scholarly journals Feasibility and Effect of Physiological-Based CPAP in Preterm Infants at Birth

2021 ◽  
Vol 9 ◽  
Author(s):  
Tessa Martherus ◽  
Kristel L. A. M. Kuypers ◽  
Stefan Böhringer ◽  
Janneke Dekker ◽  
Ruben S. G. M. Witlox ◽  
...  
Keyword(s):  
Heart Rate ◽  
Preterm Infants ◽  
Study Protocol ◽  
Spontaneous Breathing ◽  
Animal Studies ◽  
Mask Ventilation ◽  
Short Term ◽  
Lung Aeration ◽  
Inclusion Rate ◽  
Secondary Outcomes

Background: Preterm infants are commonly supported with 5–8 cmH2O CPAP. However, animal studies demonstrate that high initial CPAP levels (12–15 cmH2O) which are then reduced (termed physiological based (PB)-CPAP), improve lung aeration without adversely affecting cardiovascular function. We investigated the feasibility of PB-CPAP and the effect in preterm infants at birth.Methods: Preterm infants (24–30 weeks gestation) were randomized to PB-CPAP or 5–8 cmH2O CPAP for the first 10 min after birth. PB-CPAP consisted of 15 cmH2O CPAP that was decreased when infants were stabilized (heart rate ≥100 bpm, SpO2 ≥85%, FiO2 ≤ 0.4, spontaneous breathing) to 8 cmH2O with steps of ~2/3 cmH2O/min. Primary outcomes were feasibility and SpO2 in the first 5 min after birth. Secondary outcomes included physiological and breathing parameters and short-term neonatal outcomes. Planned enrollment was 42 infants.Results: The trial was stopped after enrolling 31 infants due to a low inclusion rate and recent changes in the local resuscitation guideline that conflict with the study protocol. Measurements were available for analysis in 28 infants (PB-CPAP n = 8, 5–8 cmH2O n = 20). Protocol deviations in the PB-CPAP group included one infant receiving 3 inflations with 15 cmH2O PEEP and two infants in which CPAP levels were decreased faster than described in the study protocol. In the 5–8 cmH2O CPAP group, three infants received 4, 10, and 12 cmH2O CPAP. During evaluations, caregivers indicated that the current PB-CPAP protocol was difficult to execute. The SpO2 in the first 5 min after birth was not different [61 (49–70) vs. 64 (47–74), p = 0.973]. However, infants receiving PB-CPAP achieved higher heart rates [121 (111–130) vs. 97 (82–119) bpm, p = 0.016] and duration of mask ventilation was shorter [0:42 (0:34–2:22) vs. 2:58 (1:36–6:03) min, p = 0.020]. Infants in the PB-CPAP group required 6:36 (5:49-11:03) min to stabilize, compared to 9:57 (6:58–15:06) min in the 5–8 cmH2O CPAP group (p = 0.256). There were no differences in short-term outcomes.Conclusion: Stabilization of preterm infants with PB-CPAP is feasible but tailoring CPAP appeared challenging. PB-CPAP did not lead to higher SpO2 but increased heart rate and shortened the duration of mask ventilation, which may reflect faster lung aeration.

scholarly journals Hypoxia-induced vagal withdrawal is independent of the hypoxic ventilatory response in men

2019 ◽  
Vol 126 (1) ◽  
pp. 124-131 ◽  
Author(s):  
Christoph Siebenmann ◽  
Camilla K. Ryrsø ◽  
Laura Oberholzer ◽  
James P. Fisher ◽  
Linda M. Hilsted ◽  
...  
Keyword(s):  
Heart Rate ◽  
Tidal Volume ◽  
Respiratory Rate ◽  
Spontaneous Breathing ◽  
Animal Studies ◽  
Pulmonary Ventilation ◽  
Vagal Activity ◽  
Adrenergic Blockade ◽  
Controlled Breathing ◽  
Vagal Withdrawal

Hypoxia increases heart rate (HR) in humans by sympathetic activation and vagal withdrawal. However, in anaesthetized dogs hypoxia increases vagal activity and reduces HR if pulmonary ventilation does not increase and we evaluated whether that observation applies to awake humans. Ten healthy males were exposed to 15 min of normoxia and hypoxia (10.5% O2), while respiratory rate and tidal volume were volitionally controlled at values identified during spontaneous breathing in hypoxia. End-tidal CO2 tension was clamped at 40 mmHg by CO2 supplementation. β-Adrenergic blockade by intravenous propranolol isolated vagal regulation of HR. During spontaneous breathing, hypoxia increased ventilation by 3.2 ± 2.1 l/min ( P = 0.0033) and HR by 8.9 ± 5.5 beats/min ( P < 0.001). During controlled breathing, respiratory rate (16.3 ± 3.2 vs. 16.4 ± 3.3 breaths/min) and tidal volume (1.05 ± 0.27 vs. 1.06 ± 0.24 l) were similar for normoxia and hypoxia, whereas the HR increase in hypoxia persisted without (8.6 ± 10.2 beats/min) and with (6.6 ± 5.6 beats/min) propranolol. Neither controlled breathing ( P = 0.80), propranolol ( P = 0.64), nor their combination ( P = 0.89) affected the HR increase in hypoxia. Arterial pressure was unaffected ( P = 0.48) by hypoxia across conditions. The hypoxia-induced increase in HR during controlled breathing and β-adrenergic blockade indicates that hypoxia reduces vagal activity in humans even when ventilation does not increase. Vagal withdrawal in hypoxia seems to be governed by the arterial chemoreflex rather than a pulmonary inflation reflex in humans. NEW & NOTEWORTHY Hypoxia accelerates the heart rate of humans by increasing sympathetic activity and reducing vagal activity. Animal studies have indicated that hypoxia-induced vagal withdrawal is governed by a pulmonary inflation reflex that is activated by the increased pulmonary ventilation in hypoxia. The present findings, however, indicate that humans experience vagal withdrawal in hypoxia even if ventilation does not increase, indicating that vagal withdrawal is governed by the arterial chemoreflex rather than a pulmonary inflation reflex.

