Name: Continuous Telemetric In Utero Tracheal Pressure Measurements in Fetal Lambs (Video) | JoVE Journal
Uploaded: 2023-12-22T12:00:00.000+00:00
Duration: 5 min 40 s
Description: Learn continuous telemetric monitoring of fetal intratracheal and amniotic pressure in pregnant ewes. This method enables stress-free data collection to optimize tracheal occlusion treatment for congenital diaphragmatic hernia.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

The authors acknowledge the surgical assistance of Jane Choi (University of Western Australia), Ellen Williams (University of Western Australia), and Veena Kurup (University of Western Australia), as well as the husbandry care of the Animal Care Services staff at the University of Western Australia. This study was supported by the Telethon Perth Children&#39;s Research Fund, National Health and Medical Research Council RF 1077691 (JJP), Metropolitan Health and Medical Research Infrastructure Fund (West Australian Government), and Australian International Research Training Program (MD).

The protocol adhered to the Australian National Health and Medical Research Council Australian code for the care and use of animals for scientific purposes18. The University of Western Australia Animal Ethics Committee prospectively approved the protocol (RA3/100/1596). Sheep were sourced from the University of Western Australia (UWA) Ridgefield farm (2018-2020). The sheep were introduced to the AAALAC-accredited UWA Large Animal Facility 2-3 weeks prior to surgical intervention. Sheep were initially housed indoors in shared raised floor pens, with single pens used in the peri-operative period. Sheep were fed pellets, oaten chaff, and lupins with a mineral mix calculated on body weight. Rooms were controlled for temperature (20.5-21.5 &#176;C) and maintained on a 12:12 h light: dark cycle. Pain and well-being were evaluated in the postoperative period twice daily for 7 days, then daily until study completion. Monitored postoperative parameters included signs of pain, orbital tightening, respiratory effort, temperature, heart rate, the surgical site, appetite and water intake, activity, lameness, coat condition, fecal consistency, preterm labor, demeanor, and signs of pregnancy toxemia. The scores attributed to each parameter triggered an intervention where necessary.
NOTE: Two recovery surgical procedures were required: ewe preparation, surgical approach and closure, and ewe recovery are the same for both surgical procedures. The first procedure is the surgical creation of the diaphragmatic hernia in the fetal lamb. The second procedure is for placement of the fetal intervention and pressure monitoring device. The study design necessitated two survival surgeries to allow for the abdominal contents to move into the chest cavity after the creation of the diaphragmatic hernia so that lung hypoplasia could develop before the subsequent intervention surgery.
1. Surgical creation of the diaphragmatic hernia in the fetal lamb
<ol>
	<li>Ewe preparation
	<ol>
		<li>At ~80 days gestation, premedicate the ewe with an intramuscular injection of acepromazine (0.04 mg/Kg) and morphine (0.3 mg/Kg).</li>
		<li>Induce anesthesia intravenously with ketamine (5 mg/Kg) and midazolam (0.25 mg/Kg).</li>
		<li>Intubate the ewe trachea with an endotracheal tube (8 mm inner diameter [ID]). Maintain anesthesia with isoflurane (1%-3% in oxygen) delivered by positive pressure ventilation (10-12 breaths/min, tidal volume 8-10 mL/kg).</li>
		<li>Establish ewe monitoring with an electrocardiogram (ECG), invasive arterial blood pressure via an ear arterial catheter, expired CO2, peripheral oxygen saturation, and temperature during surgery.</li>
		<li>Place the ewe supine on the gurney. Loop ropes around the ewe&#39;s legs and gently secure to the table.</li>
		<li>Shear wool from the ewe&#39;s abdomen and flank and then clip it close to the skin.</li>
		<li>Remove dirt and lanolin from the ewe&#39;s abdomen, flank, and groin with soap and water.</li>
		<li>Give cefazolin (20 mg/Kg) intravenously every 90 min during surgery.</li>
		<li>Transfer the ewe to the surgical theatre on a gurney.</li>
		<li>Move the ewe from the transport gurney to the surgical table.</li>
		<li>Place ewe in dorsal recumbency position on the surgical table.</li>
		<li>Secure all limbs to the surgical table with soft rope ties.</li>
		<li>Aseptic preparation of the exposed abdomen: Wash 3 times with 4% chlorhexidine surgical scrub, removing contaminated solution between each wash with 70% alcohol.</li>
		<li>Complete sterile preparation by lightly spraying 10% iodine solution on the abdomen, flank, and groins.</li>
		<li>Cover the ewe with a sterile fenestrated surgical drape so that only the abdominal incision site is exposed. Ensure that all surgical instruments, catheters, syringes, and solutions used during surgery are sterile.</li>
