Reducing inadvertent PEEP by controlling end-tidal pressures in the trachea

Mechanical ventilation using exhalation times too brief for completion of exhalation results in inadvertent positive end-expiratory pressure (IPEEP) and increased functional residual capacity (FRC). The endotracheal (ET) tube with side lumen allows us to monitor tracheal airway pressures and to determine the contributions of the ET tube to IPEEP. We hypothesized that, during rapid rate ventilation, controlling the positive end-expiratory pressure (PEEP) level in the trachea rather than at the ET tube adaptor will counter effects of the ET tube on IPEEP and result in less increase of FRC. Thirteen anesthetized rabbits were ventilated at rates of 30, 60, 90, and 120 breaths per minute (BPM). Peak inspiratory pressure was held constant, and PEEP was adjusted to 2 cmH2O, measured conventionally at the proximal end of the ET tube. Pulmonary function tests were made and then repeated while PEEP was held constant in the trachea, measured at the distal end of the ET tube. Controlling PEEP conventionally resulted in mean (+/- SE) FRC values of 13.7 +/- 3.8, 14.8 +/- 3.9, 17.1 +/- 4.5, and 21.1 +/- 5.3 ml/kg at 30, 60, 90, and 120 BPM, respectively. Controlling PEEP at the trachea yielded FRC values of 13.7 +/- 3.8, 13.6 +/- 3.4, 15.3 +/- 4.4, and 16.3 +/- 5.4 ml/kg, respectively. Increasing the ventilator rate above 60 BPM did not affect minute ventilation or blood gases. These results suggest that controlling PEEP in the trachea reduces effects of IPEEP on FRC by countering the contribution of the ET tube to the resistance of gas flow during exhalation.

Stimulation of B-chronic lymphocytic leukemia populations by recombinant interleukin-4 and other defined growth-promoting agents

Monoclonal populations from 10 cases of phenotypically well-characterized B-chronic lymphocytic leukemia (B-CLL) and from a single case of hairy cell leukemia were assessed for their ability to respond by mitogenic stimulation to a number of agents described as growth-promoting for normal B cells. These included the recombinant factors interleukin-1 (IL1), IL2, IL4, IL5, and gamma-interferon, partially purified B cell growth factor (BCGF), B cell stimulatory factor 2 (BSF2), and a CDw40 antibody to the Bp50 antigen. With only few exceptions, no factor or combination of factors stimulated B-CLL populations directly to DNA synthesis. By marked contrast, the hairy cells were responsive to IL4, BCGF, and the CDw40 antibody. B-CLL cells could become responsive with the inclusion of the phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate) as co-stimulant such that half of the populations were now activated by IL4, particularly when BCGF was also present. Populations refractory to IL4 were, nonetheless, still responsive to BCGF. In only three cases was a significant effect seen with IL2. gamma-interferon could be either inhibitory or stimulatory and, in a few cases, modulated specifically the effects of IL4. In contrast to normal B cell activations, neither the CDw40 antibody nor a calcium ionophore synergized with TPA for stimulating the majority of B-CLL populations. BSF2 was stimulatory in the two cases examined while both IL1 and IL5 were ineffective where studied. No simple correlation was observed between the patterns of responsiveness and the expression of a panel of CD markers assayed on cells both freshly isolated and after TPA stimulation. The data demonstrate a functional heterogeneity not disclosed by simple phenotypic analysis and also indicate the range of activities which can impinge on the growth regulation of monoclonal B cell populations.

Laser iridotomy

The outcome of 64 consecutive argon laser iridotomies was examined retrospectively. The patients were followed for a mean of 18 months. Argon laser iridotomy was shown to be effective in treating chronic angle-closure glaucoma, those patients without field loss faring better than those with field loss: 34% of the latter group eventually required a trabeculectomy. It is suggested that patients be carefully followed-up after iridotomy, particularly those with loss of visual field.

