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PubMed2005

Cardiopulmonary and acid-base effects of desflurane and sevoflurane in spontaneously breathing cats.

The cardiopulmonary effects of desflurane and sevoflurane anesthesia were compared in cats breathing spontaneously. Heart (HR) and respiratory (RR) rates; systolic (SAP), diastolic (DAP) and mean arterial (MAP) pressures; partial pressure of end tidal carbon dioxide (PETCO2), arterial blood pH (pH), arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2); base deficit (BD), arterial oxygen saturation (SaO2) and bicarbonate ion concentration (HCO3) were measured. Anesthesia was induced with propofol (8+/-2.3mg/kg IV) and maintained with desflurane (GD) or sevoflurane (GS), both at 1.3 MAC. Data were analyzed by analysis of variance (ANOVA), followed by the Tukey test (P<0.05). Both anesthetics showed similar effects. HR and RR decreased when compared to the basal values, but remained constant during inhalant anesthesia and PETCO2 increased with time. Both anesthetics caused acidemia and hypercapnia, but BD stayed within normal limits. Therefore, despite reducing HR and SAP (GD) when compared to the basal values, desflurane and sevoflurane provide good stability of the cardiovascular parameters during a short period of inhalant anesthesia (T20-T60). However, both volatile anesthetics cause acute respiratory acidosis in cats breathing spontaneously.

Acid-Base Equilibrium↗
PubMed2005

Neonatal thoracoscopic repair of congenital diaphragmatic hernia: selection criteria for successful outcome.

BACKGROUND/PURPOSE: Complications of open conversion, hypercarbia, and intestinal injury have plagued minimally invasive approaches to congenital diaphragmatic hernia (CDH) repair in neonates. To safely begin using minimally invasive techniques for neonatal CDH repair, we formulated preoperative selection criteria and operative techniques that would enhance chances for successful thoracoscopic primary diaphragm repair and uncomplicated outcome. METHODS: During the period from January 2003 to October 2004, neonates were selected for thoracoscopic CDH repair using anatomic and physiologic criteria. Anatomically, all patients were required to have stomach in the abdomen by radiography. Physiologically, all patients were required to be on minimal ventilator support with preoperative ventilator peak inspiratory pressures in the low 20s mm Hg. No patient could have clinical evidence of pulmonary hypertension at the time of surgery. Thoracoscopic CDH repair was performed using 3 trocars (3 and 5 mm). The hernia contents were reduced into the abdomen using 5-mm Hg insufflation, and the diaphragms were repaired primarily using interrupted 3-0 Ethibond simple sutures (Ethicon, Inc, Piscataway, NJ). Posterolateral diaphragm stitches were passed around the posterolateral ribs and tied extracorporeally. RESULTS: Thirty neonates with CDH were admitted to Children's Hospital Boston and Vanderbilt Children's Hospital during the study period. Eight patients (27%) met selection criteria and 7 underwent thoracoscopic CDH repair. Primary diaphragmatic repair was successfully accomplished thoracoscopically in all neonates without perioperative complication. Preoperative anatomic criteria correlated accurately with intact esophageal hiatus and primary diaphragm repair. Physiologically, each patient tolerated intrathoracic insufflation and CDH repair without clinical pulmonary hypertension or blood pressure lability. Three patients had intraoperative respiratory acidosis that was reversed with ventilator changes. Operative times averaged 152 minutes and ranged from 212 to 106 minutes. Postoperative mechanical ventilation ranged from 0 to 7 days, and the length of hospitalization ranged from 5 to 32 days. Longest follow-up has been 17 months. One patient required reoperation for recurrent CDH at 10 months after repair, but there have been no other long-term complications. CONCLUSIONS: Neonatal thoracoscopic CDH repair is safe in selected patients who have good preoperative pulmonary function and anatomy amenable to primary diaphragmatic repair. A wider range of neonates may be acceptable for thoracoscopic CDH repair with increasing surgical experience.

