Multiplanar 3D ultrasound imaging to assess the anatomy of the upper airway and measure the subglottic and tracheal diameters in adults.

OBJECTIVE: To evaluate the feasibility of using three-dimensional (3D) ultrasound to assess the anatomy of the airway. METHODS: 11 young volunteers were recruited for 3D ultrasound and MRI of the airway. 3D ultrasound data were obtained from the level of the true vocal cords, cricoid cartilage and upper trachea. Multiplanar 3D ultrasound images were rendered and compared visually with corresponding MRI and cadaver anatomical sections. The anteroposterior (AP) and transverse diameter of the subglottic space and transverse diameter of the upper trachea were also measured in the 3D ultrasound and MR images and compared. RESULTS: The airway anatomy was clearly delineated in the multiplanar 3D ultrasound images. It was also possible to identify the cricothyroid junction, and a simple method to measure the AP diameter of the subglottic space using this landmark is described. We were also able to accurately measure the transverse diameter of the upper trachea, but the transverse diameter of the subglottic space was overestimated using ultrasound. There was a strong correlation for the AP diameter measurement (r=0.94, p<0.05) and moderate correlation for the transverse diameter measurement (r=0.82, p=0.002) of the subglottic space, and a strong correlation for the transverse diameter measurement (r=0.91, p<0.05) of the upper trachea, in the ultrasound and MR images. CONCLUSION: The anatomy of the adult airway can be assessed using 3D ultrasound. It can also be used to accurately measure the AP diameter of the subglottic space and the transverse diameter of the upper trachea. ADVANCES IN KNOWLEDGE: This is the first report to describe the use of 3D ultrasound to evaluate the anatomy of the upper airway and accurately measure the AP diameter of the subglottic space and the transverse diameter of the upper trachea.

Aeroacoustics of T-junction merging flow.

This paper reports a numerical study of the aeroacoustics of merging flow at T-junction. The primary focus is to elucidate the acoustic generation by the flow unsteadiness. The study is conducted by performing direct aeroacoustic simulation approach, which solves the unsteady compressible Navier-Stokes equations and the perfect gas equation of state simultaneously using the conservation element and solution element method. For practical flows, the Reynolds number based on duct width is usually quite high (>10(5)). In order to properly account for the effects of flow turbulence, a large eddy simulation methodology together with a wall modeling derived from the classical logarithm wall law is adopted. The numerical simulations are performed in two dimensions and the acoustic generation physics at different ratios of side-branch to main duct flow velocities VR (=0.5,0.67,1.0,2.0) are studied. Both the levels of unsteady interactions of merging flow structures and the efficiency of acoustic generation are observed to increase with VR. Based on Curle's analogy, the major acoustic source is found to be the fluctuating wall pressure induced by the flow unsteadiness occurred in the downstream branch. A scaling between the wall fluctuating force and the efficiency of the acoustic generation is also derived.

On sound propagation from a slanted side branch into an infinitely long rectangular duct.

The transmission of sound from a slanted side branch into an infinitely long rectangular duct is studied numerically using the method of finite element with absorptive domain exit boundaries. The sound transmission coefficients associated with various acoustic modes are investigated in details. The results show that the plane wave assumption is only valid at very low frequency. It is also found that the intensities of the higher modes are stronger than that of the plane wave once they are excited. Besides, a critical side-branch slant angle is found over which a significant change of sound propagation mode takes place. This affects substantially the energy distribution between various acoustic modes inside the main duct. A simplified model is proposed to explain the phenomenon and the relationship of this critical angle with the width ratio between the side branch and the main duct is established.

Right thoracic paravertebral analgesia for hepatectomy.

Haemostatic deficiencies, common among cirrhotic patients, may deteriorate further after hepatectomy, increasing the bleeding risk associated with the use of thoracic epidural analgesia. We describe two patients who enjoyed immediate post-operative tracheal extubation and satisfactory analgesia using mainly right thoracic paravertebral analgesia after right lobe hepatectomy.

Tetracycline-induced benign intracranial hypertension.

We report on a young adolescent with benign intracranial hypertension which we attribute to the use of minocycline for acne.

The effect of povidone-iodine solution applied at the conclusion of ophthalmic surgery.

PURPOSE: Povidone-iodine 5% solution decreases the incidence of postoperative endophthalmitis when used on the eye for preoperative preparation. We sought to determine whether it also minimized conjunctival bacterial flora immediately after surgery by preventing bacteria present on the surface of the eye from entering surgical wounds. METHODS: In 42 eyes of 40 patients, at the conclusion of surgery, on an alternating basis, each patient received either a drop of a broad-spectrum antibiotic solution (polymyxin B sulfate-neomycin sulfate-gramicidin) or a 5% povidone-iodine solution in the operated-on eye. Bacterial cultures were taken before and after surgery and 24 hours later. The 38 unoperated-on eyes in the unilateral cases served as control eyes. RESULTS: Relative to the control group, povidone-iodine was effective in preventing an increase in the number of colony-forming units (P = .035), while the antibiotic was not. At 24 hours after surgery, the species count was lower in the eyes receiving povidone-iodine than in the antibiotic-treated eyes (P = .034) and was increased in the antibiotic group since the completion of surgery (P = .013), but was lower in the povidone-iodine and antibiotic groups than in the control eyes for both groups (P < .01). CONCLUSIONS: Povidone-iodine 5% solution applied to the eye at the conclusion of surgery was more effective at minimizing the number of colony-forming units and species for the first postoperative day than was a broad-spectrum antibiotic. While not true for the antibiotic, the antimicrobial effect of povidone-iodine lasted for at least 24 hours after the completion of surgery.

