Early intermittent noninvasive ventilation for acute chest syndrome in adults with sickle cell disease: a pilot study

Purpose

Alveolar hypoxia and hypoxic vasoconstriction lead to trapping of sickle cells within the pulmonary vasculature. Improving alveolar ventilation and oxygenation may improve the outcome of acute chest syndrome (ACS).

Methods

Prospective randomized single-center open study from November 1998 to February 2002 to test whether noninvasive ventilation (NIV) was more effective than oxygen alone in improving oxygenation on day 3 in adults with ACS and to evaluate the effects on pain, transfusion requirements, and length of stay.

Results

Seventy-one consecutive ACS episodes in 67 patients were randomly allocated to oxygen (n = 36) or NIV (n = 35) for 3 days in a medical step-down unit. Baseline respiratory rate and pain score were higher in the NIV group. NIV promptly lowered the respiratory rate, raised $ {\text{Pa}}_{{\text{O}_{2}}} $ , and decreased alveolar–arterial oxygen gradient $ (({\text{A}} - {\text{a}})_{{{\text{O}}_{ 2} }} ) $ , which remained unchanged with oxygen alone. $ {\text{Pa}}_{{{\text{CO}}_{ 2} }} $ significantly worsened only in the oxygen group. On day 3, the groups did not differ regarding the proportion of episodes with normal $ {\text{Pa}}_{{{\text{O}}_{ 2} }} $ (35% with NIV and 25% with oxygen; P = 0.5) or $ (({\text{A}} - {\text{a}})_{{{\text{O}}_{ 2} }} ) $ . Patient satisfaction and compliance were lower with NIV. No differences were noted in pain relief, transfusions, or length of stay. In the subgroup of patients with severe hypoxemia $ ( {\text{Pa}}_{{{\text{O}}_{ 2} }} \le 6 5\,{\text{mmHg)}} $ , physiological variables also improved faster with NIV, the differences being slightly more pronounced.

Conclusions

Respiratory rate and gas exchange improved faster with NIV. However, NIV failed to significantly reduce the number of patients remaining hypoxemic at day 3, and was associated with greater patient discomfort.     

Comparison of volumetric capnography and mixed expired gas methods to calculate physiological dead space in mechanically ventilated ICU patients

Introduction

Physiological dead space should be a routine measurement in ventilated patients but measuring dead space using the Douglas bag (DB) method is cumbersome and requires corrections for compressed ventilator gas. These factors make this method impractical in the critical care setting. Volumetric capnography (VCAP) offers a relatively simple solution to calculating dead space. Few studies have been conducted to directly compare dead space measured by VCAP and the DB method in critically unwell adults.

Method

Prospective observational study of 48 mechanically ventilated adults ICU patients. Dead space was calculated simultaneously using VCAP (CO₂SMO) and the Bohr–Enghoff equation. In total, 168 paired readings were taken. Single-breath CO₂ waveform areas under the curve were computed automatically by software to calculate physiological dead space. The calculated value of $ P_{{\bar{E}_{{{\text{CO}}_{2} }} }} $ was also recorded from the CO₂SMO device. Exhaust ventilator gas was collected in a 10-l mixing chamber. $ P_{{\bar{E}_{{{\text{CO}}_{2} }} }} $ was measured in the chamber following correction for compressed gas.

Results

The study demonstrated good agreement between physiological V _D/V _T calculated by VCAP and corrected (mean bias 0.03), and uncorrected (mean bias 0.02) Bohr–Enghoff method. There was good correlation between the two methods of measurement (VCAP vs corrected r ²?=?0.90 P?<?0.001, VCAP vs uncorrected r ²?=?0.90, P?<?0.001). There was good correlation between $ P_{{\bar{E}_{{{\text{CO}}_{2} }} }} $ calculated by the CO₂SMO and in the exhaust collected gas (mean bias 0.08).

Conclusions

VCAP shows good agreement with Douglas Bag method in measuring physiological V _D/V _T over a wide range of dead space fractions.     

