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Results for “Tidal Volume”

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PubMed1994

The oxygen cost of breathing may predict weaning from mechanical ventilation better than the respiratory rate to tidal volume ratio.

OBJECTIVE: To compare the respiratory rate to tidal volume ratio with the oxygen cost of breathing to see which could more accurately predict the outcome of ventilator weaning for surgical patients. DESIGN: Prospective comparison of two modalities used to predict the likelihood of successful ventilator weaning. PATIENTS: Twenty-eight consecutive patients with chronic respiratory insufficiency requiring long-term mechanical ventilation in the surgical intensive care unit at New England Deaconess Hospital, Boston, Mass, were studied. MAIN OUTCOME MEASURES: The oxygen cost of breathing and the respiratory rate to tidal volume ratio were measured during spontaneous breathing. Patients extubated within 2 weeks of being studied were designated as extubated while patients not extubated within this period or requiring reintubation were recorded as not extubated. RESULTS: The oxygen cost of breathing predicted successful extubation in all five patients who were extubated, and failure in 20 of 23 patients who could not be extubated (sensitivity, 100%; specificity, 87%). In contrast, the respiratory rate to tidal volume ratio predicted extubation for only two of five patients who were extubated and predicted failure in only 12 of 23 patients who could not be extubated (sensitivity, 40%; specificity, 52%). CONCLUSION: For this group of patients requiring prolonged ventilation, the oxygen cost of breathing proved to be a more reliable predictor of both successful extubation and failure.

Aged↗

PubMed2006

Mechanical ventilation with lower tidal volumes and positive end-expiratory pressure prevents alveolar coagulation in patients without lung injury.

BACKGROUND: Alveolar fibrin deposition is a hallmark of acute lung injury, resulting from activation of coagulation and inhibition of fibrinolysis. Previous studies have shown that mechanical ventilation with high tidal volumes may aggravate lung injury in patients with sepsis and acute lung injury. The authors sought to determine the effects of mechanical ventilation on the alveolar hemostatic balance in patients without preexistent lung injury. METHODS: Patients scheduled for an elective surgical procedure (lasting > or = 5 h) were randomly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure (PEEP) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP. After induction of anesthesia and 5 h later bronchoalveolar lavage fluid and blood samples were obtained, and markers of coagulation and fibrinolysis were measured. RESULTS: In contrast to mechanical ventilation with lower tidal volumes and PEEP (n = 21), the use of higher tidal volumes without PEEP (n = 19) caused activation of bronchoalveolar coagulation, as reflected by a marked increase in thrombin-antithrombin complexes, soluble tissue factor, and factor VIIa after 5 h of mechanical ventilation. Mechanical ventilation with higher tidal volumes without PEEP caused an increase in soluble thrombomodulin in lavage fluids and lower levels of bronchoalveolar activated protein C in comparison with lower tidal volumes and PEEP. Bronchoalveolar fibrinolytic activity did not change by either ventilation strategy. CONCLUSIONS: Mechanical ventilation with higher tidal volumes and no PEEP promotes procoagulant changes, which are largely prevented by the use of lower tidal volumes and PEEP.

Aged↗

PubMed1979

Contribution of rib cage and abdomen-diaphragm to tidal volume during CO2 rebreathing.

In man, there is wide interindividual range in the tidal volume response to CO2. To determine which (rib cage or abdomen-diaphragm) compartment had a greater influence on this range, ventilatory response to CO2 was measured, using Read's method, in eight men and two women seated in a constant-pressure body plethysmograph. Rib cage and abdominal tidal volume was simultaneously measured using magnetometers. Correcting for body size, the tidal volume response of the abdominal compartment was similar in all subjects, whereas that of the rib cage was larger in subjects with high tidal volume response to CO2; a significant correlation was found (P less than 0.01). Rib cage volume displacement lagged behind abdominal in all subjects; phase lag was greatest in the subject with the lowest ventilatory response to CO2. These results suggest that, at high levels of ventilation, a larger volume displacement of the rib cage may reflect a more effective coupling of the diaphragm pressure generator to it or alternatively a reduction in its impedance relative to the abdominal compartment.