	</ol>
	</li>
	<li>Surgical approach
	<ol>
		<li>Establish line-block local anesthesia by local subcutaneous and muscular infiltration of bupivacaine (5%; 9.5 mL) with a 10 mL syringe and 22 G needle.</li>
		<li>Expose the uterus by a para-midline abdominal incision (8-11 cm) through the ewe&#39;s skin, subcutaneous tissue, and linea alba made with a size 10 surgical blade with cautery as required to minimize incisional bleeding.</li>
	</ol>
	</li>
	<li>Diaphragmatic hernia creation
	<ol>
		<li>Locate the fetal head/thorax via palpation.</li>
		<li>Cover the uterus with sterile plastic wrap.</li>
		<li>Use surgical scissors to make a window (6 cm x 4 cm) in the plastic wrap.</li>
		<li>Make a 5-7 cm uterine incision through the uterus and amniotic sac with cautery cutting, avoiding uterine blood vessels and placental cotyledons.</li>
		<li>Exteriorize the fetal head and forelimbs.</li>
		<li>Use Babcock uterine clamps to seal the uterine incision edges and sterile plastic wrap tightly around the fetal abdomen to prevent amniotic fluid loss.</li>
		<li>Position the fetus on its right side and secure a second sterile plastic wrap over the exteriorized fetus to reduce loss of heat and moisture. Identify the intercostal space between the 9th and 10th ribs on the left and cut a hole in the plastic wrap with surgical scissors to access the intended fetal incision site.</li>
		<li>Establish line-block local anesthesia in the fetus by local subcutaneous and muscular infiltration of bupivacaine (5%; 0.25 mL diluted to 0.5 mL with sterile saline; 1 mL sterile syringe and 27 G needle) in the 9th intercostal space immediately adjacent to the upper border of the 10th rib to avoid subcostal vessels.</li>
		<li>Use a 60 mL sterile syringe to bathe the exposed fetal skin with warm Hartmann&#39;s solution (5-10 mL every 5-10 min) to keep the fetal skin moist throughout subsequent steps.</li>
		<li>Create a left posterolateral thoracotomy by making a 2-4 cm skin incision with electrocautery in the 9th intercostal space immediately adjacent to the cranial border of the 10th rib.</li>
		<li>Use mosquito hemostats to bluntly dissect the subcutaneous tissue, intercostal muscles, and pleural membrane to access the diaphragm.</li>
		<li>Use two small mosquito hemostats to pick up the diaphragm at each end of the intended 1 cm long hernia site and cranially elevate the diaphragm to keep it away from the underlying stomach, liver, and spleen.</li>
		<li>Make a 1 cm incision between the two hemostats using small angled scissors.</li>
		<li>Release the hemostats holding the diaphragm.</li>
		<li>Use atraumatic Potts forceps to pull the stomach superiorly through the hole in the diaphragm.</li>
		<li>Use a single tie of absorbable 5-0 polydioxanone monofilament (RB-1 taper point needle) to carefully envelop the 9th and 10th ribs to oppose the fetal ribs, avoiding the underlying lung.</li>
		<li>Close thoracotomy incision with a mattress suture (absorbable 5-0 polydioxanone monofilament).</li>
	</ol>
	</li>
	<li>Surgical closure
	<ol>
		<li>Return the fetus to the amniotic sac.</li>
		<li>Administer intra-operative meloxicam (0.25 mg/Kg; subcutaneously) to the ewe for postoperative analgesia.</li>
		<li>Replace lost amniotic fluid using warmed Hartmann&#39;s solution (~50 mL) along with intra-amniotic Piperacillin/Tazobactam (1000 mg/125 mg).</li>
		<li>Appose the opposing surfaces of the chorioamnion and adjacent uterine walls and use an absorbable polyglactin 910 braided 2-0 suture with an inverted mattress suture to close the uterus and amniotic sac together.</li>
		<li>Close the ewe&#39;s linea alba, subcutaneous tissue, and skin (absorbable polydioxanone monofilament 1, absorbable poliglecaprone 25 monofilament 3-0, and nonabsorbable polypropylene monofilament 2-0 respectively).</li>
	</ol>
	</li>
	<li>Ewe recovery and monitoring
	<ol>
		<li>Spray the abdominal wound post-operatively with waterproof dressing retention tape and cover it with a dressing to reduce the risk of postoperative wound infection.</li>
		<li>Apply a transdermal fentanyl patch (100 &#181;g/h) to the groin for additional postoperative analgesia.</li>
		<li>Recover the ewe and extubate when breathing spontaneously, then allow it to wake.</li>
		<li>Monitor ewes daily until delivery for fetal intervention surgery.</li>
		<li>Remove sutures after 14 days.</li>
	</ol>
	</li>
</ol>
2. Placement of the fetal intervention and pressure monitoring device
<ol>
	<li>Ewe preparation for fetal intervention surgery at 101 days of gestation
	<ol>
		<li>Inject medroxyprogesterone (1 mL) intramuscularly at ~85 days of gestation (term ~147 days) to reduce the risk of preterm birth.</li>
		<li>Use the same anesthetic and surgical preparation procedure used for the initial diaphragm creation surgery.