Acoustic sensor versus electrocardiographically derived respiratory rate in unstable trauma patients

Respiratory rate (RR) is important in many patient care settings; however, direct observation of RR is cumbersome and often inaccurate, and electrocardiogram-derived RR (RR_ECG) is unreliable. We asked how data derived from the first 15 min of RR recording after trauma center admission using a novel acoustic sensor (RR_a) would compare to RR_ECG and to end-tidal carbon dioxide-based RR (\({\text{RR}}_{{{\text{CO}}_{2} }}\)) from intubated patients, the “gold standard” in predicting life-saving interventions in unstable trauma patients. In a convenience sample subset of trauma patients admitted to our Level 1 trauma center, enrolled in the ONPOINT study, and monitored with RR_ECG, some of whom also had \({\text{RR}}_{{{\text{CO}}_{2} }}\) data, we collected RRa using an adhesive sensor with an integrated acoustic transducer (Masimo RRa?). Using Bland–Altman analysis of area under the receiver operating characteristic (AUROC) curves, we compared the first 15 min of continuous RRa and RR_ECG to \({\text{RR}}_{{{\text{CO}}_{2} }}\) and assessed the performance of these three parameters compared to the Revised Trauma Score (RTS) in predicting blood transfusion 3, 6, and 12 h after admission. Of the 1200 patients enrolled in ONPOINT from December 2011 to May 2013, 1191 had RR_ECG data recorded in the first 15 min, 358 had acoustic monitoring, and 14 of the latter also had \({\text{RR}}_{{{\text{CO}}_{2} }}\). The three groups did not differ demographically or in mechanism of injury. RR_a showed less bias (0.8 vs. 6.9) and better agreement than RR_ECG when compared to \({\text{RR}}_{{{\text{CO}}_{2} }}\). At \({\text{RR}}_{{{\text{CO}}_{2} }}\) 10–29 breaths per minute, RR_a was more likely to be the same as \({\text{RR}}_{{{\text{CO}}_{2} }}\) and assign the same RTS. In predicting transfusion, features derived from RR_a and RR_ECG gave AUROCs 0.59–0.66 but with true positive rate 0.70–0.89. RR_a monitoring is a non-invasive option to glean valid RR data to assist clinical decision making and could contribute to prediction models in non-intubated unstable trauma patients.     

Predictors of sildenafil effects on exercise capacity in adolescents and adults with Fontan circulation

Objective

A single dose of sildenafil improves exercise capacity in Fontan patients. However, a recent study failed to show a long-term effect of sildenafil. This study evaluated whether there are factors that might predict sildenafil effects.

Methods

We studied 36 patients (16–42 years, 14 female) with univentricular heart after various modifications of the Fontan surgery (13 APC, 16 AVC, 7 TCPC). They performed two cardiopulmonary exercise tests, with at least 120 min rest and a single dose of 50 mg sildenafil in between.

Results

After sildenafil administration, patients improved their peak oxygen uptake from 64.5 to 67.3 % predicted (p = 0.0003) without change in ventilatory efficiency ( \({\dot{\text{V}}}_{\text{E}} /{\dot{\text{V}}\text{CO}}_{2}\) slope), oxygen saturation (SpO₂) at rest or at peak exercise, respiratory exchange ratio. In addition, resting systolic blood pressure was slightly reduced after sildenafil administration. There was a moderate negative correlation of this improvement to baseline peak oxygen uptake (r = ?0.395; p = 0.017). The change in peak oxygen uptake could not be correlated to time of surgery, type of surgery, NT-pro-BNP, or to other clinical data. Nevertheless, all four patients with NT-pro-BNP levels higher than 1,000 pg/ml had the most prominent improvements in exercise capacity.

Conclusions

Fontan patients have an improved exercise capacity after a single dose of sildenafil. Patients with worse baseline peak oxygen uptake profit more.     

Automated implant segmentation in cone-beam CT using edge detection and particle counting

Purpose

To develop a fully automated, accurate and robust segmentation technique for dental implants on cone-beam CT (CBCT) images.

Methods

A head-size cylindrical polymethyl methacrylate phantom was used, containing titanium rods of 5.15 mm diameter. The phantom was scanned on 17 CBCT devices, using a total of 39 exposure protocols. Images were manually thresholded to verify the applicability of adaptive thresholding and to determine a minimum threshold value \(({T}_{\mathrm{min}})\) . A three-step automatic segmentation technique was developed. Firstly, images were pre-thresholded using \({T}_{\mathrm{min}}\) . Next, edge enhancement was performed by filtering the image with a Sobel operator. The filtered image was thresholded using an iteratively determined fixed threshold \(({T}_{\mathrm{edge}})\) and converted to binary. Finally, a particle counting method was used to delineate the rods. The segmented area of the titanium rods was compared to the actual area, which was corrected for phantom tilting.

