Acute effects of apnea bouts on hemoglobin concentration and hematocrit: a systematic review and meta-analysis.

Objective: This study aimed to systematically analyze the existing literature and conduct a meta-analysis on the acute effects of apnea on the hematological response by assessing changes in hemoglobin (Hb) concentration and hematocrit (Hct) values. Methods: Searches in Pubmed, The Cochrane Library, and Web of Science were carried out for studies in which the main intervention was voluntary hypoventilation, and Hb and Hct values were measured. Risk of bias and quality assessments were performed. Results: Nine studies with data from 160 participants were included, involving both subjects experienced in breath-hold sports and physically active subjects unrelated to breath-holding activities. The GRADE scale showed a "high" confidence for Hb concentration, with a mean absolute effect of 0.57 g/dL over control interventions. "Moderate" confidence appeared for Hct, where the mean absolute effect was 2.45% higher over control interventions. Hb concentration increased to a greater extent in the apnea group compared to the control group (MD = 0.57 g/dL [95% CI 0.28, 0.86], Z = 3.81, p = 0.0001) as occurred with Hct (MD = 2.45% [95% CI 0.98, 3.93], Z = 3.26, p = 0.001). Conclusions: Apnea bouts lead to a significant increase in the concentration of Hb and Hct with a high and moderate quality of evidence, respectively. Further trials on apnea and its application to different settings are needed.

Influence of hypercapnia and hypercapnic hypoxia on the heart rate response to apnea.

We aimed to determine the relative contribution of hypercapnia and hypoxia to the bradycardic response to apneas. We hypothesized that apneas with hypercapnia would cause greater bradycardia than normoxia, similar to the response seen with hypoxia, and that apneas with hypercapnic hypoxia would induce greater bradycardia than hypoxia or hypercapnia alone. Twenty-six healthy participants (12 females; 23 ± 2 years; BMI 24 ± 3 kg/m2) underwent three gas challenges: hypercapnia (+5 torr end tidal partial pressure of CO2 [PETCO2]), hypoxia (50 torr end tidal partial pressure of O2 [PETO2]), and hypercapnic hypoxia (combined hypercapnia and hypoxia), with each condition interspersed with normocapnic normoxia. Heart rate and rhythm, blood pressure, PETCO2, PETO2, and oxygen saturation were measured continuously. Hypercapnic hypoxic apneas induced larger bradycardia (-19 ± 16 bpm) than normocapnic normoxic apneas (-11 ± 15 bpm; p = 0.002), but had a comparable response to hypoxic (-19 ± 15 bpm; p = 0.999) and hypercapnic apneas (-14 ± 14 bpm; p = 0.059). Hypercapnic apneas were not different from normocapnic normoxic apneas (p = 0.134). After removal of the normocapnic normoxic heart rate response, the change in heart rate during hypercapnic hypoxia (-11 ± 16 bpm) was similar to the summed change during hypercapnia+hypoxia (-9 ± 10 bpm; p = 0.485). Only hypoxia contributed to this bradycardic response. Under apneic conditions, the cardiac response is driven by hypoxia.

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.

Value of integrated pulmonary index monitoring for the detection of adverse respiratory events in patients undergoing sedation for gastrointestinal system endoscopy.

