Peak Inspiratory Pressure Values Research Articles

Comparison of double-lung jet ventilation and one-lung ventilation for thoracotomy

Thoracic surgery requires immobilization of the operating area. Usually, this is achieved with one-lung ventilation (OLV), however this may still lead to some movement. High-frequency jet ventilation (HFJV) may be an alternative way of ventilation in thoracic surgery. The purpose of this study was to determine the effectiveness of HFJV as an alternative option to OLV for thoracic procedures. Sixty patients were randomized to receive either HFJV (n = 29) or OLV (n = 31) during the operation. During the course of the study 10 patients were excluded (4 patients in HFJV group and 6 patients in OLV group). The following haemodynamic and ventilatory parameters were recorded: heart rate, systolic and mean blood pressure, ventricular stroke volume, cardiac index, systemic vascular resistance, peak inspiratory pressure, oxygen saturation, PaO2 and PaCO2. Overall parameters were documented before the initiation of the chosen mode of ventilation every 15 min during the operation. Patients in both groups showed comparable cardiovascular function. Mean values of peak inspiratory pressure were significantly higher in the OLV group. Oxygen saturation values were statistically higher in the HFJV group. PaCO2 values were similar in both during surgery, but were higher in the OLV group after awakening. Mean values of shunt fraction were lower in the HFJV group. Lower values of peak inspiratory pressure were therefore associated with higher partial pressure of carbon dioxide levels in the HFJV group. In the OLV group, 44% of patients experienced a postoperative sore throat. Operating conditions were comparable. HFJV is safe option, comparable to OLV and offers some advantages for open-chest thoracic procedures.

Is there an Advantage of Using Pressure Support Ventilation with Volume Guarantee in the Initial Management of Premature Infants with Respiratory Distress Syndrome? A pilot study

To evaluate the feasibility of using the pressure support ventilation with volume guarantee (PSV-VG) as an initial ventilatory mode in preterm infants with respiratory distress syndrome (RDS) after surfactant treatment to achieve accelerated weaning of peak inspiratory pressure (PIP) and mean airway pressure (MAP). Initial 24-hour ventilatory parameters were compared in two groups of preterm infants managed by PSV-VG and the synchronized intermittent mandatory ventilation (SIMV) mode in a randomized controlled pilot study after surfactant treatment for RDS. A total of 16 babies were randomized to PSV-VG (1198+/-108 g [mean+/-SEM]; 27.9+/-0.6 weeks) and 18 babies to SIMV (birth weight 1055+/-77 g; gestational age 27.4+/-0.5 weeks). Repeated measures analysis of variance was used to compare serial values of PIP and MAP in the two groups. The PIP and MAP decreased over time (p<0.001) during the first 24 hours after surfactant administration in both groups but the decrease in MAP was faster in the SIMV group compared to PSV-VG group (p=0.035). The median numbers of blood gases during the first 24 hours were four and two in the SIMV and PSV-VG groups, respectively (p<0.001). The overall outcomes were not significantly different between the two groups. PSV-VG did not offer any ventilatory advantage over SIMV in the initial management of surfactant-treated premature newborns with RDS except for minimizing the number of blood gases.

One-Lung Ventilation with High Tidal Volumes and Zero Positive End-Expiratory Pressure Is Injurious in the Isolated Rabbit Lung Model

We tested the hypothesis that one-lung ventilation (OLV) with high tidal volumes (Vt) and zero positive end-expiratory pressure (PEEP) may lead to ventilator-induced lung injury. In an isolated, perfused rabbit lung model, Vt and PEEP were set to avoid lung collapse and overdistension in both lungs, resulting in a straight pressure-time (P-vs-t) curve during constant flow. Animals were randomized to (a) nonprotective OLV (left lung) (n = 6), with Vt values as high as before randomization and zero PEEP; (b) protective OLV (left lung) (n = 6), with 50% reduction of Vt and maintenance of PEEP as before randomization; and (c) control group (n = 6), with ventilation of two lungs as before randomization. The nonprotective OLV was associated with significantly smaller degrees of collapse and overdistension in the ventilated lung (P < 0.001). Peak inspiratory pressure values were higher in the nonprotective OLV group (P < 0.001) and increased progressively throughout the observation period (P < 0.01). The mean pulmonary artery pressure and lung weight gain values, as well as the concentration of thromboxane B2, were comparatively higher in the nonprotective OLV group (P < 0.05). A ventilatory strategy with Vt values as high as those used in the clinical setting and zero PEEP leads to ventilator-induced lung injury in this model of OLV, but this can be minimized with Vt and PEEP values set to avoid lung overdistension and collapse.

