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Blood pressure changes alter tracheobronchial cough: computational model of the respiratory-cough network and in vivo experiments in anesthetized cats.

ABSTRACT: We tested the hypothesis, motivated in part by a coordinated computational cough network model, that alterations of mean systemic arterial blood pressure (BP) influence the excitability and motor pattern of cough. Model simulations predicted suppression of coughing by stimulation of arterial baroreceptors. In vivo experiments were conducted on anesthetized spontaneously breathing cats. Cough was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms (EMG) of inspiratory parasternal, expiratory abdominal, laryngeal posterior cricoarytenoid (PCA), and thyroarytenoid muscles along with esophageal pressure (EP) and BP were recorded. Transiently elevated BP significantly reduced cough number, cough-related inspiratory, and expiratory amplitudes of EP, peak parasternal and abdominal EMG, and maximum of PCA EMG during the expulsive phase of cough, and prolonged the cough inspiratory and expiratory phases as well as cough cycle duration compared with control coughs. Latencies from the beginning of stimulation to the onset of cough-related diaphragm and abdominal activities were increased. Increases in BP also elicited bradycardia and isocapnic bradypnea. Reductions in BP increased cough number; elevated inspiratory EP amplitude and parasternal, abdominal, and inspiratory PCA EMG amplitudes; decreased total cough cycle duration; shortened the durations of the cough expiratory phase and cough-related abdominal discharge; and shortened cough latency compared with control coughs. Reduced BP also produced tachycardia, tachypnea, and hypocapnic hyperventilation. These effects of BP on coughing likely originate from interactions between barosensitive and respiratory brainstem neuronal networks, particularly by modulation of respiratory neurons within multiple respiration/cough-related brainstem areas by baroreceptor input.

SUBMITTER: Poliacek I

PROVIDER: S-EPMC3174787 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundPositive end-expiratory pressure (PEEP) has been demonstrated to decrease ventilator-induced lung injury in patients under mechanical ventilation (MV) for acute respiratory failure. Recently, some studies have proposed some beneficial effects of PEEP in ventilated patients without lung injury. The influence of PEEP on respiratory mechanics in children is not well known. Our aim was to determine the effects on respiratory mechanics of setting PEEP at 5 cmH2O in anesthetized healthy children.MethodsPatients younger than 15 years old without history of lung injury scheduled for elective surgery gave informed consent and were enrolled in the study. After usual care for general anesthesia, patients were placed on volume controlled MV. Two sets of respiratory mechanics studies were performed using inspiratory and expiratory breath hold, with PEEP 0 and 5 cmH2O. The maximum inspiratory and expiratory flow (QI and QE) as well as peak inspiratory pressure (PIP), plateau pressure (PPL) and total PEEP (tPEEP) were measured. Respiratory system compliance (CRS), inspiratory and expiratory resistances (RawI and RawE) and time constants (KTI and KTE) were calculated. Data were expressed as median and interquartile range (IQR). Wilcoxon sign test and Spearman's analysis were used. Significance was set at P <?0.05.ResultsWe included 30 patients, median age 39 (15-61.3) months old, 60% male. When PEEP increased, PIP increased from 12 (11,14) to 15.5 (14,18), and CRS increased from 0.9 (0.9,1.2) to 1.2 (0.9,1.4) mL·kg-?1·cmH2O-?1; additionally, when PEEP increased, driving pressure decreased from 6.8 (5.9,8.1) to 5.8 (4.7,7.1) cmH2O, and QE decreased from 13.8 (11.8,18.7) to 11.7 (9.1,13.5) L·min-?1 (all P <?0.01). There were no significant changes in resistance and QI.ConclusionsAnalysis of respiratory mechanics in anesthetized healthy children shows that PEEP at 5 cmH2O places the respiratory system in a better position in the P/V curve. A better understanding of lung mechanics may lead to changes in the traditional ventilatory approach, limiting injury associated with MV.