Objectives: To determine if the integrated pulmonary index detects changes in ventilation status early in patients undergoing gastrointestinal endoscopy under sedation, and to determine the risk factors affecting hypoxia. METHODS: The retrospective study was conducted at the endoscopy unit of a tertiary university hospital in Turkey and comprised data between October 2018 and December 2019 related to patients of either gender aged >18 years who were assessed as American Society of Anaesthesiologists grade I-III and underwent elective lower and upper gastrointestinal endoscopy. Monitoring was done with capnography in addition to standard procedures. Data was analysed using SPSS 23. RESULTS: Of the 154 patients, 94(%) were females and 60(%) were males. The overall mean age was 50.88±11.8 years (range: 20-70 years). Mean time under anaesthesia was 23.58±4.91 minutes and mean endoscopy time was 21.73±5.06 minutes. During the procedure, hypoxia was observed in 42(27.3%) patients, severe hypoxia in 23(14.9%) and apnoea in 70(45.5%). Mean time between apnoea and hypoxia was 12.59±7.99 seconds, between apnoea and serious hypoxia 21.07±17.64 seconds, between integrated pulmonary index score 1 and hypoxia 12.91±8.17 sec, between integrated pulmonary index score 1 and serious hypoxia 21.59±14.13 seconds, between integrated pulmonary index score <7 and hypoxia 19.63±8.89 seconds, between integrated pulmonary index score <7 and serious hypoxia 28.39±12.66 seconds, between end-tidal carbon dioxide and hypoxia 12.95±8.33 seconds, and between end-tidal carbon dioxide and serious hypoxia 21.29±7.55 seconds. With integrated pulmonary index score 1, sensitivity value for predicting hypoxia and severe hypoxia was 88.1% and 95.7%, respectively, and specificity was 67% and 60.3%, respectively. With integrated pulmonary index score <7, the corresponding values were 100%, 100%, 42% and 64.1%, respectively. CONCLUSIONS: Capnographic monitoring, especially the follow-up integrated pulmonary index score, was found to be valuable and reliable in terms of finding both time and accuracy of the risk factor in the diagnosis of respiratory events.

[Analysis of the application effect and safety of transnasal humidified rapid insufflation ventilatory exchange technique in hysteroscopic diagnostic and therapeutic surgery].

Objective: To investigate the effect and safety of transnasal humidified rapid insufflation ventilatory exchange (THRIVE) technique in hysteroscopic diagnostic and therapeutic surgery. Methods: This study was a randomized controlled trial. A total of 100 female patients undergoing hysteroscopy surgery at Beijing Tongren Hospital from September to December 2023 were selected and randomly divided into two groups by the random number table method: the THRIVE group and the mask oxygen group, with 50 patients in each group. Patients in both groups were given total intravenous anesthesia with propofol combined with remifentanil and preserved spontaneous respiration. The THRIVE group was given oxygen by the THRIVE device with an oxygen flow rate of 50 L/min, while the mask oxygen group was given oxygen by the mask with an oxygen flow rate of 5 L/min; the oxygen concentration of both groups was set at 100%. The general condition of the patients, vital signs during the operation, the amount of anesthesia drugs used and the operation time were recorded. The primary observation index was the incidence of hypoxic events in the two groups; the secondary observation indexes were the incidence and time of intraoperative apnea as well as the corresponding oxygenation interventions and the incidence of non-hypoxic adverse events. Results: The age of the THRIVE group was (42±14) years, and the age of the mask oxygen group was (43±15) years. The duration of surgery in the THRIVE group was (15.9±3.4) min, which was statistically lower than that of the mask oxygen group (16.3±4.5) min (P=0.041), and there were no differences observed in the duration of awakening time and anesthesia time (both P>0.05). There was no significant difference in the dosage of propofol, remifentanil, and intraoperative vasoactive drugs between the two groups (all P>0.05). The SpO2 of the patients in the THRIVE group at the end of the operation was (99.7±1.1) %, which was higher than that of the mask-oxygen group (99.1±1.1) % (P<0.05). There was no difference in SpO2 of the two groups at the other time points (all P>0.05). There were no differences in HR and MAP of two group patients at each time point (all P>0.05). The incidence of hypoxic events in the THRIVE group was 12.0% (6/50), which was lower than that of 28.0% (14/50) in the mask oxygen group (P=0.045). The difference in the incidence and duration of apnea between the two groups was not statistically significant (all P>0.05). There were no cases of temporary need for laryngeal mask or tracheal intubation during surgery in both groups. There was no statistically significant difference in the incidence of intraoperative body movement, dizziness, nausea and vomiting between the two groups (all P>0.05), and no cardiac, cerebral, renal or other important organ insufficiency occurred in the two weeks after surgery. Conclusion: THRIVE technology can provide effective oxygenation for patients undergoing hysteroscopic diagnosis and treatment, maintain patients' circulatory stability, and improve the safety and efficiency of surgery.

Blood pressure responses to handgrip exercise but not apnea or mental stress are enhanced in women with a recent history of preeclampsia.

