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At least 199 records · Page 11Linked to original sources

PubMed2006

Acute effects of PEEP on tidal volume and respiratory center output during synchronized ventilation in preterm infants.

BACKGROUND: Positive end expiratory pressure (PEEP) is routinely used in mechanically ventilated preterm infants to maintain lung volume. An acute increase in PEEP can affect lung mechanics and tidal volume, but it is unknown if these effects elicit compensatory changes in respiratory center output. OBJECTIVES: To investigate the acute effects of changes in PEEP on tidal volume (V(T)), lung compliance (C(L)), and respiratory center output (RCO) during synchronized intermittent mandatory ventilation (SIMV) in preterm infants at different levels of basal respiratory drive. METHODS: Preterm infants were studied during SIMV at three levels of PEEP (2, 4, and 6 cm H(2)O for 2-3 min each) and at two levels of inspired CO(2). Peak inspiratory pressure (PIP) was adjusted to maintain the same delta pressure at the airway. RCO was assessed by measuring total diaphragmatic electrical activity. The level of inspired CO(2) was adjusted by modifying the instrumental dead space. RESULTS: Sixteen preterm infants GA: 25 +/- 2 weeks, BW: 786 +/- 242 g, age: 18 +/- 15 days, SIMV: rate 14 +/- 3 b/min, Ti: 0.35 +/- 0.01 s, PIP: 16 +/- 1 cm H(2)O, and FiO(2): 0.31 +/- 0.06 were studied. At both levels of inspired CO(2), C(L), V(T), and V'(E) from spontaneous and mechanical breaths decreased significantly with higher PEEP. RCO did not change, but at lower respiratory drive, there was a trend towards an increase in RCO with higher PEEP. CONCLUSION: Higher PEEP levels can have acute negative effects on lung mechanics and ventilation in preterm infants without a sufficient compensatory increase in RCO.

Humans↗

PubMed2004

[Comparison of eight deep breaths and tidal volume breathing preoxygenation techniques in morbid obese patients].

OBJECTIVE: To compare two techniques of preoxygenation, eight deep breaths (8DB) and tidal volume breathing in obese patients by measuring end-tidal fractional oxygen concentration (FETO2) and apnea time from 100% of hemoglobin saturation to 95% (T95%). STUDY DESIGN: Prospective randomized study. METHODS: Twenty obese patients (BMI >40 kg/m2) without cardiorespiratory disease nor difficult intubation criteria were randomized into two groups of ten. One group received preoxygenation with eight deep breaths in one minute (8DB) and the other with three minutes tidal volume preoxygenation (3TV) both under FIO2 100%. FETO2 every minute of preoxygenation and T95% were measured. Data were analyzed with Mann and Whitney test. A p <0.05 was considered significant. RESULT: There was no significant difference between the groups regarding FETO2 values [84 +/- 4% (8DB) and 88 +/- 5% (3TV)] and T95% [176 +/- 23 s (8DB) and 181 +/- 35 s (3TV)]. The PETCO2 was significantly inferior in the 8DB group at the end of preoxygenation [PETCO2 =29 +/- 1 mmHg (8DB) and PETCO2 =36 +/- 5 mmHg (3TV)]. CONCLUSION: 8DB and 3TV preoxygenation techniques in morbid obese patients induce similar FETO2 and T95%. However hyperventilation effects in the 8DB group are unknown.

Adult↗

PubMed2002

Accuracy of displayed values of tidal volume in the pediatric intensive care unit.

OBJECTIVES: To assess the accuracy of the expired tidal volumes (VT(E)) displayed by one of the most frequently used ventilators that measures exhaled volume at the expiratory valve. DESIGN: Prospective study. SETTING: The intensive care units of a pediatric tertiary referral center in London, UK. PATIENTS: A total of 56 intubated children aged between 3 wks and 16.6 yrs who were clinically stable and ventilated with a Servo 300 ventilator. INTERVENTIONS: The CO2SMO Plus respiratory monitor, which measures flow at the airway opening, was validated using calibrated syringes and appropriate tracheal tubes and connections. Simultaneous in vivo recordings of VT(E) from the Servo 300 and CO2SMO Plus were compared before (displayed Servo VT(E)) and after (effective Servo VT(E)) compensating for ventilator circuit compliance. MEASUREMENTS AND MAIN RESULTS: The in vitro accuracy of the CO2SMO Plus was within +/-5% over a wide range of volumes and measurement conditions. The displayed Servo 300 VT(E) overestimated the true VT(E) by between 2% and 91%. The magnitude of error varied within and between children, according to pressure change (peak inspiratory pressure minus positive end-expiratory pressure), VT(E), and circuit size. Mean (sd) error was 32% (20%) in 40 children with displayed Servo VT(E) of <160 mL and 18% (6%) in 16 subjects with displayed Servo VT(E) of >/=160 mL. After correcting for gas compression, effective VT(E) from the Servo 300 underestimated the true VT(E) by up to 64% in the smallest infants but continued to overestimate by as much as 29% in older children. CONCLUSIONS: The accuracy of tidal volume values is crucially dependent on the site of measurement. Unless measured at the airway opening, displayed values are an inconsistent and misleading indicator of the true volumes delivered.

