Quantifying heterogeneity in an animal model of acute respiratory distress syndrome, a comparison of inspired sinewave technique to computed tomography.

The inspired sinewave technique (IST) is a non-invasive method to measure lung heterogeneity indices (including both uneven ventilation and perfusion or heterogeneity), which reveal multiple conditions of the lung and lung injury. To evaluate the reproducibility and predicted clinical outcomes of IST heterogeneity values, a comparison with a quantitative lung computed tomography (CT) scan is performed. Six anaesthetised pigs were studied after surfactant depletion by saline-lavage.

Intra-tidal PaO oscillations associated with mechanical ventilation: a pilot study to identify discrete morphologies in a porcine model.

Background: Within-breath oscillations in arterial oxygen tension (PaO) can be detected using fast responding intra-arterial oxygen sensors in animal models. These PaO signals, which rise in inspiration and fall in expiration, may represent cyclical recruitment/derecruitment and, therefore, a potential clinical monitor to allow titration of ventilator settings in lung injury. However, in hypovolaemia models, these oscillations have the potential to become inverted, such that they decline, rather than rise, in inspiration.

OxVent: Design and evaluation of a rapidly-manufactured Covid-19 ventilator.

Background: The manufacturing of any standard mechanical ventilator cannot rapidly be upscaled to several thousand units per week, largely due to supply chain limitations. The aim of this study was to design, verify and perform a pre-clinical evaluation of a mechanical ventilator based on components not required for standard ventilators, and that met the specifications provided by the Medicines and Healthcare Products Regulatory Agency (MHRA) for rapidly-manufactured ventilator systems (RMVS).

Methods: The design utilises closed-loop negative feedback control, with real-time monitoring and alarms.

Lung simulation to support non-invasive pulmonary blood flow measurement in Acute Respiratory Distress Syndrome in animals.

Patients undergoing mechanical lung ventilation are at risk of lung injury. A noninvasive bedside lung monitor may benefit these patients. The Inspired Sinewave Test (IST) can measure cardio-pulmonary parameters noninvasively.

Continuous measurement of arterial oxygenation in mechanically ventilated horses.

Background: The possibility of accurately and continuously measuring arterial oxygen partial pressure (PaO ) in horses may facilitate the management of hypoxaemia during general anaesthesia.

Objectives: The aim of this study was to evaluate the ability of a novel fibreoptic sensor to measure PaO (PaO ) continuously and in real time in horses undergoing ventilatory manoeuvres during general anaesthesia.

Study Design: In vivo experimental study.

Bedside monitoring of lung volume available for gas exchange.

Background: Bedside measurement of lung volume may provide guidance in the personalised setting of respiratory support, especially in patients with the acute respiratory distress syndrome at risk of ventilator-induced lung injury. We propose here a novel operator-independent technique, enabled by a fibre optic oxygen sensor, to quantify the lung volume available for gas exchange. We hypothesised that the continuous measurement of arterial partial pressure of oxygen (PaO) decline during a breath-holding manoeuvre could be used to estimate lung volume in a single-compartment physiological model of the respiratory system.

Lung heterogeneity and deadspace volume in animals with acute respiratory distress syndrome using the inspired sinewave test.

Acute respiratory distress syndrome (ARDS) is associated with a high rate of morbidity and mortality, as patients undergoing mechanical ventilation are at risk of ventilator-induced lung injuries.: To measure the lung heterogeneity and deadspace volume to find safer ventilator strategies. The ventilator settings could then offer homogeneous ventilation and theoretically equalize and reduce tidal strain/stress in the lung parenchyma.

A tidal lung simulation to quantify lung heterogeneity with the Inspired Sinewave Test.

We have created a lung simulation to quantify lung heterogeneity from the results of the inspired sinewave test (IST). The IST is a lung function test that is non-invasive, non-ionising and does not require patients' cooperation. A tidal lung simulation is developed to assess this test and also a method is proposed to calculate lung heterogeneity from IST results.

Real-time effects of PEEP and tidal volume on regional ventilation and perfusion in experimental lung injury.

Background: Real-time bedside information on regional ventilation and perfusion during mechanical ventilation (MV) may help to elucidate the physiological and pathophysiological effects of MV settings in healthy and injured lungs. We aimed to study the effects of positive end-expiratory pressure (PEEP) and tidal volume (V) on the distributions of regional ventilation and perfusion by electrical impedance tomography (EIT) in healthy and injured lungs.

Methods: One-hit acute lung injury model was established in 6 piglets by repeated lung lavages (injured group).

Validating the inspired sinewave technique to measure the volume of the 'baby lung' in a porcine lung-injury model.

Background: Bedside lung volume measurement could personalise ventilation and reduce driving pressure in patients with acute respiratory distress syndrome (ARDS). We investigated a modified gas-dilution method, the inspired sinewave technique (IST), to measure the effective lung volume (ELV) in pigs with uninjured lungs and in an ARDS model.

Methods: Anaesthetised mechanically ventilated pigs were studied before and after surfactant depletion by saline lavage.

Mechanical Ventilation Redistributes Blood to Poorly Ventilated Areas in Experimental Lung Injury.

Objectives: Determine the intra-tidal regional gas and blood volume distributions at different levels of atelectasis in experimental lung injury. Test the hypotheses that pulmonary aeration and blood volume matching is reduced during inspiration in the setting of minimal tidal recruitment/derecruitment and that this mismatching is an important determinant of hypoxemia.

Design: Preclinical study.

Dynamic single-slice CT estimates whole-lung dual-energy CT variables in pigs with and without experimental lung injury.

Background: Dynamic single-slice CT (dCT) is increasingly used to examine the intra-tidal, physiological variation in aeration and lung density in experimental lung injury. The ability of dCT to predict whole-lung values is unclear, especially for dual-energy CT (DECT) variables. Additionally, the effect of inspiration-related lung movement on CT variables has not yet been quantified.

Effect of nitrite on the electroencephalographic activity in the healthy brain.

Background: Nitrite is a major intravascular store for nitric oxide. The conversion of nitrite to the active nitric oxide occurs mainly under hypoxic conditions to increase blood flow where it is needed the most. The use of nitrite is, therefore, being evaluated widely to reduce the brain injury in conditions resulting in cerebral hypoxia, such as cardiac arrest, ischaemic stroke or subarachnoid haemorrhage.

Noninvasive cardiac output monitoring in a porcine model using the inspired sinewave technique: a proof-of-concept study.

Background: Cardiac output (Q˙) monitoring can support the management of high-risk surgical patients, but the pulmonary artery catheterisation required by the current 'gold standard'-bolus thermodilution (Q˙)-has the potential to cause life-threatening complications. We present a novel noninvasive and fully automated method that uses the inspired sinewave technique to continuously monitor cardiac output (Q˙).

Methods: Over successive breaths the inspired nitrous oxide (NO) concentration was forced to oscillate sinusoidally with a fixed mean (4%), amplitude (3%), and period (60 s).