Preeclampsia is a risk factor for future cardiovascular diseases. However, the mechanisms underlying this association remain unclear, limiting effective prevention strategies. Blood pressure responses to acute stimuli may reveal cardiovascular dysfunction not apparent at rest, identifying individuals at elevated cardiovascular risk. Therefore, we compared blood pressure responsiveness with acute stimuli between previously preeclamptic (PPE) women (34 ± 5 yr old, 13 ± 6 mo postpartum) and women following healthy pregnancies (Ctrl; 29 ± 3 yr old, 15 ± 4 mo postpartum). Blood pressure (finger photoplethysmography calibrated to manual sphygmomanometry-derived values; PPE: n = 12, Ctrl: n = 12) was assessed during end-expiratory apnea, mental stress, and isometric handgrip exercise protocols. Integrated muscle sympathetic nerve activity (MSNA) was assessed in a subset of participants (peroneal nerve microneurography; PPE: n = 6, Ctrl: n = 8). Across all protocols, systolic blood pressure (SBP) was higher in PPE than Ctrl (main effects of group all P < 0.05). Peak changes in SBP were stressor specific: peak increases in SBP were not different between PPE and Ctrl during apnea (8 ± 6 vs. 6 ± 5 mmHg, P = 0.32) or mental stress (9 ± 5 vs. 4 ± 7 mmHg, P = 0.06). However, peak exercise-induced increases in SBP were greater in PPE than Ctrl (11 ± 5 vs. 7 ± 7 mmHg, P = 0.04). MSNA was higher in PPE than Ctrl across all protocols (main effects of group all P < 0.05), and increases in peak MSNA were greater in PPE than Ctrl during apnea (44 ± 6 vs. 27 ± 14 burst/100 hb, P = 0.04) and exercise (25 ± 8 vs. 13 ± 11 burst/100 hb, P = 0.01) but not different between groups during mental stress (2 ± 3 vs. 0 ± 5 burst/100 hb, P = 0.41). Exaggerated pressor and sympathetic responses to certain stimuli may contribute to the elevated long-term risk for cardiovascular disease in PPE.NEW & NOTEWORTHY Women with recent histories of preeclampsia demonstrated higher systolic blood pressures across sympathoexcitatory stressors relative to controls. Peak systolic blood pressure reactivity was exacerbated in previously preeclamptic women during small muscle-mass exercises, although not during apneic or mental stress stimuli. These findings underscore the importance of assessing blood pressure control during a variety of experimental conditions in previously preeclamptic women to elucidate mechanisms that may contribute to their elevated cardiovascular disease risk.

Apnea, Intermittent Hypoxemia, and Bradycardia Events Predict Late-Onset Sepsis in Infants Born Extremely Preterm.

OBJECTIVE: The objective of this study was to examine the association of cardiorespiratory events, including apnea, periodic breathing, intermittent hypoxemia (IH), and bradycardia, with late-onset sepsis for extremely preterm infants (<29 weeks of gestational age) on vs off invasive mechanical ventilation. STUDY DESIGN: This is a retrospective analysis of data from infants enrolled in Pre-Vent (ClinicalTrials.gov identifier NCT03174301), an observational study in 5 level IV neonatal intensive care units. Clinical data were analyzed for 737 infants (mean gestational age: 26.4 weeks, SD 1.71). Monitoring data were available and analyzed for 719 infants (47 512 patient-days); of whom, 109 had 123 sepsis events. Using continuous monitoring data, we quantified apnea, periodic breathing, bradycardia, and IH. We analyzed the relationships between these daily measures and late-onset sepsis (positive blood culture >72 hours after birth and ≥5-day antibiotics). RESULTS: For infants not on a ventilator, apnea, periodic breathing, and bradycardia increased before sepsis diagnosis. During times on a ventilator, increased sepsis risk was associated with longer events with oxygen saturation <80% (IH80) and more bradycardia events before sepsis. IH events were associated with higher sepsis risk but did not dynamically increase before sepsis, regardless of ventilator status. A multivariable model including postmenstrual age, cardiorespiratory variables (apnea, periodic breathing, IH80, and bradycardia), and ventilator status predicted sepsis with an area under the receiver operator characteristic curve of 0.783. CONCLUSION: We identified cardiorespiratory signatures of late-onset sepsis. Longer IH events were associated with increased sepsis risk but did not change temporally near diagnosis. Increases in bradycardia, apnea, and periodic breathing preceded the clinical diagnosis of sepsis.

