RESUMO
BACKGROUND: Cutaneous T-cell lymphomas (CTCL) are rare cancers, which can be difficult to diagnose, are incurable and adversely affect quality of life, particularly in advanced disease. Families often provide care, but little is known about their experiences or needs while caring for their relative with advanced disease or in bereavement. OBJECTIVES: To explore the experiences of bereaved family caregivers of patients with CTCL. METHODS: Single, semi-structured qualitative interviews were conducted with bereaved family caregivers of patients with CTCL recruited via a supra-regional CTCL clinic. Transcribed interviews were analysed thematically, focusing on advanced disease, the approach of death and bereavement. RESULTS: Fifteen carers of 11 deceased patients participated. Experiences clustered under four themes: (1) complexity of care and medical intervention; (2) caregiver roles in advanced CTCL; (3) person-centred vs. organization-centred care in advanced CTCL and (4) knowing and not knowing: reflections on dying, death and bereavement. Caregivers often had vivid recollections of the challenges of caring for their relative with advanced CTCL and some took on quasi-professional roles as a result. Advanced disease made high demands on both organizational flexibility and family resources. For many caregivers, seeing disease progression was a prolonged and profoundly traumatic experience. The extent to which they were prepared for their relative's death and supported in bereavement was highly variable. Sub-themes within each theme provide more detail about caregiver experiences. CONCLUSIONS: Family caregivers should be considered part of the wider healthcare team, acknowledging their multiple roles and the challenges they encounter in looking after their relative with CTCL as the disease progresses. Their experiences highlight the importance of organizational flexibility and of good communication between healthcare providers in advanced CTCL.
Assuntos
Cuidadores/psicologia , Família/psicologia , Linfoma Cutâneo de Células T/terapia , Neoplasias Cutâneas/terapia , Assistência Terminal/psicologia , Adaptação Psicológica , Adulto , Idoso , Luto , Feminino , Humanos , Linfoma Cutâneo de Células T/mortalidade , Linfoma Cutâneo de Células T/patologia , Linfoma Cutâneo de Células T/psicologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Pesquisa Qualitativa , Qualidade de Vida , Neoplasias Cutâneas/mortalidade , Neoplasias Cutâneas/patologia , Neoplasias Cutâneas/psicologia , Inquéritos e Questionários , Assistência Terminal/métodosRESUMO
BACKGROUND: Primary cutaneous T-cell lymphoma (CTCL) is a rare but prevalent condition which can have a significant impact on many aspects of quality of life. However, there is little evidence of patients' lived experience of CTCL. OBJECTIVES: To understand in greater depth patients' experiences of living and coping with CTCL, and to inform the development of models of care for this population in line with U.K. METHODS: Semi-structured interviews were conducted with a purposive sample of patients with CTCL who attended an inner-city teaching hospital. Participants were purposively selected according to their disease stage, age, sex and ethnicity. RESULTS: Nineteen patients with CTCL (stages IB-IVB), aged between 41 and 83 years, participated in a single interview. This included 10 men; 15 people identified themselves as white British. Interviews lasted a median of 55 (range 28-170) min. Two main themes emerged: issues regarding diagnosis, particularly a perceived delay in diagnosis, and the impact of CTCL (subthemes related to physical well-being, practical concerns and psychological and social well-being and coping). CONCLUSIONS: Findings from this study illuminate the diverse effects of CTCL on patients' lives. The universal experience of delays in diagnosis was striking and a concern to patients. The disease, particularly its physical symptoms, had a significant impact on patients' lives, including employment, leisure and relationships. Despite the symptom burden and its impact, participants described effective coping strategies such as drawing on social support, maintaining normal lives and becoming well informed about CTCL. Proactive holistic assessment and management of the range of patient concerns is needed in providing care for patients with CTCL and their family and friends.
