Pulmonary function after emergence on 100% oxygen in patients with chronic obstructive pulmonary disease: a randomized, controlled trial.

BACKGROUND: During emergence from anesthesia, breathing 100% oxygen is frequently used to provide a safety margin toward hypoxemia in case an airway problem occurs. Oxygen breathing has been shown to cause pulmonary gas exchange disorders in healthy individuals. This study investigates how oxygen breathing during emergence affects lung function specifically whether oxygen breathing causes added hypoxemia in patients with chronic obstructive pulmonary disease. METHODS: This trial has been conducted in a parallel-arm, case-controlled, open-label manner. Fifty-three patients with chronic obstructive pulmonary disease were randomly allocated (computer-generated lists) to breathe either 100 or 30% oxygen balanced with nitrogen during emergence from anesthesia. Arterial blood gas measurements were taken before induction and at 5, 15, and 60 min after extubation. RESULTS: All participants tolerated the study well. Patients treated with 100% oxygen had a higher alveolar-arterial oxygen pressure gradient (primary outcome) compared with patients treated with 30% oxygen (25 vs. 20 mmHg) and compared with their baseline at the 60-min measurement (25 vs. 17 mmHg). At the 60-min measurement, arterial partial pressure of oxygen was lower in the 100% group (62 vs. 67 mmHg). Arterial partial pressure of carbon dioxide and pH were not different between groups or measurements. CONCLUSIONS: In this experiment, the authors examined oxygen breathing during emergence-a widely practiced maneuver known to generate pulmonary blood flow heterogeneity. In the observed cohort of patients already presenting with pulmonary blood flow disturbances, emergence on oxygen resulted in deterioration of oxygen-related blood gas parameters. In the perioperative care of patients with chronic obstructive pulmonary disease, oxygen breathing during emergence from anesthesia may need reconsideration.

Recombinant angiotensin-converting enzyme 2 suppresses pulmonary vasoconstriction in acute hypoxia.

OBJECTIVE: Alveolar hypoxia as a result of high altitude leads to increased pulmonary arterial pressure. The renin-angiotensin system is involved in the regulation of pulmonary arterial pressure through angiotensin-converting enzyme 2 (ACE2). It remains unknown whether ACE2 administration alters pulmonary vascular pressure in hypoxia. METHODS: We investigated 12 anesthetized pigs instrumented with arterial, central venous, and Swan-Ganz catheters exposed to normobaric hypoxia (fraction of inspired oxygen = 0.125) for 180 minutes. After taking baseline measurements in normoxia and hypoxia, ACE2 400 µg·kg(-1) was administered to 6 animals, and another 6 served as control. Ventilatory variables, arterial blood gases, ventilation/perfusion (V̇A/Q̇) relationships, and plasma angiotensin II concentrations were assessed before and at 30, 90, and 150 minutes in hypoxia after ACE2 or placebo administration. Hemodynamic variables and cardiac output were observed every 30 minutes. RESULTS: We observed lower pulmonary arterial pressure (maximum: 30 vs 39 mm Hg, P < .01) and lower pulmonary vascular resistance (maximum: 4.1 vs 7.5 Wood units, P <.01) in animals treated with ACE2. There was a trend (P =.09) toward lower angiotensin II plasma concentrations among ACE2-treated animals. Cardiac variables and systemic arterial pressure in hypoxia remained unaffected by ACE2. Ventilation/perfusion relationships and Pao(2) did not differ between groups. CONCLUSIONS: In acute pulmonary hypertension, administration of ACE2 blunts the rise in pulmonary arterial pressure that occurs in response to hypoxia. Recombinant ACE2 may be a treatment option for high altitude pulmonary edema and hypoxia-associated pulmonary hypertension.

Mobile phone-assisted basic life support augmented with a metronome.

BACKGROUND: Basic life support (BLS) performed by lay rescuers is poor. We developed software for mobile phones augmented with a metronome to improve BLS. STUDY OBJECTIVES: To assess BLS in lay rescuers with or without software assistance. METHODS: Medically untrained volunteers were randomized to run through a cardiac arrest scenario with ("assisted BLS") or without ("non-assisted BLS") the aid of a BLS software program installed on a mobile phone. RESULTS: Sixty-four lay rescuers were enrolled in the "assisted BLS" and 77 in the "non-assisted BLS" group. The "assisted BLS" when compared to the "non-assisted BLS" group, achieved a higher overall score (19.2 ± 7.5 vs. 12.9 ± 5.7 credits; p < 0.001). Moreover, the "assisted BLS" when compared to the "non-assisted" group checked (64% vs. 27%) and protected themselves more often from environmental risks (70% vs. 39%); this group also called more often for help (56% vs. 27%), opened the upper airway (78% vs. 16%), and had more correct chest compressions rates (44% ± 38% vs. 14% ± 28%; all p < 0.001). However, the "assisted BLS" when compared to the "non-assisted BLS" group, was slower in calling the dispatch center (113.6 ± 86.4 vs. 54.1 ± 45.1 s; p < 0.001) and starting chest compressions (165.3 ± 93.3 vs. 87.1 ± 53.2 s; p < 0.001). CONCLUSIONS: "Assisted BLS" augmented by a metronome resulted in a higher overall score and a better chest compression rate when compared to "non-assisted BLS." However, in the "assisted BLS" group, time to call the dispatch center and to start chest compressions was longer. In both groups, lay persons did not ventilate satisfactorily during this cardiac arrest scenario.

