Selected and shared hematological responses to apnea in elite human free divers and northern elephant seals (Mirounga angustirostris).

Despite elite human free divers achieving incredible feats in competitive free diving, there has yet to be a study that compares consummate divers, (i.e. northern elephant seals) to highly conditioned free divers (i.e., elite competitive free-diving humans). Herein, we compare these two diving models and suggest that hematological traits detected in seals reflect species-specific specializations, while hematological traits shared between the two species are fundamental mammalian characteristics. Arterial blood samples were analyzed in elite human free divers (n = 14) during a single, maximal volitional apnea and in juvenile northern elephant seals (n = 3) during rest-associated apnea. Humans and elephant seals had comparable apnea durations (∼6.5 min) and end-apneic arterial Po2 [humans: 40.4 ± 3.0 mmHg (means ± SE); seals: 27.1 ± 5.9 mmHg; P = 0.2]. Despite similar increases in arterial Pco2 (humans: 33 ± 5%; seals: 16.3 ± 5%; P = 0.2), only humans experienced reductions in pH from baseline (humans: 7.45 ± 0.01; seals: 7.39 ± 0.02) to end apnea (humans: 7.37 ± 0.01; seals: 7.38 ± 0.02; P < 0.0001). Hemoglobin P50 was greater in humans compared to elephant seals (29.9 ± 1.5 and 28.7 ± 0.6 mmHg, respectively; P = 0.046). Elephant seals overall had higher carboxyhemoglobin (COHb) levels (5.9 ± 2.6%) compared to humans (0.8 ± 1.2%; P < 0.0001); however, following apnea, COHb was reduced in seals (baseline: 6.1 ± 0.3%; end apnea: 5.6 ± 0.3%) and was slightly elevated in humans (baseline: 0.7 ± 0.1%; end apnea: 0.9 ± 0.1%; P < 0.0002, both comparisons). Our data indicate that during static apnea, seals have reduced hemoglobin P50, greater pH buffering, and increased COHb levels. The differences in hemoglobin P50 are likely due to the differences in the physiological environment between the two species during apnea, whereas enhanced pH buffering and higher COHb may represent traits selected for in elephant seals.NEW & NOTEWORTHY This study uses similar methods and protocols in elite human free divers and northern elephant seals. Using highly conditioned divers (elite free-diving humans) and highly adapted divers (northern elephant seals), we explored which hematological traits are fundamentally mammalian and which may have been selected for. We found differences in P50, which may be due to different physiological environments between species, while elevated pH buffering and carbon monoxide levels might have been selected for in seals.

Self-calibrated pulse oximetry algorithm based on photon pathlength change and the application in human freedivers.

Significance: Pulse oximetry estimates the arterial oxygen saturation of hemoglobin (SaO2) based on relative changes in light intensity at the cardiac frequency. Commercial pulse oximeters require empirical calibration on healthy volunteers, resulting in limited accuracy at low oxygen levels. An accurate, self-calibrated method for estimating SaO2 is needed to improve patient monitoring and diagnosis. Aim: Given the challenges of calibration at low SaO2 levels, we pursued the creation of a self-calibrated algorithm that can effectively estimate SaO2 across its full range. Our primary objective was to design and validate our calibration-free method using data collected from human subjects. Approach: We developed an algorithm based on diffuse optical spectroscopy measurements of cardiac pulses and the modified Beer-Lambert law (mBLL). Recognizing that the photon mean pathlength (⟨L⟩) varies with SaO2 related absorption changes, our algorithm aligns/fits the normalized ⟨L⟩ (across wavelengths) obtained from optical measurements with its analytical representation. We tested the algorithm with human freedivers performing breath-hold dives. A continuous-wave near-infrared spectroscopy probe was attached to their foreheads, and an arterial cannula was inserted in the radial artery to collect arterial blood samples at different stages of the dive. These samples provided ground-truth SaO2 via a blood gas analyzer, enabling us to evaluate the accuracy of SaO2 estimation derived from the NIRS measurement using our self-calibrated algorithm. Results: The self-calibrated algorithm significantly outperformed the conventional method (mBLL with a constant ⟨L⟩ ratio) for SaO2 estimation through the diving period. Analyzing 23 ground-truth SaO2 data points ranging from 41% to 100%, the average absolute difference between the estimated SaO2 and the ground truth SaO2 is 4.23%±5.16% for our algorithm, significantly lower than the 11.25%±13.74% observed with the conventional approach. Conclusions: By factoring in the variations in the spectral shape of ⟨L⟩ relative to SaO2, our self-calibrated algorithm enables accurate SaO2 estimation, even in subjects with low SaO2 levels.

