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At least 253 records · Page 14Linked to original sources
PubMed2006

Effects of face mask ventilation in apneic patients with a resuscitation ventilator in comparison with a bag-valve-mask.

Bag-valve-mask ventilation in an unprotected airway is often applied with a high flow rate or a short inflation time and, therefore, a high peak airway pressure, which may increase the risk of stomach inflation and subsequent pulmonary aspiration. Strategies to provide more patient safety may be a reduction in inspiratory flow and, therefore, peak airway pressure. The purpose of this study was to evaluate the effects of bag-valve-mask ventilation vs. a resuscitation ventilator on tidal volume, peak airway pressure, and peak inspiratory flow rate in apneic patients. In a crossover design, 40 adults were ventilated during induction of anesthesia with either a bag-valve-mask device with room air, or an oxygen-powered, flow-limited resuscitation ventilator. The study endpoints of expired tidal volume, minute volume, respiratory rate, peak airway pressure, delta airway pressure, peak inspiratory flow rate and inspiratory time fraction were measured using a pulmonary monitor. When compared with the resuscitation ventilator, the bag-valve-mask resulted in significantly higher (mean+/-SD) peak airway pressure (15.3+/-3 vs. 14.1+/-3 cm H2O, respectively; p=0.001) and delta airway pressure (14+/-3 vs. 12+/-3 cm H2O, respectively; p<0.001), but significantly lower oxygen saturation (95+/-3 vs. 98+/-1%, respectively; p<0.001). No patient in either group had clinically detectable stomach inflation. We conclude that the resuscitation ventilator is at least as effective as traditional bag-valve-mask or face mask resuscitation in this population of very controlled elective surgery patients.

Apnea↗
PubMed1988

Unilateral high-frequency jet ventilation during one-lung ventilation for thoracotomy.

One-lung ventilation is indicated during thoracic operations for bronchopleural fistula, pulmonary abscess, and pulmonary hemorrhage in spite of the possibility of the development of severe hypoxemia. To evaluate methods for improving oxygen transport during one-lung ventilation, we applied high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) to the nondependent lung following deflation to atmospheric pressure in each procedure, and measured the effects on cardiac output and arterial oxygenation. In each case, the dependent lung was ventilated with conventional intermittent positive pressure ventilation (IPPV). Eight patients were studied during posterolateral thoracotomy using double-lumen endobronchial tubes. HFJV or CPAP to the nondependent lung improved arterial oxygenation significantly during both closed and open stages of the surgical procedures (p less than 0.008). When the chest was open, HFJV maintained satisfactory cardiac output, whereas CPAP usually decreased cardiac output (p less than 0.008). There were no significant differences in mean partial pressure of arterial carbon dioxide between HFJV, CPAP, and deflation to atmospheric pressure. In conclusion, HFJV to the nondependent lung provides not only satisfactory oxygenation but also good cardiac output, thereby maintaining better oxygen transport than CPAP or deflation to atmospheric pressure, while the dependent lung is ventilated with IPPV during one-lung ventilation for thoracotomy.

Aged↗
PubMed2002

Assessment of regional lung ventilation in dog lungs with Gd-DTPA aerosol ventilation MR imaging.

