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At least 721 records · Page 40Linked to original sources
PubMed1984

Ventilation-perfusion relationships during halothane anaesthesia and mechanical ventilation. Effects of varying inspired oxygen concentration.

Ventilation-perfusion relationships (VA/Q), assessed by a multiple inert-gas elimination technique, were studied during halothane anaesthesia and mechanical ventilation at different inspiratory oxygen fractions (FIO2). All nine patients (mean age 65 years, five smokers) displayed unaltered VA/Q distributions with increasing FIO2 from a mean of 29% to 53%. A further increase in FIO2 to a mean of 85% caused an increase in true shunt (VA/Q = 0) from 7 to 10% of cardiac output (P less than 0.01), but no increase in "low" VA/Q (VA/Q less than 0.1). On the return to FIO2 of 29%, true shunt was reduced to the initial level. The findings may fit in with release of hypoxic vasoconstriction when FIO2 is increased to 85%, or the opening up of a certain population of shunt vessels.

Aged↗
PubMed1989

A comparison of ventilation strategies for the use of high-frequency oscillatory ventilation in the treatment of hyaline membrane disease.

To assess the efficacy of high frequency oscillatory ventilation (HFOV) in the management of infants with hyaline membrane disease (HMD), we compared two HFOV strategies with conventional positive pressure ventilation with positive end expiratory pressure (PPV) for 24 h in premature baboons (140 d gestation). Three out of 14 PPV, five out of five HFOV-E (begun at birth; 15 Hz; I:E 1:2), and none of 10 HFOV-L (begun after 3 h PPV; 10 Hz; I:E 1:2) were killed at 24 h for morphologic examination. Physiologic (Paw, Pa/AO2, IO2, B.P., pulse, blood gases) data on all animals in each group were assessed at each 3 h interval and over time. Intergroup differences in radiographs at 0 and 24 h and in morphology were quantitatively assessed by comparison with a panel of standards. All animals had radiographic HMD. Initial Paw was set higher with HFOV-E (16.8) than PPV or HFOV-L (14.1, 14.1). PPV baboons required increasing Paw to maintain constant Pa/AO2. Six out of 14 PPV animals developed airleak and three out of three had morphologic HMD. In contrast Pa/AO2 was higher in both HFOV groups at lower Paw by 24 h. None of 15 HFOV animals developed airleak. HFOV-E lungs had dramatic differences in morphology with uniform saccular opening and decreased edema and hyaline membranes compared to PPV. HFOV-L had less dramatic effects because of lower Paw and delayed application. Early use of HFOV at a high Paw favorably alters the course of HMD. Unless closely monitored, this strategy results in lung overinflation which may adversely affect venous return and cardiac output.

Animals↗
PubMed2002

Partial liquid ventilation with low dose of perflubron and a low stretch ventilation strategy improves oxygenation in a rabbit model of surfactant depletion.

To demonstrate the efficacy of partial liquid ventilation (PLV) with a low dose of perflubron (PFB), severe lung injury model followed surfactant-depleted rabbits underwent PLV with either moderate tidal volume (V(T)) and high positive end-expiratory pressure (PEEP) or high V(T) and low PEEP. PLV with low-dose PFB was effective in alleviating hypoxia in a severe lung injury model if adequate PEEP was applied. We concluded that the addition of a low dose of PFB might be beneficial to a low stretch ventilation strategy, which allows a less aggressive approach to achieve adequate oxygenation with a possible reduction in further lung injury.

Animals↗
PubMed1991

Pressure-time product during continuous positive airway pressure, pressure support ventilation, and T-piece during weaning from mechanical ventilation.

The objective of this study was to compare the effects of continuous positive airway pressure (CPAP), pressure support ventilation (PS), and T-piece on the pressure-time product (PTP) during weaning from mechanical ventilation. The PTP is an estimate of the metabolic work or oxygen consumption of the respiratory muscles. We studied 10 intubated patients recovering from acute respiratory failure of various etiologies. A modified continuous flow (flow-by) CPAP of 0 and 5 cm H2O (CPAP-0 and CPAP-5, respectively), PS of 5 cm H2O (PS-5), and T-piece were applied in random order for 30 min each. In the last 5 min of the 30-min periods, we measured the esophageal pressure and transdiaphragmatic pressure-time products--PTP(es) and PTP(di), cm H2O.s/min, respectively-multiplied by respiratory frequency. Breathing pattern, total lung resistance (RL), quasi-static lung compliance (CL), intrinsic positive end-expiratory pressure (PEEPi), end-expiratory transpulmonary pressure (Ptpexp), arterial blood gases, blood pressure, and heart rate were also measured. In comparison to T-piece, CPAP-5 decreased PTP(es) 40% (p less than 0.01) and PTP(di) 43% (p less than 0.02), whereas PS-5 decreased PTP(es) 34% (p less than 0.01) and PTP(di) 38% (p less than 0.05). The decrease in PTP(es) with CPAP-5 was associated with a significant reduction in RL, and to a less extent in PEEPi relative to airway pressure. The contribution of the decrease in PEEPi to the reduction in PTP(es) amounted to 36%. With PS-5, respiratory system mechanics and PEEPi were not significantly different compared with T-piece. With CPAP-0, PTP tended to be lower than with T-piece.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Survival and prediction of successful ventilator weaning in COPD patients requiring mechanical ventilation for more than 21 days.

