Biomedical subjects

D R Bing

Publications and source records attributed to D R Bing.

At least 19 recordsLinked to original sources

PubMed2000

Randomized controlled trial of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation following initial exogenous surfactant therapy.

We set out to evaluate the impact of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation (IMV) on the early physiologic response to surfactant replacement therapy in neonates with respiratory distress syndrome (RDS). We hypothesized that volume-targeted, patient-triggered synchronized ventilation would stabilize minute ventilation at a lower respiratory rate than that seen during volume-targeted IMV, and that synchronization would improve oxygenation and decrease variation in measured tidal volume (V(t)). This was a prospective, randomized study of 30 hospitalized neonates with RDS. Infants were randomly assigned to volume-targeted ventilation using IMV (n = 10), synchronized IMV (SIMV; n = 10), or assist/control ventilation (A/C; n = 10) after meeting eligibility requirements and before initial surfactant treatment. Following measurements of arterial blood gases and cardiovascular and respiratory parameters, infants received surfactant. Infants were studied for 6 hr following surfactant treatment. Infants assigned to each mode of ventilation had similar birth weight, gestational age, and Apgar scores at birth, and similar oxygenation indices at randomization. Three patients were eliminated from final data analysis because of exclusionary conditions unknown at randomization. Oxygenation improved significantly following surfactant therapy in all groups by 1 hr after surfactant treatment (P < 0.05). No further improvements occurred with time. Total respiratory rate was lowest (P < 0.05) and variation in tidal volume (V(t)) was least in the A/C group (P < 0. 05). Minute ventilation (V(')(E)), delivered airway pressures, respiratory system mechanics, and hemodynamic parameters were similar in all groups. We conclude that volume-targeted A/C ventilation resulted in more consistent tidal volumes at lower total respiratory rates than IMV or SIMV. Oxygenation and lung mechanics were not altered by synchronization, possibly due to the volume-targeting strategy. Of the modes studied, A/C, a fully-synchronized mode, may be the most efficient method of mechanical ventilator support in neonates receiving surfactant for treatment of RDS.

Blood Gas Analysis↗

PubMed2000

Variations in end-expiratory pressure during partial liquid ventilation: impact on gas exchange, lung compliance, and end-expiratory lung volume.

STUDY OBJECTIVES: To determine the effects of different levels of positive end-expiratory pressure (PEEP) during partial liquid ventilation (PLV) on gas exchange, lung compliance, and end-expiratory lung volume (EELV). DESIGN: Prospective animal study. SETTING: Animal physiology research laboratory. SUBJECTS: Nine piglets. INTERVENTIONS: Animals underwent saline solution lavage to produce lung injury. Perflubron was instilled via the endotracheal tube in a volume estimated to represent functional residual capacity. The initial PEEP setting was 4 cm H(2)O, and stepwise changes in PEEP were made. At 30-min intervals, the PEEP was increased to 8, then 12, then decreased back down to 8, then 4 cm H(2)O. MEASUREMENTS AND RESULTS: After 30 min at each level of PEEP, arterial blood gases, aortic and central venous pressures, heart rates, dynamic lung compliance, and changes in EELV were recorded. Paired t tests with Bonferroni correction were used to evaluate the data. There were no differences in heart rate or mean BP at the different PEEP levels. CO(2) elimination and oxygenation improved directly with the PEEP level and mean airway pressure (Paw). Compliance did not change with increasing PEEP, but did increase when PEEP was lowered. EELV changes correlated directly with the level of PEEP. CONCLUSIONS: As previously reported during gas ventilation, oxygenation and CO(2) elimination vary directly with PEEP and proximal Paw during PLV. EELV also varies directly with PEEP. Dynamic lung compliance, however, improved only when PEEP was lowered, suggesting an alteration in the distribution of perflubron due to changes in pressure-volume relationships.

Animals↗

PubMed1999

Synchronized gas and partial liquid ventilation in lung-injured animals: improved gas exchange with decreased effort.