Exhalation time effects on arterial and venous blood oxygen content and arterial PCO2 during high frequency jet ventilation of surfactant-depleted cats

Since high frequency jet ventilation (HFJV) relies on lung mechanics for the passive removal of expiratory gas, one would predict that the time allowed for exhalation would have serious effects on cardiopulmonary function. To document these effects we lavaged the lungs of ten cats with 30 ml/kg of saline six times, then sampled arterial and venous blood while the animals were ventilated conventionally at 30 BPM and then with HFJV at 600 BPM, varying inspiratory/expiratory ratios (I/E) from 1:1 to 1:5. The animals breathed 100% O2 throughout the study, and the mean airway pressure was held constant for each animal when the I/E was varied during HFJV. Decreasing the I/E from 1:1 to 1:5 during HFJV resulted in an increase of arterial oxygen content (Cao2) from 11.3 +/- 1.2S E to 13.6 +/- 1.2 ml O2/100 ml blood (P less than 0.01), a decrease of PaCO2 from 43 +/- 6 to 27 +/- 4 mm Hg, and an increase of alveolar to arterial oxygen gradient from 351 +/- 49 to 377 +/- 49 mm Hg. The ratio of systemic blood flow to oxygen consumption (Q/VO2) was similar during conventional ventilation and with HFJV at I/E of 1:1 (18.9 +/- 3.7 vs 18.0 +/- 2.9) but decreased when I/E was reduced to 1:5 during HFJV (13.9 +/- 2.1). The ratio of the product of CaO2 and Q (systemic oxygen availability) to VO2 (SO2 T/VO2) remained unchanged during all modes of ventilation (1.75 +/- 0.15). The increase in CaO2 observed when I/E was reduced from 1:1 to 1:5 during HFJV was counterbalanced by a decrease in Q/VO2 such that SO2 T/VO2 remained relatively constant.

Rapid mechanical ventilation effects on tracheal airway pressure, lung volume, and blood gases of rabbits

The purpose of this study was to demonstrate that ventilation of rabbit lungs (whose mechanics are similar to those of human infants) at rapid rates will lead to large alterations in tracheal airway pressures, tidal volume, and functional residual capacity (FRC) with only minor changes in arterial blood gases. Thirteen rabbits were ventilated at rates of 30, 60, 90, and 120 breaths per minutes (BPM) with pressures of 17/2 cm H2O. Tracheal peak inspiratory pressure (PIP) was always lower than ventilator PIP and decreased to 11 +/- 1 cm H2O at 120 BPM. Positive end-expiratory pressure (PEEP) in the trachea was always greater than 2 cm H2O and increased with rate (3.5 cm H2O at 120 BPM). Tidal volume decreased as rates were increased such that rates above 60 BPM resulted in insignificant changes in minute ventilation and arterial blood gases. However, the FRC increased from 16 (30 BPM) to 25 ml/kg (120 BPM), a 56% increase, suggesting large increases in end-expiratory alveolar pressure. We conclude that rapid-rate ventilation (greater than 60 BPM) of healthy rabbits results in significant increases in both tracheal PEEP and FRC without significantly affecting arterial blood gases. The increased tracheal PEEP and FRC are manifestations of inadvertent PEEP. The increased FRC without concomitant increase in PaO2 implicates alveolar overdistention. We speculate that rapid-rate ventilation of human infants having lung mechanics similar to rabbits, will also result in inadvertent PEEP and alveolar overdistention.

Cardiopulmonary function of cats with respiratory distress induced by N-nitroso N-methylurethane

The purposes of this study were to determine the effects of positive end-expiratory pressure (PEEP) and end-expiratory lung volume on systemic blood flow, whether PEEP levels yielding maximum systemic oxygen transport are associated with maximum lung compliance, and the effects of end-expiratory lung volume on pulmonary resistance to gas flow, in an animal model of respiratory distress. Twelve cats were inoculated with 12 mg/kg N-Nitroso N-Methylurethane (NNNMU) to induce respiratory distress. The NNNMU caused a 76% decrease in disaturated phosphatidyl-choline of lung lavage, a 34% decrease in functional residual capacity (FRC), an 80% decrease in lung compliance, an 88% increase in pulmonary resistance to gas flow, a 43% decrease in PaO2, and a 37% decrease in oxygen consumption. Systemic blood flow and systemic oxygen transport were not significantly altered by the chemically induced respiratory distress. PEEP levels of 5.1 +/- 0.8 cm H2O returned end-expiratory lung volume to normal FRC levels. Increases in PEEP caused systemic blood flow to decrease even when end-expiratory lung volume was below or equal to normal FRC levels but did not significantly affect systemic oxygen transport, lung compliance, or pulmonary resistance. We conclude that in cats with NNNMU-induced respiratory distress: PEEP causes decreases in systemic blood flow, lung compliance and systemic oxygen transport are not clear indicators of optimal PEEP level, and returning end-expiratory lung volume to normal FRC does not significantly reduce pulmonary resistance to gas flow.

