary disease with less severe nocturnal hypoxaemia (lowest arterial oxygen saturation range 78-86%) had serum erythropoietin levels (range 14-36 m-i.u./ml) which were indistinguishable from normal (range 12-44 m-i.u./ml) and showed circadian changes which were not significantly different (P = 0.35) from those in the normal subjects. 5. Thus, mild nocturnal oxygen desaturation is not associated with elevation of serum erythropoietin levels, whereas daytime hypoxaemia with associated severe nocturnal desaturation is associated with increased serum erythropoietin levels both by day and by night.

Aged↗
PubMed1992

Accuracy and significance of scoring hypopneas.

We previously reported that the best definition of hypopneas in the sleep apnea/hypopnea syndrome (SAHS) is based on reduction in thoracoabdominal movement. However, the repeatability of scoring hypopneas from thoracoabdominal movement has not been assessed, nor has the need to record flow as well as thoracoabdominal movement. Thus, two polysomnographers independently scored both apneas and hypopneas on all-night polysomnograms of patients with SAHS. There was close agreement between the polysomnographers for the number of hypopneas (r = 0.98; mean difference 11%) and for the number of apneas (r = 0.99; mean difference 8%). The agreement was similar for the durations of both hypopneas (r = 0.99; mean difference 13%) and apneas (r = 0.99; mean difference 11%). There was also close agreement between the total number of respiratory events scored with and without reference to the flow signal (r = 0.99; mean difference 1.4%) with a maximum under-recognition of 18 events per night in a subject with 237 apneas per night. Thus, hypopneas can be scored reproducibly. In addition, the value of always recording and scoring flow as well as thoracoabdominal signals is questioned.

Adult↗
PubMed1991

Dose of nebulized ipratropium bromide in acute severe asthma.

The aim of the study was to determine the maximum effective dose of nebulized ipratropium bromide, 0.5 or 1.0 mg, in the treatment of acute severe attacks of asthma. Thirty-two patients (ten males, 19-53 years) who were admitted with acute severe asthma were, in a double-blind trial, randomized to receive either 0.5 or 1.0 mg of isotonic, preservative-free ipratropium bromide nebulized in saline. Ear oxygen saturation, peak flow and heart rate were measured on admission and regularly following nebulization. Two hours after nebulization of the ipratropium, terbutaline (5 mg) was administered by nebulizer and further measurements taken 30 min later. Twenty-six patients completed the study, 13 in each group. Peak expiratory flow (PEF) increased by 51% [1211 min-1 increasing to 1831 min-1 (mean)] in the 0.5-mg ipratropium group, and by 37% (1551 min-1 to 2071 min-1) in the 1.0-mg group. There were no significant differences in heart rate or ear oxygen saturation changes between the groups. Nebulized terbutaline led to a small further rise in peak flow in both groups (341 min-1 in the 0.5-mg group; 411 min-1 in the 1.0-mg group). No side-effects were noticed in either group. We conclude that 0.5 mg of nebulized ipratropium is as effective as 1.0 mg in the treatment of acute severe asthma.

Acute Disease↗
PubMed1991

Bronchial compression as a result of lung herniation after pneumonectomy.

A patient developed severe exertional dyspnoea and stridor eight months after a right pneumonectomy for a carcinoid tumour, with a progressive loss of lung function. These events were the result of compression of the left main bronchus against the vertebral column by the mediastinal contents, which had shifted into the right hemithorax with the herniated lung.

Adult↗
PubMed1991

Morbidity in nocturnal asthma: sleep quality and daytime cognitive performance.

Most patients with asthma waken with nocturnal asthma from time to time. To assess morbidity in patients with nocturnal asthma nocturnal sleep quality, daytime sleepiness, and daytime cognitive performance were measured prospectively in 12 patients with nocturnal asthma (median age 43 years) and 12 age and intellect matched normal subjects. The median (range) percentage overnight fall in peak expiratory flow rate (PEF) was 22 (15 to 50) in the patients with nocturnal asthma and 4 (-4 to 7) in the normal subjects. The patients with asthma had poorer average scores for subjective sleep quality than the normal subjects (median paired difference 1.1 (95% confidence limits 0.1, 2.3)). Objective overnight sleep quality was also worse in the asthmatic patients, who spent more time awake at night (median difference 51 (95% CL 8.1, 74) minutes), had a longer sleep onset latency (12 (10, 30) minutes), and tended to have less stage 4 (deep) sleep (-33 (-58, 4) minutes). Daytime cognitive performance was worse in the patients with nocturnal asthma, who took a longer time to complete the trail making tests (median difference 62 (22, 75) seconds) and achieved a lower score on the paced serial addition tests (-10 (-24, -3)). Mean daytime sleep latency did not differ significantly between the two groups (2 (-3, 7) minutes). It is concluded that hospital outpatients with stable nocturnal asthma have impaired sleep quality and daytime cognitive performance even when having their usual maintenance asthma treatment.

Adult↗
PubMed1991

Accuracy of respiratory inductive plethysmograph in measuring tidal volume during sleep.

