Quantified Ataxic Breathing Can Detect Opioid-Induced Respiratory Depression Earlier in Normal Volunteers Infused with Remifentanil.

Background: Ataxic breathing (AB) is a well-known manifestation of opioid effects in animals and humans, but is not routinely included in monitoring for opioid-induced respiratory depression (OIRD). We quantified AB in normal volunteers receiving increasing doses of remifentanil. We used a support vector machine (SVM) learning approach with features derived from a modified Poincaré plot.

Volatile anesthetic gas concentration sensing using flow sensor fusion for use in Austere settings.

Flow sensors are often sensitive to the presence of volatile anesthetics. However, this sensitivity provides a unique opportunity to combine flow sensors of differing technological principles as an alternative to measuring volatile anesthetic gas concentration, particularly for austere settings. To determine the feasibility of flow sensor fusion for volatile anesthetic concentrations monitoring, eight flow sensors were tested with isoflurane, sevoflurane, and desflurane, ranging in concentrations from 0-4.

Efficient sampling for polynomial chaos-based uncertainty quantification and sensitivity analysis using weighted approximate Fekete points.

Performing uncertainty quantification (UQ) and sensitivity analysis (SA) is vital when developing a patient-specific physiological model because it can quantify model output uncertainty and estimate the effect of each of the model's input parameters on the mathematical model. By providing this information, UQ and SA act as diagnostic tools to evaluate model fidelity and compare model characteristics with expert knowledge and real world observation. Computational efficiency is an important part of UQ and SA methods and thus optimization is an active area of research.

An Automated Algorithm Incorporating Poincaré Analysis Can Quantify the Severity of Opioid-Induced Ataxic Breathing.

Background: Opioid-induced respiratory depression (OIRD) is traditionally recognized by assessment of respiratory rate, arterial oxygen saturation, end-tidal CO2, and mental status. Although an irregular or ataxic breathing pattern is widely recognized as a manifestation of opioid effects, there is no standardized method for assessing ataxic breathing severity. The purpose of this study was to explore using a machine-learning algorithm for quantifying the severity of opioid-induced ataxic breathing.

A procedure for determining subject-specific pulse oxygen saturation response.

The oxyhemoglobin dissociation curve describes the relationship between the partial pressure of oxygen and the percent of hemoglobin saturated with oxygen and varies with chemical and physical factors that differ for every patient. If variability could be determined, patient-specific oxygen therapy could be administered. We have developed a procedure for characterizing variations in the oxygen dissociation curve.

A comparison of ventilation with a non-invasive ventilator versus standard O with a nasal cannula for colonoscopy with moderate sedation using propofol.

The aim of this study was to test the effects of CPAP on moderately sedated patients undergoing colonoscopy. Our hypothesis was that CPAP can reduce the incidence and duration of obstructive apnea and hemoglobin oxygen desaturation in patients undergoing procedural sedation for colonoscopy. Two groups of consenting adult patients scheduled to undergo routine colonoscopy procedures and sedated with propofol and fentanyl were monitored in this study: control and intervention.

Evaluation and application of a method for estimating nasal end-tidal O fraction while administering supplemental O.

This paper describes a method for estimating the oxygen enhanced end-tidal fraction of oxygen (FO), the end-tidal fraction of oxygen (FO) that is raised by administering supplemental oxygen. The paper has two purposes: the first is to evaluate the method's accuracy on the bench and in volunteers; the second purpose is to demonstrate how to apply the method to compare two techniques of oxygen administration. The method estimates FO by analyzing expired oxygen as oxygen washes out of the lung.

Comparing Nasal End-Tidal Carbon Dioxide Measurement Variation and Agreement While Delivering Pulsed and Continuous Flow Oxygen in Volunteers and Patients.

Background: Supplemental oxygen is administered during procedural sedation to prevent hypoxemia. Continuous flow oxygen, the most widespread method, is generally adequate but distorts capnography. Pulsed flow oxygen is novel and ideally will not distort capnography.

Novel mandibular advancement bite block with supplemental oxygen to both nasal and oral cavity improves oxygenation during esophagogastroduodenoscopy: a bench comparison.

