Arterial Hemoglobin Saturation Research Articles

Non-arterial line cardiac output calculation misclassifies exercise pulmonary hypertension and increases risk of data loss particularly in black, Scleroderma, and Raynaud's patients during invasive exercise testing.

The direct Fick principle is the standard for calculating cardiac output (CO) to detect CO-dependent conditions like exercise pulmonary hypertension (ePH). Fick COarterial incorporates arterial haemoglobin and oxygen saturation (SaO2) with oxygen consumption from exercise testing, while Fick COnon-arterial substitutes mixed venous haemoglobin and peripheral oxygen saturation (SpO2) in the absence of an arterial line. The decision to employ an arterial catheter for exercise testing varies, and discrepancies in oxygen saturation and haemoglobin between arterial and non-arterial methods may lead to differences in Fick CO, potentially affecting ePH classification. We performed a retrospective analysis of 296 consecutive invasive CPET (iCPET) studies comparing oxygen saturation from pulse oximetry and radial arterial, arterial haemoglobin and mixed venous haemoglobin, and CO calculated with arterial and non-arterial values. We assessed the risk of misclassification of pre- and post-capillary ePH, and data loss due to inaccurate SpO2. When considering all stages from rest to peak exercise arterial and mixed venous haemoglobin demonstrated high correlation, while SpO2 and SaO2, as well as COarterial and COnon-arterial demonstrated a low correlation. Data loss was significantly higher across all stages of exercise for SpO2 (n=346/1926,18%) compared to SaO2 (n=17/1923, 0.88%). We found that pre- and post-capillary exercise pulmonary hypertension were misclassified as COnon-arterial data (n=7/41, 17.1% and n=2/23, 8.7% respectively). Patients with scleroderma and/or Raynaud's (n=11/33, 33.3%), and Black patients (n=6/19, 31.6%) had more SpO2 data loss. Reliance upon SpO2 during invasive exercise testing results in the misclassification of pre- and post-capillary ePH, and unmeasurable SpO2 for Black, scleroderma and Raynaud's patients can preclude accurate exercise calculations, thus limiting the diagnostic and prognostic value of invasive exercise testing without an arterial line.

Evaluating the Accuracy of Off-Label Placement of Pulse Oximetry Sensors in Comparison to On-Label Placement in the Adult Cardiac Intensive Care Unit Patient Population.

Continuous pulse oximetry (Spo2) is a commonly utilized tool to obtain an indirect, noninvasive measurement of hemoglobin oxygen saturation. Difficulty obtaining measurement with Spo2 sensors can lead nurses to try off-label sites until they find placement that provides a signal. Currently, there is limited evidence to support this application. The purpose of this study was to evaluate the accuracy of off-label placement of pulse oximetry sensors in comparison to on-label placement in adult cardiac intensive care patients. Data were collected on 24 participants. At the time of a medically necessary arterial blood gas laboratory draws, 4 Spo2 measurements were gathered from an on-label finger sensor, an off-label finger sensor, an on-label ear sensor, and an off-label ear sensor. Results were analyzed using 4 Pearson correlation coefficients, Bland-Altman plots, and 2 linear mixed-effect models. Our study found that while both our on-label finger and off-label finger pulse oximetry sensor overestimated when compared to the arterial hemoglobin saturation (gold standard), there was greater overestimation found with the off-label placement. Though there was not a significant difference observed between the ear probe on the nose and the gold standard, figures examining off-label ear probe and gold standard measures show that, in lower ranges of oxygen saturation, the off-site probe substantially overestimates true oxygen saturation, while in higher ranges of oxygen saturation, the off-site ear probe underestimates true oxygen saturation. No changes should be made to the current practice of using pulse oximetry sensor placement.