Tolerability of inhaled N-chlorotaurine in an acute pig streptococcal lower airway inflammation model.

BACKGROUND: Inhalation of N-chlorotaurine (NCT), an endogenous new broad spectrum non-antibiotic anti-infective, has been shown to be very well tolerated in the pig model recently. In the present study, inhaled NCT was tested for tolerability and efficacy in the infected bronchopulmonary system using the same model. METHODS: Anesthetized pigs were inoculated with 20 ml of a solution containing approximately 108 CFU/ml Streptococcus pyogenes strain d68 via a duodenal tube placed through the tracheal tube down to the carina. Two hours later, 5 ml of 1% NCT aqueous solution (test group, n = 15) or 5 ml of 0.9% NaCl (control group, n = 16) was inhaled via the tracheal tube connected to a nebulizer. Inhalation was repeated every hour, four times in total. Lung function and haemodynamics were monitored. Bronchoalveolar lavage samples were removed for determination of colony forming units (CFU), and lung samples for histology. RESULTS: Arterial pressure of oxygen (PaO2) decreased rapidly after instillation of the bacteria in all animals and showed only a slight further decrease at the end of the experiment without a difference between both groups. Pulmonary artery pressure increased to a peak 1-1.5 h after application of the bacteria, decreased in the following hour and remained constant during treatment, again similarly in both groups. Histology demonstrated granulocytic infiltration in the central parts of the lung, while this was absent in the periphery. Expression of TNF-alpha, IL-8, and haemoxygenase-1 in lung biopsies was similar in both groups. CFU counts in bronchoalveolar lavage came to 170 (10; 1388) CFU/ml (median and 25 and 75 percentiles) for the NCT treated pigs, and to 250 (10; 5.5 × 105) CFU/ml for NaCl treated pigs (p = 0.4159). CONCLUSIONS: Inhaled NCT at a concentration of 1% proved to be very well tolerated also in the infected bronchopulmonary system. This study confirms the tolerability in this delicate body region, which has been proven in healthy pigs previously. Regarding efficacy, no conclusions can be drawn, mainly because of the limited test period of the model.

[Respiratory system at high altitude: pathophysiology and novel therapy options]. / Das Respiratorische System auf großer Höhe: Pathophysiologie und neue Therapieoptionen.

This mini-review conveys information on lung function in hypoxia. Included are presentations of shape and layering of the atmosphere, physiologic basics of lung function at high altitude, pathophysiology of high altitude pulmonary edema (HAPE) and of current and potential therapy approaches for HAPE.

A prediction model for out-of-hospital cardiopulmonary resuscitation.

BACKGROUND: We created a prediction model to be used in cardiopulmonary resuscitation (CPR) attempts as a decision tool to omit futile CPR attempts and to save resources. METHODS: In this post hoc analysis, we assessed predictive parameters for neurological recovery after successful CPR. The original study was designed as a blinded, randomized, prospective, controlled, multicenter clinical trial. RESULTS: We identified 1166 prehospital cardiac arrest patients being treated with advanced cardiac life support. Seven hundred eighty-six of 1166 patients (67.4%) died at the scene and 380 of 1166 (32.6%) were brought to the hospital. Two hundred sixty-five of 1166 patients (22.7%) died in the hospital. One hundred fifteen of 1166 (9.8%) were discharged from the hospital and 92 of the 115 patients (80%) could be followed-up. Good cerebral performance was regained by 54% of discharged patients (50 of 92 patients). In 46% of patients (42/92), unconsciousness or severe disability remained. Ventricular fibrillation was more likely to have occurred in patients with good neurological recovery (42/50 = 84.0%), whereas asystole was more likely in patients with poor neurological recovery (9/42 = 21.4%). A score was developed to predict the probability of death using logistic regression analysis. Predicting death in the hospital revealed a sensitivity of 99.8% (953/955), but only a specificity of 2.9% (3/104; threshold 0.5). Predicting survival until discharge from the hospital revealed a sensitivity of 99% (103/104), but only a specificity of 8% (72/955; threshold 0.99). A receiver operating characteristic curve yielded an area under the curve of 0.795 (0.751-0.839) at a confidence interval of 95%. CONCLUSION: For out-of-hospital patients with cardiac arrest, parameters documented in the field did not allow accurate prediction of hospital survival.