We hypothesized that partial liquid ventilation (PLV) with perflubron in spontaneously breathing lung-injured animals would increase respiratory workload compared to animals treated with gas ventilation (GV), and that a fully synchronized mode, assist-control ventilation (AC), would reduce the piglets' effort when compared to intermittent mandatory ventilation (IMV) or synchronized IMV (SIMV) during both GV and PLV. Newborn piglets with saline lavage-induced lung injury were randomized to sequential 30-min periods of IMV --> SIMV --> AC (n = 5), or AC --> SIMV --> IMV (n = 5) during GV followed by PLV. Pulmonary mechanics measurements and an esophageal patient effort index (PEI, defined as the product of the area below baseline of the esophageal pressure-time curve and respiratory rate [RR]) were determined to estimate the patient's nonmechanical work of breathing, using a computer-assisted lung mechanics analyzer. GV to PLV comparisons showed no change in PEI (IMV, 57.8 vs. 49.7; SIMV, 52.3 vs. 46.8; AC, 15.7 vs. 13.7 cm H2O x s/min); intermode comparisons showed significantly decreased PEI in AC vs. IMV and SIMV during GV, and in AC vs. SIMV (AC vs. IMV, P = 0.06) during PLV. AC consistently resulted in the highest minute ventilation, lowest total respiratory rate, most physiologic pH, and least tidal volume variability. These observations suggest that synchronization with AC during GV and PLV may have substantial physiologic benefits.

Animals↗

PubMed1999

Assessment of the respiratory actions of intramuscular morphine in conscious dogs.

The actions on the respiratory system of 0.25, 0.5 and 1.0 mg kg(-1) morphine given intramuscularly were studied in conscious dogs. Dogs breathed oxygen with 0, 2 and 4 per cent CO(2), in that order, through a mask attached to a flow sensor and connected to a respiratory mechanics monitor. When a steady state period of respiration was reached breathing pure oxygen, respiratory rate, tidal volume, respiratory minute volume, peak expiratory flow rate and end tidal CO(2)(PetCO(2)) were measured. The respiratory minute volume and PetCO(2) were measured when the dogs breathed 2 and 4 per cent CO(2) in oxygen, the points plotted onto a graph and the gradient of the line, describing the PCO(2)/ventilation response, plus the intercept with the y-axis were determined. Measurements for each morphine dose were taken before injection and at 30 minutes, 1, 2, 3, 4, 6 and 8 hours post injection. The incidence of panting after morphine was dose related and it occurred in all dogs given the high dose. Morphine reduced the gradients of the PCO(2)/ventilation response lines and raised the intercept. Other changes were increased respiratory minute volume and peak expiratory flow and decreased PetCO(2) and tidal volume.

Analgesics, Opioid↗

PubMed1999

Perfluorocarbon priming and surfactant: physiologic and pathologic effects.

OBJECTIVE: To test the hypothesis that perfluorocarbon (PFC) priming before surfactant administration improves gas exchange and lung compliance, and also decreases lung injury, more than surfactant alone. DESIGN: Prospective, randomized animal study. SETTING: Animal research laboratory of Children's Hospital of St. Paul. SUBJECTS: Thirty-two newborn piglets, weighing 1.55 +/- 0.18 kg. INTERVENTIONS: We studied four groups of eight animals randomized after anesthesia, paralysis, tracheostomy, and establishment of lung injury using saline washout to receive one of the following treatments: a) surfactant alone (n = 8); b) priming with the PFC perflubron alone (n = 8); c) priming with perflubron followed by surfactant (n = 8); and d) no treatment (control; n = 8). Perflubron priming was achieved by instilling perflubron via the endotracheal tube in an amount estimated to represent the functional residual capacity, ventilating the animal for 30 mins, and then removing perflubron by suctioning. After all treatments were given, animals were mechanically ventilated for 4 hrs. MEASUREMENTS AND MAIN RESULTS: We evaluated oxygenation, airway pressures, respiratory system compliance, and hemodynamics at baseline, after induction of lung injury, and at 30-min intervals for 4 hrs. Histopathologic evaluation was carried out using a semiquantitative scoring system and by computer-assisted morphometric analysis. After all treatments, animals had decreased oxygenation indices (p < .001) and increased respiratory system compliance (p < .05). Animals in PFC groups had similar physiologic responses to treatments as animals treated with surfactant only; both the PFC-treated groups and the surfactant-treated animals required lower mean airway pressures throughout the experiment (p < .001) and had higher pH levels at 90 and 120 mins (p < .05) compared with the control group. Pathologic analysis demonstrated decreased lung injury in surfactant-treated animals compared with animals treated with PFC or the controls (p < .02). CONCLUSIONS: Priming the lung with PFC neither improved the physiologic effects of exogenous surfactant nor improved lung pathology in this animal model.

