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 21,692 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Non-biological descriptors such as jet feeding pressure and oscillator stroke volume are often used to describe HFV. This results in confusion and hinders acceptance of HFV. The goal of this paper is to show how physiological parameters which are valid during HFV can be monitored. Airway pressure measured in narrow tubes with high linear flow rates is underestimated. A relevant airway pressure must be measured well below the tracheal tube. Pressure measured higher up should be validated against peripheral pressure measurements. Minute ventilation and expired CO2 concentration can be determined with a ServoVentilator and a CO2 analyzer arranged at its exit port. Minute ventilation and CO2 elimination can thereby be continuously monitored during high frequency jet ventilation or so-called "combined high frequency jet ventilation" to prevent undetected disturbance of ventilation and perfusion. Physiological dead space can be studied for optimization of ventilatory pattern. The principle of gas analysis at the exit port of the ventilator may be used for FRC determinations with sulfur-hexafluoride.
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PMID:Monitoring of physiological parameters during high frequency ventilation (HFV). 264 35

Sudden unexplained death may be seen with treatment of craniovertebral anomalies and surgery of the upper cervical spine. Death is due to sleep-induced apnea, premonitored by periods of confusion, lethargy, and asthenia. There may be associated hypotension, bradycardia, hyponatremia, hypothermia, inappropriate antidiuretic hormone secretion, and difficulty in micturition. The potential for respiratory failure may be predicted if a CO2 response test demonstrates an attenuated or abnormal response. Apnea during sleep may be reversed by arousal or may require ventilatory support for a period of time. The condition is self-limiting, but remains the major life-threatening complication. Both apnea and autonomic dysfunction are treatable and curable with appropriate diagnosis and management.
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PMID:Occult respiratory and autonomic dysfunction in craniovertebral anomalies and upper cervical spinal disease. 375 66

Anaerobic threshold has been defined as the oxygen uptake (VO2) at which blood lactate (La) begins to rise systematically during graded exercise (Davis et al. 1982). It has become common practice in the literature to estimate the anaerobic threshold by using ventilatory and/or gas exchange alterations. However, confusion exists as to the validity of this practice. The purpose of this study was to examine the precision with which ventilatory and gas exchange techniques for determining anaerobic threshold predicted the anaerobic threshold resolved by La criteria. The anaerobic threshold was chosen using three criteria: (1) systematic increase in blood La (ATLa), (2) systematic increase in ventilatory equivalent for O2 with no change in the ventilatory equivalent for CO2 (ATVE/VO2), and (3) non-linear increase in expired ventilation graphed as a function of VO2 (ATVE). Thirteen trained male subjects performed an incremental cycle ergometer test to exhaustion in which the load was increased by 30 W every 3 minutes. Ventilation, gas exchange measures, and blood samples for La analysis were obtained every 3rd min throughout the test. In five of the thirteen subjects tested the anaerobic threshold determined by ventilatory and gas exchange alterations did not occur at the same VO2 as the ATLa. The highest correlation between a gas exchange anaerobic threshold and ATLa was found for ATVE/VO2 and was r = 0.63 (P less than 0.05). These data provide evidence that the ATLa and ATVE do not always occur simultaneously and suggest limitations in using ventilatory or gas exchange measures to estimate the ATLa.
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PMID:Precision of ventilatory and gas exchange alterations as a predictor of the anaerobic threshold. 653 32

The two-cell mouse embryo can develop in a chemically defined medium to the blastocyst stage but conditions must be strictly controlled. Fresh T6 (Whittingham's) medium is being used weekly for this purpose in our laboratory and subjected to a 5% CO2-in-air system 24 hours prior to use. Experiments were designed to determine whether two-cell embryos obtained from an F1 (CBA X C57/B1/6) X F1 cross were superior to the easily obtainable CBA X ICR cross. The aim was to get a 90% blastocyst result for use as a quality control. Eight experiments were performed over a 6-week period. The CBA two-cell embryos were compared with the F1 group under identical conditions. A total of 177 two-cell embryos were obtained from the CBA group and 214 two-cell embryos from the F1 group. In the CBA group 51 developed to the blastocyst stage (28.8%) compared with 187 in the F1 group (87.4%) (P less than 0.0001). In conclusion, it is advisable to obtain F1 mice to use weekly in the laboratory as a quality control measure. The CBA group yields poor cultures, and this leads to unnecessary laboratory confusion.
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PMID:[A comparative study of two-cell embryos of CBA and F1 mice in a human in vitro fertilization program]. 669 84

