Dynamic vocal cord behavior and stridor during emergence from general anesthesia in small children with supraglottic airway.

PURPOSE: Stridor during emergence from anesthesia is not rare in children managed with supraglottic airway (SGA). However, we know little about the mechanisms of stridor and behavior of the vocal cords (VC). This study aimed to clarify patterns of VC movement and laryngeal airway maintenance function during recovery from anesthesia in children with SGA. METHODS: This is a secondary analysis of data collected from an observational study involving 27 anesthetized children. Using a multi-panel recording system, endoscopic VC image, vital sign monitor, multi-channel tracings of respiratory variables and respiratory sound and patient's view were simultaneously captured in one monitor. Inspiratory and expiratory VC angles formed by lines connecting anterior and posterior commissures were measured at the first spontaneous breath and the breath one minute after the first breath. VC narrowing and dilation were assessed by differences of VC angles. RESULTS: Inspiratory VC narrowing (median (IQR): 5.3 (2.7, 9.1) degree at the first breath) and dilation (- 2.7 (- 3.8, - 1.7) degree at the first breath) were observed in 15 and 12 out of 27 children, respectively. The former group achieved greater tidal volume compared to the latter in one minute. Five children (19%) temporarily developed stridor-like sound from outside with inspiratory VC narrowing. The stridor-like sound was captured by microphones attached to the neck and anesthesia circuit, but was not evident from the chest. CONCLUSION: Laryngeal narrowing occurs in half of the children with SGA during emergence from anesthesia, and temporal stridor-like sound is relatively common. CLINICAL TRIAL REGISTRATION: UMIN (University Hospital Information Network) Clinical Registry: UMIN000025058 ( https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000028697 ).

Combination Therapy of High-flow Nasal Cannula and Upper-body Elevation for Postoperative Sleep-disordered Breathing: Randomized Crossover Trial.

BACKGROUND: The low acceptance rate of continuous positive airway pressure therapy in postoperative patients with untreated obstructive sleep apnea (OSA) indicates the necessity for development of an alternative postoperative airway management strategy. The authors considered whether the combination of high-flow nasal cannula and upper-body elevation could improve postoperative OSA. METHODS: This nonblinded randomized crossover study performed at a single university hospital investigated the effect on a modified apnea hypopnea index, based exclusively on the airflow signal without arterial oxygen saturation criteria (flow-based apnea hypopnea index, primary outcome), of high-flow nasal cannula (20 l · min-1 with 40% oxygen concentration) with and without upper-body elevation in patients with moderate to severe OSA. Preoperative sleep studies were performed at home (control, no head-of-bed elevation) and in hospital (30-degree head-of-bed elevation). On the first and second postoperative nights, high-flow nasal cannula was applied with or without 30-degree head-of-bed elevation, assigned in random order to 23 eligible participants. RESULTS: Twenty-two of the 23 (96%) accepted high-flow nasal cannula. Four participants resigned from the study. Control flow-based apnea hypopnea index (mean ± SD, 60 ± 12 events · h-1; n = 19) was reduced by 15 (95% CI, 6 to 30) events · h-1 with head-of-bed elevation alone (P = 0.002), 10.9 (95% CI, 1 to 21) events · h-1 with high-flow nasal cannula alone (P = 0.028), and 23 (95% CI, 13 to 32) events · h-1 with combined head-of-bed elevation and high-flow nasal cannula (P < 0.001). Compared to sole high-flow nasal cannula, additional intervention with head-of-bed elevation significantly decreased flow-based apnea hypopnea index by 12 events · h-1 (95% CI, 2 to 21; P = 0.022). High-flow nasal cannula, alone or in combination with head-of-bed elevation, also improved overnight oxygenation. No harmful events were observed. CONCLUSIONS: The combination of high-flow nasal cannula and upper-body elevation reduced OSA severity and nocturnal hypoxemia, suggesting a role for it as an alternate postoperative airway management strategy.

