Papers by RONALD M HARPER
BMJ Open, Mar 1, 2021
Bookmarks Related papers MentionsView impact
PLOS ONE, Apr 16, 2010
Bookmarks Related papers MentionsView impact
Between-sex differences for all models. Excel file showing global and main effects of RMANOVA for... more Between-sex differences for all models. Excel file showing global and main effects of RMANOVA for original model (left-most) and four models with age-related effects. For the three main effects in the original model (Table 1), the significance in models with age effects is classified via color-coding cells as "same" (green) or "changed" (orange) according to whether the P value shifted from below or above the 0.05 threshold. (XLSX 14 kb)
Bookmarks Related papers MentionsView impact
Journal of Applied Physiology, Nov 1, 2000
Bookmarks Related papers MentionsView impact
Pediatric Research, Apr 1, 1980
Bookmarks Related papers MentionsView impact
Neuroscience, Jun 1, 2010
Bookmarks Related papers MentionsView impact
The Cerebellum, Feb 28, 2012
Bookmarks Related papers MentionsView impact
Sudden unexpected death in epilepsy (SUDEP) is the leading cause of premature mortality among peo... more Sudden unexpected death in epilepsy (SUDEP) is the leading cause of premature mortality among people with epilepsy. Evidence from witnessed and monitored SUDEP cases indicate seizure-induced cardiovascular and respiratory failures; yet, the underlying mechanisms remain obscure. SUDEP occurs often during the night and early morning hours, suggesting that sleep or circadian rhythm-induced changes in physiology contribute to the fatal event. Resting-state fMRI studies have found altered functional connectivity between brain structures involved in cardiorespiratory regulation in later SUDEP cases and in individuals at high-risk of SUDEP. However, those connectivity findings have not been related to changes in cardiovascular or respiratory patterns. Here, we compared fMRI patterns of brain connectivity associated with regular and irregular cardiorespiratory rhythms in SUDEP cases with those of living epilepsy patients of varying SUDEP risk, and healthy controls. We analysed resting-state...
Bookmarks Related papers MentionsView impact
Although the mechanisms of sudden unexpected death in epilepsy (SUDEP) are not yet well understoo... more Although the mechanisms of sudden unexpected death in epilepsy (SUDEP) are not yet well understood, generalised- or focal-to-bilateral tonic-clonic seizures (TCS) are a major risk factor. Previous studies highlighted alterations in structures linked to cardio-respiratory regulation; one structure, the amygdala, was enlarged in people at high risk of SUDEP and those who subsequently died. We investigated volume changes and the microstructure of the amygdala in people with epilepsy at varied risk for SUDEP since that structure can play a key role in triggering apnea and mediating blood pressure.The study included 53 healthy subjects and 143 patients with epilepsy, the latter separated into two groups according to whether TCS occur in years before scan. We used amygdala volumetry, derived from structural MRI, and tissue microstructure, derived from diffusion MRI, to identify differences between the groups. The diffusion metrics were obtained by fitting diffusion tensor imaging (DTI) an...
Bookmarks Related papers MentionsView impact
and key wordsObjectivesSudden unexpected death in epilepsy (SUDEP) is a leading cause of death fo... more and key wordsObjectivesSudden unexpected death in epilepsy (SUDEP) is a leading cause of death for patients with epilepsy; however, the pathophysiology remains unclear. Focal-to-bilateral tonic-clonic seizures (FBTCS) are a major risk factor, and centrally-mediated respiratory depression may increase the risk further. Here, we determined volume and microstructure of the amygdala, a key structure that can trigger apnea in people with focal epilepsy, stratified by presence or absence of FBTCS, ictal central apnea (ICA) and post-ictal central apnea (PICA).Methods73 patients with only-focal seizures and 30 with FBTCS recorded during video EEG (VEEG) with respiratory monitoring were recruited prospectively during presurgical investigations. We acquired high-resolution T1-weighted anatomical and multi-shell diffusion images, and computed neurite orientation dispersion and density imaging (NODDI) metrics in all epilepsy patients and 69 healthy controls. Amygdala volumetric and microstructu...
Bookmarks Related papers MentionsView impact
Preterm human infants often show periodic breathing (PB) or apnea of prematurity (AOP), breathing... more Preterm human infants often show periodic breathing (PB) or apnea of prematurity (AOP), breathing patterns which are accompanied by intermittent hypoxia (IH). We examined cause-effect relationships between transient IH and reduced facial bone growth using a rat model. Neonatal pups from 14 timed pregnant Sprague-Dawley rats were randomly assigned to an IH condition, with oxygen altering between 10% and 21% every 4 min for 1 h immediately after birth, or to a litter-matched control group. The IH pups were compared with their age- and sex-matched control groups in body weight (WT), size of facial bones and nor-epinephrine (NE) levels in blood at 3, 4, and 5-weeks. Markedly increased activity of osteoclasts in sub-condylar regions of 3-week-old IH-treated animals appeared, as well as increased numbers of sympathetic nerve endings in the same region of tissue sections. Male IH-pups showed significantly higher levels of NE levels in sera at 3, 4 as well as 5-week-old time points. NE leve...