Female↗
PubMed2006

Oxygen supplementation during airway instrumentation improves intestinal barrier dysfunction.

BACKGROUND/PURPOSE: The study investigates the effect of airway instrumentation on the histopathology of the intestine, contribution of bacterial translocation, and whether oxygen supplementation may counteract the possible detrimental effects of this procedure. METHODS: Fifty-five Wistar rats were assigned to 3 groups. Group 1 served as control. Groups 2 and 3 underwent airway instrumentation. In addition, group 3 received oxygen supplementation during the procedure. Arterial blood gases were measured after the procedure. Samples of mesenteric lymph nodes ileum, cecum, spleen, liver, and blood were harvested for determination of bacterial growth after 24 hours. Ileum was evaluated histologically. RESULTS: In group 2, the rats presented a decrease in oxygen saturation (90% +/- 0.3%, P < .0001), hypoxemia (PaO2, 73 +/- 1.5 mm Hg; P < .0001), and respiratory acidosis (pH 7.27 +/- 0.01; PaCO2, 48 +/- 1.5 mm Hg; P < .0001) after airway instrumentation. These rats also showed evidence of intestinal injury (P < .0001) and bacterial translocation to mesenteric lymph nodes in 10 of 20 rats compared with 0 of 15 in the controls (P = .004). In group 3, oxygen supplementation provided normal arterial blood gas parameters, and led to minimal histologic changes and bacterial translocation in only 1 of 20 rats, compared with group 2 (P < .0001 and P = .005, respectively). CONCLUSIONS: The study suggests that oxygen supplementation during airway instrumentation prevents hypoxemia, intestinal damage, and bacterial translocation.

Animals↗
PubMed2000

Neutrophil degranulation and complement activation during fetal cardiac bypass.

BACKGROUND: Fetal cardiac bypass results in dysfunction of the fetoplacental unit (FPU) characterized by increased placental vascular resistance and respiratory acidosis. However the mechanisms of this dysfunction are not completely understood. To test the hypothesis that complement activation and neutrophil degranulation may contribute to the placental dysfunction associated with fetal bypass, we compared placental hemodynamics, complement activation, and neutrophil degranulation among fetuses exposed to cardiac bypass with a miniaturized bypass circuit including an in-line axial flow pump (Hemopump), fetuses undergoing bypass with a conventional roller pump circuit, and control fetuses that were similarly exposed but did not undergo bypass. METHODS: Twenty-six Western Cross sheep fetuses (median 122 days gestation) were randomly assigned to undergo cardiac bypass for 30 minutes with the Hemopump circuit (n = 8), to undergo bypass for 30 minutes with the conventional (roller pump) circuit (n = 10), or to undergo identical exposure and cannulation but not bypass (n = 8, controls). Blood samples were collected to measure white cell count and differential, and C3a and lactoferrin levels prior to bypass, at the end of bypass, and 1 and 2 hours after bypass. Hemodynamics and blood gases were also monitored. RESULTS: There was a fall in white cell count over time that continued after bypass in all groups; neutrophils and lymphocytes were affected similarly. C3a levels rose significantly from prebypass to postbypass in the roller pump group (p<0.0001) but not in either of the other groups. Lactoferrin levels rose significantly from start of bypass in both bypass groups (Hemopump p = 0.01; roller pump p<0.0001) but not in controls. The elevation in lactoferrin level coincided with worsening placental gas exchange and deteriorating cardiac function. CONCLUSIONS: Complement and neutrophil activation occurred with fetal cardiac bypass but only neutrophil activation mirrored the FPU and cardiac dysfunction, suggesting that products of neutrophil activation may be important contributing factors. Improved FPU function with a bypass circuit that has less extracorporeal surface and does not require a large priming volume may be due in part to a reduction in the magnitude of this inflammatory response.

Animals↗
PubMed2001

Hemodynamic effects of inspired carbon dioxide after the Norwood procedure.

