PubMed Health⌕ Search

Biomedical subjects

K J Peevy

Publications and source records attributed to K J Peevy.

At least 19 recordsLinked to original sources
PubMed1993

Mechanisms of ventilator-induced lung injury.

OBJECTIVES: To describe the physiologic mechanisms of ventilator-induced lung injury and to define the major ventilator and host-dependent risk factors that contribute to such injury. DATA SOURCE: Basic science and clinical studies related to ventilator-induced barotrauma and lung pathophysiology. STUDY SELECTION: Emphasis on controlled, experimental studies and clinical studies related to specific mechanisms. DATA EXTRACTION: Preference given to studies with quantitative end-points to assess damage and causal relationships. DATA SYNTHESIS: Related studies are integrated to obtain basic mechanisms of damage where possible. CONCLUSIONS: Ventilation with high tidal volumes can increase vascular filtration pressures; produce stress fractures of capillary endothelium, epithelium, and basement membrane; and cause lung rupture. Mechanical damage leads to leakage of fluid, protein, and blood into tissue and air spaces or leakage of air into tissue spaces. This process is followed by an inflammatory response and possibly a reduced defense against infection. Predisposing factors for lung injury are high peak inspiratory volumes and pressures, a high mean airway pressure, structural immaturity of lung and chest wall, surfactant insufficiency or inactivation, and preexisting lung disease. Damage can be minimized by preventing overdistention of functional lung units during therapeutic ventilation.

Barotrauma↗
PubMed1993

Association between maternal-fetal HLA-DR relationships and fetal growth.

PROBLEM: To determine whether maternal-fetal human leukocyte antigen (HLA) antigenic relationships are associated with differential fetal growth in weight. METHOD: A cohort of 659 primigravid women were enrolled in this study in the prepartum period and their neonates were subsequently examined. Anthropometric, maternal cigarette smoking behavior, health, pregnancy, and delivery data were collected; serogenetic typing was conducted on maternal and cord bloods to determine maternal and neonatal HLA antigenic phenotypes. Women and their neonates were assigned to one of the four different types of maternal-fetal relationships existing at each of the HLA-A, B, DR, and DQ loci. Birthweights were treated quantitatively and qualitatively (neonates classified as growth-retarded or normal). RESULTS: After controlling for other factors influencing birthweight (e.g., smoking, maternal body size), significantly lower birthweight trends (P < .01) were found when neonates expressed a single HLA-DR antigen and their mothers expressed a second HLA-DR antigen that was foreign (allogeneic) to their neonate. CONCLUSION: Our findings supports the hypothesis that lack of maternal immune exposure to fetal HLA antigens is associated with a slowing of fetal growth. However, in this situation slowed fetal growth is most likely to occur when the fetus is potentially exposed to maternal HLA-DR alloantigens. We believe this sheds new light on immunologic events at the maternal-fetal interface influencing fetal growth. We present one possible explanation to account for this finding.

Birth Weight↗
PubMed1992

Increased sensitivity to mechanical ventilation after surfactant inactivation in young rabbit lungs.

OBJECTIVES: To study the individual and combined effects of surfactant inactivation and mechanical ventilation on pulmonary microvascular permeability and lung compliance. DESIGN: Prospective, controlled trial. An isolated, perfused, lung model of surfactant inactivation and mechanical ventilation at 15, 30, and 45 cm H2O peak inspiratory pressure was developed in young (4 to 6 wks) New Zealand white rabbits. SETTING: Laboratory of a university-affiliated medical school. MEASUREMENTS AND MAIN RESULTS: Isolated, perfused lungs were prepared for measurement of the capillary filtration coefficient before and after one of four interventions: instillation of dioctyl succinate, a surfactant inactivator, without ventilation (group 1); ventilation without dioctyl succinate at 15, 30, or 45 cm H2O peak inspiratory pressure (group 2); ventilation after dioctyl succinate pretreatment at 15, 30, or 45 cm H2O peak inspiratory pressure (group 3); and control lungs without dioctyl succinate or ventilation (group 4). A significant increase in the capillary filtration coefficient was noted after dioctyl succinate treatment alone, after ventilation alone at 45 cm H2O peak inspiratory pressure, and after dioctyl succinate plus ventilation at 15, 30, and 45 cm H2O peak inspiratory pressure. Dioctyl succinate plus ventilation produced a significantly greater increase in the capillary filtration coefficient than ventilation alone at 15 and 45 cm H2O peak inspiratory pressure. CONCLUSIONS: These data suggest that ventilation after surfactant inactivation is more injurious to the pulmonary microvasculature than ventilation alone, and that generalized lung overdistention is not the primary mechanism for microvascular injury in the diseased, noncompliant lung. The increases seen in the capillary filtration coefficient in postventilated surfactant inactivated lungs, even at low-ventilation pressures, suggest that low peak inspiratory pressures do not overdistend the dioctyl succinate-treated lung.