PURPOSE: Gd-DTPA aerosol ventilation MR imaging was obtained using a modified aerosol delivery system with an aerosol reservoir to non-invasively assess regional lung ventilation in dogs. MATERIAL AND METHODS: Seven anesthetized, spontaneously breathing normal dogs inhaled 200 mmol Gd/l Gd-DTPA aerosol produced by an ultrasonic nebulizer, using an open-circuit aerosol delivery system with or without an aerosol reservoir. Fast gradient-echo MR images were sequentially acquired with an interval time of 1 min for 25 min before and after aerosol inhalation. The aerosol study was also performed using the aerosol delivery system with an aerosol reservoir in the same 7 dogs after airway obstruction with a balloon catheter, and in another 7 dogs after pulmonary arterial embolization with enbucrilate. An i.v. Gd-DTPA-enhanced dynamic MR study after i.v. bolus injection of a 0.1 mmol/kg dose of Gd-DTPA was combined to assess regional lung perfusion. Lung enhancement effect was evaluated by time-signal intensity curves and the subtracted ventilation- and perfusion-weighted images. RESULTS: With or without the aerosol reservoir, the normal dog lungs were gradually and gravity-dependently enhanced with time after aerosol inhalation. The use of the aerosol reservoir, however, showed significantly greater lung enhancement without a significant increase in breathing rate and with minimal reduction in PaO2 of less than 5 mm Hg in these animals. The enhancement effect of i.v. injection of Gd-DTPA at pulmonary arterial perfusion phase was significantly greater compared to that of Gd-DTPA aerosol throughout the normal lungs, and the subtracted ventilation-weighted and perfusion-weighted images showed homogeneous but gravity-dependent aerosol deposition and perfusion. These images clearly defined the regionally matched perfusion-ventilation deficits in the lung regions distal to bronchial obstruction in all the airway obstruction dogs, and the regionally mismatched perfusion-ventilation in the embolized regions of all the pulmonary arterial embolization animals. CONCLUSION: Gd-based aerosol can non-invasively image regional lung ventilation in spontaneously breathing animals, using an adequate aerosol delivery system. The combined use of Gd-DTPA perfusion MR imaging may be acceptable for defining regionally impaired lung function associated with acute airway obstruction and pulmonary arterial embolization.

Aerosols↗
PubMed1981

Differential lung ventilation with a modified ventilator.

To achieve synchronized differential pulmonary ventilation, an Ohio 560 ventilator was modified through separation of the outputs of the deep breath bellows and the tidal volume bellows and providing independent volume, flow rate, PEEP, oxygen-humidification, and alarm systems. The described ventilator modification is simple, inexpensive, and does not alter the performance characteristics of the original unmodified ventilator. Differential lung ventilation may be more easily achieved with this modified ventilator than with the simultaneous use of two ventilators or external electronic synchronizers.

Forced Expiratory Flow Rates↗
PubMed1996

Comparison of the effects of heat and moisture exchangers and heated humidifiers on ventilation and gas exchange during weaning trials from mechanical ventilation.

Heat and moisture exchangers (HME) are increasingly used to warm and humidify inspired gases in intubated ventilated patients. But these devices add dead space that may alter the alveolar ventilation. This could impair the efficiency of spontaneous ventilation (SV) during weaning trials from mechanical ventilation. Fifteen patients were tested with an HME (Hygrobac-DAR) and a heated humidifier (HH) (Fischer-Paykel MR 450) in a random order during weaning trials in SV with inspiratory pressure support. Minute ventilation VE, tidal volume), and respiratory rate were recorded and arterial blood was sampled for blood gas analysis with each device. The HME gave a significantly greater VE than the HH (9.3 +/- 0.8 L/min vs 8.1 +/- 0.8 L/min; p < 0.005), because of increased respiratory rate (21 +/- 2/min vs 19 +/- 2/min; p < 0.05). Tidal volume was unchanged for HME and HH (470 +/- 32 mL vs 458 +/- 39 mL). The higher PaCO2 with HME than with HH (44 +/- 2 mm Hg vs 42 +/- 2 mm Hg; p < 0.005) revealed an insufficient alveolar ventilation response to the increase in dead space. Arterial Po2 rose with the HME, but not significantly above the HH values (103 +/- 6 mm Hg vs 97 +/- 6 mm Hg; p = 0.055), possibly because of a positive end-expiratory pressure effect of the HME. The need to increase VE in SV when an HME is used should be taken into account during difficult weaning from mechanical ventilation.

Adult↗
PubMed2007

Evidence-based practice: use of the ventilator bundle to prevent ventilator-associated pneumonia.

