Extracellular pH defense against lactic acid in untrained and trained altitude residents

Quantifying pH-induced changes in plasma strong ion difference during experimental acidosis: clinical implications for base excess interpretation

It is commonly assumed that changes in plasma strong ion difference (SID) result in equal changes in whole blood base excess (BE). However, at varying pH, albumin ionic-binding and transerythrocyte shifts alter the SID of plasma without affecting that of whole blood (SIDwb), i.e., the BE. We hypothesize that, during acidosis, 1) an expected plasma SID (SIDexp) reflecting electrolytes redistribution can be predicted from albumin and hemoglobin's charges, and 2) only deviations in SID from SIDexp reflect changes in SIDwb, and therefore, BE. We equilibrated whole blood of 18 healthy subjects (albumin = 4.8 ± 0.2 g/dL, hemoglobin = 14.2 ± 0.9 g/dL), 18 septic patients with hypoalbuminemia and anemia (albumin = 3.1 ± 0.5 g/dL, hemoglobin = 10.4 ± 0.8 g/dL), and 10 healthy subjects after in vitro-induced isolated anemia (albumin = 5.0 ± 0.2 g/dL, hemoglobin = 7.0 ± 0.9 g/dL) with varying CO2 concentrations (2-20%). Plasma SID increased by 12.7 ± 2.1, 9.3 ± 1.7, and 7.8 ± 1.6 mEq/L, respectively (P < 0.01) and its agreement (bias[limits of agreement]) with SIDexp was strong: 0.5[-1.9; 2.8], 0.9[-0.9; 2.6], and 0.3[-1.4; 2.1] mEq/L, respectively. Separately, we added 7.5 or 15 mEq/L of lactic or hydrochloric acid to whole blood of 10 healthy subjects obtaining BE of -6.6 ± 1.7, -13.4 ± 2.2, -6.8 ± 1.8, and -13.6 ± 2.1 mEq/L, respectively. The agreement between ΔBE and ΔSID was weak (2.6[-1.1; 6.3] mEq/L), worsening with varying CO2 (2-20%): 6.3[-2.7; 15.2] mEq/L. Conversely, ΔSIDwb (the deviation of SID from SIDexp) agreed strongly with ΔBE at both constant and varying CO2: -0.1[-2.0; 1.7], and -0.5[-2.4; 1.5] mEq/L, respectively. We conclude that BE reflects only changes in plasma SID that are not expected from electrolytes redistribution, the latter being predictable from albumin and hemoglobin's charges.NEW & NOTEWORTHY This paper challenges the assumed equivalence between changes in plasma strong ion difference (SID) and whole blood base excess (BE) during in vitro acidosis. We highlight that redistribution of strong ions, in the form of albumin ionic-binding and transerythrocyte shifts, alters SID without affecting BE. We demonstrate that these expected SID alterations are predictable from albumin and hemoglobin's charges, or from the noncarbonic whole blood buffer value, allowing a better interpretation of SID and BE during in vitro acidosis.

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.

Association of Hematological Variables with Team-Sport Specific Fitness Performance

Purpose

We investigated association of hematological variables with specific fitness performance in elite team-sport players.

Methods

Hemoglobin mass (Hb_mass) was measured in 25 elite field hockey players using the optimized (2 min) CO-rebreathing method. Hemoglobin concentration ([Hb]), hematocrit and mean corpuscular hemoglobin concentration (MCHC) were analyzed in venous blood. Fitness performance evaluation included a repeated-sprint ability (RSA) test (8 x 20 m sprints, 20 s of rest) and the Yo-Yo intermittent recovery level 2 (YYIR2).

Results

Hb_mass was largely correlated (r = 0.62, P<0.01) with YYIR2 total distance covered (YYIR2_TD) but not with any RSA-derived parameters (r ranging from -0.06 to -0.32; all P>0.05). [Hb] and MCHC displayed moderate correlations with both YYIR2_TD (r = 0.44 and 0.41; both P<0.01) and RSA sprint decrement score (r = -0.41 and -0.44; both P<0.05). YYIR2_TD correlated with RSA best and total sprint times (r = -0.46, P<0.05 and -0.60, P<0.01; respectively), but not with RSA sprint decrement score (r = -0.19, P>0.05).

Conclusion

Hb_mass is positively correlated with specific aerobic fitness, but not with RSA, in elite team-sport players. Additionally, the negative relationships between YYIR2 and RSA tests performance imply that different hematological mechanisms may be at play. Overall, these results indicate that these two fitness tests should not be used interchangeably as they reflect different hematological mechanisms.