Relation between resting spleen volume and apnea-induced increases in hemoglobin mass.

Introduction: Indigenous populations renowned for apneic diving have comparatively large spleen volumes. It has been proposed that a larger spleen translates to heightened apnea-induced splenic contraction and elevations in circulating hemoglobin mass (Hbmass), which, in theory, improves O2 carrying and/or CO2/pH buffering capacities. However, the relation between resting spleen volume and apnea- induced increases in Hbmass is unknown. Therefore, we tested the hypothesis that resting spleen volume is positively related to apnea-induced increases in total Hbmass. Methods: Fourteen healthy adults (six women; 29 ± 5 years) completed a two-minute carbon monoxide rebreathe procedure to measure pre-apneas Hbmass and blood volume. Spleen length, width, and thickness were measured pre-and post-five maximal apneas via ultrasound. Spleen volume was calculated via the Pilström equation (test-retest CV:2 ± 2%). Hemoglobin concentration ([Hb]; g/dl) and hematocrit (%) were measured pre- and post-apneas via capillary blood samples. Post-apneas Hbmass was estimated as post-apnea [Hb] x pre-apnea blood volume. Data are presented as mean ± SD. Results: Spleen volume decreased from pre- (247 ± 95 mL) to post- (200 ± 82 mL, p<0.01) apneas. [Hb] (14.6 ± 1.2 vs. 14.9 ± 1.2 g/dL, p<0.01), hematocrit (44 ± 3 vs. 45 ± 3%, p=0.04), and Hbmass (1025 ± 322 vs. 1046 ± 339 g, p=0.03) increased from pre- to post-apneas. Pre-apneas spleen volume was unrelated to post-apneas increases in Hbmass (r=-0.02, p=0.47). O2 (+28 ± 31 mL, p<0.01) and CO2 (+31 ± 35 mL, p<0.01) carrying capacities increased post-apneas. Conclusion: Larger spleen volume is not associated with a greater rise in apneas-induced increases in Hbmass in non-apnea-trained healthy adults.

Physical and Physiological Predictors Determining the Maximal Static Apnea Diving Time of Male Freedivers.

This study aimed to investigate what factors determine freedivers' maximal static apnea dive time. We correlated some physical/physiological factors with male freedivers' maximum apnea diving duration. Thirty-six experienced male freedivers participated in this study. The divers participated in two days of the experiments. On the first day, apnea diving time, blood oxygen saturation (SpO2), heart rate (HR), blood pressure (BP), stress index, and blood parameters were measured before, during, and after the apnea diving in the pool. On the second day, body composition, lung capacity, resting and maximal oxygen consumption (VO2max), and the Wingate anaerobic power were measured in the laboratory. The data were analyzed with Pearson's Correlation using the SPSS 22 program. The correlation coefficient (R) of determination was set at 0.4, and the level of significance was set at p <0.05. There were positive correlations of diving experience, maximum SpO2, and lung capacity with the maximum apnea time R>0.4, P<0.05). There were negative correlations of BMI, body fat percentage, body fat mass, minimum SpO2, stress index, and total cholesterol with the maximum apnea diving time (R>-0.4, P<0.05). No correlations of age, height, weight, fat-free mass, skeletal muscle mass, HR, BP, blood glucose, beta- hydroxybutyrate, lactate, and hemoglobin levels with the maximum apnea diving time were observed (R<0.4, P>0.05). It is concluded that more experience in freediving, reduced body fat, extended SpO2 range, and increased lung capacity are the performance predictors and beneficial for freedivers to improve their maximum apnea diving performance.

Effectiveness of preoxygenation strategies: a systematic review and network meta-analysis.

