Effects of continuous positive-pressure ventilation in experimental pulmonary edema.

We compared the effects of continuous positive-pressure ventilation (CPPV), using 10 cmH2O positive end-expiratory pressure (PEEP), with intermittent positive-pressure ventilation (IPPV), on pulmonary extravascular water volume (PEWV) and lung function in dogs with pulmonary edema caused by elevated left atrial pressure and decreased colloid osmotic pressure. The PEWV was measured by gravimetric and double-isotope indicator dilution methods. Animals with high (22-33 mmHg), moderately elevated (12-20 mmHg), and normal (3-11 mmHg) left atrial pressures (Pla) were studied. The PEWV by both methods was significantly increased in the high and moderate Pla groups, the former greater than the latter (P less than 0.05). There was no difference in the PEWV between animals receiving CPPV and those receiving IPPV in both the high and moderately elevated Pla groups. However, in animals with high Pla, the Pao2 was significantly better maintained and the inflation pressure required to deliver a tidal volume of 12 ml/kg was significantly less with the use of CPPV than with IPPV. We conclude that in pulmonary edema associated with high Pla, PEEP does not reduce PEWV but does improve pulmonary function.     

Pneumoconiosis and chronic bronchitis.

Data from a major long-term epidemiological survey in the British coalmining industry were examined to determine whether bronchitis offered any protective action against the development of pneumoconiosis. No evidence of such an effect was found.     

Comparison of salbutamol given intravenously and by intermittent positive-pressure breathing in life-threatening asthma.

A double-blind crossover trial was carried out during 22 episodes of life-threatening asthma in 19 patients to compare salbutamol given as a 500 microgram intravenous injection and as a 0 . 5% solution administered by intermittent positive-pressure breathing (IPPB) for three minutes. Relief of pulsus paradoxus was significantly better after IPPB than the intravenous treatment. Both treatments significantly improved the peak expiratory flow rate. Salbutamol given intravenously produced a mean increase in heart rate of over 20 beats/min five minutes after treatment compared with the relief of tachycardia that occurred after administration by IPPB. Four patients had noticeable cardiovascular side effects after salbutamol given intravenously, but no such effects were noticed after administration by IPPB. Two patients withdrawn shortly after entry into the trial because of a worsening clinical condition had received intravenous salbutamol. It is concluded that salbutamol given by IPPB is better than that given by slow intravenous injection in severe acute asthma.     

Effects of positive-pressure ventilation on the spontaneous baroreflex in healthy subjects.

To determine the short-term effects of noninvasive positive-pressure ventilation (PPV) on spontaneous baroreflex sensitivity, we acquired time series of R-R interval and beat-to-beat blood pressure in 55 healthy volunteers (mean age 46.5 +/- 10.5 yr) who performed breathing on four occasions at frequencies of 12 and 15 breaths/min without positive pressure (control) and also using PPV of 5 mbar. By using spectral and cross-spectral analysis, R-R interval variability and systolic blood pressure variability as well as the gain (alpha-index) of the baroreceptor reflex were estimated for the low-frequency and high-frequency (HF) bands. Compared with control breathing, PPV at 12 breaths/min and 15 breaths/min led to an increase in mean R-R (P < 0.001) and blood pressure (P < 0.05). The alpha-index of the HF band increased significantly for both respiratory frequencies (P < 0.05) due to PPV. These results indicate that short-term administration of PPV in normal subjects elicits a significant enhancement in the HF index of the baroreflex gain. These findings may contribute to understanding the mechanisms, indications, and effectiveness of positive pressure breathing strategies in treating cardiorespiratory and other disease conditions.     

Results of utilization of intermittent normobaric hypoxia in patients with bronchial asthma and chronic obstructive bronchitis]

The results of intermittent normobaric hypoxytherapy in 42 patients with bronchial asthma (BA) and 14 patients with chronic obstructive bronchitis (COB) are analyzed. The positive effect is obtained in 76% of patients with BA and 92.8% of patients with COB. In the group of patients with BA the best effect was achieved for atopic form of BA--in 90% of patients, the effect was less pronounced for infection-allergic form--in 73.9% and for mixed form of BA--in 66.7%. In the process of treatment the attacks of asphyxia disappeared or became more occasional in 60.7% of patients; in 32.1% the attacks were more easily arrested or stopped independently; 33.8% of patients decreased doses of constantly taken drugs; in 33% cough ceased or decreased, sputum became to expectorate better; in 41% of patients dyspnea disappeared and considerably decreased. Improvement of the state in 54% of patients was retained for one year and more, in 29%--for 6 months, in 16.6%--for 3-4 months. The course of treatment consisted of 20-25 sessions. The patients breathed in hypoxic gas mixture containing 10% of oxygen (HGM-10) under intermittent conditions alternating with respiration of free air.