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Biomedical subjects

L G Olson

Publications and source records attributed to L G Olson.

67 records · Page 4Linked to original sources
PubMed1987

The response of the nasal airway to exercise.

Exercise causes a fall in nasal resistance that may be due to sympathetic vasoconstriction in the nasal mucosa. Other factors potentially involved in the exercise effect on nasal resistance are: increased alae nasi muscle activity, passive redistribution of blood to exercising muscle and away from the nasal mucosa, increased nasal air flow, and hyperventilation. In order to determine the importance of these factors, 6 healthy adults had nasal pressure/flow data collected at rest and after bicycle exercise at 100 to 160 W. Erect exercise with nose breathing, erect exercise with mouth breathing, voluntary isocapnic hyperventilation at the minute volumes achieved during exercise, and supine exercise were performed. The alae nasi muscles were voluntarily activated during pressure/flow measurements. The pressure/flow data were displayed on a logarithmic plot; parallel rightward shifts of this plot indicate falls in nasal resistance mediated by enlargement of the air passage. The position of the plot was defined by the flow rate at which the slope of the logarithmic plot steepens abruptly (Vtr). Erect exercise with nose breathing caused a fall in nasal resistance in all 6 subjects (mean change in Vtr, +14.4 L/min). Exercise mouth breathing and supine exercise caused similar falls in nasal resistance in all subjects (mean change of Vtr, +14.1 and +14.2 L/min, respectively). Voluntary isocapnic hyperventilation had no effect on nasal pressure/flow properties in any subject (mean change in Vtr, -1.3 L/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Nocturnal hypoxaemia and quality of sleep in patients with chronic obstructive lung disease.

Fifty patients with chronic obstructive lung disease were questioned about their sleep quality and their responses were compared with those of 40 similarly aged patients without symptomatic lung disease. Patients with chronic obstructive lung disease reported more difficulty in getting to sleep and staying asleep and more daytime sleepiness than the control group. More than twice as many patients (28%) as controls (10%) reported regular use of hypnotics. In a subgroup of 16 patients with chronic obstructive lung disease (mean FEV1 0.88 (SD 0.44) sleep, breathing, and oxygenation were measured to examine the relationship between night time hypoxaemia and sleep quality. Sleep architecture was disturbed in most patients, arousals occurring from three to 46 times an hour (mean 15 (SD 14)/h). Arterial hypoxaemia during sleep was common and frequently severe. The mean (SD) arterial oxygen saturation (SaO2) at the onset of sleep was 91% (7%). Nine patients spent at least 40% of cumulative sleeping time at an SaO2 of less than 90% and six of these patients spent 90% of sleeping time below this level. Only four of 15 patients did not develop arterial desaturation during sleep. The mean minimum SaO2 during episodes of desaturation was less in rapid eye movement (REM) sleep (72% (17%)) than in non-REM sleep (78% (10%), p less than 0.05). The predominant breathing abnormality associated with desaturation was hypoventilation; only one patient had obstructive sleep apnoea. Arousals were related to oxygenation during sleep such that the poorer a patient's arterial oxygenation throughout the night the more disturbed his sleep (arousals/h v SaO2 at or below which 40% of the total sleep time was spent: r = 0.71, p less than 0.01). Hypoxaemia during sleep was related to waking values of SaO2 and PaCO2 but not to other daytime measures of lung function.

Female↗
PubMed1986

The effects of combined morphine and prochlorperazine on ventilatory control in humans.