Assuntos
Adaptação Psicológica , Atitude Frente a Saúde , Linfoma Cutâneo de Células T/psicologia , Prurido/psicologia , Neoplasias Cutâneas/psicologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Leitos , Efeitos Psicossociais da Doença , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Cutaneous T-cell lymphoma (CTCL) is a rare, progressive cancer that can be life limiting and highly disfiguring. Patients with CTCL experience poor quality of life; however, there is little published about the experiences of their families. OBJECTIVES: To describe the impact of CTCL on family members and how they cope and adjust, to inform support services. METHODS: Semistructured qualitative interviews were conducted with adult informal caregivers of patients with CTCL recruited via a supraregional CTCL clinic. Interviews explored the history of each patient's illness, the impact of CTCL on the patient and the family, and views about family support. Data were analysed thematically using the Family Adjustment and Adaptation Response model as an interpretative framework. RESULTS: Fourteen caregivers were interviewed (11 spouses, one friend, two daughters; 10 women, four men; all white British; aged 39-85 years). Three key themes emerged: (i) demands of CTCL (the disease, caregiving, financial impact, physical and emotional intimacy); (ii) family capabilities (family support, information, healthcare provider support, other coping strategies); and (iii) adjustment and adaptation (acceptance, changes in patient-caregiver relationship and family dynamics). CTCL was central in many aspects of caregivers' lives, particularly relationships, communication and intimacy. CONCLUSIONS: Our findings demonstrate the multiple demands that CTCL places on caregivers, the capabilities and resources they draw upon to cope, and the significant impact of CTCL on the family. To support families and patients, easily accessible services are needed that include the family in the unit of care, provide support and information, and understand the process of family adjustment and adaptation.
Assuntos
Cuidadores/psicologia , Efeitos Psicossociais da Doença , Linfoma Cutâneo de Células T/psicologia , Neoplasias Cutâneas/psicologia , Adaptação Psicológica , Adulto , Idoso , Idoso de 80 Anos ou mais , Atitude Frente a Saúde , Saúde da Família , Feminino , Amigos/psicologia , Humanos , Masculino , Pessoa de Meia-Idade , Núcleo Familiar/psicologia , Qualidade de Vida , Apoio Social , Cônjuges/psicologia , Inquéritos e QuestionáriosRESUMO
BACKGROUND: Primary cutaneous T-cell lymphoma (CTCL) is progressive, can cause significant symptoms, and impacts on quality of life. Therefore supportive and palliative care might have a role in the care of patients and families. OBJECTIVES: To identify and appraise the available peer-reviewed evidence on the supportive and palliative care needs of patients and their caregivers. METHODS: A systematic review of the literature was conducted. Extracted data from eligible papers were collated in themes relating to supportive and palliative care needs and outcomes for patients, informal caregivers, health professionals and reported service models. RESULTS: Eighteen retained papers reported a symptom or quality-of-life measure. Five reported only these measures, 13 reported outcomes in relation to an intervention. Systemic therapy targeted at disease remission was the most commonly reported intervention (12/13). No quality-of-life tool was consistently used. Pruritus was frequently reported as an outcome (n = 9) often using the visual analogue scale, VAS itch. Psychosocial, spiritual and caregiver needs were reported infrequently or not at all. CONCLUSIONS: No measure is routinely used to measure supportive and palliative care outcomes in CTCL. Physical needs, particularly pruritus, were reported commonly; however, qualitative evidence of experience is limited. Caregivers' needs are rarely explored. To compare outcomes from clinical studies, a single multidimensional tool used in routine practice would be useful. Further work is needed to explore a model of service that meets the specific physical, psychosocial and spiritual needs of this group of patients and their carers.
