Brief mechanical ventilation impacts airway cartilage properties in neonatal lambs

Ventilated Infants Have Increased Dead Space and Lower Alveolar Tidal Volumes during the Early versus Recovery Phase of Respiratory Distress

BACKGROUND

Few studies have reported the measurement of anatomical dead space (Vd,an) and alveolar tidal volume (VA) in ventilated neonates with respiratory distress.

OBJECTIVE

The aim of this study was to determine the differences in Vd,an and VA in ventilated infants between the early and recovery phases of respiratory distress using volumetric -capnography (Vcap) based on ventilator graphics and capnograms.

METHODS

This study enrolled twenty-five ventilated infants (mean birth weight, 2,220 ± 635 g; mean gestational age, 34.7 ± 3.3 weeks). We adjusted respiratory settings to maintain appropriate oxygenation and tidal volume (VT), and performed Vcap based on waveforms of ventilator graphics and capnograms. Vd,an and VAwere measured in infants with respiratory disorders, immediately after intubation (early phase) and subsequently when they were clinically stable (recovery phase).

RESULTS

The early phase, with lower dynamic lung compliance, required a higher level of ventilator support, not positive end-expiratory pressure, than the recovery phase. There were significant differences between the early and recovery phases for Vd,an (mean difference in Vd,an/kg = 0.57 mL/kg; 95% confidence interval [CI], 0.38-0.77; mean difference in Vd,an/VT = 0.10; 95% CI, 0.07-0.14) and VA (mean difference in VA/kg = -0.60 mL/kg; 95% CI, -0.94 to -0.27; mean difference in VA/VT = -0.12; 95% CI, -0.15 to -0.09), despite no difference in VT.

CONCLUSIONS

We evaluated changes in Vd,an and VA during mechanical ventilation using Vcap based on waveforms. The increase in Vd,an and decrease in VA suggested dilation of the airways and collapse of the alveoli in ventilated infants with low lung compliance.

Spectroscopic Analysis of Human Tracheal Tissue during Decellularization

OBJECTIVE

To use mid-infrared (IR) spectroscopy to assess changes in the cartilaginous framework of human trachea during decellularization.

STUDY DESIGN

Laboratory-based study.

SETTING

Research laboratory.

METHODS

Six cadaveric human tracheas were decellularized using a detergent enzymatic method (DEM). Tissue samples were obtained from each specimen after 0, 1, 10, and 25 DEM cycles for histologic and spectroscopic analysis. Decellularization was confirmed using hematoxylin and eosin (H&E) and 2-(4-amidinophenyl)-1H-indole-6-carboxamidine (DAPI) staining. Changes in cartilaginous framework were examined using Fourier transform infrared imaging spectroscopy (FT-IRIS) and an attenuated total reflectance (ATR) probe in the mid-IR frequencies. Results were statistically analyzed using 1-way analysis of variance (ANOVA) and principal component analysis (PCA).

RESULTS

Six decellularized tracheal scaffolds were successfully created using a DEM protocol. Histologic examination showed near-complete nuclear loss following 25 DEM cycles. As observed with FT-IRIS analysis, the collagen absorbance signal (1336 cm-1) was predominantly in the perichondria and remained stable after 25 DEM cycles ( P = .132), while the absorbance from sugar rings in proteoglycans and nucleic acids in hyaline cartilage (1080 cm-1) showed a significant decrease after 1 DEM cycle ( P = .0007). Examination of the luminal surface of the trachea with an ATR probe showed raw mid-IR spectra consistent with cartilage. PCA showed significant separation of spectra corresponding to treatment cycle along the principal components 1 and 2.

CONCLUSION

Mid-IR spectroscopy is a viable method of monitoring changes in extracellular matrix components during the decellularization of human trachea.

Compositional Assessment of Human Tracheal Cartilage by Infrared Spectroscopy

Objectives To assess the potential of infrared fiber-optic spectroscopy to evaluate the compositional properties of human tracheal cartilage. Study Design Laboratory-based study. Methods Twenty human cadaveric distal tracheas were harvested (age range 20-78 years; 6 females, 14 males) for compositional analysis. Histologic staining, Fourier transform infrared imaging spectroscopy data on collagen and proteoglycan (PG) content, and near-infrared (NIR) fiber-optic probe spectroscopic data that reflect protein and water content were evaluated. NIR fiber-optic probe data were also obtained from the proximal trachea in 4 human cadavers (age range 51-65 years; 2 females, 2 males) in situ for comparison to distal trachea spectral data. Results In the distal trachea cohort, the spectroscopic-determined ratio of PG/amide I, indicative of the relative amount of PG, was significantly higher in the tissues from the younger group compared to the older group (0.37 ± 0.08 vs 0.32 ± 0.05, P = .05). A principal component analysis of the NIR spectral data enabled separation of spectra based on tracheal location, likely due to differences in both protein and water content. The NIR-determined water content based on the 5200-cm-1 peak was significantly higher in the distal trachea compared to the proximal trachea ( P < .001). Conclusions Establishment of normative compositional values and further elucidating differences between the segments of trachea will enable more directed research toward appropriate compositional end points in regenerative medicine for tracheal repair.

Airway damage of prematurity: The impact of prolonged intubation, ventilation, and chronic lung disease

Over the past four decades, advances in neonatal intensive care have led to the survival of smaller and more immature infants. The improved survival of very low birth weight infants is associated with long term respiratory morbidity, most frequently in the form of bronchopulmonary dysplasia. In this review, we will discuss the pathogenesis, risk factor as well as management of commonly seen acquired airway disorders associated with prematurity, prolonged intubation and ventilation.

Monitoring the Progression of Spontaneous Articular Cartilage Healing with Infrared Spectroscopy

OBJECTIVE

Evaluation of early compositional changes in healing articular cartilage is critical for understanding tissue repair and for therapeutic decision-making. Fourier transform infrared imaging spectroscopy (FT-IRIS) can be used to assess the molecular composition of harvested repair tissue. Furthermore, use of an infrared fiber-optic probe (IFOP) has the potential for translation to a clinical setting to provide molecular information in situ. In the current study, we determined the feasibility of IFOP assessment of cartilage repair tissue in a rabbit model, and assessed correlations with gold-standard histology.

DESIGN

Bilateral osteochondral defects were generated in mature white New Zealand rabbits, and IFOP data obtained from defect and adjacent regions at 2, 4, 6, 8, 12, and 16 weeks postsurgery. Tissues were assessed histologically using the modified O'Driscoll score, by FT-IRIS, and by partial least squares (PLS) modeling of IFOP spectra.

RESULTS

The FT-IRIS parameters of collagen content, proteoglycan content, and collagen index correlated significantly with modified O'Driscoll score (P = 0.05, 0.002, and 0.02, respectively), indicative of their sensitivity to tissue healing. Repair tissue IFOP spectra were distinguished from normal tissue IFOP spectra in all samples by PLS analysis. However, the PLS model for prediction of histological score had a high prediction error, which was attributed to the spectral information being acquired from the tissue surface only.

CONCLUSION

The strong correlations between FT-IRIS data and histological score support further development of the IFOP technique for clinical applications, although further studies to optimize data collection from the full sample depths are required.