		<ol>
			<li>Follow the surgical approach in steps 2.1.2.2 and 2.1.2.3, similar to steps 1.2.1-1.2.2.</li>
			<li>Establish line-block local anesthesia by local subcutaneous and muscular infiltration of bupivacaine (5 %; 9.5 mL) with a 10 mL syringe and 22 G needle.</li>
			<li>With a para-midline abdominal incision (8 - 11 cm) adjacent to the abdominal incision site used for the diaphragm creation surgery, expose the uterus with a through the ewe&#39;s skin, subcutaneous tissue, and linea alba made with a size 10 surgical blade with cautery as required to minimize incisional bleeding.</li>
		</ol>
		</li>
		<li>Additionally, administer oxytetracycline (20 mg/Kg) intramuscularly to the ewe to provide fetal antimicrobial protection against the chronically implanted monitoring device.</li>
	</ol>
	</li>
	<li>Device activation
	<ol>
		<li>Activate pressure measurement device19.</li>
		<li>Clamp pressure measurement tubing with hemostats.</li>
		<li>Place the entire device into a sterile bowl containing a mixture of 0.08% peracetic acid and 1% hydrogen peroxide for at least 1 h, ensuring the entire device is covered.</li>
		<li>Using a sterile clamp, move the device to a sterile bowl containing sterile water for at least 10 min prior to fetal implantation. Ensure the entire device is covered with sterile water.</li>
	</ol>
	</li>
	<li>Surgical approach and fetal intervention
	<ol>
		<li>Exteriorize the fetal head by hysterotomy using the same surgical approach used for the initial surgery but with adjacent uterine incisions (steps 1.1-2.2).</li>
		<li>Keep the exteriorized fetal head and neck wrapped in the sterile plastic drape to minimize loss of temperature and fluid.</li>
		<li>Instrument the trachea with a catheter for pressure measurements (Figure 1).
		<ol>
			<li>For unoccluded trachea, follow steps 2.3.3.2-2.3.3.3.</li>
			<li>Intubate the fetal lamb with a 5 French (1.67 mm ID) suction catheter with the suction connector removed to a depth of 14 cm at the corner of the lamb&#39;s mouth.</li>
			<li>Connect the external end of the catheter with a 1.59 mm (outside diameter, OD) to 3.18 mm (OD) connector to 30 cm long 3.18 mm (ID) silicone tubing.</li>
			<li>For cccluded trachea, follow steps 2.3.3.5-2.3.3.6.</li>
			<li>Intubate the fetal lamb with a 3.0 microcuff endotracheal tube with the connector removed to a depth of 14 cm to a corner of the lamb&#39;s mouth.</li>
			<li>Connect the external end of the catheter with a 3.18 mm (OD) to 3.18 mm (OD) connector to 30 cm long 3.18 mm (ID) silicone tubing.</li>
		</ol>
		</li>
		<li>Connect the other end of the 30 cm long 3.18 mm (ID) silicone tubing to the pressure measurement device by a 3.18 mm (OD) to 1.59 mm (OD) connector on the pressure measurement device.</li>
		<li>Suture the catheter at the corner of the lamb&#39;s mouth and neck (nonabsorbable nylon monofilament 4-0).</li>
		<li>Secure the pressure measurement device to the lamb&#39;s skin on the chest (nonabsorbable nylon monofilament 4-0) (Figure 2).</li>
	</ol>
	</li>
	<li>Close the fetal and ewe surgical incisions as per initial diaphragmatic hernia creation surgery (steps 1.4- 1.5).</li>
	<li>Test device
	<ol>
		<li>Test if the device is transmitting signal19.</li>
	</ol>
	</li>
	<li>Ewe recovery and monitoring
	<ol>
		<li>Recover the ewe as per the initial surgery.</li>
		<li>Monitor ewes daily until delivery.</li>
		<li>Give a second dose of medroxyprogesterone (0.5 mL) intramuscularly at ~120 days of gestation.</li>
		<li>Give betamethasone (5.7 mg) intramuscularly 48 h and 24 h before cesarean delivery to promote fetal maturation for postnatal care.</li>
	</ol>
	</li>
	<li>Lamb delivery
	<ol>
		<li>At ~142 days of gestation (term ~147-150 days), pre-medicate ewe by intramuscular injection of acepromazine (0.03 mg/Kg) and morphine (0.3 mg/Kg).</li>
		<li>Induce anesthesia intravenously with thiopental (10-15 mg/Kg), intubate the ewe with an endotracheal tube (size 8.5 mm), and maintain anesthesia by isofluorane with appropriate monitoring per earlier anesthetics.</li>
		<li>Proceed with surgical delivery of the fetus via hysterotomy as per previous surgeries, with ewe in dorsal recumbency (steps 1.1 - 2.2).</li>
		<li>Remove the monitoring device. Clean the device with water and 70% ethanol.</li>
		<li>Humanely kill the ewe with an intravenous injection of 160 mg/Kg of pentobarbitone sodium solution.</li>
		<li>Resuscitate and ventilate the lamb for 2-3 h and then humanely kill (160 mg/Kg of pentobarbitone sodium solution, intravenous injection).</li>
	</ol>
	</li>
	<li>Data
	<ol>
		<li>Download data to a laptop and analyze19. Filter the pressure data using a 6-h window. Compute the difference in pressure between amniotic and tracheal pressures.</li>
	</ol>
	</li>
</ol>

