Biomedical subjects

D R Gerstmann

Publications and source records attributed to D R Gerstmann.

At least 37 records · Page 2Linked to original sources

PubMed1991

Circulatory changes following premature delivery in a baboon model of hyaline membrane disease.

The premature baboon delivered by hysterotomy at 140 +/- 2 days (75%) gestation develops hyaline membrane disease (HMD) and left-to-right (L-R) shunting through the patent ductus arteriosus (PDA). To characterize hemodynamic changes that follow premature delivery, we measured systemic and organ blood flow, oxygen transport, and systemic vascular resistance over the first 96 h of life. We compared these measurements with those from more mature animals of the same species. Radiolabeled microspheres were used to measure organ blood flow (in ml.min-1.g-1) at 3 (n = 18), 23 (n = 17), and 96 h (n = 4) in the premature animals, and at 13 +/- 4 mo in the older animals (n = 5). Premature animals demonstrated over the first 96 h of life significant hemodynamic changes that included decreased systemic vascular resistance (P less than 0.001), increased systemic (P less than 0.05), intestinal (P less than 0.05), and hepatic blood flow (P less than 0.05), as well as resolution of L-R PDA shunting. These 96-h values were similar to those of the more mature infant baboons. Blood flow and oxygen transport to the kidneys and cerebrum did not significantly increase over the first 96 h in premature baboons and were significantly less than those of 13-mo-old animals (P less than 0.01, both). We speculate that low renal and cerebral blood flow in the 140-day premature baboon are manifestations of multisystem immaturity and, as such, may represent persistent physiological disturbances that are distinct from the severity of underlying lung disease in HMD.

Aging↗

PubMed1991

Allopurinol-induced effects in premature baboons with respiratory distress syndrome.

To test the hypothesis that administration of allopurinol could modify the response to prolonged hyperoxia in premature baboons (140 days gestation) with respiratory distress syndrome, we evaluated physiological, pathological, and lung biochemical parameters in groups of premature baboons treated with mechanical ventilation and exposed to various amounts of oxygen for 6 days. Three groups of experimental animals were studied, including animals that received oxygen as needed to maintain arterial oxygen between 60 and 80 Torr [inspiratory O2 concentration- (FIO2) PRN], animals that received 100% oxygen continuously but also received allopurinol intravenously at a dose of 10 mg.kg-1.day-1 (FIO2-1.0 + allopurinol), and animals that received 100% oxygen continuously and the vehicle for allopurinol administration (FIO2-1.0). Pathological examinations of the experimental animals showed evidence of lung injury in both 100% oxygen-exposed groups, but the allopurinol-treated animals had findings more compatible with the FIO2-PRN group, with relatively few macrophages or polymorphonuclear lymphocytes being present in lung tissue. Lungs of animals treated with allopurinol were also more distensible and had a trend toward decreased lung water compared with the FIO2-1.0 group. Allopurinol-treated animals were able to induce lung glutathione concentrations and glutathione-related and antioxidant enzyme activities compared with the normoxic control (FIO2-PRN) group. Ventilator pressure requirements were also decreased in the allopurinol-treated animals compared with the FIO2-1.0 controls after 42 h. These data suggest that treatment of hyperoxia-exposed premature baboons with allopurinol for the first 6 days of life results in significant changes in lung responses and antioxidant defenses compared with vehicle-treated baboons exposed to 100% oxygen for the same time period.

Allopurinol↗

PubMed1991

Ductal shunting and effective systemic blood flow following single dose surfactant treatment in the premature baboon with hyaline membrane disease.

We studied the hemodynamic effects of using natural surfactant in premature baboons with hyaline membrane disease (HMD). Study animals (n = 5) received a single dose of surfactant immediately after delivery and control animals (n = 8) did not. Using microspheres at 3, 8, and 23 h we found no significant differences in left ventricular output, effective systemic flow, systemic-to-pulmonary patent ductus arteriosus (PDA) shunting, or in cerebral or renal organ blood flow. However, both groups had large PDA shunts (fraction of LVO to lungs greater than 0.40-0.55 at 3 and 8 h) resulting in low systemic perfusion (less than 80 ml/min/kg). Single dose surfactant did not improve the myocardial dysfunction and low cerebral and renal blood flow which occur during treatment for HMD.