We studied survival and failure or success of weaning from mechanical ventilation (MV) in 42 consecutive chronic obstructive pulmonary disease (COPD) patients requiring prolonged MV (more than 21 days) after an episode of acute respiratory failure requiring admission to our Intermediate Intensive Care Unit (IICU). Parameters including arterial blood gases, pulmonary function tests, respiratory muscle force, neuromuscular drive, and nutritional status were recorded during a phase of clinical stability, in order to identify the features related to survival and weaning. All the patients were submitted to a comprehensive rehabilitation programme. Successful weaning from MV was defined as complete respiratory autonomy for at least 48 h. Twenty three patients were successfully weaned from MV after an average period of 44 days (Group A), requiring no further MV during their stay in hospital, whilst the remaining 19 patients were not able to be disconnected from the ventilator (Group B). The discriminant analysis showed that weaning from MV was significantly associated with arterial carbon dioxide tension (PaCO2), neuromuscular drive (P0.1), maximal inspiratory pressure (MIP), arterial oxygen tension (PaO2), the ratio of respiratory frequency to tidal volume (f/VT) and the serum protein level. Other pulmonary function tests (forced expiratory volume in one second (FEV1), FEV1/forced vital capacity (FVC), anthropometric data, nutritional status, number of pulmonary exacerbations during MV and evidence of cor pulmonale, were similar in the two groups. The discriminant equation considering PaCO2 and MIP could separate the two groups with an accuracy of 84%. The overall survival at 2 yrs was 40%; in Group B it was significantly lower than in Group A (22 vs 68%). Most of the deaths occurred within the first 120 days after intubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2005

Hypoxemia during one-lung ventilation: jet ventilation of the middle and lower lobes during right upper lobe sleeve resection.

A 64-yr-old man underwent right thoracotomy and upper lobectomy for lung carcinoma. Hypoxemia on one-lung ventilation was being managed with continuous positive airway pressure to the nondependent lung when a sleeve resection had to be performed. As this positive airway pressure would no longer be maintained with the bronchus open, an alternate method of oxygenation was necessary. This report describes the successful use of jet ventilation via an airway exchange catheter placed in the bronchus intermedius through the tracheal lumen of a left-sided double-lumen endobronchial tube. Oxygenation was maintained and surgical access was good during the 15-min resection.

High-Frequency Jet Ventilation↗
PubMed1992

The technique of inverse ratio ventilation. Steps to improve oxygenation and decrease dead space ventilation.

Inverse ratio ventilation (IRV) differs from other ventilatory techniques in that it employs a prolonged inspiratory time. In theory, pressure-control IRV allows you to maintain ventilation and oxygenation with lower peak airway and end-expiratory pressures; this may reduce the potential for lung damage secondary to shearing forces. Consider pressure-control IRV for patients with acute lung disease characterized by low lung compliance, diffuse microatelectasis, and increased intrapulmonary shunting. Currently, the chief limitation of this technique is that the patient cannot breathe spontaneously during its use. The best inspiratory to expiratory ratio is the shortest inspiratory time that improves oxygenation with minimal hemodynamic compromise; depression of cardiac output will negate any potential improvement in arterial oxygenation.

Adult↗
PubMedDate not supplied

Options for ventilating the pediatric patient. Part 1. Mechanical properties of three generations of ventilators.

The past 20 years have seen striking changes in ventilators for use in infants and children. Early in this period, we relied on traditional machines and techniques that were largely borrowed from adult medicine. The availability of second-generation machines brought better understanding of pulmonary physiology, particularly as it relates to oxygen transport. Today, third-generation ventilators very different from the others have forced abandonment of dogma concerning the manner in which molecules of gas enter and leave the lung. Their full impact cannot yet be judged, but they have shown great clinical promise and no doubt will change further our understanding of pulmonary physiology.

Child↗
PubMed2003

Effects of expiratory rib cage compression and/or prone position on oxygenation and ventilation in mechanically ventilated rabbits with induced atelectasis.

