Reliability of Pulse Oximetry during Progressive Hypoxia, Cardiopulmonary Resuscitation, and Recovery in a Piglet Model of Neonatal Hypoxic Cardiac Arrest

Hypoxic preacclimatization combining intermittent hypoxia exposure with physical exercise significantly promotes the tolerance to acute hypoxia

Background: Both hypoxia exposure and physical exercise before ascending have been proved to promote high altitude acclimatization, whether the combination of these two methods can bring about a better effect remains uncertain. Therefore, we designed this study to evaluate the effect of hypoxic preacclimatization combining intermittent hypoxia exposure (IHE) and physical exercise on the tolerance to acute hypoxia and screen the optimal preacclimatization scheme among the lowlanders. Methods: A total of 120 Han Chinese young men were enrolled and randomly assigned into four groups, including the control group and three experimental groups with hypoxic preacclimatization of 5-day rest, 5-day exercise, and 3-day exercise in a hypobaric chamber, respectively. Main physical parameters for hypoxia acclimatization, AMS incidence, physical and mental capacity were measured for each participant in the hypobaric chamber simulated to the altitude of 4500 m in the effect evaluation stage. The effect was compared between different schemes. Results: During the effect evaluation stage, SpO2 of the 5-day rest group and 5-day exercise group was significantly higher than that of the control group (p = 0.001 and p = 0.006, respectively). The participants with 5-day rest had significantly lower HR than the controls (p = 0.018). No significant differences of AMS incidence were found among the four groups, while the proportion of AMS headache symptom (moderate and severe vs. mild) was significantly lower in the 3-day exercise group than that in the control group (p = 0.002). The 5-day exercise group had significantly higher VO2max, than the other three groups (p = 0.033, p < 0.001, and p = 0.023, respectively). The 5-day exercise group also had significantly higher digital symbol and pursuit aiming test scores, while shorter color selection reaction time than the control group (p = 0.005, p = 0.005, and p = 0.004, respectively). Conclusion: Hypoxic preacclimatization combining IHE with physical exercise appears to be efficient in promoting the tolerance to acute hypoxia. Hypoxia duration and physical exercise of moderate intensity are helpful for improvement of SpO2 and HR, relief of AMS headache symptoms, and enhancement of mental and physical operation capacity.

Epinephrine vs placebo in neonatal resuscitation: ROSC and brain MRS/MRI in term piglets

BACKGROUND

We aimed to investigate the effect of epinephrine vs placebo on return of spontaneous circulation (ROSC) and brain magnetic resonance spectroscopy and imaging (MRS/MRI) in newborn piglets with hypoxic cardiac arrest (CA).

METHODS

Twenty-five piglets underwent hypoxia induced by endotracheal tube clamping until CA. The animals were randomized to CPR + intravenous epinephrine or CPR + placebo (normal saline). The primary outcome was ROSC, and secondary outcomes included time-to-ROSC, brain MRS/MRI, and composite endpoint of death or severe brain MRS/MRI abnormality.

RESULTS

ROSC was more frequent in animals treated with epinephrine than placebo; 10/13 vs 4/12, RR = 2.31 (95% CI: 1.09-5.77). We found no difference in time-to-ROSC (120 (113-211) vs 153 (116-503) seconds, p = 0.7) or 6-h survival (7/13 vs 3/12, p = 0.2). Among survivors, there was no difference between groups in brain MRS/MRI. We found no difference in the composite endpoint of death or severe brain MRS/MRI abnormality; RR = 0.7 (95% CI: 0.37-1.19).

CONCLUSIONS

Resuscitation with epinephrine compared to placebo improved ROSC frequency after hypoxic CA in newborn piglets. We found no difference in time-to-ROSC or the composite endpoint of death or severe brain MRS/MRI abnormality.

IMPACT

In a newborn piglet model of hypoxic cardiac arrest, resuscitation with epinephrine compared to placebo improved the rate of return of spontaneous circulation and more than doubled the 6-h survival. Brain MRS/MRI biomarkers were used to evaluate the effect of epinephrine vs placebo. We found no difference between groups in the composite endpoint of death or severe brain MRS/MRI abnormality. This study adds to the limited evidence regarding the effect and safety of epinephrine; the lack of high-quality evidence from randomized clinical trials was highlighted in the latest ILCOR 2020 guidelines, and newborn animal studies were specifically requested.

Pulse oximetry waveform: A non-invasive physiological predictor for the return of spontaneous circulation in cardiac arrest patients ---- A multicenter, prospective observational study

OBJECTIVE

This study aimed to investigate the predictive value of pulse oximetry plethysmography (POP) for the return of spontaneous circulation (ROSC) in cardiac arrest (CA) patients.

METHODS

This was a multicenter, observational, prospective cohort study of patients hospitalized with cardiac arrest at 14 teaching hospitals cross China from December 2013 through November 2014. The study endpoint was ROSC, defined as the restoration of a palpable pulse and an autonomous cardiac rhythm lasting for at least 20 minutes after the completion or cessation of CPR.

RESULTS

150 out-of-hospital cardiac arrest (OHCA) patients and 291 in-hospital cardiac arrest (IHCA) patients were enrolled prospectively. ROSC was achieved in 20 (13.3%) and 64 (22.0%) patients in these cohorts, respectively. In patients with complete end-tidal carbon dioxide (ETCO₂) and POP data, patients with ROSC had significantly higher levels of POP area under the curve (AUCp), wave amplitude (Amp) and ETCO₂ level during CPR than those without ROSC (all p < 0.05). Pairwise comparison of receiver operating characteristic (ROC) curve analysis indicated no significant difference was observed between ETCO₂ and Amp (p = 0.204) or AUCp (p = 0.588) during the first two minutes of resuscitation.

CONCLUSION

POP may be a novel and effective method for predicting ROSC during resuscitation, with a prognostic value similar to ETCO₂ at early stage.

Accuracy of pulse oximetry in preterm and term infants is insufficient to determine arterial oxygen saturation and tension

AIM

Oxygen saturation is frequently monitored with pulse oximetry to assess vital signs in critically ill patients. Optimally, pulse oximetry closely tracks arterial oxygen tension (PaO₂ ), which provides guidance in oxygen titration. We investigated whether monitoring peripheral oxygen saturation (SpO₂ ) could accurately guide oxygen titration in newborn infants.

METHODS

Twenty seven thousand two hundred thirty seven SpO₂ readings were retrospectively paired with arterial oxygen saturation (SaO₂ ) and PaO₂ results from blood gas analyses performed in infants with arterial catheters in place.

RESULTS

SpO₂ overestimated SaO₂ readings by 2.9 ± 5.8%. When pulse oximetry readings were within the defined oxygen saturation target range, 7809 (20.9%) SaO₂ values were below and 2830 (7.6%) exceeded the target range. In 57% of patients, PaO₂ levels < 6 kPa was diagnosed while SpO₂ readings were > 90%. PaO₂  > 11 kPa was recorded in 19% of cases, when SpO₂ readings were < 95%. Infants treated with supplemental oxygen showed a threefold increased risk of hypoxaemia compared to infants breathing room air. Sensitivity and specificity for detecting upper and lower target range limits were fair to good. For SpO₂ values below 91%, ISO quality criteria were no longer fulfilled.

CONCLUSIONS

Based on arterial blood gas analyses as reference, pulse oximetry readings did not fulfil the performance requirements for titrating oxygen in neonatal patients.