Results

Manual thresholding resulted in large variation in threshold values between CBCTs. After applying the edge-enhancing filter, a stable \({T}_{\mathrm{edge}}\) value of 7.5 % was found. Particle counting successfully detected the rods for all but one device. Deviations between the segmented and real area ranged between \(-\) 2.7 and + \(14.4\,\hbox {mm}^{2}\) with an average absolute error of \(2.8\,\hbox {mm}^{2}\) . Considering the diameter of the segmented area, submillimeter accuracy was seen for all but two data sets.

Conclusion

A segmentation technique was defined which can be applied to CBCT data for an accurate and fully automatic delineation of titanium rods. The technique was validated in vitro and will be further tested and refined on patient data.     

Rational monitoring of respiratory function during mechanical ventilation of infants and children

Oxygen and carbon dioxide homeostasis (effective pulmonary gas exchange) requires that lung exchange matches tissue exchange. The movement of gas in and out of the lung is determined by the mechanical properties of the system especially resistance and compliance and the work needed to provide this movement is supplied either by the patient's muscles or by the mechanical ventilator. If the latter is required, its optimal use demands that the user understands the relationship between the mechanical device and the mechanical properties of the patient's respiratory system so that optimal gas exchange can be provided. The following discussion provides the minimum physiological information needed for successful use of a mechanical ventilator and suggests that this requires measurement of at least four parameters: alveolar partial pressure of CO₂ (\({\text{PA}}_{{\text{CO}}_{\text{2}} }\)), arterial oxygen saturation (\({\text{Sa}}_{{\text{O}}_{\text{2}} }\)), the mechanical RC time constant (RC) and functional residual capacity (FRC).     

A Weight Index for the Standardized Uptake Value in 2-Deoxy-2-[F-18]fluoro-<Emphasis Type="SmallCaps">d</Emphasis>-glucose-Positron Emission Tomography

Introduction Known errors in the standardized uptake value (SUV) caused by variations in subject weights W encountered can be corrected by lean body mass or body surface area (bsa) algorithms replacing W in calculations. However this is infrequently done. The aims of the work here are: quantify sensitivity to W, encourage SUV correction with an approach minimally differing from tradition, and show what improvements in the SUV coefficient of variation (cv) for a population can be expected. Methods Selected for analyses were 2-deoxy-2-[F-18]fluoro-d-glucose (FDG) SUV data from positron emission tomography (PET) and PET/computed tomography (CT) scans at the University of Tennessee as well as from the literature. A weight sensitivity index was defined as −n=slope of ln(SUV/W) vs. lnW. The portion of the SUV variability due to this trend is removed by using the defined , or a virtually equal SUV _m using , with Q and ID being tissue specific-activity and injected dose. measures performance. Adapting to animal studies’ tradition, is preferred over the conventional . Results For FDG in adults from averaging over most tissues. In children, however, . Tissues have the same index if their influx constants are independent of W. Suggested, therefore, is a very simplified , which is dimensionless and keeps the same population averages as traditional SUVs. It achieves . Hence, for cv’s of SUVs below ∼1/3 improvements over tradition are possible, leading to F’s<0.95. Accounting additionally for height, as in SUV_bsa, gives very little improvement over the simplified approach here and gives essentially the same F’s as SUV _m . Conclusions Introduced here is a weight index useful in reducing variability and further understanding the SUV. Addressing weight sensitivity is appropriate where the cv of the SUVs is below about 1/3. Proposed is the very simple approach of using an average of an adult patient’s weight and ∼70 kg for FDG SUV calculations. Unlike other approaches the dimensionless population average of SUV _m s is unchanged from tradition.     

Quantitative evaluation of striated muscle injury by multiscale blob features method

Purpose

This study aimed to use the multiscale blob feature (MBF) method to quantitatively evaluate porcine striated muscle injuries.

Methods

A porcine striated muscle injury model was induced by microwave ablation and anhydrous acetic acid injection, respectively. Then, both 2D sonographic and histological features of the lesions were recorded and compared. Later, MBF was used to quantitatively evaluate the porcine striated muscle injuries by extracting the texture features from the 2D ultrasonogram via measuring eight textural parameters (Mean, SDev, NOB, \( \overline{\text{IRGL}} \), \(\overline {\text{SOB}}\), HOD, DOD, and POD).