BACKGROUND: Mortality in the early postoperative period after the Norwood procedure remains substantial. Inspired carbon dioxide (CO2) has been suggested to improve hemodynamic status in this setting. Inspired CO2 can be delivered by one of two strategies, ie, with or without an accompanying increase in minute ventilation. The hemodynamic effects of these two strategies have not previously been studied in a controlled fashion. METHODS: Seventeen infants (median age, 9 days; range, 4 to 49 days) undergoing Norwood procedures were prospectively enrolled in this crossover study. Patients were studied while sedated, paralyzed, and mechanically ventilated 1 day to 6 days after operation. The inspired oxygen fraction was kept constant (mean value, 0.24 +/- 0.01). Measurements were made at five time points: 1 = baseline; 2 = inspired CO2 with increased ventilation; 3 = baseline; 4 = inspired CO2 alone; and 5 = baseline. Mixed venous oxygen saturation was monitored using indwelling lines in the superior vena cava. RESULTS: Inspired CO2 with increased ventilation produced a rise in mean airway pressure with no change in arterial CO2 tension or pH. This strategy had no effect on hemodynamic status or oxygen delivery. Inspired CO2 alone produced a rise in arterial CO2 tension and a fall in arterial pH (respiratory acidosis). This strategy resulted in significant improvement in both variables of systemic oxygen delivery: mixed venous oxygen saturation increased from 48% +/- 2% to 56% +/- 2% (p < 0.05), and arteriovenous oxygen saturation difference decreased from 3% +/- 2% to 26% +/- 2% (p < 0.05). CONCLUSIONS: Inspired CO2 after the Norwood procedure can improve oxygen delivery. This improvement occurs only if minute ventilation is kept constant. There is no improvement if minute ventilation is increased. Clinical use of inspired CO2 may be limited by the accompanying fall in pH. Differentiation of cerebral from total-body effects of inspired CO2 will require further study.

Administration, Inhalation↗
PubMed1977

Selective bronchial intubation for the treatment of severe localized pulmonary interstitial emphysema in newborn infants.

As an alternative to lobectomy and in order to preserve lung tissue which may be potentially functional we have selectively intubated the right main bronchus in four infants 12 to 25 days old with severe, pulmonary interstitial emphysema of the left lung. In each case the localized hyperinflation disappeared within 5 to 48 hours of contralateral selective bronchial intubation. The duration of SBI was 1.5 to 5 days. Three patients benefited from the procedure; there were no serious complications. We propose that SBI should be tried in infants with severe, localized PIE which has caused mediastinal shift, compressive atelectasis, and respiratory acidosis requiring mechanical ventilation despite vigorous pulmonary therapy and usual supportive measures.

Bronchi↗
PubMed1980

Free bilirubin concentrations and bilirubin-binding affinity in term and preterm infants.

Free bilirubin concentration, bilirubin-binding capacity, and bilirubin-binding affinity were determined by peroxidase oxidation in 66 newborn infants. Twelve healthy term infants whose unconjugated bilirubin concentration was 15.8 +/- 3.7 mg/dl (mean +/- SD) had a binding capacity of 31.9 +/- 3.7 mg/dl (bilirubin: albumin molar ratio = 0.89 +/- 0.07) and Ka = 28 +/- 11 x 10(7)/M. Twelve term infants with clinical complications of asphyxia, acidosis, respiratory distress, or sepsis, and 17 preterm infants with no complications had lower serum albumin concentrations and slightly reduced binding capacity and affinity compared to the healthy term infants. Free bilirubin concentrations were similar in these three groups, averaging 8 to 9 nmol/l in each group. Twenty-five preterm infants with complications had significantly higher free bilirubin (19 +/- 11 nmol/l), lower binding capacity, and lower binding affinity than any of the other three groups (P less than 0.01 for all comparisons). Five of the 25 sick preterm infants had kernicterus at autopsy. These five infants were similar to the other 20 in birth weight, gestational age, serum bilirubin, and serum albumin level, but had significantly higher free bilirubin and significantly lower binding capacity and affinity. The data suggest that serious neonatal illness is associated with a marked reduction in bilirubin-binding capacity and affinity and an increased risk of kernicterus in preterm infants. The mechanism by which neonatal morbidity decreases bilirubin binding is not known.