Adolescent↗

PubMed2002

Partial liquid ventilation versus conventional mechanical ventilation with high PEEP and moderate tidal volume in acute respiratory failure in piglets.

This prospective randomized pilot study aimed to test the hypotheses that partial liquid ventilation combined with a high positive end-expiratory pressure (PEEP) and a moderate tidal volume results in improved gas exchange and lung mechanics without negative hemodynamic influences compared with conventional mechanical ventilation in acute lung injury in piglets. Acute lung injury was induced in 12 piglets weighing 9.0 +/- 2.4 kg by repeated i.v. injections of oleic acid and repeated lung lavages. Thereafter, the animals were randomly assigned either to partial liquid ventilation (n = 6) or conventional mechanical ventilation (n = 6) at a fractional concentration of inspired O(2) of 1.0, a PEEP of 1.2 kPa, a tidal volume < 10 mL/kg body weight (bw), a respiratory rate of 24 breaths/min, and an inspiratory/expiratory ratio of 1:2. Perfluorocarbon liquid 30 mL/kg bw was instilled into the endotracheal tube over 10 min followed by 5 mL/kg bw/h. Continuous monitoring included ECG, mean right atrial, pulmonary artery, pulmonary capillary, and arterial pressures, arterial blood gas, and partial pressure of end-tidal CO(2) measurements. When compared with control animals, partial liquid ventilation resulted in significantly better oxygenation with improved cardiac output and oxygen delivery. Dead space ventilation appeared to be lower during partial liquid ventilation compared with conventional mechanical ventilation. No significant differences were observed in airway pressures, pulmonary compliance, and airway resistance between both groups. The results of this pilot study suggest that partial liquid ventilation combined with high PEEP and moderate tidal volume improves oxygenation, dead space ventilation, cardiac output, and oxygen delivery compared with conventional mechanical ventilation in acute lung injury in piglets but has no significant influence on lung mechanics.

Acute Disease↗

PubMed1992

Variations in tidal volume with portable transport ventilators.

BACKGROUND: As intra- and interhospital transportation of ventilator-dependent patients has become more commonplace, the number of portable transport ventilators has increased. Transport ventilators should be capable of delivering consistent tidal volume (VT) from breath to breath following changes in lung-thorax compliance and airways resistance. We sought to determine the effect of changes in compliance (C) and resistance (R) on the VT delivered by eight commercially available, time-cycled transport ventilators. METHODS & MATERIALS: Each ventilator (PneuPAC Model 2, Autovent 3000, MAX, Bird Transport Mini-TXP, IC-2A, P7, E100i, and Logic 07a) was connected to a calibrated pneumotachograph and a test lung set for normal adult C (C = 100 mL/cm H2O [1.02 L/kPa]) and R (R = 2 cm H2O.s.L-1 [0.2 kPa.s.L-1]), with VT at 1,000 mL. RESULTS: As C and R were manipulated, VT varied widely. Tidal volume decreased least with the P7 and most with the Bird transport ventilator. CONCLUSION: Decreases in VT with a transport ventilator predispose patients to hypoventilation, hypercapnia, and acidemia. Tidal volume often is not monitored continuously during transport, yet large decreases in VT must not be allowed when pulmonary mechanics are unstable. Internal pressure-limiting valves, venturi flow-generating devices, and compression volume in the breathing circuit are at least three factors that affect VT with transport ventilators.

Equipment Design↗

PubMed1994

Tidal volume perception in normal subjects: the effect of altered arterial PCO2.