BACKGROUND: Preoxygenation is universally recommended before induction of general anaesthesia to prolong safe apnoea time. The optimal technique for preoxygenation is unclear. We conducted a systematic review to determine the preoxygenation technique associated with the greatest effectiveness in adult patients having general anaesthesia. METHODS: We searched six databases for randomised controlled trials of patients aged ≥16 yr, receiving general anaesthesia in any setting and comparing different preoxygenation techniques and methods. Our primary effectiveness outcome was safe apnoea time, and secondary outcomes included incidence of arterial oxygen desaturation; lowest SpO2 during airway management; time to end-tidal oxygen concentration of 90%; and [Formula: see text] and [Formula: see text] at the end of preoxygenation. We assessed the quality of evidence according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) recommendations. RESULTS: We included 52 studies of 3914 patients. High-flow nasal oxygen with patients in a head-up position was most likely to be associated with a prolonged safe apnoea time when compared with other strategies, with a mean difference (95% credible interval) of 291 (138-456) s and 203 (79-343) s compared with preoxygenation with a facemask in the supine and head-up positions, respectively. Subgroup analysis of studies without apnoeic oxygenation also showed high-flow nasal oxygen in the head-up position as the highest ranked technique, with a statistically significantly delayed mean difference (95% credible interval) safe apnoea time compared with facemask in supine and head-up positions of 222 (63-378) s and 139 (15-262) s, respectively. High-flow nasal oxygen was also the highest ranked technique for increased [Formula: see text] at the end of preoxygenation. However, the incidence of arterial desaturation was less likely to occur when a facemask with pressure support was used compared with other techniques, and [Formula: see text] was most likely to be lowest when preoxygenation took place with patients deep breathing in a supine position. CONCLUSIONS: Preoxygenation of adults before induction of general anaesthesia was most effective in terms of safe apnoea time when performed with high-flow nasal oxygen with patients in the head-up position in comparison with facemask alone. Also, high-flow nasal oxygen in the head-up position is likely to be the most effective technique to prolong safe apnoea time among those evaluated. Clinicians should consider this technique and patient position in routine practice. SYSTEMATIC REVIEW PROTOCOL: PROSPERO CRD42022326046.

SubSol-HIe is an AMPK-dependent hypoxia-responsive subnucleus of the nucleus tractus solitarius that coordinates the hypoxic ventilatory response and protects against apnoea in mice.

Functional magnetic resonance imaging (fMRI) suggests that the hypoxic ventilatory response is facilitated by the AMP-activated protein kinase (AMPK), not at the carotid bodies, but within a subnucleus (Bregma -7.5 to -7.1 mm) of the nucleus tractus solitarius that exhibits right-sided bilateral asymmetry. Here, we map this subnucleus using cFos expression as a surrogate for neuronal activation and mice in which the genes encoding the AMPK-α1 (Prkaa1) and AMPK-α2 (Prkaa2) catalytic subunits were deleted in catecholaminergic cells by Cre expression via the tyrosine hydroxylase promoter. Comparative analysis of brainstem sections, relative to controls, revealed that AMPK-α1/α2 deletion inhibited, with right-sided bilateral asymmetry, cFos expression in and thus activation of a neuronal cluster that partially spanned three interconnected anatomical nuclei adjacent to the area postrema: SolDL (Bregma -7.44 mm to -7.48 mm), SolDM (Bregma -7.44 mm to -7.48 mm) and SubP (Bregma -7.48 mm to -7.56 mm). This approximates the volume identified by fMRI. Moreover, these nuclei are known to be in receipt of carotid body afferent inputs, and catecholaminergic neurons of SubP and SolDL innervate aspects of the ventrolateral medulla responsible for respiratory rhythmogenesis. Accordingly, AMPK-α1/α2 deletion attenuated hypoxia-evoked increases in minute ventilation (normalised to metabolism), reductions in expiration time, and increases sigh frequency, but increased apnoea frequency during hypoxia. The metabolic response to hypoxia in AMPK-α1/α2 knockout mice and the brainstem and spinal cord catecholamine levels were equivalent to controls. We conclude that within the brainstem an AMPK-dependent, hypoxia-responsive subnucleus partially spans SubP, SolDM and SolDL, namely SubSol-HIe, and is critical to coordination of active expiration, the hypoxic ventilatory response and defence against apnoea.

A multicentre neonatal manikin study showed a large heterogeneity in tactile stimulation for apnoea of prematurity.

