mise à jour du
6 octobre 2002
Surgical Forum
1970; 21; 222-223
 Physiology of yawning and its application to postoperative care
RH Bartlett, P Krop, EL Hanson, FD Moore
Department of surgery, Harvard Medical School
Peter Bent Brigham Hospital Boston


Shallow breathing, decreased lung volumes, and increased transpulmonary shunting as high as 20% of the cardiac output, are consistent findings in most patients following major operations. These alterations in pulmonary function usually return to normal without becoming clinically evident, but may progress to obvious respiratory insufficiency with decreased compliance, increased work of breathing, marked shunting, retention of secretions, gross consolidation, and pneurnonitis. The causes of these phenomena are uncertain, but monotonous tidal ventilation leading to alveolar closure bas been shown to have this effect.
A maneuver which would assure voluntary sustained maximal inspiration (SMI) with glottis open, as in a prolonged yawn, should 1) equilibrate ventilation and perfusion, and 2) prevent alveolar atalectasis. An incentive spirometer, which assured these conditions, was constructed to test this hypothesis.
As the subject inhales from the device, a light turns on when he reaches a preset volume (1/2 of the measured inspiratory capacity) and stays on as long as an inspiratory flow rate of 50 cc./sec. is maintained. When total lung capacity is reached, or if the subject closes his glottis, the light turns off. The subject is instructed to light the light as long as possible by sustained maximal inspiration, indeed, simulatinga yawn.
Pulmonary and hemodynamic studies were carried out with a pneumotachograph flow and volume system, inspired and expired gas control and collection by one way valves, rapid nitrogen and C02 analyzers, intravascular catheters for pressure measuring and blood collection, and a small intraesophageal pressure transducer. Five normal volunteers and a series of postoperative patients were studied to assess the changes produced by this maneuver compared with other respiratory maneuvers, and to observe the effects of repeated SMI on pulmonary function in postoperative patients.
During yawning (SMI) negative intrathoracic pressure (-40 mm. Hg) was maintained throughout inspiration causing sustained inspiratory flow (average 200 cc./sec.) and increasing volume to total lung capacity. Right atrial pressure decreased (5 to -10 mm. Hg), mean pulnionary artery pressure decreased (15 to 0 mm. Hg), and venous return increased (measured by impedence plethysmography). Cardiac output increased slightly. ln healthy volunteers Pa O2 (air) increased slightly (90 to 94 mm. Hg) as did Pa O2 (l00% (580 to 596 mm. Hg), indicating that ventilation perfusion relationships and shunt were normal in these subjects and could not be significantly improved. Arterial pCO2 and PH were not affected by the maneuver. Rebreathing or C02 breathing caused tachypnea with increased tidal volume, giving effects qualitatively similar to SMI but these effects were not as marked and were not sustained. Cough, IPPB, a held deep breath, blow boules, and other positive pressure respiratory maneuvers produced the hemodynamic effects of the Valsalva maneuver with increased intravascular pressure, decreased venous return, and decreased cardiac output. The lung volume to which the subject inspired for positive pressure maneuvers was generally far short of total lung capacity.
ln ten postoperative patients with normal preoperative pulmonary function, vital capacity decreased to 60% of preoperative levels. Alveolar arterial gradients for oxygen while breathing 100% oxygen increased to 250 to 350 mm. Hg, corresponding to a 12% to 20% shunt. The hemodynamic effects of SMI were the same as in the normal volunteers. However, in the postoperative patients ventilation/ perfusion imbalance was demonstrated which could be reversed by SMI. Pa 02 (air), increased from 70 to 94 mm. Hg. Alveolar-arterial gradient on l00% 02 was diminished by SMI [Pa 02 (100%) 440 to 520] suggesting opening of closed alveoli. These effects were scen after five SMI maneuvers. When this was repeated on an hourly basis, the Pa 02 (room) and the Pa 02 (100%) stayed at near normal levels. Unlike forced exhalation, SMI is not painful in laparotomy patients because only inspiratory muscles are used, in fact patients accepted the incentive spirometer enthusiastically. The device has also been used to treat established atalectasis with success and has been valuable in weaning patients from prolonged ventilator management.
Hemodynamic, ventilatory, and gas exchange effects of voluntary sustained maximal inspiration (yawning) with an incentive spirometer are described.
Periodic SMI to total lung capacity can prevent or reverse postoperative hypoxemia, supporting the theory that alveolar atalectasis due to shallow ventilation is one cause of decreased lung volumes and shunt in postoperative patients.
The beneficial effects on ventilation and perfusion, and patient acceptance, suggest that use of this device may decrease the incidence of postoperative pulmonary complications, and controlled clinical studies are underway.
Bartlett RH et al The yawn maneuver: prevention and treatment of postoperative pulmonary complications Surgical Forum 1971, 22,196-198
Crosby L; Parsons LC Clinical neurologic assessment tool: development and testing of an instrument to index neurologic status.Heart Lung 1988; 18; 2; 121-9
Cahill CA Yawn maneuver to prevent atelectasis AORN 1978; 27; 5; 1000-1004
Neurological assessment of coma (pdf)
David E Bateman
J Neurol Neurosurg Psychiatry
2001; 71(suppl I); i13Ði17