Efficacy of intravenous iron therapy compared to usual treatment in iron deficient adult cyanotic congenital heart disease patients for improvement in clinical outcomes at three months

Abstract Background Iron deficiency is frequent in CCHD patients and is associated with poorer outcomes. Patients with iron deficiency anaemia are treated with oral iron which results in improved clinical outcomes. The use of intravenous iron in CCHD patients is not well studied. Purpose We aimed to compare effectiveness of intravenous iron with usual care (i.e., no therapy for CCHD patients with iron deficiency without anemia, and oral iron therapy for CCHD patients with iron deficiency anemia) on 6-minute walk distance(6MWD) after 3 months of treatment, improvement in arterial Haemoglobin saturation, Quality of life, WHO functional class and safety of intravenous Iron. Methods We enrolled 27 patients of which 13 were randomized to IV iron arm and 14 to usual treatment arm. The mean age (±SD) of enrolled patient was 23.3 (±5.55) years. 24 out of 27 patients (88.9%) were Eisenmenger Syndrome patients, while the other three patients were TOF with pulmonary atresia, DORV with pulmonary atresia and post-Fontan. 6MWD was performed to access functional capacity and WHOQOL-BREF questionnaire was used for assessment of quality of life. All the clinical findings, data and test recordings were repeated after three months. Results The mean (±SD) haemoglobin(Hb) of patients included in the study was 16.7 (±2.0) g/dl. The Hb levels improved by 0.91 (±0.85) g/dl in patients who received any form of iron therapy (IV or oral iron). Hb improvement was not significantly different between those who received IV or oral iron [IV iron: 1.15 (±0.88) g/dl, Oral iron: 0.59 (±0.79) g/dl; p= 0.12]. The baseline 6MWD was not different in both the arms (p= 0.639). The mean (±SD) 6MW distance covered in IV iron arm and usual treatment arm was 401 (±35.2) m and 408.6 (±46.5) m respectively at baseline, which improved to 425 (±28.7) m and 421.5 (±43.2) m respectively at 3 months follow up. The change in 6MWD in IV iron arm and usual treatment arm was 24 (±22.3) m and 13.1 (±16.4) m respectively. The difference of change in 6MWD between the two arms was non-significant (p= 0.157). There was a significant improvement in WHOQOL-BREF Score Domains 2,3 and 4 and there was a trend towards improvement on Domain 1 score in IV iron arm compared to usual treatment arm. WHO functional class was similar at baseline in both arms (p= 0.534). The change in WHO functional class at follow up was similar in both arms (p= 0.082) Conclusion This study demonstrated no improvement in clinical outcomes of 6MW distance, arterial hemoglobin saturation and WHO functional class. However, there was significant improvement in quality of life and iv iron was found safe and equally efficacious as oral iron for correcting iron deficiency. Further studies for determining ideal hemoglobin levels and dose of iron in CCHD patients are pertinent.

Ventilatory function and oxygen delivery at high altitude in the Himalayas

This study aimed to evaluate changes in lung function assessed by spirometry and blood gas content in healthy high-altitude sojourners during a trek in the Himalayas. A group of 19 Italian adults (11 males and 8 females, mean age 43 ± 15 years, and BMI 24.2 ± 3.7 kg/m2) were evaluated as part of a Mount Everest expedition in Nepal. Spirometry and arterial blood gas content were evaluated at baseline in Kathmandu (≈1400 m), at the Pyramid Laboratory - Observatory (peak altitude of ≈5000 m), and on return to Kathmandu 2–3 days after arrival at each site. All participants took 250 mg of acetazolamide per os once daily during the ascent. We found that arterial hemoglobin saturation, O2 and CO2 partial pressures, and the bicarbonate level all decreased (in all cases, p < 0.001 with R2 =0.70–0.90), while pHa was maintained stable at the peak altitude. Forced vital capacity (FVC) remained stable, while forced expiratory volume in 1 s (FEV1) decreased (p = 0.010, n2p =0.228), resulting in a lower FEV1/FVC ratio (p < 0.001, n2p =0.380). The best predictor for acute mountain sickness was the O2 partial pressure at the peak altitude (p = 0.004, R2 =0.39). Finger pulse oximetry overestimated peripheral saturation relative to arterial saturation. We conclude that high-altitude hypoxia alters the respiratory function and the oxygen saturation of the arterial blood hemoglobin. Additionally, air rarefaction and temperature reduction, favoring hypoxic bronchoconstriction, could affect respiration. Pulse oximetry seems not enough to assist medical decisions at high altitudes.

