Validation of a Portable Blood Gas Analyzer for Use in Challenging Field Conditions at High Altitude

Effect of Acute Ketone Monoester Ingestion on Cardiorespiratory Responses to Exercise and the Influence of Blood Acidosis

PURPOSE

This study aimed to examine the effect of KE ingestion on exercise cardiac output ( Q˙ ) and the influence of blood acidosis. We hypothesized that KE versus placebo ingestion would increase Q ˙, and coingestion of the pH buffer bicarbonate would mitigate this effect.

METHODS

In a randomized, double-blind, crossover manner, 15 endurance-trained adults (peak oxygen uptake (V̇O 2peak ), 60 ± 9 mL·kg -1 ·min -1 ) ingested either 0.2 g·kg -1 sodium bicarbonate or a salt placebo 60 min before exercise, and 0.6 g·kg -1 KE or a ketone-free placebo 30 min before exercise. Supplementation yielded three experimental conditions: basal ketone bodies and neutral pH (CON), hyperketonemia and blood acidosis (KE), and hyperketonemia and neutral pH (KE + BIC). Exercise involved 30 min of cycling at ventilatory threshold intensity, followed by determinations of V̇O 2peak and peak Q ˙.

RESULTS

Blood [β-hydroxybutyrate], a ketone body, was higher in KE (3.5 ± 0.1 mM) and KE + BIC (4.4 ± 0.2) versus CON (0.1 ± 0.0, P < 0.0001). Blood pH was lower in KE versus CON (7.30 ± 0.01 vs 7.34 ± 0.01, P < 0.001) and KE + BIC (7.35 ± 0.01, P < 0.001). Q ˙ during submaximal exercise was not different between conditions (CON: 18.2 ± 3.6, KE: 17.7 ± 3.7, KE + BIC: 18.1 ± 3.5 L·min -1 ; P = 0.4). HR was higher in KE (153 ± 9 bpm) and KE + BIC (154 ± 9) versus CON (150 ± 9, P < 0.02). V̇O 2peak ( P = 0.2) and peak Q ˙ ( P = 0.3) were not different between conditions, but peak workload was lower in KE (359 ± 61 W) and KE + BIC (363 ± 63) versus CON (375 ± 64, P < 0.02).

CONCLUSIONS

KE ingestion did not increase Q ˙ during submaximal exercise despite a modest elevation of HR. This response occurred independent of blood acidosis and was associated with a lower workload at V̇O 2peak .

How and when to measure pH in IVF culture media: validation of a portable blood gas analyzer in two IVF culture dishes for time lapse and conventional incubators

PURPOSE

Maintaining a stable pH at optimal level in human embryo culture media is crucial for embryo development but poses a challenge for all IVF laboratories. We validate analytically reliable conditions for pH measurement that are as close as possible to the embryo microenvironment during IVF.

METHODS

This was a multicentric study. A Siemens EPOC portable blood gas analyzer was used. The analytical validation was carried out under the culture medium (Global Total HSA®) conditions of use (microdroplets, under oil overlay, in a IVF incubator with (EmbryoScope®) or without a time lapse system (K system G210+®) and using IVF dishes. The validation included repeatability ("within-run" precision), total precision (between-day precision), trueness based on inter-laboratory comparison, inaccuracy based on external quality assessment and comparison to the reference technique. We also assessed the pre-analytical medium incubation time required to obtain a target value.

RESULTS

A measurement after an incubation period of 24 to 48 h is more representative of the pH to which the embryo will be exposed throughout the culture. The "within-run" and "between-day" precision show very low coefficients of variation (CV%): 0.17 to 0.22% and 0.13 to 0.34%, respectively, with IVF culture media. Trueness (% bias) range from - 0.07 to - 0.03%. We demonstrate good correlation between EPOC and reference pH electrode with an overestimation of 0.03 pH units of EPOC.

CONCLUSION

Our method demonstrates good analytical performance for IVF laboratories wishing to implement a robust quality assurance system to monitor pH in embryo culture media. Compliance with stringent pre-analytical and analytical conditions is essential.

