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Biomedical subjects

M J Rodríguez-Nieto

Publications and source records attributed to M J Rodríguez-Nieto.

6 recordsLinked to original sources
PubMed2005

Effect of pulmonary perfusion on the slopes of single-breath test of CO2.

The objective of this study was to evaluate the effects of lung perfusion on the slopes of phases II (S(II)) and III (S(III)) of a single-breath test of CO(2) (SBT-CO(2)). Fourteen patients submitted to cardiac surgery were studied during weaning from cardiopulmonary bypass (CPB). Pump flow was decreased in 20% steps, from 100% (total CPB = 2.5 l.min(-1).m(-2)) to 0%. This maneuver resulted in a progressive and opposite increase in pulmonary blood flow (PBF) while maintaining ventilator settings constant. SBT-CO(2), respiratory, and hemodynamic variables remained unchanged before and after CPB, reflecting a constant condition at those stages. S(III) was similar before and after CPB (19.6 +/- 2.8 and 18.7 +/- 2.1 mmHg/l, respectively). S(III) was lowest during 20% PBF (8.6 +/- 1.9 mmHg/l) and increased in proportion to PBF until exit from CPB (15.6 +/- 2.2 mmHg/l; P < 0.05). Similarly, S(II) and the CO(2) area under the curve increased from 163 +/- 41 mmHg/l and 4.7 +/- 0.6 ml, respectively, at 20% PBF to 313 +/- 32 mmHg/l and 7.9 +/- 0.6 ml (P < 0.05) at CPB end. When S(II) and S(III) were normalized by the mean percent expired CO(2), they remained unchanged during the protocol. In summary, the changes in PBF affect the slopes of the SBT-CO(2). Normalizing S(II) and S(III) eliminated the effect of changes in the magnitude of PBF on the shape of the SBT-CO(2) curve.

Aged↗
PubMed2004

Lower pulmonary diffusing capacity in the prone vs. supine posture.

We evaluated the effect of prone positioning on gas-transfer characteristics in normal human subjects. Single-breath (SB) and rebreathing (RB) maneuvers were employed to assess carbon monoxide diffusing capacity (DlCO), its components related to capillary blood volume (Vc) and membrane diffusing capacity (Dm), pulmonary tissue volume (Vti), and cardiac output (Qc). Alveolar volume (Va) was significantly greater prone than supine, irrespective of the test maneuver used. Nevertheless, Dl(CO) was consistently lower prone than supine, a difference that was enhanced when appropriately corrected for the higher Va prone. When adequately corrected for Va, diffusing capacity significantly decreased by 8% from supine to prone [SB: Dl(CO,corr) supine vs. prone: 32.6 +/- 2.3 (SE) vs. 30.0 +/- 2 ml x min(-1) x mmHg(-1) stpd; RB: Dl(CO,corr) supine vs. prone: 30.2 +/- 2.2 (SE) vs. 27.8 +/- 2.0 ml x min(-1) x mmHg(-1) stpd]. Both Vc and Dm showed a tendency to decrease from supine to prone, but neither reached significance. Finally, there were no significant differences in Vti or Qc between supine and prone. We interpret the lower diffusing capacity of the healthy lung in the prone posture based on the relatively larger space occupied by the heart in the dependent lung zones, leaving less space for zone 3 capillaries, and on the relatively lower position of the heart, leaving the zone 3 capillaries less engorged.

Adult↗
PubMed2002

[Non-invasive ventilation in patients with severe hypercapnic encephalopathy in a conventional hospital ward].

OBJECTIVE: To report our experience with non-invasive ventilation (NIV) at two levels of pressure (Bi-PAP) on a general respiratory medicine ward with patients in hypercapnic impaired consciousness and/or coma who had not previously been in an intensive care unit (ICU). METHODS: This was a prospective study of 13 patients, mean age 81 years (65-96), treated with NIV through a face mask. Ten had chronic obstructive pulmonary disease, with a mean FEV1 in stable condition of 35.2 14.6%. Glasgow scores upon admission were >/= 7. Arterial gases were monitored until suspension of NIV. RESULTS: After NIV for a mean 19 5 h/day in the first 48 hours and later of 6 1 h/day until a total of 74 9 h, 9 patients (69%) survived. The mean initial pH for these patients was 7.17 0.028 and the mean initial pCO2 was 101 9 mm Hg. In 7 cases (78%), coma was reversed in the first 48 h and a significant improvement in pH was observed in the 12-24 h analysis. Mean pH upon discharge was 7.44 0.013 and mean pCO2 was 54 2.8 mmHg. Four patients died, even though their initial or subsequent arterial gases at 12-24 h were not significantly different from those of the survivors. CONCLUSION: NIV on a general respiratory medicine ward can offer an alternative to oro-tracheal intubation for patients with hypercapnic impaired consciousness and/or coma who do not meet the criteria for admission to the ICU.

Acute Disease↗
PubMed2002

Similar ventilation distribution in normal subjects prone and supine during tidal breathing.

Multiple-breath washout (MBW) tests, with end-expiratory lung volume at functional residual capacity (FRC) and 90% O(2), 5% He, and 5% SF(6) as an inspired gas mixture, were performed in healthy volunteers in supine and prone postures. The semilog plot of MBW N(2) concentrations was evaluated in terms of its curvilinearity. The MBW N(2) normalized slope analysis yielded indexes of acinar and conductive ventilation heterogeneity (Verbanck S, Schuermans D, Van Muylem A, Paiva M, Noppen M, and Vincken W. J App Physiol 83: 1907-1916, 1997). Also, the difference between SF(6) and He normalized phase III slopes was computed in the first MBW expiration. Only MBW tests with similar FRC in the prone and supine postures (P > 0.1; n = 8) were considered. Prone and supine postures did not reveal any significant differences in curvilinearity, N(2) normalized slope-derived indexes of conductive or acinar ventilation heterogeneity, nor SF(6)-He normalized phase III slope difference in the first MBW expiration (P > 0.1 for all). The absence of significant changes in any of the MBW indexes suggests that ventilation heterogeneity is similar in the supine and prone postures of normal subjects breathing near FRC.

Adult↗
PubMed2001

Single-breath washouts in a rotating stretcher.

Vital capacity single-breath washouts using 90% O2-5% He-5% SF6 as a test gas mixture were performed with subjects sitting on a stool (upright) or recumbent on a stretcher (prone, supine, lateral left, lateral right, with or without rotation at end of inhalation). On the basis of the combinations of supine and prone maneuvers, gravity-dependent contributions to N2 phase III slope and N2 phase IV height in the supine posture were estimated at 18% and 68%, respectively. Whereas both He and SF6 slope decreased from supine to prone, the SF6-He slope difference actually increased (P = 0.015). N2 phase III slopes, phase IV heights, and cardiogenic oscillations were smallest in the prone posture, and we observed similarities between the modifications of He and SF6 slopes from upright to prone and from upright to short-term microgravity. These results suggest that phase III slope is partially due to emptying patterns of small units with different ventilation-to-volume ratios, corresponding to acini or groups of acini. Of all body postures under study, the prone position most reduces the inhomogeneities of ventilation during a vital capacity maneuver at both inter- and intraregional levels.

Adult↗