Results

Microwave ablation produced oval or round-like lesions, which had a pale gray color, with an echo attenuation detected at lesion center due to carbonization; anhydrous acetic acid injection produced long, stripped lesions, which had a slate-gray color, with a gas-like intense echo at lesion center. There were significant differences in Mean, \( \overline{\text{IRGL}} \) and POD between the muscle samples treated by microwave ablation and the control samples, as well as significant differences in NOB, \( \overline{\text{SOB}} \) and POD between the muscle samples treated by anhydrous acetic acid injection and the control. There were significant differences in Mean, \( \overline{\text{IRGL}} \), NOB, and \( \overline{\text{SOB}} \) between the muscle samples treated by microwave ablation and those treated by anhydrous acetic acid injection.

Conclusion

Quantitative evaluation of striated muscle injuries using the MBF method was able to differentiate the muscle injuries caused by microwave ablation and anhydrous acetic acid injection, suggesting that this method may be a potential and reliable tool for quantitative evaluation of muscle injuries.

     

A morphological study of anatomical plates for acetabular posterior column

Purposes

   The objective of this work is to explore the morphological characteristics of the acetabular posterior column using digital technology, in order to develop anatomical plates for internal fixation of acetabular posterior column fractures.

Materials and methods

   Three-dimensional reconstruction models of the pelvis were developed from computed tomography scan data of 111 adult patients. From them, the diameter (D) of the femoral head, three approximate arcs along the acetabular posterior column plate path with corresponding radius of curvature \(\hbox {R}_{1}, \hbox {R}_{2}\) and \(\hbox {R}_{3}\) , as well as an angle \(\alpha \) were measured. A statistical analysis was used to determine the most feasible method of designing anatomical plates according to the data.

Results

   The statistical analysis results showed that \(\hbox {R}_{1}, \hbox {R}_{2}\) and \(\hbox {R}_{3}\) had no correlations with D, and they also exhibited no statistically significant differences between genders. By examining the correlations between four morphological parameters of the acetabular posterior column, the results showed \(\hbox {R}_{2}\) increased along with \(\hbox {R}_{1}, \alpha \) was inversely proportional to \(\hbox {R}_{1}\) and \(\hbox {R}_{2}\) , and \(\hbox {R}_{3}\) was independent with little variation. Taking \(\hbox {R}_{1}\) as the reference, the data were divided into three groups and three types of anatomical plates were designed according to the three groups of data.

Conclusion

   The anatomical structure of the acetabular posterior column exhibits great individual differences. Anatomical plates designed in this study have higher accuracy than those conventional ones, which is helpful to the quality of fracture reduction and reduce the operation difficult. Meanwhile, they also can be conveniently used in clinic.     

G-Band Polymorphism in Natural Populations of Yellow-Legged Green Pigeon,Treron phoenicoptera phoenicoptera from Northern India

In the present study, 48 individuals of common or yellow-legged green pigeon, Treron phoenicoptera phoenicoptera (Latham), belonging to the family Columbidae of the order Columbiformes were utilized for the analysis of G-banding patterns. The birds were sampled from different geographical areas which have been grouped as three distinct populations. Population A consists of birds from Allahabad. Populations B and C consist of birds from Chotanagpur Division and Singhbhum Division of Jharkhand, respectively. Besides these individuals a single female bird from Berhampur (district Ganjam) of coastal Odisha has also been karyotyped. The diploid complement comprises of 74 chromosomes which consists seven pairs of macrochromosomes (including the sex chromosomes) and thirty pairs of microchromosomes. The bird was found to be polymorphic for chromosome pairs 1 and 2. The chromosome pair 1 was present either in a metacentric (1^m) or a subtelocentric (1^st) condition. Similarly chromosome 2 was also present as either a subtelocentric (1^st) or a metacentric (2^m). The polymorphism was explained on the basis of two independent pericentric inversions involving chromosome pairs 1 and 2. With two chromosomes, involved karyomorphs were in inversions, ideally there should be nine types of karyomorphs. In the present investigation five different karyomorphs were encountered. GTG banding (G-bands by trypsin using Giemsa) method of Seabright (Lancet 2:971–972, 1971) was adopted with some modifications. All the karyomorphs were subjected to G-banding analysis, however, consistent and reasonably good G-bands were produced only in karyomorphs 1^m1^m/2^st2^m, 1^m1^m/2^st2^st, 1^st1^st/2^st2^m of population A., 1^m1^m/2^st2^m, of population B, 1^m1^m/2^st2^st and 1^m1^m/2^st2^m of population C and 1^m1^m/2^st2^m of Berhampur, Odisha. The G-banding patterns are based on observations of ten metaphase plates of each karyomorphs. Thus, the idiogram showing schematic presentation of G-bands are based on the chromosomes showing minimal condensation which reveal optimum number of bands. The idiogram depicting G-bands have been constructed using the relative length (L^R) and centromeric indices (I^C) data. In G-banded chromosomes, the band nomenclature has been done according to the guidelines of Paris Conference (1971) and supplement (1975) for human chromosomes. The G-band pattern analysis revealed the presumed breakpoints in the chromosome pairs 1 and 2 lending further support to the pericentric inversions in these chromosome pairs. The banding sequence of the rearranged chromosome (1^st) can be described as: $$ {\text{pter}} \to {\text{p22}}::{\text{q12}} - {\text{p22}}::{\text{q12}} \to {\text{qter}}. $$ The banding sequence of the rearranged chromosome (2^m) can be described as: $$ {\text{pter}} \to {\text{p12}}::{\text{q21}} - {\text{p12}}::{\text{q21}} \to {\text{qter}}. $$ The G-banding patterns of the macrochromosomes has also been discussed.     

Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to a 3D setting using weightbearing CT

Purpose

The exact radiographic assessment of the hindfoot alignment remains challenging. This is reflected in the different measurement methods available. Weightbearing CT (WBCT) has been demonstrated to be more accurate in hindfoot measurements. However, current measurements are still performed in 2D. This study wants to assess the use of computed methods to convert the former uniplanar hindfoot measurements obtained after WBCT towards a 3D setting.

Methods

Forty-eight patients, mean age of 39.6 ± 13.2 years, with absence of hindfoot pathology were included. A WBCT was obtained, and images were subsequently segmented and analyzed using computer-aided design operations. In addition to the hindfoot angle (HA), other ankle and hindfoot parameters such as the anatomical tibia axis, talocalcaneal axis (TCA), talocrural angle, tibial inclination (TI), talar tilt, and subtalar vertical angle were determined in 2D and 3D.

Results

The mean \(\hbox {HA}_{2\mathrm{D}}\) was \(0.79^{\circ }\) of valgus ± 3.2 and the \(\hbox {HA}_{\mathrm{3D}}\) was \(8.08^{\circ }\) of valgus ± 6.5. These angles differed significantly from each other with a \(P<0.001\). The correlation between both showed to be good by \(\hbox {a}\) Pearson correlation coefficient (r) of 0.72 (\(P < 0.001\)). The \(\hbox {ICC}_{\mathrm{3D}}\) showed to be excellent when compared to the \(\hbox {ICC}_{\mathrm{2D}}\), which was good. Similar findings were obtained in other angles. The highest correlation was seen between the \(\hbox {TI}_{\mathrm{2D}}\) and \(\hbox {TI}_{\mathrm{3D}}\) (r = 0.83, \(P < 0.001\)) and an almost perfect agreement in the \(\hbox {TCA}_\mathrm{3D}\) (\(\hbox {ICC}_{\mathrm{3D}}=0.99\)).

Conclusion

This study shows a good and reliable correlation between the \(\hbox {HA}_{\mathrm{2D}}\) and \(\hbox {HA}_{\mathrm{3D}}\). However, the \(\hbox {HA}_{\mathrm{3D}}\) overcomes the shortcomings of inaccuracy and provides valuable spatial data that could be incorporated during computer-assisted surgery to assess the multiplanar correction of a hindfoot deformity.

     

Three-dimensional ultrasound measurements of carotid vessel wall and plaque thickness and their relationship with pulmonary abnormalities in ex-smokers without airflow limitation