Drug-induced respiratory depression is a major cause of serious adverse events. Adequate oxygenation is very important during sedated esophagogastroduodenoscopy (EGD). Nasal breathing often shifts to oral breathing during open mouth EGD.

A Turbine-Driven Ventilator Improves Adherence to Advanced Cardiac Life Support Guidelines During a Cardiopulmonary Resuscitation Simulation.

Background: Research has shown that increased breathing frequency during cardiopulmonary resuscitation is inversely correlated with systolic blood pressure. Rescuers often hyperventilate during cardiopulmonary resuscitation (CPR). Current American Heart Association advanced cardiac life support recommends a ventilation rate of 8-10 breaths/min.

Using the entropy of tracheal sounds to detect apnea during sedation in healthy nonobese volunteers.

Background: Undetected apnea can lead to severe hypoxia, bradycardia, and cardiac arrest. Tracheal sounds entropy has been proved to be a robust method for estimating respiratory flow, thus maybe a more reliable way to detect obstructive and central apnea during sedation.

Methods: A secondary analysis of a previous pharmacodynamics study was conducted.

Continuous monitoring of respiratory flow and CO(2):challenges of on-airway measurements.

In this article, the challenges of simultaneous respiratory gas concentration and flow measurements in a breathing circuit are reviewed. The tradeoffs that were considered in the development of a clinically useful on-airway combination CO(2)/flow sensor are discussed as well as the applications enabled by this on-airway combination CO(2)/flow sensor.

A tool predicting future mean arterial blood pressure values improves the titration of vasoactive drugs.

Background: Vasoactive drug infusion rates are titrated to achieve a desired effect, e.g., mean arterial blood pressure (MAP), rather than using infusion rates based on body weight.

Anatomic dead space cannot be predicted by body weight.

Background: Anatomic dead space (also called airway or tracheal dead space) is the part of the tidal volume that does not participate in gas exchange. Some contemporary ventilation protocols, such as the Acute Respiratory Distress Syndrome Network protocol, call for smaller tidal volumes than were traditionally delivered. With smaller tidal volumes, the percentage of each delivered breath that is wasted in the anatomic dead space is greater than it is with larger tidal volumes.

Measurement of functional residual capacity of the lung by partial CO2 rebreathing method during acute lung injury in animals.

Background: Several techniques for measuring the functional residual capacity (FRC) of the lungs in mechanically ventilated patients have been proposed, each of which is based on either nitrogen wash-out or dilution of tracer gases. These methods are expensive, difficult, time-consuming, impractical, or require an intolerably large change in the fraction of inspired oxygen. We propose a CO(2) wash-in method that allows automatic and continual FRC measurement in mechanically ventilated patients.

Rapid recovery from sevoflurane and desflurane with hypercapnia and hyperventilation.

Background: Hypercapnia with hyperventilation shortens the time between turning off the vaporizer (1 MAC) and when patients open their eyes after isoflurane anesthesia by 62%.

Methods: In the present study we tested whether a proportional shortening occurs with sevoflurane and desflurane.

Results: Consistent with a proportional shortening, we found that hypercapnia with hyperventilation decreased recovery times by 52% for sevoflurane and 64% for desflurane (when compared with normal ventilation with normocapnia).

Hypercapnia shortens emergence time from inhaled anesthesia in pigs.

Background: Anesthetic clearance from the lungs and the circle rebreathing system can be maximized using hyperventilation and high fresh gas flows. However, the concomitant clearance of CO2 decreases PAco2, thereby decreasing cerebral blood flow and slowing the clearance of anesthetic from the brain. This study shows that in addition to hyperventilation, hypercapnia (CO2 infusion or rebreathing) is a significant factor in decreasing emergence time from inhaled anesthesia.

Hypercapnic hyperventilation shortens emergence time from isoflurane anesthesia.

Background: To shorten emergence time after a procedure using volatile anesthesia, 78% of anesthesiologists recently surveyed used hyperventilation to rapidly clear the anesthetic from the lungs. Hyperventilation has not been universally adapted into clinical practice because it also decreases the Paco2, which decreases cerebral bloodflow and depresses respiratory drive. Adding deadspace to the patient's airway may be a simple and safe method of maintaining a normal or slightly increased Paco2 during hyperventilation.