Thorax: first published as 10.1136/thx.35.7.543 on 1 July 1980. Downloaded from Thorax, 1980, 35, 543-545 Streamlining of air flow in the upper airways and trachea R MARSHALL AND D J MACEY From the Departments of Chest Diseases and Radiation Physics, Churchill Hospital, Oxford ABSTRACT Streamlining of air flow in the upper airways and trachea has been investigated by inhaling 8lmkrypton through each side of the nose separately and counting over the lung fields with a gamma camera. 8lmKr inhaled through one nostril was uniformly mixed in the air stream by the time the carina was reached. Gas mixing occurs probably by a combination of diffusion and turbulent flow. Some of the early investigators of the physiology across the two tubes was recorded using a Nokia of air flow in the nose and upper airways pro- multi-channel pulse height analyser and the X duced evidence that the airstream from the two pulses. The 81mkrypton in each tube was cal- sides of the nose remained separate in the culated from the area of the profile at the site pharynx and that the air entering through one of each tube after subtraction of background nostril went mainly to the lung of the same counts. side.1-3 If this were true it would simplify ventila- tion scans of the lungs with 81mkrypton since, if INHALATION OF 8sl''Kr the radioactive gas inhaled through one nostril tlmKr has a half-life of 13 secs, so that a scan http://thorax.bmj.com/ went mainly to the lung of the same side, true over the lung fields indicates the ventilation of lateral scans of the lung could be taken without each lung.4 Before inhalation of 8lmKr the resist- appreciable interference from the other lung. ance of each nasal passage was measured by Mixing of the gas streams after leaving the two posterior rhinometry. Pressure at the mouth was sides of the nose may occur as a result of tur- measured by a pressure transducer via a plastic bulent air flow or by diffusion. Preliminary tube round which the lips were closed. Nasal air experiments were carried out using a model with flow was measured by a wire screen pneumo- streamline air flow to investigate the probable tachograph connected to a nasal mask.5 The effects of diffusion. tlmKr was inhaled through the apparatus shown on September 29, 2021 by guest. Protected copyright. i-1 fig 2. The outputs from the pneumotacho- Methods graphs, recording inspiratory air flow, were fed into the X and Y axes of a cathode-ray oscillo- MODEL OF STREAMLINE AIR FLOW scope and the oscilloscope screen photographed. Air, and air containing llmkrypton were fed at In practice the XY recording of flow through the equal rates into a smooth bore tube of 19 mm right and left nostrils was linear showing that internal diameter, approximating the diameter of the ratio of flow through both nostrils was the the trachea (fig 1). In the first 9 cm of the tube same at all times during inspiration and thus the the two gas streams were separated by a thin ratio of volumes inspired by the two nostrils metal partition so that the gas flow was stream- was the same as the ratio of flow rates. lined before the main tube was reached. Fifteen centimetres further down the tube the gas streams were divided by a thin "carina" aligned Air with the upper partition and the two gas streams -9 cm-.---- 15cm - conducted through plastic tubes lying on the col- limator of a gamma camera. An activity profile Air +81m Kr Address for reprint requests: Dr R Marshall, Department of Chest Diseases, Churchill Hospital, Oxford OX3 7LJ. Fig I Diagram of air flow model. 543 Thorax: first published as 10.1136/thx.35.7.543 on 1 July 1980. Downloaded from 544 R Marshall and D J Macey 0m .C ioo0 'I K E w " (DB0-80 c *0 o'ntn a O60- -06 .~._ -0*5 oW._ 4 -04 0-3 C 20 Transit time -02 U -01 I 14 12 10 8 6 4 2 p Gas tlow of each stream (/min ) Fig 2 Diagram of test apparatus. N=nasal Fig 3 Results of model experiment. applicator, V= valve assembly, P=pneumotachograph. The 8llnKr was eluted continuously from the Table Inhalation of 81"'Kr through each nostril generator by a stream of air at 05 to 1 1/min, separately passed along two metres of narrow bore tube, Subject Resistance Nasalflow Counts in 30 sec % of total Sln&Kr and fed into the corrugated tubing on the in- of each (% of over lung 81-Kr in right lung when spiratory side of the valve assembly just before nasal cavity total) inhaled via inhaled via the rubber flap valve. The was (cm H20 1P's Right Left Right Left subject positioned at 0-2 centrally in front of the gamma camera to take s-1 nostril nostril nostril nostril a posterior view of both lungs. The valve as- I Right 10-0 53-7 15151 20 675 51-1 564 semblies were applied to the nostrils and the Left 10-0 46-3 14 528 15 982 subject breathed with the mouth closed. 