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. Author manuscript; available in PMC: 2014 Jul 18.
Published in final edited form as: Open J Mol Integr Physiol. 2013 Nov;3(4):166–180. doi: 10.4236/ojmip.2013.34022

Table 1.

Percent changes in arterial blood gas chemistry and Alveolar-arterial gradient elicited by injections of vehicle or morphine

Percent Changes
Parameter Group +3 min +6 min +9 min +12 min +15 min +30 min
pH Vehicle 0.0 ± 0.1 0.0 ± 0.2 0.0 ± 0.1 0.0 ± 0.3 0.0 ± 0.1 0.0 ± 0.1
Morphine −1.3 ± 0.2* −0.9 ± 0.2* −0.8 ± 0.2* −0.3 ± 0.1 0.1 ± 0.1 0.0 ± 0.1
pCO2 Vehicle +0.2 ± 0.7 +0.3 ± 0.7 −0.2 ± 0.9 +0.2 ± 0.4 −0.4 ± 0.4 +0.5 ± 0.3
Morphine +27.1 ± 2.6* +37.2 ± 3.9* +26.2 ± 2.4* +13.3 ± 2.2* +1.2 ± 1.5 −0.5 ± 0.7
pO2 Vehicle +1.0 ± 1.2 0.7 ± 0.8 −0.2 ± 0.7 −0.2 ± 1.0 +0.3 ± 0.4 +0.1 ± 0.5
Morphine −41.5 ± 3.1* −36.9 ± 2.9* −27.6 ± 1.6* −12.5 ± 1.0* −1.8 ± 1.1 −1.5 ± 2.0
sO2 Vehicle −0.6 ± 1.4 +0.7 ± 1.4 −0.4 ± 1.2 −1.0 ± 0.8 0.0 ± 1.0 −0.2 ± 1.1
Morphine −17.1 ± 2.4 −16.7 ± 2.6 −11.1 ± 2.0 −3.6 ± 0.8 +0.4 ± 1.1 +0.1 ± 0.8
A-a gradient Vehicle −3 ± 9 −5 ± 6 +3 ± 5 +3 ± 5 −0 ± 2 −1 ± 4
Morphine +173 ± 31* +111 ± 15* +92 ± 16* +38 ± 6* +7 ± 7 +9 ± 13

All data are mean ± SEM. There were 8 rats in each group. A-a gradient, Alveolar-arterial gradient.

*

P < 0.05, significant percent change from Pre values.

A-a gradient = PAO2 − PaO2, where PAO2 is the partial pressure of alveolar O2 (calculated from the alveolar gas equation) and PaO2 is the partial pressure of O2 in arterial blood. PAO2 is determined by the formula, PAO2 = [(FiO2 × (Patm−PH2O) − (PaCO2/respiratory quotient)], where FiO2 is the fraction of O2 in inspired air; Patm is atmospheric pressure; PH2O is the partial pressure of water in inspired air; and PaCO2 is the partial pressure of CO2 in arterial blood. We took FiO2 of room-air to be 21% = 0.21; respiratory quotient to be 0.8; Patm to be 760 mmHg; and PH2O to be 47 mmHg [see 27,28].