Virtual scale function of gastrointestinal endoscopy for accurate polyp size estimation in real-time: a preliminary study.

SIGNIFICANCE: Polyp size is important for selecting the surveillance interval or treatment policy. Nevertheless, it is challenging to accurately estimate the polyp size during endoscopy. An easy and cost-effective function to assist in polyp size estimation is required. AIM: To propose a virtual scale function for endoscopy and evaluate its performance and expected accuracy. APPROACH: An adaptive virtual scale behavior was demonstrated. The measurement error of the virtual scale along the distance between the tip of the endoscope and the object plane was evaluated using graph paper. The accuracy of polyp size estimation by an expert endoscopist was compared with the accuracy of the biopsy forceps method using phantom images. RESULTS: The measurement errors of the virtual scale were ≤ 0.7 mm when the distance to the graph paper, which faced the tip of the endoscope, varied from 4 to 30 mm. The accuracy with the virtual scale was significantly higher than that obtained with biopsy forceps (5.3 ± 5.5 % versus 11.9 ± 9.4 % , P < 0.001). CONCLUSIONS: The virtual scale function, which operates in real-time without any additional device, can be used to estimate polyp sizes easily and accurately with endoscopy.

Determination of the optimal acquisition protocol of breath-hold PET/CT for the diagnosis of thoracic lesions.

OBJECTIVE: The aim of this study was to determine the optimal acquisition scan protocol for deep inspiration breath-hold (BH) fluoro-2-deoxy-D-glucose positron emission tomography (PET) for the examination of thoracic lesions. METHODS: We studied 32 thoracic lesions in 21 patients. Whole-body PET/computed tomography (CT) scanning with free breathing (FB) was performed for 3 min per bed position, followed by a BH-CT and five BH-PET for 20 s each. Summed BH images with total acquisition times of 40, 60, 80 and 100 s were generated (BH × 2, BH × 3, BH × 4 and BH × 5, respectively). The displacements between PET and CT images, the lesion volume of the PET image, the maximum standardized uptake value (SUVmax) and the quality of the PET image were assessed in relation to the clinical characteristics of each patient and the summation of the BH-PET images. RESULTS: BH-PET decreased the tumor volume significantly (FB: 7.23 ± 9.70 cm³, BH × 5: 4.71 ± 5.14 cm³, P<0.01) and increased the SUVmax (FB: 6.27 ± 5.41, BH × 5: 7.53 ± 6.28, P<0.01). The displacement between the PET and CT images was improved significantly in the BH scans (FB: 0.77 ± 0.53 cm, BH × 5: 0.36 ± 0.24 cm, P<0.01). In addition, aging and lung function of patients influenced the reproducibility of BH-PET. The summed BH-PET images, obtained by summation of three or more BH-PET images (total acquisition time of 60 s or more), achieved good image quality. CONCLUSION: BH-PET/CT improved the misregistration between PET and CT images and increased the SUVmax of thoracic lesions. The recommended number of BH-PET images for summation with 20 s of acquisition time is three or more.

A simple table lookup method for PET/CT partial volume correction using a point-spread function in diagnosing lymph node metastasis.

OBJECTIVE: We evaluated the partial volume effect in PET/CT images and developed a simple correction method to address this problem. METHODS: Six spheres and the background in the phantom were filled with F-18 and we thus obtained 4 different sphere-to-background (SB) ratios. Thirty-nine cervical lymph nodes in 7 patients with papillary thyroid carcinoma (15 malignant and 24 benign) were also examined as a preliminary clinical study. First, we developed recovery coefficient (RC) curves normalized to the maximum counts of the 37-mm sphere. Next, we developed a correction table to determine the true SB ratio using three parameters, including the maximum counts of both the sphere and background and the lesion diameter, by modifying the approximation formula of the RC curves including the point-spread function correction. The full width at half maximum in this formula is estimated with the function of the SB ratio. RESULTS: In the phantom study, a size-dependent underestimation of the radioactivity was observed. The degree of decline of RC was influenced by the SB ratio. In preliminary clinical examination, the difference in the SUV(max) between malignant and benign LNs thus became more prominent after the correction. The PV correction slightly improved the diagnostic accuracy from 95 to 100%. CONCLUSIONS: We developed a simple table lookup correction method for the partial volume effect of PET/CT. This new method is considered to be clinically useful for the diagnosis of cervical LN metastasis. Further examination with a greater number of subjects is required to corroborate its clinical usefulness.