Abdominal Muscles↗

PubMed2002

Tidal volume forced expiration in asthmatic infants: reproducibility and reversibility tests.

BACKGROUND: The tidal volume forced expiration technique used in infants is considered as the first practical noninvasive method of assessing airway physiology in infants. However, its role has been discussed mainly due to the high variability of the derived parameters. OBJECTIVES: The aim of the study was to assess the reproducibility of a complete measurement with the tidal volume forced expiration technique in infants as measured by the maximal flow at FRC (V(max)FRC). A second aim was to evaluate the bronchial reversibility test in infant asthma. METHODS: Thirty infants with asthma were investigated with the tidal volume forced expiration technique twice with 10 min in between and a third time 10 min after inhalation of terbutalin 0.5 mg. RESULTS: The mean V(max)FRC in the first investigation was 285 ml.s(-1) (coefficient of variation 57%), unchanged in the second investigation and significantly lower than the mean predicted value of 404 ml.s(-1). The relative difference between the 2 investigations of V(max)FRC was mean 10.5% (SD 8.4) of the absolute V(max)FRC value and independent of the size of this V(max)FRC value. The 95% confidence interval for individual changes would then be up to 27% (mean + 2 SD). The infants with the lowest V(max)FRC percent predicted decreased further in V(max)FRC after inhalation of the bronchodilator (p < 0.05). CONCLUSIONS: The tidal volume forced expiration technique was able to measure flow at late expiration with the same reproducibility as seen with spirometry in adults, even if the flow was low. We found the technique acceptable for clinical practice and research, but the results from reversibility tests are difficult to interpret. A significant change of V(max)FRC would, however, be 27% or more.

Asthma↗

PubMed1986

Influence of breathing frequency and tidal volume on cardiac output.

The aim of our experiment was to investigate the influence of increasing either breathing frequency or tidal volume on cardiac output (Q), in normocapnia. We measured Q with a CO2 rebreathing method in 6 men and 6 women in the sitting and the supine position, imposing different breathing patterns: in one set of experiments tidal volume was kept constant at 1 L while breathing frequency was randomly changed between 20, 30 and 40 breaths/min; in another breathing frequency was kept constant at 30 breaths/min while tidal volume was randomly altered between 1, 1.5 and 2 L. Switching from open circuit breathing to rebreathing (for measurement of Q) required no change in breathing pattern. From the beginning, CO2 was added to the inspired gas to maintain end-tidal FCO2 at 0.054, so as to obtain steady state conditions throughout the measurements. Q rose significantly when tidal volume was increased (938 ml/L rise in tidal volume when sitting, and 743 ml/L when supine). Breathing frequency had an insignificant effect (213 ml/10 breaths frequency increase when sitting and 142 ml/10 breaths when supine). The greater influence of ventilation on Q when sitting than when supine is best explained by the fact that in the latter position venous return is already high. There are no demonstrable differences in this effect between males and females.

Adult↗

PubMed1984

Effect of posture on upper and lower rib cage motion and tidal volume during diaphragm pacing.

We monitored changes in upper and lower rib cage dimensions and tidal volume during bilateral phrenic nerve pacing in a quadraplegic subject with a flaccid chest wall paralysis. Both upper and lower rib cage showed inward (paradoxical) motion during paced breaths in supine (horizontal) and upright positions on a tilt table. In both postures, abdominal compression changed only the lower rib cage to orthodox motion. Abdominal compression in the supine posture decreased tidal volume 10 to 20%, while end-inspiratory diaphragm length, assessed from end-expiratory volume, did not change. Abdominal compression in the upright posture caused end-expiratory volume to fall and increased tidal volume 200%. These observations suggest that isolated diaphragm contraction can move the lower ribs independently from the upper ribs and that tidal volume is determined both by the resting length of the diaphragm and by diaphragmatic load.

