Computer simulation clarifies mechanisms of carbon dioxide clearance during apnoea.

BACKGROUND: Apnoeic oxygenation can come close to matching the oxygen demands of the apnoeic patient but does not facilitate carbon dioxide (CO2) elimination, potentially resulting in dangerous hypercapnia. Numerous studies have shown that high-flow nasal oxygen administration prevents hypoxaemia, and appears to reduce the rate of increase of arterial CO2 partial pressure (PaCO2), but evidence is lacking to explain these effects. METHODS: We extended a high-fidelity computational simulation of cardiopulmonary physiology to include modules allowing variable effects of: (a) cardiogenic oscillations affecting intrathoracic gas spaces, (b) gas mixing within the anatomical dead space, (c) insufflation into the trachea or above the glottis, and (d) pharyngeal pressure oscillation. We validated this model by reproducing the methods and results of five clinical studies on apnoeic oxygenation. RESULTS: Simulated outputs best matched clinical data for model selection of parameters reflecting: (a) significant effects of cardiogenic oscillations on alveoli, both in terms of strength of the effect (4.5 cm H2O) and percentage of alveoli affected (60%), (b) augmented gas mixing within the anatomical dead space, and (c) pharyngeal pressure oscillations between 0 and 2 cm H2O at 70 Hz. CONCLUSIONS: Cardiogenic oscillations, dead space gas mixing, and micro-ventilation induced by pharyngeal pressure variations appear to be important mechanisms that combine to facilitate the clearance of CO2 during apnoea. Evolution of high-flow oxygen insufflation devices should take advantage of these insights, potentially improving apnoeic gas exchange.

Identification of an optimal CPR chest compression protocol.

In this study, we used a high-fidelity integrated computational model of the respiratory and cardiovascular systems to investigate cardiopulmonary resuscitation (CPR) after cardiac arrest in a virtual healthy subject. For the purpose of this work, a newly developed thoracic model has been integrated to the current model, to study the influence of external chest compressions upon the arrested circulation during CPR. We evaluated the chest compression (CC) parameters, namely, end compression force, compression rate, and duty cycle to optimize the coronary perfusion pressure and the systolic blood pressure, using a genetic algorithm. While the sternal displacement associated with the CC force agreed with the ERC guidelines, the CC rate and duty cycle were respectively higher and lower than the ones recommended by the ERC guidelines. The effect of these CC parameters on cardiac output (CO) were also assessed. The end compression force was the parameter with the largest impact on CO, while the compression rate and duty cycle scarcely influence it.Relevance- Our results may aid in understanding the underlying pathophysiology of cardiac arrest and help guide research into the refinement of CPR strategies, without sacrificing animals or conducting clinical trials, which are difficult to undertake in crisis scenarios.

Randomized study of phentolamine mesylate for reversal of local anesthesia.

Local anesthetic solutions frequently contain vasoconstrictors to increase the depth and/or duration of anesthesia. Generally, the duration of soft-tissue anesthesia exceeds that of pulpal anesthesia. Negative consequences of soft-tissue anesthesia include accidental lip and tongue biting as well as difficulty in eating, drinking, speaking, and smiling. A double-blind, randomized, multicenter, Phase 2 study tested the hypothesis that local injection of the vasodilator phentolamine mesylate would shorten the duration of soft-tissue anesthesia following routine dental procedures. Participants (122) received one or two cartridges of local anesthetic/vasoconstrictor prior to dental treatment. Immediately after treatment, 1.8 mL of study drug (containing 0.4 mg phentolamine mesylate or placebo) was injected per cartridge of local anesthetic used. The phentolamine was well-tolerated and reduced the median duration of soft-tissue anesthesia in the lip from 155 to 70 min (p < 0.0001).

Comparison between oscillometric and auscultatory methods of ambulatory blood pressure measurement in hemodialysis patients.