Recent studies have shown that the antiemetic neuroleptic drug, prochlorperazine, is a potent stimulant of the ventilatory response to hypoxia. To investigate whether or not this effect persisted in the presence of central depression of ventilatory drive, the effects on ventilatory control of morphine with and without prochlorperazine were studied in 12 normal humans. Measurement of resting ventilation and the ventilatory responses to progressive hypercapnia and to transient asphyxia were made before and 15 min after morphine (0.15 mg/kg) given intravenously. Prochlorperazine (12.5 mg) was then administered intravenously to 6 study subjects and saline to 6 control subjects. After a further 10 min, resting ventilation and chemoreceptor function were remeasured. After the administration of morphine, resting ventilation, the ventilatory response to hypercapnia, and the ventilatory response to asphyxia were all significantly decreased (p less than 0.01 in each case; mean effect in control and study group were, respectively, -16 and -17%, -50 and -32%, -46 and -55%). Administration of saline produced no significant additional changes in the 6 control subjects. By contrast, administration of prochlorperazine to the 6 study subjects markedly increased the ventilatory response to asphyxia to levels significantly greater than postmorphine values (p less than 0.005; 2.38 +/- 0.22 L . min-1 . % Sao2 versus 0.80 +/- 0.14 L . min-1; mean +/- SEM). Resting ventilation and ventilatory response to hypercapnia were not significantly affected by prochlorperazine. These results were not explained by differences in end-tidal PCO2 at which hypercapnic hypoxic tests were performed. It is concluded that prochlorperazine reverses the depression of the ventilatory response to asphyxia caused by morphine.

Adult↗
PubMed1985

The effect of central and peripheral dopamine-agonists on ventilation in the mouse.

This study was designed to investigate the role of central dopaminergic pathways in ventilatory control in unanaesthetised, chemoreceptor intact mice. Dopamine does not cross the blood-brain barrier and was used to selectively affect peripheral arterial chemoreceptors. Levodopa, the immediate precursor of dopamine, was given alone when it is converted to dopamine mainly in the periphery, and together with carbidopa, which prevents the peripheral conversion of levodopa to dopamine, and enhances central generation of dopamine from levodopa. Dopamine (60-240 mg X kg-1), levodopa (50-300 mg X kg-1), and levodopa with carbidopa in a constant ratio of 10:1 (33/3.3-100/10 mg X kg-1) were given by intraperitoneal injection. Ventilation was measured in 10% O2 and in 7.5% CO2 by a plethysmographic method. Levodopa with carbidopa stimulated ventilation in both 10% O2 and 7.5% CO2. Ventilation in 10% O2 increased from 55.1 +/- 1.43 ml X min-1 (mean +/- SE) to 93.8 +/- 4.75 ml X min-1 with levodopa 100 mg X kg-1/carbidopa 10 mg X kg-1 (P less than 0.01). Ventilation in 7.5% CO2 increased from 101.8 +/- 3.42 ml X min-1 to 138.5 +/- 4.94 ml X min-1 with levodopa 100 mg X kg-1/carbidopa 10 mg X kg-1 (P less than 0.05). In contrast, very high doses of dopamine alone (240 mg X kg-1) and levodopa alone (300 mg X kg-1) depressed hypoxic but not hypercapnic ventilation. Carbidopa alone had no effect of ventilation. It is concluded that dopaminergic transmission within the brain mediates pathways leading to increased ventilation.

Animals↗
PubMed1985

Ventilatory stimulation by dopamine-receptor antagonists in the mouse.

Ventilation was measured by a plethysmographic method in awake mice before and after intraperitoneal injection of neuroleptic drugs to test the hypothesis that dopaminergic mechanisms modulate control of breathing in this species. Dose-dependent augmentation of ventilation at rest and during hypoxia, and reduced ventilation during hypercapnia was demonstrated for haloperidol, droperidol, prochlorperazine and chlorpromazine (P less than 0.05 or less for each drug). Doses of drugs causing maximal increase of the ventilatory response to hypoxia were linearly related (r = 0.98, P less than 0.001) to in vitro affinity of the drugs for dopamine receptors. Despite presumed equal dopamine-receptor blockade, the drugs had unequal effects on the ventilatory response to hypoxia. Droperidol augmented hypoxic ventilation to 290% of the control value, chlorpromazine to 250% control, prochlorperazine to 190% control and haloperidol to 120% control. These differences in efficacy were in the same order as the affinities of the drugs for alpha-adrenoceptors. The effect of combined haloperidol (90 nmol kg-1) and varying doses of phentolamine (175-900 nmol kg-1) was assessed to test the hypothesis that alpha-antagonism was a factor in determining the increase in ventilation following dopamine blockade. Phentolamine caused dose-dependent augmentation of the ventilatory effects of haloperidol (P less than 0.01) but had no ventilatory effect when given alone. Carotid body resection in anaesthetized mice abolished the stimulation of hypoxic ventilation caused by droperidol. It is concluded that dopaminergic mechanisms in the carotid body modulate ventilatory control in the awake mouse. The drugs most effective in augmenting hypoxic ventilation are those that block both dopamine and alpha-adrenoceptors.