Adult↗

PubMed2003

Electrical impedance tomography: a method for monitoring regional lung aeration and tidal volume distribution?

OBJECTIVE: To demonstrate the monitoring capacity of modern electrical impedance tomography (EIT) as an indicator of regional lung aeration and tidal volume distribution. DESIGN AND SETTING: Short-term ventilation experiment in an animal research laboratory. PATIENTS AND PARTICIPANTS: One newborn piglet (body weight: 2 kg). INTERVENTIONS: Surfactant depletion by repeated bronchoalveolar lavage, surfactant administration. MEASUREMENTS AND RESULTS: EIT scanning was performed at an acquisition rate of 13 images/s during two ventilatory manoeuvres performed before and after surfactant administration. During the scanning periods of 120 s the piglet was ventilated with a tidal volume of 10 ml/kg at positive end-expiratory pressures (PEEP) in the range of 0-30 cmH(2)O, increasing and decreasing in 5 cmH(2)O steps. Local changes in aeration and ventilation with PEEP were visualised by EIT scans showing the regional shifts in end-expiratory lung volume and distribution of tidal volume, respectively. In selected regions of interest EIT clearly identified the changes in local aeration and tidal volume distribution over time and after surfactant treatment as well as the differences between stepwise inflation and deflation. CONCLUSIONS: Our data indicate that modern EIT devices provide an assessment of regional lung aeration and tidal volume and allow evaluation of immediate effects of a change in ventilation or other therapeutic intervention. Future use of EIT in a clinical setting is expected to optimise the selection of appropriate ventilation strategies.

Animals↗

PubMed1992

Estimation of tidal volume from the reservoir bag. A laboratory study.

The accuracy of 21 anaesthetists in estimating tidal volumes from reservoir bag movements was assessed using a model lung apparatus. The breathing system configuration (Mapleson A or D), the grade of anaesthetist, and the years of anaesthetic experience had no effect on accuracy. Greater precision of tidal volume estimation was observed with larger tidal volumes and lower fresh gas flows. The mean systematic error of 18 of the 21 anaesthetists was greater than zero, indicating a general tendency to overestimate tidal volume. This study therefore strengthens the view that clinical observations should be supplemented with information from continuous monitoring devices.

Anesthesia, Inhalation↗

PubMed1975

A method for the assessment of phasic vagal influence on tidal volume.

Vagal influence related to lung volume changes results in reduction in tidal volume during spontaneous breathing due primarily to premature termination of inspiration. The strength of this vagal influence was traditionally assessed by the duration of apnea following lung inflation, a method recently shown to be inadequate and potentially misleading. An alternate method is described utilizing analysis of the volume tracing of spontaneous breaths and the tracheal pressure tracing during the first breath following airway occlusion at FRC. A formula was devised which, on the basis of previous observations, should predict the tidal volume to be obtained in the absence of phasic vagal influence. The formula was tested in four pentobarbital-anesthetized rabbits using a technique of vagal cooling which rapidly eliminated the vagal influence under study. It was found that the tidal volume obtained following vagal block could be accurately predicted provided allowances were made for the vagally mediated terminal inhibition during spontaneous breathing and the relative stiffness of the respiratory system at high lung volumes.

Action Potentials↗

PubMed1996

The optimal tidal volume delivered by ventilator after pulmonary resection: its effect on cardiopulmonary hemodynamics.

