Peripheral venous blood gases and pulse-oximetry in acute cardiogenic pulmonary oedema

BACKGROUND

The role of venous blood gases as an alternative to arterial blood gases in patients with severe acute heart failure has not been established.

OBJECTIVE

To assess the correlation between arterial and peripheral venous blood gases together with pulse-oximetry (SpO2), as well as to estimate arterial values from venous samples in the first hours upon admission of patients with acute cardiogenic pulmonary oedema.

METHODS

Simultaneous venous and arterial blood samples were extracted on admission and over the next 1, 2, 3, 4, and 10 hours. SpO2 was also registered at the same intervals.

RESULTS

A total of 178 pairs of samples were obtained from 34 consecutive patients with acute cardiogenic pulmonary oedema. Arterial and venous blood gases followed a parallel course in the first hours, showing high correlation rates at all time intervals. Venous samples underestimated pH (mean difference -0.028) and overestimated CO2 (+5.1 mmHg) and bicarbonate (+1 mEq/l). Conversely, SpO2 tended to underestimate SaO2 (mean±SD: 93.1±9.1 vs. 94.2±8.4). Applying simple mathematical formulae based on these differences, arterial values were empirically calculated from venous samples, showing acceptable agreement in the Bland-Altman test. Likewise, a venous pH <7.32, pCO2 >51.3 mmHg, and bicarbonate <22.8 mEq/l could fairly identify arterial acidosis, either respiratory or metabolic, with a test accuracy of 92, 68, and 91%, respectively.

CONCLUSIONS

In patients with cardiogenic pulmonary oedema, arterial blood gas disturbances may be estimated from peripheral venous samples. By monitoring SpO2 simultaneously, arterial punctures could often be avoided.

Minimally invasive in vivo human lung tissue bioimpedance measurements during the bronchoscopy procedure

Respiratory diseases, which include diseases of the lung, pleura, bronchial tree, trachea, upper respiratory tract and of the respiratory muscles and nerves, are a common and important cause of illness and death among the population. Experimental evidences have shown that tissue lesions have different electrical properties compared with normal tissue. Therefore, lung tissues lesions may be differentiated from lung normal tissue by comparing the tissue passive electrical properties. The manuscript reports a feasibility study for minimally invasive in vivo human lung tissue tetrapolar bioimpedance measurements using a catheter during the bronchoscopy procedure based on multisine Electrical Impedance Spectroscopy (EIS) at 10 kHz - 1 MHz.

Influence of electrical stimulation on 3D-cultures of adipose tissue derived progenitor cells (ATDPCs) behavior

Tissue engineering has a fundamental role in regenerative medicine. Still today, the major motivation for cardiac regeneration is to design a platform that enables the complete tissue structure and physiological function regeneration of injured myocardium areas. Although tissue engineering approaches have been generally developed for two-dimensional (2D) culture systems, three-dimensional (3D) systems are being spotlighted as the means to mimic better in vivo cellular conditions. This manuscript examines the influence of electrical stimulation on 3D cultures of adipose tissue-derived progenitor cells (ATDPCs). ATDPCs cells were encapsulated into a self-assembling peptide nanoscaffold (RAD16-I) and continuously electro stimulated during 14-20 days with 2-ms pulses of 50mV/cm at a frequency of 1 Hz. Good cellular network formation and construct diameter reduction was observed in electro stimulated samples. Importantly, the process of electro stimulation does not disrupt cell viability or connectivity. As a future outlook, differentiation studies to cardiomyocytes-like cells will be performed analyzing gene profile and protein expression.

A new measuring and identification approach for time-varying bioimpedance using multisine electrical impedance spectroscopy

The bioimpedance measurement/identification of time-varying biological systems Z(ω, t) by means of electrical impedance spectroscopy (EIS) is still a challenge today. This paper presents a novel measurement and identification approach, the so-called parametric-in-time approach, valid for time-varying (bio-)impedance systems with a (quasi) periodic character. The technique is based on multisine EIS. Contrary to the widely used nonparametric-in-time strategy, the (bio-)impedance Z(ω, t) is assumed to be time-variant during the measurement interval. Therefore, time-varying spectral analysis tools are required. This new parametric-in-time measuring/identification technique has experimentally been validated through three independent sets of in situ measurements of in vivo myocardial impedance. We show that the time-varying myocardial impedance Z(ω, t) is dominantly periodically time varying (PTV), denoted as ZPTV(ω, t). From the temporal analysis of ZPTV(ω, t), we demonstrate that it is possible to decompose ZPTV(ω, t) into a(n) (in)finite sum of fundamental (bio-)impedance spectra, the so-called harmonic impedance spectra (HIS) Zk(ω)s with [Formula: see text]. This is similar to the well-known Fourier series of a periodic signal, but now understood at the level of a periodic system's frequency response. The HIS Zk(ω)s for [Formula: see text] actually summarize in the bi-frequency (ω, k) domain all the temporal in-cycle information about the periodic changes of Z(ω, t). For the particular case k = 0 (i.e. on the ω-axis), Z0(ω) reflects the mean in-cycle behavior of the time-varying bioimpedance. Finally, the HIS Zk(ω)s are directly identified from noisy current and voltage myocardium measurements at the multisine measurement frequencies (i.e. nonparametric-in-frequency).

Towards on line monitoring the evolution of the myocardium infarction scar with an implantable electrical impedance spectrum monitoring system

The human heart tissue has a limited capacity for regeneration. Tissue and cellular therapies based on the use of stem cells may be useful alternatives to limit the size of myocardial infarction. In this paper, the preliminary results from an experimental campaign for on-line monitoring of myocardium scar infarction are presented. This study has been carried out under a research project that has as main objective the development and application of a bioactive patch implant for regeneration of myocardial infarction. Electrical Impedance Spectroscopy (EIS) has been chosen as a tissue state monitoring technique. What is presented in this communication is the first results of an implantable EIS measurement system which has been implanted in a subset of the animals corresponding to the control group, along one month. In all the animals, the myocardial infarction was induced by the ligation of the first circumflex marginal artery. In the animal group presented, the bioactive patch scaffold and the electrodes were implanted without the stem cells load. The scaffold is a piece of decellularized human pericardium, lyophilized and rehydrated with hydrogel RAD16-I. Nanogold particles were also placed near the electrodes to improve the electrode area conductivity. The results presented correspond to the subset of animals (n = 5), which had implanted the bioimpedance system monitoring the electrical impedance spectrum in vivo during 1 month. Two electrodes were connected to the bioactive patch implant. A total of 14 logarithmically spaced frequencies were measured every 5 minutes, from 100 Hz to 200 kHz. Results show a convergence of low-frequency and high frequency impedance magnitudes along the measurement period, which is coherent with the scar formation.