Ventilation For Respiratory Failure Research Articles

Role of Dead Space in the Development and Diagnosis of Respiratory Failure

The volumes of the dead space (anatomic and alveolar) play an important role in the physiology of external respiration and information on these volumes makes the diagnosis of different respiratory disorders easier. The volume of the anatomic dead space (the last inspiratory portions) is uninvolved in the mixing with the gas of functional residual capacity (FRC) and leaves the airways unchanged in the gas composition on expiration. Mixing of the other portion of the tidal volume with FRC gas should be regarded as preparation for an alveolar gas exchange process. The increased partial value of the anatomic dead space in the tidal volume with its decrease (tachypnea) and, accordingly, reduced alveolar ventilation volume may result in ventilation respiratory failure. The time course of changes in the volume of the alveolar dead space is easily detectable from the decrease in expiratory CO2 concentrations as compared with PaCO2. The increased alveolar dead space volume suggests impaired local blood flow (thromboembolism, acute respiratory distress syndrome) in the lesser circulation and gives grounds to diagnose shunting and venous mixing. Procedures for measuring the dead space volumes are simple and may be introduced into clinical practice. Key words: anatomic dead space, alveolar dead space, functional residual capacity, respiratory failure.

OXIDATIVE STRESS AND ANTIOXIDANT STATUS IN BRONCHOALVEOLAR LAVAGE FLUID, PLASMA AND ERYTHROCYTE OF CRITICALLY MIXED ILL WITH RESPIRATORY FAILURE

Aim: Increased oxidative stress is a significant part of pathogenesis of various lung diseases. In this trial, it is aimed to determine the role of oxidative stress in patients receiving mechanical ventilation for respiratory failure (RF). Methods: The oxidative stress was evaluated by determining plasma, bronchial fluid and erythrocyte levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), ascorbic acid, alpha-tocopherol, uric acid (UA) and nitric oxide (NO) in 25 critically ill patients with RF. Twenty five patients without RF was evaluated as control group. Results: Oxidative stress (MDA, NO) levels of plasma, erythrocyte and BAL fluid in mixed critically ill with respiratory failure were higher than control group. Antioxidant levels of plasma, erythrocyte and BAL fluid in mixed critically ill with respiratory failure were lower than control group. In all parameters, there was no statistically difference as exitus and survivors in critically mixed patients. Conclusion: Oxidative stress was higher in respiratory failure than control group. The aim of the present study was to investigate the status of oxidative stress and antioxidant in mixed critically ill patients with respiratory failure as assessed by the malondialdehyde (MDA), NO, SOD, GSH-Px, vit C, vit E and uric acid measurements in bronchoalveolar lavage (BAL), erythrocyte and plasma.MATERIALS AND METHODS A total 50 subjects were examined, 25 with respiratory failure (average 65.6±12.7 years, 17 males and 8 females) and 25 patients without respiratory failure (average 55.4±9.36 years, 19 males and 6 females). The patients Table 1. Characteristics of patients and control groupMixed critically ill patients

Nonassociative Learning Promotes Respiratory Entrainment to Mechanical Ventilation

BackgroundPatient-ventilator synchrony is a major concern in critical care and is influenced by phasic lung-volume feedback control of the respiratory rhythm. Routine clinical application of positive end-expiratory pressure (PEEP) introduces a tonic input which, if unopposed, might disrupt respiratory-ventilator entrainment through sustained activation of the vagally-mediated Hering-Breuer reflex. We suggest that this potential adverse effect may be averted by two differentiator forms of nonassociative learning (habituation and desensitization) of the Hering-Breuer reflex via pontomedullary pathways.Methodology/Principal FindingsWe tested these hypotheses in 17 urethane-anesthetized adult Sprague-Dawley rats under controlled mechanical ventilation. Without PEEP, phrenic discharge was entrained 1∶1 to the ventilator rhythm. Application of PEEP momentarily dampened the entrainment to higher ratios but this effect was gradually adapted by nonassociative learning. Bilateral electrolytic lesions of the pneumotaxic center weakened the adaptation to PEEP, whereas sustained stimulation of the pneumotaxic center weakened the entrainment independent of PEEP. In all cases, entrainment was abolished after vagotomy.Conclusions/SignificanceOur results demonstrate an important functional role for pneumotaxic desensitization and extra-pontine habituation of the Hering-Breuer reflex elicited by lung inflation: acting as buffers or high-pass filters against tonic vagal volume input, these differentiator forms of nonassociative learning help to restore respiratory-ventilator entrainment in the face of PEEP. Such central sites-specific habituation and desensitization of the Hering-Breuer reflex provide a useful experimental model of nonassociative learning in mammals that is of particular significance in understanding respiratory rhythmogenesis and coupled-oscillator entrainment mechanisms, and in the clinical management of mechanical ventilation in respiratory failure.