Phantom study on three-dimensional target volume delineation by PET/CT-based auto-contouring.

OBJECTIVE: The aim of this study was to determine an appropriate threshold value for delineation of the target volume in PET/CT and to investigate whether we could delineate a target volume by phantom studies. METHODS: A phantom consisted of six spheres (phi 10-37 mm) filled with 18F solution. Data acquisition was performed PET/CT in non-motion and motion status with high 18F solution and in non-motion status with low 18F solution. In non-motion phantom experiments, we determined two types of threshold value, an absolute SUV (T(SUV)) and a percentage of the maximum SUV (T%). Delineation using threshold values was applied for all spheres and for selected large spheres (a diameter of 22 mm or larger). In motion phantom experiments, data acquisition was performed in a static mode (sPET) and a gated mode (gPET). CT scanning was performed with helical CT (HCT) and 4-dimensional CT (4DCT). RESULTS: The appropriate threshold values were aT% = 27% and aT(SUV) = 2.4 for all spheres, and sT% = 30% and sT(SUV) = 4.3 for selected spheres. For all spheres in sPET/HCT in motion, the delineated volumes were 84%-129% by the aT% and 34%-127% by the aT(SUV). In gPET/4DCT in motion, the delineated volumes were 94-103% by the aT% and 51-131% by the aT(SUV). For low radioactivity spheres, the delineated volumes were all underestimated. CONCLUSION: A threshold value of T% = 27% was proposed for auto-contouring of lung tumors. Our results also suggested that the respiratory gated data acquisition should be performed in both PET and CT for target volume delineation.

Diagnostic performance of Tc-99m HMPAO SPECT for early and late onset Alzheimer's disease: a clinical evaluation of linearization correction.

OBJECTIVE: This study examined the influence of linearization correction (LC) on brain perfusion single-photon emission computed tomography (SPECT) for the diagnosis of Alzheimer's disease (AD). METHODS: The early onset group (<65 years old) consisted of 10 patients with AD, and the late onset group (>/=65 years old) of 13 patients with AD. Age-matched controls included seven younger and seven older normal volunteers. Tc-99m hexamethyl propyleneamine oxine (HMPAO) SPECT images were reconstructed with or without LC [LC (+) or LC (-)] and a statistical analysis was performed using a three-dimensional stereotactic surface projection (3D-SSP). In addition, a fully automatic diagnostic system was developed, which calculated the proportion of the number of abnormal pixels in the superior and inferior parietal lobule, as well as in the precuneus and posterior cingulate gyrus. RESULTS: The areas under the receiver-operating characteristic curve (AUCs) of the early onset group for conventional axial SPECT images, SPECT + 3D-SSP images and the fully automatic diagnostic system were 0.71, 0.88, and 0.92 in LC (-) and 0.67, 0.85, and 0.91 in LC (+), respectively. The AUCs of the late onset group were 0.50, 0.61, and 0.79 in LC (-) and 0.49, 0.67, and 0.85 in LC (+), respectively. CONCLUSION: LC on Tc-99m HMPAO SPECT did not significantly influence the diagnostic performance for differentiating between AD and normal controls in either early or late onset AD. Further examination with individuals suffering from very mild dementia is, therefore, expected to elucidate the effect of LC on minimally hypoperfused areas.