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Biomedical subjects

L Loh

Publications and source records attributed to L Loh.

At least 37 records · Page 2Linked to original sources
PubMed1990

Abnormal respiration and sudden death during sleep in multiple system atrophy with autonomic failure.

We studied respiration during sleep in 7 patients with multiple system atrophy and autonomic failure (MSA-AF) and 7 control subjects. Although mean respiratory rate, tidal volume, and inspiratory flow rate were statistically similar in both groups, the coefficients of variability in all were significantly greater in MSA-AF patients. Four of 5 nontracheostomized had evidence of upper airway obstruction without significant oxygen desaturation. Three of these 5 patients died suddenly during sleep. MSA-AF is associated with upper airway dysfunction and disordered central respirations which can be life threatening. Evidence of even mild obstruction during sleep should warrant tracheostomy.

Aged↗
PubMed1989

Respiratory complications and their management in motor neuron disease.

Although respiratory insufficiency is common in the advanced stages of motor neuron disease, some patients may develop distressing respiratory symptoms early in the course of the disease or even present with respiratory failure or arrest. We describe 14 patients with motor neuron disease who were considered for respiratory support; 11 received such support and all derived significant symptomatic improvement without distressing prolongation of life. Of the 8 patients with typical features of amyotrophic lateral sclerosis, 7 had predominant diaphragm weakness and 1 generalized respiratory muscle weakness; 7 received negative pressure ventilation by cuirass which improved both the quality of sleep and exercise tolerance. Three patients with predominantly bulbar disease had nocturnal apnoea or hypoventilation. Two received no support. One, who also developed diaphragm weakness, was treated by a cuirass, continuous positive airway pressure (CPAP), and later nocturnal intermittent positive pressure ventilation (IPPV). Three patients with progressive muscular atrophy had predominant diaphragm weakness or nocturnal apnoea. These patients received nocturnal CPAP, cuirass or IPPV with symptomatic benefit. This series shows that some patients with motor neuron disease, mainly those with symptoms due to respiratory muscle weakness in the absence of severe bulbar impairment, derive symptomatic benefit from supported ventilation.

Adult↗
PubMed1989

Nocturnal hypoventilation in children with nonprogressive neuromuscular disease.

Eight patients between 4 and 24 years of age with nonprogressive neuromuscular disease sought medical attention because of severe nocturnal hypoventilation. There were two types of findings: subacute with progressive early morning headaches and daytime drowsiness and acute with ventilatory failure and cor pulmonale. Seven patients were ambulant. Seven were successfully treated with either a cuirass negative pressure ventilator or a positive pressure ventilator via a tracheostomy. The ventilatory assistance was only used at night and resulted in rapid resolution of early morning symptoms and a return to full daytime activity. One patient died as a result of an intercurrent respiratory infection before respiratory support could be given. It is important to be aware of this potentially life-threatening complication in patients with an otherwise good prognosis and of the benefit to be derived from active treatment.

Adolescent↗
PubMed1988

Domiciliary ventilatory support: an analysis of outcome.

Prolonged ventilatory support has been used to treat 51 patients with respiratory failure secondary to skeletal (22) or neuromuscular (29) disease. Symptomatic relief was achieved in five patients with rapidly progressive neurological disease who died within 27 months. The remaining 46 patients, aged 11-69 years at presentation, have been followed for more than two and a half years. All but 10 were treated with negative pressure ventilation from the outset, intermittent positive pressure ventilation being used initially in the others and continued at home in three. Nocturnal negative pressure ventilation has been used at home by 39 patients. A permanent tracheostomy has been maintained in 14, to facilitate positive pressure ventilation in three and to circumvent upper airway obstruction during sleep in 11. Sustained improvement in symptoms and arterial blood gas tensions has been maintained, independence and the capacity for gainful employment have been regained in those of an appropriate age, and the incidence of subsequent hospital admissions has been low. Neither the mode of presentation nor the aetiology of the restrictive ventilatory defect influenced outcome in patients with stable or only slowly progressive primary disease.