Bilirubin↗
PubMed2002

Effects of functional knock-out of alpha 1 glycine-receptors on breathing movements in oscillator mice.

The effects of a deficiency of glycinergic inhibition deriving from mutations of the glycine-receptor gene Glra1 on the breathing pattern of oscillator mice were studied. We compared the development of breathing frequency, tidal volume and minute ventilation from control mice (wild type- and heterozygous oscillator mice) with those of homozygous oscillator mice during early postnatal periods from p9 until p21. The changes of ventilation were correlated with body-weight and changes in blood-pH. During the second to third weeks of postnatal development, breathing frequency increased from 310 to 445.4 mm-1 in control mice. Oscillator mice reached a maximal value of 313.3 min-1 at p18 followed by a fast decrease to 233.0 min-1. This decrease is caused by a prolongation of expiratory duration. Tidal volume showed a steady increase from 6.6 to 15.1 microliters in control animals. In comparison, oscillator mice showed significant lower values after p14. After p15, minute ventilation of oscillator mice declined as compared with control animals leading to respiratory acidosis at p20.

Animals↗
PubMed1999

Chronic resistive loading induces diaphragm injury and ventilatory failure in the hamster.

The purpose of this study was to examine the effects of tracheal banding for 30 days on arterial blood gases, and diaphragm structure and function. Hamsters were tracheal banded (TB) or underwent a sham procedure (C) (n = 16 and 18, respectively). After 30 days, arterial blood gases from awake TB hamsters showed hypoxemia and a respiratory acidosis. Histochemical analysis of diaphragm cross-sections showed a five-fold greater area fraction of abnormal muscle; a greater variation in fiber size; and a 3% higher proportion of type 1 fibers in TB than C hamsters. In vitro physiologic studies of costal strips from TB hamsters showed lower stress (45-70% over 10-100 Hz) than C values. Maximal esophageal pressure during occlusion was 45% higher and normalized diaphragm mass was 10% higher in TB hamsters than C hamsters. We conclude that the lower stress in vitro was attributable, at least in part, to diaphragm injury. Hypercapnea was present in spite of the higher diaphragm mass and maximal esophageal pressures in banded hamsters.

Animals↗
PubMed1992

Anesthesia for patients with diaphragmatic hernia and severe dyspnea.

Problems facing a patient with severe dyspnea secondary to diaphragmatic herniation are hypoxia, hypercarbia and respiratory acidosis, and cardiovascular instability. It is easy to precipitate a crisis in these patients during anesthetic induction as a result of stress, bad positioning, induction of pneumothorax, or inappropriate anesthetic technique. These patients require a smooth, stress-free perianesthetic period with preoxygenation, positioning with the affected side down, rapid intravenous induction, endotracheal intubation, and mechanical ventilation. Maintenance with isoflurane is preferred, and nitrous oxide should be avoided. Close monitoring of the cardiovascular and pulmonary systems is essential. Recovery from anesthesia should include oxygen supplementation, pleural drainage, and local analgesia if required.

Anesthesia↗
PubMed1985

A standard comparison of esophageal obturator airway and endotracheal tube ventilation in cardiac arrest.