scholarly journals Predictors for expired CO2 in neonatal bag-mask ventilation at birth: observational study

2019 ◽  
Vol 3 (1) ◽  
pp. e000544 ◽  
Author(s):  
Kari Holte ◽  
Hege Langli Ersdal ◽  
Joar Eilevstjønn ◽  
Monica Thallinger ◽  
Jørgen Linde ◽  
...  
Keyword(s):  
Heart Rate ◽  
Birth Weight ◽  
Observational Study ◽  
Tidal Volume ◽  
Mask Ventilation ◽  
Clinical Factors ◽  
Apgar Scores ◽  
Ventilation Frequency ◽  
Lung Aeration ◽  
Bag Mask Ventilation

BackgroundExpired carbon dioxide (ECO2) indicates degree of lung aeration immediately after birth. Favourable ventilation techniques may be associated with higher ECO2 and a faster increase. Clinical condition will however also affect measured values. The aim of this study was to explore the relative impact of ventilation factors and clinical factors on ECO2 during bag-mask ventilation of near-term newborns.MethodsObservational study performed in a Tanzanian rural hospital. Side-stream measures of ECO2, ventilation data, heart rate and clinical information were recorded in 434 bag-mask ventilated newborns with initial heart rate <120 beats per minute. We studied ECO2 by clinical factors (birth weight, Apgar scores and initial heart rate) and ventilation factors (expired tidal volume, ventilation frequency, mask leak and inflation pressure) in random intercept models and Cox regression for time to ECO2 >2%.ResultsECO2 rose non-linearly with increasing expired tidal volume up to >10 mL/kg, and sufficient tidal volume was critical for the time to reach ECO2 >2%. Ventilation frequency around 30/min was associated with the highest ECO2. Higher birth weight, Apgar scores and initial heart rate were weak, but significant predictors for higher ECO2. Ventilation factors explained 31% of the variation in ECO2 compared with 11% for clinical factors.ConclusionsOur findings indicate that higher tidal volumes than currently recommended and a low ventilation frequency around 30/min are associated with improved lung aeration during newborn resuscitation. Low ECO2 may be used to identify unfavourable ventilation technique. Clinical factors are also associated with persistently low ECO2 and must be accounted for in the interpretation.

scholarly journals ActiGraph and Short-term Heart Rate Variability Study Protocol

2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Anna Luong ◽  
Madison Goodyke ◽  
Susan L. Dunn ◽  
Tracy Baynard ◽  
Ulf Bronas
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Study Protocol ◽  
Short Term ◽  
Variability Study

Effect of nitric oxide synthase inhibitors on short-term appetite and food intake in humans

1999 ◽  
Vol 276 (6) ◽  
pp. R1562-R1568 ◽  
Author(s):  
Rosalie Vozzo ◽  
Gary A. Wittert ◽  
Michael Horowitz ◽  
John E. Morley ◽  
Ian M. Chapman
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Heart Rate ◽  
Food Intake ◽  
Animal Studies ◽  
Caloric Intake ◽  
Short Term ◽  
Double Blind ◽  
Visual Analog Scales ◽  
Oxide Synthase

Animal studies suggest that nitric oxide (NO) may be a physiological regulator of appetite; NO synthase (NOS) inhibition suppresses food intake in rats, mice, and chickens. It is not known whether NO has any effect on appetite in humans. We have used N G-monomethyl-l-arginine (l-NMMA) and N G-nitro-l-arginine methyl ester (l-NAME), both competitive, nonselective inhibitors of NOS, in two separate studies to evaluate the role of NO in the short-term regulation of appetite in humans. In study I, 13 men (18–25 yr) underwent paired studies, in randomized, double-blind fashion, after an overnight fast. l-NMMA (4 mg ⋅ kg−1 ⋅ h−1) or saline (0.9%) was infused intravenously at a rate of 40 ml/h for 1.5 h. In study II, eight men (18–26 yr) underwent three randomized, double-blind studies after an overnight fast. l-NAME (75 or 180 μg ⋅ kg−1 ⋅ h−1) or saline (0.9%) was infused intravenously at a rate of 20 ml/h for 120 min. Hunger and fullness were measured using visual analog scales; blood pressure and heart rate were monitored, and 30 min before the end of the infusion, subjects were offered a cold buffet meal. Total caloric intake and the macronutrient composition of the meal were determined. Both l-NMMA ( P = 0.052) andl-NAME ( P < 0.05; both doses) decreased heart rate, l-NMMA increased diastolic blood pressure ( P < 0.01), and l-NAME increased systolic blood pressure ( P = 0.052). Neither drug had any effect on caloric intake or sensations of hunger or fullness. Despite having significant effects on cardiovascular function in the doses used, neitherl-NMMA norl-NAME had any effect on feeding, suggesting that NO does not affect short-term appetite or food intake in humans.

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