We examined the relationship between tidal volume (VT) perception and level of CO2. Ten normal subjects were connected to a volume-cycled ventilator set in control mode, and VT and respiratory rate were adjusted until subjects were comfortable. At 2 levels of CO2 which differed by 6-8 mmHg, subjects rated ten different ventilator tidal volumes which ranged from 40-200% of the VT that made them comfortable at the lower CO2. Despite large differences in inspiratory muscle activity, there was no significant difference between the two levels of CO2 for either the exponent [1.39 +/- 0.35 vs 1.36 +/- 0.49 (low CO2 vs high CO2, mean +/- SD), P > 0.5] or constant (-0.09 +/- 0.12 vs -0.14 +/- 0.17, P > 0.1) for VT perception. For the group, there was no correlation between the hypercapnic ventilatory response (HCVR) measured by rebreathing and the exponent for VT perception. We conclude that: (1) the level of CO2 does not influence magnitude estimation of VT; (2) respiratory muscle activity is not essential to VT perception; and (3) there is no correlation between the HCVR and magnitude estimation of VT.

Adult↗

PubMed1998

Tidal volume perception in a C1-C2 tetraplegic subject is blocked by airway anesthesia.

We administered lidocaine aerosol intratracheal anesthesia to a ventilator-dependent, tracheostomized C1-C2 tetraplegic subject to determine its effect on her ability to detect small changes in tidal volume. A psychophysical test of volume detection was given before and immediately after a 20 percent lidocaine aerosol was delivered through the subject's cuffed tracheostomy tube. On each of three occasions, she reliably (p < .001) detected changes in tidal volume during a control period; on two of these occasions she could not detect the same volume after inhaling the anesthetic. On one occasion the anesthetic had no effect on volume perception, possibly because copious airway secretions interfered with lidocaine uptake. Subject-blinded control tests with saline aerosol inhalation did not affect detection. We concluded that this subject's tidal volume perception depended on mechanoreceptors in the lungs and thoracic airways and that local anesthetic interrupted these sensory signals when airway secretions were not excessive.

Adult↗

PubMed1984

Model analysis of tidal volume response to inspiratory elastic loads.

Based on experimental inspiratory driving pressure waveforms and active respiratory impedance data of anesthetized cats, we made model predictions of the factors that determine the immediate (first loaded breath) intrinsic (i.e., nonneural) tidal volume compensation to added inspiratory elastic loads. The time course of driving pressure (P) was given by P = atb, where a is the pressure at 1 s from onset of inspiration and represents the intensity of neuromuscular drive, t is time, and b is an index of the shape of the driving pressure wave. For a given active respiratory impedance, tidal volume compensation to added elastic loads decreases with increasing inspiratory duration and decreasing value of b but is independent of a. We have also assessed the validity of the "effective elastance" (Lynne-Davies et al., J. Appl. Physiol. 30: 512-516, 1971) as a predictor of tidal volume responses to elastic loads. In absence of vagal feedback, the effective elastance appears to be a reliable predictor, except for short inspiratory duration and a very high intrinsic resistance.

Airway Resistance↗

PubMed1995

The effect of a cervical collar on the tidal volume of anaesthetised adult patients.

Semi-rigid cervical collars may be used to assist the stabilisation of the cervical spine during transport in patients suffering from major trauma. We have attempted to evaluate the effect of one such collar on airway patency in the presence of depressed airway reflexes. Thirty-eight patients undergoing anaesthesia via face mask with spontaneous ventilation were studied. Tidal volume was measured with the airway in three different positions, both with and without a collar. The collar made no statistically significant difference to tidal volume in any position. Changing support of the airway increased tidal volume both with and without the collar. Patients fitted with an incorrectly sized collar may develop upper airway obstruction in the presence of impaired consciousness. Experience should be gained in the correct fitting of semi-rigid collars.

Adolescent↗

PubMed1997

Effects of positive end-expiratory pressure and different tidal volumes on alveolar recruitment and hyperinflation.

