Preoxygenation in critically ill patients requiring emergency tracheal intubation

OBJECTIVE: To determine the effectiveness of preoxygenation with 100% oxygen in the critically ill patient in preparation for emergency tracheal intubation. DESIGN: Nonrandomized, controlled trial. SETTING: Large, level 1 trauma center, tertiary care intensive care unit. PATIENTS: Critically ill patients failing noninvasive respiratory support techniques who require tracheal intubation followed by mechanical ventilation. INTERVENTIONS: A baseline arterial blood gas was obtained on noninvasive therapy and 4 mins post-100% oxygen therapy with a bag-mask assembly. Best effort to achieve a tight-fitting mask seal was pursued coupled with other mask ventilation maneuvers to optimize noninvasive oxygenation and ventilation. MEASUREMENTS AND MAIN RESULTS: A total of 42 patients consecutively intubated during the 15-month study period were studied. The baseline Pao2 (mean +/- sd) with concurrent noninvasive support was 67 +/- 19.6 mm Hg (range, 43-88 mm Hg) and increased a mean of 37 mm Hg to 103.8 +/- 63.2 mm Hg after 4 mins of preoxygenation with 100% oxygen. A total of 36% of patients had minimal changes (+/-5%) in their baseline Pao2, and only 19% increased their baseline Pao2 by at least 50 mm Hg after preoxygenation maneuvers. CONCLUSIONS: The critically ill patient has little reserve to tolerate interruption of oxygen delivery and, thus, is at risk for hypoxemia during emergency airway management. Preoxygenation efforts as described in this clinical trial appear to be marginally effective in regard to providing a reasonable safeguard against hypoxemia during laryngoscopy and endotracheal intubation.     

Effects of the calcium antagonist tiapamil on pulmonary gas exchange in patients with chronic obstructive pulmonary disease who receive salbutamol

Patients with chronic obstructive pulmonary disease (COPD) and cardiovascular diseases are frequently given combination therapy with a beta 2-agonist and a calcium antagonist. Each drug is known to increase ventilation-perfusion inequalities. It was our aim to define the effects of their combination on lung function and on pulmonary gas exchange in eight subjects with COPD but partially reversible airway obstruction. Sixty minutes after placebo or 450 mg tiapamil, subjects inhaled 0.2 mg salbutamol. There was no significant effect of tiapamil on specific airway conductance and the forced expiratory volume in 1 second before or after the inhalation of salbutamol. Blood was drawn 30, 55, 80, and 100 minutes after placebo or tiapamil dosing. After placebo the mean (+/- SD) arterial oxygen tension (Pao2) fell from 67.1 +/- 7.3 to 64.4 +/- 5.5 mm Hg and the mean alveolar-arterial oxygen tension difference (AaDo2) rose from 34.6 +/- 8.4 to 40.5 +/- 6.8 mm Hg. After tiapamil the mean Pao2 fell from 68.7 +/- 7.3 to 66.4 +/- 5.8 mm Hg and the mean AaDo2 rose from 35.1 +/- 6.8 to 38.7 +/- 7.4 mm Hg. The changes in Pao2 were not significant. The increase in AaDo2 after placebo was significant, but that after tiapamil was not. We conclude that the combination of the calcium antagonist tiapamil and the bronchodilator salbutamol is safe with respect to lung function in COPD. There is no evidence that tiapamil increases beta 2-agonist-induced impairment in pulmonary gas exchange.     

Effects of long-term oxygen therapy on mortality and morbidity

In general, based on the above studies of the effects of supplemental oxygen on reducing mortality and improving sleep and exercise function in certain patient groups, patients whose disease is stable on a full medical regimen with PaO2 < or = 55 mm Hg (SaO2 < or = 88%) should be considered for LTOT. Patients with PaO2 of 55-59 mm Hg with signs of tissue hypoxemia (i.e., cor pulmonale, polycythemia, impaired cognition) should also be considered for LTOT. Oxygen therapy should also be considered for those who desaturate during sleep or exercise. These guidelines have been adopted by Medicare as reimbursement criteria and have also been endorsed by the American Thoracic Society. Indications for LTOT endorsed by the American Thoracic Society and published in the "Standards for the Diagnosis and Care of Patients with COPD" are shown in Table 6. More research is required to investigate the use of supplemental oxygen in patients who suffer nocturnal desaturation but do not have signs of end organ dysfunction, those who have an improvement in dyspnea with supplemental oxygen, and in normoxemic patients with impaired exercise performance who improve while inspiring supplemental oxygen.     