<ol><li>Harding, R., Hooper, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Regulation+of+lung+expansion+and+lung+growth+before+birth%5BTitle%5D)+AND+%22J+Appl+Physiol+%281985%29%22%5BJournal%5D)">Regulation of lung expansion and lung growth before birth.</a> J Appl Physiol (1985). 81 (1), 209-224 (1996).</li>
<li>Olver, R. E., Strang, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ion+fluxes+across+the+pulmonary+epithelium+and+the+secretion+of+lung+liquid+in+the+foetal+lamb%5BTitle%5D)+AND+%22J+Physiol%22%5BJournal%5D)">Ion fluxes across the pulmonary epithelium and the secretion of lung liquid in the foetal lamb.</a> J Physiol. 241 (2), 327-357 (1974).</li>
<li>Schittny, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+of+the+lung%5BTitle%5D)+AND+%22Cell+Tissue+Res%22%5BJournal%5D)">Development of the lung.</a> Cell Tissue Res. 367 (3), 427-444 (2017).</li>
<li>Vilos, G. A., Liggins, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Intrathoracic+pressures+in+fetal+sheep%5BTitle%5D)+AND+%22J+Dev+Physiol%22%5BJournal%5D)">Intrathoracic pressures in fetal sheep.</a> J Dev Physiol. 4 (4), 247-256 (1982).</li>
<li>Dawes, G. S., Fox, H. E., Leduc, B. M., Liggins, G. C., Richards, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Respiratory+movements+and+rapid+eye+movement+sleep+in+the+foetal+lamb%5BTitle%5D)+AND+%22J+Physiol%22%5BJournal%5D)">Respiratory movements and rapid eye movement sleep in the foetal lamb.</a> J Physiol. 220 (1), 119-143 (1972).</li>
<li>Bowes, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+of+patterns+of+respiratory+activity+in+unanesthetized+fetal+sheep+in+utero%5BTitle%5D)+AND+%22J+Appl+Physiol+Respir+Environ+Exerc+Physiol%22%5BJournal%5D)">Development of patterns of respiratory activity in unanesthetized fetal sheep in utero.</a> J Appl Physiol Respir Environ Exerc Physiol. 50 (4), 693-700 (1981).</li>
<li>Clewlow, F., Dawes, G., Johnston, B., Walker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Changes+in+breathing%2C+electrocortical+and+muscle+activity+in+unanaesthetized+fetal+lambs+with+age%5BTitle%5D)+AND+%22J+Physiol%22%5BJournal%5D)">Changes in breathing, electrocortical and muscle activity in unanaesthetized fetal lambs with age.</a> J Physiol. 341, 463-476 (1983).</li>
<li>Chapman, R. L., Dawes, G. S., Rurak, D. W., Wilds, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Breathing+movements+in+fetal+lambs+and+the+effect+of+hypercapnia%5BTitle%5D)+AND+%22J+Physiol%22%5BJournal%5D)">Breathing movements in fetal lambs and the effect of hypercapnia.</a> J Physiol. 302, 19-29 (1980).</li>
<li>Badalian, S. S., Fox, H. E., Chao, C. R., Timor-Tritsch, I. E., Stolar, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fetal+breathing+characteristics+and+postnatal+outcome+in+cases+of+congenital+diaphragmatic+hernia%5BTitle%5D)+AND+%22Am+J+Obstet+Gynecol%22%5BJournal%5D)">Fetal breathing characteristics and postnatal outcome in cases of congenital diaphragmatic hernia.</a> Am J Obstet Gynecol. 171, 970-976 (1994).</li>
<li>Badalian, S. S., Fox, H. E., Zimmer, E. Z., Fifer, W. P., Stark, R. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Patterns+of+perinasal+fluid+flow+and+contractions+of+the+diaphragm+in+the+human+fetus%5BTitle%5D)+AND+%22Ultrasound+Obstet+Gynecol%22%5BJournal%5D)">Patterns of perinasal fluid flow and contractions of the diaphragm in the human fetus.</a> Ultrasound Obstet Gynecol. 8 (2), 109-113 (1996).</li>
<li>Fox, H. E., Moessinger, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fetal+breathing+movements+and+lung+hypoplasia%3A+preliminary+human+observations%5BTitle%5D)+AND+%22Am+J+Obstet+Gynecol%22%5BJournal%5D)">Fetal breathing movements and lung hypoplasia: preliminary human observations.</a> Am J Obstet Gynecol. 151 (4), 531-533 (1985).</li>
<li>Fox, H. E., Badalian, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ultrasound+prediction+of+fetal+pulmonary+hypoplasia+in+pregnancies+complicated+by+oligohydramnios+and+in+cases+of+congenital+diaphragmatic+hernia%3A+A+review%5BTitle%5D)+AND+%22Am+J+Perinatol%22%5BJournal%5D)">Ultrasound prediction of fetal pulmonary hypoplasia in pregnancies complicated by oligohydramnios and in cases of congenital diaphragmatic hernia: A review.</a> Am J Perinatol. 11 (2), 104-108 (1994).</li>
<li>Fox, H. E., Badalian, S. S., Fifer, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Patterns+of+fetal+perinasal+fluid+flow+in+cases+of+congenital+diaphragmatic+hernia%5BTitle%5D)+AND+%22Am+J+Obstet+Gynecol%22%5BJournal%5D)">Patterns of fetal perinasal fluid flow in cases of congenital diaphragmatic hernia.</a> Am J Obstet Gynecol. 176 (4), 807-813 (1997).</li>
<li>Carmel, J. A., Friedman, F., Adams, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fetal+tracheal+ligation+and+lung+development%5BTitle%5D)+AND+%22Am+J+Dis+Child%22%5BJournal%5D)">Fetal tracheal ligation and lung development.</a> Am J Dis Child. 109, 452-456 (1965).</li>
<li>Deprest, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Randomized+trial+of+fetal+surgery+for+moderate+left+diaphragmatic+hernia%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Randomized trial of fetal surgery for moderate left diaphragmatic hernia.</a> N Engl J Med. 385 (2), 119-129 (2021).</li>