A comparison of esophageal obturator airway (EOA) and endotracheal tube (ET) ventilation was performed while standardizing the method of oxygen delivery and assuring true sampling of arterial blood. Forty-eight victims of prehospital cardiac arrest had an arterial blood gas drawn in the emergency department while being ventilated with an EOA. Endotracheal intubation was performed immediately thereafter and another blood gas was drawn. All patients without a pulse were sampled through an arterial line placed by cutdown. Patients who developed a pulse during the resuscitation were sampled percutaneously or by arterial line. Patients with a perfusing rhythm (N = 19) had the following mean EOA blood gas values: pH, 7.34 +/- .17; PCO2, 28 +/- 8 mm Hg; and PO2, 420 +/- 125 mm Hg. Their subsequent mean ET blood gas values were pH, 7.40 +/- .13; PCO2, 25 +/- 8 mm Hg; and PO2, 390 +/- 100 mm Hg. Pulseless patients (N = 29) had mean EOA blood gas values of pH, 7.36 +/- .26; PCO2, 32 +/- 21 mm Hg; and PO2, 285 +/- 192 mm Hg. Their subsequent mean ET blood gas values were pH, 7.30 +/- .21; PCO2, 36 +/- 26 mm Hg; and PO2, 260 +/- 185 mm Hg. There was no statistically significant difference in the PCO2 or PO2 obtained with EOA compared with ET ventilation. There was a significant difference in the pH corrected for respiratory acidosis in pulseless patients, but not in patients with a perfusing rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Suicidal sodium azide ingestion.

Sodium azide (NaN3) is a highly reactive, toxic, widely used chemical. Although industrial exposure is common, fatal ingestion is rare. We describe the case of a 30-year-old man who ingested 15 to 20 g of sodium azide. He became comatose within two hours and eventually expired from a combination of acidosis, respiratory depression, and ventricular fibrillation. In sufficient doses, sodium azide is rapidly fatal and there is no effective treatment.

Administration, Oral↗
PubMed1997

Effects of anoxia on intracellular free Ca2+ in isolated cardiomyocytes from turtles.

One of the most important negative consequences of hypoxic stress in the mammalian myocardium is a breakdown in intracellular calcium homeostasis. This study examines the effects of anoxic stress on intracellular calcium regulation in isolated ventricular myocytes from a hypoxia tolerant vertebrate, the western painted turtle (Chrysemys picta bellii). Isolated calcium tolerant cardiomyocytes from turtle hearts were mounted on a glass cover slip that formed the bottom of a sealed, Plexiglas perfusion chamber. Free [Ca2+]i (determined by FURA2 fluorescence) in isolated turtle cardiomyocytes averaged 31.7 +/- 3.2 nM after 30 min of normoxic perfusion (20 degrees C, pHc = 7.77). This value is on the low end of the published range for mammalian cardiomyocytes. Perfusion with anoxic Ringer equilibrated with 3% CO2, resulted in a significant increase in free [Ca2+]i to 941 +/- 494.6 nM after 60 min. Increasing the CO2 in the perfusion solution to 5% or 6% blunted this rise (peak levels after 60 min of anoxia were 420.5 +/- 176.0 nM and 393.8 +/- 132.8 nM, respectively). A further increase to 8% CO2 increased the maximal value for free [Ca2+]i to 610.9 +/- 297.5 nM. In eight cells from the 5% CO2 protocol in which [Ca2+]i was monitored during recovery, reperfusion with normoxic Ringer rapidly lowered intracellular calcium to 92.8 +/- 9.7 nM within 15 min. Anoxia at relatively high extracellular (and hence intracellular) pH results in an increase in free [Ca2+]i comparable in magnitude and time course to that seen in some mammalian cardiomyocyte preparations. Perfusion of anoxic myocytes with Ringer equilibrated with either 5% or 6% CO2 blunted this increase in intracellular calcium, possibly an example of the pH paradox effect. A more severe combination of respiratory acidosis and anoxia (8% CO2) removed this protective effect.

Animals↗
PubMed1989

[Treatment of malignant hyperthermia crisis during anesthesia].