Efficacy and indications of home oxygen therapy for patients with chronic obstructive pulmonary disease]

Efficacy of home oxygen therapy (HOT) is well established for patients with chronic obstructive pulmonary disease who fall into chronic respiratory failure. We should consider now how the quality of life improves with HOT in those patients. According to the guideline of the Japanese Respiratory Society, indications of HOT are as follows: 1) A PaO2 of less than 55 Torr at rest while breathing room air, 2) A PaO2 between 55 Torr and 60 Torr in the presence of clear evidence of cor pulmonale, pulmonary hypertension, or a long history of severe hypoxemia during sleep or during exercise. Further studies are definitely required to pick up the patients who do not necessarily meet these indications but who may benefit from HOT.     

Medications for COPD: a review of effectiveness

Chronic obstructive pulmonary disease (COPD) is a common problem among patients presenting to primary care. This condition has multiple individual and combined treatment regimens. The goals of treatment are to improve quality of life, exercise tolerance, sleep quality, and survival; and to reduce dyspnea, nocturnal symptoms, exacerbations, use of rescue medications, and hospitalizations. All patients benefit from bronchodilator medications as needed. Long-acting inhaled anticholinergics are probably more beneficial than short-acting formulations. Use of inhaled corticosteroids might benefit patients with mild COPD who have an inflammatory component or significant reversibility on spirometry. Patients with moderate to severe disease benefit from the use of long-acting inhaled anticholinergics, inhaled corticosteroids, and possibly a long-acting beta2 agonist or mucolytics. For rescue therapy, short-acting beta2 agonists or combination anticholinergics with a short-acting beta2 agonist should be used. Inhaled corticosteroids should be considered before initiating a long-acting beta2 agonist. Caution should be used if a long-acting beta2 agonist is discontinued before initiation of an inhaled corticosteroid because this may precipitate exacerbations. Evidence to support the use of mucolytics, oral theophylline, and oral corticosteroids is limited. Patients with severe hypoxemia (i.e., arterial oxygen pressure less than 55 mm Hg or oxygen saturation less than 88 percent) should be given continuous oxygen.     

Combined methylprednisolone and dexamethasone therapy for paraquat poisoning

OBJECTIVE: To report a severe case of paraquat poisoning successfully treated with repeated-pulse therapy of methylprednisolone. DESIGN: Case study. SETTING: University Hospital, Lin-Kou Medical Center, Taipei, Taiwan, Republic of China. PATIENTS: A 60-yr-old man with paraquat poisoning with severe acute renal failure (serum creatinine level of 11.8 mg/dL and serum paraquat level of 3.66 microg/mL at 10 hrs after ingestion) and severe hypoxemia (Pao2, 66.6 mm Hg). INTERVENTION: Repeated 3-day pulse therapy with methylprednisolone, one course of 2-day cyclophosphamide, and a high dose of dexamethasone for 33 days. MEASUREMENTS AND MAIN OUTCOME: Arterial blood gas analysis was obtained regularly. A chest radiography was obtained every week. The arterial blood oxygen concentrations dramatically elevated from 66 mm Hg to 97 mm Hg, and the chest radiographs markedly improved after repeated-pulse therapy with anti-inflammatory agents and cyclophosphamide. CONCLUSIONS: We successfully treated a severe paraquat poisoned patient with repeated methylprednisolone pulse therapy and prolonged dexamethasone treatment. This case demonstrates that the severe inflammation, not the fibrosis, of the lungs plays a major role in the lethal hypoxemia of patients with paraquat poisoning during the subacute period and confirms our previous hypotheses. Clearly, the use of anti-inflammatory therapy to treat paraquat-poisoned patients needs further evaluation; however, anti-inflammatory therapy may be an effective treatment after failure of standard therapies.     