BACKGROUND: The morphologic effect of positive end-expiratory pressure (PEEP) and of two tidal volumes were studied by computed tomography to determine whether setting the tidal volume (Vt) at the upper inflection point (UIP) of the pressure-volume (P-V) curve of the respiratory system or 10 ml/kg have different effects on hyperinflation and alveolar recruitment. METHODS: Alveolar recruitment and hyperinflation were quantified by computed tomography in nine patients with the acute respiratory distress syndrome (ARDS). First, end expiration was compared without PEEP and with PEEP set at the lower inflection point of the P-V curve; second, at end inspiration above PEEP, a reduced Vt set at the UIP (rVt) and a standard 10 ml/kg Vt (Vt) ending above the UIP were compared. Three lung zones were defined from computed tomographic densities: hyperdense, normal, and hyperinflated zones. RESULTS: Positive end-expiratory pressure induced a significant decrease in hyperdensities (from 46.8 +/- 18% to 38 +/- 15.1% of zero end-expiratory pressure (ZEEP) area; P < 0.02) with a concomitant increase in normal zones (from 47.3 +/- 20.9% to 56.5 +/- 13.2% of the ZEEP area; P < 0.05), and a significant increase in hyperinflation (from 8.1 +/- 5.9% to 17.8 +/- 12.7% of ZEEP area; P < 0.01). At end inspiration, a significant increase in hyperinflated areas was observed with Vt compared with rVt (33.4 +/- 17.8 vs. 26.8 +/- 17.3% of ZEEP area; P < 0.05), whereas no significant difference was observed for both normal and hyperdense zones. CONCLUSIONS: Positive end-expiratory pressure promotes alveolar recruitment; increasing Vt above the UIP seems to predominantly increase hyperinflation.

Adolescent↗

PubMed2006

The influence of tidal volume on the dynamic variables of fluid responsiveness in critically ill patients.

Respiratory-related variabilities in stroke volume and arterial pulse pressure (Delta%Pp) are proposed to predict fluid responsiveness. We investigated the influence of tidal volume (Vt) and adrenergic tone on these variables in mechanically ventilated patients. Cyclic changes in aortic velocity-time integrals (Delta%VTI(Ao), echocardiography) and Delta%Pp (catheter) were measured simultaneously before and after intravascular volume expansion, and Vt was randomly varied below and above its basal value. Intravascular volume expansion was performed by hydroxyethyl starch (100 mL, 60 s). Receiver operating characteristic curves were generated for Delta%VTI(Ao), Delta%Pp and left ventricle cross-sectional end-diastolic area (echocardiography), considering the change in stroke volume after intravascular volume expansion (> or =15%) as the response criterion. Covariance analysis was used to test the influence of Vt on Delta%VTI(Ao) and Delta%Pp. Twenty-one patients were prospectively included; 9 patients (43%) were responders to intravascular volume expansion. Delta%VTI(Ao) and Delta%Pp were higher in responders compared with nonresponders. Predictive values of Delta%VTI(Ao) and Delta%Pp were similar (threshold: 20.4% and 10.0%, respectively) and higher than that of left ventricle cross-sectional end-diastolic area at the appropriate level of Vt. Delta%Pp was slightly correlated with norepinephrine dosage. Delta%Pp increased with the increase in the level of Vt both before and after intravascular volume expansion, contrasting with an unexpected stability of Delta%VTI(Ao). In conclusion, Delta%VTI(Ao) and Delta%Pp are good predictors of intravascular fluid responsiveness but the divergent evolution of these two variables when Vt was increased needs further explanation.

Adult↗

PubMed2006

Inhalation induction using sevoflurane in children: the single-breath vital capacity technique compared to the tidal volume technique*.

The single-breath vital capacity technique is suitable for inhalation induction of anaesthesia, using sevoflurane in children aged > 5 years. The purpose of this randomised trial was to compare the single breath vital capacity technique with the conventional tidal volume technique. Seventy- three ASA 1 or 2 children were instructed during the pre-operative visit in the vital capacity technique. The main criterion measured was time to loss of the eyelash reflex. Induction was performed using a circle-absorber breathing circuit primed with sevoflurane 7% in 50% nitrous oxide/oxygen with 6 l.min(-1) fresh gas flow. Time required for induction, haemodynamic changes, airway tolerance and side-effects were recorded. The children's opinion on the technique used was scored using a visual analogue scale (0-100) and a Smiley scale (0-10). The time to loss of the eyelash reflex was found to be reduced in the vital capacity group compared to the tidal volume group. The time to central myosis, to achieve bispectral index values 60 and 40, haemodynamic changes, respiratory events and side-effect incidences were similar in both groups. However, we found that the vital capacity technique was preferred by the children to the tidal volume technique.

Anesthesia, Inhalation↗

PubMed2005

High tidal volume and positive fluid balance are associated with worse outcome in acute lung injury.