<li>Deprest, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Randomized+trial+of+fetal+surgery+for+severe+left+diaphragmatic+hernia%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Randomized trial of fetal surgery for severe left diaphragmatic hernia.</a> N Engl J Med. 385 (2), 107-118 (2021).</li>
<li>Van Calster, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+randomized+TOTAL-trials+on+fetal+surgery+for+congenital+diaphragmatic+hernia%3A+re-analysis+using+pooled+data%5BTitle%5D)+AND+%22Am+J+Obstet+Gynecol%22%5BJournal%5D)">The randomized TOTAL-trials on fetal surgery for congenital diaphragmatic hernia: re-analysis using pooled data.</a> Am J Obstet Gynecol. 226 (4), 560.e1-560.e24 (2021).</li>
<li>NHMRC. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=%22National+Health+and+Medical+Research+Council+%282013%29+Australian+Code+for+the+Care+and+Use+of+Animals+for+Scientific+Purposes%22">National Health and Medical Research Council (2013) Australian Code for the Care and Use of Animals for Scientific Purposes</a>. , 8th edition, National Health and Medical Research Council. Canberra. (2021).</li>
<li>Robbiani, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+implantable+electronic+device+for+monitoring+fetal+lung+pressure+in+a+lamb+model+of+Congenital+Diaphragmatic+Hernia%5BTitle%5D)+AND+%22IEEE+Transactions+on+Instrumentation+and+Measurement%22%5BJournal%5D)">An implantable electronic device for monitoring fetal lung pressure in a lamb model of Congenital Diaphragmatic Hernia.</a> IEEE Transactions on Instrumentation and Measurement. 71, 1-10 (2022).</li>
<li>Moessinger, A. C., Harding, R., Adamson, T. M., Singh, M., Kiu, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Role+of+lung+fluid+volume+in+growth+and+maturation+of+the+fetal+sheep+lung%5BTitle%5D)+AND+%22J+Clin+Invest%22%5BJournal%5D)">Role of lung fluid volume in growth and maturation of the fetal sheep lung.</a> J Clin Invest. 86 (4), 1270-1277 (1990).</li>
<li>Dickson, K. A., Harding, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fetal+breathing+and+pressures+in+the+trachea+and+amniotic+sac+during+oligohydramnios+in+sheep%5BTitle%5D)+AND+%22J+Appl+Physiol+%281985%29%22%5BJournal%5D)">Fetal breathing and pressures in the trachea and amniotic sac during oligohydramnios in sheep.</a> J Appl Physiol (1985). 70 (1), 293-299 (1991).</li>
<li>Alcorn, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Morphological+effects+of+chronic+tracheal+ligation+and+drainage+in+the+fetal+lamb+lung%5BTitle%5D)+AND+%22J+Anatomy%22%5BJournal%5D)">Morphological effects of chronic tracheal ligation and drainage in the fetal lamb lung.</a> J Anatomy. 123 (3), 649-660 (1977).</li>
<li>Wigglesworth, J. S., Desai, R., Hislop, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fetal+lung+growth+in+congenital+laryngeal+atresia%5BTitle%5D)+AND+%22Pediatr+Pathol%22%5BJournal%5D)">Fetal lung growth in congenital laryngeal atresia.</a> Pediatr Pathol. 7 (5-6), 515-525 (1987).</li>
<li>Khan, P. A., Cloutier, M., Piedboeuf, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tracheal+occlusion%3A+a+review+of+obstructing+fetal+lungs+to+make+them+grow+and+mature%5BTitle%5D)+AND+%22Am+J+Med+Genet+C+Semin+Med+Genet%22%5BJournal%5D)">Tracheal occlusion: a review of obstructing fetal lungs to make them grow and mature.</a> Am J Med Genet C Semin Med Genet. 145C (2), 125-138 (2007).</li>
<li>De Paepe, M. E., Johnson, B. D., Papadakis, K., Luks, F. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Lung+growth+response+after+tracheal+occlusion+in+fetal+rabbits+is+gestational+age-dependent%5BTitle%5D)+AND+%22Am+J+Respir+Cell+Mol+Biol%22%5BJournal%5D)">Lung growth response after tracheal occlusion in fetal rabbits is gestational age-dependent.</a> Am J Respir Cell Mol Biol. 21 (1), 65-76 (1999).</li>
<li>Probyn, M. E., Wallace, M. J., Hooper, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+increased+lung+expansion+on+lung+growth+and+development+near+midgestation+in+fetal+sheep%5BTitle%5D)+AND+%22Pediatr+Res%22%5BJournal%5D)">Effect of increased lung expansion on lung growth and development near midgestation in fetal sheep.</a> Pediatr Res. 47 (6), 806-812 (2000).</li>
<li>Hashim, E., Laberge, J. M., Chen, M. F., Quillen, E. W. Jr <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Reversible+tracheal+obstruction+in+the+fetal+sheep%3A+effects+on+tracheal+fluid+pressure+and+lung+growth%5BTitle%5D)+AND+%22J+Pediatr+Surg%22%5BJournal%5D)">Reversible tracheal obstruction in the fetal sheep: effects on tracheal fluid pressure and lung growth.</a> J Pediatr Surg. 30 (8), 1172-1177 (1995).</li>
<li>Hellmeyer, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Telemetric+monitoring+of+tracheal+pressure+after+tracheal+occlusion+for+treatment+of+severe+congenital+diaphragmatic+hernia%5BTitle%5D)+AND+%22Arch+Gynecol+Obstet%22%5BJournal%5D)">Telemetric monitoring of tracheal pressure after tracheal occlusion for treatment of severe congenital diaphragmatic hernia.</a> Arch Gynecol Obstet. 275 (4), 245-248 (2007).</li>
</ol>