Cardiorespiratory coupling in the bottlenose dolphin (Tursiops truncatus).

Introduction: The bottlenose dolphin (Tursiops truncatus) is an intermittent breather, where the breath begins with an exhalation followed by inhalation and an extended inter-breath interval ranging from 10 to 40 s. Breathing has been shown to alter both the instantaneous heart rate (if H) and stroke volume (iSV) in the bottlenose dolphin, with a transitory ventilatory tachycardia following the breath, and an exponential decrease to a stable if H around 40 beats • min-1 during the inter-breath period. As the total breath duration in the dolphin is around 1 s, it is not possible to assess the contribution of exhalation and inhalation to these changes in cardiac function during normal breathing. Methods: In the current study, we evaluated the if H response by separating expiration and inspiration of a breath, which allowed us to distinguish their respective contribution to the changes in if H. We studied 3 individual male bottlenose dolphins trained to hold their breath between the different respiratory phases (expiration and inhalation). Results: Our data show that inspiration causes an increase in if H, while expiration appears to result in a decrease in if H. Discussion: These data provide improved understanding of the cardiorespiratory coupling in dolphins, and show how both exhalation and inhalation alters if H.

Evaluating feasibility of functional near-infrared spectroscopy in dolphins.

Significance: Using functional near-infrared spectroscopy (fNIRS) in bottlenose dolphins (Tursiops truncatus) could help to understand how echolocating animals perceive their environment and how they focus on specific auditory objects, such as fish, in noisy marine settings. Aim: To test the feasibility of near-infrared spectroscopy (NIRS) in medium-sized marine mammals, such as dolphins, we modeled the light propagation with computational tools to determine the wavelengths, optode locations, and separation distances that maximize sensitivity to brain tissue. Approach: Using frequency-domain NIRS, we measured the absorption and reduced scattering coefficient of dolphin sculp. We assigned muscle, bone, and brain optical properties from the literature and modeled light propagation in a spatially accurate and biologically relevant model of a dolphin head, using finite-element modeling. We assessed tissue sensitivities for a range of wavelengths (600 to 1700 nm), source-detector distances (50 to 120 mm), and animal sizes (juvenile model 25% smaller than adult). Results: We found that the wavelengths most suitable for imaging the brain fell into two ranges: 700 to 900 nm and 1100 to 1150 nm. The optimal location for brain sensing positioned the center point between source and detector 30 to 50 mm caudal of the blowhole and at an angle 45 deg to 90 deg lateral off the midsagittal plane. Brain tissue sensitivity comparable to human measurements appears achievable only for smaller animals, such as juvenile bottlenose dolphins or smaller species of cetaceans, such as porpoises, or with source-detector separations ≫100 mm in adult dolphins. Conclusions: Brain measurements in juvenile or subadult dolphins, or smaller dolphin species, may be possible using specialized fNIRS devices that support optode separations of >100 mm. We speculate that many measurement repetitions will be required to overcome hemodynamic signals originating predominantly from the muscle layer above the skull. NIRS measurements of muscle tissue are feasible today with source-detector separations of 50 mm, or even less.

Substantial HbA1c Reduction Following Intermittent-Scanning Continuous Glucose Monitoring Was Not Associated With Early Worsening of Retinopathy in Type 1 Diabetes.

BACKGROUND: Early worsening of diabetic retinopathy (EWDR) was observed in the intensively treated arm of the Diabetes Control and Complications Trial (DCCT) before long-term benefits accrued. We sought to assess whether there may be an increased risk of EWDR in high-risk individuals following intermittent-scanning continuous glucose monitoring (iscCGM) commencement. METHODS: An observational study of 139 individuals with type 1 diabetes ≥5 years duration and with baseline HbA1c >75 mmol/mol (9.0%). This cohort was stratified by subsequent HbA1c response to iscCGM (best responders and non-responders). Pan-retinal photocoagulation (PRP), worsening retinopathy status and new development of retinopathy were compared between groups. RESULTS: HbA1c change was -23 mmol/mol (IQR -32 to -19) (-2.1% [-2.9 to -1.8]) in responders and +6 mmol/mol (2-12) (+0.6 [0.2-1.1]) in non-responders (P < .001). There was no difference in subsequent PRP between responders (14.1%) and non-responders (10.3%, P = .340). Baseline HbA1c (HR 1.052 per mmol/mol, P = .002) but not response category (HR 1.244, P = .664) was independently associated with the risk of requiring PRP. Worsening of retinopathy was not different between responders (16.9%) and non-responders (20.6%, P = .577), and the same was true with respect to new development of retinopathy (33.3% vs 31.8%, P = .919). CONCLUSIONS: In a cohort enriched for risk of diabetic retinopathy, reduction in HbA1c did not result in an increased risk of PRP, worsening retinopathy, or new development of retinopathy. These findings offer reassurance that substantial reduction in HbA1c is not independently associated with early worsening of diabetic eye disease in iscCGM users.