One-lung ventilation with high tidal volumes and zero positive end-expiratory pressure is injurious in the isolated rabbit lung model.

We tested the hypothesis that one-lung ventilation (OLV) with high tidal volumes (VT) and zero positive end-expiratory pressure (PEEP) may lead to ventilator-induced lung injury. In an isolated, perfused rabbit lung model, VT and PEEP were set to avoid lung collapse and overdistension in both lungs, resulting in a straight pressure-time (P-vs-t) curve during constant flow. Animals were randomized to (a) nonprotective OLV (left lung) (n = 6), with VT values as high as before randomization and zero PEEP; (b) protective OLV (left lung) (n = 6), with 50% reduction of VT and maintenance of PEEP as before randomization; and (c) control group (n = 6), with ventilation of two lungs as before randomization. The nonprotective OLV was associated with significantly smaller degrees of collapse and overdistension in the ventilated lung (P < 0.001). Peak inspiratory pressure values were higher in the nonprotective OLV group (P < 0.001) and increased progressively throughout the observation period (P < 0.01). The mean pulmonary artery pressure and lung weight gain values, as well as the concentration of thromboxane B(2), were comparatively higher in the nonprotective OLV group (P < 0.05). A ventilatory strategy with VT values as high as those used in the clinical setting and zero PEEP leads to ventilator-induced lung injury in this model of OLV, but this can be minimized with VT and PEEP values set to avoid lung overdistension and collapse. One-lung ventilation with high tidal volumes and zero positive end-expiratory pressure (PEEP) is injurious in the isolated rabbit lung model. A ventilatory strategy with tidal volumes and PEEP set to avoid lung overdistension and collapse minimizes lung injury during one-lung ventilation in this model.

Oxygen in the works of three Spanish enlightened scientist: Ignacio Ma Ruiz de Luzuriaga, Antoni Martı́ i Franqués and Antoni Cibat

To determine which of two facemask grip techniques for two-person facemask ventilation was more effective in novice clinicians, the traditional E-C clamp (EC) grip or a thenar eminence (TE) technique.Prospective, randomized, crossover comparison study.Operating room of a university hospital.60 novice clinicians (medical and paramedic students).Subjects were assigned to perform, in a random order, each of the two mask-grip techniques on consenting ASA physical status 1, 2, and 3 patients undergoing elective general anesthesia while the ventilator delivered a fixed 500 mL tidal volume (VT). In a crossover manner, subjects performed each facemask ventilation technique (EC and TE) for one minute (12 breaths/min). The primary outcome was the mean expired VT compared between techniques. As a secondary outcome, we examined mean peak inspiratory pressure (PIP).The TE grip provided greater expired VT (379 mL vs 269 mL), with a mean difference of 110 mL (P < 0.0001; 95% CI: 65, 157). Using the EC grip first had an average VT improvement of 200 mL after crossover to the TE grip (95% CI: 134, 267). When the TE grip was used first, mean VTs were greater than for EC by 24 mL (95% CI: -25, 74). When considering only the first 12 breaths delivered (prior to crossover), the TE grip resulted in mean VTs of 339 mL vs 221 mL for the EC grip (P = 0.0128; 95% CI: 26, 209). There was no significant difference in PIP values using the two grips: the TE mean (SD) was 14.2 (7.0) cm H2O, and the EC mean (SD) was 13.5 (9.0) cm H2O (P = 0.49).The TE facemask ventilation grip results in improved ventilation over the EC grip in the hands of novice providers.