AIM: Apnoea of prematurity requires prompt intervention to prevent long-term adverse outcomes, but specific recommendations about the stimulation approach are lacking. Our study investigated the modalities of tactile stimulation for apnoea of prematurity in different settings. METHODS: In this multi-country observational prospective study, nurses and physicians of the neonatal intensive care units were asked to perform a tactile stimulation on a preterm neonatal manikin simulating an apnoea. Features of the stimulation (body location and hand movements) and source of learning (training course or clinical practice) were collected. RESULTS: Overall, 112 healthcare providers from five hospitals participated in the study. During the stimulation, the most frequent location were feet (72%) and back (61%), while the most frequent techniques were rubbing (64%) and massaging (43%). Stimulation modalities different among participants according to their hospitals and their source of learning of the stimulation procedures. CONCLUSION: There was a large heterogeneity in stimulation approaches adopted by healthcare providers to counteract apnoea in a simulated preterm infant. This finding may be partially explained by the lack of specific guidelines and was influenced by the source of learning for tactile stimulation.

Apnea during moderate to deep sedation using continuous infusion of remimazolam compared to propofol and dexmedetomidine: A retrospective observational study.

Remimazolam's rapid onset and offset make it an innovative sedative for use during regional anesthesia. However, its respiratory safety profile is not well understood. We compared the continuous infusion of remimazolam with commonly used sedatives, propofol and dexmedetomidine, after regional anesthesia. In this retrospective study, the incidence of apnea (>10 seconds) was assessed in patients who underwent orthopedic surgery under regional anesthesia and received moderate to deep sedation using continuous infusion of remimazolam (group R: 0.1 mg/kg in 2 minutes followed by 0.5 mg/kg/hr). The incidence was compared with that of propofol (group P: 2-3 µg/mL target-controlled infusion) and dexmedetomidine (group D: 1 µg/kg in 10 minutes followed by 0.4-1 µg/kg/hr). Propensity score weighted multivariable logistic regression model was utilized to determine the effects of the sedative agents on the incidence of apnea. A total of 634 (191, 278, and 165 in group R, P, and D) cases were included in the final analysis. The incidence of apnea was 63.9%, 67.3%, and 48.5% in group R, P, and D, respectively. The adjusted odds ratios for apnea were 2.33 (95% CI, 1.50 to 3.61) and 2.50 (95% CI, 1.63 to 3.85) in group R and P, compared to group D. The incidence of apnea in patients receiving moderate to deep sedation using continuous infusion of remimazolam with dosage suggested in the current study was over 60%. Therefore, careful titration and respiratory monitoring is warranted.

Effectiveness of trans-nasal humidified rapid insufflation ventilatory exchange compared with standard facemask oxygenation for pre- and apneic oxygenation during anesthesia induction: A meta-analysis based on randomized controlled trials.

PURPOSE: To further identify the effectiveness of trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE) for pre- and apneic oxygenation during the anesthesia induction by comparison to facemask ventilation (FMV) based on current available evidence. METHODS: Medline, EMBASE, Web of Science, Cochrane Library and CNKI databases were searched from inception to December 22, 2023 for available randomized controlled trials (RCTs). Primary outcomes were PaO2 and PaCO2 after intubation and safe apnoea time. Secondary outcomes included the O2 desaturation, end expiratory carbon dioxide (EtCO2) and complications. The effect measures for continuous and categorical outcomes were separately the mean difference (MD) and relative risk (RR) with 95% confidence interval. RESULTS: Twelve RCTs with 403 patients in the THRIVE group and 401 patients in th FMV group were included. Pooled results demonstrated that the PaO2 after intubation was significantly higher (MD = 82.90mmHg, 95% CI: 12.25~153.54mmHg, P = 0.02) and safe apnoea time (MD = 103.81s, 95% CI: 42.07~165.56s, P = 0.001) was longer in the THRIVE group. Besides, the incidence rate of O2 desaturation (RR = 0.28, 95% CI: 0.12-0.66, P = 0.004) and gastric insufflation (RR = 0.26, 95% CI: 0.13-0.49, P<0.001) was significantly lower in the THRIVE group. CONCLUSION: Based on current evidence, THRIVE manifested better effectiveness representing as improved oxygenation, prolonged safe apnoea time and decreased risk of complications compared to standard FMV in surgical patients. Therefore, THRIVE could be served as a novel and valuable oxygenation technology for patients during anesthesia induction.