The carbon dioxide (CO2) trace versus time (time capnography) is convenient and adequate for clinical use. This is the method most commonly utilized in capnography. However, the current terminology in time capnography has not yet been standardized and is, therefore, a potential source of confusion. Standard terminology that is based on convention and logic to represent the various phases of a time capnogram is essential. The time capnogram should be considered as two segments: an inspiratory segment and an expiratory segment. The inspiratory segment is termed as phase ); the expiratory segment is divided into phases I, II, III, and, occasionally, IV. Phase I represents the CO2-free gas from the airways (anatomical dead space); phase II consists of a rapid S-shaped upswing on the tracing due to mixing of dead space gas with alveolar gas; and phase III, the alveolar plateau, represents CO2-rich gas from the alveoli. The physiologic basis of phase IV, the terminal upswing at the end of phase III, which is observed in capnograms recorded under certain circumstances (such as in pregnant subjects and obese subjects) is discussed in detail. The clinical implications of the alpha angle, which is the angle between phases II and III, and the beta angle, which is the angle between phases III and the descending limb of phase 0, are outlined. The subtle but important limitations of time capnography are reviewed; its current status as well as its future potential are explored.
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PMID:Terminology and the current limitations of time capnography: a brief review. 762 57

Conventional cw-(continuous wave) laser systems such as the CO2- and Nd:YAG-laser are well established in medical therapy for tumour resection, tissue cutting, vaporisation and coagulation. The argon-ion laser is also a "classic" laser type with applications in ophthalmology, dermatology and for micro-surgery. New lasers in the IR-range of the optical spectrum appear on the market as pulsed lasers for tissue ablation searching for their specific fields of application. There is some confusion about laser applications at the moment until the new techniques and methods have proven to be really superior to other techniques. But knowing more about the laser tissue interactions one can estimate the potential of a new laser source. This article gives a short overview over the actual laser systems and the reaction processes with soft and hard tissue.
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PMID:Thermal and non-thermal laser dissection. 800 Aug 89

The new pulsed CO2 lasers are an exciting modality. They have the ability to do what no other procedure can do with the same safety profile. The drawbacks of cost, pain and prolonged healing, however, serve to limit the lasers use to a niche, rather than replacing all other means of skin resurfacing. Skin problems of the epidermis and superficial papillary dermis are more easily and less expensively treated with chemical peeling. This includes most types of hyperpigmentation as well as actinic keratoses and poorly textured skin. This is especially true of postinflammatory hyperpigmentation, in which any procedure that creates prolonged erythema dramatically increases the risk of increased pigmentation. In these patients, the use of CO2 laser resurfacing is risky, if not even contraindicated. Skin problems of the deeper papillary dermis and reticular dermis, such as rhytides and scars, however, respond as well to laser resurfacing as they do to deep chemical peels, but with a better safety profile and a more natural clinical appearance of the healed skin. In many cases, the patient would be better served with a medium depth chemical peel of the entire face and laser resurfacing of the rhytides in the perioral or periorbital areas. This would give the patient the best clinical result with the fastest recovery. The major drawback to this type of therapy has been that the postoperative care of the two treatment regions is different. This may cause some logistical difficulties for the patient, as well as some confusion. Certainly, another option is to treat the patient on two separate occasions; that is, first peel the entire face and then later go back and laser resurface the areas of the remaining rhytides. Although this approach creates more healing time for the patient, it minimizes the areas of prolonged erythema, thereby allowing the patient a faster return to normal. As laser technology continues to advance, we can expect faster healing times and less expensive machinery. Presumably, with our current understanding of the wound healing process, we should expect better post laser treatment regimens, with associated faster healing. Therefore, it is distinctly possible that the current niche for pulsed CO2 lasers will be expanded greatly in the next year or two.
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PMID:A peeler's thoughts on skin improvement with chemical peels and laser resurfacing. 914 76