Noninvasive ventilation in acute respiratory failure

BACKGROUND: Noninvasive ventilation has assumed an important role in the management of respiratory failure in critical care units, but it must be used selectively depending on the patient's diagnosis and clinical characteristics. DATA: We review the strong evidence supporting the use of noninvasive ventilation for acute respiratory failure to prevent intubation in patients with chronic obstructive pulmonary disease exacerbations or acute cardiogenic pulmonary edema, and in immunocompromised patients, as well as to facilitate extubation in patients with chronic obstructive pulmonary disease who require initial intubation. Weaker evidence supports consideration of noninvasive ventilation for chronic obstructive pulmonary disease patients with postoperative or postextubation respiratory failure; patients with acute respiratory failure due to asthma exacerbations, pneumonia, acute lung injury, or acute respiratory distress syndrome; during bronchoscopy; or as a means of preoxygenation before intubation in critically ill patients with severe hypoxemia. CONCLUSION: Noninvasive ventilation has assumed an important role in managing patients with acute respiratory failure. Patients should be monitored closely for signs of noninvasive ventilation failure and promptly intubated before a crisis develops. The application of noninvasive ventilation by a trained and experienced intensive care unit team, with careful patient selection, should optimize patient outcomes.     

Prospective trial of high-frequency oscillation in adults with acute respiratory distress syndrome.

OBJECTIVE: To evaluate the safety and efficacy of high-frequency oscillatory ventilation (HFOV) in adult patients with the acute respiratory distress syndrome (ARDS) and oxygenation failure. DESIGN: Prospective, clinical study. SETTING: Intensive care and burn units of two university teaching hospitals. PATIENTS: Twenty-four adults (10 females, 14 males, aged 48.5 +/- 15.2 yrs, Acute Physiology and Chronic Health Evaluation II score 21.5 +/- 6.9) with ARDS (lung injury score 3.4 +/- 0.6, Pao2/Fio2 98.8 +/- 39.0 mm Hg, and oxygenation index 32.5 +/- 19.6) who met one of the following criteria: Pao2 < or =65 mm Hg with Fio2 > or =0.6, or plateau pressure > or =35 cm H2O. INTERVENTIONS: HFOV was initiated in patients with ARDS after varying periods of conventional ventilation (CV). Mean airway pressure (Paw) was initially set 5 cm H2O greater than Paw during CV, and was subsequently titrated to maintain oxygen saturation between 88% and 93% and Fio2 < or =0.60. MEASUREMENTS AND MAIN RESULTS: Fio2, Paw, pressure amplitude of oscillation, frequency, blood pressure, heart rate, and arterial blood gases were monitored during the transition from CV to HFOV, and every 8 hrs thereafter for 72 hrs. In 16 patients who had pulmonary artery catheters in place, cardiac hemodynamics were recorded at the same time intervals. Throughout the HFOV trial, Paw was significantly higher than that applied during CV. Within 8 hrs of HFOV application, and for the duration of the trial, Fio2 and Paco2 were lower, and Pao2/Fio2 was higher than baseline values during CV. Significant changes in hemodynamic variables following HFOV initiation included an increase in pulmonary artery occlusion pressure (at 8 and 40 hrs) and central venous pressure (at 16 and 40 hrs), and a reduction in cardiac output throughout the course of the study. There were no significant changes in systemic or pulmonary pressure associated with initiation and maintenance of HFOV. Complications occurring during HFOV included pneumothorax in two patients and desiccation of secretions in one patient. Survival at 30 days was 33%, with survivors having been mechanically ventilated for fewer days before institution of HFOV compared with nonsurvivors (1.6 +/- 1.2 vs. 7.8 +/- 5.8 days; p =.001). CONCLUSIONS: These findings suggest that HFOV has beneficial effects on oxygenation and ventilation, and may be a safe and effective rescue therapy for patients with severe oxygenation failure. In addition, early institution of HFOV may be advantageous.     

Long-term oxygen therapy: physiologic and economic considerations.

Long-term oxygen therapy appears to be a safe means of treating hypoxemia. It can provide many physiologic improvements and prolongs life in persons with severe chronic arterial hypoxemia at rest. Recent studies suggest that arterial hypoxia is common during exercise and sleep, and it is likely that some patients with intermittent desaturation would benefit physiologically from supplemental oxygen. Oxygen is an expensive drug, and we do not know whether its benefits are greater than its costs in patients who are not hypoxic at rest. I believe that low-flow oxygen administered as continuously as possible should be strongly considered for all patients whose PaO2 is 55 mm Hg or less at rest, regardless of whether they have cor pulmonale, and for all patients with cor pulmonale, regardless of their PaO2.     

Duration and characteristics of treatment of premature lambs with natural surfactant.