Malignant hyperthermia (MH), triggered by anaesthesia, is a rare and potentially fatal condition. It requires immediate and specific treatment. This review focuses on anticipation and organisation of treatment. Anticipation means that dantrolene should be available, that an anaesthetic machine should be kept free from all vapours of halogenated anaesthetics, and methods of cooling should be planned. A prompt availability in all operating theatres of dantrolene and the required machines is emphasized. Treatment of a MH episode includes stopping the administration of triggering agents, administering dantrolene, correcting metabolic and respiratory acidosis, and cooling. Different aspects of the cardiovascular pharmacology of dantrolene are discussed. Other drugs are seldom required if proper treatment is started soon enough after the crisis. Complications may arise during a fulminant episode. They are difficult to treat, and may lead to sequelae. A rational approach to the treatment of hyperkalaemia, circulatory and renal failure is discussed. After the crisis, dantrolene should be continued for a short time. Finally, the nonspecific signs which can give the earliest diagnosis possible of MH are discussed: an early diagnosis and early treatment with dantrolene are essential in reducing the mortality of malignant hyperthermia.

Anesthesia, General↗
PubMed2001

Physiologic changes during laparoscopy.

The short-term benefits of minimal access techniques include less pain, early mobilization, and shorter hospital stay. Nonetheless, significant data have accumulated regarding the complications associated with laparoscopic techniques, including those that are unique to laparoscopic surgery such as bile duct injury and disruption of major blood vessels. Other problems such as myocardial ischemia and respiratory acidosis are associated with the cardiopulmonary effects of pneumoperitoneum and systemic CO2 absorption. These physiologic changes, although tolerated by healthy patients, could have particular adverse consequences for infirm and critically ill patients. It would appear that minimizing IAP during insufflation decreases the risk of potentially marked cardiovascular changes and regional blood flow alterations. In turn, this could arguably decrease the risk of perioperative myocardial events, or organ dysfunction or failure. Laparoscopy in the critically ill patient is questionable because the role is not established. An ICU patient has little to gain from the benefits of early mobilization. Conversely, in the presence of raised ICP or borderline organ function, the physiologic changes associated with pneumoperitoneum and laparoscopy could have profound detrimental effects.

Hemodynamics↗
PubMed2000

Clinical, cardiopulmonary, hematological and serum biochemical effects of sevoflurane and isoflurane anesthesia in oxygen under spontaneous breathing in sheep.

Effects of sevoflurane and isoflurane anesthesia in oxygen on clinical, cardiopulmonary, hematological, and serum biochemical findings were compared in sheep breathing spontaneously undergoing minor surgical operations during short-term (60-80min) or long-term (3-4h) anesthesia. All sheep were premedicated with atropine sulfate (0.1mg/kg) intramuscularly, and 10min later, induced to anesthesia by intravenous infusion of sodium thiopental (mean 14.1+/-3.4 S.D. mg/kg). After intubation, they were anesthetized with either isoflurane or sevoflurane in oxygen at a total gas flow rate of 1.5l/min. The results revealed that recovery time with sevoflurane was more rapid than with isoflurane. Respiration rates, tidal volume, minute ventilation and heart rates during sevoflurane anesthesia were similar to those during isoflurane anesthesia. The degree of respiratory acidosis during sevoflurane anesthesia was also similar to that during isoflurane anesthesia. There were no significant differences between sevoflurane and isoflurane anesthesia in hematological and serum biochemical values.

Journal Article↗
PubMed1998

Hemodynamic and hormonal changes during pneumoperitoneum and trendelenburg positioning for operative gynecologic laparoscopy surgery.

