A model of flow and surfactant transport in an oscillatory alveolus partially filled with liquid

The flow and transport in an alveolus are of fundamental importance to partial liquid ventilation, surfactant transport, pulmonary drug administration, cell-cell signaling pathways, and gene therapy. We model the system in which an alveolus is partially filled with liquid in the presence of surfactants. By assuming a circular interface due to sufficiently strong surface tension and small surfactant activity, we combine semianalytical and numerical techniques to solve the Stokes flow and the surfactant transport equations. In the absence of surfactants, there is no steady streaming because of reversibility of Stokes flow. The presence of surfactants, however, induces a nontrivial cycle-averaged surfactant concentration gradient along the interface that generates steady streaming. The steady streaming patterns (e.g., number of vortices) particularly depend on the ratio of inspiration to expiration periods (I:EI:E ratio) and the sorption parameter KK. For an insoluble surfactant, a single vortex is formed when the I:EI:E ratio is either smaller or larger than 1:1, but the recirculations have opposite directions in the two cases. A soluble surfactant can lead to more complex flow patterns such as three vortices or saddle-point flow structures. The estimated unsteady velocity is 10−3 cm/s10−3cm∕s, and the corresponding Péclet number for transporting respiratory gas is O(1)O(1). For a cell-cell signaling molecule such as surfactant-associated protein-A for regulating surfactant secretion, the Péclet number could be O(10)O(10) or higher. Convection is either comparable to or more dominant than diffusion in these processes. The estimated steady velocity ranges from 10−6 to 10−4 cm/s10−6to10−4cm∕s, depending on I:EI:E and KK, and the corresponding steady Péclet number is between 10−8/Dm10−8∕Dm and 10−6/Dm10−6∕Dm (DmDm is the molecular diffusivity with units of cm2/scm2∕s). Therefore, for Dm ⩽ 10−8 cm2/sDm⩽10−8cm2∕s, the convective transport dominates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87925/2/031510_1.pd

Robotic Repair of Congenital Paraesophageal Hiatal Hernia

Abstract Congenital paraesophageal hiatal hernias are rare and can be associated with gastric incarceration, volvulus, mucosal ulceration, and anemia. Primary repair of the hernia and fundoplication are recommended. In this paper, we report a case of a 3-year-old child with abdominal pain who was noted to have a paraesophageal hiatal hernia with partial gastric volvulus. A 5 mm robot platform was utilized to facilitate hernia sac dissection, hiatal repair, and fundoplication.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63210/1/lap.2008.0185.pd

Effect of Perflubron-induced lung growth on pulmonary vascular remodeling in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) involves lung hypoplasia and pulmonary hypertension (PH). Post-natal Perflubron ventilation induces lung growth. This phenomenon is called Perflubon-induced lung growth (PILG). However, it does not appear to ameliorate PH in CDH. We aim to determine the effect of PILG on pulmonary vascular remodeling in neonates with CDH and PH requiring extracorporeal membrane oxygenation (ECMO)

Thoracoscopic Repair of Congenital Diaphragmatic Hernia in Neonates: Lessons Learned

Abstract Purpose: We sought to characterize our recent experience with thoracoscopic congenital diaphragmatic hernia (CDH) repair and identify patient selection factors. Methods: We reviewed the medical records of full-term neonatal (<1 month of age) patients who underwent thoracoscopic CDH repair between 2004 and 2008 (n=15). We obtained data on prenatal diagnosis, characteristics of the CDH and repair, complications, and outcome. Results: All patients were stabilized preoperatively and underwent repair at an average of 5.7+/-1.3 days. Six patients were prenatally diagnosed, including the 5 inborn. Thirteen defects were left-sided. All were intubated shortly after birth and 2 required extracorporeal membrane oxygenation (ECMO). Twelve of 15 (80%) patients underwent successful thoracoscopic primary repair, including 1 of the patients who required ECMO prior to repair. Conversion to open repair occurred in 3 of 15 (20%) patients because of the need for patch closure or intraoperative instability. Among those converted to open, all had left-sided CDH defects and 3 had stomach herniation (of 5 such patients). Patients spent an average of 6.9+/-1.0 days on the ventilator following repair. The average time until full-enteral feeding was 16.7+/-2.25 days, and average length of hospital stay was 23.8+/-2.73 days. All patients survived to discharge, and average length of follow-up was 15.3+/-3.6 months. Conclusions: Thoracoscopic repair of CDH is a safe, effective strategy in patients who have undergone prior stabilization. Stomach herniation is associated with, but does not categorically predict, conversion to open repair. ECMO use prior to repair should not be an absolute contraindication to thoracoscopic repair.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78119/1/lap.2009.0129.pd

