77373
document
Response to tubular airway resistance in normal subjects and postoperative patients . Critically ill patients must often breathe spontaneously through an endotracheal tube that acts as a fixed inspiratory and expiratory tubular airway resistor . Although this practice is common , its effect on the pattern of breathing is not known . The mean breathing patterns of seven normal , healthy male subjects and eight male patients who had undergone upper abdominal surgery 2-4 days previously were studied breathing through a mouthpiece fitted in random order with a 5 , 6 , 7 , 8 , or 15 mm diameter ( 17 mm long ) resistor . These diameters were selected because they simulate the pressure-flow relationships of adult endotracheal tubes . With the 15 mm aperture , the patients had a greater breathing frequency ( f ) than did the normal subjects ( 21 +/- 5 [ SD ] vs. 14 +/- 4 breaths/min , P less than 0.01 ) as well as a smaller mean tidal volume ( VT ) . In both groups , minute ventilation ( VE ) and f progressively decreased as resistance was increased by decreasing the aperture size from 15 to 16 mm . In the normal subjects but not the patients , VT also progressively decreased . When the diameter was decreased from 6 mm to 5 mm , there were increases in VT and decreases in f that were more marked in the normal subjects . In both groups , the changes in VE were accompanied by decreases in mean and peak inspiratory and expiratory flow rates . Throughout the study , oxygen consumption ( VO2 ) and carbon dioxide production ( VCO2 ) did not change . This , coupled with the decreases in VE resulted in decreases in the ventilatory equivalents to CO2 and O2 ( VE/VCO2 , VE/VO2 ) . ( ABSTRACT TRUNCATED AT 250 WORDS )
77374
Intervention_Physical
tubular airway resistance
77375
Intervention_Surgical
endotracheal tube
77376
Intervention_Physical
mouthpiece fitted in random order with a 5 , 6 , 7 , 8 , or 15 mm diameter ( 17 mm long ) resistor .
77377
Outcome_Physical
breathing frequency ( f )
77378
Outcome_Physical
mean tidal volume ( VT ) .
77379
Outcome_Physical
minute ventilation ( VE )
77380
Outcome_Physical
f
77381
Outcome_Physical
VT
77382
Outcome_Physical
VT
77383
Outcome_Physical
f
77384
Outcome_Physical
changes in VE
77385
Outcome_Physical
peak inspiratory and expiratory flow rates
77386
Outcome_Physical
oxygen consumption ( VO2 ) and carbon dioxide production ( VCO2 )
77387
Participant_Condition
normal
77388
Participant_Condition
Critically ill
77389
Participant_Sample-size
seven
77390
Participant_Condition
normal , healthy
77391
Participant_Sex
male
77392
Participant_Sample-size
eight
77393
Participant_Sex
male