Inferior oblique muscle injury from local anesthesia for cataract surgery.

BACKGROUND: Vertical rectus muscle injury is commonly cited as a cause of strabismus after cataract surgery. Injury to the inferior oblique muscle or nerve as a complication of cataract surgery has not been described previously. METHODS: Four patients without pre-existing strabismus who had diplopia after cataract surgery were studied. Analysis included prism and cover testing, Lancaster red-green testing, and fundus torsion assessment. RESULTS: Three patients had a delayed-onset hypertropia with fundus extorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle overaction secondary to presumed contracture. The fourth patient had an immediate-onset hypotropia with fundus intorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle paresis. Damage to a vertical rectus muscle or "unmasking" of a pre-existing superior oblique muscle paresis could not explain the history and findings in this group of four patients. CONCLUSION: The inferior oblique muscle contracture observed in three patients may have been caused by local anesthetic myotoxicity, whereas the paresis observed in one patient may have been due to mechanical trauma or anesthetic toxicity directly to the nerve innervating the muscle. Inferior oblique muscle or nerve injury should be considered as another possible cause of postoperative strabismus, especially when significant fundus torsion accompanies a vertical deviation.

The efficacy of botulinum neurotoxin A for the treatment of complete and partially recovered chronic sixth nerve palsy.

Esotropia from chronic sixth nerve palsy or paresis usually requires surgery. Chemodenervation of the antagonist medial rectus muscle, while popular for the treatment of acute sixth nerve palsies and pareses, has not been used extensively for chronic cases. In this study, 22 patients with sixth nerve palsies or partially recovered palsies of greater than 5 months duration were treated with chemodenervation. The etiologies of the sixth nerve palsies were trauma (n = 7), tumor (n = 4), infection/inflammation (n = 3), nerve compression from aneurysm or increased intracranial pressure (n = 4), congenital (n = 1), ischemia (n = 2), and idiopathic (n = 1). The mean preinjection deviation was 41 prism diopters. A total of 38 injections were administered (mean, 1.7 per patient). Each patient received an injection of 2.5 to 7.5 units (mean, 4.1) of botulinum neurotoxin A to the ipsilateral medial rectus muscle. Treatment success was assessed 6 months after the last injection. A course of chemodenervation significantly improved the alignment of 9 of the 22 patients (41%). The mean postinjection deviation was 8 delta. Seven patients (32%) had single binocular vision in primary position restored. These patients had a mean horizontal binocular field of 70 degrees (range, 40 degrees to 100 degrees). Thirteen patients (59%) had only modest improvement and required surgery. The data suggest that injection of botulinum neurotoxin A is a useful treatment for some patients with chronic sixth nerve weakness. A course of chemodenervation therapy compares less favorably with transposition surgery with concomitant neurotoxin injection for the treatment of these difficult problems.

Timing of amblyopia therapy relative to strabismus surgery.

BACKGROUND: It is taught that amblyopia must be fully reversed before surgery for esotropia is undertaken to achieve the best surgical outcome. In some cases, this means delaying surgery for many months. The alternative of operating early, before the completion of amblyopia therapy, and continuing to treat the amblyopia postoperatively has not been evaluated previously. METHODS: Forty-seven children younger than 8 years of age were identified with a history of both amblyopia and esotropia. They had no other ocular, medical, or neurologic abnormalities. They had no prior strabismus surgery. Of these 47 patients, 26 had their amblyopia fully treated before surgery, and 21 underwent surgery before completing amblyopia therapy. Five of the latter group did not require amblyopia therapy after surgery even though they were still amblyopic before operation. The motor outcome was assessed by comparing the motor alignment at 6 and 0.33 m using accommodative targets in primary position before surgery, at 6 months after surgery, and at the child's most recent visit. Motor success was defined in this study as a postoperative deviation at distance fixation of 8 prism diopters or less. The sensory result was assessed by comparing the frequency of detectable stereoacuity. RESULTS: The treatment groups did not differ significantly in age, depth of amblyopia, refractive error, or preoperative angle. There was no significant difference detected in motor or sensory outcome whether amblyopia was fully or only partially treated before surgery. CONCLUSION: Performing corrective surgery in children with esotropia before full resolution of amblyopia is safe and efficient if the amblyopia therapy is continued after surgery. This strategy permits earlier surgery without postponing the operation until full resolution of amblyopia. The finding that five patients did not require amblyopia therapy after surgery suggests that eye re-alignment itself can help reverse amblyopia in some cases.

'Hot' corneal grafts--a long-term study.

A six-year follow-up of nine of 13 eyes treated by therapeutic keratoplasty for suppurative keratitis is described. One of the thirteen cases died three years after surgery and three were lost to follow-up. Two of the nine refused reoperation after early graft failure. Of the remaining seven, three had retained good functional visual acuity. Three of the penetrating keratoplasties required regrafting two to four years later, when conditions were less critical. Long-term results indicate that therapeutic keratoplasty may be an alternative modality for the management of suppurative keratitis with satisfactory long-term optical results.