Non-invasive ventilation for respiratory failure in elderly patients

Non-invasive ventilation for respiratory failure in elderly patients

Is the Current Management of Severe Sepsis and Septic Shock Really Evidence Based?

Evidence-based medicine (EBM), a process of accurately assessing and integrating the weight carried by various levels of available evidence, (e.g., randomized controlled trials [RCTs], case-control studies, case series, and expert opinion) has become the cornerstone of good medical practice. The RCT is considered the “gold-standard” of EBM, but, while the RCT may indeed be the most statistically unbiased method of assessing an intervention, it can also have limitations and must be correctly interpreted, aided by other forms of evidence. In addition, in certain fields of medicine, such as management of patients with severe sepsis, this “high-grade” RCT evidence is in short supply [1]. The heterogeneous nature of the intensive-care-unit (ICU) population and the complexity of the disease processes involved make it difficult to show the impact of acute interventions on long-term outcomes in this setting. In addition, many treatment strategies are life saving (such as mechanical ventilation in respiratory failure, blood transfusions in acute hemorrhage, and administration of vasopressor agents in severe shock), and could not ethically be studied in a placebo-controlled RCT [1]. In view of these uncertainties, it is difficult to provide guidelines for the management of the patient with sepsis. Yet severe sepsis is a serious health-care problem, affecting some 30% of ICU admissions and associated with ICU mortality rates of around 30%; septic shock is associated with ICU mortality rates of around 50%. There is no doubt that better outcomes could be achieved in this patient population.

Clinical decision-making and mechanical ventilation in patients with respiratory failure due to an exacerbation of COPD

This paper reports a study undertaken to determine whether differences exist in practice between respiratory physicians, general physicians and intensivists or between individual clinicians in initiating mechanical ventilation in respiratory failure due to chronic obstructive pulmonary disease (COPD), the factors influencing decisionmaking and their relation to the evidence base. Of 725 questionnaires sent to clinicians, 350 (48%) were completed and analysed. Twenty-five variables were included which clinicians scored 0–3 according to their perceived relevance in the decision. The sum of all the responses was calculated for each clinician: respiratory 15–68, general 12–65, intensivists 16–64. The most important variables in withholding ventilation were lung cancer inoperable due to COPD, and nursing home resident. The least important variables were treated depression and osteoporosis. No significant differences existed in practice between specialties but there were great differences between individuals’ practices. Clinicians were influenced by similar factors, but these did not reflect documented poor outcome predictors. Guidelines are needed.

Implications for matrix metalloproteinases as modulators of pediatric lung disease.

Matrix metalloproteinases (MMPs) are a large family (>20) of cation-dependent proteinases believed to be important modulators of normal human lung development and potentially harmful mediators of lung damage. Little is known about MMP production and secretion by the lung during childhood or how alterations in MMP levels may be involved in lung damage. We examined endotracheal aspirates from children (<19 years) without lung disease for the presence of MMP activity. Only gelatinase activity was detectable, and inhibitor profiles suggest they represented one or more MMPs. Comparison of gelatinase activity, MMP expression, and MMP activity in children without pulmonary disease with children who required mechanical ventilation for respiratory failure show: 1) gelatinase activity was approximately five- to sixfold higher in respiratory failure; 2) MMP-7, MMP-8, and MMP-9 concentrations and MMP-8 and MMP-9 activities were markedly elevated in respiratory failure; and 3) MMP-7, MMP-8, and MMP-9 levels were significantly correlated in children with lung disease. These studies provide compelling evidence that specific MMPs are present in the diseased lung and may participate in the pathogenesis of pediatric respiratory failure.

Noninvasive Ventilation in Respiratory Failure Due to Cystic Fibrosis

Noninvasive Ventilation in Respiratory Failure Due to Cystic Fibrosis

Noninvasive Ventilation in Respiratory Failure Due to Cystic Fibrosis

Noninvasive positive-pressure ventilation (NIPPV) is increasingly used as an effective means of avoiding endotracheal intubation and mechanical ventilation in patients with respiratory insufficiency or failure. We retrospectively reviewed our experience with NIPPV to treat respiratory failure in five patients with cystic fibrosis (CF). Despite chronic lung disease related to CF, none of our cases were end-stage. All patients had recent pulmonary function tests showing a forced expiratory volume in 1 second (FEV1) of more than 30% predicted for age. All patients had progressive atelectasis, hypoxemia, and impending respiratory failure related to an acute pulmonary exacerbation or upper abdominal surgical procedure (open gastrostomy tube placement). Respiratory rates decreased, oxygen saturation increased, fraction of inspired oxygen (FiO2) requirement decreased, transcutaneous CO2 decreased, and atelectasis resolved with NIPPV. Use of NIPPV provides effective respiratory support while avoiding the need for endotracheal intubation. The applications of NIPPV, reports of its use in patients with CF, and the equipment required are reviewed.

