Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.
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Question: Abstract: The ability to breathe spontaneously through an endotracheal tube is a usual prerequisite before an intubated patient can have it removed. Other researchers have measured air flow resistance through endotracheal tubes. In this study, we evaluated work of breathing in joules per min and tension-time index while three normal volunteers breathed through different sized endotracheal tubes. Four 27.5-cm endotracheal tubes were used. Subjects breathed with a constant tidal volume of 500 ml. By increasing respiratory frequency, minute ventilation was increased from 5 to 30 L/min. As tube diameter decreased, work and the tension-time index increased. Changes were magnified at higher minute ventilations through the 6- and 7-mm endotracheal tubes, and the tension-time index critical fatigue level of 0.15 was approached or exceeded.

Answer: Work of breathing through different sized endotracheal tubes.

Question: Abstract: Ethane washout during low tidal volume (25-100 ml) high-frequency (3-40 Hz) ventilation (HFV) was studied in seven excised dog lungs. The lungs were initially equilibrated with 1% ethane, and then the concentration of ethane was monitored by mass spectrometry from multiple anatomic sites along the tracheobronchial tree during washout. We observed that the lung changed from a uniform distribution of ethane concentrations to a nonuniform distribution by a three-phase process. The first phase was nearly complete within the first 15 s and probably corresponds to concentration gradients being established in the central airways. During the second phase of washout, which lasted for several minutes, the concentrations in the various alveolar regions diverged. In the final phase, the regional concentrations remained at fixed ratios, and washout from all sites in the lung was at a constant fractional rate. These data are consistent with a model in which the duration of the second phase and the magnitude of the regional concentration differences established in this phase are dependent on both the magnitude of differences between regional transport paths and the nature of regional coupling by a common transport path to the airway opening.

Answer: Nonuniformity of canine lung washout by high-frequency ventilation.

Question: Abstract: To investigate the changes in diaphragm electromyogram (EMG) during the course of severe loaded breathing, we subjected five conscious adult sheep to inspiratory flow resistive breathing (resistance greater than 150 cmH2O X l-1 X s) for up to 2-3 h and studied the total EMG power per breath (iEMG) and the EMG power per unit time after dividing the duration of EMG activity within each breath into three equal parts (iEMG1, iEMG2, and iEMG3). Both total breath iEMG and transdiaphragmatic pressure (Pdi) increased, remained at a high level for a certain period of time, and then started to fall. A change in the pattern of iEMG within a breath was observed during loaded breathing. The increase in total-breath iEMG was associated mostly with an increase in iEMG3, or the last part of the EMG power within each inspiration. Similarly, the decrease in total breath iEMG was primarily due to a decrease in iEMG3. We conclude that, in sheep subjected to severe IFR loads for prolonged periods the marked increase in total-breath iEMG at the beginning of loaded breathing and the marked decrease in this iEMG at the time of decrease in Pdi are largely due to changes in iEMG that occur during the latter third of each breath. We speculate that during loaded breathing the recruitment pattern of diaphragmatic muscle fibers changes during the course of an inspiratory effort.

Answer:
Within-breath electromyographic changes during loaded breathing in adult sheep.