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Hypobaric birth room may prevent intraventricular hemorrhage in extremely low birth weights infants
Medical Hypotheses 119 (2018) 11–13
Contents lists available at ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
Hypobaric birth room may prevent intraventricular hemorrhage in extremely low birth weights infants
T
⁎
Kadir Şerafettin Tekgündüza, , Sibel Ejder Tekgündüzb a b
Ataturk University Medical Faculty, Division of Neonatology, Erzurum, Turkey İbrahim Hakkı State Hospital, Department of Obstetrics and Gynecology, Erzurum, Turkey
A R T I C LE I N FO
A B S T R A C T
Keywords: High-altitude Extremely low birth weights Hypobaric Intraventricular hemorrhage
In the early postnatal period, intraventricular hemorrhage may develop in infants with extremely low birth weights due to hemodynamic instability. One of the most significant factors in intraventricular hemorrhage development is fluctuations in the cerebral blood flow due to left-to-right shunting as a result of patent ductus arteriosus, and such cases most frequently develop intraventricular hemorrhage within the first 72 h. The frequency of intraventricular hemorrhage may be reduced through the prevention of fluctuations in the cerebral blood flow in this time frame. Based on our hypothesis, we recommend that extremely low birth weight infants should be delivered and monitored in hypobaric rooms for the first three days after birth, as this may reduce leftto-right shunting as a result of patent ductus arteriosus by preventing the rapid drops seen in pulmonary pressure after birth. A more stable hemodynamic status may be achieved by increasing the cerebral blood flow during an acute term in a hypobaric environment. Gradual transition to the normobaric status at the end of the third day may prevent the long-term negative effects of hypobaric conditions.
Introduction Fetal circulation occurs between the placenta and fetus during the intrauterine term, and pulmonary pressure is increased as the lungs are filled in with fetal lung fluid. During fetal circulation, oxygenated blood supplied by the placenta flows into the inferior vena cava through the umbilical vein, mixes with the deoxygenated blood coming from the lower extremities and with the deoxygenated blood coming from superior vena cava in the right atrium. Then, the blood that is pumped from the right ventricle to the pulmonary arteries enters the aorta through the ductus arteriosus [1]. In a fetus, the partial oxygen pressure (PaO2) of the blood in the umbilical vein varies between 30 and 35 mmHg, while the PaO2 of the blood supplying the fetal organs ranges between 26 and 28 mmHg [1]. A fetus completes its intrauterine development over 40 weeks at an atmospheric pressure that is almost equal to the pressure at the top of Mount Everest [2–4]. A term fetus is ready for postnatal adaptation. After birth, the lungs become responsible for oxygen and carbon dioxide exchange, the ductus arteriosus closes, and PaO2 levels that are considered normal for humans are achieved within minutes [1]. However, postnatal adaptation is particularly difficult for extremely low birth weight (ELBW) infants, delivered before the 28th gestational week, with a birth weight of less than 1000 g. The incidence of patent ductus arteriosus (PDA) – the ⁎
incomplete closure of ductus arteriosus – is elevated among ELBW infants due to the immaturity of the oxygen-sensitive smooth muscle cells that are present on the wall of the ductus arteriosus [1]. Systemicpulmonary (left-to-right) shunting through PDA starts within the first eight minutes of birth due to the increase in systemic blood pressure and the decrease in pulmonary pressure. At this stage, cerebral blood flow (CBF) decreases, and hemodynamic instability occurs despite normal oxygen saturation (SaO2) levels [5]. Intraventricular hemorrhage (IVH) is a considerable problem in infants with a birth weight of less than 1000 g ELBW. According to the data provided by the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network, IVH develops in 32% and grade 3 or 4 IVH develops in 16% of ELBW infants [6]. Postnatal fluctuations in CBF are the main factor that underlies an IVH etiopathogenesis in this age group. In particular, CBF fluctuations that occur postnatal within the first 72 h are responsible for IVH development, and this time frame is also associated with the highest risk of hemodynamic instability and the highest frequency of IVH [7,8]. Hypotheses Almost all of the data regarding ELBW morbidity in literature have been collected in studies carried out at sea level or close altitudes
Corresponding author. E-mail addresses: [email protected], [email protected] (K.Ş. Tekgündüz).
https://doi.org/10.1016/j.mehy.2018.07.013 Received 30 January 2018; Accepted 14 July 2018 0306-9877/ © 2018 Elsevier Ltd. All rights reserved.