Pulmonary function and gas exchange deteriorate after pulmonary resection. The vital capacity, tidal volume, and functional capacity decrease after pulmonary resection because of loss of effective lung volume and, therefore, affect the setting of the ventilator. Nineteen patients undergoing pulmonary resection were included in this study on the optimal tidal volume delivered by a ventilator. Five patients received mediastinal surgery or wedge resection of the lung, 4 had pneumonectomy, and 10 had lobectomy. Immediately after the pulmonary surgery, they were maintained with ventilatory support. Subsequently, a different setting of tidal volume on the ventilator was given for each patient, i.e., 6 ml/kg, 8 ml/kg, 10 mg/kg, and 14 ml/kg. For each setting of tidal volume, a hemodynamic study was performed including cardiac output and other parameters. With the examination of Wilk's Lambda test, there was no difference in association with different settings of tidal volume on blood pressure (F = 0.92, p = 0.51), pulmonary artery pressure (F = 0.95, p = 0.43), pulmonary vascular resistance (F = 0.24, p = 0.97), systemic vascular resistance (F = 0.42, p = 0.78), and cardiac output (F = 0.35, p = 0.93) in 3 different groups of patients. It is concluded that after pulmonary resection a patient's lungs can be inflated with a tidal volume to 14 ml/kg during ventilatory support without compromise of cardiovascular performance.

Adult↗

PubMed1998

Influence of tidal volume on the distribution of gas between the lungs and stomach in the nonintubated patient receiving positive-pressure ventilation.

OBJECTIVES: When ventilating a nonintubated patient in cardiac arrest, the European Resuscitation Council has recently recommended a decrease in the tidal volume from 0.8 to 1.2 L to 0.5 L, partly in an effort to decrease peak flow rate, and therefore, to minimize stomach inflation. The purpose of the present study was to examine the validity of the European Resuscitation Council's recommendation in terms of gas distribution between lungs and stomach in a bench model that simulates ventilation of a nonintubated patient with a self-inflatable bag representing tidal volumes of 0.5 and 0.75 L. DESIGN: A bench model of a patient with a nonintubated airway was used consisting of face mask, manikin head, training lung (lung compliance, 50 mL/cm H2O; airway resistance, 5 cm H2O/L/sec), adjustable lower esophageal sphincter pressure (LESP) and simulated stomach. SETTING: University hospital laboratory. SUBJECTS: Thirty healthcare professionals. INTERVENTIONS: Healthcare professionals performed 1-min bag-mask ventilation at each LESP level of 5, 10, and 15 cm H2O at a rate of 12 breaths/min, using an adult and pediatric self-inflating bag, respectively. Volunteers were blinded to the LESP, which was randomly varied. MEASUREMENTS AND MAIN RESULTS: Both types of self-inflating bags induced stomach inflation, with higher stomach and lower lung tidal volumes when the LESP was decreased. Lung tidal volume with the pediatric bag was significantly (p < .05) lower at all LESP levels when compared with the adult bag, and ranged between 240 mL at an LESP of 15 cm H2O and 120 mL at an LESP of 5 cm H2O. Stomach tidal volume with the adult bag ranged between 250 mL at an LESP of 15 cm H2O and increased to 550 mL at an LESP of 5 cm H2O. Stomach tidal volume with the pediatric bag was significantly lower (p < .05) at all LESP levels when compared with the adult bag and ranged between 70 mL at an LESP of 15 cm H2O and 300 mL at an LESP of 5 cm H2O. CONCLUSIONS: Our data support the recommendation of the European Resuscitation Council to decrease tidal volumes to 0.5 L when ventilating a cardiac arrest victim with an unprotected airway. A small tidal volume may be a better trade-off in the basic life support phase, as this may provide reasonable ventilation while avoiding massive stomach inflation.

Adult↗

PubMed2006

Physiological effects of oxidized exogenous surfactant in vivo: effects of high tidal volume and surfactant protein A.