Premature lambs were treated with 50 mg/kg of natural surfactant lipid by tracheal instillation either at birth or shortly thereafter when respiratory failure was documented. All lambs were delivered by cesarean section and supported on infant ventilators with 100% oxygen under conditions to mimic the care of human infants with the respiratory distress syndrome. The natural surfactant used for therapy was recovered by lavage from sheep lung. Six 120-d gestational age lambs treated at birth had an initial mean oxygen pressure (pO2) value of 270 +/- 35 mm Hg; this fell within 3 h to less than 100 mm Hg. By 8.3 +/- 0.3 h after birth the lambs were in severe respiratory failure with a mean pH less than 7.1 and a mean pCO2 greater than 70 mm Hg. Six untreated lambs had pH values below 7.0 within 40 min of life despite more intensive respiratory support than was given the treated animals. Treatment with natural surfactant of 17 lambs of 120 and 130 d gestational age after early respiratory failure resulted in a prompt increase in pO2 values from about 35 mm Hg to values over 200 mm Hg and a fall in pCO2 values to normal levels in the majority of animals. This response lasted only approximately 3 h, and a second treatment was less predictably effective.     

A new pumpless extracorporeal interventional lung assist in critical hypoxemia/hypercapnia

OBJECTIVE: Pump-driven extracorporeal gas exchange systems have been advocated in patients suffering from severe acute respiratory distress syndrome who are at risk for life-threatening hypoxemia and/or hypercapnia. This requires extended technical and staff support. DESIGN: We report retrospectively our experience with a new pumpless extracorporeal interventional lung assist (iLA) establishing an arteriovenous shunt as the driving pressure. SETTING: University hospital. PATIENTS: Ninety patients with acute respiratory distress syndrome. INTERVENTIONS: Interventional lung assist was inserted in 90 patients with acute respiratory distress syndrome. MEASUREMENTS AND MAIN RESULTS: Oxygenation improvement, carbon dioxide elimination, hemodynamic variables, and the amount of vasopressor substitution were reported before, 2 hrs after, and 24 hrs after implementation of the system. Interventional lung assist led to an acute and moderate increase in arterial oxygenation (Pao2/Fio2 ratio 2 hrs after initiation of iLA [median and interquartile range], 82 mm Hg [64-103]) compared with pre-iLA (58 mm Hg [47-78], p < .05). Oxygenation continued to improve for 24 hrs after implementation (101 mm Hg [74-142], p < .05). Hypercapnia was promptly and markedly reversed by iLA within 2 hrs (Paco2, 36 mm Hg [30-44]) in comparison with before (60 mm Hg [48-80], p < .05], which allowed a less aggressive ventilation. For hemodynamic stability, all patients received continuous norepinephrine infusion. The incidence of complications was 24.4%, mostly due to ischemia in a lower limb. Thirty-seven of 90 patients survived, creating a lower mortality rate than expected from the Sequential Organ Failure Assessment score. CONCLUSIONS: Interventional lung assist might provide a sufficient rescue measure with easy handling properties and low cost in patients with severe acute respiratory distress syndrome and persistent hypoxia/hypercapnia.     

Decrease in PaCO2 with prone position is predictive of improved outcome in acute respiratory distress syndrome