Animals↗

PubMed1998

High-frequency oscillation versus conventional ventilation following surfactant administration and partial liquid ventilation.

Surfactant followed by partial liquid ventilation (PLV) with perfluorocarbon (PFC; LiquiVent) improves oxygenation, lung compliance, and lung pathology in lung-injured animals receiving conventional ventilation (CV). In this study, we hypothesize that high-frequency oscillation (HFO) and CV will provide equivalent oxygenation in lung-injured animals following surfactant repletion and PLV, once lung volume is optimized. After saline-lavage lung injury during CV, newborn piglets were randomized to either HFO (n = 10) or CV (n = 9). HFO animals were stabilized over 15 min without optimization of lung volume; CV animals continued treatment with time-cycled, pressure-limited, volume-targeted ventilation. All animals then received 100 mg/kg of surfactant (Survanta). Thirty minutes later, all received intratracheal PFC to approximate functional residual capacity. Thirty minutes after PLV began, mean airway pressure (MAP) in both groups was increased to improve oxygenation. MAP was directly adjusted during HFO; PEEP and PIP were adjusted during IMV, maintaining a pressure sufficient to deliver 15 mL/kg tidal volume. Animals were treated for 4 h. The CV group showed improved oxygenation following surfactant administration (OI: 26.79 +/- 1.98 vs. 8.59 +/- 6.29, P < 0.0004), with little further improvement following PFC administration or adjustments in MAP. Oxygenation in HFO-treated animals did not improve following surfactant, but did improve following PFC (0I: 27.78 +/- 6.84 vs. 15.86 +/- 5.53, P < 0.005) and adjustments in MAP (OI: 15.86 +/- 5.53 vs. 8.96 +/- 2.18, P < 0.03). After MAP adjustments, there were no significant intergroup differences in oxygenation. Animals in the CV group required lower MAP than animals in the HFO group to maintain similar oxygenation. We conclude that surfactant repletion followed by PLV improves oxygenation during both CV and HFO. The initial response to administration of surfactant and PFC was different for the conventional and high-frequency oscillation groups, likely reflecting the ventilation strategy used; animals in the CV group responded most to surfactant, whereas animals in the HFO group responded most after PFC instillation. The ultimately similar oxygenation of the two groups once lung volume had been optimized suggests that HFO may be used effectively during administration of, and treatment with, surfactant and perfluorocarbon.

Animals↗

PubMed1998

Dynamics of spontaneous breathing during patient-triggered partial liquid ventilation.