Reliability of pulse oximetry at four different attachment sites in immobilized white rhinoceros (Ceratotherium simum)

ObjectivesTo determine the reliability of peripheral oxygen haemoglobin saturation (SpO2), measured by a Nonin PalmSAT 2500A pulse oximeter with 2000T transflectance probes at four attachment sites (third eyelid, cheek, rectum and tail), by comparing these measurements to arterial oxygen haemoglobin saturation (SaO2), measured by an AVOXimeter 4000 co-oximeter reference method in immobilized white rhinoceros (Ceratotherium simum). Study designRandomized crossover study. AnimalsA convenience sample of eight wild-caught male white rhinoceros. MethodsWhite rhinoceros were immobilized with etorphine (0.0026 ± 0.0002 mg kg–1, mean ± standard deviation) intramuscularly, after which the pinna was aseptically prepared for arterial blood sample collection, and four pulse oximeters with transflectance probes were fixed securely to their attachment sites (third eyelid, cheek, rectum and tail). At 30 minutes following recumbency resulting from etorphine administration, the animals were given either butorphanol (0.026 ± 0.0001 mg kg–1) or an equivalent volume of saline intravenously. At 60 minutes following recumbency, insufflated oxygen (15 L minute–1 flow rate) was provided intranasally. In total, the SpO2 paired measurements from the third eyelid (n = 80), cheek (n = 67), rectum (n = 59) and tail (n = 76) were compared with near-simultaneous SaO2 measurements using Bland-Altman to assess bias (accuracy), precision, and the area root mean squares (ARMS) method. ResultsCompared with SaO2, SpO2 measurements from the third eyelid were reliable (i.e., accurate and precise) above an SaO2 range of 70% (bias = 1, precision = 3, ARMS = 3). However, SpO2 measurements from the cheek, rectum and tail were unreliable (i.e., inaccurate or imprecise). Conclusions and clinical relevanceA Nonin PalmSAT pulse oximeter with a transflectance probe inserted into the space between the third eyelid and the sclera provided reliable SpO2 measurements when SaO2 was > 70%, in immobilized white rhinoceros.

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 s. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

An implementation of apneustic anesthesia ventilation in the horse: comparison with conventional mechanical ventilation

ObjectiveTo compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. Study designRandomized, crossover design. AnimalsA total of 10 healthy adult horses from a university-owned herd. MethodsFollowing xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (FiO2) = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)]. Horses were instrumented and ventilated with AAV or CMV for 1 hour according to predefined criteria [10 mL kg–1 tidal volume (VT), PaCO2 of 40–45 mmHg (5.3–6.0 kPa) during CMV and <60 mmHg (8.0 kPa) during AAV]. Dobutamine was administered to maintain mean arterial pressure (MAP) >65 mmHg. Cardiopulmonary data were collected at baseline, 30 and 60 minutes. The effects of ventilation mode and time were analyzed using repeated-measures anova with significance defined as p < 0.05. ResultsData from nine horses were analyzed. A significant effect of mode at one or more time points was found for respiratory rate, arterial and end-tidal CO2 tensions, arterial pH, mean airway pressure (Paw), respiratory system dynamic compliance index (CrsI), venous admixture (Q˙s/Q˙t), mean pulmonary artery pressure and systemic vascular resistance. No significant differences between modes were found for VT, FiO2, PaO2, arterial hemoglobin saturation, alveolar dead space, heart rate, MAP, cardiac index, stroke volume index, oxygen delivery index, oxygen extraction ratio and dobutamine administration. Conclusions and clinical relevanceIn dorsally recumbent anesthetized horses, both ventilation modes supported adequate oxygenation with minimal supplemental oxygen. Compared with CMV, AAV resulted in higher CrsI and lower Q˙s/Q˙t. Despite higher mean Paw with AAV, the cardiovascular effects of each mode were not different. Further trials of AAV in anesthetized horses are warranted.

