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Regulation of Breathing under Different Pulmonary ConditionsRieger-Fackeldey, Esther January 2004 (has links)
<p>The breathing pattern of preterm infants is immature and is associated with a variety of reflexes. In a patient on the ventilator these reflexes interfere with spontaneous breathing. A better understanding of the immature control of breathing could lead to further improvements in ventilatory techniques. This thesis concerns studies of pulmonary stretch receptor (PSR) and phrenic nerve activity as part of the regulation of breathing in an animal model. </p><p>During assist/control ventilation with three different inspiratory pressure waveforms in animals with healthy lungs, squarewave pressure waveform<b> </b>strongly inhibits spontaneous inspiratory activity.</p><p>During partial liquid ventilation (PLV) in animals with healthy lungs, all PSRs studied maintained their phasic character, with increased impulse frequency during inspiration. PSR activity was not higher during PLV than during gas ventilation (GV), indicating that there was no extensive stretching of the lung during PLV.</p><p>During proportional assist ventilation (PAV) the applied airway pressure is servo-controlled proportionally to the ongoing breathing effort, thereby interacting with the activity of PSRs. Peak PSR activity was higher and occurred earlier during PAV than during CPAP. The regulation of breathing is maintained during PAV in surfactant-depleted animals before and early after surfactant instillation, with a higher ventilatory response and a lower breathing effort than during CPAP in both conditions.</p><p>Both lung mechanics and gas exchange influence the regulation of breathing. Inhibition of inspiratory activity occurred at a lower arterial pH and a higher PaCO<sub>2</sub> during PLV than during GV in animals with surfactant-depleted lungs, which might be related to recruitment of a larger number of pulmonary stretch receptors during PLV.</p><p>In summary, selected aspects of the regulation of breathing were studied in an animal model with different ventilatory techniques under different lung conditions similar to those that can occur in infants.</p>
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Breathing Pattern and Lung Mechanics during Assisted Ventilation Response of Slowly Adapting Pulmonary Stretch Receptors and Effects on Phrenic Nerve Activity in Cats with Normal and Surfactant Depleted LungsSindelar, Richard January 2001 (has links)
Different modes of assisted ventilation were investigated in cats before and after lung lavage and after instillation of surfactant. The activity of single units of slowly adapting pulmonary stretch receptors (PSRs) in the vagal nerve and the integrated phrenic nerve activity were recorded. The instantaneous impulse frequency (fimp) of PSRs was calculated and related to transpulmonary pressure (Ptp), tidal volume (Vt) and the calculated energy storage of the lung (ΣP*ΔV). Respiratory rate (RR), inspiratory and expiratory time, and Vt were measured, and their coefficients of variation were calculated. During assist control (A/C) ventilation with different pressure waveforms, PNA was shorter and lower in amplitude with squarewave pressure waveform than with linear and sinusoidal pressure waveforms in cats with normal lungs, concomitantly with earlier peak fimp during inspiration and prolonged fimp during expiration. The type of pressure waveform can thus influence the spontaneous breathing effort during A/C ventilation. Proportional assist ventilation (PAV) is a new mode of assisted ventilation which servo-controls the applied airway pressure continuously in proportion to the breathing effort. After lung lavage and surfactant instillation, PAV improves ventilation markedly, with lower PNA and oesophageal pressure deflection and higher RR and variability of breathing, compared to CPAP. In addition, an earlier and higher maximal fimp was observed during PAV. Under conditions of low work and maintained control of breathing, PAV seems to be an attractive mode of ventilatory support. Low-threshold (LT) and high-threshold (HT) PSRs respond to the surfactant content of the lung partly independent of Ptp and Vt in spontaneously breathing cats, implying a possible effect of surfactant on PSRs. The PSR fimp normalized to ΣP*ΔV confirmed these findings and showed that LT and HT PSRs are intrinsically the same. After instillation of surfactant, compliance and PSR activity increased, but the breathing still remained shallow and rapid, suggesting a control of breathing less dominated by PSR activity.
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Regulation of Breathing under Different Pulmonary ConditionsRieger-Fackeldey, Esther January 2004 (has links)
The breathing pattern of preterm infants is immature and is associated with a variety of reflexes. In a patient on the ventilator these reflexes interfere with spontaneous breathing. A better understanding of the immature control of breathing could lead to further improvements in ventilatory techniques. This thesis concerns studies of pulmonary stretch receptor (PSR) and phrenic nerve activity as part of the regulation of breathing in an animal model. During assist/control ventilation with three different inspiratory pressure waveforms in animals with healthy lungs, squarewave pressure waveform strongly inhibits spontaneous inspiratory activity. During partial liquid ventilation (PLV) in animals with healthy lungs, all PSRs studied maintained their phasic character, with increased impulse frequency during inspiration. PSR activity was not higher during PLV than during gas ventilation (GV), indicating that there was no extensive stretching of the lung during PLV. During proportional assist ventilation (PAV) the applied airway pressure is servo-controlled proportionally to the ongoing breathing effort, thereby interacting with the activity of PSRs. Peak PSR activity was higher and occurred earlier during PAV than during CPAP. The regulation of breathing is maintained during PAV in surfactant-depleted animals before and early after surfactant instillation, with a higher ventilatory response and a lower breathing effort than during CPAP in both conditions. Both lung mechanics and gas exchange influence the regulation of breathing. Inhibition of inspiratory activity occurred at a lower arterial pH and a higher PaCO2 during PLV than during GV in animals with surfactant-depleted lungs, which might be related to recruitment of a larger number of pulmonary stretch receptors during PLV. In summary, selected aspects of the regulation of breathing were studied in an animal model with different ventilatory techniques under different lung conditions similar to those that can occur in infants.