Respiratory inductance plethysmography (RIP) has been widely used to measure ventilation during sleep, but its accuracy in this role has not been adequately tested. We have thus examined the accuracy of the RIP by comparing tidal volume measured with RIP with that measured by a pneumotachograph in eight unrestrained normal subjects during sleep. We have also studied the effect of posture on the accuracy of the RIP. In all sleep stages the correlation between RIP tidal volume measurements and expired volume showed relatively poor correlations (mean r = 0.49-0.60), and the bias of the measurements varied widely. Changes in posture altered the correlations between the two measurements, with no systematic differences between positions. When the subjects resumed a position, the 95% confidence intervals of tidal volume measurement did not overlap the original confidence limits in that posture on 13 of 25 occasions. This study shows that the RIP does not accurately measure tidal volume during sleep in unrestrained subjects and should only be used for semiquantitative assessment of ventilation during sleep.

Adult↗
PubMed1991

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome.

The effect of posture on upper airway dimensions was assessed for two reasons. First, some patients with untreated sleep apnea/hypopnea syndrome (SAHS) report they sleep better sitting upright. Second, to allow comparison of the differing techniques used to determine the site of maximal airway narrowing in awake patients with SAHS, as some are carried out in the erect and others in the supine posture. Lateral cephalometry was therefore carried out in 33 nonsnoring normal subjects and in 29 patients with obstructive SAHS (mean apneas plus hypopneas, 46 per hour; range, 17 to 103). In both normal subjects and patients, uvular width was increased (p less than 0.05) in the supine posture, and this was associated with significant narrowing of the retropalatal airway in the patients with SAHS (erect, 5.0 +/- SD 2.6 mm; supine, 3.6 +/- 2.8 mm; p less than 0.01). In both normal subjects and patients, the retroglossal hypopharynx widened (p less than 0.05) in the supine posture (e.g., in patients with SAHS, posterior airway space was: erect, 11.5 +/- 4.5 mm; supine, 13.4 +/- 4.8 mm; p = 0.003). In the supine posture there was anterior movement of the hyoid and neck flexion in both groups. However, a study of the effect of neck flexion in the erect posture showed that neck flexion produced no changes in airway caliber. Thus, posture is an important determinant of upper airway dimensions.

Adult↗
PubMed1991

Peripheral edema in the sleep apnea/hypopnea syndrome.

To clarify the roles of lung function, nocturnal hypoxemia and obesity in the development of peripheral edema in patients with the sleep apnea/hypopnea syndrome (SAHS), 65 consecutive SAHS patients had diagnostic sleep studies and respiratory function testing. Eighteen patients (27%) had peripheral edema without other explanation. Their sleep apnea/hypopnea index was similar to those without edema, but they were more obese (p less than 0.01) and had worse lung function (p less than 0.01) and lower oxygen saturation (SaO2) awake (p less than 0.01). These 18 became more hypoxemic during sleep than predicted from their awake SaO2 (p less than 0.005). Eleven patients with edema had evidence of pulmonary hypertension on cardiac catheterization, chest radiograph, or electrocardiograph and could be weight matched to 11 SAHS patients without edema. Those with right heart failure were more hypoxic (p less than 0.01) when awake, desaturated more frequently during sleep (p less than 0.01), and had lower FEV1% predicted (p less than 0.01). Thus, extent of both daytime and nighttime hypoxemia are important in the development of right heart failure in patients with SAHS.

Adult↗
PubMed1989

Effect of CGP 17/582, a selective beta-adrenoceptor antagonist, on the haemodynamic and hypokalaemic response to adrenaline.

1. CGP 17/582B is a new beta-adrenoceptor antagonist which on experimental studies appears to combine selective beta 1-adrenoceptor blockade with partial agonist activity (ISA). Assessing beta-adrenoceptor selectivity and the degree of partial agonist activity in vivo can be difficult. 2. In a double-blind placebo controlled crossover study we have compared the effect of oral pretreatment for 7 days with CGP (100 mg twice daily), with propranolol (non-selective beta-adrenoceptor blocker with no ISA) and metoprolol (selective beta-adrenoceptor blocker with no ISA) on resting heart rate and heart rate response to submaximal exercise on a bicycle ergometer to assess the degree of beta-adrenoceptor blockade and also the changes in blood pressure, heart rate and potassium during the intravenous infusion of (-)-adrenaline to determine the degree of beta 2-adrenoceptor blockade. 3. Subjects underwent submaximal exercise testing on the second and fifth day of each treatment period and on the seventh day received a 2 h infusion of (-)-adrenaline (0.06 microgram kg-1 min-1). Heart rate, blood pressure, plasma potassium and catecholamines were measured throughout the study period. 4. All three active treatments significantly reduced exercise induced tachycardia. The (-)-adrenaline infusion significantly reduced plasma noradrenaline levels following propranolol and metoprolol and to a lesser extent with placebo but were unaltered on CGP. Baseline heart rate was unaltered by CGP but was significantly reduced by metoprolol and propranolol. Adrenaline significantly reduced plasma potassium levels following placebo and CGP pretreatment but plasma potassium was unaltered by adrenaline with metoprolol and propranolol pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1989

Posture and nocturnal asthma.