INTRODUCTION: 24-hour ambulatory blood pressure monitoring (ABPM) is commonly used in clinical and research practice. Different methods have been used in BP recording, cuff-oscillometric or Korotkoff sound, and validation studies during ABPM have been performed on general as well as hypertensive populations. Hemodialysis (HD) patients have a high percentage of complications, such as vascular diseases, and they are subject to hyperkinetic blood flows and abrupt body weight changes secondary to HD, which can invalidate BP recording. Therefore, we wanted to compare the 2 methods on an HD population. PATIENTS AND METHODS: We performed 86 ABPMs on 44 patients (aged 60.8 +/- 17.2 years) by using a device capable of the simultaneous recording of oscillometric and auscultatory BP (A&D Takeda TM2421). The data obtained with the 2 different ABPM methods have been compared, and the differences between auscultatory and oscillometric determinations have been analyzed, as presented by Bland and Altman [1986]. RESULTS: The percentage of valid recordings was significantly higher with the oscillometric method than with the auscultatory method (93.6 +/- 11.3% vs. 71.7 +/- 17.04%, p < 0.001). 24-hour diastolic BP and night-time systolic BP were higher when recorded with the oscillometric method (DBP = 75.4 +/- 9.6 mmHg vs. 71.8 +/- 9.6 mmHg, p < 0.001, asleep SBP = 119.7+/-23.3 mmHg vs. 116.2 +/- 25.0 mmHg, p < 0.001), and the systolic night/day BP ratio was also higher(0.92 +/- 0.10vs.0.90 +/- 0.10, p < 0.001). Finally, the BP coefficient of variation ((SD/mean BP) x 100) was higher when auscultatory determinations were used (16.1 +/- 4.6 vs. 14.6 +/- 4.9). The limits of agreement between auscultatory and oscillometric BP determinations were for SBP = -6.44; 7.84 and for DBP = -3.66; 10.86. CONCLUSIONS: Differences between 24-hour oscillometric and auscultatory ABPM were reported in HD patients: the diastolic 24-hour and asleep systolic BP values and the systolic night/day ratio obtained with the oscillometric method were significantly higher. The higher coefficient of variation reported with the auscultatory method and the wider limits of agreement suggest that the 2 methods do not fully coincide and, in our opinion, the oscillometric method is preferable, due to the higher number of 24-hour valid measurements.

Effects of older brother-younger sister incest: a study of the dynamics of 17 cases.

The purpose of this study was to explore the effects of older brother-younger sister incest from the perspective of the women who experienced it in childhood or adolescent years. Dynamics in the families-of-origin were also explored, as these related or contributed to the effects from the incest. Seventeen women were interviewed, using an in-depth, semi-structured interview. Four self-report objective instruments were also administered that measure dynamics in the family-of-origin and symptomatology that is often associated with the effects of trauma. Interview and objective data were analyzed by systematically organizing the women's perceptions and conceptualizations into common themes. All of the women's families of origin were described as dysfunctional. Common effects reported included mistrust of men and women, chronic low or negative self-esteem, sexual response difficulties, and intrusive thoughts of the incest. Women regarded individual therapy, talking with supportive family and friends, and validating themselves as victims at the time of the incest as ways in which they have helped themselves to deal with the effects of the incest. These results have important implications for therapy, including serious consideration of the impact and contribution of this kind of incest on reported symptomatology, and on emerging issues and conflicts in the therapeutic process.

Variations of thoracoabdominal volumes after lung transplantation measured by opto-electronic plethysmography.

BACKGROUND: Lung function after lung transplantation (LTx) has been widely studied. On the contrary, the thoracoabdominal volume rearrangement after LTx has yet to be investigated. METHODS: Patients with cystic fibrosis and listed for double LTx at our institution were enrolled for the prospective study to explore the effects of LTx on the rearrangement of respiratory volumes in patients affected by cystic fibrosis, by utilizing the opto-electronic plethysmography (OEP), a noninvasive method to study the volume and motion of the human trunk. Rib cage and abdominal volumes were tested with OEP (OEP system, BTS, Milano, Italy). RESULTS: Eight patients were enrolled (male-to-female ratio: 1:3; mean age 29.3 ± 7.8 years). After LTx the volume changes analyzed with OEP revealed a significant decrease of the total lung capacity (TLC) as well as the functional residual capacity and residual volume when the chest wall volume was considered. Dividing the whole respiratory volume in the three compartments showed different trends. CONCLUSIONS: We consider OEP a particularly useful device in patients with severe respiratory disease, in that it allows a noninvasive estimate of the volume change of the chest wall. This study demonstrates a significant reduction of thoracoabdominal volumes in patients affected by cystic fibrosis treated with bilateral LTx. Abdomen and upper rib cage were congruent with the volume reduction, while the lower rib cage showed an opposite tendency.