Assuntos
Cuidadores/psicologia , Linfoma Cutâneo de Células T/terapia , Cuidados Paliativos/normas , Neoplasias Cutâneas/terapia , Humanos , Linfoma Cutâneo de Células T/psicologia , Avaliação das Necessidades , Avaliação de Resultados da Assistência ao Paciente , Prurido/etiologia , Qualidade de Vida , Neoplasias Cutâneas/psicologia , Apoio Social , EspiritualidadeAssuntos
Hemorragia Gastrointestinal/terapia , Neoplasias/terapia , Cuidados Paliativos , Deficiência de Vitamina K/terapia , Vitamina K/uso terapêutico , Idoso , Idoso de 80 Anos ou mais , Feminino , Hemorragia Gastrointestinal/sangue , Hemorragia Gastrointestinal/complicações , Hemorragia Gastrointestinal/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias/sangue , Neoplasias/complicações , Neoplasias/patologia , Projetos Piloto , Resultado do Tratamento , Vitamina K/sangue , Deficiência de Vitamina K/sangue , Deficiência de Vitamina K/complicações , Deficiência de Vitamina K/patologiaRESUMO
PURPOSE: Tailored and specific interventions for informal caregivers in palliative care are rare. We aimed to generate evidence to inform a subsequent appropriate intervention based on caregivers' experiences. METHOD: Single, semi-structured qualitative interviews were undertaken with 20 informal cancer caregivers of home cancer palliative care. RESULTS: Carers reported the need to be prepared for their caring role, to be visible to professionals, to receive clear and specific information about the patient's condition, and to be emotionally supported. They described challenges as uncertainty, distress at witnessing disease progression and the daily struggle with financial issues, personal time, own health and sleep problems. CONCLUSIONS: Considering the time pressures and restricted caregiver time, the intervention should be brief and should aim to enhance their visibility as service recipients, patient-specific information giving, preparation for their role, and emotional support.
Assuntos
Cuidadores/educação , Serviços de Assistência Domiciliar , Avaliação das Necessidades , Neoplasias/enfermagem , Cuidados Paliativos , Adulto , Idoso , Cuidadores/psicologia , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pesquisa Qualitativa , Reino UnidoRESUMO
PURPOSE: The relative biological effectiveness of two epithermal neutron sources, a reactor based source at Studsvik, Sweden, and a proton accelerator-based source in Birmingham, UK, was studied in relation to the proportional absorbed dose distribution as a function of neutron energy. Evidence for any interactions between the effects of biological damage induced by high- and low-linear energy transfer (LET) dose components, in this 'mixed field' irradiation, was also examined MATERIALS AND METHODS: Clonogenic survival in Chinese Hamster-derived V79 cells was used to assess biological effectiveness in this study. Cells were irradiated in suspension at 4 °C at depths of 20, 35, 50 and 65 mm in a water phantom. This prevented the repair of sublethal damage, predominantly that produced by both incident and induced γ-rays in the field, over the variable periods of exposure required to irradiate cells with the same total absorbed dose. Cell survival, as a function of the absorbed radiation dose and depth in the phantom, was compared with Monte Carlo N-Particle (MCNP) calculations of the proportional absorbed dose distribution as a function of neutron energy for the two sources. RESULTS: In terms of the dose-related reduction in clonogenic cell survival, the epithermal neutron source at Studsvik was more biologically effective than the Birmingham source at all depths considered in the phantom. Although the contribution from the high-LET dose component was greater for the Studsvik source at 20 mm depth in the phantom, at greater depths the dose contribution from the high-LET dose component at Studsvik overlap with those for the Birmingham source. However, the most striking difference is in the fast neutron component to the dose of the two sources, neutron energies>1 MeV were only associated with the Studsvik source. The relative biological effectiveness (RBE) of both sources declined slightly with depth in the phantom, as the total high-LET dose component declined. The maximum source RBE for Studsvik was 2.70±0.50 at 20 mm; reduced to 2.10±0.35 at depths of 50 and 65 mm. The corresponding values for Birmingham were 1.68±0.25 and 1.31±0.19, all values relate only to the surviving fraction of V79 cells at 37%, since RBE values are only applicable to the selected endpoint. Based on a dose reduction factor (DRF) of 1.0 for the total low-LET component to the absorbed dose, the RBE values for the high-LET dose component (fast neutrons and induced protons