PURPOSE: To examine critical care nurses' knowledge about the use of the ventilator bundle to prevent ventilator-associated pneumonia. METHOD: Published reports were reviewed for current evidence on the use of the ventilator bundle to prevent ventilator-associated pneumonia, and education sessions were held to present the findings to 61 nurses in coronary care and surgical intensive care units. Changes in the nurses' knowledge were evaluated by using a 10-item test, given both before and after the sessions. Changes in the nurses' practices related to ventilator-associated pneumonia, including elevation of the head of the bed to 30 degrees to 45 degrees , were observed in 99 intubated patients. RESULTS: After the education sessions, the nurses performed better on 8 of the 10 items tested (P from .03 to <.001). The areas of most significant improvement were elevation of the head of the bed (P < .001), charting of the elevation of the head of the bed (P= .009), oral care (P= .009), checking of the nasogastric tube for residual volume (P = .008), washing of hands before contact with patients (P < .001), and limiting the wearing of rings (P < .001) and nail polish (P = .04). Even after the education sessions, the nurses' compliance with hand-washing recommendations before contact with patients was low, though statistically some improvement was apparent. Contraindications to elevation of the head of the bed did not appear to affect the nurses' practices (P= .38). CONCLUSION: Education sessions designed to inform nurses about the ventilator bundle and its use to prevent ventilator-associated pneumonia have a significant effect on participants' knowledge and subsequent clinical practice.

Adult↗
PubMedDate not supplied

[Assisted ventilation of the lungs as a method of transition from artificial pulmonary ventilation to spontaneous respiration].

The authors describe the principal methods of assisted ventilation of the lungs used for smooth and safe transition from artificial ventilation to spontaneous respiration: trigger method, intermittent forced ventilation of the lungs, pressure support, permanent positive pressure respiration, jet high-frequency ventilation of the lungs, and two systems of the respirator response to spontaneous attempts of the patient: to pressure change and flow-by change. Basing on their own experience, the authors claim that patients with parenchymatous respiratory insufficiency better tolerate the method of pressure support, whereas those with ventilation respiratory insufficiency can be best treated by intermittent forced ventilation of the lungs. Jet high-frequency ventilation of the lungs may serve a full-value alternative to the flow-by method.

High-Frequency Ventilation↗
PubMed2002

A comparison of the effects of manual and ventilator hyperinflation on static lung compliance and sputum production in intubated and ventilated intensive care patients.

BACKGROUND AND PURPOSE: Lung hyperinflation is a technique used by physiotherapists to mobilize and remove excess bronchial secretions, reinflate areas of pulmonary collapse and improve oxygenation. Hyperinflation may be delivered by the ventilator or manually, by use of a manual resuscitation circuit, depending upon the respiratory and cardiovascular status of the patient. The effects of manual hyperinflation, with respect to excess bronchial secretions and static lung compliance, have been well-established. There is, however, only limited evidence as to the efficacy of ventilator hyperinflation as a physiotherapy treatment technique. The purpose of the present study was to compare the effects of manual hyperinflation and ventilator hyperinflation on static pulmonary compliance and sputum clearance in stable intubated and ventilated patients. METHOD: Twenty patients who met the inclusion criteria were studied. This was a double crossover study where all patients were randomly allocated to one of two treatment sequences over two days. The first sequence involved manual hyperinflation followed two hours later by ventilator hyperinflation and the order was reversed on the second day. In the second sequence, ventilator hyperinflation preceded manual hyperinflation. The variables of static pulmonary compliance and sputum wet weight were analysed by use of an analysis of variance (ANOVA) for repeated measures. Statistical significance was set at p < 0.05. RESULTS: There was no significant difference in sputum wet weight production between either technique or on either day of treatment. Static pulmonary compliance improved with both hyperinflation techniques (p < 0.05). CONCLUSIONS: Hyperinflation as part of a physiotherapy treatment can be performed with equal benefit using either a manual resuscitation circuit or a ventilator. Both methods of hyperinflation improve static pulmonary compliance and clear similar volumes of pulmonary secretions.