Oxidative damage to surfactant can decrease lung function in vivo. In the current study, our two objectives were: 1) to examine whether the adverse effects of oxidized surfactant would be accentuated in animals exposed to high tidal volume ventilation, and 2) to test whether supplementation with surfactant protein A (SP-A) could improve the function of oxidized surfactant in vivo. The first objective was addressed by evaluating the response of surfactant-deficient rats administered normal or oxidized surfactant and then subjected to low tidal volume (6 ml/kg) or high tidal volume (12 ml/kg) mechanical ventilation. Under low tidal volume conditions, rats administered oxidized surfactant had impaired lung function, as determined by lung compliance and arterial blood gas analysis, compared with nonoxidized controls. Animals subjected to high tidal volume ventilation had impaired lung function compared with low tidal volume groups, regardless of the oxidative status of the surfactant. The second experiment demonstrated a significantly superior physiological response in surfactant-deficient rats receiving SP-A containing oxidized surfactant compared with oxidized surfactant. Lavage analysis at the end of the in vivo experimentation showed no differences in the recovery of oxidized surfactant compared with nonoxidized surfactant. We conclude that minimizing excessive lung stretch during mechanical ventilation is important in the context of exogenous surfactant supplementation and that SP-A has an important biophysical role in surfactant function in conditions of oxidative stress. Furthermore, the oxidative status of the surfactant does not appear to affect the alveolar metabolism of this material.

Animals↗

PubMed1979

CO2 and exercise tidal volume.

In progressive exercise increased tidal volume (VT) accompanies increased ventilation (VE) until a VT plateau is reached. We observed in 13 subjects a correspondence between the arrival of the VT plateau and the anaerobic threshold (AT). To examine this association between a mechanical event (the VT plateau) and a metabolic event (the AT), we changed those variables that change at the AT and looked for changes in VT. We found in 13 subjects that CO2 addition to prevent alveolar hypocapnia during cycle ergometer exercise progressing to exhaustion in 12-15 min significantly elevated the VT plateau (mean increase 4.4%; P less than 0.01) as compared with a spontaneous test that induced a mean end-tidal carbon dioxide tension fall of 5.5 Torr. This VT increase was mediated by a significant increase in inspiratory time (TI; P less than 0.02); both the ratio of TI to the total breath duration (TI/Ttot) and the mean rate of inspired airflow (VT/TI) were unchanged at matched VE. Changing other variables known to change at the AT--blood lactate ion concentration and alveolar oxygen tension--left ventilatory pattern unchanged. These results suggest that hypocapnia in severe exercise measurably lowers the VT plateau in normal man.

Carbon Dioxide↗

PubMed2006

Four methods of measuring tidal volume during high-frequency oscillatory ventilation.

OBJECTIVE: Assess the accuracy of four different methods of measuring tidal volume during simulated high-frequency oscillatory ventilation. DESIGN: In vitro study. SETTING: Research laboratory. SUBJECTS: Three differential pressure pneumotachometers, a modified Pitot tube, an ultrasound flowmeter, and an adult hot wire anemometer. INTERVENTIONS: Each device was placed in series with a Sensormedics 3100B high-frequency ventilator and an 8.0-mm endotracheal tube attached to a 48.9-L plethysmograph. Inspiratory/expiratory ratio was fixed at 1:1 and mean airway pressure at 10 cm H2O. Tidal volumes were calculated at each combination of frequency (f: 3, 4, 6, 8, 10, 12 Hz) and pressure amplitude (DeltaP: 30, 60, 90 cm H2O) by digital integration of the sampled flow signals from each device and compared with those calculated from pressure changes within the plethysmograph. The protocol was repeated after incorporation of frequency-specific calibrations to the flow-measuring algorithm of each device. The hot wire anemometer was further evaluated at Fio2 of 1.0, 37 degrees C, 80% humidity, mean airway pressure of 20 cm H2O, and an inspiratory/expiratory ratio of 1:2. MEASUREMENTS AND MAIN RESULTS: Tidal volumes were 36-305 mL. Bland-Altman analysis demonstrated that each device exhibited systematic bias before frequency-specific adjustment. After frequency-specific adjustment of the flow-measuring algorithm, the two most accurate and precise devices were the Hans Rudolph pneumotachometer, which exhibited a mean error of 0.2% (95% confidence interval, -3.0% to 3.4%), and the hot wire anemometer, which had a mean error of -1.1% (95% confidence interval, -5.5% to 3.3%). The hot wire anemometer remained accurate at Fio2 1.0, 37 degrees C, 80% humidity, mean airway pressure of 20 cm H2O, and an inspiratory/expiratory ratio of 1:2. CONCLUSIONS: Tidal volume can be measured during high-frequency oscillatory ventilation using a variety of techniques. Frequency-specific calibration improves the accuracy and precision of tidal volume measurements. Hot wire anemometry exhibits stable performance characteristics across the range of temperature, humidity, Fio2, and inspiratory/expiratory ratios encountered clinically, has a small deadspace, is unaffected by mean airway pressure, and is therefore suitable for clinical applications.