This study evaluates different ventilator strategies during gas (GV) and partial liquid ventilation (PLV) in spontaneously breathing animals. We hypothesized that during PLV, spontaneously breathing animals would self-regulate respiratory parameters by increasing respiratory rate (RR) and minute ventilation (V'E) when compared to animals mechanically ventilated with gas, and further that full synchronization of each animal's effort to the ventilator cycle would decrease RR at stable tidal volumes (V(T)). We studied 12 newborn piglets (1.54 +/- 0.24 kg) undergoing GV and PLV in 3 different modes: intermittent mandatory ventilation (IMV), synchronized IMV (SIMV), and assist control ventilation (AC). Modes occurred sequentially in random order during GV first, with the same order then repeated during PLV. Animals initially received continuous positive airway pressure (CPAP) and returned to CPAP during PLV at the end of the experiment. Pressure-limited, volume-targeted ventilation was used with a tidal volume goal of 13 cc/kg. Rate was set at 10/min during IMV and SIMV, with a back-up rate of 10/min during AC. RR, V'E, mechanical (V(T)) and spontaneous tidal volumes (sV(T)) were measured breath-to-breath using a computer-assisted lung mechanics analyzer; mean values were determined over 30-min periods. Data analysis used paired t-tests with Bonferroni correction as needed (P < 0.05). Blood gases were stable in all modes during GV and PLV. RR (min(-1)) and V'E (L x min(-1)/kg) increased in all modes from GV to PLV (RR: CPAP 71 vs. 128; IMV 69 vs. 112; SIMV 65 vs. 107; AC 33 vs. 47. V'E: CPAP 0.47 vs. 0.72; IMV 0.46 vs. 0.61; SIMV 0.45 vs. 0.61; AC 0.38 vs. 0.53; P < 0.05). Intermode comparisons during PLV showed a lower RR with AC (P < 0.02), and a higher V'E with CPAP (P < 0.05). V(T) and dynamic respiratory system compliance decreased from GV to PLV (V(T) P < 0.05; C(rs,dyn) P < 0.01); sV(T) remained unchanged. V(T) and sV(T) did not differ in intermode comparisons. We conclude that during PLV, spontaneously breathing piglets with normal lungs maintain physiologic blood gases by increasing V'E through increased RR. AC produced the most efficient respiratory pattern during PLV, with increased V'E achieved by a modest increase in RR.

Animals↗

PubMed1997

Lower respiratory rates without decreases in oxygen consumption during neonatal synchronized intermittent mandatory ventilation.

OBJECTIVE: We tested the hypothesis that synchronization to patient effort during intermittent mandatory ventilation (SIMV), when compared to conventional unsynchronized intermittent mandatory ventilation (IMV), will decrease energy expenditure, as reflected by decreased oxygen consumption (VO2). DESIGN: We used a four-period crossover design. Each patient was studied over four 30-min continuous time intervals. Patients were randomized to receive initially IMV or SIMV, then crossed over such that each patient was treated twice with each modality. Data were analyzed using an analysis of variance technique. SETTING: Patients were receiving treatment in the newborn intensive care unit of Children's Hospital, St. Paul. PATIENTS: We studied 17 patients, who ranged from 23 to 37 weeks gestation, were < or = 14 days old, and had study weights from 623 to 3015 g. All were mechanically ventilated for hyaline membrane disease. MEASUREMENTS AND RESULTS: We measured and compared VO2, carbon dioxide consumption (VCO2), minute ventilation (VE), total respiratory rate, heart rate, arterial blood pressure, and arterial oxygen saturation (SaO2) values during IMV and SIMV. Total respiratory rate fell significantly during SIMV (73 +/- 26 during IMV, 57 +/- 17 during SIMV, p < 0.01) in spite of no significant change in VO2 (0.6 +/- 0.16% fall in VO2 during SIMV) or VCO2 (4.2 +/- 0.19% increase in VCO2 during SIMV) values. Moreover, there were no significant differences in heart rate, blood pressure, VE, or SaO2 values with either form of therapy. CONCLUSIONS: Though total respiratory rate fell, these data do not support the hypothesis that SIMV significantly reduces respiratory rate by decreasing oxygen consumption and carbon dioxide production during infant mechanical ventilation. Rather, the marked fall in respiratory rate may be due to a more efficient respiratory pattern.

Analysis of Variance↗

PubMed1997

Partial liquid ventilation: a comparison using conventional and high-frequency techniques in an animal model of acute respiratory failure.

