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L Freitag

Publications and source records attributed to L Freitag.

42 records · Page 3Linked to original sources
PubMed1989

Mobilization of mucus by airway oscillations.

The effects of high frequency asymmetric airway oscillations on mucus clearance were evaluated in excised tracheas of sheep, in an animal model of excessive mucus production, and in patients with bronchiectasis. Asymmetric high frequency ventilation (15 Hz) with expiratory biased flow profiles (expiratory peak-flow greater than inspiratory peak-flow) could move mucus droplets towards the pharynx in rigid and flexible tracheas by gas-liquid interaction. In rigid tracheas the mucus was transported towards the periphery of the model lung if the oscillations were inspiratory biased. In very collapsible tracheas, however, even inspiratory biased oscillations moved the mucus cephalad. Parameters influencing direction and speed of mucus are airflow profile, peak-flow, airway compliance and lung resistance. Gamma-camera studies showed that in anesthetized dogs radiolabeled artificial mucus followed the direction of the bias during high frequency ventilation. In five human volunteers with bronchiectasis and excessive secretions the asymmetric airway oscillations were superimposed during spontaneous breathing using a mouthpiece. Airway wall vibrations following the pressure swings of the oscillator could be observed. During forced expiration inward bulging of the posterior membranes of trachea and bronchi occurred at the negative pressure phase of the oscillations. This event was associated with increased appearance of sputum in the central airways. We conclude that high frequency ventilation with asymmetric flow profiles applied via tube or mouthpiece might be an effective future treatment of mucostasis.

Airway Resistance↗
PubMed1989

Removal of excessive bronchial secretions by asymmetric high-frequency oscillations.

The present study evaluated whether high-frequency oscillations (HFO) with biased flow profiles applied at the airway opening are capable of altering mucus clearance. In eight anesthetized sheep, artificial mucus (100 P) was infused continuously (1 ml/min) into the left main bronchus via a cannula inserted through the dorsal wall of the left main bronchus after thoracotomy. Outcoming mucus was collected every 10 min from the end of a cuffed orotracheal tube. Animals were ventilated with a Harvard respirator at a low frequency with superimposed HFO at 14 Hz with asymmetrical waveforms generated by a digitally controlled electromagnetic piston pump (expiratory bias: peak expiratory flow 3.8 l/s, peak inspiratory flow 1.3 l/s; inspiratory bias: reverse of expiratory bias). The influence of posture and of HFO airflow bias on mucus clearance was determined. In the horizontal position, mucus clearance with expiratory biased HFO was 3.5 +/- 2 (SD) ml/10 min. Head-down tilt produced a clearance of 3.1 +/- 3 ml/10 min; addition of HFO with expiratory bias increased clearance to 11.0 +/- 2.0 ml/10 min (P less than 0.05). No clearance occurred with inspiratory biased HFO during head-down tilt. These results indicate that expiratory biased HFO at the airway opening can clear excessive airway secretions and augment clearance by postural drainage.

Animals↗
PubMed1989

[Use of microcomputers in polysomnography].

Constantly falling prices and increasing power combine to make the personal computer an attractive alternative to established recording devices for use in polysomnography. Apart from its price advantage, digital recording of psychophysiological signals offers the possibility of selective display (compression and zooming to parts of special interest), and also semi-automatic evaluation. In order to be able to feed the data acquired in the sleep laboratory into the computer, an interface for signal matching, an analog/digital converter, and suitable software, are required. In order to reduce the wealth of data to the clinically relevant (and, in the last resort, also manageable) amount, preprocessing hardware, such as EEG filters, snore detectors, etc., are required. The system we recommend comprises individual hardware, modules for the pickup of physiological signals, and flexibly combinable software routines that permit adaptation to any future expansions of changing medical problems.

Humans↗
PubMed1987

Laser smoke effect on the bronchial system.

The photoresection of endobronchial tumors produces smoke which is partly inhaled by the patient as well as the surgical staff. In an animal study we investigated whether a single exposure or repetitive exposures to smoke might have harmful side effects on the airways. Eleven sheep were exposed to smoke produced by laser-vaporizing (6,500 J) sections of bronchial tissue (1 cm3) in a Plexiglas chamber. The smoke analysis revealed 0.92 mg/liter particles with a mean particle size of 0.54 micron. Carbon monoxide content was estimated as 0.04%. We measured the effects of one or three separate ten-minute exposures on airway resistance, gas exchange, and mucociliary clearance rate in the trachea. We found that the smoke inhalation resulted in a decrease of arterial PO2 with relatively little change in airway mechanics. Tracheal mucus velocity, a marker of lung mucociliary clearance, was significantly depressed in a dose-dependent manner with increasing smoke exposures. Results of bronchoalveolar lavages performed before and one day after the exposure showed that the smoke inhalation induced a severe inflammation with dramatic increases of inflammatory cells. The total number of cells per milliliter lavage return increased from 3.2 million to 25 million; percent neutrophils increased from 2.3 to 45.6% and percent macrophages decreased from 86 to 41%. These findings indicate that the side effects of smoke inhalation during intrabronchial laser surgery should not be neglected. The impairment of the defense mechanism of the lung combined with the inflammation as well as hypoxia might be fatal in compromised patients. Effective smoke removal devices should be developed to protect the patient as well as the surgeon.

Animals↗