The outcome of early pressure-controlled inverse ratio ventilation on patients with severe acute respiratory distress syndrome in surgical intensive care unit

Background: Pressure-controlled inverse ratio ventilation (PC-IRV) was used in patients with acute respiratory distress syndrome (ARDS) after failed volume-cycled conventional ratio ventilation (VC-CRV). The aim of this study was to evaluate the outcome of early PC-IRV in severe ARDS. Methods: Twenty patients with severe ARDS were switched from VC-CRV to PC-IRV if they failed to maintain SaO 2 >90% by the following criteria: peak inspiratory pressure (PIP) >35 cm H 2O, FIO 2 = 60%, and positive end-expiratory pressure (PEEP) 10 cm H 2O. Results: The values of PIP, mean airway pressure, minute volumes, and lung injury score in VC-CRV were 43.9 ± 8.0 cm H 2O, 19.5 ± 6.4 cm H 2O, 11.0 ± 2.1 L/min, and 2.8 ± 0.2 respectively. In PC-IRV, the corresponding data were 31.8 ± 5.1 cm H 2O, 25.4 ± 4.6 cm H 2O, 8.3 ± 0.9 L/min, and 2.5 ± 0.4. All of these parameters were significantly different. Fifteen patients (75%) survived their intensive care unit stay. Conclusions: Early PC-IRV in severe ARDS improves oxygenation, facilitates tapering of high fraction of inspiratory oxygen, and decreases high PEEP or PIP, and then results in the improvement of the patient’s outcome.

Remifentanil infusion facilitates early recovery for obese outpatients undergoing laparoscopic cholecystectomy.

D espite the well known adverse effects of obesity, it is still the most common nutritional disorder in the United States. Unfortunately, there is a paucity of data supporting the use of one anesthetic technique over another in obese (versus nonobese) patient populations. Prolonged emergence time from general anesthesia in obese patients can be problematic in the ambulatory setting because it can delay the early recovery process. Cork et al. (1) reported that the use of IV anesthetic and analgesic drugs does not guarantee a shorter emergence period in the obese population. Because remifentanil can reduce the required endtidal concentration of volatile anesthetics by up to 50% (2,3), we hypothesized that the use of a remifentanil infusion during a sevoflurane-based anesthetic would facilitate emergence from anesthesia in obese patients undergoing ambulatory surgery.

Inhalation injury severity scoring system: a quantitative method.

Inhalation injury, a major contributor to burn-related mortality, has been difficult to quantify. A scoring system paralleling current adult respiratory distress syndrome systems has the potential to distinguish survivors from nonsurvivors. The utility of the PaO2/FiO2 (P/F) ratio in predicting injury severity was first examined. In a review of 120 patients with inhalation injury, those with P/F ratios greater than or equal to 300 after resuscitation were more likely to survive than those with ratios less than 300. The P/F ratio had no value when obtained before resuscitation. Next, a scoring system was developed to assist in comparing the severity of injury in ventilator-dependent patients with burns. Measurements were recorded prospectively in four categories: chest x-ray evaluation, P/F ratio, peak inspiratory pressure, and bronchoscopy. When comparing survivors (20) versus nonsurvivors (6), significant differences were found early (day 0, day 1, and week 1) for P/F ratio and overall severity score. Differences were seen later (week 1 and week 2) for chest x-ray evaluation and peak inspiratory pressure values. Because of low numbers the value of bronchoscopy could not be evaluated. The role of an inhalation injury severity scoring system for predicting survival should be examined in larger prospective trials.

Aerosolized Versus Instilled Exogenous Surfactant in a Nonuniform Pattern of Lung Injury