Adolescent↗
PubMed1993

High-frequency ventilation and conventional mechanical ventilation in newborn babies with respiratory distress syndrome: a prospective, randomized trial.

OBJECTIVE: Morbidity and mortality remain high amongst babies ventilated for a respiratory distress syndrome (RDS). Whether newly developed ventilators allowing high frequency ventilation such as high frequency flow interrupted ventilation (HFFIV) could decrease the morbidity and the mortality was investigated in a randomized study. DESIGN: Preterm babies weighing < or = 1800 g suffering from RDS and ventilated by conventional mechanical ventilation (CMV) were randomized to be further ventilated either by CMV (group CMV) or by HFFIV (group HFFIV) when peak inspiratory pressure (PIP) on CMV was > or = 20 cmH2O. SETTING: The study was undertaken in the neonatal intensive care unit of the Erasmus Hospital. PATIENTS: 24 patients entered into the investigation and were randomized but 2 patients were removed from the study because the switch over to HFFIV failed. Eight of the 12 CMV patients and 5 of the 10 HFFIV patients completed the study. MEASUREMENTS AND RESULTS: Clinical variables, blood gas analysis and ventilatory variables were looked at. There were no differences in mortality, in incidence of air leaks and pulmonary complications or in blood gas analysis. Bronchopulmonary dysplasia was not decreased by the use of HFFIV. CONCLUSION: It is concluded that HFFIV is safe although it offers no concrete advantages over CMV when applied as we did in a low pressure approach.

Female↗
PubMed2002

Comparative bench study of triggering, pressurization, and cycling between the home ventilator VPAP II and three ICU ventilators.

OBJECTIVE: To compare triggering, pressurization, and cycling of the home ventilator VPAP II with those of three ICU ventilators (Evita 4, Galileo, and Servo 300). DESIGN AND SETTING: Two-compartment lung model study in a research laboratory, university hospital. METHODS: One compartment was driven by an ICU ventilator to mimic "patient" inspiratory effort, while the other was connected to the tested ventilator. Pressure support of 10, 15, 20, and 25 cmH2O, and inspiratory efforts of 5, 10, 15, 20, and 25 cmH2O (inspiratory time 1 s) were used in normal, obstructive, and restrictive conditions. Triggering delay (Td), triggering workload, pressurization at 300 and 500 ms, and difference between the "patient's" inspiratory time and that of the ventilator were analyzed. RESULTS: No difference was noted in triggering workload between VPAP II, Evita 4, and Galileo while Servo 300 had a lower value. Pressurization at 300 ms on Evita 4 and Servo 300 reached 75% of the ideal value, on Galileo 35%, and on VPAP II 45%. Pressurization at 500 ms on Evita 4 and Servo 300 reached 85% of the ideal value, on Galileo 50%, and on VPAP II 55%. Cycling was delayed in obstructive conditions and premature in restrictive conditions with each of the devices. CONCLUSIONS: The VPAP II performed as well as one ICU ventilator and less well than two. Home devices for noninvasive ventilation in acute respiratory failure outside the ICU could prove attractive as they are smaller, less costly, and easier to use than ICU machines.

Equipment Design↗
PubMed1995

1988: unilateral high-frequency jet ventilation during one-lung ventilation for thoracotomy. Updated in 1995.

One-lung ventilation is indicated during thoracic operations for bronchopleural fistula, pulmonary abscess, and pulmonary hemorrhage in spite of the possibility of the development of severe hypoxemia. To evaluate methods for improving oxygen transport during one-lung ventilation, we applied high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) to the nondependent lung following deflation to atmospheric pressure in each procedure, and measured the effects on cardiac output and arterial oxygenation. In each case, the dependent lung was ventilated with conventional intermittent positive pressure ventilation (IPPV). Eight patients were studied during posterolateral thoracotomy using double-lumen endobronchial tubes. HFJV or CPAP to the nondependent lung improved arterial oxygenation significantly during both closed and open stages of the surgical procedures (p < 0.008). When the chest was open, HFJV maintained satisfactory cardiac output, whereas CPAP usually decreased cardiac output (p < 0.008). There were no significant differences in mean partial pressure of arterial carbon dioxide between HFJV, CPAP, and deflation to atmospheric pressure. In conclusion, HFJV to the nondependent lung provides not only satisfactory oxygenation but also good cardiac output, thereby maintaining better oxygen transport than CPAP or deflation to atmospheric pressure, while the dependent lung is ventilated with IPPV during one-lung ventilation for thoracotomy.