The relationship between carotid disease and modestly abnormal airflow in ex-smokers without chronic obstructive pulmonary disease (COPD) is not well-understood. We generated 3D ultrasound measurements of carotid vessel-wall-plus-plaque thickness (VWT) and vessel wall volume (VWV) to quantify and evaluate such carotid ultrasound measurements in ex- and never-smokers without airflow limitation. These patients did not fulfill the diagnostic criteria for COPD. We also investigated the relationship of carotid atherosclerosis with pulmonary phenotypes of COPD. We evaluated 61 subjects without a clinical diagnosis of pulmonary or vascular diseases including 34 never-smokers (72?±?6 year) and 27 ex-smokers (73?±?9 year). We measured mean VWT (\(\overline{VWT}\)) and mean VWT specific to carotid regions-of-interest (\({{\overline{VWT}}_{S}}\)) and evaluated potential differences between ex- and never-smokers. Carotid ultrasound and pulmonary disease measurement relationships were also evaluated using correlation coefficients (r) and multivariate regression analyses. Ex-smokers had a significantly greater \(\overline{VWT}\) (p?=?0.003) and \({{\overline{VWT}}_{S}}\) (p?<?0.00001) than never-smokers, whereas a significant difference between the two groups was not detected by VWV (p?=?1.0). There were significant correlations between the ventilation defect percent (VDP) measured by MRI with \(\overline{VWT}\) (r?=?0.42, p?=?0.001) and \({{\overline{VWT}}_{S}}\) (r?=?0.56, p?=?0.00001). Multivariate regression models showed that VDP significantly predicted \(\overline{VWT}\) (β?=?0.38, p?=?0.004) and \({{\overline{VWT}}_{S}}\) (β?=?0.50, p?=?0.00001). VWT-based measurements detected differences in vessel-wall-plus-plaque burden in ex- and never-smokers, which were not revealed using VWV. There were significant correlations between cardiovascular and pulmonary disease biomarkers in these ex-smokers who did not have a clinical diagnosis of pulmonary or carotid disease.     

Mesh-based method for measuring intracranial volume in patients with craniosynostosis

Purpose

   Craniosynostosis may lead to reduced intracranial volume (ICV) and disturb normal brain growth and development. Thus, ICV is an important parameter with respect to the surgical outcome. Current methods for ICV determination from computed tomography (CT) images have drawbacks. The aim of this study was to investigate the performance of the novel mesh-based method (MBM) for ICV determination with craniosynostosis patients.

Methods

   Twenty-two patients operated on for scaphocephaly were included in this study. ICVs from preoperative, one-week postoperative, and one-year postoperative CT images were measured with MBM. The level of agreement with the manual segmentation method (MSM) was determined for the measurements of preoperative and one-year postoperative datasets. Repeatability was determined with re-measurements of six datasets. Measurement time was recorded for MBM.

Results

   Mean $(\pm \text{ SD})$ preoperative ICV values were 895.0 $\pm $ 153.1 $\text{ cm}^{3}$ and 896.4 $\pm $ 147.2 $\text{ cm}^{3}$ as measured with MBM and MSM, respectively. Corresponding one-year postoperative values were 1,238.3 $\pm $ 118.7 $\text{ cm}^{3}$ and 1,250.1 $\pm $ 117.5 $\text{ cm}^{3}$ . The MBM allowed ICV determination from one-week postoperative datasets. Measurement time with MBM was 4

Conclusions

   MBM is an efficient method for determining the ICV of craniosynostosis patients, allowing the measurement of skulls with bony defects. The repeatability and short measurement time of MBM are attributable to the user interference and assessment of the measurement process.     

Ventilator-related causes of lung injury: the mechanical power

Purpose

We hypothesized that the ventilator-related causes of lung injury may be unified in a single variable: the mechanical power. We assessed whether the mechanical power measured by the pressure–volume loops can be computed from its components: tidal volume (TV)/driving pressure (?P _aw), flow, positive end-expiratory pressure (PEEP), and respiratory rate (RR). If so, the relative contributions of each variable to the mechanical power can be estimated.

Methods

We computed the mechanical power by multiplying each component of the equation of motion by the variation of volume and RR:

$${\text{Power}}_{\text{rs}} = {\text{RR}} \cdot \left\{ {\Delta V^{2} \cdot \left[ {\frac{1}{2} \cdot {\text{EL}}_{\text{rs}} + {\text{RR}} \cdot \frac{{\left( {1 + I:E} \right)}}{60 \cdot I:E} \cdot R_{\text{aw}} } \right] + \Delta V \cdot {\text{PEEP}}} \right\},$$

where ?V is the tidal volume, EL_rs is the elastance of the respiratory system, I:E is the inspiratory-to-expiratory time ratio, and R _aw is the airway resistance. In 30 patients with normal lungs and in 50 ARDS patients, mechanical power was computed via the power equation and measured from the dynamic pressure–volume curve at 5 and 15 cmH₂O PEEP and 6, 8, 10, and 12 ml/kg TV. We then computed the effects of the individual component variables on the mechanical power.