Partial pressure of oxygen in adipose tissue and its relationship with fatness in a natural animal model of extreme fat deposition, the grey seal.

Excessive adiposity is associated with altered oxygen tension and comorbidities in humans. In contrast, marine mammals have high adiposity with no apparent detrimental effects. However, partial pressure of oxygen (Po2 ) in their subcutaneous adipose tissue (blubber) and its relationship with fatness have not been reported. We measured Po2 and temperature at different blubber depths in 12 healthy juvenile grey seals. Fatness was estimated from blubber thickness and morphometric parameters. Simultaneously, we monitored breathing pattern; heart rate and arterial blood saturation with a pulse oximeter; and relative changes in total hemoglobin, deoxyhemoglobin, and oxyhemoglobin in blubber capillaries using near-infrared spectroscopy (NIRS) as proxies for local oxygenation changes. Blubber Po2 ranged from 14.5 to 71.4 mmHg (39.2 ± 14.1 mmHg), which is similar to values reported in other species. Blubber Po2 was strongly and negatively associated with fatness (LME: p < 0.0001, R2marginal = 0.53, R2conditional = 0.64, n = 10), but not with blubber depth. No other parameters explained variability in Po2 , suggesting arterial blood and local oxygen delivery did not vary within and between measurements. The fall in blubber Po2 with increased fatness in seals is consistent with other animal models of rapid fat deposition. However, the Po2  levels at which blubber becomes hypoxic and consequences of low blubber Po2 for its health and function, particularly in very fat individuals, remain unknown. How seals avoid detrimental effects of low oxygen tension in adipose tissue, despite their high and fluctuating adiposity, is a fruitful avenue to explore.

Shining new light on sensory brain activation and physiological measurement in seals using wearable optical technology.

Sensory ecology and physiology of free-ranging animals is challenging to study but underpins our understanding of decision-making in the wild. Existing non-invasive human biomedical technology offers tools that could be harnessed to address these challenges. Functional near-infrared spectroscopy (fNIRS), a wearable, non-invasive biomedical imaging technique measures oxy- and deoxyhaemoglobin concentration changes that can be used to detect localized neural activation in the brain. We tested the efficacy of fNIRS to detect cortical activation in grey seals (Halichoerus grypus) and identify regions of the cortex associated with different senses (vision, hearing and touch). The activation of specific cerebral areas in seals was detected by fNIRS in responses to light (vision), sound (hearing) and whisker stimulation (touch). Physiological parameters, including heart and breathing rate, were also extracted from the fNIRS signal, which allowed neural and physiological responses to be monitored simultaneously. This is, to our knowledge, the first time fNIRS has been used to detect cortical activation in a non-domesticated or laboratory animal. Because fNIRS is non-invasive and wearable, this study demonstrates its potential as a tool to quantitatively investigate sensory perception and brain function while simultaneously recording heart rate, tissue and arterial oxygen saturation of haemoglobin, perfusion changes and breathing rate in free-ranging animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

Fur seals do, but sea lions don't - cross taxa insights into exhalation during ascent from dives.