STUDY OBJECTIVES: Recent data have suggested that ventilatory strategy could influence outcomes from acute lung injury (ALI) and ARDS. We tested the hypothesis that infection/sepsis and use of higher tidal volumes than those applied in the ARDS Network (ARDSnet) study (> 7.4 mL/kg of predicted body weight) would worsen outcome in patients with ALI/ARDS. DESIGN: International cohort, observational study. SETTING: One hundred ninety-eight European ICUs participating in the Sepsis Occurrence in Acutely Ill Patients study. PATIENTS OR PARTICIPANTS: All 3,147 adult patients admitted to one of the participating ICUs between May 1, 2002, and May 15, 2002. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Patients were followed up until death, hospital discharge, or for 60 days. Of the 3,147 patients, 393 patients (12.5%) had ALI/ARDS. ICU and hospital mortality was higher in patients with ALI/ARDS than those without ALI/ARDS (38.9% vs 15.6% and 45.5% vs 21.0%, respectively; p < 0.001). A multivariable logistic regression analysis with ICU outcome as the dependent factor showed that the independent risks for mortality were as follows: presence of cancer, use of tidal volumes higher than those used by the ARDSnet study, degree of multiorgan dysfunction, and higher mean fluid balance. Sepsis, septic shock, and oxygenation at the onset of ALI/ARDS were not independently associated with higher mortality rates. CONCLUSIONS: In addition to comorbidities and organ dysfunction, high tidal volumes and positive fluid balance are associated with a worse outcome from ALI/ARDS.

Aged↗

PubMed1993

Role of tidal volume, FRC, and end-inspiratory volume in the development of pulmonary edema following mechanical ventilation.

Mechanical ventilation with high peak inspiratory pressure and large tidal volume (VT) produces permeability pulmonary edema. Whether it is mean or peak inspiratory pressure (i.e., mean or end-inspiratory volume) that is the major determinant of ventilation-induced lung injury is unsettled. Rats were ventilated with increasing tidal volumes starting from different degrees of FRC that were set by increasing end-expiratory pressure during positive-pressure ventilation. Pulmonary edema was assessed by the measurement of extravascular lung water content. The importance of permeability alterations was evaluated by measurement of dry lung weight and determination of albumin distribution space. Pulmonary edema with permeability alterations occurred regardless of the value of positive end-expiratory pressure (PEEP), provided the increase in VT was large enough. Similarly, edema occurred even during normal VT ventilation provided the increase in PEEP was large enough. Furthermore, moderate increases in VT or PEEP that were innocuous when applied alone, produced edema when combined. The effect of PEEP was not the consequence of raised airway pressure but of the increase in FRC since similar observations were made in animals ventilated with negative inspiratory pressure. However, although permeability alterations were similar, edema was less marked in animals ventilated with PEEP than in those ventilated with zero end-expiratory pressure (ZEEP) with the same end-inspiratory pressure. This "beneficial" effect of PEEP was probably the consequence of hemodynamic alterations. Indeed, infusion of dopamine to correct the drop in systemic arterial pressure that occurred during PEEP ventilation resulted in a significant increase in pulmonary edema. In conclusion, rather than VT or FRC value, the end-inspiratory volume is probably the main determinant of ventilation-induced edema. Hemodynamic status plays an important role in modulating the amount of edema during lung overinflation but does not fundamentally modify the characteristics of this edema which is consistently associated with major permeability alterations. These results may be relevant for ventilatory strategies during acute respiratory failure.

Albumins↗

PubMed1984

Deadspace and the single breath test for carbon dioxide during anaesthesia and artificial ventilation. Effects of tidal volume and frequency of respiration.

Using the single breath test for carbon dioxide (SBT-CO2), the components of physiological deadspace were investigated during anaesthesia with IPPV in 58 patients. A square-wave inspiratory flow and an end-inspiratory pause (25% and 10% of cycle time, respectively) were used. At tidal volumes of 0.45 litre (f = 17 b.p.m.), and 0.75 litre (f = 9 b.p.m.), median values for VDphys/VT were 0.44 and 0.31. Increasing VT and decreasing f did not change airway deadspace (VDaw) so that the fraction VDaw/VT was decreased (P less than 0.001). The alveolar deadspace fraction, VDalv/VTalv, was decreased in 93% of patients (P less than 0.001). These improvements with increasing VT can be attributed to beneficial effects on gas distribution and diffusion time. Patients with large alveolar deadspaces had steeply sloping SBT-CO2 phase III, and increased expiratory time constants of the respiratory system. The median arterial--end-tidal PCO2 difference, (PaCO2-PE'CO2), was 0.6 kPa at small and 0.3 kPa at large tidal volumes (P less than 0.001). Three patients had zero and four had negative (PaCO2-PE'CO2) values at large tidal volumes. When phase III slopes steeply, negative (PaCO2-PE'CO2) values may be observed in the presence of alveolar deadspace.