Hemoglobin oxygen affinity in patients with cystic fibrosis

In patients with cystic fibrosis lung damages cause arterial hypoxia. As a typical compensatory reaction one might expect changes in oxygen affinity of hemoglobin. Therefore position (standard half saturation pressure P₅₀st) and slope (Hill’s n) of the O₂ dissociation curve as well as the Bohr coefficients (BC) for CO₂ and lactic acid were determined in blood of 14 adult patients (8 males, 6 females) and 14 healthy controls (6 males, 8 females). While Hill’s n amounted to approximately 2.6 in all subjects, P₅₀st was slightly increased by 1mmHg in both patient groups (controls male 26.7±0.2, controls female 27.0±0.1, patients male 27.7±0.5, patients female 28.0±0.3 mmHg; mean and standard error, overall p<0.01). Main cause was a rise of 1–2 µmol/g hemoglobin in erythrocytic 2,3-biphosphoglycerate concentration. One patient only, clearly identified as an outlier and with the mutation G551D, showed a reduction of both P₅₀st (24.5 mmHg) and [2,3-biphosphoglycerate] (9.8 µmol/g hemoglobin). There were no differences in BCCO₂, but small sex differences in the BC for lactic acid in the controls which were not detectable in the patients. Causes for the right shift of the O₂ dissociation curve might be hypoxic stimulation of erythrocytic glycolysis and an increased red cell turnover both causing increased [2,3-biphosphoglycerate]. However, for situations with additional hypercapnia as observed in exercising patients a left shift seems to be a more favourable adaptation in cystic fibrosis. Additionally when in vivo PO₂ values were corrected to the standard conditions they mostly lay left of the in vitro O₂ dissociation curve in both patients and controls. This hints to unknown fugitive factors influencing oxygen affinity.

Effects of gas exchange on acid-base balance

This paper describes the interactions between ventilation and acid-base balance under a variety of conditions including rest, exercise, altitude, pregnancy, and various muscle, respiratory, cardiac, and renal pathologies. We introduce the physicochemical approach to assessing acid-base status and demonstrate how this approach can be used to quantify the origins of acid-base disorders using examples from the literature. The relationships between chemoreceptor and metaboreceptor control of ventilation and acid-base balance summarized here for adults, youth, and in various pathological conditions. There is a dynamic interplay between disturbances in acid-base balance, that is, exercise, that affect ventilation as well as imposed or pathological disturbances of ventilation that affect acid-base balance. Interactions between ventilation and acid-base balance are highlighted for moderate- to high-intensity exercise, altitude, induced acidosis and alkalosis, pregnancy, obesity, and some pathological conditions. In many situations, complete acid-base data are lacking, indicating a need for further research aimed at elucidating mechanistic bases for relationships between alterations in acid-base state and the ventilatory responses.

Non-viral systemic delivery of siRNA or antisense oligonucleotides targeted to Jun N-terminal kinase 1 prevents cellular hypoxic damage

Many pathological conditions and environmental impacts lead to the development of severe tissue hypoxia that aggravates the primary disorder, provokes cell death, and limits the patient’s recovery. We hypothesized that suppression of Jun N-terminal kinase 1 (JNK1) will limit tissue damage induced by severe hypoxia. To test the hypothesis, antisense oligonucleotides (ASO) or small interfering RNA (siRNA) targeted to JNK1 mRNA were incorporated or complexed with neutral or cationic liposomes, respectively, and administered systemically to mice prior to hypoxia exposure. The animals were placed in a special chamber ventilated with room air (normoxia) or a gas mixture containing 6% O₂ and 94% N₂ (hypoxia). Liposomes, ASO, and siRNA were found to accumulate in the lungs, kidney, spleen, and heart. Only trace amounts of liposomes and their payloads (ASO and siRNA) were found in the brain. The down regulation of JNK1 protein limited activation of cell death signal, apoptotic, and necrotic tissue damage under hypoxic conditions. Consequently, we were able to verify our hypothesis and provide proof of concept of a unique approach to the prevention of cellular hypoxic damage by the suppression of JNK1 signaling pathways after the efficient delivery of ASO or siRNA.

Altitude-induced changes in muscle contractile properties

Because of its high energetic demand, skeletal muscle is sensitive to changes in the partial pressure of oxygen. Most human studies on in vivo skeletal muscle function during hypoxia were performed with voluntary contractions. However, skeletal muscle function is not only characterized by voluntary maximal or repeated force- generating capacity, but also by force generated by evoked muscle contractions (i.e., force-frequency properties). This mini-review reports on the effects of acute or prolonged exposure to hypoxia on human skeletal muscle performance and contractile properties. The latter depend on both the amount and type of contractile proteins and the efficiency of the cellular mechanism of excitation-contraction coupling. Observations on humans indicate that hypoxia (during simulated ascent or brief exposure) exerts modest influences on the membrane propagation of the muscle action potentials during voluntary contractions. Overall in humans, in physiological conditions, including that of climbing Mt. Everest, there is extraordinarily little that changes with regard to maximal force-generating capacity. Interestingly, it appears that the adaptations to chronic hypoxia minimize the effects on skeletal muscle dysfunction (i.e., impairment during fatigue resistance exercise and in muscle contractile properties) that may occur during acute hypoxia for some isolated muscle exercises. Only sustained isometric exercise exceeding a certain intensity (30% MVC) and causing substantial and sustained ischemia is not affected by acute hypoxia.