On the dysfunctional hemoglobins and cyanosis connection: practical implications for the clinical detection and differentiation of methemoglobinemia and sulfhemoglobinemia

Angiogenesis-elicited spectral responses of early invasive skin melanoma: Implications for the evaluation of lesion progression

Early invasive skin melanoma (EISM) associated with partial tumor invasion to the thin and optically complex papillary dermis (PD) represents a critical stage before the onset of metastasis. EISM lesions may be accompanied by angiogenesis, which can alter the PD's blood and fibril contents. A comprehensive understanding about these interconnected processes is essential for enhancing the efficacy of EISM optical evaluation methodologies. Employing a first-principles computational approach supported by measured data, we systematically assess the impact that angiogenesis can have on the EISM's spectral responses. Our findings indicate that these responses are discernibly affected by angiogenesis under distinct physiological conditions, with more substantial tissue alterations leading to accentuated spectral changes in the 550-600 nm region. Accordingly, we propose the use of a customized low-cost spectral index to monitor these processes. Furthermore, our investigation provides a high-fidelity in silico platform for interdisciplinary research on the photobiology of evolving skin melanomas.

Sulfhemoglobinemia in a 53-Year-Old With a History of Phenazopyridine Misuse

Sulfhemoglobin is formed by the irreversible bonding of sulfur atoms to the heme molecule. Oxygen is then unable to bind the heme molecule, rendering the hemoglobin molecule unable to carry oxygen. The most common etiology of sulfhemoglobinemia is the use/misuse of sulfur-containing medications such as AZO. Unlike methemoglobin, sulfhemoglobin, due to its irreversible binding, has no antidote, and the treatment is ultimately supportive. We present a case of a 53-year-old female who presented to the emergency room endorsing dysuria and was noted to have abnormally low oxygen saturation (SpO2) despite having high arterial oxygen pressure (PaO2) on blood gas. History was significant for dysuria developed while traveling and the use of over-the-counter AZO four times daily for the past 10 days. She was diagnosed with a presumed dyshemoglobinemia and, upon return of send-out labs, was confirmed to have sulfhemoglobinemia attributed to phenazopyridine. This case highlights the importance of the recognition of potential dyshemoglobinemias and consideration of sulfhemoglobinemia as a potential causative etiology, especially in patients taking sulfur-containing medications.

A 77-Year-Old Woman With Capillary Hypoxia and Perioral Cyanosis

CASE PRESENTATION

A 77-year-old woman with asthma, hypothyroidism, irritable bowel syndrome, overactive bladder, and multiple rheumatologic conditions was sent from the clinic to the ED for evaluation of hypoxia. In the clinic, she reported dizziness without shortness of breath and was noted to have perioral cyanosis with an oxygen saturation measured by pulse oximetry (Spo₂) of 80%. She was given a nonrebreather mask delivering oxygen at 8 L/min, but the Spo₂ remained at 77% to 82%. In the ED, the patient reported intermittent shortness of breath, 2 to 3 days of mild left lower extremity swelling, and a brief episode of lightheadedness earlier in the day that had since resolved. She denied fevers/chills, upper respiratory symptoms, and chest pain. She had been referred to the pulmonology clinic 3 years earlier to evaluate mild hypoxia with Spo₂ readings in the low 90% range, but pulmonary function testing failed to identify an etiology. There was no history of VTE. Her rheumatologic conditions included osteoarthritis, rheumatoid arthritis, Sjögren's syndrome, and fibromyalgia.

In Silico Assessment of Tanning Masking Effects on Skin Chromatic Attributes Elicited by Anemia and Hyperbilirubinemia

Changes in skin appearance are among the most recognizable symptoms of a number of medical conditions. The interpretation of such changes, however, may be inadvertently biased by normal physiological processes affecting skin optical properties. In this paper, we assess the impact of one of the most common of these processes, tanning, on variations in skin chromatic attributes elicited by two ubiquitous and serious medical conditions, anemia and hyperbilirubinemia. We employ a first-principles investigation approach centered on the use of predictive computer simulations of light and skin interactions, and on well-established colorimetry methods. In our in silico experiments, we considered skin chromatic attributes resulting from distinct anemia severity levels and hyperbilirubinemia tox-icity stages. Our findings highlight qualitative and quantitative aspects that need to be considered in the visual screening and monitoring of these conditions, notably when they occur with the concomitant presence of tanning-induced changes in the cutaneous tissues' melanin pigmentation and thickness.