We present an unusual case of weaning failure. A 67-yr-old man presented with confusion, hyponatremia, and hypercapnic respiratory failure that necessitated mechanical ventilation. CXR revealed a right hilar mass (non-small-cell carcinoma on biopsy). Level of consciousness improved with treatment of his hyponatremia. However, attempts at weaning were complicated by hypercapnia with no overt distress. Resistance and elastance were only slightly abnormal, excluding mechanics as a cause of respiratory failure. Maximal inspiratory pressure (MIP) and vital capacity (VC) were reduced at -15 cm H2O and 0.97 L, respectively. Limb muscle strength was well preserved, suggesting isolated respiratory muscle weakness. During a weaning trial respiratory rate increased from 7 to 40 breaths/min as PCO2 increased from 56 to 89 mm Hg, confirming an intact respiratory pacemaker and good response to CO2. However, spontaneous Pdi was only 1 to 2 cm H2O (< 20% of Pdimax) despite profound hypercapnia. The fact that the patient did not utilize a greater fraction of his pressure-generating capacity suggested preferential impairment of the automatic respiratory centers. MRI showed a large central metastatic lesion in the rostral medulla with only a thin rim of uninvolved tissue. This case illustrates the utility of relating the magnitude of spontaneous efforts to maximal voluntary efforts as a means of localizing the site of involvement in cases of respiratory muscle weakness. It also demonstrates that a large medullary mass lesion may selectively impair brainstem modulation of respiratory pressure output while sparing other medullary functions, and in particular the pacemaking function of the respiratory centers.
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PMID:Medullary metastasis causing impairment of respiratory pressure output with intact respiratory rhythm. 987 56

The animal and human studies presented, at first glance, present a confusing and conflicting story. In regards to the animal studies, much of this confusion can be traced to the use of a variety of different models, none of which truly reproduces the human situation. Nonetheless, there is much to be gleaned from these efforts. The authors present conceptualization of the port wound tumor dilemma follows. In order for wound tumors to develop, viable tumor cells must be liberated from the primary tumor and find transport to a wound. Rarely, patients with colon tumors will present with or will develop widespread intraabdominal carcinomatosis. These tumors have the ability to spontaneously shed considerable numbers of viable cells which have the ability to implant on uninjured peritoneal surfaces. Unfortunately, the surgeon has little chance for success in these patients with either open or minimally invasive methods. Fortunately, most colon adenocarcinomas do not spread in this manner. Differences in the clinical behavior and manifestations of colon tumors most likely reflect the genetic makeup of individual tumors. Colonic neoplasm's ability to invade and metastasize varies considerably from tumor to tumor. Thankfully, as mentioned, the vast majority of colon tumors are not prone to cause carcinomatosis. Despite this fact, the human data available suggests that tumor cells can be found in the peritoneal cavity using sophisticated methods in about half of the patients after colectomy. If this is the case, then why aren't more wound tumors seen? Logic dictates that there must be a critical number of free intraabdominal cells above which successful wound seeding is likely. It makes sense that traumatization of the tumor will result in increased numbers of liberated cells. Therefore, surgical approach and technique should impact considerably on outcome. For the majority of colon tumors, if the lesion is assiduously avoided during mobilization and resection, it is unlikely that enough tumor cells will be shed to result in port site tumors. The recent interim results of the Cleveland Clinic's and the Barcelona randomized trials certainly support such a hypothesis. With over 300 patients enrolled (combined series) and with an average follow up of over 2 years, in neither trial has a port site tumor been noted. Similarly, with an average follow up of just under 3 years, Franklin et al noted that there were no port site tumors in their prospective trial of 191 consecutive laparoscopic colectomies for cancer. In the clinical setting, experience and surgical expertise seem to be the best predictor of outcome, in regards to wound tumors. The few animal studies that allow assessment of the impact of technique (i.e. those that utilize an intraabdominal solid tumor model which allows tumor excision) indeed support this hypothesis. In these studies poor technique resulted in significantly more wound tumors. Furthermore, it has been shown that for laparoscopic procedures, there is a definite learning period during which the incidence of wound tumors is considerably higher than that of open resection. With experience the laparoscopic incidence falls to that of open resection. Furthermore, a number of recent studies suggest that is possible to lower the incidence of wound tumors via peritoneal and wound irrigation with a variety of agents. These animal study results are in keeping with the recent clinical results. Both would suggest that given proper and adequate training and with sufficient attention being paid to avoid tumor handling that the incidence of wound tumors will be as low as that following open colectomy. How large a part, if any, does the CO2 pneumoperitoneum play in the port wound tumor story? Certainly, the results of the bulk of the animal studies performed, to date, have suggested that the CO2 pneumoperitoneum plays a critical role in the development of port wound tumors. With few exceptions, these studies have utilized tumor cel
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PMID:Review of investigations regarding the etiology of port site tumor recurrence. 1019 87

Carbon dioxide laser resurfacing has been a valuable procedure for facial skin rejuvenation since the early 1990s, largely replacing medium and deep chemical peels and dermabrasion. The introduction of the erbium:YAG laser for resurfacing has caused confusion about its role. Because of its ability to resurface very superficially it has been limited by many laser surgeons to treating only superficial rhytides and sun damage. However, it is the equal of CO2 in improving deep rhytides but with quicker healing and fewer side-effects.
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PMID:Controversies in skin resurfacing: the role of erbium. 1136 Apr 17


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