Objective: The number and types of surgical procedures being preformed using laparoscopic technique is increasing due to technological advances. Recent studies suggest the carbon dioxide pneumoperitoneum and patient positioning causes hemodynamic alterations, respiratory acidosis, and a release of stress hormones. However, to date, no studies have investigated the physiological effect of laparoscopic procedures lasting more than 60 minutes on the stress response and the effect of Trendelenburg positioning. The purpose of this study was to identify the physiological effect of pneumoperitoneum and positioning during prolonged laparoscopy on hemodynamic (cardiac index, mean arterial pressure, heart rate, systemic vascular resistance, and stroke volume), metabolic (arterial blood gases), and hormone (arginine vasopressin, aldosterone, and plasma renin activity) parameters. We hypothesized that pneumoperitoneum and patient positioning will alter the hemodynamic, hormone, and metabolic parameters.Methods: The study was longitudinal in design and sampled a total of 31 healthy subjects having a gynecologic oncologic laparoscopic procedure at Hurley Medical Center, Flint, Michigan. The subjects were randomly assigned one of three groups receiving an initial insufflation pressure of either 10, 15, or 18 mmHg. After obtaining informed consent hemodynamic, metabolic, and hormone measurements were obtained at the following times: 1) pre-induction, 2) post-induction, 3) post-insufflation, 4) post-Trendelenburg 5 minutes and at 30, 60, 90, and 120 minutes post-insufflation. The results were analyzed using multivariate analysis of variance for repeated measures with a P <.05. A power of 0.9 was obtained to identify changes over time.Results: During the time course of the study the hemodynamic, metabolic, and hormonal parameters showed significant alterations. The most dramatic hemodynamic changes occurred post-insufflation characterized by a decrease in cardiac index and stroke volume with a concurrent increase in systemic vascular resistance. The metabolic parameters showed a significant decrease in pH and corresponding increase in PaCO(2). However, the pH and PaCO(2) remained within normal limits through the study. As part of the study's protocol the investigators increased minute volume to control for a rise in PaCO(2) during the procedure. A significant increase was noted in aldosterone and arginine vasopressin at post-insufflation and Trendelenburg positioning. Plasma renin activity showed a dramatic increase following post-insufflation. None of the subjects developed any post anesthetic complications.Conclusion: Our study demonstrated that pneumoperitoneum and Trendelenburg positioning cause statistically significant elevations in the stress hormones and concurrently cause a decrease in hemodynamic parameters. A healthy patient may tolerate these changes but a patient with cardiovascular disease or pulmonary problems may not be able to compensate as efficiently.

Journal Article↗
PubMed2002

Helium-oxygen ventilation.

Because of its low density, the He/O2 mixture markedly affects the dynamics of gas-flow, increasing inspiratory and expiratory flows, reducing WOB and respiratory acidosis, and relieving dyspnea in various clinical situations associated with obstructive airway disease. The magnitude of these changes varies according to the proportion of turbulent, transitional, and laminar flow conditions. These effects, however, last only as long as the patient breathes the He/O2 mixture, because it has no curative effect on the cause of airway obstruction. Thus, He/O2 ventilation is mostly useful while awaiting the effects of more definitive treatment. Evidence shows that He/O2 ventilation can improve pathophysiologic and clinical parameters in spontaneously breathing patients with upper airway obstruction, asthma. COPD, bronchopulmonary dysplasia. and bronchiolitis. Furthermore. He/O2 ventilation may prove to be a valuable adjunct in decompensated COPD patients, during both NIV and conventional mechanical ventilation. Despite promising results, however, there are two primary pitfalls to He/O2 ventilation. First, the consequences of the physical properties of the He/O2 mixture on various ventilator functions, the major differences between machines, and the correction factors to apply (if necessary) should be known. Second, in this age of cost control, particular attention should be paid to the cost-benefit ratio of He/O2 ventilation. Indeed, despite clinical evidence that the pathophysiologic principles on which He/O2 ventilation rests can be translated into favorable short-term physiologic and subjective effects, there is presently no evidence of a significant effect on patient outcome. Hence, before He/O2 ventilation can be recommended for widespread use, prospective outcome studies should be conducted in patients who suffer from the conditions discussed in this article to identify which, if any, are most likely to receive a benefit. Meanwhile, the authors recommend that He/O2 ventilation be reserved for patients who have a severe condition and who do not respond to the classic validated treatment modalities.

Clinical Trials as Topic↗