Association of Caffeine Daily Dose With Respiratory Outcomes in Preterm Neonates: A Retrospective Cohort Study.

Apnea and poor respiratory drive increase the risk of extubation failure (EF) and prolonged invasive mechanical ventilation (IMV) in preterm neonates (pre-nates) with respiratory distress. Caffeine citrate (CC) is often prescribed for pre-nates in doses of 5-10 mg/kg in 24 h. This study aimed to evaluate the most effective dosage regimen (5 mg/kg/day vs >5-10 mg/kg/day) to prevent apnea and EF with minimal caffeine-associated potential side effects (CC-APSEs) in pre-nates. This one-year retrospective cohort study included all the eligible neonates admitted to NICU and received CC-therapy till 28 days of life (DOL) or discharge. Based on CC-daily dose formed LD-caffeine-group (5 mg/kg/day) and HD-caffeine-group (>5-10 mg/kg/day). Antenatal, prenatal, and postnatal characteristics, CC-regimen, comorbidities, and CC-APSEs were compared between the groups. Predictors of apnea and EF were analyzed through logistic regression. There were 181 and 72 neonates in the LD and HD-caffeine-groups respectively. In HD-caffeine-group daily CC-dose was 7 to 7.5 mg/kg/day in 93% of neonates and >7.5 to 10 mg/kg/day in only 7%. Significantly fewer neonates experienced apnea and EF in the HD-caffeine-group till 28DOL or discharge. This difference was even greater in the subgroup of ≤28 weeks GA (15.6% vs 40.0%; P < .01). In HD-caffeine-group the incidence of severe/moderate-BPD was significantly lower and the frequency of CC-APSEs was higher. Multivariate analysis showed that; the smaller the GA higher the risk of apnea (AOR = 0.510, 95% CI 0.483-0.999) and EF (AOR = 0.787, 95% CI 0.411-0.997). The HD-caffeine was inversely associated with developing apnea (AOR = 0.244, 95% CI 0.053-0.291) and EF (AOR = 0.103, 95% CI 0.098-2.976). IMV-duration before extubation (AOR = 2.229, 95% CI 1.672-2.498) and severe/moderate-BPD (AOR = 2.410, 95%CI 1.104-2.952) had a high risk of EF. Initiating early HD-caffeine may prevent apnea and extubation failure in preterm neonates. Optimization of caffeine initiation time and dosages can be a safe and feasible approach to decrease the burden of neonatal respiratory morbidities.

Pulmonary strain and end-expiratory lung volume during apnea test: a comparative analysis using electrical impedance tomography.

The apnea test, employed for brain death assessment, aims to demonstrate the absence of respiratory drive due to hypercapnia. The tracheal oxygen insufflation apnea test mode (I-AT) involves disconnecting the patient from invasive mechanical ventilation (iMV) for approximately 8 minutes while maintaining oxygenation. This test supports the diagnosis of brain death based on a specified increase in PaCO2. Common complications include hypoxemia and hemodynamic instability, and lung collapse-induced reduction in end-expiratory lung volume (EELV). In our case series utilizing electrical impedance tomography (EIT), we observed that continuous positive airway pressure during the apnea test (CPAP-AT) effectively mitigated lung collapse. This resulted in improved pulmonary strain compared to the disconnection of iMV. These findings suggest the potential benefits of routine CPAP-AT, particularly for potential lung donors, emphasizing the relevance of our study in providing quantitative insights into EELV loss and its association with pulmonary strain and potential lung injury.