OBJECTIVE: To determine whether gas exchange improvement in response to the prone position is associated with an improved outcome in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). DESIGN: Retrospective analysis of patients in the pronation arm of a controlled randomized trial on prone positioning and patients enrolled in a previous pilot study of the prone position. SETTING: Twenty-eight Italian and two Swiss intensive care units. PATIENTS: We studied 225 patients meeting the criteria for ALI or ARDS. INTERVENTIONS: Patients were in prone position for 10 days for 6 hrs/day if they met ALI/ARDS criteria when assessed each morning. Respiratory variables were recorded before and after 6 hrs of pronation with unchanged ventilatory settings. MEASUREMENTS AND MAIN RESULTS: We measured arterial blood gas alterations to the first pronation and the 28-day mortality rate. The independent risk factors for death in the general population were the Pao2/Fio2 ratio (odds ratio, 0.992; confidence interval, 0.986-0.998), the minute ventilation/Paco2 ratio (odds ratio, 1.003; confidence interval, 1.000-1.006), and the concentration of plasma creatinine (odds ratio, 1.385; confidence interval, 1.116-1.720). Pao2 responders (defined as the patients who increased their Pao2/Fio2 by > or =20 mm Hg, 150 patients, mean increase of 100.6 +/- 61.6 mm Hg [13.4 +/- 8.2 kPa]) had an outcome similar to the nonresponders (59 patients, mean decrease -6.3 +/- 23.7 mm Hg [-0.8 +/- 3.2 kPa]; mortality rate 44% and 46%, respectively; relative risk, 1.04; confidence interval, 0.74-1.45, p =.65). The Paco2 responders (defined as patients whose Paco2 decreased by > or =1 mm Hg, 94 patients, mean decrease -6.0 +/- 6 mm Hg [-0.8 +/- 0.8 kPa]) had an improved survival when compared with nonresponders (115 patients, mean increase 6 +/- 6 mm Hg [0.8 +/- 0.8 kPa]; mortality rate 35.1% and 52.2%, respectively; relative risk, 1.48; confidence interval, 1.07-2.05, p =.01). CONCLUSION: ALI/ARDS patients who respond to prone positioning with reduction of their Paco2 show an increased survival at 28 days. Improved efficiency of alveolar ventilation (decreased physiologic deadspace ratio) is an important marker of patients who will survive acute respiratory failure.     

Comparison of prone positioning and high-frequency oscillatory ventilation in patients with acute respiratory distress syndrome

OBJECTIVE: Both prone position and high-frequency oscillatory ventilation (HFOV) have the potential to facilitate lung recruitment, and their combined use could thus be synergetic on gas exchange. Keeping the lung open could also potentially be lung protective. The aim of this study was to compare physiologic and proinflammatory effects of HFOV, prone positioning, or their combination in severe acute respiratory distress syndrome (ARDS). DESIGN:: Prospective, comparative randomized study. SETTING: A medical intensive care unit. PATIENTS: Thirty-nine ARDS patients with a Pao2/Fio2 ratio <150 mm Hg at positive end-expiratory pressure > or =5 cm H2O. INTERVENTIONS: After 12 hrs on conventional lung-protective mechanical ventilation (tidal volume 6 mL/kg of ideal body weight, plateau pressure not exceeding the upper inflection point, and a maximum of 35 cm H2O; supine-CV), 39 patients were randomized to receive one of the following 12-hr periods: conventional lung-protective mechanical ventilation in prone position (prone-CV), HFOV in supine position (supine-HFOV), or HFOV in prone position (prone-HFOV). MEASUREMENTS AND MAIN RESULTS: Prone-CV (from 138 +/- 58 mm Hg to 217 +/- 110 mm Hg, p < .0001) and prone-HFOV (from 126 +/- 40 mm Hg to 227 +/- 64 mm Hg, p < 0.0001) improved the Pao2/Fio2 ratio whereas supine-HFOV did not alter the Pao2/Fio2 ratio (from 134 +/- 57 mm Hg to 138 +/- 48 mm Hg). The oxygenation index ({mean airway pressure x Fio2 x 100}/Pao2) decreased in the prone-CV and prone-HFOV groups and was lower than in the supine-HFOV group. Interleukin-8 increased significantly in the bronchoalveolar lavage fluid (BALF) in supine-HFOV and prone-HFOV groups compared with prone-CV and supine-CV. Neutrophil counts were higher in the supine-HFOV group than in the prone-CV group. CONCLUSIONS: Although HFOV in the supine position does not improve oxygenation or lung inflammation, the prone position increases oxygenation and reduces lung inflammation in ARDS patients. Prone-HFOV produced similar improvement in oxygenation like prone-CV but was associated with higher BALF indexes of inflammation. In contrast, supine-HFOV did not improve gas exchange and was associated with enhanced lung inflammation.     

The hospital stage of the long-term oxygen therapy of chronic lung failure in patients with chronic obstructive bronchitis]

The authors analyze the role of the initial inpatient stage of long-term oxygen therapy (LOT) in combined treatment of chronic pulmonary failure in patients with chronic obstructive bronchitis, lung emphysema, and pneumosclerosis. The treatment lasted 30 days both in the main and in the control groups. In addition to basic therapy, the main group patients received 38% O2 for 15 h a day. To decrease the risk of PaCO2 elevation with a possible respiratory disorder, particularly in patients with initial hypercapnia, it is suggested that a special oxygen test with simultaneous control of acid-base balance and gas composition of the arterial blood may be carried out. In contrast to the control group, the main group patients demonstrated an improvement of gas composition of the arterial blood and of the parameters such as the alveolar-arterial gradient according to O2, the physiological pulmonary shunt. The combined use of oxygen therapy and resistance at expiration made it possible to ameliorate a number of external respiration function parameters, diffusion lung capacity, and enhanced the effect of oxygen therapy. It is shown that patients with PaO2 may be given LOT within the range of 60-69 mm Hg, provided the pulmonary physiological shunt exceeds 20%.     