Medical Hypotheses 119 (2018) 11–13
K.Ş. Tekgündüz, S.E. Tekgündüz
sufficient tissue oxygenation (DO2); cardiac output, O2 and Hb. These factors can be formulated as follows [19]:
(below 1,500 m), and so there is a paucity of data on ELBW morbidity at high altitudes [9,10]. Could a physiological transition be achieved when a preterm infant is delivered at a high altitude region that is similar to the conditions a fetus complete intrauterine development under a low partial oxygen pressure? While there is currently no clear answer to this question we raised, a previous study reported IVH in 8.7% of 80 ELBW infants who were delivered at high altitudes (1800–2000 m) and who underwent transfontanelle USG imaging [9]. Unlike infants delivered at sea level, studies showed that the pulmonary pressure did not drop immediately after birth in infants delivered at high altitudes [10,11]. The hypothesis presented here suggests that the risk of IVH in ELBW infants may be reduced under controlled hypobaric conditions that mimic high altitudes by preventing the rapid drop in postnatal pulmonary pressure, and therefore ensuring hemodynamic stability by reducing the amount of left-to-right shunting and systemic leak. If ELBW infants are delivered and monitored during the initial postnatal days under controlled hypobaric conditions, CBF could be kept more stable with an effect that mimics high altitudes.
DO2 = Cardiac Output × 1. 34∗ (Hgb ×SaO2∗∗) + (Pa02×0.003∗∗∗) *
1.34: Is the oxygen binding capacity of Hb, and should be included in the g/L unit. ** SaO2 is included as a decimal number (e.g. 95% → 0.95). (As this formula initially estimates O2 in the blood supplied to the tissues, the saturation value on pulse-oximetry should be used.) **** Dissolved O2 can be disregarded. Echocardiographic (ECHO) investigations should be performed to estimate the cardiac output while the patient is being monitored in the controlled hypobaric room. It is possible to calculate DO2, and therefore cerebral oxygenation, based on pulse-oximetry results and measurements of the blood gases. At this stage, an ECHO can also be utilized to measure the amount of shunting through PDA and to calculate systemic leak. Based on these measurements, if the cardiac output inclines to drop and the Hb levels and SaO2 are found to be normal despite the left-to-right shunting through PDA, the atmospheric pressure in the hypobaric room can be slightly decreased, for instance, to 781 hPa, which is equal to the pressure at 2100 m. In such a situation, we would expect an increase in pulmonary vascular resistance and a decrease in the systemic leak through PDA under the influence of the effects of the hypobaric conditions. In contrast, in the event of a drop in SaO2 values and a gradual increase in the O2 requirement, or if a pulmonary-tosystemic (right-to-left) shunting through PDA in ECHO is noted, the pressure in the hypobaric room could be increased. With all these adjustments, the hypobaric room becomes a dynamic part of ELBW monitoring.
Evaluation of the hypotheses The effects of high altitudes are not limited to hypoxia. Increased sympathetic activity on ascent causes an initial mild increase in blood pressure, a moderate increase in heart rate and cardiac output and an increase in venous tone [12]. Cerebral blood flow increases at high altitudes during the acute term [13,14]. Of course, in the event of ongoing hypoxia, CBF will decrease due to the decreased cardiac output, and hypoxic damage will be more prominent in the tissues. Altitudes over 1500 m are defined as high altitudes. High altitude disease, characterized by pulmonary and cerebral edema, has been reported at an altitude of 2100 m, although the incidence of this disease increases significantly at altitudes above 4000 m [15,16]. Hypothetically, the atmospheric pressure in a birthing room for ELBW infants could be adjusted to equal the pressure found at 1500–2000 m altitude, and today, atmospheric pressures in hyperbaric rooms could be adjusted to reflect hypobaric conditions [17]. It would be appropriate to divide the postnatal monitoring period for ELBW infants in hypobaric rooms into three sections.