Validation of Noninvasive Assessment of Pulmonary Gas Exchange in Patients with Chronic Obstructive Pulmonary Disease during Initial Exposure to High Altitude

Investigation of pulmonary gas exchange efficacy usually requires arterial blood gas analysis (aBGA) to determine arterial partial pressure of oxygen (mPaO₂) and compute the Riley alveolar-to-arterial oxygen difference (A-aDO₂); that is a demanding and invasive procedure. A noninvasive approach (AGM100), allowing the calculation of PaO₂ (cPaO₂) derived from pulse oximetry (SpO₂), has been developed, but this has not been validated in a large cohort of chronic obstructive pulmonary disease (COPD) patients. Our aim was to conduct a validation study of the AG100 in hypoxemic moderate-to-severe COPD. Concurrent measurements of cPaO₂ (AGM100) and mPaO₂ (EPOC, portable aBGA device) were performed in 131 moderate-to-severe COPD patients (mean ±SD FEV₁: 60 ± 10% of predicted value) and low-altitude residents, becoming hypoxemic (i.e., SpO₂ < 94%) during a short stay at 3100 m (Too-Ashu, Kyrgyzstan). Agreements between cPaO₂ (AGM100) and mPaO₂ (EPOC) and between the O₂-deficit (calculated as the difference between end-tidal pressure of O₂ and cPaO₂ by the AGM100) and Riley A-aDO₂ were assessed. Mean bias (±SD) between cPaO₂ and mPaO₂ was 2.0 ± 4.6 mmHg (95% Confidence Interval (CI): 1.2 to 2.8 mmHg) with 95% limits of agreement (LoA): -7.1 to 11.1 mmHg. In multivariable analysis, larger body mass index (p = 0.046), an increase in SpO₂ (p < 0.001), and an increase in PaCO₂-PETCO₂ difference (p < 0.001) were associated with imprecision (i.e., the discrepancy between cPaO₂ and mPaO₂). The positive predictive value of cPaO₂ to detect severe hypoxemia (i.e., PaO₂ ≤ 55 mmHg) was 0.94 (95% CI: 0.87 to 0.98) with a positive likelihood ratio of 3.77 (95% CI: 1.71 to 8.33). The mean bias between O₂-deficit and A-aDO₂ was 6.2 ± 5.5 mmHg (95% CI: 5.3 to 7.2 mmHg; 95%LoA: -4.5 to 17.0 mmHg). AGM100 provided an accurate estimate of PaO₂ in hypoxemic patients with COPD, but the precision for individual values was modest. This device is promising for noninvasive assessment of pulmonary gas exchange efficacy in COPD patients.

Patient Care Alterations After Point-of-Care Laboratory Testing During Critical Care Transport

OBJECTIVE

Point-of-care laboratory testing (POCT) is associated with a reduced time to testing results and critical decision making within emergency departments. POCT is an essential clinical assessment tool because laboratory data are used to support timely critical decisions regarding acute medical conditions onditions ; however, there is currently limited research to support the use of POCT in the critical care transport environment. Few studies have evaluated the changes in patient care that occur after POCT during critical care transport. This study aims to contribute to the limited data available correlating prehospital POCT and changes in patient care.

METHODS

After institutional review board approval, a retrospective review of patients transported by a critical care transport team between October 1, 2013 and September 31, 2015 was completed. During the study period, 11,454 patients were transported, and 632 (5.51%) received POCT testing.

RESULTS

Patient care changes were noted in 244 (38.6%) patient tests. The most frequent patient care alterations were ventilator settings (10.9%), electrolyte changes (10.4%), and unit bed upgrades (7.1%). POCT most frequently altered care for patients with post-cardiac arrest syndrome (64.7%), sepsis/septic shock (61.8%), diabetic ketoacidosis (54.5%), or pneumonia (49.3%).

CONCLUSION

Patient care alterations occurred in 38.6% of patients undergoing POCT. Patient care was most frequently changed when patients were diagnosed with post-arrest, sepsis/septic shock, diabetic ketoacidosis, and pneumonia.