Spelling suggestions: "subject:"ventilatory"" "subject:"ventillatory""
1 |
Applications of electrical impedance tomography in respiratory medicineHarris, Nigel D. January 1991 (has links)
No description available.
|
2 |
Some factors affecting respiration in manBascom, Daphne Ayn January 1991 (has links)
No description available.
|
3 |
Effects of work intensity on the dynamics of pulmonary gas exchange during exercise in humansOzyener, Fadil January 2000 (has links)
No description available.
|
4 |
Ventilatory constraints and breathlessness during exercise in the elderly, in the obese, and in those with mild airflow limitationOfir, Dror 08 July 2008 (has links)
Breathlessness during activity is increasingly recognized as a common symptom in the elderly, in older individuals with minor airway obstruction due to tobacco smoking, and in those with obesity. The underlying mechanisms of perceived respiratory difficulty in each of these populations remain unknown and are largely unstudied.
Objective: The main purpose of this original research was to elucidate the alterations in central ventilatory drive and in dynamic ventilatory mechanics that might explain the origin of increased breathlessness during exercise in these three populations.
General Hypothesis: In individuals with largely preserved resting pulmonary function, increased intensity of breathlessness during activity will arise as a result of measurable abnormalities of dynamic ventilatory mechanics, central respiratory drive, or both in combination.
General Methods: We examined sensory-mechanical relationships during cardio-pulmonary exercise testing in each population (total n=146). We compared indices of ventilatory control (ventilation, pulmonary gas exchange and metabolic load), dynamic mechanics (breathing pattern and operating lung volumes) and ratings of dyspnea intensity in three well characterized cohorts: elderly versus younger; smokers with minor airway obstruction versus age-matched non-smokers, and obese versus lean participants.
Results: Individuals across all three study populations had preserved resting pulmonary function. Compared with their respective control groups all three symptomatic groups demonstrated consistent abnormalities in dynamic airway function during exercise [expiratory flow limitation (EFL), dynamic increases in end expiratory lung volume, and restricted tidal volume response]; all had greater ventilatory requirements reflecting variable ventilation-perfusion and metabolic abnormalities. In all three groups, intensity of breathlessness increased as ventilatory demand approached capacity. In the elderly (with or without airway obstruction), breathlessness intensity ratings at a standardized ventilation during exercise correlated with indices of mechanical volume restriction secondary to EFL. In obese individuals, increased ventilatory drive secondary to increased metabolic loading (and not mechanical abnormalities) was the primary factor contributing to exertional breathlessness.
Conclusion: Although the origin of breathlessness during physical exertion in the elderly (with or without minor airway obstruction) and in obese individuals is multi-factorial, we identified the central etiological importance of the combination of increased ventilatory drive and restrictive dynamic mechanical constraints to increasing ventilation. / Thesis (Ph.D, Physiology) -- Queen's University, 2008-07-02 14:17:41.602
|
5 |
A familial comparison of hypoxic sensitivity in two South-African populationsTerblanche, Jonathan Steed 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Chapter 1 presents a general literature review on the acute isocapnic hypoxic ventilatory
response (HVR).
The main findings from Chapter 2 indicate that our modified breathing circuit effectively
measured the HVR while maintaining isocapnia. The measured ventilatory variables
changed significantly with repeated short-term exposure to hypoxia over a 30-minute
period, and the within- and between-day variability did not differ significantly.
Furthermore, the variability in the HVR response (as measured by the coefficient of
variation, (CV» amounted to approximately 27% between tests in both parameters.
Repeated measures are recommended in future determinations of the HVR.
In Chapter 3 the main findings were that hypoxic sensitivity does not differ between
Caucasian and Xhosa sea-level populations in South Africa, and that ventilatory
components in both normoxia and hypoxia differed between these two populations. Two
distinct patterns of breathing were evident: shallow, rapid breathing among Xhosa
subjects, and deeper, slower breathing among Caucasians. Moreover, lower arterial
oxygen saturation levels during hypoxia among Xhosa subjects suggest that these two
patterns of breathing differ in the effectiveness with which they oxygenate the blood.
Inter-individual variation in HVR within each population is of the same high magnitude
as that reported in the literature (Beall et al., 1997), further supporting the use of repeated
measures in future studies.
As previously reported (Sahn et al., 1977, Reeves et al., 1993), in Chapter 3 I document a
significant correlation between HVR and partial pressure of end-tidal CO2 (PETCO).
Future studies of HVR should consider PETCO2 as a covariate, despite the fact that my
analyses of covariance (ANCOV A) showed no inter-population differences in HVR.