Results

Computed and measured mechanical powers were similar at 5 and 15 cmH₂O PEEP both in normal subjects and in ARDS patients (slopes = 0.96, 1.06, 1.01, 1.12 respectively, R ² > 0.96 and p < 0.0001 for all). The mechanical power increases exponentially with TV, ?P _aw, and flow (exponent = 2) as well as with RR (exponent = 1.4) and linearly with PEEP.

Conclusions

The mechanical power equation may help estimate the contribution of the different ventilator-related causes of lung injury and of their variations. The equation can be easily implemented in every ventilator’s software.

     

Continuous intravascular monitoring of PO2 and PCO2. A comparativein vitro-in vivo study

Two electrodes placed at the tip of catheters forin vivo determinations of and respectively, were tested in dogs. Results were satisfactory when compared to a highly accurate reference method, correlation coefficients were close to 1 (P < 10^–9). Means of the differences were respectively –1.74 ± 1.14 torr for the probe (P < 0.01) and –1.62 ± 0.72 torr for the sensor (P < 0.0001). While no drift was detected in the electrode that of the was significant but negligible compared to the variability of measurements. Thus, for values between 20 and 85 torr, and values between 20 and 140 torr,in vivo monitoring is sufficiently reliable for clinical use.This study was supported by a grant-in-aid from I.N.S.E.R.M., C.N.R.S. and Paris VII University.     

Accuracy of 3D cephalometric measurements based on an automatic knowledge-based landmark detection algorithm

Purpose

To evaluate the accuracy of three-dimensional cephalometric measurements obtained through an automatic landmark detection algorithm compared to those obtained through manual identification.

Methods

The study demonstrates a comparison of 51 cephalometric measurements (28 linear, 16 angles and 7 ratios) on 30 CBCT (cone beam computed tomography) images. The analysis was performed to compare measurements based on 21 cephalometric landmarks detected automatically and those identified manually by three observers.

Results

Inter-observer ICC for each landmark was found to be excellent (\({>}0.9\)) among three observers. The unpaired t-test revealed that there was no statistically significant difference in the measurements based on automatically detected and manually identified landmarks. The difference between the manual and automatic observation for each measurement was reported as an error. The highest mean error in the linear and angular measurements was found to be 2.63 mm (\(\hbox {Or}_{\mathrm{L}}\hbox {-Or}_{\mathrm{R}}\) distance) and \(2.12^{\circ }\) (\(\hbox {Co}_{\mathrm{L}}\hbox {-Go}_{\mathrm{L}}\)-Me angle), respectively. The highest mean error in the group of distance ratios was 0.03 (for N-Me/N-ANS and \(\hbox {Go}_{\mathrm{R}}\hbox {-Gn/S-N}\)).

Conclusion

Cephalometric measurements computed from automatic detection of landmarks on 3D CBCT image were as accurate as those computed from manual identification.

     

Understanding the meaning of the shunt fraction calculation

The pulmonary shunt fraction ( \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) ) is frequently calculated in critically ill patients to monitor the effectiveness of pulmonary oxygenation. The breathing of pure oxygen often results in higher calculated \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) values that have been attributed to the development of atelectasis, ventilation-perfusion imbalance, or both. To interpret properly the changes in calculated \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) that occur when the inspired oxygen fraction is altered, the changes produced in all the variables affecting \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) must be known. This tutorial presents an in-depth analysis of the four variables affecting the calculation of \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) \(\dot Vo_2 \) (oxygen uptake), \(\dot Qt\) (cardiac output), Cc'O₂(oxygen content in pulmonary end capillaries), and \(C\bar vO_2 \) (oxygen content in mixed venous blood). These variables are related according to the following equation, which derived by combining the Fick and the classic shunt equations: \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}} = 1 - [({{{{\dot Vo_2 } \mathord{\left/ {\vphantom {{\dot Vo_2 } {\dot Qt}}} \right. \kern-0em} {\dot Qt}})} \mathord{\left/ {\vphantom {{{{\dot Vo_2 } \mathord{\left/ {\vphantom {{\dot Vo_2 } {\dot Qt}}} \right. \kern-0em} {\dot Qt}})} {(Cc'O_2 }}} \right. \kern-0em} {(Cc'O_2 }} - C\bar vO_2 )]\) . Three-dimensional surface representations relating these variables are also presented to help the reader understand the effects of these variables on the calculated \({{\dot Qs} \mathord{\left/ {\vphantom {{\dot Qs} {\dot Qt}}} \right. \kern-0em} {\dot Qt}}\) .     

