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Anita K Simonds

Publications and source records attributed to Anita K Simonds.

14 recordsLinked to original sources
PubMed2007

Oximetry feedback flow control simulation for oxygen therapy.

OBJECTIVES: For many with Chronic Obstructive Pulmonary Disease (COPD), arterial oxygen saturation while receiving Long-Term Oxygen Therapy (LTOT) falls below an acceptable threshold (SpO(2) < 90%) for extended periods during routine daily activities. Using a closed-loop controller, we have evaluated a simulated method to automatically regulate the oxygen flow-rate in response to the measured oxygen demand. METHODS: The closed-loop control scheme was implemented in a computer simulation on Simulink. Feedback from a pulse oximeter was used to maintain a target SpO(2) of 91% by changing the oxygen flow-rate to the patient. The controller was evaluated using a model to approximate the patient's arterial oxygen saturation response, including hypoxic events from artificial disturbances as well as recorded patient oximetry data. RESULTS: The simulated controller produced improvement in arterial oxygen saturation throughout a wide range of disturbance frequencies. It suppressed disturbances with periods greater than a couple of minutes by more than -10 dB. When evaluated with patient oximetry recordings, the controller on average reduced the time spent with arterial blood saturation below threshold by 76%. Given the same volume of oxygen, the closed-loop controller also produced a 63% improvement compared to fixed flow-rate LTOT. CONCLUSIONS: The simulation findings indicate an optimized matching between oxygen supply and demand, maintaining SpO(2) above threshold to improve therapeutic efficacy compared to standard LTOT.

Algorithms↗
PubMed2006

Sleep-disordered breathing in a general heart failure population: relationships to neurohumoral activation and subjective symptoms.

The aim of this study was to determine the prevalence of sleep-related breathing disorders (SDB) in a UK general heart failure (HF) population, and assess its impact on neurohumoral markers and symptoms of sleepiness and quality of life. Eighty-four ambulatory patients (72 male, mean (SD) age 68.6 (10) yrs) attending UK HF clinics underwent an overnight recording of respiratory impedance, SaO2 and heart rate using a portable monitor (Nexan). Brain natriuretic peptide (BNP) and urinary catecholamines were measured. Subjective sleepiness and the impairment in quality of life were assessed (Epworth Sleepiness Scale (ESS), SF-36 Health Performance Score). SDB was classified using the Apnoea/Hypopnoea Index (AHI). The prevalence of SDB (AHI > 15 events h(-1)) was 24%, increasing from 15% in mild-to-moderate HF to 39% in severe HF. Patients with SDB had significantly higher levels of BNP and noradrenaline than those without SDB (mean (SD) BNP: 187 (119) versus 73 (98) pg mL(-1), P = 0.02; noradrenaline: 309 (183) versus 225 (148) nmol/24 h, P = 0.05). There was no significant difference in reported sleepiness or in any domain of SF-36, between groups with and without SDB (ESS: 7.8 (4.7) versus 7.5 (3.6), P = 0.87). In summary, in a general HF clinic population, the prevalence of SDB increased with the severity of HF. Patients with SDB had higher activation of a neurohumoral marker and more severe HF. Unlike obstructive sleep apnoea, SDB in HF had little discernible effect on sleepiness or quality of life as measured by standard subjective scales.

Aged↗
PubMed2006

Recent advances in respiratory care for neuromuscular disease.

The impact of ventilatory support on the natural history of neuromuscular disease (NMD) has become clearer over the last 2 decades as techniques have been more widely applied. Noninvasive ventilation (NIV) allows some patients with nonprogressive pathology to live to nearly normal life expectancy, extends survival by many years in patients with other conditions (eg, Duchenne muscular dystrophy), and in those patients with rapidly deteriorating disease (eg, amyotrophic lateral sclerosis) survival may be increased, but symptoms can be palliated even if mortality is not reduced. A growing number of children with NMD are surviving to adulthood with the aid of ventilatory support. The combination of NIV with cough-assist techniques decreases pulmonary morbidity and hospital admissions. Trials have confirmed that NIV works in part by enhancing chemosensitivity, and in patients with many different neuromuscular conditions the most effective time to introduce NIV is when symptomatic sleep-disordered breathing develops.

Adult↗
PubMed2005

The determinants of therapeutic levels of continuous positive airway pressure in elderly sleep apnea patients.

We have examined the role of age on the continuous positive airway pressure (CPAP) levels required to treat two groups of elderly (n=70) and young (n=70) sleep apneic patients, matched for disease severity (apnea/hypopnea index), body mass index and neck circumference. Elderly patients required lower CPAP levels compared to young [mean (sd): 6.9(1.9)cm H(2)O and 9.4(3.5)cm H(2)O, respectively; P<0.0001]. To investigate this finding, we studied the effects of CPAP and its components (inspiratory and expiratory positive airway pressure) on lung volume and upper airway resistance in two groups of elderly [n=9, age 71.7(3.3) years] and young [n=9, age 36.7(4.4)] patients with sleep apnea during wakefulness. CPAP produced a greater decrease in airway resistance (P=0.009) and a greater increase in lung volume (P=0.008) in the elderly compared to young patients. We conclude that both the greater lung inflation and the greater direct splinting of the upper airway contributed to the lower CPAP level required by the elderly. Ageing may be an important determinant of therapeutic CPAP levels in clinical practice, especially in older sleep apneic patients.

