Biomedical subjects

S Weeks

Publications and source records attributed to S Weeks.

51 records · Page 3Linked to original sources

PubMed1982

Onset of respiration in infants delivered by cesarean section.

We studied the ventilatory parameters and the pattern of breathing including the onset of respiration in 20 healthy infants immediately after cesarean-section delivery. In eight of the infants further measurements were obtained at 60 min of life. The pattern of breathing immediately after delivery is very irregular with a marked tendency to keep the lung inflated mainly through interruptions of expiration. After the first expiration some air remains in the lung representing the formation of functional residual capacity (FRC). FRC obtained with the first breath is proportional to the previous inspired volume and is the largest contribution towards the full establishment of FRC. Tidal volume and FRC of the first breath are similar to that reported in babies delivered vaginally, which suggests that the forces required for lung inflation are similar in the two groups of infants. The first breath tends to be deeper and slower and has a longer expiratory time than subsequent breaths. At 60 min of life the respiratory pattern becomes more regular, tidal volume is further decreased, and respiratory frequency is increased through a reduction of expiratory time.

Adult↗

PubMed1982

Dynamics of breathing in infants.

Passive compliance (C) has been measured in 10 infants at 10--90 min after birth and in 10 infants at a few days of life by recording mouth pressure after airways occlusions at end inspiration. From the slope of the expiratory flow-volume curve, the passive time constant (tau) and resistance (R = tau/C) have been also computed. Examination of the changes of C with time and of the expiratory flow-volume curves indicates that the end-expiratory volume is maintained above functional residual capacity at both ages, but significantly more so at a few days (7.6 ml) than at 10--90 min (3.5 ml). The passive time constant (tau = C . R) is shorter at the early age due to the smaller C. The active compliance (C') and resistance (R') values have been estimated from the pressure generated by the infant when the airways are occluded at end expiration. The active time constant of the respiratory system (tau' = C' . R') is less than tau, due to a smaller active compliance, particularly at a few days. The active resistance is on the contrary similar to R. The active stiffening of the respiratory system provides more stability of the infant's respiratory system and a more ready volume response for any given change in pressure; its price, however, is a higher work of breathing. At optimal breathing rates, in fact, the active work is 127% (10--90 min) to 183% (a few days) higher than that computed from the passive values. The inspiratory flow wave tends to be squared at both ages minimizing the energy losses due to friction.

Airway Resistance↗

PubMed1982

Respiration in newborns: development of the control of breathing.

The pattern of breathing has been studied in human infants at 10, 60, and 90 min, and at a few days after birth. The major characteristics of the pattern of breathing in the immediate period after birth is a marked variability that decreases progressively with time. Interruptions of expiration and peak expiratory flows occurring late in expiration are common findings at 10 to 90 min of age but are infrequent at a few days. From 10 to 90 min to a few days of life the tidal volume increases and respiratory rate decreases with no changes in minute ventilation. The decrease in respiratory rate is due to proportional increases in both inspiratory and expiratory time. Infants born vaginally behave similarly to those delivered by cesarean section except with regard to tidal volume, which at 10 min is closer to the value measured at a few days; this may be the result of the mechanics of the vaginal delivery, which results in less fluid to be absorbed from the lung at birth. Vagal respiratory reflexes are present at birth and the prolongation of inspiratory time during occlusion at end expiration appears to decrease from 10, 60, and 90 min to a few days of age. Values of mouth pressure at 0.1 s after an occlusion at end expiration are higher at 10 min after birth than at 60 and 90 min. Because mean inspiratory flow is similar in this time period it could indicate a progressive increase in the compliance of the respiratory system, possibly reflecting the absorption of pulmonary fluid.

Anesthesia, Epidural↗

PubMed1979