from the nitrogen capture reaction) was 14.5 and 7.05 for the Studsvik and Birmingham neutron sources, respectively. This is well outside the range of RBE historically reported values for V79 cells for the same level of cell survival for fast neutrons. The calculation of RBE values, based on the proportional absorbed dose distribution as a function of neutron energy, from historical data, and using a RBE of 1.8 for the dose from the nitrogen capture reaction, suggests RBE values for the total high-LET dose component of 3.1-2.8 and 2.5-2.0 for Studsvik and Birmingham, respectively, values again declining with depth in the phantom. CONCLUSIONS: The overall biological effectiveness of the mixed field irradiation from an epithermal neutron sources depends on the composition and quality of the different dose components. The experimentally derived RBE values for the total high-LET dose components in these 'mixed field' irradiations are well in excess of historical data for fast neutrons. The difference between the historically expected and the observed RBE values is attributed to the interactions between the damage produced by high- and low-LET radiation.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Nêutrons Rápidos , Fibroblastos/efeitos da radiação , Transferência Linear de Energia , Animais , Linhagem Celular , Sobrevivência Celular/efeitos da radiação , Cricetinae , Cricetulus , Relação Dose-Resposta à Radiação , Fibroblastos/citologia , Fibroblastos/metabolismo , Método de Monte Carlo , Imagens de Fantasmas , Prótons , Eficiência Biológica RelativaRESUMO
BACKGROUND: Many patients with advanced cancer are malnourished. Anorexia is common, as is the use of chemotherapy, which may cause nausea and poor appetite. Ten per cent of these patients experience haemorrhagic events. AIM: Since vitamin K deficiency (VKD) causes bleeding, to establish the prevalence of VKD in patients with advanced cancer receiving palliative care. METHODS: Serum concentrations of vitamin K(1) and undercarboxylated factor II (PIVKA-II) were determined in 46 (17 male/29 female) inpatients aged 26-85 (mean 58) years. INR and liver function tests (bilirubin, ALT, GGT and ALP) were also performed. RESULTS: Vitamin K(1) was below the lower limit of the reference range (0.33 nmol/l) in 22% of patients. 78% of patients had some degree of functional VKD indicated by raised (>0.2 AU/ml) PIVKA-II. Six patients (13%) had a prolonged INR, all of whom had raised PIVKA-II and GGT; 4 also had vitamin K(1) <0.33 nmol/l. Three patients (6.5%) had clinically significant VKD characterised by INR >1.5, PIVKA-II >10 AU/ml, and undetectable vitamin K(1). CONCLUSIONS: Patients with advanced cancer are prone to VKD which, while usually subclinical, may develop to a clinically relevant prolongation of the INR. Serum measurements of vitamin K(1) and PIVKA-II can be used to detect VKD and monitor vitamin K status before an increased risk of bleeding develops.
Assuntos
Transtornos Hemostáticos/etiologia , Neoplasias/complicações , Cuidados Paliativos , Deficiência de Vitamina K/etiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores/sangue , Feminino , Humanos , Coeficiente Internacional Normatizado , Masculino , Pessoa de Meia-Idade , Neoplasias/sangue , Precursores de Proteínas/sangue , Protrombina , Vitamina K 1/sangue , Deficiência de Vitamina K/sangue , Deficiência de Vitamina K/diagnósticoRESUMO
This study aimed to define and prioritize the need for specialist palliative care (SPC) in cancer outpatient clinics. A validated assessment tool, the Symptoms and Concerns Checklist, was used to determine the prevalence and severity of symptoms and concerns. The checklist was completed by 480 outpatients with a cancer diagnosis. Sixty patients from each of eight primary tumour groups (lung, breast, gastrointestinal, gynaecological, urological, head and neck, brain and lymphoma) were recruited. The majority of patients (over 90%) rated 27 of the 29 checklist items, reporting a mean of 10 items as current problems. The influences of disease site and status, demographic factors and treatment on the number and type of symptoms and concerns reported were investigated. The highest number of symptoms and concerns and most severe problems were reported by patients with lung cancer, followed by those with brain tumours; the lowest by those with lymphoma and urological tumours. A high proportion of patients (83%) reported one or more items likely to benefit from SPC intervention. The results of this study suggest an extensive need for better symptom control in all cancer outpatients and in centres where SPC resources are limited, priority could be given to patients attending lung and brain tumour clinics.
