[Salbutamol improves diaphragmatic contractility in chronic airway obstruction]. / El salbutamol mejora la contractilidad diafragmática en la obstrucción crónica de la vía aérea.

INTRODUCTION: Chronic airflow obstruction in conditions such as chronic obstructive pulmonary disease is associated with respiratory muscle dysfunction. Our aim was to study the effects of salbutamol-a beta-adrenergic agonist known to improve muscle strength in physiologic and pathologic conditions-on diaphragm contractility in an animal model of chronic airway obstruction achieved by tracheal banding. MATERIALS AND METHODS: Twenty-four Sprague-Dawley rats were randomized into a control group and 3 tracheal banding groups, 1 that received acute salbutamol treatment, 1 that received chronic salbutamol treatment, and 1 that received nothing. Arterial blood gases, acid-base balance, and in vitro diaphragmatic contractility were evaluated by measuring peak twitch tension, contraction time, contraction velocity, half-relaxation time, relaxation velocity, and force-frequency curves. RESULTS: The 3 study groups had significantly reduced arterial pH and increased PaCO2 and bicarbonate levels compared to the control group (P<.05). The untreated tracheal banding group had significantly reduced peak twitch tension and contraction velocity, and a significantly lower force-frequency curve in comparison with the other groups (P<.05). The chronic treatment group had a higher relaxation velocity than the untreated study group (P<.05). The mean (SE) peak twitch tension values were 6.46 (0.90)N/cm(2) for the control group, 3.28 (0.55)N/cm(2) for the untreated tracheal banding group, 6.18 (0.71)N/cm(2) for the acute treatment group, and 7.09 (0.59)N/cm(2) for the chronic treatment group. CONCLUSIONS: Diaphragmatic dysfunction associated with chronic airflow obstruction improves with both the acute and chronic administration of salbutamol. The mechanisms involved in respiratory muscle dysfunction warrant further study.

Effect of supplementing a high-fat, low-carbohydrate enteral formula in COPD patients.

OBJECTIVE: One of the goals in treating patients with chronic obstructive pulmonary disease (COPD) who suffer from hypoxemia, hypercapnia, and malnutrition is to correct the malnutrition without increasing the respiratory quotient and minimize the production of carbon dioxide. This 3-wk study evaluated the efficacy of feeding a high-fat, low-carbohydrate (CHO) nutritional supplement as opposed to a high-carbohydrate diet in COPD patients on parameters of pulmonary function.S METHODS: Sixty COPD patients with low body weight (<90% ideal body weight) were randomized to the control group, which received dietary counseling for a high-CHO diet (15% protein, 20% to 30% fat, and 60% to 70% CHO), or the experimental group, which received two to three cans (237 mL/can) of a high-fat, low-CHO oral supplement (16.7% protein, 55.1% fat, and 28.2% CHO) in the evening as part of the diet. Measurements of lung function (forced expiratory volume in 1 s or volume of air exhaled in 1 s of maximal expiration, minute ventilation, oxygen consumption per unit time, carbon dioxide production in unit time, and respiratory quotient) and blood gases (pH, arterial carbon dioxide tension, and arterial oxygen tension) were taken at baseline and after 3 wk. RESULTS: Lung function measurements decreased significantly and forced expiratory volume increased significantly in the experimental group. CONCLUSION: This study demonstrates that pulmonary function in COPD patients can be significantly improved with a high-fat, low-CHO oral supplement as compared with the traditional high-CHO diet.

Oxygen application by a nasal probe prevents hypoxia but not rebreathing of carbon dioxide in patients undergoing eye surgery under local anaesthesia.