Neural control of mechanical ventilation in respiratory failure.

Mechanical ventilation is a life-saving intervention for the management of acute respiratory failure. Its objective is to reduce excessive respiratory effort while improving gas exchange. By applying positive pressure to the airway, the mechanical ventilator assumes to a varying extent the work necessary to breathe, thereby unloading the respiratory muscles. In its most basic form, called controlled mechanical ventilation, a pre-set tidal volume is delivered at a fixed rate, irrespective of the patient’s own breathing pattern. If the mechanical and natural respiratory cycles are not matched, however, the patient ‘fights’ the ventilator, causing discomfort, gas exchange deterioration and cardiovascular impairment 1 . To avoid discoordination between the patient and the ventilator, it is often necessary to suppress the patient’s intrinsic respiratory drive with the use of hyperventilation, sedation or even muscle paralysis, which increase the risk of complications due to excessive ventilation 2‐3 , drug-related adverse effects

Use of high-frequency and nonconventional ventilation for respiratory failure.

Over the past several years, many new strategies have evolved for improving the care of patients with acute lung injury and respiratory failure. Although many of these new modalities remain unproven, some show much promise for decreasing the morbidity and mortality seen in critically ill patients who need assisted ventilation. In this review, we discuss recent data concerning four of these modalities: high frequency ventilation, prone positioning, tracheal gas insufflation, and partial liquid ventilation.

Haemodynamic and endocrinological effects of noninvasive mechanical ventilation in respiratory failure.

The aim of this study was to investigate the haemodynamic and endocrinological effects of noninvasive positive pressure ventilation (NIPPV). Eleven patients with oedema and recent hypercapnic and hypoxaemic worsening of a chronic respiratory insufficiency were included. Echocardiography, cardiac radionuclide assessment, blood catecholamines, salt and water handling hormones were measured at admission and discharge (long study (LS)). To discriminate between the action of NIPPV and other treatments, measurements were performed on the fourth day, for 4 h without NIPPV and 4 h with NIPPV (short study (SS)). NIPPV entailed a correction of P(a,CO2) and an increase of P(a,O2) in LS and SS. Oedema disappeared. Body weight decreased (from 85+/-42 to 81+/-40 kg) during LS. Systolic and mean pulmonary arterial pressure decreased in LS and SS. Right ventricular ejection fraction increased in LS. Left ventricular ejection fraction did not change. Cardiac index was normal on admission and then decreased. Natriuretic peptides and catecholamines were increased on admission, whereas plasma renin activity, aldosterone and vasopressin were normal. We suggest that in these patients, oedema can occur independently of renin-angiotensin-aldosterone-vasopressin and with a normal cardiac output. Noninvasive positive pressure ventilation allowed a correction of blood gases, associated with the resolution of oedema, a decrease in pulmonary arterial pressures and an increase in right ventricular ejection fraction.

Noninvasive Monitoring of Carbon Dioxide During Respiratory Failure in Toddlers and Infants

We prospectively compared the accuracy of two noninvasive monitors of arterial CO2 (end-tidal and transcutaneous) in mechanically ventilated infants and toddlers with respiratory failure. The study included infants and toddlers less than 48 mo of age who required tracheal intubation and mechanical ventilation for respiratory failure. In each patient, both ETCO2 and transcutaneous CO2 (TC-CO2) were simultaneously monitored and compared with PaCO2 when an arterial blood gas analysis was performed. The cohort for the study included 25 toddlers and infants ranging in age from 1 to 40 mo and in weight from 3.3 to 19.1 kg. A total of 100 sample sets (PaCO2, ETCO2, TC-CO2) was compared. The ETCO2 to PaCO2 difference was 6.8 +/- 5.1 mm Hg, while the TC-CO2 to PaCO2 difference was 2.3 +/- 1.3 mm Hg (P < 0.0001). The absolute difference of the TC-CO2 and PaCO2 was 4 mm Hg or less in 96 of the 100 values, while the ETCO2 to PaCO2 difference was 4 mm Hg or less in 38 of the 100 values (P < 0.0001). Bland-Altman analysis revealed a bias of -0.68 with a precision of +/-2.35 when comparing the TC-CO2 and the PaCO2 and a bias of -6.68 with a precision of +/-5.01 when comparing ETCO2 with PaCO2. In neonates and infants with respiratory failure, TC-CO2 monitoring provided a more accurate estimation of PaCO2 than ETCO2 monitoring.