Management of gases during diving is not well understood across marine mammal species. Prior to diving, phocid (true) seals generally exhale, a behaviour thought to assist with the prevention of decompression sickness. Otariid seals (fur seals and sea lions) have a greater reliance on their lung oxygen stores, and inhale prior to diving. One otariid, the Antarctic fur seal (Arctocephalus gazella), then exhales during the final 50-85% of the return to the surface, which may prevent another gas management issue: shallow-water blackout. Here, we compare data collected from animal-attached tags (video cameras, hydrophones and conductivity sensors) deployed on a suite of otariid seal species to examine the ubiquity of ascent exhalations for this group. We find evidence for ascent exhalations across four fur seal species, but that such exhalations are absent for three sea lion species. Fur seals and sea lions are no longer genetically separated into distinct subfamilies, but are morphologically distinguished by the thick underfur layer of fur seals. Together with their smaller size and energetic dives, we suggest their air-filled fur might underlie the need to perform these exhalations, although whether to reduce buoyancy and ascent speed, for the avoidance of shallow-water blackout or to prevent other cardiovascular management issues in their diving remains unclear. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.

When the human brain goes diving: using near-infrared spectroscopy to measure cerebral and systemic cardiovascular responses to deep, breath-hold diving in elite freedivers.

Continuous measurements of haemodynamic and oxygenation changes in free living animals remain elusive. However, developments in biomedical technologies may help to fill this knowledge gap. One such technology is continuous-wave near-infrared spectroscopy (CW-NIRS)-a wearable and non-invasive optical technology. Here, we develop a marinized CW-NIRS system and deploy it on elite competition freedivers to test its capacity to function during deep freediving to 107 m depth. We use the oxyhaemoglobin and deoxyhaemoglobin concentration changes measured with CW-NIRS to monitor cerebral haemodynamic changes and oxygenation, arterial saturation and heart rate. Furthermore, using concentration changes in oxyhaemoglobin engendered by cardiac pulsation, we demonstrate the ability to conduct additional feature exploration of cardiac-dependent haemodynamic changes. Freedivers showed cerebral haemodynamic changes characteristic of apnoeic diving, while some divers also showed considerable elevations in venous blood volumes close to the end of diving. Some freedivers also showed pronounced arterial deoxygenation, the most extreme of which resulted in an arterial saturation of 25%. Freedivers also displayed heart rate changes that were comparable to diving mammals both in magnitude and patterns of change. Finally, changes in cardiac waveform associated with heart rates less than 40 bpm were associated with changes indicative of a reduction in vascular compliance. The success here of CW-NIRS to non-invasively measure a suite of physiological phenomenon in a deep-diving mammal highlights its efficacy as a future physiological monitoring tool for human freedivers as well as free living animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Near-Infrared Spectroscopy as a Tool for Marine Mammal Research and Care.

Developments in wearable human medical and sports health trackers has offered new solutions to challenges encountered by eco-physiologists attempting to measure physiological attributes in freely moving animals. Near-infrared spectroscopy (NIRS) is one such solution that has potential as a powerful physio-logging tool to assess physiology in freely moving animals. NIRS is a non-invasive optics-based technology, that uses non-ionizing radiation to illuminate biological tissue and measures changes in oxygenated and deoxygenated hemoglobin concentrations inside tissues such as skin, muscle, and the brain. The overall footprint of the device is small enough to be deployed in wearable physio-logging devices. We show that changes in hemoglobin concentration can be recorded from bottlenose dolphins and gray seals with signal quality comparable to that achieved in human recordings. We further discuss functionality, benefits, and limitations of NIRS as a standard tool for animal care and wildlife tracking for the marine mammal research community.

Assessment of the effect of the COVID-19 lockdown on glycaemic control in people with type 1 diabetes using flash glucose monitoring.

AIM: To describe the effect of the stringent lockdown measures, introduced in the UK on 23 March 2020 to curtail the transmission of COVID-19, on glycaemic control in people with type 1 diabetes using flash glucose monitoring. METHODS: We undertook an observational study of 572 individuals with type 1 diabetes for whom paired flash glucose monitoring data were available between early March and May 2020. The primary outcome was change in flash glucose monitoring variables. We also assessed clinical variables associated with change in glycaemic control. RESULTS: Percentage of time in range increased between March and May 2020 [median (interquartile range) 53 (41-64)% vs 56 (45-68)%; P < 0.001], with associated improvements in standard deviation of glucose (P <0.001) and estimated HbA1c (P <0.001). There was a small reduction in the number of individuals meeting the hypoglycaemia target of <5% per day (64% vs 58%; P = 0.004). Comparing changes in flash glucose monitoring data from March to May in 2019 with the same period in 2020 confirmed that these differences were confined to 2020. Socio-economic deprivation was an independent predictor of a ≥5% reduction in time in range during lockdown (odds ratio 0.45 for people in the two most affluent Scottish Index of Multiple Deprivation quintiles; P <0.001). CONCLUSIONS: Lockdown was not associated with a significant deterioration in glycaemic control in people with type 1 diabetes using flash glucose monitoring. However, socio-economic deprivation appeared to increase the risk of decline in glycaemic control, which has implications for how support is focused in challenging times.