Project description:The role of the cerebellum in controlling the cough motor pattern is not well understood. We hypothesized that cerebellectomy would disinhibit motor drive to respiratory muscles during cough. Cough was induced by mechanical stimulation of the tracheobronchial airways in anesthetized, spontaneously breathing adult cats (8 male, 1 female), and electromyograms (EMGs) were recorded from upper airway, chest wall, and abdominal respiratory muscles. Cough trials were performed before and at two time points after total cerebellectomy (10 minutes and >1 hour). Unlike a prior report in paralyzed, decerebrated, and artificially ventilated animals, we observed that cerebellectomy had no effect on cough frequency. After cerebellectomy, thoracic inspiratory muscle EMG magnitudes increased during cough (diaphragm EMG increased by 14% at 10 minutes, p = 0.04; parasternal by 34% at 10 minutes and by 32% at >1 hour, p = 0.001 and 0.03 respectively). During cough at 10 minutes after cerebellectomy, inspiratory esophageal pressure was increased by 44% (p = 0.004), thyroarytenoid (laryngeal adductor) muscle EMG amplitude increased 13% (p = 0.04), and no change was observed in the posterior cricoarytenoid (laryngeal abductor) EMG. Cough phase durations did not change. Blood pressure and heart rate were reduced after cerebellectomy, and respiratory rate also decreased due to an increase in duration of the expiratory phase of breathing. Changes in cough-related EMG magnitudes of respiratory muscles suggest that the cerebellum exerts inhibitory control of cough motor drive, but not cough number or phase timing in response to mechanical stimuli in this model early after cerebellectomy. However, results varied widely at >1 hour after cerebellectomy, with some animals exhibiting enhancement or suppression of one or more components of the cough motor behavior. These results suggest that, while the cerebellum and behavior-related sensory feedback regulate cough, it may be difficult to predict the nature of the modulation based on total cerebellectomy.

Project description:Arterial blood pressure (BP) can be measured directly using an invasive intra-arterial method. This method is considered a gold standard, however it is potentially hazardous and requires expensive equipment and professional skills. Therefore, two non-invasive methods-Doppler ultrasonic sphygmomanometry and oscillometry-have been introduced in veterinary medicine. Their accuracy has so far been reliably evaluated in various animal species, however only one study included a small group of goats. Therefore, we carried out a large-scale study which aimed to evaluate agreement between the two non-invasive methods and invasive intra-arterial BP measurement in anesthetized goats at various age. The study included 122 goats of two Polish local breeds (Polish White Improved and Polish Fawn Improved): 67 adult females, 35 adult males, and 20 two-month-old female kids. Goats were anesthetized with the intravenous mixture of xylazine and ketamine. BP was measured simultaneously with the three methods in each goat with 7 measurements on average taken. The study showed that according to the criteria of the American College of Veterinary Internal Medicine (ACVIM) oscillometric method yielded BP measurements sufficiently consistent with invasive intra-arterial method in anesthetized adult goats- 95% of oscillometric BP measurements were expected to differ from invasive BP measurements by at most ±20-25 mmHg. The agreement was worse in goat kids-oscillometry significantly overestimated invasive BP measurements, which resulted in highly asymmetrical 95% limits of agreement. Doppler systolic BP very poorly conformed to invasive systolic BP both in adult goats and in kids and all the ACVIM criteria were violated. Concluding, oscillometry, but not Doppler ultrasonic sphygmomanometry, may be regarded as an alternative to invasive BP measurement in large-scale scientific studies involving adult goats, however, individual oscillometric BP measurements should be treated with caution as estimated 95% limits of agreement were wide.

Project description:With computational biology striving to provide more accurate theoretical accounts of biological systems, use of increasingly complex computational models seems inevitable. However, this trend engenders a challenge of optimal experimental design: due to the flexibility of complex models, it is difficult to intuitively design experiments that will efficiently expose differences between candidate models or allow accurate estimation of their parameters. This challenge is well exemplified in associative learning research. Associative learning theory has a rich tradition of computational modeling, resulting in a growing space of increasingly complex models, which in turn renders manual design of informative experiments difficult. Here we propose a novel method for computational optimization of associative learning experiments. We first formalize associative learning experiments using a low number of tunable design variables, to make optimization tractable. Next, we combine simulation-based Bayesian experimental design with Bayesian optimization to arrive at a flexible method of tuning design variables. Finally, we validate the proposed method through extensive simulations covering both the objectives of accurate parameter estimation and model selection. The validation results show that computationally optimized experimental designs have the potential to substantially improve upon manual designs drawn from the literature, even when prior information guiding the optimization is scarce. Computational optimization of experiments may help address recent concerns over reproducibility by increasing the expected utility of studies, and it may even incentivize practices such as study pre-registration, since optimization requires a pre-specified analysis plan. Moreover, design optimization has the potential not only to improve basic research in domains such as associative learning, but also to play an important role in translational research. For example, design of behavioral and physiological diagnostic tests in the nascent field of computational psychiatry could benefit from an optimization-based approach, similar to the one presented here.

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Blood pressure changes alter tracheobronchial cough: computational model of the respiratory-cough network and in vivo experiments in anesthetized cats.

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