An antigenic study of human plasma cells in normal tissue and in myeloma: identification of a novel plasma cell associated antigen

A mouse monoclonal antibody named BU11 which detects an antigen strongly expressed on human plasma cells is described. The antibody stains plasma cells in tonsil sections, fresh and cultured plasmacytoid cells from the bone marrow of patients with multiple myeloma and cells of the plasmacytoid cell line RPMI 8226 used as the immunogen. In vitro studies of pokeweed mitogen (PWM) stimulated peripheral blood B cells and Epstein-Barr virus (EBV) stimulated tonsil B cells show that the antigen is present mainly on cells coexpressing the OKT10 antigen and containing cytoplasmic immunoglobulin (cIg). The BU11 antigen is expressed weakly on some normal B cells and is not present on T cells, monocytes or granulocytes. The antigen is of molecular weight 58kD under reducing conditions and is biochemically distinct from previously described plasma cell antigens.

The functional residual capacity of infants with respiratory distress syndrome

Positive end-expiratory pressure (PEEP) is used in the treatment of infants with respiratory distress syndrome (RDS) to prevent atelectasis, recruit alveolar space and return the functional residual capacity (FRC) toward normal volumes. This study determined the FRC range of 15 prematurely born infants with RDS receiving PEEP. Ventilator settings were controlled clinically using predominantly results of arterial blood-gas analyses. Measurements of arterial blood-gases and FRC (N2 washout) were made during the infants' second day of life. The FRC of the infants on a PEEP of 4.5 +/- 1.3 cmH2O ranged widely from 3 to 33 ml/kg with a mean of 14.5 ml/kg; 17 +/- 2 ml/kg was considered normal. The FRC was within one SD of the mean in only three of the 15 infants (20%) and outside of two SD of normal in seven (47%). A linear regression of calculated alveolar-arterial oxygen gradient (AaDo2) with FRC yielded a correlation coefficient r = 0.825. The AaDo2 values could be used to identify six of the seven infants having FRC outside of 2SD from normal. We conclude that convential methods of PEEP selection for infants with RDS seldom result in a normalization of FRC. Calculated AaDo2 values may be used to identify most RDS infants with FRC widely divergent from normal values.

The accuracy of glucose monitoring by diabetic individuals in their home setting

This study evaluated the accuracy of patient self- monitoring of blood glucose. Determinations were performed at home with simultaneous collec tions of whole blood into capillary tubes. Specimens were mailed to the laboratory where they were analyzed by a glucose-oxidase analyzer. A significant correlation was observed between pa tient determined and laboratory determined glucose values. However, patient-determined values differed from the laboratory values by >+20% in 53.8% of the samples. Inaccuracies were unrelated to training format, time since train ing, type of monitor, age, sex, duration of diabetes, frequency of monitor use, educational level, or knowledge of monitoring technique.

Effects of end-expiratory lung volume on lung mechanics in normal and edematous lungs

This study determined the effects of end-expiratory pressures (EEP) and alterations in end-expiratory lung volume (EELV) on lung compliance (CL) and pulmonary resistance to gas flow (RP) in 20 cats with normal and edematous lungs. EELV was varied using EEP ranging from -8 to +10 cm H2O. Negative EEP was used to decrease EELV of the healthy lung causing CL to decrease and RP to increase. Positive EEP in the healthy lung also caused CL to decrease but did not significantly affect RP. After inducing pulmonary edema using alloxan, functional residual capacity (FRC) decreased 38%, CL decreased 66% and RP increased 106% (p less than 0.001). An EEP of 4 cm H2O returned EELV to normal FRC levels and produced maximum values for CL. Increases in EEP to 4 cm H2O also caused decreases in RP in the edematous lungs but further increase did not cause significant changes in RP. These results show that (1) relatively low levels of EEP returned EELV to normal FRC levels in alloxan-induced pulmonary edema, and (2) optimal lung mechanics were obtained when EELV was equal to or slightly above normal FRC values in both healthy and edematous lungs.

Subclasses of IgG on the surface of human lymphocytes: a study with monoclonal antibodies

Cells from sIgG+ B lymphoblastoid cell lines, sIgG+ B cell neoplasms and from tonsils, adult and cord blood and fetal spleen were tested for IgG subclass expression using a panel of monoclonal antibodies. IgG1 was in all cases the commonest subclass except on blood lymphocytes, when approximately equal numbers of cells expressing IgG1 and IgG2 were found. No evidence for multiple subclass isotype expression was found.