Section 3 – Transition to normobaric conditions After the patient is given postnatal care for 72 h in a hypobaric room, a step-wise transition should be made to normobaric conditions. Very high altitudes are known to increase the incidence of BPD and PDA among preterm infants [10,11]. However, we should highlight that persistent pulmonary hypertension is an untoward condition, and it is known that pulmonary pressure decreases at low altitudes [20]. We believe that the transition to normobaric conditions should be gradual, and that dynamic monitoring should be continued during this transition period. The pressure could firstly be adjusted to 835 hPa, corresponding to an altitude of 1500 m, after which, adjustments could be made according to the atmospheric pressure at altitudes defined as low altitude.
Section 1 – Birth and neonatal resuscitation We recommend that the pressure in the controlled hypobaric room in which the delivery will occur be adjusted to 790 hPa, which is equal to the atmospheric pressure at 2000 m altitude. This altitude will be tolerated by the mother as well. It would also be appropriate for the hypobaric room to be within the neonatal intensive care unit given that the patient will be monitored here for the first three days. Due to the effects of the hypobaric conditions encountered immediately after birth, the infant will also be exposed to a lower degree of oxidative damage during the initial seconds. The resuscitation steps for the ELBW infant, as defined in the Neonatal Resuscitation Program (NRP), should again be performed in the same environment [18]. For ELBW infants, the NRP guidelines recommend the initiation of resuscitation with oxygen support at a concentration of 21–30%. The oxygen supply that is given to the infant does not change the atmospheric pressure [9]. Treatments, such as surfactants or inotropic supplements, should be administered in line with the relevant indications during the first day of monitoring.
Discussion Among all the mortalities in ELBW infants, IVH is particularly important, in that it can give rise to irreversible neurodevelopmental disorders. A hypobaric room hypothesis is suggested as a means of stabilizing CBF and reducing the incidence of IVH. The high frequency of PDA and consequent left-to-right shunting are key factors in this regard [21]. Treatment is recommended only for hemodynamically significant PDA (HsPDA) in preterm infants [20]. Hypobaric conditions aim to ensure hemodynamic stability by reducing shunting through PDA, therefore, the possibility of HsPDA is indeed reduced when the infant is kept in a hypobaric room for the first three days after birth. The pulmonary pressure in such infants could be reduced through the administration of surfactants during the first days of life, although leftto-right shunting through PDA still plays a role in the development of pulmonary hemorrhaging [22,23]. Accordingly, incidences of pulmonary hemorrhaging may also be expected to decrease under hypobaric conditions. It is currently difficult to predict how the first 72 h spent under
Section 2 – Monitoring The monitoring of ELBW infants is a dynamic process, and this process should also include the monitoring of the controlled hypobaric room. There are three significant factors that play specific roles in 12
Medical Hypotheses 119 (2018) 11–13
K.Ş. Tekgündüz, S.E. Tekgündüz
hypobaric conditions, followed by a gradual transition to a normobaric condition, will affect morbidities, such as BPD, NEK and ROP, in ELBW infants. To our knowledge, there is not any research into the consequences of transferring to low altitudes in patients who were delivered at high altitudes. In conclusion, our hypothesis suggested that postnatal hemodynamic adaptation in ELBW infants could be more safely achieved under hypobaric conditions. We predict that the frequency of IVH will be reduced as a result of the decrease in the systemic leak through PDA and the increase of CBF during the acute period.