La prueba de apnea es una técnica diagnóstica ampliamente utilizada para la evaluación de la muerte cerebral, con el objetivo de demostrar la ausencia de impulso respiratorio debido a la hipercapnia. La variante de la prueba de apnea con insuflación de oxígeno traqueal (I-AT) implica desconectar al paciente de la ventilación mecánica invasiva (iVM) durante aproximadamente 8 minutos, manteniendo la oxigenación mediante un catéter de insuflación. Esta prueba respalda el diagnóstico de muerte cerebral cuando se determina un aumento de la PaCO 2 superior a 20 mmHg en comparación con el valor inicial o un nivel de PaCO 2 superior a 60 mmHg al final de la prueba. En nuestra serie de casos, la implementación de la tomografía de impedancia eléctrica (EIT) reveló que la prueba de apnea con presión positiva continua (CPAPAT) mitiga eficazmente el colapso pulmonar. Este enfoque resulta en una mejora en la tensión pulmonar en comparación con la desconexión de iMV, demostrando su relevancia en el contexto de potenciales donantes de pulmones.

Parametric analysis of an integrated cardio-respiratory model in preterm newborns during apnea.

The analysis of the complex interactions involved in the acute physiological response to apnea-bradycardia events in preterm newborns remains a challenging task. This paper presents a novel integrated model of cardio-respiratory interactions, adapted to preterm newborns. A sensitivity analysis, based Morris' screening method, was applied to study the effects of physiological parameters on heart rate and desaturation, during the simulation of a 15-seconds apnea-bradycardia episode. The most sensitive parameters are associated with fundamental, integrative physiological mechanisms involving: (i) respiratory mechanics (intermediate airways and lung compliance), (ii) fraction of inspired oxygen, (iii) metabolic rates (oxygen consumption rate), (iv) heart rate regulation and (v) chemoreflex (gain). Results highlight the relevant influence of physiological variables, involved in preterm apnea-bradycardia events.

The interaction of breath holding and muscle mechanoreflex on cardiovascular responses in breath-hold divers and non-breath-hold divers.

Cardiovascular responses to diving are characterized by two opposing responses: tachycardia resulting from exercise and bradycardia resulting from the apnea. The convergence of bradycardia and tachycardia may determine the cardiovascular responses to diving. The purpose of this study was to investigate the interaction of breath holding and muscle mechanoreflex on cardiovascular responses in breath-hold divers (BHDs) and non-BHDs. We compared the cardiovascular responses to combined apnea and the mechanoreflex in BHDs and non-BHDs. All participants undertook three trials-apnea, passive leg cycling (PLC), and combined trials-for 30 s after rest. Cardiovascular variables were measured continuously. Nine BHD (male:female, 4:5; [means ± SD] age, 35 ± 6 years; height, 168.6 ± 4.6 cm; body mass, 58.4 ± 5.9 kg) and eight non-BHD (male:female, 4:4; [means ± SD] age, 35 ± 7 years; height, 163.9 ± 9.1 cm; body mass, 55.6 ± 7.2 kg) participants were included. Compared to the resting baseline, heart rate (HR) and cardiac output (CO) significantly decreased during the combined trial in the BHD group, while they significantly increased during the combined trials in the non-BHD group (P < 0.05). Changes in the HR and CO were significantly lower in the BHD group than in the non-BHD group in the combined trial (P < 0.05). These results suggest that bradycardia with apnea in BHDs is prioritized over tachycardia with the mechanoreflex, whereas that in non-BHDs is not. This finding implies that diving training changes the interaction between apnea and the mechanoreflex in cardiovascular control.

Association of Cannabis with Apneic Episodes in a Breastfed Infant: A Case Study.

Background: The use of cannabis and its perceived safety among pregnant and breastfeeding women has increased in the context of expanding legalization. Current guidelines recommend abstaining from the use of cannabis while pregnant or breastfeeding due to the potential for harm, although there is still much that is unknown in this field. Case Presentation: A 5-week-old infant presented with recurrent apneic episodes and a positive urine delta-9-tetrahydrocannabinol (THC) screening test. The infant's mother reported regular cannabis use for treatment of depression and anxiety while pregnant and breastfeeding. The infant was subsequently transitioned to formula feedings, and the infant's condition improved. Conclusion: Cannabis and its active metabolites can be transferred into breast milk and may have deleterious neurologic effects on infants. However, a causal relationship between cannabis exposure and short- or long-term neurologic sequelae has not yet been definitively established. Further studies are warranted to assess the safety of maternal cannabis use for breastfed infants.