Assuntos
Avaliação das Necessidades , Neoplasias/terapia , Cuidados Paliativos , Inquéritos e Questionários , Adulto , Fatores Etários , Idoso , Fadiga , Feminino , Identidade de Gênero , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias/psicologia , Análise de Regressão , Estresse PsicológicoRESUMO
This study explores the similarities and differences between subjective assessments of dyspnoea and objective spirometric indices of respiratory function in advanced cancer. Of 155 patients investigated, 71 (46%) were dyspnoeic and 108 (70%) had spirometry (94 post-salbutamol). Of the 94, 84 had height and weight measured to calculate predicted spirometry. Average dyspnoea levels over 24 h were measured by patient visual analogue scales (VASMe 24). Forced expiratory volume after 1 s (FEV1) and forced vital capacity (FVC) were almost always lower than predicted, indicating frequent impaired respiratory function. Mean spirometric increase post-salbutamol was 21% for FEV1 and 12% for FVC. Correlations between VAS dyspnoea scores and spirometry were low; hence, the latter cannot be relied upon as a measure of the former. Respiratory impairment tended to be obstructive (mean FEV1/FVC = 65%).
Assuntos
Albuterol , Broncodilatadores , Dispneia/diagnóstico , Neoplasias/complicações , Espirometria/métodos , Doença Crônica , Feminino , Volume Expiratório Forçado/fisiologia , Humanos , Masculino , Neoplasias/fisiopatologia , Cuidados Paliativos , Estudos Prospectivos , Assistência Terminal , Capacidade Vital/fisiologiaRESUMO
With a growing interest in the use of accelerator-based epithermal neutron sources for BNCT programs, in particular those based upon the 7Li(p,n)7Be reaction, there is a need to address the question of "what is the best proton energy to use?" This paper considers this question by using radiation transport calculations to investigate a range of proton energies from 2.15 to 3.5 MeV and a range of moderator sizes. This study has moved away completely from the use of empty therapy beam parameters and instead defines the beam quality and optimizes the moderator design using widely accepted in-phantom treatment planning figures of merit. It is concluded that up to a proton energy of about 2.8 MeV there is no observed variation in the achievable therapy beam quality, but a price is paid in terms of treatment time for not choosing the upper limit of this range. For higher proton energies, the beam quality falls, but with no improvement in treatment time for optimum configurations.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Berílio , Fenômenos Biofísicos , Biofísica , Terapia por Captura de Nêutron de Boro/instrumentação , Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Neoplasias Encefálicas/radioterapia , Simulação por Computador , Humanos , Lítio , Imagens de Fantasmas , Prótons , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Radioterapia de Alta Energia/instrumentação , Radioterapia de Alta Energia/métodos , Radioterapia de Alta Energia/estatística & dados numéricosRESUMO
The absorbed dose in a phantom or patient in boron neutron capture therapy (BNCT) and boron neutron capture enhanced fast neutron therapy (BNCEFNT) is deposited by gamma rays, neutrons of a range of energies and the 10B reaction products. These dose components are commonly measured with paired (TE/Mg) ion chambers and foil activation technique. In the present work, we have investigated the use of paired tissue equivalent (TE) and TE+ l0B proportional counters as an alternate and complementary dosimetry technique for use in these neutron beams. We first describe various aspects of counter operation, uncertainties in dose measurement, and interpretation of the data. We then present measurements made in the following radiation fields: An epithermal beam at the University of Birmingham in the United Kingdom, a d(48.5) + Be fast neutron therapy beam at Harper Hospital in Detroit, and a 252Cf radiation field. In the epithermal beam, our measured gamma and neutron dose rates compare very well with the values calculated using Monte Carlo methods. The measured 10B dose rates show a systematic difference of approximately 35% when compared to the calculations. The measured neutron+gamma dose rates in the fast neutron beam are in good agreement with those measured using a calibrated A-150 TEP (tissue equivalent plastic) ion chamber. The measured 10B dose rates compare very well with those measured using other methods. In the 252Cf radiation field, the measured dose rates for all three components agree well with other Monte Carlo calculations and measurements. Based on these results, we conclude that the paired low-pressure proportional counters can be used to establish an independent technique of dose measurement in these radiation fields.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Terapia por Captura de Nêutron de Boro/instrumentação , Califórnio/uso terapêutico , Nêutrons Rápidos , Raios gama , Imagens de Fantasmas , Prótons , Radiometria/instrumentação , Dosagem RadioterapêuticaRESUMO
Near-field designs of Fresnel and Gabor zone plates are computationally analyzed by using versions that allow the foci to be brought closer to the plate than in the usual far-field applications. It is found that the Fresnel plate has a dominant primary conjugate pair of foci well inside the far-field region and a more intense primary focus and smaller off-focal-plane sidelobes than the near-field Gabor systems, thus yielding a superior imaging performance.