OBJECTIVE: To test the hypothesis that high-frequency ventilation (HFV), when compared with conventional techniques, enhances respiratory gas exchange during partial liquid ventilation (PLV). DESIGN: A four-period crossover design. SETTING: Animal research laboratory of Children's Health Care-St. Paul. SUBJECTS: Thirty-two newborn piglets, weighing 1.40 +/- 0.39 kg. INTERVENTIONS: Animals were divided into four groups of eight animals: a) PLV with high-frequency jet ventilation; b) PLV with jet ventilation using a background intermittent mandatory ventilation (IMV) rate; c) PLV with high-frequency oscillation; or d) PLV with high-frequency flow interruption using a background IMV rate. After anesthesia, paralysis, and tracheotomy, a normal saline wash procedure produced lung injury. Perfluorocarbon was then instilled via the endotracheal tube in an amount estimated to represent functional residual capacity. Animals received randomly either PLV using conventional techniques or PLV using the selected HFV technique as initial treatment. Then, animals were crossed over to the alternative treatment at equal mean airway pressure, as measured at the endotracheal tube tip. This sequence was repeated for a total of four crossover periods, such that all animals were treated twice with PLV using conventional techniques and twice with PLV using HFV. MEASUREMENTS AND MAIN RESULTS: We measured airway pressures at the endotracheal tube tip, aortic and central venous blood pressures, arterial blood gases, and respiratory system mechanics at baseline, after induction of lung injury, and at specified intervals throughout the experiment. Measurements were made before and 15 mins after crossovers, then ventilators were adjusted to normalize gas exchange. Measurements were again made 30 mins later, at the end of the treatment period. All types of PLV provided adequate gas exchange. Only PLV using jet ventilation with IMV produced gas exchange equal to that seen during PLV using conventional techniques at equivalent mean airway pressure. By the end of the treatment periods, only PLV using high-frequency oscillation continued to require higher airway pressure than PLV using conventional techniques for equivalent gas exchange. CONCLUSIONS: Gas exchange was not enhanced during PLV-HFV. Application of HFV with PLV provides no clear acute physiologic advantages to PLV using more conventional techniques.

Animals↗

PubMed1997

Prolonged partial liquid ventilation using conventional and high-frequency ventilatory techniques: gas exchange and lung pathology in an animal model of respiratory distress syndrome.

OBJECTIVE: To evaluate the effect of prolonged partial liquid ventilation with perflubron (partial liquid ventilation), using conventional and high-frequency ventilatory techniques, on gas exchange, hemodynamics, and lung pathology in an animal model of lung injury. DESIGN: Prospective, randomized, controlled study. SETTING: Animal laboratory of the Infant Pulmonary Research Center, Children's Health Care-St. Paul. SUBJECTS: Thirty-six newborn piglets. INTERVENTIONS: We studied newborn piglets with lung injury induced by saline lavage. Animals were randomized into one of five treatment groups: a) conventional gas ventilation (n = 8); b) partial liquid ventilation with conventional ventilation (n = 7); c) partial liquid ventilation with high-frequency jet ventilation (n = 7); d) partial liquid ventilation with high-frequency oscillation (n = 7); and e) partial liquid ventilation with high-frequency flow interruption (n = 7). After induction of lung injury, all partial liquid ventilation animals received intratracheal perflubron to approximate functional residual capacity. After 30 mins of stabilization, animals randomized to high-frequency ventilation were changed to their respective high-frequency modes. Hemodynamics and blood gases were measured before and after lung injury, after perflubron administration, and then every 4 hrs for 20 hrs. Histopathologic evaluation was carried out using semiquantitative scoring and computer-assisted morphometric analysis on pulmonary tissue from animals surviving at least 16 hrs. MEASUREMENTS AND MAIN RESULTS: All animals developed acidosis and hypoxemia after lung injury. Oxygenation significantly (p < .001) improved after perflubron administration in all partial liquid ventilation groups. After 4 hrs, oxygenation was similar in all ventilator groups. The partial liquid ventilation-jet ventilation group had the highest pH; intergroup differences were seen at 16 and 20 hrs (p < .05). The partial liquid ventilation-oscillation group required higher mean airway pressure; intergroup differences were significant at 4 and 8 hrs (p < .05). Aortic pressures, central venous pressures, and heart rates were not different at any time point. Survival rate was significantly lower in the partial liquid ventilation-flow interruption group (p < .05). All partial liquid ventilation-treated animals had less lung injury compared with gas-ventilated animals by both histologic and morphometric analysis (p < .05). The lower lobes of all partial liquid ventilation-treated animals demonstrated less damage than the upper lobes, although scores reached significance (p < .05) only in the partial liquid ventilation-conventional ventilation animals. CONCLUSIONS: In this animal model, partial liquid ventilation using conventional or high-frequency ventilation provided rapid and sustained improvements in oxygenation without adverse hemodynamic consequences. Animals treated with partial liquid ventilation-flow interruption had a significantly decreased survival rate vs. animals treated with the other studied techniques. Histopathologic and morphometric analysis showed significantly less injury in the lower lobes of lungs from animals treated with partial liquid ventilation. High-frequency ventilation techniques did not further improve pathologic outcome.