Tanning-Elicited Variations in the Ultraviolet Absorption Spectra of the Cutaneous Tissues: Skin Photobiology and Photomedicine Implications

When ultraviolet radiation is absorbed within the cutaneous tissues, it can trigger a number of phenomena that can have detrimental or beneficial consequences to an individual's health. Tanning is among the most visually noticeable of these phenomena. It may result in significant changes in skin pigmentation and thickness. These spectrally-dependent physiological responses, in turn, can elicit variations in the ultraviolet absorption profiles of the cutaneous tissues and, consequently, alter the occurrence of other ultraviolet-induced photobiological processes such as the breaking of DNA strands and the synthesis of previtamin D3. These tanning-elicited variations in the cutaneous tissues' absorption profiles is often tied to the increased presence of melanin throughout these tissues. However, during the tanning, shifts in the relative content of this pigment within certain skin layers can also be observed. In particular, the stratum basale, the innermost epidermal layer where melanogenesis takes place, can have its relative melanin content significantly reduced in comparison with other epidermal layers. Since the aforementioned photobiological phenomena are preferentially brought about within this layer, such pigmentation shifts may have a more pivotal role in skin photobiology than has been assumed to date. Accordingly, in this work, we investigate the impact of spectrally-dependent tanning-elicited physiological responses, with a particular focus on the inter-layer melanin distribution patterns, on the absorption profiles of the main cutaneous tissues. We also examine how variations in these absorption profiles may alter the outcomes of photo-triggered phenomena associated with the onset of different medical conditions. Our findings are expected to contribute to the advance of the current understanding about skin photobiology, which is indispensable for the success of photomedicine initiatives involving this highly complex organ.

On the Sensitivity of Skin Spectral Responses to Variations in the Thickness of the Cutaneous Tissues

A wide range of devices are being routinely used in the noninvasive screening and monitoring of medical conditions through the analysis of skin spectral responses. The correct interpretation of these responses often depends on the availability of high-fidelity characterization datasets for the selected specimens. More specifically, the higher their fidelity, the more effective the quantification of changes observed in a given biophysical variable of interest. Skin thickness is among the most relevant of these parameters since it plays a pivotal role in the attenuation (scattering and absorption) of light traversing the cutaneous tissues. Transient and permanent physiological processes, such as tanning and ageing, can result in significant time-dependent thickness variations. These, in turn, can introduce biases in the comparison of skin spectral responses obtained at different time instances. In this paper, we investigate the impact of thickness variations on skin reflectance with respect to different regions of light spectrum. Our findings are expected to contribute to the mitigation of interpretation errors and, thus, to the enhancement of noninvasive screening and monitoring procedures based on skin spectral responses.

In Vivo Transcutaneous Monitoring of Hemoglobin Derivatives Using a Red-Green-Blue Camera-Based Spectral Imaging Technique

Cyanosis is a pathological condition that is characterized by a bluish discoloration of the skin or mucous membranes. It may result from a number of medical conditions, including disorders of the respiratory system and central nervous system, cardiovascular diseases, peripheral vascular diseases, deep vein thrombosis, and regional ischemia. Cyanosis can also be elicited from methemoglobin. Therefore, a simple, rapid, and simultaneous monitoring of changes in oxygenated hemoglobin and deoxygenated hemoglobin is useful for protective strategies against organ ischemic injury. We previously developed a red-green-blue camera-based spectral imaging method for the measurements of melanin concentration, oxygenated hemoglobin concentration (C_HbO), deoxygenated hemoglobin concentration (C_HbR), total hemoglobin concentration (C_HbT) and tissue oxygen saturation (StO₂) in skin tissues. We leveraged this approach in this study and extended it to the simultaneous quantifications of methemoglobin concentration (C_metHb), C_HbO, C_HbR, and StO₂. The aim of the study was to confirm the feasibility of the method to monitor C_metHb, C_HbO, C_HbR, C_HbT, and StO₂. We performed in vivo experiments using rat dorsal skin during methemoglobinemia induced by the administration of sodium nitrite (NaNO₂) and changing the fraction of inspired oxygen (FiO₂), including normoxia, hypoxia, and anoxia. Spectral diffuse reflectance images were estimated from an RGB image by the Wiener estimation method. Multiple regression analysis based on Monte Carlo simulations of light transport was used to estimate C_HbO, C_HbR, C_metHb, C_HbT, and StO₂. C_metHb rapidly increased with a half-maximum time of less than 30 min and reached maximal values nearly 60 min after the administration of NaNO₂, whereas StO₂ dramatically dropped after the administration of NaNO₂, indicating the temporary production of methemoglobin and severe hypoxemia during methemoglobinemia. Time courses of C_HbT and StO₂, while changing the FiO₂, coincided with well-known physiological responses to hyperoxia, normoxia, and hypoxia. The results indicated the potential of this method to evaluate changes in skin hemodynamics due to loss of tissue viability and vitality.