Adult↗
PubMed2005

Overnight changes in the cerebral vascular response to isocapnic hypoxia and hypercapnia in healthy humans: protection against stroke.

BACKGROUND AND PURPOSE: The reduction in hypercapnic cerebral vascular reactivity that occurs in the morning after sleep is associated with an increased risk of cerebral ischemia and stroke. It is not known if the cerebral vascular response to hypoxia is similarly reduced in the morning, but such a reduction could be considered a further risk factor for cerebral vascular disease. METHODS: To test if the cerebral vascular response to hypoxia is reduced in the morning, the overnight changes in the left middle cerebral artery velocity (MCAV) in response to isocapnic hypoxia (IH) and hypercapnia before and after a normal night sleep were determined in 18 individuals. RESULTS: From evening to morning, hypercapnic cerebral vascular reactivity decreased significantly (evening 2.0+/-0.4, morning 1.3+/-0.2 cm/sec/mm Hg; P<0.05); in contrast, the increase in MCAV in response to IH (-10% SaO2) was unchanged (evening 9.0+/-1.4, morning 8.7+/-2.2%; P>0.05). CONCLUSIONS: Our findings indicate that substantial differences exist in the regulation of the cerebral circulation in response to hypoxia and hypercapnia on waking from sleep. An intact cerebral vascular response to IH, during this time period, could be interpreted as a protective mechanism against cerebral ischemia and stroke; this is of particular relevance to patients with obstructive sleep apnea who arouse from sleep during hypoxia.

Adult↗
PubMed2005

Ethical aspects of home long term ventilation in children with neuromuscular disease.

Increasing numbers of children and young adults are now receiving home ventilation. Whereas in some neuromuscular conditions the outcome and quality of life gains are clear cut; in others eg Spinal Muscular Atrophy Type I there are a few outcome studies with conflicting results and it is more difficult to balance the ethical concepts of beneficence, non-maleficence, autonomy and distributive justice. As a result there are widespread variations in the clinical management of these children. This article examines decision-making in these areas seen from the perspective of the individual, the family and society.

Child↗
PubMed2004

Occlusion of the upper airway does not augment the cardiovascular response to arousal from sleep in humans.

The cardiovascular response to an arousal from sleep at the termination of an obstructive apnea is more than double that to a spontaneous arousal. We investigated the hypothesis that stimulation of respiratory mechanoreceptors, by inspiring against an occluded airway during an arousal from sleep, augments the accompanying cardiovascular response. Arousals (>10 s) from stage 2 sleep were induced by a 1-s auditory tone (85 dB) during a concomitant 1-s inspiratory occlusion (O) and without an occlusion [i.e., control arousal (C)] in 15 healthy men (mean +/- SE: age, 25 +/- 1 yr). Arousals were associated with a significant increase in mean arterial blood pressure (MAP) at 4 s (P < 0.001) and a significant decrease in R-R interval at 3 s (P < 0.001). However, the magnitude of the cardiovascular response was not different during C compared with O (MAP: C, 86 +/- 3 to 104 +/- 3 mmHg; O, 86 +/- 3 to 105 +/- 3 mmHg; P = 0.99. R-R interval: C, 1.12 +/- 0.03 to 0.89 +/- 0.04 s; O, 1.11 +/- 0.02 to 0.87 +/- 0.02 s, P = 0.99). Ventilation significantly increased during arousals under both conditions at the second breath (P < 0.001); this increase was not different between the two conditions (C: 4.40 +/- 0.29 to 6.76 +/- 0.61 l/min, O: 4.35 +/- 0.34 to 7.65 +/- 0.73 l/min; P = 0.31). We conclude that stimulation of the respiratory mechanoreceptors by transient upper airway occlusion is unlikely to interact with the arousal-related autonomic outflow to augment the cardiovascular response in healthy young men.

Acoustic Stimulation↗
PubMed2004

Cerebral blood flow response to isocapnic hypoxia during slow-wave sleep and wakefulness.