Adolescent↗
PubMed1987

Diaphragm paralysis causing ventilatory failure in an adult with the rigid spine syndrome.

A syndrome consisting of a rigid spine and myopathy predominantly affecting proximal limb muscles has been previously described in children, and as with most neuromuscular disorders, the respiratory muscles appear to be affected only at an advanced stage in the disease. We describe an adult male with this syndrome who presented with ventilatory failure caused by severe respiratory muscle weakness and who demonstrated profound nocturnal arterial oxygen desaturation, particularly during rapid eye movement sleep. Treatment with negative pressure ventilation initially resulted in only modest improvements in symptoms, blood gas tensions, and nocturnal desaturation. The cause of this only partial improvement was upper airway obstruction provoked by the mode of ventilatory support used. After tracheostomy there was a dramatic and sustained improvement in symptoms and blood gas tensions and complete abolition of nocturnal arterial oxygen desaturation. This is the first report of an adult with the rigid spine syndrome presenting with ventilatory failure and cor pulmonale due to severe respiratory muscle weakness.

Adult↗
PubMed1986

Changes in plasma vasopressin concentration in association with coronary artery surgery or thymectomy.

Plasma vasopressin concentrations in 14 patients undergoing coronary artery surgery were compared with those in eight patients undergoing thymectomy. Vasopressin concentrations increased similarly in both groups on sternotomy. A second, and more marked increase was noted in the patients requiring cardiopulmonary bypass. Haemodynamic stimuli could be responsible in both groups and might explain both the similarities and the differences between the groups.

Adult↗
PubMed1985

The respiratory activity of human levator costae muscles and its modification by posture.

The activation of the levator costae, a set of axial muscles inserted between each rib and the vertebra immediately rostral, has been studied electromyographically in a human subject, standing upright, with head erect ('neutral' posture). Caudal levator costae muscles (T9, and T10) are active during eupnoea. Periodic activity in phase with inspiration occurs in admixture with different levels of tonic activity that is strongly influenced by posture. Postural changes and various voluntary respiratory manoeuvres which should lengthen or shorten the levator costae muscles increase and decrease, respectively, their activity in the 'neutral' posture. The tonic activity was most readily enhanced by contralateral flexion of the spine, and this could bring to threshold phasic activity not otherwise present. Conversely, ipsilateral flexion could abolish both phasic and tonic components. Active expiratory efforts and static voluntary relaxation of the respiratory muscles could diminish or abolish levator costae activity. Paradoxically, chest-directed inspiratory efforts maintained at elevated lung volume with open glottis could also diminish or abolish levator costae activity. We attribute this to shortening of the levator costae muscles and unloading of their muscle spindles by the elevation of the ribs due to the action of the external intercostal and parasternal muscles. The results are discussed in relation to the mechanical coupling between the diaphragm and the lower rib cage; emphasis is given to the possible independent motions of the lower two or three ribs and the abductor action of their corresponding levator costae muscles, based on anatomico-physiological considerations.

Chin↗
PubMed1984

Anticholinesterase drugs in the treatment of chronic pain.

Two patients with severe thalamic pain and one patient with causalgia from the shoulder-hand syndrome are described whose pain was markedly improved or abolished by anticholinesterase drugs. Both short-acting parenteral and oral anticholinesterase preparations were employed. Anticholinesterase drugs are a new and potentially valuable approach to the treatment of chronic pain.

Arm↗
PubMed1984

Evaluation of Spirolog I volume meter.

A volume meter (Dräger Spirolog I) is evaluated for clinical use. It works on the principle of a constant temperature anemometer and displays tidal volume, minute volume and frequency. It was found that the volume recorded was hardly affected by oxygen concentration, humidity or temperature but was affected by high concentrations of nitrous oxide and during the operation of diathermy.

Electrocoagulation↗
PubMed1984

High frequency ventilation and gas diffusion.