Early high-flow nasal cannula oxygen therapy in adults with acute hypoxemic respiratory failure in the ED: A before-after study

ObjectivesTo compare clinical impact after early initiation of high-flow nasal cannula oxygen therapy (HFNC) versus standard oxygen in patients admitted to an emergency department (ED) for acute hypoxemic respiratory failure.MethodsWe performed a prospective before-after study at EDs in two centers including patients with acute hypoxemic respiratory failure defined by a respiratory rate above 25 breaths/min or signs of increased breathing effort under additional oxygen for a pulse oximetry above 92%. Patients with cardiogenic pulmonary edema or exacerbation of chronic lung disease were excluded. All patients were treated with standard oxygen during the first period and with HFNC during the second. The primary outcome was the proportion of patients with improved respiratory failure 1 h after treatment initiation (respiratory rate ≤ 25 breaths/min without signs of increased breathing effort). Dyspnea and blood gases were also assessed.ResultsAmong the 102 patients included, 48 were treated with standard oxygen and 54 with HFNC. One hour after treatment initiation, patients with HFNC were much more likely to recover from respiratory failure than those treated with standard oxygen: 61% (33 of 54 patients) versus 15% (7 of 48 patients), P < 0.001. They also showed greater improvement in oxygenation (increase in PaO₂ was 31 mm Hg [0–67] vs. 9 [−9–36], P = 0.02), and in feeling of breathlessness.ConclusionsAs compared to standard oxygen, patients with acute hypoxemic respiratory failure treated with HFNC at the ED had better oxygenation, less breathlessness and were more likely to show improved respiratory failure 1 h after initiation.     

Home oxygen therapy

Oxygen therapy is one of the principal non-pharmacologic treatments for severe chronic obstructive pulmonary disease (COPD) patients. Home oxygen therapy(HOT), or long-term oxygen therapy(LTOT) for 15 hours or more per day, can improve the survival rate of severe COPD patients with beneficial effects on hemodynamic state, hematological characteristic, exercise capacity, lung mechanics, and mental state. Oxygen therapy is indicated in cases of severe chronic respiratory failure with PaO2 of 55 Torr or less, or in cases with PaO2 of 60 Torr or less in whom there is remarkable hypoxia during sleep or during exercise. The induction of oxygen therapy needs evaluations of oxygen desaturation during exercise and sleep as well as hypoxia at rest. It also required to consider CO2 narcosis.     

Oxygen therapy for hypercapnic patients with chronic obstructive pulmonary disease and acute respiratory failure: a randomized, controlled pilot study

OBJECTIVE: To investigate the effect of oxygen therapy on outcome and on symptomatic hypercapnia. DESIGN: Randomized, controlled, single-blind study. SETTING: Multidisciplinary intensive care unit of a university teaching hospital. PATIENTS: Patients admitted with a clinical diagnosis of an acute exacerbation of chronic obstructive pulmonary disease and a PaO2 <6.6 kPa (50 mm Hg) and PaCO2 >6.6 kPa (50 mm Hg) on air. INTERVENTIONS: Patients received oxygen therapy titrated to increase arterial oxygen tension to >6.6 kPa (50 mm Hg) or >9 kPa (70 mm Hg). Patients in the low-oxygen tension group also received doxapram if they developed an acidosis with pH <7.2, whereas those in the high-oxygen tension group received doxapram if they developed symptomatic acidosis. Bronchodilator, steroid, and antibiotic therapy was standardized. MEASUREMENTS AND MAIN RESULTS: Two patients in the low-oxygen tension group (n = 17) required mechanical ventilation and another one died. No patients in the high-oxygen group (n = 17) had a poor outcome, but this difference was not significant. No patient in either group became comatose or developed an acute cardiac arrhythmia. CONCLUSIONS: Traditional teaching related to oxygen therapy for hypercapnic patients with an acute exacerbation of chronic obstructive pulmonary disease may be incorrect. A large randomized, controlled study is required to confirm this impression.     