INTRODUCTION: Expiratory rib cage compression is a chest physiotherapy technique known as "squeezing" technique in Japan. It has been claimed that rib cage compression effectively treats and/or prevents lung collapse, but no studies have been reported on rib cage compression focused on improving ventilation and/or oxygenation in subjects with collapsed lung. Therefore, we studied whether rib cage compression, with and without prone positioning, improves the ratio of P(aO)(2) to fraction of inspired oxygen (P(aO)(2)/F(IO)(2)), P(aCO)(2), or dynamic compliance of the respiratory system. METHODS: We used anesthetized adult rabbits with induced atelectasis. An endotracheal tube and an 18-gauge catheter were placed into the airway via a tracheostoma, and pressure-controlled mechanical ventilation was used. To create atelectasis, artificial mucus was infused into the airway via the catheter. The rabbits were randomly assigned to one of 4 groups ( = 10 in each group): (1) supine without rib cage compression, (2) supine with rib cage compression, (3) prone without rib cage compression, and (4) prone with rib cage compression. Each rib cage compression session lasted for 5 min and was repeated 5 times every 30 min. After these interventions for 180 min all animals were placed in the supine position for 120 min. RESULTS: The prone-position groups had significantly higher P(aO)(2)/F(IO)(2) than the supine-position groups at 60 min after the beginning of the intervention, and at 60, 90, and 120 min after the end of the intervention (p < 0.05). Rib cage compression did not significantly affect P(aO)(2)/F(IO)(2), P(aO)(2), or dynamic compliance. CONCLUSIONS: It is unlikely that rib cage compression re-expands collapsed lung. Prone positioning improved oxygenation in rabbits with induced atelectasis.

Animals↗
PubMed1992

[A comparative study of the effects of control ventilation and synchronized intermittent mandatory ventilation on hemodynamic and blood gases in patients with chronic obstructive pulmonary disease].

Effects of control ventilation (CV) and synchronized intermittent mandatory ventilation (SIMV) were comparatively studied in 9 patients with chronic obstructive pulmonary disease. Cardiac index (from 2.99 +/- 0.65 to 3.60 +/- 0.651.min-1.m-2, P < 0.05) and oxygen delivery index (from 537 +/- 89 to 645 +/- 101 ml.min-1.m-2, P < 0.05) were significantly increased during SIMV comparing with CV. Mixed venous oxygen tension (from 5.63 +/- 0.66 to 6.06 +/- 0.59 kPa, P < 0.01) was improved by SIMV. The results showed that SIMV could improve cardiac output, oxygen delivery and oxygen supply of tissue.

Aged↗
PubMed1989

High frequency oscillatory and conventional mechanical ventilation in experimental surfactant deficiency: a study using a new infant ventilator technique.

The performance of a new infant ventilator system had to be evaluated. Technically it is characterized by flow (V)- and pressure (P)-transducers mounted immediately near the endotracheal tube. A microcomputer works as a function generator and governs servo-controllers for V and P thus offering a multiplicity of different modes both of the conventional (CMV) and high frequency oscillatory (HFO) type. The additional dead space imposed by the system is identical with its internal compressible volume of 2 ml. Serial pulmonary lavages were performed in 17 adult rabbits while on CMV. PaO2 per unit of mean airway pressure (MAP) decreased thereby from 95.9 +/- 29.3 to 9.0 +/- 6.7 (kPa/kPa). The animals were then alternately ventilated by HFO (5, 10, or 20 Hz) and CMV, at matched MAP's. No significant difference in PaO2 between the two methods was revealed in intra-animal comparisons except a slight superiority of CMV at MAP's above 1.7 kPa (P less than 0.05). There was no clear linear relationship between PaO2 and MAP both at CMV and HFO. A strong increase in PaO2 often occurred beyond a MAP threshold. In 37 postlavage HFO runs at 5 Hz in 13 animals volume amplitudes of 3.19 +/- 0.5 ml/kg of bodyweight resulted in PaCO2 levels of 6.29 +/- 1.87 kPa. Except in one experiment (10 Hz) volume amplitudes below the natural dead space produced arterial hypercapnia.

Animals↗
PubMed1993

[The effect of the ventilation rate on air particle and air microbe concentration in operating rooms with conventional ventilation. 1. Measurement without surgical activity].

The question was if a reduction of airborne particles and bacteria in conventionally (turbulently), ventilated operating theatres in comparison to Laminar-Airflow (LAF) operating theatres does occur at high air-exchange-rates. Within the framework of energy consumption measures the influence of air-exchange-rates on airborne particle and bacteria concentrations was determined in two identical operating theatres with conventional ventilation (wall diffusor panel) at the air-exchange-rates 7.5, 10, 15 and 20/h without surgical activity. This was established by means of the statistical procedure of analysis of variance. Especially for the comparison of the air-exchange-rates 7.5 and 15/h statistical differences were found for airborne particle concentrations in supply and ambient air. Concerning airborne bacteria concentrations no differences were found among the various air-exchange-rates. Explanation of variance is quite high for non-viable particles (supply air: 37%, ambient air: 81%) but negligible for viable particles (bacteria) with values below 15%.