[9] Caner I, Tekgunduz KS, Temuroglu A, Demirelli Y, Kara M. Evaluation of premature infants hospitalized in neonatal intensive care unit between 2010–2012. [Epub 2014 Aug 26]. Eurasian J Med 2015 Feb;47(1):13–20. https://doi.org/10.5152/ eajm.2014.38. [10] AlShehri Mohammed A. Are preterm infants at high altitude at greater risk for the development of bronchopulmonary dysplasia? J Trop Pediatr 2014;60(1):68–73. [11] Niermeyer Susan. Cardiopulmonary transition in the high altitude infant. High Altitude Med Biol July 2004;4(2):225–39. [12] Paralikar SJ, Paralikar JH. High-altitude medicine. Indian J Occup Environ Med 2010;14(1):6–12. https://doi.org/10.4103/0019-5278.64608. [13] Schoene RB. Illnesses at high altitude. Chest 2008;134:402. [14] American West JB. College of Physicians, American Physiological Society. The physiologic basis of high-altitude diseases. Ann Intern Med 2004;141:789. [15] Wu TY, Ding SQ, Liu JL, et al. Who should not go high: chronic disease and work at altitude during construction of the Qinghai-Tibet railroad. High Alt Med Biol 2007;8:88. [16] Hackett PH, Rennie D, Levine HD. The incidence, importance, and prophylaxis of acute mountain sickness. Lancet 1976;2:1149. [17] Boussen S, Coulange M, Fournier M, Gainnier M, Michelet P, Micoli C, et al. Evaluation of transport ventilators at mild simulated altitude: a bench study in a hypobaric chamber. Respiratory Care 2014;59(8):1233–41. [18] Wyckoff MH, Aziz K, Escobedo MB, Kapadia VS, Kattwinkel J, Perlman JM, et al. Part 13: Neonatal Resuscitation 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2015;132(suppl 2):S543–60. [19] Needleman JP, Setty BN, Varlotta L, Dampier C, Allen JL. Measurement of hemoglobin saturation by oxygen in children and adolescents with sickle cell disease. Pediatr Pulmonol 1999;28:423. [20] Ulrich S, Schneider SR, Bloch KE. Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: A systematic review. J Appl Physiol 1985. https://doi.org/10.1152/japplphysiol. 00186.2017. [Epub ahead of print]. [21] William E. Benitz, Patent Ductus arteriosus. In: Fanaroff and Martin’s NeonatalPerinatal Medicine Diseases of the Fetus and Infant 10th edıtıon. chapter 83, pp 1223-30. [22] Härkin P, Marttila R, Pokka T, Saarela T, Hallman M. Morbidities associated with patent ductus arteriosus in preterm infants. Nationwide cohort study. J Matern Fetal Neonatal Med 2017:1–8. https://doi.org/10.1080/14767058.2017.1347921. [23] Moira A. Crowley, Neonatal Respiratory Disorders. In: Fanaroff and Martin’s Neonatal-Perinatal Medicine Diseases of the Fetus and Infant 10th edıtıon, Chapter 74, pp 1113–35.
