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Figure 2. A representative polysomnographic recording is illustrated, showing the change in upper inspiratory airflow (VI) (top channel) and nasal pressure (Pn) (second channel from top). As shown, progressively sub-atmospheric levels of nasal pressure (Pn) were applied in stepwise manner (left to right) and kept constant at each pressure level for 5 or 6 breaths. At Pn values below 3 cm H₂O, inspiratory flow limitation ensued, as indicated by a flattening of the inspiratory airflow contour (see downward arrow from left), while the esophageal pressure (Peso) continued to become increasingly more negative. We obtained maximal inspiratory flow (VImax) by taking the difference between zero inspiratory flow and maximal inspiratory flow, as illustrated by the dotted lines. A period of zero flow was accompanied by similar changes in esophageal pressure (Peso), hypopharyngeal pressure (Phypo), and oropharyngeal pressure (Poro) during inspiratory efforts, together with failure of these pressure changes to be transmitted to the nasopharynx. Similar findings were observed in all subjects.

J DENT RES, Vol. 84, No. 6, 554-558 (2005)
DOI: 10.1177/154405910508400613

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