Previous studies have shown that the underlying patterns of lung injury influence subsequent responses to aerosolized exogenous surfactant. The purpose of this study was to compare aerosolized versus tracheally instilled surfactant in a nonuniform lung injury. Adult sheep underwent whole lung lavage with subsequent HCl instillation into the right middle lobe (RML) and lingula (LING) to create a nonuniform injury. Animals were treated with either nebulized surfactant (Neb.Surf.), tracheally instilled surfactant (Inst.Surf.), or nebulized saline (Neb. Saline). PaO2, alveolar-arterial O2 gradient (PAO2-PaO2), PaCO2, and peak inspiratory pressure (PIP) values all significantly improved during 180 min of continuous aerosolization for Neb.Surf. animals compared with pretreatment values (p < 0.01) and with the other two treatment groups (p < 0.01). Although PaO2 and (PAO2-PaO2) values improved for the Inst.Surf. group by 180 min after treatment (p < 0.05), PaCO2 and PIP values were significantly increased 30 min after surfactant instillation (p < 0.05). Neb. Saline animals had no significant changes in physiologic parameters over 180 min. Approximately 8% of the total aerosolized surfactant deposited in lung tissue was recovered from the more severely damaged RML and LING, compared with approximately 50% of the total instilled surfactant recovered from these lobes. This resulted in significantly greater percentages of the total aerosolized surfactant deposited in each of the remaining lobes compared with the percent deposition of instilled surfactant (p < 0.05). Both the underlying pattern of lung injury and the exogenous surfactant delivery technique may influence clinical responses to surfactant therapy in patients with the adult respiratory distress syndrome (ARDS).

Pulmonary Barotrauma in Mechanical Ventilation: Patterns and Risk Factors

The incidence of mediastinal emphysema (ME) and pneumothorax (PTX) was analyzed to determine the roentgenographic patterns and risk factors for the development of barotrauma in a population of mechanically ventilated patients. The roentgenograms of 139 intubated patients admitted to our medical intensive care unit over a ten-month period were evaluated for the presence of ME and PTX. Barotrauma was diagnosed in 34 of these patients, and ME was the initial manifestation in 24 patients. Of these patients with initial ME, ten subsequently developed PTX, a positive predictive value of 42 percent. The adult respiratory distress syndrome (ARDS) patient population was at highest risk for barotrauma, with an intermediate risk seen in those admitted with COPD or pneumonia. Values of peak inspiratory pressure, positive end-expiratory pressure level, respiratory rate, tidal volume, and minute ventilation were significantly elevated in patients who developed barotrauma as compared with patients who did not develop barotrauma. However, these elevations in part reflect the high incidence of barotrauma in the ARDS population, a patient group in which all of the above parameters were elevated.

Lack of relationship between the true airway pressure and the pressure displayed with an infant ventilator

To establish if the pressure indicated in the manometer of an infant ventilator (IV 100B, Sechrist, Anaheim, CA) reflects the true pressure delivered to the proximal airway during mechanical ventilation in the neonatal ICU. With approval of our Institutional Research Board, data were collected prospectively. Peak inspiratory pressure and end-expiratory pressure were measured at the "Y" piece of the breathing tubing. Pressure readings from the conventional ventilator's manometer were compared with simultaneously obtained measurements using an electronic monitor. This study was conducted in a 45-bed neonatal ICU, admitting 700 to 750 newborns per year. Twelve neonates who required mechanical ventilation were included in the study. Specific interventions were not made by study design. Measurements routinely obtained were compared. Two hundred seventy-five simultaneous measurements of peak inspiratory pressure and positive end-expiratory pressure were compared. Peak inspiratory pressure values were higher with the electronic monitor in 273 (99%) of 275 measurements and the mean of the differences between the electronic monitor and ventilator's manometer was statistically significant (p less than .001). For positive end-expiratory pressure measurements, values indicated by the electronic monitor were lower in 152 (55%) of 275 determinations, equal in 65 (23%), and higher in 58 (21%) determinations. Percent variations between methods ranged from 0% to 140% for peak inspiratory pressures and from 0% to 500% for positive end-expiratory pressure. These data demonstrate that it is impossible to know the true pressure delivered to the proximal airway of a neonate during mechanical ventilation by observing the ventilator pressure manometer. The manometer readings consistently underestimate the true peak inspiratory pressure values and are very unpredictable regarding positive end-expiratory pressure values. These findings support the use of other methods to monitor the proximal airway pressure besides the ventilator's manometer in the neonatal ICU. Furthermore, mean airway pressure should not be calculated from the pressure readings obtained from the tested ventilator's manometer.