Adrenergic alpha-Antagonists↗
PubMed1984

Ventilatory control in two asthmatics resuscitated from respiratory arrest.

Two female patients revived from fulminant attacks of asthma are described. Ventilatory responses to asphyxia in these patients were 0.70 +/- 0.10 l min-1 % SaO2-1 and 0.64 +/- 0.21 l min-1 % SaO2-1 (mean +/- SEM), respectively. These values were significantly less than the responses of seven normal female subjects (1.54 +/- 0.11 l min-1 % SaO2-1 mean +/- SEM; p less than 0.01). Ventilatory responses to hypercapnia of the two patients were in the low normal range. Dopamine-receptor blockade with prochlorperazine significantly increased the ventilatory response to asphyxia in normal subjects (p less than 0.05 or less for each subject) but did not alter the depressed responses in the asthmatic patients. In one patient, naloxone in a dose of 400 micrograms reversed the decreased ventilatory responsiveness; the response to asphyxia was increased from 0.72 l min-1 % SaO-1 to 1.80 l min-1 % SaO2-1 (p less than 0.01) and the response to hypercapnia was increased from 0.90 l min-1 mmHg-1 to 4.80 l min-1 mmHg-1 (p less than 0.01). Naloxone had no effect in the second asthmatic patient nor in five normal subjects. Defective chemoreceptor responses to chemical stimuli may play a role in sudden death from asthma; endogenous opioids may mediate this disorder of ventilatory control.

Adult↗
PubMed1983

Breathing during sleep: the responses to asphyxia and prochlorperazine in normal subjects and patients with obstructive sleep apnea.

The effects of sleep and prochlorperazine (12.5 mg intravenous bolus) on the ventilatory and arousal responses to asphyxia were studied in normal subjects and patients with obstructive sleep apnea (OSA). The ventilatory response to asphyxia was reduced during non-rapid eye movement sleep in the six normal subjects studied (1.93 +/- 0.18 l min-1.% SaO2 awake vs. 1.01 +/- 0.10 l min-1.% SaO2 asleep; mean +/- SEM; p less than 0.01) (SaO2 = arterial oxygen saturation). In the two normal subjects studied during sleep following prochlorperazine administration, ventilatory responsiveness was increased (p less than 0.05) but arousal response to asphyxia was depressed (p less than 0.025). Although prochlorperazine increased waking ventilatory responsiveness to asphyxia in five of six patients with OSA (2.26 +/- 0.44 l min-1.% SaO2 vs. 4.77 +/- 1.39 l min-1.% SaO2; mean +/- SEM; p less than 0.01), the drug had no clinically significant effect on upper airway obstruction during sleep; in three patients, apnea frequency was slightly reduced but in four of six patients severity of hypoxemia during apnea was increased with drug administration. We conclude that prochlorperazine administration is unlikely to benefit patients with obstructive sleep apnea despite its ventilatory effects during wakefulness and sleep. This lack of effect may be explained by separate effects of the drug on ventilatory and arousal responses to asphyxia.

Adult↗
PubMed1982

Augmentation of ventilatory response to asphyxia by prochlorperazine in humans.