Bookmarks Related papers MentionsView impact
Frontiers in Neurology
BackgroundThe clinical presentation of COVID-19 suggests altered breathing control - tachypnoea, ... more BackgroundThe clinical presentation of COVID-19 suggests altered breathing control - tachypnoea, relative lack of dyspnoea, and often a discrepancy between severity of clinical and radiological findings. Few studies characterize and analyse the contribution of breathing drivers and their ventilatory and perceptual responses.AimTo establish the prevalence of inappropriate ventilatory and perceptual response in COVID-19, by characterizing the relationships between respiratory rate (RR), dyspnoea and arterial blood gas (ABG) in a cohort of COVID-19 patients at presentation to hospital, and their post-Covid respiratory sequelae at follow-up.MethodsWe conducted a retrospective cohort study including consecutive adult patients admitted to hospital with confirmed COVID-19 between 1st March 2020 and 30th April 2020. In those with concurrent ABG, RR and documented dyspnoea status on presentation, we documented patient characteristics, disease severity, and outcomes at hospital and 6-week pos...
Bookmarks Related papers MentionsView impact
Sleep Medicine
Bookmarks Related papers MentionsView impact
Right-handed subjects only, between-gyri differences for all models. Excel file showing global an... more Right-handed subjects only, between-gyri differences for all models. Excel file showing global and main effects of RMANOVA for original model (left-most) and four models with age-related effects. The effects are compared with the models with all subjects (Additional file 3), and the significance classified via color-coding cells as "same" (green) or "changed" (orange) according to whether the P value shifted from below or above the 0.05 threshold. (XLSX 12 kb)
Bookmarks Related papers MentionsView impact
Sleep apneas are associated with disturbances of blood gas saturation, heart rate and rhythm, art... more Sleep apneas are associated with disturbances of blood gas saturation, heart rate and rhythm, arterial pressure, and neurobehavioral state. The purpose of the present study was to analyze cardiac rhythm activity in apneic individuals during nocturnal polysomnography and to correlate these findings with evidence of previously diagnosed cardiovascular dysfunction.
Bookmarks Related papers MentionsView impact
Circulation, 2007
BACKGROUND: Heart failure (HF) patients have gray matter injury in brain regions regulating auton... more BACKGROUND: Heart failure (HF) patients have gray matter injury in brain regions regulating autonomic and cognitive functions. The pathophysiology underlying affected gray matter is unknown, but likely involves processes that also damage neural tracts/white matter connecting injured regions. However, the extent and location of any white matter damage in HF is unclear. METHODS: To determine if HF patients show structural injury in white matter, we examined 17 HF patients (12 male, age 54 ± 8 years, LVEF 0.28±0.07, atrial fibrillation 3 [17%]) and 51 healthy controls (49 male, age 50 ± 7 years) using diffusion tensor imaging during brain MRI. We calculated fractional anisotropy (FA- a measure of white matter change). Whole-brain maps of FA for each subject were aligned, smoothed, and compared using ANCOVA, with age as a covariate. Significance was set at p RESULTS: Widespread regions showed injury in HF patients as indicated by significantly reduced FA; no areas showed higher FA in HF...
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Circulation, 2010
A significant issue in heart failure (HF) is diminished cognitive function, including memory, lea... more A significant issue in heart failure (HF) is diminished cognitive function, including memory, learning, and planning deficits. A basal ganglia structure, the putamen, serves many of these memory an...
Bookmarks Related papers MentionsView impact
Journal of Applied Physiology, 1994
In humans, the location of brain regions responsible for mediating the ventilatory response to CO... more In humans, the location of brain regions responsible for mediating the ventilatory response to CO2 remains unknown. Most of the available knowledge has been derived from animal studies or from pathophysiological correlations in patients presenting altered control of breathing. Magnetic resonance imaging at a specific pulse sequence designed to assess changes in brain tissue microcirculation was performed in 11 healthy volunteers, during steady-state conditions, while breathing 100% O2 or 5% CO2-95% O2. In one subject, 10% CO2-90% O2 was employed to examine a dose-response effect. Significant changes in image signal intensity consistently occurred in ventral and dorsal regions of medullary structures as well as in the midline pons and ventral cerebellum. These responses appeared to be dose dependent and reproducible. Magnetic resonance imaging revealed patterns of activation in brain stem and cerebellar regions during hypercapnic ventilatory challenge. These areas may underlie mechan...
Bookmarks Related papers MentionsView impact
Journal of the Acoustical Society of America, 2016
We hypothesized that premature infants exposed to womb-like sounds would show decreased apneic, h... more We hypothesized that premature infants exposed to womb-like sounds would show decreased apneic, hypoxemic, and bradycardic events. We believed these findings could be explained by the auditory system exerting influence over the autonomic system and potentially enhancing parasympathetic tone in neonates. Twenty premature infants without comorbidities, 32 to 37 weeks corrected, were their own controls. Infants were exposed to four 6-hour blocks of alternating womb-like sounds with intervening silence. Continuous ECG, respiratory, and oxygen saturation data were collected. Cortisol and alpha amylase salivary samples were obtained at study onset and offset during the 24-hour study period. Intermittent hypoxemic episodes significantly decreased from study onset (p = 0.03), along with bradycardic episodes (p = 0.05). No reductions in apneic events, cortisol levels, alpha amylase levels, or changes in heart rate variability were found. Exposing premature infants to womb-like sounds reduces...
Bookmarks Related papers MentionsView impact
Uploads
Papers by RONALD M HARPER