Chain of events analysis in diving accidents treated by the Royal Netherlands Navy 1966-2023

Introduction

Diving injuries are influenced by a multitude of factors. Literature analysing the full chain of events in diving accidents influencing the occurrence of diving injuries is limited. A previously published 'chain of events analysis' (CEA) framework consists of five steps that may sequentially lead to a diving fatality. This study applied four of these steps to predominately non-lethal diving injuries and aims to determine the causes of diving injuries sustained by divers treated by the Diving Medical Centre of the Royal Netherlands Navy.

Methods

This retrospective cohort study was performed on diving injuries treated by the Diving Medical Centre between 1966 and 2023. Baseline characteristics and information pertinent to all four steps of the reduced CEA model were extracted and recorded in a database.

Results

A total of 288 cases met the inclusion criteria. In 111 cases, all four steps of the CEA model could be applied. Predisposing factors were identified in 261 (90%) cases, triggers in 142 (49%), disabling agents in 195 (68%), and 228 (79%) contained a (possible-) disabling condition. The sustained diving injury led to a fatality in seven cases (2%). The most frequent predisposing factor was health conditions (58%). Exertion (19%), primary diver errors (18%), and faulty equipment (17%) were the most frequently identified triggers. The ascent was the most frequent disabling agent (52%).

Conclusions

The CEA framework was found to be a valuable tool in this analysis. Health factors present before diving were identified as the most frequent predisposing factors. Arterial gas emboli were the most lethal injury mechanism.

Modern assessment of pulmonary function in divers cannot rely on old reference values

INTRODUCTION

Pulmonary function testing (PFT) is an important part of dive medical examinations. Depending on the standard used to assess fitness to dive, different reference sets and fixed cut-off points are used. Reference values are part of an ongoing debate regarding the validity and accuracy related to different age groups, sex and ethnic backgrounds. The Global Lung Initiative (GLI) has provided an all-age reference set which corrects for sex and ethnicity (GLI-2012); this has had substantial impact on pulmonary medicine.

METHOD

We present an algorithm that can be used to standardise analysis of PFT in divers using the GLI-2012 reference set. Differences in the analysis of PFT between the ECSC/ERS-1993 and the GLI-2012 reference values are illustrated by means of three case reports.

CONCLUSION

Using a valid database of reference values increases accuracy and might prevent additional medical investigations and/or incorrect assessment of fitness to dive. Although our algorithm needs further evaluation to ensure its validity, the preliminary results are promising. Whatever algorithm is used, we urge dive medical physicians to consider using valid reference sets when analysing PFT for assessment of fitness to dive.

Toll-like receptors in human chondrocytes and osteoarthritic cartilage

BACKGROUND AND PURPOSE

Degenerating cartilage releases potential danger signals that react with Toll-like receptor (TLR) type danger receptors. We investigated the presence and regulation of TLR1, TLR2, and TLR9 in human chondrocytes.

METHODS

We studied TLR1, TLR2, TLR4, and TLR9 mRNA (qRT-PCR) and receptor proteins (by immunostaining) in primary mature healthy chondrocytes, developing chondrocytes, and degenerated chondrocytes in osteoarthritis (OA) tissue sections of different OARSI grades. Effects of a danger signal and of a pro-inflammatory cytokine on TLRs were also studied.

RESULTS

In primary 2D-chondrocytes, TLR1 and TLR2 were strongly expressed. Stimulation of 2D and 3D chondrocytes with a TLR1/2-specific danger signal increased expression of TLR1 mRNA 1.3- to 1.8-fold, TLR2 mRNA 2.6- to 2.8-fold, and TNF-α mRNA 4.5- to 9-fold. On the other hand, TNF-α increased TLR1 mRNA] expression 16-fold, TLR2 mRNA expression 143- to 201-fold, and TNF-α mRNA expression 131- to 265-fold. TLR4 and TLR9 mRNA expression was not upregulated. There was a correlation between worsening of OA and increased TLR immunostaining in the superficial and middle cartilage zones, while chondrocytes assumed a CD166(×) progenitor phenotype. Correspondingly, TLR expression was high soon after differentiation of mesenchymal stem cells to chondrocytes. With maturation, it declined (TLR2, TLR9).

INTERPRETATION

Mature chondrocytes express TLR1 and TLR2 and may react to cartilage matrix/chondrocyte-derived danger signals or degradation products. This leads to synthesis of pro-inflammatory cytokines, which stimulate further TLR and cytokine expression, establishing a vicious circle. This suggests that OA can act as an autoinflammatory disease and links the old mechanical wear-and-tear concept with modern biochemical views of OA. These findings suggest that the chondrocyte itself is the earliest and most important inflammatory cell in OA.

High mobility group box-1 (HMGB-1) in osteoarthritic cartilage

OBJECTIVES

Nucleosomal high mobility group box-1 (HMGB-1) is translocated and released from necrotic and activated cells as an endogenous danger signal (alarmin) and cytokine. It was hypothesised that it plays a role in osteoarthritis (OA). characterised by cellular activation, inflammation and enchondral bone formation.

METHODS

Bovine knee joint samples, collected from culled animals, were scored using histologic/histochemical grading to intact looking, mild, moderate or severe and immunohistochemically stained for HMGB-1. Chondrocyte pellets, produced from human bone marrow-derived mesenchymal stem cells and stimulated with tumour necrosis factor-a (TNF-alpha), were similarly stained.

RESULTS

In healthy looking OA cartilage chondrocyte nuclei were usually HMGB-1 negative and in mild OA staining was restricted to nuclei. In moderate OA lesions HMGB-1 was also seen in the cytoplasm and occasionally pericellular matrix and in severe OA lesions often also in intra- and inter-territorial matrix. The tidemark in healthy cartilage did not contain HMGB-1, which however was seen at this interface as linear deposits even in intact-looking and mild OA lesions, as multiple wave-like deposits in moderate and as heavy granular deposits in severe lesions. TNF-alpha stimulation of chondrocytes caused translocation of HMGB-1 from the nucleus to the cytoplasm.

CONCLUSIONS

In resting chondrocytes tight nucleosomal HMGB-1 binding might cause steric hindrance of immunostaining. TNF-alpha- or OA-mediated activation leads to nuclear staining and cytoplasmic translocation. Advancing OA leads to increasingly intense extra-/pericellular deposition of HMGB-1 alarmin, indicating local chondrocyte activation and/or necrosis. In particular, HMGB-1 at the tidemark might play a role in the pathological thickening of subchondral bone plate/osteophyte formation.