High-Frequency Jet Ventilation↗
PubMed2003

Percutaneous transtracheal ventilation: effects of a new oxygen flow modulator on oxygenation and ventilation in pigs compared with a hand triggered emergency jet injector.

The application of percutaneous transtracheal jet ventilation for emergency ventilation depends on special equipment which is often not available outside the operating room. The oxygen flow modulator is a new specially designed device for emergency ventilation using a low pressure oxygen supply. We studied the effects of the new device in comparison with a hand triggered emergency jet injector on oxygenation and ventilation in six pigs (21+/-1 kg). The animals were anaesthetized, tracheally intubated, and mechanically ventilated. Following central venous and pulmonary artery catheterization, a Paratrend 7 sensor was placed in the left femoral artery for continuous measurements of PaO(2) and PaCO(2). Then an emergency transtracheal airway catheter was inserted into the trachea after surgical exposure. In randomized order each animal was ventilated via the transtracheal airway catheter with the hand triggered emergency jet injector (inspiratory/expiratory (I/E) ratio of 1:1; respiratory rate of 60 min(-1); driving pressure 1.5 bar; FjetO(2) 1.0) and the oxygen flow modulator (FiO(2) 1.0 at an oxygen flow of 15 l min(-1); respiratory rate of 60 min(-1); I/E ratio of approximately 1:1) for 15 min each. After each phase of the experiment respiratory and hemodynamic variables were measured. Whereas PaO(2) was not significantly different between the two devices, PaCO(2) was higher during the hand-triggered jet ventilation. Thus, the efficacy of the oxygen flow modulator during the experiment was comparable with the efficacy of the hand triggered emergency jet injector.

Animals↗
PubMed2003

The effect of high-frequency ventilation of the lungs on postbypass oxygenation: A comparison with other ventilation methods applied during cardiopulmonary bypass.

OBJECTIVE: To compare the effect of high-frequency ventilation versus other ventilation methods applied during cardiopulmonary bypass on postbypass oxygenation. DESIGN: Prospective, randomized study. SETTING: University hospital. PARTICIPANTS: Seventy-five patients undergoing coronary artery bypass graft surgery. INTERVENTIONS: Patients were allocated to 5 equal groups of different ventilation methods during bypass. Groups 1 and 2 received high-frequency, low-volume ventilation with 100% and 21% oxygen, respectively. Groups 3 and 4 received 5 cm H(2)O of continuous positive airway pressure (CPAP) with either 100% or 21% oxygen. Patients from group 5 were disconnected from the ventilator during the bypass period. MEASUREMENTS AND MAIN RESULTS: Spirometry data, blood gas analysis, oxygen saturation as measured by pulse oximetry, and end-tidal carbon dioxide were recorded 5 minutes before chest opening, 5 minutes before bypass, 5 minutes after bypass, 5 minutes after chest closure and 6, 12, 18, and 24 hours after surgery. There were no differences in compliance and mean airway pressures. Alveolar-to-arterial oxygen gradients increased, and PaO(2) decreased significantly (p < 0.05) in all groups 5 minutes after bypass and this trend continued in the postoperative period. Patients from group 3 had higher PaO(2) and lower alveolar-to-arterial oxygen gradients, 5 minutes after weaning from bypass (p < 0.05). Extubation times were similar in all groups. CONCLUSIONS: The alveolar-arterial oxygen gradient was lower, and the PaO(2) was higher 5 minutes after bypass in patients receiving CPAP (100% O(2)) as compared with those ventilated with high-frequency ventilation.

