The evaluation of a non-invasive respiratory volume monitor in surgical patients undergoing elective surgery with general anesthesia.

Continuous respiratory assessment is especially important during post-operative care following extubation. Respiratory depression and subsequent adverse outcomes can arise due to opioid administration and/or residual anesthetics. A non-invasive respiratory volume monitor (RVM) has been developed that provides continuous, real-time, measurements of minute ventilation (MV), tidal volume (TV), and respiratory rate (RR) via a standardized set of thoracic electrodes. Previous work demonstrated accuracy of the RVM versus standard spirometry and its utility in demonstrating response to opioids in postoperative patients. This study evaluated the correlation between RVM measurements of MV, TV and RR to ventilator measurements during general anesthesia (GA). Continuous digital RVM and ventilator traces, as well as RVM measurements of MV, TV and RR, were analyzed from ten patients (mean 62.6±7.4 years; body mass index 28.6±5.2 kg/m2) undergoing surgery with GA. RVM data were compared to ventilator data and bias, precision and accuracy were calculated. The average MV difference between the RVM and ventilator was -0.10 L/min (bias: -1.3%, precision: 6.6%, accuracy: 9.0%. The average TV difference was 40 mL (bias: 0.4%, precision: 7.3%, accuracy: 9.1%). The average RR difference was -0.22 breaths/minute (bias: -1.8%, precision: 3.7% accuracy: 4.1%). Correlations between the RVM traces and the ventilator were compared at various points with correlations>0.90 throughout. Pairing the close correlation to ventilator measurements in intubated patients demonstrated by this study with previously described accuracy compared to spirometry in non-intubated patients, the RVM can be considered to have the capability to provide continuity of ventilation monitoring post-extubation This supports the use of real-time continuous RVM measurements to drive post-operative and post-extubation protocols, initiate therapeutic interventions and improve patient safety.

The mouse S100A15 ortholog parallels genomic organization, structure, gene expression, and protein-processing pattern of the human S100A7/A15 subfamily during epidermal maturation.

The calcium-binding proteins of the human S100A7/A15 (hS100A7/A15) subfamily are differentially expressed in normal and pathological epidermis. The hS100A7 (psoriasin) and S100A15 reside in a chromosomal cluster of highly similar paralogs. To exploit the power of mouse models for determining functions of gene products, the corresponding S100A7/A15 ortholog was cloned and examined in murine skin. The single mouse S100A15 (mS100A15) gene encodes a protein of 104 amino acids with a predicted molecular weight of 12,870 Da and two EF-hand calcium binding sites. Using gene-specific primers and specific antibodies, expression of mS100A15 in both skin and isolated keratinocytes is confined to differentiating granular and cornified epidermal cells. Immunoblotting of epidermal extracts revealed a series of high molecular weight bands that are also recognized by an antibody for transglutaminase-mediated protein crosslinks. mS100A15 expression is upregulated in cultured keratinocytes induced to differentiate by calcium or phorbol esters. Maximal induction occurs concordantly with expression of late differentiation markers. Induction is enhanced in keratinocytes overexpressing protein kinase Calpha and is dependent on activator protein-1 transcription factors. The regulation, expression pattern and crosslinking of mS100A15 are consistent with the characteristics of the human orthologs, providing a valid surrogate model to study changes in these proteins associated with cutaneous pathologies.

Continuous noninvasive respiratory volume monitoring for the identification of patients at risk for opioid-induced respiratory depression and obstructive breathing patterns.

BACKGROUND: Opioid-induced respiratory depression (OIRD) and postoperative apnea (POA) can lead to complications after surgery or traumatic injury. Previously, real-time monitoring of respiratory insufficiency and identification of apneic events have been difficult. A noninvasive respiratory volume monitor (RVM) that reports minute ventilation (MV), tidal volume, and respiratory rate is now available. The RVM was used to report the effect of opioids on respiratory status as well as demonstrate apneic breathing patterns in a hospital postanesthesia care unit. METHODS: RVM traces were collected from 132 patients. Predicted MV (MVPRED) for each patient was used to calculate and the "percent predicted" MV (MVMEASURED / MVPRED × 100%) before opioid administration. Patients were stratified patients into two categories: "at risk," MV of less than 80% MVPRED, and "not at risk," MV of 80% MVPRED or greater. After opioid dosing, patients with MV of less than 40% MVPRED were categorized as "unsafe." POA was defined as more than five apneic or hypopneic events per hour. RESULTS: Of the 132 patients, 50 received opioids. Baseline MV was 7.2 ± 0.5 L/min. The MV-based protocol classified 18 of 50 patients as at risk before opioid administration. After the first opioid dose administration, at-risk patients experienced an average MV decrease (36.7% ± 8.5% MVPRED) and 13 of 18 decreased into unsafe; the 32 not at-risk patients experienced a lesser average MV decrease (76.9% ± 6.3% MVPRED). Only 1 of 32 not at-risk patients had a decrease in MV to unsafe. The proposed protocol had a sensitivity of 93% and a specificity of 86%. Of the 132 patients, 26 displayed POA. Of the 26 patients, 12 experienced POA without receiving opioids. Of the 26 patients with POA, 14 also received opioids, and of those, 6 were classified as unsafe. CONCLUSION: This investigation indicates that at risk and unsafe respiratory patterns occur frequently after procedure. RVM provides continuous noninvasive objective measurements of OIRD and POA. The RVM may prove a useful tool in opioid dosing and in recognition and management of POA and strong potential value in the rapid detection of OIRD and apnea in the contemporary combat casualty environment. LEVEL OF EVIDENCE: Care management study, level V.