Adolescent↗

PubMed1980

Effects of sighs and different tidal volumes on compliance, functional residual capacity and arterial oxygen tension in normal and hypoxemic dogs.

In order to assess the usefulness of sighs in preventing deterioration of arterial PO2 (PaO2), functional residual capacity (FRC), and compliance in hypoxemic patients, the authors studied 20 anesthetized and paralyzed dogs. The dogs were ventilated with either normal (11.5 ml/kg) or large (23 ml/kg) tidal volumes and their lungs were either normal or made edematous with oleic acid injection. Sighs (46 ml/kg) were administered periodically and PaO2, FRC, and compliance were measured at intervals between sighs. In dogs with normal lungs, regardless of tidal volume, sighs produced a transient increase in compliance and FRC but PaO2 was not significantly affected. In dogs with pulmonary edema, sighs produced inconsistent effects on FRC and compliance and, interestingly, PaO2 decreased after the sighs may be unnecessary in patients with pulmonary edema, especially when they are already receiving large tidal volumes.

Animals↗

PubMed1999

The effects of epimysial electrode location on phrenic nerve recruitment and the relation between tidal volume and interpulse interval.

Electrode location is of vital importance to diaphragm pacing devices using electrodes implanted on the diaphragm. Complete phrenic nerve recruitment with a single epimysial electrode implanted on the abdominal surface of the diaphragm required placement within 1 cm of the motor point. Recruitment could be increased further using multiple electrodes, provided the electrodes were implanted on opposite sides of the phrenic nerve motor point. The location of the implanted electrode relative to the phrenic nerve motor point also affected the relation between the stimulus interpulse interval (IPI) and the measured tidal volume. Specifically, we found that electrodes implanted lateral to the phrenic nerve motor point had different tidal volume--IPI relations than electrodes placed anterior or posterior to the motor point. We concluded that properly placed epimysial electrodes are required to obtain adequate phrenic nerve recruitment for full time ventilation and knowledge of the relative location of the electrode with respect to motor point is necessary to predict the tidal volume produced by a specific IPI.

Animals↗

PubMed2002

Ventilation with high tidal volume induces inflammatory lung injury.

Mechanical ventilation with high tidal volumes (V(T)) has been shown to induce lung injury. We examined the hypothesis that this procedure induces lung injury with inflammatory features. Anesthetized male Wistar rats were randomized into three groups: group 1 (N = 12): V(T) = 7 ml/kg, respiratory rate (RR) = 50 breaths/min; group 2 (N = 10): V(T) = 21 ml/kg, RR = 16 breaths/min; group 3 (N = 11): V(T) = 42 ml/kg, RR = 8 breaths/min. The animals were ventilated with fraction of inspired oxygen of 1 and positive end-expiratory pressure of 2 cmH2O. After 4 h of ventilation, group 3, compared to groups 1 and 2, had lower PaO2 [280 (range 73-458) vs 517 (range 307-596), and 547 mmHg (range 330-662), respectively, P<0.05], higher wet lung weight [3.62 +/- 0.91 vs 1.69 +/- 0.48 and 1.44 +/- 0.20 g, respectively, P<0.05], and higher wet lung weight/dry lung weight ratio [18.14 (range 11.55-26.31) vs 7.80 (range 4.79-12.18), and 6.34 (range 5.92-7.04), respectively, P<0.05]. Total cell and neutrophil counts were higher in group 3 compared to groups 1 and 2 (P<0.05), as were baseline TNF-alpha concentrations [134 (range <10-386) vs 16 (range <10-24), and 17 pg/ml (range <10-23), respectively, P<0.05]. Serum TNF-alpha concentrations reached a higher level in group 3, but without statistical significance. These results suggest that mechanical ventilation with high V T induces lung injury with inflammatory characteristics. This ventilatory strategy can affect the release of TNF-alpha in the lungs and can reach the systemic circulation, a finding that may have relevance for the development of a systemic inflammatory response.

Animals↗