Non-invasive determination of alveolar pressure during mechanical ventilation.
The development of inadvertent positive end-expiratory pressure (PEEPi) in ventilated infants is of clinical relevance and difficult to measure non-invasively. A method for estimating end-expiratory alveolar pressure by applying a multiple regression analysis to airway opening pressure, flow and volume recordings during mechanical ventilation was evaluated. In eight open-chested, paralysed and mechanically ventilated mongrel dogs, alveolar pressure was measured directly with "alveolar capsules". Alteration of ventilation patterns and addition of a resistive element were used in three dogs to induce different levels of PEEPi. End-expiratory alveolar pressure measured directly and determined from multilinear regression of airway opening pressure correlated well (mean error 0.06 +/- 0.53 (+/- SD) hPa, limits of agreement -1.16 to +1.04 hPa). The other five dogs received inhalation challenges, two with histamine, two with hypertonic saline and one with methacholine resulting in a mean increase of respiratory system resistance of 230% (range 141-489%) of the baseline values. The mean error in determining PEEPi was 0.54 +/- 0.37 hPa, the limits of agreement were -0.20 to 1.28 hPa. The method was then applied to seven mechanically-ventilated children (aged 2 months to 8 yrs, weight 4.9-23.5 kg) and the results were compared to the pressure at which inspiration began (equalling PEEPi). Seventy eight measurements were performed during open heart surgery, while compliance changed by between 3 and 186% of baseline values due to the surgical procedures. PEEPi estimated by multiple regression agreed well with the pressure at which inspiration began (mean difference 0.25 +/- 0.68 hPa, limits of agreement -1.12 to 1.62 hPa).(ABSTRACT TRUNCATED AT 250 WORDS)
Nicolai
T
T
Clinical Sciences Division, Western Australian Research Institute for Child Health, Perth.
Lanteri
C
C
Freezer
N
N
Sly
P D
PD
D000818:Animals; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D004285:Dogs; D005652:Functional Residual Capacity; D006801:Humans; D007223:Infant; D008954:Models, Biological; D011312:Pressure; D011650:Pulmonary Alveoli / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012044:Regression Analysis; D012121:Respiration, Artificial