Animals↗
PubMed1990

Barotrauma and microvascular injury in lungs of nonadult rabbits: effect of ventilation pattern.

To study the pulmonary microvascular injury produced by ventilation barotrauma, the isolated perfused lungs of 4 to 6-wk-old New Zealand white rabbits were ventilated by one of the following methods: peak inspiratory pressure (PIP) 23 cm H2O, gas flow rate 1.1 L/min (group 1); PIP 27 cm H2O, gas flow rate 6.9 L/min (group 2); PIP 50 cm H2O, gas flow rate 1.9 L/min (group 3); or PIP 53 cm H2O, gas flow rate 8.3 L/min (group 4). Microvascular permeability was assessed using the capillary filtration coefficient (Kfc) before and 5, 30, and 60 min after a 15-min period of ventilation. Baseline Kfc was not significantly different between groups. A significant increase over the baseline Kfc was noted at 60 min in group 2 and in all postventilation Kfc values in groups 3 and 4 (p less than .05). Group 1 Kfc values did not change significantly after ventilation. At all post-ventilation times, values for Kfc were significantly greater in groups 3 and 4 than in group 1 (p less than .05). Group 4 Kfc values were significantly greater than those in group 2 at 5 and 30 min postventilation. These data indicate that high PIP, and to a lesser extent, high gas flow rates cause microvascular injury in the compliant nonadult lung and suggest that the combination of high PIP and high gas flow rates are the most threatening to microvascular integrity.

Animals↗
PubMed1989

Chest wall restriction limits high airway pressure-induced lung injury in young rabbits.

High peak inspiratory pressures (PIP) during mechanical ventilation can induce lung injury. In the present study we compare the respective roles of high tidal volume with high PIP in intact immature rabbits to determine whether the increase in capillary permeability is the result of overdistension of the lung or direct pressure effects. New Zealand White rabbits were assigned to one of three protocols, which produced different degrees of inspiratory volume limitation: intact closed-chest animals (CC), closed-chest animals with a full-body plaster cast (C), and isolated excised lungs (IL). The intact animals were ventilated at 15, 30, or 45 cmH2O PIP for 1 h, and the lungs of the CC and C groups were placed in an isolated lung perfusion system. Microvascular permeability was evaluated using the capillary filtration coefficient (Kfc). Base-line Kfc for isolated lungs before ventilation was 0.33 +/- 0.31 ml.min-1.cmH2O-1.100g-1 and was not different from the Kfc in the CC group ventilated with 15 cmH2O PIP. Kfc increased by 850% after ventilation with only 15 cmH2O PIP in the unrestricted IL group, and in the CC group Kfc increased by 31% after 30 cmH2O PIP and 430% after 45 cmH2O PIP. Inspiratory volume limitation by the plaster cast in the C group prevented any significant increase in Kfc at the PIP values used. These data indicate that volume distension of the lung rather than high PIP per se produces microvascular damage in the immature rabbit lung.

Animals↗
PubMed1988

Ibuprofen in experimental group B streptococcal shock.

A rabbit model was used to characterize the effects of high (Group II, 100 mg/kg) and low (Group III, 10 mg/kg) dose ibuprofen in modulating the hemodynamic and hematologic manifestations of group B streptococcal shock. Short-term survival was significantly increased with ibuprofen pretreatment. Ibuprofen failed to prevent GBS-induced shock, although shock was favorably modified in a dose dependent manner. Likewise, GBS-induced increases in 6KPGF1a and TxB2 were not prevented but were modified in Group II at 120 min. However, neutropenia, thrombocytopenia, and acidosis were not prevented by pretreatment with ibuprofen and may have been exacerbated. Thus, ibuprofen modifies but does not prevent GBS-induced hemodynamic and hematologic manifestation.

