A surgical access device comprising: (a) a proximal end portion (1102, 1202) configured to support a seal assembly having an insufflation port; (b) a cannula tube (1104, 1204) extending distally from the proximal end portion and having an inner surface that defines a lumen (1112, 1212) extending longitudinally through the cannula tube, wherein the cannula tube is configured to be inserted distally through a body cavity wall of a patient, wherein the lumen (1112, 1212) is configured to guide a surgical instrument shaft distally through the cannula tube (1104, 1204) for accessing a body cavity of the patient; and (c) at least one channel formed in the inner surface (1110, 1210) of the cannula tube, wherein the at least one channel extends longitudinally between a proximal end of the lumen (1112, 1212) and a distal end of the lumen (1112, 1212), wherein the at least one channel (1120, 1220) is configured to direct a gas therethrough at least one of to or from the insufflation port of the seal assembly while a surgical instrument shaft is disposed within the lumen (1112, 1212), wherein a proximal end of the at least one channel (1120, 1220) has a greater width than a distal end of the at least one channel (1120, 1220), characterised in that either: (i) a width of the at least one channel tapers uniformly from a proximal end of the at least one channel to a distal end of the at least one channel, or (ii) the at least one channel includes a proximal channel portion and a distal channel portion, wherein the proximal channel portion has a first uniform width along a length thereof, wherein the distal channel portion has a second uniform width along a length thereof, wherein the first uniform width is greater than the second uniform width, wherein the at least one channel further includes a medial channel portion between the proximal channel portion and the distal channel portion, wherein the medial channel portion defines a stepped transition between the proximal channel portion and the distal channel portion. (a) a proximal end portion (1102, 1202) configured to support a seal assembly having an insufflation port; (b) a cannula tube (1104, 1204) extending distally from the proximal end portion and having an inner surface that defines a lumen (1112, 1212) extending longitudinally through the cannula tube, wherein the cannula tube is configured to be inserted distally through a body cavity wall of a patient, wherein the lumen (1112, 1212) is configured to guide a surgical instrument shaft distally through the cannula tube (1104, 1204) for accessing a body cavity of the patient; and (c) at least one channel formed in the inner surface (1110, 1210) of the cannula tube, wherein the at least one channel extends longitudinally between a proximal end of the lumen (1112, 1212) and a distal end of the lumen (1112, 1212), wherein the at least one channel (1120, 1220) is configured to direct a gas therethrough at least one of to or from the insufflation port of the seal assembly while a surgical instrument shaft is disposed within the lumen (1112, 1212), wherein a proximal end of the at least one channel (1120, 1220) has a greater width than a distal end of the at least one channel (1120, 1220), characterised in that either: (i) a width of the at least one channel tapers uniformly from a proximal end of the at least one channel to a distal end of the at least one channel, or (ii) the at least one channel includes a proximal channel portion and a distal channel portion, wherein the proximal channel portion has a first uniform width along a length thereof, wherein the distal channel portion has a second uniform width along a length thereof, wherein the first uniform width is greater than the second uniform width, wherein the at least one channel further includes a medial channel portion between the proximal channel portion and the distal channel portion, wherein the medial channel portion defines a stepped transition between the proximal channel portion and the distal channel portion. (i) a width of the at least one channel tapers uniformly from a proximal end of the at least one channel to a distal end of the at least one channel, or (ii) the at least one channel includes a proximal channel portion and a distal channel portion, wherein the proximal channel portion has a first uniform width along a length thereof, wherein the distal channel portion has a second uniform width along a length thereof, wherein the first uniform width is greater than the second uniform width, wherein the at least one channel further includes a medial channel portion between the proximal channel portion and the distal channel portion, wherein the medial channel portion defines a stepped transition between the proximal channel portion and the distal channel portion.