The effect of the dopamine-receptor blocking agent prochlorperazine on the ventilatory response to hypercapnic hypoxia was studied in six healthy adults. Repeated episodes of transient hypoxia were induced at the mixed venous PCO2 level by a nonrebreathing technique in five males and one female before and after an intravenous bolus injection of prochlorperazine mesylate (12.5 mg = 10 mg base). The ventilatory response to CO2 was also studied before and after drug administration. Prochlorperazine produced a modest (15%) increase in resting ventilation (P less than 0.05) but a marked increase in the ventilatory response to asphyxia such that the group mean response was double the control value [2.0 +/- 0.7 vs. 4.2 +/- 1.5 l . min-1 . % arterial O2 saturation (%SaO2); P less than 0.001]. Two-thirds of this change in ventilatory response was due to an increase in frequency response to hypoxia (0.34 +/- 0.20 vs. 0.81 +/- 0.52 breaths . min-1 . %SaO2; P less than 0.001). The position of the ventilatory response line, as judged by the computed ventilation at 95% SaO2, was increased by prochlorperazine (22.2 +/- 9.6 vs. 35.9 +/- 10.9 l . min-1; P less than 0.01) due to an increase in both tidal volume (P less than 0.05) and frequency of breathing (P less than 0.0125). The ventilatory response to CO2 was unchanged by drug injection. In separate experiments prochlorperazine was shown to 1) increase the ventilatory response to steady-state eucapnic hypoxia (P less than 0.01) demonstrating that the drug effect was not dependent on either the presence of hypercapnia or rapidly changing states of arterial oxygenation; and 2) reverse the depressant effect of intravenously infused dopamine hydrochloride (5 micrograms . kg-1 . min-1) on the ventilatory response to transient asphyxia (P less than 0.01). We conclude that prochlorperazine augments hypoxic responsiveness in humans. The mechanism may be blockade of dopaminergic receptors that modulate carotid body discharge.

Adult↗
PubMed1982

Ventilatory responsiveness to hypercapnic hypoxia during dopamine infusion in humans.

The effect of dopamine on the ventilatory response to transient asphyxia was examined to test the hypothesis that dopaminergic mechanisms modulate carotid body function in humans and to determine whether a change in ventilatory responsiveness is effected by changes in tidal volume or breathing frequency. Five healthy adults were subjected to brief episodes of hypercapnic hypoxia before and at the end of a 45-min intravenous infusion of dopamine hydrochloride (5 micrograms/kg/min). Mean ventilatory response to hypercapnic hypoxia decreased from 1.71 +/- 0.33 L/min/% SaO2 (+/- SD) to 1.30 +/- 0.28 L/min/% SaO2 (p less than 0.05) during dopamine infusion. The fall in ventilatory response was due to a fall in the frequency of breathing (p less than 0.01). Dopamine infusion also produced a small decrease in resting minute ventilation (p less than 0.05) and a small increase in resting end-tidal PCO2 (p less than 0.05). No change was noted in the ventilatory response to progressive hypercapnia. These findings suggest that dopamine acts at the carotid body to depress its response to transient hypoxic stimulation and that this effect is to selectively slow the rate of breathing.

Adult↗
PubMedDate not supplied

A pilot randomized controlled trial of dexamphetamine in patients with chronic fatigue syndrome.

This study determined whether dexamphetamine improved symptoms and quality of life in patients with chronic fatigue syndrome. The setting was a specialized clinic within a tertiary referral hospital. This was a 6-week parallel-group, placebo-controlled trial with random allocation. There was a 2-week dose-adjustment phase and a 4-week stable treatment period. Outcome measures were the Fatigue Severity Scale, the Medical Outcomes Study 36-item Short-Form Health Survey, and two patient-determined outcomes. Ten patients were randomly assigned to dexamphetamine, and 10 were assigned to placebo. Fatigue Severity Scale scores improved in nine of 10 dexamphetamine and four of 10 placebo patients. The change in mean score was statistically significant. There were large but statistically nonsignificant changes in scores for the Short-Form Health Survey domains vitality and physical functioning. Dexamphetamine may be useful in the management of chronic fatigue syndrome; a larger and longer trial is justified by these results.

Adolescent↗