Oxygen cost of breathing during fatiguing inspiratory resistive loads

Fd, McCool; Tao, Ge; De, Leith; Fg, Hoppin

doi:10.1152/jappl.1989.66.5.2045

Cited by 34 publications

(25 citation statements)

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“…The effect is similar to that resulting from a lung volume increase of 15-20% of vital capacity, which in adults would translate into a 40-50% reduction in diaphragm strength and endurance. 17 The decreased diaphragmatic resting length demonstrated in healthy infants 16 would impair diaphragm strength and is consistent with our finding of a lower Pimax in the prone position. Our results, therefore, suggest that respiratory muscle strength was lower in the prone position; thus, to achieve higher tidal volumes in that position, infants' respiratory efforts must have been more effective.…”

Section: Discussionsupporting

confidence: 90%

Effect of posture on respiratory function and drive in preterm infants prior to discharge

Leipälä

Bhat

Rafferty

et al. 2003

Pediatric Pulmonology

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Our objective was to determine the effect of posture on respiratory function and drive in prematurely born infants immediately prior to discharge. Twenty infants (6 oxygen-dependent), median gestational age 29 weeks (range, 25-32), were studied at a median postconceptional age (PCA) of 36 weeks (range, 33-39). On 2 successive days, infants were studied both supine and prone; each posture was maintained for 3 hr. The order on each day in which postures were studied was randomized between infants. At the end of each 3-hr period, tidal volume (Vt), inspiratory (Ti) and expiratory (Te) time, respiratory rate, and minute ventilation were measured. In addition, respiratory drive was assessed by measuring the pressure generated in the first 100 msec of an imposed airway occlusion (P(0.1)), and respiratory muscle strength was assessed by recording the maximum inspiratory pressure (Pimax) generated against an occlusion which was maintained for at least five breaths. Overall, tidal volume was higher (P < 0.05), but respiratory rate (P < 0.05), P(0.1) (P < 0.05), and Pimax (P < 0.05) were lower in the prone compared to the supine position. There were no significant differences in Ti or Te between the two postures. In oxygen-dependent infants only, minute volume was higher in the prone position (P < 0.05). In conclusion, posture-related differences in respiratory function are present in prematurely born infants studied prior to neonatal unit discharge.

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Section: Discussionsupporting

confidence: 90%

Effect of posture on respiratory function and drive in preterm infants prior to discharge

Leipälä

Bhat

Rafferty

et al. 2003

Pediatric Pulmonology

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show abstract

“…24 In adults such an increase in lung volume results in a 40-50% reduction in diaphragm strength and endurance. 25 Thus it is not surprising that we found that PIMAX was lower in the prone than in the supine posture.…”

Section: Discussionmentioning

confidence: 75%

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants

Dimitriou

Greenough²,

Pink

et al. 2002

Archives of Disease in Childhood - Fetal and Neonatal Edition

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Objective: To determine if differences in respiratory muscle strength could explain any posture related effects on oxygenation in convalescent neonates. Methods: Infants were examined in three postures: supine, supine with head up tilt of 45°, and prone. A subsequent study was performed to determine the influence of head position in the supine posture. In each posture/head position, oxygen saturation (SaO 2 ) was determined and respiratory muscle strength assessed by measurement of the maximum inspiratory pressure (PIMAX). Patients: Twenty infants, median gestational age 34.5 weeks (range 25-43), and 10 infants, median gestational age 33 weeks (range 30-36), were entered into the first and second study respectively. Results: Oxygenation was higher in the prone and supine with 45°head up tilt postures than in the supine posture (p<0.001), whereas PIMAX was higher in the supine and supine with head up tilt of 45°p ostures than in the prone posture (p<0.001). Head position did not influence the effect of posture on PIMAX or oxygenation. Conclusion: Superior oxygenation in the prone posture in convalescent infants was not explained by greater respiratory muscle strength, as this was superior in the supine posture.

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“…Assuming that transdiaphragmatic pressure was similar in both positions, we reasoned that diaphragm work per breath is increased when infants are prone. As the work of breathing increases, the oxygen cost of breathing increases and inspiratory muscle endurance decreases 32. We acknowledge that measurements of tidal volume or transdiaphragmatic pressure in these infants would have strengthened this conclusion.…”

Section: Discussionmentioning

confidence: 81%

Effects of the supine and prone position on diaphragm thickness in healthy term infants

Rehan

Nakashima²,

Gutman³

et al. 2000

Archives of Disease in Childhood

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Background-The physiological basis underlying the decline in the incidence of sudden infant death syndrome (SIDS) associated with changing the sleep position from prone to supine remains unknown. Aims-To evaluate diaphragm thickness (t di ) and shortening in healthy term infants in the prone and supine positions in order to determine whether changes in body position would aVect diaphragm resting length and the degree of diaphragm shortening during inspiration. Methods-In 16 healthy term infants, diaphragm thickness at the level of the zone of apposition on the right side was measured using ultrasonography. Heart rate (HR), breathing frequency (f), and transcutaneous oxyhaemoglobin saturation (SaO 2 ) were recorded simultaneously during diaphragm imaging with the infants in the supine and prone positions during quiet sleep. Results-At end expiratory (EEV) and at end inspiratory lung volumes (EIV), t di increased significantly in the prone position. The change in t di during tidal breathing was also greater when the infant was prone. SaO 2 , HR, and f were not significantly diVerent at EEV and at EIV in both positions. Conclusion-In healthy term infants, placed in the prone position, the diaphragm is significantly thicker and, therefore, shorter, both at EEV and EIV. Diaphragm shortening during tidal breathing is greater when the infant is prone. In the prone position, the decreased diaphragm resting length would impair diaphragm strength, and the additional diaphragm shortening during tidal breathing represents added work performed by the diaphragm. This may compromise an infant's capacity to respond to stressful situations when placed in the prone position and may contribute to the association of SIDS with prone position.

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Oxygen cost of breathing during fatiguing inspiratory resistive loads

Cited by 34 publications

References 0 publications

Effect of posture on respiratory function and drive in preterm infants prior to discharge

Effect of posture on respiratory function and drive in preterm infants prior to discharge

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants

Effects of the supine and prone position on diaphragm thickness in healthy term infants

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