Air Microbiology↗
PubMed1996

[Intermittent nasal positive pressure ventilation with a ventilator in accordance with the Medical Device Regulation III (MedGV III). Clinical experiences with the BREAS PV 201 in 19 patients].

UNLABELLED: During the period from January to September 1995, 19 patients suffering from ventilatory insufficiency were adjusted to nocturnal nasal intermittent positive pressure ventilation (nIPP) therapy with a new ventilatory apparatus conforming to German regulations governing medical equipment (MedGV III). This equipment had not been available previously. 5 patients were suffering from obstructive ventilatory disorder, 5 patients from an underlying neurological disease and 3 patients from thoracic restriction. In 6 patients the reason for their ventilatory disorder was obesity hypoventilation or disorder of central ventilatory regulation. The average age was 54 years (15-73 years). Whereas 14 patients were suffering from global respiratory insufficiency already during the day, the others had marked respiratory disorder only at night. In all cases ventilation was carried out during the whole night. RESULTS: nIPPV achieved normoxia in all patients whereas in 10 patients hypercapnia was not completely eliminated. In all cases, however, the previously elevated pCO2 could be reduced. Hence, sufficient nIPPV can be achieved also with a respirator complying with the new German MedGV III regulations.

Adolescent↗
PubMed1986

Prolonged high-frequency jet ventilation in a patient with bronchopleural fistula. An alternative mode of ventilation.

We report a case of bronchopleural fistula (BPF) in a patient submitted to conventional mechanical ventilation in which high frequency jet ventilation (HFJV) was applied during five consecutive days. Gas exchange was adequate, the bronchial secretions could easily be cleared and the patient adapted comfortably to HFJV. In spite of PEEP levels between 4 and 8 mm Hg, the leak through the BPF ceased completely.

Bronchial Fistula↗
PubMed2004

Mechanical ventilation in orbit: emphasis on closed-loop ventilation.

As part of a Crew Health Care Maintenance System onboard the International Space Station, the National Aeronautics and Space Administration has included a Respiratory Support Pack (RSP) to resuscitate or sustain a crew member with an acute impairment in pulmonary function. This article provides a critical appraisal of the RSP and of current strategies for mechanical ventilation in space. Various closed-loop ventilation strategies are reviewed,and their appropriateness for respiratory support in space is explored. Recommendations are made for enhancing and upgrading the current RSP to provide an injured crew member with the best possible chance of survival.

Aerospace Medicine↗
PubMed1987

Randomized trial of high-frequency jet ventilation versus conventional ventilation in respiratory distress syndrome.

To compare high-frequency jet ventilation (HFJV) with pressure-limited time-cycled conventional ventilation (CV), we randomized 41 infants with clinical and radiographic evidence of respiratory distress syndrome during the first day of life to receive either HFJV or CV. Standardized ventilatory protocols were used for 48 hours, after which CV was administered to both groups. Despite comparable oxygenation (arterial/alveolar oxygen tension ratio), mean airway pressure was lower in the HFJV group (9 +/- 2 vs 13 +/- 2 cm H2O, P less than 0.001), and thus the arterial/alveolar oxygen tension ratio corrected for mean airway pressure was improved in the HFJV group (P less than 0.05). PaCO2 was lower during HFJV (37 +/- 3 vs 42 +/- 3 mm Hg, P less than 0.05) despite a comparable peak inspiratory pressure. The incidence of air leaks, progression of intraventricular hemorrhage, and mortality during the 48-hour period did not differ between the two groups. Bronchoscopies in eight infants given HFJV and five given CV revealed no microscopic evidence of necrotizing tracheobronchitis, but one infant given HFJV had evidence of necrotizing tracheitis at autopsy. We conclude that for 48 hours during the acute stage of respiratory distress syndrome, HFJV can maintain adequate gas exchange at lower mean airway pressure than during CV, without an increase in the incidence of side effects.

Clinical Trials as Topic↗
PubMed1994

Tracheostomy ventilation versus diaphragmatic pacemaker ventilation in high spinal cord injury.

We have made a retrospective comparative study of patients with spinal cord injury, nine with a diaphragmatic pacemaker and 13 with mechanical ventilation. Clinical outcome, cost and subjective satisfaction with both modalities have been evaluated. The functional status was the same with both types of treatment. Proper management of an electric wheelchair and optimal phonation were attained, respectively, in 100% and 89% of pacers and in 77% and 77% of mechanically ventilated. The rate of hospital discharge and satisfaction with the treatment were significantly better for pacers. The time devoted to ventilatory assistance and cost were also more favourable in this group.

Adult↗