Pre-operative optimisation for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a condition commonly present in older people undergoing surgery and confers an increased risk of postoperative complications and mortality. Although predominantly a respiratory disease, it frequently has extra‐pulmonary manifestations and typically occurs in the context of other long‐term conditions. Patients experience a range of symptoms that affect their quality of life, functional ability and clinical outcomes. In this review, we discuss the evidence for techniques to optimise the care of people with chronic obstructive pulmonary disease in the peri‐operative period, and address potential new interventions to improve outcomes. The article centres on pulmonary rehabilitation, widely available for the treatment of stable chronic obstructive pulmonary disease, but less often used in a peri‐operative setting. Current evidence is largely at high risk of bias, however. Before surgery it is important to ensure that what have been called the ‘five fundamentals’ of chronic obstructive pulmonary disease treatment are achieved: smoking cessation; pulmonary rehabilitation; vaccination; self‐management; and identification and optimisation of co‐morbidities. Pharmacological treatment should also be optimised, and some patients may benefit from lung volume reduction surgery. Psychological and behavioural factors are important, but are currently poorly understood in the peri‐operative period. Considerations of the risk and benefits of delaying surgery to ensure the recommended measures are delivered depends on patient characteristics and the nature and urgency of the planned intervention

The Filter Detection Task for measurement of breathing-related interoception and metacognition

The study of the brain’s processing of sensory inputs from within the body (‘interoception’) has been gaining rapid popularity in neuroscience, where interoceptive disturbances are thought to exist across a wide range of chronic physiological and psychological conditions. Here we present a task and analysis procedure to quantify specific dimensions of breathing-related interoception, including interoceptive sensitivity, decision bias, metacognitive bias, and metacognitive performance. Two major developments address some of the challenges presented by low trial numbers in interoceptive experiments: (i) a novel adaptive algorithm to maintain task performance at 70–75% accuracy; (ii) an extended hierarchical metacognitive model to estimate regression parameters linking metacognitive performance to relevant (e.g. clinical) variables. We demonstrate the utility of the task and analysis developments, using both simulated data and three empirical datasets. This methodology represents an important step towards accurately quantifying interoceptive dimensions from a simple experimental procedure that is compatible with clinical settings

Chronic breathlessness: re-thinking the symptom

Is chronic breathlessness a symptom or a syndrome? Although hotly debated, we would like to suggest an alternative viewpoint. Here, we speculate that the argument over chronic breathlessness being considered as either a symptom or syndrome both holds us within a reductionist framework, and somewhat misses the point

Use of consensus term and definition for delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage

Background and purpose: In 2010, a multidisciplinary research group proposed a consensus term and definition for the complication of delayed cerebral ischaemia (DCI) following aneurysmal subarachnoid haemorrhage (SAH). We assessed the use of this term and its definition as an endpoint in observational studies and clinical trials. Methods: Firstly, we performed a MEDLINE abstract search from Jan 2008 to Dec 2017 for observational cohort studies and clinical trials to investigate the used terminology over the years. Next, we studied trends in citations of the original paper citing the consensus definitions since publication in 2010. Results: The number of publications citing the 2010 consensus definitions has steadily increased from 18 in 2011 to 54 in 2017. Between 2010 and 2017, 527 papers were published with delayed cerebral ischemia, or another term to describe the same complication, as an endpoint. However, the term delayed cerebral ischemia was used only in 131/527 (25%) of papers and only 14/81 (17%) of clinical trials/cohort studies published in 2017 cited the consensus definitions when outlining study endpoints. Conclusions: Despite publication of consensus terminology and definitions for DCI in 2010, the majority of cohort studies and clinical trials in patients with SAH are not using these. Researchers and editors should be reminded of the importance of using these consensus terminology and definitions in future studies, which will promote the comparability of results between studies, understand the true impact of an intervention, aggregate results in meta- analyses, and construct guidelines with a high level of evidence

Chronic breathlessness: re-thinking the symptom

Is chronic breathlessness a symptom or a syndrome? Although hotly debated, we would like to suggest an alternative viewpoint. Here, we speculate that the argument over chronic breathlessness being considered as either a symptom or syndrome both holds us within a reductionist framework, and somewhat misses the point

Modeling of dynamic cerebrovascular reactivity to spontaneous and externally induced CO2 fluctuations in the human brain using BOLD-fMRI

