Marcin Michnikowski

Development of an electronic manometer for intrapleural pressure monitoring.

Background: Measurement of intrapleural pressure is useful during various pleural procedures. However, a pleural manometer is rarely available. Objectives: The aim of this study was to (1) construct an electronic pleural manometer, (2) assess the accuracy of the measurements done with the new device, (3) calculate the costs of the manometer construction and (4) perform an initial evaluation of the device in a clinical setting. Methods: Only widely accessible elements were used to construct the device. A vascular pressure transducer was used to transform pressure into an electronic signal. Reliability of the measurements was evaluated in a laboratory setting in a prospective, single-blind manner by comparing the results with those measured by a water manometer. Functionality of the device was assessed during therapeutic thoracentesis. The cost of the new pleural manometer was calculated. Results: We built a small, portable device which can precisely measure intrapleural pressure. The measurement results showed very high agreement with those registered with a water manometer (r = 0.999; p < 0.001). The initial evaluation of the electronic manometer during therapeutic thoracentesis showed it was easy to use. The total time needed for 6 measurements after withdrawal of different volumes of pleural fluid in 1 patient did not exceed 6 min. The total cost of the device was calculated to be <2,000 EUR. Conclusions: In the face of very limited offer of commercially available pleural manometers, it is possible to successfully construct a self-made, reliable, electronic pleural manometer at modest costs. The device is easy to use and enables data display and storage in the personal computer.

Cough during therapeutic thoracentesis: friend or foe?

We report intriguing preliminary observations on the effect of cough on pleural pressure changes during therapeutic thoracentesis. We found that cough‐related elevation of pleural pressure persisted even when the cough had stopped. Thus, we hypothesize that cough during therapeutic thoracentesis may have a beneficial effect preventing the excessive drop in pleural pressure. The true role of cough‐related elevation of pleural pressure is unknown, but it seems to be an interesting subject for further research.

A new endotracheal tube for infants--laboratory and clinical assessment: a preliminary study.

Conventional endotracheal pediatric tubes offer high resistance due to their small diameters and relatively high flow during ventilation. Any increase of the diameter of the tube lumen decreases the airway resistance and subsequently, the work of breathing (WOB). We compared ventilation mechanics using a new, cone‐shaped endotracheal tube of our design to the Cole and standard tubes.

The use of a virtual patient to follow pleural pressure changes associated with therapeutic thoracentesis

Purpose Influence of therapeutic thoracentesis on the pleural pressure (Pp) has been discussed in many clinical studies, however reasons of Pp changes are not precisely established. The aim of the study was to use a previously elaborated virtual cardiopulmonary patient (VP) in analysis of impact of physiological factors on Pp during the procedure. Methods Simulations were performed on VP with default values of parameters for which VP simulated the respiratory system of the average 50-year-old healthy Polish woman according to spirometric examination. Alterations of Pp and the amplitude of Pp changes related to breathing (AP) were analyzed. Model parameters related to chosen factors were deviated from their default values to analyze the degree of their impact on Pp and AP. The analysis was based on and supported by our own clinical data. Results The Pp and AP alteration intensity appeared to be most sensitive to the compliances of the rib cage and mediastinum, and the nonlinearity of the dependence between the recoil pressure and the lung volume: the lower the compliances and the higher the nonlinearity were, the deeper the Pp fall during the procedure and the bigger the AP increase were observed. Conclusions Experiments in silico are very useful in analyzing sophisticated physiological and medical problems. They made it possible to show which factors are particularly responsible for changes in Pp during thoracentesis. In the future, they may be useful in establishing objective conditions under which thoracentesis needs to be stopped.

The use of a virtual patient to follow changes in arterial blood gases associated with therapeutic thoracentesis

Purposes: Some controversies exist on the effect of therapeutic thoracentesis (TT) on arterial blood oxygen tension. The aim of this study was to evaluate this issue using a previously developed virtual patient. Methods: The analysis was based and supported by clinical data collected during 36 TT. Pleural pressure and transcutaneous oxygen and carbon dioxide pressures (PtcO2 and PtcCO2) were measured during pleural fluid withdrawal. Arterial blood oxygen tension and arterial CO2 tension (PaO2 and PaCO2) were analysed in simulations that mimicked TT. Minute ventilation was adjusted to maintain arterial CO2 tension at a constant level unless arterial blood oxygen tension fell below 8 kPa. Specifically, the influence of hypoxic pulmonary vasoconstriction efficiency was tested. Results: In patients, PtcCO2 remained at an approximately constant level (average amplitude: 0.63 ± 0.29 kPa), while some fluctuations of PtcO2 were observed (amplitude: (1.65 ± 1.18 kPa) were observed. In 42% of patients, TT was associated with decrease in PtcCO2. Simulations showed the following: (a) there were similar PaO2 fluctuations in the virtual patient; (b) the lower the hypoxic pulmonary vasoconstriction efficiency, the more pronounced the PaO2 fall during fluid withdrawal; and (c) the lower the atelectatic lung areas recruitment rate, the slower the PaO2 normalization. The decrease in PaO2 was caused by an increase of pulmonary shunt. Conclusion: Therapeutic thoracentesis may cause both an increase and a decrease in PaO2 during the procedure. Pleural pressure decrease, caused by pleural fluid withdrawal, improves the perfusion of atelectatic lung areas. If the rate of recruitment of these areas is low, a lack of ventilation causes the arterial blood oxygen tension to fall. Effective hypoxic pulmonary vasoconstriction may protect against the pulmonary shunt.

The impact of the intubation model upon ventilation parameters

The impact of various shaped endotracheal tubes on ventilation parameters has been preliminary assessed in this study. Two uncuffed pediatric tubes of different designs: a standard tube (cylindrical) and a new tube of smooth cone shape (3, 3.5 and 4 mm ID) have been examined under IPPV mode ventilation and using infant lung model. The total inspiratory flow resistance (Ri), peak inspiratory preassure (PIP) and work of breathing (WOB) have been determined under intubation with the standard and the cone shaped tube, and also for non-intubated infant lung model. The significant reduction of the Ri, PIP and WOB has been received when the standard tube had been changed with the new cone tube. The results have been confirmed in a case clinic study.

Comparison of a standard paediatric tube with a novel tube of unconventional shape

Aim: Two types of uncuffed paediatric tubes of different designs: a standard tube with a constant internal diameter and a new tube of smooth cone shape were assessed in the model study. Material and Method: The tube resistance to air flow was calculated on the basis of measurements, in which pressure/flow characteristics of the tubes of 3, 3.5 and 4 mm in inner (tracheal) diameter were collected. The flow was controlled by PC and ranged from −30 to +30 lpm. It was measured by a flow sensor (Cole Parmer 00139RN, accuracy: 1%), while the drop of pressure along a tube length was measured by a pressure sensor (JUMO dTrans pO2 B40.4385, accuracy: 0,05%). Patient’s resistive work of breathing (RWOB) was received by simulation of spontaneous breathing of an intubated infant. Simple RC-model of lungs and an endotracheal tube was used for simulation. Results: The air flow resistance of the cone shaped tube was about 40% lower than resistance of the standard tube. RWOB of the virtual infant intubated with the cone tube was decreased by about 20%, in comparison to the situation when a standard tube was used. Conclusion: Using the new cone shaped tube can be more beneficial than the standard tube from a patient’s point of view (when his lungs ventilation is still supported but he is able to breath spontaneously) and ventilation efficiency.

Preliminary clinical evaluation of a new differential lung ventilation set-up

Aim: The objective of this study was to access the ability to control and stabilize ventilation of each lung by a newly developed flow/ventilator divider.