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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Initial studies have shown that the intravascular oxygenator and carbon dioxide removal device (IVOX, Cardiopulmonics, Inc., Salt Lake City, UT) removes approximately 30% of VCO2. After noting increased CO2 removal with increased venous CO2, we developed a conceptual analytical model based on data obtained from patients and laboratory experiments. Increasing the CO2 gradient across the hollow fiber membranes of IVOX increases the operating efficiency of the device. Using the patient management technique of permissive hypercapnia (limiting tidal volumes, respiratory rates, and airway pressures) serves to increase the CO2 gradient across the membrane. The conceptual analytical model predicts that a PaCO2 of 75-80 mm Hg is required to obtain a CO2 gradient that results in IVOX CO2 removal of approximately 90-100 ml CO2/min. This technique may allow a broader application of both permissive hypercapnia and IVOX in acute respiratory failure.
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PMID:Intracorporeal CO2 removal and permissive hypercapnia to reduce airway pressure in acute respiratory failure. The theoretical basis for permissive hypercapnia with IVOX. 832 69

Nasal intermittent positive-pressure ventilation (NIPPV) has been used for domiciliary ventilatory support, and to avoid intubation for acute respiratory failure in patients with chronic airflow limitation (CAL). Its role in weaning patients from assisted ventilation in intensive care has not been defined. We have used NIPPV to wean 14 patients with respiratory disease who were referred either because of predicted difficulty in weaning or failure to wean using standard techniques. Twelve patients were ventilated for acute respiratory failure; eight patients had CAL and four had chest wall or neuromuscular disease. Two further patients with chest disease were difficult to wean following surgery. Weaning was successful in 13 patients. NIPPV corrected hypoxia, reduced hypercapnia and was well tolerated. Weaning from NIPPV was achieved in all patients with CAL, although three patients with chest wall disease later required domiciliary ventilatory support. All but one of the patients survived to leave hospital. NIPPV may have an important role in weaning from assisted ventilation, particularly in patients with underlying chronic respiratory disease. This preliminary report needs to be followed by a controlled study comparing NIPPV with established weaning methods.
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PMID:Nasal intermittent positive-pressure ventilation in weaning intubated patients with chronic respiratory disease from assisted intermittent, positive-pressure ventilation. 849 99

Experimental and clinical use of the intravascular oxygenator (IVOX), an intravenacaval gas exchange device, in acute respiratory failure yielded a CO2 transfer of 40-70 ml/min (approximately 30% of adult CO2 production) at normocapnia. Although significant, this rate of CO2 removal is not clinically useful. To maximize CO2 transfer, given the same gas exchange properties and structure design of the IVOX, the authors analyzed the effects of permissive hypercapnia (stepwise increase in arterial blood pCO2 up to 100 mmHg) and active blood mixing (with an intraaortic balloon pump) on different sizes of IVOX (sizes 7, 8, and 9 mm, surface area 0.21, 0.32, and 0.41 m2, respectively) using a previously established ex vivo circuit to model the human vena cava. The CO2 net transfer coefficient (KCO2) was averaged for all sizes and applied to extrapolate the surface area requirements under different pCO2 and with active blood mixing. Results showed that KCO2 increased in a linear relationship with blood flow. Increases in blood flow and blood pCO2 further increase CO2 removal and decrease surface area requirements. For blood flow at 4.0 L/min, the membrane surface area required for 150 ml/min CO2 removal at blood pCO2 of 40 mmHg is 1.76 m2, but can be decreased to 0.47 m2 at blood pCO2 of 80 mmHg, and further to 0.42 m2 with additional active blood mixing. A 0.42 m2 surface area is associated with an O2 transfer of 80 ml/min without and 107 ml/min with active blood mixing. It is concluded that CO2 removal by IVOX alone is limited by insufficient surface area and the resistance in the blood-surface boundary layer. The combination of permissive hypercapnia, adequate blood flow, and active blood mixing can substantially improve CO2 removal and can therefore achieve clinically significant CO2 removal by intravenacaval gas exchange devices during severe respiratory failure.
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PMID:Stragegies to reduce surface area requirements for carbon dioxide removal for an intravenacaval gas exchange device. 857 69