In Chapter 4 I report that regression analysis shows that the HVR of parents is not a
predictor of that of their offspring. No significant heritability was evident for any of the
additional key variables of hypoxic VE ,hypoxic Sa02, and the CV for HVR, but a priori
analyses showed that I tested too few subjects to be able to demonstrate heritability (or
the lack thereof) conclusively by means of regression analyses. Importantly, repeatability
estimates within populations (86 %) revealed that despite its high variability, the HVR is
highly repeatable, and therefore remains a useful comparative research tool for studies of
human adaptation to hypoxia. / AFRIKAANSE OPSOMMING: Hoofstuk 1 gee 'n algemene literatuuroorsig van die akute isokapniese hipoksiese
ventilatoriese reaksie (HVR).
Die hoofbevindinge uit Hoofstuk 2 dui aan dat ons gemodifiseerde asemhalingsbaan
HVR effektief meet terwyl isokapniese toestande gehantaaf word. Die ventilatoriese
veranderlikes gemeet, het betekenisvol verskil met herhaalde korttermyn blootstelling aan
hipoksie in a 30-minuut periode, en die binne- en tussen-daagse afwykbaarheid het nie
betekenisvol verskil nie. Verder het die afwykbaarheid van die HVR reaksie (soos bepaal
deur die koëffisiënt van variasie (KV)) ongeveer 27 % beloop tussen toetse van beide
parameters. Herhaalde metings word vir toekomstige bepalings van die HVR voorgestel.
In Hoofstuk 3 was die hoofbevindinge dat hipoksiese sensitiwiteit nie verskil tussen
Kaukasiese- en Xhosa- seevlak populasies in Suid-Afrika nie, en dat ventilatoriese
komponente in beide normoksie en hipoksie verskillend was tussen hierdie twee
populasies. Twee definitiewe asemhalingspatrone was duidelik merkbaar: vlak, vinnige
asemhaling in Xhosa proefpersone, en dieper, stadiger asemhaling in Kaukasiërs. Verder
het laer arteriële suurstof versadigingsvlakke gedurende hipoksie in Xhosa proefpersone
daarop gedui dat hierdie twee asemhalingspatrone moontlik verskil in hul effektiwiteit
om die bloed met suurstof te verryk.
Inter-individuele variasie in HVR binne elke populasie was van dieselfde groot omvang
as wat in die literatuur gerapporteer word (Beall et al., 1997), wat die gebruik van
herhaalde metings in toekomstige studies verder ondersteun.
Soos voorheen gerapporteer (Sahn et al., 1977, Reeves et al., 1993), dokumenteer ek in
Hoofstuk 3 'n merkbare korrelasie tussen HVR en parsiële druk van eind-tidale CO2
(PET CO2
). Verdere HVR studies behoort PET CO2 as a kovariant te beskou, ten spyte van
die feit dat my analise van kovariansie (ANCOV A) geen inter-populasie verskille in
HVR getoon het nie.
In Hoofstuk 4 rapporteer ek dat regressie analise bewys dat die HVR van ouers nie 'n
voorspeller van dié van hul kinders is nie. Geen betekenisvolle oorerflikheid was duidelik
vir enige van die addisionele sleutelveranderlikes van hipoksiese VE ,hipoksiese Sa02, of
die KV van HVR nie, maar 'n vorige analise het getoon dat ek te min proefpersone
getoets het om oorerflikheid (of die gebrek daaraan) m.b.v. regressie analises te kan
demonstreer. Dit is belangrik dat intra-populasie herhaalbaarheidsskattings (86 %) getoon
het dat ten spyte van sy hoë afwykbaarheid, die HVR hoogs herhaalbaar is, en daarom 'n
nuttige vergelykende navorsingshulpmiddel is vir studies rakende menslike aanpassing by
hipoksie.
|
6 |
An investigation into the influence of self-contained breathing apparatus (SCBA) upon lung function, inspiratory muscle strength and breathlessness in fire-fightersDonovan, Kerry J. January 1999 (has links)
No description available.