Aged↗
PubMed1995

[Ventilation during tracheotomy in extensive, 90% laryngeal stenosis using superimposed high frequency jet ventilation via the jet laryngoscope].

In a 35-year old male patient with laryngeal carcinoma an acute respiratory insufficiency with early hypoxaemia developed due to massive laryngeal stenosis. An endotracheal intubation was not possible since the available lumen was too small. Tracheotomy using local anaesthesia was not possible since spontaneous respiration with a Venturi mask applying 100% oxygen was not sufficient and the patient was becoming restless and agitated due to the hypoxaemia. Transcutaneous jet ventilation was considered to be too risky since the needle would have to pass highly vascularised tumour tissue and the detection of such a small rest lumen would have been quite difficult. Ventilating the patient using a percutaneous catheter would have been very risky as well since, due to the massive stenosis, a sufficient expiration would not be likely and therefore was considered to carry a high risk of barotrauma. The patient was ventilated under general anaesthesia via a specially designed endoscopy tube with integrated jet nozzles applying superimposed high frequency jet ventilation above the stenosis. Since it was possible to achieve sufficient ventilation during the inspection of the larynx the jet laryngoscope was left in place and the supporting apparatus was covered with sterile drapes. The tracheotomy was performed using the superimposed high frequency jet ventilation. Throughout the procedure oxygenation and ventilation were adequate. The laryngectomy performed several days later revealed a cauliflower type protrusion into the tracheal lumen and a 5 cm long stenosis of the larynx with a lumen of 3 mm.

Adult↗
PubMed1994

Understanding the pressure cost of ventilation: why does high-frequency ventilation work?

OBJECTIVES: To understand when the use of high-frequency ventilation would be advantageous, we formulated the problem of achieving adequate alveolar ventilation at minimal pressure cost by dividing it into two simpler problems: a) the pressure cost per unit of convective oscillatory flow; and b) the convective flow cost necessary to achieve a unit of alveolar ventilation. METHODS: Simple solutions for each of these cost functions were formulated using established models of gas exchange and lung mechanics, including the effects of lung inflation tidal volume and respiratory frequency in alveolar ventilation, nonlinear lung tissue compliance, and alveolar recruitment and derecruitment. Solutions to these models were combined to assess the total pressure cost of high-frequency ventilation as a function of the ventilatory settings and the pathophysiologic variables of the patient. MAIN RESULTS: The model predicted that for variables applicable to an infant with respiratory distress syndrome, the selection of positive end-expiratory pressure (PEEP) becomes critical because the penalties in pressure cost are amplified for both high and low values of PEEP. The selection of frequency is not as critical for frequencies > 10 Hz, although it is more important than in the normal neonatal lung. CONCLUSIONS: This analysis illustrates the importance of using high-frequency ventilation in infant respiratory distress syndrome and of optimizing the amount of PEEP. It also points out the danger of barotrauma in the derecruited lung. When the lungs are in a derecruited state, the combinations of frequency, PEEP, and tidal volume that yield adequate ventilation with safe distention of recruited alveoli are severely limited.

Animals↗
PubMed2005

High-frequency oscillatory ventilation and ventilator-induced lung injury.