Socio-economic differences in cardiovascular disease risk factor prevalence in people with type 2 diabetes in Scotland: a cross-sectional study.

AIM: To describe the association between socio-economic status and prevalence of key cardiovascular risk factors in people with type 2 diabetes in Scotland. METHODS: A cross-sectional study of 264 011 people with type 2 diabetes in Scotland in 2016 identified from the population-based diabetes register. Socio-economic status was defined using quintiles of the area-based Scottish Index of Multiple Deprivation (SIMD) with quintile (Q)1 and Q5 used to identify the most- and least-deprived fifths of the population, respectively. Logistic regression models adjusted for age, sex, health board, history of cardiovascular disease and duration of diabetes were used to estimate odds ratios (ORs) for Q1 compared with Q5 for each risk factor. RESULTS: The mean (sd) age of the study population was 66.7 (12.8) years, 56% were men, 24% were in Q1 and 15% were in Q5. Crude prevalence in Q1/Q5 was 24%/8.8% for smoking, 62%/49% for BMI ≥ 30 kg/m2 , 44%/40% for HbA1c ≥ 58 mmol/mol (7.5%), 31%/31% for systolic blood pressure (SBP) ≥ 140 mmHg, and 24%/25% for total cholesterol ≥ 5 mmol/l, respectively. ORs [95% confidence intervals (CI)] were 3.08 (2.95-3.21) for current smoking, 1.48 (1.44-1.52) for BMI ≥ 30 kg/m2 , 1.11 (1.08-1.15) for HbA1c ≥ 58 mmol/mol (7.5%), 1.03 (1.00-1.06) for SBP ≥ 140 mmHg and 0.87 (0.84-0.90) for total cholesterol ≥ 5 mmol/l. CONCLUSIONS: Socio-economic deprivation is associated with higher prevalence of smoking, BMI ≥ 30 kg/m2 and HbA1c ≥ 58 mmol/mol (7.5%), and lower prevalence of total cholesterol ≥ 5 mmol/l among people with type 2 diabetes in Scotland. Effective approaches to reducing inequalities are required as well as reducing risk factor prevalence across the whole population.

Socio-economic status and mortality in people with type 1 diabetes in Scotland 2006-2015: a retrospective cohort study.

AIMS: To describe the association between socio-economic status and mortality in a nation-wide cohort of people with type 1 diabetes in Scotland and to compare patterns over time and with the general population. METHODS: A retrospective cohort study was performed using data for people with type 1 diabetes from a population-based register linked to mortality records. Socio-economic status was derived from quintiles of an area-based measure: the Scottish Index of Multiple Deprivation. Sex-specific directly age-standardized mortality rates for each Scottish Index of Multiple Deprivation quintile and rate ratios comparing the most vs least deprived quintile were calculated for two time periods: 2006-2010 and 2011-2015. Data for the population without type 1 diabetes between 2011 and 2015 were available for comparison. RESULTS: Data for 3802 deaths among 33 547 people with type 1 diabetes were available. The age-standardized mortality rate per 1000 person-years decreased over time (from 2006-2010 to 2011-2015) for men and women with type 1 diabetes: 24.8 to 20.2 and 22.5 to 17.6, respectively. Mortality in populations with and without type 1 diabetes was generally higher for men than women and was inversely associated with socio-economic status. Rate ratios for the most vs least deprived groups increased over time among people with type 1 diabetes (men: 2.49 to 2.81; women: 1.92 to 2.86) and were higher than among populations without type 1 diabetes in 2011-2015 (men: 2.06; women: 1.66). CONCLUSIONS: Socio-economic deprivation was associated with a steeper mortality gradient in people with type 1 diabetes than in the population without type 1 diabetes in Scotland. Age-standardized mortality has decreased over time but socio-economic inequalities may be increasing.

The effect of DAFNE education, continuous subcutaneous insulin infusion, or both in a population with type 1 diabetes in Scotland.