Conflict of interest statement The authors declare no conflict of interest. References [1] Bernstein Daniel. The fetal to neonatal circulatory transition. In: Kliegman Robert M, Stanton Bonita F, St Geme Joseph W, Schor Nina F, editors. Nelson Textbook of Pediatrics. 20th ed.2016. p. 2161–2 [Chapter 421]. [2] Eastman NJ. Mount Everest in utero. Am J Obstet Gynecol 1954;67:701–11. [3] Grocott MP, Martin DS, Levett DZ, McMorrow R, Windsor J, Montgomery HE. Arterial blood gases and oxygen content in climbers on Mount Everest. N Engl J Med 2009;360:140–9. [4] Martin DS, Khosravi M, Grocott MP, Mythen MG. Concepts in hypoxia reborn. [Epub 2010 Jul 30]. Crit Care 2010;14(4):315. https://doi.org/10.1186/cc9078. [5] Noori S, Wlodaver A, Gottipati V, McCoy M, Schultz D, Escobedo M. Transitional changes in cardiac and cerebral hemodynamics in term neonates at birth. J Pediatr 2012;160(6):943–8. [6] Stoll BJ, Hansen NI, Bell EF, Shankaran S, Laptook AR, Walsh MC, et al. Neonatal outcomes of extremely preterm infants from the NICHD Neonatal Research Network. Pediatrics 2010;126:443. [7] Soul JS, Hammer PE, Tsuji M, Saul JP, Bassan H, Limperopoulos C, et al. Fluctuating pressure-passivity is common in the cerebral circulation of sick premature infants. Pediatr Res 2007;61:467. [8] Noori S, Seri I. Hemodynamic antecedents of peri/intraventricular hemorrhage in very preterm neonates. Semin Fetal Neonatal Med 2015;20:232.
13
Contents lists available at ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
Hypobaric birth room may prevent intraventricular hemorrhage in extremely low birth weights infants
T
⁎
Kadir Şerafettin Tekgündüza, , Sibel Ejder Tekgündüzb a b
Ataturk University Medical Faculty, Division of Neonatology, Erzurum, Turkey İbrahim Hakkı State Hospital, Department of Obstetrics and Gynecology, Erzurum, Turkey
A R T I C LE I N FO
A B S T R A C T
Keywords: High-altitude Extremely low birth weights Hypobaric Intraventricular hemorrhage
In the early postnatal period, intraventricular hemorrhage may develop in infants with extremely low birth weights due to hemodynamic instability. One of the most significant factors in intraventricular hemorrhage development is fluctuations in the cerebral blood flow due to left-to-right shunting as a result of patent ductus arteriosus, and such cases most frequently develop intraventricular hemorrhage within the first 72 h. The frequency of intraventricular hemorrhage may be reduced through the prevention of fluctuations in the cerebral blood flow in this time frame. Based on our hypothesis, we recommend that extremely low birth weight infants should be delivered and monitored in hypobaric rooms for the first three days after birth, as this may reduce leftto-right shunting as a result of patent ductus arteriosus by preventing the rapid drops seen in pulmonary pressure after birth. A more stable hemodynamic status may be achieved by increasing the cerebral blood flow during an acute term in a hypobaric environment. Gradual transition to the normobaric status at the end of the third day may prevent the long-term negative effects of hypobaric conditions.
Introduction Fetal circulation occurs between the placenta and fetus during the intrauterine term, and pulmonary pressure is increased as the lungs are filled in with fetal lung fluid. During fetal circulation, oxygenated blood supplied by the placenta flows into the inferior vena cava through the umbilical vein, mixes with the deoxygenated blood coming from the lower extremities and with the deoxygenated blood coming from superior vena cava in the right atrium. Then, the blood that is pumped from the right ventricle to the pulmonary arteries enters the aorta through the ductus arteriosus [1]. In a fetus, the partial oxygen pressure (PaO2) of the blood in the umbilical vein varies between 30 and 35 mmHg, while the PaO2 of the blood supplying the fetal organs ranges between 26 and 28 mmHg [1]. A fetus completes its intrauterine development over 40 weeks at an atmospheric pressure that is almost equal to the pressure at the top of Mount Everest [2–4]. A term fetus is ready for postnatal adaptation. After birth, the lungs become responsible for oxygen and carbon dioxide exchange, the ductus arteriosus closes, and PaO2 levels that are considered normal for humans are achieved within minutes [1]. However, postnatal adaptation is particularly difficult for extremely low birth weight (ELBW) infants, delivered before the 28th gestational week, with a birth weight of less than 1000 g. The incidence of patent ductus arteriosus (PDA) – the ⁎
incomplete closure of ductus arteriosus – is elevated among ELBW infants due to the immaturity of the oxygen-sensitive smooth muscle cells that are present on the wall of the ductus arteriosus [1]. Systemicpulmonary (left-to-right) shunting through PDA starts within the first eight minutes of birth due to the increase in systemic blood pressure and the decrease in pulmonary pressure. At this stage, cerebral blood flow (CBF) decreases, and hemodynamic instability occurs despite normal oxygen saturation (SaO2) levels [5]. Intraventricular hemorrhage (IVH) is a considerable problem in infants with a birth weight of less than 1000 g ELBW. According to the data provided by the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network, IVH develops in 32% and grade 3 or 4 IVH develops in 16% of ELBW infants [6]. Postnatal fluctuations in CBF are the main factor that underlies an IVH etiopathogenesis in this age group. In particular, CBF fluctuations that occur postnatal within the first 72 h are responsible for IVH development, and this time frame is also associated with the highest risk of hemodynamic instability and the highest frequency of IVH [7,8]. Hypotheses Almost all of the data regarding ELBW morbidity in literature have been collected in studies carried out at sea level or close altitudes
Corresponding author. E-mail addresses: [email protected], [email protected] (K.Ş. Tekgündüz).