Animals↗

PubMed1997

Exogenous surfactant and partial liquid ventilation: physiologic and pathologic effects.

We compared the effects of surfactant and partial liquid ventilation (PLV), and the impact of administration order, on oxygenation, respiratory system compliance (Crs), hemodynamics, and lung pathology in an animal lung injury model. We studied four groups: surfactant alone (S; n = 8); partial liquid ventilation alone (PLV-only; n = 8); surfactant followed by partial liquid ventilation (S-PLV; n = 8); and partial liquid ventilation-followed by surfactant (PLV-S; n = 8). Following treatments, all animals had improved oxygenation index (OI) and Crs. Animals in PLV groups showed continued improvement over 2 h (% change OI: PLV-S -83% versus S -47%, p < 0.05; % change Crs: S-PLV 73% versus S 13%, p < 0.05). We also saw administration-order effects: surfactant before PLV improved Crs (0.92 ml/cm H2O after surfactant versus 1.13 ml/cm H2O after PLV, p < 0.02) without changing OI, whereas surfactant after PLV did not change Crs and OI increased (5.01 after PLV versus 8.92 after surfactant, p < 0.03). Hemodynamics were not different between groups. Pathologic analysis demonstrated decreased lung injury in dependent lobes of all PLV-treated animals, and in all lobes of S-PLV animals, when compared with the lobes of the S animals (p < 0.05). We conclude that surfactant therapy in combination with PLV improved oxygenation, respiratory system mechanics, and lung pathology to a greater degree than surfactant therapy alone. Administration order affected initial physiologic response and ultimate pathology: surfactant given before PLV produced the greatest improvements in pathologic outcomes.

Animals↗

PubMed1996

Mechanical ventilation of the newborn. An overview.

Mechanical ventilation of the newborn infant is an ever-changing area. Its evolution has been hampered and stimulated by problems of small size, inadequate technology, unexpected complications, and changing expectations. With synchronized ventilation, a new technique in the neonatal ICU, clinicians again are reassessing their assumptions. HFV, a "new" technique for 15 years, has found a niche in the treatment of infants failing CV. Its use as an initial therapy for RDS, advocated by some, remains controversial. Monitoring gas flow patterns, tidal and minute volumes, and lung mechanics has become a part of the CV, but complications still occur. The only thing certain is that change will continue.

History, 20th Century↗

PubMed1995

Evaluation of pulmonary function and analgesia in dogs after intercostal thoracotomy and use of morphine administered intramuscularly or intrapleurally and bupivacaine administered intrapleurally.