|
7 |
The LKB1-AMPK signalling pathway drives the hypoxic ventilatory response by regulating brainstem nuclei but not the carotid bodyMahmoud, Amira Dia January 2015 (has links)
Ventilatory drive is mediated by respiratory central pattern generators that are located in the brainstem, which are continuously modulated by specialised peripheral and central chemoreceptors to adjust ventilatory patterns according to changes in arterial PO2. These specialised oxygen-sensing chemoreceptors are activated in response to acute reductions in arterial PO2 and ultimately trigger a respiratory response that acts to restore oxygen-levels. However, the molecular mechanism by which mammals are able to regulate their breathing pattern in such a manner during hypoxia remains controversial. Therefore, the studies performed in this thesis aimed to investigate the possibility that this process may be mediated by the liver kinase B 1 (LKB1)/ AMP-activated protein kinase (AMPK) signalling pathway, which is central to cellular adaptations to metabolic stress. This first involved the development of transgenic mice in which Lkb1 or AMPK were deleted. Global knockout of Lkb1 (Sakamoto, 2006) or AMPK activity (Viollet et al., 2009) are embryonic lethal. Thus, the Cre/loxP system was used to develop transgenic mice that had either Lkb1 or both isoforms of the AMPK catalytic α- subunit (α1 and α2) conditionally knocked out in catecholaminergic cells (including therein hypoxia-activated cells of the brainstem and carotid body) by driving Cre expression through a tyrosine-hydroxylase-specific promoter region. The consequent effects on the ventilatory response to hypoxia were then examined using unrestrained whole-body plethysmography. This demonstrated that, in contrast to the hyperventilation evoked in controls, increased ventilation was virtually abolished in the Lkb1 and AMPK α1 and α2 double knockouts during hypoxia. Both knockout mice also exhibited periods of hypoventilation with frequent apnoeas during hypoxia. Additionally, studies on single AMPK α1 and AMPK α2 knockouts identified that the ventilatory dysfunction in AMPK α1 and α2 double knockouts was primarily caused by AMPK α1 deletion. In contrast, the severe ventilatory abnormalities exhibited during hypoxia following the deletion of Lkb1 and AMPK in catecholaminergic cells were mostly reversed upon exposure of mice to hypoxia with hypercapnia. Also, the ventilatory response to hypercapnia alone was without any major effect as a result of Lkb1 deletion or the dual-deletion of AMPK α1 and α2 catalytic subunits in catecholaminergic cells. This thesis therefore demonstrates, for the first time, that the LKB1-AMPK signalling pathway is key to respiratory adaptations during hypoxia, by regulating catecholaminergic oxygen-sensing cells, thus protecting against hypoventilation and apnoeas. The LKB1-AMPK signaling pathway can thereby determine oxygen and energy supply at both a cellular and whole-body level.
|
8 |
The Role of GABAA Receptor-mediated Neurotransmission in Ventilatory Acclimatisation to HypoxiaPhe, Balinda Siou Ing 26 February 2009 (has links)
Exposure to chronic hypoxia (CH) leads to ventilatory acclimatisation to hypoxia (VAH) which is a time-dependent increase in breathing. This study examined the role of the GABAA receptor in establishing VAH. Rats were exposed to CH or control (normoxic) conditions for 10 days during which the GABAA receptor antagonist, bicuculline, was infused systemically or directly into the nucleus of the solitary tract (NTS). Acute breathing trials were then performed to measure resting ventilation and ventilatory chemoreflexes. Systemic administration of bicuculline caused reductions in breathing during acute hypoxia and acute hypercapnia in the control but not the CH animals. Continuous infusion of bicuculline in to the NTS caused a reduction in the acute hypoxic ventilatory response in animals exposed to CH but not in the control animals. The results indicate that exposure to CH alters the GABAA-mediated regulation of acute ventilatory chemoreflexes both in the NTS and elsewhere in the brain.
|
9 |
Description of the Dynamic Responses to Hypoxia:Ventilation, Cerebral Blood Flow (CBF), Blood Pressure (BP), and Heart Rate (HR)Battisti, Anne Marie Gabrielle 04 September 2012 (has links)
This thesis describes experiments to measure the ventilatory response to hypoxia at a constant (isocapnic) level of CO2 (HVR) in 18 subjects. So as to provide a complete picture of the autonomic responses, middle cerebral artery velocity, a surrogate for cerebral blood flow (CBF), as well as finger plethysmography blood pressure (BP) were also measured. Ventilatory responses have been previously described only in terms of an acute peak followed by a decline. However, rather than a single type of response, I found four types categorized as: Decline, Double, Plateau, or No response. The Double pattern, characterized by a second peak of response was the most common, yet is described here for the first time. These patterns are also characteristic of the CBF and BP responses. Furthermore the temporal correlations between these brainstem-controlled responses are also reported here for the first time.
|
10 |
Description of the Dynamic Responses to Hypoxia:Ventilation, Cerebral Blood Flow (CBF), Blood Pressure (BP), and Heart Rate (HR)Battisti, Anne Marie Gabrielle 04 September 2012 (has links)
This thesis describes experiments to measure the ventilatory response to hypoxia at a constant (isocapnic) level of CO2 (HVR) in 18 subjects. So as to provide a complete picture of the autonomic responses, middle cerebral artery velocity, a surrogate for cerebral blood flow (CBF), as well as finger plethysmography blood pressure (BP) were also measured. Ventilatory responses have been previously described only in terms of an acute peak followed by a decline. However, rather than a single type of response, I found four types categorized as: Decline, Double, Plateau, or No response. The Double pattern, characterized by a second peak of response was the most common, yet is described here for the first time. These patterns are also characteristic of the CBF and BP responses. Furthermore the temporal correlations between these brainstem-controlled responses are also reported here for the first time.
|
Page generated in 0.0657 seconds