Animals↗

PubMed1991

Bacterial colonization and infection studies in the premature baboon with bronchopulmonary dysplasia.

Microbial colonization and infection patterns were prospectively evaluated in premature baboons with and without bronchopulmonary dysplasia (BPD) to assess if prolonged hyperoxia would predispose to a different pattern of microbial colonization and/or a higher risk of respiratory infection. Forty baboons were delivered by hysterotomy at 75% of gestation and randomized into two groups. Group I (control or PRN) animals were placed immediately on high-frequency oscillation at 15 Hz; I:E ratio 1:2, and changed to positive-pressure ventilation at 48 to 72 h. They were maintained on clinically appropriate oxygen at minimal ventilator settings for the remainder of the 21-day experimental period. Group II (oxygen-treated or BPD) animals were ventilated with PPV and FIO2 1.0 for 7 days followed by FIO2 0.8 for 14 days. All animals were treated with antibiotics during some portion of the 21-day course. Specimens from nose, oropharynx, trachea, and rectum were cultured for both aerobes and anaerobes throughout the neonatal intensive care unit (NICU) course. A subset of animals from both groups were killed at 21 days and lung, liver, spleen, and gastric contents were cultured quantitatively at autopsy. Findings showed that coagulase-negative staphylococci were the predominant organisms that colonized the neonate in the NICU. Lung infections were seen to evolve through sequential pathogenetic steps: colonization of the upper respiratory tract, with concomitant or subsequent colonization of the trachea with comparable organism and ultimate recovery of the same organisms at autopsy in the lungs of animals with pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

High-frequency oscillatory ventilation versus intermittent mandatory ventilation: early hemodynamic effects in the premature baboon with hyaline membrane disease.

We studied the hemodynamic consequences during the first 24 h of life in premature baboons (140 d) with hyaline membrane disease that were treated with high-frequency oscillatory ventilation (HFOV) or conventional intermittent mandatory ventilation (IMV). Cardiac output and organ blood flow were measured at three time-points using the radiolabeled microsphere technique. Seven of seven HFOV and six of eight IMV animals survived the 24-h period. By design, initial mean airway pressure (Paw) was higher in the HFOV group (p less than 0.01). HFOV Paw was progressively reduced during the study period because of improving oxygenation as measured by the arterial to alveolar oxygen ratio. In contrast, it was necessary to increase Paw in the IMV animals to maintain the arterial to alveolar oxygen ratio. By 23 h, the IMV group required higher Paw than the HFOV group (p less than 0.05) and had a lower arterial to alveolar oxygen ratio (p less than 0.05). We found no significant differences in left ventricular output, effective systemic flow, organ blood flow, or central venous pressure between the two groups at 3, 8, or 23 h. The HFOV strategy used in our study resulted in significant improvement in oxygenation during the initial 24 h of treatment without adverse effect on left ventricular output, cerebral blood flow, or central venous pressure. We conclude that when appropriate changes in Paw are made during HFOV in response to improvement in arterial oxygenation and changes in lung inflation as assessed by chest radiographs HFOV can be achieved without depressing cardiovascular dynamics more than during conventional therapy with IMV.

Animals↗

PubMed1991

High-frequency ventilation: issues of strategy.

Although each high-frequency ventilator has functional characteristics that are design related, it now appears that when used with similar treatment strategies and within their functional limitations, similar clinical outcomes can be realized. Optimized treatment protocols must vary depending on the pulmonary disease to be treated, with strategies during treatment for pulmonary injury different from those used in pulmonary injury prevention. It is still unclear whether any one particular high-frequency ventilator will have specific disadvantages that cannot be overcome by device modification and that are inherent in a particular HFV methodology. Experimental and clinical data suggest that HFV will contribute significantly in reducing neonatal pulmonary morbidity and aid in the prevention of chronic pulmonary disease.

Clinical Protocols↗

PubMed1990

Toxic effects associated with the administration of deferoxamine in the premature baboon with hyaline membrane disease.