AIM: To investigate the effect of DAFNE and continuous subcutaneous insulin infusion in clinical practice. METHODS: Within NHS Lothian, continuous subcutaneous insulin infusion started in 2004 and DAFNE education began in 2006. We extracted anonymized data from the national database for all those aged > 18 years with type 1 diabetes having a Dose Adjustment For Normal Eating course or continuous subcutaneous insulin infusion start date (n = 4617). RESULTS: In total, 956 persons received DAFNE education, and 505 had received an insulin pump, 208 of whom had DAFNE education followed by insulin pump. Mean (SD) HbA1c before DAFNE education was 68 (15) mmol/mol (8.4% [1.4%]) and 66 (13) mmol/mol (8.2% [1.2%]) before continuous subcutaneous insulin infusion. In the year following DAFNE education, the mean fall in within-person HbA1c was 3.8 mmol/mol (95% CI 4.0 to 3.4; 0.3% [0.4% to 0.3%]). Those with the poorest control (HbA1c ≥ 85 mmol/mol [9.9%]) experienced the largest decline (15.7 mmol/mol [1.4%]). Those in the lowest HbA1c band at initiation (< 53 mmol/mmol [7.0%]) experienced a rise. In the year following continuous subcutaneous insulin infusion initiation there was a mean fall in within-person HbA1c of 6.6 mmol/mol (6.8 to 6.4; 0.6% [0.6% to 0.6%]). In those with the poorest control (HbA1c ≥ 85 mmol/mol [9.9%]), the mean fall in HbA1c was 22.2 mmol/mol (23 to 21; 2.0% [2.1% to 1.9%]). Continuous subcutaneous insulin infusion effectiveness was not different with or without DAFNE education. The effects of both interventions were sustained over 5 years. CONCLUSIONS: Both DAFNE education and insulin pump therapy had the greatest effect on HbA1c in those with higher baseline values. There was little difference to attained HbA1c when Dose Adjustment For Normal Eating education was introduced before insulin pump therapy.

Shining new light on mammalian diving physiology using wearable near-infrared spectroscopy.

Investigation of marine mammal dive-by-dive blood distribution and oxygenation has been limited by a lack of noninvasive technology for use in freely diving animals. Here, we developed a noninvasive near-infrared spectroscopy (NIRS) device to measure relative changes in blood volume and haemoglobin oxygenation continuously in the blubber and brain of voluntarily diving harbour seals. Our results show that seals routinely exhibit preparatory peripheral vasoconstriction accompanied by increased cerebral blood volume approximately 15 s before submersion. These anticipatory adjustments confirm that blood redistribution in seals is under some degree of cognitive control that precedes the mammalian dive response. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to ambient air. We suggest that this frequent and reproducible reoxygenation pattern, without access to ambient air, is underpinned by previously unrecognised changes in cerebral drainage. The ability to track blood volume and oxygenation in different tissues using NIRS will facilitate a more accurate understanding of physiological plasticity in diving animals in an increasingly disturbed and exploited environment.

Validation and determination of taselisib, a ß-sparing phosphoinositide 3-kinase (PI3K) inhibitor, in human plasma by LC-MS/MS.

A liquid chromatographic-tandem mass spectrometry (LC-MS/MS) method for the determination of taselisib (GDC-0032, RO5537381) concentrations in human plasma has been developed and validated to support bioanalysis of clinical samples. Solid phase extraction (SPE) was used to extract plasma samples (50µL) and the resulting samples were analyzed using reversed phase chromatography and mass spectrometry coupled with an atmospheric pressure chemical ionization interface. The mass analysis of taselisib was performed using multiple reaction monitoring transitions in positive ionization mode. The method was validated over the calibration curve range 0.400-400ng/mL using linear regression and 1/x(2) weighting. The within-run relative standard deviation (%RSD) ranged from 1.3 to 5.6%, while the between-run %RSD varied from 2.0 to 4.5% for LLOQ, low, medium, medium high and high QCs. The accuracy ranged from 94.7 to 100.3% of nominal for within-run and 96.0-99.0% of nominal for between-run for the same QCs. Extraction recovery of taselisib was between 83.8% and 92.9%. Stability of taselisib was established in human plasma for 977days at -20°C and -70°C and established in sample extracts for 96h when stored at 2 - 8°C. Stable-labeled internal standard was used to minimize matrix effects. Mean single dose pharmacokinetic parameters determined using this method for a phase I/II clinical trial were: Cmax=35.2ng/mL, AUC0-inf=1570ngh/mL, and T1/2=39.3h.