ASSESSMENT OF ARTERIAL BLOOD GAS COMPOSITION DEPENDING ON THE DEGREE OF MORBID OBESITY IN PATIENTS IN BARIATRIC SURGERY

Abstract. The work is devoted to the study of arterial blood gas parameters and comparison of capnographic determination of carbon dioxide at the end of exhalation (EtCO2) and the real pressure of carbon dioxide in arterial blood (paCO2) depending on the degree of morbid obesity in patients who were to undergo surgical bariatric interventions in 2012-2021. The study included 61 patients, whose age ranged from 22 to 69 years, body mass index from 40 to 91 kg/m2. The patients were divided into 3 groups depending on the degree of morbid obesity: group 1 - 20 patients with body mass index ≥ 40 (grade 3); group 2 - 25 patients with body mass index ≥ 50 (grade 4); group 3 - 16 patients with body mass index ≥ 60 (grade 5). Based on the data obtained, it was found that the state of the arterial blood gas composition indicates the presence of respiratory function disorders in patients with morbid obesity, which significantly reduce the compensatory capabilities of the body. Arterial hemoglobin saturation with oxygen (SaO2) tended to decrease, reaching a minimum in patients of the 1st group. The studied parameters of the arterial blood gas composition in patients of group 1 tended to worsen, and in patients of groups 2 and 3 they significantly worsened with an increase in the degree of morbid obesity. The maximum disruption of arterial blood gases was found in patients with a body mass index ≥ 60. The partial pressure of carbon dioxide at the end of exhalation (EtCO2) in patients with morbid obesity does not correspond to the partial pressure of carbon dioxide in arterial blood (paCO2).

Yogic breathing in hypobaric environment: breathing exercising and its effect on hypobaric hypoxemia and heart rate at 3,650-m elevation.

High altitude sojourn is a risk factor for hypobaric hypoxemia and subsequent altitude sickness. The aim of this study was to analyze the effect of new type of yogic breathing—Maheshwarananda’s new Modified Bhujangini Pranayama performed by active yoga practitioners—on the arterial haemoglobin saturation of oxygen (measured by the pulse oximetry - SpO2) and the heart rate compared to normal spontaneous resting breathing. A pilot prospective study was conducted in the Himalayas at an altitude of 3,650 m. We monitored SpO2 and pulse rate in 34 experienced yoga practitioners. Within the 3 measurement days at the altitude of 3,650 m, the mean value of SpO2 increased from 89.11± 4.78 to 93.26±4.44 (P<0.001) after the yogic breathing exercise. No significant changes were observed in pulse rate (P<0.230) measured before and after yogic breathing. The new Yogic breathing—Maheshwarananda’s Modified Bhujangini Pranayama—is increasing the arterial haemoglobin saturation compared to normal resting spontaneous breathing. The heart rate was not affected by this type of yogic breathing.

ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients.

ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients.

Effect of Red Nail Polish on Pulse Oximetry Reading

Background: Pulse oximetry is a beat-to-beat, non-invasive and virtually risk-free method of assessing continuous arterial hemoglobin saturation. It is now a standard for monitoring care in the operating room and the post-anesthesia care unit. It is also widely used in the critical care setting. Numerous factors including dark skin, pigmentation, henna dye, nail polish etc. could lead to inaccuracy or ambiguous information about oxygen saturation. In many cultures, women decorate their fingernails with different colors of nail polish.&#x0D; Objectives: The purpose of this study was to determine the effect of red nail polish on the measurement of oxygen saturation.&#x0D; Materials and Methods: One hundred young women were recruited for this study and red nail polish was used to color the index finger of the non-dominant hand; the middle finger of the same hand was the control. Blood oxygen saturation was simultaneously measured by two calibrated pulse oximeters with two minutes interval for 30 minutes.&#x0D; Results: Red nail polish did not affect pulse oximetry measurement of oxygen saturation. There was no statistically significant difference between the control and the red nail polished fingers.&#x0D; Conclusion: Application of red nail polish does not cause statistically significant error in the measurement of oxygen saturation in young healthy individuals.&#x0D; KYAMC Journal Vol. 11, No.-4, January 2021, Page 181-183

Assessment of pulse co-oximetry technology after in vivo adjustment in anaesthetized dogs