Acetazolamide Causes Worsening Acidosis in Uncompensated COPD Exacerbations: Increased Awareness Needed for Patient Safety

BackgroundAcetazolamide has been studied extensively in post-hypercapnic alkalosis as a tool to facilitate ventilator weaning in chronic obstructive pulmonary disease (COPD). It has also been utilized to facilitate respiratory drive in nonmechanically ventilated patients with COPD. Although this is generally a forgiving intervention, providers must carefully select patients for this medication, as it can cause severe acidosis and deterioration of clinical status in severe COPD cases. The present report describes two cases of patients who developed worsening acidosis and hypercapnia after receiving acetazolamide in acute respiratory failure.Case ReportCase 1 was a 72-year-old obese male with COPD who was dependent on supplemental oxygen and presented to the emergency department (ED) with acute on chronic hypercapnic respiratory failure. He was given a one-time dose of acetazolamide in the ED for “respiratory failure made worse by severe metabolic alkalosis.” His arterial blood gas (ABG) worsened overnight, accompanied by decreased mental status: pH 7.32, paCO₂ 82 mm Hg, paO₂ 50 mm Hg, HCO₃ 41.7 mmol/L, FiO₂ 32% to pH 7.21, paCO₂ 91.7 mm Hg, paO₂ 59 mm Hg, HCO₃ 36.6 mmol/L, and FiO₂ 32%. Case 2 was a 62-year-old male with COPD who was dependent on supplemental oxygen and presented to the ED with acute on chronic hypercapnic respiratory failure. He was given acetazolamide in the ED with similar results: ABG on presentation pH 7.37, paCO₂ 79.3 mm Hg, paO₂ 77.6 mm Hg, HCO₃ 45.5 mmol/L, and FiO₂ 32%. The next morning, ABG was pH 7.29, paCO₂ 79 mm Hg, paO₂ 77 mm Hg, HCO₃ 45.5 mmol/L, and FiO₂ 32%.Why Should an Emergency Physician Be Aware of This?Acetazolamide given early in the uncompensated setting can worsen acidosis and potentiate clinical deterioration.     

Early evolution of arterial oxygenation in severe community-acquired pneumonia: a prospective observational study

PURPOSE: Acute respiratory failure requiring mechanical ventilation in severe community-acquired pneumonia has been shown to be a significant negative prognostic factor. We analyzed the early evolution of the Pao(2)/Fio(2) ratio and evaluated its clinical value as an outcome predictor. MATERIALS AND METHODS: This is a prospective study conducted in a tertiary referral hospital. In 62 adult patients requiring early mechanical ventilation due to severe community-acquired pneumonia, we measured serial changes in Pao(2)/Fio(2) ratio and other clinical variables within the first 48 hours of mechanical ventilation and compared the difference between survivors and nonsurvivors. RESULTS: The initial Pao(2)/Fio(2) ratio was lower in nonsurvivors (n = 27) than in survivors (n = 35) (158.0 +/- 55.8 vs 117.9 +/- 50.6, P = .025). Over the next 48 hours, the ratio increased significantly in survivors but not in nonsurvivors (analysis of variance, P < .001). An increase in Pao(2)/Fio(2) ratio greater than 56 mm Hg had a sensitivity of 75% and a specificity of 81% of survival. A definite causative pathogen was identified in 36 patients (58%) and the 3 most commonly isolated pathogens were Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae. Ten patients received inadequate initial empirical antimicrobial therapy, in which the Pao(2)/Fio(2) ratio change was significantly less than those who were adequately treated (analysis of variance, P < .001). Mortality was much higher (86% [6/7]) in patients who received inadequate antibiotics and where Pao(2)/Fio(2) ratio change was less than 56 mm Hg. On multivariate analysis, trend changes in Pao(2)/Fio(2) ratio over 48 hours, shock, and Acute Physiology and Chronic Health Evaluation II score were documented to be independent predictors of mortality. CONCLUSIONS: A progressive improvement of Pao(2)/Fio(2) ratio during the first 48 hours of mechanical ventilation indicates favorable outcome. Serial measurement of this ratio should be considered in decision making for therapeutic strategy.