The efficiency of CO2 removal was studied using a simple lung model with a high frequency positive pressure device (up to 100 b.p.m.) with and without an anatomical deadspace. At a constant minute ventilation without an anatomical dead space, the efficiency of CO2 elimination increased with increasing frequency. However, when a dead space was introduced, the efficiency of CO2 elimination decreased with increasing frequency. Using a high frequency oscillation technique (360 to 900 b.p.m.), it was not possible to maintain a reasonable CO2 elimination with tidal volumes less than the anatomical dead space. In this model there was no evidence that accelerated diffusion was a factor in CO2 removal during high frequency ventilation or oscillation.

Humans↗
PubMed1984

Acupuncture versus medical treatment for migraine and muscle tension headaches.

In 48 patients with chronic migraine and muscle tension headaches, a comparison was made between a prophylactic course of acupuncture and of medical treatment. It was intended that all patients should have 3 months with both forms of treatment, but 19 were unwilling to change from one form of prophylaxis to the other. Twenty-four of 41 patients improved on acupuncture, the improvement being very marked in nine; nine of 36 patients improved on medical treatment, the improvement being marked in three. Of the 29 patients who changed from one form of treatment to the other, a larger proportion preferred acupuncture to medical treatment. A beneficial response to acupuncture was more likely when the patient had local tender muscular points. The presence of depressive features did not preclude satisfactory treatment with acupuncture. No major side effects were encountered with acupuncture.

Acupuncture Therapy↗
PubMed1983

Depression of nociceptive sympathetic reflexes by the intrathecal administration of midazolam.

The effect of the intrathecal administration of midazolam 0.5-1.0 mg in 1-2 ml of physiological saline solution, has been observed on responses evoked in renal sympathetic nerves by supramaximal electrical stimulation of radial and tibial nerves. In artificially ventilated dogs anaesthetized with alpha-chloralose, the intrathecal administration of midazolam caused a marked depression of reflexes evoked from the tibial nerve but had no effect on either spontaneous sympathetic activity or reflexes evoked by radial nerve stimulation. Neither the small amount (1-2 microliters) of benzyl alcohol, present as a preservative (administered intrathecally), nor midazolam 1 mg kg-1 i.v. caused any significant depression of the evoked somato--sympathetic reflexes. The effects of intrathecal midazolam were reversed by the benzodiazepine antagonists Ro 15-1788 1 mg kg-1 i.v. and Ro 15-3505 1-2 mg kg-1 i.v. but not by naloxone 2 mg i.v. It is suggested that the antinociceptive effect of locally applied midazolam could be the result of a non-opioid GABA-mediated system which may have implications in the management of pain.

Animals↗
PubMed1983

Measurement of pulmonary venous and arterial pH oscillations in dogs using catheter tip pH electrodes.

Respiratory pH oscillations were studied in situ in the aorta and superior vena cava of rabbits, and in the pulmonary vein and aorta of open-chested dogs, using catheter tip pH electrodes. Preliminary experiments on two spontaneously breathing rabbits showed pH oscillations of 0.006-0.010 pH units in the ascending aorta at a respiratory rate of 40/min. No oscillations were apparent in the superior vena cava. In anaesthetized, ventilated dogs, the delay from the upstroke in airway pressure to the onset of the alkaline limb of the pH oscillation was 1.15 +/- 0.9 s in the pulmonary vein and 4.1 +/- 0.1 s in the descending aorta (mean + S.E. of mean, n = 28 tracings in four dogs). Pulmonary venous oscillations were equal to or larger in amplitude than those in the aorta. Aortic oscillations became proportionately smaller at shorter respiratory cycle lengths, although both were related to tidal volume. Stop flow experiments were performed using a pH electrode placed in situ in the left atrium inside a wide-bore tube. A small fall in pH occurred when flow was stopped (-0.0036 +/- 0.0012, mean +/- S.E. of mean, n = 22 recordings in four dogs). The findings were not dependent upon the phase of the oscillation at which flow was stopped. Mean plasma free haemoglobin was very low (1.6 mg/dl), indicating minimal haemolysis of the blood withdrawn past the electrode. It is concluded that the plasma CO2 hydration reaction is virtually at equilibrium by the time blood reaches the pulmonary vein.

Animals↗