The authors declare that no conflicts of interest exist.

Fetal lung liquid fills the potential airspaces during gestation and is vital for normal lung development1. Altering the normal lung liquid amount and pressure affects fetal lung growth: narrowing or constriction of the fetal trachea leads to lung hyperplasia; conversely, oligohydramnios and chronic drainage of lung fluid cause lung hypoplasia20,21,22,23. Tracheal occlus...

Normal lung development and growth rely upon the expansion of the potential airspaces with fetal lung liquid and the controlled efflux of the lung liquid into the amniotic space1,2,3,4,5. Fetal lung liquid production and the resistance of the upper airways create an in utero intrathoracic pressure1. Historically, in utero measurements of fetal airway pressures were obtained using external pressure sensors via catheters tunneled through the abdominal wall to the fetal trachea5,6,7,8,9,10,11,12,13. The use of these catheters and external sensors (distal to the measurement site) may dampen the pressure signal and necessitate restricted movement of the ewe for continuous measurement or measurements obtained at intervals across gestation. This study aimed to develop a method that allows continuous monitoring of fetal intratracheal and amniotic pressure in unrestrained pregnant animals. The continuous measurements of fetal intratracheal and amniotic pressure will provide a complete understanding of how these pressures change throughout the day over the course of gestation.
Human fetuses with congenital diaphragmatic hernia (CDH) have lung hypoplasia due to herniation of the stomach, the bowel, and the liver (in the most severe cases) into the chest cavity. Lung hyperplasia in infants with tracheal atresia (narrowing of the trachea) highlighted the potential of therapeutic tracheal occlusion for antenatal treatment of CDH14. Tracheal occlusion using an intra-tracheal balloon reduces the severity of lung hypoplasia in fetuses with CDH but at the cost of an increased risk of premature birth15,16,17. An additional risk of aspiration or suffocation exists if the balloon is not removed before birth. Consequently, current tracheal occlusion protocols require a second fetal procedure to remove the balloon occlusion before birth17. The optimal occlusion pressure and duration required to improve lung hypoplasia with tracheal occlusion is unknown, but this knowledge is vital for the optimization of in utero corrective treatments for CDH.
We tested the method using fetal lambs with a surgically created diaphragmatic hernia with and without an occluded trachea.