Nocturnal hypoxia is a major pathological factor associated with cardiorespiratory disease. During wakefulness, a decrease in arterial O2 tension results in a decrease in cerebral vascular tone and a consequent increase in cerebral blood flow; however, the cerebral vascular response to hypoxia during sleep is unknown. In the present study, we determined the cerebral vascular reactivity to isocapnic hypoxia during wakefulness and during stage 3/4 non-rapid eye movement (NREM) sleep. In 13 healthy individuals, left middle cerebral artery velocity (MCAV) was measured with the use of transcranial Doppler ultrasound as an index of cerebral blood flow. During wakefulness, in response to isocapnic hypoxia (arterial O2 saturation -10%), the mean (+/-SE) MCAV increased by 12.9 +/- 2.2% (P < 0.001); during NREM sleep, isocapnic hypoxia was associated with a -7.4 +/- 1.6% reduction in MCAV (P <0.001). Mean arterial blood pressure was unaffected by isocapnic hypoxia (P >0.05); R-R interval decreased similarly in response to isocapnic hypoxia during wakefulness (-21.9 +/- 10.4%; P <0.001) and sleep (-20.5 +/- 8.5%; P <0.001). The failure of the cerebral vasculature to react to hypoxia during sleep suggests a major state-dependent vulnerability associated with the control of the cerebral circulation and may contribute to the pathophysiologies of stroke and sleep apnea.

Adult↗
PubMed2004

Living and dying with respiratory failure: facilitating decision making.

Respiratory failure is a predictable cause of death in end stage lung disease including COPD and neuromuscular disorders, and the symptom burden for these individuals in the last six months of life is significant. Palliative care services are less well-developed for patients with chronic disorders compared to those with malignant disease; and communication problems can be compounded by a mismatch in expectations between patients and health care providers on prognosis and other issues. Most patients want more information about their illness to facilitate participation in decision making. Noninvasive ventilation may extend life and palliate symptoms in neuromuscular disorders such as Duchenne muscular dystrophy and motor neurone disease/ALS.

Decision Making↗
PubMed2004

Apnea and history.

Explore the source record for details and available documents.

Famous Persons↗
PubMed2003

Cardiovascular response to arousal from sleep under controlled conditions of central and peripheral chemoreceptor stimulation in humans.

The cardiovascular response to an arousal occurring at the termination of an obstructive apnea is almost double that to a spontaneous arousal. We investigated the hypothesis that central plus peripheral chemoreceptor stimulation, induced by hypercapnic hypoxia (HH), augments the cardiovascular response to arousal from sleep. Auditory-induced arousals during normoxia and HH (>10-s duration) were analyzed in 13 healthy men [age 24 +/- 1 (SE) yr]. Subjects breathed on a respiratory circuit that held arterial blood gases constant, despite the increased ventilation associated with arousal. Arousals were associated with a significant increase in mean arterial blood pressure at 5 s (P < 0.001) and with a significant decrease in the R-R interval at 3 s (P < 0.001); however, the magnitude of the changes was not significantly different during normoxia compared with HH (mean arterial blood pressure: normoxia, 91 +/- 4 to 106 +/- 4 mmHg; HH, 91 +/- 4 to 109 +/- 5 mmHg; P = 0.32; R-R interval: normoxia, 1.12 +/- 0.04 to 0.90 +/- 0.05 s; HH, 1.09 +/- 0.05 to 0.82 +/- 0.03 [corrected] s; P = 0.78). Mean ventilation increased significantly at the second breath postarousal for both conditions (P < 0.001), but the increase was not significantly different between the two conditions (normoxia, 5.35 +/- 0.40 to 9.57 +/- 1.69 l/min; HH, 8.57 +/- 0.63 to 11.98 +/- 0.70 l/min; P = 0.71). We conclude that combined central and peripheral chemoreceptor stimulation with the use of HH does not interact with the autonomic outflow associated with arousal from sleep to augment the cardiovascular response.

Acoustic Stimulation↗
PubMed2002

Long-term ventilation in obstructive ventilatory disorders.

A large randomized, controlled study of NIV plus LTOT versus LTOT in patients with COPD is needed that evaluates morbidity, mortality, quality of life, and health economic impact. It is to be hoped that funding for this type of study will be forthcoming. In the meantime, it reasonably can be concluded from existing evidence that domiciliary NIV is unlikely to be effective in most patients with stable COPD, particularly if they are normocapnic. A subgroup of patients with severe hypercapnia, poor tolerance of LTOT, marked nocturnal hypoventilation, or recurrent infective exacerbations may benefit from domiciliary NIV. Systematic evaluation is required in patients with CF or bronchiectasis.

Cross-Over Studies↗
PubMed2002

Respiratory complications of the muscular dystrophies.

Pulmonary complications including chest infections, atelectasis, pulmonary hypoplasia and ventilatory failure are the leading cause of death in the muscular dystrophies and atrophies. Ventilatory insufficiency is virtually inevitable in Duchenne muscular dystrophy and type 1 spinal muscular atrophy (SMA), but more variable in limb-girdle, congenital, and facioscapulohumeral muscular dystrophy. A cardiomyopathy may complicate Duchenne, Becker, and Emery-Dreifuss muscular dystrophies. Most patients respond well to ventilatory support with reduced pulmonary morbidity and extended survival. Careful monitoring and anticipation of complications are important so that ventilatory assistance can be started in a timely fashion.

Journal Article↗