Animals↗
PubMed1987

Characterization of polymorphonuclear leukocyte aggregation in vitro induced by heat-inactivated group B streptococcus.

We studied the aggregatory characteristics of human polymorphonuclear leukocytes (PMNs) in response to heat-inactivated group B streptococcus. PMNs suspended in physiologic salt solution do not aggregate to heat-inactivated group B streptococcus (GBS) unless the GBS is previously opsonized in autologous plasma. The aggregating activity of both opsonized GBS and activated plasma are reduced if the plasma is decomplemented before incubation with GBS. Pretreatment of PMNs with pronase inhibited opsonized GBS-induced aggregation, suggesting aggregation via cell membrane receptors for opsonic fragments of C3. Pronase pretreatment had no significant effect on aggregation induced by activated plasma or arachidonic acid. Unlike PMNs in physiologic salt solution, PMNs suspended in plasma aggregate when stimulated by unopsonized GBS. GBS aggregates PMNs via complement cascade activation, opsonization, and interaction with cell membrane receptors to stimulate cellular mechanisms resulting in PMN aggregation.

Bacterial Vaccines↗
PubMed1987

In vitro inhibition of group B streptococcus-induced polymorphonuclear leukocyte aggregation.

Evidence suggests that part of the pathophysiologic response seen in group B streptococcal (GBS) sepsis may be due to polymorphonuclear leukocyte (PMN) activation. Indomethacin (INDO), which inhibits eicosanoid metabolism, attenuates the pathophysiologic response stimulated by GBS, possibly due to inhibition of PMN aggregation. We examined the capability of two eicosanoid metabolism inhibitors, INDO and nordihydroguaiaretic acid (NDGA), to inhibit PMN aggregation induced by heat-inactivated opsonized GBS and GBS-activated plasma. Opsonized GBS-induced PMN aggregation was inhibited by INDO (50-500 microM) and NDGA (1-100 microM). Over similar concentration ranges, INDO and NDGA had no significant effect on PMN aggregation induced by GBS-activated plasma. PMNs in plasma aggregate in response to unopsonized GBS. The stimuli for aggregation are opsonized GBS and GBS-activated plasma. INDO (50-500 microM) was unable to inhibit aggregation under this condition. Over the same concentration range in which INDO inhibited opsonized GBS-induced PMN aggregation, INDO was unable to inhibit opsonized GBS-induced superoxide production in PMNs. NDGA was examined but was found to interfere with the assay. The above evidence suggests PMN aggregation via eicosanoid metabolism may play a role in GBS-induced sepsis, which may be attenuated by agents such as INDO and NDGA.

Bacterial Vaccines↗
PubMed1986

Prostaglandin synthetase inhibition in group B streptococcal shock: hematologic and hemodynamic effects.

A rabbit model of group B Streptococcal (GBS) shock was used to study the effects of prostaglandin synthetase inhibition on the hemodynamic and hematologic response to GBS shock. The infusion of heat-killed GBS in groups I and II produced significant decreases in mean arterial pressure, neutrophil counts, and platelet counts (p less than 0.05), and significant rises in concentrations of thromboxane B2 and 6-Keto-PGF1 alpha, the stable metabolites of thromboxane A2 and prostacyclin (p less than 0.05). Administration of indomethacin (4 mg/kg) after GBS infusion (group II) was associated with a significant rise in mean arterial pressure and a significant decline in thromboxane B2 and 6-Keto-PGF1 alpha concentrations (p less than 0.05) but had no effect on GBS-induced hematologic alterations. Indomethacin administration before GBS infusion (group III) prevented alterations in mean arterial pressure and was associated with a decrease in thromboxane B2 and 6-Keto-PGF1 alpha concentrations. Indomethacin in group III did not prevent neutropenia and thrombocytopenia and may have exacerbated neutropenia. Alteration of experimental GBS shock with prostaglandin synthetase inhibition produces disparate hemodynamic and hematologic response.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

The comparison of myocardial dysfunction in three forms of experimental septic shock.