Effects of bovine surfactant in premature lambs after intra-tracheal application

Twenty-two premature lambs (gestational age 124-125 days, term 144-160 days) were intubated and supported by infant ventilators immediately after delivery. Respiratory rate was 60/min, inspiratory time 0.4 s, peak inspiratory pressure (PIP) 35 cm H2O, positive endexpiratory pressure (PEEP) 2 cm H2O, FiO2 1.0. 15 min after delivery 10 lambs (group 1) were treated with 35 mg/kg body weight bovine surfactant (SF-RI 1), whereas 1 ml/kg body weight saline was instilled in 12 lambs as controls (group 2). Sequential measurements of blood gases and acid base status (every 30 min) as well as continuous registration of PIP, PEEP, respiratory rate and tidal volume (TV) were performed in all lambs for 300 min. PIP was varied between 20 and 40 cm H2O in order to attain paCO2 values between 35 and 50 mm Hg. Significantly improved oxygenation was observed in group 1 lambs with maximum differences 30 min after delivery for 2 h. Ventilation was likewise affected: paCO2 and PIP values were significantly lower in the surfactant-treated animals (group 1). Total lung-thorax compliances (calculated from TV and delta P, i.e. PIP-PEEP) per kg body weight also significantly reflected the improvement of pulmonary function in group 1 compared to group 2 lambs. Intratracheal instillation of SF-RI 1 improved gas exchange in premature lambs, whereas control animals exhibited severe respiratory failure characteristic of respiratory distress syndrome (RDS).

The effect of artificial ventilation on cardiovascular status and on heart rate conditioning in the curarized rat.

ABSTRACTThe relationship between artificial ventilation, cardiovascular status, and operant conditioning in the curarized rat was investigated in a series of studies. Two respiratory parameters, peak inspiratory pressure (PIP) and respiratory rate (RR), were sequentially altered in curarized rats while heart rate and variability, and mean blood pressure were recorded. Heart rate increases or decreases were also rewarded in curarized rats ventilated at differing PIP values, 20 cm H2O or 12 cm H2O. Heart rate and variability were also recorded in non‐curarized rats. At PIP 12, heart rate and variability in the curarized rat was very similar to that of the non‐curarized rat. These subjects responded to operant contingencies. Subjects ventilated at PIP 20, however, showed elevated, invariant, and unresponsive heart rates. Ventilation therefore, proved an important determinant of cardiovasculur status and conditionability in the curarized rat. RR was not related to heart rate or variability. Neither PIP nor RR affected blood pressure.

Septic Lung and Shock Lung in Man

Two series of patients were studied by serial measurements of blood gas exchange and pulmonarmonary dysfunction and to evaluate the dangers of respiratory failure in post traumatic patients. There were 27 patients who had sustained profound hemorrhagic shock and massive blood replacement averaging 9.7 liters and 38 patients who suffered general peritonitis or other forms of fulminating nonthoracic sepsis. All were supported by endotrachael intubation and volume controlled ventilators. The overall mortality for the post shock patients without sepsis was 12% while in the septic patients it was 35%. The maximal pulmonary arteriovenous shunt encountered in the post hemorrhagic shock patients at 36 hours averaged 20 plus or minus 8% and was accompanied by high cardiac indices (average 5.1 plus or minus 1.3 L/M-2/min) but no significant rise of pulmonary arterial pressure or peak inspiratory pressure (PIP). Severe pulmonary dysfunction subsequently occurred only in those patients who later became septic. The studies on the septic patients were divided according to the magnitude of the cardiac indices (the high indices averaged 4.8 plus or minus 1.6L/M-2/min) and thelow indices averaged 1.9 plus or minus 1.0 L/M-2/min. In the former, the average maximal shunt of 30 plus or minus 6% was sustained for 4 or more days, accompanied by an elevation of PIP to 36 plus or minus 6 cm H2O and by Pa pressure of 28 plus or minus 5 mm Hg. The patients in low output septic shock usually had an associated bronchopneumonia and had an average venous admixture of 34 plus or minus 8% and PIP values of 41 plus or minus 8 cm H2O. The mean Pa pressure in this group was 29 plus or minus 6 mm Hg.