Elastic pressure-volume curves of the respiratory system reveal a high tendency to lung collapse in young pigs.
OBJECTIVE
To study pressure-volume (P/V) curves over a wide pressure and volume range in pigs.


METHODS
Dynamic and static P/V curves (P(dyn)/V and P(st)/V) and compliance of the respiratory system were studied. The effects of recruitment, positive end-expiratory pressure (PEEP) and body position were analysed.


METHODS
Research animal laboratory.


METHODS
Seven anaesthetised, paralysed and ventilated healthy pigs of 21 kg.


METHODS
P/V curves up to a pressure of about 40 cmH(2)O were recorded with a computer-controlled ventilator. P(st)/V curves were obtained with the static occlusion method and P(dyn)/V curves during an insufflation at a low, constant flow rate.


RESULTS
P(dyn)/V recording showed a complex pattern. During the insufflation compliance increased, fell, increased and fell again. A 2nd P(dyn)/V recording immediately following the 1st one was displaced towards higher volumes and showed only one maximum of compliance. The difference between the two curves reflected: (1) lung collapse during a period of 5 min of ventilation at zero end-expiratory pressure (ZEEP) following a recruitment manoeuvre, (2) recruitment during the measurement of the 1st P(dyn)/V curve. These observations were similar in the supine and in the left lateral position. After ventilation at PEEP, 4 cmH(2)O, the signs of collapse and recruitment were reduced. It was confirmed that PEEP offers a partial protection against collapse. P(st)/V curves showed higher volumes and higher compliance values compared to P(dyn)/V curves. This reflects the influence of viscoelastance on P(dyn)/V curves.


CONCLUSIONS
The study demonstrates a particularly strong tendency to lung collapse in pigs.
Liu
J M
JM
Department of Clinical Physiology, University Hospital, S-221 85 Lund, Sweden.
De Robertis
E
E
Blomquist
S
S
Dahm
P L
PL
Svantesson
C
C
Jonson
B
B
D000367:Age Factors; D000403:Airway Resistance; D000818:Animals; D004195:Disease Models, Animal; D008170:Lung Compliance; D008176:Lung Volume Measurements; D017711:Nonlinear Dynamics; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods*; D011187:Posture; D001261:Pulmonary Atelectasis / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D012131:Respiratory Insufficiency / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D013552:Swine