Assuntos
Modelos Teóricos , Radiação , Fenômenos Eletromagnéticos , Análise de FourierRESUMO
This paper is concerned with the proposed Birmingham accelerator-based epithermal neutron beam for boron neutron capture therapy (BNCT). In particular, the option of producing a therapy beam at an orthogonal direction to the incoming protons is considered. Monte Carlo radiation transport simulations, both with and without a head phantom, have shown that an orthogonal beam geometry is not only acceptable but is indeed beneficial, in terms of a lower mean neutron energy and an enhanced therapeutic ratio for the same useful neutron fluence in the therapy beam. Typical treatment times for various beam options have been calculated, and range from 20 to 48 min with a 5 mA beam of 2.8 MeV protons, if the maximum photon-equivalent dose delivered to healthy tissue is to be 12.6 Gy Eq. The effects of proton beam diameter upon the therapy beam parameters have also been considered.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Nêutrons , Aceleradores de Partículas/instrumentação , Terapia por Captura de Nêutron de Boro/instrumentação , Simulação por Computador , Relação Dose-Resposta à Radiação , Transferência de Energia , Método de Monte Carlo , Imagens de Fantasmas , Prótons , Dosagem RadioterapêuticaRESUMO
This paper is concerned with the proposed Birmingham accelerator-based epithermal neutron beam for boron neutron capture therapy (BNCT). Details of the final moderator design, such as beam delimiter, shield, and beam exit surface shape are considered. Monte Carlo radiation transport simulations with a head and body phantom have shown that a simple flat moderator beam exit surface is preferable to the previously envisioned spherical design. Dose rates to individual body organs during treatment have been calculated using a standard MIRD phantom. We have shown that a simple polyethylene shield, doped with natural lithium, is sufficient to provide adequate protection to the rest of the body during head irradiations. The effect upon the head phantom dose distributions of the use of such a shield to delimit the therapy beam has been evaluated.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Nêutrons , Aceleradores de Partículas/instrumentação , Simulação por Computador , Relação Dose-Resposta à Radiação , Transferência de Energia , Método de Monte Carlo , Imagens de Fantasmas , PrótonsRESUMO
This paper presents the results of an experimental investigation into the performance of the Birmingham accelerator-based epithermal BNCT beam. In-phantom gold foil activation and boron trifluoride tube measurements have been used. The results have been compared with calculated response rates using Monte Carlo modeling of the entire neutron system from source to phantom and detector. The excellent agreement obtained gives us confidence in the validity of the simulations and our ability to predict accurately the neutronic performance of our BNCT facility.
Assuntos
Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Fenômenos Biofísicos , Biofísica , Boranos , Terapia por Captura de Nêutron de Boro/instrumentação , Ouro , Humanos , Modelos Teóricos , Método de Monte Carlo , Imagens de FantasmasRESUMO
This paper describes a method by which the activity of an immobilized enzyme can be modulated electrochemically at an electrode. The particular example studied, involving the enzyme firefly luciferase being immobilized in a gelatin film of thickness <1 µm, provides a useful model system since changes in the catalytic activity can be measured instantaneously through the natural bioluminescent emission. Using this biointerfacial arrangement, we have been able to demonstrate the reversible switching off and on of the enzyme's activity. Through a series of mechanistic studies, we have been able to determine that the bioluminescence response is modulated (on long time scales) as a consequence of the electrochemical depletion of protons at the electrode interface resulting in a local increase in pH.