Continuous monitoring of intrinsic PEEP based on expired CO2 kinetics: an experimental validation study.

BACKGROUND: Quantification of intrinsic PEEP (PEEPi) has important implications for patients subjected to invasive mechanical ventilation. A new non-invasive breath-by-breath method (etCO2D) for determination of PEEPi is evaluated. METHODS: In 12 mechanically ventilated pigs, dynamic hyperinflation was induced by interposing a resistance in the endotracheal tube. Airway pressure, flow, and exhaled CO2 were measured at the airway opening. Combining different I:E ratios, respiratory rates, and tidal volumes, 52 different levels of PEEPi (range 1.8-11.7 cmH2O; mean 8.45 ± 0.32 cmH2O) were studied. The etCO2D is based on the detection of the end-tidal dilution of the capnogram. This is measured at the airway opening by means of a CO2 sensor in which a 2-mm leak is added to the sensing chamber. This allows to detect a capnogram dilution with fresh air when the pressure coming from the ventilator exceeds the PEEPi. This method was compared with the occlusion method. RESULTS: The etCO2D method detected PEEPi step changes of 0.2 cmH2O. Reference and etCO2D PEEPi presented a good correlation (R2 0.80, P < 0.0001) and good agreement, bias - 0.26, and limits of agreement ± 1.96 SD (2.23, - 2.74) (P < 0.0001). CONCLUSIONS: The etCO2D method is a promising accurate simple way of continuously measure and monitor PEEPi. Its clinical validity needs, however, to be confirmed in clinical studies and in conditions with heterogeneous lung diseases.

Comparative effects of clomipramine and duloxetine on detrusor and striated sphincter function in male and female rabbits.

OBJECTIVE: Serotonin and norepinephrine systems are involved in the neural control of lower urinary tract function. The aim of this study was to compare the response on striated anal sphincter electromyographic (SAS-EMG) activity and cystometric parameters, when duloxetine and clomipramine were intravenously administrated. METHODS: The effects of intravenous 1 and 2 mg./Kg. duloxetine or clomipramine on lower urinary tract function were studied in a total of 32 male and 32 female rabbits, under nonirritative conditions (intravesical infusion of saline) and in a model of bladder irritation (i.e., transvesical infusion of 0.5% acetic acid). A transurethral double-lumen catheter in male rabbits, and a subcutaneous cystostomy in female rabbits, were used for liquid infusion and recording of intravesical pressure during a cystometrogram. Simultaneously, SAS-EMG was recorded through electromyography electrodes placed in the perianal striated muscle. RESULTS: Cystometric parameters: Under irritative conditions, 2 mg./Kg. clomipramine in male rabbits and 1 or 2 mg./Kg. in female rabbits, depending on the dose, increased bladder capacity (BC), contraction duration (CD) and intercontraction interval (ICI), and decreased baseline pressure (BP). In male and female rabbits, duloxetine dose-dependently increased BC, CD and ICI. Under nonirritative conditions, clomipramine at 2 mg./Kg. and duloxetine dose-dependently solely increased BC in female rabbits. Electromyographic activity: A marked effect on SAS-EMG activity of duloxetine under irritative conditions was revealed in male and female rabbits. Under these conditions, clomipramine increased SAS-EMG activity only in female rabbits. Under nonirritative conditions, 2 mg./Kg. duloxetine increased SAS-EMG activity only in female rabbits. CONCLUSIONS: The stronger effects on the SAS-EMG activity were produced by duloxetine in female rabbits under irritated bladder conditions. Clomipramine, under irritative conditions, had a relaxing effect on intravesical pressure, which is not the case with duloxetine.

Experimental methods for "in vivo" study of detruso-sphincteric pharmacological response: a critical review.

OBJECTIVE: We review "in vivo" methods most commonly used for the investigation of detruso-sphincteric pharmacological response. We compare this information with the procedures used in our Institution for these purposes. METHODS: The medical databases MEDLINE, EMBASE and Pascal Biomed were searched to identify articles on this subject. The methods used have been critically analyzed and compared with the methods used in our experiments. RESULTS: The "in vivo" dynamic investigation of vesico-sphincteric function began at our Institution in the late 70s. Methods for the study of vesical or urethral dynamic behaviour have been devised to be applied independently or simultaneously. Great difficulties have been encountered, both in our experience and in the work of revised authors, in the integrated investigation of Lower Urinary Tract function. Methods to overcome these drawbacks have been proposed. CONCLUSIONS: Methods for "in vivo" studies of physiological and pharmacological detruso-sphincteric function are presented and compared with current procedures found in the literature. It is highlighted that an integrated method for the simultaneous study of vesico-sphincteric function is a difficult challenge yet to be taken up.