Adult↗

PubMed1987

Initial mechanical ventilator settings for pediatric patients: clinical judgement in selection of tidal volume.

Guidelines for selection of initial mechanical ventilator settings for pediatric patients were evaluated. Protocols specifying tidal volume or peak inspiratory pressure are difficult to apply for infants and children because of leaks at uncuffed endotracheal tubes, compression loss in ventilators, and inaccuracy of settings for intended tidal volume. To avoid these difficulties, the selection of tidal volume was based on subjective clinical observations: visible chest excursion and audible air entry at least simulating normal breathing. In 76 consecutive patients, use of the guidelines resulted in satisfactory PaCO2 for 97% and PaO2 for 89% of infants and children with a wide variety of respiratory disorders. Adequacy of gas exchange was not related to the patient's age, type of ventilator, tightness of fit of the endotracheal tube, or presence of spontaneous breathing. These results support a simple, versatile method of teaching selection of initial mechanical ventilator settings, relying on clinical judgment for regulation of tidal volume.

Airway Resistance↗

PubMed2002

Tidal volume increases do not affect alveolar mechanics in normal lung but cause alveolar overdistension and exacerbate alveolar instability after surfactant deactivation.

OBJECTIVE: We utilized microscopy to measure the impact of increasing tidal volume on individual alveolar mechanics (i.e., the dynamic change in alveolar size during tidal ventilation) in the living porcine lung. DESIGN: In three anesthetized, mechanically ventilated pigs, we observed normal alveoli (n = 27) and alveoli after surfactant deactivation by Tween 20 lavage (n = 26) at three different tidal volumes (6, 12, and 15 mL/kg). Alveolar area was measured at peak inspiration (I) and at end expiration (E) by image analysis and I minus E was calculated as an index of alveolar stability (I-Edelta). MEASUREMENTS AND MAIN RESULTS: In normal alveoli, increasing tidal volume did not change alveolar area at I (6 mL/kg = 9726 +/- 848 microm; 15 mL/kg = 9,637 +/- 884 microm ), E (6 mL/kg = 9747 +/- 800 microm; 15 mL/kg = 9742 +/- 853 microm ), or I-Edelta (6 mL/kg = -21 +/- 240 microm; 15 mL/kg = -105 +/- 229 microm ). In contrast, with surfactant deactivation, increasing tidal volume significantly increased alveolar area at I (6 mL/kg = 11,413 +/- 1032 microm; 15 mL/kg = 13,917 +/- 1214 microm ), at E (6 mL/kg = 10,462 +/- 906 microm; 15 mL/kg = 12,000 +/- 1066 microm ), and I-Edelta (6 mL/kg = 825 +/- 276 microm; 15 mL/kg = 1917 +/- 363 microm ). Moreover, alveolar instability (increased I-Edelta) was significantly increased at all tidal volumes with altered surface tension when compared with normal alveoli. CONCLUSIONS: We conclude that high tidal volume ventilation does not alter alveolar mechanics in the normal lung; however, in the surfactant-deactivated lung, it causes alveolar overdistension and exacerbates alveolar instability.

Animals↗

PubMed2001

Protective effects of low tidal volume ventilation in a rabbit model of Pseudomonas aeruginosa-induced acute lung injury.