https://doi.org/10.1016/j.mehy.2018.07.013 Received 30 January 2018; Accepted 14 July 2018 0306-9877/ © 2018 Elsevier Ltd. All rights reserved.
Medical Hypotheses 119 (2018) 11–13
K.Ş. Tekgündüz, S.E. Tekgündüz
sufficient tissue oxygenation (DO2); cardiac output, O2 and Hb. These factors can be formulated as follows [19]:
(below 1,500 m), and so there is a paucity of data on ELBW morbidity at high altitudes [9,10]. Could a physiological transition be achieved when a preterm infant is delivered at a high altitude region that is similar to the conditions a fetus complete intrauterine development under a low partial oxygen pressure? While there is currently no clear answer to this question we raised, a previous study reported IVH in 8.7% of 80 ELBW infants who were delivered at high altitudes (1800–2000 m) and who underwent transfontanelle USG imaging [9]. Unlike infants delivered at sea level, studies showed that the pulmonary pressure did not drop immediately after birth in infants delivered at high altitudes [10,11]. The hypothesis presented here suggests that the risk of IVH in ELBW infants may be reduced under controlled hypobaric conditions that mimic high altitudes by preventing the rapid drop in postnatal pulmonary pressure, and therefore ensuring hemodynamic stability by reducing the amount of left-to-right shunting and systemic leak. If ELBW infants are delivered and monitored during the initial postnatal days under controlled hypobaric conditions, CBF could be kept more stable with an effect that mimics high altitudes.
DO2 = Cardiac Output × 1. 34∗ (Hgb ×SaO2∗∗) + (Pa02×0.003∗∗∗) *
1.34: Is the oxygen binding capacity of Hb, and should be included in the g/L unit. ** SaO2 is included as a decimal number (e.g. 95% → 0.95). (As this formula initially estimates O2 in the blood supplied to the tissues, the saturation value on pulse-oximetry should be used.) **** Dissolved O2 can be disregarded. Echocardiographic (ECHO) investigations should be performed to estimate the cardiac output while the patient is being monitored in the controlled hypobaric room. It is possible to calculate DO2, and therefore cerebral oxygenation, based on pulse-oximetry results and measurements of the blood gases. At this stage, an ECHO can also be utilized to measure the amount of shunting through PDA and to calculate systemic leak. Based on these measurements, if the cardiac output inclines to drop and the Hb levels and SaO2 are found to be normal despite the left-to-right shunting through PDA, the atmospheric pressure in the hypobaric room can be slightly decreased, for instance, to 781 hPa, which is equal to the pressure at 2100 m. In such a situation, we would expect an increase in pulmonary vascular resistance and a decrease in the systemic leak through PDA under the influence of the effects of the hypobaric conditions. In contrast, in the event of a drop in SaO2 values and a gradual increase in the O2 requirement, or if a pulmonary-tosystemic (right-to-left) shunting through PDA in ECHO is noted, the pressure in the hypobaric room could be increased. With all these adjustments, the hypobaric room becomes a dynamic part of ELBW monitoring.