We hypothesized that administration of the iron chelator deferoxamine would inhibit iron-catalyzed free radical generation and lessen the severity of oxygen-induced pulmonary injury. To evaluate its efficacy and safety in premature infants, we administered deferoxamine by intravenous infusion to five premature baboons with hyaline membrane disease supported with conventional ventilation and 100% oxygen for 6 days. Seven animals served as controls. Deferoxamine treatment was initiated at 10 mg/kg per hour but, after the precipitous death of the first animal, was progressively reduced to 1.25 mg/kg per hour in the other animals. Four of five deferoxamine-treated baboons developed cardiovascular collapse and all five died by 42 hours. Five of the seven control animals survived the 6-day experimental period. Since cardiovascular toxic effects have not previously been reported, these findings suggest unique vulnerability of the immature cardiovascular system to iron chelation.

Animals↗

PubMed1990

Left ventricular dysfunction following ligation of the ductus arteriosus in the preterm baboon.

We evaluated the effect of early closure of the patent ductus arteriosus (PDA) on cardiac performance in a preterm baboon model of hyaline membrane disease. Eleven baboon fetuses were delivered at 75% gestation, resuscitated, and treated with conventional ventilation. The animals were divided into two groups, and underwent left thoracotomy at 2 hr of age. Group 1 (N = 5) had ductal infiltration with formalin to maintain ductal patency. Group 2 (N = 6) had ductal ligation. Hemodynamic parameters were compared between groups before and after surgical intervention. Examination of cardiovascular function was performed at intervals over a 24-hr period using two-dimensional, M-mode, and pulsed Doppler echocardiography. Ventricular performance was significantly worse in the ligation animals as demonstrated by reduced left and right ventricular outputs and reduced left ventricular shortening. However, pulmonary disease and arterial blood gases were not different. Early ligation was also associated with significantly increased systemic vascular resistance. We conclude that early ductal ligation leads to impaired ventricular performance in the premature primate. We hypothesize that the PDA may protect the immature ventricle by preventing pressure overload during adaptation to postnatal life.

Animals↗

PubMed1990

Proximal, tracheal, and alveolar pressures during high-frequency oscillatory ventilation in a normal rabbit model.

To study the effect of different high-frequency oscillatory ventilation parameters on airway pressure, we measured oscillatory pressure amplitude ([Paw[) and mean airway pressure (Paw) at three sites in open-chested normal rabbits: proximal, trachea, and alveolus. Five animals were studied to test a new pleural capsule design, which was then used in two groups of animals to measure right upper (n = 4) or middle (n = 5) lobe alveolar pressures. Animals were randomly sequenced through combinations of frequency (10, 15, and 20 Hz) and fractional inspiratory time (Ti) (0.3 and 0.5) while normoxic and eucapnic. During capsule testing, we noted that alveolar pressures increased (p less than 0.05) with increasing capsule mass, suggesting that compressive forces from the capsule may alter the capsule measurement. We thus used a low-mass (430 mg) transducer system in the rabbit high-frequency oscillatory ventilation experiments. Using multifactorial analysis of variance, we found significant main effects of Ti on Paw, and of measurement site on both [Paw[ and Paw (all p less than 0.009). Frequency did not influence variations in either [Paw[ or Paw. For both Ti settings, alveolar upper lobe Paw was lower compared with that of the middle lobe (p less than 0.0005). Lengthening Ti (0.3 to 0.5) increased tracheal Paw in each capsule group (p less than 0.0005). At Ti = 0.5, tracheal Paw exceeded Paw measured proximally (p less than 0.05). Our data support in vivo alveolar Paw inhomogeneity and demonstrate significant changes in pressures within the lung related to Ti during high-frequency oscillatory ventilation.

Analysis of Variance↗

PubMed1990

High-frequency oscillatory ventilation and extracorporeal membrane oxygenation for the treatment of acute neonatal respiratory failure.