This prospective study assessed, in 10 conscious patients without a history of chronic respiratory disease, the feasibility of mechanical pressure support ventilation with PEEP by face mask for the treatment of acute respiratory failure without hypercapnia. Pressure support level was determined to obtain a VT of 5 to 10 mL.kg-1 and a decrease of respiratory rate of more than 20%. FIO2 and PEEP levels were determined to obtain a SpO2 > 92% and a PaO2 > 70 mmHg. The efficiency of the technique was assessed through the time course of respiratory rate, PaO2, PaCO2 and SaO2. The technique was efficient in all patients and tracheal intubation was not required. During face mask ventilation, a significant decrease in respiratory rate and an increase in PaO2 and SaO2 were observed. Pressure support ventilation with PEEP by face mask is an efficient technique for the treatment of acute non hypercapnic respiratory failure in conscious and cooperative patients.
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PMID:[Inspiratory aid with facial masks during acute respiratory failure without hypercapnia]. 873 48

There is a growing body of evidence suggesting that high levels of inflation pressure and high levels of PEEP may be injurious to lung tissue and other organ systems. Limiting peak alveolar pressures below 35 cm H2O may help in avoiding these injuries. The findings have led to the development of a lung-protective strategy that is based on physiologic parameters. This strategy, often using permissive hypercapnia and pressure-limited modes of ventilation, may gain widespread use in the near future. If this strategy reduces barotrauma, a reduction in the length of time on mechanical ventilation and mortality rates can be anticipated. At our center we routinely initiate mechanical ventilation in patients with acute lung injury, using tidal volumes of approximately 6 mL/kg. This may be decreased further if peak alveolar pressures exceed 30 to 35 cm H2O. PEEP is added to maximize alveolar recruitment and oxygenation. Optimal PEEP is located at the inflection point of the respiratory compliance curve. Usually a PEEP of 8 to 12 cm H2O is sufficient. Although we usually initiate mechanical ventilation with a volume-cycled mode, we are not hesitant to switch rapidly to a pressure-limited mode if results are unsatisfactory. We believe that more attention to the potential harmful effects of pressure and volume on lung architecture may result in further improvement of survival in patients with acute respiratory failure.
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PMID:High-inflation pressure and positive end-expiratory pressure. Injurious to the lung? Yes. 883 94

We report on a 45-year old woman with daytime sleepiness, polycythemia, hypoxemia and hypercapnia, admitted to hospital on three occasions in a 10 month period for acute respiratory failure. Polysomnography demonstrated apneas of central type, testing of the respiratory drive suggested central alveolar hypoventilation and magnetic resonance imaging showed an Arnold-Chiari malformation with syringomyelia. The originality of this case is the absence of any neurologic sign, respiratory failure being the sole manifestation of the Arnold-Chiari malformation.
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PMID:[Isolated respiratory insufficiency in Arnold-Chiari malformation]. 892

An 18-year-old, previously healthy male presented with bilateral pneumonia and acute respiratory failure with severe carbon dioxide retention. The presence of mild brainstem signs and hypoventilation led to the discovery of a platybasia, basilar invagination, and kinking of the medulla oblongata with early syrinx. He was operated upon but postoperatively was noted to have a mixed type of sleep apnea. This case illustrates the diagnostic challenge in acute respiratory failure in a previously healthy young person and the possible pathogenic mechanisms underlying it.
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PMID:A cranio-cervical malformation presenting as acute respiratory failure. 893 17