Evaluation of the hypotheses The effects of high altitudes are not limited to hypoxia. Increased sympathetic activity on ascent causes an initial mild increase in blood pressure, a moderate increase in heart rate and cardiac output and an increase in venous tone [12]. Cerebral blood flow increases at high altitudes during the acute term [13,14]. Of course, in the event of ongoing hypoxia, CBF will decrease due to the decreased cardiac output, and hypoxic damage will be more prominent in the tissues. Altitudes over 1500 m are defined as high altitudes. High altitude disease, characterized by pulmonary and cerebral edema, has been reported at an altitude of 2100 m, although the incidence of this disease increases significantly at altitudes above 4000 m [15,16]. Hypothetically, the atmospheric pressure in a birthing room for ELBW infants could be adjusted to equal the pressure found at 1500–2000 m altitude, and today, atmospheric pressures in hyperbaric rooms could be adjusted to reflect hypobaric conditions [17]. It would be appropriate to divide the postnatal monitoring period for ELBW infants in hypobaric rooms into three sections.
Section 3 – Transition to normobaric conditions After the patient is given postnatal care for 72 h in a hypobaric room, a step-wise transition should be made to normobaric conditions. Very high altitudes are known to increase the incidence of BPD and PDA among preterm infants [10,11]. However, we should highlight that persistent pulmonary hypertension is an untoward condition, and it is known that pulmonary pressure decreases at low altitudes [20]. We believe that the transition to normobaric conditions should be gradual, and that dynamic monitoring should be continued during this transition period. The pressure could firstly be adjusted to 835 hPa, corresponding to an altitude of 1500 m, after which, adjustments could be made according to the atmospheric pressure at altitudes defined as low altitude.
Section 1 – Birth and neonatal resuscitation We recommend that the pressure in the controlled hypobaric room in which the delivery will occur be adjusted to 790 hPa, which is equal to the atmospheric pressure at 2000 m altitude. This altitude will be tolerated by the mother as well. It would also be appropriate for the hypobaric room to be within the neonatal intensive care unit given that the patient will be monitored here for the first three days. Due to the effects of the hypobaric conditions encountered immediately after birth, the infant will also be exposed to a lower degree of oxidative damage during the initial seconds. The resuscitation steps for the ELBW infant, as defined in the Neonatal Resuscitation Program (NRP), should again be performed in the same environment [18]. For ELBW infants, the NRP guidelines recommend the initiation of resuscitation with oxygen support at a concentration of 21–30%. The oxygen supply that is given to the infant does not change the atmospheric pressure [9]. Treatments, such as surfactants or inotropic supplements, should be administered in line with the relevant indications during the first day of monitoring.
Discussion Among all the mortalities in ELBW infants, IVH is particularly important, in that it can give rise to irreversible neurodevelopmental disorders. A hypobaric room hypothesis is suggested as a means of stabilizing CBF and reducing the incidence of IVH. The high frequency of PDA and consequent left-to-right shunting are key factors in this regard [21]. Treatment is recommended only for hemodynamically significant PDA (HsPDA) in preterm infants [20]. Hypobaric conditions aim to ensure hemodynamic stability by reducing shunting through PDA, therefore, the possibility of HsPDA is indeed reduced when the infant is kept in a hypobaric room for the first three days after birth. The pulmonary pressure in such infants could be reduced through the administration of surfactants during the first days of life, although leftto-right shunting through PDA still plays a role in the development of pulmonary hemorrhaging [22,23]. Accordingly, incidences of pulmonary hemorrhaging may also be expected to decrease under hypobaric conditions. It is currently difficult to predict how the first 72 h spent under
Section 2 – Monitoring The monitoring of ELBW infants is a dynamic process, and this process should also include the monitoring of the controlled hypobaric room. There are three significant factors that play specific roles in 12
Medical Hypotheses 119 (2018) 11–13
K.Ş. Tekgündüz, S.E. Tekgündüz
hypobaric conditions, followed by a gradual transition to a normobaric condition, will affect morbidities, such as BPD, NEK and ROP, in ELBW infants. To our knowledge, there is not any research into the consequences of transferring to low altitudes in patients who were delivered at high altitudes. In conclusion, our hypothesis suggested that postnatal hemodynamic adaptation in ELBW infants could be more safely achieved under hypobaric conditions. We predict that the frequency of IVH will be reduced as a result of the decrease in the systemic leak through PDA and the increase of CBF during the acute period.
