Can anyone tell the negative airway pressure in the trachea during inhalation, during calm respiration but also in a forced deep inhalation, model human 60 - 80 kg?
hi karen,
interesting question ...
i don't know how detailed you want/need to know this. as far as i remember according to typical physiology books: normal intrathoracic negative pressures during spontaneous respiration are between -5 to -20 cmH2O, and i assume it will be similar in the trachea, however, i do not know the exact pressurue gradient lowering this value in the trachea, apparently it has to be higher than in the alveoli to keep air flowing. however in obstruction maximum numbers such as -140 cmH2O have been observed.
christoph
The exact valu have a big variation based on different variables those determine the muscular mass and performance. The main impact of this values in clinical practice are as criteria to predict extubation tolerance in some complicated cases. However, there are not in value alone. Even in healthy persons it could be influenced deeply be airway resistance, therefore it's measuring is difficult and varies with type and diameter and other physical characteristics of airway and muscular performance.
-25 cmH2O is minimal negative pressure that along with other criteria, could predict successful extubation in presence Oral tracheal tube. Values should be determine based on age and sex in Spirometry test. There are different values but it seems that about -45 for female and -60 for men are a good estimat in normal breathing person (1).
1. Hautmann H1, Hefele S, Schotten K, Huber RM. Maximal inspiratory mouth pressures (PIMAX) in healthy subjects--what is the lower limit of normal?Respir Med. 2000 Jul;94(7):689-93.
Perhaps placement of an espohageal ballon with measurements of transpulmonary pressure would be a preferred technique.
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