Phospholipids in tracheal effluent from infants with severe respiratory distress syndrome

The physiologic aberration that causes abnormal alveolar surface tension in the lungs of infants with RDS was investigated by measuring relative quantities of surfactant-related phospholipids in tracheal effluent from infants with RDS. A preliminary study in premature lambs demonstrated that the percent DSPC (molar ratio of DSPC to total phospholipid) is similar in tracheal effluent and lung lavagate. The percent DSPC in tracheal effluent from human infants with RDS was similar to the percent DSPC in effluent from non-RDS infants on the first day of life (47.4% +/- 2.9 vs 46.7% +/- 1.2), and remained constant during the first 8 days of life. Phosphatidylglycerol (PG) was universally absent in effluent from RDS infants on the first and second day of life but appeared by the eighth day of life in all infants who remained intubated. PG was present in tracheal effluent from only 10 of 16 non-RDS infants on the first day of life. These findings suggest that, in regard to the surface-active lecithin content, surfactant from RDS infants is qualitatively normal and that the absence of RDS is not dependent on the presence of PG.

T-cell proliferation and expression of MHC class II antigens

Two monoclonal antibodies to major histocompatibility complex (MHC) class II antigens, which in combination identify beta chains encoded by the SB and DR loci, were used to investigate which of these gene products were expressed at the cell surface of unstimulated T cells and at various stages of mitogen-induced T-cell maturation. In tests on blood lymphocytes from healthy donors 12% of T cells expressed class II antigens, but only SB antigens were expressed. During activation of T lymphocytes, SB-coded antigens were expressed before DR antigens, and the kinetics of SB expression correlated with the proliferative response of T cells. These results and consideration of recent reports from other laboratories lead us to suggest that SB-coded class II antigens play a role in T-cell proliferation.

Blood glucose discrimination training with insulin-dependent diabetics: a clinical note

Two insulin-dependent diabetic adults were exposed to a blood glucose discrimination training program. Following baseline, during which subjects estimated their blood glucose levels twice daily, subjects received immediate feedback regarding the accuracy of their estimates. The procedure resulted in a large increase in accuracy of blood glucose level estimation. The implications of the findings were discussed.

The body boundary experience of women in labor: a framework for care

This paper discusses the relevance of a body boundary framework for considering the nursing care needs of the woman during labor. Careful analysis of the woman's behaviors during labor reveals three distinct body boundary-oriented phases. These include: (a) a controlled-boundary intact phase, (b) a regressive-boundary permeable phase, and (c) a desperate-boundary diffuse phase. The first two phases occur in all labors; the last phase occurs when the woman is unable to remain in control of her body because of extreme body boundary distortions. The primary nursing care objective for the laboring woman should be to help the woman maintain a sense of body boundary intactness throughout her labor. Achieving this important objective requires that the nurse be aware of when and how the woman uses the nurse's presence to foster feelings of boundary intactness. The nurse involved in the care of the woman in labor must be an interaction specialist. She needs to be adapt at reading the woman's body cues, in understanding the meaning of her behaviors, and in providing care at appropriate times using appropriate contact modalities. Offering the woman help and understanding based on knowledge of body boundary changes during labor optimize the woman's ability to endure and will enhance her chances for feeling positively about herself in the childbearing endeavor.

Oxygen consumption of infants with respiratory distress syndrome

The objective of this research was to determine the oxygen consumption of newborn infants with respiratory distress syndrome in the first 4 days of life. Serial determinations of oxygen consumption were made in 14 infants with respiratory distress syndrome receiving positive end-expiratory pressures. The mean (+/- SE) oxygen consumption determined at 24, 48, 72, and 96 h postnatal age were 8.3 +/- 0.9, 6.5 +/- 0.8, 5.5 +/- 0.5, and 5.3 +/- 0.6 ml/min/kg, respectively. The level of oxygen consumption at 24 h postnatal age was significantly greater than the levels determined at 48, 72, and 96 h (p less than 0.03). The oxygen levels found at 72 and 96 h of age were comparable to those determined for healthy preterm infants. A linear regression of serial oxygen consumption and weight loss yielded a 'fair' (r = 0.5) correlation with a significant inference (p less than 0.01).