<table><tbody><tr><td>1.59 mm (outside diameter, OD) to 3.18 mm (OD) connector</td><td>Qosina</td><td>11913</td><td></td></tr><tr><td>3.18 mm (OD) to 3.18 mm (OD) connector</td><td>Qosina</td><td>11684</td><td></td></tr><tr><td>70 % Alcohol</td><td>Henry Schein</td><td>1127067</td><td></td></tr><tr><td>Absorbable poliglecaprone 25 monofilament 3-0</td><td>Riverpoint Medical</td><td>Q316</td><td></td></tr><tr><td>Absorbable polydioxanone monofilament 1</td><td>Riverpoint Medical</td><td>D879</td><td></td></tr><tr><td>Absorbable polyglactin 910 braided 2-0</td><td>Riverpoint Medical</td><td>V317</td><td></td></tr><tr><td>Absorbable polydioxanone monofilament 5-0</td><td>Riverpoint Medical</td><td>D303</td><td></td></tr><tr><td>Acepromazine</td><td>Ceva Animal Health</td><td>APVMA No: 36680</td><td></td></tr><tr><td>Babcock, uterine forceps 6.25 inch</td><td>Roboz</td><td>RS-8022</td><td></td></tr><tr><td>Betamethasone</td><td>Merck Sharp &amp;amp; Dohme</td><td>Aust R 18777</td><td></td></tr><tr><td>Blade, size 10</td><td>Becton Dickinson</td><td>371110</td><td></td></tr><tr><td>Blade, size 15</td><td>Becton Dickinson</td><td>371115</td><td></td></tr><tr><td>Bupivacaine</td><td>Pfizer Australia Pty Ltd</td><td>AUST R 11312</td><td></td></tr><tr><td>Cefazolin</td><td>AFT pharmaceuticals</td><td>AUST R 171582</td><td></td></tr><tr><td>Chlorhexidine</td><td>Henry Schein</td><td>0404-0175-02</td><td></td></tr><tr><td>Endotracheal tube (size 8.0)</td><td>&amp;nbsp;Jorgen Kruuse</td><td>272411</td><td></td></tr><tr><td>Forceps, Potts-Smith</td><td>Roboz</td><td>RS-5314</td><td></td></tr><tr><td>Iodine solution (10 %)</td><td>Henry Schein</td><td>6907281</td><td></td></tr><tr><td>Isoflurane</td><td>Piramal Critical Care&amp;nbsp;</td><td>APVMA No: 53120/112272&lt;br/&gt; M. L. No.:220/AP/MD/96/B&amp;amp;F/R</td><td></td></tr><tr><td>Ketamine</td><td>Ceva Animal Health</td><td>APVMA 37711/58317&lt;br/&gt; KETALAB04</td><td></td></tr><tr><td>Hartmanns Solution</td><td>Baxter&amp;nbsp;</td><td>AUST R 48510</td><td></td></tr><tr><td>Hemostats, Mosquito forceps curved delicate</td><td>Roboz</td><td>RS-7271</td><td></td></tr><tr><td>Medroxyprogesterone acetate</td><td>Pfizer Australia Pty Ltd</td><td>AUST R 12300</td><td></td></tr><tr><td>Meloxicam</td><td>Ilium</td><td>APVMA Approval No.: 62535/127884&lt;br/&gt; LI0119V1</td><td></td></tr><tr><td>Methocel</td><td>Colorcon&amp;nbsp;</td><td>ID34435</td><td></td></tr><tr><td>Microcuff endotracheal tube (3.0)</td><td>Halyard</td><td>35111</td><td></td></tr><tr><td>Midazolam</td><td>Mylan</td><td>AUST R 160205</td><td></td></tr><tr><td>Morphine</td><td>Pfizer Australia Pty Ltd</td><td>AUST R 101240</td><td></td></tr><tr><td>Needle, 22 G</td><td>Becton Dickinson</td><td>305155</td><td></td></tr><tr><td>Needle, 27 G</td><td>Becton Dickinson</td><td>305109</td><td></td></tr><tr><td>Nonabsorbable nylon monofilament 4-0</td><td>Riverpoint Medical</td><td>662BL</td><td></td></tr><tr><td>Nonabsorbable polypropylene monofilament 2-0</td><td>Riverpoint Medical</td><td>P8411</td><td></td></tr><tr><td>OpSite Transparent Film</td><td>Smith and Nephew</td><td>66000040</td><td></td></tr><tr><td>Oxytetracycline</td><td>Norbrook</td><td>APVMA Approval No: 53087/49616</td><td></td></tr><tr><td>Pentobarbitone sodium 300 mg/mL</td><td>Jurox</td><td>APVMA 36208</td><td></td></tr><tr><td>Peracetic acid/hydrogen peroxide</td><td>Medivators Inc&amp;nbsp;</td><td>ref: 78401-649</td><td></td></tr><tr><td>Piperacillin/Tazobactam&amp;nbsp;</td><td>Sandoz Pty Ltd</td><td>AUST R 140840</td><td></td></tr><tr><td>Scissors, Metzenbaum Surgical 7 inch straight</td><td>Roboz</td><td>RS-6955SC</td><td></td></tr><tr><td>Scissors, Vannas 0.15 mm tip width</td><td>Roboz</td><td>RS-5618</td><td></td></tr><tr><td>Silicone tubing (1.59 mm inside diameter)</td><td>Qosina</td><td>T2013</td><td></td></tr><tr><td>Suction catheter (5 French)</td><td>Covidien</td><td>30500</td><td></td></tr><tr><td>Syringe, 1 mL</td><td>Becton Dickinson</td><td>309659</td><td></td></tr><tr><td>Syringe, 10 mL</td><td>Becton Dickinson</td><td>309604</td><td></td></tr><tr><td>Syringe, 60 mL</td><td>Becton Dickinson</td><td>309654</td><td></td></tr><tr><td>Telemetry device</td><td>Politecnico di Milano</td><td>-</td><td>Not commercially available</td></tr><tr><td>Thiopentone sodium</td><td>Jurox Pty Ltd</td><td>APVMA No. 51520/5g/0809</td><td></td></tr><tr><td>Transdermal fentanyl patch</td><td>Janssen-Cilag Pty Ltd</td><td>AUST R 112371</td><td></td></tr></tbody></table>