BACKGROUND/AIM: Hypoxia and carbon dioxide rebreathing are potential problems during eye surgery in spontaneously breathing patients. The aim of the present study was to determine effectiveness of nasal application of oxygen to prevent hypoxia and carbon dioxide accumulation in spontaneously breathing patients undergoing cataract surgery. METHODS: Oxygenation and carbon dioxide rebreathing were examined in 40 elderly patients using two different methods of oxygen supply-nasal v ambient air-with a constant flow of 2 l/min. Partial pressure of carbon dioxide under ophthalmic drapes, transcutaneous pressure of carbon dioxide, and the respiratory rate were measured during 25 minutes while oxygen was supplied via a nasal cannula or into the ambient air under the drapes. RESULTS: In both groups carbon dioxide accumulation under the drapes, carbon dioxide rebreathing, tachypnoea, and an increase in peripheral oxygen saturation occurred. No significant differences were found between the two methods. CONCLUSION: Nasal application of oxygen prevented hypoxia but did not prevent carbon dioxide accumulation in patients undergoing eye surgery under retrobulbar anaesthesia. Additionally, as a side effect when using nasal probes, irritation of the nose was described in half of the patients investigated.

New equipment to prevent carbon dioxide rebreathing during eye surgery under retrobulbar anaesthesia.

BACKGROUND: Carbon dioxide concentration under ophthalmic drapes increases during eye surgery under local anaesthesia. A new prototype has been designed which combines continuous suction of carbon dioxide enriched air and continuous oxygen insufflation under ophthalmic drapes to prevent carbon dioxide accumulation in spontaneously breathing patients undergoing cataract surgery. METHODS: In a prospective randomised single blind study the effectiveness of this new prototype was examined in 50 unpremedicated elderly patients. In 25 patients suction was applied under ophthalmic drapes, whereas in the other 25 patients no suction was used. In all cases oxygen was insufflated under the drapes at a constant flow of 2 l/min. Carbon dioxide concentration in the ambient air surrounding the patient's head under ophthalmic drapes, transcutaneous partial pressure of carbon dioxide, respiratory rate, and oxygen saturation were measured. RESULTS: Carbon dioxide concentration under the drapes, transcutaneous partial pressure of carbon dioxide, and respiratory rate remained unchanged in the suction group, whereas in the non-suction group these values increased significantly. Oxygen saturation rose significantly in both groups without differences between the groups. CONCLUSION: Application of this new prototype for continuous aspiration of carbon dioxide enriched air prevents carbon dioxide rebreathing and subsequent hypercapnia associated with an elevated respiratory rate. This new equipment may therefore be useful in patients undergoing ophthalmic surgery under retrobulbar anaesthesia.

[Hypercapnea during facial surgery under local anesthesia].

We examined the ventilation of patients whose faces were draped during facial surgery under local anesthesia. Ten patients who underwent eye surgery received hydroxyzine 25 mg and pentazocine 15 mg i.m. before local anesthesia. Arterial blood samples and end-tidal respiratory gases from nasal cannulae were collected at the following selected times: before draping their faces, 10 min, 30 min, 60 min after draping, and after the drapes were removed. Both arterial carbon dioxide tension (42 +/- 1 mmHg before draping and 46 +/- 1 mmHg at 10 min) and end-tidal carbon dioxide tension (33 +/- 2 mmHg before draping and 36 +/- 1 mmHg at 10 min) were elevated significantly after their faces were draped. Hypercapnea was completely eliminated by suctioning the expired gases. It is concluded that hypercapnea is inevitable during face or neck surgery under local anesthesia, and that the expired gases should be monitored and removed.

[Correction of hypocapnia in hypoxic humans using biofeedback of alveolar carbon dioxide pressure]. / Ustranenie gipokapnii u cheloveka v gipoksicheskikh usloviiakh s pomoshch'iu bioupravleniia al'veoliarnym napriazheniem dvuokisi ugleroda.

Reactions of the respiratory system to the inhalation of a hypoxic gas mixture were compared when the test subjects (young healthy men) practised normal breathing or breathing with a stable alveolar PCO2. In the latter case the test subjects controlled their lung ventilation using the biofeedback technique. In this manner hyperventilation and related hypocapnia were eliminated. The possibility of practical application of biofeedback to the control of man's respiration in situations that may cause hypocapnia is discussed.