Axoplasmic flow of tritiated proline in the corticospinal tract of the rat

The rates of axoplasmic transport were studied in the corticospinal tract of the rat by injecting tritiated proline into the sensory-motor cortex and subsequently analyzing the distribution of incorporated label in the spinal cord at intervals after injection. A mathematical model of the anatomy of the corticospinal tract was developed and used in analysis of the data. The rate of a fast component was calculated to be 240–420 mm per day, which is comparable with rates of fast components in the peripheral nervous system (PNS), but considerably greater than rates in other tracts in the central nervous system. A slow component was calculated to have a transport rate of 3–8 mm per day which is greater than rates found either in the CNS or PNS. This higher rate may be related to the greater length of the corticospinal tract as compared to other CNS tracts studied.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47674/1/441_2004_Article_BF00249212.pd

Chest Radiographs Are Valuable in Demonstrating Clinically Significant Pacemaker Complications That Require Reoperation

AbstractPurposeTo evaluate the utility of chest radiography in demonstrating clinically significant pacemaker complications that required reoperation.MethodsIn this retrospective case-controlled series, we identified 14 consecutive adults who required pacemaker reoperation and who had chest radiographs available for review (6 men, 8 women; mean age, 71 years [range, 43–95 years]). Ten patients had pacemakers implanted at our institution, and 4 were referred for reoperation. Forty-two controls, 3 for each patient, had postoperative chest radiographs and normal device function (25 men, 17 women; mean age 76 years [range, 37–96 years]). All postoperative chest radiographs, including 1-year follow-ups, were blindly reviewed by at least 2 of 4 radiologists for lead perforation and position of right atrial and right ventricular leads. Follow-up radiographs were assessed for lead perforation, lead displacement, and lead fracture. Data were analysed by using the Fisher exact test.ResultsOf the patients, 1.7% (10/581) required reoperation for pacemaker dysfunction (noncapture, oversensing, abnormal atrial and ventricular thresholds, failing impedance), extracardiac stimulation, and lead perforation and/or displacement. There were no lead fractures. Chest radiographs demonstrated pacemaker complications in 57% of patients (8/14) at a median of 2 days (<1–32 days) after implantation and in 5% of the controls (2/42) (P < .0001). None of the abnormalities were noted on the official reports. Among subgroups, chest radiographs were abnormal for the following indications: pacemaker dysfunction in 4 of 7 patients versus 0 of 21 controls (P = .0017), extracardiac stimulation in 1 of 3 patients vs 0 of 9 controls (P = .25), and lead perforation and/or displacement in 3 of 4 patients vs 2 of 12 controls (P = .06).ConclusionsChest radiographs are useful after pacemaker placement and demonstrate the majority of complications that require reoperation. Familiarity with the expected normal position of the leads, appearances of pacemaker complications, and comparison with prior radiographs is crucial in rendering a correct diagnosis that guides patient management

Severe myocardial dysfunction during extracorporeal membrane oxygenation

Of the 102 neonates with respiratory fallure supported with extracorporeal membrane oxygenation (ECMO) at this institution between 1984 and 1987, 8 patients developed severe myocardial dysfunction that was noted shortly after onset of bypass. The neonates in the cardiac dysfunction group were more hypoxic (average PaO2 = 26 +/- 8 mm Hg v 41 +/- 19 mm Hg, P &lt; .01) in the immediate pre-ECMO period. Seventy-five percent were unstable hemodynamically (6 hypotensive, 3 bradycardic, 2 sustained cardiac arrest, 4 required epinephrine pressor support). On ECMO, 5 of the 8 neonates developed an ischemic cardiomyopathy that lasted for less than 24 hours and resolved without therapeutic intervention. In the other 3 cases, prolonged periods of dysfunction were noted and afterload reduction through administration of tolazoline or hydralazine was beneficial. These 8 patients serve to demonstrate the reversible nature of postischemic cardiac dysfunction in patients on ECMO and in the neonatal population in general.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30274/1/0000675.pd

Transport of unstable respiratory failure patients on extracorporeal life support

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31292/1/0000198.pd