In this work, we investigate the regional characteristics of the dynamic interactions between arterial CO2 and BOLD (dynamic cerebrovascular reactivity - dCVR) during normal breathing and hypercapnic, externally induced step CO2 challenges. To obtain dCVR curves at each voxel, we use a custom set of basis functions based on the Laguerre and gamma basis sets. This allows us to obtain robust dCVR estimates both in larger regions of interest (ROIs), as well as in individual voxels. We also implement classification schemes to identify brain regions with similar dCVR characteristics. Our results reveal considerable variability of dCVR across different brain regions, as well as during different experimental conditions (normal breathing and hypercapnic challenges), suggesting a differential response of cerebral vasculature to spontaneous CO2 fluctuations and larger, externally induced CO2 changes that are possibly associated with the underlying differences in mean arterial CO2 levels. The clustering results suggest that anatomically distinct brain regions are characterized by different dCVR curves that in some cases do not exhibit the standard, positive valued curves that have been previously reported. They also reveal a consistent set of dCVR cluster shapes for resting and forcing conditions, which exhibit different distribution patterns across brain voxels

Breathlessness and the brain: the role of expectation

Purpose of review Breathlessness debilitates countless people with a wide range of common diseases. For some people, the experience of breathlessness is poorly explained by the findings of medical tests. This disparity complicates diagnostic and treatment options and means that disease-modifying treatments do not always have the expected effect upon symptoms. These observations suggest that brain processing of respiratory perceptions may be somewhat independent of disease processes. This may help to explain the dissonance observed in some patients between physical disease markers and the lived experience of breathlessness. Recent findings A body of breathlessness research using functional neuroimaging has identified a relatively consistent set of brain areas that are associated with breathlessness. These areas include the insula, cingulate and sensory cortices, the amygdala and the periaqueductal gray matter. We interpret these findings in the context of new theories of perception that emphasize the importance of distributed brain networks. Within this framework, these perceptual networks function by checking an internal model (a set of expectations) against peripheral sensory inputs, instead of the brain acting as a passive signal transducer. Furthermore, other factors beyond the physiology of breathlessness can influence the system. Summary A person's expectations and mood are major contributors to the function of the brain networks that generate perceptions of breathlessness. Breathlessness, therefore, arises from inferences made by the brain's integration of both expectations and sensory inputs. By better understanding individual differences across these contributing perceptual factors, we will be better poised to develop targeted and individualized treatments for breathlessness that could complement disease-modifying therapies.</p

The midbrain periaqueductal gray as an integrative and interoceptive neural structure for breathing

The periaqueductal gray (PAG) plays a critical role in autonomic function and behavioural responses to threatening stimuli. Recent evidence has revealed the PAG's potential involvement in the perception of breathlessness, a highly threatening respiratory symptom. In this review, we outline the current evidence in animals and humans on the role of the PAG in respiratory control and in the perception of breathlessness. While recent work has unveiled dissociable brain activity within the lateral PAG during perception of breathlessness and ventrolateral PAG during conditioned anticipation in healthy humans, this is yet to be translated into diseases dominated by breathlessness symptomology, such as chronic obstructive pulmonary disease. Understanding how the sub-structures of the PAG differentially interact with interoceptive brain networks involved in the perception of breathlessness will help towards understanding discordant symptomology, and may reveal treatment targets for those debilitated by chronic and pervasive breathlessness

Modeling of dynamic cerebrovascular reactivity to spontaneous and externally induced CO2 fluctuations in the human brain using BOLD-fMRI

In this work, we investigate the regional characteristics of the dynamic interactions between arterial CO2 and BOLD (dynamic cerebrovascular reactivity - dCVR) during normal breathing and hypercapnic, externally induced step CO2 challenges. To obtain dCVR curves at each voxel, we use a custom set of basis functions based on the Laguerre and gamma basis sets. This allows us to obtain robust dCVR estimates both in larger regions of interest (ROIs), as well as in individual voxels. We also implement classification schemes to identify brain regions with similar dCVR characteristics. Our results reveal considerable variability of dCVR across different brain regions, as well as during different experimental conditions (normal breathing and hypercapnic challenges), suggesting a differential response of cerebral vasculature to spontaneous CO2 fluctuations and larger, externally induced CO2 changes that are possibly associated with the underlying differences in mean arterial CO2 levels. The clustering results suggest that anatomically distinct brain regions are characterized by different dCVR curves that in some cases do not exhibit the standard, positive valued curves that have been previously reported. They also reveal a consistent set of dCVR cluster shapes for resting and forcing conditions, which exhibit different distribution patterns across brain voxels

Adverse respiratory effects of opioids for chronic breathlessness: learning lessons from chronic pain

Fear of fatal respiratory depression is a major driver limiting opioid prescription for persistent breathlessness in chronic obstructive pulmonary disease (COPD) [1–6], but is this fear warranted? In a recent systematic review and meta-analysis, VERBERKT et al. [7] did not detect significant or clinically relevant respiratory adverse events associated with opioid treatment for chronic breathlessness in COPD. Rather, they concluded that “clinicians’ fears of respiratory obtundation with low-dose opioids seem to be unfounded”. Here, we critically evaluate these conclusions