To investigate whether the supine posture caused sustained bronchoconstriction and could thus contribute to the development of nocturnal asthma, nine patients with nocturnal asthma were studied on two consecutive days, lying supine for four hours on one day and sitting upright for four hours on the other, the order of the two postures being randomised. Peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), and forced vital capacity (FVC) were measured immediately before and after the four hours and over the subsequent hour. There was no significant difference between the erect and supine posture for PEF (248 v 248 l/min), FEV1 (1.31 v 1.22 l), or FVC (2.34 v 2.28 l) at the end of the four hours, nor did any significant change develop subsequently. Thus the supine posture is not associated with prolonged bronchoconstriction. As each patient had previously shown an average overnight fall in PEF of more than 20%, this study strongly suggests that the supine posture is not an important cause of overnight bronchoconstriction.

Adult↗
PubMed1989

Pulmonary hemodynamics, gas exchange, and the severity of emphysema as assessed by quantitative CT scan in chronic bronchitis and emphysema.

We have used the CT transthoracic scan to measure regional lung density in vivo, as our previous studies have shown that this correlates with the increase in size of distal air spaces, which is a defining characteristic of emphysema. We have studied 32 patients with chronic airflow limitation (FEV1, 15 to 68% predicted) caused by chronic bronchitis and emphysema (synonym, COPD), with a wide range of arterial PO2 (38 to 90 mm Hg) and PCO2 (32 to 63 mm Hg) while breathing air at rest. We could find no significant relationships between the extent of emphysema (as assessed in vivo by the EMI number defining the lowest fifth percentile of the CT density histogram of the lung fields) and either arterial blood gas tensions, mean pulmonary arterial pressure, cardiac output, or calculated total pulmonary vascular resistance while at rest (n = 32) or during supine leg exercise (n = 29). We conclude that the extent of emphysema does not correlate with the clinical or pathologic features of the "pink and puffing" (i.e., mild hypoxemia, no CO2 retention, no pulmonary hypertension, etc.) or "blue and bloated" (i.e., hypoxemia, CO2 retention, pulmonary hypertension) pattern of patients with COPD nor to the spectrum of hemodynamic and gas exchange abnormalities that commonly occur in patients between these two extreme examples. Thus, "pink puffers" should not be equated with "the emphysematous" pattern of this disease. Although these clinicophysiologic patterns remain valid as descriptions, they do not relate to the extent of underlying emphysema in COPD.

Aged↗
PubMed1989

Ventilatory and arousal responses to added inspiratory resistance during sleep.

Airway resistance increases during sleep. We have determined the ventilatory and arousal responses to the addition of inspiratory resistance of 4, 7, or 10 cmH2O/L/s during sleep in 10 normal men who slept wearing valved face masks. Insufficient ventilatory response data were obtained during rapid eye movement (REM) sleep to allow adequate analysis. The immediate responses to loading were decreases in tidal volume (VT), breathing frequency (f), and minute ventilation (VE), with no difference between wakefulness and Stage 2 and Stage 3/4 sleep in the effects of loading on VT and VE, but f fell more during wakefulness than during sleep (p less than 0.05) because of a greater lengthening of inspired time (TI) (p less than 0.05). During the first 10 breaths, occlusion pressure (P0.1) increased similarly in all EEG stages. Averaging responses during the 2-min periods when resistances were applied, the only variable to differ between EEG stages was TI, which increased more in wakefulness than in Stage 2 or Stage 3/4 sleep (p less than 0.01). Arousal within 2 min of application of resistance occurred less frequently from Stage 3/4 sleep than from Stage 2 or REM sleep (p less than 0.02). The study demonstrates that sleep modifies the changes in respiratory timing produced by resistive loading without having a major effect on ventilation or P0.1 responses. The low frequency of arousal from Stage 3/4 sleep with loading may explain why asthmatics rarely awaken from this stage with wheeze.

Adult↗
PubMed1989

Clinical features of the sleep apnoea/hypopnoea syndrome.

The sleep apnoea/hypopnoea syndrome has been reported to be rare in Britain. We have offered a clinical service for the diagnosis and treatment of this condition in Scotland for four years during which there has been an increase in referral rate from 19 patients in year 1 to 61 in year 4. We report the clinical features of the 80 patients. Seventy-eight snored and 70 were somnolent, each falling asleep at least once each day when not in bed. Ten reported falling asleep whilst driving or flying. Twenty-nine slept restlessly, 28 were not refreshed by sleep and 21 had nocturnal choking attacks. Ankle swelling was reported by 26 and 25 were hypertensive (diastolic BP greater than 95 mmHg). Two had hyperthyroidism and one acromegaly. Nineteen have been successfully treated by continuous positive airway pressure therapy at home. The data suggest that regional centres should be established in Britain to diagnose and treat this condition.

Adolescent↗