Eighteen dogs undergoing lateral thoracotomy at the left fifth intercostal space were randomly assigned to 1 of 3 postoperative analgesic treatment groups of 6 dogs each as follows: group A, morphine, 1.0 mg/kg of body weight, IM; group B, 0.5% bupivacaine, 1.5 mg/kg given interpleurally; and group C, morphine, 1.0 mg/kg given interpleurally. Heart rate, respiratory rate, arterial blood pressure, arterial blood gas tensions, alveolar-arterial oxygen differences, rectal temperature, pain score, and pulmonary mechanics were recorded hourly for the first 8 hours after surgery, and at postoperative hours 12, 24, and 48. These values were compared with preoperative (control) values for each dog. Serum morphine and cortisol concentrations were measured at 10, 20, and 30 minutes, hours 1 to 8, and 12 hours after treatment administration. All dogs had significant decreases in pHa, PaO2, and oxygen saturation of hemoglobin, and significant increases in PaCO2 and alveolar-arterial oxygen differences in the postoperative period, but these changes were less severe in group-B dogs. Decreases of 50% in lung compliance, and increases of 100 to 200% in work of breathing and of 185 to 383% in pulmonary resistance were observed in all dogs after surgery. Increases in work of breathing were lower, and returned to preoperative values earlier in group-B dogs. The inspiratory time-to-total respiratory time ratio was significantly higher in group-B dogs during postoperative hours 5 to 8, suggesting improved analgesia. Blood pressure was significantly lower in group-A dogs for the postoperative hour. Significant decreases in rectal temperature were observed in all dogs after surgery, and hypothermia was prolonged in dogs of groups A and C. Significant differences in pain score were not observed between treatment groups. Cortisol concentration was high in all dogs after anesthesia and surgery, and was significantly increased in group-B dogs at hours 4 and 8. Significant differences in serum morphine concentration between groups A and C were only observed 10 minutes after treatment administration. In general, significant differences in physiologic variables between groups A and C were not observed. Results of the study indicate that the anesthesia and thoracotomy are associated with significant alterations in pulmonary function and lung mechanics. Interpleurally administered bupivacaine appears to be associated with fewer blood gas alterations and earlier return to normal of certain pulmonary function values. Interpleural administration of morphine does not appear to provide any advantages, in terms of analgesia or pulmonary function, compared with its IM administration.

Analgesia↗

PubMed1993

The effects of bedside pulmonary mechanics testing during infant mechanical ventilation: a retrospective analysis.

We examined the effects of regular bedside testing of pulmonary mechanics (PM) on the outcome of 468 acutely ill, mechanically ventilated neonates. During the first of two 18-month study periods, 217 infants were mechanically ventilated without the assistance of PM measurements. During the second 18-month period, 251 infants were ventilated with the assistance of at least daily PM measurements. Using data obtained from the PM tests, we adjusted the infants' ventilators to maintain tidal volume, inspiratory time, and pressure-volume loops within predetermined limits. With the exception of the PM measurements, given the limitations of retrospective analyses, both groups of infants received identical medical and nursing care. The infants ventilated with the assistance of PM testing developed fewer pneumothoraces (4.0%; 10/251) vs. no PM testing, 10.1% (22/217); P < 0.05 by Chi-square analysis]. Infants weighing less than 1,500 g ventilated with the assistance of PM measurements had less intraventricular hemorrhage (IVH) overall, most notably, less grades I and II IVH (total IVH-PM testing, 39.1% vs. no PM testing, 65.7%; P < 0.01; Grades I-II IVH-PM testing, 30.4% vs. no PM testing, 54.9%; P < 0.01). IVH incidence was decreased independent of pneumothorax occurrence. Survival rates, incidences of bronchopulmonary dysplasia, and durations of mechanical ventilation and hospitalization were similar. This retrospective analysis suggests that PM testing during infant mechanical ventilation reduces common acute ventilator-associated complications.

Bronchopulmonary Dysplasia↗

PubMed1990

Effect of spontaneous and mechanical breathing on dynamic lung mechanics in hyaline membrane disease.

We measured then compared the dynamic lung mechanics of spontaneous breaths and mechanical breaths in 9 mechanically ventilated neonates with hyaline membrane disease. All were receiving intermittent mandatory ventilation. All breathed spontaneously between ventilator breaths. Tidal volume, transpulmonary pressure, dynamic lung compliance, airways resistance, and peak inspiratory and peak expiratory gas flows were determined for both the mechanical and the spontaneous breaths. The mechanical breaths consistently had larger tidal volumes, higher transpulmonary pressures, higher airway resistance, and lower lung compliance values (P less than 0.05). Peak inspiratory and expiratory gas flows were also higher (P less than 0.01) during mechanical breathing. The spontaneous breaths generated by patients and the mechanical breaths generated by mechanical ventilators are different. The lung mechanics measurements of these two different types of breathing should be collected, analyzed, and reported separately.

Humans↗

PubMed1989

Comparison of high-frequency oscillatory ventilation and high-frequency jet ventilation in cats with normal lungs.