OBJECTIVE: To determine whether low "stretch" mechanical ventilation protects animals from clinical sepsis after direct acute lung injury with Pseudomonas aeruginosa as compared with high "stretch" ventilation. DESIGN: Prospective study. SETTING: Experimental animal laboratory. SUBJECTS: Twenty-seven anesthetized and paralyzed rabbits. INTERVENTIONS: P. aeruginosa (109 colony forming units) was instilled into the right lungs of rabbits that were then ventilated at a tidal volume of either 15 mL/kg (n = 11) or 6 mL/kg (n = 7) for 8 hrs. Control animals were ventilated at a tidal volume of either 15 mL/kg (n = 4) or 6 mL/kg (n = 5) for 8 hrs, but an instillate without bacteria was used. A positive end-expiratory pressure of 3-5 cm H2O was used for all experiments. Radiolabeled albumin was used as a marker of alveolar epithelial permeability. MEASUREMENTS AND MAIN RESULTS: Hemodynamics, arterial blood gas determination, alveolar permeability, wet-to-dry ratios on lungs, and time course of bacteremia were determined. When final values were compared with the values at the beginning of the experiment, there were significant decreases in mean arterial pressure (from 104 +/- 15 to 57 +/- 20 mm Hg), pH (from 7.46 +/- 0.04 to 7.24 +/- 15), Pao2 (from 528 +/- 35 to 129 +/- 104 torr [70.4 +/- 4.7 to 17.2 +/- 13.9 kPa]), and temperature (from 38.2 +/- 1 to 36.2 +/- 1.2 degrees C) in the high tidal volume group, whereas no significant differences were found in the low tidal volume group. Decreased alveolar permeability was shown in the low tidal volume group, as was decreased extravascular lung water in the uninstilled lung in the low tidal volume group (12.7 +/- 2.5 vs. 4.3 +/- 0.45 g H2O/g dry lung). No noteworthy difference was noted in the time course of bacteremia, although there was a trend toward earlier bacteremia in the high tidal volume group. CONCLUSIONS: In our animal model of P. aeruginosa-induced acute lung injury, low tidal volume ventilation was correlated with improved oxygenation, hemodynamic status, and acid-base status as well as decreased alveolar permeability and contralateral extravascular lung water.

Animals↗

PubMed2004

Use of low tidal volume in septic shock may decrease severity of subsequent acute lung injury.

Recent studies have indicated that protective lung strategies may improve outcomes in acute lung injury. We hypothesized that the use of a lower tidal volume early during septic shock may protect against the subsequent development of acute lung injury. Fourteen fasted, anesthetized, invasively monitored, mechanically ventilated, female sheep (26.4 +/- 4.5 kg) underwent cecal ligation and perforation to induce sepsis. Sheep were then randomized to ventilation with low (6 mL/kg) or high (12 mL/kg) tidal volumes. A positive end-expiratory pressure of 10 cm H(2)O was applied in each case. Ringer's lactate was titrated to maintain pulmonary artery occlusion pressure at baseline levels. No vasoactive agents or antibiotics were used. Survival time was longer in the low- than in the high-tidal-volume group (21.8 +/- 2.4 vs. 17.6 +/- 4.1 h, respectively, P < 0.05). The times to develop hypotension and anuria were longer in the low-tidal-volume group (18.1 +/- 3.1 vs. 12.0 +/- 2.8 h, P < 0.05, and 17.6 +/- 1.6 vs. 14.1 +/- 3.8 h, P < 0.05). Although the Pao2/Fio2 tended to be lower in the low- than in the high-tidal-volume group (P = 0.06), postmortem examination showed a lower lung tissue wet/dry ratio in the low- than in the high-tidal-volume group (7.1 +/- 0.5 vs. 9.1 +/- 0.7, P < 0.05). A low-tidal-volume ventilation strategy applied early during septic shock may be beneficial in terms of reducing the amount of lung edema and prolonging survival time.

Animals↗