continuous telemetric in utero tracheal pressure measurements in fetal lambs

Continuous Telemetric In Utero Tracheal Pressure Measurements in Fetal Lambs

Normal in utero lung development and growth rely upon the expansion of airspaces and the controlled efflux of lung liquid into the amniotic space. Infants with congenital diaphragmatic hernia (CDH) also have lung hypoplasia due to occupation of the chest cavity by the stomach and bowel and, in the most severe cases, the liver. Balloon tracheal occlusion reduces the severity of lung hypoplasia in fetuses with CDH but increases the risk of premature birth. Understanding the optimal occlusion pressure and duration required to improve lung hypoplasia with tracheal occlusion is essential to improving in utero corrective treatments for CDH. The study reports a new method for continuous measurement of the intratracheal and amniotic pressures in an unoccluded and occluded fetal lamb surgical model of CDH. Time-pregnant Merino ewes underwent two recovery hysterotomies: the first at ~80 days of gestation to create the CDH, and the second at ~101 days of gestation to occlude the fetal trachea and implant an intratracheal and amniotic pressure measurement device. Lambs were delivered at ~142 days, and the pressure measurement device was removed and cleaned. The data were downloaded and filtered using a 6 h window. Transrespiratory pressure was calculated.

Congenital diaphragmatic hernia creation and pressure measurement device insertion were performed in 28 fetal lambs (14 unoccluded and 14 balloon occluded). Fifteen fetal lambs (6 unoccluded and 9 balloon occluded) survived to near term (142 days gestation; term ~147 days gestation). Pressure measurement recordings of 14 days were successful in 8 fetal lambs (4 unoccluded and 4 balloon occluded).
Pressure measurements were analyzed from the two groups of fetal lambs following the completion of...

Optimization of occlusion pressure and duration required to improve lung hypoplasia with tracheal occlusion is essential to improve in utero corrective treatments for congenital diaphragmatic hernia (CDH). This study reports a new method for continuous measurement of the tracheal pressure in an occluded and unoccluded fetal lamb surgical model of CDH.

Normal in utero lung development and growth rely upon the expansion of airspaces and the controlled efflux of lung liquid into the amniotic space. Infants ...

continuous-telemetric-utero-tracheal-pressure-measurements-fetal

Research

JoVE Journal

Medicine

Measuring left ventricular pressure (LV) in embryonic and neonatal mice is described. Pressure is measured by inserting a needle connected to a fluid-filled transducer into the LV under ultrasound guidance. Care must be taken to maintain normal cardiac function during the experimental protocol.

Measuring Left Ventricular Pressure in Late Embryonic and Neonatal Mice

This manuscript provides a protocol for implanting telemeters in the mouse for the purpose of measuring intrauterine pressures during pregnancy.

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

The chronically instrumented non-anesthetized fetal sheep model is used to study human fetal development in health and disease, because it permits surgical placement and maintenance of catheters and electrodes, repetitive blood sampling, substance injection, recording of bioelectrical activity, and in vivo imaging. We describe the procedures required to establish this model.

Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings

Invasive instrumentation of the fetal lamb provides accurate physiologic measurements of the transitioning circulation in a model that closely mimics the newly born infant.

The Perinatal Asphyxiated Lamb Model: A Model for Newborn Resuscitation

The present protocol describes a method to deliver drugs and gene expression-modifying agents perivascularly in an in utero developing fetus. Importantly, the effect of drugs/agents on blood flow can be measured with the progression of pregnancy.

In Vivo Real-Time Study of Drug Effects on Carotid Blood Flow in the Ovine Fetus

This protocol describes the surgical methodology for implanting a large animal wireless telemetry device to enable continuous and long-term collection of hemodynamic data, including heart rate, arterial blood pressure, inferior and superior vena cava pressures, and cardiac rhythm.

Wireless Telemetry Device Implantation in a Fontan Ovine Model for Continuous and Long-Term Hemodynamic Monitoring

The mouse model of in utero transplantation is a versatile tool that can be used to study the potential clinical applications of stem cell transplantation and gene therapy in the fetus.  In this protocol, we present a general approach to performing this...

A Mouse Model of in Utero Transplantation

Transgenic mice have been extremely useful in ascribing physiological function to genes. As such, research in general, and functional studies of airway, in particular, have undergone a remarkable shift toward murine models. Here we provide protocols for in vitro trachea constriction studies to evaluate smooth muscle function in murine airway.

In vitro Measurements of Tracheal Constriction Using Mice

In order to understand the molecular mechanisms of the ethanol-induced developmental damage, we have developed a zebrafish model of ethanol exposure and are exploring the physical, cellular, and genetic alterations that occur after ethanol exposure1.  We then seek to find potential interventions and rapidly test them in this animal model.

Assessing Teratogenic Changes in a Zebrafish Model of Fetal Alcohol Exposure

Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development. High-frequency ultrasound imaging has improved 2-D resolution and can provide excellent information on early cardiac development and is an ideal method to detect the impact on cardiac structure and function prior to death.

Murine Fetal Echocardiography

Learn continuous telemetric monitoring of fetal intratracheal and amniotic pressure in pregnant ewes. This method enables stress-free data collection to optimize tracheal occlusion treatment for congenital diaphragmatic hernia.

Continuous Telemetric In Utero Tracheal Pressure Measurements in Fetal Lambs

Explore More Videos