Impaired pulmonary gas exchange can result from lung parenchymal failure inducing oxygenation deficiency and fatigue of the respiratory muscles, which is characterized by hypercapnia or a combination of both mechanisms. Contractility of and coordination between the diaphragm and the thoracoabdominal respiratory muscles predominantly determine the efficiency of spontaneous breathing. Sepsis, cardiac failure, malnutrition or acute changes of the load conditions may induce fatigue of the respiratory muscles. Augmentation of spontaneous breathing is not only achieved by the application of different technical principles or devices; it also has to improve perfusion, metabolism, load conditions and contractility of the respiratory muscles. Intermittent mandatory ventilation (IMV) allows spontaneous breathing of the patient and augments alveolar ventilation by periodically applying positive airway pressure tidal volumes, which are generated by the respirator. Potential advantages include lower mean airway pressure (PAW), as compared with controlled mechanical ventilation, and improved haemodynamics. Suboptimal IMV systems may impose increased work and oxygen cost of breathing, fatigue of the respiratory muscles and CO2 retention. During pressure support ventilation (PSV), inspiratory alterations of PAW or gas flow (trigger) are detected by the respirator, which delivers a gas flow to maintain PAW at a fixed value (usually 5-20 cm H2O) during inspiration. PSV may be combined with other modalities of respiratory therapy such as IMV or CPAP. Claimed advantages of PSV include decreased effort of breathing, reduced systemic and respiratory muscle consumption of oxygen, prophylaxis of diaphragmatic fatigue and an improved extubation rate after prolonged periods of mechanical ventilation. Minimum alveolar ventilation is not guaranteed during PSV; thus, close observation of the patient is mandatory to avoid serious respiratory complications. Continuous positive airway pressure breathing (CPAP) maintains PAW above atmospheric pressure throughout the respiratory cycle, which may increase functional residual capacity and decrease the effort of breathing. CPAP has been conceptually designed for the augmentation of spontaneous breathing and requires the intact central and peripheral regulation of the respiratory system. Airway pressure release ventilation (APRV) improves alveolar ventilation by intermittent release of PAW, which is kept above atmospheric pressure by means of a high-flow CPAP system. The opening of an expiratory valve for 1-2 s induces a decreased PAW and lung volume, which increases rapidly to pre-exhalation values after closure of the valve due to the high gas flow within the circuit (90-100 1/min). APRV may improve haemodynamics and VA/Q distribution as compared with conventional mechanical ventilation. Biphasic positive airway pressure (BIPAP) is characterized by the combination of spontaneous breathing and time-regulated, pressure-controlled mechanical ventilation. During the respiratory cycle the ventilator generates two alternating CPAP levels, which can be modified with regard to time and pressure. As with APRV, alveolar ventilation is maintained even if the spontaneous breathing efforts of the patient cease, which improves the safety of both modes of respiratory therapy. The contribution of spontaneous breathing to total minute ventilation may be important, since a decreased shunt and improved VA/Q relationship have been observed in experimental non-cardiogenic lung oedema. These data give support to the concept that spontaneous breathing should be maintained and augmented in the setting of acute respiratory failure.
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PMID:[Augmented spontaneous breathing]. 896 3

Noninvasive mechanical ventilation (NMV) now represents the first step in the management of acute on chronic respiratory failure (A/CRF). During the last 5 yrs, many studies have confirmed the feasibility of NMV in an acute setting, either by facial or nasal interface, used in addition to volumetric or barometric respirators, to manage A/CRF. The best indications for NMV are slowly progressive A/CRF, frequently represented by chronic obstructive pulmonary disease (COPD), or restrictive pulmonary disease. The criteria to initiate NMV in such patients are worsening of respiratory status and arterial blood gas (ABG) values, with increased hypoxia, hypercapnia and respiratory acidosis, despite optimal management with medication, physiotherapy and oxygen therapy. Respiratory encephalopathy is not an absolute contraindication; however, bronchial hypersecretion indicates that care is needed under NMV. Invasive mechanical ventilation with endotracheal (ET) intubation is discussed in the case of failure of NMV, when clinical status and ABG values worsen in spite of it. The signal for ET intubation is then obvious, represented by severe dyspnoea leading to respiratory pauses or arrest, severe cyanosis, and signs of haemodynamic instability. Despite immediate evidence of ominous cardiorespiratory inefficiency, ET intubation may be delayed and often avoided with the help of NMV. Criteria should be studied to identify guidelines for cessation of NMV, in order not to continue with the technique too long considering the safety of the patient. Indications for NMV in other kinds of ARF have received less study and are more controversial.
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PMID:Noninvasive mechanical ventilation and acute respiratory failure: indications and limitations. 915 23

A number of attempts have been made to develop measures of severity of illness for patients in the intensive care unit (ICU), but the impact of these indices in a Respiratory Intensive Care Unit (RICU) has not really been studied. At present, outcome can be accurately predicted in approximately 85% of ICU patients, while no data are available for the RICU. These indices will be reviewed in the article. The sophisticated Mortality Probability Model (MPM) II is used to predict the outcome of ICU patients. This technique is based on statistically-derived weights for its variables. The "most popular" indices are the Acute Physiology and Chronic Health Education (APACHE), the Simplified Acute Physiological Score (SAPS) and the Therapeutic Intervention Scoring System (TISS). Overall, the predictive accuracy of the latest APACHE III equation and score is rather good, but there are important limitations concerning its use in the RICU. The SAPS includes 17 variables, and can be considered as a simplified version of APACHE sharing with it the same problems of application. The TISS requires data on approximately 70 treatment variables and assigns each a score ranging 1-4. A high score represents serious intervention, while a low score illness requires much less medical or nursing intervention. The sum of these scores indicates severity of illness because more critical patients are presumed to require higher levels of interventions. The RICU is also characterized by the use of noninvasive mechanical ventilation (NMV) in the treatment of acute respiratory failure. Some indices able to predict the success of NMV, have been developed recently during a brief trial of NMV, and included the level of acidosis and hypercapnia.
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PMID:Scoring of severity in patients admitted to a respiratory intensive care unit. 915 27


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