Effects of positive end-expiratory pressure (PEEP) or prolonged inspiration time on lung mechanics, gas exchange and hemodynamics in differential pulmonary ventilation

In the case of patients with unilateral lung disorders one must anticipate a further increase in the intake volume of the more elastic lung and a decrease in intake volume of the less elastic lung when the inspiratory pressure is increased or the inspiratory time is extended within the framework of mechanical ventilation. Therefore, differential pulmonary ventilation lends itself for the treatment of unilateral damage of the lung by enabling the selective application of a positive end-expiratory pressure or an inverse inspiratory time. For a better understanding of the overlapping pathophysiologic reactions, the changes in lung mechanics, haemodynamics and gas exchange were measured on the healthy lung with unilateral application of a positive and expiratory pressure or an increased inspiratory time. Thirteen male and female patients, who had to undergo intracranial surgery were ventilated with two synchronized servoventilators using a Carlens tube. The positive end expiratory pressure varied in the right lung in spans of 6 cm each, 0-12 cm H2O, inspiratory time varied 34-70%. The left lung was ventilated with a 35% inspiratory time and an end expiratory pressure of 0. The respiratory intake volume was divided up into 45% (left lung) and 55% (right lung) based on the physiological difference in size between the left and right lung. Our results show that a directed unilateral application of a positive end expiratory pressure or an increased inspiratory time does not have any relevant damaging effects on the other lung. It can be expected that in the case of non-differentiated mechanical ventilation the ensuing unequal distribution of alveolar ventilation and perfusion with consecutive increase of intrapulmonary shunt volume can be decreased by the discriminate treatment of each lung.     

New PEEP device--application of PEEP and CPAP during manually operated ventilation (author's transl)]

A new PEEP device has been developed for use with manually operated resuscitators. The PEEP valve can be combined with adult resuscitators as well as with neonatal resuscitators (40 g). The PEEP can be varied between 0 and +10 cm H2O. With this new PEEP device it is now possible to apply PEEP during manually operated artificial ventilation, e.g. during transportation etc.     

The influence of dopamine of kidney function during continuous positive-pressure ventilation (PEEP) (author's transl)]

In a group of 20 patients the influence of continuous positive-pressure Ventilation (PEEP) on cardiac output, kidney function and renal and intrarenal hemodynamics was investigated. During ventilation with PEEP 10 ccm H2O a reduction of cardiac output, glomerular filtrationrate, sodium excretion and urinary output was observed. Renal blood flow, especially the cortical fraction, also decreased. Dopamine infusion, in a dose of 4 ng.kg-1.min-1, during continuous PEEP-ventilation, induced an increase of cardiac output, glomerular filtrationrate, renal sodium excretion and diuresis. The decreased renal cortical perfusion particularly was improved by Dopamine application.     

A device for prolonged releasing of anticancer drug--bleomycin (author's transl)

We reported a new dosage-form for intracranial administration which releases Bleomycin (BLM) for more than twenty days. The new dosage-form is a tablet which is a compressed form of lactose and BLM, further capsulized by ethylcellulose or Eudragit retard S. Two kinds of tablets were prepared: early-releasing type and late-releasing type, which differ with regard to ingredients and thickness of the capsule. In a buffer solution at 37 degrees C, the early-release tablet released BLM for 7 days and the late-type for between 20 and 30 days. The late-releasing type was used in the following experiments. BLM tablets were implanted into femoral muscle and peritoneal cavity of rats, and the residual BLM content in each tablet was measured after various periods. In femoral muscle, the half life of BLM in the tablet was 13 days and BLM was no longer found in the tablet after 30 days. In peritoneal cavity, the half life of BLM in the tablet was 15 days and 20% of the BLM still remained in the tablet after 30 days. The half life was 11 days in tablets implanted into the cerebrum of dogs. Following implantation of 4 tablets (12mg. p) into the cerebrum of dogs, CSF levels of BLM could be measured till the 20th day. Histological studies on dog cerebrum revealed a thin capsule consisting of collagenous fibers surrounding the tablet and small round cells or gliosis were seen around the capsule.     