8"mKr 2 Right 4-8 63-0 13 933 13 095 594 572 was introduced into the inspired air to one nostril Left 9-1 37-0 9481 9778 and after waiting about 30 seconds for equilibra- 3 Right 7-8 48-9 10051 9382 http://thorax.bmj.com/ 50 5 49-4 tion the output of the gamma camera was Left 5-8 51-1 9864 9612 recorded on videotape. After recording for 1-2 4 Right 16-7 48-2 17341 17468 49-3 48-4 min the UlmKr input was transferred to the other Left nostril without disturbing the subject and the 14-4 51-8 17 781 18 680 camera output again recorded. The videotape recordings were played back Discussion and counts made from equal areas of compar- able regions in the and left fields. right lung Preferential passage of air from one side of the on September 29, 2021 by guest. Protected copyright. Measurements were made on four subjects nose to the lung of the same side had been sug- with no signs or symptoms of nasal disease and gested by Chauvet6 and some of the early investi- with no significant abnormality in the ventilation gations on both man and animals seemed to and perfusion lung scans. support this theory. Mink' used a wire covered Results with red litmus paper, held across the pharynx in various positions while breathing ammonia The results of the model experiment are shown vapour through one nostril. From the change in in fig 3. colour of the litmus paper he was able to deter- The results of the lung scans and measure- mine that the air stream after leaving the choana ments of nasal resistance are shown in the table. passed to the posterolateral part of the pharynx, Examination of the counts over the lungs shows then came more anteriorly behind the tongue but that there is no appreciable difference in the stayed on the same side of the pharynx. Wotzilka count whether the 8111mKr is inhaled via the right and Schramek2 investigated the deposition of or left nostril. 81mKr in the dead space at the carbon particles inhaled by rabbits through one end of expiration has been shown to have only nostril. The particles went mainly to the lung of about 10% of the activity of the inspired gas the same side. Dishoeck3 found that carbon dust and the reinspiration of this gas has a negligible inhaled through one side of the nose could be effect on the distribution of radioactivity in the found on both sides of the pharynx but if one two lungs. side of the nose was narrowed the carbon dust Thorax: first published as 10.1136/thx.35.7.543 on 1 July 1980. Downloaded from Streamlining of air flow in the upper airways and trachea 545 inhaled through that nostril stayed mainly on the the krypton had passed into the opposite stream same side of the pharynx and, he believed, went during this transit time. If gas flow in the upper mainly to the lung of the same side. He carried airways of man was as smooth as in the model out experiments breathing oxygen through one that we used one would expect a much higher side of the nose and nitrogen through the other concentration of krypton in the lung on the same and showed that the gas expired through each side as the nostril through which the krypton is nostril had the same composition. In that experi- inhaled, than one would in the other lung. The ment further opportunity for mixing of the gas measurements with 8lmKr show that the com- streams occurred during recombination of the bination of diffusion and turbulent flow result in streams from the two lungs and passage up the complete mixing of the gas streams from the trachea. Before using 8lmkrypton in the model two sides of the nose by the time that the gas experiment we made measurements, in two dif- reaches the carina, even in the subject in whom ferent models, with air passed down one side of one nostril was relatively constricted. Thus the the tube and 100% oxygen down the other. In theory that inhalation of 81mKr through one side all experiments, when the gas flow down each of the nose might allow lateral scintigrams to be tube fell below 6 1/min the mixing of the streams taken has been shown to be invalid.