E-Health and telemedicine

Purpose

To compare the accuracy of a navigation system for oral implantology using either a head-mounted display (HMD) or a monitor as a device for visualization.

Methods

Drilling experiments in plastic mandibles were performed by seven investigators supported by a navigation system using an HMD. A set of drilling experiments was carried out using a traditional monitor setup as standard of reference. Prior to the experiments, CT scans of the mandibles were performed. Positions of the boreholes were determined with the planning software Mimics $^{\circledR }$ . In order to find the correct positions of the boreholes, individuals had to match two pairs of crosshairs. By an infrared tracking device, the navigation system was able to spot the artificial jaw and the angular piece of the drill allowing for the navigation. After the experiments, a second CT scan was acquired: (i) to identify the beginning and the end of the boreholes, (ii) to compare the positions of the planned implant and the boreholes and (iii) to calculate the deviations.

Results

Overall deviation of the starting point of the borehole was $1.24 \pm 0.84\,\mathrm{mm}$ for the HMD and $1.12 \pm 0.68\,\mathrm{mm}$ for the monitor, $2.68 \pm 1.65\,\mathrm{mm}$ of the end point of the borehole for the HMD and $2.46 \pm 1.34\,\mathrm{mm}$ for the monitor. The mean deviation of the axis was $4.68^{\circ }\pm 3.7^{\circ }$ for the HMD and $4.53^{\circ }\pm 4.17^{\circ }$ for the monitor.

Conclusions

As overall accuracies do not differ significantly, the two methods seem to be equal. Personal skills seem to be crucial as the results show remarkable differences among the test persons. The results of our study demonstrate that the use of an HMD has no major drawbacks compared to the monitor setting. The striking advantage is that the surgeon is no longer obliged to turn his head away from the operation site during navigation, as all data relevant for the procedure are superimposed on the image of the real world in his field of view.     

Development of a vibration haptic simulator for shoulder arthroplasty

Purpose

Glenoid reaming is a technically challenging step during shoulder arthroplasty that could possibly be learned during simulation training. Creation of a realistic simulation using vibration feedback in this context is innovative. Our study focused on the development and internal validation of a novel glenoid reaming simulator for potential use as a training tool.

Methods

Vibration and force profiles associated with glenoid reaming were quantified during a cadaveric experiment. Subsequently, a simulator was fabricated utilizing a haptic vibration transducer with high- and low-fidelity amplifiers; system calibration was performed matching vibration peak–peak values for both amplifiers. Eight experts performed simulated reaming trials. The experts were asked to identify isolated layer profiles produced by the simulator. Additionally, experts’ efficiency to successfully perform a simulated glenoid ream based solely on vibration feedback was recorded.

Results

Cadaveric experimental cartilage reaming produced lower vibrations compared to subchondral and cancellous bones (\(p\le 0.03\)). Gain calibration of a lower-fidelity (3.5 \({g}_{\mathrm{pk-pk}}, 0.36\,{g}_{\mathrm{rms}})\) and higher-fidelity (3.4 \({g}_{\mathrm{pk-pk}}, 0.33\,{g}_{\mathrm{rms}})\) amplifier resulted in values similar to the cadaveric experimental benchmark (3.5 \({g}_{\mathrm{pk-pk}}, 0.30\,{g}_{\mathrm{rms}})\). When identifying random tissue layer samples, experts were correct \(52\pm 9\%\) of the time and success rate varied with tissue type (\(p=0.003\)). During simulated reaming, the experts stopped at the targeted subchondral bone with a success rate of \(78\pm 24\%\). The fidelity of the simulation did not have an effect on accuracy, applied force, or reaming time (\(p>0.05\)). However, the applied force tended to increase with trial number (\(p=0.047\)).

Conclusions

Development of the glenoid reaming simulator, coupled with expert evaluation furthered our understanding of the role of haptic vibration feedback during glenoid reaming. This study was the first to (1) propose, develop and examine simulated glenoid reaming, and (2) explore the use of haptic vibration feedback in the realm of shoulder arthroplasty.