ObjectiveTo compare values of haemoglobin concentration (SpHb), arterial haemoglobin saturation (SpO2) and calculated arterial oxygen content (SpOC), measured noninvasively with a pulse co-oximeter before and after in vivo adjustment (via calibration of the device using a measured haemoglobin concentration) with those measured invasively using a spectrophotometric-based blood gas analyser in anaesthetized dogs. Study designProspective observational clinical study. AnimalsA group of 39 adult dogs. MethodsIn all dogs after standard instrumentation, the dorsal metatarsal artery was catheterised for blood sampling, and a pulse co-oximeter probe was applied to the tongue for noninvasive measurements. Paired data for SpHb, SpO2 and SpOC from the pulse co-oximeter and haemoglobin arterial oxygen saturation (SaO2) and arterial oxygen content (CaO2) from the blood gas analyser were obtained before and after in vivo adjustment. Bland–Altman analysis for repeated measurements was used to evaluate the bias, precision and agreement between the pulse co-oximeter and the blood gas analyser. Data are presented as mean differences and 95% limits of agreement (LoA). ResultsA total of 39 data pairs were obtained before in vivo adjustment. The mean invasively measured haemoglobin–SpHb difference was –2.7 g dL−1 with LoA of –4.9 to –0.5 g dL−1. After in vivo adjustment, 104 data pairs were obtained. The mean invasively measured haemoglobin–SpHb difference was –0.2 g dL−1 with LoA of –1.1 to 0.6 g dL−1. The mean SaO2–SpO2 difference was 0.86% with LoA of –0.8% to 2.5% and that between CaO2–SpOC was 0.66 mL dL–1 with LoA of –2.59 to 3.91 mL dL–1. ConclusionsBefore in vivo adjustment, pulse co-oximeter derived values overestimated the spectrophotometric-based blood gas analyser haemoglobin and CaO2 values. After in vivo adjustment, the accuracy, precision and LoA markedly improved. Therefore, in vivo adjustment is recommended when using this device to monitor SpHb in anaesthetised dogs.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function.

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Oxygen availability in a HAPE-positive and a HAPE-negative woman before and during a visit to 3480 meters

BackgroundTesting the hypoxic ventilatory response (HVR) at low-altitude helps to detect those who do not hyperventilate appropriately in hypoxia but might not necessarily predict the HVR and the risk to develop acute mountain sickness (AMS) at high altitude. However, a low HVR seems to be particularly prevalent in individuals susceptible to high-altitude pulmonary edema (HAPE+). In this short communication, we assessed differences in physiological parameters in two comparable women before and 3 hours after exposure to 3,480 meters. One woman had a (clinically diagnosed) history of high-altitude pulmonary edema (HAPE+) while the other did well at previous exposures to high altitude (HAPE-). MethodsHeart rate, blood pressure, ventilation, arterial blood gas variables, arterial haemoglobin saturation, haemoglobin concentration, arterial oxygen content and delta plasma volume were measured or calculated before and after arrival at high altitude. ResultsAt high altitude, plasma volume decreased in the HAPE- woman which in turn increased haemoglobin concentration. Ventilation was elevated in the HAPE- but not in the HAPE + woman. Arterial oxygen content fell in the HAPE + while it was preserved in the HAPE- woman. This resulted from lower peripheral oxygen saturation (-35%), lower haemoglobin concentration (-12%) and lower arterial partial pressure of oxygen (-59%) in the HAPE+. ConclusionConsiderable haemoglobin desaturation and lack of haemoconcentration were characteristics of the HAPE + woman when exposed to high altitude, while the higher arterial oxygen content in the HAPE- woman was related to both haemoconcentration and hyperventilation (and associated haemoglobin saturation).

27-Year-Old Woman With Fever, Headache, and Anemia

27-Year-Old Woman With Fever, Headache, and Anemia

Carry-Over Quality of Pre-acclimatization to Altitude Elicited by Intermittent Hypoxia: A Participant-Blinded, Randomized Controlled Trial on Antedated Acclimatization to Altitude.

Intermittent normobaric hypoxia (IH) is increasingly used to pre-acclimatize for a sojourn to high altitude. There is a number of hypoxia – protocols observing the hypoxic ventilatory response (HVR), but little is known about the carry – over quality of the Lake Louise Score (LLS). We thus studied a week – long, 1 h per day poikilocapnic hypoxia protocol on whether acclimatization could be carried over for one week. Rationale for this was that it usually takes one week to get from Europe, Britain or the United States to the base camp of a major mountain. Forty-nine healthy volunteers of both sexes were exposed to daily bouts of 1 h at an inspiratory fraction of oxygen (FiO2) of 0.11 or 0.21 (control) for 7 consecutive days. Seven days after cessation of IH or sham exposures participants were again subjected to hypoxia (FiO2 = 0.11) for 6 h and measurements of isocapnic HVR and blood gases out of the arterialized earlobe were taken and LLS was assessed. In those with IH exposures LLS was reduced which was not the case in those with sham exposure (87 vs. 50%). Changes in HVR or the arterial hemoglobin saturation were not observed. Gender neither affected LLS nor HVR nor blood gases or carry -over quality. We found that our week – long, hypoxia protocol grants a reduction in LLS that can be carried over the time span of one week. In this way, antedated acclimatization may improve safety and comfort on the mountain.