Forty-six (92%) outborn and four (8%) inborn term or near-term neonates were admitted for extracorporeal membrane oxygenation (ECMO) treatment to a neonatal intensive care unit between July 1, 1985, and November 1, 1987. All infants had PAO2-PaO2 greater than or equal to 600 mm Hg in spite of aggressive conventional ventilatory and pharmacologic therapy. All patients were offered rescue treatment with high-frequency oscillatory ventilation (HFOV), and only if there was no improvement in PAO2-PaO2 with HFOV were infants treated using ECMO. Four patients died before receiving an adequate trial of HFOV and before emergency ECMO support could be initiated; 21 patients, all of whom survived to hospital discharge, responded to HFOV; 25 patients ultimately required ECMO therapy for cardiopulmonary support, with 22 (88%) surviving to discharge. Neonates responding to HFOV were of slightly younger gestational age (38 +/- 2 weeks vs 40 +/- 2 weeks, mean +/- SD; P less than .001) and more frequently had clinical evidence of pneumonia (11 of 21 vs 2 of 25; P less than .002). There was no statistically significant difference in outcome with respect to the number of ventilator days, hospital days, or survival between patients responding to HFOV and patients who required ECMO. Morbidity was increased in ECMO patients, with bleeding abnormalities, seizures, and renal failure occurring more frequently than in HFOV-treated infants. Overall, 92% (46 of 50) of the patients were treated with a staged protocol using HFOV before ECMO. A total of 46% (21 of 46) responded to HFOV treatment alone and did not require ECMO therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal Membrane Oxygenation↗

PubMed1989

A comparison of ventilation strategies for the use of high-frequency oscillatory ventilation in the treatment of hyaline membrane disease.

To assess the efficacy of high frequency oscillatory ventilation (HFOV) in the management of infants with hyaline membrane disease (HMD), we compared two HFOV strategies with conventional positive pressure ventilation with positive end expiratory pressure (PPV) for 24 h in premature baboons (140 d gestation). Three out of 14 PPV, five out of five HFOV-E (begun at birth; 15 Hz; I:E 1:2), and none of 10 HFOV-L (begun after 3 h PPV; 10 Hz; I:E 1:2) were killed at 24 h for morphologic examination. Physiologic (Paw, Pa/AO2, IO2, B.P., pulse, blood gases) data on all animals in each group were assessed at each 3 h interval and over time. Intergroup differences in radiographs at 0 and 24 h and in morphology were quantitatively assessed by comparison with a panel of standards. All animals had radiographic HMD. Initial Paw was set higher with HFOV-E (16.8) than PPV or HFOV-L (14.1, 14.1). PPV baboons required increasing Paw to maintain constant Pa/AO2. Six out of 14 PPV animals developed airleak and three out of three had morphologic HMD. In contrast Pa/AO2 was higher in both HFOV groups at lower Paw by 24 h. None of 15 HFOV animals developed airleak. HFOV-E lungs had dramatic differences in morphology with uniform saccular opening and decreased edema and hyaline membranes compared to PPV. HFOV-L had less dramatic effects because of lower Paw and delayed application. Early use of HFOV at a high Paw favorably alters the course of HMD. Unless closely monitored, this strategy results in lung overinflation which may adversely affect venous return and cardiac output.

Animals↗

PubMed1989

Oxygen delivery rate and sufficiency of oxygenation during ECMO in newborn baboons.

Minimum acceptable O2 delivery (DO2) during extracorporeal membrane oxygenation (ECMO) remains to be defined in a newborn primate model. The right atrium, carotid artery, and femoral artery were cannulated, and the ductus arteriosus, aorta, and pulmonary artery ligated in neonatal baboons (Papio cynocephalus) under a combination of ketamine, diazepam, and pancuronium. The internal jugular vein was also cannulated retrograde to the level of the occipital ridge. We measured hemoglobin, pH, arterial and venous PO2 (both from the pump circuit and from the cerebral venous site), serum lactate and bicarbonate concentrations, and pump flow, and we calculated hemoglobin saturations, (DO2), O2 consumption (VO2), systemic O2 extraction, and cerebral O2 extraction. Six baboons were studied during each of two phases of the experiment. In the first, flow rates were varied sequentially from 200 to 50 ml.kg-1.min-1 with saturation maximized. In the second, flow was maintained at 200 ml.kg-1.min-1 and saturation was reduced sequentially from 100 to 38%. VO2 fell significantly below baseline at a flow rate of 50 ml.kg-1.min-1 and a DO2 of 8 +/- 2 (SE) ml.kg-1.min-1 in phase 1 and at DO2 of 12 +/- 5 in phase 2. Both systemic and cerebral O2 extraction rose significantly at a flow of 100 ml.kg-1.min-1 and DO2 of 17 +/- 4 ml.kg-1.min-1 in phase 1, whereas neither rose with decreasing DO2 in phase 2. In fact, cerebral extraction fell significantly DO2 of 16 +/- 6 ml.kg-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Role of lung injury in the pathogenesis of hyaline membrane disease in premature baboons.