The antagonistic effect of physostigmine on sedation by lormetazepam (author's transl)

The purpose of this study was to determine the arousal effect of physostigmine after lormetazepam sedation on the human EEG. 12 male volunteers received 2 mg/kg bm lormetazepam and 30 minutes later physostigmine 2 mg preceded by atropine 1 mg. Generally an arousal effect of physostigmine could be clinically observed and more objectively demonstrated by reduced sleep stages in the vigilosomnogram (p less than 0.05). 2 volunteers did not fall asleep. 9 volunteers were awake 5-12 minutes after termination of physostigmine injection. 1 volunteer did not show any effect. Resedation and parasympathetic side effects did not occur. In earlier studies deep sleep stages after lormetazepam 1 or 2 mg/70 kg bm lasted 70 to 120 minutes. Physostigmine is recommended to counteract undesirable benzodiazepine induced sedation.     

Data processing in the blood gas laboratory (author's transl)

A computer-assisted system for the calculation of derived blood-gas and acid-base parameters, consisting of an analysator (AVL 937) desk calculator (HP 9825A) and external printer (HP 5150A) is described. For the calculation of the derived parameters corrections were made for patient temperature, plasma protein, reduced haemoglobin and CO2-carbamino haemoglobin. The time needed for calculating and feed back was shortened.     

Effect of prolonged inspiratory time on gas exchange during robot-assisted laparoscopic urologic surgery

Background

Gas exchange disturbance may develop during urologic robotic laparoscopic surgery with the patient in a steep Trendelenburg position. This study investigated whether prolonged inspiratory time could mitigate gas exchange disturbances including hypercapnia.

Methods

In this randomized cross-over trial, 32 patients scheduled for robot-assisted urologic surgery were randomized to receive an inspiratory to expiratory time ratio (I:E) of 1:1 for the first hour of pneumoperitoneum followed by 1:2 for last period of surgery (group A, n?=?17) or I:E of 1:2 followed by 1:1 (group B, n?=?15). Arterial blood gas analysis, airway pressure and hemodynamic variables were assessed at four time points (T1: 10?min after induction of general anesthesia, T2: 1?h after the initiation of pneumoperitoneum, T3: 1?h after T2 and T4: at skin closure). The carry over effect of initial I:E was also evaluated over the next hour through arterial blood gas analysis.

Results

There was a significant decrease in partial pressure of oxygen in arterial blood (PaO₂) for both groups at T2 and T3 compared to T1 but in group B the PaO₂ at T4 was not decreased from the baseline. Partial pressure of carbon dioxide in arterial blood (PaCO₂) increased with I:E of 1:2 but did not significantly increase with I:E of 1:1; however, there were no differences in PaO₂ and PaCO₂ between the groups.

Conclusion

Decreased oxygenation by pneumoperitoneum was improved and PaCO₂ did not increase after 1 h of I:E of 1:1; however, the effect of equal ratio ventilation longer than 1 h remains to be determined. There was no carryover effect of the two different I:E ratios.

     

The effect of calcitonin on contractile function of skeletal muscles (author's transl)

The analgesic effect of calcitonin in osteoporosis has been considered to originate from its actions on bone metabolism. However, the author assumed a possible presence of other mechanism, since the analgesic effect of calcitonin manifests in an extremely early phase in which an increase in bone mass is hardly conceivable. Namely, the author postulated that its analgesic effect is due to its actions on body trunk muscles, and investigated experimentally the effect of calcitonin on skeletal muscles. The following results were obtained. 1) Recovery from decreased twitch contraction of M. triceps surae was shown in vivo in rats treated with calcitonin, with dose-response relationship. 2) Calcitonin exerted no effect on partial blockade by dTc, in neuro-muscular junction. Therefore, the neuro-muscular junction is probably not the site of the actions of calcitonin. 3. In an in vitro study on isolated M. soleus, the decrease contraction was recovered after treatment with calcitonin. A correlation was found between this recovery and the dose of calcitonin. 4) In the calcitonin treated muscle, a pronounced persistence of normal contraction was demonstrated in contrast to the control group. 5) Calcitonin appears to facilitate Ca release through exerting actions on Ca transport system in the sarcoplasmic reticulum. From these results, it was shown that calcitonin appears to possess an activity to elevate contractile ability of skeletal muscles. This activity is considered to be derived from its effect on sarcoplasmic reticulum. This activity of calcitonin on contractile function of skeletal muscles indicates the presence of a mechanism relating to skeletal muscles in the analgesic effect on low back pain in osteoporosis.