The female menstrual cycle: impact on cardiovascular, ventilatory and neuromuscular responses to whole body exercise

BACKGROUNDThe female menstrual cycle (MC) is characterized by varying levels of endogenous sex hormones. Previous investigations have indicated that fluctuating levels of estrogen and progesterone may influence vascular function, ventilatory chemosensitivity, and exercise‐induced fatigue throughout the MC. However, a comprehensive analysis of the role of these sex hormones on determining cardiovascular, ventilatory, and neuromuscular responses during whole body exercise is currently lacking. Therefore, the purpose of this study was to investigate cardiovascular, ventilatory and neuromuscular responses to submaximal cycling exercise of eumenorrheic females throughout the MC.METHODSFemales were studied during three MC phases: early follicular (EF; days 1–4), late follicular (LF; days 8–12), and mid luteal (ML; days 8–10 post LH peak). Prior to exercise, venous blood was collected each visit to characterize endogenous hormone concentrations. Subjects cycled at 50 W, 75 W, 100 W, and 80% Wpeak (129 ± 12 W) for 4 min per stage. Heart rate (HR), mean arterial pressure (MAP), femoral artery blood flow (QL, Doppler ultrasound), minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), and estimated arterial hemoglobin saturation (SpO2) were quantified throughout all cycling trials. Preto post‐exercise changes in potentiated quadriceps twitches (ΔQtw) were used to quantify peripheral locomotor muscle fatigue.RESULTSHR, MAP, and QL were not different at any intensity throughout the MC (P &gt; 0.4). VE, VO2, VCO2 were also not different throughout the MC (P &gt; 0.2). Furthermore, neither hemoglobin content, nor SpO2 and arterial oxygen content changed significantly across the MC (P &gt; 0.1). Consequently, leg O2 delivery during exercise at all intensities were similar during the MC. Finally, exercise‐induced peripheral fatigue was not different throughout the MC (ΔQtw: ~47%; P = 0.2).CONCLUSIONFluctuating endogenous female sex hormones do not significantly influence central or peripheral hemodynamics or the ventilatory response to submaximal whole‐body exercise. Similarly, the exercise‐induced development of peripheral fatigue also remains unaltered across the MC during submaximal cycling exercise of the same duration and intensity. Although depending on the research question, these data suggest that controlling for MC phase may not be necessary when examining cardioventailtory or neuromuscular responses to whole body exercise in females, and should encourage the participation of more females in these types of studies.Support or Funding InformationNational Heart, Lung, and Blood Institute (HL‐116579)

Using continuous overnight pulse oximetry to guide home oxygen therapy in chronic neonatal lung disease

The aims of this study are: (i) to survey the knowledge of paediatric clinicians using overnight continuous pulse oximetry data to guide management of infants with chronic neonatal lung disease (CNLD); (ii) to assess the ability of paediatric clinicians to interpret overnight continuous pulse oximetry data; and (iii) to describe the overnight oximetry interpretation practices of paediatric respiratory specialists. Paediatric clinicians from three tertiary teaching hospitals completed an anonymous survey regarding overnight continuous pulse oximetry in chronic neonatal lung disease. Using a modified Delphi technique, paediatric respiratory specialists participated in a concordance exercise and discussions to establish consensus interpretations for 25 oximetry studies. Paediatric clinicians were invited to complete the same exercise as a comparison. Self-rated knowledge from 74 surveyed clinicians was proportional to clinical experience. Twenty paediatric clinicians and nine paediatric respiratory specialists completed the oximetry exercise with scores of 64% (κ = 0.25) and 80% (κ = 0.45), respectively. Individual parameters like a mean peripheral arterial haemoglobin saturation (SpO2 ) below 93% and percentage time spent below SpO2 93% correlated poorly with the consensus interpretations. Paediatric respiratory specialists instead relied on visual analysis of SpO2 waveforms, utilising the frequency and depth of desaturations to guide management. Interpretation of overnight oximetry data is variable amongst both paediatric clinicians and respiratory specialists. This likely reflects inadequate evidence defining clinically significant intermittent hypoxaemia, whether in terms of desaturation duration, frequency or nadir.