To test the hypothesis that hyaline membrane disease (HMD) has a multifactorial etiology in which barotrauma plays a major role, we compared the immediate institution of high-frequency oscillatory ventilation (HFOV; 15 Hz, n = 5) with positive-pressure ventilation with positive end-expiratory pressure (PPV; n = 7) in premature baboons (140-days gestation) with HMD. Measurements of ventilation settings and physiological parameters were obtained and arterial-to-alveolar O2 (PaO2-to-PAO2) ratio and oxygenation index [(PaO2/PAO2)-to-mean airway pressure ratio (IO2)] were calculated. At death (24 h), static pressure-volume (PV) curves were performed, and phospholipids (PL) and platelet-activating factor (PAF) were measured in lung lavage fluid. Morphological inflation patterns were analyzed using a panel of standards. By design, mean airway pressure was initially higher (19 vs. 13 cmH2O) in the HFOV animals. PaO2-to-PAO2 ratio and IO2 progressively deteriorated in the PPV animals and then stabilized at significantly lower levels than with HFOV. PV curves from HFOV animals had significant increases in lung volume at maximum distending pressure, deflation volume at 10 cmH2O, and hysteresis area compared with PPV, which showed no hysteresis. Seven of seven PPV and only one of five HFOV animals had morphological findings of HMD. PL amount and composition in both groups were consistent with immaturity, even though the quantity was significantly greater in the PPV group. PAF was present (greater than or equal to 0.10 pmol) in six of seven PPV and in the only HFOV animal with HMD. We conclude that HFOV protected PL-deficient premature baboons from changes in gas exchange, lung mechanics, and morphology typical of HMD in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Influence of ventilatory technique on pulmonary baroinjury in baboons with hyaline membrane disease.

To assess the influence of ventilatory technique on pulmonary baroinjury in experimental hyaline membrane disease, we randomized 24 premature baboons to six treatment groups according to ventilator (PPV, positive pressure ventilator; HFO, high frequency oscillator; HFI, high frequency flow interrupter) and O2 therapy FIO2 as clinically indicated, or FIO2 1.0). PaCO2 was adjusted by varying pressure amplitude, and for PPV, also by rate (less than 60/min). HFO and HFI were set at a frequency of 10 Hz. Animals were cared for with standard NICU techniques until death or sacrifice at 11 days. One animal died at delivery and was excluded from data analysis. There were no intergroup differences in Paw, Pa/AO2, PaCO2 or oxygenation index (IO2 = [Pa/AO2]/Paw) prior to death of the first study animal at 13 h. Animals who subsequently developed airleak had higher Paw, lower Pa/AO2 and lower IO2 during this period. The degree of airleak was significantly less with HFO compared to PPV or HFI. The effect of O2 exposure did not appear different with respect to the degree of airleak or the frequency of severe tracheal injury, although survival was shortened. Severe tracheal injury was more frequent with HFI compared to PPV or HFO. BPD was found only in 100% O2 exposed animals surviving greater than 1 wk. Management of premature baboons with HFO and appropriate O2 resulted in less severe airleak, 100% survival, and no evidence of severe tracheal injury or BPD. These outcomes were not achieved with clinically similar strategies using PPV or HFI.

Animals↗

PubMed1988

High-frequency ventilation: its various techniques and clinical applications.

High-frequency ventilation can be considered to be ventilation with a tidal volume close to or less than the anatomical dead space. The various techniques of high-frequency ventilation will be discussed including high-frequency positive pressure ventilation, high-frequency jet ventilation or high-frequency flow interruption, and high-frequency oscillatory ventilation. The clinical application of the various types of high-frequency ventilation will be discussed including their use during surgical procedures, their use for various kinds of barotrauma, their usefulness in respiratory failure, their use in newborns with hyaline membrane disease, and their usefulness for respiratory support in emergency situations involving cardiopulmonary resuscitation. The potential use for high-frequency ventilation in the management of battlefield casualties and air evacuation of critically ill patients will also be discussed.

Barotrauma↗

PubMed1987

Extracorporeal membrane oxygenation and high-frequency oscillatory ventilation: potential therapeutic relationships.