A rabbit model of septic shock was used to determine if myocardial dysfunction is a common component of shock due to diverse neonatal pathogens, and prostaglandins modulate septic myocardial dysfunction. The infusion of heat-killed Escherichia coli (group I), Haemophilus influenzae (group II), or Staphylococcus epidermidis (group III) produced significant decreases in the first derivative of left ventricular pressure with respect to time (p less than 0.05). Each organism also produced significant changes in mean arterial pressure, cardiac output, and heart rate, while pulmonary artery pressure was altered in groups I and III. Saline-infused control animals (group IV) exhibited no significant changes in any hemodynamic variable. Blood gas variables were not significantly changed in any group. These cardiovascular changes appeared dependent on arachidonic acid metabolism since indomethacin pretreatment prevented the cardiovascular changes induced by bacterial infusion. These results suggest that septic myocardial dysfunction is a common component of gram-negative and gram-positive septic shock, and that myocardial dysfunction is modulated by prostaglandin products.

Animals↗
PubMed1986

Epidemiology of inguinal hernia in preterm neonates.

We have studied the epidemiology of inguinal hernias in preterm infants. Inguinal hernias occur with increased frequency in infants less than or equal to 32 weeks' gestational age or less than or equal to 1,250 g birth weight. Among infants less than or equal to 32 weeks' gestational age, intrauterine growth retardation significantly increases the risk for development of inguinal hernias, especially in male infants. Our data demonstrate a previously unrecognized association between neonatal inguinal hernia and intrauterine growth retardation.

Alabama↗
PubMed1985

Myocardial dysfunction in group B streptococcal shock.

A rabbit model of group B Streptococcal (GBS) shock was used to determine if myocardial dysfunction contributes to GBS shock and, if so, to ascertain if prostaglandins modulate this dysfunction. The infusion of heat-killed GBS (group I) produced a dramatic decrease in the first derivative of left ventricular pressure with respect to time (LVdP/dt) from baseline values (p less than 0.05). LVdP/dt remained stable in rabbits pretreated with indomethacin (group II) and in saline-infused control rabbits (group III), and was significantly different at 30 min from LVdP/dt in group I (p less than 0.05). Values for group I mean arterial pressure, cardiac output, pulmonary vascular resistance, and heart rate and for pH and pO2 after GBS infusion were all significantly different from baseline values and from postinfusion values for groups II and III (p less than 0.05). Systemic vascular resistance and left ventricular end diastolic pressure did not change significantly in any group at any time interval. These results indicate a primary role for myocardial dysfunction in the pathogenesis of GBS shock, and suggest strongly that prostaglandins modulate GBS-induced myocardial dysfunction.

Animals↗
PubMed1985

Transcutaneous oxygen monitoring: economic impact on neonatal care.

Five years (1978 to 1982) of respiratory care data were reviewed to determine the changes in patient charges, hospital costs, and frequency of neonatal blood gas analysis created by the introduction of transcutaneous oxygen monitoring. During the 4 years of transcutaneous oxygen monitoring (1979 to 1982), an estimated $196,000 reduction in patient charges was accomplished. When reduced patient charges were balanced with the increased cost to the hospital for equipment, supplies, and personnel time, a net reduction of more than $100,000 for health care delivery was achieved. Transcutaneous oxygen monitoring is an example of technologic achievement in which society receives both economic and medical benefits.

Costs and Cost Analysis↗
PubMed1983

Abnormal fetal heart rate patterns and percentage of creatine phosphokinase-2.

Eighteen term newborn infants who had been evaluated by internal fetal heart rate (FHR) monitoring were studied to correlate fetal monitor tracings with Apgar scores and serum creatine phosphokinase-1 (CPK2) the myocardium-specific isoenzyme of CPK. The percentage of CPK2 at 30 +/- 6 hours did not correlate significantly with Apgar scores. However, values for the percentage of CPK2 at 30 +/- 6 hours were significantly higher in neonates with abnormal FHR tracings than in those with normal FHR tracings (p less than 0.01). These preliminary data suggest that subtle intrapartum asphyxial injury may be present without adversely affecting Apgar scores.

Apgar Score↗