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Função colinérgica cardiorrespiratória no núcleo do trato solitárioFuruya, Werner Issao 26 August 2013 (has links)
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Previous issue date: 2013-08-26 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / The nucleus of the solitary tract (NTS) is the primary synaptic site of the
peripheral baroreceptors and chemoreceptors. It has been shown that acetylcholine
(ACh) microinjected into the NTS of rats induces hypotension and bradycardia.
However, the contribution of cholinergic mechanisms at different NTS subnuclei
(intermediate and commissural) as well as the cholinergic receptors blockade on the
control of sympathetic (SNA) and phrenic (PNA) nerve activities have not been
studied yet. In this study we assessed the role of ACh and its cholinergic receptors at
the intermediate NTS (iNTS) and commissural NTS (cNTS) on the control of SNA,
PNA and electrophysiological properties of these subnuclei neurons, as well as on
baro and chemoreflex responses. Decorticated arterially-perfused in situ preparations
of male juvenile rats were used to record SNA and PNA. Microinjections of ACh and
cholinergic antagonists were performed into the iNTS or cNTS. Coronal slices of the
brainstem containing either cNTS or iNTS subnuclei were obtained from male
juvenile rats and used in whole cell patch clamp – current clamp recordings. It was
observed that ACh microinjected into the iNTS inhibited both SNA and PNA. These
effects were reduced by the pre-treatment with atropine (muscarinic antagonist) or
mecamylamine (nicotinic antagonist). The cholinergic antagonists into the iNTS did
not change the effects on SNA and PNA induced by baro and chemoreflex activation.
In contrast, microinjections of ACh into the cNTS did not induce changes in SNA, but
increased PNA. Despite the absence of changes in SNA, ACh into the cNTS
changed the pattern of respiratory-sympathetic coupling. Both atropine and
mecamylamine into the cNTS inhibited the ACh-induced tachypnea, but only
mecamylamine inhibited the chemoreflex-induced tachypnea and the ACh-induced
change in respiratory-sympathetic coupling. In vitro studies demonstrated that ACh
promotes depolarization in both iNTS and cNTS neurons. Both muscarinic and
nicotinic antagonism in the iNTS inhibited the ACh-induced depolarization. However,
only nicotinic antagonist was effective in diminishing this response in the cNTS. The
results suggest that ACh plays an important role in the control of cardiovascular and
respiratory activities, with distinct functions between iNTS and cNTS. This cholinergic
control involves activation of both muscarinic and nicotinic receptors within NTS, but
only nicotinic receptors are involved in the chemoreflex tachypneic response. / O núcleo do trato solitário (NTS) é o sítio primário de aferências dos
barorreceptores arteriais e quimiorreceptores. Sabe-se que a acetilcolina (ACh)
injetada no NTS de ratos provoca hipotensão e bradicardia. Entretanto, não se sabe
até o momento qual o papel do sistema colinérgico nos diferentes subnúcleos do
NTS (intermediário ou comissural) ou o bloqueio de seus receptores na atividade
simpática (SNA) ou na atividade do frênico (PNA). No presente estudo avaliamos os
efeitos da ACh e seus receptores no NTS intermediário (NTSi) e comissural (NTSc)
sobre a SNA, PNA e sobre as propriedades eletrofisiológicas dos neurônios desses
subnúcleos, bem como nas respostas do baro e quimiorreflexos. Preparações in situ
decorticadas de ratos jovens foram utilizadas para registro da SNA e PNA, e ACh e
antagonistas colinérgicos foram microinjetados no NTSi ou NTSc. Cortes coronais
bulbares contendo o NTSi ou NTSc foram obtidos de ratos jovens e utilizados para
registro de neurônios através da técnica whole cell patch clamp – current clamp. Foi
observado que a microinjeção de ACh no NTSi inibe tanto a SNA quanto a PNA,
sendo que tais efeitos são inibidos pelo tratamento com atropina (antagonista
muscarínico) ou mecamilamina (antagonista nicotínico). Os antagonistas colinérgicos
no NTSi não alteraram os efeitos na SNA e PNA induzidos pela ativação do baro e
quimiorreflexos. Por outro lado, microinjeções de ACh no NTSc não altera a SNA
mas promove aumento da PNA. Apesar de não alterar a SNA, a ACh no NTSc
promove alterações no acoplamento simpato-respiratório. Tanto a atropina quanto a
mecamilamina microinjetadas no NTSc inibiram a taquipnéia induzida pela ACh, mas
apenas a mecamilamina inibiu a taquipnéia resultante do quimiorreflexo e a
alteração no acoplamento simpato-respiratório induzida pela ACh no NTSc. Nos
estudos in vitro, observamos que a ACh promove respostas de despolarização em
neurônios tanto do NTSi quanto do NTSc. O bloqueio de receptores tanto nicotínicos
quanto muscarínicos no NTSi diminui a despolarização evocada pela ACh. No
entanto, apenas o antagonista nicotínico foi capaz de diminuir essa resposta no
NTSc. Os resultados sugerem que a ACh desempenha um importante papel no
controle cardiorrespiratório, com funções distintas entre NTSi e NTSc. Esse controle
colinérgico envolve a ativação de receptores tanto nicotínicos quanto muscarínicos
no NTS, mas apenas receptores nicotínicos estão envolvidos na resposta de
taquipnéia do quimiorreflexo. / FAPESP: 2010/17218-0
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