Eighteen neonates 33 to 42 wk gestational age with severe respiratory failure were referred for extracorporeal membrane oxygenation (ECMO). Sixteen ultimately met the ECMO criteria, of whom 15 were first offered high-frequency oscillatory ventilation (HFOV). Seven responded to HFOV alone and did not require ECMO treatment. Eight of the nine remaining patients were placed on ECMO support with HOFV. Infants who responded to HFOV alone tended to have pneumonia more than meconium aspiration, to be smaller and more immature, to have higher Apgar scores, and to have suffered severe hypoxia (alveolar-arterial oxygen pressure difference over 600 torr) for less time than the ECMO group. Although patient numbers are small, a trend is noted which favors HFOV treatment alone in terms of the duration of HFOV, the total duration of assisted ventilation, the rapidity with which extubation was accomplished, and the length of hospital stay.

Birth Weight↗

PubMed1987

Oxygen toxicity in the premature baboon with hyaline membrane disease.

Immaturity, pulmonary barotrauma, and oxygen toxicity have been implicated in the pathogenesis of bronchopulmonary dysplasia (BPD). Although the physiologic and biochemical consequences of oxygen toxicity have been described in newborn and adult animals, there have been no controlled observations in prematures. We compared the physiologic and morphologic effects of prolonged hyperoxia with those of clinically appropriate oxygen in premature baboons with hyaline membrane disease (HMD) supported with conventional positive pressure ventilation and continuous distending airway pressure (PPV/PEEP). Twenty-one premature baboons were delivered at 140 days gestation, intubated and resuscitated, and supported with PPV/PEEP and standard NICU techniques for 11 days. The FIO2, PaO2, PaCO2, pHa, ventilator and airway pressures, and blood pressure were intermittently measured and recorded. The physiologic observations could be divided into 3 distinct phases. During Phase 1 (0 to 42 h) there were no significant intergroup differences, and (a/A)PO2 and IO2 (oxygenation index; (a/A)PO2/Paw) remained stable. In Phase 2 (43 to 96 h) there was a rapid improvement in (a/A)PO2 and IO2 in both groups, but the response in the hyperoxic animals was significantly dampened. During Phase 3 (97 to 264 h) there was continued improvement in the "prn" animals, which contrasted with progressive deterioration in those exposed to FIO2 1.0. Five of 11 "prn" and 3 of 10 FIO2 1.0 baboons developed air leaks during Phase 1 or early Phase 2. Four of 10 of the hyperoxic animals died after the late onset of air leak. Pathologic changes of BPD were found in all FIO2 1.0 animals surviving more than 6 days but in none of the "prn" long-term survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Ventilatory management of infant baboons with hyaline membrane disease: the use of high frequency ventilation.

We tested the hypothesis that high frequency oscillatory ventilation (HFOV) would result in decreased pulmonary barotrauma in infants with hyaline membrane disease by comparing HFOV at 10 Hz to conventional positive pressure ventilation with continual distending airway pressure (PPV/PEEP) in premature baboons with hyaline membrane disease. Nineteen baboon fetuses were randomized to one of two treatment groups, delivered at 140 +/- 2 days, and, after stabilization and instrumentation of PPV/PEEP, placed in their respective ventilator group. Animals on conventional ventilation were managed by adjustment of tidal volume and frequency (to 1 Hz) to keep PaCO2 below 55 and by adjustment of the mean airway pressure. One of the "HFOV" group died of cardiovascular complications before going on HFOV and was eliminated from data analysis. The remaining HFOV baboons survived the 11-day experimental period without evidence of airleak. Six of the 11 prematures treated with PPV/PEEP developed pulmonary interstitial emphysema and/or pneumothorax and five of the animals died within 48 h. The intergroup differences in airleak were significant (p less than 0.05). Mean airway pressure (measured at the proximal airway) was higher initially with HFOV but then was lowered more rapidly than in the PPV/PEEP animals. The arterial to alveolar oxygen ratio rose and the FIO2 could be lowered more rapidly with HFOV than with conventional ventilation. These differences reached significance by 20 h. After 60 h there were no significant differences between HFOV and the PPV/PEEP survivors. HFOV resulted in more uniform saccular expansion, higher arterial to alveolar oxygen ratio, less oxygen exposure, and decreased acute barotrauma when compared to PPV/PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