22.3
Capacidade Pulmonar
O ar nos pulmões é medido em volumes e capacidades. As medidas de volume pulmonar refletem a quantidade de ar respirado, libertado ou deixado após uma…
O tamanho do pulmão pode variar conforme a experiência e o tamanho do corpo. A quantidade de ar que pode entrar ou sair dos pulmões é medida em quatro volumes. Funções únicas como inalação e quatro valores comparativos de capacidades de vários volumes.
A quantidade de ar normalmente inalada e exalada é chamada de volume corrente, enquanto o ar que ainda pode ser respirado dentro ou fora após a inalação normal ou exalação é referido como inspiração e volume expiratório de reserva. O quarto volume é a quantidade de ar que permanece nos pulmões depois da expiração do volume de reserva, conhecido como volume de reserva residual, a pequena quantidade de ar que não sai dos pulmões, mantendo-os inflados. Este montante combinado com os outros volumes é a capacidade pulmonar total, todo o montante de ar que os pulmões podem segurar, aproximadamente seis litros.
Dentro de um único ciclo respiratório, a quantidade máxima de ar que pode ser movida dentro ou fora é a capacidade vital, essencialmente um somatório do volume e ambos os volumes de reserva. As demais capacidades são a capacidade inspiratória, o quanto pode ser inalado após a expiração normal, e a capacidade residual funcional, o quanto de ar resta após expirar. Em última análise, essas medidas são usadas para diagnosticar doenças pulmonares, como asma onde mais ar permanece nos pulmões, demorando mais para exalação, ou a fibrose pulmonar onde o volume é rapidamente esvaziado, resultando em falta de ar.
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Q1: What is the difference between lung volumes and lung capacities?
Lung volumes measure air during single respiratory functions like inhalation or exhalation, while lung capacities represent sums of two or more volume measures. There are four lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. Four capacities combine these volumes to show total air movement potential during breathing cycles.
Q2: How much air does tidal volume represent in normal breathing?
Tidal volume is the amount of air normally inhaled and exhaled during a regular breath without forced effort. This is the baseline air movement during quiet, resting breathing. It represents the air exchanged during each normal respiratory cycle before any reserve volumes are engaged.
Q3: What is residual volume and why does it matter?
Residual volume is the small amount of air remaining in the lungs after forced exhalation, keeping the lungs inflated and preventing collapse. This air cannot be voluntarily expelled. Combined with other volumes, residual volume contributes to total lung capacity, approximately six liters in adult males and 4.2 liters in adult females.
Q4: What does vital capacity measure during breathing?
Vital capacity is the maximum volume of air that can be exhaled after maximal inhalation, representing the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume. It measures the maximal amount of air that can be moved in or out during a single respiratory cycle, excluding residual volume.
Q5: How do inspiratory and expiratory reserve volumes differ?
Inspiratory reserve volume is the additional air that can be inhaled after normal inhalation, while expiratory reserve volume is the extra air that can be exhaled after normal exhalation. Together with tidal volume, these reserves determine how much extra breathing capacity exists beyond routine respiration and are essential for activities requiring increased oxygen intake.
Q6: How are lung capacity measurements used to diagnose respiratory diseases?
Lung capacity measurements help identify diseases by revealing abnormal air retention or rapid emptying patterns. In asthma, more air remains in the lungs, prolonging exhalation. In pulmonary fibrosis, lung volume empties rapidly, causing shortness of breath. These measurements provide objective data for diagnosing and monitoring respiratory conditions.
Q7: What is functional residual capacity and how is it calculated?
Functional residual capacity is the volume of air remaining in the lungs after normal exhalation, calculated as the sum of expiratory reserve volume and residual volume. This measurement shows how much air stays in the lungs during quiet breathing and is important for understanding gas exchange and transport during the respiratory cycle.