INTRODUCTION: Although mechanical ventilation is lifesaving for patients with acute respiratory distress syndrome, it can cause ventilator-induced lung injury. To minimize ventilator-induced lung injury, different ventilatory strategies have been developed. One of the strategies is the use of high-frequency oscillatory ventilation (HFOV). THEORETICAL BACKGROUNDS OF VENTILATOR-INDUCED LUNG INJURY AND HFOV: Because of the novel gas exchange mechanisms, HFOV can provide adequate gas exchange using extremely small tidal volumes and maintain high end-expiratory lung volume without inducing overdistension, which should result in minimization of ventilator-induced lung injury. STUDIES OF HFOV AND LUNG INJURY: There are convincing clinical and animal data indicating that HFOV is an ideal lung-protective ventilatory strategy, particularly in the setting of neonatal respiratory failure, if lung volume recruitment is performed. CLINICAL IMPLICATION OF HFOV IN ADULT ACUTE RESPIRATORY DISTRESS SYNDROME: A recent clinical trial demonstrated early (<16 hrs) improvement in oxygenation with HFOV and a 30-day mortality of 37% with HFOV vs. 52% with pressure-controlled ventilation (p = .102), suggesting that HFOV is as effective and safe as the conventional strategy in adult acute respiratory distress syndrome. Future studies examining optimal algorithms of HFOV using clinically relevant animal models, and patients with acute respiratory distress syndrome, are imperative to determine whether the wide-spread application of HFOV is warranted in adult acute respiratory distress syndrome.

Adult↗
PubMed1990

Intermittent high frequency ventilation. Clinical evaluation of a new mode of ventilation.

In this first clinical study of a new mode of ventilation, called intermittent high frequency ventilation (IHFV), a comparison was made in ten patients after myocardial revascularization, between normal ventilation, high frequency ventilation (HFV) and IHFV at 15, 60, 100 and 160 breaths per min (b.p.m.). During IHFV the ventilation was interrupted for 3 s 7 times per min. The measured mean trapped gas volumes were 219 ml at 60 b.p.m. and 716 ml at 160 b.p.m. At 160 b.p.m. during IHFV, the mean, mean airway pressures, pulmonary artery (PAP) and capillary wedge pressures and the Paco2 were decreased, while the cardiac output increased. When the Paco2 was maintained constant, IHFV also allowed a reduction in the mean peak and mean airway pressures. This new mode of ventilation can prevent sustained increases in the lung volume and provide a reduction in intrapulmonary pressures. It also permits the measurement of the trapped gas volume and end-tidal CO2 gas concentrations several times a minute for the clinical management of patients during high frequency ventilation.

Evaluation Studies as Topic↗
PubMed1995

Interfacing between spontaneous breathing and mechanical ventilation affects ventilation-perfusion distributions in experimental bronchoconstriction.

The effect of interfacing between spontaneous and mechanical ventilation on ventilation-perfusion (VA/Q) distributions was determined during pressure-support ventilation (PSV) and in the presence and absence of spontaneous breathing during biphasic positive airway pressure (BIPAP) in 10 pigs with methacholine-induced bronchoconstriction. Whereas BIPAP without spontaneous breathing provides full and PSV breath-to-breath synchronized ventilatory support, BIPAP allows unrestricted spontaneous breathing throughout the mechanical cycle. Compared with BIPAP with and without spontaneous breathing, PSV effected an increase in ventilatory rate (p < 0.05) and a higher minute ventilation (VE) (p < 0.05). Spontaneous breathing during BIPAP accounted for 15 +/- 1% of the VE and increased cardiac output (CO) from 4.5 +/- 0.2 to 5.3 +/- 0.2 L/min (p < 0.05), Pao2 from 55 +/- 3 to 80 +/- 4 mm Hg (p < 0.05), and oxygen delivery (DO2) from 442 +/- 39 to 630 +/- 43 ml/min (p < 0.05). PSV did not increase CO, Pao2, and DO2. Spontaneous breathing did not affect oxygen consumption. During BIPAP spontaneous breathing accounted for a 15 +/- 2% decrease (p < 0.05) in blood flow to shunt units and a 16 +/- 2% increase (p < 0.05) in the perfusion of normal VA/Q units. Perfusion of shunt and normal VA/Q units was similar during PSV and BIPAP without spontaneous breathing. Dead space ventilation decreased with spontaneous breathing during BIPAP by 12% compared with PSV (p < 0.05). Dispersion of ventilation distribution was lowest during BIPAP. Uncoupling of spontaneous and mechanical ventilation during BIPAP improved gas exchange by allowing better VA/Q matching during experimental bronchoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