Awareness during CPR on cardiac arrest due to aortic dissection

Awareness during CPR is formerly reported in the literature but only in rare cases and it is still not clear whether these cases have anything in common.&#x0D; A case report regarding a 69-year old male patient.&#x0D; The patient was admitted to the hospital due to 3 days dyspeptic symptoms and sudden onset of dyspnoea a few hours before arriva. During admission a short period of tachycardia (250/min) is followed by asystolic cardiac arrest. CPR is immediately initiated. By the arrival of the cardio-resuscitation-team, the patient has a peripheral hemoglobin saturation of 100% and a high level of awareness with open eyes and movement of the head and both arms and legs. Re-evaluation of the hearts rhythm after 3 minutes still shows asystoli. A total of 10 mg of Epinephrine is administered in boluses of 1 mg every 3-5 minutes. By the 3ed hand-off for rhythm evaluation, the patient is orally intubated. A total of 5 arterial gas samples are done during the 90 minute CPR, and despite a decrease in pH to 7,11 and lactate of 18 after 90 minutes all other markers remain within the normal range, and both the arterial and peripheral hemoglobin saturation remains 100%. The level of awareness does not decrease notably during the 90 minutes. Echocardiography shows a heart with no noticeable ultrasonic movement. A projection visualizing the aortic arch raises suspicion of an aortic dissection. The autopsy shows he has have suffered a complete aortic dissection&#x0D; High level of awareness plus saturation and arterial gas almost within the normal range through all 90 minutes indicate very effective chest compressions and peripheral and cerebral blood flow. Even though the patient had a poor prognosis (complete aortic dissection and refractory asystole), termination of CPR raised ethical questions in the team as the patient was still conscious once the resuscitation was terminated by 90 minutes. Awareness during CPR also raises the question of proper sedation doing resuscitation, which is currently not part of the guidelines. Further research regarding pain relief during CPR as well as increased focus on communicative and ethical aspects during CPR is needed.

Evaluation of pulse co-oximetry to determine haemoglobin saturation with oxygen and haemoglobin concentration in anaesthetized horses: a retrospective study

ObjectiveThis study compared the values of variables measured by pulse co-oximetry (Masimo Radical 7; Masimo Europe Limited, UK) with those measured by a co-oximeter-enabled blood gas analyser (Siemens Rapid-point 500; Siemens Healthcare Limited, UK) in anaesthetized horses. Study designRetrospective study. AnimalsA total of 30 anaesthetized horses. MethodsIn total, 47 heparinized arterial blood samples were collected for blood gas analysis to determine haemoglobin concentration (tHb, g L–1) and percentage of haemoglobin saturation with oxygen (SaO2). Arterial haemoglobin saturation with oxygen was determined noninvasively by pulse co-oximetry (Masimo SpO2). Pulse co-oximetry also provided arterial haemoglobin concentration (SpHb) and arterial oxygen content (SpCaO2). Arterial oxygen content was calculated (CaO2) in 39 samples using SaO2 and the value of Hüfner’s constant used by Masimo Radical 7 (1.3 mL g–1). Data were compared using Bland–Altman analysis, correlation tests, accuracy root mean square (ARMS) statistics and total allowable error, where available. ResultsLow bias but wide limits of agreement (LoA) were found between Masimo SpO2 and SaO2 (bias = –1.4%, LoA = –4.0 to 1.3%), with an ARMS of 3%. Compared with tHb, SpHb showed low bias (6.2 g L–1) but wide LoA (–39.6 to 52.6 g L–1); its % bias (5.2%) was still within the 7% limits recommended by the Clinical Laboratory Improvement Amendments (CLIA) for humans. When comparing SpCaO2 and CaO2, the bias and LoA were –0.2 mL dL–1 and –6.7 to 6.2 mL dL–1, respectively. Conclusions and clinical relevanceMasimo SpO2 was acceptable for current ARMS standards, and SpHb measurements also met CLIA limits. The wide LoA in this study, however, suggest that the Masimo Radical 7 cannot be recommended as a substitute for direct measurements. As blood gas machines, pulse oximeters and co-oximeters use algorithms based on human haemoglobin, no true gold standard exists for horses.