[9] Caner I, Tekgunduz KS, Temuroglu A, Demirelli Y, Kara M. Evaluation of premature infants hospitalized in neonatal intensive care unit between 2010–2012. [Epub 2014 Aug 26]. Eurasian J Med 2015 Feb;47(1):13–20. https://doi.org/10.5152/ eajm.2014.38. [10] AlShehri Mohammed A. Are preterm infants at high altitude at greater risk for the development of bronchopulmonary dysplasia? J Trop Pediatr 2014;60(1):68–73. [11] Niermeyer Susan. Cardiopulmonary transition in the high altitude infant. High Altitude Med Biol July 2004;4(2):225–39. [12] Paralikar SJ, Paralikar JH. High-altitude medicine. Indian J Occup Environ Med 2010;14(1):6–12. https://doi.org/10.4103/0019-5278.64608. [13] Schoene RB. Illnesses at high altitude. Chest 2008;134:402. [14] American West JB. College of Physicians, American Physiological Society. The physiologic basis of high-altitude diseases. Ann Intern Med 2004;141:789. [15] Wu TY, Ding SQ, Liu JL, et al. Who should not go high: chronic disease and work at altitude during construction of the Qinghai-Tibet railroad. High Alt Med Biol 2007;8:88. [16] Hackett PH, Rennie D, Levine HD. The incidence, importance, and prophylaxis of acute mountain sickness. Lancet 1976;2:1149. [17] Boussen S, Coulange M, Fournier M, Gainnier M, Michelet P, Micoli C, et al. Evaluation of transport ventilators at mild simulated altitude: a bench study in a hypobaric chamber. Respiratory Care 2014;59(8):1233–41. [18] Wyckoff MH, Aziz K, Escobedo MB, Kapadia VS, Kattwinkel J, Perlman JM, et al. Part 13: Neonatal Resuscitation 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2015;132(suppl 2):S543–60. [19] Needleman JP, Setty BN, Varlotta L, Dampier C, Allen JL. Measurement of hemoglobin saturation by oxygen in children and adolescents with sickle cell disease. Pediatr Pulmonol 1999;28:423. [20] Ulrich S, Schneider SR, Bloch KE. Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: A systematic review. J Appl Physiol 1985. https://doi.org/10.1152/japplphysiol. 00186.2017. [Epub ahead of print]. [21] William E. Benitz, Patent Ductus arteriosus. In: Fanaroff and Martin’s NeonatalPerinatal Medicine Diseases of the Fetus and Infant 10th edıtıon. chapter 83, pp 1223-30. [22] Härkin P, Marttila R, Pokka T, Saarela T, Hallman M. Morbidities associated with patent ductus arteriosus in preterm infants. Nationwide cohort study. J Matern Fetal Neonatal Med 2017:1–8. https://doi.org/10.1080/14767058.2017.1347921. [23] Moira A. Crowley, Neonatal Respiratory Disorders. In: Fanaroff and Martin’s Neonatal-Perinatal Medicine Diseases of the Fetus and Infant 10th edıtıon, Chapter 74, pp 1113–35.
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