Noninvasive Positive Pressure Ventilation To Treat Respiratory Failure

To review the clinical use of noninvasive positive pressure ventilation, including its efficacy with acute and chronic forms of respiratory failure, its mechanism of action, and its implementation. Studies were identified through a MEDLINE search using the key words respiratory failure and mechanical ventilation and through a manual review of reference lists of published articles. All original studies relating to the use of noninvasive positive pressure ventilation in respiratory failure were included. Because of the paucity of controlled trials, cohort studies were not excluded. Study design, numbers and diagnoses of patients, ventilator modes, and success and complication rates were extracted and compiled. For acute respiratory failure, studies report improved gas exchange and avoidance of intubation in 60% to 80% of patients with chronic obstructive pulmonary disease, restrictive thoracic disease, congestive heart failure, pneumonia, or postoperative extubation failure. However, the patients were highly selected, and relatively few studies have been published, only one of which was a randomized controlled trial. For chronic respiratory failure due to restrictive thoracic disease, all studies report improved gas exchange and symptoms of hypoventilation after prolonged nocturnal use, although no study was controlled. Some cohort studies of patients with severe chronic obstructive pulmonary disease yielded favorable results, but longer-term, randomized, controlled studies showed minimal, if any, benefit. Noninvasive positive pressure ventilation is effective in the treatment of chronic respiratory failure due to restrictive thoracic diseases. The routine use of such treatment for chronic respiratory failure due to chronic obstructive pulmonary disease and for acute respiratory failure needs to be studied in randomized controlled trials in better-defined patient subsets.

Assisting Ventilation in Respiratory Failure by Negative Pressure Ventilation and by Rocking Bed

The present study was undertaken to evaluate the effectiveness of acute ventilation by rocking bed (RB) and by negative-pressure ventilator (NPV) on arterial oxygenation and carbon dioxide tension in seven patients in whom respiratory failure (PaCO2 [+/- SD], 64 +/- 4 mm Hg; PaO2, 54 +/- 10 mm Hg) was consequent on nonobstructive ventilatory impairment. The increase in SaO2 (percent above baseline, 5 percent RB and 6 percent NPV) was similar for both methods, but a greater fall in PCO2 (percentage change in PCO2, 3 percent RB; 15 percent NPV; p less than 0.05) was observed during NPV. Diaphragmatic and accessory muscle electrical activity was markedly reduced during NPV but remained unchanged or increased on RB. Asynchronous breathing was frequently observed with RB but only rarely with NPV. These preliminary results suggest that effective mechanical ventilatory support could be achieved with either RB or NPV. However, their long-term effects as compared with those of positive-pressure ventilation remain to be explored.

Differential Mechanical Ventilation in Respiratory Failure Due to Severe Unilateral Lung Disease

Severe unilateral lung disease that produces respiratory failure may necessitate mechanical ventilatory support to sustain gas exchange. This article describes the successful use of differential lung ventilation in the management of one patient with diffuse unilateral pneumonia and another with a postoperative bronchopleural fistula after standard methods of mechanical ventilation failed to provide adequate gas exchange for these patients.

Traumatic laryngo-tracheal stenosis

Traumatic laryngo-tracheal stenosis is a disastrous sequelae to blunt and open trauma of the neck, to assisted ventilation for respiratory failure, and following tracheostomy. We have come across 11 such cases during the period 1970–1976. We have made certain observations and suggest some guidelines to prevent its occurrence.

LOBAR OPACIFICATION OF THE LUNG AFTER TRACHEAL EXTUBATION IN NEONATES

PULMONARY ATELECTASIS has long been recognized as a postoperative and postendotracheal extubation complication in surgical patients, both adults and pediatric, '-~ and has been attributed to splinting from incisional pain, in addition to other factors. Postextubation lobar opacification has occurred frequently in our non-operated newborn infants who have received mechanical ventilation for respiratory failure in the newborn period. This phenomenon is apparently widespread? -7 but its significance in the delicate postextubation process following prolonged mechanical ventilation has not been reported. Anticipation and prompt recognition of this problem may result in effective therapy? The risk factors that might predispose to this complication and allow its anticipation, however, have not been delineated. We have reviewed our recent experience with neonates who developed postextubation lobar opacification and with similar infants who did not develop the complication, in an attempt to determine its significance and to predict, if possible, which infants may be at high risk. MATERIALS AND METHODS The records of all neonates who were intubated with endotracheal tubes in the Holden Perintal Unit of C.S. Mott Children's Hospital from January to June, 1975, were reviewed. Twenty-seven patients with birth weights of 1.1 to 4.7 kg had positive pressure intermittent mandatory ventilation or, in two cases, continuous positive airway pressure applied through endotracheal tubes for more than eight hours. In 17 infants the primary diagnosis was respiratory distress syndrome and prematurity. Four neonates were asphyxiated. Other single diagnoses included meconium aspiration, congenital heart disease,

Regulation of alveolar ventilation in respiratory failure

Regulation of alveolar ventilation in respiratory failure

The effect of mechanical ventilation after open-heart surgery.

The effect of mechanical ventilation after open-heart surgery.