Four adult cats received alternating high-frequency oscillatory ventilation (HFOV) and high-frequency jet ventilation (HFJV) at equivalent proximal airway pressures. Physiologic measurements were made before and after each ventilator change. Proximal airway pressures were then adjusted as necessary to reestablish normal pH and PaCO2 values. Aortic, pulmonary artery, and central venous pressures were monitored. Cardiac outputs were measured. Pulmonary and systemic vascular resistance, intrapulmonary shunt, and alveolar-arterial oxygen gradient were determined. Following the change from HFOV to HFJV at similar proximal airway pressures, HFJV always produced higher pH values (P less than 0.0001), higher PaO2 values (P less than 0.05), lower PaCO2 values (P less than 0.0001), as well as higher cardiac outputs (P less than 0.01), lower pulmonary artery pressures (P less than 0.001), and lower pulmonary vascular resistances (P less than 0.001). Following the reciprocal crossover, from HFJV to HFOV, HFJV pH values were again higher (P less than 0.001), and PaCO2 values were again lower (P less than 0.001). A comparison of HFOV and HFJV at similar pH and PaCO2 values showed that HFOV consistently required higher peak inspiratory pressures (P less than 0.001), higher mean airway pressure (P less than 0.001), and higher pressure wave amplitudes (P less than 0.001). Under the circumstances of this study, HFJV produced better gas exchange at lower proximal airway pressures.

Airway Resistance↗

PubMed1989

Determining optimum inspiratory time during intermittent positive pressure ventilation in surfactant-depleted cats.

This study compares two methods of selecting inspiratory time (Ti) during mechanical ventilation. One selects a standard Ti producing a brief inspiratory pressure plateau (P). The other uses simultaneous pressure, flow and tidal volume (VT) waveforms, generated by a computer-assisted lung mechanics analyzer, to reduce Ti to the point where Vt ceases to accumulate and flow returns to zero. This method does not produce a pressure plateau (NP). Following saline lung washout, ten intubated, paralyzed surfactant-depleted cats were ventilated with pressure-preset infant ventilators at constant measured VT and rates. Five animals were initially ventilated with P (Ti = 0.98 +/- 0.02 s) and five with NP (Ti = 0.77 +/- 0.10 s). Ti was then varied to produce P or NP by using a four-period crossover design. All other ventilator variables remained constant. Intravascular pressures, thermodilution cardiac outputs, arterial and mixed venous blood gases and oxygen saturations, airway pressures, Ti, VT, and gas flows were measured; respiratory system mechanics, alveolar-arterial oxygen gradients, and intrapulmonary shunts were determined for each study period. When P and NP states were compared, only mean airway pressures differed (10.1 vs. 8.9 cmH2O; P less than 0.001). Blood gas values, intravascular pressures, cardiac output, and respiratory system mechanics were all similar. Under the conditions of this study, there was no advantage to prolonging Ti beyond the point where VT ceased to accumulate.

Airway Resistance↗

PubMed1988

Identifying lung overdistention during mechanical ventilation by using volume-pressure loops.

We measured the pulmonary mechanics of 23 mechanically ventilated neonates. Airway pressures, inspiratory and expiratory flows were simultaneously measured. Values for respiratory system mechanics were then derived from these data by using a personal computer and a special software program. Volume-pressure (V-P) loops and respiratory system compliance values were determined for representative mechanical breaths. Twelve infants had normal-appearing V-P loops. Eleven had V-P loops characteristic of lung overdistention, showing decreasing changes in volume with progressive increases in pressure. To quantify this visual observation, we determined the change in compliance during the last 20% of inspiration (C20). We then compared this value to the total compliance value for the entire breath (C) using the ratio C20/C. Mean values for C, C20, and C20/C were compared for the two patient groups. Total respiratory system compliance values were similar. C20 values were decreased in those patients with V-P loops showing overdistention. C20/C values were significantly decreased in those patients with V-P loop evidence of overdistention. Patients with V-P loop evidence of overdistention all had C20/C values less than 0.8. Those with normal-appearing V-P loops all had C20/C values greater than 1.0. The C20/C ratio appears to effectively quantitate visual V-P loop evidence of lung overdistention during mechanical ventilation.

Barotrauma↗